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util-linux/misc-utils/mcookie.c

201 lines
4.6 KiB

/* mcookie.c -- Generates random numbers for xauth
* Created: Fri Feb 3 10:42:48 1995 by faith@cs.unc.edu
* Revised: Fri Mar 19 07:48:01 1999 by faith@acm.org
* Public Domain 1995, 1999 Rickard E. Faith (faith@acm.org)
* This program comes with ABSOLUTELY NO WARRANTY.
*
* This program gathers some random bits of data and used the MD5
* message-digest algorithm to generate a 128-bit hexadecimal number for
* use with xauth(1).
*
* NOTE: Unless /dev/random is available, this program does not actually
* gather 128 bits of random information, so the magic cookie generated
* will be considerably easier to guess than one might expect.
*
* 1999-02-22 Arkadiusz Miśkiewicz <misiek@pld.ORG.PL>
* - added Native Language Support
* 1999-03-21 aeb: Added some fragments of code from Colin Plumb.
*
*/
#include "c.h"
#include "md5.h"
#include "nls.h"
#include "closestream.h"
#include "randutils.h"
#include "strutils.h"
#include "xalloc.h"
#include "all-io.h"
#include <fcntl.h>
#include <getopt.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <unistd.h>
enum {
BUFFERSIZE = 4096,
RAND_BYTES = 128
};
struct mcookie_control {
struct UL_MD5Context ctx;
char **files;
size_t nfiles;
uint64_t maxsz;
unsigned int verbose:1;
};
/* The basic function to hash a file */
static uint64_t hash_file(struct mcookie_control *ctl, int fd)
{
unsigned char buf[BUFFERSIZE];
uint64_t wanted, count;
wanted = ctl->maxsz ? ctl->maxsz : sizeof(buf);
for (count = 0; count < wanted; ) {
size_t rdsz = sizeof(buf);
ssize_t r;
if (wanted - count < rdsz)
rdsz = wanted - count;
r = read_all(fd, (char *) buf, rdsz);
if (r <= 0)
break;
ul_MD5Update(&ctl->ctx, buf, r);
count += r;
}
/* Separate files with a null byte */
buf[0] = '\0';
ul_MD5Update(&ctl->ctx, buf, 1);
return count;
}
static void __attribute__((__noreturn__)) usage(void)
{
FILE *out = stdout;
fputs(USAGE_HEADER, out);
fprintf(out, _(" %s [options]\n"), program_invocation_short_name);
fputs(USAGE_SEPARATOR, out);
fputs(_("Generate magic cookies for xauth.\n"), out);
fputs(USAGE_OPTIONS, out);
fputs(_(" -f, --file <file> use file as a cookie seed\n"), out);
fputs(_(" -m, --max-size <num> limit how much is read from seed files\n"), out);
fputs(_(" -v, --verbose explain what is being done\n"), out);
fputs(USAGE_SEPARATOR, out);
printf(USAGE_HELP_OPTIONS(23));
fputs(USAGE_ARGUMENTS, out);
printf(USAGE_ARG_SIZE(_("<num>")));
printf(USAGE_MAN_TAIL("mcookie(1)"));
exit(EXIT_SUCCESS);
}
static void randomness_from_files(struct mcookie_control *ctl)
{
size_t i;
for (i = 0; i < ctl->nfiles; i++) {
const char *fname = ctl->files[i];
size_t count;
int fd;
if (*fname == '-' && !*(fname + 1))
fd = STDIN_FILENO;
else
fd = open(fname, O_RDONLY);
if (fd < 0) {
warn(_("cannot open %s"), fname);
} else {
count = hash_file(ctl, fd);
if (ctl->verbose)
fprintf(stderr,
P_("Got %zu byte from %s\n",
"Got %zu bytes from %s\n", count),
count, fname);
if (fd != STDIN_FILENO && close(fd))
err(EXIT_FAILURE, _("closing %s failed"), fname);
}
}
}
int main(int argc, char **argv)
{
struct mcookie_control ctl = { .verbose = 0 };
size_t i;
unsigned char digest[UL_MD5LENGTH];
unsigned char buf[RAND_BYTES];
int c;
static const struct option longopts[] = {
{"file", required_argument, NULL, 'f'},
{"max-size", required_argument, NULL, 'm'},
{"verbose", no_argument, NULL, 'v'},
{"version", no_argument, NULL, 'V'},
{"help", no_argument, NULL, 'h'},
{NULL, 0, NULL, 0}
};
setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
close_stdout_atexit();
while ((c = getopt_long(argc, argv, "f:m:vVh", longopts, NULL)) != -1) {
switch (c) {
case 'v':
ctl.verbose = 1;
break;
case 'f':
if (!ctl.files)
ctl.files = xmalloc(sizeof(char *) * argc);
ctl.files[ctl.nfiles++] = optarg;
break;
case 'm':
ctl.maxsz = strtosize_or_err(optarg,
_("failed to parse length"));
break;
case 'V':
print_version(EXIT_SUCCESS);
case 'h':
usage();
default:
errtryhelp(EXIT_FAILURE);
}
}
if (ctl.maxsz && ctl.nfiles == 0)
warnx(_("--max-size ignored when used without --file"));
ul_MD5Init(&ctl.ctx);
randomness_from_files(&ctl);
free(ctl.files);
ul_random_get_bytes(&buf, RAND_BYTES);
ul_MD5Update(&ctl.ctx, buf, RAND_BYTES);
if (ctl.verbose)
fprintf(stderr, P_("Got %d byte from %s\n",
"Got %d bytes from %s\n", RAND_BYTES),
RAND_BYTES, random_tell_source());
ul_MD5Final(digest, &ctl.ctx);
for (i = 0; i < UL_MD5LENGTH; i++)
printf("%02x", digest[i]);
putchar('\n');
return EXIT_SUCCESS;
}