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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * 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
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package sun.security.provider.certpath;

import java.io.IOException;
import java.io.OutputStream;
import java.net.*;
import java.security.cert.CertificateException;
import java.security.cert.CertPathValidatorException;
import java.security.cert.CertPathValidatorException.BasicReason;
import java.security.cert.CRLReason;
import java.security.cert.Extension;
import java.security.cert.X509Certificate;
import java.util.Base64;
import java.util.Date;
import java.util.List;
import java.util.Map;

import sun.security.action.GetPropertyAction;
import sun.security.util.Debug;
import sun.security.util.Event;
import sun.security.util.IOUtils;
import sun.security.x509.AccessDescription;
import sun.security.x509.AuthorityInfoAccessExtension;
import sun.security.x509.GeneralName;
import sun.security.x509.GeneralNameInterface;
import sun.security.x509.PKIXExtensions;
import sun.security.x509.URIName;
import sun.security.x509.X509CertImpl;

import static java.nio.charset.StandardCharsets.UTF_8;

/**
 * This is a class that checks the revocation status of a certificate(s) using
 * OCSP. It is not a PKIXCertPathChecker and therefore can be used outside
 * the CertPathValidator framework. It is useful when you want to
 * just check the revocation status of a certificate, and you don't want to
 * incur the overhead of validating all the certificates in the
 * associated certificate chain.
 *
 * @author Sean Mullan
 */
public final class OCSP {

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

    private static final int DEFAULT_CONNECT_TIMEOUT = 15000;
    private static final int DEFAULT_READ_TIMEOUT = 15000;

    /**
     * Integer value indicating the timeout length, in milliseconds, to be
     * used for establishing a connection to an OCSP responder. A timeout of
     * zero is interpreted as an infinite timeout.
     */
    private static final int CONNECT_TIMEOUT = initializeTimeout(
            "com.sun.security.ocsp.timeout", DEFAULT_CONNECT_TIMEOUT);

    /**
     * Integer value indicating the timeout length, in milliseconds, to be
     * used for reading an OCSP response from the responder.  A timeout of
     * zero is interpreted as an infinite timeout.
     */
    private static final int READ_TIMEOUT = initializeTimeout(
            "com.sun.security.ocsp.readtimeout", DEFAULT_READ_TIMEOUT);

    /**
     * Boolean value indicating whether OCSP client can use GET for OCSP
     * requests. There is an ambiguity in RFC recommendations.
     *
     * RFC 5019 says a stronger thing, "MUST":
     *    "When sending requests that are less than or equal to 255 bytes in
     *     total (after encoding) including the scheme and delimiters (http://),
     *     server name and base64-encoded OCSPRequest structure, clients MUST
     *     use the GET method (to enable OCSP response caching)."
     *
     * RFC 6960 says a weaker thing, "MAY":
     *    "HTTP-based OCSP requests can use either the GET or the POST method to
     *     submit their requests.  To enable HTTP caching, small requests (that
     *     after encoding are less than 255 bytes) MAY be submitted using GET."
     *
     * For performance reasons, we default to stronger behavior. But this
     * option also allows to fallback to weaker behavior in case of compatibility
     * problems.
     */
    private static final boolean USE_GET = initializeBoolean(
            "com.sun.security.ocsp.useget", "true");

    /**
     * Initialize the timeout length by getting the OCSP timeout
     * system property. If the property has not been set, or if its
     * value is negative, set the timeout length to the default.
     */
    private static int initializeTimeout(String prop, int def) {
        int timeoutVal =
                GetPropertyAction.privilegedGetTimeoutProp(prop, def, debug);
        if (debug != null) {
            debug.println(prop + " set to " + timeoutVal + " milliseconds");
        }
        return timeoutVal;
    }

    private static boolean initializeBoolean(String prop, String def) {
        String flag = GetPropertyAction.privilegedGetProperty(prop, def);
        boolean value = Boolean.parseBoolean(flag);
        if (debug != null) {
            debug.println(prop + " set to " + value);
        }
        return value;
    }

    private OCSP() {}

    /**
     * Checks the revocation status of a list of certificates using OCSP.
     *
     * @param certIds the CertIds to be checked
     * @param responderURI the URI of the OCSP responder
     * @param issuerInfo the issuer's certificate and/or subject and public key
     * @param responderCert the OCSP responder's certificate
     * @param date the time the validity of the OCSP responder's certificate
     *    should be checked against. If null, the current time is used.
     * @param extensions zero or more OCSP extensions to be included in the
     *    request.  If no extensions are requested, an empty {@code List} must
     *    be used.  A {@code null} value is not allowed.
     * @return the OCSPResponse
     * @throws IOException if there is an exception connecting to or
     *    communicating with the OCSP responder
     * @throws CertPathValidatorException if an exception occurs while
     *    encoding the OCSP Request or validating the OCSP Response
     */
    static OCSPResponse check(List<CertId> certIds, URI responderURI,
                              OCSPResponse.IssuerInfo issuerInfo,
                              X509Certificate responderCert, Date date,
                              List<Extension> extensions, String variant)
        throws IOException, CertPathValidatorException
    {
        byte[] nonce = null;
        for (Extension ext : extensions) {
            if (ext.getId().equals(PKIXExtensions.OCSPNonce_Id.toString())) {
                nonce = ext.getValue();
            }
        }

        OCSPResponse ocspResponse;
        try {
            byte[] response = getOCSPBytes(certIds, responderURI, extensions);
            ocspResponse = new OCSPResponse(response);

            // verify the response
            ocspResponse.verify(certIds, issuerInfo, responderCert, date,
                    nonce, variant);
        } catch (IOException ioe) {
            throw new CertPathValidatorException(
                "Unable to determine revocation status due to network error",
                ioe, null, -1, BasicReason.UNDETERMINED_REVOCATION_STATUS);
        }

        return ocspResponse;
    }


    /**
     * Send an OCSP request, then read and return the OCSP response bytes.
     *
     * @param certIds the CertIds to be checked
     * @param responderURI the URI of the OCSP responder
     * @param extensions zero or more OCSP extensions to be included in the
     *    request.  If no extensions are requested, an empty {@code List} must
     *    be used.  A {@code null} value is not allowed.
     *
     * @return the OCSP response bytes
     *
     * @throws IOException if there is an exception connecting to or
     *    communicating with the OCSP responder
     */
    public static byte[] getOCSPBytes(List<CertId> certIds, URI responderURI,
            List<Extension> extensions) throws IOException {
        OCSPRequest request = new OCSPRequest(certIds, extensions);
        byte[] bytes = request.encodeBytes();
        String responder = responderURI.toString();

        if (debug != null) {
            debug.println("connecting to OCSP service at: " + responder);
        }
        Event.report(Event.ReporterCategory.CRLCHECK, "event.ocsp.check",
                responder);

        URL url;
        HttpURLConnection con = null;
        try {
            StringBuilder encodedGetReq = new StringBuilder(responder);
            if (!responder.endsWith("/")) {
                encodedGetReq.append("/");
            }
            encodedGetReq.append(URLEncoder.encode(
                    Base64.getEncoder().encodeToString(bytes), UTF_8));

            if (USE_GET && encodedGetReq.length() <= 255) {
                url = new URI(encodedGetReq.toString()).toURL();
                con = (HttpURLConnection)url.openConnection();
                con.setConnectTimeout(CONNECT_TIMEOUT);
                con.setReadTimeout(READ_TIMEOUT);
                con.setDoOutput(true);
                con.setDoInput(true);
                con.setRequestMethod("GET");
            } else {
                url = responderURI.toURL();
                con = (HttpURLConnection)url.openConnection();
                con.setConnectTimeout(CONNECT_TIMEOUT);
                con.setReadTimeout(READ_TIMEOUT);
                con.setDoOutput(true);
                con.setDoInput(true);
                con.setRequestMethod("POST");
                con.setRequestProperty
                    ("Content-type", "application/ocsp-request");
                con.setRequestProperty
                    ("Content-length", String.valueOf(bytes.length));
                OutputStream out = con.getOutputStream();
                out.write(bytes);
                out.flush();
            }

            // Check the response.  Non-200 codes will generate an exception
            // but path validation may complete successfully if revocation info
            // can be obtained elsewhere (e.g. CRL).
            int respCode = con.getResponseCode();
            if (respCode != HttpURLConnection.HTTP_OK) {
                String msg = "Received HTTP error: " + respCode + " - " +
                        con.getResponseMessage();
                if (debug != null) {
                    debug.println(msg);
                }
                throw new IOException(msg);
            }

            int contentLength = con.getContentLength();
            return (contentLength == -1) ? con.getInputStream().readAllBytes() :
                    IOUtils.readExactlyNBytes(con.getInputStream(),
                            contentLength);
        } catch (URISyntaxException urise) {
            throw new IOException(urise);
        } finally {
            if (con != null) {
                con.disconnect();
            }
        }
    }

    /**
     * Returns the URI of the OCSP Responder as specified in the
     * certificate's Authority Information Access extension, or null if
     * not specified.
     *
     * @param cert the certificate
     * @return the URI of the OCSP Responder, or null if not specified
     */
    // Called by com.sun.deploy.security.TrustDecider
    public static URI getResponderURI(X509Certificate cert) {
        try {
            return getResponderURI(X509CertImpl.toImpl(cert));
        } catch (CertificateException ce) {
            // treat this case as if the cert had no extension
            return null;
        }
    }

    static URI getResponderURI(X509CertImpl certImpl) {

        // Examine the certificate's AuthorityInfoAccess extension
        AuthorityInfoAccessExtension aia =
            certImpl.getAuthorityInfoAccessExtension();
        if (aia == null) {
            return null;
        }

        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) {
                    URIName uri = (URIName) generalName.getName();
                    return uri.getURI();
                }
            }
        }
        return null;
    }

    /**
     * The Revocation Status of a certificate.
     */
    public interface RevocationStatus {
        enum CertStatus { GOOD, REVOKED, UNKNOWN }

        /**
         * Returns the revocation status.
         */
        CertStatus getCertStatus();
        /**
         * Returns the time when the certificate was revoked, or null
         * if it has not been revoked.
         */
        Date getRevocationTime();
        /**
         * Returns the reason the certificate was revoked, or null if it
         * has not been revoked.
         */
        CRLReason getRevocationReason();

        /**
         * Returns a Map of additional extensions.
         */
        Map<String, Extension> getSingleExtensions();
    }
}