/*
 * MD5C.C - RSA Data Security, Inc., MD5 message-digest algorithm
 *
 * Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
 * rights reserved.
 *
 * License to copy and use this software is granted provided that it
 * is identified as the "RSA Data Security, Inc. MD5 Message-Digest
 * Algorithm" in all material mentioning or referencing this software
 * or this function.
 *
 * License is also granted to make and use derivative works provided
 * that such works are identified as "derived from the RSA Data
 * Security, Inc. MD5 Message-Digest Algorithm" in all material
 * mentioning or referencing the derived work.
 *
 * RSA Data Security, Inc. makes no representations concerning either
 * the merchantability of this software or the suitability of this
 * software for any particular purpose. It is provided "as is"
 * without express or implied warranty of any kind.
 *
 * These notices must be retained in any copies of any part of this
 * documentation and/or software.
 *
 * This code is the same as the code published by RSA Inc.  It has been
 * edited for clarity and style only.
 */

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

static void MD5Transform(uint32_t[4], const unsigned char[64]);

#define Encode memcpy
#define Decode memcpy

static unsigned char PADDING[64] = {
    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
};

/* F, G, H and I are basic MD5 functions. */
#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))

/* ROTATE_LEFT rotates x left n bits. */
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))

/*
 * FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
 * Rotation is separate from addition to prevent recomputation.
 */
#define FF(a, b, c, d, x, s, ac) { \
        (a) += F ((b), (c), (d)) + (x) + (uint32_t)(ac); \
        (a) = ROTATE_LEFT ((a), (s)); \
        (a) += (b); \
        }
#define GG(a, b, c, d, x, s, ac) { \
        (a) += G ((b), (c), (d)) + (x) + (uint32_t)(ac); \
        (a) = ROTATE_LEFT ((a), (s)); \
        (a) += (b); \
        }
#define HH(a, b, c, d, x, s, ac) { \
        (a) += H ((b), (c), (d)) + (x) + (uint32_t)(ac); \
        (a) = ROTATE_LEFT ((a), (s)); \
        (a) += (b); \
        }
#define II(a, b, c, d, x, s, ac) { \
        (a) += I ((b), (c), (d)) + (x) + (uint32_t)(ac); \
        (a) = ROTATE_LEFT ((a), (s)); \
        (a) += (b); \
        }

/* MD5 initialization. Begins an MD5 operation, writing a new context. */

void MD5Init(MD5_CTX * context)
{
    context->count[0] = context->count[1] = 0;

    /* Load magic initialization constants.  */
    context->state[0] = 0x67452301;
    context->state[1] = 0xefcdab89;
    context->state[2] = 0x98badcfe;
    context->state[3] = 0x10325476;
}

/*
 * MD5 block update operation. Continues an MD5 message-digest
 * operation, processing another message block, and updating the
 * context.
 */

void MD5Update(MD5_CTX * context, const void *in, size_t inputLen)
{
    unsigned int i, idx, partLen;
    const unsigned char *input = in;

    /* Compute number of bytes mod 64 */
    idx = (unsigned int)((context->count[0] >> 3) & 0x3F);

    /* Update number of bits */
    if ((context->count[0] += ((uint32_t) inputLen << 3))
        < ((uint32_t) inputLen << 3))
        context->count[1]++;
    context->count[1] += ((uint32_t) inputLen >> 29);

    partLen = 64 - idx;

    /* Transform as many times as possible. */
    if (inputLen >= partLen) {
        memcpy((void *)&context->buffer[idx], (const void *)input, partLen);
        MD5Transform(context->state, context->buffer);

        for (i = partLen; i + 63 < inputLen; i += 64)
            MD5Transform(context->state, &input[i]);

        idx = 0;
    } else
        i = 0;

    /* Buffer remaining input */
    memcpy((void *)&context->buffer[idx], (const void *)&input[i],
           inputLen - i);
}

/*
 * MD5 padding. Adds padding followed by original length.
 */

static void MD5Pad(MD5_CTX * context)
{
    unsigned char bits[8];
    unsigned int idx, padLen;

    /* Save number of bits */
    Encode(bits, context->count, 8);

    /* Pad out to 56 mod 64. */
    idx = (unsigned int)((context->count[0] >> 3) & 0x3f);
    padLen = (idx < 56) ? (56 - idx) : (120 - idx);
    MD5Update(context, PADDING, padLen);

    /* Append length (before padding) */
    MD5Update(context, bits, 8);
}

/*
 * MD5 finalization. Ends an MD5 message-digest operation, writing the
 * the message digest and zeroizing the context.
 */

void MD5Final(unsigned char digest[16], MD5_CTX * context)
{
    /* Do padding. */
    MD5Pad(context);

    /* Store state in digest */
    Encode(digest, context->state, 16);

    /* Zeroize sensitive information. */
    memset((void *)context, 0, sizeof(*context));
}

/* MD5 basic transformation. Transforms state based on block. */

static void MD5Transform(state, block)
uint32_t state[4];
const unsigned char block[64];
{
    uint32_t a = state[0], b = state[1], c = state[2], d = state[3], x[16];

    Decode(x, block, 64);

    /* Round 1 */
#define S11 7
#define S12 12
#define S13 17
#define S14 22
    FF(a, b, c, d, x[0], S11, 0xd76aa478);      /* 1 */
    FF(d, a, b, c, x[1], S12, 0xe8c7b756);      /* 2 */
    FF(c, d, a, b, x[2], S13, 0x242070db);      /* 3 */
    FF(b, c, d, a, x[3], S14, 0xc1bdceee);      /* 4 */
    FF(a, b, c, d, x[4], S11, 0xf57c0faf);      /* 5 */
    FF(d, a, b, c, x[5], S12, 0x4787c62a);      /* 6 */
    FF(c, d, a, b, x[6], S13, 0xa8304613);      /* 7 */
    FF(b, c, d, a, x[7], S14, 0xfd469501);      /* 8 */
    FF(a, b, c, d, x[8], S11, 0x698098d8);      /* 9 */
    FF(d, a, b, c, x[9], S12, 0x8b44f7af);      /* 10 */
    FF(c, d, a, b, x[10], S13, 0xffff5bb1);     /* 11 */
    FF(b, c, d, a, x[11], S14, 0x895cd7be);     /* 12 */
    FF(a, b, c, d, x[12], S11, 0x6b901122);     /* 13 */
    FF(d, a, b, c, x[13], S12, 0xfd987193);     /* 14 */
    FF(c, d, a, b, x[14], S13, 0xa679438e);     /* 15 */
    FF(b, c, d, a, x[15], S14, 0x49b40821);     /* 16 */

    /* Round 2 */
#define S21 5
#define S22 9
#define S23 14
#define S24 20
    GG(a, b, c, d, x[1], S21, 0xf61e2562);      /* 17 */
    GG(d, a, b, c, x[6], S22, 0xc040b340);      /* 18 */
    GG(c, d, a, b, x[11], S23, 0x265e5a51);     /* 19 */
    GG(b, c, d, a, x[0], S24, 0xe9b6c7aa);      /* 20 */
    GG(a, b, c, d, x[5], S21, 0xd62f105d);      /* 21 */
    GG(d, a, b, c, x[10], S22, 0x2441453);      /* 22 */
    GG(c, d, a, b, x[15], S23, 0xd8a1e681);     /* 23 */
    GG(b, c, d, a, x[4], S24, 0xe7d3fbc8);      /* 24 */
    GG(a, b, c, d, x[9], S21, 0x21e1cde6);      /* 25 */
    GG(d, a, b, c, x[14], S22, 0xc33707d6);     /* 26 */
    GG(c, d, a, b, x[3], S23, 0xf4d50d87);      /* 27 */
    GG(b, c, d, a, x[8], S24, 0x455a14ed);      /* 28 */
    GG(a, b, c, d, x[13], S21, 0xa9e3e905);     /* 29 */
    GG(d, a, b, c, x[2], S22, 0xfcefa3f8);      /* 30 */
    GG(c, d, a, b, x[7], S23, 0x676f02d9);      /* 31 */
    GG(b, c, d, a, x[12], S24, 0x8d2a4c8a);     /* 32 */

    /* Round 3 */
#define S31 4
#define S32 11
#define S33 16
#define S34 23
    HH(a, b, c, d, x[5], S31, 0xfffa3942);      /* 33 */
    HH(d, a, b, c, x[8], S32, 0x8771f681);      /* 34 */
    HH(c, d, a, b, x[11], S33, 0x6d9d6122);     /* 35 */
    HH(b, c, d, a, x[14], S34, 0xfde5380c);     /* 36 */
    HH(a, b, c, d, x[1], S31, 0xa4beea44);      /* 37 */
    HH(d, a, b, c, x[4], S32, 0x4bdecfa9);      /* 38 */
    HH(c, d, a, b, x[7], S33, 0xf6bb4b60);      /* 39 */
    HH(b, c, d, a, x[10], S34, 0xbebfbc70);     /* 40 */
    HH(a, b, c, d, x[13], S31, 0x289b7ec6);     /* 41 */
    HH(d, a, b, c, x[0], S32, 0xeaa127fa);      /* 42 */
    HH(c, d, a, b, x[3], S33, 0xd4ef3085);      /* 43 */
    HH(b, c, d, a, x[6], S34, 0x4881d05);       /* 44 */
    HH(a, b, c, d, x[9], S31, 0xd9d4d039);      /* 45 */
    HH(d, a, b, c, x[12], S32, 0xe6db99e5);     /* 46 */
    HH(c, d, a, b, x[15], S33, 0x1fa27cf8);     /* 47 */
    HH(b, c, d, a, x[2], S34, 0xc4ac5665);      /* 48 */

    /* Round 4 */
#define S41 6
#define S42 10
#define S43 15
#define S44 21
    II(a, b, c, d, x[0], S41, 0xf4292244);      /* 49 */
    II(d, a, b, c, x[7], S42, 0x432aff97);      /* 50 */
    II(c, d, a, b, x[14], S43, 0xab9423a7);     /* 51 */
    II(b, c, d, a, x[5], S44, 0xfc93a039);      /* 52 */
    II(a, b, c, d, x[12], S41, 0x655b59c3);     /* 53 */
    II(d, a, b, c, x[3], S42, 0x8f0ccc92);      /* 54 */
    II(c, d, a, b, x[10], S43, 0xffeff47d);     /* 55 */
    II(b, c, d, a, x[1], S44, 0x85845dd1);      /* 56 */
    II(a, b, c, d, x[8], S41, 0x6fa87e4f);      /* 57 */
    II(d, a, b, c, x[15], S42, 0xfe2ce6e0);     /* 58 */
    II(c, d, a, b, x[6], S43, 0xa3014314);      /* 59 */
    II(b, c, d, a, x[13], S44, 0x4e0811a1);     /* 60 */
    II(a, b, c, d, x[4], S41, 0xf7537e82);      /* 61 */
    II(d, a, b, c, x[11], S42, 0xbd3af235);     /* 62 */
    II(c, d, a, b, x[2], S43, 0x2ad7d2bb);      /* 63 */
    II(b, c, d, a, x[9], S44, 0xeb86d391);      /* 64 */

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

    /* Zeroize sensitive information. */
    memset((void *)x, 0, sizeof(x));
}