/*

 * Copyright (c) 1996, 2018, 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.*;

import java.nio.ByteBuffer;

import java.security.SecureRandom;

import java.util.Arrays;

/*

 * RandomCookie ... SSL hands standard format random cookies (nonces)

 * around.  These know how to encode/decode themselves on SSL streams,

 * and can be created and printed.

 *

 * @author David Brownell

 */

final class RandomCookie {

    final byte[] randomBytes = new byte[32];   // exactly 32 bytes

    private static final byte[] hrrRandomBytes = new byte[] {

            (byte)0xCF, (byte)0x21, (byte)0xAD, (byte)0x74,

            (byte)0xE5, (byte)0x9A, (byte)0x61, (byte)0x11,

            (byte)0xBE, (byte)0x1D, (byte)0x8C, (byte)0x02,

            (byte)0x1E, (byte)0x65, (byte)0xB8, (byte)0x91,

            (byte)0xC2, (byte)0xA2, (byte)0x11, (byte)0x16,

            (byte)0x7A, (byte)0xBB, (byte)0x8C, (byte)0x5E,

            (byte)0x07, (byte)0x9E, (byte)0x09, (byte)0xE2,

            (byte)0xC8, (byte)0xA8, (byte)0x33, (byte)0x9C

        };

    private static final byte[] t12Protection = new byte[] {

            (byte)0x44, (byte)0x4F, (byte)0x57, (byte)0x4E,

            (byte)0x47, (byte)0x52, (byte)0x44, (byte)0x01

        };

    private static final byte[] t11Protection = new byte[] {

            (byte)0x44, (byte)0x4F, (byte)0x57, (byte)0x4E,

            (byte)0x47, (byte)0x52, (byte)0x44, (byte)0x00

        };

    static final RandomCookie hrrRandom = new RandomCookie(hrrRandomBytes);

    RandomCookie(SecureRandom generator) {

        generator.nextBytes(randomBytes);

    }

    // Used for server random generation with version downgrade protection.

    RandomCookie(HandshakeContext context) {

        SecureRandom generator = context.sslContext.getSecureRandom();

        generator.nextBytes(randomBytes);

        // TLS 1.3 has a downgrade protection mechanism embedded in the

        // server's random value.  TLS 1.3 servers which negotiate TLS 1.2

        // or below in response to a ClientHello MUST set the last eight

        // bytes of their Random value specially.

        byte[] protection = null;

        if (context.maximumActiveProtocol.useTLS13PlusSpec()) {

            if (!context.negotiatedProtocol.useTLS13PlusSpec()) {

                if (context.negotiatedProtocol.useTLS12PlusSpec()) {

                    protection = t12Protection;

                } else {

                    protection = t11Protection;

                }

            }

        } else if (context.maximumActiveProtocol.useTLS12PlusSpec()) {

            if (!context.negotiatedProtocol.useTLS12PlusSpec()) {

                protection = t11Protection;

            }

        }

        if (protection != null) {

            System.arraycopy(protection, 0, randomBytes,

                    randomBytes.length - protection.length, protection.length);

        }

    }

    RandomCookie(ByteBuffer m) throws IOException {

        m.get(randomBytes);

    }

    private RandomCookie(byte[] randomBytes) {

        System.arraycopy(randomBytes, 0, this.randomBytes, 0, 32);

    }

    @Override

    public String toString() {

        return "random_bytes = {" + Utilities.toHexString(randomBytes) + "}";

    }

    boolean isHelloRetryRequest() {

        return Arrays.equals(hrrRandomBytes, randomBytes);

    }

    // Used for client random validation of version downgrade protection.

    boolean isVersionDowngrade(HandshakeContext context) {

        if (context.maximumActiveProtocol.useTLS13PlusSpec()) {

            if (!context.negotiatedProtocol.useTLS13PlusSpec()) {

                return isT12Downgrade() || isT11Downgrade();

            }

        } else if (context.maximumActiveProtocol.useTLS12PlusSpec()) {

            if (!context.negotiatedProtocol.useTLS12PlusSpec()) {

                return isT11Downgrade();

            }

        }

        return false;

    }

    private boolean isT12Downgrade() {

        return Utilities.equals(randomBytes, 24, 32, t12Protection, 0, 8);

    }

    private boolean isT11Downgrade() {

        return Utilities.equals(randomBytes, 24, 32, t11Protection, 0, 8);

    }

}