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/* One way encryption based on MD5 sum.
Compatible with the behavior of MD5 crypt introduced in FreeBSD 2.0.
Copyright (C) 1996-2017 Free Software Foundation, Inc.
This 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.
This 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 this library; if not, see
<https://www.gnu.org/licenses/>. */
#include "crypt-port.h"
#include "alg-md5.h"
#include <errno.h>
#if INCLUDE_md5crypt
/* 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[] = "$1$";
/* The maximum length of an MD5 salt string (just the actual salt, not
the entire prefix). */
#define SALT_LEN_MAX 8
/* The length of an MD5-hashed password string, including the
terminating NUL character. Prefix (including its NUL) + 8 bytes of
salt + separator + 22 bytes of hashed password. */
#define MD5_HASH_LENGTH \
(sizeof (md5_salt_prefix) + SALT_LEN_MAX + 1 + 22)
static_assert (MD5_HASH_LENGTH <= CRYPT_OUTPUT_SIZE,
"CRYPT_OUTPUT_SIZE is too small for MD5");
/* An md5_buffer holds all of the sensitive intermediate data. */
struct md5_buffer
{
MD5_CTX ctx;
uint8_t result[16];
};
static_assert (sizeof (struct md5_buffer) <= ALG_SPECIFIC_SIZE,
"ALG_SPECIFIC_SIZE is too small for MD5");
/* This entry point is equivalent to the `crypt' function in Unix
libcs. */
void
crypt_md5crypt_rn (const char *phrase, size_t phr_size,
const char *setting, size_t ARG_UNUSED (set_size),
uint8_t *output, size_t out_size,
void *scratch, size_t scr_size)
{
/* This shouldn't ever happen, but... */
if (out_size < MD5_HASH_LENGTH || scr_size < sizeof (struct md5_buffer))
{
errno = ERANGE;
return;
}
struct md5_buffer *buf = scratch;
MD5_CTX *ctx = &buf->ctx;
uint8_t *result = buf->result;
char *cp = (char *)output;
const char *salt = setting;
size_t salt_size;
size_t cnt;
/* 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_size = strspn (salt, b64t);
if (salt[salt_size] && salt[salt_size] != '$')
{
errno = EINVAL;
return;
}
if (salt_size > SALT_LEN_MAX)
salt_size = SALT_LEN_MAX;
/* Compute alternate MD5 sum with input PHRASE, SALT, and PHRASE. The
final result will be added to the first context. */
MD5_Init (ctx);
/* Add phrase. */
MD5_Update (ctx, phrase, phr_size);
/* Add salt. */
MD5_Update (ctx, salt, salt_size);
/* Add phrase again. */
MD5_Update (ctx, phrase, phr_size);
/* Now get result of this (16 bytes). */
MD5_Final (result, ctx);
/* Prepare for the real work. */
MD5_Init (ctx);
/* Add the phrase string. */
MD5_Update (ctx, phrase, phr_size);
/* Because the SALT argument need not always have the salt prefix we
add it separately. */
MD5_Update (ctx, md5_salt_prefix, sizeof (md5_salt_prefix) - 1);
/* The last part is the salt string. This must be at most 8
characters and it ends at the first `$' character (for
compatibility with existing implementations). */
MD5_Update (ctx, salt, salt_size);
/* Add for any character in the phrase one byte of the alternate sum. */
for (cnt = phr_size; cnt > 16; cnt -= 16)
MD5_Update (ctx, result, 16);
MD5_Update (ctx, result, cnt);
/* For the following code we need a NUL byte. */
*result = '\0';
/* The original implementation now does something weird: for every 1
bit in the phrase the first 0 is added to the buffer, for every 0
bit the first character of the phrase. This does not seem to be
what was intended but we have to follow this to be compatible. */
for (cnt = phr_size; cnt > 0; cnt >>= 1)
MD5_Update (ctx, (cnt & 1) != 0 ? (const char *) result : phrase, 1);
/* Create intermediate result. */
MD5_Final (result, ctx);
/* 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 phrase or last result. */
if ((cnt & 1) != 0)
MD5_Update (ctx, phrase, phr_size);
else
MD5_Update (ctx, result, 16);
/* Add salt for numbers not divisible by 3. */
if (cnt % 3 != 0)
MD5_Update (ctx, salt, salt_size);
/* Add phrase for numbers not divisible by 7. */
if (cnt % 7 != 0)
MD5_Update (ctx, phrase, phr_size);
/* Add phrase or last result. */
if ((cnt & 1) != 0)
MD5_Update (ctx, result, 16);
else
MD5_Update (ctx, phrase, phr_size);
/* Create intermediate result. */
MD5_Final (result, ctx);
}
/* Now we can construct the result string. It consists of three
parts. We already know that there is enough space at CP. */
memcpy (cp, md5_salt_prefix, sizeof (md5_salt_prefix) - 1);
cp += sizeof (md5_salt_prefix) - 1;
memcpy (cp, salt, salt_size);
cp += salt_size;
*cp++ = '$';
#define b64_from_24bit(B2, B1, B0, N) \
do { \
unsigned int w = ((((unsigned int)(B2)) << 16) | \
(((unsigned int)(B1)) << 8) | \
((unsigned int)(B0))); \
int n = (N); \
while (n-- > 0) \
{ \
*cp++ = b64t[w & 0x3f]; \
w >>= 6; \
} \
} while (0)
b64_from_24bit (result[0], result[6], result[12], 4);
b64_from_24bit (result[1], result[7], result[13], 4);
b64_from_24bit (result[2], result[8], result[14], 4);
b64_from_24bit (result[3], result[9], result[15], 4);
b64_from_24bit (result[4], result[10], result[5], 4);
b64_from_24bit (0, 0, result[11], 2);
*cp = '\0';
}
void
gensalt_md5crypt_rn (unsigned long count,
const uint8_t *rbytes, size_t nrbytes,
uint8_t *output, size_t output_size)
{
if (count != 0)
{
errno = EINVAL;
return;
}
gensalt_sha_rn ('1', 8, 1000, 1000, 1000, 1000,
rbytes, nrbytes, output, output_size);
}
#endif
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