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+/* md5-crypt - One way encryption based on MD5 sum.
+Copyright (C) 1996 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 Library General Public License as
+published by the Free Software Foundation; either version 2 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
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB. If
+not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+Boston, MA 02111-1307, USA. */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/param.h>
+
+#include "md5.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";
+
+
+/* Prototypes for local functions. */
+extern char *md5_crypt_r __P ((const char *key, const char *salt, char *buffer,
+ int buflen));
+extern char *md5_crypt __P ((const char *key, const char *salt));
+
+
+
+/* This entry point is equivalent to the `crypt' function in Unix
+ libcs. */
+char *
+md5_crypt_r (key, salt, buffer, buflen)
+ const char *key;
+ const char *salt;
+ char *buffer;
+ int buflen;
+{
+ unsigned char alt_result[16];
+ struct md5_ctx ctx;
+ struct md5_ctx alt_ctx;
+ size_t salt_len;
+ size_t key_len;
+ size_t cnt;
+ char *cp;
+
+ /* 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, "$"), 8);
+ key_len = strlen (key);
+
+ /* Prepare for the real work. */
+ md5_init_ctx (&ctx);
+
+ /* Add the key string. */
+ md5_process_bytes (key, key_len, &ctx);
+
+ /* Because the SALT argument need not always have the salt prefix we
+ add it separately. */
+ md5_process_bytes (md5_salt_prefix, sizeof (md5_salt_prefix) - 1, &ctx);
+
+ /* The last part is the salt string. This must be at most 8
+ characters and it ends at the first `$' character (for
+ compatibility which existing solutions). */
+ md5_process_bytes (salt, salt_len, &ctx);
+
+
+ /* Compute alternate MD5 sum with input KEY, SALT, and KEY. The
+ final result will be added to the first context. */
+ md5_init_ctx (&alt_ctx);
+
+ /* Add key. */
+ md5_process_bytes (key, key_len, &alt_ctx);
+
+ /* Add salt. */
+ md5_process_bytes (salt, salt_len, &alt_ctx);
+
+ /* Add key again. */
+ md5_process_bytes (key, key_len, &alt_ctx);
+
+ /* Now get result of this (16 bytes) and add it to the other
+ context. */
+ md5_finish_ctx (&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_process_bytes (alt_result, 16, &ctx);
+ md5_process_bytes (alt_result, cnt, &ctx);
+
+ /* For the following code we need a NUL byte. */
+ *alt_result = '\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_process_bytes ((cnt & 1) != 0 ? (const char *) alt_result : key, 1,
+ &ctx);
+
+ /* Create intermediate result. */
+ md5_finish_ctx (&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 (&ctx);
+
+ /* Add key or last result. */
+ if ((cnt & 1) != 0)
+ md5_process_bytes (key, key_len, &ctx);
+ else
+ md5_process_bytes (alt_result, 16, &ctx);
+
+ /* Add salt for numbers not divisible by 3. */
+ if (cnt % 3 != 0)
+ md5_process_bytes (salt, salt_len, &ctx);
+
+ /* Add key for numbers not divisible by 7. */
+ if (cnt % 7 != 0)
+ md5_process_bytes (key, key_len, &ctx);
+
+ /* Add key or last result. */
+ if ((cnt & 1) != 0)
+ md5_process_bytes (alt_result, 16, &ctx);
+ else
+ md5_process_bytes (key, key_len, &ctx);
+
+ /* Create intermediate result. */
+ md5_finish_ctx (&ctx, alt_result);
+ }
+
+ /* Now we can construct the result string. It consists of three
+ parts. */
+ cp = stpncpy (buffer, md5_salt_prefix, MAX (0, buflen));
+ buflen -= sizeof (md5_salt_prefix);
+
+ cp = stpncpy (cp, salt, MIN ((size_t) buflen, salt_len));
+ 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)
+ {
+ __set_errno (ERANGE);
+ buffer = NULL;
+ }
+ 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. */
+ memset (alt_result, '\0', sizeof (alt_result));
+
+ return buffer;
+}
+
+
+char *
+md5_crypt (key, salt)
+ const char *key;
+ const char *salt;
+{
+ /* We don't want to have an arbitrary limit in the size of the
+ password. We can compute the size of the result in advance and
+ so we can prepare the buffer we pass to `md5_crypt_r'. */
+ static char *buffer = NULL;
+ static int buflen = 0;
+ int needed = 3 + strlen (salt) + 1 + 26 + 1;
+
+ if (buflen < needed)
+ {
+ buflen = needed;
+ if ((buffer = realloc (buffer, buflen)) == NULL)
+ return NULL;
+ }
+
+ return md5_crypt_r (key, salt, buffer, buflen);
+}