/*---------------------------------------------------------------------------*
 |              PDFlib - A library for generating PDF on the fly             |
 +---------------------------------------------------------------------------+
 | Copyright (c) 1997-2002 PDFlib GmbH and Thomas Merz. All rights reserved. |
 +---------------------------------------------------------------------------+
 |    This software is NOT in the public domain.  It can be used under two   |
 |    substantially different licensing terms:                               |
 |                                                                           |
 |    The commercial license is available for a fee, and allows you to       |
 |    - ship a commercial product based on PDFlib                            |
 |    - implement commercial Web services with PDFlib                        |
 |    - distribute (free or commercial) software when the source code is     |
 |      not made available                                                   |
 |    Details can be found in the file PDFlib-license.pdf.                   |
 |                                                                           |
 |    The "Aladdin Free Public License" doesn't require any license fee,     |
 |    and allows you to                                                      |
 |    - develop and distribute PDFlib-based software for which the complete  |
 |      source code is made available                                        |
 |    - redistribute PDFlib non-commercially under certain conditions        |
 |    - redistribute PDFlib on digital media for a fee if the complete       |
 |      contents of the media are freely redistributable                     |
 |    Details can be found in the file aladdin-license.pdf.                  |
 |                                                                           |
 |    These conditions extend to ports to other programming languages.       |
 |    PDFlib is distributed with no warranty of any kind. Commercial users,  |
 |    however, will receive warranty and support statements in writing.      |
 *---------------------------------------------------------------------------*/

/* $Id: p_md5.c,v 1.1.4.3 2002/01/07 18:26:29 tm Exp $
 *
 * PDFlib MD5 message digest routines
 *
 */

/* This is a slightly modified version of the RSA reference
 * implementation for MD5, which originally contained
 * the following copyright notice:
 */

/*  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.
*/

#include "string.h"

#include "p_md5.h"

/* Constants for MD5_Transform 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 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) + (MD5_UINT4)(ac); \
	(a) = ROTATE_LEFT ((a), (s)); \
	(a) += (b); \
}
#define GG(a, b, c, d, x, s, ac) { \
	(a) += G ((b), (c), (d)) + (x) + (MD5_UINT4)(ac); \
	(a) = ROTATE_LEFT ((a), (s)); \
	(a) += (b); \
}
#define HH(a, b, c, d, x, s, ac) { \
	(a) += H ((b), (c), (d)) + (x) + (MD5_UINT4)(ac); \
	(a) = ROTATE_LEFT ((a), (s)); \
	(a) += (b); \
}
#define II(a, b, c, d, x, s, ac) { \
	(a) += I ((b), (c), (d)) + (x) + (MD5_UINT4)(ac); \
	(a) = ROTATE_LEFT ((a), (s)); \
	(a) += (b); \
}


/* Encodes input (MD5_UINT4) into output (unsigned char). Assumes len is
 * a multiple of 4.
 */
static void Encode(unsigned char *output, MD5_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 (MD5_UINT4). Assumes len is
 * a multiple of 4.
 */
static void Decode(MD5_UINT4 *output, unsigned char *input, unsigned int len)
{
    unsigned int i, j;

    for (i = 0, j = 0; j < len; i++, j += 4)
	output[i] = ((MD5_UINT4) input[j]) |
		    (((MD5_UINT4) input[j+1]) << 8) |
		    (((MD5_UINT4) input[j+2]) << 16) |
		    (((MD5_UINT4) input[j+3]) << 24);
}

/* MD5 basic transformation. Transforms state based on block.
 */
static void MD5_Transform(MD5_UINT4 state[4], unsigned char block[64])
{
    MD5_UINT4 a = state[0];
    MD5_UINT4 b = state[1];
    MD5_UINT4 c = state[2];
    MD5_UINT4 d = state[3];
    MD5_UINT4 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.
    */
    memset (x, 0, sizeof (x));
}

/* MD5 initialization. Begins an MD5 operation, writing a new context.
 */
void MD5_Init(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 MD5_Update(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] += ((MD5_UINT4) inputLen << 3))
	< ((MD5_UINT4) inputLen << 3))
	context->count[1]++;

    context->count[1] += ((MD5_UINT4) inputLen >> 29);

    partLen = 64 - index;

    /* Transform as many times as possible.
    */
    if (inputLen >= partLen) {
	memcpy(&context->buffer[index], input, partLen);
	MD5_Transform(context->state, context->buffer);

	for (i = partLen; i + 63 < inputLen; i += 64)
	    MD5_Transform (context->state, &input[i]);

	index = 0;
    }
    else
	i = 0;

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

/* MD5 finalization. Ends an MD5 message-digest operation, writing the
 * the message digest and zeroizing the context.
 */
void MD5_Final(unsigned char digest[MD5_DIGEST_LENGTH], 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);
    MD5_Update(context, PADDING, padLen);

    /* Append length (before padding) */
    MD5_Update(context, bits, 8);

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

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