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package java.security.cert;

import java.security.AccessController;

import java.security.InvalidAlgorithmParameterException;

import java.security.NoSuchAlgorithmException;

import java.security.NoSuchProviderException;

import java.security.PrivilegedAction;

import java.security.Provider;

import java.security.Security;

import sun.security.util.Debug;

import sun.security.jca.*;

import sun.security.jca.GetInstance.Instance;

/**

 * A class for building certification paths (also known as certificate chains).

 * <p>

 * This class uses a provider-based architecture.

 * To create a <code>CertPathBuilder</code>, call

 * one of the static <code>getInstance</code> methods, passing in the

 * algorithm name of the <code>CertPathBuilder</code> desired and optionally

 * the name of the provider desired.

 * <p>

 * Once a <code>CertPathBuilder</code> object has been created, certification

 * paths can be constructed by calling the {@link #build build} method and

 * passing it an algorithm-specific set of parameters. If successful, the

 * result (including the <code>CertPath</code> that was built) is returned

 * in an object that implements the <code>CertPathBuilderResult</code>

 * interface.

 *

 * <p> Every implementation of the Java platform is required to support the

 * following standard <code>CertPathBuilder</code> algorithm:

 * <ul>

 * <li><tt>PKIX</tt></li>

 * </ul>

 * This algorithm is described in the <a href=

 * "{@docRoot}/../technotes/guides/security/StandardNames.html#CertPathBuilder">

 * CertPathBuilder section</a> of the

 * Java Cryptography Architecture Standard Algorithm Name Documentation.

 * Consult the release documentation for your implementation to see if any

 * other algorithms are supported.

 *

 * <p>

 * <b>Concurrent Access</b>

 * <p>

 * The static methods of this class are guaranteed to be thread-safe.

 * Multiple threads may concurrently invoke the static methods defined in

 * this class with no ill effects.

 * <p>

 * However, this is not true for the non-static methods defined by this class.

 * Unless otherwise documented by a specific provider, threads that need to

 * access a single <code>CertPathBuilder</code> instance concurrently should

 * synchronize amongst themselves and provide the necessary locking. Multiple

 * threads each manipulating a different <code>CertPathBuilder</code> instance

 * need not synchronize.

 *

 * @see CertPath

 *

 * @since       1.4

 * @author      Sean Mullan

 * @author      Yassir Elley

 */

public class CertPathBuilder {

    /*

     * Constant to lookup in the Security properties file to determine

     * the default certpathbuilder type. In the Security properties file,

     * the default certpathbuilder type is given as:

     * <pre>

     * certpathbuilder.type=PKIX

     * </pre>

     */

    private static final String CPB_TYPE = "certpathbuilder.type";

    private static final Debug debug = Debug.getInstance("certpath");

    private CertPathBuilderSpi builderSpi;

    private Provider provider;

    private String algorithm;

    /**

     * Creates a <code>CertPathBuilder</code> object of the given algorithm,

     * and encapsulates the given provider implementation (SPI object) in it.

     *

     * @param builderSpi the provider implementation

     * @param provider the provider

     * @param algorithm the algorithm name

     */

    protected CertPathBuilder(CertPathBuilderSpi builderSpi, Provider provider,

        String algorithm)

    {

        this.builderSpi = builderSpi;

        this.provider = provider;

        this.algorithm = algorithm;

    }

    /**

     * Returns a <code>CertPathBuilder</code> object that implements the

     * specified algorithm.

     *

     * <p> This method traverses the list of registered security Providers,

     * starting with the most preferred Provider.

     * A new CertPathBuilder object encapsulating the

     * CertPathBuilderSpi implementation from the first

     * Provider that supports the specified algorithm is returned.

     *

     * <p> Note that the list of registered providers may be retrieved via

     * the {@link Security#getProviders() Security.getProviders()} method.

     *

     * @param algorithm the name of the requested <code>CertPathBuilder</code>

     *  algorithm.  See the CertPathBuilder section in the <a href=

     *  "{@docRoot}/../technotes/guides/security/StandardNames.html#CertPathBuilder">

     * Java Cryptography Architecture Standard Algorithm Name Documentation</a>

     * for information about standard algorithm names.

     *

     * @return a <code>CertPathBuilder</code> object that implements the

     *          specified algorithm.

     *

     * @throws NoSuchAlgorithmException if no Provider supports a

     *          CertPathBuilderSpi implementation for the

     *          specified algorithm.

     *

     * @see java.security.Provider

     */

    public static CertPathBuilder getInstance(String algorithm)

            throws NoSuchAlgorithmException {

        Instance instance = GetInstance.getInstance("CertPathBuilder",

            CertPathBuilderSpi.class, algorithm);

        return new CertPathBuilder((CertPathBuilderSpi)instance.impl,

            instance.provider, algorithm);

    }

    /**

     * Returns a <code>CertPathBuilder</code> object that implements the

     * specified algorithm.

     *

     * <p> A new CertPathBuilder object encapsulating the

     * CertPathBuilderSpi implementation from the specified provider

     * is returned.  The specified provider must be registered

     * in the security provider list.

     *

     * <p> Note that the list of registered providers may be retrieved via

     * the {@link Security#getProviders() Security.getProviders()} method.

     *

     * @param algorithm the name of the requested <code>CertPathBuilder</code>

     *  algorithm.  See the CertPathBuilder section in the <a href=

     *  "{@docRoot}/../technotes/guides/security/StandardNames.html#CertPathBuilder">

     * Java Cryptography Architecture Standard Algorithm Name Documentation</a>

     * for information about standard algorithm names.

     *

     * @param provider the name of the provider.

     *

     * @return a <code>CertPathBuilder</code> object that implements the

     *          specified algorithm.

     *

     * @throws NoSuchAlgorithmException if a CertPathBuilderSpi

     *          implementation for the specified algorithm is not

     *          available from the specified provider.

     *

     * @throws NoSuchProviderException if the specified provider is not

     *          registered in the security provider list.

     *

     * @exception IllegalArgumentException if the <code>provider</code> is

     *          null or empty.

     *

     * @see java.security.Provider

     */

    public static CertPathBuilder getInstance(String algorithm, String provider)

           throws NoSuchAlgorithmException, NoSuchProviderException {

        Instance instance = GetInstance.getInstance("CertPathBuilder",

            CertPathBuilderSpi.class, algorithm, provider);

        return new CertPathBuilder((CertPathBuilderSpi)instance.impl,

            instance.provider, algorithm);

    }

    /**

     * Returns a <code>CertPathBuilder</code> object that implements the

     * specified algorithm.

     *

     * <p> A new CertPathBuilder object encapsulating the

     * CertPathBuilderSpi implementation from the specified Provider

     * object is returned.  Note that the specified Provider object

     * does not have to be registered in the provider list.

     *

     * @param algorithm the name of the requested <code>CertPathBuilder</code>

     *  algorithm.  See the CertPathBuilder section in the <a href=

     *  "{@docRoot}/../technotes/guides/security/StandardNames.html#CertPathBuilder">

     * Java Cryptography Architecture Standard Algorithm Name Documentation</a>

     * for information about standard algorithm names.

     *

     * @param provider the provider.

     *

     * @return a <code>CertPathBuilder</code> object that implements the

     *          specified algorithm.

     *

     * @exception NoSuchAlgorithmException if a CertPathBuilderSpi

     *          implementation for the specified algorithm is not available

     *          from the specified Provider object.

     *

     * @exception IllegalArgumentException if the <code>provider</code> is

     *          null.

     *

     * @see java.security.Provider

     */

    public static CertPathBuilder getInstance(String algorithm,

            Provider provider) throws NoSuchAlgorithmException {

        Instance instance = GetInstance.getInstance("CertPathBuilder",

            CertPathBuilderSpi.class, algorithm, provider);

        return new CertPathBuilder((CertPathBuilderSpi)instance.impl,

            instance.provider, algorithm);

    }

    /**

     * Returns the provider of this <code>CertPathBuilder</code>.

     *

     * @return the provider of this <code>CertPathBuilder</code>

     */

    public final Provider getProvider() {

        return this.provider;

    }

    /**

     * Returns the name of the algorithm of this <code>CertPathBuilder</code>.

     *

     * @return the name of the algorithm of this <code>CertPathBuilder</code>

     */

    public final String getAlgorithm() {

        return this.algorithm;

    }

    /**

     * Attempts to build a certification path using the specified algorithm

     * parameter set.

     *

     * @param params the algorithm parameters

     * @return the result of the build algorithm

     * @throws CertPathBuilderException if the builder is unable to construct

     *  a certification path that satisfies the specified parameters

     * @throws InvalidAlgorithmParameterException if the specified parameters

     * are inappropriate for this <code>CertPathBuilder</code>

     */

    public final CertPathBuilderResult build(CertPathParameters params)

        throws CertPathBuilderException, InvalidAlgorithmParameterException

    {

        return builderSpi.engineBuild(params);

    }

    /**

     * Returns the default <code>CertPathBuilder</code> type as specified in

     * the Java security properties file, or the string "PKIX"

     * if no such property exists. The Java security properties file is

     * located in the file named <JAVA_HOME>/lib/security/java.security.

     * <JAVA_HOME> refers to the value of the java.home system property,

     * and specifies the directory where the JRE is installed.

     *

     * <p>The default <code>CertPathBuilder</code> type can be used by

     * applications that do not want to use a hard-coded type when calling one

     * of the <code>getInstance</code> methods, and want to provide a default

     * type in case a user does not specify its own.

     *

     * <p>The default <code>CertPathBuilder</code> type can be changed by

     * setting the value of the "certpathbuilder.type" security property

     * (in the Java security properties file) to the desired type.

     *

     * @return the default <code>CertPathBuilder</code> type as specified

     * in the Java security properties file, or the string "PKIX"

     * if no such property exists.

     */

    public final static String getDefaultType() {

        String cpbtype;

        cpbtype = AccessController.doPrivileged(new PrivilegedAction<String>() {

            public String run() {

                return Security.getProperty(CPB_TYPE);

            }

        });

        if (cpbtype == null) {

            cpbtype = "PKIX";

        }

        return cpbtype;

    }

}