gnupg/cipher/md5.c

/* md5.c - MD5 Message-Digest Algorithm
 *	Copyright (C) 1995, 1996, 1998 Free Software Foundation, Inc.
 *
 * according to the definition of MD5 in RFC 1321 from April 1992.
 * NOTE: This is *not* the same file as the one from glibc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */
/* Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1995.  */
/* modified for GnuPG by <werner.koch@guug.de> */

/* Test values:
 * ""                  D4 1D 8C D9 8F 00 B2 04  E9 80 09 98 EC F8 42 7E
 * "a"                 0C C1 75 B9 C0 F1 B6 A8  31 C3 99 E2 69 77 26 61
 * "abc                90 01 50 98 3C D2 4F B0  D6 96 3F 7D 28 E1 7F 72
 * "message digest"    F9 6B 69 7D 7C B7 93 8D  52 5A 2F 31 AA F1 61 D0
 */

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "util.h"
#include "md5.h"
#include "memory.h"


typedef struct {
    u32 A,B,C,D;	  /* chaining variables */
    u32 total[2];
    u32  buflen;
    char buffer[128];
} MD5_CONTEXT;



#ifdef BIG_ENDIAN_HOST
  #define SWAP(n) \
    (((n) << 24) | (((n) & 0xff00) << 8) | (((n) >> 8) & 0xff00) | ((n) >> 24))
#else
  #define SWAP(n) (n)
#endif

/* This array contains the bytes used to pad the buffer to the next
   64-byte boundary.  (RFC 1321, 3.1: Step 1)  */
static const unsigned char fillbuf[64] = { 0x80, 0 /* , 0, 0, ...  */ };

static void
md5_init( MD5_CONTEXT *ctx )
{
    ctx->A = 0x67452301;
    ctx->B = 0xefcdab89;
    ctx->C = 0x98badcfe;
    ctx->D = 0x10325476;

    ctx->total[0] = ctx->total[1] = 0;
    ctx->buflen = 0;
}




/* These are the four functions used in the four steps of the MD5 algorithm
   and defined in the RFC 1321.  The first function is a little bit optimized
   (as found in Colin Plumbs public domain implementation).  */
/* #define FF(b, c, d) ((b & c) | (~b & d)) */
#define FF(b, c, d) (d ^ (b & (c ^ d)))
#define FG(b, c, d) FF (d, b, c)
#define FH(b, c, d) (b ^ c ^ d)
#define FI(b, c, d) (c ^ (b | ~d))


/****************
 * transform n*64 bytes
 */
static void
transform( MD5_CONTEXT *ctx, const void *buffer, size_t len )
{
    u32 correct_words[16];
    const u32 *words = buffer;
    size_t nwords = len / sizeof(u32);
    const u32 *endp = words + nwords;
    u32 A = ctx->A;
    u32 B = ctx->B;
    u32 C = ctx->C;
    u32 D = ctx->D;

    /* First increment the byte count.	RFC 1321 specifies the possible
       length of the file up to 2^64 bits.  Here we only compute the
       number of bytes.  Do a double word increment.  */
    ctx->total[0] += len;
    if( ctx->total[0] < len )
	++ctx->total[1];


    /* Process all bytes in the buffer with 64 bytes in each round of
       the loop.  */
    while(words < endp) {
	u32 *cwp = correct_words;
	u32 A_save = A;
	u32 B_save = B;
	u32 C_save = C;
	u32 D_save = D;

      /* First round: using the given function, the context and a constant
	 the next context is computed.	Because the algorithm's processing
	 unit is a 32-bit word, and it is determined to work on words in
	 little endian byte order, we perhaps have to change the byte order
	 before the computation.  To reduce the work for the next steps
	 we store the swapped words in the array CORRECT_WORDS.  */

#define OP(a, b, c, d, s, T)						\
      do								\
	{								\
	  a += FF (b, c, d) + (*cwp++ = SWAP (*words)) + T;		\
	  ++words;							\
	  CYCLIC (a, s);						\
	  a += b;							\
	}								\
      while (0)

      /* It is unfortunate that C does not provide an operator for
	 cyclic rotation.  Hope the C compiler is smart enough.  */
#define CYCLIC(w, s) (w = (w << s) | (w >> (32 - s)))

	/* Before we start, one word about the strange constants.
	   They are defined in RFC 1321 as

	   T[i] = (int) (4294967296.0 * fabs (sin (i))), i=1..64
	 */

	/* Round 1.  */
	OP (A, B, C, D,  7, 0xd76aa478);
	OP (D, A, B, C, 12, 0xe8c7b756);
	OP (C, D, A, B, 17, 0x242070db);
	OP (B, C, D, A, 22, 0xc1bdceee);
	OP (A, B, C, D,  7, 0xf57c0faf);
	OP (D, A, B, C, 12, 0x4787c62a);
	OP (C, D, A, B, 17, 0xa8304613);
	OP (B, C, D, A, 22, 0xfd469501);
	OP (A, B, C, D,  7, 0x698098d8);
	OP (D, A, B, C, 12, 0x8b44f7af);
	OP (C, D, A, B, 17, 0xffff5bb1);
	OP (B, C, D, A, 22, 0x895cd7be);
	OP (A, B, C, D,  7, 0x6b901122);
	OP (D, A, B, C, 12, 0xfd987193);
	OP (C, D, A, B, 17, 0xa679438e);
	OP (B, C, D, A, 22, 0x49b40821);

	/* For the second to fourth round we have the possibly swapped words
	   in CORRECT_WORDS.  Redefine the macro to take an additional first
	   argument specifying the function to use.  */
#undef OP
#define OP(f, a, b, c, d, k, s, T)  \
	do								  \
	  {								  \
	    a += f (b, c, d) + correct_words[k] + T;			  \
	    CYCLIC (a, s);						  \
	    a += b;							  \
	  }								  \
	while (0)

	/* Round 2.  */
	OP (FG, A, B, C, D,  1,  5, 0xf61e2562);
	OP (FG, D, A, B, C,  6,  9, 0xc040b340);
	OP (FG, C, D, A, B, 11, 14, 0x265e5a51);
	OP (FG, B, C, D, A,  0, 20, 0xe9b6c7aa);
	OP (FG, A, B, C, D,  5,  5, 0xd62f105d);
	OP (FG, D, A, B, C, 10,  9, 0x02441453);
	OP (FG, C, D, A, B, 15, 14, 0xd8a1e681);
	OP (FG, B, C, D, A,  4, 20, 0xe7d3fbc8);
	OP (FG, A, B, C, D,  9,  5, 0x21e1cde6);
	OP (FG, D, A, B, C, 14,  9, 0xc33707d6);
	OP (FG, C, D, A, B,  3, 14, 0xf4d50d87);
	OP (FG, B, C, D, A,  8, 20, 0x455a14ed);
	OP (FG, A, B, C, D, 13,  5, 0xa9e3e905);
	OP (FG, D, A, B, C,  2,  9, 0xfcefa3f8);
	OP (FG, C, D, A, B,  7, 14, 0x676f02d9);
	OP (FG, B, C, D, A, 12, 20, 0x8d2a4c8a);

	/* Round 3.  */
	OP (FH, A, B, C, D,  5,  4, 0xfffa3942);
	OP (FH, D, A, B, C,  8, 11, 0x8771f681);
	OP (FH, C, D, A, B, 11, 16, 0x6d9d6122);
	OP (FH, B, C, D, A, 14, 23, 0xfde5380c);
	OP (FH, A, B, C, D,  1,  4, 0xa4beea44);
	OP (FH, D, A, B, C,  4, 11, 0x4bdecfa9);
	OP (FH, C, D, A, B,  7, 16, 0xf6bb4b60);
	OP (FH, B, C, D, A, 10, 23, 0xbebfbc70);
	OP (FH, A, B, C, D, 13,  4, 0x289b7ec6);
	OP (FH, D, A, B, C,  0, 11, 0xeaa127fa);
	OP (FH, C, D, A, B,  3, 16, 0xd4ef3085);
	OP (FH, B, C, D, A,  6, 23, 0x04881d05);
	OP (FH, A, B, C, D,  9,  4, 0xd9d4d039);
	OP (FH, D, A, B, C, 12, 11, 0xe6db99e5);
	OP (FH, C, D, A, B, 15, 16, 0x1fa27cf8);
	OP (FH, B, C, D, A,  2, 23, 0xc4ac5665);

	/* Round 4.  */
	OP (FI, A, B, C, D,  0,  6, 0xf4292244);
	OP (FI, D, A, B, C,  7, 10, 0x432aff97);
	OP (FI, C, D, A, B, 14, 15, 0xab9423a7);
	OP (FI, B, C, D, A,  5, 21, 0xfc93a039);
	OP (FI, A, B, C, D, 12,  6, 0x655b59c3);
	OP (FI, D, A, B, C,  3, 10, 0x8f0ccc92);
	OP (FI, C, D, A, B, 10, 15, 0xffeff47d);
	OP (FI, B, C, D, A,  1, 21, 0x85845dd1);
	OP (FI, A, B, C, D,  8,  6, 0x6fa87e4f);
	OP (FI, D, A, B, C, 15, 10, 0xfe2ce6e0);
	OP (FI, C, D, A, B,  6, 15, 0xa3014314);
	OP (FI, B, C, D, A, 13, 21, 0x4e0811a1);
	OP (FI, A, B, C, D,  4,  6, 0xf7537e82);
	OP (FI, D, A, B, C, 11, 10, 0xbd3af235);
	OP (FI, C, D, A, B,  2, 15, 0x2ad7d2bb);
	OP (FI, B, C, D, A,  9, 21, 0xeb86d391);
	/* Add the starting values of the context.  */
	A += A_save;
	B += B_save;
	C += C_save;
	D += D_save;
    }

    /* Put checksum in context given as argument.  */
    ctx->A = A;
    ctx->B = B;
    ctx->C = C;
    ctx->D = D;
}



/* The routine updates the message-digest context to
 * account for the presence of each of the characters inBuf[0..inLen-1]
 * in the message whose digest is being computed.
 */
static void
md5_write( MD5_CONTEXT *ctx, const void *buffer, size_t len)
{
    /* When we already have some bits in our internal buffer concatenate
       both inputs first.  */
    if (ctx->buflen != 0)
      {
	size_t left_over = ctx->buflen;
	size_t add = 128 - left_over > len ? len : 128 - left_over;

	memcpy (&ctx->buffer[left_over], buffer, add);
	ctx->buflen += add;

	if (left_over + add > 64)
	  {
	    transform(ctx, ctx->buffer, (left_over + add) & ~63);
	    /* The regions in the following copy operation cannot overlap.  */
	    memcpy (ctx->buffer, &ctx->buffer[(left_over + add) & ~63],
		    (left_over + add) & 63);
	    ctx->buflen = (left_over + add) & 63;
	  }

	buffer = (const char *) buffer + add;
	len -= add;
      }

    /* Process available complete blocks.  */
    if (len > 64)
      {
	transform( ctx, buffer, len & ~63);
	buffer = (const char *) buffer + (len & ~63);
	len &= 63;
      }

    /* Move remaining bytes in internal buffer.  */
    if (len > 0)
      {
	memcpy (ctx->buffer, buffer, len);
	ctx->buflen = len;
      }
}



/* The routine final terminates the message-digest computation and
 * ends with the desired message digest in mdContext->digest[0...15].
 * The handle is prepared for a new MD5 cycle.
 * Returns 16 bytes representing the digest.
 */

static void
md5_final( MD5_CONTEXT *ctx )
{
    /* Take yet unprocessed bytes into account.  */
    u32 bytes = ctx->buflen;
    size_t pad;

    /* Now count remaining bytes.  */
    ctx->total[0] += bytes;
    if( ctx->total[0] < bytes )
	++ctx->total[1];

    pad = bytes >= 56 ? 64 + 56 - bytes : 56 - bytes;
    memcpy (&ctx->buffer[bytes], fillbuf, pad);

    /* Put the 64-bit file length in *bits* at the end of the buffer.  */
    *(u32 *) &ctx->buffer[bytes + pad] = SWAP (ctx->total[0] << 3);
    *(u32 *) &ctx->buffer[bytes + pad + 4] = SWAP ((ctx->total[1] << 3) |
						    (ctx->total[0] >> 29));

    /* Process last bytes.  */
    transform( ctx, ctx->buffer, bytes + pad + 8);

    /* Store the result in buffer */
    ((u32 *)ctx->buffer)[0] = SWAP (ctx->A);
    ((u32 *)ctx->buffer)[1] = SWAP (ctx->B);
    ((u32 *)ctx->buffer)[2] = SWAP (ctx->C);
    ((u32 *)ctx->buffer)[3] = SWAP (ctx->D);
}

static byte *
md5_read( MD5_CONTEXT *hd )
{
    return hd->buffer;
}

/****************
 * Return some information about the algorithm.  We need algo here to
 * distinguish different flavors of the algorithm.
 * Returns: A pointer to string describing the algorithm or NULL if
 *	    the ALGO is invalid.
 */
const char *
md5_get_info( int algo, size_t *contextsize,
	       byte **r_asnoid, int *r_asnlen, int *r_mdlen,
	       void (**r_init)( void *c ),
	       void (**r_write)( void *c, byte *buf, size_t nbytes ),
	       void (**r_final)( void *c ),
	       byte *(**r_read)( void *c )
	     )
{
    static byte asn[18] = /* Object ID is 1.2.840.113549.2.5 */
		    { 0x30, 0x20, 0x30, 0x0c, 0x06, 0x08, 0x2a, 0x86,0x48,
		      0x86, 0xf7, 0x0d, 0x02, 0x05, 0x05, 0x00, 0x04, 0x10 };

    if( algo != 1 )
	return NULL;

    *contextsize = sizeof(MD5_CONTEXT);
    *r_asnoid = asn;
    *r_asnlen = DIM(asn);
    *r_mdlen = 16;
    *r_init  = (void (*)(void *))md5_init;
    *r_write = (void (*)(void *, byte*, size_t))md5_write;
    *r_final = (void (*)(void *))md5_final;
    *r_read  = (byte *(*)(void *))md5_read;

    return "MD5";
}



/* end of file */