/*

 * 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.io.IOException;

import java.util.*;

import java.security.*;

import java.security.cert.*;

import javax.security.auth.x500.X500Principal;

import sun.security.x509.X509CertImpl;

import sun.security.x509.NetscapeCertTypeExtension;

import sun.security.util.DerValue;

import sun.security.util.DerInputStream;

import sun.security.util.DerOutputStream;

import sun.security.util.ObjectIdentifier;

/**

 * A simple validator implementation. It is based on code from the JSSE

 * X509TrustManagerImpl. This implementation is designed for compatibility with

 * deployed certificates and previous J2SE versions. It will never support

 * more advanced features and will be deemphasized in favor of the PKIX

 * validator going forward.

 *

 * @author Andreas Sterbenz

 */

public final class SimpleValidator extends Validator {

    // Constants for the OIDs we need

    final static String OID_BASIC_CONSTRAINTS = "2.5.29.19";

    final static String OID_NETSCAPE_CERT_TYPE = "2.16.840.1.113730.1.1";

    final static String OID_KEY_USAGE = "2.5.29.15";

    final static String OID_EXTENDED_KEY_USAGE = "2.5.29.37";

    final static String OID_EKU_ANY_USAGE = "2.5.29.37.0";

    final static ObjectIdentifier OBJID_NETSCAPE_CERT_TYPE =

        NetscapeCertTypeExtension.NetscapeCertType_Id;

    private final static String NSCT_SSL_CA =

                                NetscapeCertTypeExtension.SSL_CA;

    private final static String NSCT_CODE_SIGNING_CA =

                                NetscapeCertTypeExtension.OBJECT_SIGNING_CA;

    /**

     * The trusted certificates as:

     * Map (X500Principal)subject of trusted cert -> List of X509Certificate

     * The list is used because there may be multiple certificates

     * with an identical subject DN.

     */

    private Map<X500Principal, List<X509Certificate>> trustedX500Principals;

    /**

     * Set of the trusted certificates. Present only for

     * getTrustedCertificates().

     */

    private Collection<X509Certificate> trustedCerts;

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

        super(TYPE_SIMPLE, variant);

        this.trustedCerts = trustedCerts;

        trustedX500Principals =

                        new HashMap<X500Principal, List<X509Certificate>>();

        for (X509Certificate cert : trustedCerts) {

            X500Principal principal = cert.getSubjectX500Principal();

            List<X509Certificate> list = trustedX500Principals.get(principal);

            if (list == null) {

                // this actually should be a set, but duplicate entries

                // are not a problem and we can avoid the Set overhead

                list = new ArrayList<X509Certificate>(2);

                trustedX500Principals.put(principal, list);

            }

            list.add(cert);

        }

    }

    public Collection<X509Certificate> getTrustedCertificates() {

        return trustedCerts;

    }

    /**

     * Perform simple validation of chain. The arguments otherCerts and

     * parameter are ignored.

     */

    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");

        }

        // make sure chain includes a trusted cert

        chain = buildTrustedChain(chain);

        Date date = validationDate;

        if (date == null) {

            date = new Date();

        }

        // verify top down, starting at the certificate issued by

        // the trust anchor

        for (int i = chain.length - 2; i >= 0; i--) {

            X509Certificate issuerCert = chain[i + 1];

            X509Certificate cert = chain[i];

            // no validity check for code signing certs

            if ((variant.equals(VAR_CODE_SIGNING) == false)

                        && (variant.equals(VAR_JCE_SIGNING) == false)) {

                cert.checkValidity(date);

            }

            // check name chaining

            if (cert.getIssuerX500Principal().equals(

                        issuerCert.getSubjectX500Principal()) == false) {

                throw new ValidatorException

                        (ValidatorException.T_NAME_CHAINING, cert);

            }

            // check signature

            try {

                cert.verify(issuerCert.getPublicKey());

            } catch (GeneralSecurityException e) {

                throw new ValidatorException

                        (ValidatorException.T_SIGNATURE_ERROR, cert, e);

            }

            // check extensions for CA certs

            if (i != 0) {

                checkExtensions(cert, i);

            }

        }

        return chain;

    }

    private void checkExtensions(X509Certificate cert, int index)

            throws CertificateException {

        Set<String> critSet = cert.getCriticalExtensionOIDs();

        if (critSet == null) {

            critSet = Collections.<String>emptySet();

        }

        // Check the basic constraints extension

        checkBasicConstraints(cert, critSet, index);

        // Check the key usage and extended key usage extensions

        checkKeyUsage(cert, critSet);

        // check Netscape certificate type extension

        checkNetscapeCertType(cert, critSet);

        if (!critSet.isEmpty()) {

            throw new ValidatorException

                ("Certificate contains unknown critical extensions: " + critSet,

                ValidatorException.T_CA_EXTENSIONS, cert);

        }

    }

    private void checkNetscapeCertType(X509Certificate cert,

            Set<String> critSet) throws CertificateException {

        if (variant.equals(VAR_GENERIC)) {

            // nothing

        } else if (variant.equals(VAR_TLS_CLIENT)

                || variant.equals(VAR_TLS_SERVER)) {

            if (getNetscapeCertTypeBit(cert, NSCT_SSL_CA) == false) {

                throw new ValidatorException

                        ("Invalid Netscape CertType extension for SSL CA "

                        + "certificate",

                        ValidatorException.T_CA_EXTENSIONS, cert);

            }

            critSet.remove(OID_NETSCAPE_CERT_TYPE);

        } else if (variant.equals(VAR_CODE_SIGNING)

                || variant.equals(VAR_JCE_SIGNING)) {

            if (getNetscapeCertTypeBit(cert, NSCT_CODE_SIGNING_CA) == false) {

                throw new ValidatorException

                        ("Invalid Netscape CertType extension for code "

                        + "signing CA certificate",

                        ValidatorException.T_CA_EXTENSIONS, cert);

            }

            critSet.remove(OID_NETSCAPE_CERT_TYPE);

        } else {

            throw new CertificateException("Unknown variant " + variant);

        }

    }

    /**

     * Get the value of the specified bit in the Netscape certificate type

     * extension. If the extension is not present at all, we return true.

     */

    static boolean getNetscapeCertTypeBit(X509Certificate cert, String type) {

        try {

            NetscapeCertTypeExtension ext;

            if (cert instanceof X509CertImpl) {

                X509CertImpl certImpl = (X509CertImpl)cert;

                ObjectIdentifier oid = OBJID_NETSCAPE_CERT_TYPE;

                ext = (NetscapeCertTypeExtension)certImpl.getExtension(oid);

                if (ext == null) {

                    return true;

                }

            } else {

                byte[] extVal = cert.getExtensionValue(OID_NETSCAPE_CERT_TYPE);

                if (extVal == null) {

                    return true;

                }

                DerInputStream in = new DerInputStream(extVal);

                byte[] encoded = in.getOctetString();

                encoded = new DerValue(encoded).getUnalignedBitString()

                                                                .toByteArray();

                ext = new NetscapeCertTypeExtension(encoded);

            }

            Boolean val = (Boolean)ext.get(type);

            return val.booleanValue();

        } catch (IOException e) {

            return false;

        }

    }

    private void checkBasicConstraints(X509Certificate cert,

            Set<String> critSet, int index) throws CertificateException {

        critSet.remove(OID_BASIC_CONSTRAINTS);

        int constraints = cert.getBasicConstraints();

        // reject, if extension missing or not a CA (constraints == -1)

        if (constraints < 0) {

            throw new ValidatorException("End user tried to act as a CA",

                ValidatorException.T_CA_EXTENSIONS, cert);

        }

        if (index - 1 > constraints) {

            throw new ValidatorException("Violated path length constraints",

                ValidatorException.T_CA_EXTENSIONS, cert);

        }

    }

    /*

     * Verify the key usage and extended key usage for intermediate

     * certificates.

     */

    private void checkKeyUsage(X509Certificate cert, Set<String> critSet)

            throws CertificateException {

        critSet.remove(OID_KEY_USAGE);

        // EKU irrelevant in CA certificates

        critSet.remove(OID_EXTENDED_KEY_USAGE);

        // check key usage extension

        boolean[] keyUsageInfo = cert.getKeyUsage();

        if (keyUsageInfo != null) {

            // keyUsageInfo[5] is for keyCertSign.

            if ((keyUsageInfo.length < 6) || (keyUsageInfo[5] == false)) {

                throw new ValidatorException

                        ("Wrong key usage: expected keyCertSign",

                        ValidatorException.T_CA_EXTENSIONS, cert);

            }

        }

    }

    /**

     * Build a trusted certificate chain. This method always returns a chain

     * with a trust anchor as the final cert in the chain. If no trust anchor

     * could be found, a CertificateException is thrown.

     */

    private X509Certificate[] buildTrustedChain(X509Certificate[] chain)

            throws CertificateException {

        List<X509Certificate> c = new ArrayList<X509Certificate>(chain.length);

        // scan chain starting at EE cert

        // if a trusted certificate is found, append it and return

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

            X509Certificate cert = chain[i];

            X509Certificate trustedCert = getTrustedCertificate(cert);

            if (trustedCert != null) {

                c.add(trustedCert);

                return c.toArray(CHAIN0);

            }

            c.add(cert);

        }

        // check if we can append a trusted cert

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

        X500Principal subject = cert.getSubjectX500Principal();

        X500Principal issuer = cert.getIssuerX500Principal();

        if (subject.equals(issuer) == false) {

            List<X509Certificate> list = trustedX500Principals.get(issuer);

            if (list != null) {

                X509Certificate trustedCert = list.iterator().next();

                c.add(trustedCert);

                return c.toArray(CHAIN0);

            }

        }

        // no trusted cert found, error

        throw new ValidatorException(ValidatorException.T_NO_TRUST_ANCHOR);

    }

    /**

     * Return a trusted certificate that matches the input certificate,

     * or null if no such certificate can be found. This method also handles

     * cases where a CA re-issues a trust anchor with the same public key and

     * same subject and issuer names but a new validity period, etc.

     */

    private X509Certificate getTrustedCertificate(X509Certificate cert) {

        Principal certSubjectName = cert.getSubjectX500Principal();

        List<X509Certificate> list = trustedX500Principals.get(certSubjectName);

        if (list == null) {

            return null;

        }

        Principal certIssuerName = cert.getIssuerX500Principal();

        PublicKey certPublicKey = cert.getPublicKey();

        for (X509Certificate mycert : list) {

            if (mycert.equals(cert)) {

                return cert;

            }

            if (!mycert.getIssuerX500Principal().equals(certIssuerName)) {

                continue;

            }

            if (!mycert.getPublicKey().equals(certPublicKey)) {

                continue;

            }

            // All tests pass, this must be the one to use...

            return mycert;

        }

        return null;

    }

}