/*	$OpenBSD: md5.c,v 1.4 2014/12/28 10:04:35 tedu Exp $	*/

/*
 * This code implements the MD5 message-digest algorithm.
 * The algorithm is due to Ron Rivest.	This code was
 * written by Colin Plumb in 1993, no copyright is claimed.
 * This code is in the public domain; do with it what you wish.
 *
 * Equivalent code is available from RSA Data Security, Inc.
 * This code has been tested against that, and is equivalent,
 * except that you don't need to include two pages of legalese
 * with every copy.
 *
 * To compute the message digest of a chunk of bytes, declare an
 * MD5Context structure, pass it to MD5Init, call MD5Update as
 * needed on buffers full of bytes, and then call MD5Final, which
 * will fill a supplied 16-byte array with the digest.
 */

#include "md5.h"

#include <stdint.h>
#include <string.h>

#define PUT_BIT_LE(i, cp, value) \
	do { \
		(cp)[i] = (uint8_t)(((value) >> 8 * i) & 0xFF); \
	} while (0)

#define PUT_64BIT_LE(cp, value) \
	do { \
		PUT_BIT_LE(7, cp, value); \
		PUT_BIT_LE(6, cp, value); \
		PUT_BIT_LE(5, cp, value); \
		PUT_BIT_LE(4, cp, value); \
		PUT_BIT_LE(3, cp, value); \
		PUT_BIT_LE(2, cp, value); \
		PUT_BIT_LE(1, cp, value); \
		PUT_BIT_LE(0, cp, value); \
	} while (0)

#define PUT_32BIT_LE(cp, value) \
	do { \
		PUT_BIT_LE(3, cp, value); \
		PUT_BIT_LE(2, cp, value); \
		PUT_BIT_LE(1, cp, value); \
		PUT_BIT_LE(0, cp, value); \
	} while (0)

static uint8_t PADDING[MD5_BLOCK_LENGTH] = {0x80,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0,
	0};

/*
 * Start MD5 accumulation.  Set bit count to 0 and buffer to mysterious
 * initialization constants.
 */
void MD5Init(MD5_CTX *ctx)
{
	ctx->count = 0;
	ctx->state[0] = 0x67452301;
	ctx->state[1] = 0xefcdab89;
	ctx->state[2] = 0x98badcfe;
	ctx->state[3] = 0x10325476;
}

/*
 * Update context to reflect the concatenation of another buffer full
 * of bytes.
 */
void MD5Update(MD5_CTX *ctx, const void *inputptr, size_t len)
{
	const uint8_t *input = inputptr;
	size_t have, need;

	/* Check how many bytes we already have and how many more we need. */
	have = (size_t)((ctx->count >> 3) & (MD5_BLOCK_LENGTH - 1));
	need = MD5_BLOCK_LENGTH - have;

	/* Update bitcount */
	ctx->count += (uint64_t)len << 3;

	if (len >= need) {
		if (have != 0) {
			memcpy(ctx->buffer + have, input, need);
			MD5Transform(ctx->state, ctx->buffer);
			input += need;
			len -= need;
			have = 0;
		}

		/* Process data in MD5_BLOCK_LENGTH-byte chunks. */
		while (len >= MD5_BLOCK_LENGTH) {
			MD5Transform(ctx->state, input);
			input += MD5_BLOCK_LENGTH;
			len -= MD5_BLOCK_LENGTH;
		}
	}

	/* Handle any remaining bytes of data. */
	if (len != 0)
		memcpy(ctx->buffer + have, input, len);
}

/*
 * Final wrapup - pad to 64-byte boundary with the bit pattern
 * 1 0* (64-bit count of bits processed, MSB-first)
 */
void MD5Final(unsigned char digest[MD5_DIGEST_LENGTH], MD5_CTX *ctx)
{
	uint8_t count[8];
	size_t padlen;
	int i;

	/* Convert count to 8 bytes in little endian order. */
	PUT_64BIT_LE(count, ctx->count);

	/* Pad out to 56 mod 64. */
	padlen =
		MD5_BLOCK_LENGTH - ((ctx->count >> 3) & (MD5_BLOCK_LENGTH - 1));
	if (padlen < 1 + 8)
		padlen += MD5_BLOCK_LENGTH;
	MD5Update(ctx, PADDING, padlen - 8); /* padlen - 8 <= 64 */
	MD5Update(ctx, count, 8);

	for (i = 0; i < 4; i++)
		PUT_32BIT_LE(digest + i * 4, ctx->state[i]);
	memset(ctx, 0, sizeof(*ctx)); /* in case it's sensitive */
}

/* The four core functions - F1 is optimized somewhat */

/* #define F1(x, y, z) (x & y | ~x & z) */
#define F1(x, y, z) (z ^ (x & (y ^ z)))
#define F2(x, y, z) F1(z, x, y)
#define F3(x, y, z) (x ^ y ^ z)
#define F4(x, y, z) (y ^ (x | ~z))

/* This is the central step in the MD5 algorithm. */
#define MD5STEP(f, w, x, y, z, data, s) \
	(w += f(x, y, z) + data, w = w << s | w >> (32 - s), w += x)

/*
 * The core of the MD5 algorithm, this alters an existing MD5 hash to
 * reflect the addition of 16 longwords of new data.  MD5Update blocks
 * the data and converts bytes into longwords for this routine.
 */
void MD5Transform(uint32_t state[4], const uint8_t block[MD5_BLOCK_LENGTH])
{
	uint32_t a, b, c, d, in[MD5_BLOCK_LENGTH / 4];

#if BYTE_ORDER == LITTLE_ENDIAN
	memcpy(in, block, sizeof(in));
#else
	for (a = 0; a < MD5_BLOCK_LENGTH / 4; a++) {
		in[a] = (uint32_t)((uint32_t)(block[a * 4 + 0]) |
				   (uint32_t)(block[a * 4 + 1]) << 8 |
				   (uint32_t)(block[a * 4 + 2]) << 16 |
				   (uint32_t)(block[a * 4 + 3]) << 24);
	}
#endif

	a = state[0];
	b = state[1];
	c = state[2];
	d = state[3];

	MD5STEP(F1, a, b, c, d, in[0] + 0xd76aa478, 7);
	MD5STEP(F1, d, a, b, c, in[1] + 0xe8c7b756, 12);
	MD5STEP(F1, c, d, a, b, in[2] + 0x242070db, 17);
	MD5STEP(F1, b, c, d, a, in[3] + 0xc1bdceee, 22);
	MD5STEP(F1, a, b, c, d, in[4] + 0xf57c0faf, 7);
	MD5STEP(F1, d, a, b, c, in[5] + 0x4787c62a, 12);
	MD5STEP(F1, c, d, a, b, in[6] + 0xa8304613, 17);
	MD5STEP(F1, b, c, d, a, in[7] + 0xfd469501, 22);
	MD5STEP(F1, a, b, c, d, in[8] + 0x698098d8, 7);
	MD5STEP(F1, d, a, b, c, in[9] + 0x8b44f7af, 12);
	MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
	MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7be, 22);
	MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122, 7);
	MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193, 12);
	MD5STEP(F1, c, d, a, b, in[14] + 0xa679438e, 17);
	MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821, 22);

	MD5STEP(F2, a, b, c, d, in[1] + 0xf61e2562, 5);
	MD5STEP(F2, d, a, b, c, in[6] + 0xc040b340, 9);
	MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51, 14);
	MD5STEP(F2, b, c, d, a, in[0] + 0xe9b6c7aa, 20);
	MD5STEP(F2, a, b, c, d, in[5] + 0xd62f105d, 5);
	MD5STEP(F2, d, a, b, c, in[10] + 0x02441453, 9);
	MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
	MD5STEP(F2, b, c, d, a, in[4] + 0xe7d3fbc8, 20);
	MD5STEP(F2, a, b, c, d, in[9] + 0x21e1cde6, 5);
	MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6, 9);
	MD5STEP(F2, c, d, a, b, in[3] + 0xf4d50d87, 14);
	MD5STEP(F2, b, c, d, a, in[8] + 0x455a14ed, 20);
	MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905, 5);
	MD5STEP(F2, d, a, b, c, in[2] + 0xfcefa3f8, 9);
	MD5STEP(F2, c, d, a, b, in[7] + 0x676f02d9, 14);
	MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);

	MD5STEP(F3, a, b, c, d, in[5] + 0xfffa3942, 4);
	MD5STEP(F3, d, a, b, c, in[8] + 0x8771f681, 11);
	MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
	MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380c, 23);
	MD5STEP(F3, a, b, c, d, in[1] + 0xa4beea44, 4);
	MD5STEP(F3, d, a, b, c, in[4] + 0x4bdecfa9, 11);
	MD5STEP(F3, c, d, a, b, in[7] + 0xf6bb4b60, 16);
	MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
	MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6, 4);
	MD5STEP(F3, d, a, b, c, in[0] + 0xeaa127fa, 11);
	MD5STEP(F3, c, d, a, b, in[3] + 0xd4ef3085, 16);
	MD5STEP(F3, b, c, d, a, in[6] + 0x04881d05, 23);
	MD5STEP(F3, a, b, c, d, in[9] + 0xd9d4d039, 4);
	MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
	MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
	MD5STEP(F3, b, c, d, a, in[2] + 0xc4ac5665, 23);

	MD5STEP(F4, a, b, c, d, in[0] + 0xf4292244, 6);
	MD5STEP(F4, d, a, b, c, in[7] + 0x432aff97, 10);
	MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7, 15);
	MD5STEP(F4, b, c, d, a, in[5] + 0xfc93a039, 21);
	MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3, 6);
	MD5STEP(F4, d, a, b, c, in[3] + 0x8f0ccc92, 10);
	MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47d, 15);
	MD5STEP(F4, b, c, d, a, in[1] + 0x85845dd1, 21);
	MD5STEP(F4, a, b, c, d, in[8] + 0x6fa87e4f, 6);
	MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
	MD5STEP(F4, c, d, a, b, in[6] + 0xa3014314, 15);
	MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
	MD5STEP(F4, a, b, c, d, in[4] + 0xf7537e82, 6);
	MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235, 10);
	MD5STEP(F4, c, d, a, b, in[2] + 0x2ad7d2bb, 15);
	MD5STEP(F4, b, c, d, a, in[9] + 0xeb86d391, 21);

	state[0] += a;
	state[1] += b;
	state[2] += c;
	state[3] += d;
}
