summaryrefslogtreecommitdiffstats
path: root/modules/pam_timestamp/pam_timestamp.c
blob: e29ce6e906f218cb76a62338c3d92c89cfce8152 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
/******************************************************************************
 * A module for Linux-PAM that will cache authentication results, inspired by
 * (and implemented with an eye toward being mixable with) sudo.
 *
 * Copyright (c) 2002 Red Hat, Inc.
 * Written by Nalin Dahyabhai <nalin@redhat.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, and the entire permission notice in its entirety,
 *    including the disclaimer of warranties.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 *
 * ALTERNATIVELY, this product may be distributed under the terms of
 * the GNU Public License, in which case the provisions of the GPL are
 * required INSTEAD OF the above restrictions.  (This clause is
 * necessary due to a potential bad interaction between the GPL and
 * the restrictions contained in a BSD-style copyright.)
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#define PAM_SM_AUTH
#define PAM_SM_SESSION

#include "config.h"

#include <sys/stat.h>
#include <sys/types.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <sys/time.h>
#include <unistd.h>
#include <utmp.h>
#include <syslog.h>
#include <paths.h>
#include "hmacsha1.h"

#include <security/pam_modules.h>
#include <security/_pam_macros.h>
#include <security/pam_ext.h>
#include <security/pam_modutil.h>

/* The default timeout we use is 5 minutes, which matches the sudo default
 * for the timestamp_timeout parameter. */
#define DEFAULT_TIMESTAMP_TIMEOUT (5 * 60)
#define MODULE "pam_timestamp"
#define TIMESTAMPDIR _PATH_VARRUN "/" MODULE
#define TIMESTAMPKEY TIMESTAMPDIR "/_pam_timestamp_key"

/* Various buffers we use need to be at least as large as either PATH_MAX or
 * LINE_MAX, so choose the larger of the two. */
#if (LINE_MAX > PATH_MAX)
#define BUFLEN LINE_MAX
#else
#define BUFLEN PATH_MAX
#endif

/* Return PAM_SUCCESS if the given directory looks "safe". */
static int
check_dir_perms(pam_handle_t *pamh, const char *tdir)
{
	char scratch[BUFLEN];
	struct stat st;
	int i;
	/* Check that the directory is "safe". */
	if ((tdir == NULL) || (strlen(tdir) == 0)) {
		return PAM_AUTH_ERR;
	}
	/* Iterate over the path, checking intermediate directories. */
	memset(scratch, 0, sizeof(scratch));
	for (i = 0; (tdir[i] != '\0') && (i < (int)sizeof(scratch)); i++) {
		scratch[i] = tdir[i];
		if ((scratch[i] == '/') || (tdir[i + 1] == '\0')) {
			/* We now have the name of a directory in the path, so
			 * we need to check it. */
			if ((lstat(scratch, &st) == -1) && (errno != ENOENT)) {
				pam_syslog(pamh, LOG_ERR,
				       "unable to read `%s': %m",
				       scratch);
				return PAM_AUTH_ERR;
			}
			if (!S_ISDIR(st.st_mode)) {
				pam_syslog(pamh, LOG_ERR,
				       "`%s' is not a directory",
				       scratch);
				return PAM_AUTH_ERR;
			}
			if (S_ISLNK(st.st_mode)) {
				pam_syslog(pamh, LOG_ERR,
				       "`%s' is a symbolic link",
				       scratch);
				return PAM_AUTH_ERR;
			}
			if (st.st_uid != 0) {
				pam_syslog(pamh, LOG_ERR,
				       "`%s' owner UID != 0",
				       scratch);
				return PAM_AUTH_ERR;
			}
			if (st.st_gid != 0) {
				pam_syslog(pamh, LOG_ERR,
				       "`%s' owner GID != 0",
				       scratch);
				return PAM_AUTH_ERR;
			}
			if ((st.st_mode & (S_IWGRP | S_IWOTH)) != 0) {
				pam_syslog(pamh, LOG_ERR,
				       "`%s' permissions are lax",
				       scratch);
				return PAM_AUTH_ERR;
			}
		}
	}
	return PAM_SUCCESS;
}

/* Validate a tty pathname as actually belonging to a tty, and return its base
 * name if it's valid. */
static const char *
check_tty(const char *tty)
{
	/* Check that we're not being set up to take a fall. */
	if ((tty == NULL) || (strlen(tty) == 0)) {
		return NULL;
	}
	/* Pull out the meaningful part of the tty's name. */
	if (strchr(tty, '/') != NULL) {
		if (strncmp(tty, "/dev/", 5) != 0) {
			/* Make sure the device node is actually in /dev/,
			 * noted by Michal Zalewski. */
			return NULL;
		}
		tty = strrchr(tty, '/') + 1;
	}
	/* Make sure the tty wasn't actually a directory (no basename). */
	if (!strlen(tty) || !strcmp(tty, ".") || !strcmp(tty, "..")) {
		return NULL;
	}
	return tty;
}

/* Determine the right path name for a given user's timestamp. */
static int
format_timestamp_name(char *path, size_t len,
		      const char *timestamp_dir,
		      const char *tty,
		      const char *ruser,
		      const char *user)
{
	if (strcmp(ruser, user) == 0) {
		return snprintf(path, len, "%s/%s/%s", timestamp_dir,
				ruser, tty);
	} else {
		return snprintf(path, len, "%s/%s/%s:%s", timestamp_dir,
				ruser, tty, user);
	}
}

/* Check if a given timestamp date, when compared to a current time, fits
 * within the given interval. */
static int
timestamp_good(time_t then, time_t now, time_t interval)
{
	if (((now >= then) && ((now - then) < interval)) ||
	    ((now < then) && ((then - now) < (2 * interval)))) {
		return PAM_SUCCESS;
	}
	return PAM_AUTH_ERR;
}

static int
check_login_time(const char *ruser, time_t timestamp)
{
	struct utmp utbuf, *ut;
	time_t oldest_login = 0;

	setutent();
	while(
#ifdef HAVE_GETUTENT_R
	      !getutent_r(&utbuf, &ut)
#else
	      (ut = getutent()) != NULL
#endif
	      ) {
		if (ut->ut_type != USER_PROCESS) {
			continue;
		}
		if (strncmp(ruser, ut->ut_user, sizeof(ut->ut_user)) != 0) {
			continue;
		}
		if (oldest_login == 0 || oldest_login > ut->ut_tv.tv_sec) {
			oldest_login = ut->ut_tv.tv_sec;
		}
	}
	endutent();
	if(oldest_login == 0 || timestamp < oldest_login) {
		return PAM_AUTH_ERR;
	}
	return PAM_SUCCESS;
}

#ifndef PAM_TIMESTAMP_MAIN
static int
get_ruser(pam_handle_t *pamh, char *ruserbuf, size_t ruserbuflen)
{
	const void *ruser;
	struct passwd *pwd;

	if (ruserbuf == NULL || ruserbuflen < 1)
		return -2;
	/* Get the name of the source user. */
	if (pam_get_item(pamh, PAM_RUSER, &ruser) != PAM_SUCCESS) {
		ruser = NULL;
	}
	if ((ruser == NULL) || (strlen(ruser) == 0)) {
		/* Barring that, use the current RUID. */
		pwd = pam_modutil_getpwuid(pamh, getuid());
		if (pwd != NULL) {
			ruser = pwd->pw_name;
		}
	} else {
		/*
		 * This ruser is used by format_timestamp_name as a component
		 * of constructed timestamp pathname, so ".", "..", and '/'
		 * are disallowed to avoid potential path traversal issues.
		 */
		if (!strcmp(ruser, ".") ||
		    !strcmp(ruser, "..") ||
		    strchr(ruser, '/')) {
			ruser = NULL;
		}
	}
	if (ruser == NULL || strlen(ruser) >= ruserbuflen) {
		*ruserbuf = '\0';
		return -1;
	}
	strcpy(ruserbuf, ruser);
	return 0;
}

/* Get the path to the timestamp to use. */
static int
get_timestamp_name(pam_handle_t *pamh, int argc, const char **argv,
		   char *path, size_t len)
{
	const char *user, *tty;
	const void *void_tty;
	const char *tdir = TIMESTAMPDIR;
	char ruser[BUFLEN];
	int i, debug = 0;

	/* Parse arguments. */
	for (i = 0; i < argc; i++) {
		if (strcmp(argv[i], "debug") == 0) {
			debug = 1;
		}
	}
	for (i = 0; i < argc; i++) {
		if (strncmp(argv[i], "timestampdir=", 13) == 0) {
			tdir = argv[i] + 13;
			if (debug) {
				pam_syslog(pamh, LOG_DEBUG,
				       "storing timestamps in `%s'",
				       tdir);
			}
		}
	}
	i = check_dir_perms(pamh, tdir);
	if (i != PAM_SUCCESS) {
		return i;
	}
	/* Get the name of the target user. */
	if (pam_get_user(pamh, &user, NULL) != PAM_SUCCESS) {
		user = NULL;
	}
	if ((user == NULL) || (strlen(user) == 0)) {
		return PAM_AUTH_ERR;
	}
	if (debug) {
		pam_syslog(pamh, LOG_DEBUG, "becoming user `%s'", user);
	}
	/* Get the name of the source user. */
	if (get_ruser(pamh, ruser, sizeof(ruser)) || strlen(ruser) == 0) {
		return PAM_AUTH_ERR;
	}
	if (debug) {
		pam_syslog(pamh, LOG_DEBUG, "currently user `%s'", ruser);
	}
	/* Get the name of the terminal. */
	if (pam_get_item(pamh, PAM_TTY, &void_tty) != PAM_SUCCESS) {
		tty = NULL;
	} else {
		tty = void_tty;
	}
	if ((tty == NULL) || (strlen(tty) == 0)) {
		tty = ttyname(STDIN_FILENO);
		if ((tty == NULL) || (strlen(tty) == 0)) {
			tty = ttyname(STDOUT_FILENO);
		}
		if ((tty == NULL) || (strlen(tty) == 0)) {
			tty = ttyname(STDERR_FILENO);
		}
		if ((tty == NULL) || (strlen(tty) == 0)) {
			/* Match sudo's behavior for this case. */
			tty = "unknown";
		}
	}
	if (debug) {
		pam_syslog(pamh, LOG_DEBUG, "tty is `%s'", tty);
	}
	/* Snip off all but the last part of the tty name. */
	tty = check_tty(tty);
	if (tty == NULL) {
		return PAM_AUTH_ERR;
	}
	/* Generate the name of the file used to cache auth results.  These
	 * paths should jive with sudo's per-tty naming scheme. */
	if (format_timestamp_name(path, len, tdir, tty, ruser, user) >= (int)len) {
		return PAM_AUTH_ERR;
	}
	if (debug) {
		pam_syslog(pamh, LOG_DEBUG, "using timestamp file `%s'", path);
	}
	return PAM_SUCCESS;
}

/* Tell the user that access has been granted. */
static void
verbose_success(pam_handle_t *pamh, long diff)
{
	pam_info(pamh, _("Access granted (last access was %ld seconds ago)."), diff);
}

int
pam_sm_authenticate(pam_handle_t *pamh, int flags, int argc, const char **argv)
{
	struct stat st;
	time_t interval = DEFAULT_TIMESTAMP_TIMEOUT;
	int i, fd, debug = 0, verbose = 0;
	char path[BUFLEN], *p, *message, *message_end;
	long tmp;
	const void *void_service;
	const char *service;
	time_t now, then;

	/* Parse arguments. */
	for (i = 0; i < argc; i++) {
		if (strcmp(argv[i], "debug") == 0) {
			debug = 1;
		}
	}
	for (i = 0; i < argc; i++) {
		if (strncmp(argv[i], "timestamp_timeout=", 18) == 0) {
			tmp = strtol(argv[i] + 18, &p, 0);
			if ((p != NULL) && (*p == '\0')) {
				interval = tmp;
				if (debug) {
					pam_syslog(pamh, LOG_DEBUG,
					       "setting timeout to %ld"
					       " seconds", (long)interval);
				}
			}
		} else
		if (strcmp(argv[i], "verbose") == 0) {
			verbose = 1;
			if (debug) {
				pam_syslog(pamh, LOG_DEBUG,
				       "becoming more verbose");
			}
		}
	}

	if (flags & PAM_SILENT) {
		verbose = 0;
	}

	/* Get the name of the timestamp file. */
	if (get_timestamp_name(pamh, argc, argv,
			       path, sizeof(path)) != PAM_SUCCESS) {
		return PAM_AUTH_ERR;
	}

	/* Get the name of the service. */
	if (pam_get_item(pamh, PAM_SERVICE, &void_service) != PAM_SUCCESS) {
		service = NULL;
	} else {
		service = void_service;
	}
	if ((service == NULL) || (strlen(service) == 0)) {
		service = "(unknown)";
	}

	/* Open the timestamp file. */
	fd = open(path, O_RDONLY | O_NOFOLLOW);
	if (fd == -1) {
		if (debug) {
			pam_syslog(pamh, LOG_DEBUG,
			       "cannot open timestamp `%s': %m",
			       path);
		}
		return PAM_AUTH_ERR;
	}

	if (fstat(fd, &st) == 0) {
		int count;
		void *mac;
		size_t maclen;
		char ruser[BUFLEN];

		/* Check that the file is owned by the superuser. */
		if ((st.st_uid != 0) || (st.st_gid != 0)) {
			pam_syslog(pamh, LOG_ERR, "timestamp file `%s' is "
			       "not owned by root", path);
			close(fd);
			return PAM_AUTH_ERR;
		}

		/* Check that the file is a normal file. */
		if (!(S_ISREG(st.st_mode))) {
			pam_syslog(pamh, LOG_ERR, "timestamp file `%s' is "
			       "not a regular file", path);
			close(fd);
			return PAM_AUTH_ERR;
		}

		/* Check that the file is the expected size. */
		if (st.st_size == 0) {
			/* Invalid, but may have been created by sudo. */
			close(fd);
			return PAM_AUTH_ERR;
		}
		if (st.st_size !=
		    (off_t)(strlen(path) + 1 + sizeof(then) + hmac_sha1_size())) {
			pam_syslog(pamh, LOG_NOTICE, "timestamp file `%s' "
			       "appears to be corrupted", path);
			close(fd);
			return PAM_AUTH_ERR;
		}

		/* Read the file contents. */
		message = malloc(st.st_size);
		count = 0;
                if (!message) {
			close(fd);
			return PAM_BUF_ERR;
		}
		while (count < st.st_size) {
			i = read(fd, message + count, st.st_size - count);
			if ((i == 0) || (i == -1)) {
				break;
			}
			count += i;
		}
		if (count < st.st_size) {
			pam_syslog(pamh, LOG_NOTICE, "error reading timestamp "
				"file `%s': %m", path);
			close(fd);
			free(message);
			return PAM_AUTH_ERR;
		}
		message_end = message + strlen(path) + 1 + sizeof(then);

		/* Regenerate the MAC. */
		hmac_sha1_generate_file(pamh, &mac, &maclen, TIMESTAMPKEY, 0, 0,
					message, message_end - message);
		if ((mac == NULL) ||
		    (memcmp(path, message, strlen(path)) != 0) ||
		    (memcmp(mac, message_end, maclen) != 0)) {
			pam_syslog(pamh, LOG_NOTICE, "timestamp file `%s' is "
				"corrupted", path);
			close(fd);
			free(mac);
			free(message);
			return PAM_AUTH_ERR;
		}
		free(mac);
		memmove(&then, message + strlen(path) + 1, sizeof(then));
		free(message);

		/* Check oldest login against timestamp */
		if (get_ruser(pamh, ruser, sizeof(ruser)))
		{
			close(fd);
			return PAM_AUTH_ERR;
		}
		if (check_login_time(ruser, then) != PAM_SUCCESS)
		{
			pam_syslog(pamh, LOG_NOTICE, "timestamp file `%s' is "
			       "older than oldest login, disallowing "
			       "access to %s for user %s",
			       path, service, ruser);
			close(fd);
			return PAM_AUTH_ERR;
		}

		/* Compare the dates. */
		now = time(NULL);
		if (timestamp_good(then, now, interval) == PAM_SUCCESS) {
			close(fd);
			pam_syslog(pamh, LOG_NOTICE, "timestamp file `%s' is "
			       "only %ld seconds old, allowing access to %s "
			       "for user %s", path, (long) (now - st.st_mtime),
			       service, ruser);
			if (verbose) {
				verbose_success(pamh, now - st.st_mtime);
			}
			return PAM_SUCCESS;
		} else {
			close(fd);
			pam_syslog(pamh, LOG_NOTICE, "timestamp file `%s' has "
			       "unacceptable age (%ld seconds), disallowing "
			       "access to %s for user %s",
			       path, (long) (now - st.st_mtime),
			       service, ruser);
			return PAM_AUTH_ERR;
		}
	}
	close(fd);

	/* Fail by default. */
	return PAM_AUTH_ERR;
}

int
pam_sm_setcred(pam_handle_t *pamh UNUSED, int flags UNUSED, int argc UNUSED, const char **argv UNUSED)
{
	return PAM_SUCCESS;
}

int
pam_sm_open_session(pam_handle_t *pamh, int flags UNUSED, int argc, const char **argv)
{
	char path[BUFLEN], subdir[BUFLEN], *text, *p;
	void *mac;
	size_t maclen;
	time_t now;
	int fd, i, debug = 0;

	/* Parse arguments. */
	for (i = 0; i < argc; i++) {
		if (strcmp(argv[i], "debug") == 0) {
			debug = 1;
		}
	}

	/* Get the name of the timestamp file. */
	if (get_timestamp_name(pamh, argc, argv,
			       path, sizeof(path)) != PAM_SUCCESS) {
		return PAM_SESSION_ERR;
	}

	/* Create the directory for the timestamp file if it doesn't already
	 * exist. */
	for (i = 1; path[i] != '\0'; i++) {
		if (path[i] == '/') {
			/* Attempt to create the directory. */
			strncpy(subdir, path, i);
			subdir[i] = '\0';
			if (mkdir(subdir, 0700) == 0) {
				/* Attempt to set the owner to the superuser. */
			        if (lchown(subdir, 0, 0) != 0) {
					if (debug) {
						pam_syslog(pamh, LOG_DEBUG,
						    "error setting permissions on `%s': %m",
						    subdir);
					}
					return PAM_SESSION_ERR;
				}
			} else {
				if (errno != EEXIST) {
					if (debug) {
						pam_syslog(pamh, LOG_DEBUG,
						    "error creating directory `%s': %m",
						    subdir);
					}
					return PAM_SESSION_ERR;
				}
			}
		}
	}

	/* Generate the message. */
	text = malloc(strlen(path) + 1 + sizeof(now) + hmac_sha1_size());
	if (text == NULL) {
		pam_syslog(pamh, LOG_CRIT, "unable to allocate memory: %m");
		return PAM_SESSION_ERR;
	}
	p = text;

	strcpy(text, path);
	p += strlen(path) + 1;

	now = time(NULL);
	memmove(p, &now, sizeof(now));
	p += sizeof(now);

	/* Generate the MAC and append it to the plaintext. */
	hmac_sha1_generate_file(pamh, &mac, &maclen,
				TIMESTAMPKEY,
				0, 0,
				text, p - text);
	if (mac == NULL) {
		pam_syslog(pamh, LOG_ERR, "failure generating MAC: %m");
		free(text);
		return PAM_SESSION_ERR;
	}
	memmove(p, mac, maclen);
	p += maclen;
	free(mac);

	/* Open the file. */
	fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
	if (fd == -1) {
		pam_syslog(pamh, LOG_ERR, "unable to open `%s': %m", path);
		free(text);
		return PAM_SESSION_ERR;
	}

	/* Attempt to set the owner to the superuser. */
	if (fchown(fd, 0, 0) != 0) {
	  if (debug) {
	    pam_syslog(pamh, LOG_DEBUG,
		       "error setting ownership of `%s': %m",
		       path);
	  }
	  close(fd);
	  free(text);
	  return PAM_SESSION_ERR;
	}


	/* Write the timestamp to the file. */
	if (write(fd, text, p - text) != p - text) {
		pam_syslog(pamh, LOG_ERR, "unable to write to `%s': %m", path);
		close(fd);
		free(text);
		return PAM_SESSION_ERR;
	}

	/* Close the file and return successfully. */
	close(fd);
	free(text);
	pam_syslog(pamh, LOG_DEBUG, "updated timestamp file `%s'", path);
	return PAM_SUCCESS;
}

int
pam_sm_close_session(pam_handle_t *pamh UNUSED, int flags UNUSED, int argc UNUSED, const char **argv UNUSED)
{
	return PAM_SUCCESS;
}

#else /* PAM_TIMESTAMP_MAIN */

#define USAGE "Usage: %s [[-k] | [-d]] [target user]\n"
#define CHECK_INTERVAL 7

int
main(int argc, char **argv)
{
	int i, retval = 0, dflag = 0, kflag = 0;
	const char *target_user = NULL, *user = NULL, *tty = NULL;
	struct passwd *pwd;
	struct timeval tv;
	fd_set write_fds;
	char path[BUFLEN];
	struct stat st;

	/* Check that there's nothing funny going on with stdio. */
	if ((fstat(STDIN_FILENO, &st) == -1) ||
	    (fstat(STDOUT_FILENO, &st) == -1) ||
	    (fstat(STDERR_FILENO, &st) == -1)) {
		/* Appropriate the "no controlling tty" error code. */
		return 3;
	}

	/* Parse arguments. */
	while ((i = getopt(argc, argv, "dk")) != -1) {
		switch (i) {
			case 'd':
				dflag++;
				break;
			case 'k':
				kflag++;
				break;
			default:
				fprintf(stderr, USAGE, argv[0]);
				return 1;
				break;
		}
	}

	/* Bail if both -k and -d are given together. */
	if ((kflag + dflag) > 1) {
		fprintf(stderr, USAGE, argv[0]);
		return 1;
	}

	/* Check that we're setuid. */
	if (geteuid() != 0) {
		fprintf(stderr, "%s must be setuid root\n",
			argv[0]);
		retval = 2;
	}

	/* Check that we have a controlling tty. */
	tty = ttyname(STDIN_FILENO);
	if ((tty == NULL) || (strlen(tty) == 0)) {
		tty = ttyname(STDOUT_FILENO);
	}
	if ((tty == NULL) || (strlen(tty) == 0)) {
		tty = ttyname(STDERR_FILENO);
	}
	if ((tty == NULL) || (strlen(tty) == 0)) {
		tty = "unknown";
	}

	/* Get the name of the invoking (requesting) user. */
	pwd = getpwuid(getuid());
	if (pwd == NULL) {
		retval = 4;
	}

	/* Get the name of the target user. */
	user = strdup(pwd->pw_name);
	if (user == NULL) {
		retval = 4;
	} else {
		target_user = (optind < argc) ? argv[optind] : user;
		if ((strchr(target_user, '.') != NULL) ||
		    (strchr(target_user, '/') != NULL) ||
		    (strchr(target_user, '%') != NULL)) {
			fprintf(stderr, "unknown user: %s\n",
				target_user);
			retval = 4;
		}
	}

	/* Sanity check the tty to make sure we should be checking
	 * for timestamps which pertain to it. */
	if (retval == 0) {
		tty = check_tty(tty);
		if (tty == NULL) {
			fprintf(stderr, "invalid tty\n");
			retval = 6;
		}
	}

	do {
		/* Sanity check the timestamp directory itself. */
		if (retval == 0) {
			if (check_dir_perms(NULL, TIMESTAMPDIR) != PAM_SUCCESS) {
				retval = 5;
			}
		}

		if (retval == 0) {
			/* Generate the name of the timestamp file. */
			format_timestamp_name(path, sizeof(path), TIMESTAMPDIR,
					      tty, user, target_user);
		}

		if (retval == 0) {
			if (kflag) {
				/* Remove the timestamp. */
				if (lstat(path, &st) != -1) {
					retval = unlink(path);
				}
			} else {
				/* Check the timestamp. */
				if (lstat(path, &st) != -1) {
					/* Check oldest login against timestamp */
					if (check_login_time(user, st.st_mtime) != PAM_SUCCESS) {
						retval = 7;
					} else if (!timestamp_good(st.st_mtime, time(NULL),
							    DEFAULT_TIMESTAMP_TIMEOUT) == PAM_SUCCESS) {
						retval = 7;
					}
				} else {
					retval = 7;
				}
			}
		}

		if (dflag > 0) {
			struct timeval now;
			/* Send the would-be-returned value to our parent. */
			signal(SIGPIPE, SIG_DFL);
			fprintf(stdout, "%d\n", retval);
			fflush(stdout);
			/* Wait. */
			gettimeofday(&now, NULL);
			tv.tv_sec = CHECK_INTERVAL;
			/* round the sleep time to get woken up on a whole second */
			tv.tv_usec = 1000000 - now.tv_usec;
			if (now.tv_usec < 500000)
				tv.tv_sec--;
			FD_ZERO(&write_fds);
			FD_SET(STDOUT_FILENO, &write_fds);
			select(STDOUT_FILENO + 1,
			       NULL, NULL, &write_fds,
			       &tv);
			retval = 0;
		}
	} while (dflag > 0);

	return retval;
}

#endif