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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      */
PKIXBuilderParameters(Set<TrustAnchor> trustAnchors, CertSelector targetConstraints)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      */
PKIXBuilderParameters(KeyStore keystore, CertSelector targetConstraints)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      */
setMaxPathLength(int maxPathLength)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      */
getMaxPathLength()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      */
toString()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 }
200