/*
 * The Sleuth Kit 
 *
 */

/* 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.
 */

/** \file md5c.c
 * Local copy of RSA Data Security, Inc. MD5 Message-Digest Algorithm.
 */
#include "tsk_base_i.h"

/* Constants for MD5Transform routine.
 */
#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21

static void MD5Transform(UINT4[4], unsigned char[64]);
static void Encode(unsigned char *, UINT4 *, unsigned int);
static void Decode(UINT4 *, unsigned char *, unsigned int);
static void MD5_memcpy(POINTER, POINTER, unsigned int);
static void MD5_memset(POINTER, int, unsigned int);

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) + (UINT4)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define GG(a, b, c, d, x, s, ac) { \
 (a) += G ((b), (c), (d)) + (x) + (UINT4)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define HH(a, b, c, d, x, s, ac) { \
 (a) += H ((b), (c), (d)) + (x) + (UINT4)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define II(a, b, c, d, x, s, ac) { \
 (a) += I ((b), (c), (d)) + (x) + (UINT4)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }

/**
 * \ingroup baselib
 * Initialize a MD5 context structure so that data can be added to it. 
 * @param context Pointer to context to initialize
 */
void
TSK_MD5_Init(TSK_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;
}

/**
 * \ingroup baselib
 * Add data to an initialized MD5 operation.  
 * @param context Initialized context to add data to
 * @param input Buffer of data to process
 * @param inputLen Number of bytes in input
 */
void
TSK_MD5_Update(TSK_MD5_CTX * context, unsigned char *input,
    unsigned int inputLen)
{
    unsigned int i, index, partLen;

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

    /* Update number of bits */
    if ((context->count[0] += ((UINT4) inputLen << 3))
        < ((UINT4) inputLen << 3))
        context->count[1]++;
    context->count[1] += ((UINT4) inputLen >> 29);

    partLen = 64 - index;

    /* Transform as many times as possible.
     */
    if (inputLen >= partLen) {
        MD5_memcpy
            ((POINTER) & context->buffer[index], (POINTER) input, partLen);
        MD5Transform(context->state, context->buffer);

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

        index = 0;
    }
    else
        i = 0;

    /* Buffer remaining input */
    MD5_memcpy
        ((POINTER) & context->buffer[index], (POINTER) & input[i],
        inputLen - i);
}

/**
 * \ingroup baselib
 * Cacluate the MD5 hash of the data added to this context.   Context 
 * will be zeroed after this call.
 * @param digest Buffer to store MD5 value in.
 * @param context Context that has data added to it.
 */
void
TSK_MD5_Final(unsigned char digest[16], TSK_MD5_CTX * context)
{
    unsigned char bits[8];
    unsigned int index, padLen;

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

    /* Pad out to 56 mod 64.
     */
    index = (unsigned int) ((context->count[0] >> 3) & 0x3f);
    padLen = (index < 56) ? (56 - index) : (120 - index);
    TSK_MD5_Update(context, PADDING, padLen);

    /* Append length (before padding) */
    TSK_MD5_Update(context, bits, 8);
    /* Store state in digest */
    Encode(digest, context->state, 16);

    /* Zeroize sensitive information.
     */
    MD5_memset((POINTER) context, 0, sizeof(*context));
}

/* MD5 basic transformation. Transforms state based on block.
 */
static void
MD5Transform(state, block)
  UINT4 state[4];
  unsigned char block[64];
{
    UINT4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];

    Decode(x, block, 64);

    /* Round 1 */
    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 */
    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 */
    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 */
    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.
     */
    MD5_memset((POINTER) x, 0, sizeof(x));
}

/* Encodes input (UINT4) into output (unsigned char). Assumes len is
  a multiple of 4.
 */
static void
Encode(output, input, len)
  unsigned char *output;
  UINT4 *input;
  unsigned int len;
{
    unsigned int i, j;

    for (i = 0, j = 0; j < len; i++, j += 4) {
        output[j] = (unsigned char) (input[i] & 0xff);
        output[j + 1] = (unsigned char) ((input[i] >> 8) & 0xff);
        output[j + 2] = (unsigned char) ((input[i] >> 16) & 0xff);
        output[j + 3] = (unsigned char) ((input[i] >> 24) & 0xff);
    }
}

/* Decodes input (unsigned char) into output (UINT4). Assumes len is
  a multiple of 4.
 */
static void
Decode(output, input, len)
  UINT4 *output;
  unsigned char *input;
  unsigned int len;
{
    unsigned int i, j;

    for (i = 0, j = 0; j < len; i++, j += 4)
        output[i] = ((UINT4) input[j]) | (((UINT4) input[j + 1]) << 8) |
            (((UINT4) input[j + 2]) << 16) | (((UINT4) input[j + 3]) <<
            24);
}

/* Note: Replace "for loop" with standard memcpy if possible.
 */

static void
MD5_memcpy(output, input, len)
  POINTER output;
  POINTER input;
  unsigned int len;
{
    unsigned int i;

    for (i = 0; i < len; i++)
        output[i] = input[i];
}

/* Note: Replace "for loop" with standard memset if possible.
 */
static void
MD5_memset(output, value, len)
  POINTER output;
  int value;
  unsigned int len;
{
    unsigned int i;

    for (i = 0; i < len; i++)
        ((char *) output)[i] = (char) value;
}
