/*
 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.security.provider.certpath;

import java.io.IOException;
import java.security.GeneralSecurityException;
import java.security.Principal;
import java.security.cert.CertificateException;
import java.security.cert.CertPathValidatorException;
import java.security.cert.CertStore;
import java.security.cert.CertStoreException;
import java.security.cert.PKIXBuilderParameters;
import java.security.cert.PKIXCertPathChecker;
import java.security.cert.PKIXParameters;
import java.security.cert.PKIXReason;
import java.security.cert.TrustAnchor;
import java.security.cert.X509Certificate;
import java.security.cert.X509CertSelector;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.LinkedList;
import java.util.Set;

import javax.security.auth.x500.X500Principal;

import sun.security.provider.certpath.PKIX.BuilderParams;
import sun.security.util.Debug;
import sun.security.x509.Extension;
import static sun.security.x509.PKIXExtensions.*;
import sun.security.x509.X500Name;
import sun.security.x509.X509CertImpl;
import sun.security.x509.PolicyMappingsExtension;

/**
 * This class represents a reverse builder, which is able to retrieve
 * matching certificates from CertStores and verify a particular certificate
 * against a ReverseState.
 *
 * @since       1.4
 * @author      Sean Mullan
 * @author      Yassir Elley
 */

class ReverseBuilder extends Builder {

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

    private final Set<String> initPolicies;

    /**
     * Initialize the builder with the input parameters.
     *
     * @param params the parameter set used to build a certification path
     */
    ReverseBuilder(BuilderParams buildParams) {
        super(buildParams);

        Set<String> initialPolicies = buildParams.initialPolicies();
        initPolicies = new HashSet<String>();
        if (initialPolicies.isEmpty()) {
            // if no initialPolicies are specified by user, set
            // initPolicies to be anyPolicy by default
            initPolicies.add(PolicyChecker.ANY_POLICY);
        } else {
            initPolicies.addAll(initialPolicies);
        }
    }

    /**
     * Retrieves all certs from the specified CertStores that satisfy the
     * requirements specified in the parameters and the current
     * PKIX state (name constraints, policy constraints, etc).
     *
     * @param currentState the current state.
     *        Must be an instance of <code>ReverseState</code>
     * @param certStores list of CertStores
     */
    @Override
    Collection<X509Certificate> getMatchingCerts
        (State currState, List<CertStore> certStores)
        throws CertStoreException, CertificateException, IOException
    {
        ReverseState currentState = (ReverseState) currState;

        if (debug != null)
            debug.println("In ReverseBuilder.getMatchingCerts.");

        /*
         * The last certificate could be an EE or a CA certificate
         * (we may be building a partial certification path or
         * establishing trust in a CA).
         *
         * Try the EE certs before the CA certs. It will be more
         * common to build a path to an end entity.
         */
        Collection<X509Certificate> certs =
            getMatchingEECerts(currentState, certStores);
        certs.addAll(getMatchingCACerts(currentState, certStores));

        return certs;
    }

    /*
     * Retrieves all end-entity certificates which satisfy constraints
     * and requirements specified in the parameters and PKIX state.
     */
    private Collection<X509Certificate> getMatchingEECerts
        (ReverseState currentState, List<CertStore> certStores)
        throws CertStoreException, CertificateException, IOException {

        /*
         * Compose a CertSelector to filter out
         * certs which do not satisfy requirements.
         *
         * First, retrieve clone of current target cert constraints, and
         * then add more selection criteria based on current validation state.
         */
        X509CertSelector sel = (X509CertSelector) targetCertConstraints.clone();

        /*
         * Match on issuer (subject of previous cert)
         */
        sel.setIssuer(currentState.subjectDN);

        /*
         * Match on certificate validity date.
         */
        sel.setCertificateValid(buildParams.date());

        /*
         * Policy processing optimizations
         */
        if (currentState.explicitPolicy == 0)
            sel.setPolicy(getMatchingPolicies());

        /*
         * If previous cert has a subject key identifier extension,
         * use it to match on authority key identifier extension.
         */
        /*if (currentState.subjKeyId != null) {
          AuthorityKeyIdentifierExtension authKeyId = new AuthorityKeyIdentifierExtension(
                (KeyIdentifier) currentState.subjKeyId.get(SubjectKeyIdentifierExtension.KEY_ID),
                null, null);
        sel.setAuthorityKeyIdentifier(authKeyId.getExtensionValue());
        }*/

        /*
         * Require EE certs
         */
        sel.setBasicConstraints(-2);

        /* Retrieve matching certs from CertStores */
        HashSet<X509Certificate> eeCerts = new HashSet<>();
        addMatchingCerts(sel, certStores, eeCerts, true);

        if (debug != null) {
            debug.println("ReverseBuilder.getMatchingEECerts got "
                          + eeCerts.size() + " certs.");
        }
        return eeCerts;
    }

    /*
     * Retrieves all CA certificates which satisfy constraints
     * and requirements specified in the parameters and PKIX state.
     */
    private Collection<X509Certificate> getMatchingCACerts
        (ReverseState currentState, List<CertStore> certStores)
        throws CertificateException, CertStoreException, IOException {

        /*
         * Compose a CertSelector to filter out
         * certs which do not satisfy requirements.
         */
        X509CertSelector sel = new X509CertSelector();

        /*
         * Match on issuer (subject of previous cert)
         */
        sel.setIssuer(currentState.subjectDN);

        /*
         * Match on certificate validity date.
         */
        sel.setCertificateValid(buildParams.date());

        /*
         * Match on target subject name (checks that current cert's
         * name constraints permit it to certify target).
         * (4 is the integer type for DIRECTORY name).
         */
        byte[] subject = targetCertConstraints.getSubjectAsBytes();
        if (subject != null) {
            sel.addPathToName(4, subject);
        } else {
            X509Certificate cert = targetCertConstraints.getCertificate();
            if (cert != null) {
                sel.addPathToName(4,
                                  cert.getSubjectX500Principal().getEncoded());
            }
        }

        /*
         * Policy processing optimizations
         */
        if (currentState.explicitPolicy == 0)
            sel.setPolicy(getMatchingPolicies());

        /*
         * If previous cert has a subject key identifier extension,
         * use it to match on authority key identifier extension.
         */
        /*if (currentState.subjKeyId != null) {
          AuthorityKeyIdentifierExtension authKeyId = new AuthorityKeyIdentifierExtension(
                (KeyIdentifier) currentState.subjKeyId.get(SubjectKeyIdentifierExtension.KEY_ID),
                                null, null);
          sel.setAuthorityKeyIdentifier(authKeyId.getExtensionValue());
        }*/

        /*
         * Require CA certs
         */
        sel.setBasicConstraints(0);

        /* Retrieve matching certs from CertStores */
        ArrayList<X509Certificate> reverseCerts = new ArrayList<>();
        addMatchingCerts(sel, certStores, reverseCerts, true);

        /* Sort remaining certs using name constraints */
        Collections.sort(reverseCerts, new PKIXCertComparator());

        if (debug != null)
            debug.println("ReverseBuilder.getMatchingCACerts got " +
                          reverseCerts.size() + " certs.");
        return reverseCerts;
    }

    /*
     * This inner class compares 2 PKIX certificates according to which
     * should be tried first when building a path to the target. For
     * now, the algorithm is to look at name constraints in each cert and those
     * which constrain the path closer to the target should be
     * ranked higher. Later, we may want to consider other components,
     * such as key identifiers.
     */
    class PKIXCertComparator implements Comparator<X509Certificate> {

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

        @Override
        public int compare(X509Certificate cert1, X509Certificate cert2) {

            /*
             * if either cert certifies the target, always
             * put at head of list.
             */
            X500Principal targetSubject = buildParams.targetSubject();
            if (cert1.getSubjectX500Principal().equals(targetSubject)) {
                return -1;
            }
            if (cert2.getSubjectX500Principal().equals(targetSubject)) {
                return 1;
            }

            int targetDist1;
            int targetDist2;
            try {
                X500Name targetSubjectName = X500Name.asX500Name(targetSubject);
                targetDist1 = Builder.targetDistance(
                    null, cert1, targetSubjectName);
                targetDist2 = Builder.targetDistance(
                    null, cert2, targetSubjectName);
            } catch (IOException e) {
                if (debug != null) {
                    debug.println("IOException in call to Builder.targetDistance");
                    e.printStackTrace();
                }
                throw new ClassCastException
                    ("Invalid target subject distinguished name");
            }

            if (targetDist1 == targetDist2)
                return 0;

            if (targetDist1 == -1)
                return 1;

            if (targetDist1 < targetDist2)
                return -1;

            return 1;
        }
    }

    /**
     * Verifies a matching certificate.
     *
     * This method executes any of the validation steps in the PKIX path validation
     * algorithm which were not satisfied via filtering out non-compliant
     * certificates with certificate matching rules.
     *
     * If the last certificate is being verified (the one whose subject
     * matches the target subject, then the steps in Section 6.1.4 of the
     * Certification Path Validation algorithm are NOT executed,
     * regardless of whether or not the last cert is an end-entity
     * cert or not. This allows callers to certify CA certs as
     * well as EE certs.
     *
     * @param cert the certificate to be verified
     * @param currentState the current state against which the cert is verified
     * @param certPathList the certPathList generated thus far
     */
    @Override
    void verifyCert(X509Certificate cert, State currState,
        List<X509Certificate> certPathList)
        throws GeneralSecurityException
    {
        if (debug != null) {
            debug.println("ReverseBuilder.verifyCert(SN: "
                + Debug.toHexString(cert.getSerialNumber())
                + "\n  Subject: " + cert.getSubjectX500Principal() + ")");
        }

        ReverseState currentState = (ReverseState) currState;

        /* we don't perform any validation of the trusted cert */
        if (currentState.isInitial()) {
            return;
        }

        // Don't bother to verify untrusted certificate more.
        currentState.untrustedChecker.check(cert,
                                    Collections.<String>emptySet());

        /*
         * check for looping - abort a loop if
         * ((we encounter the same certificate twice) AND
         * ((policyMappingInhibited = true) OR (no policy mapping
         * extensions can be found between the occurrences of the same
         * certificate)))
         * in order to facilitate the check to see if there are
         * any policy mapping extensions found between the occurrences
         * of the same certificate, we reverse the certpathlist first
         */
        if ((certPathList != null) && (!certPathList.isEmpty())) {
            List<X509Certificate> reverseCertList = new ArrayList<>();
            for (X509Certificate c : certPathList) {
                reverseCertList.add(0, c);
            }

            boolean policyMappingFound = false;
            for (X509Certificate cpListCert : reverseCertList) {
                X509CertImpl cpListCertImpl = X509CertImpl.toImpl(cpListCert);
                PolicyMappingsExtension policyMappingsExt =
                        cpListCertImpl.getPolicyMappingsExtension();
                if (policyMappingsExt != null) {
                    policyMappingFound = true;
                }
                if (debug != null)
                    debug.println("policyMappingFound = " + policyMappingFound);
                if (cert.equals(cpListCert)) {
                    if ((buildParams.policyMappingInhibited()) ||
                        (!policyMappingFound)){
                        if (debug != null)
                            debug.println("loop detected!!");
                        throw new CertPathValidatorException("loop detected");
                    }
                }
            }
        }

        /* check if target cert */
        boolean finalCert = cert.getSubjectX500Principal().equals(buildParams.targetSubject());

        /* check if CA cert */
        boolean caCert = (cert.getBasicConstraints() != -1 ? true : false);

        /* if there are more certs to follow, verify certain constraints */
        if (!finalCert) {

            /* check if CA cert */
            if (!caCert)
                throw new CertPathValidatorException("cert is NOT a CA cert");

            /* If the certificate was not self-issued, verify that
             * remainingCerts is greater than zero
             */
            if ((currentState.remainingCACerts <= 0) && !X509CertImpl.isSelfIssued(cert)) {
                    throw new CertPathValidatorException
                        ("pathLenConstraint violated, path too long", null,
                         null, -1, PKIXReason.PATH_TOO_LONG);
            }

            /*
             * Check keyUsage extension (only if CA cert and not final cert)
             */
            KeyChecker.verifyCAKeyUsage(cert);

        } else {

            /*
             * If final cert, check that it satisfies specified target
             * constraints
             */
            if (targetCertConstraints.match(cert) == false) {
                throw new CertPathValidatorException("target certificate " +
                    "constraints check failed");
            }
        }

        /*
         * Check revocation.
         */
        if (buildParams.revocationEnabled() && currentState.revChecker != null) {
            currentState.revChecker.check(cert, Collections.<String>emptySet());
        }

        /* Check name constraints if this is not a self-issued cert */
        if (finalCert || !X509CertImpl.isSelfIssued(cert)){
            if (currentState.nc != null) {
                try {
                    if (!currentState.nc.verify(cert)){
                        throw new CertPathValidatorException
                            ("name constraints check failed", null, null, -1,
                             PKIXReason.INVALID_NAME);
                    }
                } catch (IOException ioe) {
                    throw new CertPathValidatorException(ioe);
                }
            }
        }

        /*
         * Check policy
         */
        X509CertImpl certImpl = X509CertImpl.toImpl(cert);
        currentState.rootNode = PolicyChecker.processPolicies
            (currentState.certIndex, initPolicies,
            currentState.explicitPolicy, currentState.policyMapping,
            currentState.inhibitAnyPolicy,
            buildParams.policyQualifiersRejected(), currentState.rootNode,
            certImpl, finalCert);

        /*
         * Check CRITICAL private extensions
         */
        Set<String> unresolvedCritExts = cert.getCriticalExtensionOIDs();
        if (unresolvedCritExts == null) {
            unresolvedCritExts = Collections.<String>emptySet();
        }

        /*
         * Check that the signature algorithm is not disabled.
         */
        currentState.algorithmChecker.check(cert, unresolvedCritExts);

        for (PKIXCertPathChecker checker : currentState.userCheckers) {
            checker.check(cert, unresolvedCritExts);
        }

        /*
         * Look at the remaining extensions and remove any ones we have
         * already checked. If there are any left, throw an exception!
         */
        if (!unresolvedCritExts.isEmpty()) {
            unresolvedCritExts.remove(BasicConstraints_Id.toString());
            unresolvedCritExts.remove(NameConstraints_Id.toString());
            unresolvedCritExts.remove(CertificatePolicies_Id.toString());
            unresolvedCritExts.remove(PolicyMappings_Id.toString());
            unresolvedCritExts.remove(PolicyConstraints_Id.toString());
            unresolvedCritExts.remove(InhibitAnyPolicy_Id.toString());
            unresolvedCritExts.remove(SubjectAlternativeName_Id.toString());
            unresolvedCritExts.remove(KeyUsage_Id.toString());
            unresolvedCritExts.remove(ExtendedKeyUsage_Id.toString());

            if (!unresolvedCritExts.isEmpty())
                throw new CertPathValidatorException
                    ("Unrecognized critical extension(s)", null, null, -1,
                     PKIXReason.UNRECOGNIZED_CRIT_EXT);
        }

        /*
         * Check signature.
         */
        if (buildParams.sigProvider() != null) {
            cert.verify(currentState.pubKey, buildParams.sigProvider());
        } else {
            cert.verify(currentState.pubKey);
        }
    }

    /**
     * Verifies whether the input certificate completes the path.
     * This checks whether the cert is the target certificate.
     *
     * @param cert the certificate to test
     * @return a boolean value indicating whether the cert completes the path.
     */
    @Override
    boolean isPathCompleted(X509Certificate cert) {
        return cert.getSubjectX500Principal().equals(buildParams.targetSubject());
    }

    /** Adds the certificate to the certPathList
     *
     * @param cert the certificate to be added
     * @param certPathList the certification path list
     */
    @Override
    void addCertToPath(X509Certificate cert,
        LinkedList<X509Certificate> certPathList) {
        certPathList.addLast(cert);
    }

    /** Removes final certificate from the certPathList
     *
     * @param certPathList the certification path list
     */
    @Override
    void removeFinalCertFromPath(LinkedList<X509Certificate> certPathList) {
        certPathList.removeLast();
    }
}
