mdw@git.distorted.org.uk Git - become/blob - src/noise.c

   1 /* -*-c-*-
   2  *
   3  * $Id: noise.c,v 1.1 1997/08/07 09:45:26 mdw Exp $
   4  *
   5  * Collection of environmental noise
   6  *
   7  * (c) 1997 EBI
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of `become'
  13  *
  14  * `Become' is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU General Public License as published by
  16  * the Free Software Foundation; either version 2 of the License, or
  17  * (at your option) any later version.
  18  *
  19  * `Become' is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with `become'; if not, write to the Free Software Foundation,
  26  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  27  */
  28
  29 /*----- Revision history --------------------------------------------------*
  30  *
  31  * $Log: noise.c,v $
  32  * Revision 1.1  1997/08/07 09:45:26  mdw
  33  * New source file added to acquire environmental noise and add it to the
  34  * randomness pool (see `rand.c').
  35  *
  36  */
  37
  38 /*----- Header files ------------------------------------------------------*/
  39
  40 /* --- ANSI headers --- */
  41
  42 #include <ctype.h>
  43 #include <errno.h>
  44 #include <stdio.h>
  45 #include <stdlib.h>
  46 #include <string.h>
  47 #include <time.h>
  48
  49 /* --- Unix headers --- */
  50
  51 #include <sys/types.h>
  52 #include <sys/time.h>
  53
  54 #include "config.h"
  55 #if defined(HAVE_GETRUSAGE)
  56 #  include <sys/resource.h>
  57 #elif defined(HAVE_VTIMES)
  58 #  include <sys/vtimes.h>
  59 #endif
  60
  61 #include <sys/wait.h>
  62
  63 #include <fcntl.h>
  64 #include <unistd.h>
  65
  66 /* --- Local headers --- */
  67
  68 #include "noise.h"
  69 #include "rand.h"
  70 #include "utils.h"
  71
  72 /*----- Main code ---------------------------------------------------------*/
  73
  74 /* --- @noise__shell@ --- *
  75  *
  76  * Arguments:   @const char *cmd@ = pointer to a shell command
  77  *
  78  * Returns:     ---
  79  *
  80  * Use:         Adds the output of the shell command to the randomness pool.
  81  *              Some care is taken to do the Right Thing when running setuid.
  82  */
  83
  84 static void noise__shell(const char *cmd)
  85 {
  86   int pfd[2];
  87   pid_t pid;
  88
  89   /* --- Create a pipe for talking to the child --- */
  90
  91   if (pipe(pfd))
  92     return;
  93
  94   /* --- Create the child process --- */
  95
  96   pid = fork();
  97   if (pid < 0)
  98     return;
  99
 100   if (pid == 0) {
 101     int fd;
 102     char *argv[] = { "/bin/sh", "-c", 0, 0 };
 103     char *env[] = {
 104       "PATH=/bin:/usr/bin:/usr/ucb:/usr/etc:/sbin:/usr/sbin",
 105       0
 106     };
 107
 108     /* --- Become whoever I'm being run as --- */
 109
 110     setuid(getuid());
 111
 112     /* --- Close the old standard streams --- */
 113
 114     close(0);
 115     close(1);
 116     close(2);
 117
 118     /* --- Set up stdin and stderr to be empty, and stdout as our pipe --- */
 119
 120     if (((fd = open("/dev/null", O_RDONLY)) != 0 &&
 121          (fd = dup2(fd, 0)) != 0) ||
 122         ((fd = dup2(pfd[1], 1)) != 1) ||
 123         ((fd = open("/dev/null", O_WRONLY)) != 2 &&
 124          (fd = dup2(fd, 2)) != 2))
 125       goto child_fail;
 126
 127     /* --- Close the original pipe file descriptors --- */
 128
 129     close(pfd[0]);
 130     close(pfd[1]);
 131     burn(pfd);
 132
 133     /* --- Now run the child process --- */
 134
 135     argv[2] = (char *)cmd;              /* POSIX screwed up the prototype */
 136     execve("/bin/sh", argv, env);
 137
 138     /* --- Something went horribly wrong --- */
 139
 140   child_fail:
 141     _exit(127);
 142   }
 143
 144   /* --- Now read from the child until it's all done --- */
 145
 146   {
 147     char buf[1024];
 148     ssize_t sz;
 149
 150     close(pfd[1]);
 151     for (;;) {
 152       sz = read(pfd[0], buf, sizeof(buf));
 153       if (sz == 0 || (sz < 0 && sz != EINTR))
 154         break;
 155       rand_add(buf, sz);
 156     }
 157     close(pfd[0]);
 158     rand_add(pfd, sizeof(pfd));
 159     burn(buf); burn(pfd);
 160   }
 161
 162   /* --- The child should be dead now, so wait for it --- */
 163
 164   {
 165     int st;
 166
 167     wait(&st);
 168     rand_add(&st, sizeof(st));
 169     rand_add(&pid, sizeof(pid));
 170   }
 171 }
 172
 173 /* --- @noise_acquire@ --- *
 174  *
 175  * Arguments:   ---
 176  *
 177  * Returns:     ---
 178  *
 179  * Use:         Attempts to acquire an amount of random noise from the
 180  *              environment.  A lot of it's not actually much good, but
 181  *              it's better than nothing.  There's probably a bit or two's
 182  *              worth in each item which gets added.
 183  */
 184
 185 void noise_acquire(void)
 186 {
 187   /* --- Try a real random number source --- *
 188    *
 189    * Some operating systems (notably Linux) provide a `/dev/random' which
 190    * contains distilled random numbers from the outside world.
 191    */
 192
 193   {
 194     int fd;
 195     int f;
 196     unsigned char buff[64];
 197     ssize_t sz;
 198
 199     if ((fd = open("/dev/random", O_RDONLY) >= 0) &&
 200         (f = fcntl(fd, F_GETFL, 0)) >= 0 &&
 201         fcntl(fd, F_SETFL, f | O_NONBLOCK) >= 0 &&
 202         (sz = read(fd, buff, sizeof(buff))) > 0) {
 203       rand_add(buff, sz);
 204       burn(buff);
 205     }
 206     if (fd >= 0)
 207       close(fd);
 208   }
 209
 210   /* --- Squeeze some entropy from the current time --- */
 211
 212   {
 213     struct timeval tv;
 214     clock_t c;
 215
 216     gettimeofday(&tv, 0);
 217     c = clock();
 218     rand_add(&tv, sizeof(tv));
 219     rand_add(&c, sizeof(c));
 220     burn(tv); burn(c);
 221   }
 222
 223   /* --- Try some commands which ask the outside world some questions --- */
 224
 225   noise__shell("ps auxww");
 226   noise__shell("ps -ef");
 227   noise__shell("df");
 228   /* @noise__shell("netstat -a");@ -- takes too long */
 229
 230   /* --- Get our resource usage to see if that's at all interesting --- */
 231
 232 #if defined(HAVE_GETRUSAGE)
 233   {
 234     struct rusage ru;
 235     getrusage(RUSAGE_SELF, &ru);
 236     rand_add(&ru, sizeof(ru));
 237     getrusage(RUSAGE_CHILDREN, &ru);
 238     rand_add(&ru, sizeof(ru));
 239     burn(ru);
 240   }
 241 #elif defined(HAVE_VTIMES)
 242   {
 243     struct vtimes vt, vtc;
 244     vtimes(&vt, &vtc);
 245     rand_add(&vt, sizeof(vt));
 246     rand_add(&vtc, sizeof(vtc));
 247     burn(vt); burn(vtc);
 248   }
 249 #endif
 250
 251   /* --- Squeeze some more entropy from the current time --- */
 252
 253   {
 254     struct timeval tv;
 255     clock_t c;
 256
 257     gettimeofday(&tv, 0);
 258     c = clock();
 259     rand_add(&tv, sizeof(tv));
 260     rand_add(&c, sizeof(c));
 261     burn(tv); burn(c);
 262   }
 263
 264   /* --- Done -- churn the random pool --- */
 265
 266   rand_churn();
 267 }
 268
 269 /*----- That's all, folks -------------------------------------------------*/