1#include <stdint.h>
  2#include <string.h>
  3
  4//NOTE: This is only intended for use in file identification
  5//Please do not use this in a cryptographic setting as no attempts have been
  6//made at avoiding side channel attacks
  7
  8static uint32_t rotleft(uint32_t val, uint32_t shift)
  9{
 10	return val << shift | val >> (32-shift);
 11}
 12
 13static void sha1_step(uint32_t *state, uint32_t f, uint32_t k, uint32_t w)
 14{
 15	uint32_t tmp = rotleft(state[0], 5) + f + state[4] + k + w;
 16	state[4] = state[3];
 17	state[3] = state[2];
 18	state[2] = rotleft(state[1], 30);
 19	state[1] = state[0];
 20	state[0] = tmp;
 21}
 22
 23static void sha1_chunk(uint8_t *chunk, uint32_t *hash)
 24{
 25	uint32_t state[5], w[80];
 26	memcpy(state, hash, sizeof(state));
 27	for (uint32_t src = 0; src < 64; src += 4)
 28	{
 29		w[src >> 2] = chunk[src] << 24 | chunk[src+1] << 16 | chunk[src+2] << 8 | chunk[src+3];
 30	}
 31	for (uint32_t cur = 16; cur < 80; cur++)
 32	{
 33		w[cur] = rotleft(w[cur-3] ^ w[cur-8] ^ w[cur-14] ^ w[cur-16], 1);
 34	}
 35	for (uint32_t cur = 0; cur < 20; cur++)
 36	{
 37		sha1_step(state, (state[1] & state[2]) | ((~state[1]) & state[3]), 0x5A827999, w[cur]);
 38	}
 39	for (uint32_t cur = 20; cur < 40; cur++)
 40	{
 41		sha1_step(state, state[1] ^ state[2] ^ state[3], 0x6ED9EBA1, w[cur]);
 42	}
 43	for (uint32_t cur = 40; cur < 60; cur++)
 44	{
 45		sha1_step(state, (state[1] & state[2]) | (state[1] & state[3]) | (state[2] & state[3]), 0x8F1BBCDC, w[cur]);
 46	}
 47	for (uint32_t cur = 60; cur < 80; cur++)
 48	{
 49		sha1_step(state, state[1] ^ state[2] ^ state[3], 0xCA62C1D6, w[cur]);
 50	}
 51	for (uint32_t i = 0; i < 5; i++)
 52	{
 53		hash[i] += state[i];
 54	}
 55}
 56
 57void sha1(uint8_t *data, uint64_t size, uint8_t *out)
 58{
 59	uint32_t hash[5] = {0x67452301, 0xEFCDAB89, 0x98BADCFE, 0x10325476, 0xC3D2E1F0};
 60	uint8_t last[128];
 61	uint32_t last_size = 0;
 62	if ((size & 63) != 0) {
 63		for (uint32_t src = size - (size & 63); src < size; src++)
 64		{
 65			last[last_size++] = data[src];
 66		}
 67	}
 68	uint64_t bitsize = size * 8;
 69	size -= last_size;
 70	last[last_size++] = 0x80;
 71	while ((last_size & 63) != 56)
 72	{
 73		last[last_size++] = 0;
 74	}
 75	
 76	last[last_size++] = bitsize >> 56;
 77	last[last_size++] = bitsize >> 48;
 78	last[last_size++] = bitsize >> 40;
 79	last[last_size++] = bitsize >> 32;
 80	last[last_size++] = bitsize >> 24;
 81	last[last_size++] = bitsize >> 16;
 82	last[last_size++] = bitsize >> 8;
 83	last[last_size++] = bitsize;
 84	
 85	for (uint64_t cur = 0; cur < size; cur += 64)
 86	{
 87		sha1_chunk(data + cur, hash);
 88	}
 89	for (uint64_t cur = 0; cur < last_size; cur += 64)
 90	{
 91		sha1_chunk(last + cur, hash);
 92	}
 93	for (uint32_t cur = 0; cur < 20; cur += 4)
 94	{
 95		uint32_t val = hash[cur >> 2];
 96		out[cur] = val >> 24;
 97		out[cur+1] = val >> 16;
 98		out[cur+2] = val >> 8;
 99		out[cur+3] = val;
100	}
101}