crypt/sha256-block.c

   1 #include <stdint.h>
   2
   3 /* Process LEN bytes of BUFFER, accumulating context into CTX.
   4    It is assumed that LEN % 64 == 0.  */
   5 void
   6 sha256_process_block (const void *buffer, size_t len, struct sha256_ctx *ctx)
   7 {
   8   const uint32_t *words = buffer;
   9   size_t nwords = len / sizeof (uint32_t);
  10   uint32_t a = ctx->H[0];
  11   uint32_t b = ctx->H[1];
  12   uint32_t c = ctx->H[2];
  13   uint32_t d = ctx->H[3];
  14   uint32_t e = ctx->H[4];
  15   uint32_t f = ctx->H[5];
  16   uint32_t g = ctx->H[6];
  17   uint32_t h = ctx->H[7];
  18
  19   /* First increment the byte count.  FIPS 180-2 specifies the possible
  20      length of the file up to 2^64 bits.  Here we only compute the
  21      number of bytes.  */
  22   ctx->total64 += len;
  23
  24   /* Process all bytes in the buffer with 64 bytes in each round of
  25      the loop.  */
  26   while (nwords > 0)
  27     {
  28       uint32_t W[64];
  29       uint32_t a_save = a;
  30       uint32_t b_save = b;
  31       uint32_t c_save = c;
  32       uint32_t d_save = d;
  33       uint32_t e_save = e;
  34       uint32_t f_save = f;
  35       uint32_t g_save = g;
  36       uint32_t h_save = h;
  37
  38       /* Operators defined in FIPS 180-2:4.1.2.  */
  39 #define Ch(x, y, z) ((x & y) ^ (~x & z))
  40 #define Maj(x, y, z) ((x & y) ^ (x & z) ^ (y & z))
  41 #define S0(x) (CYCLIC (x, 2) ^ CYCLIC (x, 13) ^ CYCLIC (x, 22))
  42 #define S1(x) (CYCLIC (x, 6) ^ CYCLIC (x, 11) ^ CYCLIC (x, 25))
  43 #define R0(x) (CYCLIC (x, 7) ^ CYCLIC (x, 18) ^ (x >> 3))
  44 #define R1(x) (CYCLIC (x, 17) ^ CYCLIC (x, 19) ^ (x >> 10))
  45
  46       /* It is unfortunate that C does not provide an operator for
  47          cyclic rotation.  Hope the C compiler is smart enough.  */
  48 #define CYCLIC(w, s) ((w >> s) | (w << (32 - s)))
  49
  50       /* Compute the message schedule according to FIPS 180-2:6.2.2 step 2.  */
  51       for (unsigned int t = 0; t < 16; ++t)
  52         {
  53           W[t] = SWAP (*words);
  54           ++words;
  55         }
  56       for (unsigned int t = 16; t < 64; ++t)
  57         W[t] = R1 (W[t - 2]) + W[t - 7] + R0 (W[t - 15]) + W[t - 16];
  58
  59       /* The actual computation according to FIPS 180-2:6.2.2 step 3.  */
  60       for (unsigned int t = 0; t < 64; ++t)
  61         {
  62           uint32_t T1 = h + S1 (e) + Ch (e, f, g) + K[t] + W[t];
  63           uint32_t T2 = S0 (a) + Maj (a, b, c);
  64           h = g;
  65           g = f;
  66           f = e;
  67           e = d + T1;
  68           d = c;
  69           c = b;
  70           b = a;
  71           a = T1 + T2;
  72         }
  73
  74       /* Add the starting values of the context according to FIPS 180-2:6.2.2
  75          step 4.  */
  76       a += a_save;
  77       b += b_save;
  78       c += c_save;
  79       d += d_save;
  80       e += e_save;
  81       f += f_save;
  82       g += g_save;
  83       h += h_save;
  84
  85       /* Prepare for the next round.  */
  86       nwords -= 16;
  87     }
  88
  89   /* Put checksum in context given as argument.  */
  90   ctx->H[0] = a;
  91   ctx->H[1] = b;
  92   ctx->H[2] = c;
  93   ctx->H[3] = d;
  94   ctx->H[4] = e;
  95   ctx->H[5] = f;
  96   ctx->H[6] = g;
  97   ctx->H[7] = h;
  98 }