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  1. /*********************************************************************
  2. * Filename:   sha256.c
  3. * Author:     Brad Conte (brad AT bradconte.com)
  4. * Copyright:
  5. * Disclaimer: This code is presented "as is" without any guarantees.
  6. * Details:    Implementation of the SHA-256 hashing algorithm.
  7.               SHA-256 is one of the three algorithms in the SHA2
  8.               specification. The others, SHA-384 and SHA-512, are not
  9.               offered in this implementation.
  10.               Algorithm specification can be found here:
  11.                * http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf
  12.               This implementation uses little endian byte order.
  13. *********************************************************************/
  14.  
  15. /*************************** HEADER FILES ***************************/
  16. #include <stdlib.h>
  17. #include <string.h>
  18. #include "sha256.h"
  19.  
  20. /****************************** MACROS ******************************/
  21. #define ROTLEFT(a,b) (((a) << (b)) | ((a) >> (32-(b))))
  22. #define ROTRIGHT(a,b) (((a) >> (b)) | ((a) << (32-(b))))
  23.  
  24. #define CH(x,y,z) (((x) & (y)) ^ (~(x) & (z)))
  25. #define MAJ(x,y,z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
  26. #define EP0(x) (ROTRIGHT(x,2) ^ ROTRIGHT(x,13) ^ ROTRIGHT(x,22))
  27. #define EP1(x) (ROTRIGHT(x,6) ^ ROTRIGHT(x,11) ^ ROTRIGHT(x,25))
  28. #define SIG0(x) (ROTRIGHT(x,7) ^ ROTRIGHT(x,18) ^ ((x) >> 3))
  29. #define SIG1(x) (ROTRIGHT(x,17) ^ ROTRIGHT(x,19) ^ ((x) >> 10))
  30.  
  31. /**************************** VARIABLES *****************************/
  32. static const WORD k[64] = {
  33.         0x428a2f98,0x71374491,0xb5c0fbcf,0xe9b5dba5,0x3956c25b,0x59f111f1,0x923f82a4,0xab1c5ed5,
  34.         0xd807aa98,0x12835b01,0x243185be,0x550c7dc3,0x72be5d74,0x80deb1fe,0x9bdc06a7,0xc19bf174,
  35.         0xe49b69c1,0xefbe4786,0x0fc19dc6,0x240ca1cc,0x2de92c6f,0x4a7484aa,0x5cb0a9dc,0x76f988da,
  36.         0x983e5152,0xa831c66d,0xb00327c8,0xbf597fc7,0xc6e00bf3,0xd5a79147,0x06ca6351,0x14292967,
  37.         0x27b70a85,0x2e1b2138,0x4d2c6dfc,0x53380d13,0x650a7354,0x766a0abb,0x81c2c92e,0x92722c85,
  38.         0xa2bfe8a1,0xa81a664b,0xc24b8b70,0xc76c51a3,0xd192e819,0xd6990624,0xf40e3585,0x106aa070,
  39.         0x19a4c116,0x1e376c08,0x2748774c,0x34b0bcb5,0x391c0cb3,0x4ed8aa4a,0x5b9cca4f,0x682e6ff3,
  40.         0x748f82ee,0x78a5636f,0x84c87814,0x8cc70208,0x90befffa,0xa4506ceb,0xbef9a3f7,0xc67178f2
  41. };
  42.  
  43. /*********************** FUNCTION DEFINITIONS ***********************/
  44. void sha256_transform(SHA256_CTX *ctx, const BYTE data[])
  45. {
  46.         WORD a, b, c, d, e, f, g, h, i, j, t1, t2, m[64];
  47.  
  48.         for (i = 0, j = 0; i < 16; ++i, j += 4)
  49.                 m[i] = (data[j] << 24) | (data[j + 1] << 16) | (data[j + 2] << 8) | (data[j + 3]);
  50.         for ( ; i < 64; ++i)
  51.                 m[i] = SIG1(m[i - 2]) + m[i - 7] + SIG0(m[i - 15]) + m[i - 16];
  52.  
  53.         a = ctx->state[0];
  54.         b = ctx->state[1];
  55.         c = ctx->state[2];
  56.         d = ctx->state[3];
  57.         e = ctx->state[4];
  58.         f = ctx->state[5];
  59.         g = ctx->state[6];
  60.         h = ctx->state[7];
  61.  
  62.         for (i = 0; i < 64; ++i) {
  63.                 t1 = h + EP1(e) + CH(e,f,g) + k[i] + m[i];
  64.                 t2 = EP0(a) + MAJ(a,b,c);
  65.                 h = g;
  66.                 g = f;
  67.                 f = e;
  68.                 e = d + t1;
  69.                 d = c;
  70.                 c = b;
  71.                 b = a;
  72.                 a = t1 + t2;
  73.         }
  74.  
  75.         ctx->state[0] += a;
  76.         ctx->state[1] += b;
  77.         ctx->state[2] += c;
  78.         ctx->state[3] += d;
  79.         ctx->state[4] += e;
  80.         ctx->state[5] += f;
  81.         ctx->state[6] += g;
  82.         ctx->state[7] += h;
  83. }
  84.  
  85. void sha256_init(SHA256_CTX *ctx)
  86. {
  87.         ctx->datalen = 0;
  88.         ctx->bitlen = 0;
  89.         ctx->state[0] = 0x6a09e667;
  90.         ctx->state[1] = 0xbb67ae85;
  91.         ctx->state[2] = 0x3c6ef372;
  92.         ctx->state[3] = 0xa54ff53a;
  93.         ctx->state[4] = 0x510e527f;
  94.         ctx->state[5] = 0x9b05688c;
  95.         ctx->state[6] = 0x1f83d9ab;
  96.         ctx->state[7] = 0x5be0cd19;
  97. }
  98.  
  99. void sha256_update(SHA256_CTX *ctx, const BYTE data[], size_t len)
  100. {
  101.         WORD i;
  102.  
  103.         for (i = 0; i < len; ++i) {
  104.                 ctx->data[ctx->datalen] = data[i];
  105.                 ctx->datalen++;
  106.                 if (ctx->datalen == 64) {
  107.                         sha256_transform(ctx, ctx->data);
  108.                         ctx->bitlen += 512;
  109.                         ctx->datalen = 0;
  110.                 }
  111.         }
  112. }
  113.  
  114. void sha256_final(SHA256_CTX *ctx, BYTE hash[])
  115. {
  116.         WORD i;
  117.  
  118.         i = ctx->datalen;
  119.  
  120.         // Pad whatever data is left in the buffer.
  121.         if (ctx->datalen < 56) {
  122.                 ctx->data[i++] = 0x80;
  123.                 while (i < 56)
  124.                         ctx->data[i++] = 0x00;
  125.         }
  126.         else {
  127.                 ctx->data[i++] = 0x80;
  128.                 while (i < 64)
  129.                         ctx->data[i++] = 0x00;
  130.                 sha256_transform(ctx, ctx->data);
  131.                 memset(ctx->data, 0, 56);
  132.         }
  133.  
  134.         // Append to the padding the total message's length in bits and transform.
  135.         ctx->bitlen += ctx->datalen * 8;
  136.         ctx->data[63] = ctx->bitlen;
  137.         ctx->data[62] = ctx->bitlen >> 8;
  138.         ctx->data[61] = ctx->bitlen >> 16;
  139.         ctx->data[60] = ctx->bitlen >> 24;
  140.         ctx->data[59] = ctx->bitlen >> 32;
  141.         ctx->data[58] = ctx->bitlen >> 40;
  142.         ctx->data[57] = ctx->bitlen >> 48;
  143.         ctx->data[56] = ctx->bitlen >> 56;
  144.         sha256_transform(ctx, ctx->data);
  145.  
  146.         // Since this implementation uses little endian byte ordering and SHA uses big endian,
  147.         // reverse all the bytes when copying the final state to the output hash.
  148.         for (i = 0; i < 4; ++i) {
  149.                 hash[i]      = (ctx->state[0] >> (24 - i * 8)) & 0x000000ff;
  150.                 hash[i + 4]  = (ctx->state[1] >> (24 - i * 8)) & 0x000000ff;
  151.                 hash[i + 8]  = (ctx->state[2] >> (24 - i * 8)) & 0x000000ff;
  152.                 hash[i + 12] = (ctx->state[3] >> (24 - i * 8)) & 0x000000ff;
  153.                 hash[i + 16] = (ctx->state[4] >> (24 - i * 8)) & 0x000000ff;
  154.                 hash[i + 20] = (ctx->state[5] >> (24 - i * 8)) & 0x000000ff;
  155.                 hash[i + 24] = (ctx->state[6] >> (24 - i * 8)) & 0x000000ff;
  156.                 hash[i + 28] = (ctx->state[7] >> (24 - i * 8)) & 0x000000ff;
  157.         }
  158. }
  159.