source/lib/genrand.c

   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 2.2
   4
   5    Functions to create reasonable random numbers for crypto use.
   6
   7    Copyright (C) Jeremy Allison 2001
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 2 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program; if not, write to the Free Software
  21    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  22 */
  23
  24 #include "includes.h"
  25
  26 static unsigned char hash[258];
  27 static uint32 counter;
  28 unsigned char *reseed_data;
  29 size_t reseed_data_size;
  30
  31 /****************************************************************
  32  Copy any user given reseed data.
  33 *****************************************************************/
  34
  35 void set_rand_reseed_data(unsigned char *data, size_t len)
  36 {
  37         SAFE_FREE(reseed_data);
  38         reseed_data_size = 0;
  39
  40         reseed_data = (unsigned char *)memdup(data, len);
  41         if (reseed_data)
  42                 reseed_data_size = len;
  43 }
  44
  45 /****************************************************************
  46  Setup the seed.
  47 *****************************************************************/
  48
  49 static void seed_random_stream(unsigned char *seedval, size_t seedlen)
  50 {
  51         unsigned char j = 0;
  52         size_t ind;
  53
  54         for (ind = 0; ind < 256; ind++)
  55                 hash[ind] = (unsigned char)ind;
  56
  57         for( ind = 0; ind < 256; ind++) {
  58                 unsigned char tc;
  59
  60                 j += (hash[ind] + seedval[ind%seedlen]);
  61
  62                 tc = hash[ind];
  63                 hash[ind] = hash[j];
  64                 hash[j] = tc;
  65         }
  66
  67         hash[256] = 0;
  68         hash[257] = 0;
  69 }
  70
  71 /****************************************************************
  72  Get datasize bytes worth of random data.
  73 *****************************************************************/
  74
  75 static void get_random_stream(unsigned char *data, size_t datasize)
  76 {
  77         unsigned char index_i = hash[256];
  78         unsigned char index_j = hash[257];
  79         size_t ind;
  80
  81         for( ind = 0; ind < datasize; ind++) {
  82                 unsigned char tc;
  83                 unsigned char t;
  84
  85                 index_i++;
  86                 index_j += hash[index_i];
  87
  88                 tc = hash[index_i];
  89                 hash[index_i] = hash[index_j];
  90                 hash[index_j] = tc;
  91
  92                 t = hash[index_i] + hash[index_j];
  93                 data[ind] = hash[t];
  94         }
  95
  96         hash[256] = index_i;
  97         hash[257] = index_j;
  98 }
  99
 100 /****************************************************************
 101  Get a 16 byte hash from the contents of a file.
 102  Note that the hash is not initialised.
 103 *****************************************************************/
 104
 105 static void do_filehash(char *fname, unsigned char *the_hash)
 106 {
 107         unsigned char buf[1011]; /* deliberate weird size */
 108         unsigned char tmp_md4[16];
 109         int fd, n;
 110
 111         fd = sys_open(fname,O_RDONLY,0);
 112         if (fd == -1)
 113                 return;
 114
 115         while ((n = read(fd, (char *)buf, sizeof(buf))) > 0) {
 116                 mdfour(tmp_md4, buf, n);
 117                 for (n=0;n<16;n++)
 118                         the_hash[n] ^= tmp_md4[n];
 119         }
 120         close(fd);
 121 }
 122
 123 /**************************************************************
 124  Try and get a good random number seed. Try a number of
 125  different factors. Firstly, try /dev/urandom - use if exists.
 126
 127  We use /dev/urandom as a read of /dev/random can block if
 128  the entropy pool dries up. This leads clients to timeout
 129  or be very slow on connect.
 130
 131  If we can't use /dev/urandom then seed the stream random generator
 132  above...
 133 **************************************************************/
 134
 135 static int do_reseed(BOOL use_fd, int fd)
 136 {
 137         unsigned char seed_inbuf[40];
 138         uint32 v1, v2; struct timeval tval; pid_t mypid;
 139         struct passwd *pw;
 140
 141         if (use_fd) {
 142                 if (fd != -1)
 143                         return fd;
 144
 145                 fd = sys_open( "/dev/urandom", O_RDONLY,0);
 146                 if(fd >= 0)
 147                         return fd;
 148         }
 149
 150 #ifdef __INSURE__
 151         memset(seed_inbuf, '\0', sizeof(seed_inbuf));
 152 #endif
 153
 154         /* Add in some secret file contents */
 155
 156         do_filehash("/etc/shadow", &seed_inbuf[0]);
 157 #ifdef WITH_TDB_SAM
 158         do_filehash(lp_tdb_passwd_file(), &seed_inbuf[16]);
 159 #else
 160         do_filehash(lp_smb_passwd_file(), &seed_inbuf[16]);
 161 #endif
 162
 163         /*
 164          * Add in the root encrypted password.
 165          * On any system where security is taken
 166          * seriously this will be secret.
 167          */
 168
 169         pw = sys_getpwnam("root");
 170         if (pw && pw->pw_passwd) {
 171                 size_t i;
 172                 unsigned char md4_tmp[16];
 173                 mdfour(md4_tmp, (unsigned char *)pw->pw_passwd, strlen(pw->pw_passwd));
 174                 for (i=0;i<16;i++)
 175                         seed_inbuf[8+i] ^= md4_tmp[i];
 176         }
 177
 178         /*
 179          * Add the counter, time of day, and pid.
 180          */
 181
 182         GetTimeOfDay(&tval);
 183         mypid = sys_getpid();
 184         v1 = (counter++) + mypid + tval.tv_sec;
 185         v2 = (counter++) * mypid + tval.tv_usec;
 186
 187         SIVAL(seed_inbuf, 32, v1 ^ IVAL(seed_inbuf, 32));
 188         SIVAL(seed_inbuf, 36, v2 ^ IVAL(seed_inbuf, 36));
 189
 190         /*
 191          * Add any user-given reseed data.
 192          */
 193
 194         if (reseed_data) {
 195                 size_t i;
 196                 for (i = 0; i < sizeof(seed_inbuf); i++)
 197                         seed_inbuf[i] ^= reseed_data[i % reseed_data_size];
 198         }
 199
 200         seed_random_stream(seed_inbuf, sizeof(seed_inbuf));
 201
 202         return -1;
 203 }
 204
 205 /*******************************************************************
 206  Interface to the (hopefully) good crypto random number generator.
 207 ********************************************************************/
 208
 209 void generate_random_buffer( unsigned char *out, int len, BOOL do_reseed_now)
 210 {
 211         static BOOL done_reseed = False;
 212         static int urand_fd = -1;
 213         unsigned char md4_buf[64];
 214         unsigned char tmp_buf[16];
 215         unsigned char *p;
 216
 217         if(!done_reseed || do_reseed_now) {
 218                 urand_fd = do_reseed(True, urand_fd);
 219                 done_reseed = True;
 220         }
 221
 222         if (urand_fd != -1 && len > 0) {
 223
 224                 if (read(urand_fd, out, len) == len)
 225                         return; /* len bytes of random data read from urandom. */
 226
 227                 /* Read of urand error, drop back to non urand method. */
 228                 close(urand_fd);
 229                 urand_fd = -1;
 230                 do_reseed(False, -1);
 231                 done_reseed = True;
 232         }
 233
 234         /*
 235          * Generate random numbers in chunks of 64 bytes,
 236          * then md4 them & copy to the output buffer.
 237          * This way the raw state of the stream is never externally
 238          * seen.
 239          */
 240
 241         p = out;
 242         while(len > 0) {
 243                 int copy_len = len > 16 ? 16 : len;
 244
 245                 get_random_stream(md4_buf, sizeof(md4_buf));
 246                 mdfour(tmp_buf, md4_buf, sizeof(md4_buf));
 247                 memcpy(p, tmp_buf, copy_len);
 248                 p += copy_len;
 249                 len -= copy_len;
 250         }
 251 }
 252
 253 /*******************************************************************
 254  Use the random number generator to generate a random string.
 255 ********************************************************************/
 256
 257 static char c_list[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+_-#.,";
 258
 259 char *generate_random_str(size_t len)
 260 {
 261         static unsigned char retstr[256];
 262         size_t i;
 263
 264         memset(retstr, '\0', sizeof(retstr));
 265
 266         if (len > sizeof(retstr)-1)
 267                 len = sizeof(retstr) -1;
 268         generate_random_buffer( retstr, len, False);
 269         for (i = 0; i < len; i++)
 270                 retstr[i] = c_list[ retstr[i] % sizeof(c_list) ];
 271
 272         retstr[i] = '\0';
 273
 274         return (char *)retstr;
 275 }