source3/lib/genrand.c

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