sha256.c

/* public domain sha256 implementation based on fips180-3 */
#include <stdint.h>
#include <string.h>

#include "sha256.h"

static uint32_t ror(uint32_t n, int k) { return (n >> k) | (n << (32-k)); }
#define Ch(x,y,z)  (z ^ (x & (y ^ z)))
#define Maj(x,y,z) ((x & y) | (z & (x | y)))
#define S0(x)      (ror(x,2) ^ ror(x,13) ^ ror(x,22))
#define S1(x)      (ror(x,6) ^ ror(x,11) ^ ror(x,25))
#define R0(x)      (ror(x,7) ^ ror(x,18) ^ (x>>3))
#define R1(x)      (ror(x,17) ^ ror(x,19) ^ (x>>10))

#define INNER_PADDING '\x36'
#define OUTER_PADDING '\x5c'

#define BLOCK_LENGTH 64

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
};

static void
processblock(struct sha256 *s, const uint8_t *buf)
{
	uint32_t W[64], t1, t2, a, b, c, d, e, f, g, h;
	int i;

	for (i = 0; i < 16; i++) {
		W[i] = (uint32_t)buf[4*i]<<24;
		W[i] |= (uint32_t)buf[4*i+1]<<16;
		W[i] |= (uint32_t)buf[4*i+2]<<8;
		W[i] |= buf[4*i+3];
	}
	for (; i < 64; i++)
		W[i] = R1(W[i-2]) + W[i-7] + R0(W[i-15]) + W[i-16];
	a = s->h[0];
	b = s->h[1];
	c = s->h[2];
	d = s->h[3];
	e = s->h[4];
	f = s->h[5];
	g = s->h[6];
	h = s->h[7];
	for (i = 0; i < 64; i++) {
		t1 = h + S1(e) + Ch(e,f,g) + K[i] + W[i];
		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;
	}
	s->h[0] += a;
	s->h[1] += b;
	s->h[2] += c;
	s->h[3] += d;
	s->h[4] += e;
	s->h[5] += f;
	s->h[6] += g;
	s->h[7] += h;
}

static void
pad(struct sha256 *s)
{
	unsigned r = s->len % 64;

	s->buf[r++] = 0x80;
	if (r > 56) {
		memset(s->buf + r, 0, 64 - r);
		r = 0;
		processblock(s, s->buf);
	}
	memset(s->buf + r, 0, 56 - r);
	s->len *= 8;
	s->buf[56] = s->len >> 56;
	s->buf[57] = s->len >> 48;
	s->buf[58] = s->len >> 40;
	s->buf[59] = s->len >> 32;
	s->buf[60] = s->len >> 24;
	s->buf[61] = s->len >> 16;
	s->buf[62] = s->len >> 8;
	s->buf[63] = s->len;
	processblock(s, s->buf);
}

static void normalize_key(uint8_t * const key, const char * const input_key, size_t len) {
	if (len <= BLOCK_LENGTH) {
		memcpy(key, input_key, len);
		memset(key + len, '\0', BLOCK_LENGTH - len);
	}
	else {
		struct sha256 s;
		sha256Init(&s);
		sha256Update(&s, input_key, len);
		sha256Sum(&s, key);
		memset(key + SHA256_DIGEST_LENGTH, '\0', BLOCK_LENGTH - SHA256_DIGEST_LENGTH);
	}
}

int generateHash(uint8_t *hashedDataOut, uint8_t *data, size_t dataLen, uint8_t *keyInput, size_t keyInputLen)
{
	if (hashedDataOut == NULL ||
		data == NULL ||
		keyInput == NULL ||
		dataLen == 1 ||
		keyInputLen == 0)
		return -1;

	uint8_t key[BLOCK_LENGTH];

	normalize_key(key, keyInput, keyInputLen);

	struct sha256 inner_s;

	sha256Init(&inner_s);

	uint8_t inner_key[BLOCK_LENGTH];
	uint8_t outer_key[BLOCK_LENGTH];

	for (size_t i = 0; i < BLOCK_LENGTH; i++) {
		inner_key[i] = key[i] ^ INNER_PADDING;
		outer_key[i] = key[i] ^ OUTER_PADDING;
	}

	sha256Update(&inner_s, inner_key, BLOCK_LENGTH);
	sha256Update(&inner_s, data, dataLen);

	uint8_t inner_hash[SHA256_DIGEST_LENGTH];
	sha256Sum(&inner_s, inner_hash);

	struct sha256 outer_s;
	sha256Init(&outer_s);
	sha256Update(&outer_s, outer_key, BLOCK_LENGTH);
	sha256Update(&outer_s, inner_hash, SHA256_DIGEST_LENGTH);

	uint8_t hmac[SHA256_DIGEST_LENGTH];
	sha256Sum(&outer_s, hmac);

	memcpy(hashedDataOut, hmac, SHA256_DIGEST_LENGTH);

	return 0;
}

void
sha256Init(void *ctx)
{
	struct sha256 *s = ctx;
	s->len = 0;
	s->h[0] = 0x6a09e667;
	s->h[1] = 0xbb67ae85;
	s->h[2] = 0x3c6ef372;
	s->h[3] = 0xa54ff53a;
	s->h[4] = 0x510e527f;
	s->h[5] = 0x9b05688c;
	s->h[6] = 0x1f83d9ab;
	s->h[7] = 0x5be0cd19;
}

void
sha256Sum(void *ctx, uint8_t md[SHA256_DIGEST_LENGTH])
{
	struct sha256 *s = ctx;
	int i;

	pad(s);
	for (i = 0; i < 8; i++) {
		md[4*i] = s->h[i] >> 24;
		md[4*i+1] = s->h[i] >> 16;
		md[4*i+2] = s->h[i] >> 8;
		md[4*i+3] = s->h[i];
	}
}

void
sha256Update(void *ctx, const void *m, unsigned long len)
{
	struct sha256 *s = ctx;
	const uint8_t *p = m;
	unsigned r = s->len % 64;

	s->len += len;
	if (r) {
		if (len < 64 - r) {
			memcpy(s->buf + r, p, len);
			return;
		}
		memcpy(s->buf + r, p, 64 - r);
		len -= 64 - r;
		p += 64 - r;
		processblock(s, s->buf);
	}
	for (; len >= 64; len -= 64, p += 64)
		processblock(s, p);
	memcpy(s->buf, p, len);
}