/* SaslClient.java --
Copyright (C) 2003, 2004 Free Software Foundation, Inc.
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package javax.security.sasl;
/**
* <p>Performs SASL authentication as a client.</p>
*
* <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 <code>SaslClient</code> instance process challenges
* and create responses according to the SASL mechanism implemented by the
* <code>SaslClient</code>. As the authentication proceeds, the instance
* encapsulates the state of a SASL client's authentication exchange.</p>
*
* <p>Here's an example of how an LDAP library might use a <code>SaslClient</code>.
* It first gets an instance of a SaslClient:</p>
* <pre>
*SaslClient sc =
* Sasl.createSaslClient(mechanisms, authorizationID, protocol,
* serverName, props, callbackHandler);
* </pre>
*
* <p>It can then proceed to use the client for authentication. For example, an
* LDAP library might use the client as follows:</p>
* <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>
*
* <p>If the mechanism has an initial response, the library invokes
* {@link #evaluateChallenge(byte[])} with an empty challenge to get the initial
* response. Protocols such as IMAP4, which do not include an initial response
* with their first authentication command to the server, initiate the
* authentication without first calling {@link #hasInitialResponse()} or
* {@link #evaluateChallenge(byte[])}. 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 {@link #evaluateChallenge(byte[])}
* with an empty challenge.</p>
*
* @see Sasl
* @see SaslClientFactory
*/
public 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.
*/
String getMechanismName();
/**
* Determines if this mechanism has an optional initial response. If
* <code>true</code>, caller should call {@link #evaluateChallenge(byte[])}
* with an empty array to get the initial response.
*
* @return <code>true</code> if this mechanism has an initial response.
*/
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 <code>null</code> reponse to send to the server. It
* is <code>null</code> 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.
* @throws SaslException if an error occurred while processing the challenge
* or generating a response.
*/
byte[] evaluateChallenge(byte[] challenge) throws SaslException;
/**
* Determines if 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 <code>true</code> if the authentication exchange has completed;
* <code>false</code> otherwise.
*/
boolean isComplete();
/**
* <p>Unwraps a byte array received from the server. This method can be
* called only after the authentication exchange has completed (i.e., when
* {@link #isComplete()} returns <code>true</code>) and only if the
* authentication exchange has negotiated integrity and/or privacy as the
* quality of protection; otherwise, an {@link IllegalStateException} is
* thrown.</p>
*
* <p><code>incoming</code> is the contents of the SASL buffer as defined in
* RFC 2222 without the leading four octet field that represents the length.
* <code>offset</code> and <code>len</code> specify the portion of incoming
* to use.</p>
*
* @param incoming a non-null byte array containing the encoded bytes from
* the server.
* @param offset the starting position at <code>incoming</code> of the bytes
* to use.
* @param len the number of bytes from <code>incoming</code> to use.
* @return a non-null byte array containing the decoded bytes.
* @throws SaslException if <code>incoming</code> cannot be successfully
* unwrapped.
* @throws IllegalStateException if the authentication exchange has not
* completed, or if the negotiated quality of protection has neither
* integrity nor privacy.
*/
byte[] unwrap(byte[] incoming, int offset, int len) throws SaslException;
/**
* <p>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
* {@link #isComplete()} returns <code>true</code>) and only if the
* authentication exchange has negotiated integrity and/or privacy as the
* quality of protection; otherwise, an {@link IllegalStateException} is
* thrown.</p>
*
* <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. <code>offset</code> and <code>len</code> specify
* the portion of <code>outgoing</code> to use.</p>
*
* @param outgoing a non-null byte array containing the bytes to encode.
* @param offset the starting position at <code>outgoing</code> of the bytes
* to use.
* @param len the number of bytes from <code>outgoing</code> to use.
* @return a non-null byte array containing the encoded bytes.
* @throws SaslException if <code>outgoing</code> cannot be successfully
* wrapped.
* @throws IllegalStateException if the authentication exchange has not
* completed, or if the negotiated quality of protection has neither
* integrity nor privacy.
*/
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 {@link #isComplete()}
* returns <code>true</code>); otherwise, an {@link IllegalStateException} is
* thrown.
*
* @param propName the non-null property name.
* @return the value of the negotiated property. If <code>null</code>, the
* property was not negotiated or is not applicable to this mechanism.
* @throws IllegalStateException if this authentication exchange has not
* completed.
*/
Object getNegotiatedProperty(String propName) throws SaslException;
/**
* Disposes of any system resources or security-sensitive information the
* <code>SaslClient</code> might be using. Invoking this method invalidates
* the <code>SaslClient</code> instance. This method is idempotent.
*
* @throws SaslException if a problem was encountered while disposing of the
* resources.
*/
void dispose() throws SaslException;
}