/*
 * Copyright (C) 2001 Niels Moller
 *  
 * 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 <stdio.h>
#include <string.h>

#include "cltypes.h"
#include "sha256.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))

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

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,
};

#define EXPAND(W,i) \
( W[(i) & 15 ] += (s1(W[((i)-2) & 15]) + W[((i)-7) & 15] + s0(W[((i)-15) & 15])) )

#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)

#ifndef EXTRACT_UCHAR
#define EXTRACT_UCHAR(p)  (*(const unsigned char *)(p))
#endif

#define STRING2INT(s) ((((((EXTRACT_UCHAR(s) << 8)    \
			 | EXTRACT_UCHAR(s+1)) << 8)  \
			 | EXTRACT_UCHAR(s+2)) << 8)  \
			 | EXTRACT_UCHAR(s+3))

#ifndef EXTRACT_UCHAR
#define EXTRACT_UCHAR(p)  (*(const mutils_word8 *)(p))
#endif

#define STRING2INT(s) ((((((EXTRACT_UCHAR(s) << 8)    \
			 | EXTRACT_UCHAR(s+1)) << 8)  \
			 | EXTRACT_UCHAR(s+2)) << 8)  \
			 | EXTRACT_UCHAR(s+3))

/* 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 char 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 unsigned char *block)
{
	uint32_t data[SHA256_DATA_LENGTH];
	uint16_t 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] = STRING2INT(block);

	sha256_transform(ctx->state, data);
}

void
sha256_update(struct sha256_ctx *ctx, const unsigned char *buffer, uint32_t length)
{
	uint32_t left;

	if (ctx->index) {	/* Try to fill partial block */
		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];
	uint32_t i;
	uint32_t 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] = STRING2INT(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 char *s)
{
	uint32_t i;

	if (s!=NULL)
		for (i = 0; i < _SHA256_DIGEST_LENGTH; i++) {
			*s++ = ctx->state[i] >> 24;
			*s++ = 0xff & (ctx->state[i] >> 16);
			*s++ = 0xff & (ctx->state[i] >> 8);
			*s++ = 0xff & ctx->state[i];
		}
}