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/*-
 * Copyright (c) 2003 Poul-Henning Kamp
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <inttypes.h>
#include <md5.h>
#include <string.h>

/*
 * UNIX password
 */

static char *
_crypt_to64(char *s, uint32_t v, int n)
{
	static const char itoa64[64] = "./0123456789"
		"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

	while (--n >= 0) {
		*s++ = itoa64[v&0x3f];
		v >>= 6;
	}
	return s;
}

char *
crypt_md5(const char *pw, const char *salt)
{
	MD5_CTX	ctx,ctx1;
	unsigned long l;
	int sl, pl;
	uint32_t i;
	uint8_t final[MD5_SIZE];
	const char *sp;
	static char passwd[120]; /* Output buffer */
	static const char magic[] = "$1$";
	char *p;
	const int magic_len = sizeof magic - 1;
	int pwlen = strlen(pw);

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

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

	/* Compute the salt length:
	   it stops at the first '$', max 8 chars */
	for (sl = 0; sl < 8 && sp[sl] && sp[sl] != '$'; sl++)
		;

	MD5Init(&ctx);

	/* The password first, since that is what is most unknown */
	MD5Update(&ctx, pw, pwlen);

	/* Then our magic string */
	MD5Update(&ctx, magic, magic_len);

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

	/* Then just as many characters of the MD5(pw,salt,pw) */
	MD5Init(&ctx1);
	MD5Update(&ctx1, pw, pwlen);
	MD5Update(&ctx1, sp, sl);
	MD5Update(&ctx1, pw, pwlen);
	MD5Final(final, &ctx1);
	for (pl = pwlen; pl > 0; pl -= MD5_SIZE)
		MD5Update(&ctx, final, pl > MD5_SIZE ? MD5_SIZE : pl);

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

	/* Then something really weird... */
	for (i = pwlen; i; i >>= 1)
		if (i & 1)
		    MD5Update(&ctx, final, 1);
		else
		    MD5Update(&ctx, pw, 1);

	/* Now make the output string */
	p = passwd;

	memcpy(p, magic, magic_len);
	p += magic_len;

	memcpy(p, sp, sl);
	p += sl;

	*p++ = '$';

	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...
	 */
	for (i = 0; i < 1000; i++) {
		MD5Init(&ctx1);
		if(i & 1)
			MD5Update(&ctx1, pw, pwlen);
		else
			MD5Update(&ctx1, final, MD5_SIZE);

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

		if(i % 7)
			MD5Update(&ctx1, pw, pwlen);

		if(i & 1)
			MD5Update(&ctx1, final, MD5_SIZE);
		else
			MD5Update(&ctx1, pw, pwlen);
		MD5Final(final, &ctx1);
	}

	l = (final[ 0]<<16) | (final[ 6]<<8) | final[12];
	p = _crypt_to64(p, l, 4);
	l = (final[ 1]<<16) | (final[ 7]<<8) | final[13];
	p = _crypt_to64(p, l, 4);
	l = (final[ 2]<<16) | (final[ 8]<<8) | final[14];
	p = _crypt_to64(p, l, 4);
	l = (final[ 3]<<16) | (final[ 9]<<8) | final[15];
	p = _crypt_to64(p, l, 4);
	l = (final[ 4]<<16) | (final[10]<<8) | final[ 5];
	p = _crypt_to64(p, l, 4);
	l = final[11];
	p = _crypt_to64(p, l, 2);
	*p = '\0';

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

	return passwd;
}

#ifdef TEST
#include <stdio.h>

int main(int argc, char *argv[])
{
	int i;

	for (i = 2; i < argc; i += 2) {
		puts(crypt_md5(argv[i], argv[i-1]));
	}
	return 0;
}

#endif