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

   1 /* -*-c-*-
   2  *
   3  * $Id: noise.c,v 1.4 1998/02/20 17:52:32 mdw Exp $
   4  *
   5  * Collection of environmental noise
   6  *
   7  * (c) 1998 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 1.4  1998/02/20 17:52:32  mdw
  33  * Don't use `df' for noise gathering, because it gets upset when NFS
  34  * servers aren't responding.
  35  *
  36  * Revision 1.3  1998/01/12 16:46:19  mdw
  37  * Fix copyright date.
  38  *
  39  * Revision 1.2  1997/08/20  16:19:57  mdw
  40  * Fix test for `/dev/random' so that it doesn't close `stdin' if it fails!
  41  *
  42  * Revision 1.1  1997/08/07 09:45:26  mdw
  43  * New source file added to acquire environmental noise and add it to the
  44  * randomness pool (see `rand.c').
  45  *
  46  */
  47
  48 /*----- Header files ------------------------------------------------------*/
  49
  50 /* --- ANSI headers --- */
  51
  52 #include <ctype.h>
  53 #include <errno.h>
  54 #include <stdio.h>
  55 #include <stdlib.h>
  56 #include <string.h>
  57 #include <time.h>
  58
  59 /* --- Unix headers --- */
  60
  61 #include <sys/types.h>
  62 #include <sys/time.h>
  63
  64 #include "config.h"
  65 #if defined(HAVE_GETRUSAGE)
  66 #  include <sys/resource.h>
  67 #elif defined(HAVE_VTIMES)
  68 #  include <sys/vtimes.h>
  69 #endif
  70
  71 #include <sys/wait.h>
  72
  73 #include <fcntl.h>
  74 #include <unistd.h>
  75
  76 /* --- Local headers --- */
  77
  78 #include "noise.h"
  79 #include "rand.h"
  80 #include "utils.h"
  81
  82 /*----- Main code ---------------------------------------------------------*/
  83
  84 /* --- @noise__shell@ --- *
  85  *
  86  * Arguments:   @const char *cmd@ = pointer to a shell command
  87  *
  88  * Returns:     ---
  89  *
  90  * Use:         Adds the output of the shell command to the randomness pool.
  91  *              Some care is taken to do the Right Thing when running setuid.
  92  */
  93
  94 static void noise__shell(const char *cmd)
  95 {
  96   int pfd[2];
  97   pid_t pid;
  98
  99   /* --- Create a pipe for talking to the child --- */
 100
 101   if (pipe(pfd))
 102     return;
 103
 104   /* --- Create the child process --- */
 105
 106   pid = fork();
 107   if (pid < 0)
 108     return;
 109
 110   if (pid == 0) {
 111     int fd;
 112     char *argv[] = { "/bin/sh", "-c", 0, 0 };
 113     char *env[] = {
 114       "PATH=/bin:/usr/bin:/usr/ucb:/usr/etc:/sbin:/usr/sbin",
 115       0
 116     };
 117
 118     /* --- Become whoever I'm being run as --- */
 119
 120     setuid(getuid());
 121
 122     /* --- Close the old standard streams --- */
 123
 124     close(0);
 125     close(1);
 126     close(2);
 127
 128     /* --- Set up stdin and stderr to be empty, and stdout as our pipe --- */
 129
 130     if (((fd = open("/dev/null", O_RDONLY)) != 0 &&
 131          (fd = dup2(fd, 0)) != 0) ||
 132         ((fd = dup2(pfd[1], 1)) != 1) ||
 133         ((fd = open("/dev/null", O_WRONLY)) != 2 &&
 134          (fd = dup2(fd, 2)) != 2))
 135       goto child_fail;
 136
 137     /* --- Close the original pipe file descriptors --- */
 138
 139     close(pfd[0]);
 140     close(pfd[1]);
 141     burn(pfd);
 142
 143     /* --- Now run the child process --- */
 144
 145     argv[2] = (char *)cmd;              /* POSIX screwed up the prototype */
 146     execve("/bin/sh", argv, env);
 147
 148     /* --- Something went horribly wrong --- */
 149
 150   child_fail:
 151     _exit(127);
 152   }
 153
 154   /* --- Now read from the child until it's all done --- */
 155
 156   {
 157     char buf[1024];
 158     ssize_t sz;
 159
 160     close(pfd[1]);
 161     for (;;) {
 162       sz = read(pfd[0], buf, sizeof(buf));
 163       if (sz == 0 || (sz < 0 && sz != EINTR))
 164         break;
 165       rand_add(buf, sz);
 166     }
 167     close(pfd[0]);
 168     rand_add(pfd, sizeof(pfd));
 169     burn(buf); burn(pfd);
 170   }
 171
 172   /* --- The child should be dead now, so wait for it --- */
 173
 174   {
 175     int st;
 176
 177     wait(&st);
 178     rand_add(&st, sizeof(st));
 179     rand_add(&pid, sizeof(pid));
 180   }
 181 }
 182
 183 /* --- @noise_acquire@ --- *
 184  *
 185  * Arguments:   ---
 186  *
 187  * Returns:     ---
 188  *
 189  * Use:         Attempts to acquire an amount of random noise from the
 190  *              environment.  A lot of it's not actually much good, but
 191  *              it's better than nothing.  There's probably a bit or two's
 192  *              worth in each item which gets added.
 193  */
 194
 195 void noise_acquire(void)
 196 {
 197   /* --- Try a real random number source --- *
 198    *
 199    * Some operating systems (notably Linux) provide a `/dev/random' which
 200    * contains distilled random numbers from the outside world.
 201    */
 202
 203   {
 204     int fd;
 205     int f;
 206     unsigned char buff[64];
 207     ssize_t sz;
 208
 209     if ((fd = open("/dev/random", O_RDONLY)) >= 0 &&
 210         (f = fcntl(fd, F_GETFL, 0)) >= 0 &&
 211         fcntl(fd, F_SETFL, f | O_NONBLOCK) >= 0 &&
 212         (sz = read(fd, buff, sizeof(buff))) > 0) {
 213       rand_add(buff, sz);
 214       burn(buff);
 215     }
 216     if (fd >= 0)
 217       close(fd);
 218   }
 219
 220   /* --- Squeeze some entropy from the current time --- */
 221
 222   {
 223     struct timeval tv;
 224     clock_t c;
 225
 226     gettimeofday(&tv, 0);
 227     c = clock();
 228     rand_add(&tv, sizeof(tv));
 229     rand_add(&c, sizeof(c));
 230     burn(tv); burn(c);
 231   }
 232
 233   /* --- Try some commands which ask the outside world some questions --- */
 234
 235   noise__shell("ps auxww");
 236   noise__shell("ps -ef");
 237   /* @noise__shell("df");@ -- irritates NFS */
 238   noise__shell("netstat -an");
 239
 240   /* --- Get our resource usage to see if that's at all interesting --- */
 241
 242 #if defined(HAVE_GETRUSAGE)
 243   {
 244     struct rusage ru;
 245     getrusage(RUSAGE_SELF, &ru);
 246     rand_add(&ru, sizeof(ru));
 247     getrusage(RUSAGE_CHILDREN, &ru);
 248     rand_add(&ru, sizeof(ru));
 249     burn(ru);
 250   }
 251 #elif defined(HAVE_VTIMES)
 252   {
 253     struct vtimes vt, vtc;
 254     vtimes(&vt, &vtc);
 255     rand_add(&vt, sizeof(vt));
 256     rand_add(&vtc, sizeof(vtc));
 257     burn(vt); burn(vtc);
 258   }
 259 #endif
 260
 261   /* --- Squeeze some more entropy from the current time --- */
 262
 263   {
 264     struct timeval tv;
 265     clock_t c;
 266
 267     gettimeofday(&tv, 0);
 268     c = clock();
 269     rand_add(&tv, sizeof(tv));
 270     rand_add(&c, sizeof(c));
 271     burn(tv); burn(c);
 272   }
 273
 274   /* --- Done -- churn the random pool --- */
 275
 276   rand_churn();
 277 }
 278
 279 /*----- That's all, folks -------------------------------------------------*/