1 files changed, 96 insertions, 0 deletions
diff --git a/crypt/sha256-block.c b/crypt/sha256-block.c
new file mode 100644
index 0000000..a163e25
--- /dev/null
+++ b/crypt/sha256-block.c
@@ -0,0 +1,96 @@
+/* Process LEN bytes of BUFFER, accumulating context into CTX.
+   It is assumed that LEN % 64 == 0.  */
+void
+sha256_process_block (const void *buffer, size_t len, struct sha256_ctx *ctx)
+{
+  const uint32_t *words = buffer;
+  size_t nwords = len / sizeof (uint32_t);
+  uint32_t a = ctx->H[0];
+  uint32_t b = ctx->H[1];
+  uint32_t c = ctx->H[2];
+  uint32_t d = ctx->H[3];
+  uint32_t e = ctx->H[4];
+  uint32_t f = ctx->H[5];
+  uint32_t g = ctx->H[6];
+  uint32_t h = ctx->H[7];
+
+  /* First increment the byte count.  FIPS 180-2 specifies the possible
+     length of the file up to 2^64 bits.  Here we only compute the
+     number of bytes.  */
+  ctx->total64 += len;
+
+  /* Process all bytes in the buffer with 64 bytes in each round of
+     the loop.  */
+  while (nwords > 0)
+    {
+      uint32_t W[64];
+      uint32_t a_save = a;
+      uint32_t b_save = b;
+      uint32_t c_save = c;
+      uint32_t d_save = d;
+      uint32_t e_save = e;
+      uint32_t f_save = f;
+      uint32_t g_save = g;
+      uint32_t h_save = h;
+
+      /* Operators defined in FIPS 180-2:4.1.2.  */
+#define Ch(x, y, z) ((x & y) ^ (~x & z))
+#define Maj(x, y, z) ((x & y) ^ (x & z) ^ (y & z))
+#define S0(x) (CYCLIC (x, 2) ^ CYCLIC (x, 13) ^ CYCLIC (x, 22))
+#define S1(x) (CYCLIC (x, 6) ^ CYCLIC (x, 11) ^ CYCLIC (x, 25))
+#define R0(x) (CYCLIC (x, 7) ^ CYCLIC (x, 18) ^ (x >> 3))
+#define R1(x) (CYCLIC (x, 17) ^ CYCLIC (x, 19) ^ (x >> 10))
+
+      /* It is unfortunate that C does not provide an operator for
+	 cyclic rotation.  Hope the C compiler is smart enough.  */
+#define CYCLIC(w, s) ((w >> s) | (w << (32 - s)))
+
+      /* Compute the message schedule according to FIPS 180-2:6.2.2 step 2.  */
+      for (unsigned int t = 0; t < 16; ++t)
+	{
+	  W[t] = SWAP (*words);
+	  ++words;
+	}
+      for (unsigned int t = 16; t < 64; ++t)
+	W[t] = R1 (W[t - 2]) + W[t - 7] + R0 (W[t - 15]) + W[t - 16];
+
+      /* The actual computation according to FIPS 180-2:6.2.2 step 3.  */
+      for (unsigned int t = 0; t < 64; ++t)
+	{
+	  uint32_t T1 = h + S1 (e) + Ch (e, f, g) + K[t] + W[t];
+	  uint32_t T2 = S0 (a) + Maj (a, b, c);
+	  h = g;
+	  g = f;
+	  f = e;
+	  e = d + T1;
+	  d = c;
+	  c = b;
+	  b = a;
+	  a = T1 + T2;
+	}
+
+      /* Add the starting values of the context according to FIPS 180-2:6.2.2
+	 step 4.  */
+      a += a_save;
+      b += b_save;
+      c += c_save;
+      d += d_save;
+      e += e_save;
+      f += f_save;
+      g += g_save;
+      h += h_save;
+
+      /* Prepare for the next round.  */
+      nwords -= 16;
+    }
+
+  /* Put checksum in context given as argument.  */
+  ctx->H[0] = a;
+  ctx->H[1] = b;
+  ctx->H[2] = c;
+  ctx->H[3] = d;
+  ctx->H[4] = e;
+  ctx->H[5] = f;
+  ctx->H[6] = g;
+  ctx->H[7] = h;
+}