libyahoo2/crypt.c

   1 /* One way encryption based on MD5 sum.
   2    Copyright (C) 1996, 1997, 1999, 2000 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 /* warmenhoven took this file and made it work with the md5.[ch] we
  22  * already had. isn't that lovely. people should just use linux or
  23  * freebsd, crypt works properly on those systems. i hate solaris */
  24
  25 #if HAVE_CONFIG_H
  26 #  include <config.h>
  27 #endif
  28
  29 #if HAVE_STRING_H
  30 #  include <string.h>
  31 #elif HAVE_STRINGS_H
  32 #  include <strings.h>
  33 #endif
  34
  35 #include <stdlib.h>
  36 #include "yahoo_util.h"
  37
  38 #include "md5.h"
  39
  40 /* Define our magic string to mark salt for MD5 "encryption"
  41    replacement.  This is meant to be the same as for other MD5 based
  42    encryption implementations.  */
  43 static const char md5_salt_prefix[] = "$1$";
  44
  45 /* Table with characters for base64 transformation.  */
  46 static const char b64t[64] =
  47         "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
  48
  49 char *yahoo_crypt(char *key, char *salt)
  50 {
  51         char *buffer = NULL;
  52         int buflen = 0;
  53         int needed = 3 + strlen(salt) + 1 + 26 + 1;
  54
  55         md5_byte_t alt_result[16];
  56         md5_state_t ctx;
  57         md5_state_t alt_ctx;
  58         size_t salt_len;
  59         size_t key_len;
  60         size_t cnt;
  61         char *cp;
  62
  63         if (buflen < needed) {
  64                 buflen = needed;
  65                 if ((buffer = realloc(buffer, buflen)) == NULL)
  66                         return NULL;
  67         }
  68
  69         /* Find beginning of salt string.  The prefix should normally always
  70            be present.  Just in case it is not.  */
  71         if (strncmp(md5_salt_prefix, salt, sizeof(md5_salt_prefix) - 1) == 0)
  72                 /* Skip salt prefix.  */
  73                 salt += sizeof(md5_salt_prefix) - 1;
  74
  75         salt_len = MIN(strcspn(salt, "$"), 8);
  76         key_len = strlen(key);
  77
  78         /* Prepare for the real work.  */
  79         md5_init(&ctx);
  80
  81         /* Add the key string.  */
  82         md5_append(&ctx, (md5_byte_t *)key, key_len);
  83
  84         /* Because the SALT argument need not always have the salt prefix we
  85            add it separately.  */
  86         md5_append(&ctx, (md5_byte_t *)md5_salt_prefix,
  87                 sizeof(md5_salt_prefix) - 1);
  88
  89         /* The last part is the salt string.  This must be at most 8
  90            characters and it ends at the first `$' character (for
  91            compatibility which existing solutions).  */
  92         md5_append(&ctx, (md5_byte_t *)salt, salt_len);
  93
  94         /* Compute alternate MD5 sum with input KEY, SALT, and KEY.  The
  95            final result will be added to the first context.  */
  96         md5_init(&alt_ctx);
  97
  98         /* Add key.  */
  99         md5_append(&alt_ctx, (md5_byte_t *)key, key_len);
 100
 101         /* Add salt.  */
 102         md5_append(&alt_ctx, (md5_byte_t *)salt, salt_len);
 103
 104         /* Add key again.  */
 105         md5_append(&alt_ctx, (md5_byte_t *)key, key_len);
 106
 107         /* Now get result of this (16 bytes) and add it to the other
 108            context.  */
 109         md5_finish(&alt_ctx, alt_result);
 110
 111         /* Add for any character in the key one byte of the alternate sum.  */
 112         for (cnt = key_len; cnt > 16; cnt -= 16)
 113                 md5_append(&ctx, alt_result, 16);
 114         md5_append(&ctx, alt_result, cnt);
 115
 116         /* For the following code we need a NUL byte.  */
 117         alt_result[0] = '\0';
 118
 119         /* The original implementation now does something weird: for every 1
 120            bit in the key the first 0 is added to the buffer, for every 0
 121            bit the first character of the key.  This does not seem to be
 122            what was intended but we have to follow this to be compatible.  */
 123         for (cnt = key_len; cnt > 0; cnt >>= 1)
 124                 md5_append(&ctx,
 125                         (cnt & 1) != 0 ? alt_result : (md5_byte_t *)key, 1);
 126
 127         /* Create intermediate result.  */
 128         md5_finish(&ctx, alt_result);
 129
 130         /* Now comes another weirdness.  In fear of password crackers here
 131            comes a quite long loop which just processes the output of the
 132            previous round again.  We cannot ignore this here.  */
 133         for (cnt = 0; cnt < 1000; ++cnt) {
 134                 /* New context.  */
 135                 md5_init(&ctx);
 136
 137                 /* Add key or last result.  */
 138                 if ((cnt & 1) != 0)
 139                         md5_append(&ctx, (md5_byte_t *)key, key_len);
 140                 else
 141                         md5_append(&ctx, alt_result, 16);
 142
 143                 /* Add salt for numbers not divisible by 3.  */
 144                 if (cnt % 3 != 0)
 145                         md5_append(&ctx, (md5_byte_t *)salt, salt_len);
 146
 147                 /* Add key for numbers not divisible by 7.  */
 148                 if (cnt % 7 != 0)
 149                         md5_append(&ctx, (md5_byte_t *)key, key_len);
 150
 151                 /* Add key or last result.  */
 152                 if ((cnt & 1) != 0)
 153                         md5_append(&ctx, alt_result, 16);
 154                 else
 155                         md5_append(&ctx, (md5_byte_t *)key, key_len);
 156
 157                 /* Create intermediate result.  */
 158                 md5_finish(&ctx, alt_result);
 159         }
 160
 161         /* Now we can construct the result string.  It consists of three
 162            parts.  */
 163
 164         strncpy(buffer, md5_salt_prefix, MAX(0, buflen));
 165         cp = buffer + strlen(buffer);
 166         buflen -= sizeof(md5_salt_prefix);
 167
 168         strncpy(cp, salt, MIN((size_t) buflen, salt_len));
 169         cp = cp + strlen(cp);
 170         buflen -= MIN((size_t) buflen, salt_len);
 171
 172         if (buflen > 0) {
 173                 *cp++ = '$';
 174                 --buflen;
 175         }
 176 #define b64_from_24bit(B2, B1, B0, N) \
 177         do { \
 178                 unsigned int w = ((B2) << 16) | ((B1) << 8) | (B0); \
 179                 int n = (N); \
 180                 while (n-- > 0 && buflen > 0) { \
 181                         *cp++ = b64t[w & 0x3f]; \
 182                         --buflen; \
 183                         w >>= 6; \
 184                 }\
 185         } while (0)
 186
 187         b64_from_24bit(alt_result[0], alt_result[6], alt_result[12], 4);
 188         b64_from_24bit(alt_result[1], alt_result[7], alt_result[13], 4);
 189         b64_from_24bit(alt_result[2], alt_result[8], alt_result[14], 4);
 190         b64_from_24bit(alt_result[3], alt_result[9], alt_result[15], 4);
 191         b64_from_24bit(alt_result[4], alt_result[10], alt_result[5], 4);
 192         b64_from_24bit(0, 0, alt_result[11], 2);
 193         if (buflen <= 0) {
 194                 FREE(buffer);
 195         } else
 196                 *cp = '\0';     /* Terminate the string.  */
 197
 198         /* Clear the buffer for the intermediate result so that people
 199            attaching to processes or reading core dumps cannot get any
 200            information.  We do it in this way to clear correct_words[]
 201            inside the MD5 implementation as well.  */
 202         md5_init(&ctx);
 203         md5_finish(&ctx, alt_result);
 204         memset(&ctx, '\0', sizeof(ctx));
 205         memset(&alt_ctx, '\0', sizeof(alt_ctx));
 206
 207         return buffer;
 208 }