1 /* $OpenBSD: ssh-agent.c,v 1.278 2021/04/03 06:18:41 djm Exp $ */
2 /*
3 * Author: Tatu Ylonen <[email protected]>
4 * Copyright (c) 1995 Tatu Ylonen <[email protected]>, Espoo, Finland
5 * All rights reserved
6 * The authentication agent program.
7 *
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose. Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
13 *
14 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
15 *
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
18 * are met:
19 * 1. Redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer.
21 * 2. Redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
26 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
27 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
28 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
29 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
30 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
31 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
32 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
33 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
34 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
35 */
36
37 #include "includes.h"
38 __RCSID("$FreeBSD$");
39
40 #include <sys/types.h>
41 #include <sys/param.h>
42 #include <sys/resource.h>
43 #include <sys/stat.h>
44 #include <sys/socket.h>
45 #include <sys/wait.h>
46 #ifdef HAVE_SYS_TIME_H
47 # include <sys/time.h>
48 #endif
49 #ifdef HAVE_SYS_UN_H
50 # include <sys/un.h>
51 #endif
52 #include "openbsd-compat/sys-queue.h"
53
54 #ifdef WITH_OPENSSL
55 #include <openssl/evp.h>
56 #include "openbsd-compat/openssl-compat.h"
57 #endif
58
59 #include <errno.h>
60 #include <fcntl.h>
61 #include <limits.h>
62 #ifdef HAVE_PATHS_H
63 # include <paths.h>
64 #endif
65 #ifdef HAVE_POLL_H
66 # include <poll.h>
67 #endif
68 #include <signal.h>
69 #include <stdarg.h>
70 #include <stdio.h>
71 #include <stdlib.h>
72 #include <time.h>
73 #include <string.h>
74 #include <unistd.h>
75 #ifdef HAVE_UTIL_H
76 # include <util.h>
77 #endif
78
79 #include "xmalloc.h"
80 #include "ssh.h"
81 #include "ssh2.h"
82 #include "sshbuf.h"
83 #include "sshkey.h"
84 #include "authfd.h"
85 #include "compat.h"
86 #include "log.h"
87 #include "misc.h"
88 #include "digest.h"
89 #include "ssherr.h"
90 #include "match.h"
91 #include "msg.h"
92 #include "ssherr.h"
93 #include "pathnames.h"
94 #include "ssh-pkcs11.h"
95 #include "sk-api.h"
96
97 #ifndef DEFAULT_ALLOWED_PROVIDERS
98 # define DEFAULT_ALLOWED_PROVIDERS "/usr/lib*/*,/usr/local/lib*/*"
99 #endif
100
101 /* Maximum accepted message length */
102 #define AGENT_MAX_LEN (256*1024)
103 /* Maximum bytes to read from client socket */
104 #define AGENT_RBUF_LEN (4096)
105
106 typedef enum {
107 AUTH_UNUSED = 0,
108 AUTH_SOCKET = 1,
109 AUTH_CONNECTION = 2,
110 } sock_type;
111
112 typedef struct socket_entry {
113 int fd;
114 sock_type type;
115 struct sshbuf *input;
116 struct sshbuf *output;
117 struct sshbuf *request;
118 } SocketEntry;
119
120 u_int sockets_alloc = 0;
121 SocketEntry *sockets = NULL;
122
123 typedef struct identity {
124 TAILQ_ENTRY(identity) next;
125 struct sshkey *key;
126 char *comment;
127 char *provider;
128 time_t death;
129 u_int confirm;
130 char *sk_provider;
131 } Identity;
132
133 struct idtable {
134 int nentries;
135 TAILQ_HEAD(idqueue, identity) idlist;
136 };
137
138 /* private key table */
139 struct idtable *idtab;
140
141 int max_fd = 0;
142
143 /* pid of shell == parent of agent */
144 pid_t parent_pid = -1;
145 time_t parent_alive_interval = 0;
146
147 /* pid of process for which cleanup_socket is applicable */
148 pid_t cleanup_pid = 0;
149
150 /* pathname and directory for AUTH_SOCKET */
151 char socket_name[PATH_MAX];
152 char socket_dir[PATH_MAX];
153
154 /* Pattern-list of allowed PKCS#11/Security key paths */
155 static char *allowed_providers;
156
157 /* locking */
158 #define LOCK_SIZE 32
159 #define LOCK_SALT_SIZE 16
160 #define LOCK_ROUNDS 1
161 int locked = 0;
162 u_char lock_pwhash[LOCK_SIZE];
163 u_char lock_salt[LOCK_SALT_SIZE];
164
165 extern char *__progname;
166
167 /* Default lifetime in seconds (0 == forever) */
168 static int lifetime = 0;
169
170 static int fingerprint_hash = SSH_FP_HASH_DEFAULT;
171
172 /* Refuse signing of non-SSH messages for web-origin FIDO keys */
173 static int restrict_websafe = 1;
174
175 /*
176 * Client connection count; incremented in new_socket() and decremented in
177 * close_socket(). When it reaches 0, ssh-agent will exit. Since it is
178 * normally initialized to 1, it will never reach 0. However, if the -x
179 * option is specified, it is initialized to 0 in main(); in that case,
180 * ssh-agent will exit as soon as it has had at least one client but no
181 * longer has any.
182 */
183 static int xcount = 1;
184
185 static void
close_socket(SocketEntry * e)186 close_socket(SocketEntry *e)
187 {
188 int last = 0;
189
190 if (e->type == AUTH_CONNECTION) {
191 debug("xcount %d -> %d", xcount, xcount - 1);
192 if (--xcount == 0)
193 last = 1;
194 }
195 close(e->fd);
196 sshbuf_free(e->input);
197 sshbuf_free(e->output);
198 sshbuf_free(e->request);
199 memset(e, '\0', sizeof(*e));
200 e->fd = -1;
201 e->type = AUTH_UNUSED;
202 if (last)
203 cleanup_exit(0);
204 }
205
206 static void
idtab_init(void)207 idtab_init(void)
208 {
209 idtab = xcalloc(1, sizeof(*idtab));
210 TAILQ_INIT(&idtab->idlist);
211 idtab->nentries = 0;
212 }
213
214 static void
free_identity(Identity * id)215 free_identity(Identity *id)
216 {
217 sshkey_free(id->key);
218 free(id->provider);
219 free(id->comment);
220 free(id->sk_provider);
221 free(id);
222 }
223
224 /* return matching private key for given public key */
225 static Identity *
lookup_identity(struct sshkey * key)226 lookup_identity(struct sshkey *key)
227 {
228 Identity *id;
229
230 TAILQ_FOREACH(id, &idtab->idlist, next) {
231 if (sshkey_equal(key, id->key))
232 return (id);
233 }
234 return (NULL);
235 }
236
237 /* Check confirmation of keysign request */
238 static int
confirm_key(Identity * id,const char * extra)239 confirm_key(Identity *id, const char *extra)
240 {
241 char *p;
242 int ret = -1;
243
244 p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT);
245 if (p != NULL &&
246 ask_permission("Allow use of key %s?\nKey fingerprint %s.%s%s",
247 id->comment, p,
248 extra == NULL ? "" : "\n", extra == NULL ? "" : extra))
249 ret = 0;
250 free(p);
251
252 return (ret);
253 }
254
255 static void
send_status(SocketEntry * e,int success)256 send_status(SocketEntry *e, int success)
257 {
258 int r;
259
260 if ((r = sshbuf_put_u32(e->output, 1)) != 0 ||
261 (r = sshbuf_put_u8(e->output, success ?
262 SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
263 fatal_fr(r, "compose");
264 }
265
266 /* send list of supported public keys to 'client' */
267 static void
process_request_identities(SocketEntry * e)268 process_request_identities(SocketEntry *e)
269 {
270 Identity *id;
271 struct sshbuf *msg;
272 int r;
273
274 debug2_f("entering");
275
276 if ((msg = sshbuf_new()) == NULL)
277 fatal_f("sshbuf_new failed");
278 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
279 (r = sshbuf_put_u32(msg, idtab->nentries)) != 0)
280 fatal_fr(r, "compose");
281 TAILQ_FOREACH(id, &idtab->idlist, next) {
282 if ((r = sshkey_puts_opts(id->key, msg,
283 SSHKEY_SERIALIZE_INFO)) != 0 ||
284 (r = sshbuf_put_cstring(msg, id->comment)) != 0) {
285 error_fr(r, "compose key/comment");
286 continue;
287 }
288 }
289 if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
290 fatal_fr(r, "enqueue");
291 sshbuf_free(msg);
292 }
293
294
295 static char *
agent_decode_alg(struct sshkey * key,u_int flags)296 agent_decode_alg(struct sshkey *key, u_int flags)
297 {
298 if (key->type == KEY_RSA) {
299 if (flags & SSH_AGENT_RSA_SHA2_256)
300 return "rsa-sha2-256";
301 else if (flags & SSH_AGENT_RSA_SHA2_512)
302 return "rsa-sha2-512";
303 } else if (key->type == KEY_RSA_CERT) {
304 if (flags & SSH_AGENT_RSA_SHA2_256)
305 return "[email protected]";
306 else if (flags & SSH_AGENT_RSA_SHA2_512)
307 return "[email protected]";
308 }
309 return NULL;
310 }
311
312 /*
313 * Attempt to parse the contents of a buffer as a SSH publickey userauth
314 * request, checking its contents for consistency and matching the embedded
315 * key against the one that is being used for signing.
316 * Note: does not modify msg buffer.
317 * Optionally extract the username and session ID from the request.
318 */
319 static int
parse_userauth_request(struct sshbuf * msg,const struct sshkey * expected_key,char ** userp,struct sshbuf ** sess_idp)320 parse_userauth_request(struct sshbuf *msg, const struct sshkey *expected_key,
321 char **userp, struct sshbuf **sess_idp)
322 {
323 struct sshbuf *b = NULL, *sess_id = NULL;
324 char *user = NULL, *service = NULL, *method = NULL, *pkalg = NULL;
325 int r;
326 u_char t, sig_follows;
327 struct sshkey *mkey = NULL;
328
329 if (userp != NULL)
330 *userp = NULL;
331 if (sess_idp != NULL)
332 *sess_idp = NULL;
333 if ((b = sshbuf_fromb(msg)) == NULL)
334 fatal_f("sshbuf_fromb");
335
336 /* SSH userauth request */
337 if ((r = sshbuf_froms(b, &sess_id)) != 0)
338 goto out;
339 if (sshbuf_len(sess_id) == 0) {
340 r = SSH_ERR_INVALID_FORMAT;
341 goto out;
342 }
343 if ((r = sshbuf_get_u8(b, &t)) != 0 || /* SSH2_MSG_USERAUTH_REQUEST */
344 (r = sshbuf_get_cstring(b, &user, NULL)) != 0 || /* server user */
345 (r = sshbuf_get_cstring(b, &service, NULL)) != 0 || /* service */
346 (r = sshbuf_get_cstring(b, &method, NULL)) != 0 || /* method */
347 (r = sshbuf_get_u8(b, &sig_follows)) != 0 || /* sig-follows */
348 (r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 || /* alg */
349 (r = sshkey_froms(b, &mkey)) != 0) /* key */
350 goto out;
351 if (t != SSH2_MSG_USERAUTH_REQUEST ||
352 sig_follows != 1 ||
353 strcmp(service, "ssh-connection") != 0 ||
354 !sshkey_equal(expected_key, mkey) ||
355 sshkey_type_from_name(pkalg) != expected_key->type) {
356 r = SSH_ERR_INVALID_FORMAT;
357 goto out;
358 }
359 if (strcmp(method, "publickey") != 0) {
360 r = SSH_ERR_INVALID_FORMAT;
361 goto out;
362 }
363 if (sshbuf_len(b) != 0) {
364 r = SSH_ERR_INVALID_FORMAT;
365 goto out;
366 }
367 /* success */
368 r = 0;
369 debug3_f("well formed userauth");
370 if (userp != NULL) {
371 *userp = user;
372 user = NULL;
373 }
374 if (sess_idp != NULL) {
375 *sess_idp = sess_id;
376 sess_id = NULL;
377 }
378 out:
379 sshbuf_free(b);
380 sshbuf_free(sess_id);
381 free(user);
382 free(service);
383 free(method);
384 free(pkalg);
385 sshkey_free(mkey);
386 return r;
387 }
388
389 /*
390 * Attempt to parse the contents of a buffer as a SSHSIG signature request.
391 * Note: does not modify buffer.
392 */
393 static int
parse_sshsig_request(struct sshbuf * msg)394 parse_sshsig_request(struct sshbuf *msg)
395 {
396 int r;
397 struct sshbuf *b;
398
399 if ((b = sshbuf_fromb(msg)) == NULL)
400 fatal_f("sshbuf_fromb");
401
402 if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) != 0 ||
403 (r = sshbuf_consume(b, 6)) != 0 ||
404 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* namespace */
405 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0 || /* reserved */
406 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* hashalg */
407 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0) /* H(msg) */
408 goto out;
409 if (sshbuf_len(b) != 0) {
410 r = SSH_ERR_INVALID_FORMAT;
411 goto out;
412 }
413 /* success */
414 r = 0;
415 out:
416 sshbuf_free(b);
417 return r;
418 }
419
420 /*
421 * This function inspects a message to be signed by a FIDO key that has a
422 * web-like application string (i.e. one that does not begin with "ssh:".
423 * It checks that the message is one of those expected for SSH operations
424 * (pubkey userauth, sshsig, CA key signing) to exclude signing challenges
425 * for the web.
426 */
427 static int
check_websafe_message_contents(struct sshkey * key,struct sshbuf * data)428 check_websafe_message_contents(struct sshkey *key, struct sshbuf *data)
429 {
430 if (parse_userauth_request(data, key, NULL, NULL) == 0) {
431 debug_f("signed data matches public key userauth request");
432 return 1;
433 }
434 if (parse_sshsig_request(data) == 0) {
435 debug_f("signed data matches SSHSIG signature request");
436 return 1;
437 }
438
439 /* XXX check CA signature operation */
440
441 error("web-origin key attempting to sign non-SSH message");
442 return 0;
443 }
444
445 /* ssh2 only */
446 static void
process_sign_request2(SocketEntry * e)447 process_sign_request2(SocketEntry *e)
448 {
449 u_char *signature = NULL;
450 size_t slen = 0;
451 u_int compat = 0, flags;
452 int r, ok = -1;
453 char *fp = NULL;
454 struct sshbuf *msg = NULL, *data = NULL;
455 struct sshkey *key = NULL;
456 struct identity *id;
457 struct notifier_ctx *notifier = NULL;
458
459 debug_f("entering");
460
461 if ((msg = sshbuf_new()) == NULL || (data = sshbuf_new()) == NULL)
462 fatal_f("sshbuf_new failed");
463 if ((r = sshkey_froms(e->request, &key)) != 0 ||
464 (r = sshbuf_get_stringb(e->request, data)) != 0 ||
465 (r = sshbuf_get_u32(e->request, &flags)) != 0) {
466 error_fr(r, "parse");
467 goto send;
468 }
469
470 if ((id = lookup_identity(key)) == NULL) {
471 verbose_f("%s key not found", sshkey_type(key));
472 goto send;
473 }
474 if (id->confirm && confirm_key(id, NULL) != 0) {
475 verbose_f("user refused key");
476 goto send;
477 }
478 if (sshkey_is_sk(id->key)) {
479 if (strncmp(id->key->sk_application, "ssh:", 4) != 0 &&
480 !check_websafe_message_contents(key, data)) {
481 /* error already logged */
482 goto send;
483 }
484 if ((id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD)) {
485 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
486 SSH_FP_DEFAULT)) == NULL)
487 fatal_f("fingerprint failed");
488 notifier = notify_start(0,
489 "Confirm user presence for key %s %s",
490 sshkey_type(id->key), fp);
491 }
492 }
493 /* XXX support PIN required FIDO keys */
494 if ((r = sshkey_sign(id->key, &signature, &slen,
495 sshbuf_ptr(data), sshbuf_len(data), agent_decode_alg(key, flags),
496 id->sk_provider, NULL, compat)) != 0) {
497 error_fr(r, "sshkey_sign");
498 goto send;
499 }
500 /* Success */
501 ok = 0;
502 send:
503 notify_complete(notifier, "User presence confirmed");
504
505 if (ok == 0) {
506 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
507 (r = sshbuf_put_string(msg, signature, slen)) != 0)
508 fatal_fr(r, "compose");
509 } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
510 fatal_fr(r, "compose failure");
511
512 if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
513 fatal_fr(r, "enqueue");
514
515 sshbuf_free(data);
516 sshbuf_free(msg);
517 sshkey_free(key);
518 free(fp);
519 free(signature);
520 }
521
522 /* shared */
523 static void
process_remove_identity(SocketEntry * e)524 process_remove_identity(SocketEntry *e)
525 {
526 int r, success = 0;
527 struct sshkey *key = NULL;
528 Identity *id;
529
530 debug2_f("entering");
531 if ((r = sshkey_froms(e->request, &key)) != 0) {
532 error_fr(r, "parse key");
533 goto done;
534 }
535 if ((id = lookup_identity(key)) == NULL) {
536 debug_f("key not found");
537 goto done;
538 }
539 /* We have this key, free it. */
540 if (idtab->nentries < 1)
541 fatal_f("internal error: nentries %d", idtab->nentries);
542 TAILQ_REMOVE(&idtab->idlist, id, next);
543 free_identity(id);
544 idtab->nentries--;
545 success = 1;
546 done:
547 sshkey_free(key);
548 send_status(e, success);
549 }
550
551 static void
process_remove_all_identities(SocketEntry * e)552 process_remove_all_identities(SocketEntry *e)
553 {
554 Identity *id;
555
556 debug2_f("entering");
557 /* Loop over all identities and clear the keys. */
558 for (id = TAILQ_FIRST(&idtab->idlist); id;
559 id = TAILQ_FIRST(&idtab->idlist)) {
560 TAILQ_REMOVE(&idtab->idlist, id, next);
561 free_identity(id);
562 }
563
564 /* Mark that there are no identities. */
565 idtab->nentries = 0;
566
567 /* Send success. */
568 send_status(e, 1);
569 }
570
571 /* removes expired keys and returns number of seconds until the next expiry */
572 static time_t
reaper(void)573 reaper(void)
574 {
575 time_t deadline = 0, now = monotime();
576 Identity *id, *nxt;
577
578 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
579 nxt = TAILQ_NEXT(id, next);
580 if (id->death == 0)
581 continue;
582 if (now >= id->death) {
583 debug("expiring key '%s'", id->comment);
584 TAILQ_REMOVE(&idtab->idlist, id, next);
585 free_identity(id);
586 idtab->nentries--;
587 } else
588 deadline = (deadline == 0) ? id->death :
589 MINIMUM(deadline, id->death);
590 }
591 if (deadline == 0 || deadline <= now)
592 return 0;
593 else
594 return (deadline - now);
595 }
596
597 static int
parse_key_constraint_extension(struct sshbuf * m,char ** sk_providerp)598 parse_key_constraint_extension(struct sshbuf *m, char **sk_providerp)
599 {
600 char *ext_name = NULL;
601 int r;
602
603 if ((r = sshbuf_get_cstring(m, &ext_name, NULL)) != 0) {
604 error_fr(r, "parse constraint extension");
605 goto out;
606 }
607 debug_f("constraint ext %s", ext_name);
608 if (strcmp(ext_name, "[email protected]") == 0) {
609 if (sk_providerp == NULL) {
610 error_f("%s not valid here", ext_name);
611 r = SSH_ERR_INVALID_FORMAT;
612 goto out;
613 }
614 if (*sk_providerp != NULL) {
615 error_f("%s already set", ext_name);
616 r = SSH_ERR_INVALID_FORMAT;
617 goto out;
618 }
619 if ((r = sshbuf_get_cstring(m, sk_providerp, NULL)) != 0) {
620 error_fr(r, "parse %s", ext_name);
621 goto out;
622 }
623 } else {
624 error_f("unsupported constraint \"%s\"", ext_name);
625 r = SSH_ERR_FEATURE_UNSUPPORTED;
626 goto out;
627 }
628 /* success */
629 r = 0;
630 out:
631 free(ext_name);
632 return r;
633 }
634
635 static int
parse_key_constraints(struct sshbuf * m,struct sshkey * k,time_t * deathp,u_int * secondsp,int * confirmp,char ** sk_providerp)636 parse_key_constraints(struct sshbuf *m, struct sshkey *k, time_t *deathp,
637 u_int *secondsp, int *confirmp, char **sk_providerp)
638 {
639 u_char ctype;
640 int r;
641 u_int seconds, maxsign = 0;
642
643 while (sshbuf_len(m)) {
644 if ((r = sshbuf_get_u8(m, &ctype)) != 0) {
645 error_fr(r, "parse constraint type");
646 goto out;
647 }
648 switch (ctype) {
649 case SSH_AGENT_CONSTRAIN_LIFETIME:
650 if (*deathp != 0) {
651 error_f("lifetime already set");
652 r = SSH_ERR_INVALID_FORMAT;
653 goto out;
654 }
655 if ((r = sshbuf_get_u32(m, &seconds)) != 0) {
656 error_fr(r, "parse lifetime constraint");
657 goto out;
658 }
659 *deathp = monotime() + seconds;
660 *secondsp = seconds;
661 break;
662 case SSH_AGENT_CONSTRAIN_CONFIRM:
663 if (*confirmp != 0) {
664 error_f("confirm already set");
665 r = SSH_ERR_INVALID_FORMAT;
666 goto out;
667 }
668 *confirmp = 1;
669 break;
670 case SSH_AGENT_CONSTRAIN_MAXSIGN:
671 if (k == NULL) {
672 error_f("maxsign not valid here");
673 r = SSH_ERR_INVALID_FORMAT;
674 goto out;
675 }
676 if (maxsign != 0) {
677 error_f("maxsign already set");
678 r = SSH_ERR_INVALID_FORMAT;
679 goto out;
680 }
681 if ((r = sshbuf_get_u32(m, &maxsign)) != 0) {
682 error_fr(r, "parse maxsign constraint");
683 goto out;
684 }
685 if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) {
686 error_fr(r, "enable maxsign");
687 goto out;
688 }
689 break;
690 case SSH_AGENT_CONSTRAIN_EXTENSION:
691 if ((r = parse_key_constraint_extension(m,
692 sk_providerp)) != 0)
693 goto out; /* error already logged */
694 break;
695 default:
696 error_f("Unknown constraint %d", ctype);
697 r = SSH_ERR_FEATURE_UNSUPPORTED;
698 goto out;
699 }
700 }
701 /* success */
702 r = 0;
703 out:
704 return r;
705 }
706
707 static void
process_add_identity(SocketEntry * e)708 process_add_identity(SocketEntry *e)
709 {
710 Identity *id;
711 int success = 0, confirm = 0;
712 char *fp, *comment = NULL, *sk_provider = NULL;
713 char canonical_provider[PATH_MAX];
714 time_t death = 0;
715 u_int seconds = 0;
716 struct sshkey *k = NULL;
717 int r = SSH_ERR_INTERNAL_ERROR;
718
719 debug2_f("entering");
720 if ((r = sshkey_private_deserialize(e->request, &k)) != 0 ||
721 k == NULL ||
722 (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) {
723 error_fr(r, "parse");
724 goto out;
725 }
726 if (parse_key_constraints(e->request, k, &death, &seconds, &confirm,
727 &sk_provider) != 0) {
728 error_f("failed to parse constraints");
729 sshbuf_reset(e->request);
730 goto out;
731 }
732
733 if (sk_provider != NULL) {
734 if (!sshkey_is_sk(k)) {
735 error("Cannot add provider: %s is not an "
736 "authenticator-hosted key", sshkey_type(k));
737 goto out;
738 }
739 if (strcasecmp(sk_provider, "internal") == 0) {
740 debug_f("internal provider");
741 } else {
742 if (realpath(sk_provider, canonical_provider) == NULL) {
743 verbose("failed provider \"%.100s\": "
744 "realpath: %s", sk_provider,
745 strerror(errno));
746 goto out;
747 }
748 free(sk_provider);
749 sk_provider = xstrdup(canonical_provider);
750 if (match_pattern_list(sk_provider,
751 allowed_providers, 0) != 1) {
752 error("Refusing add key: "
753 "provider %s not allowed", sk_provider);
754 goto out;
755 }
756 }
757 }
758 if ((r = sshkey_shield_private(k)) != 0) {
759 error_fr(r, "shield private");
760 goto out;
761 }
762 if (lifetime && !death)
763 death = monotime() + lifetime;
764 if ((id = lookup_identity(k)) == NULL) {
765 id = xcalloc(1, sizeof(Identity));
766 TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
767 /* Increment the number of identities. */
768 idtab->nentries++;
769 } else {
770 /* key state might have been updated */
771 sshkey_free(id->key);
772 free(id->comment);
773 free(id->sk_provider);
774 }
775 /* success */
776 id->key = k;
777 id->comment = comment;
778 id->death = death;
779 id->confirm = confirm;
780 id->sk_provider = sk_provider;
781
782 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT,
783 SSH_FP_DEFAULT)) == NULL)
784 fatal_f("sshkey_fingerprint failed");
785 debug_f("add %s %s \"%.100s\" (life: %u) (confirm: %u) "
786 "(provider: %s)", sshkey_ssh_name(k), fp, comment, seconds,
787 confirm, sk_provider == NULL ? "none" : sk_provider);
788 free(fp);
789 /* transferred */
790 k = NULL;
791 comment = NULL;
792 sk_provider = NULL;
793 success = 1;
794 out:
795 free(sk_provider);
796 free(comment);
797 sshkey_free(k);
798 send_status(e, success);
799 }
800
801 /* XXX todo: encrypt sensitive data with passphrase */
802 static void
process_lock_agent(SocketEntry * e,int lock)803 process_lock_agent(SocketEntry *e, int lock)
804 {
805 int r, success = 0, delay;
806 char *passwd;
807 u_char passwdhash[LOCK_SIZE];
808 static u_int fail_count = 0;
809 size_t pwlen;
810
811 debug2_f("entering");
812 /*
813 * This is deliberately fatal: the user has requested that we lock,
814 * but we can't parse their request properly. The only safe thing to
815 * do is abort.
816 */
817 if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0)
818 fatal_fr(r, "parse");
819 if (pwlen == 0) {
820 debug("empty password not supported");
821 } else if (locked && !lock) {
822 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
823 passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0)
824 fatal("bcrypt_pbkdf");
825 if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) {
826 debug("agent unlocked");
827 locked = 0;
828 fail_count = 0;
829 explicit_bzero(lock_pwhash, sizeof(lock_pwhash));
830 success = 1;
831 } else {
832 /* delay in 0.1s increments up to 10s */
833 if (fail_count < 100)
834 fail_count++;
835 delay = 100000 * fail_count;
836 debug("unlock failed, delaying %0.1lf seconds",
837 (double)delay/1000000);
838 usleep(delay);
839 }
840 explicit_bzero(passwdhash, sizeof(passwdhash));
841 } else if (!locked && lock) {
842 debug("agent locked");
843 locked = 1;
844 arc4random_buf(lock_salt, sizeof(lock_salt));
845 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
846 lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0)
847 fatal("bcrypt_pbkdf");
848 success = 1;
849 }
850 freezero(passwd, pwlen);
851 send_status(e, success);
852 }
853
854 static void
no_identities(SocketEntry * e)855 no_identities(SocketEntry *e)
856 {
857 struct sshbuf *msg;
858 int r;
859
860 if ((msg = sshbuf_new()) == NULL)
861 fatal_f("sshbuf_new failed");
862 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
863 (r = sshbuf_put_u32(msg, 0)) != 0 ||
864 (r = sshbuf_put_stringb(e->output, msg)) != 0)
865 fatal_fr(r, "compose");
866 sshbuf_free(msg);
867 }
868
869 #ifdef ENABLE_PKCS11
870 static void
process_add_smartcard_key(SocketEntry * e)871 process_add_smartcard_key(SocketEntry *e)
872 {
873 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
874 char **comments = NULL;
875 int r, i, count = 0, success = 0, confirm = 0;
876 u_int seconds = 0;
877 time_t death = 0;
878 struct sshkey **keys = NULL, *k;
879 Identity *id;
880
881 debug2_f("entering");
882 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
883 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
884 error_fr(r, "parse");
885 goto send;
886 }
887 if (parse_key_constraints(e->request, NULL, &death, &seconds, &confirm,
888 NULL) != 0) {
889 error_f("failed to parse constraints");
890 goto send;
891 }
892 if (realpath(provider, canonical_provider) == NULL) {
893 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
894 provider, strerror(errno));
895 goto send;
896 }
897 if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) {
898 verbose("refusing PKCS#11 add of \"%.100s\": "
899 "provider not allowed", canonical_provider);
900 goto send;
901 }
902 debug_f("add %.100s", canonical_provider);
903 if (lifetime && !death)
904 death = monotime() + lifetime;
905
906 count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments);
907 for (i = 0; i < count; i++) {
908 k = keys[i];
909 if (lookup_identity(k) == NULL) {
910 id = xcalloc(1, sizeof(Identity));
911 id->key = k;
912 keys[i] = NULL; /* transferred */
913 id->provider = xstrdup(canonical_provider);
914 if (*comments[i] != '\0') {
915 id->comment = comments[i];
916 comments[i] = NULL; /* transferred */
917 } else {
918 id->comment = xstrdup(canonical_provider);
919 }
920 id->death = death;
921 id->confirm = confirm;
922 TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
923 idtab->nentries++;
924 success = 1;
925 }
926 /* XXX update constraints for existing keys */
927 sshkey_free(keys[i]);
928 free(comments[i]);
929 }
930 send:
931 free(pin);
932 free(provider);
933 free(keys);
934 free(comments);
935 send_status(e, success);
936 }
937
938 static void
process_remove_smartcard_key(SocketEntry * e)939 process_remove_smartcard_key(SocketEntry *e)
940 {
941 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
942 int r, success = 0;
943 Identity *id, *nxt;
944
945 debug2_f("entering");
946 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
947 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
948 error_fr(r, "parse");
949 goto send;
950 }
951 free(pin);
952
953 if (realpath(provider, canonical_provider) == NULL) {
954 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
955 provider, strerror(errno));
956 goto send;
957 }
958
959 debug_f("remove %.100s", canonical_provider);
960 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
961 nxt = TAILQ_NEXT(id, next);
962 /* Skip file--based keys */
963 if (id->provider == NULL)
964 continue;
965 if (!strcmp(canonical_provider, id->provider)) {
966 TAILQ_REMOVE(&idtab->idlist, id, next);
967 free_identity(id);
968 idtab->nentries--;
969 }
970 }
971 if (pkcs11_del_provider(canonical_provider) == 0)
972 success = 1;
973 else
974 error_f("pkcs11_del_provider failed");
975 send:
976 free(provider);
977 send_status(e, success);
978 }
979 #endif /* ENABLE_PKCS11 */
980
981 /*
982 * dispatch incoming message.
983 * returns 1 on success, 0 for incomplete messages or -1 on error.
984 */
985 static int
process_message(u_int socknum)986 process_message(u_int socknum)
987 {
988 u_int msg_len;
989 u_char type;
990 const u_char *cp;
991 int r;
992 SocketEntry *e;
993
994 if (socknum >= sockets_alloc)
995 fatal_f("sock %u >= allocated %u", socknum, sockets_alloc);
996 e = &sockets[socknum];
997
998 if (sshbuf_len(e->input) < 5)
999 return 0; /* Incomplete message header. */
1000 cp = sshbuf_ptr(e->input);
1001 msg_len = PEEK_U32(cp);
1002 if (msg_len > AGENT_MAX_LEN) {
1003 debug_f("socket %u (fd=%d) message too long %u > %u",
1004 socknum, e->fd, msg_len, AGENT_MAX_LEN);
1005 return -1;
1006 }
1007 if (sshbuf_len(e->input) < msg_len + 4)
1008 return 0; /* Incomplete message body. */
1009
1010 /* move the current input to e->request */
1011 sshbuf_reset(e->request);
1012 if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 ||
1013 (r = sshbuf_get_u8(e->request, &type)) != 0) {
1014 if (r == SSH_ERR_MESSAGE_INCOMPLETE ||
1015 r == SSH_ERR_STRING_TOO_LARGE) {
1016 error_fr(r, "parse");
1017 return -1;
1018 }
1019 fatal_fr(r, "parse");
1020 }
1021
1022 debug_f("socket %u (fd=%d) type %d", socknum, e->fd, type);
1023
1024 /* check whether agent is locked */
1025 if (locked && type != SSH_AGENTC_UNLOCK) {
1026 sshbuf_reset(e->request);
1027 switch (type) {
1028 case SSH2_AGENTC_REQUEST_IDENTITIES:
1029 /* send empty lists */
1030 no_identities(e);
1031 break;
1032 default:
1033 /* send a fail message for all other request types */
1034 send_status(e, 0);
1035 }
1036 return 1;
1037 }
1038
1039 switch (type) {
1040 case SSH_AGENTC_LOCK:
1041 case SSH_AGENTC_UNLOCK:
1042 process_lock_agent(e, type == SSH_AGENTC_LOCK);
1043 break;
1044 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
1045 process_remove_all_identities(e); /* safe for !WITH_SSH1 */
1046 break;
1047 /* ssh2 */
1048 case SSH2_AGENTC_SIGN_REQUEST:
1049 process_sign_request2(e);
1050 break;
1051 case SSH2_AGENTC_REQUEST_IDENTITIES:
1052 process_request_identities(e);
1053 break;
1054 case SSH2_AGENTC_ADD_IDENTITY:
1055 case SSH2_AGENTC_ADD_ID_CONSTRAINED:
1056 process_add_identity(e);
1057 break;
1058 case SSH2_AGENTC_REMOVE_IDENTITY:
1059 process_remove_identity(e);
1060 break;
1061 case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
1062 process_remove_all_identities(e);
1063 break;
1064 #ifdef ENABLE_PKCS11
1065 case SSH_AGENTC_ADD_SMARTCARD_KEY:
1066 case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
1067 process_add_smartcard_key(e);
1068 break;
1069 case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
1070 process_remove_smartcard_key(e);
1071 break;
1072 #endif /* ENABLE_PKCS11 */
1073 default:
1074 /* Unknown message. Respond with failure. */
1075 error("Unknown message %d", type);
1076 sshbuf_reset(e->request);
1077 send_status(e, 0);
1078 break;
1079 }
1080 return 1;
1081 }
1082
1083 static void
new_socket(sock_type type,int fd)1084 new_socket(sock_type type, int fd)
1085 {
1086 u_int i, old_alloc, new_alloc;
1087
1088 debug_f("type = %s", type == AUTH_CONNECTION ? "CONNECTION" :
1089 (type == AUTH_SOCKET ? "SOCKET" : "UNKNOWN"));
1090 if (type == AUTH_CONNECTION) {
1091 debug("xcount %d -> %d", xcount, xcount + 1);
1092 ++xcount;
1093 }
1094 set_nonblock(fd);
1095
1096 if (fd > max_fd)
1097 max_fd = fd;
1098
1099 for (i = 0; i < sockets_alloc; i++)
1100 if (sockets[i].type == AUTH_UNUSED) {
1101 sockets[i].fd = fd;
1102 if ((sockets[i].input = sshbuf_new()) == NULL ||
1103 (sockets[i].output = sshbuf_new()) == NULL ||
1104 (sockets[i].request = sshbuf_new()) == NULL)
1105 fatal_f("sshbuf_new failed");
1106 sockets[i].type = type;
1107 return;
1108 }
1109 old_alloc = sockets_alloc;
1110 new_alloc = sockets_alloc + 10;
1111 sockets = xrecallocarray(sockets, old_alloc, new_alloc,
1112 sizeof(sockets[0]));
1113 for (i = old_alloc; i < new_alloc; i++)
1114 sockets[i].type = AUTH_UNUSED;
1115 sockets_alloc = new_alloc;
1116 sockets[old_alloc].fd = fd;
1117 if ((sockets[old_alloc].input = sshbuf_new()) == NULL ||
1118 (sockets[old_alloc].output = sshbuf_new()) == NULL ||
1119 (sockets[old_alloc].request = sshbuf_new()) == NULL)
1120 fatal_f("sshbuf_new failed");
1121 sockets[old_alloc].type = type;
1122 }
1123
1124 static int
handle_socket_read(u_int socknum)1125 handle_socket_read(u_int socknum)
1126 {
1127 struct sockaddr_un sunaddr;
1128 socklen_t slen;
1129 uid_t euid;
1130 gid_t egid;
1131 int fd;
1132
1133 slen = sizeof(sunaddr);
1134 fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen);
1135 if (fd == -1) {
1136 error("accept from AUTH_SOCKET: %s", strerror(errno));
1137 return -1;
1138 }
1139 if (getpeereid(fd, &euid, &egid) == -1) {
1140 error("getpeereid %d failed: %s", fd, strerror(errno));
1141 close(fd);
1142 return -1;
1143 }
1144 if ((euid != 0) && (getuid() != euid)) {
1145 error("uid mismatch: peer euid %u != uid %u",
1146 (u_int) euid, (u_int) getuid());
1147 close(fd);
1148 return -1;
1149 }
1150 new_socket(AUTH_CONNECTION, fd);
1151 return 0;
1152 }
1153
1154 static int
handle_conn_read(u_int socknum)1155 handle_conn_read(u_int socknum)
1156 {
1157 char buf[AGENT_RBUF_LEN];
1158 ssize_t len;
1159 int r;
1160
1161 if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) {
1162 if (len == -1) {
1163 if (errno == EAGAIN || errno == EINTR)
1164 return 0;
1165 error_f("read error on socket %u (fd %d): %s",
1166 socknum, sockets[socknum].fd, strerror(errno));
1167 }
1168 return -1;
1169 }
1170 if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0)
1171 fatal_fr(r, "compose");
1172 explicit_bzero(buf, sizeof(buf));
1173 for (;;) {
1174 if ((r = process_message(socknum)) == -1)
1175 return -1;
1176 else if (r == 0)
1177 break;
1178 }
1179 return 0;
1180 }
1181
1182 static int
handle_conn_write(u_int socknum)1183 handle_conn_write(u_int socknum)
1184 {
1185 ssize_t len;
1186 int r;
1187
1188 if (sshbuf_len(sockets[socknum].output) == 0)
1189 return 0; /* shouldn't happen */
1190 if ((len = write(sockets[socknum].fd,
1191 sshbuf_ptr(sockets[socknum].output),
1192 sshbuf_len(sockets[socknum].output))) <= 0) {
1193 if (len == -1) {
1194 if (errno == EAGAIN || errno == EINTR)
1195 return 0;
1196 error_f("read error on socket %u (fd %d): %s",
1197 socknum, sockets[socknum].fd, strerror(errno));
1198 }
1199 return -1;
1200 }
1201 if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0)
1202 fatal_fr(r, "consume");
1203 return 0;
1204 }
1205
1206 static void
after_poll(struct pollfd * pfd,size_t npfd,u_int maxfds)1207 after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds)
1208 {
1209 size_t i;
1210 u_int socknum, activefds = npfd;
1211
1212 for (i = 0; i < npfd; i++) {
1213 if (pfd[i].revents == 0)
1214 continue;
1215 /* Find sockets entry */
1216 for (socknum = 0; socknum < sockets_alloc; socknum++) {
1217 if (sockets[socknum].type != AUTH_SOCKET &&
1218 sockets[socknum].type != AUTH_CONNECTION)
1219 continue;
1220 if (pfd[i].fd == sockets[socknum].fd)
1221 break;
1222 }
1223 if (socknum >= sockets_alloc) {
1224 error_f("no socket for fd %d", pfd[i].fd);
1225 continue;
1226 }
1227 /* Process events */
1228 switch (sockets[socknum].type) {
1229 case AUTH_SOCKET:
1230 if ((pfd[i].revents & (POLLIN|POLLERR)) == 0)
1231 break;
1232 if (npfd > maxfds) {
1233 debug3("out of fds (active %u >= limit %u); "
1234 "skipping accept", activefds, maxfds);
1235 break;
1236 }
1237 if (handle_socket_read(socknum) == 0)
1238 activefds++;
1239 break;
1240 case AUTH_CONNECTION:
1241 if ((pfd[i].revents & (POLLIN|POLLERR)) != 0 &&
1242 handle_conn_read(socknum) != 0) {
1243 goto close_sock;
1244 }
1245 if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 &&
1246 handle_conn_write(socknum) != 0) {
1247 close_sock:
1248 if (activefds == 0)
1249 fatal("activefds == 0 at close_sock");
1250 close_socket(&sockets[socknum]);
1251 activefds--;
1252 break;
1253 }
1254 break;
1255 default:
1256 break;
1257 }
1258 }
1259 }
1260
1261 static int
prepare_poll(struct pollfd ** pfdp,size_t * npfdp,int * timeoutp,u_int maxfds)1262 prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp, u_int maxfds)
1263 {
1264 struct pollfd *pfd = *pfdp;
1265 size_t i, j, npfd = 0;
1266 time_t deadline;
1267 int r;
1268
1269 /* Count active sockets */
1270 for (i = 0; i < sockets_alloc; i++) {
1271 switch (sockets[i].type) {
1272 case AUTH_SOCKET:
1273 case AUTH_CONNECTION:
1274 npfd++;
1275 break;
1276 case AUTH_UNUSED:
1277 break;
1278 default:
1279 fatal("Unknown socket type %d", sockets[i].type);
1280 break;
1281 }
1282 }
1283 if (npfd != *npfdp &&
1284 (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL)
1285 fatal_f("recallocarray failed");
1286 *pfdp = pfd;
1287 *npfdp = npfd;
1288
1289 for (i = j = 0; i < sockets_alloc; i++) {
1290 switch (sockets[i].type) {
1291 case AUTH_SOCKET:
1292 if (npfd > maxfds) {
1293 debug3("out of fds (active %zu >= limit %u); "
1294 "skipping arming listener", npfd, maxfds);
1295 break;
1296 }
1297 pfd[j].fd = sockets[i].fd;
1298 pfd[j].revents = 0;
1299 pfd[j].events = POLLIN;
1300 j++;
1301 break;
1302 case AUTH_CONNECTION:
1303 pfd[j].fd = sockets[i].fd;
1304 pfd[j].revents = 0;
1305 /*
1306 * Only prepare to read if we can handle a full-size
1307 * input read buffer and enqueue a max size reply..
1308 */
1309 if ((r = sshbuf_check_reserve(sockets[i].input,
1310 AGENT_RBUF_LEN)) == 0 &&
1311 (r = sshbuf_check_reserve(sockets[i].output,
1312 AGENT_MAX_LEN)) == 0)
1313 pfd[j].events = POLLIN;
1314 else if (r != SSH_ERR_NO_BUFFER_SPACE)
1315 fatal_fr(r, "reserve");
1316 if (sshbuf_len(sockets[i].output) > 0)
1317 pfd[j].events |= POLLOUT;
1318 j++;
1319 break;
1320 default:
1321 break;
1322 }
1323 }
1324 deadline = reaper();
1325 if (parent_alive_interval != 0)
1326 deadline = (deadline == 0) ? parent_alive_interval :
1327 MINIMUM(deadline, parent_alive_interval);
1328 if (deadline == 0) {
1329 *timeoutp = -1; /* INFTIM */
1330 } else {
1331 if (deadline > INT_MAX / 1000)
1332 *timeoutp = INT_MAX / 1000;
1333 else
1334 *timeoutp = deadline * 1000;
1335 }
1336 return (1);
1337 }
1338
1339 static void
cleanup_socket(void)1340 cleanup_socket(void)
1341 {
1342 if (cleanup_pid != 0 && getpid() != cleanup_pid)
1343 return;
1344 debug_f("cleanup");
1345 if (socket_name[0])
1346 unlink(socket_name);
1347 if (socket_dir[0])
1348 rmdir(socket_dir);
1349 }
1350
1351 void
cleanup_exit(int i)1352 cleanup_exit(int i)
1353 {
1354 cleanup_socket();
1355 _exit(i);
1356 }
1357
1358 /*ARGSUSED*/
1359 static void
cleanup_handler(int sig)1360 cleanup_handler(int sig)
1361 {
1362 cleanup_socket();
1363 #ifdef ENABLE_PKCS11
1364 pkcs11_terminate();
1365 #endif
1366 _exit(2);
1367 }
1368
1369 static void
check_parent_exists(void)1370 check_parent_exists(void)
1371 {
1372 /*
1373 * If our parent has exited then getppid() will return (pid_t)1,
1374 * so testing for that should be safe.
1375 */
1376 if (parent_pid != -1 && getppid() != parent_pid) {
1377 /* printf("Parent has died - Authentication agent exiting.\n"); */
1378 cleanup_socket();
1379 _exit(2);
1380 }
1381 }
1382
1383 static void
usage(void)1384 usage(void)
1385 {
1386 fprintf(stderr,
1387 "usage: ssh-agent [-c | -s] [-Ddx] [-a bind_address] [-E fingerprint_hash]\n"
1388 " [-P allowed_providers] [-t life]\n"
1389 " ssh-agent [-a bind_address] [-E fingerprint_hash] [-P allowed_providers]\n"
1390 " [-t life] command [arg ...]\n"
1391 " ssh-agent [-c | -s] -k\n");
1392 exit(1);
1393 }
1394
1395 int
main(int ac,char ** av)1396 main(int ac, char **av)
1397 {
1398 int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0;
1399 int sock, ch, result, saved_errno;
1400 char *shell, *format, *pidstr, *agentsocket = NULL;
1401 #ifdef HAVE_SETRLIMIT
1402 struct rlimit rlim;
1403 #endif
1404 extern int optind;
1405 extern char *optarg;
1406 pid_t pid;
1407 char pidstrbuf[1 + 3 * sizeof pid];
1408 size_t len;
1409 mode_t prev_mask;
1410 int timeout = -1; /* INFTIM */
1411 struct pollfd *pfd = NULL;
1412 size_t npfd = 0;
1413 u_int maxfds;
1414
1415 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1416 sanitise_stdfd();
1417
1418 /* drop */
1419 setegid(getgid());
1420 setgid(getgid());
1421 setuid(geteuid());
1422
1423 platform_disable_tracing(0); /* strict=no */
1424
1425 #ifdef RLIMIT_NOFILE
1426 if (getrlimit(RLIMIT_NOFILE, &rlim) == -1)
1427 fatal("%s: getrlimit: %s", __progname, strerror(errno));
1428 #endif
1429
1430 __progname = ssh_get_progname(av[0]);
1431 seed_rng();
1432
1433 while ((ch = getopt(ac, av, "cDdksE:a:O:P:t:x")) != -1) {
1434 switch (ch) {
1435 case 'E':
1436 fingerprint_hash = ssh_digest_alg_by_name(optarg);
1437 if (fingerprint_hash == -1)
1438 fatal("Invalid hash algorithm \"%s\"", optarg);
1439 break;
1440 case 'c':
1441 if (s_flag)
1442 usage();
1443 c_flag++;
1444 break;
1445 case 'k':
1446 k_flag++;
1447 break;
1448 case 'O':
1449 if (strcmp(optarg, "no-restrict-websafe") == 0)
1450 restrict_websafe = 0;
1451 else
1452 fatal("Unknown -O option");
1453 break;
1454 case 'P':
1455 if (allowed_providers != NULL)
1456 fatal("-P option already specified");
1457 allowed_providers = xstrdup(optarg);
1458 break;
1459 case 's':
1460 if (c_flag)
1461 usage();
1462 s_flag++;
1463 break;
1464 case 'd':
1465 if (d_flag || D_flag)
1466 usage();
1467 d_flag++;
1468 break;
1469 case 'D':
1470 if (d_flag || D_flag)
1471 usage();
1472 D_flag++;
1473 break;
1474 case 'a':
1475 agentsocket = optarg;
1476 break;
1477 case 't':
1478 if ((lifetime = convtime(optarg)) == -1) {
1479 fprintf(stderr, "Invalid lifetime\n");
1480 usage();
1481 }
1482 break;
1483 case 'x':
1484 xcount = 0;
1485 break;
1486 default:
1487 usage();
1488 }
1489 }
1490 ac -= optind;
1491 av += optind;
1492
1493 if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag))
1494 usage();
1495
1496 if (allowed_providers == NULL)
1497 allowed_providers = xstrdup(DEFAULT_ALLOWED_PROVIDERS);
1498
1499 if (ac == 0 && !c_flag && !s_flag) {
1500 shell = getenv("SHELL");
1501 if (shell != NULL && (len = strlen(shell)) > 2 &&
1502 strncmp(shell + len - 3, "csh", 3) == 0)
1503 c_flag = 1;
1504 }
1505 if (k_flag) {
1506 const char *errstr = NULL;
1507
1508 pidstr = getenv(SSH_AGENTPID_ENV_NAME);
1509 if (pidstr == NULL) {
1510 fprintf(stderr, "%s not set, cannot kill agent\n",
1511 SSH_AGENTPID_ENV_NAME);
1512 exit(1);
1513 }
1514 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr);
1515 if (errstr) {
1516 fprintf(stderr,
1517 "%s=\"%s\", which is not a good PID: %s\n",
1518 SSH_AGENTPID_ENV_NAME, pidstr, errstr);
1519 exit(1);
1520 }
1521 if (kill(pid, SIGTERM) == -1) {
1522 perror("kill");
1523 exit(1);
1524 }
1525 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n";
1526 printf(format, SSH_AUTHSOCKET_ENV_NAME);
1527 printf(format, SSH_AGENTPID_ENV_NAME);
1528 printf("echo Agent pid %ld killed;\n", (long)pid);
1529 exit(0);
1530 }
1531
1532 /*
1533 * Minimum file descriptors:
1534 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) +
1535 * a few spare for libc / stack protectors / sanitisers, etc.
1536 */
1537 #define SSH_AGENT_MIN_FDS (3+1+1+1+4)
1538 if (rlim.rlim_cur < SSH_AGENT_MIN_FDS)
1539 fatal("%s: file descriptor rlimit %lld too low (minimum %u)",
1540 __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS);
1541 maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS;
1542
1543 parent_pid = getpid();
1544
1545 if (agentsocket == NULL) {
1546 /* Create private directory for agent socket */
1547 mktemp_proto(socket_dir, sizeof(socket_dir));
1548 if (mkdtemp(socket_dir) == NULL) {
1549 perror("mkdtemp: private socket dir");
1550 exit(1);
1551 }
1552 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
1553 (long)parent_pid);
1554 } else {
1555 /* Try to use specified agent socket */
1556 socket_dir[0] = '\0';
1557 strlcpy(socket_name, agentsocket, sizeof socket_name);
1558 }
1559
1560 /*
1561 * Create socket early so it will exist before command gets run from
1562 * the parent.
1563 */
1564 prev_mask = umask(0177);
1565 sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
1566 if (sock < 0) {
1567 /* XXX - unix_listener() calls error() not perror() */
1568 *socket_name = '\0'; /* Don't unlink any existing file */
1569 cleanup_exit(1);
1570 }
1571 umask(prev_mask);
1572
1573 /*
1574 * Fork, and have the parent execute the command, if any, or present
1575 * the socket data. The child continues as the authentication agent.
1576 */
1577 if (D_flag || d_flag) {
1578 log_init(__progname,
1579 d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO,
1580 SYSLOG_FACILITY_AUTH, 1);
1581 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
1582 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
1583 SSH_AUTHSOCKET_ENV_NAME);
1584 printf("echo Agent pid %ld;\n", (long)parent_pid);
1585 fflush(stdout);
1586 goto skip;
1587 }
1588 pid = fork();
1589 if (pid == -1) {
1590 perror("fork");
1591 cleanup_exit(1);
1592 }
1593 if (pid != 0) { /* Parent - execute the given command. */
1594 close(sock);
1595 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid);
1596 if (ac == 0) {
1597 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
1598 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
1599 SSH_AUTHSOCKET_ENV_NAME);
1600 printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf,
1601 SSH_AGENTPID_ENV_NAME);
1602 printf("echo Agent pid %ld;\n", (long)pid);
1603 exit(0);
1604 }
1605 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
1606 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
1607 perror("setenv");
1608 exit(1);
1609 }
1610 execvp(av[0], av);
1611 perror(av[0]);
1612 exit(1);
1613 }
1614 /* child */
1615 log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0);
1616
1617 if (setsid() == -1) {
1618 error("setsid: %s", strerror(errno));
1619 cleanup_exit(1);
1620 }
1621
1622 (void)chdir("/");
1623 if (stdfd_devnull(1, 1, 1) == -1)
1624 error_f("stdfd_devnull failed");
1625
1626 #ifdef HAVE_SETRLIMIT
1627 /* deny core dumps, since memory contains unencrypted private keys */
1628 rlim.rlim_cur = rlim.rlim_max = 0;
1629 if (setrlimit(RLIMIT_CORE, &rlim) == -1) {
1630 error("setrlimit RLIMIT_CORE: %s", strerror(errno));
1631 cleanup_exit(1);
1632 }
1633 #endif
1634
1635 skip:
1636
1637 cleanup_pid = getpid();
1638
1639 #ifdef ENABLE_PKCS11
1640 pkcs11_init(0);
1641 #endif
1642 new_socket(AUTH_SOCKET, sock);
1643 if (ac > 0)
1644 parent_alive_interval = 10;
1645 idtab_init();
1646 ssh_signal(SIGPIPE, SIG_IGN);
1647 ssh_signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN);
1648 ssh_signal(SIGHUP, cleanup_handler);
1649 ssh_signal(SIGTERM, cleanup_handler);
1650
1651 if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1)
1652 fatal("%s: pledge: %s", __progname, strerror(errno));
1653 platform_pledge_agent();
1654
1655 while (1) {
1656 prepare_poll(&pfd, &npfd, &timeout, maxfds);
1657 result = poll(pfd, npfd, timeout);
1658 saved_errno = errno;
1659 if (parent_alive_interval != 0)
1660 check_parent_exists();
1661 (void) reaper(); /* remove expired keys */
1662 if (result == -1) {
1663 if (saved_errno == EINTR)
1664 continue;
1665 fatal("poll: %s", strerror(saved_errno));
1666 } else if (result > 0)
1667 after_poll(pfd, npfd, maxfds);
1668 }
1669 /* NOTREACHED */
1670 }
1671