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package sun.security.validator;

import java.util.*;

import java.security.*;

import java.security.cert.*;

import javax.security.auth.x500.X500Principal;

import sun.security.action.GetBooleanAction;

import sun.security.provider.certpath.AlgorithmChecker;

/**

 * 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.

 * <p>

 * {@code PKIXValidator} objects are immutable once they have been created.

 * Please DO NOT add methods that can change the state of an instance once

 * it has been created.

 *

 * @author Andreas Sterbenz

 */

public final class PKIXValidator extends Validator {

    /**

     * Flag indicating whether to enable revocation check for the PKIX trust

     * manager. Typically, this will only work if the PKIX implementation

     * supports CRL distribution points as we do not manually setup CertStores.

     */

    private static final boolean checkTLSRevocation =

        AccessController.doPrivileged

            (new GetBooleanAction("com.sun.net.ssl.checkRevocation"));

    private final Set<X509Certificate> trustedCerts;

    private final PKIXBuilderParameters parameterTemplate;

    private int certPathLength = -1;

    // needed only for the validator

    private final Map<X500Principal, List<PublicKey>> trustedSubjects;

    private final CertificateFactory factory;

    private final boolean plugin;

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

        super(TYPE_PKIX, variant);

        this.trustedCerts = (trustedCerts instanceof Set) ?

                            (Set<X509Certificate>)trustedCerts :

                            new HashSet<X509Certificate>(trustedCerts);

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

        for (X509Certificate cert : trustedCerts) {

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

        }

        try {

            parameterTemplate = new PKIXBuilderParameters(trustAnchors, null);

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

        } catch (InvalidAlgorithmParameterException e) {

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

        } catch (CertificateException e) {

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

        }

        setDefaultParameters(variant);

        plugin = variant.equals(VAR_PLUGIN_CODE_SIGNING);

        trustedSubjects = setTrustedSubjects();

    }

    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;

        try {

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

        } catch (CertificateException e) {

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

        }

        plugin = variant.equals(VAR_PLUGIN_CODE_SIGNING);

        trustedSubjects = setTrustedSubjects();

    }

    /**

     * Populate the trustedSubjects Map using the DN and public keys from

     * the list of trusted certificates

     *

     * @return Map containing each subject DN and one or more public keys

     *    tied to those DNs.

     */

    private Map<X500Principal, List<PublicKey>> setTrustedSubjects() {

        Map<X500Principal, List<PublicKey>> subjectMap = new HashMap<>();

        for (X509Certificate cert : trustedCerts) {

            X500Principal dn = cert.getSubjectX500Principal();

            List<PublicKey> keys;

            if (subjectMap.containsKey(dn)) {

                keys = subjectMap.get(dn);

            } else {

                keys = new ArrayList<PublicKey>();

                subjectMap.put(dn, keys);

            }

            keys.add(cert.getPublicKey());

        }

        return subjectMap;

    }

    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() { // mutable, should be private

        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) {

        if ((variant == Validator.VAR_TLS_SERVER) ||

                (variant == Validator.VAR_TLS_CLIENT)) {

            parameterTemplate.setRevocationEnabled(checkTLSRevocation);

        } else {

            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() { // mutable, should be private

        return parameterTemplate;

    }

    @Override

    X509Certificate[] engineValidate(X509Certificate[] chain,

            Collection<X509Certificate> otherCerts,

            List<byte[]> responseList,

            AlgorithmConstraints constraints,

            Object parameter) throws CertificateException {

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

            throw new CertificateException

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

        }

        // Check if 'parameter' affects 'pkixParameters'

        PKIXBuilderParameters pkixParameters = null;

        if (parameter instanceof Timestamp && plugin) {

            try {

                        (PKIXBuilderParameters) parameterTemplate.clone(),

            } catch (InvalidAlgorithmParameterException e) {

                // ignore exception

            }

        } else {

            pkixParameters = (PKIXBuilderParameters) parameterTemplate.clone();

        }

        // add new algorithm constraints checker

        if (constraints != null) {

        }

        // attach it to the PKIXBuilderParameters.

        if (!responseList.isEmpty()) {

            addResponses(pkixParameters, chain, responseList);

        }

        // check that chain is in correct order and check if chain contains

        // trust anchor

        X500Principal prevIssuer = null;

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

            X509Certificate cert = chain[i];

            X500Principal dn = cert.getSubjectX500Principal();

            if (i != 0 && !dn.equals(prevIssuer)) {

                // chain is not ordered correctly, call builder instead

                return doBuild(chain, otherCerts, pkixParameters);

            }

            // Check if chain[i] is already trusted. It may be inside

            // trustedCerts, or has the same dn and public key as a cert

            // inside trustedCerts. The latter happens when a CA has

            // updated its cert with a stronger signature algorithm in JRE

            // but the weak one is still in circulation.

            if (trustedCerts.contains(cert) ||          // trusted cert

                    (trustedSubjects.containsKey(dn) && // replacing ...

                     trustedSubjects.get(dn).contains(  // ... weak cert

                        cert.getPublicKey()))) {

                if (i == 0) {

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

                }

                // Remove and call validator on partial chain [0 .. i-1]

                X509Certificate[] newChain = new X509Certificate[i];

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

                return doValidate(newChain, pkixParameters);

            }

            prevIssuer = cert.getIssuerX500Principal();

        }

        // apparently issued by trust anchor?

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

        X500Principal issuer = last.getIssuerX500Principal();

        X500Principal subject = last.getSubjectX500Principal();

        if (trustedSubjects.containsKey(issuer) &&

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

            return doValidate(chain, pkixParameters);

        }

        // 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

                try {

                    pkixParameters.setTrustAnchors

                        (Collections.singleton(new TrustAnchor

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

                } catch (InvalidAlgorithmParameterException iape) {

                    // should never occur, but ...

                    throw new CertificateException(iape);

                }

                doValidate(newChain, pkixParameters);

            }

            // 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, pkixParameters);

    }

    private boolean isSignatureValid(List<PublicKey> keys,

            X509Certificate sub) {

        if (plugin) {

            for (PublicKey key: keys) {

                try {

                    sub.verify(key);

                    return true;

                } catch (Exception ex) {

                    continue;

                }

            }

            return false;

        }

        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) {

        @SuppressWarnings("deprecation")

        Date date = validationDate;

        if (date != null) {

            params.setDate(date);

        }

    }

    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,

        PKIXBuilderParameters params) throws CertificateException {

        try {

            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);

        }

    }

    /**

     * For OCSP Stapling, add responses that came in during the handshake

     * into a {@code PKIXRevocationChecker} so we can evaluate them.

     *

     * @param pkixParams the pkixParameters object that will be used in

     * path validation.

     * @param chain the chain of certificates to verify

     * @param responseList a {@code List} of zero or more byte arrays, each

     * one being a DER-encoded OCSP response (per RFC 6960).  Entries

     * in the List must match the order of the certificates in the

     * chain parameter.

     */

    private static void addResponses(PKIXBuilderParameters pkixParams,

            X509Certificate[] chain, List<byte[]> responseList) {

        if (pkixParams.isRevocationEnabled()) {

            try {

                // Make a modifiable copy of the CertPathChecker list

                PKIXRevocationChecker revChecker = null;

                List<PKIXCertPathChecker> checkerList =

                        new ArrayList<>(pkixParams.getCertPathCheckers());

                // Find the first PKIXRevocationChecker in the list

                for (PKIXCertPathChecker checker : checkerList) {

                    if (checker instanceof PKIXRevocationChecker) {

                        revChecker = (PKIXRevocationChecker)checker;

                        break;

                    }

                }

                // If we still haven't found one, make one

                if (revChecker == null) {

                    revChecker = (PKIXRevocationChecker)CertPathValidator.

                            getInstance("PKIX").getRevocationChecker();

                    checkerList.add(revChecker);

                }

                // Each response in the list should be in parallel with

                // the certificate list.  If there is a zero-length response

                // treat it as being absent.  If the user has provided their

                // own PKIXRevocationChecker with pre-populated responses, do

                // not overwrite them with the ones from the handshake.

                Map<X509Certificate, byte[]> responseMap =

                        revChecker.getOcspResponses();

                int limit = Integer.min(chain.length, responseList.size());

                for (int idx = 0; idx < limit; idx++) {

                    byte[] respBytes = responseList.get(idx);

                    if (respBytes != null && respBytes.length > 0 &&

                            !responseMap.containsKey(chain[idx])) {

                        responseMap.put(chain[idx], respBytes);

                    }

                }

                // Add the responses and push it all back into the

                // PKIXBuilderParameters

                revChecker.setOcspResponses(responseMap);

                pkixParams.setCertPathCheckers(checkerList);

            } catch (NoSuchAlgorithmException exc) {

                // This should not occur, but if it does happen then

                // stapled OCSP responses won't be part of revocation checking.

                // Clients can still fall back to other means of revocation

                // checking.

            }

        }

    }

}