public abstract class

SSLSocket

extends Socket
java.lang.Object
   ↳ java.net.Socket
     ↳ javax.net.ssl.SSLSocket
Known Direct Subclasses

Class Overview

This class extends Sockets and provides secure socket using protocols such as the "Secure Sockets Layer" (SSL) or IETF "Transport Layer Security" (TLS) protocols.

Such sockets are normal stream sockets, but they add a layer of security protections over the underlying network transport protocol, such as TCP. Those protections include:

  • Integrity Protection. SSL protects against modification of messages by an active wiretapper.
  • Authentication. In most modes, SSL provides peer authentication. Servers are usually authenticated, and clients may be authenticated as requested by servers.
  • Confidentiality (Privacy Protection). In most modes, SSL encrypts data being sent between client and server. This protects the confidentiality of data, so that passive wiretappers won't see sensitive data such as financial information or personal information of many kinds.

These kinds of protection are specified by a "cipher suite", which is a combination of cryptographic algorithms used by a given SSL connection. During the negotiation process, the two endpoints must agree on a ciphersuite that is available in both environments. If there is no such suite in common, no SSL connection can be established, and no data can be exchanged.

The cipher suite used is established by a negotiation process called "handshaking". The goal of this process is to create or rejoin a "session", which may protect many connections over time. After handshaking has completed, you can access session attributes by using the getSession method. The initial handshake on this connection can be initiated in one of three ways:

  • calling startHandshake which explicitly begins handshakes, or
  • any attempt to read or write application data on this socket causes an implicit handshake, or
  • a call to getSession tries to set up a session if there is no currently valid session, and an implicit handshake is done.

If handshaking fails for any reason, the SSLSocket is closed, and no futher communications can be done.

There are two groups of cipher suites which you will need to know about when managing cipher suites:

  • Supported cipher suites: all the suites which are supported by the SSL implementation. This list is reported using getSupportedCipherSuites.
  • Enabled cipher suites, which may be fewer than the full set of supported suites. This group is set using the setEnabledCipherSuites method, and queried using the getEnabledCipherSuites method. Initially, a default set of cipher suites will be enabled on a new socket that represents the minimum suggested configuration.

Implementation defaults require that only cipher suites which authenticate servers and provide confidentiality be enabled by default. Only if both sides explicitly agree to unauthenticated and/or non-private (unencrypted) communications will such a ciphersuite be selected.

When SSLSockets are first created, no handshaking is done so that applications may first set their communication preferences: what cipher suites to use, whether the socket should be in client or server mode, etc. However, security is always provided by the time that application data is sent over the connection.

You may register to receive event notification of handshake completion. This involves the use of two additional classes. HandshakeCompletedEvent objects are passed to HandshakeCompletedListener instances, which are registered by users of this API. SSLSockets are created by SSLSocketFactorys, or by accepting a connection from a SSLServerSocket.

A SSL socket must choose to operate in the client or server mode. This will determine who begins the handshaking process, as well as which messages should be sent by each party. Each connection must have one client and one server, or handshaking will not progress properly. Once the initial handshaking has started, a socket can not switch between client and server modes, even when performing renegotiations.

See Also

Summary

Protected Constructors
SSLSocket()
Used only by subclasses.
SSLSocket(String host, int port)
Used only by subclasses.
SSLSocket(InetAddress address, int port)
Used only by subclasses.
SSLSocket(String host, int port, InetAddress clientAddress, int clientPort)
Used only by subclasses.
SSLSocket(InetAddress address, int port, InetAddress clientAddress, int clientPort)
Used only by subclasses.
Public Methods
abstract void addHandshakeCompletedListener(HandshakeCompletedListener listener)
Registers an event listener to receive notifications that an SSL handshake has completed on this connection.
abstract boolean getEnableSessionCreation()
Returns true if new SSL sessions may be established by this socket.
abstract String[] getEnabledCipherSuites()
Returns the names of the SSL cipher suites which are currently enabled for use on this connection.
abstract String[] getEnabledProtocols()
Returns the names of the protocol versions which are currently enabled for use on this connection.
abstract boolean getNeedClientAuth()
Returns true if the socket will require client authentication.
SSLParameters getSSLParameters()
Returns the SSLParameters in effect for this SSLSocket.
abstract SSLSession getSession()
Returns the SSL Session in use by this connection.
abstract String[] getSupportedCipherSuites()
Returns the names of the cipher suites which could be enabled for use on this connection.
abstract String[] getSupportedProtocols()
Returns the names of the protocols which could be enabled for use on an SSL connection.
abstract boolean getUseClientMode()
Returns true if the socket is set to use client mode when handshaking.
abstract boolean getWantClientAuth()
Returns true if the socket will request client authentication.
abstract void removeHandshakeCompletedListener(HandshakeCompletedListener listener)
Removes a previously registered handshake completion listener.
abstract void setEnableSessionCreation(boolean flag)
Controls whether new SSL sessions may be established by this socket.
abstract void setEnabledCipherSuites(String[] suites)
Sets the cipher suites enabled for use on this connection.
abstract void setEnabledProtocols(String[] protocols)
Sets the protocol versions enabled for use on this connection.
abstract void setNeedClientAuth(boolean need)
Configures the socket to require client authentication.
void setSSLParameters(SSLParameters params)
Applies SSLParameters to this socket.
abstract void setUseClientMode(boolean mode)
Configures the socket to use client (or server) mode when handshaking.
abstract void setWantClientAuth(boolean want)
Configures the socket to request client authentication.
abstract void startHandshake()
Starts an SSL handshake on this connection.
[Expand]
Inherited Methods
From class java.net.Socket
From class java.lang.Object

Protected Constructors

protected SSLSocket ()

Used only by subclasses. Constructs an uninitialized, unconnected TCP socket.

protected SSLSocket (String host, int port)

Used only by subclasses. Constructs a TCP connection to a named host at a specified port. This acts as the SSL client.

Parameters
host name of the host with which to connect
port number of the server's port
Throws
IOException if an I/O error occurs when creating the socket
UnknownHostException if the host is not known

protected SSLSocket (InetAddress address, int port)

Used only by subclasses. Constructs a TCP connection to a server at a specified address and port. This acts as the SSL client.

Parameters
address the server's host
port its port
Throws
IOException if an I/O error occurs when creating the socket

protected SSLSocket (String host, int port, InetAddress clientAddress, int clientPort)

Used only by subclasses. Constructs an SSL connection to a named host at a specified port, binding the client side of the connection a given address and port. This acts as the SSL client.

Parameters
host name of the host with which to connect
port number of the server's port
clientAddress the client's host
clientPort number of the client's port
Throws
IOException if an I/O error occurs when creating the socket
UnknownHostException if the host is not known

protected SSLSocket (InetAddress address, int port, InetAddress clientAddress, int clientPort)

Used only by subclasses. Constructs an SSL connection to a server at a specified address and TCP port, binding the client side of the connection a given address and port. This acts as the SSL client.

Parameters
address the server's host
port its port
clientAddress the client's host
clientPort number of the client's port
Throws
IOException if an I/O error occurs when creating the socket

Public Methods

public abstract void addHandshakeCompletedListener (HandshakeCompletedListener listener)

Registers an event listener to receive notifications that an SSL handshake has completed on this connection.

Parameters
listener the HandShake Completed event listener
Throws
IllegalArgumentException if the argument is null.
See Also

public abstract boolean getEnableSessionCreation ()

Returns true if new SSL sessions may be established by this socket.

Returns
  • true indicates that sessions may be created; this is the default. false indicates that an existing session must be resumed
See Also

public abstract String[] getEnabledCipherSuites ()

Returns the names of the SSL cipher suites which are currently enabled for use on this connection. When an SSLSocket is first created, all enabled cipher suites support a minimum quality of service. Thus, in some environments this value might be empty.

Even if a suite has been enabled, it might never be used. (For example, the peer does not support it, the requisite certificates (and private keys) for the suite are not available, or an anonymous suite is enabled but authentication is required.

Returns
  • an array of cipher suite names
See Also

public abstract String[] getEnabledProtocols ()

Returns the names of the protocol versions which are currently enabled for use on this connection.

Returns
  • an array of protocols
See Also

public abstract boolean getNeedClientAuth ()

Returns true if the socket will require client authentication. This option is only useful to sockets in the server mode.

Returns
  • true if client authentication is required, or false if no client authentication is desired.
See Also

public SSLParameters getSSLParameters ()

Returns the SSLParameters in effect for this SSLSocket. The ciphersuites and protocols of the returned SSLParameters are always non-null.

Returns
  • the SSLParameters in effect for this SSLSocket.

public abstract SSLSession getSession ()

Returns the SSL Session in use by this connection. These can be long lived, and frequently correspond to an entire login session for some user. The session specifies a particular cipher suite which is being actively used by all connections in that session, as well as the identities of the session's client and server.

This method will initiate the initial handshake if necessary and then block until the handshake has been established.

If an error occurs during the initial handshake, this method returns an invalid session object which reports an invalid cipher suite of "SSL_NULL_WITH_NULL_NULL".

Returns
  • the SSLSession

public abstract String[] getSupportedCipherSuites ()

Returns the names of the cipher suites which could be enabled for use on this connection. Normally, only a subset of these will actually be enabled by default, since this list may include cipher suites which do not meet quality of service requirements for those defaults. Such cipher suites might be useful in specialized applications.

Returns
  • an array of cipher suite names
See Also

public abstract String[] getSupportedProtocols ()

Returns the names of the protocols which could be enabled for use on an SSL connection.

Returns
  • an array of protocols supported

public abstract boolean getUseClientMode ()

Returns true if the socket is set to use client mode when handshaking.

Returns
  • true if the socket should do handshaking in "client" mode
See Also

public abstract boolean getWantClientAuth ()

Returns true if the socket will request client authentication. This option is only useful for sockets in the server mode.

Returns
  • true if client authentication is requested, or false if no client authentication is desired.
See Also

public abstract void removeHandshakeCompletedListener (HandshakeCompletedListener listener)

Removes a previously registered handshake completion listener.

Parameters
listener the HandShake Completed event listener
Throws
IllegalArgumentException if the listener is not registered, or the argument is null.
See Also

public abstract void setEnableSessionCreation (boolean flag)

Controls whether new SSL sessions may be established by this socket. If session creations are not allowed, and there are no existing sessions to resume, there will be no successful handshaking.

Parameters
flag true indicates that sessions may be created; this is the default. false indicates that an existing session must be resumed
See Also

public abstract void setEnabledCipherSuites (String[] suites)

Sets the cipher suites enabled for use on this connection.

Each cipher suite in the suites parameter must have been listed by getSupportedCipherSuites(), or the method will fail. Following a successful call to this method, only suites listed in the suites parameter are enabled for use.

See getEnabledCipherSuites() for more information on why a specific ciphersuite may never be used on a connection.

Parameters
suites Names of all the cipher suites to enable
Throws
IllegalArgumentException when one or more of the ciphers named by the parameter is not supported, or when the parameter is null.
See Also

public abstract void setEnabledProtocols (String[] protocols)

Sets the protocol versions enabled for use on this connection.

The protocols must have been listed by getSupportedProtocols() as being supported. Following a successful call to this method, only protocols listed in the protocols parameter are enabled for use.

Parameters
protocols Names of all the protocols to enable.
Throws
IllegalArgumentException when one or more of the protocols named by the parameter is not supported or when the protocols parameter is null.
See Also

public abstract void setNeedClientAuth (boolean need)

Configures the socket to require client authentication. This option is only useful for sockets in the server mode.

A socket's client authentication setting is one of the following:

  • client authentication required
  • client authentication requested
  • no client authentication desired

Unlike setWantClientAuth(boolean), if this option is set and the client chooses not to provide authentication information about itself, the negotiations will stop and the connection will be dropped.

Calling this method overrides any previous setting made by this method or setWantClientAuth(boolean).

Parameters
need set to true if client authentication is required, or false if no client authentication is desired.
See Also

public void setSSLParameters (SSLParameters params)

Applies SSLParameters to this socket.

This means:

  • if params.getCipherSuites() is non-null, setEnabledCipherSuites() is called with that value
  • if params.getProtocols() is non-null, setEnabledProtocols() is called with that value
  • if params.getNeedClientAuth() or params.getWantClientAuth() return true, setNeedClientAuth(true) and setWantClientAuth(true) are called, respectively; otherwise setWantClientAuth(false) is called.

Parameters
params the parameters
Throws
IllegalArgumentException if the setEnabledCipherSuites() or the setEnabledProtocols() call fails

public abstract void setUseClientMode (boolean mode)

Configures the socket to use client (or server) mode when handshaking.

This method must be called before any handshaking occurs. Once handshaking has begun, the mode can not be reset for the life of this socket.

Servers normally authenticate themselves, and clients are not required to do so.

Parameters
mode true if the socket should start its handshaking in "client" mode
Throws
IllegalArgumentException if a mode change is attempted after the initial handshake has begun.
See Also

public abstract void setWantClientAuth (boolean want)

Configures the socket to request client authentication. This option is only useful for sockets in the server mode.

A socket's client authentication setting is one of the following:

  • client authentication required
  • client authentication requested
  • no client authentication desired

Unlike setNeedClientAuth(boolean), if this option is set and the client chooses not to provide authentication information about itself, the negotiations will continue.

Calling this method overrides any previous setting made by this method or setNeedClientAuth(boolean).

Parameters
want set to true if client authentication is requested, or false if no client authentication is desired.
See Also

public abstract void startHandshake ()

Starts an SSL handshake on this connection. Common reasons include a need to use new encryption keys, to change cipher suites, or to initiate a new session. To force complete reauthentication, the current session could be invalidated before starting this handshake.

If data has already been sent on the connection, it continues to flow during this handshake. When the handshake completes, this will be signaled with an event. This method is synchronous for the initial handshake on a connection and returns when the negotiated handshake is complete. Some protocols may not support multiple handshakes on an existing socket and may throw an IOException.

Throws
IOException on a network level error
See Also