/*	$OpenBSD: md5crypt.c,v 1.9 1997/07/23 20:58:27 kstailey 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 $
 *
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char rcsid[] = "$OpenBSD: md5crypt.c,v 1.9 1997/07/23 20:58:27 kstailey Exp $";
#endif /* LIBC_SCCS and not lint */

#include <unistd.h>
#include "md5.h"

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

static void to64(unsigned char *s, uint32_t v, int n)
{
	while (--n >= 0) {
		*s++ = itoa64[v&0x3f];
		v >>= 6;
	}
}

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

#define R(F,P,Q,R) to64(p, (F[P]<<16) | (F[Q]<<8) | F[R], 4); p += 4
#define magic (unsigned char *)"$1$"

char *md5crypt(const char *pw, const char *salt) /*EXTRACT_INCL*/
{
	static char passwd[40];
	const unsigned char *sp,*ep;
	unsigned char final[16], *p = (unsigned char *)pw;
	int sl,i,pw_len = str_len(pw);
	MD5_CTX	ctx,ctx1;

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

	/* If it starts with the magic string, then skip that */
	if (!byte_diff(sp,3,magic))
		sp += 3;

	/* 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 */
	MD5_Update(&ctx,p,pw_len);

	/* Then our magic string */
	MD5_Update(&ctx,magic,3);

	/* 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,p,pw_len);
	MD5_Update(&ctx1,sp,sl);
	MD5_Update(&ctx1,p,pw_len);
	MD5_Final(final,&ctx1);
	for (i = pw_len; i > 0; i -= 16)
		MD5_Update(&ctx,final,(i>16) ? 16 : i);

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

	/* Then something really weird... */
	for (i = pw_len; i ; i >>= 1)
		if(i&1)
		    MD5_Update(&ctx, final, 1);
		else
		    MD5_Update(&ctx, p, 1);

	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,p,pw_len);
		else
			MD5_Update(&ctx1,final,16);

		if(i % 3)
			MD5_Update(&ctx1,sp,sl);

		if(i % 7)
			MD5_Update(&ctx1,p,pw_len);

		if(i & 1)
			MD5_Update(&ctx1,final,16);
		else
			MD5_Update(&ctx1,p,pw_len);
		MD5_Final(final,&ctx1);
	}

	/* Now make the output string */
	p = (unsigned char *)passwd + 3 + sl;
	byte_copy(passwd, 3, magic);
	byte_copy(passwd+3, sl, sp);
	*p++ = '$';

	R(final, 0, 6,12);
	R(final, 1, 7,13);
	R(final, 2, 8,14);
	R(final, 3, 9,15);
	R(final, 4,10, 5);
	to64(p,final[11],2);
	p[2] = 0;

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

	return passwd;
}