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: Mon Sep 25 23:44:43 1995 by r.faith@ieee.org
   4  * Public Domain 1995 Rickard E. Faith (faith@cs.unc.edu)
   5  * This program comes with ABSOLUTELY NO WARRANTY.
   6  *
   7  * $Id: mcookie.c,v 1.5 1997/07/06 00:13:06 aebr Exp $
   8  *
   9  * This program gathers some random bits of data and used the MD5
  10  * message-digest algorithm to generate a 128-bit hexadecimal number for
  11  * use with xauth(1).
  12  *
  13  * NOTE: Unless /dev/random is available, this program does not actually
  14  * gather 128 bits of random information, so the magic cookie generated
  15  * will be considerably easier to guess than one might expect.
  16  */
  17
  18 #ifdef __linux__
  19 #define HAVE_GETTIMEOFDAY 1
  20 #endif
  21
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <fcntl.h>
  25 #include "md5.h"
  26 #if HAVE_GETTIMEOFDAY
  27 #include <sys/time.h>
  28 #include <unistd.h>
  29 #endif
  30
  31 #define MAXBUFFERSIZE 512
  32
  33 struct rngs {
  34    const char *path;
  35    int        length;
  36 } rngs[] = {
  37    { "/dev/random",              16 },
  38    { "/dev/urandom",            128 },
  39    { "/proc/stat",    MAXBUFFERSIZE },
  40    { "/proc/loadavg", MAXBUFFERSIZE },
  41    { "/dev/audio",    MAXBUFFERSIZE },
  42 };
  43 #define RNGS (sizeof(rngs)/sizeof(struct rngs))
  44
  45 int Verbose = 0;
  46
  47 int main( int argc, char **argv )
  48 {
  49    int               i;
  50    struct MD5Context ctx;
  51    unsigned char     digest[16];
  52    unsigned char     buf[MAXBUFFERSIZE];
  53    int               fd;
  54    int               c;
  55    pid_t             pid;
  56    char              *file = NULL;
  57    int               r;
  58 #if HAVE_GETTIMEOFDAY
  59    struct timeval    tv;
  60    struct timezone   tz;
  61 #else
  62    long int          t;
  63 #endif
  64
  65    while ((c = getopt( argc, argv, "vf:" )) != EOF)
  66       switch (c) {
  67       case 'v': ++Verbose;     break;
  68       case 'f': file = optarg; break;
  69       }
  70
  71    MD5Init( &ctx );
  72
  73 #if HAVE_GETTIMEOFDAY
  74    gettimeofday( &tv, &tz );
  75    MD5Update( &ctx, (unsigned char *)&tv, sizeof( tv ) );
  76 #else
  77    time( &t );
  78    MD5Update( &ctx, (unsigned char *)&t, sizeof( t ) );
  79 #endif
  80    pid = getppid();
  81    MD5Update( &ctx, (unsigned char *)&pid, sizeof( pid ));
  82    pid = getpid();
  83    MD5Update( &ctx, (unsigned char *)&pid, sizeof( pid ));
  84
  85    if (file) {
  86       int count = 0;
  87
  88       if (file[0] == '-' && !file[1]) fd = fileno(stdin);
  89       else if ((fd = open( file, O_RDONLY )) <0) {
  90          fprintf( stderr, "Could not open %s\n", file );
  91       }
  92
  93       while ((r = read( fd, buf, sizeof( buf ) )) > 0) {
  94          MD5Update( &ctx, buf, r );
  95          count += r;
  96       }
  97       if (Verbose)
  98          fprintf( stderr, "Got %d bytes from %s\n", count, file );
  99
 100       if (file[0] != '-' || file[1]) close( fd );
 101    }
 102
 103    for (i = 0; i < RNGS; i++) {
 104       if ((fd = open( rngs[i].path, O_RDONLY|O_NONBLOCK )) >= 0) {
 105          r = read( fd, buf, sizeof( buf ) );
 106          if (r > 0)
 107             MD5Update( &ctx, buf, r );
 108          else
 109             r = 0;
 110          close( fd );
 111          if (Verbose)
 112             fprintf( stderr, "Got %d bytes from %s\n", r, rngs[i].path );
 113          if (r >= rngs[i].length) break;
 114       } else if (Verbose)
 115          fprintf( stderr, "Could not open %s\n", rngs[i].path );
 116    }
 117
 118    MD5Final( digest, &ctx );
 119    for (i = 0; i < 16; i++) printf( "%02x", digest[i] );
 120    putchar ( '\n' );
 121
 122    return 0;
 123 }