001/* SaslClient.java --
002   Copyright (C) 2003, 2004, 2005 Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
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006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
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014General Public License for more details.
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01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
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037
038
039package javax.security.sasl;
040
041/**
042 * <p>Performs SASL authentication as a client.</p>
043 *
044 * <p>A protocol library such as one for LDAP gets an instance of this class in
045 * order to perform authentication defined by a specific SASL mechanism.
046 * Invoking methods on the <code>SaslClient</code> instance process challenges
047 * and create responses according to the SASL mechanism implemented by the
048 * <code>SaslClient</code>. As the authentication proceeds, the instance
049 * encapsulates the state of a SASL client's authentication exchange.</p>
050 *
051 * <p>Here's an example of how an LDAP library might use a <code>SaslClient</code>.
052 * It first gets an instance of a SaslClient:</p>
053 * <pre>
054 *SaslClient sc =
055 *      Sasl.createSaslClient(mechanisms, authorizationID, protocol,
056 *                            serverName, props, callbackHandler);
057 * </pre>
058 *
059 * <p>It can then proceed to use the client for authentication. For example, an
060 * LDAP library might use the client as follows:</p>
061 * <pre>
062 * // Get initial response and send to server
063 *byte[] response = sc.hasInitialResponse()
064 *      ? sc.evaluateChallenge(new byte[0]) : null;
065 *LdapResult res = ldap.sendBindRequest(dn, sc.getName(), response);
066 *while (!sc.isComplete()
067 *       && ((res.status == SASL_BIND_IN_PROGRESS) || (res.status == SUCCESS))) {
068 *   response = sc.evaluateChallenge( res.getBytes() );
069 *   if (res.status == SUCCESS) {
070 *      // we're done; don't expect to send another BIND
071 *      if ( response != null ) {
072 *         throw new SaslException(
073 *               "Protocol error: attempting to send response after completion");
074 *      }
075 *      break;
076 *   }
077 *   res = ldap.sendBindRequest(dn, sc.getName(), response);
078 *}
079 *if (sc.isComplete() && (res.status == SUCCESS) ) {
080 *   String qop = (String)sc.getNegotiatedProperty(Sasl.QOP);
081 *   if ((qop != null)
082 *         && (qop.equalsIgnoreCase("auth-int")
083 *            || qop.equalsIgnoreCase("auth-conf"))) {
084 *      // Use SaslClient.wrap() and SaslClient.unwrap() for future
085 *      // communication with server
086 *      ldap.in = new SecureInputStream(sc, ldap.in);
087 *      ldap.out = new SecureOutputStream(sc, ldap.out);
088 *   }
089 *}
090 * </pre>
091 *
092 * <p>If the mechanism has an initial response, the library invokes
093 * {@link #evaluateChallenge(byte[])} with an empty challenge to get the initial
094 * response. Protocols such as IMAP4, which do not include an initial response
095 * with their first authentication command to the server, initiate the
096 * authentication without first calling {@link #hasInitialResponse()} or
097 * {@link #evaluateChallenge(byte[])}. When the server responds to the command,
098 * it sends an initial challenge. For a SASL mechanism in which the client sends
099 * data first, the server should have issued a challenge with no data. This will
100 * then result in a call (on the client) to {@link #evaluateChallenge(byte[])}
101 * with an empty challenge.</p>
102 *
103 * @see Sasl
104 * @see SaslClientFactory
105 *
106 * @since 1.5
107 */
108public interface SaslClient
109{
110
111  /**
112   * Returns the IANA-registered mechanism name of this SASL client. (e.g.
113   * "CRAM-MD5", "GSSAPI").
114   *
115   * @return a non-null string representing the IANA-registered mechanism name.
116   */
117  String getMechanismName();
118
119  /**
120   * Determines if this mechanism has an optional initial response. If
121   * <code>true</code>, caller should call {@link #evaluateChallenge(byte[])}
122   * with an empty array to get the initial response.
123   *
124   * @return <code>true</code> if this mechanism has an initial response.
125   */
126  boolean hasInitialResponse();
127
128  /**
129   * Evaluates the challenge data and generates a response. If a challenge is
130   * received from the server during the authentication process, this method is
131   * called to prepare an appropriate next response to submit to the server.
132   *
133   * @param challenge the non-null challenge sent from the server. The
134   * challenge array may have zero length.
135   * @return the possibly <code>null</code> reponse to send to the server. It
136   * is <code>null</code> if the challenge accompanied a "SUCCESS" status and
137   * the challenge only contains data for the client to update its state and no
138   * response needs to be sent to the server. The response is a zero-length
139   * byte array if the client is to send a response with no data.
140   * @throws SaslException if an error occurred while processing the challenge
141   * or generating a response.
142   */
143  byte[] evaluateChallenge(byte[] challenge) throws SaslException;
144
145  /**
146   * Determines if the authentication exchange has completed. This method may
147   * be called at any time, but typically, it will not be called until the
148   * caller has received indication from the server (in a protocol-specific
149   * manner) that the exchange has completed.
150   *
151   * @return <code>true</code> if the authentication exchange has completed;
152   * <code>false</code> otherwise.
153   */
154  boolean isComplete();
155
156  /**
157   * <p>Unwraps a byte array received from the server. This method can be
158   * called only after the authentication exchange has completed (i.e., when
159   * {@link #isComplete()} returns <code>true</code>) and only if the
160   * authentication exchange has negotiated integrity and/or privacy as the
161   * quality of protection; otherwise, an {@link IllegalStateException} is
162   * thrown.</p>
163   *
164   * <p><code>incoming</code> is the contents of the SASL buffer as defined in
165   * RFC 2222 without the leading four octet field that represents the length.
166   * <code>offset</code> and <code>len</code> specify the portion of incoming
167   * to use.</p>
168   *
169   * @param incoming a non-null byte array containing the encoded bytes from
170   * the server.
171   * @param offset the starting position at <code>incoming</code> of the bytes
172   * to use.
173   * @param len the number of bytes from <code>incoming</code> to use.
174   * @return a non-null byte array containing the decoded bytes.
175   * @throws SaslException if <code>incoming</code> cannot be successfully
176   * unwrapped.
177   * @throws IllegalStateException if the authentication exchange has not
178   * completed, or if the negotiated quality of protection has neither
179   * integrity nor privacy.
180   */
181  byte[] unwrap(byte[] incoming, int offset, int len) throws SaslException;
182
183  /**
184   * <p>Wraps a byte array to be sent to the server. This method can be called
185   * only after the authentication exchange has completed (i.e., when
186   * {@link #isComplete()} returns <code>true</code>) and only if the
187   * authentication exchange has negotiated integrity and/or privacy as the
188   * quality of protection; otherwise, an {@link IllegalStateException} is
189   * thrown.</p>
190   *
191   * <p>The result of this method will make up the contents of the SASL buffer
192   * as defined in RFC 2222 without the leading four octet field that
193   * represents the length. <code>offset</code> and <code>len</code> specify
194   * the portion of <code>outgoing</code> to use.</p>
195   *
196   * @param outgoing a non-null byte array containing the bytes to encode.
197   * @param offset the starting position at <code>outgoing</code> of the bytes
198   * to use.
199   * @param len the number of bytes from <code>outgoing</code> to use.
200   * @return a non-null byte array containing the encoded bytes.
201   * @throws SaslException if <code>outgoing</code> cannot be successfully
202   * wrapped.
203   * @throws IllegalStateException if the authentication exchange has not
204   * completed, or if the negotiated quality of protection has neither
205   * integrity nor privacy.
206   */
207  byte[] wrap(byte[] outgoing, int offset, int len) throws SaslException;
208
209  /**
210   * Retrieves the negotiated property. This method can be called only after
211   * the authentication exchange has completed (i.e., when {@link #isComplete()}
212   * returns <code>true</code>); otherwise, an {@link IllegalStateException} is
213   * thrown.
214   *
215   * @param propName the non-null property name.
216   * @return the value of the negotiated property. If <code>null</code>, the
217   * property was not negotiated or is not applicable to this mechanism.
218   * @throws IllegalStateException if this authentication exchange has not
219   * completed.
220   */
221  Object getNegotiatedProperty(String propName);
222
223  /**
224   * Disposes of any system resources or security-sensitive information the
225   * <code>SaslClient</code> might be using. Invoking this method invalidates
226   * the <code>SaslClient</code> instance. This method is idempotent.
227   *
228   * @throws SaslException if a problem was encountered while disposing of the
229   * resources.
230   */
231  void dispose() throws SaslException;
232}