pkixbuilderparameters.java

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/*
 * @(#)PKIXBuilderParameters.java	1.11 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.security.cert;

import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidParameterException;
import java.util.Set;

/**
 * Parameters used as input for the PKIX <code>CertPathBuilder</code> 
 * algorithm.
 * <p>
 * A PKIX <code>CertPathBuilder</code> uses these parameters to {@link 
 * CertPathBuilder#build build} a <code>CertPath</code> which has been 
 * validated according to the PKIX certification path validation algorithm.
 *
 * <p>To instantiate a <code>PKIXBuilderParameters</code> object, an
 * application must specify one or more <i>most-trusted CAs</i> as defined by
 * the PKIX certification path validation algorithm. The most-trusted CA 
 * can be specified using one of two constructors. An application 
 * can call {@link #PKIXBuilderParameters(Set, CertSelector) 
 * PKIXBuilderParameters(Set, CertSelector)}, specifying a 
 * <code>Set</code> of <code>TrustAnchor</code> objects, each of which 
 * identifies a most-trusted CA. Alternatively, an application can call 
 * {@link #PKIXBuilderParameters(KeyStore, CertSelector)
 * PKIXBuilderParameters(KeyStore, CertSelector)}, specifying a 
 * <code>KeyStore</code> instance containing trusted certificate entries, each 
 * of which will be considered as a most-trusted CA.
 *
 * <p>In addition, an application must specify constraints on the target 
 * certificate that the <code>CertPathBuilder</code> will attempt 
 * to build a path to. The constraints are specified as a 
 * <code>CertSelector</code> object. These constraints should provide the 
 * <code>CertPathBuilder</code> with enough search criteria to find the target 
 * certificate. Minimal criteria for an <code>X509Certificate</code> usually 
 * include the subject name and/or one or more subject alternative names.
 * If enough criteria is not specified, the <code>CertPathBuilder</code> 
 * may throw a <code>CertPathBuilderException</code>.
 * <p>
 * <b>Concurrent Access</b>
 * <p>
 * Unless otherwise specified, the methods defined in this class are not
 * thread-safe. Multiple threads that need to access a single
 * object concurrently should synchronize amongst themselves and
 * provide the necessary locking. Multiple threads each manipulating
 * separate objects need not synchronize.
 *
 * @see CertPathBuilder
 * 
 * @version 	1.11 01/23/03
 * @since 	1.4
 * @author	Sean Mullan
 */
public class PKIXBuilderParameters extends PKIXParameters {

    private int maxPathLength = 5;

    /**
     * Creates an instance of <code>PKIXBuilderParameters</code> with
     * the specified <code>Set</code> of most-trusted CAs. 
     * Each element of the set is a {@link TrustAnchor TrustAnchor}.
     *
     * <p>Note that the <code>Set</code> is copied to protect against
     * subsequent modifications.
     *
     * @param trustAnchors a <code>Set</code> of <code>TrustAnchor</code>s
     * @param targetConstraints a <code>CertSelector</code> specifying the 
     * constraints on the target certificate 
     * @throws InvalidAlgorithmParameterException if <code>trustAnchors</code> 
     * is empty <code>(trustAnchors.isEmpty() == true)</code>
     * @throws NullPointerException if <code>trustAnchors</code> is 
     * <code>null</code>
     * @throws ClassCastException if any of the elements of
     * <code>trustAnchors</code> are not of type 
     * <code>java.security.cert.TrustAnchor</code>
     */
    public PKIXBuilderParameters(Set trustAnchors, CertSelector 
	targetConstraints) throws InvalidAlgorithmParameterException
    {
        super(trustAnchors);
	setTargetCertConstraints(targetConstraints);
    }

    /**
     * Creates an instance of <code>PKIXBuilderParameters</code> that
     * populates the set of most-trusted CAs from the trusted
     * certificate entries contained in the specified <code>KeyStore</code>.
     * Only keystore entries that contain trusted <code>X509Certificate</code>s
     * are considered; all other certificate types are ignored.
     *
     * @param keystore a <code>KeyStore</code> from which the set of 
     * most-trusted CAs will be populated
     * @param targetConstraints a <code>CertSelector</code> specifying the 
     * constraints on the target certificate 
     * @throws KeyStoreException if <code>keystore</code> has not been 
     * initialized
     * @throws InvalidAlgorithmParameterException if <code>keystore</code> does
     * not contain at least one trusted certificate entry
     * @throws NullPointerException if <code>keystore</code> is 
     * <code>null</code>
     */
    public PKIXBuilderParameters(KeyStore keystore, 
        CertSelector targetConstraints) 
        throws KeyStoreException, InvalidAlgorithmParameterException 
    {
	super(keystore);
	setTargetCertConstraints(targetConstraints);
    }

    /**
     * Sets the value of the maximum number of non-self-issued intermediate
     * certificates that may exist in a certification path. A certificate
     * is self-issued if the DNs that appear in the subject and issuer
     * fields are identical and are not empty. Note that the last certificate
     * in a certification path is not an intermediate certificate, and is not
     * included in this limit. Usually the last certificate is an end entity
     * certificate, but it can be a CA certificate. A PKIX 
     * <code>CertPathBuilder</code> instance must not build 
     * paths longer than the length specified.
     *
     * <p> A value of 0 implies that the path can only contain
     * a single certificate. A value of -1 implies that the
     * path length is unconstrained (i.e. there is no maximum).
     * The default maximum path length, if not specified, is 5.
     * Setting a value less than -1 will cause an exception to be thrown.
     *
     * <p> If any of the CA certificates contain the 
     * <code>BasicConstraintsExtension</code>, the value of the
     * <code>pathLenConstraint</code> field of the extension overrides
     * the maximum path length parameter whenever the result is a
     * certification path of smaller length.
     *
     * @param maxPathLength the maximum number of non-self-issued intermediate
     *  certificates that may exist in a certification path
     * @throws InvalidParameterException if <code>maxPathLength</code> is set 
     *  to a value less than -1
     *
     * @see #getMaxPathLength
     */
    public void setMaxPathLength(int maxPathLength) {
	if (maxPathLength < -1) {
	    throw new InvalidParameterException("the maximum path "
		+ "length parameter can not be less than -1");
	}
	this.maxPathLength = maxPathLength;
    }

    /**
     * Returns the value of the maximum number of intermediate non-self-issued
     * certificates that may exist in a certification path. See
     * the {@link #setMaxPathLength} method for more details.
     *
     * @return the maximum number of non-self-issued intermediate certificates 
     *  that may exist in a certification path, or -1 if there is no limit
     *
     * @see #setMaxPathLength
     */
    public int getMaxPathLength() {
        return maxPathLength;
    }

    /**
     * Returns a formatted string describing the parameters.
     *
     * @return a formatted string describing the parameters
     */
    public String toString() {
        StringBuffer sb = new StringBuffer();
        sb.append("[\n");
	sb.append(super.toString());
	sb.append("  Maximum Path Length: " + maxPathLength + "\n");
	sb.append("]\n");
	return sb.toString();
    }
}