Java tutorial
/* * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ 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 {@code SaslClient} instance * process challenges and create responses according to the SASL * mechanism implemented by the {@code SaslClient}. * 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 {@code SaslClient}. * It first gets an instance of a {@code SaslClient}: *<blockquote><pre>{@code * 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>{@code * // 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 * {@code evaluateChallenge()} 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 {@code hasInitialResponse()} * or {@code evaluateChallenge()}. * 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 {@code evaluateChallenge()} 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 {@code evaluateChallenge()} 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 response 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 {@code isComplete()} returns true) and only if * the authentication exchange has negotiated integrity and/or privacy * as the quality of protection; otherwise, an * {@code IllegalStateException} is thrown. *<p> * {@code incoming} is the contents of the SASL buffer as defined in RFC 2222 * without the leading four octet field that represents the length. * {@code offset} and {@code len} specify the portion of {@code incoming} * to use. * * @param incoming A non-null byte array containing the encoded bytes * from the server. * @param offset The starting position at {@code incoming} of the bytes to use. * @param len The number of bytes from {@code incoming} to use. * @return A non-null byte array containing the decoded bytes. * @exception SaslException if {@code incoming} 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 {@code isComplete()} returns true) and only if * the authentication exchange has negotiated integrity and/or privacy * as the quality of protection; otherwise, an * {@code IllegalStateException} 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. * {@code offset} and {@code len} specify the portion of {@code outgoing} * to use. * * @param outgoing A non-null byte array containing the bytes to encode. * @param offset The starting position at {@code outgoing} of the bytes to use. * @param len The number of bytes from {@code outgoing} to use. * @return A non-null byte array containing the encoded bytes. * @exception SaslException if {@code outgoing} 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 {@code isComplete()} returns true); otherwise, an * {@code IllegalStateException} is thrown. * <p> * The {@link Sasl} class includes several well-known property names * (For example, {@link Sasl#QOP}). A SASL provider can support other * properties which are specific to the vendor and/or a mechanism. * * @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; }