misc-utils/mcookie.c

   1 /* mcookie.c -- Generates random numbers for xauth
   2  * Created: Fri Feb  3 10:42:48 1995 by faith@cs.unc.edu
   3  * Revised: Fri Mar 19 07:48:01 1999 by faith@acm.org
   4  * Public Domain 1995, 1999 Rickard E. Faith (faith@acm.org)
   5  * This program comes with ABSOLUTELY NO WARRANTY.
   6  *
   7  * This program gathers some random bits of data and used the MD5
   8  * message-digest algorithm to generate a 128-bit hexadecimal number for
   9  * use with xauth(1).
  10  *
  11  * NOTE: Unless /dev/random is available, this program does not actually
  12  * gather 128 bits of random information, so the magic cookie generated
  13  * will be considerably easier to guess than one might expect.
  14  *
  15  * 1999-02-22 Arkadiusz Mi¶kiewicz <misiek@pld.ORG.PL>
  16  * - added Native Language Support
  17  * 1999-03-21 aeb: Added some fragments of code from Colin Plumb.
  18  *
  19  */
  20
  21 #include "c.h"
  22 #include "md5.h"
  23 #include "nls.h"
  24 #include "closestream.h"
  25
  26 #include <fcntl.h>
  27 #include <getopt.h>
  28 #include <stddef.h>
  29 #include <stdio.h>
  30 #include <stdlib.h>
  31 #include <sys/time.h>
  32 #include <unistd.h>
  33
  34 #define BUFFERSIZE      4096
  35
  36 struct rngs {
  37         const char *path;
  38         int minlength, maxlength;
  39 } rngs[] = {
  40         {"/dev/random",         16, 16},  /* 16 bytes = 128 bits suffice */
  41         {"/proc/interrupts",     0,  0},
  42         {"/proc/slabinfo",       0,  0},
  43         {"/proc/stat",           0,  0},
  44         {"/dev/urandom",        32, 64},
  45 };
  46
  47 #define RNGS (sizeof(rngs)/sizeof(struct rngs))
  48
  49 /* The basic function to hash a file */
  50 static off_t hash_file(struct MD5Context *ctx, int fd)
  51 {
  52         off_t count = 0;
  53         ssize_t r;
  54         unsigned char buf[BUFFERSIZE];
  55
  56         while ((r = read(fd, buf, sizeof(buf))) > 0) {
  57                 MD5Update(ctx, buf, r);
  58                 count += r;
  59         }
  60         /* Separate files with a null byte */
  61         buf[0] = '\0';
  62         MD5Update(ctx, buf, 1);
  63         return count;
  64 }
  65
  66 static void __attribute__ ((__noreturn__)) usage(FILE * out)
  67 {
  68         fputs(_("\nUsage:\n"), out);
  69         fprintf(out,
  70               _(" %s [options]\n"), program_invocation_short_name);
  71
  72         fputs(_("\nOptions:\n"), out);
  73         fputs(_(" -f, --file <file> use file as a cookie seed\n"
  74                 " -v, --verbose     explain what is being done\n"
  75                 " -V, --version     output version information and exit\n"
  76                 " -h, --help        display this help and exit\n\n"), out);
  77
  78         exit(out == stderr ? EXIT_FAILURE : EXIT_SUCCESS);
  79 }
  80
  81 int main(int argc, char **argv)
  82 {
  83         size_t i;
  84         struct MD5Context ctx;
  85         unsigned char digest[MD5LENGTH];
  86         unsigned char buf[BUFFERSIZE];
  87         int fd;
  88         int c;
  89         pid_t pid;
  90         char *file = NULL;
  91         int verbose = 0;
  92         int r;
  93         struct timeval tv;
  94         struct timezone tz;
  95
  96         static const struct option longopts[] = {
  97                 {"file", required_argument, NULL, 'f'},
  98                 {"verbose", no_argument, NULL, 'v'},
  99                 {"version", no_argument, NULL, 'V'},
 100                 {"help", no_argument, NULL, 'h'},
 101                 {NULL, 0, NULL, 0}
 102         };
 103
 104         setlocale(LC_ALL, "");
 105         bindtextdomain(PACKAGE, LOCALEDIR);
 106         textdomain(PACKAGE);
 107         atexit(close_stdout);
 108
 109         while ((c =
 110                 getopt_long(argc, argv, "f:vVh", longopts, NULL)) != -1)
 111                 switch (c) {
 112                 case 'v':
 113                         verbose = 1;
 114                         break;
 115                 case 'f':
 116                         file = optarg;
 117                         break;
 118                 case 'V':
 119                         printf(UTIL_LINUX_VERSION);
 120                         return EXIT_SUCCESS;
 121                 case 'h':
 122                         usage(stdout);
 123                 default:
 124                         usage(stderr);
 125                 }
 126
 127         MD5Init(&ctx);
 128         gettimeofday(&tv, &tz);
 129         MD5Update(&ctx, (unsigned char *) &tv, sizeof(tv));
 130
 131         pid = getppid();
 132         MD5Update(&ctx, (unsigned char *) &pid, sizeof(pid));
 133         pid = getpid();
 134         MD5Update(&ctx, (unsigned char *) &pid, sizeof(pid));
 135
 136         if (file) {
 137                 int count = 0;
 138
 139                 if (file[0] == '-' && !file[1])
 140                         fd = STDIN_FILENO;
 141                 else
 142                         fd = open(file, O_RDONLY);
 143
 144                 if (fd < 0) {
 145                         warn(_("cannot open %s"), file);
 146                 } else {
 147                         count = hash_file(&ctx, fd);
 148                         if (verbose)
 149                                 fprintf(stderr,
 150                                         _("Got %d bytes from %s\n"), count,
 151                                         file);
 152
 153                         if (fd != STDIN_FILENO)
 154                                 if (close(fd))
 155                                         err(EXIT_FAILURE,
 156                                             _("closing %s failed"), file);
 157                 }
 158         }
 159
 160         for (i = 0; i < RNGS; i++) {
 161                 if ((fd = open(rngs[i].path, O_RDONLY | O_NONBLOCK)) >= 0) {
 162                         int count = sizeof(buf);
 163
 164                         if (rngs[i].maxlength && count > rngs[i].maxlength)
 165                                 count = rngs[i].maxlength;
 166                         r = read(fd, buf, count);
 167                         if (r > 0)
 168                                 MD5Update(&ctx, buf, r);
 169                         else
 170                                 r = 0;
 171                         close(fd);
 172                         if (verbose)
 173                                 fprintf(stderr,
 174                                         _("Got %d bytes from %s\n"), r,
 175                                         rngs[i].path);
 176                         if (rngs[i].minlength && r >= rngs[i].minlength)
 177                                 break;
 178                 } else if (verbose)
 179                         warn(_("cannot open %s"), rngs[i].path);
 180         }
 181
 182         MD5Final(digest, &ctx);
 183         for (i = 0; i < MD5LENGTH; i++)
 184                 printf("%02x", digest[i]);
 185         putchar('\n');
 186
 187         return EXIT_SUCCESS;
 188 }