/* sha256.c - an implementation of SHA-256/224 hash functions

 * based on FIPS 180-3 (Federal Information Processing Standart).

 *

 * Copyright (c) 2010, Aleksey Kravchenko <rhash.admin@gmail.com>

 *

 * Permission to use, copy, modify, and/or distribute this software for any

 * purpose with or without fee is hereby granted.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH

 * REGARD TO THIS SOFTWARE  INCLUDING ALL IMPLIED WARRANTIES OF  MERCHANTABILITY

 * AND FITNESS.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,

 * INDIRECT,  OR CONSEQUENTIAL DAMAGES  OR ANY DAMAGES WHATSOEVER RESULTING FROM

 * LOSS OF USE,  DATA OR PROFITS,  WHETHER IN AN ACTION OF CONTRACT,  NEGLIGENCE

 * OR OTHER TORTIOUS ACTION,  ARISING OUT OF  OR IN CONNECTION  WITH THE USE  OR

 * PERFORMANCE OF THIS SOFTWARE.

 */

#include <string.h>

#include "byte_order.h"

#include "sha256.h"

/* SHA-224 and SHA-256 constants for 64 rounds. These words represent

 * the first 32 bits of the fractional parts of the cube

 * roots of the first 64 prime numbers. */

static const unsigned rhash_k256[64] = {

  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

};

/* The SHA256/224 functions defined by FIPS 180-3, 4.1.2 */

/* Optimized version of Ch(x,y,z)=((x & y) | (~x & z)) */

#define Ch(x,y,z)  ((z) ^ ((x) & ((y) ^ (z))))

/* Optimized version of Maj(x,y,z)=((x & y) ^ (x & z) ^ (y & z)) */

#define Maj(x,y,z) (((x) & (y)) ^ ((z) & ((x) ^ (y))))

#define Sigma0(x) (ROTR32((x), 2) ^ ROTR32((x), 13) ^ ROTR32((x), 22))

#define Sigma1(x) (ROTR32((x), 6) ^ ROTR32((x), 11) ^ ROTR32((x), 25))

#define sigma0(x) (ROTR32((x), 7) ^ ROTR32((x), 18) ^ ((x) >>  3))

#define sigma1(x) (ROTR32((x),17) ^ ROTR32((x), 19) ^ ((x) >> 10))

/* Recalculate element n-th of circular buffer W using formula

 *   W[n] = sigma1(W[n - 2]) + W[n - 7] + sigma0(W[n - 15]) + W[n - 16]; */

#define RECALCULATE_W(W,n) (W[n] += \

  (sigma1(W[(n - 2) & 15]) + W[(n - 7) & 15] + sigma0(W[(n - 15) & 15])))

#define ROUND(a,b,c,d,e,f,g,h,k,data) { \

  unsigned T1 = h + Sigma1(e) + Ch(e,f,g) + k + (data); \

  d += T1, h = T1 + Sigma0(a) + Maj(a,b,c); }

#define ROUND_1_16(a,b,c,d,e,f,g,h,n) \

  ROUND(a,b,c,d,e,f,g,h, rhash_k256[n], W[n] = be2me_32(block[n]))

#define ROUND_17_64(a,b,c,d,e,f,g,h,n) \

  ROUND(a,b,c,d,e,f,g,h, k[n], RECALCULATE_W(W, n))

/**

 * Initialize context before calculating hash.

 *

 * @param ctx context to initialize

 */

void rhash_sha256_init(sha256_ctx* ctx)

{

  /* Initial values. These words were obtained by taking the first 32

   * bits of the fractional parts of the square roots of the first

   * eight prime numbers. */

  static const unsigned SHA256_H0[8] = {

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

    0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19

  };

  memset(ctx->message, 0, sizeof(ctx->message));

  ctx->length = 0;

  ctx->digest_length = sha256_hash_size;

  /* initialize algorithm state */

  memcpy(ctx->hash, SHA256_H0, sizeof(ctx->hash));

}

/**

 * Initialize context before calculating hash.

 *

 * @param ctx context to initialize

 */

void rhash_sha224_init(struct sha256_ctx* ctx)

{

  /* Initial values from FIPS 180-3. These words were obtained by taking

   * bits from 33th to 64th of the fractional parts of the square

   * roots of ninth through sixteenth prime numbers. */

  static const unsigned SHA224_H0[8] = {

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

    0xffc00b31, 0x68581511, 0x64f98fa7, 0xbefa4fa4

  };

  memset(ctx->message, 0, sizeof(ctx->message));

  ctx->length = 0;

  ctx->digest_length = sha224_hash_size;

  memcpy(ctx->hash, SHA224_H0, sizeof(ctx->hash));

}

/**

 * The core transformation. Process a 512-bit block.

 *

 * @param hash algorithm state

 * @param block the message block to process

 */

static void rhash_sha256_process_block(unsigned hash[8], unsigned block[16])

{

  unsigned A, B, C, D, E, F, G, H;

  unsigned W[16];

  const unsigned* k;

  int i;

  A = hash[0], B = hash[1], C = hash[2], D = hash[3];

  E = hash[4], F = hash[5], G = hash[6], H = hash[7];

  /* Compute SHA using alternate Method: FIPS 180-3 6.1.3 */

  ROUND_1_16(A, B, C, D, E, F, G, H, 0);

  ROUND_1_16(H, A, B, C, D, E, F, G, 1);

  ROUND_1_16(G, H, A, B, C, D, E, F, 2);

  ROUND_1_16(F, G, H, A, B, C, D, E, 3);

  ROUND_1_16(E, F, G, H, A, B, C, D, 4);

  ROUND_1_16(D, E, F, G, H, A, B, C, 5);

  ROUND_1_16(C, D, E, F, G, H, A, B, 6);

  ROUND_1_16(B, C, D, E, F, G, H, A, 7);

  ROUND_1_16(A, B, C, D, E, F, G, H, 8);

  ROUND_1_16(H, A, B, C, D, E, F, G, 9);

  ROUND_1_16(G, H, A, B, C, D, E, F, 10);

  ROUND_1_16(F, G, H, A, B, C, D, E, 11);

  ROUND_1_16(E, F, G, H, A, B, C, D, 12);

  ROUND_1_16(D, E, F, G, H, A, B, C, 13);

  ROUND_1_16(C, D, E, F, G, H, A, B, 14);

  ROUND_1_16(B, C, D, E, F, G, H, A, 15);

  for (i = 16, k = &rhash_k256[16]; i < 64; i += 16, k += 16) {

    ROUND_17_64(A, B, C, D, E, F, G, H,  0);

    ROUND_17_64(H, A, B, C, D, E, F, G,  1);

    ROUND_17_64(G, H, A, B, C, D, E, F,  2);

    ROUND_17_64(F, G, H, A, B, C, D, E,  3);

    ROUND_17_64(E, F, G, H, A, B, C, D,  4);

    ROUND_17_64(D, E, F, G, H, A, B, C,  5);

    ROUND_17_64(C, D, E, F, G, H, A, B,  6);

    ROUND_17_64(B, C, D, E, F, G, H, A,  7);

    ROUND_17_64(A, B, C, D, E, F, G, H,  8);

    ROUND_17_64(H, A, B, C, D, E, F, G,  9);

    ROUND_17_64(G, H, A, B, C, D, E, F, 10);

    ROUND_17_64(F, G, H, A, B, C, D, E, 11);

    ROUND_17_64(E, F, G, H, A, B, C, D, 12);

    ROUND_17_64(D, E, F, G, H, A, B, C, 13);

    ROUND_17_64(C, D, E, F, G, H, A, B, 14);

    ROUND_17_64(B, C, D, E, F, G, H, A, 15);

  }

  hash[0] += A, hash[1] += B, hash[2] += C, hash[3] += D;

  hash[4] += E, hash[5] += F, hash[6] += G, hash[7] += H;

}

/**

 * Calculate message hash.

 * Can be called repeatedly with chunks of the message to be hashed.

 *

 * @param ctx the algorithm context containing current hashing state

 * @param msg message chunk

 * @param size length of the message chunk

 */

void rhash_sha256_update(sha256_ctx* ctx, const unsigned char* msg, size_t size)

{

  size_t index = (size_t)ctx->length & 63;

  ctx->length += size;

  /* fill partial block */

  if (index) {

    size_t left = sha256_block_size - index;

    memcpy((char*)ctx->message + index, msg, (size < left ? size : left));

    if (size < left) return;

    /* process partial block */

    rhash_sha256_process_block(ctx->hash, (unsigned*)ctx->message);

    msg  += left;

    size -= left;

  }

  while (size >= sha256_block_size) {

    unsigned* aligned_message_block;

    if (IS_ALIGNED_32(msg)) {

      /* the most common case is processing of an already aligned message

      without copying it */

      aligned_message_block = (unsigned*)msg;

    } else {

      memcpy(ctx->message, msg, sha256_block_size);

      aligned_message_block = (unsigned*)ctx->message;

    }

    rhash_sha256_process_block(ctx->hash, aligned_message_block);

    msg  += sha256_block_size;

    size -= sha256_block_size;

  }

  if (size) {

    memcpy(ctx->message, msg, size); /* save leftovers */

  }

}

/**

 * Store calculated hash into the given array.

 *

 * @param ctx the algorithm context containing current hashing state

 * @param result calculated hash in binary form

 */

void rhash_sha256_final(sha256_ctx* ctx, unsigned char* result)

{

  size_t index = ((unsigned)ctx->length & 63) >> 2;

  unsigned shift = ((unsigned)ctx->length & 3) * 8;

  /* pad message and run for last block */

  /* append the byte 0x80 to the message */

  ctx->message[index]   &= le2me_32(~(0xFFFFFFFFu << shift));

  ctx->message[index++] ^= le2me_32(0x80u << shift);

  /* if no room left in the message to store 64-bit message length */

  if (index > 14) {

    /* then fill the rest with zeros and process it */

    while (index < 16) {

      ctx->message[index++] = 0;

    }

    rhash_sha256_process_block(ctx->hash, ctx->message);

    index = 0;

  }

  while (index < 14) {

    ctx->message[index++] = 0;

  }

  ctx->message[14] = be2me_32( (unsigned)(ctx->length >> 29) );

  ctx->message[15] = be2me_32( (unsigned)(ctx->length << 3) );

  rhash_sha256_process_block(ctx->hash, ctx->message);

  if (result) be32_copy(result, 0, ctx->hash, ctx->digest_length);

}