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+/* sha256.h
+ *
+ * The sha256 hash function.
+ */
+
+/* nettle, low-level cryptographics library
+ *
+ * Copyright (C) 2001 Niels M�ller
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * The nettle library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with the nettle library; see the file COPYING.LIB. If not, write to
+ * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/* Modelled after the sha1.c code by Peter Gutmann. */
+
+#include "sha.h"
+
+#include "macros.h"
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* A block, treated as a sequence of 32-bit words. */
+#define SHA256_DATA_LENGTH 16
+
+#define ROTR(n,x) ((x)>>(n) | ((x)<<(32-(n))))
+#define SHR(n,x) ((x)>>(n))
+
+/* The SHA256 functions. The Choice function is the same as the SHA1
+ function f1, and the majority function is the same as the SHA1 f3
+ function. They can be optimized to save one boolean operation each
+ - thanks to Rich Schroeppel, rcs@cs.arizona.edu for discovering
+ this */
+
+/* #define Choice(x,y,z) ( ( (x) & (y) ) | ( ~(x) & (z) ) ) */
+#define Choice(x,y,z) ( (z) ^ ( (x) & ( (y) ^ (z) ) ) )
+/* #define Majority(x,y,z) ( ((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)) ) */
+#define Majority(x,y,z) ( ((x) & (y)) ^ ((z) & ((x) ^ (y))) )
+
+#define S0(x) (ROTR(2,(x)) ^ ROTR(13,(x)) ^ ROTR(22,(x)))
+#define S1(x) (ROTR(6,(x)) ^ ROTR(11,(x)) ^ ROTR(25,(x)))
+
+#define s0(x) (ROTR(7,(x)) ^ ROTR(18,(x)) ^ SHR(3,(x)))
+#define s1(x) (ROTR(17,(x)) ^ ROTR(19,(x)) ^ SHR(10,(x)))
+
+/* Generated by the shadata program. */
+static const uint32_t
+K[64] =
+{
+ 0x428a2f98UL, 0x71374491UL, 0xb5c0fbcfUL, 0xe9b5dba5UL,
+ 0x3956c25bUL, 0x59f111f1UL, 0x923f82a4UL, 0xab1c5ed5UL,
+ 0xd807aa98UL, 0x12835b01UL, 0x243185beUL, 0x550c7dc3UL,
+ 0x72be5d74UL, 0x80deb1feUL, 0x9bdc06a7UL, 0xc19bf174UL,
+ 0xe49b69c1UL, 0xefbe4786UL, 0xfc19dc6UL, 0x240ca1ccUL,
+ 0x2de92c6fUL, 0x4a7484aaUL, 0x5cb0a9dcUL, 0x76f988daUL,
+ 0x983e5152UL, 0xa831c66dUL, 0xb00327c8UL, 0xbf597fc7UL,
+ 0xc6e00bf3UL, 0xd5a79147UL, 0x6ca6351UL, 0x14292967UL,
+ 0x27b70a85UL, 0x2e1b2138UL, 0x4d2c6dfcUL, 0x53380d13UL,
+ 0x650a7354UL, 0x766a0abbUL, 0x81c2c92eUL, 0x92722c85UL,
+ 0xa2bfe8a1UL, 0xa81a664bUL, 0xc24b8b70UL, 0xc76c51a3UL,
+ 0xd192e819UL, 0xd6990624UL, 0xf40e3585UL, 0x106aa070UL,
+ 0x19a4c116UL, 0x1e376c08UL, 0x2748774cUL, 0x34b0bcb5UL,
+ 0x391c0cb3UL, 0x4ed8aa4aUL, 0x5b9cca4fUL, 0x682e6ff3UL,
+ 0x748f82eeUL, 0x78a5636fUL, 0x84c87814UL, 0x8cc70208UL,
+ 0x90befffaUL, 0xa4506cebUL, 0xbef9a3f7UL, 0xc67178f2UL,
+};
+
+/* The initial expanding function. The hash function is defined over an
+ 64-word expanded input array W, where the first 16 are copies of the input
+ data, and the remaining 64 are defined by
+
+ W[ t ] = s1(W[t-2] + W[t-7] + s0(W[i-15] + W[i-16]
+
+ This implementation generates these values on the fly in a circular
+ buffer - thanks to Colin Plumb, colin@nyx10.cs.du.edu for this
+ optimization.
+*/
+
+#define EXPAND(W,i) \
+( W[(i) & 15 ] += (s1(W[((i)-2) & 15]) + W[((i)-7) & 15] + s0(W[((i)-15) & 15])) )
+
+/* The prototype SHA sub-round. The fundamental sub-round is:
+
+ T1 = h + S1(e) + Choice(e,f,g) + K[t] + W[t]
+ T2 = S0(a) + Majority(a,b,c)
+ a' = T1+T2
+ b' = a
+ c' = b
+ d' = c
+ e' = d + T1
+ f' = e
+ g' = f
+ h' = g
+
+ but this is implemented by unrolling the loop 8 times and renaming
+ the variables
+ ( h, a, b, c, d, e, f, g ) = ( a, b, c, d, e, f, g, h ) each
+ iteration. This code is then replicated 8, using the next 8 values
+ from the W[] array each time */
+
+/* FIXME: We can probably reorder this to optimize away at least one
+ * of T1 and T2. It's crucial that DATA is only used once, as that
+ * argument will have side effects. */
+#define ROUND(a,b,c,d,e,f,g,h,k,data) do { \
+ uint32_t T1 = h + S1(e) + Choice(e,f,g) + k + data; \
+ uint32_t T2 = S0(a) + Majority(a,b,c); \
+ d += T1; \
+ h = T1 + T2; \
+} while (0)
+
+/* Initialize the SHA values */
+
+void
+sha256_init(struct sha256_ctx *ctx)
+{
+ /* Initial values, also generated by the shadata program. */
+ static const uint32_t H0[_SHA256_DIGEST_LENGTH] =
+ {
+ 0x6a09e667UL, 0xbb67ae85UL, 0x3c6ef372UL, 0xa54ff53aUL,
+ 0x510e527fUL, 0x9b05688cUL, 0x1f83d9abUL, 0x5be0cd19UL,
+ };
+
+ memcpy(ctx->state, H0, sizeof(H0));
+
+ /* Initialize bit count */
+ ctx->count_low = ctx->count_high = 0;
+
+ /* Initialize buffer */
+ ctx->index = 0;
+}
+
+/* Perform the SHA transformation. Note that this code, like MD5, seems to
+ break some optimizing compilers due to the complexity of the expressions
+ and the size of the basic block. It may be necessary to split it into
+ sections, e.g. based on the four subrounds
+
+ Note that this function destroys the data area */
+
+static void
+sha256_transform(uint32_t *state, uint32_t *data)
+{
+ uint32_t A, B, C, D, E, F, G, H; /* Local vars */
+ unsigned i;
+ const uint32_t *k;
+ uint32_t *d;
+
+ /* Set up first buffer and local data buffer */
+ A = state[0];
+ B = state[1];
+ C = state[2];
+ D = state[3];
+ E = state[4];
+ F = state[5];
+ G = state[6];
+ H = state[7];
+
+ /* Heavy mangling */
+ /* First 16 subrounds that act on the original data */
+
+ for (i = 0, k = K, d = data; i<16; i+=8, k += 8, d+= 8)
+ {
+ ROUND(A, B, C, D, E, F, G, H, k[0], d[0]);
+ ROUND(H, A, B, C, D, E, F, G, k[1], d[1]);
+ ROUND(G, H, A, B, C, D, E, F, k[2], d[2]);
+ ROUND(F, G, H, A, B, C, D, E, k[3], d[3]);
+ ROUND(E, F, G, H, A, B, C, D, k[4], d[4]);
+ ROUND(D, E, F, G, H, A, B, C, k[5], d[5]);
+ ROUND(C, D, E, F, G, H, A, B, k[6], d[6]);
+ ROUND(B, C, D, E, F, G, H, A, k[7], d[7]);
+ }
+
+ for (; i<64; i += 16, k+= 16)
+ {
+ ROUND(A, B, C, D, E, F, G, H, k[ 0], EXPAND(data, 0));
+ ROUND(H, A, B, C, D, E, F, G, k[ 1], EXPAND(data, 1));
+ ROUND(G, H, A, B, C, D, E, F, k[ 2], EXPAND(data, 2));
+ ROUND(F, G, H, A, B, C, D, E, k[ 3], EXPAND(data, 3));
+ ROUND(E, F, G, H, A, B, C, D, k[ 4], EXPAND(data, 4));
+ ROUND(D, E, F, G, H, A, B, C, k[ 5], EXPAND(data, 5));
+ ROUND(C, D, E, F, G, H, A, B, k[ 6], EXPAND(data, 6));
+ ROUND(B, C, D, E, F, G, H, A, k[ 7], EXPAND(data, 7));
+ ROUND(A, B, C, D, E, F, G, H, k[ 8], EXPAND(data, 8));
+ ROUND(H, A, B, C, D, E, F, G, k[ 9], EXPAND(data, 9));
+ ROUND(G, H, A, B, C, D, E, F, k[10], EXPAND(data, 10));
+ ROUND(F, G, H, A, B, C, D, E, k[11], EXPAND(data, 11));
+ ROUND(E, F, G, H, A, B, C, D, k[12], EXPAND(data, 12));
+ ROUND(D, E, F, G, H, A, B, C, k[13], EXPAND(data, 13));
+ ROUND(C, D, E, F, G, H, A, B, k[14], EXPAND(data, 14));
+ ROUND(B, C, D, E, F, G, H, A, k[15], EXPAND(data, 15));
+ }
+
+ /* Update state */
+ state[0] += A;
+ state[1] += B;
+ state[2] += C;
+ state[3] += D;
+ state[4] += E;
+ state[5] += F;
+ state[6] += G;
+ state[7] += H;
+}
+
+static void
+sha256_block(struct sha256_ctx *ctx, const uint8_t *block)
+{
+ uint32_t data[SHA256_DATA_LENGTH];
+ int i;
+
+ /* Update block count */
+ if (!++ctx->count_low)
+ ++ctx->count_high;
+
+ /* Endian independent conversion */
+ for (i = 0; i<SHA256_DATA_LENGTH; i++, block += 4)
+ data[i] = READ_UINT32(block);
+
+ sha256_transform(ctx->state, data);
+}
+
+void
+sha256_update(struct sha256_ctx *ctx,
+ unsigned length, const uint8_t *buffer)
+{
+ if (ctx->index)
+ { /* Try to fill partial block */
+ unsigned left = SHA256_DATA_SIZE - ctx->index;
+ if (length < left)
+ {
+ memcpy(ctx->block + ctx->index, buffer, length);
+ ctx->index += length;
+ return; /* Finished */
+ }
+ else
+ {
+ memcpy(ctx->block + ctx->index, buffer, left);
+ sha256_block(ctx, ctx->block);
+ buffer += left;
+ length -= left;
+ }
+ }
+ while (length >= SHA256_DATA_SIZE)
+ {
+ sha256_block(ctx, buffer);
+ buffer += SHA256_DATA_SIZE;
+ length -= SHA256_DATA_SIZE;
+ }
+ /* Buffer leftovers */
+ /* NOTE: The corresponding sha1 code checks for the special case length == 0.
+ * That seems supoptimal, as I suspect it increases the number of branches. */
+
+ memcpy(ctx->block, buffer, length);
+ ctx->index = length;
+}
+
+/* Final wrapup - pad to SHA1_DATA_SIZE-byte boundary with the bit pattern
+ 1 0* (64-bit count of bits processed, MSB-first) */
+
+void
+sha256_final(struct sha256_ctx *ctx)
+{
+ uint32_t data[SHA256_DATA_LENGTH];
+ int i;
+ int words;
+
+ i = ctx->index;
+
+ /* Set the first char of padding to 0x80. This is safe since there is
+ always at least one byte free */
+
+ assert(i < SHA256_DATA_SIZE);
+ ctx->block[i++] = 0x80;
+
+ /* Fill rest of word */
+ for( ; i & 3; i++)
+ ctx->block[i] = 0;
+
+ /* i is now a multiple of the word size 4 */
+ words = i >> 2;
+ for (i = 0; i < words; i++)
+ data[i] = READ_UINT32(ctx->block + 4*i);
+
+ if (words > (SHA256_DATA_LENGTH-2))
+ { /* No room for length in this block. Process it and
+ * pad with another one */
+ for (i = words ; i < SHA256_DATA_LENGTH; i++)
+ data[i] = 0;
+ sha256_transform(ctx->state, data);
+ for (i = 0; i < (SHA256_DATA_LENGTH-2); i++)
+ data[i] = 0;
+ }
+ else
+ for (i = words ; i < SHA256_DATA_LENGTH - 2; i++)
+ data[i] = 0;
+
+ /* There are 512 = 2^9 bits in one block */
+ data[SHA256_DATA_LENGTH-2] = (ctx->count_high << 9) | (ctx->count_low >> 23);
+ data[SHA256_DATA_LENGTH-1] = (ctx->count_low << 9) | (ctx->index << 3);
+ sha256_transform(ctx->state, data);
+}
+
+void
+sha256_digest(const struct sha256_ctx *ctx,
+ unsigned length,
+ uint8_t *digest)
+{
+ unsigned i;
+ unsigned words;
+ unsigned leftover;
+
+ assert(length <= SHA256_DIGEST_SIZE);
+
+ words = length / 4;
+ leftover = length % 4;
+
+ for (i = 0; i < words; i++, digest += 4)
+ WRITE_UINT32(digest, ctx->state[i]);
+
+ if (leftover)
+ {
+ uint32_t word;
+ unsigned j = leftover;
+
+ assert(i < _SHA256_DIGEST_LENGTH);
+
+ word = ctx->state[i];
+
+ switch (leftover)
+ {
+ default:
+ abort();
+ case 3:
+ digest[--j] = (word >> 8) & 0xff;
+ /* Fall through */
+ case 2:
+ digest[--j] = (word >> 16) & 0xff;
+ /* Fall through */
+ case 1:
+ digest[--j] = (word >> 24) & 0xff;
+ }
+ }
+}