1 /* One way encryption based on MD5 sum.
2 Compatible with the behavior of MD5 crypt introduced in FreeBSD 2.0.
3 Copyright (C) 1996,1997,1999,2000,2001,2002 Free Software Foundation, Inc.
4 This file is part of the GNU C Library.
5 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
7 The GNU C Library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Lesser General Public
9 License as published by the Free Software Foundation; either
10 version 2.1 of the License, or (at your option) any later version.
12 The GNU C Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
17 You should have received a copy of the GNU Lesser General Public
18 License along with the GNU C Library; if not, write to the Free
19 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
26 #include <sys/param.h>
31 /* Define our magic string to mark salt for MD5 "encryption"
32 replacement. This is meant to be the same as for other MD5 based
33 encryption implementations. */
34 static const char md5_salt_prefix[] = "$1$";
36 /* Table with characters for base64 transformation. */
37 static const char b64t[64] =
38 "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
41 /* Prototypes for local functions. */
42 extern char *__md5_crypt_r (const char *key, const char *salt,
43 char *buffer, int buflen);
44 extern char *__md5_crypt (const char *key, const char *salt);
47 /* This entry point is equivalent to the `crypt' function in Unix
50 __md5_crypt_r (key, salt, buffer, buflen)
56 unsigned char alt_result[16]
57 __attribute__ ((__aligned__ (__alignof__ (md5_uint32))));
59 struct md5_ctx alt_ctx;
64 char *copied_key = NULL;
65 char *copied_salt = NULL;
67 /* Find beginning of salt string. The prefix should normally always
68 be present. Just in case it is not. */
69 if (strncmp (md5_salt_prefix, salt, sizeof (md5_salt_prefix) - 1) == 0)
70 /* Skip salt prefix. */
71 salt += sizeof (md5_salt_prefix) - 1;
73 salt_len = MIN (strcspn (salt, "$"), 8);
74 key_len = strlen (key);
76 if ((key - (char *) 0) % __alignof__ (md5_uint32) != 0)
78 char *tmp = (char *) alloca (key_len + __alignof__ (md5_uint32));
80 memcpy (tmp + __alignof__ (md5_uint32)
81 - (tmp - (char *) 0) % __alignof__ (md5_uint32),
83 assert ((key - (char *) 0) % __alignof__ (md5_uint32) == 0);
86 if ((salt - (char *) 0) % __alignof__ (md5_uint32) != 0)
88 char *tmp = (char *) alloca (salt_len + __alignof__ (md5_uint32));
90 memcpy (tmp + __alignof__ (md5_uint32)
91 - (tmp - (char *) 0) % __alignof__ (md5_uint32),
93 assert ((salt - (char *) 0) % __alignof__ (md5_uint32) == 0);
96 /* Prepare for the real work. */
97 __md5_init_ctx (&ctx);
99 /* Add the key string. */
100 __md5_process_bytes (key, key_len, &ctx);
102 /* Because the SALT argument need not always have the salt prefix we
103 add it separately. */
104 __md5_process_bytes (md5_salt_prefix, sizeof (md5_salt_prefix) - 1, &ctx);
106 /* The last part is the salt string. This must be at most 8
107 characters and it ends at the first `$' character (for
108 compatibility which existing solutions). */
109 __md5_process_bytes (salt, salt_len, &ctx);
112 /* Compute alternate MD5 sum with input KEY, SALT, and KEY. The
113 final result will be added to the first context. */
114 __md5_init_ctx (&alt_ctx);
117 __md5_process_bytes (key, key_len, &alt_ctx);
120 __md5_process_bytes (salt, salt_len, &alt_ctx);
123 __md5_process_bytes (key, key_len, &alt_ctx);
125 /* Now get result of this (16 bytes) and add it to the other
127 __md5_finish_ctx (&alt_ctx, alt_result);
129 /* Add for any character in the key one byte of the alternate sum. */
130 for (cnt = key_len; cnt > 16; cnt -= 16)
131 __md5_process_bytes (alt_result, 16, &ctx);
132 __md5_process_bytes (alt_result, cnt, &ctx);
134 /* For the following code we need a NUL byte. */
137 /* The original implementation now does something weird: for every 1
138 bit in the key the first 0 is added to the buffer, for every 0
139 bit the first character of the key. This does not seem to be
140 what was intended but we have to follow this to be compatible. */
141 for (cnt = key_len; cnt > 0; cnt >>= 1)
142 __md5_process_bytes ((cnt & 1) != 0 ? (const char *) alt_result : key, 1,
145 /* Create intermediate result. */
146 __md5_finish_ctx (&ctx, alt_result);
148 /* Now comes another weirdness. In fear of password crackers here
149 comes a quite long loop which just processes the output of the
150 previous round again. We cannot ignore this here. */
151 for (cnt = 0; cnt < 1000; ++cnt)
154 __md5_init_ctx (&ctx);
156 /* Add key or last result. */
158 __md5_process_bytes (key, key_len, &ctx);
160 __md5_process_bytes (alt_result, 16, &ctx);
162 /* Add salt for numbers not divisible by 3. */
164 __md5_process_bytes (salt, salt_len, &ctx);
166 /* Add key for numbers not divisible by 7. */
168 __md5_process_bytes (key, key_len, &ctx);
170 /* Add key or last result. */
172 __md5_process_bytes (alt_result, 16, &ctx);
174 __md5_process_bytes (key, key_len, &ctx);
176 /* Create intermediate result. */
177 __md5_finish_ctx (&ctx, alt_result);
180 /* Now we can construct the result string. It consists of three
182 cp = __stpncpy (buffer, md5_salt_prefix, MAX (0, buflen));
183 buflen -= sizeof (md5_salt_prefix) - 1;
185 cp = __stpncpy (cp, salt, MIN ((size_t) MAX (0, buflen), salt_len));
186 buflen -= MIN ((size_t) MAX (0, buflen), salt_len);
194 #define b64_from_24bit(B2, B1, B0, N) \
196 unsigned int w = ((B2) << 16) | ((B1) << 8) | (B0); \
198 while (n-- > 0 && buflen > 0) \
200 *cp++ = b64t[w & 0x3f]; \
207 b64_from_24bit (alt_result[0], alt_result[6], alt_result[12], 4);
208 b64_from_24bit (alt_result[1], alt_result[7], alt_result[13], 4);
209 b64_from_24bit (alt_result[2], alt_result[8], alt_result[14], 4);
210 b64_from_24bit (alt_result[3], alt_result[9], alt_result[15], 4);
211 b64_from_24bit (alt_result[4], alt_result[10], alt_result[5], 4);
212 b64_from_24bit (0, 0, alt_result[11], 2);
215 __set_errno (ERANGE);
219 *cp = '\0'; /* Terminate the string. */
221 /* Clear the buffer for the intermediate result so that people
222 attaching to processes or reading core dumps cannot get any
223 information. We do it in this way to clear correct_words[]
224 inside the MD5 implementation as well. */
225 __md5_init_ctx (&ctx);
226 __md5_finish_ctx (&ctx, alt_result);
227 memset (&ctx, '\0', sizeof (ctx));
228 memset (&alt_ctx, '\0', sizeof (alt_ctx));
229 if (copied_key != NULL)
230 memset (copied_key, '\0', key_len);
231 if (copied_salt != NULL)
232 memset (copied_salt, '\0', salt_len);
238 # define libc_freeres_ptr(decl) decl
240 libc_freeres_ptr (static char *buffer);
243 __md5_crypt (const char *key, const char *salt)
245 /* We don't want to have an arbitrary limit in the size of the
246 password. We can compute the size of the result in advance and
247 so we can prepare the buffer we pass to `md5_crypt_r'. */
249 int needed = 3 + strlen (salt) + 1 + 26 + 1;
257 new_buffer = (char *) realloc (buffer, buflen);
258 if (new_buffer == NULL)
264 return __md5_crypt_r (key, salt, buffer, buflen);
269 __attribute__ ((__destructor__))