This guide covers the following topics:
Data that travels across a network can easily be accessed by someone who is not the intended recipient. When the data includes private information, such as passwords and credit card numbers, steps must be taken to make the data unintelligible to unauthorized parties. It is also important to ensure that the data has not been modified, either intentionally or unintentionally, during transport. The Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols were designed to help protect the privacy and integrity of data while it is being transferred across a network.
The Java Secure Socket Extension (JSSE) enables secure Internet communications. It provides a framework and an implementation for a Java version of the SSL and TLS protocols and includes functionality for data encryption, server authentication, message integrity, and optional client authentication. Using JSSE, developers can provide for the secure passage of data between a client and a server running any application protocol (such as HTTP, Telnet, or FTP) over TCP/IP. For an introduction to SSL, see Secure Sockets Layer (SSL) Protocol Overview.
By abstracting the complex underlying security algorithms and handshaking mechanisms, JSSE minimizes the risk of creating subtle but dangerous security vulnerabilities. Furthermore, it simplifies application development by serving as a building block that developers can integrate directly into their applications.
JSSE provides both an application programming interface (API)
framework and an implementation of that API. The JSSE API
supplements the core network and cryptographic services defined by
the java.security and java.net packages
by providing extended networking socket classes, trust managers,
key managers, SSL contexts, and a socket factory framework for
encapsulating socket creation behavior. Because the
SSLSocket class is based on a blocking I/O model, the
Java Development Kit (JDK) includes a nonblocking
SSLEngine class to enable implementations to choose
their own I/O methods.
The JSSE API is capable of supporting SSL versions 2.0 and 3.0 and TLS version 1.0. These security protocols encapsulate a normal bidirectional stream socket, and the JSSE API adds transparent support for authentication, encryption, and integrity protection. The JSSE implementation shipped with the JDK supports SSL 3.0 and TLS 1.0. It does not implement SSL 2.0.
JSSE is a security component of the Java SE platform, and is based on the same design principles found elsewhere in the Java Cryptography Architecture (JCA) framework. This framework for cryptography-related security components allows them to have implementation independence and, whenever possible, algorithm independence. JSSE uses the cryptographic service providers defined by the JCA framework.
Other security components in the Java SE platform include the Java Authentication and Authorization Service (JAAS) and the Java Security Tools. JSSE encompasses many of the same concepts and algorithms as those in JCA but automatically applies them underneath a simple stream socket API.
The JSSE API was designed to allow other SSL/TLS protocol and Public Key Infrastructure (PKI) implementations to be plugged in seamlessly. Developers can also provide alternative logic to determine if remote hosts should be trusted or what authentication key material should be sent to a remote host.
JSSE includes the following important features:
SSLSocket, SSLServerSocket, and
SSLEngine)| Cryptographic Algorithm Footnote 1 | Cryptographic Process | Key Lengths (Bits) |
|---|---|---|
| Rivest Shamir Adleman (RSA) | Authentication and key exchange | 512 and larger |
| Rivest Cipher 4 (RC4) | Bulk encryption | 128 128 (40 effective) |
| Data Encryption Standard (DES) | Bulk encryption | 64 (56 effective) 64 (40 effective) |
| Triple DES (3DES) | Bulk encryption | 192 (112 effective) |
| Advanced Encryption Standard (AES) | Bulk encryption | 256 Footnote 2 128 |
| Diffie-Hellman (DH) | Key agreement | 1024 512 |
| Digital Signature Algorithm (DSA) | Authentication | 1024 |
Footnote 1 The SunJSSE implementation uses the JCA for all its cryptographic algorithms.
Footnote 2 Cipher suites that use AES_256 require installation of the Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files. See Java SE Download Page.
The JSSE standard API, available in the javax.net
and javax.net.ssl packages, provides:
SSLEngine).Oracle's implementation of Java SE includes a JSSE provider named SunJSSE, which comes preinstalled and preregistered with the JCA. This provider supplies the following cryptographic services:
More information about this provider is available in the SunJSSE section of the Oracle Providers Documentation.
The following list contains links to online documentation and names of books about related subjects:
The java-home variable placeholder is used throughout this document to refer to the directory where the Java Runtime Environment (JRE) is installed. This directory is determined based on whether you are running JSSE with or without the JDK installed. The JDK includes the JRE, but it is located on a different level in the file hierarchy.
To see the default location of java-home for different installations, refer to Table 2.
| Operating System | JDK | JRE |
|---|---|---|
| Solaris/Linux | ~/jdk1.8.0/jre | ~/jre1.8.0 |
| Windows | C:\jdk1.8.0\jre | C:\jre1.8.0 |
Note: The tilde (~) in the path name represents the current user's home directory on Solaris, Linux, or Mac OS X operating systems.
Several terms relating to cryptography are used within this document. This section defines some of these terms.
The process of confirming the identity of a party with whom one is communicating.
A combination of cryptographic parameters that define the security algorithms and key sizes used for authentication, key agreement, encryption, and integrity protection.
A digitally signed statement vouching for the identity and public key of an entity (person, company, and so on). Certificates can either be self-signed or issued by a Certificate Authority (CA) — an entity that is trusted to issue valid certificates for other entities. Well-known CAs include VeriSign, Entrust, and GTE CyberTrust. X509 is a common certificate format that can be managed by the JDK's keytool.
An algorithm that is used to produce a relatively small fixed-size string of bits (called a hash) from an arbitrary block of data. A cryptographic hash function is similar to a checksum and has three primary characteristics: it is a one-way function, meaning that it is not possible to produce the original data from the hash; a small change in the original data produces a large change in the resulting hash; and it does not require a cryptographic key.
Sometimes referred to simply as provider for short, the Java Cryptography Architecture (JCA) defines it as a package (or set of packages) that implements one or more engine classes for specific cryptographic algorithms. An engine class defines a cryptographic service in an abstract fashion without a concrete implementation.
A digital equivalent of a handwritten signature. It is used to ensure that data transmitted over a network was sent by whoever claims to have sent it and that the data has not been modified in transit. For example, an RSA-based digital signature is calculated by first computing a cryptographic hash of the data and then encrypting the hash with the sender's private key.
Encryption is the process of using a complex algorithm to convert an original message (cleartext) to an encoded message (ciphertext) that is unintelligible unless it is decrypted. Decryption is the inverse process of producing cleartext from ciphertext.
The algorithms used to encrypt and decrypt data typically come in two categories: secret key (symmetric) cryptography and public key (asymmetric) cryptography.
The negotiation phase during which the two socket peers agree to use a new or existing session. The handshake protocol is a series of messages exchanged over the record protocol. At the end of the handshake, new connection-specific encryption and integrity protection keys are generated based on the key agreement secrets in the session.
A method by which two parties cooperate to establish a common key. Each side generates some data, which is exchanged. These two pieces of data are then combined to generate a key. Only those holding the proper private initialization data can obtain the final key. Diffie-Hellman (DH) is the most common example of a key agreement algorithm.
A method by which keys are exchanged. One side generates a private key and encrypts it using the peer's public key (typically RSA). The data is transmitted to the peer, who decrypts the key using the corresponding private key.
Key managers and trust managers use keystores for their key material. A key manager manages a keystore and supplies public keys to others as needed (for example, for use in authenticating the user to others). A trust manager decides who to trust based on information in the truststore it manages.
A keystore is a database of key material. Key material is used for a variety of purposes, including authentication and data integrity. Various types of keystores are available, including PKCS12 and Oracle's JKS.
Generally speaking, keystore information can be grouped into two
categories: key entries and trusted certificate entries. A key
entry consists of an entity's identity and its private key, and can
be used for a variety of cryptographic purposes. In contrast, a
trusted certificate entry contains only a public key in addition to
the entity's identity. Thus, a trusted certificate entry cannot be
used where a private key is required, such as in a
javax.net.ssl.KeyManager. In the JDK implementation of
JKS, a keystore may contain both key entries and trusted
certificate entries.
A truststore is a keystore that is used when making decisions about what to trust. If you receive data from an entity that you already trust, and if you can verify that the entity is the one that it claims to be, then you can assume that the data really came from that entity.
An entry should only be added to a truststore if the user trusts that entity. By either generating a key pair or by importing a certificate, the user gives trust to that entry. Any entry in the truststore is considered a trusted entry.
It may be useful to have two different keystore files: one containing just your key entries, and the other containing your trusted certificate entries, including CA certificates. The former contains private information, whereas the latter does not. Using two files instead of a single keystore file provides a cleaner separation of the logical distinction between your own certificates (and corresponding private keys) and others' certificates. To provide more protection for your private keys, store them in a keystore with restricted access, and provide the trusted certificates in a more publicly accessible keystore if needed.
Provides a way to check the integrity of information transmitted over or stored in an unreliable medium, based on a secret key. Typically, MACs are used between two parties that share a secret key in order to validate information transmitted between these parties.
A MAC mechanism that is based on cryptographic hash functions is referred to as HMAC. HMAC can be used with any cryptographic hash function, such as Message Digest 5 (MD5) and Secure Hash Algorithm (SHA), in combination with a secret shared key. HMAC is specified in RFC 2104.
A cryptographic system that uses an encryption algorithm in which two keys are produced. One key is made public, whereas the other is kept private. The public key and the private key are cryptographic inverses; what one key encrypts only the other key can decrypt. Public-key cryptography is also called asymmetric cryptography.
A protocol that packages all data (whether application-level or as part of the handshake process) into discrete records of data much like a TCP stream socket converts an application byte stream into network packets. The individual records are then protected by the current encryption and integrity protection keys.
A cryptographic system that uses an encryption algorithm in which the same key is used both to encrypt and decrypt the data. Secret-key cryptography is also called symmetric cryptography.
A named collection of state information including authenticated peer identity, cipher suite, and key agreement secrets that are negotiated through a secure socket handshake and that can be shared among multiple secure socket instances.
See keystore/truststore.
Secure Sockets Layer (SSL) is the most widely used protocol for implementing cryptography on the web. SSL uses a combination of cryptographic processes to provide secure communication over a network. This section provides an introduction to SSL and the cryptographic processes it uses.
SSL provides a secure enhancement to the standard TCP/IP sockets protocol used for Internet communications. As shown in Table 3, the secure sockets layer is added between the transport layer and the application layer in the standard TCP/IP protocol stack. The application most commonly used with SSL is Hypertext Transfer Protocol (HTTP), the protocol for Internet web pages. Other applications, such as Net News Transfer Protocol (NNTP), Telnet, Lightweight Directory Access Protocol (LDAP), Interactive Message Access Protocol (IMAP), and File Transfer Protocol (FTP), can be used with SSL as well.
Note: There is currently no standard for secure FTP.
| TCP/IP Layer | Protocol |
|---|---|
| Application Layer | HTTP, NNTP, Telnet, FTP, and so on |
| Secure Sockets Layer | SSL |
| Transport Layer | TCP |
| Internet Layer | IP |
SSL was developed by Netscape in 1994, and with input from the Internet community, has evolved to become a standard. It is now under the control of the international standards organization, the Internet Engineering Task Force (IETF). The IETF renamed SSL to Transport Layer Security (TLS), and released the first specification, version 1.0, in January 1999. TLS 1.0 is a modest upgrade to the most recent version of SSL, version 3.0. The differences between SSL 3.0 and TLS 1.0 are minor. TLS 1.1 was released in April 2006, and TLS 1.2 in August 2008. However, these updated versions are not as widely supported as TLS 1.0 and SSL 3.0.
Transferring sensitive information over a network can be risky due to the following issues:
SSL addresses each of these issues. It addresses the first issue by optionally allowing each of two communicating parties to ensure the identity of the other party in a process called authentication. Once the parties are authenticated, SSL provides an encrypted connection between the two parties for secure message transmission. Encrypting the communication between the two parties provides privacy and therefore addresses the second issue. The encryption algorithms used with SSL include a secure hash function, which is similar to a checksum. This ensures that data is not modified in transit. The secure hash function addresses the third issue of data integrity.
Note: Both authentication and encryption are optional, and depend on the the negotiated cipher suites between the two entities.
An e-commerce transaction is an obvious example of when to use SSL. In an e-commerce transaction, it would be foolish to assume that you can guarantee the identity of the server with whom you are communicating. It would be easy enough for someone to create a phony web site promising great services if only you enter your credit card number. SSL allows you, the client, to authenticate the identity of the server. It also allows the server to authenticate the identity of the client, although in Internet transactions, this is seldom done.
Once the client and the server are comfortable with each other's identity, SSL provides privacy and data integrity through the encryption algorithms that it uses. This allows sensitive information, such as credit card numbers, to be transmitted securely over the Internet.
Although SSL provides authentication, privacy, and data integrity, it does not provide nonrepudiation services. Nonrepudiation means that an entity that sends a message cannot later deny sending it. When the digital equivalent of a signature is associated with a message, the communication can later be proved. SSL alone does not provide nonrepudiation.
One of the reasons that SSL is effective is that it uses several different cryptographic processes. SSL uses public-key cryptography to provide authentication, and secret-key cryptography with digital signatures to provide for privacy and data integrity. Before you can understand SSL, it is helpful to understand these cryptographic processes.
The primary purpose of cryptography is to make it difficult for an unauthorized third party to access and understand private communication between two parties. It is not always possible to restrict all unauthorized access to data, but private data can be made unintelligible to unauthorized parties through the process of encryption. Encryption uses complex algorithms to convert the original message (cleartext) to an encoded message (ciphertext). The algorithms used to encrypt and decrypt data that is transferred over a network typically come in two categories: secret-key cryptography and public-key cryptography. These forms of cryptography are explained in the following subsections.
Both secret-key cryptography and public-key cryptography depend on the use of an agreed-upon cryptographic key or pair of keys. A key is a string of bits that is used by the cryptographic algorithm or algorithms during the process of encrypting and decrypting the data. A cryptographic key is like a key for a lock; only with the right key can you open the lock.
Safely transmitting a key between two communicating parties is not a trivial matter. A public key certificate enables a party to safely transmit its public key, while ensuring the receiver of the authenticity of the public key. Public key certificates are described in a later section.
The descriptions of the cryptographic processes that follow use conventions widely used by the security community: the two communicating parties are labeled with the names Alice and Bob. The unauthorized third party, also known as the attacker, is named Charlie.
With secret-key cryptography, both communicating parties, Alice and Bob, use the same key to encrypt and decrypt the messages. Before any encrypted data can be sent over the network, both Alice and Bob must have the key and must agree on the cryptographic algorithm that they will use for encryption and decryption.
One of the major problems with secret-key cryptography is the logistical issue of how to get the key from one party to the other without allowing access to an attacker. If Alice and Bob are securing their data with secret-key cryptography, and if Charlie gains access to their key, then Charlie can understand any secret messages he intercepts between Alice and Bob. Not only can Charlie decrypt Alice's and Bob's messages, but he can also pretend that he is Alice and send encrypted data to Bob. Bob will not know that the message came from Charlie, not Alice.
Once the problem of secret key distribution is solved, secret-key cryptography can be a valuable tool. The algorithms provide excellent security and encrypt data relatively quickly. The majority of the sensitive data sent in an SSL session is sent using secret-key cryptography.
Secret-key cryptography is also called symmetric cryptography because the same key is used to both encrypt and decrypt the data. Well-known secret-key cryptographic algorithms include the Data Encryption Standard (DES), Triple DES (3DES), Rivest Cipher 2 (RC2), and Rivest Cipher 4 (RC4).
Public-key cryptography solves the logistical problem of key distribution by using both a public key and a private key. The public key can be sent openly through the network while the private key is kept private by one of the communicating parties. The public and the private keys are cryptographic inverses of each other; what one key encrypts, the other key will decrypt.
Assume that Bob wants to send a secret message to Alice using public-key cryptography. Alice has both a public key and a private key, so she keeps her private key in a safe place and sends her public key to Bob. Bob encrypts the secret message to Alice using Alice's public key. Alice can later decrypt the message with her private key.
If Alice encrypts a message using her private key and sends the encrypted message to Bob, then Bob can be sure that the data he receives comes from Alice; if Bob can decrypt the data with Alice's public key, the message must have been encrypted by Alice with her private key, and only Alice has Alice's private key. The problem is that anybody else can read the message as well because Alice's public key is public. Although this scenario does not allow for secure data communication, it does provide the basis for digital signatures. A digital signature is one of the components of a public key certificate, and is used in SSL to authenticate a client or a server. Public key certificates and digital signatures are described in later sections.
Public-key cryptography is also called asymmetric cryptography because different keys are used to encrypt and decrypt the data. A well-known public key cryptographic algorithm often used with SSL is the Rivest Shamir Adleman (RSA) algorithm. Another public key algorithm used with SSL that is designed specifically for secret key exchange is the Diffie-Hellman (DH) algorithm. Public-key cryptography requires extensive computations, making it very slow. It is therefore typically used only for encrypting small pieces of data, such as secret keys, rather than for the bulk of encrypted data communications.
Both secret-key cryptography and public-key cryptography have strengths and weaknesses. With secret-key cryptography, data can be encrypted and decrypted quickly, but because both communicating parties must share the same secret key information, the logistics of exchanging the key can be a problem. With public-key cryptography, key exchange is not a problem because the public key does not need to be kept secret, but the algorithms used to encrypt and decrypt data require extensive computations, and are therefore very slow.
A public key certificate provides a safe way for an entity to pass on its public key to be used in asymmetric cryptography. The public key certificate avoids the following situation: if Charlie creates his own public key and private key, he can claim that he is Alice and send his public key to Bob. Bob will be able to communicate with Charlie, but Bob will think that he is sending his data to Alice.
A public key certificate can be thought of as the digital equivalent of a passport. It is issued by a trusted organization and provides identification for the bearer. A trusted organization that issues public key certificates is known as a Certificate Authority (CA). The CA can be likened to a notary public. To obtain a certificate from a CA, one must provide proof of identity. Once the CA is confident that the applicant represents the organization it says it represents, the CA signs the certificate attesting to the validity of the information contained within the certificate.
A public key certificate contains the following fields:
If Bob only accepts Alice's public key as valid when she sends it in a public key certificate, then Bob will not be fooled into sending secret information to Charlie when Charlie masquerades as Alice.
Multiple certificates may be linked in a certificate chain. When a certificate chain is used, the first certificate is always that of the sender. The next is the certificate of the entity that issued the sender's certificate. If more certificates are in the chain, then each is that of the authority that issued the previous certificate. The final certificate in the chain is the certificate for a root CA. A root CA is a public certificate authority that is widely trusted. Information for several root CAs is typically stored in the client's Internet browser. This information includes the CA's public key. Well-known CAs include VeriSign, Entrust, and GTE CyberTrust.
When sending encrypted data, SSL typically uses a cryptographic hash function to ensure data integrity. The hash function prevents Charlie from tampering with data that Alice sends to Bob.
A cryptographic hash function is similar to a checksum. The main difference is that whereas a checksum is designed to detect accidental alterations in data, a cryptographic hash function is designed to detect deliberate alterations. When data is processed by a cryptographic hash function, a small string of bits, known as a hash, is generated. The slightest change to the message typically makes a large change in the resulting hash. A cryptographic hash function does not require a cryptographic key. Two hash functions often used with SSL are Message Digest 5 (MD5) and Secure Hash Algorithm (SHA). SHA was proposed by the U.S. National Institute of Standards and Technology (NIST).
If Alice wants to be sure that Charlie does not tamper with her message to Bob, then she can calculate an HMAC for her message and append the HMAC to her original message. She can then encrypt the message plus the HMAC using a secret key that she shares with Bob. When Bob decrypts the message and calculates the HMAC, he will be able to tell if the message was modified in transit. With SSL, an HMAC is used with the transmission of secure data.
Once a cryptographic hash is created for a message, the hash is encrypted with the sender's private key. This encrypted hash is called a digital signature.
Communication using SSL begins with an exchange of information between the client and the server. This exchange of information is called the SSL handshake. The SSL handshake includes the following stages:
The SSL session begins with a negotiation between the client and the server as to which cipher suite they will use. A cipher suite is a set of cryptographic algorithms and key sizes that a computer can use to encrypt data. The cipher suite includes information about the public key exchange algorithms or key agreement algorithms, and cryptographic hash functions. The client tells the server which cipher suites it has available, and the server chooses the best mutually acceptable cipher suite.
In SSL, the authentication step is optional, but in the example of an e-commerce transaction over the web, the client will generally want to authenticate the server. Authenticating the server allows the client to be sure that the server represents the entity that the client believes the server represents.
To prove that a server belongs to the organization that it claims to represent, the server presents its public key certificate to the client. If this certificate is valid, then the client can be sure of the identity of the server.
The client and server exchange information that allows them to agree on the same secret key. For example, with RSA, the client uses the server's public key, obtained from the public key certificate, to encrypt the secret key information. The client sends the encrypted secret key information to the server. Only the server can decrypt this message because the server's private key is required for this decryption.
Both the client and the server now have access to the same secret key. With each message, they use the cryptographic hash function, chosen in the first step of the handshake, and shared secret information, to compute an HMAC that they append to the message. They then use the secret key and the secret key algorithm negotiated in the first step of the handshake to encrypt the secure data and the HMAC. The client and server can now communicate securely using their encrypted and hashed data.
The previous section provides a high-level description of the SSL handshake, which is the exchange of information between the client and the server prior to sending the encrypted message. This section provides more detail.
Figure 1 shows the sequence of messages that are exchanged in the SSL handshake. Messages that are sent only in certain situations are noted as optional. Each of the SSL messages is described below the figure.
The SSL messages are sent in the following order:
Note: Only a few Internet server applications ask for a certificate from the client.
close_notify message to inform the peer that the
connection is closed.If the parameters generated during an SSL session are saved, then these parameters can sometimes be reused for future SSL sessions. Saving SSL session parameters allows encrypted communication to begin much more quickly.
Once the initial handshake is finished and application data is flowing, either side is free to initiate a new handshake at any time. An application might like to use a stronger cipher suite for especially critical operations, or a server application might want to require client authentication.
Regardless of the reason, the new handshake takes place over the existing encrypted session, and application data and handshake messages are interleaved until a new session is established.
Your application can initiate a new handshake by using one of the following methods:
SSLSocket.startHandshake()SSLEngine.beginHandshake()Note that a protocol flaw related to renegotiation was found in 2009. The protocol and the Java SE implementation have both been fixed. For more information, see Transport Layer Security (TLS) Renegotiation Issue.
When using raw SSLSocket and SSLEngine
classes, you should always check the peer's credentials before
sending any data. The SSLSocket and
SSLEngine classes do not automatically verify that the
host name in a URL matches the host name in the peer's credentials.
An application could be exploited with URL spoofing if the host
name is not verified.
Protocols such as HTTPS (HTTP Over TLS) do require host name verification. Applications can use HostnameVerifier to override the default HTTPS host name rules. See HttpsURLConnection for more information.
To communicate securely, both sides of the connection must be
SSL-enabled. In the JSSE API, the endpoint classes of the
connection are SSLSocket and SSLEngine.
In Figure 2, the major classes used to create
SSLSocket and SSLEngine are laid out in a
logical ordering. The text following the diagram, explains the
contents of the illustration.
An SSLSocket is created either by an
SSLSocketFactory or by an SSLServerSocket
accepting an inbound connection. In turn, an
SSLServerSocket is created by an
SSLServerSocketFactory. Both
SSLSocketFactory and
SSLServerSocketFactory objects are created by an
SSLContext. An SSLEngine is created
directly by an SSLContext, and relies on the
application to handle all I/O.
Note: When using raw SSLSocket or
SSLEngine classes, you should always check the peer's
credentials before sending any data. The SSLSocket and
SSLEngine classes do not automatically verify, for
example, that the host name in a URL matches the host name in the
peer's credentials. An application could be exploited with URL
spoofing if the host name is not verified.
There are two ways to obtain and initialize an
SSLContext:
getDefault() method on either the
SSLSocketFactory or
SSLServerSocketFactory class. This method creates a
default SSLContext with a default
KeyManager, TrustManager, and
SecureRandom (a secure random number generator). A
default KeyManagerFactory and
TrustManagerFactory are used to create the
KeyManager and TrustManager,
respectively. The key material used is found in the default
keystore and truststore, as determined by system properties
described in Customizing the Default
Keystores and Truststores, Store Types, and Store
Passwords.getInstance() on the SSLContext class,
and then initialize the context by calling the instance's proper
init() method. One variant of the init()
method takes three arguments: an array of KeyManager
objects, an array of TrustManager objects, and a
SecureRandom object. The KeyManager and
TrustManager objects are created by either
implementing the appropriate interfaces or using the
KeyManagerFactory and TrustManagerFactory
classes to generate implementations. The
KeyManagerFactory and TrustManagerFactory
can then each be initialized with key material contained in the
KeyStore passed as an argument to the
init() method of the TrustManagerFactory
or KeyManagerFactory classes. Finally, the
getTrustManagers() method (in
TrustManagerFactory) and getKeyManagers()
method (in KeyManagerFactory) can be called to obtain
the array of trust managers or key managers, one for each type of
trust or key material.Once an SSL connection is established, an
SSLSession is created which contains various
information, such as identities established and cipher suite used.
The SSLSession is then used to describe an ongoing
relationship and state information between two entities. Each SSL
connection involves one session at a time, but that session may be
used on many connections between those entities, simultaneously or
sequentially.
The core JSSE classes are part of the javax.net and
javax.net.ssl packages.
The abstract javax.net.SocketFactory class is used
to create sockets. Subclasses of this class are factories that
create particular subclasses of sockets and thus provide a general
framework for the addition of public socket-level functionality.
For example, see SSLSocketFactory and
SSLServerSocketFactory.
The abstract javax.net.ServerSocketFactory class is
analogous to the SocketFactory class, but is used
specifically for creating server sockets.
Socket factories are a simple way to capture a variety of policies related to the sockets being constructed, producing such sockets in a way that does not require special configuration of the code that asks for the sockets:
java.net.Socket (or
javax.net.ssl.SSLSocket), so that they can directly
expose new APIs for features such as compression, security, record
marking, statistics collection, or firewall tunneling.The javax.net.ssl.SSLSocketFactory class acts as a
factory for creating secure sockets. This class is an abstract
subclass of javax.net.SocketFactory.
Secure socket factories encapsulate the details of creating and initially configuring secure sockets. This includes authentication keys, peer certificate validation, enabled cipher suites, and the like.
The javax.net.ssl.SSLServerSocketFactory class is
analogous to the SSLSocketFactory class, but is used
specifically for creating server sockets.
The following ways can be used to obtain an
SSLSocketFactory:
SSLSocketFactory.getDefault() static method.SSLSocketFactory parameter that can be called by
clients to specify which SSLSocketFactory to use when
creating sockets (for example,
javax.net.ssl.HttpsURLConnection).The default factory is typically configured to support server authentication only so that sockets created by the default factory do not leak any more information about the client than a normal TCP socket would.
Many classes that create and use sockets do not need to know the details of socket creation behavior. Creating sockets through a socket factory passed in as a parameter is a good way of isolating the details of socket configuration, and increases the reusability of classes that create and use sockets.
You can create new socket factory instances either by
implementing your own socket factory subclass or by using another
class which acts as a factory for socket factories. One example of
such a class is SSLContext, which is provided with the
JSSE implementation as a provider-based configuration class.
The javax.net.ssl.SSLSocket class is a subclass of
the standard Java java.net.Socket class. It supports
all of the standard socket methods and adds methods specific to
secure sockets. Instances of this class encapsulate the SSLContext under which they were created. There
are APIs to control the creation of secure socket sessions for a
socket instance, but trust and key management are not directly
exposed.
The javax.net.ssl.SSLServerSocket class is
analogous to the SSLSocket class, but is used
specifically for creating server sockets.
To prevent peer spoofing, you should always verify the credentials presented to an
SSLSocket.
Note: Due to the complexity of the SSL and TLS
protocols, it is difficult to predict whether incoming bytes on a
connection are handshake or application data, and how that data
might affect the current connection state (even causing the process
to block). In the Oracle JSSE implementation, the
available() method on the object obtained by
SSLSocket.getInputStream() returns a count of the
number of application data bytes successfully decrypted from the
SSL connection but not yet read by the application.
SSLSocket can be obtained in one of the
following ways:
SSLSocket can be created by an instance of
SSLSocketFactory via one of the
several createSocket() methods of that class.SSLSocket can be created through the
accept() method of the SSLServerSocket
class.SSL/TLS is becoming increasingly popular. It is being used in a wide variety of applications across a wide range of computing platforms and devices. Along with this popularity come demands to use SSL/TLS with different I/O and threading models to satisfy the applications' performance, scalability, footprint, and other requirements. There are demands to use SSL/TLS with blocking and nonblocking I/O channels, asynchronous I/O, arbitrary input and output streams, and byte buffers. There are demands to use it in highly scalable, performance-critical environments, requiring management of thousands of network connections.
Abstraction of the I/O transport mechanism using the
SSLEngine class in Java SE allows applications to use
the SSL/TLS protocols in a transport-independent way, and thus
frees application developers to choose transport and computing
models that best meet their needs. Not only does this abstraction
allow applications to use nonblocking I/O channels and other I/O
models, it also accommodates different threading models. This
effectively leaves the I/O and threading decisions up to the
application developer. Because of this flexibility, the application
developer must manage I/O and threading (complex topics in and of
themselves), as well as have some understanding of the SSL/TLS
protocols. The abstraction is therefore an advanced API: beginners
should use SSLSocket.
Users of other Java programming language APIs such as the Java Generic Security Services (Java GSS) and the Java Simple Authentication Security Layer (Java SASL) will notice similarities in that the application is also responsible for transporting data.
The core class is javax.net.ssl.SSLEngine.
It encapsulates an SSL/TLS state machine and operates on inbound
and outbound byte buffers supplied by the user of the
SSLEngine class. The diagram in Figure
3 illustrates the flow of data from the application, through
SSLEngine, to the transport mechanism, and back.
The application, shown on the left, supplies application
(plaintext) data in an application buffer and passes it to
SSLEngine. The SSLEngine object processes
the data contained in the buffer, or any handshaking data, to
produce SSL/TLS encoded data and places it to the network buffer
supplied by the application. The application is then responsible
for using an appropriate transport (shown on the right) to send the
contents of the network buffer to its peer. Upon receiving SSL/TLS
encoded data from its peer (via the transport), the application
places the data into a network buffer and passes it to
SSLEngine. The SSLEngine object processes
the network buffer's contents to produce handshaking data or
application data.
An instance of the SSLEngine class can be in one of
the following states:
To create an SSLEngine object, you use the
SSLContext.createSSLEngine() method. You must
configure the engine to act as a client or a server, and set other
configuration parameters, such as which cipher suites to use and
whether to require client authentication.
Example 1 illustrates how to create an
SSLEngine object.
Note: The server name and port number are not used for communicating with the server (all transport is the responsibility of the application). They are hints to the JSSE provider to use for SSL session caching, and for Kerberos-based cipher suite implementations to determine which server credentials should be obtained.
import javax.net.ssl.*;
import java.security.*;
// Create and initialize the SSLContext with key material
char[] passphrase = "passphrase".toCharArray();
// First initialize the key and trust material
KeyStore ksKeys = KeyStore.getInstance("JKS");
ksKeys.load(new FileInputStream("testKeys"), passphrase);
KeyStore ksTrust = KeyStore.getInstance("JKS");
ksTrust.load(new FileInputStream("testTrust"), passphrase);
// KeyManagers decide which key material to use
KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509");
kmf.init(ksKeys, passphrase);
// TrustManagers decide whether to allow connections
TrustManagerFactory tmf = TrustManagerFactory.getInstance("SunX509");
tmf.init(ksTrust);
sslContext = SSLContext.getInstance("TLS");
sslContext.init(kmf.getKeyManagers(), tmf.getTrustManagers(), null);
// Create the engine
SSLEngine engine = sslContext.createSSLengine(hostname, port);
// Use as client
engine.setUseClientMode(true);
The two main SSLEngine methods are
wrap() and unwrap(). They are responsible
for generating and consuming network data respectively. Depending
on the state of the SSLEngine object, this data might
be handshake or application data.
Each SSLEngine object has several phases during its
lifetime. Before application data can be sent or received, the
SSL/TLS protocol requires a handshake to establish cryptographic
parameters. This handshake requires a series of back-and-forth
steps by the SSLEngine object. The "SSL Handshake" section provides more details
about the handshake itself.
During the initial handshaking, the wrap() and
unwrap() methods generate and consume handshake data,
and the application is responsible for transporting the data. The
wrap() and unwrap() method sequence is
repeated until the handshake is finished. Each
SSLEngine operation generates an instance of the
SSLEngineResult class, in which the
SSLEngineResult.HandshakeStatus field is used to
determine what operation must occur next to move the handshake
along.
Table 4 shows the sequence of methods called during a typical handshake, with corresponding messages and statuses.
| Client | SSL/TLS Message | HandshakeStatus |
|---|---|---|
wrap() |
ClientHello |
NEED_UNWRAP |
unwrap() |
ServerHello/Cert/ServerHelloDone |
NEED_WRAP |
wrap() |
ClientKeyExchange |
NEED_WRAP |
wrap() |
ChangeCipherSpec |
NEED_WRAP |
wrap() |
Finished |
NEED_UNWRAP |
unwrap() |
ChangeCipherSpec |
NEED_UNWRAP |
unwrap() |
Finished |
FINISHED |
When handshaking is complete, further calls to
wrap() will attempt to consume application data and
package it for transport. The unwrap() method will
attempt the opposite.
To send data to the peer, the application first supplies the
data that it wants to send via SSLEngine.wrap() to
obtain the corresponding SSL/TLS encoded data. The application then
sends the encoded data to the peer using its chosen transport
mechanism. When the application receives the SSL/TLS encoded data
from the peer via the transport mechanism, it supplies this data to
the SSLEngine via SSLEngine.unwrap() to
obtain the plaintext data sent by the peer.
Example 2 shows an SSL application that uses
a nonblocking SocketChannel to communicate with its
peer.
Note: The example can be made more robust and
scalable by using a Selector with the nonblocking
SocketChannel.
In Example 2, the string hello
is sent to the peer by encoding it using the SSLEngine
created in Example 1. It uses information from
the SSLSession to determine how large the byte buffers
should be.
// Create a nonblocking socket channel
SocketChannel socketChannel = SocketChannel.open();
socketChannel.configureBlocking(false);
socketChannel.connect(new InetSocketAddress(hostname, port));
// Complete connection
while (!socketChannel.finishedConnect()) {
// do something until connect completed
}
// Create byte buffers to use for holding application and encoded data
SSLSession session = engine.getSession();
ByteBuffer myAppData = ByteBuffer.allocate(session.getApplicationBufferSize());
ByteBuffer myNetData = ByteBuffer.allocate(session.getPacketBufferSize());
ByteBuffer peerAppData = ByteBuffer.allocate(session.getApplicationBufferSize());
ByteBuffer peerNetData = ByteBuffer.allocate(session.getPacketBufferSize());
// Do initial handshake
doHandshake(socketChannel, engine, myNetData, peerNetData);
myAppData.put("hello".getBytes());
myAppData.flip();
while (myAppData.hasRemaining()) {
// Generate SSL/TLS encoded data (handshake or application data)
SSLEngineResult res = engine.wrap(myAppData, myNetData);
// Process status of call
if (res.getStatus() == SSLEngineResult.Status.OK) {
myAppData.compact();
// Send SSL/TLS encoded data to peer
while(myNetData.hasRemaining()) {
int num = socketChannel.write(myNetData);
if (num == 0) {
// no bytes written; try again later
}
}
}
// Handle other status: BUFFER_OVERFLOW, CLOSED
...
}
Example 3 illustrates how to read data from
the same nonblocking SocketChannel and extract the
plaintext data from it by using the SSLEngine created
in Example 1. Each iteration of this code may or
may not produce plaintext data, depending on whether handshaking is
in progress.
// Read SSL/TLS encoded data from peer
int num = socketChannel.read(peerNetData);
if (num == -1) {
// The channel has reached end-of-stream
} else if (num == 0) {
// No bytes read; try again ...
} else {
// Process incoming data
peerNetData.flip();
res = engine.unwrap(peerNetData, peerAppData);
if (res.getStatus() == SSLEngineResult.Status.OK) {
peerNetData.compact();
if (peerAppData.hasRemaining()) {
// Use peerAppData
}
}
// Handle other status: BUFFER_OVERFLOW, BUFFER_UNDERFLOW, CLOSED
...
}
To indicate the status of the engine and what actions the
application should take, the SSLEngine.wrap() and
SSLEngine.unwrap() methods return an SSLEngineResult
instance, as shown in Example 2. This
SSLEngineResult object contains two pieces of status
information: the overall status of the engine and the handshaking
status.
The possible overall statuses are represented by the
SSLEngineResult.Status enum. The following statuses
are available:
OKCLOSEDSSLEngine or the operation
could not be completed because it was already closed.BUFFER_UNDERFLOWBUFFER_OVERFLOWExample 4 illustrates how to handle the
BUFFER_UNDERFLOW and BUFFER_OVERFLOW
statuses of the SSLEngine.unwrap() method. It uses
SSLSession.getApplicationBufferSize() and
SSLSession.getPacketBufferSize() to determine how
large to make the byte buffers.
SSLEngineResult res = engine.unwrap(peerNetData, peerAppData);
switch (res.getStatus()) {
case BUFFER_OVERFLOW:
// Maybe need to enlarge the peer application data buffer.
if (engine.getSession().getApplicationBufferSize() > peerAppData.capacity()) {
// enlarge the peer application data buffer
} else {
// compact or clear the buffer
}
// retry the operation
break;
case BUFFER_UNDERFLOW:
// Maybe need to enlarge the peer network packet buffer
if (engine.getSession().getPacketBufferSize() > peerNetData.capacity()) {
// enlarge the peer network packet buffer
} else {
// compact or clear the buffer
}
// obtain more inbound network data and then retry the operation
break;
// Handle other status: CLOSED, OK
...
}
The possible handshaking statuses are represented by the
SSLEngineResult.HandshakeStatus enum. They represent
whether handshaking has completed, whether the caller must obtain
more handshaking data from the peer or send more handshaking data
to the peer, and so on.
Having two statuses per result allows the SSLEngine to indicate
that the application must take two actions: one in response to the
handshaking and one representing the overall status of the
wrap() and unwrap() methods. For example,
the engine might, as the result of a single
SSLEngine.unwrap() call, return
SSLEngineResult.Status.OK to indicate that the input
data was processed successfully and
SSLEngineResult.HandshakeStatus.NEED_UNWRAP to
indicate that the application should obtain more SSL/TLS encoded
data from the peer and supply it to SSLEngine.unwrap()
again so that handshaking can continue. As you can see, the
previous examples were greatly simplified; they would need to be
expanded significantly to properly handle all of these
statuses.
Example 5 illustrates how to process
handshaking data by checking handshaking status and the overall
status of the wrap() and unwrap()
methods.
void doHandshake(SocketChannel socketChannel, SSLEngine engine,
ByteBuffer myNetData, ByteBuffer peerNetData) throws Exception {
// Create byte buffers to use for holding application data
int appBufferSize = engine.getSession().getApplicationBufferSize();
ByteBuffer myAppData = ByteBuffer.allocate(appBufferSize);
ByteBuffer peerAppData = ByteBuffer.allocate(appBufferSize);
// Begin handshake
engine.beginHandshake();
SSLEngineResult.HandshakeStatus hs = engine.getHandshakeStatus();
// Process handshaking message
while (hs != SSLEngineResult.HandshakeStatus.FINISHED &&
hs != SSLEngineResult.HandshakeStatus.NOT_HANDSHAKING) {
switch (hs) {
case NEED_UNWRAP:
// Receive handshaking data from peer
if (socketChannel.read(peerNetData) < 0) {
// The channel has reached end-of-stream
}
// Process incoming handshaking data
peerNetData.flip();
SSLEngineResult res = engine.unwrap(peerNetData, peerAppData);
peerNetData.compact();
hs = res.getHandshakeStatus();
// Check status
switch (res.getStatus()) {
case OK :
// Handle OK status
break;
// Handle other status: BUFFER_UNDERFLOW, BUFFER_OVERFLOW, CLOSED
...
}
break;
case NEED_WRAP :
// Empty the local network packet buffer.
myNetData.clear();
// Generate handshaking data
res = engine.wrap(myAppData, myNetData);
hs = res.getHandshakeStatus();
// Check status
switch (res.getStatus()) {
case OK :
myNetData.flip();
// Send the handshaking data to peer
while (myNetData.hasRemaining()) {
socketChannel.write(myNetData);
}
break;
// Handle other status: BUFFER_OVERFLOW, BUFFER_UNDERFLOW, CLOSED
...
}
break;
case NEED_TASK :
// Handle blocking tasks
break;
// Handle other status: // FINISHED or NOT_HANDSHAKING
...
}
}
// Processes after handshaking
...
}
During handshaking, an SSLEngine might encounter
tasks that can block or take a long time. For example, a
TrustManager may need to connect to a remote
certificate validation service, or a KeyManager might
need to prompt a user to determine which certificate to use as part
of client authentication. To preserve the nonblocking nature of
SSLEngine, when the engine encounters such a task, it
will return SSLEngineResult.HandshakeStatus.NEED_TASK.
Upon receiving this status, the application should invoke
SSLEngine.getDelegatedTask() to get the task, and
then, using the threading model appropriate for its requirements,
process the task. The application might, for example, obtain
threads from a thread pool to process the tasks, while the main
thread handles other I/O.
The following code executes each task in a newly created thread:
if (res.getHandshakeStatus() == SSLEngineResult.HandshakeStatus.NEED_TASK) {
Runnable task;
while ((task = engine.getDelegatedTask()) != null) {
new Thread(task).start();
}
}
The SSLEngine will block future wrap()
and unwrap() calls until all of the outstanding tasks
are completed.
For an orderly shutdown of an SSL/TLS connection, the SSL/TLS
protocols require transmission of close messages. Therefore, when
an application is done with the SSL/TLS connection, it should first
obtain the close messages from the SSLEngine, then
transmit them to the peer using its transport mechanism, and
finally shut down the transport mechanism. Example
6 illustrates this.
// Indicate that application is done with engine
engine.closeOutbound();
while (!engine.isOutboundDone()) {
// Get close message
SSLEngineResult res = engine.wrap(empty, myNetData);
// Check res statuses
// Send close message to peer
while(myNetData.hasRemaining()) {
int num = socketChannel.write(myNetData);
if (num == 0) {
// no bytes written; try again later
}
myNetData().compact();
}
}
// Close transport
socketChannel.close();
In addition to an application explicitly closing the
SSLEngine, the SSLEngine might be closed
by the peer (via receipt of a close message while it is processing
handshake data), or by the SSLEngine encountering an
error while processing application or handshake data, indicated by
throwing an SSLException. In such cases, the
application should invoke SSLEngine.wrap() to get the
close message and send it to the peer until
SSLEngine.isOutboundDone() returns true
(as shown in Example 6), or until the
SSLEngineResult.getStatus() returns
CLOSED.
In addition to orderly shutdowns, there can also be unexpected
shutdowns when the transport link is severed before close messages
are exchanged. In the previous examples, the application might get
-1 or IOException when trying to read from
the nonblocking SocketChannel, or get
IOException when trying to write to the non-blocking
SocketChannel. When you get to the end of your input data,
you should call engine.closeInbound(), which will
verify with the SSLEngine that the remote peer has
closed cleanly from the SSL/TLS perspective. Then the application
should still try to shut down cleanly by using the procedure in
Example 6. Obviously, unlike
SSLSocket, the application using
SSLEngine must deal with more state transitions,
statuses, and programming. For more information about writing an
SSLEngine-based application, see Sample Code Illustrating the Use of an
SSLEngine.
The javax.net.ssl.SSLSession interface represents a
security context negotiated between the two peers of an
SSLSocket or SSLEngine connection. After
a session has been arranged, it can be shared by future
SSLSocket or SSLEngine objects connected
between the same two peers.
In some cases, parameters negotiated during the handshake are
needed later in the handshake to make decisions about trust. For
example, the list of valid signature algorithms might restrict the
certificate types that can be used for authentication. The
SSLSession can be retrieved during the
handshake by calling getHandshakeSession() on an
SSLSocket or SSLEngine. Implementations
of TrustManager or KeyManager can use the
getHandshakeSession() method to get information about
session parameters to help them make decisions.
A fully initialized SSLSession contains the cipher
suite that will be used for communications over a secure socket as
well as a nonauthoritative hint as to the network address of the
remote peer, and management information such as the time of
creation and last use. A session also contains a shared master
secret negotiated between the peers that is used to create
cryptographic keys for encrypting and guaranteeing the integrity of
the communications over an SSLSocket or
SSLEngine connection. The value of this master secret
is known only to the underlying secure socket implementation and is
not exposed through the SSLSession API.
In Java SE, a TLS 1.2 session is represented by
ExtendedSSLSession, an implementation of
SSLSession. The ExtendedSSLSession class
adds methods that describe the signature algorithms that are
supported by the local implementation and the peer. The
getRequestedServerNames() method called on an
ExtendedSSLSession instance is used to obtain a list
of SNIServerName objects in the requested Server Name Indication (SNI) extension. The
server should use the requested server names to guide its selection
of an appropriate authentication certificate, and/or other aspects
of the security policy. The client should use the requested server
names to guide its endpoint identification of the peer's identity,
and/or other aspects of the security policy.
Calls to the getPacketBufferSize() and
getApplicationBufferSize() methods on
SSLSession are used to determine the appropriate
buffer sizes used by SSLEngine.
Note: The SSL/TLS protocols specify that
implementations are to produce packets containing at most 16
kilobytes (KB) of plain text. However, some implementations violate
the specification and generate large records up to 32 KB. If the
SSLEngine.unwrap() code detects large inbound packets,
then the buffer sizes returned by SSLSession will be
updated dynamically. Applications should always check the BUFFER_OVERFLOW and
BUFFER_UNDERFLOW statuses and enlarge the
corresponding buffers if necessary. SunJSSE will always send
standard compliant 16 KB records and allow incoming 32 KB records.
For a workaround, see the System property
jsse.SSLEngine.acceptLargeFragments in Customizing JSSE.
The HTTPS protocol is similar to HTTP, but HTTPS first
establishes a secure channel via SSL/TLS sockets and then verifies the identity of the peer before
requesting or receiving data. The
javax.net.ssl.HttpsURLConnection class extends the
java.net.HttpsURLConnection class and adds support for
HTTPS-specific features. For more information about how HTTPS URLs
are constructed and used, see the API specification sections about
the java.net.URL,
java.net.URLConnection,
java.net.HttpURLConnection,
and javax.net.ssl.HttpURLConnection
classes.
Upon obtaining an HttpsURLConnection instance, you
can configure a number of HTTP and HTTPS parameters before actually
initiating the network connection via the
URLConnection.connect() method. Of particular interest
are:
In some situations, it is desirable to specify the
SSLSocketFactory that an
HttpsURLConnection instance uses. For example, you
might want to tunnel through a proxy type that is not supported by
the default implementation. The new SSLSocketFactory
could return sockets that have already performed all necessary
tunneling, thus allowing HttpsURLConnection to use
additional proxies.
The HttpsURLConnection class has a default
SSLSocketFactory that is assigned when the class is
loaded (this is the factory returned by the
SSLSocketFactory.getDefault() method). Future
instances of HttpsURLConnection will inherit the
current default SSLSocketFactory until a new default
SSLSocketFactory is assigned to the class via the
static HttpsURLConnection.setDefaultSSLSocketFactory()
method. Once an instance of HttpsURLConnection has
been created, the inherited SSLSocketFactory on this
instance can be overridden with a call to the
setSSLSocketFactory() method.
Note: Changing the default static
SSLSocketFactory has no effect on existing instances
of HttpsURLConnection. A call to the
setSSLSocketFactory() method is necessary to change
the existing instances.
You can obtain the per-instance or per-class
SSLSocketFactory by making a call to the
getSSLSocketFactory() or
getDefaultSSLSocketFactory() method, respectively.
If the host name of the URL does not match the host name in the
credentials received as part of the SSL/TLS handshake, then it is
possible that URL spoofing has occurred. If the implementation
cannot determine a host name match with reasonable certainty, then
the SSL implementation performs a callback to the instance's
assigned HostnameVerifier for further checking. The
host name verifier can take whatever steps are necessary to make
the determination, such as performing host name pattern matching or
perhaps opening an interactive dialog box. An unsuccessful
verification by the host name verifier closes the connection. For
more information regarding host name verification, see RFC 2818.
The setHostnameVerifier() and
setDefaultHostnameVerifier() methods operate in a
similar manner to the setSSLSocketFactory() and
setDefaultSSLSocketFactory() methods, in that
HostnameVerifier objects are assigned on a
per-instance and per-class basis, and the current values can be
obtained by a call to the getHostnameVerifier() or
getDefaultHostnameVerifier() method.
The classes and interfaces in this section are provided to
support the creation and initialization of SSLContext
objects, which are used to create SSLSocketFactory,
SSLServerSocketFactory, and SSLEngine
objects. The support classes and interfaces are part of the
javax.net.ssl package.
Three of the classes described in this section (SSLContext, KeyManagerFactory, and
TrustManagerFactory) are
engine classes. An engine class is an API class for
specific algorithms (or protocols, in the case of
SSLContext), for which implementations may be provided
in one or more Cryptographic Service Provider (provider) packages.
For more information about providers and engine classes, see the
"Design Principles" and "Concepts" sections of the Java Cryptography Architecture
Reference Guide.
The SunJSSE provider that comes standard with JSSE provides
SSLContext, KeyManagerFactory, and
TrustManagerFactory implementations, as well as
implementations for engine classes in the standard
java.security API. Table 5 lists
implementations supplied by SunJSSE.
| Engine Class Implemented | Algorithm or Protocol |
|---|---|
KeyStore |
PKCS12 |
KeyManagerFactory |
PKIX, SunX509 |
TrustManagerFactory |
PKIX (X509 or SunPKIX), SunX509 |
SSLContext |
SSLv3, TLSv1, TLSv1.1, TLSv1.2 |
The javax.net.ssl.SSLContext class is an engine
class for an implementation of a secure socket protocol. An
instance of this class acts as a factory for SSL socket factories
and SSL engines. An SSLContext object holds all of the
state information shared across all objects created under that
context. For example, session state is associated with the
SSLContext when it is negotiated through the handshake
protocol by sockets created by socket factories provided by the
context. These cached sessions can be reused and shared by other
sockets created under the same context.
Each instance is configured through its init method
with the keys, certificate chains, and trusted root CA certificates
that it needs to perform authentication. This configuration is
provided in the form of key and trust managers. These managers
provide support for the authentication and key agreement aspects of
the cipher suites supported by the context.
Currently, only X.509-based managers are supported.
Like other JCA provider-based engine classes,
SSLContext objects are created using the
getInstance() factory methods of the
SSLContext class. These static methods each return an
instance that implements at least the requested secure
socket protocol. The returned instance may implement other
protocols, too. For example, getInstance("TLSv1") may
return an instance that implements TLSv1, TLSv1.1, and TLSv1.2. The
getSupportedProtocols() method returns a list of
supported protocols when an SSLSocket,
SSLServerSocket, or SSLEngine is created
from this context. You can control which protocols are actually
enabled for an SSL connection by using the
setEnabledProtocols(String[] protocols) method.
Note: An SSLContext object is
automatically created, initialized, and statically assigned to the
SSLSocketFactory class when you call the
SSLSocketFactory.getDefault() method. Therefore, you
do not have to directly create and initialize an
SSLContext object (unless you want to override the
default behavior).
To create an SSLContext object by calling the
getInstance() factory method, you must specify the
protocol name. You may also specify which provider you want to
supply the implementation of the requested protocol:
public static SSLContext getInstance(String
protocol);public static SSLContext getInstance(String protocol,
String provider);public static SSLContext getInstance(String protocol,
Provider provider);If just a protocol name is specified, then the system will determine whether an implementation of the requested protocol is available in the environment. If there is more than one implementation, then it will determine whether there is a preferred one.
If both a protocol name and a provider are specified, then the system will determine whether an implementation of the requested protocol is in the provider requested. If there is no implementation, an exception will be thrown.
A protocol is a string (such as "SSL") that
describes the secure socket protocol desired. Common protocol names
for SSLContext objects are defined in Appendix A.
An SSLContext can be obtained as follows:
SSLContext sc = SSLContext.getInstance("SSL");
A newly created SSLContext should be initialized by
calling the init method:
public void init(KeyManager[] km, TrustManager[] tm, SecureRandom random);
If the KeyManager[] parameter is null, then an
empty KeyManager will be defined for this context. If
the TrustManager[] parameter is null, then the
installed security providers will be searched for the
highest-priority implementation of the TrustManagerFactory, from
which an appropriate TrustManager will be obtained.
Likewise, the SecureRandom parameter may be null, in
which case a default implementation will be used.
If the internal default context is used, (for example, an
SSLContext is created by
SSLSocketFactory.getDefault() or
SSLServerSocketFactory.getDefault()), then a default KeyManager and
TrustManager are created. The default
SecureRandom implementation is also chosen.
The primary responsibility of the TrustManager is
to determine whether the presented authentication credentials
should be trusted. If the credentials are not trusted, then the
connection will be terminated. To authenticate the remote identity
of a secure socket peer, you must initialize an
SSLContext object with one or more
TrustManager objects. You must pass one
TrustManager for each authentication mechanism that is
supported. If null is passed into the SSLContext
initialization, then a trust manager will be created for you.
Typically, a single trust manager supports authentication based on
X.509 public key certificates (for example,
X509TrustManager). Some secure socket implementations
may also support authentication based on shared secret keys,
Kerberos, or other mechanisms.
TrustManager objects are created either by a
TrustManagerFactory, or by providing a concrete
implementation of the interface.
The javax.net.ssl.TrustManagerFactory is an engine
class for a provider-based service that acts as a factory for one
or more types of TrustManager objects. Because it is
provider-based, additional factories can be implemented and
configured to provide additional or alternative trust managers that
provide more sophisticated services or that implement
installation-specific authentication policies.
SSLContext, except for passing an algorithm name
string instead of a protocol name to the getInstance()
method:
TrustManagerFactory tmf = TrustManagerFactory.getInstance(String algorithm);
TrustManagerFactory tmf = TrustManagerFactory.getInstance(String algorithm, String provider);
TrustManagerFactory tmf = TrustManagerFactory.getInstance(String algorithm, Provider provider);
A sample call is as follows:
TrustManagerFactory tmf = TrustManagerFactory.getInstance("PKIX", "SunJSSE");
The preceding call creates an instance of the SunJSSE provider's PKIX trust manager factory. This factory can be used to create trust managers that provide X.509 PKIX-based certification path validity checking.
When initializing an SSLContext, you can use trust
managers created from a trust manager factory, or you can write
your own trust manager, for example, using the CertPath
API. For details, see the Java PKI Programmer's
Guide. You do not need to use a trust manager factory if you
implement a trust manager using the X509TrustManager
interface.
A newly created factory should be initialized by calling one of
the init() methods:
public void init(KeyStore ks);
public void init(ManagerFactoryParameters spec);
Call whichever init() method is appropriate for the
TrustManagerFactory you are using. If you are not
sure, then ask the provider vendor.
For many factories, such as the SunX509
TrustManagerFactory from the SunJSSE provider, the
KeyStore is the only information required to
initialize the TrustManagerFactory and thus the first
init method is the appropriate one to call. The
TrustManagerFactory will query the
KeyStore for information about which remote
certificates should be trusted during authorization checks.
Sometimes, initialization parameters other than a
KeyStore are needed by a provider. Users of that
provider are expected to pass an implementation of the appropriate
ManagerFactoryParameters as defined by the provider.
The provider can then call the specified methods in the
ManagerFactoryParameters implementation to obtain the
needed information.
For example, suppose the TrustManagerFactory
provider requires initialization parameters B, R, and S from any
application that wants to use that provider. Like all providers
that require initialization parameters other than a
KeyStore, the provider requires the application to
provide an instance of a class that implements a particular
ManagerFactoryParameters subinterface. In the example,
suppose that the provider requires the calling application to
implement and create an instance of
MyTrustManagerFactoryParams and pass it to the second
init() method. The following example illustrates what
MyTrustManagerFactoryParams can look like:
public interface MyTrustManagerFactoryParams extends ManagerFactoryParameters {
public boolean getBValue();
public float getRValue();
public String getSValue():
}
Some trust managers can make trust decisions without being
explicitly initialized with a KeyStore object or any
other parameters. For example, they may access trust material from
a local directory service via LDAP, use a remote online certificate
status checking server, or access default trust material from a
standard local location.
The default trust manager algorithm is PKIX. It can be changed
by editing the ssl.TrustManagerFactory.algorithm
property in the java.security file.
The PKIX trust manager factory uses the CertPath PKIX
implementation from an installed security provider. The trust
manager factory can be initialized using the normal
init(KeyStore ks) method, or by passing CertPath
parameters to the the PKIX trust manager using the
javax.net.ssl.CertPathTrustManagerParameters
class.
The following example illustrates how to get the trust manager to use a particular LDAP certificate store and enable revocation checking:
import javax.net.ssl.*;
import java.security.cert.*;
import java.security.KeyStore;
...
// Create PKIX parameters
KeyStore anchors = KeyStore.getInstance("JKS");
anchors.load(new FileInputStream(anchorsFile));
CertPathParameters pkixParams = new PKIXBuilderParameters(anchors, new X509CertSelector());
// Specify LDAP certificate store to use
LDAPCertStoreParameters lcsp = new LDAPCertStoreParameters("ldap.imc.org", 389);
pkixParams.addCertStore(CertStore.getInstance("LDAP", lcsp));
// Specify that revocation checking is to be enabled
pkixParams.setRevocationEnabled(true);
// Wrap PKIX parameters as trust manager parameters
ManagerFactoryParameters trustParams = new CertPathTrustManagerParameters(pkixParams);
// Create TrustManagerFactory for PKIX-compliant trust managers
TrustManagerFactory factory = TrustManagerFactory.getInstance("PKIX");
// Pass parameters to factory to be passed to CertPath implementation
factory.init(trustParams);
// Use factory
SSLContext ctx = SSLContext.getInstance("TLS");
ctx.init(null, factory.getTrustManagers(), null);
If the init(KeyStore ks) method is used, then
default PKIX parameters are used with the exception that revocation
checking is disabled. It can be enabled by setting the
com.sun.net.ssl.checkRevocation system property to
true. This setting requires that the CertPath
implementation can locate revocation information by itself. The
PKIX implementation in the provider can do this in many cases but
requires that the system property
com.sun.security.enableCRLDP be set to
true.
For more information about PKIX and the CertPath API, see the Java PKI Programmer's Guide.
The javax.net.ssl.X509TrustManager interface
extends the general TrustManager interface. It must be
implemented by a trust manager when using X.509-based
authentication.
To support X.509 authentication of remote socket peers through
JSSE, an instance of this interface must be passed to the
init method of an SSLContext object.
You can either implement this interface directly yourself or
obtain one from a provider-based TrustManagerFactory
(such as that supplied by the SunJSSE provider). You could also
implement your own interface that delegates to a factory-generated
trust manager. For example, you might do this to filter the
resulting trust decisions and query an end-user through a graphical
user interface.
Note: If a null KeyStore parameter is passed to
the SunJSSE PKIX or SunX509 TrustManagerFactory, then
the factory uses the following process to try to find trust
material:
If the javax.net.ssl.trustStore property is
defined, then the TrustManagerFactory attempts to find
a file using the file name specified by that system property, and
uses that file for the KeyStore parameter. If the
javax.net.ssl.trustStorePassword system property is
also defined, then its value is used to check the integrity of the
data in the truststore before opening it.
If the javax.net.ssl.trustStore property is defined
but the specified file does not exist, then a default
TrustManager using an empty keystore is created.
javax.net.ssl.trustStore system property
was not specified, then:
/lib/security/jssecacerts exists,
that file is used;/lib/security/cacerts exists, that
file is used;For information about what java-home refers to, see The Installation Directory.
The factory looks for a file specified via the
javax.net.ssl.trustStore security property or for the
jssecacerts file before checking for a cacerts file.
Therefore, you can provide a JSSE-specific set of trusted root
certificates separate from ones that might be present in cacerts
for code-signing purposes.
If the supplied X509TrustManager behavior is not
suitable for your situation, then you can create your own
X509TrustManager by either creating and registering
your own TrustManagerFactory or by implementing the
X509TrustManager interface directly.
The following example illustrates a
MyX509TrustManager class that enhances the default
SunJSSE X509TrustManager behavior by providing
alternative authentication logic when the default
X509TrustManager fails:
class MyX509TrustManager implements X509TrustManager {
/*
* The default PKIX X509TrustManager9. Decisions are delegated
* to it, and a fall back to the logic in this class is performed
* if the default X509TrustManager does not trust it.
*/
X509TrustManager pkixTrustManager;
MyX509TrustManager() throws Exception {
// create a "default" JSSE X509TrustManager.
KeyStore ks = KeyStore.getInstance("JKS");
ks.load(new FileInputStream("trustedCerts"), "passphrase".toCharArray());
TrustManagerFactory tmf = TrustManagerFactory.getInstance("PKIX");
tmf.init(ks);
TrustManager tms [] = tmf.getTrustManagers();
/*
* Iterate over the returned trust managers, looking
* for an instance of X509TrustManager. If found,
* use that as the default trust manager.
*/
for (int i = 0; i < tms.length; i++) {
if (tms[i] instanceof X509TrustManager) {
pkixTrustManager = (X509TrustManager) tms[i];
return;
}
}
/*
* Find some other way to initialize, or else the
* constructor fails.
*/
throw new Exception("Couldn't initialize");
}
/*
* Delegate to the default trust manager.
*/
public void checkClientTrusted(X509Certificate[] chain, String authType)
throws CertificateException {
try {
pkixTrustManager.checkClientTrusted(chain, authType);
} catch (CertificateException excep) {
// do any special handling here, or rethrow exception.
}
}
/*
* Delegate to the default trust manager.
*/
public void checkServerTrusted(X509Certificate[] chain, String authType)
throws CertificateException {
try {
pkixTrustManager.checkServerTrusted(chain, authType);
} catch (CertificateException excep) {
/*
* Possibly pop up a dialog box asking whether to trust the
* cert chain.
*/
}
}
/*
* Merely pass this through.
*/
public X509Certificate[] getAcceptedIssuers() {
return pkixTrustManager.getAcceptedIssuers();
}
}
Once you have created such a trust manager, assign it to an
SSLContext via the init() method, as in
the following example. Future SocketFactories created
from this SSLContext will use your new
TrustManager when making trust decisions.
TrustManager[] myTMs = new TrustManager[] { new MyX509TrustManager() };
SSLContext ctx = SSLContext.getInstance("TLS");
ctx.init(null, myTMs, null);
You can enhance MyX509TrustManager to handle
dynamic keystore updates. When a checkClientTrusted or
checkServerTrusted test fails and does not establish a
trusted certificate chain, you can add the required trusted
certificate to the keystore. You must create a new
pkixTrustManager from the
TrustManagerFactory initialized with the updated
keystore. When you establish a new connection (using the previously
initialized SSLContext), the newly added certificate
will be used when making trust decisions.
The X509ExtendedTrustManager class is an abstract
implementation of the X509TrustManager interface. It
adds methods for connection-sensitive trust management. In
addition, it enables endpoint verification at the TLS layer.
In TLS 1.2 and later, both client and server can specify which
hash and signature algorithms they will accept. To authenticate the
remote side, authentication decisions must be based on both X509
certificates and the local accepted hash and signature algorithms.
The local accepted hash and signature algorithms can be obtained
using the
ExtendedSSLSession.getLocalSupportedSignatureAlgorithms()
method.
The ExtendedSSLSession object can be retrieved by
calling the SSLSocket.getHandshakeSession() method or
the SSLEngine.getHandshakeSession() method.
The X509TrustManager interface is not
connection-sensitive. It provides no way to access
SSLSocket or SSLEngine session
properties.
Besides TLS 1.2 support, the
X509ExtendedTrustManager class also supports algorithm
constraints and SSL layer host name verification. For JSSE
providers and trust manager implementations, the
X509ExtendedTrustManager class is highly recommended
over the legacy X509TrustManager interface.
You can either create an X509ExtendedTrustManager
subclass yourself (which is outlined in the following section) or
obtain one from a provider-based TrustManagerFactory
(such as that supplied by the SunJSSE provider). In Java SE 7, the
PKIX or SunX509 TrustManagerFactory returns an
X509ExtendedTrustManager instance.
This section outlines how to create a subclass of
X509ExtendedTrustManager in nearly the same way as
described for X509TrustManager.
The following example illustrates how to create a class that
uses the PKIX TrustManagerFactory to locate a default
X509ExtendedTrustManager that will be used to make
decisions about trust. If the default trust manager fails for any
reason, then the subclass is can add other behavior. In the
example, these locations are indicated by comments in the
catch clauses.
import java.io.*;
import java.net.*;
import java.security.*;
import java.security.cert.*;
import javax.net.ssl.*;
public class MyX509ExtendedTrustManager extends X509ExtendedTrustManager {
/*
* The default PKIX X509ExtendedTrustManager. Decisions are
* delegated to it, and a fall back to the logic in this class is
* performed if the default X509ExtendedTrustManager does not
* trust it.
*/
X509ExtendedTrustManager pkixTrustManager;
MyX509ExtendedTrustManager() throws Exception {
// create a "default" JSSE X509ExtendedTrustManager.
KeyStore ks = KeyStore.getInstance("JKS");
ks.load(new FileInputStream("trustedCerts"), "passphrase".toCharArray());
TrustManagerFactory tmf = TrustManagerFactory.getInstance("PKIX");
tmf.init(ks);
TrustManager tms [] = tmf.getTrustManagers();
/*
* Iterate over the returned trust managers, looking
* for an instance of X509ExtendedTrustManager. If found,
* use that as the default trust manager.
*/
for (int i = 0; i < tms.length; i++) {
if (tms[i] instanceof X509ExtendedTrustManager) {
pkixTrustManager = (X509ExtendedTrustManager) tms[i];
return;
}
}
/*
* Find some other way to initialize, or else we have to fail the
* constructor.
*/
throw new Exception("Couldn't initialize");
}
/*
* Delegate to the default trust manager.
*/
public void checkClientTrusted(X509Certificate[] chain, String authType)
throws CertificateException {
try {
pkixTrustManager.checkClientTrusted(chain, authType);
} catch (CertificateException excep) {
// do any special handling here, or rethrow exception.
}
}
/*
* Delegate to the default trust manager.
*/
public void checkServerTrusted(X509Certificate[] chain, String authType)
throws CertificateException {
try {
pkixTrustManager.checkServerTrusted(chain, authType);
} catch (CertificateException excep) {
/*
* Possibly pop up a dialog box asking whether to trust the
* cert chain.
*/
}
}
/*
* Connection-sensitive verification.
*/
public void checkClientTrusted(X509Certificate[] chain, String authType, Socket socket)
throws CertificateException {
try {
pkixTrustManager.checkClientTrusted(chain, authType, socket);
} catch (CertificateException excep) {
// do any special handling here, or rethrow exception.
}
}
public void checkClientTrusted(X509Certificate[] chain, String authType, SSLEngine engine)
throws CertificateException {
try {
pkixTrustManager.checkClientTrusted(chain, authType, engine);
} catch (CertificateException excep) {
// do any special handling here, or rethrow exception.
}
}
public void checkServerTrusted(X509Certificate[] chain, String authType, Socket socket)
throws CertificateException {
try {
pkixTrustManager.checkServerTrusted(chain, authType, socket);
} catch (CertificateException excep) {
// do any special handling here, or rethrow exception.
}
}
public void checkServerTrusted(X509Certificate[] chain, String authType, SSLEngine engine)
throws CertificateException {
try {
pkixTrustManager.checkServerTrusted(chain, authType, engine);
} catch (CertificateException excep) {
// do any special handling here, or rethrow exception.
}
}
/*
* Merely pass this through.
*/
public X509Certificate[] getAcceptedIssuers() {
return pkixTrustManager.getAcceptedIssuers();
}
}
The primary responsibility of the KeyManager is to
select the authentication credentials that will eventually be sent
to the remote host. To authenticate yourself (a local secure socket
peer) to a remote peer, you must initialize an
SSLContext object with one or more
KeyManager objects. You must pass one
KeyManager for each different authentication mechanism
that will be supported. If null is passed into the
SSLContext initialization, then an empty
KeyManager will be created. If the internal default
context is used (for example, an SSLContext created by
SSLSocketFactory.getDefault() or
SSLServerSocketFactory.getDefault()), then a default KeyManager is
created. Typically, a single key manager supports authentication
based on X.509 public key certificates. Some secure socket
implementations may also support authentication based on shared
secret keys, Kerberos, or other mechanisms.
KeyManager objects are created either by a
KeyManagerFactory, or by providing a concrete
implementation of the interface.
The javax.net.ssl.KeyManagerFactory class is an
engine class for a provider-based service that acts as a factory
for one or more types of KeyManager objects. The
SunJSSE provider implements a factory that can return a basic X.509
key manager. Because it is provider-based, additional factories can
be implemented and configured to provide additional or alternative
key managers.
You create an instance of this class in a similar manner to
SSLContext, except for passing an algorithm name
string instead of a protocol name to the getInstance()
method:
KeyManagerFactory kmf = getInstance(String algorithm);
KeyManagerFactory kmf = getInstance(String algorithm, String provider);
KeyManagerFactory kmf = getInstance(String algorithm, Provider provider);
A sample call as follows:
KeyManagerFactory kmf = KeyManagerFactory.getInstance("SunX509", "SunJSSE");
The preceding call creates an instance of the SunJSSE provider's default key manager factory, which provides basic X.509-based authentication keys.
A newly created factory should be initialized by calling one of
the init methods:
public void init(KeyStore ks, char[] password);
public void init(ManagerFactoryParameters spec);
Call whichever init method is appropriate for the
KeyManagerFactory you are using. If you are not sure,
then ask the provider vendor.
For many factories, such as the default SunX509
KeyManagerFactory from the SunJSSE provider, the
KeyStore and password are the only information
required to initialize the KeyManagerFactory and thus
the first init method is the appropriate one to call.
The KeyManagerFactory will query the
KeyStore for information about which private key and
matching public key certificates should be used for authenticating
to a remote socket peer. The password parameter specifies the
password that will be used with the methods for accessing keys from
the KeyStore. All keys in the KeyStore
must be protected by the same password.
Sometimes initialization parameters other than a
KeyStore and password are needed by a provider. Users
of that provider are expected to pass an implementation of the
appropriate ManagerFactoryParameters as defined by the
provider. The provider can then call the specified methods in the
ManagerFactoryParameters implementation to obtain the
needed information.
Some factories can provide access to authentication material
without being initialized with a KeyStore object or
any other parameters. For example, they may access key material as
part of a login mechanism such as one based on JAAS, the Java
Authentication and Authorization Service.
As previously indicated, the SunJSSE provider supports a SunX509
factory that must be initialized with a KeyStore
parameter.
The javax.net.ssl.X509KeyManager interface extends
the general KeyManager interface. It must be
implemented by a key manager for X.509-based authentication. To
support X.509 authentication to remote socket peers through JSSE,
an instance of this interface must be passed to the
init() method of an SSLContext
object.
You can either implement this interface directly yourself or
obtain one from a provider-based KeyManagerFactory
(such as that supplied by the SunJSSE provider). You could also
implement your own interface that delegates to a factory-generated
key manager. For example, you might do this to filter the resulting
keys and query an end-user through a graphical user interface.
If the default X509KeyManager behavior is not
suitable for your situation, then you can create your own
X509KeyManager in a way similar to that shown in
Creating Your Own X509TrustManager.
The X509ExtendedKeyManager abstract class is an
implementation of the X509KeyManager interface that
allows for connection-specific key selection. It adds two methods
that select a key alias for client or server based on the key type,
allowed issuers, and current SSLEngine:
public String chooseEngineClientAlias(String[] keyType,
Principal[] issuers, SSLEngine engine)public String chooseEngineServerAlias(String keyType,
Principal[] issuers, SSLEngine engine)If a key manager is not an instance of the
X509ExtendedKeyManager class, then it will not work
with the SSLEngine class.
For JSSE providers and key manager implementations, the
X509ExtendedKeyManager class is highly recommended
over the legacy X509KeyManager interface.
In TLS 1.2 and later, both client and server can specify which
hash and signature algorithms they will accept. To pass the
authentication required by the remote side, local key selection
decisions must be based on both X509 certificates and the remote
accepted hash and signature algorithms. The remote accepted hash
and signature algorithms can be retrieved using the
ExtendedSSLSession.getPeerSupportedSignatureAlgorithms()
method.
You can create your own X509ExtendedKeyManager
subclass in a way similar to that shown in Creating Your Own X509ExtendedTrustManager.
Support for the Server Name Indication (SNI) extension on the server side enables the key manager to check the server name and select the appropriate key accordingly. For example, suppose there are three key entries with certificates in the keystore:
cn=www.example.comcn=www.example.orgcn=www.example.netIf the ClientHello message requests to connect to
www.example.net in the SNI extension, then the server
should be able to select the certificate with subject
cn=www.example.net.
Historically, there has been confusion regarding the
functionality of a TrustManager and a
KeyManager.
A TrustManager determines whether the remote
authentication credentials (and thus the connection) should be
trusted.
A KeyManager determines which authentication
credentials to send to the remote host.
These classes are provided as part of the JSSE API to support
the creation, use, and management of secure sockets. They are less
likely to be used by secure socket applications than are the core
and support classes. The secondary support classes and interfaces
are part of the javax.net.ssl and
javax.security.cert packages.
The SSLParameters class encapsulates the following
parameters that affect a TLS connection:
You can retrieve the current SSLParameters for an
SSLSocket or SSLEngine by using the
following methods:
getSSLParameters() in an SSLSocket,
SSLServerSocket, and SSLEnginegetDefaultSSLParameters() and
getSupportedSSLParamters() in an
SSLContextYou can assign SSLParameters with the
setSSLParameters() method in an
SSLSocket, SSLServerSocket and
SSLEngine.
You can explicitly set the server name indication with the
SSLParameters.setServerNames() method. The server name
indication in client mode also affects endpoint identification. In
the implementation of X509ExtendedTrustManager, it
uses the server name indication retrieved by the
ExtendedSSLSession.getRequestedServerNames() method.
The following example illustrates this functionality:
SSLSocketFactory factory = ...
SSLSocket sslSocket = factory.createSocket("172.16.10.6", 443);
// SSLEngine sslEngine = sslContext.createSSLEngine("172.16.10.6", 443);
SNIHostName serverName = new SNIHostName("www.example.com");
List<SNIServerName> serverNames = new ArrayList<>(1);
serverNames.add(serverName);
SSLParameters params = sslSocket.getSSLParameters();
params.setServerNames(serverNames);
sslSocket.setSSLParameters(params);
// sslEngine.setSSLParameters(params);
In the preceding example, the host name in the server name
indication (www.example.com) will be used to make
endpoint identification against the peer's identity presented in
the end-entity's X.509 certificate.
During TLS handshaking, the client requests to negotiate a cipher suite from a list of cryptographic options that it supports, starting with its first preference. Then, the server selects a single cipher suite from the list of cipher suites requested by the client. Normally, the selection honors the client's preference. However, to mitigate the risks of using weak cipher suites, the server may select cipher suites based on its own preference rather than the client's preference, by invoking the method SSLParameters.setUseCipherSuitesOrder(true).
The javax.net.ssl.SSLSessionContext interface is a
grouping of SSLSession
objects associated with a single entity. For example, it could be
associated with a server or client that participates in many
sessions concurrently. The methods in this interface enable the
enumeration of all sessions in a context and allow lookup of
specific sessions via their session IDs.
An SSLSessionContext may optionally be obtained
from an SSLSession by calling the SSLSession
getSessionContext() method. The context may be
unavailable in some environments, in which case the
getSessionContext() method returns null.
The javax.net.ssl.SSLSessionBindingListener
interface is implemented by objects that are notified when they are
being bound or unbound from an SSLSession.
The javax.net.ssl.SSLSessionBindingEvent class
defines the event communicated to an SSLSessionBindingListener
when it is bound or unbound from an SSLSession.
The javax.net.ssl.HandShakeCompletedListener
interface is an interface implemented by any class that is notified
of the completion of an SSL protocol handshake on a given
SSLSocket connection.
The javax.net.ssl.HandShakeCompletedEvent class
define the event communicated to a HandShakeCompletedListener
upon completion of an SSL protocol handshake on a given
SSLSocket connection.
If the SSL/TLS implementation's standard host name verification
logic fails, then the implementation calls the
verify() method of the class that implements this
interface and is assigned to this HttpsURLConnection
instance. If the callback class can determine that the host name is
acceptable given the parameters, it reports that the connection
should be allowed. An unacceptable response causes the connection
to be terminated.
For example:
public class MyHostnameVerifier implements HostnameVerifier {
public boolean verify(String hostname, SSLSession session) {
// pop up an interactive dialog box
// or insert additional matching logic
if (good_address) {
return true;
} else {
return false;
}
}
}
//...deleted...
HttpsURLConnection urlc = (HttpsURLConnection)
(new URL("https://www.example.com/")).openConnection();
urlc.setHostnameVerifier(new MyHostnameVerifier());
See The HttpsURLConnection
Class for more information about how to assign the
HostnameVerifier to the
HttpsURLConnection.
Many secure socket protocols perform authentication using public key certificates, also called X.509 certificates. This is the default authentication mechanism for the SSL/TLS protocols.
The java.security.cert.X509Certificate abstract
class provides a standard way to access the attributes of X.509
certificates.
Note: The
javax.security.cert.X509Certificate class is supported
only for backward compatibility with previous (1.0.x and 1.1.x)
versions of JSSE. New applications should use the
java.security.cert.X509Certificate class instead.
The java.security.AlgorithmConstraints interface is
used for controlling allowed cryptographic algorithms.
AlgorithmConstraints defines three
permits() methods. These methods tell whether an
algorithm name or a key is permitted for certain cryptographic
functions. Cryptographic functions are represented by a set of
CryptoPrimitive, which is an enumeration containing
fields like STREAM_CIPHER,
MESSAGE_DIGEST, and SIGNATURE.
Thus, an AlgorithmConstraints implementation can
answer questions like: Can I use this key with this algorithm for
the purpose of a cryptographic operation?
An AlgorithmConstraints object can be associated
with an SSLParameters object by using the new
setAlgorithmConstraints() method. The current
AlgorithmConstraints object for an
SSLParameters object is retrieved using the
getAlgorithmConstraints() method.
The StandardConstants class is used to represent
standard constants definitions in JSSE.
StandardConstants.SNI_HOST_NAME represents a domain
name server (DNS) host name in a Server
Name Indication (SNI) extension, which can be used when
instantiating an SNIServerName or
SNIMatcher object.
An instance of the abstract SNIServerName class
represents a server name in the Server Name
Indication (SNI) extension. It is instantiated using the type
and encoded value of the specified server name.
You can use the getType() and
getEncoded() methods to return the server name type
and a copy of the encoded server name value, respectively. The
equals() method can be used to check if some other
object is "equal" to this server name. The hashCode()
method returns a hash code value for this server name. To get a
string representation of the server name (including the server name
type and encoded server name value), use the
toString() method.
An instance of the abstract SNIMatcher class
performs match operations on an SNIServerName object.
Servers can use information from the Server
Name Indication (SNI) extension to decide if a specific
SSLSocket or SSLEngine should accept a
connection. For example, when multiple "virtual" or "name-based"
servers are hosted on a single underlying network address, the
server application can use SNI information to determine whether
this server is the exact server that the client wants to access.
Instances of this class can be used by a server to verify the
acceptable server names of a particular type, such as host
names.
The SNIMatcher class is instantiated using the
specified server name type on which match operations will be
performed. To match a given SNIServerName, use the
matches() method. To return the server name type of
the given SNIMatcher object, use the
getType() method.
An instance of the SNIHostName class (which extends
the SNIServerName class) represents a server name of
type "host_name" (see The
StandardConstants Class) in the Server
Name Indication (SNI) extension. To instantiate an
SNIHostName, specify the fully qualified DNS host name
of the server (as understood by the client) as a
String argument. The argument is illegal in the
following cases:
You can also instantiate an SNIHostName by
specifying the encoded host name value as a byte array. This method
is typically used to parse the encoded name value in a requested
SNI extension. Otherwise, use the SNIHostName(String
hostname) constructor. The encoded argument is
illegal in the following cases:
Note: The encoded byte array
passed in as an argument is cloned to protect against subsequent
modification.
To return the host name of an SNIHostName object in
US-ASCII encoding, use the getAsciiName() method. To
compare a server name to another object, use the
equals() method (comparison is not
case-sensitive). To return a hash code value of an
SNIHostName, use the hashCode() method.
To return a string representation of an SNIHostName,
including the DNS host name, use the toString()
method.
You can create an SNIMatcher object for an
SNIHostName object by passing a regular expression
representing one or more host names to match to the
createSNIMatcher() method.
JSSE includes a standard implementation that can be customized by plugging in different implementations or specifying the default keystore, and so on. Table 6 summarizes which aspects can be customized, what the defaults are, and which mechanisms are used to provide customization. The first column of the table provides links to more detailed descriptions of each designated aspect and how to customize it.
Some of the customizations are done by setting system property or security property values. Sections following the table explain how to set such property values.
Note: Many of the properties shown in this table are currently used by the JSSE implementation, but there is no guarantee that they will continue to have the same names and types (system or security) or even that they will exist at all in future releases. All such properties are flagged with an asterisk (*). They are documented here for your convenience for use with the JSSE implementation.
| Customizable Item | Default | How to Customize |
|---|---|---|
| X509Certificate implementation | X509Certificate implementation from Oracle | cert.provider.x509v1
security property |
| HTTPS protocol implementation | Implementation from Oracle |
java.protocol.handler.pkgs system property |
| Provider implementation | SunJSSE | The security.provider.n=
line in security properties file |
Default SSLSocketFactory
implementation |
SSLSocketFactory
implementation from Oracle |
*
ssl.SocketFactory.provider security property |
Default
SSLServerSocketFactory implementation |
SSLServerSocketFactory
implementation from Oracle |
*
ssl.ServerSocketFactory.provider security
property |
| Default keystore | None | * javax.net.ssl.keyStore
system property.Note that the value NONE may be specified. This
setting is appropriate if the keystore is not file-based (for
example, it resides in a hardware token). |
| Default keystore password | None | *
javax.net.ssl.keyStorePassword system property.It is inadvisable to specify the password in a way that exposes it to discovery by other users, for example, specifying the password on the command line. To keep the password secure, have the application prompt for the password, or specify the password in a properly protected option file. |
| Default keystore provider | None | *
javax.net.ssl.keyStoreProvider system property |
| Default keystore type |
KeyStore.getDefaultType() |
*
javax.net.ssl.keyStoreType system property |
| Default truststore | jssecacerts, if it
exists. Otherwise, cacerts. |
*
javax.net.ssl.trustStore system property |
| Default truststore password | None | *
javax.net.ssl.trustStorePassword system property.It is inadvisable to specify the password in a way that exposes it to discovery by other users, for example, specifying the password on the command line. To keep the password secure, have the application prompt for the password, or specify the password in a properly protected option file. |
| Default truststore provider | None | *
javax.net.ssl.trustStoreProvider system property |
| Default truststore type |
KeyStore.getDefaultType() |
*
javax.net.ssl.trustStoreType system propertyNote that the value NONE may be specified. This
setting is appropriate if the truststore is not file-based (for
example, it resides in a hardware token). |
| Default key manager factory algorithm name | SunX509 |
ssl.KeyManagerFactory.algorithm security property |
| Default trust manager factory algorithm name | PKIX |
ssl.TrustManagerFactory.algorithm security
property |
| Disabled certificate verification cryptographic algorithms | MD2, RSA keySize < 1024 |
jdk.certpath.disabledAlgorithms security property |
| Disabled cipher suite cryptographic algorithms | None |
jdk.tls.disabledAlgorithms security property |
| Default proxy host | None | * https.proxyHost system
property |
| Default proxy port | 80 | * https.proxyPort system
property |
| Server Name Indication option | true |
* jsse.enableSNIExtension
system property.Server Name Indication (SNI) is a TLS extension, defined in RFC 6066. It enables TLS connections to virtual servers, in which multiple servers for different network names are hosted at a single underlying network address. Some very old SSL/TLS vendors may not be able handle SSL/TLS extensions. In this case, set this property to false
to disable the SNI extension. |
| Default cipher suites | Determined by the socket factory | * https.cipherSuites
system property. This contains a comma-separated list of cipher
suite names specifying which cipher suites to enable for use on
this HttpsURLConnection. See the
SSLSocket.setEnabledCipherSuites(String[])
method. |
| Default handshaking protocols | Determined by the socket factory | * https.protocols system
property.This contains a comma-separated list of protocol suite names specifying which protocol suites to enable on this HttpsURLConnection. See the
SSLSocket.setEnabledProtocols(String[])
method. |
| Default HTTPS port | 443 | * Customize via port
field in the HTTPS URL. |
| JCE encryption algorithms used by the SunJSSE provider | SunJCE implementations | Give alternative JCE algorithm providers a higher preference order than the SunJCE provider |
| Default sizing buffers for large SSL/TLS packets | None | *
jsse.SSLEngine.acceptLargeFragments system
property.By setting this system property to true,
SSLSession will size buffers to handle large data packets by default. This may cause
applications to allocate unnecessarily large SSLEngine
buffers. Instead, applications should dynamically check for buffer overflow
conditions and resize buffers as appropriate. |
| Allow Unsafe SSL/TLS Renegotiations | false |
* sun.security.ssl.allowUnsafeRenegotiation system
property.Setting this system property to true permits full
(unsafe) legacy renegotiation. |
| Allow Legacy Hello Messages (Renegotiations) | true |
* sun.security.ssl.allowLegacyHelloMessages system
property.Setting this system property to true allows the peer
to handshake without requiring the proper RFC 5746 messages. |
| Default Enabled TLS Protocols | None | jdk.tls.client.protocols system
property.To enable specific SunJSSE protocols on the client, specify them in a comma-separated list within quotation marks; all other supported protocols are then disabled on the client. For example, if the value of this property is "TLSv1,TLSv1.1", then the default protocol settings on the client for TLSv1 and TLSv1.1 are enabled on the client, while SSLv3, TLSv1.2, and SSLv2Hello are disabled on the client. |
| Size of ephemeral Diffie-Hellman keys | 1024 bits | jdk.tls.ephemeralDHKeySize system property. |
* This property is currently used by the JSSE implementation, but it is not guaranteed to be examined and used by other implementations. If it is examined by another implementation, then that implementation should handle it in the same manner as the JSSE implementation does. There is no guarantee the property will continue to exist or be of the same type (system or security) in future releases.
Note: Some items are customized by setting
java.lang.System properties, whereas others are
customized by setting java.security.Security
properties. The following sections explain how to set values for
both types of properties.
You can customize some aspects of JSSE by setting system properties. There are several ways to set these properties:
To set a system property statically, use the -D
option of the java command. For example, to run an
application named MyApp and set the
javax.net.ssl.trustStore system property to specify a
truststore named MyCacertsFile,
enter the following:
java -Djavax.net.ssl.trustStore=MyCacertsFile MyApp
To set a system property dynamically, call the
java.lang.System.setProperty() method in your
code:
System.setProperty("propertyName", "propertyValue");
For example, a setProperty() call corresponding to
the previous example for setting the
javax.net.ssl.trustStore system property to specify a
truststore named "MyCacertsFile" would be:
System.setProperty("javax.net.ssl.trustStore", "MyCacertsFile");
In the Java Deployment environment (Plug-In/Web Start), there are several ways to set the system properties. For more information, see Java Rich Internet Applications Development and Deployment.
Use the Java Control Panel to set the Runtime Environment
Property on a local or per-VM basis. This creates a local
deployment.properties file. Deployers can also
distribute an enterprise wide deployment.properties
file by using the deployment.config mechanism. For
more information, see Deployment Configuration File and
Properties.
To set a property for a specific applet, use the HTML subtag
<PARAM> "java_arguments" within the
<APPLET> tag. For more information, see the
java_arguments
section of the Java Rich Internet Applications
Guide.
To set the property in a specific Java Web Start application or
applet using Plugin2, use the JNLP property subelement
of the resources element. For more information, see
the resources
Element section of the Java Web Start Guide.
You can customize some aspects of JSSE by setting security properties. You can set a security property either statically or dynamically:
To set a security property statically, add a line to the security properties file. The security properties file is located at java-home/lib/security/java.security.
java-home refers to the directory where the JRE is installed, as described in The Installation Directory.
To specify a security property value in the security properties file, you add a line of the following form:
propertyName=propertyValue
For example, suppose that you want to specify a different key
manager factory algorithm name than the default SunX509. You do
this by specifying the algorithm name as the value of a security
property named ssl.KeyManagerFactory.algorithm. For
example, to set the value to MyX509, add the following line to the
security properties file:
ssl.KeyManagerFactory.algorithm=MyX509
To set a security property dynamically, call the
java.security.Security.setProperty method in your
code:
Security.setProperty("propertyName," "propertyValue");
For example, a call to the setProperty() method
corresponding to the previous example for specifying the key
manager factory algorithm name would be:
Security.setProperty("ssl.KeyManagerFactory.algorithm", "MyX509");
The X509Certificate implementation returned by the
X509Certificate.getInstance() method is by default the
implementation from the JSSE implementation.
You can optionally cause a different implementation to be
returned. To do so, specify the name (and package) of the other
implementation's class as the value of a security property named
cert.provider.x509v1. For example, if the class is
called MyX509CertificateImpl and it appears in the
com.cryptox package, then you should add the following
line to the security properties file:
cert.provider.x509v1=com.cryptox.MyX509CertificateImpl
You can communicate securely with an SSL-enabled web server by
using the HTTPS URL scheme for the java.net.URL class.
The JDK provides a default HTTPS URL implementation.
If you want an alternative HTTPS protocol implementation to be
used, set the java.protocol.handler.pkgs system property to include the new class name.
This action causes the specified classes to be found and loaded
before the JDK default classes. See the java.net.URL
class documentation for details.
Note: In past JSSE releases, you had to set the
java.protocol.handler.pkgs system property during JSSE
installation. This step is no longer required unless you want to
obtain an instance of
com.sun.net.ssl.HttpsURLConnection. For more
information, see Code Using the
HttpsURLConnection Class in the "Troubleshooting" section.
JDK 1.4 and later releases come standard with a JSSE
Cryptographic Service Provider, or provider for short, named
SunJSSE. Providers are essentially packages that implement one or
more engine classes for specific cryptographic algorithms. The JSSE
engine classes are SSLContext,
KeyManagerFactory, and
TrustManagerFactory. For more information about
providers and engine classes, see the Java Cryptography Architecture
Reference Guide.
Note: The transformation strings used when
SunJSSE calls Cipher.getInstance() are
"RSA/ECB/PKCS1Padding", "RC4", "DES/CBC/NoPadding", and
"DESede/CBC/NoPadding". For further information about the
Cipher class and transformation strings see the
Java Cryptography Architecture
Reference Guide.
Before it can be used, a provider must be registered, either statically or dynamically. You do not need to register the SunJSSE provider because it is preregistered. If you want to use other providers, read the following sections to see how to register them.
You register a provider statically by adding a line of the following form to the security properties file:
security.provider.n=providerClassName
This declares a provider, and specifies its preference order
n. The preference order is the order in which
providers are searched for requested algorithms (when no specific
provider is requested). "1" is the most preferred, followed by "2",
and so on.
The providerClassName is the fully qualified name of the provider class. You obtain this name from the provider vendor.
The standard security provider and the SunJSSE provider shipped
with JDK 6 are automatically registered for you; the following
lines appear in the java.security security properties
file to register the SunJCE security provider with
preference order 5 and the SunJSSE provider with preference order
4:
security.provider.1=sun.security.pkcs11.SunPKCS11 \
${java.home}/lib/security/sunpkcs11-solaris.cfg
security.provider.2=sun.security.provider.Sun
security.provider.3=sun.security.rsa.SunRsaSign
security.provider.4=com.sun.net.ssl.internal.ssl.Provider
security.provider.5=com.sun.crypto.provider.SunJCE
security.provider.6=sun.security.jgss.SunProvider
security.provider.7=com.sun.security.sasl.Provider
To use another JSSE provider, add a line registering the other provider, giving it whatever preference order you prefer.
You can have more than one JSSE provider registered at the same time. The registered providers may include different implementations for different algorithms for different engine classes, or they may have support for some or all of the same types of algorithms and engine classes. When a particular engine class implementation for a particular algorithm is searched for, if no specific provider is specified for the search, then the providers are searched in preference order and the implementation from the first provider that supplies an implementation for the specified algorithm is used.
Instead of registering a provider statically, you can add the
provider dynamically at runtime by calling the
Security.addProvider() method at the beginning of your
program. For example, to dynamically add a provider whose provider
class name is MyProvider and whose
MyProvider class resides in the com.ABC
package, you would call:
Security.addProvider(new com.ABC.MyProvider());
The Security.addProvider() method adds the
specified provider to the next available preference position.
This type of registration is not persistent and can only be done by a program with sufficient permissions.
Whenever a default SSLSocketFactory or
SSLServerSocketFactory is created (via a call to
SSLSocketFactory.getDefault or
SSLServerSocketFactory.getDefault), and this default
SSLSocketFactory (or
SSLServerSocketFactory) comes from the JSSE reference
implementation, a default SSLContext is associated
with the socket factory. (The default socket factory will come from
the JSSE implementation.)
This default SSLContext is initialized with a
default KeyManager and a default
TrustManager. If a keystore is specified by the
javax.net.ssl.keyStore system
property and an appropriate
javax.net.ssl.keyStorePassword system property, then the
KeyManager created by the default
SSLContext will be a KeyManager
implementation for managing the specified keystore. (The actual
implementation will be as specified in Customizing the Default Key and Trust
Managers.) If no such system property is specified, then the
keystore managed by the KeyManager will be a new empty
keystore.
Generally, the peer acting as the server in the handshake will
need a keystore for its KeyManager in order to obtain credentials
for authentication to the client. However, if one of the anonymous
cipher suites is selected, then the server's
KeyManager keystore is not necessary. And, unless the
server requires client authentication, the peer acting as the
client does not need a KeyManager keystore. Thus, in
these situations it may be OK if no
javax.net.ssl.keyStore system property value is
defined.
Similarly, if a truststore is specified by the
javax.net.ssl.trustStore system property, then the
TrustManager created by the default
SSLContext will be a TrustManager
implementation for managing the specified truststore. In this case,
if such a property exists but the file it specifies does not, then
no truststore is used. If no javax.net.ssl.trustStore
property exists, then a default truststore is searched for. If a
truststore named java-home/lib/security/jssecacerts is
found, it is used. If not, then a truststore named
java-home/lib/security/cacerts is searched for and used
(if it exists). For more information about java-home,
see The Installation Directory. Finally, if
a truststore is still not found, then the truststore managed by the
TrustManager will be a new empty truststore.
Note: The JDK ships with a limited number of trusted root certificates in the java-home/lib/security/cacerts file. As documented in keytool reference pages, it is your responsibility to maintain (that is, add and remove) the certificates contained in this file if you use this file as a truststore.
Depending on the certificate configuration of the servers that you contact, you may need to add additional root certificates. Obtain the needed specific root certificates from the appropriate vendor.
If the javax.net.ssl.keyStoreType and/or
javax.net.ssl.keyStorePassword system properties are
also specified, then they are treated as the default
KeyManager keystore type and password, respectively.
If no type is specified, then the default type is that returned by
the KeyStore.getDefaultType() method, which is the
value of the keystore.type security property, or "jks"
if no such security property is specified. If no keystore password
is specified, then it is assumed to be a blank string "".
Similarly, if the javax.net.ssl.trustStoreType
and/or javax.net.ssl.trustStorePassword system
properties are also specified, then they are treated as the default
truststore type and password, respectively. If no type is
specified, then the default type is that returned by the
KeyStore.getDefaultType() method. If no truststore
password is specified, then it is assumed to be a blank string
"".
Note: This section describes the current JSSE reference implementation behavior. The system properties described in this section are not guaranteed to continue to have the same names and types (system or security) or even to exist at all in future releases. They are also not guaranteed to be examined and used by any other JSSE implementations. If they are examined by an implementation, then that implementation should handle them in the same manner as the JSSE reference implementation does, as described herein.
As noted in Customizing the Default
Keystores and Truststores, Store Types, and Store Passwords,
whenever a default SSLSocketFactory or
SSLServerSocketFactory is created, and this default
SSLSocketFactory (or
SSLServerSocketFactory) comes from the JSSE reference
implementation, a default SSLContext is associated
with the socket factory.
This default SSLContext is initialized with a
KeyManager and a TrustManager. The
KeyManager and/or TrustManager supplied
to the default SSLContext will be an implementation
for managing the specified keystore or truststore, as described in
the aforementioned section.
The KeyManager implementation chosen is determined
by first examining the ssl.KeyManagerFactory.algorithm
security property. If such a property
value is specified, then a KeyManagerFactory
implementation for the specified algorithm is searched for. The
implementation from the first provider that supplies an
implementation is used. Its getKeyManagers() method is
called to determine the KeyManager to supply to the
default SSLContext. Technically,
getKeyManagers() returns an array of
KeyManager objects, one KeyManager for
each type of key material. If no such security property value is
specified, then the default value of SunX509 is used to perform the
search.
Note: A KeyManagerFactory
implementation for the SunX509 algorithm is supplied by the SunJSSE
provider. The KeyManager that it specifies is a
javax.net.ssl.X509KeyManager implementation.
Similarly, the TrustManager implementation chosen
is determined by first examining the
ssl.TrustManagerFactory.algorithm security property.
If such a property value is specified, then a
TrustManagerFactory implementation for the specified
algorithm is searched for. The implementation from the first
provider that supplies an implementation is used. Its
getTrustManagers() method is called to determine the
TrustManager to supply to the default
SSLContext. Technically,
getTrustManagers() returns an array of
TrustManager objects, one TrustManager
for each type of trust material. If no such security property value
is specified, then the default value of PKIX is used to perform the
search.
Note: A TrustManagerFactory
implementation for the PKIX algorithm is supplied by the SunJSSE
provider. The TrustManager that it specifies is a
javax.net.ssl.X509TrustManager implementation.
Note: This section describes the current JSSE reference implementation behavior. The system properties described in this section are not guaranteed to continue to have the same names and types (system or security) or even to exist at all in future releases. They are also not guaranteed to be examined and used by any other JSSE implementations. If they are examined by an implementation, then that implementation should handle them in the same manner as the JSSE reference implementation does, as described herein.
The cryptographic hash algorithm MD2 is no longer considered secure. Java SE 7 included two new security properties and a new API that support disabling specific cryptographic algorithms.
The jdk.tls.disabledAlgorithms property applies to
TLS handshaking, whereas the jdk.certpath.disabledAlgorithms
property applies to certification path processing.
From JDK 8 onwards, the default value of jdk.certpath.disabledAlgorithms includes RSA keySize < 1024. This means the use of certificates with RSA key size less than 1024 bits in length is restricted. The default value of jdk.certpath.disabledAlgorithms is now as follows:
jdk.certpath.disabledAlgorithms=MD2, RSA keySize < 1024
This means that any certificate signed with MD2 or with a RSA key of size < 1024, is not acceptable.
Each security property contains a list of cryptographic algorithms that will not be used during certification path processing. The exact syntax of the properties is described in the java-home/lib/security/java.security file, but is briefly summarized here. The algorithm names are separated by commas. Furthermore, you can also specify certain key sizes that cannot be used.
For example, the following line in java.security
specifies that the MD2 and DSA algorithms must not be used for
certification path processing, and RSA is disabled for key sizes
less than 2048 bits.
jdk.certpath.disabledAlgorithms=MD2, DSA, RSA keySize < 2048
The SunJSSE provider uses the SunJCE implementation for all its
cryptographic needs. Although it is recommended that you leave the
provider at its regular position, you can use implementations from
other JCA or JCE providers by registering them before the
SunJCE provider. The standard JCA
mechanism can be used to configure providers, either statically
via the security properties file
java-home/lib/security/java.security, or dynamically via
the addProvider() or insertProviderAt()
method in the java.security.Security class. For
information about java-home, see The
Installation Directory.
Diffie-Hellman (DH) keys of sizes less than 1024 bits have been deprecated because of their insufficient strength. In JDK 8, you can customize the ephemeral DH key size with the system property jdk.tls.ephemeralDHKeySize. This system property does not impact DH key sizes in ServerKeyExchange messages for exportable cipher suites. It impacts only the DHE_RSA, DHE_DSS, and DH_anon-based cipher suites in the JSSE Oracle provider.
You can specify one of the following values for this property:
legacy: The JSSE Oracle provider preserves the legacy behavior (for example, using ephemeral DH keys of sizes 512 bits and 768 bits) of JDK 7 and earlier releases.matched: For non-exportable anonymous cipher suites, the DH key size in ServerKeyExchange messages is 1024 bits. For X.509 certificate based authentication (of non-exportable cipher suites), the DH key size matching the corresponding authentication key is used, except that the size must be between 1024 bits and 2048 bits. For example, if the public key size of an authentication certificate is 2048 bits, then the ephemeral DH key size should be 2048 bits unless the cipher suite is exportable. This key sizing scheme keeps the cryptographic strength consistent between authentication keys and key-exchange keys.The following table summaries the minimum and maximum acceptable DH key sizes for each of the possible values for the system property jdk.tls.ephemeralDHKeySize:
Value of jdk.tls.ephemeralDHKeySize |
Undefined | legacy |
matched |
Integer value (fixed) |
|---|---|---|---|---|
| Exportable DH key size | 512 | 512 | 512 | 512 |
| Non-exportable anonymous cipher suites | 1024 | 768 | 1024 | The fixed key size is specified by a valid integer property value, which must be between 1024 and 2048, inclusively. |
| Authentication certificate | 1024 | 768 | The key size is the same as the authentication certificate, but must be between 1024 bits and 2048 bits, inclusively. However, the SunJCE provider only supports 2048-bit DH keys larger than 1024 bits. Consequently, you may use the values 1024 or 2048 only. | The fixed key size is specified by a valid integer property value, which must be between 1024 and 2048, inclusively. |
In the fall of 2009, a flaw was discovered in the SSL/TLS protocols. A fix to the protocol was developed by the IETF TLS Working Group, and current versions of the JDK contain this fix. This section describes the situation in much more detail, along with interoperability issues when communicating with older implementations that do not contain this protocol fix.
The vulnerability allowed for man-in-the-middle (MITM) attacks where chosen plain text could be injected as a prefix to a TLS connection. This vulnerability did not allow an attacker to decrypt or modify the intercepted network communication once the client and server have successfully negotiated a session between themselves.
Additional information is available at CVE-2009-3555 (posted on Mitre's Common Vulnerabilities and Exposures List, 2009) and Understanding the TLS Renegotiation Attack (posted on Eric Rescorla's blog, Educated Guesswork, November 5, 2009).
The fix for this issue was handled in two phases:
Phase 1: Until a protocol fix could be developed, an interim fix that disabled SSL/TLS renegotiations by default was made available in the March 30, 2010 Java SE and Java for Business Critical Patch Update.
Phase 2: The IETF issued RFC 5746, which addresses the renegotiation protocol flaw. The following table lists the JDK and JRE releases that include the fix which implements RFC 5746 and supports secure renegotiation.
| JDK Family | Vulnerable Releases | Phase 1 Fix (Disable Renegotiations) | Phase 2 Fix (RFC 5746) |
|---|---|---|---|
| JDK and JRE 6 | Update 18 and earlier | Updates 19 through 21 | Update 22 |
| JDK and JRE 5.0 | Update 23 and earlier | Updates 24 through 25 | Update 26 |
| JDK and JRE 1.4.2 | Update 25 and earlier | Updates 26 through 27 | Update 28 |
Note: Applications that do not require renegotiations are not affected by the Phase 2 default configuration. However applications that require renegotiations (for example, web servers that initially allow for anonymous client browsing, but later require SSL/TLS authenticated clients):
The SunJSSE implementation reenables renegotiations by default for connections to peers compliant with RFC 5746. That is, both the client and server must support RFC 5746 in order to securely renegotiate. SunJSSE provides some interoperability modes for connections with peers that have not been upgraded, but users are strongly encouraged to update both their client and server implementations as soon as possible.
With the Phase 2 fix, SunJSSE has three renegotiation interoperability modes. Each mode fully supports the RFC 5746 secure renegotiation, but has these added semantics when communicating with a peer that has not been upgraded:
Strict mode: Requires both client and server be upgraded to RFC 5746 and to send the proper RFC 5746 messages. If not, the initial (or subsequent) handshaking will fail and the connection will be terminated.
Interoperable mode (default): Use of the proper RFC 5746 messages is optional; however, legacy (original SSL/TLS specifications) renegotiations are disabled if the proper messages are not used. Initial legacy connections are still allowed, but legacy renegotiations are disabled. This is the best mix of security and interoperability, and is the default setting.
Insecure mode: Permits full legacy renegotiation. Most interoperable with legacy peers but vulnerable to the original MITM attack.
The three mode distinctions only affect a connection with a peer that has not been upgraded. Ideally, strict (full RFC 5746) mode should be used for all clients and servers; however, it will take some time for all deployed SSL/TLS implementations to support RFC 5746, because the interoperable mode is the current default.
Table 8 contains interoperability information about the modes for various cases in which the client and/or server are either updated to support RFC 5746 or not.
| Client | Server | Mode |
|---|---|---|
| Updated | Updated |
Secure renegotiation in all modes. |
| Legacy Footnote 1 | Updated |
|
| Updated | Legacy Footnote 1 |
|
| Legacy Footnote 1 | Legacy Footnote 1 | Existing SSL/TLS behavior, vulnerable to the MITM attack. |
Footnote 1 "Legacy" means the original SSL/TLS specifications (that is, not RFC 5746).
Footnote 2 SunJSSE Phase 1 implementations reject renegotiations unless specifically reenabled. If renegotiations are reenabled, then they will be treated as "Legacy" by the peer that is compliant with RFC 5746, because they do not send the proper RFC 5746 messages.
Footnote 3 In SSL/TLS, renegotiations can
be initiated by either side. Like the Phase 1 fix, applications
communicating with a peer that has not been upgraded in
Interoperable mode and that attempt to initiate renegotiation (via
SSLSocket.startHandshake() or
SSLEngine.beginHandshake()) will receive an
SSLHandshakeException (IOException) and
the connection will be shut down (handshake_failure).
Applications that receive a renegotiation request from a peer that
has not been upgraded will respond according to the type of
connection in place:
no_renegotiation(100)
will be sent to the peer and the connection will remain open. Older
versions of SunJSSE will shut down the connection when a
no_renegotiation alert is received.SSLHandshakeException,
and the connection will be closed (handshake_failure).
The no_renegotiation alert is not defined in the SSLv3
specification.The following system properties are used to set the mode:
sun.security.ssl.allowUnsafeRenegotiation
(introduced in Phase 1) controls whether legacy (unsafe)
renegotiations are permitted.sun.security.ssl.allowLegacyHelloMessages
(introduced in Phase 2) allows the peer to perform the handshake
process without requiring the proper RFC 5746 messages.| Mode | allowLegacyHelloMessages |
allowUnsafeRenegotiation |
|---|---|---|
| Strict | false | false |
| Interoperable (default) | true | false |
| Insecure | true | true |
Caution: Do not reenable the insecure SSL/TLS renegotiation, as this would reestablish the vulnerability.
For information about how to configure a specific mode by setting a system property, see How to Specify a java.lang.System Property.
All peers should be updated to RFC 5746-compliant implementation as soon as possible. Even with this RFC 5746 fix, communications with peers that have not been upgraded will be affected if a renegotiation is necessary. Here are a few suggested options:
Restructure the peer to not require renegotiation.
Renegotiations are typically used by web servers that initially allow for anonymous client browsing but later require SSL/TLS authenticated clients, or that may initially allow weak cipher suites but later need stronger ones. The alternative is to require client authentication or strong cipher suites during the initial negotiation. There are a couple of options for doing so:
If an application has a browse mode until a certain point is reached and a renegotiation is required, then you can restructure the server to eliminate the browse mode and require all initial connections be strong.
Break the server into two entities, with the browse mode occurring on one entity, and using a second entity for the more secure mode. When the renegotiation point is reached, transfer any relevant information between the servers.
Both of these options require a fair amount of work, but will not reopen the original security flaw.
Set renegotiation interoperability mode to "insecure" using the system properties.
See the Description of the Phase 2 Fix for information and warnings.
RFC 5746 defines two new data structures, which are mentioned here for advanced users:
Either of these can be used to signal that an implementation is RFC 5746-compliant and can perform secure renegotiations. For more relevant technical discussions, see the IETF email discussion from November 2009 to February 2010.
RFC 5746 enables clients to send either an SCSV or RI in the
first ClientHello. For maximum interoperability,
SunJSSE uses the SCSV by default, as a few TLS/SSL servers do not
handle unknown extensions correctly. The presence of the SCSV in
the enabled cipher suites
(SSLSocket.setEnabledCipherSuites() or
SSLEngine.setEnabledCipherSuites()) determines whether
the SCSV is sent in the initial ClientHello, or if an
RI should be sent instead.
SSLv2 does not support SSL/TLS extensions. If the
SSLv2Hello protocol is enabled, then the SCSV is sent
in the initial ClientHello.
As previously mentioned, the Phase 1 Fix was to disable
renegotiations by default until a fix compliant with RFC 5746 could
be developed. Renegotiations could be reenabled by setting the
sun.security.ssl.allowUnsafeRenegotiation system
property. The Phase 2 fix uses the same
sun.security.ssl.allowUnsafeRenegotiation system
property, but also requires it to use RFC 5746 messages.
All applications should upgrade to the Phase 2 RFC 5746 fix as soon as possible.
The Java Cryptography Architecture (JCA) is a set of packages that provides a framework and implementations for encryption, key generation and key agreement, and message authentication code (MAC) algorithms. The SunJSSE provider uses JCA exclusively for all of its cryptographic operations and can automatically take advantage of JCE features and enhancements, including JCA's support for PKCS#11. This support enables the SunJSSE provider to use hardware cryptographic accelerators for significant performance improvements and to use smartcards as keystores for greater flexibility in key and trust management.
Use of hardware cryptographic accelerators is automatic if JCA has been configured to use the Oracle PKCS#11 provider, which in turn has been configured to use the underlying accelerator hardware. The provider must be configured before any other JCA providers in the provider list. For details on how to configure the Oracle PKCS#11 provider, see the PKCS#11 Guide.
Support for PKCS#11 in JCA also enables access to smartcards as
a keystore. For details on how to configure the type and location
of the keystores to be used by JSSE, see the Customizing JSSE section. To
use a smartcard as a keystore or truststore, set the
javax.net.ssl.keyStoreType and
javax.net.ssl.trustStoreType system properties,
respectively, to pkcs11, and set the
javax.net.ssl.keyStore and
javax.net.ssl.trustStore system properties,
respectively, to NONE. To specify the use of a
specific provider, use the
javax.net.ssl.keyStoreProvider and
javax.net.ssl.trustStoreProvider system properties
(for example, set them to SunPKCS11-joe). By using
these properties, you can configure an application that previously
depended on these properties to access a file-based keystore to use
a smartcard keystore with no changes to the application.
Some applications request the use of keystores programmatically.
These applications can continue to use the existing APIs to
instantiate a Keystore and pass it to its key manager
and trust manager. If the Keystore instance refers to
a PKCS#11 keystore backed by a Smartcard, then the JSSE application
will have access to the keys on the smartcard.
smartcards (and other removable tokens) have additional
requirements for an X509KeyManager. Different
smartcards can be present in a smartcard reader during the lifetime
of a Java application, and they can be protected using different
passwords.
The java.security.KeyStore.Builder
class abstracts the construction and initialization of a
KeyStore object. It supports the use of
CallbackHandler for password prompting, and its
subclasses can be used to support additional features as desired by
an application. For example, it is possible to implement a
Builder that allows individual KeyStore
entries to be protected with different passwords. The
javax.net.ssl.KeyStoreBuilderParameters class then can
be used to initialize a KeyManagerFactory using one or more of
these Builder objects.
A X509KeyManager implementation in the SunJSSE
provider called NewSunX509 supports these parameters. If multiple
certificates are available, it attempts to pick a certificate with
the appropriate key usage and prefers valid to expired
certificates.
The following example illustrates how to tell JSSE to use both a PKCS#11 keystore (which might in turn use a smartcard) and a PKCS#12 file-based keystore.
import javax.net.ssl.*;
import java.security.KeyStore.*;
...
// Specify keystore builder parameters for PKCS#11 keystores
Builder scBuilder = Builder.newInstance("PKCS11", null,
new CallbackHandlerProtection(myGuiCallbackHandler));
// Specify keystore builder parameters for a specific PKCS#12 keystore
Builder fsBuilder = Builder.newInstance("PKCS12", null,
new File(pkcsFileName), new PasswordProtection(pkcsKsPassword));
// Wrap them as key manager parameters
ManagerFactoryParameters ksParams = new KeyStoreBuilderParameters(
Arrays.asList(new Builder[] { scBuilder, fsBuilder }) );
// Create KeyManagerFactory
KeyManagerFactory factory = KeyManagerFactory.getInstance("NewSunX509");
// Pass builder parameters to factory
factory.init(ksParams);
// Use factory
SSLContext ctx = SSLContext.getInstance("TLS");
ctx.init(factory.getKeyManagers(), null, null);
The SunJSSE provider has support for Kerberos cipher suites, as described in RFC 2712. The following cipher suites are supported but not enabled by default:
To enable the use of these cipher suites, you must do so
explicitly. For more information, see the API documentation for the
SSLEngine.setEnabledCipherSuites() and
SSLSocket.setEnabledCipherSuites() methods. As
with all other SSL/TLS cipher suites, if a cipher suite is not
supported by the peer, then it will not be selected during cipher
negotiation. Furthermore, if the application and/or server cannot
acquire the necessary Kerberos credentials, then the Kerberos
cipher suites also will not be selected.
The following is an example of a TLS client that will only use
the TLS_KRB5_WITH_DES_CBC_SHA cipher suite:
// Create socket
SSLSocketFactory sslsf = (SSLSocketFactory) SSLSocketFactory.getDefault();
SSLSocket sslSocket = (SSLSocket) sslsf.createSocket(tlsServer, serverPort);
// Enable only one cipher suite
String enabledSuites[] = { "TLS_KRB5_WITH_DES_CBC_SHA" };
sslSocket.setEnabledCipherSuites(enabledSuites);
You must have the Kerberos infrastructure set up in your
deployment environment before you can use the Kerberos cipher
suites with JSSE. In particular, both the TLS client and server
must have accounts set up with the Kerberos Key Distribution Center
(KDC). At runtime, if one or more of the Kerberos cipher suites
have been enabled, then the TLS client and server will acquire
their Kerberos credentials associated with their respective account
from the KDC. For example, a TLS server running on the machine
mach1.imc.org in the Kerberos realm
IMC.ORG must have an account with the name
host/mach1.imc.org@IMC.ORG and be configured to use
the KDC for IMC.ORG. For information about using
Kerberos with Java SE, see the Kerberos Requirements
document.
An application can acquire its Kerberos credentials by using the Java Authentication and Authorization Service (JAAS) and a Kerberos login module. The JDK comes with a Kerberos login module. You can use the Kerberos cipher suites with JSSE with or without JAAS programming, similar to how you can use the Java Generic Security Services (Java GSS) with or without JAAS programming.
To use the Kerberos cipher suites with JSSE without JAAS
programming, you must use the index names
com.sun.net.ssl.server or other for the
TLS server JAAS configuration entry, and
com.sun.net.ssl.client or other for the
TLS client, and set the
javax.security.auth.useSubjectCredsOnly system
property to false. For example, a TLS server that is not using JAAS
programming might have the following JAAS configuration file:
com.sun.net.ssl.server {
com.sun.security.auth.module.Krb5LoginModule required
principal="host/mach1.imc.org@IMC.ORG"
useKeyTab=true
keyTab=mach1.keytab
storeKey=true;
};
An example of how to use Java GSS and Kerberos without JAAS programming is described in the Java GSS Tutorial. You can adapt it to use JSSE by replacing Java GSS calls with JSSE calls.
To use the Kerberos cipher suites with JAAS programming, you can
use any index name because your application is responsible for
creating the JAAS LoginContext using the index name,
and then wrapping the JSSE calls inside of a
Subject.doAs() or
Subject.doAsPrivileged() call. An example of how to
use JAAS with Java GSS and Kerberos is described in the Java GSS Tutorial. You
can adapt it to use JSSE by replacing Java GSS calls with JSSE
calls.
If you have trouble using or configuring the JSSE application to use Kerberos, see the Troubleshooting section of the Java GSS Tutorial.
To determine the identity of the peer of an SSL connection, use
the getPeerPrincipal() method in the following
classes:
javax.net.ssl.SSLSessionjavax.net.ssl.HttpsURLConnectionjavax.net.HandshakeCompletedEventSimilarly, to get the identity that was sent to the peer (to
identify the local entity), use the
getLocalPrincipal() method in these classes. For
X509-based cipher suites, these methods will return an instance of
javax.security.auth.x500.X500Principal; for Kerberos
cipher suites, these methods will return an instance of
javax.security.auth.kerberos.KerberosPrincipal.
JSSE applications use getPeerCertificates() and
similar methods in javax.net.ssl.SSLSession,
javax.net.ssl.HttpsURLConnection, and
javax.net.HandshakeCompletedEvent classes to obtain
information about the peer. When the peer does not have any
certificates, SSLPeerUnverifiedException is
thrown.
If the application must determine only the identity of the peer
or identity sent to the peer, then it should use the
getPeerPrincipal() and
getLocalPrincipal() methods, respectively. It should
use getPeerCertificates() and
getLocalCertificates() methods only if it must examine
the contents of those certificates. Furthermore, the application
must be prepared to handle the case where an authenticated peer
might not have any certificate.
When the security manager has been enabled, in addition to the
SocketPermission needed to communicate with the peer,
a TLS client application that uses the Kerberos cipher suites also
needs the following permission:
javax.security.auth.kerberos.ServicePermission(serverPrincipal, "initiate");
In the preceding code, serverPrincipal is the Kerberos
principal name of the TLS server that the TLS client will be
communicating with (such as
host/mach1.imc.org@IMC.ORG). A TLS server application
needs the following permission:
javax.security.auth.kerberos.ServicePermission(serverPrincipal, "accept");
In the preceding code, serverPrincipal is the Kerberos
principal name of the TLS server (such as
host/mach1.imc.org@IMC.ORG). If the server or client
must contact the KDC (for example, if its credentials are not
cached locally), then it also needs the following permission:
javax.security.auth.kerberos.ServicePermission(tgtPrincipal, "initiate");In the preceding code, tgtPrincipal is the principal name of the KDC (such as
krbtgt/IMC.ORG@IMC.ORG).
The PKCS#12 (Personal
Information Exchange Syntax Standard) specifies a portable
format for storage and/or transport of a user's private keys,
certificates, miscellaneous secrets, and other items. The SunJSSE
provider supplies a complete implementation of the PKCS12
java.security.KeyStore format for reading and writing
PKCS12 files. This format is also supported by other toolkits and
applications for importing and exporting keys and certificates,
such as Netscape/Mozilla, Microsoft's Internet Explorer, and
OpenSSL. For example, these implementations can export client
certificates and keys into a file using the .p12 file name
extension.
With the SunJSSE provider, you can access PKCS12 keys through
the KeyStore API with a keystore type of PKCS12. In
addition, you can list the installed keys and associated
certificates by using the keytool command with the
-storetype option set to pkcs12. For more
information about keytool, see Security Tools.
The SNI extension is a feature that extends the SSL/TLS
protocols to indicate what server name the client is attempting to
connect to during handshaking. Servers can use server name
indication information to decide if specific SSLSocket
or SSLEngine instances should accept a connection. For
example, when multiple virtual or name-based servers are hosted on
a single underlying network address, the server application can use
SNI information to determine whether this server is the exact
server that the client wants to access. Instances of this class can
be used by a server to verify the acceptable server names of a
particular type, such as host names. For more information, see
section 3 of TLS
Extensions (RFC 6066).
Developers of client applications can explicitly set the server
name indication using the
SSLParameters.setServerNames(List<SNIServerName>
serverNames) method. The following example illustrates this
functionality:
SSLSocketFactory factory = ...
SSLSocket sslSocket = factory.createSocket("172.16.10.6", 443);
// SSLEngine sslEngine = sslContext.createSSLEngine("172.16.10.6", 443);
SNIHostName serverName = new SNIHostName("www.example.com");
List<SNIServerName> serverNames = new ArrayList<>(1);
serverNames.add(serverName);
SSLParameters params = sslSocket.getSSLParameters();
params.setServerNames(serverNames);
sslSocket.setSSLParameters(params);
// sslEngine.setSSLParameters(params);
Developers of server applications can use the
SNIMatcher class to decide how to recognize server
name indication. The following two examples illustrate this
functionality:
Example 1
SSLSocket sslSocket = sslServerSocket.accept();
SNIMatcher matcher = SNIHostName.createSNIMatcher("www\\.example\\.(com|org)");
Collection<SNIMatcher> matchers = new ArrayList<>(1);
matchers.add(matcher);
SSLParameters params = sslSocket.getSSLParameters();
params.setSNIMatchers(matchers);
sslSocket.setSSLParameters(params);
Example 2
SSLServerSocket sslServerSocket = ...;
SNIMatcher matcher = SNIHostName.createSNIMatcher("www\\.example\\.(com|org)");
Collection<SNIMatcher> matchers = new ArrayList<>(1);
matchers.add(matcher);
SSLParameters params = sslServerSocket.getSSLParameters();
params.setSNIMatchers(matchers);
sslServerSocket.setSSLParameters(params);
SSLSocket sslSocket = sslServerSocket.accept();
The following list provides examples for the behavior of the
SNIMatcher when receiving various server name
indication requests in the ClientHello message:
Matcher configured to www\\.example\\.com:
www.example.com,
then it will be accepted and a confirmation will be sent in the
ServerHello message.www.example.org,
then it will be rejected with an unrecognized_name
fatal error.Matcher configured to www\\.invalid\\.com:
www.example.com,
then it will be rejected with an unrecognized_name
fatal error.www.example.org,
then it will be accepted and a confirmation will be sent in the
ServerHello message.Matcher is not configured:
Any requested host name will be accepted but no confirmation will be sent in the ServerHello message.
For descriptions of new classes that implement the SNI extension, see:
For examples, see Using the Server Name Indication (SNI) Extension.
This section contains information for troubleshooting JSSE. First, it provides some common configuration problems and ways to solve them, and then it describes helpful debugging utilities.
This section describes some common configuration problems that might arise when you use JSSE.
Problem: When negotiating an SSL connection, the client
or server throws a CertificateException.
Cause 1: This is generally caused by the remote side sending a certificate that is unknown to the local side.
Solution 1: The best way to debug this type of problem is to turn on debugging (see Debugging Utilities) and watch as certificates are loaded and when certificates are received via the network connection. Most likely, the received certificate is unknown to the trust mechanism because the wrong trust file was loaded. Refer to the following sections for more information:
Cause 2: The system clock is not set correctly. In this case, the perceived time may be outside the validity period on one of the certificates, and unless the certificate can be replaced with a valid one from a truststore, the system must assume that the certificate is invalid, and therefore throw the exception.
Solution 2: Correct the system clock time.
Problem: Attempt to store trusted certificates in PKCS12
keystore throws java.security.KeyStoreException:
TrustedCertEntry not supported.
Cause: Storing trusted certificates in a PKCS12 keystore is not supported. PKCS12 is mainly used to deliver private keys with the associated certificate chains. It does not have any notion of "trusted" certificates. In terms of interoperability, other PKCS12 vendors have the same restriction. Browsers such as Mozilla and Internet Explorer do not accept a PKCS12 file with only trusted certificates.
Solution: Use the JKS keystore for storing trusted certificates.
Problem: When running a program that uses JSSE, an exception occurs indicating that an SSL service is not available. For example, an exception similar to one of the following is thrown:
Exception in thread "main" java.net.SocketException:
no SSL Server Sockets
Exception in thread "main":
SSL implementation not available
Cause: There was a problem with SSLContext
initialization, for example, due to an incorrect password on a
keystore or a corrupted keystore (a JDK vendor once shipped a
keystore in an unknown format, and that caused this type of
error).
Solution: Check initialization parameters. Ensure that
any keystores specified are valid and that the passwords specified
are correct. One way that you can check this is by trying to use
the keytool
command-line utility to examine the keystores and the relevant
contents.
Problem: When trying to run a simple SSL server program, the following exception is thrown:
Exception in thread "main" javax.net.ssl.SSLException:
No available certificate corresponding to the SSL cipher suites which are enabled...
Cause: Various cipher suites require certain types of key
material. For example, if an RSA cipher suite is enabled, then an
RSA keyEntry must be available in the keystore. If no
such key is available, then this cipher suite cannot be used. This
exception is thrown if there are no available key entries for all
of the cipher suites enabled.
Solution: Create key entries for the various cipher suite types, or use an anonymous suite. Anonymous cipher suites are inherently dangerous because they are vulnerable to MITM (man-in-the-middle) attacks. For more information, see RFC 2246.
Refer to the following sections to learn how to pass the correct keystore and certificates:
Problem 1: When handshaking, the client and/or server throw this exception.
Cause 1: Both sides of an SSL connection must agree on a common cipher suite. If the intersection of the client's cipher suite set with the server's cipher suite set is empty, then you will see this exception.
Solution 1: Configure the enabled cipher suites to
include common cipher suites, and be sure to provide an appropriate
keyEntry for asymmetric cipher suites. Also see
Runtime Exception: "No available
certificate..." in this section.)
Problem 2: When using Netscape Navigator or Microsoft Internet Explorer to access files on a server that only has DSA-based certificates, a runtime exception occurs indicating that there are no cipher suites in common.
Cause 2: By default, keyEntries created with
keytool use DSA public keys. If only DSA
keyEntries exist in the keystore, then only DSA-based
cipher suites can be used. By default, Navigator and Internet
Explorer send only RSA-based cipher suites. Because the
intersection of client and server cipher suite sets is empty, this
exception is thrown.
Solution 2: To interact with Navigator or Internet
Explorer, you should create certificates that use RSA-based keys.
To do this, specify the -keyalg RSA option when using
keytool. For example:
keytool -genkeypair -alias duke -keystore testkeys -keyalg rsa
Problem: JSSE seems to stall on first access.
Cause: JSSE must have a secure source of random numbers. The initialization takes a while.
Solution: Provide an alternative generator of random numbers, or initialize ahead of time when the overhead will not be noticed:
SecureRandom sr = new SecureRandom(); sr.nextInt(); SSLContext.init(..., ..., sr);
The java-home/lib/security/java.security file also
provides a way to specify the source of seed data for
SecureRandom. See the contents of the file for more
information.
Problem: The following code snippet was written using
com.sun.net.ssl.HttpsURLConnection in JSSE 1.0.x:
import com.sun.net.ssl.*;
...deleted...
HttpsURLConnection urlc = new URL("https://example.com/").openConnection();
When running under JSSE 1.0.x, this code returns a
javax.net.ssl.HttpsURLConnection object and throws a
ClassCastException.
Cause: By default, opening an HTTPS URL will create a
javax.net.ssl.HttpsURLConnection.
Solution: Previous releases of the JDK (release 6 and
earlier) did not ship with an HTTPS URL implementation. The JSSE
1.0.x implementation did provide such an HTTPS URL handler, and the
installation guide described how to set the URL handler search path
to obtain a JSSE 1.0.x
com.sun.net.ssl.HttpsURLConnection implementation.
In the JDK, there is an HTTPS handler in the default URL handler
search path. It returns an instance of
javax.net.ssl.HttpsURLConnection. By prepending the
old JSSE 1.0.x implementation path to the URL search path via the
java.protocol.handler.pkgs variable, you can still
obtain a com.sun.net.ssl.HttpsURLConnection, and the
code will no longer throw cast exceptions.
% java -Djava.protocol.handler.pkgs=com.sun.net.ssl.internal.www.protocol YourClass
System.setProperty("java.protocol.handler.pkgs", "com.sun.net.ssl.internal.www.protocol");
Problem: A socket attempts to connect, sends a ClientHello message, and is immediately disconnected.
Cause: Some SSL/TLS servers will disconnect if a ClientHello message is received in a format they do not understand or with a protocol version number that they do not support.
Solution: Try adjusting the enabled protocols on the client side. This involves modifying or invoking some of the following system properties and methods:
https.protocols for the HttpsURLConnection classjdk.tls.client.protocolsSSLContext.getInstance methodSSLEngine.setEnabledProtocols methodSSLSocket.setEnabledProtocols methodSSLParameters.setProtocols and SSLEngine.setSSLParameters methodsSSLParameters.setProtocols and SSLSocket.setSSLParameters methodsSome older server implementations speak only SSLv3 and do not
understand TLS. Ideally, these implementations should negotiate
to SSLv3, but some simply hang up. For backwards compatibility,
some SSL/TLS implementations (such as SunJSSE) can send SSLv3/TLS
ClientHello messages encapsulated in an SSLv2 ClientHello packet.
The SunJSSE provider supports this feature. (See the section Protocols, which lists the protocols that are enabled by default for the SunJSSE provider.) If you want to use this feature, add the SSLv2Hello protocol to the enabled protocol list, if necessary.
Similarly, some other older server implementations can speak to TLSv1 but do not understand TLSv1.1 or TLSv1.2. In this situation, consider using a SSL/TLS version fallback scheme:
For example, if the enabled protocol list on the client is SSLv3, TLSv1, TLSv1.1, and TLSv1.2, a typical SSL/TLS version fallback scheme may look like:
Note: A fallback to a previous version normally means security strength downgrading to a weaker protocol. It is not suggested to use a fallback scheme unless it is really necessary, and you clearly know that the server does not support a higher protocol version.
Problem: A handshake is attempted and fails when it cannot find a required algorithm. Examples might include:
Exception in thread ...deleted...
...deleted...
Caused by java.security.NoSuchAlgorithmException: Cannot find any
provider supporting RSA/ECB/PKCS1Padding
or
Caused by java.security.NoSuchAlgorithmException: Cannot find any
provider supporting AES/CBC/NoPadding
Cause: SunJSSE uses JCE for all its cryptographic
algorithms. By default, the Oracle JDK will use the Standard
Extension ClassLoader to load the SunJCE provider located in
java-home/lib/ext/sunjce_provider.jar. If the file
cannot be found or loaded, or if the SunJCE provider has been
deregistered from the Provider mechanism and an
alternative implementation from JCE is not available, then this
exception will be thrown.
Solution: Ensure that the SunJCE is available by checking
that the file is loadable and that the provider is registered with
the Provider interface. Try to run the following code
in the context of your SSL connection:
import javax.crypto.*;
System.out.println("=====Where did you get AES=====");
Cipher c = Cipher.getInstance("AES/CBC/NoPadding");
System.out.println(c.getProvider());
Problem: If you receive a
com.sun.deploy.net.FailedDownloadException when trying
to obtain application resources from your web server over SSL, and
your web server uses the virtual host with Server Name Indication
(SNI) extension (such as Apache HTTP Server), then you may have not
configured your web server correctly.
Cause: Because Java SE 7 supports the SNI extension in
the JSSE client, the requested host name of the virtual server is
included in the first message sent from the client to the server
during the SSL handshake. The server may deny the client's request
for a connection if the requested host name (the server name
indication) does not match the expected server name, which should
be specified in the virtual host's configuration. This triggers an
SSL handshake unrecognized name alert, which results in a
FailedDownloadException being thrown.
Solution: To better diagnose the problem, enable tracing
through the Java Console.
See Tracing and
Logging for more information. If the cause of the problem is
javax.net.ssl.SSLProtocolException: handshake alert:
unrecognized_name, it is likely that the virtual host
configuration for SNI is incorrect. If you are using Apache HTTP
Server, see Name-based
Virtual Host Support for information about configuring virtual
hosts. In particular, ensure that the ServerName
directive is configured properly in a
<VirtualHost> block.
For more information, see the following:
JSSE provides dynamic debug tracing support. This is similar to
the support used for debugging access control failures in the Java
SE platform. The generic Java dynamic debug tracing support is
accessed with the java.security.debug system property,
whereas the JSSE-specific dynamic debug tracing support is accessed
with the javax.net.debug system property.
Note: The debug utility is not an
officially supported feature of JSSE.
To view the options of the JSSE dynamic debug utility, use the
following command-line option on the java command:
-Djavax.net.debug=help
Note: If you specify the value
help with either dynamic debug utility when running a
program that does not use any classes that the utility was designed
to debug, you will not get the debugging options.
The following complete example shows how to get a list of the debug options for an application named MyApp that uses some of the JSSE classes:
java -Djavax.net.debug=help MyApp
MyApp will not run after the debug help information is printed, as the help code causes the application to exit.
Current options are:
all turn on all debugging
ssl turn on ssl debugging
The following can be used with ssl:
record enable per-record tracing
handshake print each handshake message
keygen print key generation data
session print session activity
defaultctx print default SSL initialization
sslctx print SSLContext tracing
sessioncache print session cache tracing
keymanager print key manager tracing
trustmanager print trust manager tracing
handshake debugging can be widened with:
data hex dump of each handshake message
verbose verbose handshake message printing
record debugging can be widened with:
plaintext hex dump of record plaintext
packet print raw SSL/TLS packets
The javax.net.debug property value must be either
all or ssl, optionally followed by debug
specifiers. You can use one or more options. You do not have
to have a separator between options, although a separator such as a
colon (:) or a comma (,) helps readability. It does not matter what
separators you use, and the ordering of the option keywords is also
not important.
For an introduction to reading this debug information, see the guide, Debugging SSL/TLS Connections.
The following are examples of using the
javax.net.debug property:
To view all debugging messages:
java -Djavax.net.debug=all MyApp
To view the hexadecimal dumps of each handshake message, enter the following (the colons are optional):
java -Djavax.net.debug=ssl:handshake:data MyApp
To view the hexadecimal dumps of each handshake message, and to print trust manager tracing, enter the following (the commas are optional):
java -Djavax.net.debug=SSL,handshake,data,trustmanager MyApp
The following code examples are included in this section:
This section provides examples of source code that illustrate how to use JSSE to convert an unsecure socket connection to a secure socket connection. The code in this section is excerpted from the book Java SE 6 Network Security by Marco Pistoia, et. al.
First, "Socket Example Without SSL" shows sample code that can be used to set up communication between a client and a server using unsecure sockets. This code is then modified in "Socket Example with SSL" to use JSSE to set up secure socket communication.
The following examples demonstrates server-side and client-side code for setting up an unsecure socket connection.
In a Java program that acts as a server and communicates with a client using sockets, the socket communication is set up with code similar to the following:
import java.io.*;
import java.net.*;
. . .
int port = availablePortNumber;
ServerSocket s;
try {
s = new ServerSocket(port);
Socket c = s.accept();
OutputStream out = c.getOutputStream();
InputStream in = c.getInputStream();
// Send messages to the client through
// the OutputStream
// Receive messages from the client
// through the InputStream
} catch (IOException e) { }
The client code to set up communication with a server using sockets is similar to the following:
import java.io.*;
import java.net.*;
. . .
int port = availablePortNumber;
String host = "hostname";
try {
s = new Socket(host, port);
OutputStream out = s.getOutputStream();
InputStream in = s.getInputStream();
// Send messages to the server through
// the OutputStream
// Receive messages from the server
// through the InputStream
} catch (IOException e) { }
The following examples demonstrate server-side and client-side code for setting up a secure socket connection.
In a Java program that acts as a server and communicates with a client using secure sockets, the socket communication is set up with code similar to the following. Differences between this program and the one for communication using unsecure sockets are highlighted in bold.
import java.io.*;
import javax.net.ssl.*;
. . .
int port = availablePortNumber;
SSLServerSocket s;
try {
SSLServerSocketFactory sslSrvFact =
(SSLServerSocketFactory)SSLServerSocketFactory.getDefault();
s = (SSLServerSocket)sslSrvFact.createServerSocket(port);
SSLSocket c = (SSLSocket)s.accept();
OutputStream out = c.getOutputStream();
InputStream in = c.getInputStream();
// Send messages to the client through
// the OutputStream
// Receive messages from the client
// through the InputStream
}
catch (IOException e) {
}
The client code to set up communication with a server using secure sockets is similar to the following, where differences with the unsecure version are highlighted in bold:
import java.io.*;
import javax.net.ssl.*;
. . .
int port = availablePortNumber;
String host = "hostname";
try {
SSLSocketFactory sslFact =
(SSLSocketFactory)SSLSocketFactory.getDefault();
SSLSocket s = (SSLSocket)sslFact.createSocket(host, port);
OutputStream out = s.getOutputStream();
InputStream in = s.getInputStream();
// Send messages to the server through
// the OutputStream
// Receive messages from the server
// through the InputStream
}
catch (IOException e) {
}
The JSSE sample programs illustrate how to use JSSE to:
When you use the sample code, be aware that the sample programs are designed to illustrate how to use JSSE. They are not designed to be robust applications.
Note: Setting up secure communications involves
complex algorithms. The sample programs provide no feedback during
the setup process. When you run the programs, be patient: you may
not see any output for a while. If you run the programs with the
javax.net.debug system property set to
all, you will see more feedback. For an introduction
to reading this debug information, see the guide, Debugging SSL/TLS Connections.
Most of the sample code is located in the samples subdirectory of the same directory as that containing the document you are reading. Follow that link to see a listing of all the sample code files and text files. That page also provides a link to a ZIP file that you can download to obtain all the sample code files, which is helpful if you are viewing this documentation from the web.
The following sections describe the samples. For more information, see README.txt.
The sample programs in the samples/sockets
directory illustrate how to set up a secure socket connection
between a client and a server.
When running the sample client programs, you can communicate
with an existing server, such as a commercial web server, or you
can communicate with the sample server program,
ClassFileServer. You can run the sample client and the
sample server programs on different machines connected to the same
network, or you can run them both on one machine but from different
terminal windows.
All the sample SSLSocketClient* programs in the
samples/sockets/client directory (and URLReader*
programs described in Sample Code
Illustrating HTTPS Connections) can be run with the
ClassFileServer sample server program. An example of
how to do this is shown in Running
SSLSocketClientWithClientAuth with ClassFileServer. You can
make similar changes to run URLReader,
SSLSocketClient, or
SSLSocketClientWithTunneling with
ClassFileServer.
If an authentication error occurs during communication between
the client and the server (whether using a web server or
ClassFileServer), it is most likely because the
necessary keys are not in the truststore
(trust key database). For example, the ClassFileServer
uses a keystore called testkeys containing the private
key for localhost as needed during the SSL handshake.
The testkeys keystore is included in the same
samples/sockets/server directory as the
ClassFileServer source. If the client cannot find a
certificate for the corresponding public key of
localhost in the truststore it consults, then an
authentication error will occur. Be sure to use the
samplecacerts truststore (which contains the public
key and certificate of the localhost), as described in
the next section.
When running the sample programs that create a secure socket
connection between a client and a server, you will need to make the
appropriate certificates file (truststore) available. For both the
client and the server programs, you should use the certificates
file samplecacerts from the samples
directory. Using this certificates file will allow the client to
authenticate the server. The file contains all the common
Certificate Authority (CA) certificates shipped with the JDK (in
the cacerts file), plus a certificate for localhost
needed by the client to authenticate localhost when
communicating with the sample server ClassFileServer.
The ClassFileServer uses a keystore containing the
private key for localhost that corresponds to the
public key in samplecacerts.
To make the samplecacerts file available to both
the client and the server, you can either copy it to the file
java-home/lib/security/jssecacerts, rename it to
cacerts, and use it to replace the
java-home/lib/security/cacerts file, or add the
following option to the command line when running the
java command for both the client and the server:
-Djavax.net.ssl.trustStore=path_to_samplecacerts_file
For more information about java-home, see The JRE Installation Directory.
The password for the samplecacerts truststore is
changeit. You can substitute your own certificates in
the samples by using the keytool utility.
If you use a browser, such as Netscape Navigator or Microsoft's
Internet Explorer, to access the sample SSL server provided in the
ClassFileServer example, then a dialog box may pop up
with the message that it does not recognize the certificate. This
is normal because the certificate used with the sample programs is
self-signed and is for testing only. You can accept the certificate
for the current session. After testing the SSL server, you should
exit the browser, which deletes the test certificate from the
browser's namespace.
For client authentication, a separate duke
certificate is available in the appropriate directories. The public
key and certificate is also stored in the
samplecacerts file.
The SSLSocketClient.java
program demonstrates how to create a client that uses an
SSLSocket to send an HTTP request and to get a
response from an HTTPS server. The output of this program is the
HTML source for
https://www.verisign.com/index.html.
You must not be behind a firewall to run this program as
provided. If you run it from behind a firewall, you will get an
UnknownHostException because JSSE cannot find a path
through your firewall to www.verisign.com. To create
an equivalent client that can run from behind a firewall, set up
proxy tunneling as illustrated in the sample program
SSLSocketClientWithTunneling.
The SSLSocketClientWithTunneling.java program illustrates how to do proxy tunneling to access a secure web server from behind a firewall. To run this program, you must set the following Java system properties to the appropriate values:
java -Dhttps.proxyHost=webproxy -Dhttps.proxyPort=ProxyPortNumber SSLSocketClientWithTunneling
Note: Proxy specifications with the
-D options are optional. Replace webproxy with
the name of your proxy host and ProxyPortNumber with the
appropriate port number.
The program will return the HTML source file from
https://www.verisign.com/index.html.
The SSLSocketClientWithClientAuth.java
program shows how to set up a key manager to do client
authentication if required by a server. This program also assumes
that the client is not outside a firewall. You can modify the
program to connect from inside a firewall by following the example
in SSLSocketClientWithTunneling.
To run this program, you must specify three parameters: host,
port, and requested file path. To mirror the previous examples, you
can run this program without client authentication by setting the
host to www.verisign.com, the port to
443, and the requested file path to
https://www.verisign.com/. The output when using these
parameters is the HTML for the website
https://www.verisign.com/.
To run SSLSocketClientWithClientAuth to do client
authentication, you must access a server that requests client
authentication. You can use the sample program
ClassFileServer as this server. This is described in
the following sections.
The program referred to herein as ClassFileServer
is made up of two files: ClassFileServer.java
and ClassServer.java.
To execute them, run ClassFileServer.class, which
requires the following parameters:
port can be any available unused port number, for
example, you can use the number 2001.docroot indicates the directory on the server that
contains the file you want to retrieve. For example, on Solaris,
you can use /home/userid/ (where userid refers to
your particular UID), whereas on Microsoft Windows systems, you can
use c:\.TLS is an optional parameter that indicates that
the server is to use SSL or TLS.true is an optional parameter that indicates that
client authentication is required. This parameter is only consulted
if the TLS parameter is set.Note: The TLS and
true parameters are optional. If you omit them,
indicating that an ordinary (not TLS) file server should be used,
without authentication, then nothing happens. This is because one
side (the client) is trying to negotiate with TLS, while the other
(the server) is not, so they cannot communicate.
Note: The server expects GET requests in the
form GET /path_to_file.
You can use the sample programs SSLSocketClientWithClientAuth
and ClassFileServer to set up authenticated
communication, where the client and server are authenticated to
each other. You can run both sample programs on different machines
connected to the same network, or you can run them both on one
machine but from different terminal windows or command prompt
windows. To set up both the client and the server, do the
following:
ClassFileServer from one machine
or terminal window, as described in Running
ClassFileServer.SSLSocketClientWithClientAuth on
another machine or terminal window.
SSLSocketClientWithClientAuth requires the following
parameters:
host is the host name of the machine that you are
using to run ClassFileServer.port is the same port that you specified for
ClassFileServer.requestedfilepath indicates the path to the file
that you want to retrieve from the server. You must give this
parameter as /filepath. Forward slashes are required
in the file path because it is used as part of a GET statement,
which requires forward slashes regardless of what type of operating
system you are running. The statement is formed as follows:
"GET " + requestedfilepath + " HTTP/1.0"
Note: You can modify the other
SSLClient* applications' GET commands to
connect to a local machine running
ClassFileServer.
There are two primary APIs for accessing secure communications
through JSSE. One way is through a socket-level API that can be
used for arbitrary secure communications, as illustrated by the
SSLSocketClient,
SSLSocketClientWithTunneling, and
SSLSocketClientWithClientAuth (with and without
ClassFileServer) sample programs.
A second, and often simpler, way is through the standard Java
URL API. You can communicate securely with an SSL-enabled web
server by using the HTTPS URL protocol or scheme using the
java.net.URL class.
Support for HTTPS URL schemes is implemented in many of the common browsers, which allows access to secured communications without requiring the socket-level API provided with JSSE.
An example URL is https://www.verisign.com.
The trust and key management for the HTTPS URL implementation is
environment-specific. The JSSE implementation provides an HTTPS URL
implementation. To use a different HTTPS protocol implementation,
set the java.protocol.handler.pkgs system property to the package name. See the
java.net.URL class documentation for details.
The samples that you can download with JSSE include two sample
programs that illustrate how to create an HTTPS connection. Both of
these sample programs (URLReader.java and
URLReaderWithOptions.java)
are in the samples/urls directory.
The URLReader.java
program illustrates using the URL class to access a secure site.
The output of this program is the HTML source for
https://www.verisign.com/. By default, the HTTPS
protocol implementation included with JSSE is used. To use a
different implementation, set the system property
java.protocol.handler.pkgs value to be the name of the
package containing the implementation.
If you are running the sample code behind a firewall, then you
must set the https.proxyHost and
https.proxyPort system properties. For example, to use
the proxy host "webproxy" on port 8080, you can use the following
options for the java command:
-Dhttps.proxyHost=webproxy -Dhttps.proxyPort=8080
Alternatively, you can set the system properties within the
source code with the java.lang.System method
setProperty(). For example, instead of using the
command-line options, you can include the following lines in your
program:
System.setProperty("java.protocol.handler.pkgs", "com.ABC.myhttpsprotocol");
System.setProperty("https.proxyHost", "webproxy");
System.setProperty("https.proxyPort", "8080");
The URLReaderWithOptions.java program is essentially the same as the URLReader.java program, except that it allows you to optionally input any or all of the following system properties as arguments to the program when you run it:
java.protocol.handler.pkgshttps.proxyHosthttps.proxyPorthttps.cipherSuitesTo run URLReaderWithOptions, enter the following
command:
java URLReaderWithOptions [-h proxyhost -p proxyport] [-k protocolhandlerpkgs] [-c ciphersarray]
Note: Multiple protocol handlers can be
included in the protocolhandlerpkgs argument as a list
with items separated by vertical bars. Multiple SSL cipher suite
names can be included in the ciphersarray argument as
a list with items separated by commas. The possible cipher suite
names are the same as those returned by the
SSLSocket.getSupportedCipherSuites() method. The suite
names are taken from the SSL and TLS protocol specifications.
You need a protocolhandlerpkgs argument only if you
want to use an HTTPS protocol handler implementation other than the
default one provided by Oracle.
If you are running the sample code behind a firewall, then you must include arguments for the proxy host and the proxy port. Additionally, you can include a list of cipher suites to enable.
Here is an example of running URLReaderWithOptions
and specifying the proxy host "webproxy" on port 8080:
java URLReaderWithOptions -h webproxy -p 8080
The sample code in the samples/rmi directory illustrates how to create a secure Java Remote Method Invocation (RMI) connection. The sample code is based on an RMI example that is basically a "Hello World" example modified to install and use a custom RMI socket factory.
For more information about Java RMI, see the Java RMI documentation. This web page points to Java RMI tutorials and other information about Java RMI.
SSLEngine gives application developers flexibility
when choosing I/O and compute strategies. Rather than tie the
SSL/TLS implementation to a specific I/O abstraction (such as
single-threaded SSLSockets), SSLEngine
removes the I/O and compute constraints from the SSL/TLS
implementation.
As mentioned earlier, SSLEngine is an advanced API,
and is not appropriate for casual use. Some introductory sample
code is provided here that helps illustrate its use. The first demo
removes most of the I/O and threading issues, and focuses on many
of the SSLEngine methods. The second demo is a more realistic
example showing how SSLEngine might be combined with
Java NIO to create a rudimentary HTTP/HTTPS server.
The SSLEngineSimpleDemo
is a very simple application that focuses on the operation of the
SSLEngine while simplifying the I/O and threading
issues. This application creates two SSLEngine objects
that exchange SSL/TLS messages via common ByteBuffer
objects. A single loop serially performs all of the engine
operations and demonstrates how a secure connection is established
(handshaking), how application data is transferred, and how the
engine is closed.
The SSLEngineResult provides a great deal of
information about the current state of the SSLEngine.
This example does not examine all of the states. It simplifies the
I/O and threading issues to the point that this is not a good
example for a production environment; nonetheless, it is useful to
demonstrate the overall function of the SSLEngine.
To fully exploit the flexibility provided by
SSLEngine, you must first understand complementary
APIs, such as I/O and threading models.
An I/O model that large-scale application developers find of use
is the NIO SocketChannel. NIO was introduced in part
to solve some of the scaling problem inherent in the
java.net.Socket API. SocketChannel has
many different modes of operation including:
Sample code for a basic HTTP server is provided that not only
demonstrates many of the new NIO APIs, but also shows how
SSLEngine can be employed to create a secure HTTPS
server. The server is not production quality, but does show many of
these new APIs in action.
Inside the samples directory is a README.txt file that
introduces the server, explains how to build and configure the
server, and provides a brief overview of the code layout. The files
of most interest for SSLEngine users are
ChannelIO.java and
ChannelIOSecure.java.
Note: The server example discussed in this section is included in the JDK. You can find the code bundled in the jdk-home/samples/nio/server directory.
This section demonstrates how you can use the
keytool utility to create a simple JKS keystore
suitable for use with JSSE. First you make a keyEntry
(with public and private keys) in the keystore, and then you make a
corresponding trustedCertEntry (public keys only) in a
truststore. For client authentication, you follow a similar process
for the client's certificates.
Note: Storing trust anchors in PKCS12 is not supported. Users should use JKS for storing trust anchors and PKCS12 for private keys.
Note: It is beyond the scope of this example to
explain each step in detail. For more information, see the
keytool documentation for Solaris, Linux, or Mac OS X
or Microsoft Windows.
User input is shown in bold.
Create a new keystore and self-signed certificate with corresponding public and private keys.
% keytool -genkeypair -alias duke -keyalg RSA -validity 7 -keystore keystore
Enter keystore password: password
What is your first and last name?
[Unknown]: Duke
What is the name of your organizational unit?
[Unknown]: Java Software
What is the name of your organization?
[Unknown]: Oracle, Inc.
What is the name of your City or Locality?
[Unknown]: Palo Alto
What is the name of your State or Province?
[Unknown]: CA
What is the two-letter country code for this unit?
[Unknown]: US
Is CN=Duke, OU=Java Software, O="Oracle, Inc.",
L=Palo Alto, ST=CA, C=US correct?
[no]: yes
Enter key password for <duke>
(RETURN if same as keystore password): <CR>
Examine the keystore. Notice that the entry type is
keyEntry, which means that this entry has a private
key associated with it).
% keytool -list -v -keystore keystore
Enter keystore password: password
Keystore type: jks
Keystore provider: SUN
Your keystore contains 1 entry
Alias name: duke
Creation date: Dec 20, 2001
Entry type: keyEntry
Certificate chain length: 1
Certificate[1]:
Owner: CN=Duke, OU=Java Software, O="Oracle, Inc.",
L=Palo Alto, ST=CA, C=US
Issuer: CN=Duke, OU=Java Software, O="Oracle, Inc.", L=Palo Alto, ST=CA, C=US
Serial number: 3c22adc1
Valid from: Thu Dec 20 19:34:25 PST 2001 until: Thu Dec 27 19:34:25 PST 2001
Certificate fingerprints:
MD5: F1:5B:9B:A1:F7:16:CF:25:CF:F4:FF:35:3F:4C:9C:F0
SHA1: B2:00:50:DD:B6:CC:35:66:21:45:0F:96:AA:AF:6A:3D:E4:03:7C:74
Export and examine the self-signed certificate.
% keytool -export -alias duke -keystore keystore -rfc -file duke.cer
Enter keystore password: password
Certificate stored in file <duke.cer>
% cat duke.cer
-----BEGIN CERTIFICATE-----
MIICXjCCAccCBDwircEwDQYJKoZIhvcNAQEEBQAwdjELMAkGA1UEBhMCVVMxCzAJBgNVBAgTAkNB
MRIwEAYDVQQHEwlQYWxvIEFsdG8xHzAdBgNVBAoTFlN1biBNaWNyb3N5c3RlbXMsIEluYy4xFjAU
BgNVBAsTDUphdmEgU29mdHdhcmUxDTALBgNVBAMTBER1a2UwHhcNMDExMjIxMDMzNDI1WhcNMDEx
MjI4MDMzNDI1WjB2MQswCQYDVQQGEwJVUzELMAkGA1UECBMCQ0ExEjAQBgNVBAcTCVBhbG8gQWx0
bzEfMB0GA1UEChMWU3VuIE1pY3Jvc3lzdGVtcywgSW5jLjEWMBQGA1UECxMNSmF2YSBTb2Z0d2Fy
ZTENMAsGA1UEAxMERHVrZTCBnzANBgkqhkiG9w0BAQEFAAOBjQAwgYkCgYEA1loObJzNXsi5aSr8
N4XzDksD6GjTHFeqG9DUFXKEOQetfYXvA8F9uWtz8WInrqskLTNzwXgmNeWkoM7mrPpK6Rf5M3G1
NXtYzvxyi473Gh1h9k7tjJvqSVKO7E1oFkQYeUPYifxmjbSMVirWZgvo2UmA1c76oNK+NhoHJ4qj
eCUCAwEAATANBgkqhkiG9w0BAQQFAAOBgQCRPoQYw9rWWvfLPQuPXowvFmuebsTc28qI7iFWm6BJ
TT/qdmzti7B5MHOt9BeVEft3mMeBU0CS2guaBjDpGlf+zsK/UUi1w9C4mnwGDZzqY/NKKWtLxabZ
5M+4MAKLZ92ePPKGpobM2CPLfM8ap4IgAzCbBKd8+CMp8yFmifze9Q==
-----END CERTIFICATE-----
Alternatively, you could generate a Certificate Signing Request
(CSR) with -certreq and send that to a Certificate
Authority (CA) for signing, but that is beyond the scope of this
example.
Import the certificate into a new truststore.
% keytool -import -alias dukecert -file duke.cer -keystore truststore
Enter keystore password: trustword
Owner: CN=Duke, OU=Java Software, O="Oracle, Inc.", L=Palo Alto, ST=CA, C=US
Issuer: CN=Duke, OU=Java Software, O="Oracle, Inc.", L=Palo Alto, ST=CA, C=US
Serial number: 3c22adc1
Valid from: Thu Dec 20 19:34:25 PST 2001 until: Thu Dec 27 19:34:25 PST 2001
Certificate fingerprints:
MD5: F1:5B:9B:A1:F7:16:CF:25:CF:F4:FF:35:3F:4C:9C:F0
SHA1: B2:00:50:DD:B6:CC:35:66:21:45:0F:96:AA:AF:6A:3D:E4:03:7C:74
Trust this certificate? [no]: yes
Certificate was added to keystore
Examine the truststore. Note that the entry type is
trustedCertEntry, which means that a private key is
not available for this entry. It also means that this file is not
suitable as a keystore of the KeyManager.
% keytool -list -v -keystore truststore
Enter keystore password: trustword
Keystore type: jks
Keystore provider: SUN
Your keystore contains 1 entry
Alias name: dukecert
Creation date: Dec 20, 2001
Entry type: trustedCertEntry
Owner: CN=Duke, OU=Java Software, O="Oracle, Inc.", L=Palo Alto, ST=CA, C=US
Issuer: CN=Duke, OU=Java Software, O="Oracle, Inc.", L=Palo Alto, ST=CA, C=US
Serial number: 3c22adc1
Valid from: Thu Dec 20 19:34:25 PST 2001 until: Thu Dec 27 19:34:25 PST 2001
Certificate fingerprints:
MD5: F1:5B:9B:A1:F7:16:CF:25:CF:F4:FF:35:3F:4C:9C:F0
SHA1: B2:00:50:DD:B6:CC:35:66:21:45:0F:96:AA:AF:6A:3D:E4:03:7C:74
Now run your applications with the appropriate keystores.
Because this example assumes that the default
X509KeyManager and X509TrustManager are
used, you select the keystores using the system properties
described in Customizing
JSSE.
% java -Djavax.net.ssl.keyStore=keystore -Djavax.net.ssl.keyStorePassword=password Server
% java -Djavax.net.ssl.trustStore=truststore -Djavax.net.ssl.trustStorePassword=trustword Client
Note: This example authenticated the server only. For client authentication, provide a similar keystore for the client's keys and an appropriate truststore for the server.
This section provides code examples that illustrate how you can use the Server Name Indication (SNI) extension for client-side and server-side applications, and how it can be applied to a virtual infrastructure.
For all examples in this section, to apply the parameters after
you set them, call the setSSLParameters(SSLParameters)
method on the corresponding SSLSocket,
SSLEngine, or SSLServerSocket object.
The following is a list of use cases that require understanding of the SNI extension for developing a client application:
Case 1. The client wants to access
www.example.com.
Set the host name explicitly:
SNIHostName serverName = new SNIHostName("www.example.com");
List<SNIServerName> serverNames = new ArrayList<>(1);
serverNames.add(serverName);
sslParameters.setServerNames(serverNames);
The client should always specify the host name explicitly.
Case 2. The client does not want to use SNI because the server does not support it.
Disable SNI with an empty server name list:
List<SNIServerName> serverNames = new ArrayList<>(1);
sslParameters.setServerNames(serverNames);
Case 3. The client wants to access URL
https://www.example.com.
Oracle providers will set the host name in the SNI extension by default, but third-party providers may not support the default server name indication. To keep your application provider-independent, always set the host name explicitly.
Case 4. The client wants to switch a socket from server mode to client mode.
First switch the mode with the following method:
sslSocket.setUseClientMode(true). Then reset the
server name indication parameters on the socket.
The following is a list of use cases that require understanding of the SNI extension for developing a server application:
Case 1. The server wants to accept all server name indication types.
If you do not have any code dealing with the SNI extension, then the server ignores all server name indication types.
Case 2. The server wants to deny all server name indications
of type host_name.
Set an invalid server name pattern for
host_name:
SNIMatcher matcher = SNIHostName.createSNIMatcher("");
Collection<SNIMatcher> matchers = new ArrayList<>(1);
matchers.add(matcher);
sslParameters.setSNIMatchers(matchers);
Another way is to create an SNIMatcher subclass
with a matches() method that always returns
false:
class DenialSNIMatcher extends SNIMatcher {
DenialSNIMatcher() {
super(StandardConstants.SNI_HOST_NAME);
}
@Override
public boolean matches(SNIServerName serverName) {
return false;
}
}
SNIMatcher matcher = new DenialSNIMatcher();
Collection<SNIMatcher> matchers = new ArrayList<>(1);
matchers.add(matcher);
sslParameters.setSNIMatchers(matchers);
Case 3. The server wants to accept connections to any host
names in the example.com domain.
Set the recognizable server name for host_name as a
pattern that includes all *.example.com addresses:
SNIMatcher matcher = SNIHostName.createSNIMatcher("(.*\\.)*example\\.com");
Collection<SNIMatcher> matchers = new ArrayList<>(1);
matchers.add(matcher);
sslParameters.setSNIMatchers(matchers);
Case 4. The server wants to switch a socket from client mode to server mode.
First switch the mode with the following method:
sslSocket.setUseClientMode(false). Then reset the
server name indication parameters on the socket.
This section describes how to use the Server Name Indication
(SNI) extension from within a virtual infrastructure. It
illustrates how to create a parser for ClientHello messages from a
socket, provides examples of virtual server dispatchers using
SSLSocket and SSLEngine, describes what
happens when the SNI extension is not available, and demonstrates
how to create a failover SSLContext.
Applications must implement an API to parse the ClientHello
messages from a socket. The following examples illustrate the
SSLCapabilities and SSLExplorer classes
that can perform these functions.
SSLCapabilities.java
encapsulates the SSL/TLS security capabilities during handshaking
(that is, the list of cipher suites to be accepted in an SSL/TLS
handshake, the record version, the hello version, and the server
name indication). It can be retrieved by exploring the network data
of an SSL/TLS connection via the SSLExplorer.explore()
method.
SSLExplorer.java
explores the initial ClientHello message from a TLS client, but it
does not initiate handshaking or consume network data. The
SSLExplorer.explore() method parses the ClientHello
message, and retrieves the security parameters into
SSLCapabilities. The method must be called before
handshaking occurs on any TLS connections.
This section describes the procedure for using a virtual server
dispatcher based on SSLSocket.
Register the server name handler.
At this step, the application may create different
SSLContext objects for different server name
indications, or link a certain server name indication to a
specified virtual machine or distributed system.
For example, if the server name is www.example.org,
then the registered server name handler may be for a local virtual
hosting web service. The local virtual hosting web service will use
the specified SSLContext. If the server name is
www.example.com, then the registered server name
handler may be for a virtual machine hosting on
10.0.0.36. The handler may map this connection to the
virtual machine.
Create a ServerSocket and accept the new
connection.
ServerSocket serverSocket = new ServerSocket(serverPort);
Socket socket = serverSocket.accept();
Read and buffer bytes from the socket input stream, and then explore the buffered bytes.
InputStream ins = socket.getInputStream();
byte[] buffer = new byte[0xFF];
int position = 0;
SSLCapabilities capabilities = null;
// Read the header of TLS record
while (position < SSLExplorer.RECORD_HEADER_SIZE) {
int count = SSLExplorer.RECORD_HEADER_SIZE - position;
int n = ins.read(buffer, position, count);
if (n < 0) {
throw new Exception("unexpected end of stream!");
}
position += n;
}
// Get the required size to explore the SSL capabilities
int recordLength = SSLExplorer.getRequiredSize(buffer, 0, position);
if (buffer.length < recordLength) {
buffer = Arrays.copyOf(buffer, recordLength);
}
while (position < recordLength) {
int count = recordLength - position;
int n = ins.read(buffer, position, count);
if (n < 0) {
throw new Exception("unexpected end of stream!");
}
position += n;
}
// Explore
capabilities = SSLExplorer.explore(buffer, 0, recordLength);
if (capabilities != null) {
System.out.println("Record version: " + capabilities.getRecordVersion());
System.out.println("Hello version: " + capabilities.getHelloVersion());
}
Get the requested server name from the explored capabilities.
List<SNIServerName> serverNames = capabilities.getServerNames();
Look for the registered server name handler for this server name indication.
If the service of the host name is resident in a virtual machine or another distributed system, then the application must forward the connection to the destination. The application will need to read and write the raw internet data, rather then the SSL application from the socket stream.
Socket destinationSocket = new Socket(serverName, 443);
// Forward buffered bytes and network data from the current socket to the destinationSocket.
If the service of the host name is resident in the same process,
and the host name service can use the SSLSocket
directly, then the application will need to set the
SSLSocket instance to the server:
// Get service context from registered handler
// or create the context
SSLContext serviceContext = ...
SSLSocketFactory serviceSocketFac = serviceContext.getSSLSocketFactory();
// wrap the buffered bytes
ByteArrayInputStream bais = new ByteArrayInputStream(buffer, 0, position);
SSLSocket serviceSocket = (SSLSocket)serviceSocketFac.createSocket(socket, bais, true);
// Now the service can use serviceSocket as usual.
This section describes the procedure for using a virtual server
dispatcher based on SSLEngine.
Register the server name handler.
At this step, the application may create different
SSLContext objects for different server name
indications, or link a certain server name indication to a
specified virtual machine or distributed system.
For example, if the server name is www.example.org,
then the registered server name handler may be for a local virtual
hosting web service. The local virtual hosting web service will use
the specified SSLContext. If the server name is
www.example.com, then the registered server name
handler may be for a virtual machine hosting on
10.0.0.36. The handler may map this connection to the
virtual machine.
Create a ServerSocket or
ServerSocketChannel and accept the new
connection.
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
serverSocketChannel.bind(...);
...
SocketChannel socketChannel = serverSocketChannel.accept();
Read and buffer bytes from the socket input stream, and then explore the buffered bytes.
ByteBuffer buffer = ByteBuffer.allocate(0xFF);
SSLCapabilities capabilities = null;
while (true) {
// ensure the capacity
if (buffer.remaining() == 0) {
ByteBuffer oldBuffer = buffer;
buffer = ByteBuffer.allocate(buffer.capacity() + 0xFF);
buffer.put(oldBuffer);
}
int n = sc.read(buffer);
if (n < 0) {
throw new Exception("unexpected end of stream!");
}
int position = buffer.position();
buffer.flip();
capabilities = explorer.explore(buffer);
buffer.rewind();
buffer.position(position);
buffer.limit(buffer.capacity());
if (capabilities != null) {
System.out.println("Record version: " +
capabilities.getRecordVersion());
System.out.println("Hello version: " +
capabilities.getHelloVersion());
break;
}
}
buffer.flip(); // reset the buffer position and limitation
Get the requested server name from the explored capabilities.
List<SNIServerName> serverNames = capabilities.getServerNames();
Look for the registered server name handler for this server name indication.
If the service of the host name is resident in a virtual machine or another distributed system, then the application must forward the connection to the destination. The application will need to read and write the raw internet data, rather then the SSL application from the socket stream.
Socket destinationSocket = new Socket(serverName, 443);
// Forward buffered bytes and network data from the current socket to the destinationSocket.
If the service of the host name is resident in the same process,
and the host name service can use the SSLEngine
directly, then the application will simply feed the net data to the
SSLEngine instance:
// Get service context from registered handler
// or create the context
SSLContext serviceContext = ...
SSLEngine serviceEngine = serviceContext.createSSLEngine();
// Now the service can use the buffered bytes and other byte buffer as usual.
If there is no server name indication in a ClientHello message, then there is no way to select the proper service according to SNI. For such cases, the application may need to specify a default service, so that the connection can be delegated to it if there is no server name indication.
The SSLExplorer.explore() method does not check the
validity of SSL/TLS contents. If the record format does not comply
with SSL/TLS specification, or the explore() method is
invoked after handshaking has started, then the method may throw an
IOException and be unable to produce network data. In
such cases, handle the exception thrown by
SSLExplorer.explore() by using a failover
SSLContext, which is not used to negotiate an SSL/TLS
connection, but to close the connection with the proper alert
message. The following example illustrates a failover
SSLContext. You can find an example of the
DenialSNIMatcher class in Case 2 of the Typical Server-Side Usage Examples.
byte[] buffer = ... // buffered network data
boolean failed = true; // SSLExplorer.explore() throws an exception
SSLContext context = SSLContext.getInstance("TLS");
// the failover SSLContext
context.init(null, null, null);
SSLSocketFactory sslsf = context.getSocketFactory();
ByteArrayInputStream bais = new ByteArrayInputStream(buffer, 0, position);
SSLSocket sslSocket = (SSLSocket)sslsf.createSocket(socket, bais, true);
SNIMatcher matcher = new DenialSNIMatcher();
Collection<SNIMatcher> matchers = new ArrayList<>(1);
matchers.add(matcher);
SSLParameters params = sslSocket.getSSLParameters();
params.setSNIMatchers(matchers); // no recognizable server name
sslSocket.setSSLParameters(params);
try {
InputStream sslIS = sslSocket.getInputStream();
sslIS.read();
} catch (Exception e) {
System.out.println("Server exception " + e);
} finally {
sslSocket.close();
}
The JDK Security API requires and uses a set of standard names for algorithms, certificates and keystore types. The specification names previously found here in Appendix A and in the other security specifications (JCA, CertPath) have been combined in the Standard Names document. Specific provider information can be found in the Oracle Provider Documentation.
JSSE is fully pluggable and does not restrict the use of third-party JSSE providers in any way.
