/**********************************************************************

 *                        gost89.c                                    *

 *             Copyright (c) 2005-2006 Cryptocom LTD                  *

 *         This file is distributed under the same license as OpenSSL *

 *                                                                    *

 *          Implementation of GOST 28147-89 encryption algorithm      *

 *            No OpenSSL libraries required to compile and use        *

 *                              this code                             *

 **********************************************************************/

#include <string.h>

#include "gost89.h"

/*-

   Substitution blocks from RFC 4357

   Note: our implementation of gost 28147-89 algorithm

   uses S-box matrix rotated 90 degrees counterclockwise, relative to

   examples given in RFC.

*/

/* Substitution blocks from test examples for GOST R 34.11-94*/

gost_subst_block GostR3411_94_TestParamSet = {

    {0X1, 0XF, 0XD, 0X0, 0X5, 0X7, 0XA, 0X4, 0X9, 0X2, 0X3, 0XE, 0X6, 0XB,

     0X8, 0XC}

    ,

    {0XD, 0XB, 0X4, 0X1, 0X3, 0XF, 0X5, 0X9, 0X0, 0XA, 0XE, 0X7, 0X6, 0X8,

     0X2, 0XC}

    ,

    {0X4, 0XB, 0XA, 0X0, 0X7, 0X2, 0X1, 0XD, 0X3, 0X6, 0X8, 0X5, 0X9, 0XC,

     0XF, 0XE}

    ,

    {0X6, 0XC, 0X7, 0X1, 0X5, 0XF, 0XD, 0X8, 0X4, 0XA, 0X9, 0XE, 0X0, 0X3,

     0XB, 0X2}

    ,

    {0X7, 0XD, 0XA, 0X1, 0X0, 0X8, 0X9, 0XF, 0XE, 0X4, 0X6, 0XC, 0XB, 0X2,

     0X5, 0X3}

    ,

    {0X5, 0X8, 0X1, 0XD, 0XA, 0X3, 0X4, 0X2, 0XE, 0XF, 0XC, 0X7, 0X6, 0X0,

     0X9, 0XB}

    ,

    {0XE, 0XB, 0X4, 0XC, 0X6, 0XD, 0XF, 0XA, 0X2, 0X3, 0X8, 0X1, 0X0, 0X7,

     0X5, 0X9}

    ,

    {0X4, 0XA, 0X9, 0X2, 0XD, 0X8, 0X0, 0XE, 0X6, 0XB, 0X1, 0XC, 0X7, 0XF,

     0X5, 0X3}

};

/* Substitution blocks for hash function 1.2.643.2.9.1.6.1  */

gost_subst_block GostR3411_94_CryptoProParamSet = {

    {0x1, 0x3, 0xA, 0x9, 0x5, 0xB, 0x4, 0xF, 0x8, 0x6, 0x7, 0xE, 0xD, 0x0,

     0x2, 0xC}

    ,

    {0xD, 0xE, 0x4, 0x1, 0x7, 0x0, 0x5, 0xA, 0x3, 0xC, 0x8, 0xF, 0x6, 0x2,

     0x9, 0xB}

    ,

    {0x7, 0x6, 0x2, 0x4, 0xD, 0x9, 0xF, 0x0, 0xA, 0x1, 0x5, 0xB, 0x8, 0xE,

     0xC, 0x3}

    ,

    {0x7, 0x6, 0x4, 0xB, 0x9, 0xC, 0x2, 0xA, 0x1, 0x8, 0x0, 0xE, 0xF, 0xD,

     0x3, 0x5}

    ,

    {0x4, 0xA, 0x7, 0xC, 0x0, 0xF, 0x2, 0x8, 0xE, 0x1, 0x6, 0x5, 0xD, 0xB,

     0x9, 0x3}

    ,

    {0x7, 0xF, 0xC, 0xE, 0x9, 0x4, 0x1, 0x0, 0x3, 0xB, 0x5, 0x2, 0x6, 0xA,

     0x8, 0xD}

    ,

    {0x5, 0xF, 0x4, 0x0, 0x2, 0xD, 0xB, 0x9, 0x1, 0x7, 0x6, 0x3, 0xC, 0xE,

     0xA, 0x8}

    ,

    {0xA, 0x4, 0x5, 0x6, 0x8, 0x1, 0x3, 0x7, 0xD, 0xC, 0xE, 0x0, 0x9, 0x2,

     0xB, 0xF}

};

/* Test paramset from GOST 28147 */

gost_subst_block Gost28147_TestParamSet = {

    {0xC, 0x6, 0x5, 0x2, 0xB, 0x0, 0x9, 0xD, 0x3, 0xE, 0x7, 0xA, 0xF, 0x4,

     0x1, 0x8}

    ,

    {0x9, 0xB, 0xC, 0x0, 0x3, 0x6, 0x7, 0x5, 0x4, 0x8, 0xE, 0xF, 0x1, 0xA,

     0x2, 0xD}

    ,

    {0x8, 0xF, 0x6, 0xB, 0x1, 0x9, 0xC, 0x5, 0xD, 0x3, 0x7, 0xA, 0x0, 0xE,

     0x2, 0x4}

    ,

    {0x3, 0xE, 0x5, 0x9, 0x6, 0x8, 0x0, 0xD, 0xA, 0xB, 0x7, 0xC, 0x2, 0x1,

     0xF, 0x4}

    ,

    {0xE, 0x9, 0xB, 0x2, 0x5, 0xF, 0x7, 0x1, 0x0, 0xD, 0xC, 0x6, 0xA, 0x4,

     0x3, 0x8}

    ,

    {0xD, 0x8, 0xE, 0xC, 0x7, 0x3, 0x9, 0xA, 0x1, 0x5, 0x2, 0x4, 0x6, 0xF,

     0x0, 0xB}

    ,

    {0xC, 0x9, 0xF, 0xE, 0x8, 0x1, 0x3, 0xA, 0x2, 0x7, 0x4, 0xD, 0x6, 0x0,

     0xB, 0x5}

    ,

    {0x4, 0x2, 0xF, 0x5, 0x9, 0x1, 0x0, 0x8, 0xE, 0x3, 0xB, 0xC, 0xD, 0x7,

     0xA, 0x6}

};

/* 1.2.643.2.2.31.1 */

gost_subst_block Gost28147_CryptoProParamSetA = {

    {0xB, 0xA, 0xF, 0x5, 0x0, 0xC, 0xE, 0x8, 0x6, 0x2, 0x3, 0x9, 0x1, 0x7,

     0xD, 0x4}

    ,

    {0x1, 0xD, 0x2, 0x9, 0x7, 0xA, 0x6, 0x0, 0x8, 0xC, 0x4, 0x5, 0xF, 0x3,

     0xB, 0xE}

    ,

    {0x3, 0xA, 0xD, 0xC, 0x1, 0x2, 0x0, 0xB, 0x7, 0x5, 0x9, 0x4, 0x8, 0xF,

     0xE, 0x6}

    ,

    {0xB, 0x5, 0x1, 0x9, 0x8, 0xD, 0xF, 0x0, 0xE, 0x4, 0x2, 0x3, 0xC, 0x7,

     0xA, 0x6}

    ,

    {0xE, 0x7, 0xA, 0xC, 0xD, 0x1, 0x3, 0x9, 0x0, 0x2, 0xB, 0x4, 0xF, 0x8,

     0x5, 0x6}

    ,

    {0xE, 0x4, 0x6, 0x2, 0xB, 0x3, 0xD, 0x8, 0xC, 0xF, 0x5, 0xA, 0x0, 0x7,

     0x1, 0x9}

    ,

    {0x3, 0x7, 0xE, 0x9, 0x8, 0xA, 0xF, 0x0, 0x5, 0x2, 0x6, 0xC, 0xB, 0x4,

     0xD, 0x1}

    ,

    {0x9, 0x6, 0x3, 0x2, 0x8, 0xB, 0x1, 0x7, 0xA, 0x4, 0xE, 0xF, 0xC, 0x0,

     0xD, 0x5}

};

/* 1.2.643.2.2.31.2 */

gost_subst_block Gost28147_CryptoProParamSetB = {

    {0x0, 0x4, 0xB, 0xE, 0x8, 0x3, 0x7, 0x1, 0xA, 0x2, 0x9, 0x6, 0xF, 0xD,

     0x5, 0xC}

    ,

    {0x5, 0x2, 0xA, 0xB, 0x9, 0x1, 0xC, 0x3, 0x7, 0x4, 0xD, 0x0, 0x6, 0xF,

     0x8, 0xE}

    ,

    {0x8, 0x3, 0x2, 0x6, 0x4, 0xD, 0xE, 0xB, 0xC, 0x1, 0x7, 0xF, 0xA, 0x0,

     0x9, 0x5}

    ,

    {0x2, 0x7, 0xC, 0xF, 0x9, 0x5, 0xA, 0xB, 0x1, 0x4, 0x0, 0xD, 0x6, 0x8,

     0xE, 0x3}

    ,

    {0x7, 0x5, 0x0, 0xD, 0xB, 0x6, 0x1, 0x2, 0x3, 0xA, 0xC, 0xF, 0x4, 0xE,

     0x9, 0x8}

    ,

    {0xE, 0xC, 0x0, 0xA, 0x9, 0x2, 0xD, 0xB, 0x7, 0x5, 0x8, 0xF, 0x3, 0x6,

     0x1, 0x4}

    ,

    {0x0, 0x1, 0x2, 0xA, 0x4, 0xD, 0x5, 0xC, 0x9, 0x7, 0x3, 0xF, 0xB, 0x8,

     0x6, 0xE}

    ,

    {0x8, 0x4, 0xB, 0x1, 0x3, 0x5, 0x0, 0x9, 0x2, 0xE, 0xA, 0xC, 0xD, 0x6,

     0x7, 0xF}

};

/* 1.2.643.2.2.31.3 */

gost_subst_block Gost28147_CryptoProParamSetC = {

    {0x7, 0x4, 0x0, 0x5, 0xA, 0x2, 0xF, 0xE, 0xC, 0x6, 0x1, 0xB, 0xD, 0x9,

     0x3, 0x8}

    ,

    {0xA, 0x9, 0x6, 0x8, 0xD, 0xE, 0x2, 0x0, 0xF, 0x3, 0x5, 0xB, 0x4, 0x1,

     0xC, 0x7}

    ,

    {0xC, 0x9, 0xB, 0x1, 0x8, 0xE, 0x2, 0x4, 0x7, 0x3, 0x6, 0x5, 0xA, 0x0,

     0xF, 0xD}

    ,

    {0x8, 0xD, 0xB, 0x0, 0x4, 0x5, 0x1, 0x2, 0x9, 0x3, 0xC, 0xE, 0x6, 0xF,

     0xA, 0x7}

    ,

    {0x3, 0x6, 0x0, 0x1, 0x5, 0xD, 0xA, 0x8, 0xB, 0x2, 0x9, 0x7, 0xE, 0xF,

     0xC, 0x4}

    ,

    {0x8, 0x2, 0x5, 0x0, 0x4, 0x9, 0xF, 0xA, 0x3, 0x7, 0xC, 0xD, 0x6, 0xE,

     0x1, 0xB}

    ,

    {0x0, 0x1, 0x7, 0xD, 0xB, 0x4, 0x5, 0x2, 0x8, 0xE, 0xF, 0xC, 0x9, 0xA,

     0x6, 0x3}

    ,

    {0x1, 0xB, 0xC, 0x2, 0x9, 0xD, 0x0, 0xF, 0x4, 0x5, 0x8, 0xE, 0xA, 0x7,

     0x6, 0x3}

};

/* 1.2.643.2.2.31.4 */

gost_subst_block Gost28147_CryptoProParamSetD = {

    {0x1, 0xA, 0x6, 0x8, 0xF, 0xB, 0x0, 0x4, 0xC, 0x3, 0x5, 0x9, 0x7, 0xD,

     0x2, 0xE}

    ,

    {0x3, 0x0, 0x6, 0xF, 0x1, 0xE, 0x9, 0x2, 0xD, 0x8, 0xC, 0x4, 0xB, 0xA,

     0x5, 0x7}

    ,

    {0x8, 0x0, 0xF, 0x3, 0x2, 0x5, 0xE, 0xB, 0x1, 0xA, 0x4, 0x7, 0xC, 0x9,

     0xD, 0x6}

    ,

    {0x0, 0xC, 0x8, 0x9, 0xD, 0x2, 0xA, 0xB, 0x7, 0x3, 0x6, 0x5, 0x4, 0xE,

     0xF, 0x1}

    ,

    {0x1, 0x5, 0xE, 0xC, 0xA, 0x7, 0x0, 0xD, 0x6, 0x2, 0xB, 0x4, 0x9, 0x3,

     0xF, 0x8}

    ,

    {0x1, 0xC, 0xB, 0x0, 0xF, 0xE, 0x6, 0x5, 0xA, 0xD, 0x4, 0x8, 0x9, 0x3,

     0x7, 0x2}

    ,

    {0xB, 0x6, 0x3, 0x4, 0xC, 0xF, 0xE, 0x2, 0x7, 0xD, 0x8, 0x0, 0x5, 0xA,

     0x9, 0x1}

    ,

    {0xF, 0xC, 0x2, 0xA, 0x6, 0x4, 0x5, 0x0, 0x7, 0x9, 0xE, 0xD, 0x1, 0xB,

     0x8, 0x3}

};

const byte CryptoProKeyMeshingKey[] = {

    0x69, 0x00, 0x72, 0x22, 0x64, 0xC9, 0x04, 0x23,

    0x8D, 0x3A, 0xDB, 0x96, 0x46, 0xE9, 0x2A, 0xC4,

    0x18, 0xFE, 0xAC, 0x94, 0x00, 0xED, 0x07, 0x12,

    0xC0, 0x86, 0xDC, 0xC2, 0xEF, 0x4C, 0xA9, 0x2B

};

/* Initialization of gost_ctx subst blocks*/

static void kboxinit(gost_ctx * c, const gost_subst_block * b)

{

    int i;

    for (i = 0; i < 256; i++) {

        c->k87[i] = (word32) (b->k8[i >> 4] << 4 | b->k7[i & 15]) << 24;

        c->k65[i] = (b->k6[i >> 4] << 4 | b->k5[i & 15]) << 16;

        c->k43[i] = (b->k4[i >> 4] << 4 | b->k3[i & 15]) << 8;

        c->k21[i] = b->k2[i >> 4] << 4 | b->k1[i & 15];

    }

}

/* Part of GOST 28147 algorithm moved into separate function */

static word32 f(gost_ctx * c, word32 x)

{

    x = c->k87[x >> 24 & 255] | c->k65[x >> 16 & 255] |

        c->k43[x >> 8 & 255] | c->k21[x & 255];

    /* Rotate left 11 bits */

    return x << 11 | x >> (32 - 11);

}

/* Low-level encryption routine - encrypts one 64 bit block*/

void gostcrypt(gost_ctx * c, const byte * in, byte * out)

{

    register word32 n1, n2;     /* As named in the GOST */

    n1 = in[0] | (in[1] << 8) | (in[2] << 16) | ((word32) in[3] << 24);

    n2 = in[4] | (in[5] << 8) | (in[6] << 16) | ((word32) in[7] << 24);

    /* Instead of swapping halves, swap names each round */

    n2 ^= f(c, n1 + c->k[0]);

    n1 ^= f(c, n2 + c->k[1]);

    n2 ^= f(c, n1 + c->k[2]);

    n1 ^= f(c, n2 + c->k[3]);

    n2 ^= f(c, n1 + c->k[4]);

    n1 ^= f(c, n2 + c->k[5]);

    n2 ^= f(c, n1 + c->k[6]);

    n1 ^= f(c, n2 + c->k[7]);

    n2 ^= f(c, n1 + c->k[0]);

    n1 ^= f(c, n2 + c->k[1]);

    n2 ^= f(c, n1 + c->k[2]);

    n1 ^= f(c, n2 + c->k[3]);

    n2 ^= f(c, n1 + c->k[4]);

    n1 ^= f(c, n2 + c->k[5]);

    n2 ^= f(c, n1 + c->k[6]);

    n1 ^= f(c, n2 + c->k[7]);

    n2 ^= f(c, n1 + c->k[0]);

    n1 ^= f(c, n2 + c->k[1]);

    n2 ^= f(c, n1 + c->k[2]);

    n1 ^= f(c, n2 + c->k[3]);

    n2 ^= f(c, n1 + c->k[4]);

    n1 ^= f(c, n2 + c->k[5]);

    n2 ^= f(c, n1 + c->k[6]);

    n1 ^= f(c, n2 + c->k[7]);

    n2 ^= f(c, n1 + c->k[7]);

    n1 ^= f(c, n2 + c->k[6]);

    n2 ^= f(c, n1 + c->k[5]);

    n1 ^= f(c, n2 + c->k[4]);

    n2 ^= f(c, n1 + c->k[3]);

    n1 ^= f(c, n2 + c->k[2]);

    n2 ^= f(c, n1 + c->k[1]);

    n1 ^= f(c, n2 + c->k[0]);

    out[0] = (byte) (n2 & 0xff);

    out[1] = (byte) ((n2 >> 8) & 0xff);

    out[2] = (byte) ((n2 >> 16) & 0xff);

    out[3] = (byte) (n2 >> 24);

    out[4] = (byte) (n1 & 0xff);

    out[5] = (byte) ((n1 >> 8) & 0xff);

    out[6] = (byte) ((n1 >> 16) & 0xff);

    out[7] = (byte) (n1 >> 24);

}

/* Low-level decryption routine. Decrypts one 64-bit block */

void gostdecrypt(gost_ctx * c, const byte * in, byte * out)

{

    register word32 n1, n2;     /* As named in the GOST */

    n1 = in[0] | (in[1] << 8) | (in[2] << 16) | ((word32) in[3] << 24);

    n2 = in[4] | (in[5] << 8) | (in[6] << 16) | ((word32) in[7] << 24);

    n2 ^= f(c, n1 + c->k[0]);

    n1 ^= f(c, n2 + c->k[1]);

    n2 ^= f(c, n1 + c->k[2]);

    n1 ^= f(c, n2 + c->k[3]);

    n2 ^= f(c, n1 + c->k[4]);

    n1 ^= f(c, n2 + c->k[5]);

    n2 ^= f(c, n1 + c->k[6]);

    n1 ^= f(c, n2 + c->k[7]);

    n2 ^= f(c, n1 + c->k[7]);

    n1 ^= f(c, n2 + c->k[6]);

    n2 ^= f(c, n1 + c->k[5]);

    n1 ^= f(c, n2 + c->k[4]);

    n2 ^= f(c, n1 + c->k[3]);

    n1 ^= f(c, n2 + c->k[2]);

    n2 ^= f(c, n1 + c->k[1]);

    n1 ^= f(c, n2 + c->k[0]);

    n2 ^= f(c, n1 + c->k[7]);

    n1 ^= f(c, n2 + c->k[6]);

    n2 ^= f(c, n1 + c->k[5]);

    n1 ^= f(c, n2 + c->k[4]);

    n2 ^= f(c, n1 + c->k[3]);

    n1 ^= f(c, n2 + c->k[2]);

    n2 ^= f(c, n1 + c->k[1]);

    n1 ^= f(c, n2 + c->k[0]);

    n2 ^= f(c, n1 + c->k[7]);

    n1 ^= f(c, n2 + c->k[6]);

    n2 ^= f(c, n1 + c->k[5]);

    n1 ^= f(c, n2 + c->k[4]);

    n2 ^= f(c, n1 + c->k[3]);

    n1 ^= f(c, n2 + c->k[2]);

    n2 ^= f(c, n1 + c->k[1]);

    n1 ^= f(c, n2 + c->k[0]);

    out[0] = (byte) (n2 & 0xff);

    out[1] = (byte) ((n2 >> 8) & 0xff);

    out[2] = (byte) ((n2 >> 16) & 0xff);

    out[3] = (byte) (n2 >> 24);

    out[4] = (byte) (n1 & 0xff);

    out[5] = (byte) ((n1 >> 8) & 0xff);

    out[6] = (byte) ((n1 >> 16) & 0xff);

    out[7] = (byte) (n1 >> 24);

}

/* Encrypts several blocks in ECB mode */

void gost_enc(gost_ctx * c, const byte * clear, byte * cipher, int blocks)

{

    int i;

    for (i = 0; i < blocks; i++) {

        gostcrypt(c, clear, cipher);

        clear += 8;

        cipher += 8;

    }

}

/* Decrypts several blocks in ECB mode */

void gost_dec(gost_ctx * c, const byte * cipher, byte * clear, int blocks)

{

    int i;

    for (i = 0; i < blocks; i++) {

        gostdecrypt(c, cipher, clear);

        clear += 8;

        cipher += 8;

    }

}

/* Encrypts several full blocks in CFB mode using 8byte IV */

void gost_enc_cfb(gost_ctx * ctx, const byte * iv, const byte * clear,

                  byte * cipher, int blocks)

{

    byte cur_iv[8];

    byte gamma[8];

    int i, j;

    const byte *in;

    byte *out;

    memcpy(cur_iv, iv, 8);

    for (i = 0, in = clear, out = cipher; i < blocks; i++, in += 8, out += 8) {

        gostcrypt(ctx, cur_iv, gamma);

        for (j = 0; j < 8; j++) {

            cur_iv[j] = out[j] = in[j] ^ gamma[j];

        }

    }

}

/* Decrypts several full blocks in CFB mode using 8byte IV */

void gost_dec_cfb(gost_ctx * ctx, const byte * iv, const byte * cipher,

                  byte * clear, int blocks)

{

    byte cur_iv[8];

    byte gamma[8];

    int i, j;

    const byte *in;

    byte *out;

    memcpy(cur_iv, iv, 8);

    for (i = 0, in = cipher, out = clear; i < blocks; i++, in += 8, out += 8) {

        gostcrypt(ctx, cur_iv, gamma);

        for (j = 0; j < 8; j++) {

            out[j] = (cur_iv[j] = in[j]) ^ gamma[j];

        }

    }

}

/* Encrypts one block using specified key */

void gost_enc_with_key(gost_ctx * c, byte * key, byte * inblock,

                       byte * outblock)

{

    gost_key(c, key);

    gostcrypt(c, inblock, outblock);

}

/* Set 256 bit  key into context */

void gost_key(gost_ctx * c, const byte * k)

{

    int i, j;

    for (i = 0, j = 0; i < 8; i++, j += 4) {

        c->k[i] =

            k[j] | (k[j + 1] << 8) | (k[j + 2] << 16) | ((word32) k[j + 3] <<

                                                         24);

    }

}

/* Retrieve 256-bit key from context */

void gost_get_key(gost_ctx * c, byte * k)

{

    int i, j;

    for (i = 0, j = 0; i < 8; i++, j += 4) {

        k[j] = (byte) (c->k[i] & 0xFF);

        k[j + 1] = (byte) ((c->k[i] >> 8) & 0xFF);

        k[j + 2] = (byte) ((c->k[i] >> 16) & 0xFF);

        k[j + 3] = (byte) ((c->k[i] >> 24) & 0xFF);

    }

}

/* Initalize context. Provides default value for subst_block */

void gost_init(gost_ctx * c, const gost_subst_block * b)

{

    if (!b) {

        b = &GostR3411_94_TestParamSet;

    }

    kboxinit(c, b);

}

/* Cleans up key from context */

void gost_destroy(gost_ctx * c)

{

    int i;

    for (i = 0; i < 8; i++)

        c->k[i] = 0;

}

/*

 * Compute GOST 28147 mac block Parameters gost_ctx *c - context initalized

 * with substitution blocks and key buffer - 8-byte mac state buffer block

 * 8-byte block to process.

 */

void mac_block(gost_ctx * c, byte * buffer, const byte * block)

{

    register word32 n1, n2;     /* As named in the GOST */

    int i;

    for (i = 0; i < 8; i++) {

        buffer[i] ^= block[i];

    }

    n1 = buffer[0] | (buffer[1] << 8) | (buffer[2] << 16) | ((word32)

                                                             buffer[3] << 24);

    n2 = buffer[4] | (buffer[5] << 8) | (buffer[6] << 16) | ((word32)

                                                             buffer[7] << 24);

    /* Instead of swapping halves, swap names each round */

    n2 ^= f(c, n1 + c->k[0]);

    n1 ^= f(c, n2 + c->k[1]);

    n2 ^= f(c, n1 + c->k[2]);

    n1 ^= f(c, n2 + c->k[3]);

    n2 ^= f(c, n1 + c->k[4]);

    n1 ^= f(c, n2 + c->k[5]);

    n2 ^= f(c, n1 + c->k[6]);

    n1 ^= f(c, n2 + c->k[7]);

    n2 ^= f(c, n1 + c->k[0]);

    n1 ^= f(c, n2 + c->k[1]);

    n2 ^= f(c, n1 + c->k[2]);

    n1 ^= f(c, n2 + c->k[3]);

    n2 ^= f(c, n1 + c->k[4]);

    n1 ^= f(c, n2 + c->k[5]);

    n2 ^= f(c, n1 + c->k[6]);

    n1 ^= f(c, n2 + c->k[7]);

    buffer[0] = (byte) (n1 & 0xff);

    buffer[1] = (byte) ((n1 >> 8) & 0xff);

    buffer[2] = (byte) ((n1 >> 16) & 0xff);

    buffer[3] = (byte) (n1 >> 24);

    buffer[4] = (byte) (n2 & 0xff);

    buffer[5] = (byte) ((n2 >> 8) & 0xff);

    buffer[6] = (byte) ((n2 >> 16) & 0xff);

    buffer[7] = (byte) (n2 >> 24);

}

/* Get mac with specified number of bits from MAC state buffer */

void get_mac(byte * buffer, int nbits, byte * out)

{

    int nbytes = nbits >> 3;

    int rembits = nbits & 7;

    int mask = rembits ? ((1 < rembits) - 1) : 0;

    int i;

    for (i = 0; i < nbytes; i++)

        out[i] = buffer[i];

    if (rembits)

        out[i] = buffer[i] & mask;

}

/*

 * Compute mac of specified length (in bits) from data. Context should be

 * initialized with key and subst blocks

 */

int gost_mac(gost_ctx * ctx, int mac_len, const unsigned char *data,

             unsigned int data_len, unsigned char *mac)

{

    byte buffer[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };

    byte buf2[8];

    unsigned int i;

    for (i = 0; i + 8 <= data_len; i += 8)

        mac_block(ctx, buffer, data + i);

    if (i < data_len) {

        memset(buf2, 0, 8);

        memcpy(buf2, data + i, data_len - i);

        mac_block(ctx, buffer, buf2);

        i += 8;

    }

    if (i == 8) {

        memset(buf2, 0, 8);

        mac_block(ctx, buffer, buf2);

    }

    get_mac(buffer, mac_len, mac);

    return 1;

}

/* Compute MAC with non-zero IV. Used in some RFC 4357 algorithms */

int gost_mac_iv(gost_ctx * ctx, int mac_len, const unsigned char *iv,

                const unsigned char *data, unsigned int data_len,

                unsigned char *mac)

{

    byte buffer[8];

    byte buf2[8];

    unsigned int i;

    memcpy(buffer, iv, 8);

    for (i = 0; i + 8 <= data_len; i += 8)

        mac_block(ctx, buffer, data + i);

    if (i < data_len) {

        memset(buf2, 0, 8);

        memcpy(buf2, data + i, data_len - i);

        mac_block(ctx, buffer, buf2);

        i += 8;

    }

    if (i == 8) {

        memset(buf2, 0, 8);

        mac_block(ctx, buffer, buf2);

    }

    get_mac(buffer, mac_len, mac);

    return 1;

}

/* Implements key meshing algorithm by modifing ctx and IV in place */

void cryptopro_key_meshing(gost_ctx * ctx, unsigned char *iv)

{

    unsigned char newkey[32], newiv[8];

    /* Set static keymeshing key */

    /* "Decrypt" key with keymeshing key */

    gost_dec(ctx, CryptoProKeyMeshingKey, newkey, 4);

    /* set new key */

    gost_key(ctx, newkey);

    /* Encrypt iv with new key */

    gostcrypt(ctx, iv, newiv);

    memcpy(iv, newiv, 8);

}