/*
 * Copyright 2003-2008 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.provider.certpath;

import java.io.*;
import java.math.BigInteger;
import java.util.*;
import java.security.AccessController;
import java.security.Principal;
import java.security.PrivilegedAction;
import java.security.Security;
import java.security.cert.*;
import java.net.*;
import javax.security.auth.x500.X500Principal;

import sun.security.util.*;
import sun.security.x509.*;

/**
 * OCSPChecker is a <code>PKIXCertPathChecker</code> that uses the
 * Online Certificate Status Protocol (OCSP) as specified in RFC 2560
 * <a href="http://www.ietf.org/rfc/rfc2560.txt">
 * http://www.ietf.org/rfc/rfc2560.txt</a>.
 *
 * @author      Ram Marti
 */
class OCSPChecker extends PKIXCertPathChecker {

    public static final String OCSP_ENABLE_PROP = "ocsp.enable";
    public static final String OCSP_URL_PROP = "ocsp.responderURL";
    public static final String OCSP_CERT_SUBJECT_PROP =
        "ocsp.responderCertSubjectName";
    public static final String OCSP_CERT_ISSUER_PROP =
        "ocsp.responderCertIssuerName";
    public static final String OCSP_CERT_NUMBER_PROP =
        "ocsp.responderCertSerialNumber";

    private static final String HEX_DIGITS = "0123456789ABCDEFabcdef";
    private static final Debug DEBUG = Debug.getInstance("certpath");
    private static final boolean dump = false;

    // Supported extensions
    private static final int OCSP_NONCE_DATA[] =
        { 1, 3, 6, 1, 5, 5, 7, 48, 1, 2 };
    private static final ObjectIdentifier OCSP_NONCE_OID;
    static {
        OCSP_NONCE_OID = ObjectIdentifier.newInternal(OCSP_NONCE_DATA);
    }

    private int remainingCerts;

    private X509Certificate[] certs;

    private CertPath cp;

    private PKIXParameters pkixParams;

    /**
     * Default Constructor
     *
     * @param certPath the X509 certification path
     * @param pkixParams the input PKIX parameter set
     * @exception CertPathValidatorException Exception thrown if cert path
     * does not validate.
     */
    OCSPChecker(CertPath certPath, PKIXParameters pkixParams)
        throws CertPathValidatorException {

        this.cp = certPath;
        this.pkixParams = pkixParams;
        List<? extends Certificate> tmp = cp.getCertificates();
        certs = tmp.toArray(new X509Certificate[tmp.size()]);
        init(false);
    }

    /**
     * Initializes the internal state of the checker from parameters
     * specified in the constructor
     */
    public void init(boolean forward) throws CertPathValidatorException {
        if (!forward) {
            remainingCerts = certs.length + 1;
        } else {
            throw new CertPathValidatorException(
                "Forward checking not supported");
        }
    }

    public boolean isForwardCheckingSupported() {
        return false;
    }

    public Set<String> getSupportedExtensions() {
        return Collections.<String>emptySet();
    }

    /**
     * Sends an OCSPRequest for the certificate to the OCSP Server and
     * processes the response back from the OCSP Server.
     *
     * @param cert the Certificate
     * @param unresolvedCritExts the unresolved critical extensions
     * @exception CertPathValidatorException Exception is thrown if the
     *            certificate has been revoked.
     */
    public void check(Certificate cert, Collection<String> unresolvedCritExts)
        throws CertPathValidatorException {

        InputStream in = null;
        OutputStream out = null;

        // Decrement the certificate counter
        remainingCerts--;

        try {
            X509Certificate responderCert = null;
            boolean seekResponderCert = false;
            X500Principal responderSubjectName = null;
            X500Principal responderIssuerName = null;
            BigInteger responderSerialNumber = null;

            boolean seekIssuerCert = true;
            X509CertImpl issuerCertImpl = null;
            X509CertImpl currCertImpl =
                X509CertImpl.toImpl((X509Certificate)cert);

            /*
             * OCSP security property values, in the following order:
             *   1. ocsp.responderURL
             *   2. ocsp.responderCertSubjectName
             *   3. ocsp.responderCertIssuerName
             *   4. ocsp.responderCertSerialNumber
             */
            String[] properties = getOCSPProperties();

            // Check whether OCSP is feasible before seeking cert information
            URL url = getOCSPServerURL(currCertImpl, properties);

            // When responder's subject name is set then the issuer/serial
            // properties are ignored
            if (properties[1] != null) {
                responderSubjectName = new X500Principal(properties[1]);

            } else if (properties[2] != null && properties[3] != null) {
                responderIssuerName = new X500Principal(properties[2]);
                // remove colon or space separators
                String value = stripOutSeparators(properties[3]);
                responderSerialNumber = new BigInteger(value, 16);

            } else if (properties[2] != null || properties[3] != null) {
                throw new CertPathValidatorException(
                    "Must specify both ocsp.responderCertIssuerName and " +
                    "ocsp.responderCertSerialNumber properties");
            }

            // If the OCSP responder cert properties are set then the
            // identified cert must be located in the trust anchors or
            // in the cert stores.
            if (responderSubjectName != null || responderIssuerName != null) {
                seekResponderCert = true;
            }

            // Set the issuer certificate to the next cert in the chain
            // (unless we're processing the final cert).
            if (remainingCerts < certs.length) {
                issuerCertImpl = X509CertImpl.toImpl(certs[remainingCerts]);
                seekIssuerCert = false; // done

                // By default, the OCSP responder's cert is the same as the
                // issuer of the cert being validated.
                if (! seekResponderCert) {
                    responderCert = certs[remainingCerts];
                    if (DEBUG != null) {
                        DEBUG.println("Responder's certificate is the same " +
                            "as the issuer of the certificate being validated");
                    }
                }
            }

            // Check anchor certs for:
            //    - the issuer cert (of the cert being validated)
            //    - the OCSP responder's cert
            if (seekIssuerCert || seekResponderCert) {

                if (DEBUG != null && seekResponderCert) {
                    DEBUG.println("Searching trust anchors for responder's " +
                        "certificate");
                }

                // Extract the anchor certs
                Iterator anchors = pkixParams.getTrustAnchors().iterator();
                if (! anchors.hasNext()) {
                    throw new CertPathValidatorException(
                        "Must specify at least one trust anchor");
                }

                X500Principal certIssuerName =
                    currCertImpl.getIssuerX500Principal();
                while (anchors.hasNext() &&
                        (seekIssuerCert || seekResponderCert)) {

                    TrustAnchor anchor = (TrustAnchor)anchors.next();
                    X509Certificate anchorCert = anchor.getTrustedCert();
                    X500Principal anchorSubjectName =
                        anchorCert.getSubjectX500Principal();

                    if (dump) {
                        System.out.println("Issuer DN is " + certIssuerName);
                        System.out.println("Subject DN is " +
                            anchorSubjectName);
                    }

                    // Check if anchor cert is the issuer cert
                    if (seekIssuerCert &&
                        certIssuerName.equals(anchorSubjectName)) {

                        issuerCertImpl = X509CertImpl.toImpl(anchorCert);
                        seekIssuerCert = false; // done

                        // By default, the OCSP responder's cert is the same as
                        // the issuer of the cert being validated.
                        if (! seekResponderCert && responderCert == null) {
                            responderCert = anchorCert;
                            if (DEBUG != null) {
                                DEBUG.println("Responder's certificate is the" +
                                    " same as the issuer of the certificate " +
                                    "being validated");
                            }
                        }
                    }

                    // Check if anchor cert is the responder cert
                    if (seekResponderCert) {
                        // Satisfy the responder subject name property only, or
                        // satisfy the responder issuer name and serial number
                        // properties only
                        if ((responderSubjectName != null &&
                             responderSubjectName.equals(anchorSubjectName)) ||
                            (responderIssuerName != null &&
                             responderSerialNumber != null &&
                             responderIssuerName.equals(
                                anchorCert.getIssuerX500Principal()) &&
                             responderSerialNumber.equals(
                                anchorCert.getSerialNumber()))) {

                            responderCert = anchorCert;
                            seekResponderCert = false; // done
                        }
                    }
                }
                if (issuerCertImpl == null) {
                    throw new CertPathValidatorException(
                        "No trusted certificate for " +
                        currCertImpl.getIssuerDN());
                }

                // Check cert stores if responder cert has not yet been found
                if (seekResponderCert) {
                    if (DEBUG != null) {
                        DEBUG.println("Searching cert stores for responder's " +
                            "certificate");
                    }
                    X509CertSelector filter = null;
                    if (responderSubjectName != null) {
                        filter = new X509CertSelector();
                        filter.setSubject(responderSubjectName.getName());
                    } else if (responderIssuerName != null &&
                        responderSerialNumber != null) {
                        filter = new X509CertSelector();
                        filter.setIssuer(responderIssuerName.getName());
                        filter.setSerialNumber(responderSerialNumber);
                    }
                    if (filter != null) {
                        List<CertStore> certStores = pkixParams.getCertStores();
                        for (CertStore certStore : certStores) {
                            Iterator i =
                                certStore.getCertificates(filter).iterator();
                            if (i.hasNext()) {
                                responderCert = (X509Certificate) i.next();
                                seekResponderCert = false; // done
                                break;
                            }
                        }
                    }
                }
            }

            // Could not find the certificate identified in the OCSP properties
            if (seekResponderCert) {
                throw new CertPathValidatorException(
                    "Cannot find the responder's certificate " +
                    "(set using the OCSP security properties).");
            }

            // Construct an OCSP Request
            OCSPRequest ocspRequest =
                new OCSPRequest(currCertImpl, issuerCertImpl);

            // Use the URL to the OCSP service that was created earlier
            HttpURLConnection con = (HttpURLConnection)url.openConnection();
            if (DEBUG != null) {
                DEBUG.println("connecting to OCSP service at: " + url);
            }

            // Indicate that both input and output will be performed,
            // that the method is POST, and that the content length is
            // the length of the byte array

            con.setDoOutput(true);
            con.setDoInput(true);
            con.setRequestMethod("POST");
            con.setRequestProperty("Content-type", "application/ocsp-request");
            byte[] bytes = ocspRequest.encodeBytes();
            CertId certId = ocspRequest.getCertId();

            con.setRequestProperty("Content-length",
                String.valueOf(bytes.length));
            out = con.getOutputStream();
            out.write(bytes);
            out.flush();

            // Check the response
            if (DEBUG != null &&
                con.getResponseCode() != HttpURLConnection.HTTP_OK) {
                DEBUG.println("Received HTTP error: " + con.getResponseCode() +
                    " - " + con.getResponseMessage());
            }
            in = con.getInputStream();

            int contentLength = con.getContentLength();
            if (contentLength == -1) {
                contentLength = Integer.MAX_VALUE;
            }

            byte[] response = new byte[contentLength];
            int total = 0;
            int count = 0;
            while (count != -1 && total < contentLength) {
                count = in.read(response, total, response.length - total);
                total += count;
            }

            OCSPResponse ocspResponse = new OCSPResponse(response, pkixParams,
                responderCert);
            // Check that response applies to the cert that was supplied
            if (! certId.equals(ocspResponse.getCertId())) {
                throw new CertPathValidatorException(
                    "Certificate in the OCSP response does not match the " +
                    "certificate supplied in the OCSP request.");
            }
            SerialNumber serialNumber = currCertImpl.getSerialNumberObject();
            int certOCSPStatus = ocspResponse.getCertStatus(serialNumber);

            if (DEBUG != null) {
                DEBUG.println("Status of certificate (with serial number " +
                    serialNumber.getNumber() + ") is: " +
                    OCSPResponse.certStatusToText(certOCSPStatus));
            }

            if (certOCSPStatus == OCSPResponse.CERT_STATUS_REVOKED) {
                throw new CertPathValidatorException(
                    new CertificateRevokedException(
                        ocspResponse.getRevocationTime(),
                        ocspResponse.getRevocationReason(),
                        responderCert.getSubjectX500Principal(),
                        ocspResponse.getSingleExtensions()));

            } else if (certOCSPStatus == OCSPResponse.CERT_STATUS_UNKNOWN) {
                throw new CertPathValidatorException(
                    "Certificate's revocation status is unknown", null, cp,
                    remainingCerts);
            }
        } catch (Exception e) {
            throw new CertPathValidatorException(e);
        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException ioe) {
                    throw new CertPathValidatorException(ioe);
                }
            }
            if (out != null) {
                try {
                    out.close();
                } catch (IOException ioe) {
                    throw new CertPathValidatorException(ioe);
                }
            }
        }
    }

    /*
     * The OCSP security property values are in the following order:
     *   1. ocsp.responderURL
     *   2. ocsp.responderCertSubjectName
     *   3. ocsp.responderCertIssuerName
     *   4. ocsp.responderCertSerialNumber
     */
    private static URL getOCSPServerURL(X509CertImpl currCertImpl,
        String[] properties)
        throws CertificateParsingException, CertPathValidatorException {

        if (properties[0] != null) {
           try {
                return new URL(properties[0]);
           } catch (java.net.MalformedURLException e) {
                throw new CertPathValidatorException(e);
           }
        }

        // Examine the certificate's AuthorityInfoAccess extension

        AuthorityInfoAccessExtension aia =
            currCertImpl.getAuthorityInfoAccessExtension();
        if (aia == null) {
            throw new CertPathValidatorException(
                "Must specify the location of an OCSP Responder");
        }

        List<AccessDescription> descriptions = aia.getAccessDescriptions();
        for (AccessDescription description : descriptions) {
            if (description.getAccessMethod().equals(
                AccessDescription.Ad_OCSP_Id)) {

                GeneralName generalName = description.getAccessLocation();
                if (generalName.getType() == GeneralNameInterface.NAME_URI) {
                    try {
                        URIName uri = (URIName) generalName.getName();
                        return (new URL(uri.getName()));

                    } catch (java.net.MalformedURLException e) {
                        throw new CertPathValidatorException(e);
                    }
                }
            }
        }

        throw new CertPathValidatorException(
            "Cannot find the location of the OCSP Responder");
    }

    /*
     * Retrieves the values of the OCSP security properties.
     */
    private static String[] getOCSPProperties() {
        final String[] properties = new String[4];

        AccessController.doPrivileged(
            new PrivilegedAction<Void>() {
                public Void run() {
                    properties[0] = Security.getProperty(OCSP_URL_PROP);
                    properties[1] =
                        Security.getProperty(OCSP_CERT_SUBJECT_PROP);
                    properties[2] =
                        Security.getProperty(OCSP_CERT_ISSUER_PROP);
                    properties[3] =
                        Security.getProperty(OCSP_CERT_NUMBER_PROP);
                    return null;
                }
            });

        return properties;
    }

    /*
     * Removes any non-hexadecimal characters from a string.
     */
    private static String stripOutSeparators(String value) {
        char[] chars = value.toCharArray();
        StringBuilder hexNumber = new StringBuilder();
        for (int i = 0; i < chars.length; i++) {
            if (HEX_DIGITS.indexOf(chars[i]) != -1) {
                hexNumber.append(chars[i]);
            }
        }
        return hexNumber.toString();
    }
}