/*	$OpenBSD: md5crypt.c,v 1.17 2014/04/03 15:55:29 beck Exp $	*/

/*
 * Copyright (c) 2000 Poul-Henning Kamp <phk@FreeBSD.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * If we meet some day, and you think this stuff is worth it, you
 * can buy me a beer in return. Poul-Henning Kamp
 */

#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <md5.h>
#include <string.h>

static unsigned char itoa64[] =		/* 0 ... 63 => ascii - 64 */
	"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

static void to64(char *, u_int32_t, int);

static void
to64(char *s, u_int32_t v, int n)
{
	while (--n >= 0) {
		*s++ = itoa64[v&0x3f];
		v >>= 6;
	}
}

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

char *md5crypt(const char *pw, const char *salt);

char *
md5crypt(const char *pw, const char *salt)
{
	/*
	 * This string is the magic for this algorithm.
	 * Having it this way, we can get better later on.
	 */
	static unsigned char	*magic = (unsigned char *)"$1$";

	static char     passwd[120], *p;
	static const unsigned char *sp,*ep;
	unsigned char	final[16];
	int sl,pl,i;
	MD5_CTX	ctx,ctx1;
	u_int32_t l;

	/* Refine the salt first */
	sp = (const unsigned char *)salt;

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

	/* 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;

	MD5Init(&ctx);

	/* The password first, since that is what is most unknown */
	MD5Update(&ctx,(const unsigned char *)pw,strlen(pw));

	/* Then our magic string */
	MD5Update(&ctx,magic,strlen((const char *)magic));

	/* Then the raw salt */
	MD5Update(&ctx,sp,sl);

	/* Then just as many characters of the MD5(pw,salt,pw) */
	MD5Init(&ctx1);
	MD5Update(&ctx1,(const unsigned char *)pw,strlen(pw));
	MD5Update(&ctx1,sp,sl);
	MD5Update(&ctx1,(const unsigned char *)pw,strlen(pw));
	MD5Final(final,&ctx1);
	for(pl = strlen(pw); pl > 0; pl -= 16)
		MD5Update(&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 = strlen(pw); i ; i >>= 1)
		if(i&1)
		    MD5Update(&ctx, final, 1);
		else
		    MD5Update(&ctx, (const unsigned char *)pw, 1);

	/* Now make the output string */
	snprintf(passwd, sizeof(passwd), "%s%.*s$", (char *)magic,
	    sl, (const char *)sp);

	MD5Final(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...
	 * On a modern machine, with possible GPU optimization,
	 * this will run a lot faster than that.
	 */
	for(i=0;i<1000;i++) {
		MD5Init(&ctx1);
		if(i & 1)
			MD5Update(&ctx1,(const unsigned char *)pw,strlen(pw));
		else
			MD5Update(&ctx1,final,16);

		if(i % 3)
			MD5Update(&ctx1,sp,sl);

		if(i % 7)
			MD5Update(&ctx1,(const unsigned char *)pw,strlen(pw));

		if(i & 1)
			MD5Update(&ctx1,final,16);
		else
			MD5Update(&ctx1,(const unsigned char *)pw,strlen(pw));
		MD5Final(final,&ctx1);
	}

	p = passwd + strlen(passwd);

	l = (final[ 0]<<16) | (final[ 6]<<8) | final[12]; to64(p,l,4); p += 4;
	l = (final[ 1]<<16) | (final[ 7]<<8) | final[13]; to64(p,l,4); p += 4;
	l = (final[ 2]<<16) | (final[ 8]<<8) | final[14]; to64(p,l,4); p += 4;
	l = (final[ 3]<<16) | (final[ 9]<<8) | final[15]; to64(p,l,4); p += 4;
	l = (final[ 4]<<16) | (final[10]<<8) | final[ 5]; to64(p,l,4); p += 4;
	l =		       final[11]		; 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;
}