001    /* SaslClient.java --
002       Copyright (C) 2003, 2004, 2005 Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
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021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
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026    As a special exception, the copyright holders of this library give you
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036    exception statement from your version. */
037    
038    
039    package 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     */
108    public 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    }