/*

 * Copyright (c) 2015, Oracle and/or its affiliates. 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.  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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.security.ssl;

import java.io.IOException;

import javax.net.ssl.SSLProtocolException;

import java.security.MessageDigest;

import java.security.SecureRandom;

import sun.security.ssl.HandshakeMessage.ClientHello;

/*

 * HelloVerifyRequest cookie manager

 */

final class HelloCookieManager {

    // the cookie secret life time

    private static long COOKIE_TIMING_WINDOW = 3600000;     // in milliseconds

    private static int  COOKIE_MAX_LENGTH_DTLS10 = 32;      // 32 bytes

    private static int  COOKIE_MAX_LENGTH_DTLS12 = 0xFF;    // 2^8 -1 bytes

    private final SecureRandom          secureRandom;

    private final MessageDigest         cookieDigest;

    private int                         cookieVersion;      // allow to wrap

    private long                        secretLifetime;

    private byte[]                      cookieSecret;

    private int                         prevCookieVersion;

    private byte[]                      prevCookieSecret;

    HelloCookieManager(SecureRandom secureRandom) {

        this.secureRandom = secureRandom;

        this.cookieDigest = JsseJce.getMessageDigest("SHA-256");

        this.cookieVersion = secureRandom.nextInt();

        this.secretLifetime = 0;

        this.cookieSecret = null;

        this.prevCookieVersion = 0;

        this.prevCookieSecret = null;

    }

    // Used by server side to generate cookies in HelloVerifyRequest message.

    synchronized byte[] getCookie(ClientHello clientHelloMsg) {

        if (secretLifetime < System.currentTimeMillis()) {

            if (cookieSecret != null) {

                prevCookieVersion = cookieVersion;

                prevCookieSecret = cookieSecret.clone();

            } else {

                cookieSecret = new byte[32];

            }

            cookieVersion++;

            secureRandom.nextBytes(cookieSecret);

            secretLifetime = System.currentTimeMillis() + COOKIE_TIMING_WINDOW;

        }

        clientHelloMsg.updateHelloCookie(cookieDigest);

        byte[] cookie = cookieDigest.digest(cookieSecret);      // 32 bytes

        cookie[0] = (byte)((cookieVersion >> 24) & 0xFF);

        cookie[1] = (byte)((cookieVersion >> 16) & 0xFF);

        cookie[2] = (byte)((cookieVersion >> 8) & 0xFF);

        cookie[3] = (byte)(cookieVersion & 0xFF);

        return cookie;

    }

    // Used by server side to check the cookie in ClientHello message.

    synchronized boolean isValid(ClientHello clientHelloMsg) {

        byte[] cookie = clientHelloMsg.cookie;

        // no cookie exchange or not a valid cookie length

        if ((cookie == null) || (cookie.length != 32)) {

            return false;

        }

        int version = ((cookie[0] & 0xFF) << 24) |

                      ((cookie[1] & 0xFF) << 16) |

                      ((cookie[2] & 0xFF) << 8) |

                       (cookie[3] & 0xFF);

        byte[] secret;

        if (version == cookieVersion) {

            secret = cookieSecret;

        } else if (version == prevCookieVersion) {

            secret = prevCookieSecret;

        } else {

            return false;       // may be out of the timing window

        }

        clientHelloMsg.updateHelloCookie(cookieDigest);

        byte[] target = cookieDigest.digest(secret);            // 32 bytes

        for (int i = 4; i < 32; i++) {

            if (cookie[i] != target[i]) {

                return false;

            }

        }

        return true;

    }

    // Used by client side to check the cookie in HelloVerifyRequest message.

    static void checkCookie(ProtocolVersion protocolVersion,

            byte[] cookie) throws IOException {

        if (cookie != null && cookie.length != 0) {

            int limit = COOKIE_MAX_LENGTH_DTLS12;

            if (protocolVersion.v == ProtocolVersion.DTLS10.v) {

                limit = COOKIE_MAX_LENGTH_DTLS10;

            }

            if (cookie.length > COOKIE_MAX_LENGTH_DTLS10) {

                throw new SSLProtocolException(

                        "Invalid HelloVerifyRequest.cookie (length = " +

                         cookie.length + " bytes)");

            }

        }

        // Otherwise, no cookie exchange.

    }

}