/*
 * This is an OpenSSL-compatible implementation of the RSA Data Security,
 * Inc. MD5 Message-Digest Algorithm.
 *
 * Written by Solar Designer <solar at openwall.com> in 2001, and placed
 * in the public domain.  There's absolutely no warranty.
 *
 * This differs from Colin Plumb's older public domain implementation in
 * that no 32-bit integer data type is required, there's no compile-time
 * endianness configuration, and the function prototypes match OpenSSL's.
 * The primary goals are portability and ease of use.
 *
 * This implementation is meant to be fast, but not as fast as possible.
 * Some known optimizations are not included to reduce source code size
 * and avoid compile-time configuration.
 */

#include <string.h>
#include "md5.h"

/*
 * The basic MD5 functions.
 *
 * F is optimized compared to its RFC 1321 definition just like in Colin
 * Plumb's implementation.
 */
#define F(x, y, z)	((z) ^ ((x) & ((y) ^ (z))))
#define G(x, y, z)	((y) ^ ((z) & ((x) ^ (y))))
#define H(x, y, z)	((x) ^ (y) ^ (z))
#define I(x, y, z)	((y) ^ ((x) | ~(z)))

/*
 * The MD5 transformation for all four rounds.
 */
#define STEP(f, a, b, c, d, x, t, s) \
    (a) += f((b), (c), (d)) + (x) + (t); \
    (a) = (((a) << (s)) | (((a) & 0xffffffff) >> (32 - (s)))); \
    (a) += (b);

/*
 * SET reads 4 input bytes in little-endian byte order and stores them
 * in a properly aligned word in host byte order.
 *
 * The check for little-endian architectures which tolerate unaligned
 * memory accesses is just an optimization.  Nothing will break if it
 * doesn't work.
 */
#if defined(__i386__) || defined(__vax__)
# define SET(n) (*(MD5_u32plus *)&ptr[(n) * 4])
# define GET(n) SET(n)
#else
# define SET(n) \
    (ctx->block[(n)] = \
    (MD5_u32plus)ptr[(n) * 4] | \
    ((MD5_u32plus)ptr[(n) * 4 + 1] << 8) | \
    ((MD5_u32plus)ptr[(n) * 4 + 2] << 16) | \
    ((MD5_u32plus)ptr[(n) * 4 + 3] << 24))
# define GET(n) \
    (ctx->block[(n)])
#endif

/*
 * This processes one or more 64-byte data blocks, but does NOT update
 * the bit counters.  There're no alignment requirements.
 */
static void *body(MD5_CTX *ctx, void *data, unsigned long size)
{
    unsigned char *ptr;
    MD5_u32plus a, b, c, d;
    MD5_u32plus saved_a, saved_b, saved_c, saved_d;

    ptr = data;

    a = ctx->a;
    b = ctx->b;
    c = ctx->c;
    d = ctx->d;

    do {
	saved_a = a;
	saved_b = b;
	saved_c = c;
	saved_d = d;

	/* Round 1 */
	STEP(F, a, b, c, d, SET(0),  0xd76aa478, 7)
	STEP(F, d, a, b, c, SET(1),  0xe8c7b756, 12)
	STEP(F, c, d, a, b, SET(2),  0x242070db, 17)
	STEP(F, b, c, d, a, SET(3),  0xc1bdceee, 22)
	STEP(F, a, b, c, d, SET(4),  0xf57c0faf, 7)
	STEP(F, d, a, b, c, SET(5),  0x4787c62a, 12)
	STEP(F, c, d, a, b, SET(6),  0xa8304613, 17)
	STEP(F, b, c, d, a, SET(7),  0xfd469501, 22)
	STEP(F, a, b, c, d, SET(8),  0x698098d8, 7)
	STEP(F, d, a, b, c, SET(9),  0x8b44f7af, 12)
	STEP(F, c, d, a, b, SET(10), 0xffff5bb1, 17)
	STEP(F, b, c, d, a, SET(11), 0x895cd7be, 22)
	STEP(F, a, b, c, d, SET(12), 0x6b901122, 7)
	STEP(F, d, a, b, c, SET(13), 0xfd987193, 12)
	STEP(F, c, d, a, b, SET(14), 0xa679438e, 17)
	STEP(F, b, c, d, a, SET(15), 0x49b40821, 22)

	/* Round 2 */
	STEP(G, a, b, c, d, GET(1),  0xf61e2562, 5)
	STEP(G, d, a, b, c, GET(6),  0xc040b340, 9)
	STEP(G, c, d, a, b, GET(11), 0x265e5a51, 14)
	STEP(G, b, c, d, a, GET(0),  0xe9b6c7aa, 20)
	STEP(G, a, b, c, d, GET(5),  0xd62f105d, 5)
	STEP(G, d, a, b, c, GET(10), 0x02441453, 9)
	STEP(G, c, d, a, b, GET(15), 0xd8a1e681, 14)
	STEP(G, b, c, d, a, GET(4),  0xe7d3fbc8, 20)
	STEP(G, a, b, c, d, GET(9),  0x21e1cde6, 5)
	STEP(G, d, a, b, c, GET(14), 0xc33707d6, 9)
	STEP(G, c, d, a, b, GET(3),  0xf4d50d87, 14)
	STEP(G, b, c, d, a, GET(8),  0x455a14ed, 20)
	STEP(G, a, b, c, d, GET(13), 0xa9e3e905, 5)
	STEP(G, d, a, b, c, GET(2),  0xfcefa3f8, 9)
	STEP(G, c, d, a, b, GET(7),  0x676f02d9, 14)
	STEP(G, b, c, d, a, GET(12), 0x8d2a4c8a, 20)

	/* Round 3 */
	STEP(H, a, b, c, d, GET(5),  0xfffa3942, 4)
	STEP(H, d, a, b, c, GET(8),  0x8771f681, 11)
	STEP(H, c, d, a, b, GET(11), 0x6d9d6122, 16)
	STEP(H, b, c, d, a, GET(14), 0xfde5380c, 23)
	STEP(H, a, b, c, d, GET(1),  0xa4beea44, 4)
	STEP(H, d, a, b, c, GET(4),  0x4bdecfa9, 11)
	STEP(H, c, d, a, b, GET(7),  0xf6bb4b60, 16)
	STEP(H, b, c, d, a, GET(10), 0xbebfbc70, 23)
	STEP(H, a, b, c, d, GET(13), 0x289b7ec6, 4)
	STEP(H, d, a, b, c, GET(0),  0xeaa127fa, 11)
	STEP(H, c, d, a, b, GET(3),  0xd4ef3085, 16)
	STEP(H, b, c, d, a, GET(6),  0x04881d05, 23)
	STEP(H, a, b, c, d, GET(9),  0xd9d4d039, 4)
	STEP(H, d, a, b, c, GET(12), 0xe6db99e5, 11)
	STEP(H, c, d, a, b, GET(15), 0x1fa27cf8, 16)
	STEP(H, b, c, d, a, GET(2),  0xc4ac5665, 23)

	/* Round 4 */
	STEP(I, a, b, c, d, GET(0),  0xf4292244, 6)
	STEP(I, d, a, b, c, GET(7),  0x432aff97, 10)
	STEP(I, c, d, a, b, GET(14), 0xab9423a7, 15)
	STEP(I, b, c, d, a, GET(5),  0xfc93a039, 21)
	STEP(I, a, b, c, d, GET(12), 0x655b59c3, 6)
	STEP(I, d, a, b, c, GET(3),  0x8f0ccc92, 10)
	STEP(I, c, d, a, b, GET(10), 0xffeff47d, 15)
	STEP(I, b, c, d, a, GET(1),  0x85845dd1, 21)
	STEP(I, a, b, c, d, GET(8),  0x6fa87e4f, 6)
	STEP(I, d, a, b, c, GET(15), 0xfe2ce6e0, 10)
	STEP(I, c, d, a, b, GET(6),  0xa3014314, 15)
	STEP(I, b, c, d, a, GET(13), 0x4e0811a1, 21)
	STEP(I, a, b, c, d, GET(4),  0xf7537e82, 6)
	STEP(I, d, a, b, c, GET(11), 0xbd3af235, 10)
	STEP(I, c, d, a, b, GET(2),  0x2ad7d2bb, 15)
	STEP(I, b, c, d, a, GET(9),  0xeb86d391, 21)

	a += saved_a;
	b += saved_b;
	c += saved_c;
	d += saved_d;

	ptr += MD5_BLOCK_SZ;
    } while (size -= MD5_BLOCK_SZ);

    ctx->a = a;
    ctx->b = b;
    ctx->c = c;
    ctx->d = d;

    return ptr;
}

void MD5_Init(MD5_CTX *ctx)
{
    ctx->a = 0x67452301;
    ctx->b = 0xefcdab89;
    ctx->c = 0x98badcfe;
    ctx->d = 0x10325476;

    ctx->lo = 0;
    ctx->hi = 0;
}

void MD5_Update(MD5_CTX *ctx, void *data, unsigned long size)
{
    MD5_u32plus saved_lo;
    unsigned long used, free;

    saved_lo = ctx->lo;
    if ((ctx->lo = (saved_lo + size) & 0x1fffffff) < saved_lo)
	ctx->hi++;

    ctx->hi += size >> 29;

    used = saved_lo & 0x3f;

    if (used)
    {
	free = MD5_BLOCK_SZ - used;

	if (size < free)
	{
	    memcpy(&ctx->buffer[used], data, size);
	    return;
	}

	memcpy(&ctx->buffer[used], data, free);
	data = (unsigned char *)data + free;
	size -= free;
	body(ctx, ctx->buffer, MD5_BLOCK_SZ);
    }

    if (size >= MD5_BLOCK_SZ)
    {
	data = body(ctx, data, size & ~(unsigned long)0x3f);
	size &= 0x3f;
    }

    memcpy(ctx->buffer, data, size);
}

void MD5_Final(unsigned char *result, MD5_CTX *ctx)
{
    unsigned long used, free;

    used = ctx->lo & 0x3f;

    ctx->buffer[used++] = 0x80;

    free = MD5_BLOCK_SZ - used;

    if (free < 8)
    {
	memset(&ctx->buffer[used], 0, free);
	body(ctx, ctx->buffer, MD5_BLOCK_SZ);
	used = 0;
	free = MD5_BLOCK_SZ;
    }

    memset(&ctx->buffer[used], 0, free - 8);

    ctx->lo <<= 3;
    ctx->buffer[56] = ctx->lo;
    ctx->buffer[57] = ctx->lo >> 8;
    ctx->buffer[58] = ctx->lo >> 16;
    ctx->buffer[59] = ctx->lo >> 24;
    ctx->buffer[60] = ctx->hi;
    ctx->buffer[61] = ctx->hi >> 8;
    ctx->buffer[62] = ctx->hi >> 16;
    ctx->buffer[63] = ctx->hi >> 24;

    body(ctx, ctx->buffer, MD5_BLOCK_SZ);

    result[0]  = ctx->a;
    result[1]  = ctx->a >> 8;
    result[2]  = ctx->a >> 16;
    result[3]  = ctx->a >> 24;
    result[4]  = ctx->b;
    result[5]  = ctx->b >> 8;
    result[6]  = ctx->b >> 16;
    result[7]  = ctx->b >> 24;
    result[8]  = ctx->c;
    result[9]  = ctx->c >> 8;
    result[10] = ctx->c >> 16;
    result[11] = ctx->c >> 24;
    result[12] = ctx->d;
    result[13] = ctx->d >> 8;
    result[14] = ctx->d >> 16;
    result[15] = ctx->d >> 24;

    memset(ctx, 0, sizeof(*ctx));
}