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/* One way encryption based on MD5 sum.
Copyright (C) 1996, 1997, 1999, 2000 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA. */
/* warmenhoven took this file and made it work with the md5.[ch] we
* already had. isn't that lovely. people should just use linux or
* freebsd, crypt works properly on those systems. i hate solaris */
#if HAVE_CONFIG_H
# include <config.h>
#endif
#if HAVE_STRING_H
# include <string.h>
#elif HAVE_STRINGS_H
# include <strings.h>
#endif
#include <stdlib.h>
#include "crypt.h"
#include "md5.h"
/* for MIN and MAX */
#include "libyahoo.h"
/* Define our magic string to mark salt for MD5 "encryption"
replacement. This is meant to be the same as for other MD5 based
encryption implementations. */
static const char md5_salt_prefix[] = "$1$";
/* Table with characters for base64 transformation. */
static const char b64t[64] =
"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
char *yahoo_crypt(const char *key, const char *salt)
{
char *buffer = NULL;
int buflen = 0;
int needed = 3 + strlen (salt) + 1 + 26 + 1;
md5_byte_t alt_result[16];
md5_state_t ctx;
md5_state_t alt_ctx;
size_t salt_len;
size_t key_len;
size_t cnt;
char *cp;
if (buflen < needed) {
buflen = needed;
if ((buffer = realloc(buffer, buflen)) == NULL)
return NULL;
}
/* Find beginning of salt string. The prefix should normally always
be present. Just in case it is not. */
if (strncmp (md5_salt_prefix, salt, sizeof (md5_salt_prefix) - 1) == 0)
/* Skip salt prefix. */
salt += sizeof (md5_salt_prefix) - 1;
salt_len = MIN (strcspn (salt, "$"), 8);
key_len = strlen (key);
/* Prepare for the real work. */
md5_init(&ctx);
/* Add the key string. */
md5_append(&ctx, (md5_byte_t *)key, key_len);
/* Because the SALT argument need not always have the salt prefix we
add it separately. */
md5_append(&ctx, (md5_byte_t *)md5_salt_prefix, sizeof (md5_salt_prefix) - 1);
/* The last part is the salt string. This must be at most 8
characters and it ends at the first `$' character (for
compatibility which existing solutions). */
md5_append(&ctx, (md5_byte_t *)salt, salt_len);
/* Compute alternate MD5 sum with input KEY, SALT, and KEY. The
final result will be added to the first context. */
md5_init(&alt_ctx);
/* Add key. */
md5_append(&alt_ctx, (md5_byte_t *)key, key_len);
/* Add salt. */
md5_append(&alt_ctx, (md5_byte_t *)salt, salt_len);
/* Add key again. */
md5_append(&alt_ctx, (md5_byte_t *)key, key_len);
/* Now get result of this (16 bytes) and add it to the other
context. */
md5_finish(&alt_ctx, alt_result);
/* Add for any character in the key one byte of the alternate sum. */
for (cnt = key_len; cnt > 16; cnt -= 16)
md5_append(&ctx, alt_result, 16);
md5_append(&ctx, alt_result, cnt);
/* For the following code we need a NUL byte. */
alt_result[0] = '\0';
/* The original implementation now does something weird: for every 1
bit in the key the first 0 is added to the buffer, for every 0
bit the first character of the key. This does not seem to be
what was intended but we have to follow this to be compatible. */
for (cnt = key_len; cnt > 0; cnt >>= 1)
md5_append(&ctx, (cnt & 1) != 0 ? alt_result : (md5_byte_t *)key, 1);
/* Create intermediate result. */
md5_finish(&ctx, alt_result);
/* Now comes another weirdness. In fear of password crackers here
comes a quite long loop which just processes the output of the
previous round again. We cannot ignore this here. */
for (cnt = 0; cnt < 1000; ++cnt) {
/* New context. */
md5_init(&ctx);
/* Add key or last result. */
if ((cnt & 1) != 0)
md5_append(&ctx, (md5_byte_t *)key, key_len);
else
md5_append(&ctx, alt_result, 16);
/* Add salt for numbers not divisible by 3. */
if (cnt % 3 != 0)
md5_append(&ctx, (md5_byte_t *)salt, salt_len);
/* Add key for numbers not divisible by 7. */
if (cnt % 7 != 0)
md5_append(&ctx, (md5_byte_t *)key, key_len);
/* Add key or last result. */
if ((cnt & 1) != 0)
md5_append(&ctx, alt_result, 16);
else
md5_append(&ctx, (md5_byte_t *)key, key_len);
/* Create intermediate result. */
md5_finish(&ctx, alt_result);
}
/* Now we can construct the result string. It consists of three
parts. */
strncpy(buffer, md5_salt_prefix, MAX (0, buflen));
cp = buffer + strlen(buffer);
buflen -= sizeof (md5_salt_prefix);
strncpy(cp, salt, MIN ((size_t) buflen, salt_len));
cp = cp + strlen(cp);
buflen -= MIN ((size_t) buflen, salt_len);
if (buflen > 0) {
*cp++ = '$';
--buflen;
}
#define b64_from_24bit(B2, B1, B0, N) \
do { \
unsigned int w = ((B2) << 16) | ((B1) << 8) | (B0); \
int n = (N); \
while (n-- > 0 && buflen > 0) { \
*cp++ = b64t[w & 0x3f]; \
--buflen; \
w >>= 6; \
}\
} while (0)
b64_from_24bit (alt_result[0], alt_result[6], alt_result[12], 4);
b64_from_24bit (alt_result[1], alt_result[7], alt_result[13], 4);
b64_from_24bit (alt_result[2], alt_result[8], alt_result[14], 4);
b64_from_24bit (alt_result[3], alt_result[9], alt_result[15], 4);
b64_from_24bit (alt_result[4], alt_result[10], alt_result[5], 4);
b64_from_24bit (0, 0, alt_result[11], 2);
if (buflen <= 0) {
FREE(buffer);
} else
*cp = '\0'; /* Terminate the string. */
/* Clear the buffer for the intermediate result so that people
attaching to processes or reading core dumps cannot get any
information. We do it in this way to clear correct_words[]
inside the MD5 implementation as well. */
md5_init(&ctx);
md5_finish(&ctx, alt_result);
memset (&ctx, '\0', sizeof (ctx));
memset (&alt_ctx, '\0', sizeof (alt_ctx));
return buffer;
}
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