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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
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7    * published by the Free Software Foundation.  Oracle designates this
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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
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24   */
25  
26  package java.security.cert;
27  
28  import java.security.KeyStore;
29  import java.security.KeyStoreException;
30  import java.security.InvalidAlgorithmParameterException;
31  import java.security.InvalidParameterException;
32  import java.util.Set;
33  
34  /**
35   * Parameters used as input for the PKIX {@code CertPathBuilder}
36   * algorithm.
37   * <p>
38   * A PKIX {@code CertPathBuilder} uses these parameters to {@link
39   * CertPathBuilder#build build} a {@code CertPath} which has been
40   * validated according to the PKIX certification path validation algorithm.
41   *
42   * <p>To instantiate a {@code PKIXBuilderParameters} object, an
43   * application must specify one or more <i>most-trusted CAs</i> as defined by
44   * the PKIX certification path validation algorithm. The most-trusted CA
45   * can be specified using one of two constructors. An application
46   * can call {@link #PKIXBuilderParameters(Set, CertSelector)
47   * PKIXBuilderParameters(Set, CertSelector)}, specifying a
48   * {@code Set} of {@code TrustAnchor} objects, each of which
49   * identifies a most-trusted CA. Alternatively, an application can call
50   * {@link #PKIXBuilderParameters(KeyStore, CertSelector)
51   * PKIXBuilderParameters(KeyStore, CertSelector)}, specifying a
52   * {@code KeyStore} instance containing trusted certificate entries, each
53   * of which will be considered as a most-trusted CA.
54   *
55   * <p>In addition, an application must specify constraints on the target
56   * certificate that the {@code CertPathBuilder} will attempt
57   * to build a path to. The constraints are specified as a
58   * {@code CertSelector} object. These constraints should provide the
59   * {@code CertPathBuilder} with enough search criteria to find the target
60   * certificate. Minimal criteria for an {@code X509Certificate} usually
61   * include the subject name and/or one or more subject alternative names.
62   * If enough criteria is not specified, the {@code CertPathBuilder}
63   * may throw a {@code CertPathBuilderException}.
64   * <p>
65   * <b>Concurrent Access</b>
66   * <p>
67   * Unless otherwise specified, the methods defined in this class are not
68   * thread-safe. Multiple threads that need to access a single
69   * object concurrently should synchronize amongst themselves and
70   * provide the necessary locking. Multiple threads each manipulating
71   * separate objects need not synchronize.
72   *
73   * @see CertPathBuilder
74   *
75   * @since       1.4
76   * @author      Sean Mullan
77   */
78  public class PKIXBuilderParameters extends PKIXParameters {
79  
80      private int maxPathLength = 5;
81  
82      /**
83       * Creates an instance of {@code PKIXBuilderParameters} with
84       * the specified {@code Set} of most-trusted CAs.
85       * Each element of the set is a {@link TrustAnchor TrustAnchor}.
86       *
87       * <p>Note that the {@code Set} is copied to protect against
88       * subsequent modifications.
89       *
90       * @param trustAnchors a {@code Set} of {@code TrustAnchor}s
91       * @param targetConstraints a {@code CertSelector} specifying the
92       * constraints on the target certificate
93       * @throws InvalidAlgorithmParameterException if {@code trustAnchors}
94       * is empty {@code (trustAnchors.isEmpty() == true)}
95       * @throws NullPointerException if {@code trustAnchors} is
96       * {@code null}
97       * @throws ClassCastException if any of the elements of
98       * {@code trustAnchors} are not of type
99       * {@code java.security.cert.TrustAnchor}
100      */
101     public PKIXBuilderParameters(Set<TrustAnchor> trustAnchors, CertSelector
102         targetConstraints) throws InvalidAlgorithmParameterException
103     {
104         super(trustAnchors);
105         setTargetCertConstraints(targetConstraints);
106     }
107 
108     /**
109      * Creates an instance of {@code PKIXBuilderParameters} that
110      * populates the set of most-trusted CAs from the trusted
111      * certificate entries contained in the specified {@code KeyStore}.
112      * Only keystore entries that contain trusted {@code X509Certificate}s
113      * are considered; all other certificate types are ignored.
114      *
115      * @param keystore a {@code KeyStore} from which the set of
116      * most-trusted CAs will be populated
117      * @param targetConstraints a {@code CertSelector} specifying the
118      * constraints on the target certificate
119      * @throws KeyStoreException if {@code keystore} has not been
120      * initialized
121      * @throws InvalidAlgorithmParameterException if {@code keystore} does
122      * not contain at least one trusted certificate entry
123      * @throws NullPointerException if {@code keystore} is
124      * {@code null}
125      */
126     public PKIXBuilderParameters(KeyStore keystore,
127         CertSelector targetConstraints)
128         throws KeyStoreException, InvalidAlgorithmParameterException
129     {
130         super(keystore);
131         setTargetCertConstraints(targetConstraints);
132     }
133 
134     /**
135      * Sets the value of the maximum number of non-self-issued intermediate
136      * certificates that may exist in a certification path. A certificate
137      * is self-issued if the DNs that appear in the subject and issuer
138      * fields are identical and are not empty. Note that the last certificate
139      * in a certification path is not an intermediate certificate, and is not
140      * included in this limit. Usually the last certificate is an end entity
141      * certificate, but it can be a CA certificate. A PKIX
142      * {@code CertPathBuilder} instance must not build
143      * paths longer than the length specified.
144      *
145      * <p> A value of 0 implies that the path can only contain
146      * a single certificate. A value of -1 implies that the
147      * path length is unconstrained (i.e. there is no maximum).
148      * The default maximum path length, if not specified, is 5.
149      * Setting a value less than -1 will cause an exception to be thrown.
150      *
151      * <p> If any of the CA certificates contain the
152      * {@code BasicConstraintsExtension}, the value of the
153      * {@code pathLenConstraint} field of the extension overrides
154      * the maximum path length parameter whenever the result is a
155      * certification path of smaller length.
156      *
157      * @param maxPathLength the maximum number of non-self-issued intermediate
158      *  certificates that may exist in a certification path
159      * @throws InvalidParameterException if {@code maxPathLength} is set
160      *  to a value less than -1
161      *
162      * @see #getMaxPathLength
163      */
164     public void setMaxPathLength(int maxPathLength) {
165         if (maxPathLength < -1) {
166             throw new InvalidParameterException("the maximum path "
167                 + "length parameter can not be less than -1");
168         }
169         this.maxPathLength = maxPathLength;
170     }
171 
172     /**
173      * Returns the value of the maximum number of intermediate non-self-issued
174      * certificates that may exist in a certification path. See
175      * the {@link #setMaxPathLength} method for more details.
176      *
177      * @return the maximum number of non-self-issued intermediate certificates
178      *  that may exist in a certification path, or -1 if there is no limit
179      *
180      * @see #setMaxPathLength
181      */
182     public int getMaxPathLength() {
183         return maxPathLength;
184     }
185 
186     /**
187      * Returns a formatted string describing the parameters.
188      *
189      * @return a formatted string describing the parameters
190      */
191     public String toString() {
192         StringBuffer sb = new StringBuffer();
193         sb.append("[\n");
194         sb.append(super.toString());
195         sb.append("  Maximum Path Length: " + maxPathLength + "\n");
196         sb.append("]\n");
197         return sb.toString();
198     }
199 }