1 /*
2 * Copyright 2000-2003 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.security.cert;
27
28 import java.util.Collection;
29 import java.util.Set;
30
31 /**
32 * An abstract class that performs one or more checks on an
33 * <code>X509Certificate</code>.
34 *
35 * <p>A concrete implementation of the <code>PKIXCertPathChecker</code> class
36 * can be created to extend the PKIX certification path validation algorithm.
37 * For example, an implementation may check for and process a critical private
38 * extension of each certificate in a certification path.
39 *
40 * <p>Instances of <code>PKIXCertPathChecker</code> are passed as parameters
41 * using the {@link PKIXParameters#setCertPathCheckers setCertPathCheckers}
42 * or {@link PKIXParameters#addCertPathChecker addCertPathChecker} methods
43 * of the <code>PKIXParameters</code> and <code>PKIXBuilderParameters</code>
44 * class. Each of the <code>PKIXCertPathChecker</code>s {@link #check check}
45 * methods will be called, in turn, for each certificate processed by a PKIX
46 * <code>CertPathValidator</code> or <code>CertPathBuilder</code>
47 * implementation.
48 *
49 * <p>A <code>PKIXCertPathChecker</code> may be called multiple times on
50 * successive certificates in a certification path. Concrete subclasses
51 * are expected to maintain any internal state that may be necessary to
52 * check successive certificates. The {@link #init init} method is used
53 * to initialize the internal state of the checker so that the certificates
54 * of a new certification path may be checked. A stateful implementation
55 * <b>must</b> override the {@link #clone clone} method if necessary in
56 * order to allow a PKIX <code>CertPathBuilder</code> to efficiently
57 * backtrack and try other paths. In these situations, the
58 * <code>CertPathBuilder</code> is able to restore prior path validation
59 * states by restoring the cloned <code>PKIXCertPathChecker</code>s.
60 *
61 * <p>The order in which the certificates are presented to the
62 * <code>PKIXCertPathChecker</code> may be either in the forward direction
63 * (from target to most-trusted CA) or in the reverse direction (from
64 * most-trusted CA to target). A <code>PKIXCertPathChecker</code> implementation
65 * <b>must</b> support reverse checking (the ability to perform its checks when
66 * it is presented with certificates in the reverse direction) and <b>may</b>
67 * support forward checking (the ability to perform its checks when it is
68 * presented with certificates in the forward direction). The
69 * {@link #isForwardCheckingSupported isForwardCheckingSupported} method
70 * indicates whether forward checking is supported.
71 * <p>
72 * Additional input parameters required for executing the check may be
73 * specified through constructors of concrete implementations of this class.
74 * <p>
75 * <b>Concurrent Access</b>
76 * <p>
77 * Unless otherwise specified, the methods defined in this class are not
78 * thread-safe. Multiple threads that need to access a single
79 * object concurrently should synchronize amongst themselves and
80 * provide the necessary locking. Multiple threads each manipulating
81 * separate objects need not synchronize.
82 *
83 * @see PKIXParameters
84 * @see PKIXBuilderParameters
85 *
86 * @since 1.4
87 * @author Yassir Elley
88 * @author Sean Mullan
89 */
90 public abstract class PKIXCertPathChecker implements Cloneable {
91
92 /**
93 * Default constructor.
94 */
95 protected PKIXCertPathChecker() {}
96
97 /**
98 * Initializes the internal state of this <code>PKIXCertPathChecker</code>.
99 * <p>
100 * The <code>forward</code> flag specifies the order that
101 * certificates will be passed to the {@link #check check} method
102 * (forward or reverse). A <code>PKIXCertPathChecker</code> <b>must</b>
103 * support reverse checking and <b>may</b> support forward checking.
104 *
105 * @param forward the order that certificates are presented to
106 * the <code>check</code> method. If <code>true</code>, certificates
107 * are presented from target to most-trusted CA (forward); if
108 * <code>false</code>, from most-trusted CA to target (reverse).
109 * @throws CertPathValidatorException if this
110 * <code>PKIXCertPathChecker</code> is unable to check certificates in
111 * the specified order; it should never be thrown if the forward flag
112 * is false since reverse checking must be supported
113 */
114 public abstract void init(boolean forward)
115 throws CertPathValidatorException;
116
117 /**
118 * Indicates if forward checking is supported. Forward checking refers
119 * to the ability of the <code>PKIXCertPathChecker</code> to perform
120 * its checks when certificates are presented to the <code>check</code>
121 * method in the forward direction (from target to most-trusted CA).
122 *
123 * @return <code>true</code> if forward checking is supported,
124 * <code>false</code> otherwise
125 */
126 public abstract boolean isForwardCheckingSupported();
127
128 /**
129 * Returns an immutable <code>Set</code> of X.509 certificate extensions
130 * that this <code>PKIXCertPathChecker</code> supports (i.e. recognizes, is
131 * able to process), or <code>null</code> if no extensions are supported.
132 * <p>
133 * Each element of the set is a <code>String</code> representing the
134 * Object Identifier (OID) of the X.509 extension that is supported.
135 * The OID is represented by a set of nonnegative integers separated by
136 * periods.
137 * <p>
138 * All X.509 certificate extensions that a <code>PKIXCertPathChecker</code>
139 * might possibly be able to process should be included in the set.
140 *
141 * @return an immutable <code>Set</code> of X.509 extension OIDs (in
142 * <code>String</code> format) supported by this
143 * <code>PKIXCertPathChecker</code>, or <code>null</code> if no
144 * extensions are supported
145 */
146 public abstract Set<String> getSupportedExtensions();
147
148 /**
149 * Performs the check(s) on the specified certificate using its internal
150 * state and removes any critical extensions that it processes from the
151 * specified collection of OID strings that represent the unresolved
152 * critical extensions. The certificates are presented in the order
153 * specified by the <code>init</code> method.
154 *
155 * @param cert the <code>Certificate</code> to be checked
156 * @param unresolvedCritExts a <code>Collection</code> of OID strings
157 * representing the current set of unresolved critical extensions
158 * @exception CertPathValidatorException if the specified certificate does
159 * not pass the check
160 */
161 public abstract void check(Certificate cert,
162 Collection<String> unresolvedCritExts)
163 throws CertPathValidatorException;
164
165 /**
166 * Returns a clone of this object. Calls the <code>Object.clone()</code>
167 * method.
168 * All subclasses which maintain state must support and
169 * override this method, if necessary.
170 *
171 * @return a copy of this <code>PKIXCertPathChecker</code>
172 */
173 public Object clone() {
174 try {
175 return super.clone();
176 } catch (CloneNotSupportedException e) {
177 /* Cannot happen */
178 throw new InternalError(e.toString());
179 }
180 }
181 }
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