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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.KeyIdentifier;
import sun.security.x509.NetscapeCertTypeExtension;
import sun.security.util.DerValue;
import sun.security.util.DerInputStream;
import sun.security.util.ObjectIdentifier;

import sun.security.provider.certpath.AlgorithmChecker;
import sun.security.provider.certpath.UntrustedChecker;

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.
 SimpleValidator 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/**
 * 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.
 * <p>
 * {@code SimpleValidator} 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 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.
/**
     * 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 final Map<X500Principal, List<X509Certificate>>
                                            trustedX500Principals;

    
Set of the trusted certificates. Present only for
getTrustedCertificates().
/**
     * Set of the trusted certificates. Present only for
     * getTrustedCertificates().
     */
    private final 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.
/**
     * Perform simple validation of chain. The arguments otherCerts and
     * parameter are ignored.
     */
    @Override
    X509Certificate[] engineValidate(X509Certificate[] chain,
            Collection<X509Certificate> otherCerts,
            AlgorithmConstraints constraints,
            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();
        }

        // create distrusted certificates checker
        UntrustedChecker untrustedChecker = new UntrustedChecker();

        // check if anchor is untrusted
        X509Certificate anchorCert = chain[chain.length - 1];
        try {
            untrustedChecker.check(anchorCert, Collections.<String>emptySet());
        } catch (CertPathValidatorException cpve) {
            throw new ValidatorException(
                "Untrusted certificate: "+ anchorCert.getSubjectX500Principal(),
                ValidatorException.T_UNTRUSTED_CERT, anchorCert, cpve);
        }

        // create default algorithm constraints checker
        TrustAnchor anchor = new TrustAnchor(anchorCert, null);
        AlgorithmChecker defaultAlgChecker =
                new AlgorithmChecker(anchor, variant);

        // create application level algorithm constraints checker
        AlgorithmChecker appAlgChecker = null;
        if (constraints != null) {
            appAlgChecker = new AlgorithmChecker(anchor, constraints, null,
                    null, variant);
        }

        // verify top down, starting at the certificate issued by
        // the trust anchor
        int maxPathLength = chain.length - 1;
        for (int i = chain.length - 2; i >= 0; i--) {
            X509Certificate issuerCert = chain[i + 1];
            X509Certificate cert = chain[i];

            // check untrusted certificate
            try {
                // Untrusted checker does not care about the unresolved
                // critical extensions.
                untrustedChecker.check(cert, Collections.<String>emptySet());
            } catch (CertPathValidatorException cpve) {
                throw new ValidatorException(
                    "Untrusted certificate: " + cert.getSubjectX500Principal(),
                    ValidatorException.T_UNTRUSTED_CERT, cert, cpve);
            }

            // check certificate algorithm
            try {
                // Algorithm checker does not care about the unresolved
                // critical extensions.
                defaultAlgChecker.check(cert, Collections.<String>emptySet());
                if (appAlgChecker != null) {
                    appAlgChecker.check(cert, Collections.<String>emptySet());
                }
            } catch (CertPathValidatorException cpve) {
                throw new ValidatorException
                        (ValidatorException.T_ALGORITHM_DISABLED, cert, cpve);
            }

            // 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) {
                maxPathLength = checkExtensions(cert, maxPathLength);
            }
        }

        return chain;
    }

    private int checkExtensions(X509Certificate cert, int maxPathLen)
            throws CertificateException {
        Set<String> critSet = cert.getCriticalExtensionOIDs();
        if (critSet == null) {
            critSet = Collections.<String>emptySet();
        }

        // Check the basic constraints extension
        int pathLenConstraint =
                checkBasicConstraints(cert, critSet, maxPathLen);

        // 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);
        }

        return pathLenConstraint;
    }

    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.
/**
     * 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 = ext.get(type);
            return val.booleanValue();
        } catch (IOException e) {
            return false;
        }
    }

    private int checkBasicConstraints(X509Certificate cert,
            Set<String> critSet, int maxPathLen) 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 the certificate is self-issued, ignore the pathLenConstraint
        // checking.
        if (!X509CertImpl.isSelfIssued(cert)) {
            if (maxPathLen <= 0) {
                throw new ValidatorException("Violated path length constraints",
                    ValidatorException.T_CA_EXTENSIONS, cert);
            }

            maxPathLen--;
        }

        if (maxPathLen > constraints) {
            maxPathLen = constraints;
        }

        return maxPathLen;
    }

    /*
     * 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.
/**
     * 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();
        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.
/**
     * 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;
    }

}