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 *

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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

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package sun.security.provider.certpath;

import java.io.IOException;

import java.security.AccessController;

import java.security.InvalidAlgorithmParameterException;

import java.security.cert.CertPath;

import java.security.cert.CertPathParameters;

import java.security.cert.CertPathValidatorException;

import java.security.cert.CertPathValidatorSpi;

import java.security.cert.CertPathValidatorResult;

import java.security.cert.PKIXCertPathChecker;

import java.security.cert.PKIXCertPathValidatorResult;

import java.security.cert.PKIXParameters;

import java.security.cert.PKIXReason;

import java.security.cert.PolicyNode;

import java.security.cert.TrustAnchor;

import java.security.cert.X509Certificate;

import java.security.cert.X509CertSelector;

import java.util.Collections;

import java.util.List;

import java.util.ArrayList;

import java.util.Date;

import java.util.Set;

import javax.security.auth.x500.X500Principal;

import sun.security.util.Debug;

/**

 * This class implements the PKIX validation algorithm for certification

 * paths consisting exclusively of <code>X509Certificates</code>. It uses

 * the specified input parameter set (which must be a

 * <code>PKIXParameters</code> object) and signature provider (if any).

 *

 * @since       1.4

 * @author      Yassir Elley

 */

public class PKIXCertPathValidator extends CertPathValidatorSpi {

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

    private Date testDate;

    private List<PKIXCertPathChecker> userCheckers;

    private String sigProvider;

    private BasicChecker basicChecker;

    /**

     * Default constructor.

     */

    public PKIXCertPathValidator() {}

    /**

     * Validates a certification path consisting exclusively of

     * <code>X509Certificate</code>s using the PKIX validation algorithm,

     * which uses the specified input parameter set.

     * The input parameter set must be a <code>PKIXParameters</code> object.

     *

     * @param cp the X509 certification path

     * @param param the input PKIX parameter set

     * @return the result

     * @exception CertPathValidatorException Exception thrown if cert path

     * does not validate.

     * @exception InvalidAlgorithmParameterException if the specified

     * parameters are inappropriate for this certification path validator

     */

    public CertPathValidatorResult engineValidate(CertPath cp,

        CertPathParameters param)

        throws CertPathValidatorException, InvalidAlgorithmParameterException

    {

        if (debug != null)

            debug.println("PKIXCertPathValidator.engineValidate()...");

        if (!(param instanceof PKIXParameters)) {

            throw new InvalidAlgorithmParameterException("inappropriate "

                + "parameters, must be an instance of PKIXParameters");

        }

        if (!cp.getType().equals("X.509") && !cp.getType().equals("X509")) {

            throw new InvalidAlgorithmParameterException("inappropriate "

                + "certification path type specified, must be X.509 or X509");

        }

        PKIXParameters pkixParam = (PKIXParameters) param;

        // Make sure that none of the trust anchors include name constraints

        // (not supported).

        Set<TrustAnchor> anchors = pkixParam.getTrustAnchors();

        for (TrustAnchor anchor : anchors) {

            if (anchor.getNameConstraints() != null) {

                throw new InvalidAlgorithmParameterException

                    ("name constraints in trust anchor not supported");

            }

        }

        // the certpath which has been passed in (cp)

        // has the target cert as the first certificate - we

        // need to keep this cp so we can return it

        // in case of an exception and for policy qualifier

        // processing - however, for certpath validation,

        // we need to create a reversed path, where we reverse the

        // ordering so that the target cert is the last certificate

        // Must copy elements of certList into a new modifiable List before

        // calling Collections.reverse().

        ArrayList<X509Certificate> certList = new ArrayList<X509Certificate>

            ((List<X509Certificate>)cp.getCertificates());

        if (debug != null) {

            if (certList.isEmpty()) {

                debug.println("PKIXCertPathValidator.engineValidate() "

                    + "certList is empty");

            }

            debug.println("PKIXCertPathValidator.engineValidate() "

                + "reversing certpath...");

        }

        Collections.reverse(certList);

        // now certList has the target cert as the last cert and we

        // can proceed with normal validation

        populateVariables(pkixParam);

        // Retrieve the first certificate in the certpath

        // (to be used later in pre-screening)

        X509Certificate firstCert = null;

        if (!certList.isEmpty()) {

            firstCert = certList.get(0);

        }

        CertPathValidatorException lastException = null;

        // We iterate through the set of trust anchors until we find

        // one that works at which time we stop iterating

        for (TrustAnchor anchor : anchors) {

            X509Certificate trustedCert = anchor.getTrustedCert();

            if (trustedCert != null) {

                if (debug != null) {

                    debug.println("PKIXCertPathValidator.engineValidate() "

                        + "anchor.getTrustedCert() != null");

                }

                // if this trust anchor is not worth trying,

                // we move on to the next one

                if (!isWorthTrying(trustedCert, firstCert)) {

                    continue;

                }

                if (debug != null) {

                    debug.println("anchor.getTrustedCert()."

                        + "getSubjectX500Principal() = "

                        + trustedCert.getSubjectX500Principal());

                }

            } else {

                if (debug != null) {

                    debug.println("PKIXCertPathValidator.engineValidate(): "

                        + "anchor.getTrustedCert() == null");

                }

            }

            try {

                PolicyNodeImpl rootNode = new PolicyNodeImpl(null,

                    PolicyChecker.ANY_POLICY, null, false,

                    Collections.singleton(PolicyChecker.ANY_POLICY), false);

                PolicyNode policyTree =

                    doValidate(anchor, cp, certList, pkixParam, rootNode);

                // if this anchor works, return success

                return new PKIXCertPathValidatorResult(anchor, policyTree,

                    basicChecker.getPublicKey());

            } catch (CertPathValidatorException cpe) {

                // remember this exception

                lastException = cpe;

            }

        }

        // could not find a trust anchor that verified

        // (a) if we did a validation and it failed, use that exception

        if (lastException != null) {

            throw lastException;

        }

        // (b) otherwise, generate new exception

        throw new CertPathValidatorException

            ("Path does not chain with any of the trust anchors",

             null, null, -1, PKIXReason.NO_TRUST_ANCHOR);

    }

    /**

     * Internal method to do some simple checks to see if a given cert is

     * worth trying to validate in the chain.

     */

    private boolean isWorthTrying(X509Certificate trustedCert,

                                  X509Certificate firstCert)

    {

        if (debug != null) {

            debug.println("PKIXCertPathValidator.isWorthTrying() checking "

                + "if this trusted cert is worth trying ...");

        }

        if (firstCert == null) {

            return true;

        }

        // the subject of the trusted cert should match the

        // issuer of the first cert in the certpath

        X500Principal trustedSubject = trustedCert.getSubjectX500Principal();

        if (trustedSubject.equals(firstCert.getIssuerX500Principal())) {

            if (debug != null)

                debug.println("YES - try this trustedCert");

            return true;

        } else {

            if (debug != null)

                debug.println("NO - don't try this trustedCert");

            return false;

        }

    }

    /**

     * Internal method to setup the internal state

     */

    private void populateVariables(PKIXParameters pkixParam)

    {

        // default value for testDate is current time

        testDate = pkixParam.getDate();

        if (testDate == null) {

            testDate = new Date(System.currentTimeMillis());

        }

        userCheckers = pkixParam.getCertPathCheckers();

        sigProvider = pkixParam.getSigProvider();

        if (pkixParam.isRevocationEnabled()) {

            // Examine OCSP security property

        }

    }

    /**

     * Internal method to actually validate a constructed path.

     *

     * @return the valid policy tree

     */

    private PolicyNode doValidate(

            TrustAnchor anchor, CertPath cpOriginal,

            ArrayList<X509Certificate> certList, PKIXParameters pkixParam,

            PolicyNodeImpl rootNode) throws CertPathValidatorException

    {

        int certPathLen = certList.size();

        basicChecker = new BasicChecker(anchor, testDate, sigProvider, false);

        KeyChecker keyChecker = new KeyChecker(certPathLen,

            pkixParam.getTargetCertConstraints());

        ConstraintsChecker constraintsChecker =

            new ConstraintsChecker(certPathLen);

        PolicyChecker policyChecker =

            new PolicyChecker(pkixParam.getInitialPolicies(), certPathLen,

                              pkixParam.isExplicitPolicyRequired(),

                              pkixParam.isPolicyMappingInhibited(),

                              pkixParam.isAnyPolicyInhibited(),

                              pkixParam.getPolicyQualifiersRejected(),

                              rootNode);

        ArrayList<PKIXCertPathChecker> certPathCheckers =

            new ArrayList<PKIXCertPathChecker>();

        // add standard checkers that we will be using

        certPathCheckers.add(keyChecker);

        certPathCheckers.add(constraintsChecker);

        certPathCheckers.add(policyChecker);

        certPathCheckers.add(basicChecker);

        // only add a revocationChecker if revocation is enabled

        if (pkixParam.isRevocationEnabled()) {

            // Use OCSP if it has been enabled

                OCSPChecker ocspChecker =

                certPathCheckers.add(ocspChecker);

            }

            // Always use CRLs

            certPathCheckers.add(revocationChecker);

        }

        // add user-specified checkers

        certPathCheckers.addAll(userCheckers);

        PKIXMasterCertPathValidator masterValidator =

            new PKIXMasterCertPathValidator(certPathCheckers);

        masterValidator.validate(cpOriginal, certList);

        return policyChecker.getPolicyTree();

    }

}