/*

 * Copyright 2002-2006 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * 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).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package sun.security.validator;

import java.util.*;

import java.security.*;

import java.security.cert.*;

import javax.security.auth.x500.X500Principal;

/**

 * Validator implementation built on the PKIX CertPath API. This

 * implementation will be emphasized going forward.<p>

 *

 * Note that the validate() implementation tries to use a PKIX validator

 * if that appears possible and a PKIX builder otherwise. This increases

 * performance and currently also leads to better exception messages

 * in case of failures.

 *

 * @author Andreas Sterbenz

 */

public final class PKIXValidator extends Validator {

    // enable use of the validator if possible

    private final static boolean TRY_VALIDATOR = true;

    private final Set<X509Certificate> trustedCerts;

    private final PKIXBuilderParameters parameterTemplate;

    private int certPathLength = -1;

    // needed only for the validator

    private Map<X500Principal, X509Certificate> trustedSubjects;

    private CertificateFactory factory;

    private boolean plugin = false;

    PKIXValidator(String variant, Collection<X509Certificate> trustedCerts) {

        super(TYPE_PKIX, variant);

        if (trustedCerts instanceof Set) {

            this.trustedCerts = (Set<X509Certificate>)trustedCerts;

        } else {

            this.trustedCerts = new HashSet<X509Certificate>(trustedCerts);

        }

        Set<TrustAnchor> trustAnchors = new HashSet<TrustAnchor>();

        for (X509Certificate cert : trustedCerts) {

            trustAnchors.add(new TrustAnchor(cert, null));

        }

        try {

            parameterTemplate = new PKIXBuilderParameters(trustAnchors, null);

        } catch (InvalidAlgorithmParameterException e) {

            throw new RuntimeException("Unexpected error: " + e.toString(), e);

        }

        setDefaultParameters(variant);

        initCommon();

    }

    PKIXValidator(String variant, PKIXBuilderParameters params) {

        super(TYPE_PKIX, variant);

        trustedCerts = new HashSet<X509Certificate>();

        for (TrustAnchor anchor : params.getTrustAnchors()) {

            X509Certificate cert = anchor.getTrustedCert();

            if (cert != null) {

                trustedCerts.add(cert);

            }

        }

        parameterTemplate = params;

        initCommon();

    }

    private void initCommon() {

        if (TRY_VALIDATOR == false) {

            return;

        }

        trustedSubjects = new HashMap<X500Principal, X509Certificate>();

        for (X509Certificate cert : trustedCerts) {

            trustedSubjects.put(cert.getSubjectX500Principal(), cert);

        }

        try {

            factory = CertificateFactory.getInstance("X.509");

        } catch (CertificateException e) {

            throw new RuntimeException("Internal error", e);

        }

        plugin = variant.equals(VAR_PLUGIN_CODE_SIGNING);

    }

    public Collection<X509Certificate> getTrustedCertificates() {

        return trustedCerts;

    }

    /**

     * Returns the length of the last certification path that is validated by

     * CertPathValidator. This is intended primarily as a callback mechanism

     * for PKIXCertPathCheckers to determine the length of the certification

     * path that is being validated. It is necessary since engineValidate()

     * may modify the length of the path.

     *

     * @return the length of the last certification path passed to

     *   CertPathValidator.validate, or -1 if it has not been invoked yet

     */

    public int getCertPathLength() {

        return certPathLength;

    }

    /**

     * Set J2SE global default PKIX parameters. Currently, hardcoded to disable

     * revocation checking. In the future, this should be configurable.

     */

    private void setDefaultParameters(String variant) {

        parameterTemplate.setRevocationEnabled(false);

    }

    /**

     * Return the PKIX parameters used by this instance. An application may

     * modify the parameters but must make sure not to perform any concurrent

     * validations.

     */

    public PKIXBuilderParameters getParameters() {

        return parameterTemplate;

    }

    X509Certificate[] engineValidate(X509Certificate[] chain,

            Collection<X509Certificate> otherCerts, Object parameter)

            throws CertificateException {

        if ((chain == null) || (chain.length == 0)) {

            throw new CertificateException

                ("null or zero-length certificate chain");

        }

        if (TRY_VALIDATOR) {

            // check if chain contains trust anchor

            for (int i = 0; i < chain.length; i++) {

                if (trustedCerts.contains(chain[i])) {

                    if (i == 0) {

                        return new X509Certificate[] {chain[0]};

                    }

                    // Remove and call validator

                    X509Certificate[] newChain = new X509Certificate[i];

                    System.arraycopy(chain, 0, newChain, 0, i);

                    return doValidate(newChain);

                }

            }

            // not self issued and apparently issued by trust anchor?

            X509Certificate last = chain[chain.length - 1];

            X500Principal issuer = last.getIssuerX500Principal();

            X500Principal subject = last.getSubjectX500Principal();

            if (trustedSubjects.containsKey(issuer) && !issuer.equals(subject)

                && isSignatureValid(trustedSubjects.get(issuer), last)) {

                return doValidate(chain);

            }

            // don't fallback to builder if called from plugin/webstart

            if (plugin) {

                // Validate chain even if no trust anchor is found. This

                // allows plugin/webstart to make sure the chain is

                // otherwise valid

                if (chain.length > 1) {

                    X509Certificate[] newChain =

                        new X509Certificate[chain.length-1];

                    System.arraycopy(chain, 0, newChain, 0, newChain.length);

                    // temporarily set last cert as sole trust anchor

                    PKIXBuilderParameters params =

                        (PKIXBuilderParameters) parameterTemplate.clone();

                    try {

                        params.setTrustAnchors

                            (Collections.singleton(new TrustAnchor

                                (chain[chain.length-1], null)));

                    } catch (InvalidAlgorithmParameterException iape) {

                        // should never occur, but ...

                        throw new CertificateException(iape);

                    }

                    doValidate(newChain, params);

                }

                // if the rest of the chain is valid, throw exception

                // indicating no trust anchor was found

                throw new ValidatorException

                    (ValidatorException.T_NO_TRUST_ANCHOR);

            }

            // otherwise, fall back to builder

        }

        return doBuild(chain, otherCerts);

    }

    private boolean isSignatureValid(X509Certificate iss, X509Certificate sub) {

        if (plugin) {

            try {

                sub.verify(iss.getPublicKey());

            } catch (Exception ex) {

                return false;

            }

            return true;

        }

        return true; // only check if PLUGIN is set

    }

    private static X509Certificate[] toArray(CertPath path, TrustAnchor anchor)

            throws CertificateException {

        List<? extends java.security.cert.Certificate> list =

                                                path.getCertificates();

        X509Certificate[] chain = new X509Certificate[list.size() + 1];

        list.toArray(chain);

        X509Certificate trustedCert = anchor.getTrustedCert();

        if (trustedCert == null) {

            throw new ValidatorException

                ("TrustAnchor must be specified as certificate");

        }

        chain[chain.length - 1] = trustedCert;

        return chain;

    }

    /**

     * Set the check date (for debugging).

     */

    private void setDate(PKIXBuilderParameters params) {

        Date date = validationDate;

        if (date != null) {

            params.setDate(date);

        }

    }

    private X509Certificate[] doValidate(X509Certificate[] chain)

            throws CertificateException {

        PKIXBuilderParameters params =

            (PKIXBuilderParameters)parameterTemplate.clone();

        return doValidate(chain, params);

    }

    private X509Certificate[] doValidate(X509Certificate[] chain,

            PKIXBuilderParameters params) throws CertificateException {

        try {

            setDate(params);

            // do the validation

            CertPathValidator validator = CertPathValidator.getInstance("PKIX");

            CertPath path = factory.generateCertPath(Arrays.asList(chain));

            certPathLength = chain.length;

            PKIXCertPathValidatorResult result =

                (PKIXCertPathValidatorResult)validator.validate(path, params);

            return toArray(path, result.getTrustAnchor());

        } catch (GeneralSecurityException e) {

            throw new ValidatorException

                ("PKIX path validation failed: " + e.toString(), e);

        }

    }

    private X509Certificate[] doBuild(X509Certificate[] chain,

        Collection<X509Certificate> otherCerts) throws CertificateException {

        try {

            PKIXBuilderParameters params =

                (PKIXBuilderParameters)parameterTemplate.clone();

            setDate(params);

            // setup target constraints

            X509CertSelector selector = new X509CertSelector();

            selector.setCertificate(chain[0]);

            params.setTargetCertConstraints(selector);

            // setup CertStores

            Collection<X509Certificate> certs =

                                        new ArrayList<X509Certificate>();

            certs.addAll(Arrays.asList(chain));

            if (otherCerts != null) {

                certs.addAll(otherCerts);

            }

            CertStore store = CertStore.getInstance("Collection",

                                new CollectionCertStoreParameters(certs));

            params.addCertStore(store);

            // do the build

            CertPathBuilder builder = CertPathBuilder.getInstance("PKIX");

            PKIXCertPathBuilderResult result =

                (PKIXCertPathBuilderResult)builder.build(params);

            return toArray(result.getCertPath(), result.getTrustAnchor());

        } catch (GeneralSecurityException e) {

            throw new ValidatorException

                ("PKIX path building failed: " + e.toString(), e);

        }

    }

}