sha256.c

/*
 * SHA-256 implementation
 * Public domain, based on FIPS 180-4
 */

#include "sha256.h"
#include <string.h>

static const uint32_t k[64] =
{
	0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
	0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
	0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
	0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
	0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
	0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
	0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
	0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
	0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
	0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
	0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
	0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
	0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
	0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
	0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
	0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
};

#define ROTR(x, n) ( ((x) >> (n)) | ((x) << (32 - (n))) )
#define CH(x, y, z) ( ((x) & (y)) ^ (~(x) & (z)) )
#define MAJ(x, y, z) ( ((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)) )
#define EP0(x) ( ROTR(x, 2) ^ ROTR(x, 13) ^ ROTR(x, 22) )
#define EP1(x) ( ROTR(x, 6) ^ ROTR(x, 11) ^ ROTR(x, 25) )
#define SIG0(x) ( ROTR(x, 7) ^ ROTR(x, 18) ^ ((x) >> 3) )
#define SIG1(x) ( ROTR(x, 17) ^ ROTR(x, 19) ^ ((x) >> 10) )

static void sha256_transform( SHA256_CTX *ctx, const uint8_t data[64] )
{
	uint32_t a, b, c, d, e, f, g, h, t1, t2, w[64];
	int i;

	for ( i = 0; i < 16; i++ )
	{
		w[i] = ((uint32_t)data[i * 4] << 24)
		     | ((uint32_t)data[i * 4 + 1] << 16)
		     | ((uint32_t)data[i * 4 + 2] << 8)
		     | ((uint32_t)data[i * 4 + 3]);
	}
	for ( i = 16; i < 64; i++ )
	{
		w[i] = SIG1( w[i - 2] ) + w[i - 7] + SIG0( w[i - 15] ) + w[i - 16];
	}

	a = ctx->state[0];
	b = ctx->state[1];
	c = ctx->state[2];
	d = ctx->state[3];
	e = ctx->state[4];
	f = ctx->state[5];
	g = ctx->state[6];
	h = ctx->state[7];

	for ( i = 0; i < 64; i++ )
	{
		t1 = h + EP1( e ) + CH( e, f, g ) + k[i] + w[i];
		t2 = EP0( a ) + MAJ( a, b, c );
		h = g;
		g = f;
		f = e;
		e = d + t1;
		d = c;
		c = b;
		b = a;
		a = t1 + t2;
	}

	ctx->state[0] += a;
	ctx->state[1] += b;
	ctx->state[2] += c;
	ctx->state[3] += d;
	ctx->state[4] += e;
	ctx->state[5] += f;
	ctx->state[6] += g;
	ctx->state[7] += h;
}

void sha256_init( SHA256_CTX *ctx )
{
	ctx->datalen = 0;
	ctx->bitlen = 0;
	ctx->state[0] = 0x6a09e667;
	ctx->state[1] = 0xbb67ae85;
	ctx->state[2] = 0x3c6ef372;
	ctx->state[3] = 0xa54ff53a;
	ctx->state[4] = 0x510e527f;
	ctx->state[5] = 0x9b05688c;
	ctx->state[6] = 0x1f83d9ab;
	ctx->state[7] = 0x5be0cd19;
}

void sha256_update( SHA256_CTX *ctx, const uint8_t *data, size_t len )
{
	size_t i;

	for ( i = 0; i < len; i++ )
	{
		ctx->data[ctx->datalen] = data[i];
		ctx->datalen++;
		if ( ctx->datalen == 64 )
		{
			sha256_transform( ctx, ctx->data );
			ctx->bitlen += 512;
			ctx->datalen = 0;
		}
	}
}

void sha256_final( SHA256_CTX *ctx, uint8_t hash[32] )
{
	uint32_t i;

	i = ctx->datalen;

	/* Pad the message */
	if ( ctx->datalen < 56 )
	{
		ctx->data[i++] = 0x80;
		while ( i < 56 )
		{
			ctx->data[i++] = 0x00;
		}
	}
	else
	{
		ctx->data[i++] = 0x80;
		while ( i < 64 )
		{
			ctx->data[i++] = 0x00;
		}
		sha256_transform( ctx, ctx->data );
		memset( ctx->data, 0, 56 );
	}

	/* Append the total message length in bits */
	ctx->bitlen += (uint64_t)ctx->datalen * 8;
	ctx->data[63] = (uint8_t)( ctx->bitlen );
	ctx->data[62] = (uint8_t)( ctx->bitlen >> 8 );
	ctx->data[61] = (uint8_t)( ctx->bitlen >> 16 );
	ctx->data[60] = (uint8_t)( ctx->bitlen >> 24 );
	ctx->data[59] = (uint8_t)( ctx->bitlen >> 32 );
	ctx->data[58] = (uint8_t)( ctx->bitlen >> 40 );
	ctx->data[57] = (uint8_t)( ctx->bitlen >> 48 );
	ctx->data[56] = (uint8_t)( ctx->bitlen >> 56 );
	sha256_transform( ctx, ctx->data );

	/* Big-endian output */
	for ( i = 0; i < 8; i++ )
	{
		hash[i * 4]     = (uint8_t)( ctx->state[i] >> 24 );
		hash[i * 4 + 1] = (uint8_t)( ctx->state[i] >> 16 );
		hash[i * 4 + 2] = (uint8_t)( ctx->state[i] >> 8 );
		hash[i * 4 + 3] = (uint8_t)( ctx->state[i] );
	}
}