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 extern int DEBUGLEVEL;
  27
  28
  29 static unsigned char hash[258];
  30 static uint32 counter;
  31 unsigned char *reseed_data;
  32 size_t reseed_data_size;
  33
  34 /****************************************************************
  35  Copy any user given reseed data.
  36 *****************************************************************/
  37
  38 void set_rand_reseed_data(unsigned char *data, size_t len)
  39 {
  40         if (reseed_data)
  41                 free(reseed_data);
  42         reseed_data_size = 0;
  43
  44         reseed_data = (unsigned char *)memdup(data, len);
  45         if (reseed_data)
  46                 reseed_data_size = len;
  47 }
  48
  49 /****************************************************************
  50  Setup the seed.
  51 *****************************************************************/
  52
  53 static void seed_random_stream(unsigned char *seedval, size_t seedlen)
  54 {
  55         unsigned char j = 0;
  56         size_t ind;
  57
  58         for (ind = 0; ind < 256; ind++)
  59                 hash[ind] = (unsigned char)ind;
  60
  61         for( ind = 0; ind < 256; ind++) {
  62                 unsigned char tc;
  63
  64                 j += (hash[ind] + seedval[ind%seedlen]);
  65
  66                 tc = hash[ind];
  67                 hash[ind] = hash[j];
  68                 hash[j] = tc;
  69         }
  70
  71         hash[256] = 0;
  72         hash[257] = 0;
  73 }
  74
  75 /****************************************************************
  76  Get datasize bytes worth of random data.
  77 *****************************************************************/
  78
  79 static void get_random_stream(unsigned char *data, size_t datasize)
  80 {
  81         unsigned char index_i = hash[256];
  82         unsigned char index_j = hash[257];
  83         size_t ind;
  84
  85         for( ind = 0; ind < datasize; ind++) {
  86                 unsigned char tc;
  87                 unsigned char t;
  88
  89                 index_i++;
  90                 index_j += hash[index_i];
  91
  92                 tc = hash[index_i];
  93                 hash[index_i] = hash[index_j];
  94                 hash[index_j] = tc;
  95
  96                 t = hash[index_i] + hash[index_j];
  97                 data[ind] = hash[t];
  98         }
  99
 100         hash[256] = index_i;
 101         hash[257] = index_j;
 102 }
 103
 104 /****************************************************************
 105  Get a 16 byte hash from the contents of a file.
 106  Note that the hash is not initialised.
 107 *****************************************************************/
 108
 109 static void do_filehash(char *fname, unsigned char *the_hash)
 110 {
 111         unsigned char buf[1011]; /* deliberate weird size */
 112         unsigned char tmp_md4[16];
 113         int fd, n;
 114
 115         fd = sys_open(fname,O_RDONLY,0);
 116         if (fd == -1)
 117                 return;
 118
 119         while ((n = read(fd, (char *)buf, sizeof(buf))) > 0) {
 120                 mdfour(tmp_md4, buf, n);
 121                 for (n=0;n<16;n++)
 122                         the_hash[n] ^= tmp_md4[n];
 123         }
 124         close(fd);
 125 }
 126
 127 /**************************************************************
 128  Try and get a good random number seed. Try a number of
 129  different factors. Firstly, try /dev/urandom - use if exists.
 130
 131  We use /dev/urandom as a read of /dev/random can block if
 132  the entropy pool dries up. This leads clients to timeout
 133  or be very slow on connect.
 134
 135  If we can't use /dev/urandom then seed the stream random generator
 136  above...
 137 **************************************************************/
 138
 139 static int do_reseed(BOOL use_fd, int fd)
 140 {
 141         unsigned char seed_inbuf[40];
 142         uint32 v1, v2; struct timeval tval; pid_t mypid;
 143         struct passwd *pw;
 144
 145         if (use_fd) {
 146                 if (fd != -1)
 147                         return fd;
 148
 149                 fd = sys_open( "/dev/urandom", O_RDONLY,0);
 150                 if(fd >= 0)
 151                         return fd;
 152         }
 153
 154 #ifdef __INSURE__
 155         memset(seed_inbuf, '\0', sizeof(seed_inbuf));
 156 #endif
 157
 158         /* Add in some secret file contents */
 159
 160         do_filehash("/etc/shadow", &seed_inbuf[0]);
 161 #ifdef WITH_TDB_SAM
 162         do_filehash(lp_tdb_passwd_file(), &seed_inbuf[16]);
 163 #else
 164         do_filehash(lp_smb_passwd_file(), &seed_inbuf[16]);
 165 #endif
 166
 167         /*
 168          * Add in the root encrypted password.
 169          * On any system where security is taken
 170          * seriously this will be secret.
 171          */
 172
 173         pw = sys_getpwnam("root");
 174         if (pw && pw->pw_passwd) {
 175                 size_t i;
 176                 unsigned char md4_tmp[16];
 177                 mdfour(md4_tmp, (unsigned char *)pw->pw_passwd, strlen(pw->pw_passwd));
 178                 for (i=0;i<16;i++)
 179                         seed_inbuf[8+i] ^= md4_tmp[i];
 180         }
 181
 182         /*
 183          * Add the counter, time of day, and pid.
 184          */
 185
 186         GetTimeOfDay(&tval);
 187         mypid = sys_getpid();
 188         v1 = (counter++) + mypid + tval.tv_sec;
 189         v2 = (counter++) * mypid + tval.tv_usec;
 190
 191         SIVAL(seed_inbuf, 32, v1 ^ IVAL(seed_inbuf, 32));
 192         SIVAL(seed_inbuf, 36, v2 ^ IVAL(seed_inbuf, 36));
 193
 194         /*
 195          * Add any user-given reseed data.
 196          */
 197
 198         if (reseed_data) {
 199                 size_t i;
 200                 for (i = 0; i < sizeof(seed_inbuf); i++)
 201                         seed_inbuf[i] ^= reseed_data[i % reseed_data_size];
 202         }
 203
 204         seed_random_stream(seed_inbuf, sizeof(seed_inbuf));
 205
 206         return -1;
 207 }
 208
 209 /*******************************************************************
 210  Interface to the (hopefully) good crypto random number generator.
 211 ********************************************************************/
 212
 213 void generate_random_buffer( unsigned char *out, int len, BOOL do_reseed_now)
 214 {
 215         static BOOL done_reseed = False;
 216         static int urand_fd = -1;
 217         unsigned char md4_buf[64];
 218         unsigned char tmp_buf[16];
 219         unsigned char *p;
 220
 221         if(!done_reseed || do_reseed_now) {
 222                 urand_fd = do_reseed(True, urand_fd);
 223                 done_reseed = True;
 224         }
 225
 226         if (urand_fd != -1 && len > 0) {
 227
 228                 if (read(urand_fd, out, len) == len)
 229                         return; /* len bytes of random data read from urandom. */
 230
 231                 /* Read of urand error, drop back to non urand method. */
 232                 close(urand_fd);
 233                 urand_fd = -1;
 234                 do_reseed(False, -1);
 235                 done_reseed = True;
 236         }
 237
 238         /*
 239          * Generate random numbers in chunks of 64 bytes,
 240          * then md4 them & copy to the output buffer.
 241          * This way the raw state of the stream is never externally
 242          * seen.
 243          */
 244
 245         p = out;
 246         while(len > 0) {
 247                 int copy_len = len > 16 ? 16 : len;
 248
 249                 get_random_stream(md4_buf, sizeof(md4_buf));
 250                 mdfour(tmp_buf, md4_buf, sizeof(md4_buf));
 251                 memcpy(p, tmp_buf, copy_len);
 252                 p += copy_len;
 253                 len -= copy_len;
 254         }
 255 }
 256
 257 /*******************************************************************
 258  Use the random number generator to generate a random string.
 259 ********************************************************************/
 260
 261 static char c_list[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+_-#.,";
 262
 263 char *generate_random_str(size_t len)
 264 {
 265         static unsigned char retstr[256];
 266         size_t i;
 267
 268         memset(retstr, '\0', sizeof(retstr));
 269
 270         if (len > sizeof(retstr)-1)
 271                 len = sizeof(retstr) -1;
 272         generate_random_buffer( retstr, len, False);
 273         for (i = 0; i < len; i++)
 274                 retstr[i] = c_list[ retstr[i] % sizeof(c_list) ];
 275
 276         retstr[i] = '\0';
 277
 278         return (char *)retstr;
 279 }