/*	$OpenBSD: md5crypt.c,v 1.16 2013/04/21 18:31:56 tedu Exp $	*/

/*
 * ----------------------------------------------------------------------------
 * "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: crypt.c,v 1.5 1996/10/14 08:34:02 phk Exp $
 *
 */

#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;
}