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| 1 | /* | ||
| 2 | * Copyright (c) 1999, 2005, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package javax.security.auth.callback; | ||
| 27 | |||
| 28 | /** | ||
| 29 | * <p> An application implements a <code>CallbackHandler</code> and passes | ||
| 30 | * it to underlying security services so that they may interact with | ||
| 31 | * the application to retrieve specific authentication data, | ||
| 32 | * such as usernames and passwords, or to display certain information, | ||
| 33 | * such as error and warning messages. | ||
| 34 | * | ||
| 35 | * <p> CallbackHandlers are implemented in an application-dependent fashion. | ||
| 36 | * For example, implementations for an application with a graphical user | ||
| 37 | * interface (GUI) may pop up windows to prompt for requested information | ||
| 38 | * or to display error messages. An implementation may also choose to obtain | ||
| 39 | * requested information from an alternate source without asking the end user. | ||
| 40 | * | ||
| 41 | * <p> Underlying security services make requests for different types | ||
| 42 | * of information by passing individual Callbacks to the | ||
| 43 | * <code>CallbackHandler</code>. The <code>CallbackHandler</code> | ||
| 44 | * implementation decides how to retrieve and display information | ||
| 45 | * depending on the Callbacks passed to it. For example, | ||
| 46 | * if the underlying service needs a username and password to | ||
| 47 | * authenticate a user, it uses a <code>NameCallback</code> and | ||
| 48 | * <code>PasswordCallback</code>. The <code>CallbackHandler</code> | ||
| 49 | * can then choose to prompt for a username and password serially, | ||
| 50 | * or to prompt for both in a single window. | ||
| 51 | * | ||
| 52 | * <p> A default <code>CallbackHandler</code> class implementation | ||
| 53 | * may be specified in the <i>auth.login.defaultCallbackHandler</i> | ||
| 54 | * security property. The security property can be set | ||
| 55 | * in the Java security properties file located in the file named | ||
| 56 | * <JAVA_HOME>/lib/security/java.security. | ||
| 57 | * <JAVA_HOME> refers to the value of the java.home system property, | ||
| 58 | * and specifies the directory where the JRE is installed. | ||
| 59 | * | ||
| 60 | * <p> If the security property is set to the fully qualified name of a | ||
| 61 | * <code>CallbackHandler</code> implementation class, | ||
| 62 | * then a <code>LoginContext</code> will load the specified | ||
| 63 | * <code>CallbackHandler</code> and pass it to the underlying LoginModules. | ||
| 64 | * The <code>LoginContext</code> only loads the default handler | ||
| 65 | * if it was not provided one. | ||
| 66 | * | ||
| 67 | * <p> All default handler implementations must provide a public | ||
| 68 | * zero-argument constructor. | ||
| 69 | * | ||
| 70 | */ | ||
| 71 | public interface CallbackHandler { | ||
| 72 | |||
| 73 | /** | ||
| 74 | * <p> Retrieve or display the information requested in the | ||
| 75 | * provided Callbacks. | ||
| 76 | * | ||
| 77 | * <p> The <code>handle</code> method implementation checks the | ||
| 78 | * instance(s) of the <code>Callback</code> object(s) passed in | ||
| 79 | * to retrieve or display the requested information. | ||
| 80 | * The following example is provided to help demonstrate what an | ||
| 81 | * <code>handle</code> method implementation might look like. | ||
| 82 | * This example code is for guidance only. Many details, | ||
| 83 | * including proper error handling, are left out for simplicity. | ||
| 84 | * | ||
| 85 | * <pre> | ||
| 86 | * public void handle(Callback[] callbacks) | ||
| 87 | * throws IOException, UnsupportedCallbackException { | ||
| 88 | * | ||
| 89 | * for (int i = 0; i < callbacks.length; i++) { | ||
| 90 | * if (callbacks[i] instanceof TextOutputCallback) { | ||
| 91 | * | ||
| 92 | * // display the message according to the specified type | ||
| 93 | * TextOutputCallback toc = (TextOutputCallback)callbacks[i]; | ||
| 94 | * switch (toc.getMessageType()) { | ||
| 95 | * case TextOutputCallback.INFORMATION: | ||
| 96 | * System.out.println(toc.getMessage()); | ||
| 97 | * break; | ||
| 98 | * case TextOutputCallback.ERROR: | ||
| 99 | * System.out.println("ERROR: " + toc.getMessage()); | ||
| 100 | * break; | ||
| 101 | * case TextOutputCallback.WARNING: | ||
| 102 | * System.out.println("WARNING: " + toc.getMessage()); | ||
| 103 | * break; | ||
| 104 | * default: | ||
| 105 | * throw new IOException("Unsupported message type: " + | ||
| 106 | * toc.getMessageType()); | ||
| 107 | * } | ||
| 108 | * | ||
| 109 | * } else if (callbacks[i] instanceof NameCallback) { | ||
| 110 | * | ||
| 111 | * // prompt the user for a username | ||
| 112 | * NameCallback nc = (NameCallback)callbacks[i]; | ||
| 113 | * | ||
| 114 | * // ignore the provided defaultName | ||
| 115 | * System.err.print(nc.getPrompt()); | ||
| 116 | * System.err.flush(); | ||
| 117 | * nc.setName((new BufferedReader | ||
| 118 | * (new InputStreamReader(System.in))).readLine()); | ||
| 119 | * | ||
| 120 | * } else if (callbacks[i] instanceof PasswordCallback) { | ||
| 121 | * | ||
| 122 | * // prompt the user for sensitive information | ||
| 123 | * PasswordCallback pc = (PasswordCallback)callbacks[i]; | ||
| 124 | * System.err.print(pc.getPrompt()); | ||
| 125 | * System.err.flush(); | ||
| 126 | * pc.setPassword(readPassword(System.in)); | ||
| 127 | * | ||
| 128 | * } else { | ||
| 129 | * throw new UnsupportedCallbackException | ||
| 130 | * (callbacks[i], "Unrecognized Callback"); | ||
| 131 | * } | ||
| 132 | * } | ||
| 133 | * } | ||
| 134 | * | ||
| 135 | * // Reads user password from given input stream. | ||
| 136 | * private char[] readPassword(InputStream in) throws IOException { | ||
| 137 | * // insert code to read a user password from the input stream | ||
| 138 | * } | ||
| 139 | * </pre> | ||
| 140 | * | ||
| 141 | * @param callbacks an array of <code>Callback</code> objects provided | ||
| 142 | * by an underlying security service which contains | ||
| 143 | * the information requested to be retrieved or displayed. | ||
| 144 | * | ||
| 145 | * @exception java.io.IOException if an input or output error occurs. <p> | ||
| 146 | * | ||
| 147 | * @exception UnsupportedCallbackException if the implementation of this | ||
| 148 | * method does not support one or more of the Callbacks | ||
| 149 | * specified in the <code>callbacks</code> parameter. | ||
| 150 | */ | ||
| 151 | void handle(Callback[] callbacks) | ||
| 152 | throws java.io.IOException, UnsupportedCallbackException; | ||
| 153 | } | ||