source4/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 #include "system/iconv.h"
  25 #include "lib/crypto/crypto.h"
  26
  27 static unsigned char hash[258];
  28 static uint32 counter;
  29
  30 static BOOL done_reseed = False;
  31 static void (*reseed_callback)(int *newseed);
  32
  33 /****************************************************************
  34  Copy any user given reseed data.
  35 *****************************************************************/
  36
  37 void set_rand_reseed_callback(void (*fn)(int *))
  38 {
  39         reseed_callback = fn;
  40         set_need_random_reseed();
  41 }
  42
  43 void set_need_random_reseed(void)
  44 {
  45         done_reseed = False;
  46 }
  47
  48 static void get_rand_reseed_data(int *reseed_data)
  49 {
  50         if (reseed_callback) {
  51                 reseed_callback(reseed_data);
  52         } else {
  53                 *reseed_data = 0;
  54         }
  55 }
  56
  57 /****************************************************************
  58  Setup the seed.
  59 *****************************************************************/
  60
  61 static void seed_random_stream(unsigned char *seedval, size_t seedlen)
  62 {
  63         unsigned char j = 0;
  64         size_t ind;
  65
  66         for (ind = 0; ind < 256; ind++)
  67                 hash[ind] = (unsigned char)ind;
  68
  69         for( ind = 0; ind < 256; ind++) {
  70                 unsigned char tc;
  71
  72                 j += (hash[ind] + seedval[ind%seedlen]);
  73
  74                 tc = hash[ind];
  75                 hash[ind] = hash[j];
  76                 hash[j] = tc;
  77         }
  78
  79         hash[256] = 0;
  80         hash[257] = 0;
  81 }
  82
  83 /****************************************************************
  84  Get datasize bytes worth of random data.
  85 *****************************************************************/
  86
  87 static void get_random_stream(unsigned char *data, size_t datasize)
  88 {
  89         unsigned char index_i = hash[256];
  90         unsigned char index_j = hash[257];
  91         size_t ind;
  92
  93         for( ind = 0; ind < datasize; ind++) {
  94                 unsigned char tc;
  95                 unsigned char t;
  96
  97                 index_i++;
  98                 index_j += hash[index_i];
  99
 100                 tc = hash[index_i];
 101                 hash[index_i] = hash[index_j];
 102                 hash[index_j] = tc;
 103
 104                 t = hash[index_i] + hash[index_j];
 105                 data[ind] = hash[t];
 106         }
 107
 108         hash[256] = index_i;
 109         hash[257] = index_j;
 110 }
 111
 112 /****************************************************************
 113  Get a 16 byte hash from the contents of a file.
 114  Note that the hash is not initialised.
 115 *****************************************************************/
 116
 117 static void do_filehash(const char *fname, unsigned char *the_hash)
 118 {
 119         unsigned char buf[1011]; /* deliberate weird size */
 120         unsigned char tmp_md4[16];
 121         int fd, n;
 122
 123         fd = open(fname,O_RDONLY,0);
 124         if (fd == -1)
 125                 return;
 126
 127         while ((n = read(fd, (char *)buf, sizeof(buf))) > 0) {
 128                 mdfour(tmp_md4, buf, n);
 129                 for (n=0;n<16;n++)
 130                         the_hash[n] ^= tmp_md4[n];
 131         }
 132         close(fd);
 133 }
 134
 135 /**************************************************************
 136  Try and get a good random number seed. Try a number of
 137  different factors. Firstly, try /dev/urandom - use if exists.
 138
 139  We use /dev/urandom as a read of /dev/random can block if
 140  the entropy pool dries up. This leads clients to timeout
 141  or be very slow on connect.
 142
 143  If we can't use /dev/urandom then seed the stream random generator
 144  above...
 145 **************************************************************/
 146
 147 static int do_reseed(BOOL use_fd, int fd)
 148 {
 149         unsigned char seed_inbuf[40];
 150         uint32 v1, v2; struct timeval tval; pid_t mypid;
 151         int reseed_data = 0;
 152
 153         if (use_fd) {
 154                 if (fd != -1)
 155                         return fd;
 156
 157                 fd = open( "/dev/urandom", O_RDONLY,0);
 158                 if(fd >= 0)
 159                         return fd;
 160         }
 161
 162         /* Add in some secret file contents */
 163
 164         do_filehash("/etc/shadow", &seed_inbuf[0]);
 165         do_filehash(lp_smb_passwd_file(), &seed_inbuf[16]);
 166
 167         /*
 168          * Add the counter, time of day, and pid.
 169          */
 170
 171         GetTimeOfDay(&tval);
 172         mypid = getpid();
 173         v1 = (counter++) + mypid + tval.tv_sec;
 174         v2 = (counter++) * mypid + tval.tv_usec;
 175
 176         SIVAL(seed_inbuf, 32, v1 ^ IVAL(seed_inbuf, 32));
 177         SIVAL(seed_inbuf, 36, v2 ^ IVAL(seed_inbuf, 36));
 178
 179         /*
 180          * Add any user-given reseed data.
 181          */
 182
 183         get_rand_reseed_data(&reseed_data);
 184         if (reseed_data) {
 185                 size_t i;
 186                 for (i = 0; i < sizeof(seed_inbuf); i++)
 187                         seed_inbuf[i] ^= ((char *)(&reseed_data))[i % sizeof(reseed_data)];
 188         }
 189
 190         seed_random_stream(seed_inbuf, sizeof(seed_inbuf));
 191
 192         return -1;
 193 }
 194
 195 /*******************************************************************
 196  Interface to the (hopefully) good crypto random number generator.
 197 ********************************************************************/
 198
 199 void generate_random_buffer(uint8_t *out, int len)
 200 {
 201         static int urand_fd = -1;
 202         unsigned char md4_buf[64];
 203         unsigned char tmp_buf[16];
 204         unsigned char *p;
 205
 206         if(!done_reseed) {
 207                 urand_fd = do_reseed(True, urand_fd);
 208                 done_reseed = True;
 209         }
 210
 211         if (urand_fd != -1 && len > 0) {
 212
 213                 if (read(urand_fd, out, len) == len)
 214                         return; /* len bytes of random data read from urandom. */
 215
 216                 /* Read of urand error, drop back to non urand method. */
 217                 close(urand_fd);
 218                 urand_fd = -1;
 219                 do_reseed(False, -1);
 220                 done_reseed = True;
 221         }
 222
 223         /*
 224          * Generate random numbers in chunks of 64 bytes,
 225          * then md4 them & copy to the output buffer.
 226          * This way the raw state of the stream is never externally
 227          * seen.
 228          */
 229
 230         p = out;
 231         while(len > 0) {
 232                 int copy_len = len > 16 ? 16 : len;
 233
 234                 get_random_stream(md4_buf, sizeof(md4_buf));
 235                 mdfour(tmp_buf, md4_buf, sizeof(md4_buf));
 236                 memcpy(p, tmp_buf, copy_len);
 237                 p += copy_len;
 238                 len -= copy_len;
 239         }
 240 }
 241
 242 /*
 243   very basic password quality checker
 244 */
 245 BOOL check_password_quality(const char *s)
 246 {
 247         int has_digit=0, has_capital=0, has_lower=0;
 248         while (*s) {
 249                 if (isdigit(*s)) {
 250                         has_digit++;
 251                 } else if (isupper(*s)) {
 252                         has_capital++;
 253                 } else if (islower(*s)) {
 254                         has_lower++;
 255                 }
 256                 s++;
 257         }
 258
 259         return has_digit && has_lower && has_capital;
 260 }
 261
 262 /*******************************************************************
 263  Use the random number generator to generate a random string.
 264 ********************************************************************/
 265
 266 char *generate_random_str_list(TALLOC_CTX *mem_ctx, size_t len, const char *list)
 267 {
 268         size_t i;
 269         size_t list_len = strlen(list);
 270
 271         char *retstr = talloc_array_p(mem_ctx, char, len + 1);
 272         if (!retstr) return NULL;
 273
 274         generate_random_buffer((uint8_t *)retstr, len);
 275         for (i = 0; i < len; i++) {
 276                 retstr[i] = list[retstr[i] % list_len];
 277         }
 278         retstr[i] = '\0';
 279
 280         return retstr;
 281 }
 282
 283 char *generate_random_str(TALLOC_CTX *mem_ctx, size_t len)
 284 {
 285         char *retstr;
 286         const char *c_list = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+_-#.,";
 287
 288 again:
 289         retstr = generate_random_str_list(mem_ctx, len, c_list);
 290         if (!retstr) return NULL;
 291
 292         /* we need to make sure the random string passes basic quality tests
 293            or it might be rejected by windows as a password */
 294         if (len >= 7 && !check_password_quality(retstr)) {
 295                 talloc_free(retstr);
 296                 goto again;
 297         }
 298
 299         return retstr;
 300 }