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

 *                          gosthash.c                                *

 *             Copyright (c) 2005-2006 Cryptocom LTD                  *

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

 *                                                                    *

 *    Implementation of GOST R 34.11-94 hash function                 *

 *       uses on gost89.c and gost89.h Doesn't need OpenSSL           *

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

#include <string.h>

#include "gost89.h"

#include "gosthash.h"

/*

 * Use OPENSSL_malloc for memory allocation if compiled with

 * -DOPENSSL_BUILD, and libc malloc otherwise

 */

#ifndef MYALLOC

# ifdef OPENSSL_BUILD

#  include <openssl/crypto.h>

#  define MYALLOC(size) OPENSSL_malloc(size)

#  define MYFREE(ptr) OPENSSL_free(ptr)

# else

#  define MYALLOC(size) malloc(size)

#  define MYFREE(ptr) free(ptr)

# endif

#endif

/*

 * Following functions are various bit meshing routines used in GOST R

 * 34.11-94 algorithms

 */

static void swap_bytes(byte * w, byte * k)

{

    int i, j;

    for (i = 0; i < 4; i++)

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

            k[i + 4 * j] = w[8 * i + j];

}

/* was A_A */

static void circle_xor8(const byte * w, byte * k)

{

    byte buf[8];

    int i;

    memcpy(buf, w, 8);

    memmove(k, w + 8, 24);

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

        k[i + 24] = buf[i] ^ k[i];

}

/* was R_R */

static void transform_3(byte * data)

{

    unsigned short int acc;

    acc = (data[0] ^ data[2] ^ data[4] ^ data[6] ^ data[24] ^ data[30]) |

        ((data[1] ^ data[3] ^ data[5] ^ data[7] ^ data[25] ^ data[31]) << 8);

    memmove(data, data + 2, 30);

    data[30] = acc & 0xff;

    data[31] = acc >> 8;

}

/* Adds blocks of N bytes modulo 2**(8*n). Returns carry*/

static int add_blocks(int n, byte * left, const byte * right)

{

    int i;

    int carry = 0;

    int sum;

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

        sum = (int)left[i] + (int)right[i] + carry;

        left[i] = sum & 0xff;

        carry = sum >> 8;

    }

    return carry;

}

/* Xor two sequences of bytes */

static void xor_blocks(byte * result, const byte * a, const byte * b,

                       size_t len)

{

    size_t i;

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

        result[i] = a[i] ^ b[i];

}

/*

 *      Calculate H(i+1) = Hash(Hi,Mi)

 *      Where H and M are 32 bytes long

 */

static int hash_step(gost_ctx * c, byte * H, const byte * M)

{

    byte U[32], W[32], V[32], S[32], Key[32];

    int i;

    /* Compute first key */

    xor_blocks(W, H, M, 32);

    swap_bytes(W, Key);

    /* Encrypt first 8 bytes of H with first key */

    gost_enc_with_key(c, Key, H, S);

    /* Compute second key */

    circle_xor8(H, U);

    circle_xor8(M, V);

    circle_xor8(V, V);

    xor_blocks(W, U, V, 32);

    swap_bytes(W, Key);

    /* encrypt second 8 bytes of H with second key */

    gost_enc_with_key(c, Key, H + 8, S + 8);

    /* compute third key */

    circle_xor8(U, U);

    U[31] = ~U[31];

    U[29] = ~U[29];

    U[28] = ~U[28];

    U[24] = ~U[24];

    U[23] = ~U[23];

    U[20] = ~U[20];

    U[18] = ~U[18];

    U[17] = ~U[17];

    U[14] = ~U[14];

    U[12] = ~U[12];

    U[10] = ~U[10];

    U[8] = ~U[8];

    U[7] = ~U[7];

    U[5] = ~U[5];

    U[3] = ~U[3];

    U[1] = ~U[1];

    circle_xor8(V, V);

    circle_xor8(V, V);

    xor_blocks(W, U, V, 32);

    swap_bytes(W, Key);

    /* encrypt third 8 bytes of H with third key */

    gost_enc_with_key(c, Key, H + 16, S + 16);

    /* Compute fourth key */

    circle_xor8(U, U);

    circle_xor8(V, V);

    circle_xor8(V, V);

    xor_blocks(W, U, V, 32);

    swap_bytes(W, Key);

    /* Encrypt last 8 bytes with fourth key */

    gost_enc_with_key(c, Key, H + 24, S + 24);

    for (i = 0; i < 12; i++)

        transform_3(S);

    xor_blocks(S, S, M, 32);

    transform_3(S);

    xor_blocks(S, S, H, 32);

    for (i = 0; i < 61; i++)

        transform_3(S);

    memcpy(H, S, 32);

    return 1;

}

/*

 * Initialize gost_hash ctx - cleans up temporary structures and set up

 * substitution blocks

 */

int init_gost_hash_ctx(gost_hash_ctx * ctx,

                       const gost_subst_block * subst_block)

{

    memset(ctx, 0, sizeof(gost_hash_ctx));

    ctx->cipher_ctx = (gost_ctx *) MYALLOC(sizeof(gost_ctx));

    if (!ctx->cipher_ctx) {

        return 0;

    }

    gost_init(ctx->cipher_ctx, subst_block);

    return 1;

}

/*

 * Free cipher CTX if it is dynamically allocated. Do not use

 * if cipher ctx is statically allocated as in OpenSSL implementation of

 * GOST hash algroritm

 *

 */

void done_gost_hash_ctx(gost_hash_ctx * ctx)

{

    /*

     * No need to use gost_destroy, because cipher keys are not really secret

     * when hashing

     */

    MYFREE(ctx->cipher_ctx);

}

/*

 * reset state of hash context to begin hashing new message

 */

int start_hash(gost_hash_ctx * ctx)

{

    if (!ctx->cipher_ctx)

        return 0;

    memset(&(ctx->H), 0, 32);

    memset(&(ctx->S), 0, 32);

    ctx->len = 0L;

    ctx->left = 0;

    return 1;

}

/*

 * Hash block of arbitrary length

 *

 *

 */

int hash_block(gost_hash_ctx * ctx, const byte * block, size_t length)

{

    if (ctx->left) {

        /*

         * There are some bytes from previous step

         */

        unsigned int add_bytes = 32 - ctx->left;

        if (add_bytes > length) {

            add_bytes = length;

        }

        memcpy(&(ctx->remainder[ctx->left]), block, add_bytes);

        ctx->left += add_bytes;

        if (ctx->left < 32) {

            return 1;

        }

        block += add_bytes;

        length -= add_bytes;

        hash_step(ctx->cipher_ctx, ctx->H, ctx->remainder);

        add_blocks(32, ctx->S, ctx->remainder);

        ctx->len += 32;

        ctx->left = 0;

    }

    while (length >= 32) {

        hash_step(ctx->cipher_ctx, ctx->H, block);

        add_blocks(32, ctx->S, block);

        ctx->len += 32;

        block += 32;

        length -= 32;

    }

    if (length) {

        memcpy(ctx->remainder, block, ctx->left = length);

    }

    return 1;

}

/*

 * Compute hash value from current state of ctx

 * state of hash ctx becomes invalid and cannot be used for further

 * hashing.

 */

int finish_hash(gost_hash_ctx * ctx, byte * hashval)

{

    byte buf[32];

    byte H[32];

    byte S[32];

    ghosthash_len fin_len = ctx->len;

    byte *bptr;

    memcpy(H, ctx->H, 32);

    memcpy(S, ctx->S, 32);

    if (ctx->left) {

        memset(buf, 0, 32);

        memcpy(buf, ctx->remainder, ctx->left);

        hash_step(ctx->cipher_ctx, H, buf);

        add_blocks(32, S, buf);

        fin_len += ctx->left;

    }

    memset(buf, 0, 32);

    bptr = buf;

    fin_len <<= 3;              /* Hash length in BITS!! */

    while (fin_len > 0) {

        *(bptr++) = (byte) (fin_len & 0xFF);

        fin_len >>= 8;

    };

    hash_step(ctx->cipher_ctx, H, buf);

    hash_step(ctx->cipher_ctx, H, S);

    memcpy(hashval, H, 32);

    return 1;

}