uclibc-ng/libcrypt/md5.c

/*
 * 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.
 *
 * $FreeBSD: src/lib/libmd/md5c.c,v 1.9.2.1 1999/08/29 14:57:12 peter Exp $
 *
 * This code is the same as the code published by RSA Inc.  It has been
 * edited for clarity and style only.
 *
 * ----------------------------------------------------------------------------
 * The md5_crypt() function was taken from freeBSD's libcrypt and contains 
 * this license: 
 *    "THE BEER-WARE LICENSE" (Revision 42):
 *     <phk@login.dknet.dk> wrote this file.  As long as you retain this notice you
 *     can do whatever you want with this stuff. If we meet some day, and you think
 *     this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
 *
 * $FreeBSD: src/lib/libcrypt/crypt.c,v 1.7.2.1 1999/08/29 14:56:33 peter Exp $
 *
 * ----------------------------------------------------------------------------
 * On April 19th, 2001 md5_crypt() was modified to make it reentrant 
 * by Erik Andersen <andersen@uclibc.org>
 *
 *
 * June 28, 2001             Manuel Novoa III
 *
 * "Un-inlined" code using loops and static const tables in order to
 * reduce generated code size (on i386 from approx 4k to approx 2.5k).
 *
 * June 29, 2001             Manuel Novoa III
 *
 * Completely removed static PADDING array.
 *
 * Reintroduced the loop unrolling in MD5_Transform and added the
 * MD5_SIZE_OVER_SPEED option for configurability.  Define below as:
 *       0    fully unrolled loops
 *       1    partially unrolled (4 ops per loop)
 *       2    no unrolling -- introduces the need to swap 4 variables (slow)
 *       3    no unrolling and all 4 loops merged into one with switch
 *               in each loop (glacial)
 * On i386, sizes are roughly (-Os -fno-builtin):
 *     0: 3k     1: 2.5k     2: 2.2k     3: 2k
 *
 *
 * Since SuSv3 does not require crypt_r, modified again August 7, 2002
 * by Erik Andersen to remove reentrance stuff...
 */

/*
 * Valid values are  1 (fastest/largest) to 3 (smallest/slowest).
 */
#define MD5_SIZE_OVER_SPEED 3

/**********************************************************************/

#include <sys/types.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <crypt.h>
#include <sys/cdefs.h>
	
/* MD5 context. */
struct MD5Context {
  u_int32_t state[4];	/* state (ABCD) */
  u_int32_t count[2];	/* number of bits, modulo 2^64 (lsb first) */
  unsigned char buffer[64];	/* input buffer */
};

static void   __md5_Init (struct MD5Context *);
static void   __md5_Update (struct MD5Context *, const unsigned char *, unsigned int);
static void   __md5_Pad (struct MD5Context *);
static void   __md5_Final (unsigned char [16], struct MD5Context *);
static void __md5_Transform __P((u_int32_t [4], const unsigned char [64]));


static const char __md5__magic[] = "$1$";	/* This string is magic for this algorithm.  Having 
						   it this way, we can get better later on */
static const unsigned char __md5_itoa64[] =		/* 0 ... 63 => ascii - 64 */
	"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";



#ifdef i386
#define __md5_Encode memcpy
#define __md5_Decode memcpy
#else /* i386 */

/*
 * __md5_Encodes input (u_int32_t) into output (unsigned char). Assumes len is
 * a multiple of 4.
 */

static void
__md5_Encode (output, input, len)
	unsigned char *output;
	u_int32_t *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);
	}
}

/*
 * __md5_Decodes input (unsigned char) into output (u_int32_t). Assumes len is
 * a multiple of 4.
 */

static void
__md5_Decode (output, input, len)
	u_int32_t *output;
	const unsigned char *input;
	unsigned int len;
{
	unsigned int i, j;

	for (i = 0, j = 0; j < len; i++, j += 4)
		output[i] = ((u_int32_t)input[j]) | (((u_int32_t)input[j+1]) << 8) |
		    (((u_int32_t)input[j+2]) << 16) | (((u_int32_t)input[j+3]) << 24);
}
#endif /* i386 */

/* 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) + (u_int32_t)(ac); \
	(a) = ROTATE_LEFT ((a), (s)); \
	(a) += (b); \
	}
#define GG(a, b, c, d, x, s, ac) { \
	(a) += G ((b), (c), (d)) + (x) + (u_int32_t)(ac); \
	(a) = ROTATE_LEFT ((a), (s)); \
	(a) += (b); \
	}
#define HH(a, b, c, d, x, s, ac) { \
	(a) += H ((b), (c), (d)) + (x) + (u_int32_t)(ac); \
	(a) = ROTATE_LEFT ((a), (s)); \
	(a) += (b); \
	}
#define II(a, b, c, d, x, s, ac) { \
	(a) += I ((b), (c), (d)) + (x) + (u_int32_t)(ac); \
	(a) = ROTATE_LEFT ((a), (s)); \
	(a) += (b); \
	}

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

static void __md5_Init (struct MD5Context *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.
 */

static void __md5_Update ( struct MD5Context *context, const 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] += ((u_int32_t)inputLen << 3))
	    < ((u_int32_t)inputLen << 3))
		context->count[1]++;
	context->count[1] += ((u_int32_t)inputLen >> 29);

	partLen = 64 - index;

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

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

static void __md5_Pad ( struct MD5Context *context)
{
	unsigned char bits[8];
	unsigned int index, padLen;
	unsigned char PADDING[64];

	memset(PADDING, 0, sizeof(PADDING));
	PADDING[0] = 0x80;

	/* Save number of bits */
	__md5_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);
}

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

static void __md5_Final ( unsigned char digest[16], struct MD5Context *context)
{
	/* Do padding. */
	__md5_Pad (context);

	/* Store state in digest */
	__md5_Encode (digest, context->state, 16);

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

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

static void
__md5_Transform (state, block)
	u_int32_t state[4];
	const unsigned char block[64];
{
	u_int32_t a, b, c, d, x[16];

#if MD5_SIZE_OVER_SPEED > 1
	u_int32_t temp;
	const char *ps;

	static const char S[] = {
		7, 12, 17, 22,
		5, 9, 14, 20,
		4, 11, 16, 23,
		6, 10, 15, 21
	};
#endif /* MD5_SIZE_OVER_SPEED > 1 */

#if MD5_SIZE_OVER_SPEED > 0
	const u_int32_t *pc;
	const char *pp;
	int i;

	static const u_int32_t C[] = {
								/* round 1 */
		0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
		0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
		0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
		0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
								/* round 2 */
		0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
		0xd62f105d, 0x2441453,  0xd8a1e681, 0xe7d3fbc8,
		0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
		0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
								/* round 3 */
		0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
		0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
		0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x4881d05,
		0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
								/* round 4 */
		0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
		0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
		0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
		0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391
	};

	static const char P[] = {
		0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, /* 1 */
		1, 6, 11, 0, 5, 10, 15, 4, 9, 14, 3, 8, 13, 2, 7, 12, /* 2 */
		5, 8, 11, 14, 1, 4, 7, 10, 13, 0, 3, 6, 9, 12, 15, 2, /* 3 */
		0, 7, 14, 5, 12, 3, 10, 1, 8, 15, 6, 13, 4, 11, 2, 9  /* 4 */
	};

#endif /* MD5_SIZE_OVER_SPEED > 0 */

	__md5_Decode (x, block, 64);

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

#if MD5_SIZE_OVER_SPEED > 2
	pc = C; pp = P; ps = S - 4;

	for ( i = 0 ; i < 64 ; i++ ) {
		if ((i&0x0f) == 0) ps += 4;
		temp = a;
		switch (i>>4) {
			case 0:
				temp += F(b,c,d);
				break;
			case 1:
				temp += G(b,c,d);
				break;
			case 2:
				temp += H(b,c,d);
				break;
			case 3:
				temp += I(b,c,d);
				break;
		}
		temp += x[(int)(*pp++)] + *pc++;
		temp = ROTATE_LEFT(temp, ps[i&3]);
		temp += b;
		a = d; d = c; c = b; b = temp;
	}
#elif MD5_SIZE_OVER_SPEED > 1
	pc = C; pp = P; ps = S;

	/* Round 1 */
	for ( i = 0 ; i < 16 ; i++ ) {
		FF (a, b, c, d, x[(int)(*pp++)], ps[i&0x3], *pc++);
		temp = d; d = c; c = b; b = a; a = temp;
	}

	/* Round 2 */
	ps += 4;
	for ( ; i < 32 ; i++ ) {
		GG (a, b, c, d, x[(int)(*pp++)], ps[i&0x3], *pc++);
		temp = d; d = c; c = b; b = a; a = temp;
	}
	/* Round 3 */
	ps += 4;
	for ( ; i < 48 ; i++ ) {
		HH (a, b, c, d, x[(int)(*pp++)], ps[i&0x3], *pc++);
		temp = d; d = c; c = b; b = a; a = temp;
	}

	/* Round 4 */
	ps += 4;
	for ( ; i < 64 ; i++ ) {
		II (a, b, c, d, x[(int)(*pp++)], ps[i&0x3], *pc++);
		temp = d; d = c; c = b; b = a; a = temp;
	}
#elif MD5_SIZE_OVER_SPEED > 0
	pc = C; pp = P;

	/* Round 1 */
	for ( i = 0 ; i < 4 ; i++ ) {
		FF (a, b, c, d, x[(int)(*pp++)],  7, *pc++);
		FF (d, a, b, c, x[(int)(*pp++)], 12, *pc++);
		FF (c, d, a, b, x[(int)(*pp++)], 17, *pc++);
		FF (b, c, d, a, x[(int)(*pp++)], 22, *pc++);
	}

	/* Round 2 */
	for ( i = 0 ; i < 4 ; i++ ) {
		GG (a, b, c, d, x[(int)(*pp++)],  5, *pc++);
		GG (d, a, b, c, x[(int)(*pp++)],  9, *pc++);
		GG (c, d, a, b, x[(int)(*pp++)], 14, *pc++);
		GG (b, c, d, a, x[(int)(*pp++)], 20, *pc++);
	}
	/* Round 3 */
	for ( i = 0 ; i < 4 ; i++ ) {
		HH (a, b, c, d, x[(int)(*pp++)],  4, *pc++);
		HH (d, a, b, c, x[(int)(*pp++)], 11, *pc++);
		HH (c, d, a, b, x[(int)(*pp++)], 16, *pc++);
		HH (b, c, d, a, x[(int)(*pp++)], 23, *pc++);
	}

	/* Round 4 */
	for ( i = 0 ; i < 4 ; i++ ) {
		II (a, b, c, d, x[(int)(*pp++)],  6, *pc++);
		II (d, a, b, c, x[(int)(*pp++)], 10, *pc++);
		II (c, d, a, b, x[(int)(*pp++)], 15, *pc++);
		II (b, c, d, a, x[(int)(*pp++)], 21, *pc++);
	}
#else
	/* 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 */
#endif

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

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


static void __md5_to64( char *s, unsigned long v, int n)
{
	while (--n >= 0) {
		*s++ = __md5_itoa64[v&0x3f];
		v >>= 6;
	}
}

/*
 * UNIX password
 *
 * Use MD5 for what it is best at...
 */

extern char * __md5_crypt( const char *pw, const char *salt)
{
	/* Static stuff */
	static const char *sp, *ep;
	static char passwd[120], *p;

	unsigned char	final[17];	/* final[16] exists only to aid in looping */
	int sl,pl,i,__md5__magic_len,pw_len;
	struct MD5Context ctx,ctx1;
	unsigned long l;

	/* Refine the Salt first */
	sp = salt;

	/* If it starts with the magic string, then skip that */
	__md5__magic_len = strlen(__md5__magic);
	if(!strncmp(sp,__md5__magic,__md5__magic_len))
		sp += __md5__magic_len;

	/* It stops at the first '$', max 8 chars */
	for(ep=sp;*ep && *ep != '$' && ep < (sp+8);ep++)
		continue;

	/* get the length of the true salt */
	sl = ep - sp;

	__md5_Init(&ctx);

	/* The password first, since that is what is most unknown */
	pw_len = strlen(pw);
	__md5_Update(&ctx,pw,pw_len);

	/* Then our magic string */
	__md5_Update(&ctx,__md5__magic,__md5__magic_len);

	/* Then the raw salt */
	__md5_Update(&ctx,sp,sl);

	/* Then just as many characters of the MD5(pw,salt,pw) */
	__md5_Init(&ctx1);
	__md5_Update(&ctx1,pw,pw_len);
	__md5_Update(&ctx1,sp,sl);
	__md5_Update(&ctx1,pw,pw_len);
	__md5_Final(final,&ctx1);
	for(pl = pw_len; pl > 0; pl -= 16)
		__md5_Update(&ctx,final,pl>16 ? 16 : pl);

	/* Don't leave anything around in vm they could use. */
	memset(final,0,sizeof final);

	/* Then something really weird... */
	for (i = pw_len; i ; i >>= 1) {
		__md5_Update(&ctx, ((i&1) ? final : (const unsigned char *) pw), 1);
	}

	/* Now make the output string */
	strcpy(passwd,__md5__magic);
	strncat(passwd,sp,sl);
	strcat(passwd,"$");

	__md5_Final(final,&ctx);

	/*
	 * and now, just to make sure things don't run too fast
	 * On a 60 Mhz Pentium this takes 34 msec, so you would
	 * need 30 seconds to build a 1000 entry dictionary...
	 */
	for(i=0;i<1000;i++) {
		__md5_Init(&ctx1);
		if(i & 1)
			__md5_Update(&ctx1,pw,pw_len);
		else
			__md5_Update(&ctx1,final,16);

		if(i % 3)
			__md5_Update(&ctx1,sp,sl);

		if(i % 7)
			__md5_Update(&ctx1,pw,pw_len);

		if(i & 1)
			__md5_Update(&ctx1,final,16);
		else
			__md5_Update(&ctx1,pw,pw_len);
		__md5_Final(final,&ctx1);
	}

	p = passwd + strlen(passwd);

	final[16] = final[5];
	for ( i=0 ; i < 5 ; i++ ) {
		l = (final[i]<<16) | (final[i+6]<<8) | final[i+12];
		__md5_to64(p,l,4); p += 4;
	}
	l = final[11];
	__md5_to64(p,l,2); p += 2;
	*p = '\0';

	/* Don't leave anything around in vm they could use. */
	memset(final,0,sizeof final);

	return passwd;
}