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 <stdio.h>
  22 #include <stdlib.h>
  23 #include <fcntl.h>
  24 #include "md5.h"
  25 #include <sys/time.h>
  26 #include <unistd.h>
  27 #include "nls.h"
  28
  29 #define BUFFERSIZE 4096
  30
  31 struct rngs {
  32    const char *path;
  33    int minlength, maxlength;
  34 } rngs[] = {
  35    { "/dev/random",              16,  16 }, /* 16 bytes = 128 bits suffice */
  36    { "/proc/interrupts",          0,   0 },
  37    { "/proc/slabinfo",            0,   0 },
  38    { "/proc/stat",                0,   0 },
  39    { "/dev/urandom",             32,  64 },
  40 };
  41 #define RNGS (sizeof(rngs)/sizeof(struct rngs))
  42
  43 int Verbose = 0;
  44
  45 /* The basic function to hash a file */
  46 static off_t
  47 hash_file(struct MD5Context *ctx, int fd)
  48 {
  49    off_t count = 0;
  50    ssize_t r;
  51    unsigned char buf[BUFFERSIZE];
  52
  53    while ((r = read(fd, buf, sizeof(buf))) > 0) {
  54       MD5Update(ctx, buf, r);
  55       count += r;
  56    }
  57    /* Separate files with a null byte */
  58    buf[0] = 0;
  59    MD5Update(ctx, buf, 1);
  60    return count;
  61 }
  62
  63 int main( int argc, char **argv )
  64 {
  65    int               i;
  66    struct MD5Context ctx;
  67    unsigned char     digest[16];
  68    unsigned char     buf[BUFFERSIZE];
  69    int               fd;
  70    int               c;
  71    pid_t             pid;
  72    char              *file = NULL;
  73    int               r;
  74    struct timeval    tv;
  75    struct timezone   tz;
  76
  77    setlocale(LC_ALL, "");
  78    bindtextdomain(PACKAGE, LOCALEDIR);
  79    textdomain(PACKAGE);
  80
  81    while ((c = getopt( argc, argv, "vf:" )) != -1)
  82       switch (c) {
  83       case 'v': ++Verbose;     break;
  84       case 'f': file = optarg; break;
  85       }
  86
  87    MD5Init( &ctx );
  88    gettimeofday( &tv, &tz );
  89    MD5Update( &ctx, (unsigned char *)&tv, sizeof( tv ) );
  90
  91    pid = getppid();
  92    MD5Update( &ctx, (unsigned char *)&pid, sizeof( pid ));
  93    pid = getpid();
  94    MD5Update( &ctx, (unsigned char *)&pid, sizeof( pid ));
  95
  96    if (file) {
  97       int count = 0;
  98
  99       if (file[0] == '-' && !file[1])
 100          fd = fileno(stdin);
 101       else
 102          fd = open( file, O_RDONLY );
 103
 104       if (fd < 0) {
 105          fprintf( stderr, _("Could not open %s\n"), file );
 106       } else {
 107          count = hash_file( &ctx, fd );
 108          if (Verbose)
 109             fprintf( stderr, _("Got %d bytes from %s\n"), count, file );
 110
 111          if (file[0] != '-' || file[1]) close( fd );
 112       }
 113    }
 114
 115    for (i = 0; i < RNGS; i++) {
 116       if ((fd = open( rngs[i].path, O_RDONLY|O_NONBLOCK )) >= 0) {
 117          int count = sizeof(buf);
 118
 119          if (rngs[i].maxlength && count > rngs[i].maxlength)
 120             count = rngs[i].maxlength;
 121          r = read( fd, buf, count );
 122          if (r > 0)
 123             MD5Update( &ctx, buf, r );
 124          else
 125             r = 0;
 126          close( fd );
 127          if (Verbose)
 128             fprintf( stderr, _("Got %d bytes from %s\n"), r, rngs[i].path );
 129          if (rngs[i].minlength && r >= rngs[i].minlength)
 130             break;
 131       } else if (Verbose)
 132          fprintf( stderr, _("Could not open %s\n"), rngs[i].path );
 133    }
 134
 135    MD5Final( digest, &ctx );
 136    for (i = 0; i < 16; i++) printf( "%02x", digest[i] );
 137    putchar ( '\n' );
 138
 139    /*
 140     * The following is important for cases like disk full, so shell scripts
 141     * can bomb out properly rather than think they succeeded.
 142     */
 143    if (fflush(stdout) < 0 || fclose(stdout) < 0)
 144       return 1;
 145
 146    return 0;
 147 }