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