/*

 * Copyright (c) 2002, 2021, 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.provider;

import java.util.Arrays;

import java.util.Objects;

import jdk.internal.vm.annotation.IntrinsicCandidate;

import static sun.security.provider.ByteArrayAccess.*;

/**

 * This class implements the Secure Hash Algorithm SHA-256 developed by

 * the National Institute of Standards and Technology along with the

 * National Security Agency.

 *

 * <p>It implements java.security.MessageDigestSpi, and can be used

 * through Java Cryptography Architecture (JCA), as a pluggable

 * MessageDigest implementation.

 *

 * @since       1.4.2

 * @author      Valerie Peng

 * @author      Andreas Sterbenz

 */

abstract class SHA2 extends DigestBase {

    private static final int ITERATION = 64;

    // Constants for each round

    private static final int[] ROUND_CONSTS = {

        0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,

        0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,

        0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,

        0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,

        0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,

        0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,

        0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,

        0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,

        0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,

        0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,

        0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,

        0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,

        0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,

        0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,

        0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,

        0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2

    };

    // buffer used by implCompress()

    private int[] W;

    // state of this object

    private int[] state;

    // initial state value. different between SHA-224 and SHA-256

    private final int[] initialHashes;

    /**

     * Creates a new SHA object.

     */

    SHA2(String name, int digestLength, int[] initialHashes) {

        super(name, digestLength, 64);

        this.initialHashes = initialHashes;

        state = new int[8];

        resetHashes();

    }

    /**

     * Resets the buffers and hash value to start a new hash.

     */

    void implReset() {

        resetHashes();

        if (W != null) {

            Arrays.fill(W, 0);

        }

    }

    private void resetHashes() {

        System.arraycopy(initialHashes, 0, state, 0, state.length);

    }

    void implDigest(byte[] out, int ofs) {

        long bitsProcessed = bytesProcessed << 3;

        int index = (int)bytesProcessed & 0x3f;

        int padLen = (index < 56) ? (56 - index) : (120 - index);

        engineUpdate(padding, 0, padLen);

        i2bBig4((int)(bitsProcessed >>> 32), buffer, 56);

        i2bBig4((int)bitsProcessed, buffer, 60);

        implCompress(buffer, 0);

        i2bBig(state, 0, out, ofs, engineGetDigestLength());

    }

    /**

     * Process the current block to update the state variable state.

     */

    void implCompress(byte[] buf, int ofs) {

        implCompressCheck(buf, ofs);

        implCompress0(buf, ofs);

    }

    private void implCompressCheck(byte[] buf, int ofs) {

        Objects.requireNonNull(buf);

        // Checks similar to those performed by the method 'b2iBig64'

        // are sufficient for the case when the method 'implCompress0' is

        // replaced with a compiler intrinsic.

        if (ofs < 0 || (buf.length - ofs) < 64) {

            throw new ArrayIndexOutOfBoundsException();

        }

    }

    // The method 'implCompressImpl' seems not to use its parameters.

    // The method can, however, be replaced with a compiler intrinsic

    // that operates directly on the array 'buf' (starting from

    // offset 'ofs') and not on array 'W', therefore 'buf' and 'ofs'

    // must be passed as parameter to the method.

    @IntrinsicCandidate

    private void implCompress0(byte[] buf, int ofs) {

        if (W == null) {

            W = new int[64];

        }

        b2iBig64(buf, ofs, W);

        // The first 16 ints are from the byte stream, compute the rest of

        // the W[]'s

        for (int t = 16; t < ITERATION; t++) {

            int W_t2 = W[t - 2];

            int W_t15 = W[t - 15];

            // S(x,s) is right rotation of x by s positions:

            //   S(x,s) = (x >>> s) | (x << (32 - s))

            // R(x,s) is right shift of x by s positions:

            //   R(x,s) = (x >>> s)

            // delta0(x) = S(x, 7) ^ S(x, 18) ^ R(x, 3)

            int delta0_W_t15 =

                    ((W_t15 >>>  7) | (W_t15 << 25)) ^

                    ((W_t15 >>> 18) | (W_t15 << 14)) ^

                     (W_t15 >>>  3);

            // delta1(x) = S(x, 17) ^ S(x, 19) ^ R(x, 10)

            int delta1_W_t2 =

                    ((W_t2 >>> 17) | (W_t2 << 15)) ^

                    ((W_t2 >>> 19) | (W_t2 << 13)) ^

                     (W_t2 >>> 10);

            W[t] = delta0_W_t15 + delta1_W_t2 + W[t-7] + W[t-16];

        }

        int a = state[0];

        int b = state[1];

        int c = state[2];

        int d = state[3];

        int e = state[4];

        int f = state[5];

        int g = state[6];

        int h = state[7];

        for (int i = 0; i < ITERATION; i++) {

            // S(x,s) is right rotation of x by s positions:

            //   S(x,s) = (x >>> s) | (x << (32 - s))

            // sigma0(x) = S(x,2) xor S(x,13) xor S(x,22)

            int sigma0_a =

                    ((a >>>  2) | (a << 30)) ^

                    ((a >>> 13) | (a << 19)) ^

                    ((a >>> 22) | (a << 10));

            // sigma1(x) = S(x,6) xor S(x,11) xor S(x,25)

            int sigma1_e =

                    ((e >>>  6) | (e << 26)) ^

                    ((e >>> 11) | (e << 21)) ^

                    ((e >>> 25) | (e <<  7));

            // ch(x,y,z) = (x and y) xor ((complement x) and z)

            int ch_efg = (e & f) ^ ((~e) & g);

            // maj(x,y,z) = (x and y) xor (x and z) xor (y and z)

            int maj_abc = (a & b) ^ (a & c) ^ (b & c);

            int T1 = h + sigma1_e + ch_efg + ROUND_CONSTS[i] + W[i];

            int T2 = sigma0_a + maj_abc;

            h = g;

            g = f;

            f = e;

            e = d + T1;

            d = c;

            c = b;

            b = a;

            a = T1 + T2;

        }

        state[0] += a;

        state[1] += b;

        state[2] += c;

        state[3] += d;

        state[4] += e;

        state[5] += f;

        state[6] += g;

        state[7] += h;

    }

    public Object clone() throws CloneNotSupportedException {

        SHA2 copy = (SHA2) super.clone();

        copy.state = copy.state.clone();

        copy.W = null;

        return copy;

    }

    /**

     * SHA-224 implementation class.

     */

    public static final class SHA224 extends SHA2 {

        private static final int[] INITIAL_HASHES = {

            0xc1059ed8, 0x367cd507, 0x3070dd17, 0xf70e5939,

            0xffc00b31, 0x68581511, 0x64f98fa7, 0xbefa4fa4

        };

        public SHA224() {

            super("SHA-224", 28, INITIAL_HASHES);

        }

    }

    /**

     * SHA-256 implementation class.

     */

    public static final class SHA256 extends SHA2 {

        private static final int[] INITIAL_HASHES = {

            0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,

            0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19

        };

        public SHA256() {

            super("SHA-256", 32, INITIAL_HASHES);

        }

    }

}