summaryrefslogtreecommitdiff
path: root/ssh-agent.c
blob: 68de56ce69d88243da01e714c2c5ac3c186d6ec7 (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
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
/* $OpenBSD: ssh-agent.c,v 1.229 2018/04/09 23:54:49 djm Exp $ */
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * The authentication agent program.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 *
 * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
 *
 * 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, this list of conditions and the following disclaimer.
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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.
 */

#include "includes.h"

#include <sys/types.h>
#include <sys/param.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/socket.h>
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
#endif
#ifdef HAVE_SYS_UN_H
# include <sys/un.h>
#endif
#include "openbsd-compat/sys-queue.h"

#ifdef WITH_OPENSSL
#include <openssl/evp.h>
#include "openbsd-compat/openssl-compat.h"
#endif

#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#ifdef HAVE_PATHS_H
# include <paths.h>
#endif
#ifdef HAVE_POLL_H
# include <poll.h>
#endif
#include <signal.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
#include <unistd.h>
#ifdef HAVE_UTIL_H
# include <util.h>
#endif

#include "xmalloc.h"
#include "ssh.h"
#include "sshbuf.h"
#include "sshkey.h"
#include "authfd.h"
#include "compat.h"
#include "log.h"
#include "misc.h"
#include "digest.h"
#include "ssherr.h"
#include "match.h"

#ifdef ENABLE_PKCS11
#include "ssh-pkcs11.h"
#endif

#ifndef DEFAULT_PKCS11_WHITELIST
# define DEFAULT_PKCS11_WHITELIST "/usr/lib*/*,/usr/local/lib*/*"
#endif

/* Maximum accepted message length */
#define AGENT_MAX_LEN	(256*1024)

typedef enum {
	AUTH_UNUSED,
	AUTH_SOCKET,
	AUTH_CONNECTION
} sock_type;

typedef struct {
	int fd;
	sock_type type;
	struct sshbuf *input;
	struct sshbuf *output;
	struct sshbuf *request;
} SocketEntry;

u_int sockets_alloc = 0;
SocketEntry *sockets = NULL;

typedef struct identity {
	TAILQ_ENTRY(identity) next;
	struct sshkey *key;
	char *comment;
	char *provider;
	time_t death;
	u_int confirm;
} Identity;

struct idtable {
	int nentries;
	TAILQ_HEAD(idqueue, identity) idlist;
};

/* private key table */
struct idtable *idtab;

int max_fd = 0;

/* pid of shell == parent of agent */
pid_t parent_pid = -1;
time_t parent_alive_interval = 0;

/* pid of process for which cleanup_socket is applicable */
pid_t cleanup_pid = 0;

/* pathname and directory for AUTH_SOCKET */
char socket_name[PATH_MAX];
char socket_dir[PATH_MAX];

/* PKCS#11 path whitelist */
static char *pkcs11_whitelist;

/* locking */
#define LOCK_SIZE	32
#define LOCK_SALT_SIZE	16
#define LOCK_ROUNDS	1
int locked = 0;
u_char lock_pwhash[LOCK_SIZE];
u_char lock_salt[LOCK_SALT_SIZE];

extern char *__progname;

/* Default lifetime in seconds (0 == forever) */
static long lifetime = 0;

static int fingerprint_hash = SSH_FP_HASH_DEFAULT;

static void
close_socket(SocketEntry *e)
{
	close(e->fd);
	e->fd = -1;
	e->type = AUTH_UNUSED;
	sshbuf_free(e->input);
	sshbuf_free(e->output);
	sshbuf_free(e->request);
}

static void
idtab_init(void)
{
	idtab = xcalloc(1, sizeof(*idtab));
	TAILQ_INIT(&idtab->idlist);
	idtab->nentries = 0;
}

static void
free_identity(Identity *id)
{
	sshkey_free(id->key);
	free(id->provider);
	free(id->comment);
	free(id);
}

/* return matching private key for given public key */
static Identity *
lookup_identity(struct sshkey *key)
{
	Identity *id;

	TAILQ_FOREACH(id, &idtab->idlist, next) {
		if (sshkey_equal(key, id->key))
			return (id);
	}
	return (NULL);
}

/* Check confirmation of keysign request */
static int
confirm_key(Identity *id)
{
	char *p;
	int ret = -1;

	p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT);
	if (p != NULL &&
	    ask_permission("Allow use of key %s?\nKey fingerprint %s.",
	    id->comment, p))
		ret = 0;
	free(p);

	return (ret);
}

static void
send_status(SocketEntry *e, int success)
{
	int r;

	if ((r = sshbuf_put_u32(e->output, 1)) != 0 ||
	    (r = sshbuf_put_u8(e->output, success ?
	    SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
}

/* send list of supported public keys to 'client' */
static void
process_request_identities(SocketEntry *e)
{
	Identity *id;
	struct sshbuf *msg;
	int r;

	if ((msg = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
	    (r = sshbuf_put_u32(msg, idtab->nentries)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	TAILQ_FOREACH(id, &idtab->idlist, next) {
		if ((r = sshkey_puts_opts(id->key, msg, SSHKEY_SERIALIZE_INFO))
		     != 0 ||
		    (r = sshbuf_put_cstring(msg, id->comment)) != 0) {
			error("%s: put key/comment: %s", __func__,
			    ssh_err(r));
			continue;
		}
	}
	if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	sshbuf_free(msg);
}


static char *
agent_decode_alg(struct sshkey *key, u_int flags)
{
	if (key->type == KEY_RSA) {
		if (flags & SSH_AGENT_RSA_SHA2_256)
			return "rsa-sha2-256";
		else if (flags & SSH_AGENT_RSA_SHA2_512)
			return "rsa-sha2-512";
	}
	return NULL;
}

/* ssh2 only */
static void
process_sign_request2(SocketEntry *e)
{
	const u_char *data;
	u_char *signature = NULL;
	size_t dlen, slen = 0;
	u_int compat = 0, flags;
	int r, ok = -1;
	struct sshbuf *msg;
	struct sshkey *key = NULL;
	struct identity *id;

	if ((msg = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	if ((r = sshkey_froms(e->request, &key)) != 0 ||
	    (r = sshbuf_get_string_direct(e->request, &data, &dlen)) != 0 ||
	    (r = sshbuf_get_u32(e->request, &flags)) != 0) {
		error("%s: couldn't parse request: %s", __func__, ssh_err(r));
		goto send;
	}

	if ((id = lookup_identity(key)) == NULL) {
		verbose("%s: %s key not found", __func__, sshkey_type(key));
		goto send;
	}
	if (id->confirm && confirm_key(id) != 0) {
		verbose("%s: user refused key", __func__);
		goto send;
	}
	if ((r = sshkey_sign(id->key, &signature, &slen,
	    data, dlen, agent_decode_alg(key, flags), compat)) != 0) {
		error("%s: sshkey_sign: %s", __func__, ssh_err(r));
		goto send;
	}
	/* Success */
	ok = 0;
 send:
	sshkey_free(key);
	if (ok == 0) {
		if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
		    (r = sshbuf_put_string(msg, signature, slen)) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));
	} else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	sshbuf_free(msg);
	free(signature);
}

/* shared */
static void
process_remove_identity(SocketEntry *e)
{
	int r, success = 0;
	struct sshkey *key = NULL;
	Identity *id;

	if ((r = sshkey_froms(e->request, &key)) != 0) {
		error("%s: get key: %s", __func__, ssh_err(r));
		goto done;
	}
	if ((id = lookup_identity(key)) == NULL) {
		debug("%s: key not found", __func__);
		goto done;
	}
	/* We have this key, free it. */
	if (idtab->nentries < 1)
		fatal("%s: internal error: nentries %d",
		    __func__, idtab->nentries);
	TAILQ_REMOVE(&idtab->idlist, id, next);
	free_identity(id);
	idtab->nentries--;
	sshkey_free(key);
	success = 1;
 done:
	send_status(e, success);
}

static void
process_remove_all_identities(SocketEntry *e)
{
	Identity *id;

	/* Loop over all identities and clear the keys. */
	for (id = TAILQ_FIRST(&idtab->idlist); id;
	    id = TAILQ_FIRST(&idtab->idlist)) {
		TAILQ_REMOVE(&idtab->idlist, id, next);
		free_identity(id);
	}

	/* Mark that there are no identities. */
	idtab->nentries = 0;

	/* Send success. */
	send_status(e, 1);
}

/* removes expired keys and returns number of seconds until the next expiry */
static time_t
reaper(void)
{
	time_t deadline = 0, now = monotime();
	Identity *id, *nxt;

	for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
		nxt = TAILQ_NEXT(id, next);
		if (id->death == 0)
			continue;
		if (now >= id->death) {
			debug("expiring key '%s'", id->comment);
			TAILQ_REMOVE(&idtab->idlist, id, next);
			free_identity(id);
			idtab->nentries--;
		} else
			deadline = (deadline == 0) ? id->death :
			    MINIMUM(deadline, id->death);
	}
	if (deadline == 0 || deadline <= now)
		return 0;
	else
		return (deadline - now);
}

static void
process_add_identity(SocketEntry *e)
{
	Identity *id;
	int success = 0, confirm = 0;
	u_int seconds, maxsign;
	char *comment = NULL;
	time_t death = 0;
	struct sshkey *k = NULL;
	u_char ctype;
	int r = SSH_ERR_INTERNAL_ERROR;

	if ((r = sshkey_private_deserialize(e->request, &k)) != 0 ||
	    k == NULL ||
	    (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) {
		error("%s: decode private key: %s", __func__, ssh_err(r));
		goto err;
	}

	while (sshbuf_len(e->request)) {
		if ((r = sshbuf_get_u8(e->request, &ctype)) != 0) {
			error("%s: buffer error: %s", __func__, ssh_err(r));
			goto err;
		}
		switch (ctype) {
		case SSH_AGENT_CONSTRAIN_LIFETIME:
			if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) {
				error("%s: bad lifetime constraint: %s",
				    __func__, ssh_err(r));
				goto err;
			}
			death = monotime() + seconds;
			break;
		case SSH_AGENT_CONSTRAIN_CONFIRM:
			confirm = 1;
			break;
		case SSH_AGENT_CONSTRAIN_MAXSIGN:
			if ((r = sshbuf_get_u32(e->request, &maxsign)) != 0) {
				error("%s: bad maxsign constraint: %s",
				    __func__, ssh_err(r));
				goto err;
			}
			if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) {
				error("%s: cannot enable maxsign: %s",
				    __func__, ssh_err(r));
				goto err;
			}
			break;
		default:
			error("%s: Unknown constraint %d", __func__, ctype);
 err:
			sshbuf_reset(e->request);
			free(comment);
			sshkey_free(k);
			goto send;
		}
	}

	success = 1;
	if (lifetime && !death)
		death = monotime() + lifetime;
	if ((id = lookup_identity(k)) == NULL) {
		id = xcalloc(1, sizeof(Identity));
		TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
		/* Increment the number of identities. */
		idtab->nentries++;
	} else {
		/* key state might have been updated */
		sshkey_free(id->key);
		free(id->comment);
	}
	id->key = k;
	id->comment = comment;
	id->death = death;
	id->confirm = confirm;
send:
	send_status(e, success);
}

/* XXX todo: encrypt sensitive data with passphrase */
static void
process_lock_agent(SocketEntry *e, int lock)
{
	int r, success = 0, delay;
	char *passwd;
	u_char passwdhash[LOCK_SIZE];
	static u_int fail_count = 0;
	size_t pwlen;

	/*
	 * This is deliberately fatal: the user has requested that we lock,
	 * but we can't parse their request properly. The only safe thing to
	 * do is abort.
	 */
	if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (pwlen == 0) {
		debug("empty password not supported");
	} else if (locked && !lock) {
		if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
		    passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0)
			fatal("bcrypt_pbkdf");
		if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) {
			debug("agent unlocked");
			locked = 0;
			fail_count = 0;
			explicit_bzero(lock_pwhash, sizeof(lock_pwhash));
			success = 1;
		} else {
			/* delay in 0.1s increments up to 10s */
			if (fail_count < 100)
				fail_count++;
			delay = 100000 * fail_count;
			debug("unlock failed, delaying %0.1lf seconds",
			    (double)delay/1000000);
			usleep(delay);
		}
		explicit_bzero(passwdhash, sizeof(passwdhash));
	} else if (!locked && lock) {
		debug("agent locked");
		locked = 1;
		arc4random_buf(lock_salt, sizeof(lock_salt));
		if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
		    lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0)
			fatal("bcrypt_pbkdf");
		success = 1;
	}
	explicit_bzero(passwd, pwlen);
	free(passwd);
	send_status(e, success);
}

static void
no_identities(SocketEntry *e)
{
	struct sshbuf *msg;
	int r;

	if ((msg = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
	    (r = sshbuf_put_u32(msg, 0)) != 0 ||
	    (r = sshbuf_put_stringb(e->output, msg)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	sshbuf_free(msg);
}

#ifdef ENABLE_PKCS11
static void
process_add_smartcard_key(SocketEntry *e)
{
	char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
	int r, i, count = 0, success = 0, confirm = 0;
	u_int seconds;
	time_t death = 0;
	u_char type;
	struct sshkey **keys = NULL, *k;
	Identity *id;

	if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
	    (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
		error("%s: buffer error: %s", __func__, ssh_err(r));
		goto send;
	}

	while (sshbuf_len(e->request)) {
		if ((r = sshbuf_get_u8(e->request, &type)) != 0) {
			error("%s: buffer error: %s", __func__, ssh_err(r));
			goto send;
		}
		switch (type) {
		case SSH_AGENT_CONSTRAIN_LIFETIME:
			if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) {
				error("%s: buffer error: %s",
				    __func__, ssh_err(r));
				goto send;
			}
			death = monotime() + seconds;
			break;
		case SSH_AGENT_CONSTRAIN_CONFIRM:
			confirm = 1;
			break;
		default:
			error("%s: Unknown constraint type %d", __func__, type);
			goto send;
		}
	}
	if (realpath(provider, canonical_provider) == NULL) {
		verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
		    provider, strerror(errno));
		goto send;
	}
	if (match_pattern_list(canonical_provider, pkcs11_whitelist, 0) != 1) {
		verbose("refusing PKCS#11 add of \"%.100s\": "
		    "provider not whitelisted", canonical_provider);
		goto send;
	}
	debug("%s: add %.100s", __func__, canonical_provider);
	if (lifetime && !death)
		death = monotime() + lifetime;

	count = pkcs11_add_provider(canonical_provider, pin, &keys);
	for (i = 0; i < count; i++) {
		k = keys[i];
		if (lookup_identity(k) == NULL) {
			id = xcalloc(1, sizeof(Identity));
			id->key = k;
			id->provider = xstrdup(canonical_provider);
			id->comment = xstrdup(canonical_provider); /* XXX */
			id->death = death;
			id->confirm = confirm;
			TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
			idtab->nentries++;
			success = 1;
		} else {
			sshkey_free(k);
		}
		keys[i] = NULL;
	}
send:
	free(pin);
	free(provider);
	free(keys);
	send_status(e, success);
}

static void
process_remove_smartcard_key(SocketEntry *e)
{
	char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
	int r, success = 0;
	Identity *id, *nxt;

	if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
	    (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
		error("%s: buffer error: %s", __func__, ssh_err(r));
		goto send;
	}
	free(pin);

	if (realpath(provider, canonical_provider) == NULL) {
		verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
		    provider, strerror(errno));
		goto send;
	}

	debug("%s: remove %.100s", __func__, canonical_provider);
	for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
		nxt = TAILQ_NEXT(id, next);
		/* Skip file--based keys */
		if (id->provider == NULL)
			continue;
		if (!strcmp(canonical_provider, id->provider)) {
			TAILQ_REMOVE(&idtab->idlist, id, next);
			free_identity(id);
			idtab->nentries--;
		}
	}
	if (pkcs11_del_provider(canonical_provider) == 0)
		success = 1;
	else
		error("%s: pkcs11_del_provider failed", __func__);
send:
	free(provider);
	send_status(e, success);
}
#endif /* ENABLE_PKCS11 */

/* dispatch incoming messages */

static int
process_message(u_int socknum)
{
	u_int msg_len;
	u_char type;
	const u_char *cp;
	int r;
	SocketEntry *e;

	if (socknum >= sockets_alloc) {
		fatal("%s: socket number %u >= allocated %u",
		    __func__, socknum, sockets_alloc);
	}
	e = &sockets[socknum];

	if (sshbuf_len(e->input) < 5)
		return 0;		/* Incomplete message header. */
	cp = sshbuf_ptr(e->input);
	msg_len = PEEK_U32(cp);
	if (msg_len > AGENT_MAX_LEN) {
		debug("%s: socket %u (fd=%d) message too long %u > %u",
		    __func__, socknum, e->fd, msg_len, AGENT_MAX_LEN);
		return -1;
	}
	if (sshbuf_len(e->input) < msg_len + 4)
		return 0;		/* Incomplete message body. */

	/* move the current input to e->request */
	sshbuf_reset(e->request);
	if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 ||
	    (r = sshbuf_get_u8(e->request, &type)) != 0) {
		if (r == SSH_ERR_MESSAGE_INCOMPLETE ||
		    r == SSH_ERR_STRING_TOO_LARGE) {
			debug("%s: buffer error: %s", __func__, ssh_err(r));
			return -1;
		}
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	}

	debug("%s: socket %u (fd=%d) type %d", __func__, socknum, e->fd, type);

	/* check wheter agent is locked */
	if (locked && type != SSH_AGENTC_UNLOCK) {
		sshbuf_reset(e->request);
		switch (type) {
		case SSH2_AGENTC_REQUEST_IDENTITIES:
			/* send empty lists */
			no_identities(e);
			break;
		default:
			/* send a fail message for all other request types */
			send_status(e, 0);
		}
		return 0;
	}

	switch (type) {
	case SSH_AGENTC_LOCK:
	case SSH_AGENTC_UNLOCK:
		process_lock_agent(e, type == SSH_AGENTC_LOCK);
		break;
	case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
		process_remove_all_identities(e); /* safe for !WITH_SSH1 */
		break;
	/* ssh2 */
	case SSH2_AGENTC_SIGN_REQUEST:
		process_sign_request2(e);
		break;
	case SSH2_AGENTC_REQUEST_IDENTITIES:
		process_request_identities(e);
		break;
	case SSH2_AGENTC_ADD_IDENTITY:
	case SSH2_AGENTC_ADD_ID_CONSTRAINED:
		process_add_identity(e);
		break;
	case SSH2_AGENTC_REMOVE_IDENTITY:
		process_remove_identity(e);
		break;
	case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
		process_remove_all_identities(e);
		break;
#ifdef ENABLE_PKCS11
	case SSH_AGENTC_ADD_SMARTCARD_KEY:
	case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
		process_add_smartcard_key(e);
		break;
	case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
		process_remove_smartcard_key(e);
		break;
#endif /* ENABLE_PKCS11 */
	default:
		/* Unknown message.  Respond with failure. */
		error("Unknown message %d", type);
		sshbuf_reset(e->request);
		send_status(e, 0);
		break;
	}
	return 0;
}

static void
new_socket(sock_type type, int fd)
{
	u_int i, old_alloc, new_alloc;

	set_nonblock(fd);

	if (fd > max_fd)
		max_fd = fd;

	for (i = 0; i < sockets_alloc; i++)
		if (sockets[i].type == AUTH_UNUSED) {
			sockets[i].fd = fd;
			if ((sockets[i].input = sshbuf_new()) == NULL)
				fatal("%s: sshbuf_new failed", __func__);
			if ((sockets[i].output = sshbuf_new()) == NULL)
				fatal("%s: sshbuf_new failed", __func__);
			if ((sockets[i].request = sshbuf_new()) == NULL)
				fatal("%s: sshbuf_new failed", __func__);
			sockets[i].type = type;
			return;
		}
	old_alloc = sockets_alloc;
	new_alloc = sockets_alloc + 10;
	sockets = xreallocarray(sockets, new_alloc, sizeof(sockets[0]));
	for (i = old_alloc; i < new_alloc; i++)
		sockets[i].type = AUTH_UNUSED;
	sockets_alloc = new_alloc;
	sockets[old_alloc].fd = fd;
	if ((sockets[old_alloc].input = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	if ((sockets[old_alloc].output = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	if ((sockets[old_alloc].request = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	sockets[old_alloc].type = type;
}

static int
handle_socket_read(u_int socknum)
{
	struct sockaddr_un sunaddr;
	socklen_t slen;
	uid_t euid;
	gid_t egid;
	int fd;

	slen = sizeof(sunaddr);
	fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen);
	if (fd < 0) {
		error("accept from AUTH_SOCKET: %s", strerror(errno));
		return -1;
	}
	if (getpeereid(fd, &euid, &egid) < 0) {
		error("getpeereid %d failed: %s", fd, strerror(errno));
		close(fd);
		return -1;
	}
	if ((euid != 0) && (getuid() != euid)) {
		error("uid mismatch: peer euid %u != uid %u",
		    (u_int) euid, (u_int) getuid());
		close(fd);
		return -1;
	}
	new_socket(AUTH_CONNECTION, fd);
	return 0;
}

static int
handle_conn_read(u_int socknum)
{
	char buf[1024];
	ssize_t len;
	int r;

	if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) {
		if (len == -1) {
			if (errno == EAGAIN || errno == EINTR)
				return 0;
			error("%s: read error on socket %u (fd %d): %s",
			    __func__, socknum, sockets[socknum].fd,
			    strerror(errno));
		}
		return -1;
	}
	if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	explicit_bzero(buf, sizeof(buf));
	process_message(socknum);
	return 0;
}

static int
handle_conn_write(u_int socknum)
{
	ssize_t len;
	int r;

	if (sshbuf_len(sockets[socknum].output) == 0)
		return 0; /* shouldn't happen */
	if ((len = write(sockets[socknum].fd,
	    sshbuf_ptr(sockets[socknum].output),
	    sshbuf_len(sockets[socknum].output))) <= 0) {
		if (len == -1) {
			if (errno == EAGAIN || errno == EINTR)
				return 0;
			error("%s: read error on socket %u (fd %d): %s",
			    __func__, socknum, sockets[socknum].fd,
			    strerror(errno));
		}
		return -1;
	}
	if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	return 0;
}

static void
after_poll(struct pollfd *pfd, size_t npfd)
{
	size_t i;
	u_int socknum;

	for (i = 0; i < npfd; i++) {
		if (pfd[i].revents == 0)
			continue;
		/* Find sockets entry */
		for (socknum = 0; socknum < sockets_alloc; socknum++) {
			if (sockets[socknum].type != AUTH_SOCKET &&
			    sockets[socknum].type != AUTH_CONNECTION)
				continue;
			if (pfd[i].fd == sockets[socknum].fd)
				break;
		}
		if (socknum >= sockets_alloc) {
			error("%s: no socket for fd %d", __func__, pfd[i].fd);
			continue;
		}
		/* Process events */
		switch (sockets[socknum].type) {
		case AUTH_SOCKET:
			if ((pfd[i].revents & (POLLIN|POLLERR)) != 0)
				handle_socket_read(socknum);
			break;
		case AUTH_CONNECTION:
			if ((pfd[i].revents & (POLLIN|POLLERR)) != 0 &&
			    handle_conn_read(socknum) != 0) {
				close_socket(&sockets[socknum]);
				break;
			}
			if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 &&
			    handle_conn_write(socknum) != 0)
				close_socket(&sockets[socknum]);
			break;
		default:
			break;
		}
	}
}

static int
prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp)
{
	struct pollfd *pfd = *pfdp;
	size_t i, j, npfd = 0;
	time_t deadline;

	/* Count active sockets */
	for (i = 0; i < sockets_alloc; i++) {
		switch (sockets[i].type) {
		case AUTH_SOCKET:
		case AUTH_CONNECTION:
			npfd++;
			break;
		case AUTH_UNUSED:
			break;
		default:
			fatal("Unknown socket type %d", sockets[i].type);
			break;
		}
	}
	if (npfd != *npfdp &&
	    (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL)
		fatal("%s: recallocarray failed", __func__);
	*pfdp = pfd;
	*npfdp = npfd;

	for (i = j = 0; i < sockets_alloc; i++) {
		switch (sockets[i].type) {
		case AUTH_SOCKET:
		case AUTH_CONNECTION:
			pfd[j].fd = sockets[i].fd;
			pfd[j].revents = 0;
			/* XXX backoff when input buffer full */
			pfd[j].events = POLLIN;
			if (sshbuf_len(sockets[i].output) > 0)
				pfd[j].events |= POLLOUT;
			j++;
			break;
		default:
			break;
		}
	}
	deadline = reaper();
	if (parent_alive_interval != 0)
		deadline = (deadline == 0) ? parent_alive_interval :
		    MINIMUM(deadline, parent_alive_interval);
	if (deadline == 0) {
		*timeoutp = -1; /* INFTIM */
	} else {
		if (deadline > INT_MAX / 1000)
			*timeoutp = INT_MAX / 1000;
		else
			*timeoutp = deadline * 1000;
	}
	return (1);
}

static void
cleanup_socket(void)
{
	if (cleanup_pid != 0 && getpid() != cleanup_pid)
		return;
	debug("%s: cleanup", __func__);
	if (socket_name[0])
		unlink(socket_name);
	if (socket_dir[0])
		rmdir(socket_dir);
}

void
cleanup_exit(int i)
{
	cleanup_socket();
	_exit(i);
}

/*ARGSUSED*/
static void
cleanup_handler(int sig)
{
	cleanup_socket();
#ifdef ENABLE_PKCS11
	pkcs11_terminate();
#endif
	_exit(2);
}

static void
check_parent_exists(void)
{
	/*
	 * If our parent has exited then getppid() will return (pid_t)1,
	 * so testing for that should be safe.
	 */
	if (parent_pid != -1 && getppid() != parent_pid) {
		/* printf("Parent has died - Authentication agent exiting.\n"); */
		cleanup_socket();
		_exit(2);
	}
}

static void
usage(void)
{
	fprintf(stderr,
	    "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n"
	    "                 [-P pkcs11_whitelist] [-t life] [command [arg ...]]\n"
	    "       ssh-agent [-c | -s] -k\n");
	exit(1);
}

int
main(int ac, char **av)
{
	int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0;
	int sock, fd, ch, result, saved_errno;
	char *shell, *format, *pidstr, *agentsocket = NULL;
#ifdef HAVE_SETRLIMIT
	struct rlimit rlim;
#endif
	extern int optind;
	extern char *optarg;
	pid_t pid;
	char pidstrbuf[1 + 3 * sizeof pid];
	size_t len;
	mode_t prev_mask;
	int timeout = -1; /* INFTIM */
	struct pollfd *pfd = NULL;
	size_t npfd = 0;

	ssh_malloc_init();	/* must be called before any mallocs */
	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
	sanitise_stdfd();

	/* drop */
	setegid(getgid());
	setgid(getgid());

	platform_disable_tracing(0);	/* strict=no */

#ifdef WITH_OPENSSL
	OpenSSL_add_all_algorithms();
#endif

	__progname = ssh_get_progname(av[0]);
	seed_rng();

	while ((ch = getopt(ac, av, "cDdksE:a:P:t:")) != -1) {
		switch (ch) {
		case 'E':
			fingerprint_hash = ssh_digest_alg_by_name(optarg);
			if (fingerprint_hash == -1)
				fatal("Invalid hash algorithm \"%s\"", optarg);
			break;
		case 'c':
			if (s_flag)
				usage();
			c_flag++;
			break;
		case 'k':
			k_flag++;
			break;
		case 'P':
			if (pkcs11_whitelist != NULL)
				fatal("-P option already specified");
			pkcs11_whitelist = xstrdup(optarg);
			break;
		case 's':
			if (c_flag)
				usage();
			s_flag++;
			break;
		case 'd':
			if (d_flag || D_flag)
				usage();
			d_flag++;
			break;
		case 'D':
			if (d_flag || D_flag)
				usage();
			D_flag++;
			break;
		case 'a':
			agentsocket = optarg;
			break;
		case 't':
			if ((lifetime = convtime(optarg)) == -1) {
				fprintf(stderr, "Invalid lifetime\n");
				usage();
			}
			break;
		default:
			usage();
		}
	}
	ac -= optind;
	av += optind;

	if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag))
		usage();

	if (pkcs11_whitelist == NULL)
		pkcs11_whitelist = xstrdup(DEFAULT_PKCS11_WHITELIST);

	if (ac == 0 && !c_flag && !s_flag) {
		shell = getenv("SHELL");
		if (shell != NULL && (len = strlen(shell)) > 2 &&
		    strncmp(shell + len - 3, "csh", 3) == 0)
			c_flag = 1;
	}
	if (k_flag) {
		const char *errstr = NULL;

		pidstr = getenv(SSH_AGENTPID_ENV_NAME);
		if (pidstr == NULL) {
			fprintf(stderr, "%s not set, cannot kill agent\n",
			    SSH_AGENTPID_ENV_NAME);
			exit(1);
		}
		pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr);
		if (errstr) {
			fprintf(stderr,
			    "%s=\"%s\", which is not a good PID: %s\n",
			    SSH_AGENTPID_ENV_NAME, pidstr, errstr);
			exit(1);
		}
		if (kill(pid, SIGTERM) == -1) {
			perror("kill");
			exit(1);
		}
		format = c_flag ? "unsetenv %s;\n" : "unset %s;\n";
		printf(format, SSH_AUTHSOCKET_ENV_NAME);
		printf(format, SSH_AGENTPID_ENV_NAME);
		printf("echo Agent pid %ld killed;\n", (long)pid);
		exit(0);
	}
	parent_pid = getpid();

	if (agentsocket == NULL) {
		/* Create private directory for agent socket */
		mktemp_proto(socket_dir, sizeof(socket_dir));
		if (mkdtemp(socket_dir) == NULL) {
			perror("mkdtemp: private socket dir");
			exit(1);
		}
		snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
		    (long)parent_pid);
	} else {
		/* Try to use specified agent socket */
		socket_dir[0] = '\0';
		strlcpy(socket_name, agentsocket, sizeof socket_name);
	}

	/*
	 * Create socket early so it will exist before command gets run from
	 * the parent.
	 */
	prev_mask = umask(0177);
	sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
	if (sock < 0) {
		/* XXX - unix_listener() calls error() not perror() */
		*socket_name = '\0'; /* Don't unlink any existing file */
		cleanup_exit(1);
	}
	umask(prev_mask);

	/*
	 * Fork, and have the parent execute the command, if any, or present
	 * the socket data.  The child continues as the authentication agent.
	 */
	if (D_flag || d_flag) {
		log_init(__progname,
		    d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO,
		    SYSLOG_FACILITY_AUTH, 1);
		format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
		printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
		    SSH_AUTHSOCKET_ENV_NAME);
		printf("echo Agent pid %ld;\n", (long)parent_pid);
		fflush(stdout);
		goto skip;
	}
	pid = fork();
	if (pid == -1) {
		perror("fork");
		cleanup_exit(1);
	}
	if (pid != 0) {		/* Parent - execute the given command. */
		close(sock);
		snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid);
		if (ac == 0) {
			format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
			printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
			    SSH_AUTHSOCKET_ENV_NAME);
			printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf,
			    SSH_AGENTPID_ENV_NAME);
			printf("echo Agent pid %ld;\n", (long)pid);
			exit(0);
		}
		if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
		    setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
			perror("setenv");
			exit(1);
		}
		execvp(av[0], av);
		perror(av[0]);
		exit(1);
	}
	/* child */
	log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0);

	if (setsid() == -1) {
		error("setsid: %s", strerror(errno));
		cleanup_exit(1);
	}

	(void)chdir("/");
	if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
		/* XXX might close listen socket */
		(void)dup2(fd, STDIN_FILENO);
		(void)dup2(fd, STDOUT_FILENO);
		(void)dup2(fd, STDERR_FILENO);
		if (fd > 2)
			close(fd);
	}

#ifdef HAVE_SETRLIMIT
	/* deny core dumps, since memory contains unencrypted private keys */
	rlim.rlim_cur = rlim.rlim_max = 0;
	if (setrlimit(RLIMIT_CORE, &rlim) < 0) {
		error("setrlimit RLIMIT_CORE: %s", strerror(errno));
		cleanup_exit(1);
	}
#endif

skip:

	cleanup_pid = getpid();

#ifdef ENABLE_PKCS11
	pkcs11_init(0);
#endif
	new_socket(AUTH_SOCKET, sock);
	if (ac > 0)
		parent_alive_interval = 10;
	idtab_init();
	signal(SIGPIPE, SIG_IGN);
	signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN);
	signal(SIGHUP, cleanup_handler);
	signal(SIGTERM, cleanup_handler);

	if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1)
		fatal("%s: pledge: %s", __progname, strerror(errno));
	platform_pledge_agent();

	while (1) {
		prepare_poll(&pfd, &npfd, &timeout);
		result = poll(pfd, npfd, timeout);
		saved_errno = errno;
		if (parent_alive_interval != 0)
			check_parent_exists();
		(void) reaper();	/* remove expired keys */
		if (result < 0) {
			if (saved_errno == EINTR)
				continue;
			fatal("poll: %s", strerror(saved_errno));
		} else if (result > 0)
			after_poll(pfd, npfd);
	}
	/* NOTREACHED */
}