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package javax.security.sasl;
/**
* Performs SASL authentication as a client.
*<p>
* A protocol library such as one for LDAP gets an instance of this
* class in order to perform authentication defined by a specific SASL
* mechanism. Invoking methods on the <tt>SaslClient</tt> instance
* process challenges and create responses according to the SASL
* mechanism implemented by the <tt>SaslClient</tt>.
* As the authentication proceeds, the instance
* encapsulates the state of a SASL client's authentication exchange.
*<p>
* Here's an example of how an LDAP library might use a <tt>SaslClient</tt>.
* It first gets an instance of a <tt>SaslClient</tt>:
*<blockquote><pre>
* SaslClient sc = Sasl.createSaslClient(mechanisms,
* authorizationId, protocol, serverName, props, callbackHandler);
*</pre></blockquote>
* It can then proceed to use the client for authentication.
* For example, an LDAP library might use the client as follows:
*<blockquote><pre>
* // Get initial response and send to server
* byte[] response = (sc.hasInitialResponse() ? sc.evaluateChallenge(new byte[0]) :
* null);
* LdapResult res = ldap.sendBindRequest(dn, sc.getName(), response);
* while (!sc.isComplete() &&
* (res.status == SASL_BIND_IN_PROGRESS || res.status == SUCCESS)) {
* response = sc.evaluateChallenge(res.getBytes());
* if (res.status == SUCCESS) {
* // we're done; don't expect to send another BIND
* if (response != null) {
* throw new SaslException(
* "Protocol error: attempting to send response after completion");
* }
* break;
* }
* res = ldap.sendBindRequest(dn, sc.getName(), response);
* }
* if (sc.isComplete() && res.status == SUCCESS) {
* String qop = (String) sc.getNegotiatedProperty(Sasl.QOP);
* if (qop != null
* && (qop.equalsIgnoreCase("auth-int")
* || qop.equalsIgnoreCase("auth-conf"))) {
*
* // Use SaslClient.wrap() and SaslClient.unwrap() for future
* // communication with server
* ldap.in = new SecureInputStream(sc, ldap.in);
* ldap.out = new SecureOutputStream(sc, ldap.out);
* }
* }
*</pre></blockquote>
*
* If the mechanism has an initial response, the library invokes
* <tt>evaluateChallenge()</tt> with an empty
* challenge and to get initial response.
* Protocols such as IMAP4, which do not include an initial response with
* their first authentication command to the server, initiates the
* authentication without first calling <tt>hasInitialResponse()</tt>
* or <tt>evaluateChallenge()</tt>.
* When the server responds to the command, it sends an initial challenge.
* For a SASL mechanism in which the client sends data first, the server should
* have issued a challenge with no data. This will then result in a call
* (on the client) to <tt>evaluateChallenge()</tt> with an empty challenge.
*
* @since 1.5
*
* @see Sasl
* @see SaslClientFactory
*
* @author Rosanna Lee
* @author Rob Weltman
*/
public abstract interface SaslClient {
/**
* Returns the IANA-registered mechanism name of this SASL client.
* (e.g. "CRAM-MD5", "GSSAPI").
* @return A non-null string representing the IANA-registered mechanism name.
*/
public abstract String getMechanismName();
/**
* Determines whether this mechanism has an optional initial response.
* If true, caller should call <tt>evaluateChallenge()</tt> with an
* empty array to get the initial response.
*
* @return true if this mechanism has an initial response.
*/
public abstract boolean hasInitialResponse();
/**
* Evaluates the challenge data and generates a response.
* If a challenge is received from the server during the authentication
* process, this method is called to prepare an appropriate next
* response to submit to the server.
*
* @param challenge The non-null challenge sent from the server.
* The challenge array may have zero length.
*
* @return The possibly null reponse to send to the server.
* It is null if the challenge accompanied a "SUCCESS" status and the challenge
* only contains data for the client to update its state and no response
* needs to be sent to the server. The response is a zero-length byte
* array if the client is to send a response with no data.
* @exception SaslException If an error occurred while processing
* the challenge or generating a response.
*/
public abstract byte[] evaluateChallenge(byte[] challenge)
throws SaslException;
/**
* Determines whether the authentication exchange has completed.
* This method may be called at any time, but typically, it
* will not be called until the caller has received indication
* from the server
* (in a protocol-specific manner) that the exchange has completed.
*
* @return true if the authentication exchange has completed; false otherwise.
*/
public abstract boolean isComplete();
/**
* Unwraps a byte array received from the server.
* This method can be called only after the authentication exchange has
* completed (i.e., when <tt>isComplete()</tt> returns true) and only if
* the authentication exchange has negotiated integrity and/or privacy
* as the quality of protection; otherwise, an
* <tt>IllegalStateException</tt> is thrown.
*<p>
* <tt>incoming</tt> is the contents of the SASL buffer as defined in RFC 2222
* without the leading four octet field that represents the length.
* <tt>offset</tt> and <tt>len</tt> specify the portion of <tt>incoming</tt>
* to use.
*
* @param incoming A non-null byte array containing the encoded bytes
* from the server.
* @param offset The starting position at <tt>incoming</tt> of the bytes to use.
* @param len The number of bytes from <tt>incoming</tt> to use.
* @return A non-null byte array containing the decoded bytes.
* @exception SaslException if <tt>incoming</tt> cannot be successfully
* unwrapped.
* @exception IllegalStateException if the authentication exchange has
* not completed, or if the negotiated quality of protection
* has neither integrity nor privacy.
*/
public abstract byte[] unwrap(byte[] incoming, int offset, int len)
throws SaslException;
/**
* Wraps a byte array to be sent to the server.
* This method can be called only after the authentication exchange has
* completed (i.e., when <tt>isComplete()</tt> returns true) and only if
* the authentication exchange has negotiated integrity and/or privacy
* as the quality of protection; otherwise, an
* <tt>IllegalStateException</tt> is thrown.
*<p>
* The result of this method will make up the contents of the SASL buffer
* as defined in RFC 2222 without the leading four octet field that
* represents the length.
* <tt>offset</tt> and <tt>len</tt> specify the portion of <tt>outgoing</tt>
* to use.
*
* @param outgoing A non-null byte array containing the bytes to encode.
* @param offset The starting position at <tt>outgoing</tt> of the bytes to use.
* @param len The number of bytes from <tt>outgoing</tt> to use.
* @return A non-null byte array containing the encoded bytes.
* @exception SaslException if <tt>outgoing</tt> cannot be successfully
* wrapped.
* @exception IllegalStateException if the authentication exchange has
* not completed, or if the negotiated quality of protection
* has neither integrity nor privacy.
*/
public abstract byte[] wrap(byte[] outgoing, int offset, int len)
throws SaslException;
/**
* Retrieves the negotiated property.
* This method can be called only after the authentication exchange has
* completed (i.e., when <tt>isComplete()</tt> returns true); otherwise, an
* <tt>IllegalStateException</tt> is thrown.
*
* @param propName The non-null property name.
* @return The value of the negotiated property. If null, the property was
* not negotiated or is not applicable to this mechanism.
* @exception IllegalStateException if this authentication exchange
* has not completed
*/
public abstract Object getNegotiatedProperty(String propName);
/**
* Disposes of any system resources or security-sensitive information
* the SaslClient might be using. Invoking this method invalidates
* the SaslClient instance. This method is idempotent.
* @throws SaslException If a problem was encountered while disposing
* the resources.
*/
public abstract void dispose() throws SaslException;
}