/*

 * 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

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 */

package sun.security.provider.certpath;

import java.io.*;

import java.math.BigInteger;

import java.security.*;

import java.security.cert.CertificateException;

import java.security.cert.CertificateParsingException;

import java.security.cert.CertPathValidatorException;

import java.security.cert.CRLReason;

import java.security.cert.X509Certificate;

import java.util.Collections;

import java.util.Date;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import sun.misc.HexDumpEncoder;

import sun.security.x509.*;

import sun.security.util.*;

/**

 * This class is used to process an OCSP response.

 * The OCSP Response is defined

 * in RFC 2560 and the ASN.1 encoding is as follows:

 * <pre>

 *

 *  OCSPResponse ::= SEQUENCE {

 *      responseStatus         OCSPResponseStatus,

 *      responseBytes          [0] EXPLICIT ResponseBytes OPTIONAL }

 *

 *   OCSPResponseStatus ::= ENUMERATED {

 *       successful            (0),  --Response has valid confirmations

 *       malformedRequest      (1),  --Illegal confirmation request

 *       internalError         (2),  --Internal error in issuer

 *       tryLater              (3),  --Try again later

 *                                   --(4) is not used

 *       sigRequired           (5),  --Must sign the request

 *       unauthorized          (6)   --Request unauthorized

 *   }

 *

 *   ResponseBytes ::=       SEQUENCE {

 *       responseType   OBJECT IDENTIFIER,

 *       response       OCTET STRING }

 *

 *   BasicOCSPResponse       ::= SEQUENCE {

 *      tbsResponseData      ResponseData,

 *      signatureAlgorithm   AlgorithmIdentifier,

 *      signature            BIT STRING,

 *      certs                [0] EXPLICIT SEQUENCE OF Certificate OPTIONAL }

 *

 *   The value for signature SHALL be computed on the hash of the DER

 *   encoding ResponseData.

 *

 *   ResponseData ::= SEQUENCE {

 *      version              [0] EXPLICIT Version DEFAULT v1,

 *      responderID              ResponderID,

 *      producedAt               GeneralizedTime,

 *      responses                SEQUENCE OF SingleResponse,

 *      responseExtensions   [1] EXPLICIT Extensions OPTIONAL }

 *

 *   ResponderID ::= CHOICE {

 *      byName               [1] Name,

 *      byKey                [2] KeyHash }

 *

 *   KeyHash ::= OCTET STRING -- SHA-1 hash of responder's public key

 *   (excluding the tag and length fields)

 *

 *   SingleResponse ::= SEQUENCE {

 *      certID                       CertID,

 *      certStatus                   CertStatus,

 *      thisUpdate                   GeneralizedTime,

 *      nextUpdate         [0]       EXPLICIT GeneralizedTime OPTIONAL,

 *      singleExtensions   [1]       EXPLICIT Extensions OPTIONAL }

 *

 *   CertStatus ::= CHOICE {

 *       good        [0]     IMPLICIT NULL,

 *       revoked     [1]     IMPLICIT RevokedInfo,

 *       unknown     [2]     IMPLICIT UnknownInfo }

 *

 *   RevokedInfo ::= SEQUENCE {

 *       revocationTime              GeneralizedTime,

 *       revocationReason    [0]     EXPLICIT CRLReason OPTIONAL }

 *

 *   UnknownInfo ::= NULL -- this can be replaced with an enumeration

 *

 * </pre>

 *

 * @author      Ram Marti

 */

public final class OCSPResponse {

    public enum ResponseStatus {

        SUCCESSFUL,            // Response has valid confirmations

        MALFORMED_REQUEST,     // Illegal confirmation request

        INTERNAL_ERROR,        // Internal error in issuer

        TRY_LATER,             // Try again later

        UNUSED,                // is not used

        SIG_REQUIRED,          // Must sign the request

        UNAUTHORIZED           // Request unauthorized

    };

    private static ResponseStatus[] rsvalues = ResponseStatus.values();

    private static final Debug DEBUG = Debug.getInstance("certpath");

    private static final boolean dump = false;

    private static final ObjectIdentifier OCSP_BASIC_RESPONSE_OID =

        ObjectIdentifier.newInternal(new int[] { 1, 3, 6, 1, 5, 5, 7, 48, 1, 1});

    private static final ObjectIdentifier OCSP_NONCE_EXTENSION_OID =

        ObjectIdentifier.newInternal(new int[] { 1, 3, 6, 1, 5, 5, 7, 48, 1, 2});

    private static final int CERT_STATUS_GOOD = 0;

    private static final int CERT_STATUS_REVOKED = 1;

    private static final int CERT_STATUS_UNKNOWN = 2;

    // ResponderID CHOICE tags

    private static final int NAME_TAG = 1;

    private static final int KEY_TAG = 2;

    // Object identifier for the OCSPSigning key purpose

    private static final String KP_OCSP_SIGNING_OID = "1.3.6.1.5.5.7.3.9";

    private final ResponseStatus responseStatus;

    private final Map<CertId, SingleResponse> singleResponseMap;

    // Maximum clock skew in milliseconds (15 minutes) allowed when checking

    // validity of OCSP responses

    private static final long MAX_CLOCK_SKEW = 900000;

    // an array of all of the CRLReasons (used in SingleResponse)

    private static CRLReason[] values = CRLReason.values();

    /*

     * Create an OCSP response from its ASN.1 DER encoding.

     */

    OCSPResponse(byte[] bytes, Date dateCheckedAgainst,

        X509Certificate responderCert)

        throws IOException, CertPathValidatorException {

        // OCSPResponse

        if (dump) {

            HexDumpEncoder hexEnc = new HexDumpEncoder();

            System.out.println("OCSPResponse bytes are...");

            System.out.println(hexEnc.encode(bytes));

        }

        DerValue der = new DerValue(bytes);

        if (der.tag != DerValue.tag_Sequence) {

            throw new IOException("Bad encoding in OCSP response: " +

                "expected ASN.1 SEQUENCE tag.");

        }

        DerInputStream derIn = der.getData();

        // responseStatus

        int status = derIn.getEnumerated();

        if (status >= 0 && status < rsvalues.length) {

            responseStatus = rsvalues[status];

        } else {

            // unspecified responseStatus

            throw new IOException("Unknown OCSPResponse status: " + status);

        }

        if (DEBUG != null) {

            DEBUG.println("OCSP response status: " + responseStatus);

        }

        if (responseStatus != ResponseStatus.SUCCESSFUL) {

            // no need to continue, responseBytes are not set.

            singleResponseMap = Collections.emptyMap();

            return;

        }

        // responseBytes

        der = derIn.getDerValue();

        if (!der.isContextSpecific((byte)0)) {

            throw new IOException("Bad encoding in responseBytes element " +

                "of OCSP response: expected ASN.1 context specific tag 0.");

        }

        DerValue tmp = der.data.getDerValue();

        if (tmp.tag != DerValue.tag_Sequence) {

            throw new IOException("Bad encoding in responseBytes element " +

                "of OCSP response: expected ASN.1 SEQUENCE tag.");

        }

        // responseType

        derIn = tmp.data;

        ObjectIdentifier responseType = derIn.getOID();

        if (responseType.equals(OCSP_BASIC_RESPONSE_OID)) {

            if (DEBUG != null) {

                DEBUG.println("OCSP response type: basic");

            }

        } else {

            if (DEBUG != null) {

                DEBUG.println("OCSP response type: " + responseType);

            }

            throw new IOException("Unsupported OCSP response type: " +

                responseType);

        }

        // BasicOCSPResponse

        DerInputStream basicOCSPResponse =

            new DerInputStream(derIn.getOctetString());

        DerValue[] seqTmp = basicOCSPResponse.getSequence(2);

        if (seqTmp.length < 3) {

            throw new IOException("Unexpected BasicOCSPResponse value");

        }

        DerValue responseData = seqTmp[0];

        // Need the DER encoded ResponseData to verify the signature later

        byte[] responseDataDer = seqTmp[0].toByteArray();

        // tbsResponseData

        if (responseData.tag != DerValue.tag_Sequence) {

            throw new IOException("Bad encoding in tbsResponseData " +

                "element of OCSP response: expected ASN.1 SEQUENCE tag.");

        }

        DerInputStream seqDerIn = responseData.data;

        DerValue seq = seqDerIn.getDerValue();

        // version

        if (seq.isContextSpecific((byte)0)) {

            // seq[0] is version

            if (seq.isConstructed() && seq.isContextSpecific()) {

                //System.out.println ("version is available");

                seq = seq.data.getDerValue();

                int version = seq.getInteger();

                if (seq.data.available() != 0) {

                    throw new IOException("Bad encoding in version " +

                        " element of OCSP response: bad format");

                }

                seq = seqDerIn.getDerValue();

            }

        }

        // responderID

        short tag = (byte)(seq.tag & 0x1f);

        if (tag == NAME_TAG) {

            if (DEBUG != null) {

                X500Name responderName = new X500Name(seq.getData());

                DEBUG.println("OCSP Responder name: " + responderName);

            }

        } else if (tag == KEY_TAG) {

            // Ignore, for now

        } else {

            throw new IOException("Bad encoding in responderID element of " +

                "OCSP response: expected ASN.1 context specific tag 0 or 1");

        }

        // producedAt

        seq = seqDerIn.getDerValue();

        if (DEBUG != null) {

            Date producedAtDate = seq.getGeneralizedTime();

            DEBUG.println("OCSP response produced at: " + producedAtDate);

        }

        // responses

        DerValue[] singleResponseDer = seqDerIn.getSequence(1);

        singleResponseMap

            = new HashMap<CertId, SingleResponse>(singleResponseDer.length);

        if (DEBUG != null) {

            DEBUG.println("OCSP number of SingleResponses: "

                + singleResponseDer.length);

        }

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

            SingleResponse singleResponse

                = new SingleResponse(singleResponseDer[i]);

            singleResponseMap.put(singleResponse.getCertId(), singleResponse);

        }

        // responseExtensions

        if (seqDerIn.available() > 0) {

            seq = seqDerIn.getDerValue();

            if (seq.isContextSpecific((byte)1)) {

                DerValue[] responseExtDer = seq.data.getSequence(3);

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

                    Extension responseExtension

                        = new Extension(responseExtDer[i]);

                    if (DEBUG != null) {

                        DEBUG.println("OCSP extension: " + responseExtension);

                    }

                    if (responseExtension.getExtensionId().equals(

                        OCSP_NONCE_EXTENSION_OID)) {

                        /*

                        ocspNonce =

                            responseExtension[i].getExtensionValue();

                         */

                    } else if (responseExtension.isCritical())  {

                        throw new IOException(

                            "Unsupported OCSP critical extension: " +

                            responseExtension.getExtensionId());

                    }

                }

            }

        }

        // signatureAlgorithmId

        AlgorithmId sigAlgId = AlgorithmId.parse(seqTmp[1]);

        // signature

        byte[] signature = seqTmp[2].getBitString();

        X509CertImpl[] x509Certs = null;

        // if seq[3] is available , then it is a sequence of certificates

        if (seqTmp.length > 3) {

            // certs are available

            DerValue seqCert = seqTmp[3];

            if (!seqCert.isContextSpecific((byte)0)) {

                throw new IOException("Bad encoding in certs element of " +

                    "OCSP response: expected ASN.1 context specific tag 0.");

            }

            DerValue[] certs = seqCert.getData().getSequence(3);

            x509Certs = new X509CertImpl[certs.length];

            try {

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

                    x509Certs[i] = new X509CertImpl(certs[i].toByteArray());

                }

            } catch (CertificateException ce) {

                throw new IOException("Bad encoding in X509 Certificate", ce);

            }

        }

        // Check whether the cert returned by the responder is trusted

        if (x509Certs != null && x509Certs[0] != null) {

            X509CertImpl cert = x509Certs[0];

            // First check if the cert matches the responder cert which

            // was set locally.

            if (cert.equals(responderCert)) {

                // cert is trusted, now verify the signed response

            // Next check if the cert was issued by the responder cert

            // which was set locally.

            } else if (cert.getIssuerX500Principal().equals(

                responderCert.getSubjectX500Principal())) {

                // Check for the OCSPSigning key purpose

                try {

                    List<String> keyPurposes = cert.getExtendedKeyUsage();

                    if (keyPurposes == null ||

                        !keyPurposes.contains(KP_OCSP_SIGNING_OID)) {

                        throw new CertPathValidatorException(

                            "Responder's certificate not valid for signing " +

                            "OCSP responses");

                    }

                } catch (CertificateParsingException cpe) {

                    // assume cert is not valid for signing

                    throw new CertPathValidatorException(

                        "Responder's certificate not valid for signing " +

                        "OCSP responses", cpe);

                }

                // check the validity

                try {

                    if (dateCheckedAgainst == null) {

                        cert.checkValidity();

                    } else {

                        cert.checkValidity(dateCheckedAgainst);

                    }

                } catch (GeneralSecurityException e) {

                    throw new CertPathValidatorException(

                        "Responder's certificate not within the " +

                        "validity period", e);

                }

                // check for revocation

                //

                // A CA may specify that an OCSP client can trust a

                // responder for the lifetime of the responder's

                // certificate. The CA does so by including the

                // extension id-pkix-ocsp-nocheck.

                //

                Extension noCheck =

                    cert.getExtension(PKIXExtensions.OCSPNoCheck_Id);

                if (noCheck != null) {

                    if (DEBUG != null) {

                        DEBUG.println("Responder's certificate includes " +

                            "the extension id-pkix-ocsp-nocheck.");

                    }

                } else {

                    // we should do the revocation checking of the

                    // authorized responder in a future update.

                }

                // verify the signature

                try {

                    cert.verify(responderCert.getPublicKey());

                    responderCert = cert;

                    // cert is trusted, now verify the signed response

                } catch (GeneralSecurityException e) {

                    responderCert = null;

                }

            } else {

                throw new CertPathValidatorException(

                    "Responder's certificate is not authorized to sign " +

                    "OCSP responses");

            }

        }

        // Confirm that the signed response was generated using the public

        // key from the trusted responder cert

        if (responderCert != null) {

            if (!verifyResponse(responseDataDer, responderCert,

                sigAlgId, signature)) {

                throw new CertPathValidatorException(

                    "Error verifying OCSP Responder's signature");

            }

        } else {

            // Need responder's cert in order to verify the signature

            throw new CertPathValidatorException(

                "Unable to verify OCSP Responder's signature");

        }

    }

    /**

     * Returns the OCSP ResponseStatus.

     */

    ResponseStatus getResponseStatus() {

        return responseStatus;

    }

    /*

     * Verify the signature of the OCSP response.

     * The responder's cert is implicitly trusted.

     */

    private boolean verifyResponse(byte[] responseData, X509Certificate cert,

        AlgorithmId sigAlgId, byte[] signBytes)

        throws CertPathValidatorException {

        try {

            Signature respSignature = Signature.getInstance(sigAlgId.getName());

            respSignature.initVerify(cert);

            respSignature.update(responseData);

            if (respSignature.verify(signBytes)) {

                if (DEBUG != null) {

                    DEBUG.println("Verified signature of OCSP Responder");

                }

                return true;

            } else {

                if (DEBUG != null) {

                    DEBUG.println(

                        "Error verifying signature of OCSP Responder");

                }

                return false;

            }

        } catch (InvalidKeyException ike) {

            throw new CertPathValidatorException(ike);

        } catch (NoSuchAlgorithmException nsae) {

            throw new CertPathValidatorException(nsae);

        } catch (SignatureException se) {

            throw new CertPathValidatorException(se);

        }

    }

    /**

     * Returns the SingleResponse of the specified CertId, or null if

     * there is no response for that CertId.

     */

    SingleResponse getSingleResponse(CertId certId) {

        return singleResponseMap.get(certId);

    }

    /*

     * A class representing a single OCSP response.

     */