1 /* $OpenBSD: ssh-agent.c,v 1.278 2021/04/03 06:18:41 djm Exp $ */
2 /*
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, 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
39 #include <sys/types.h>
40 #include <sys/param.h>
41 #include <sys/resource.h>
42 #include <sys/stat.h>
43 #include <sys/socket.h>
44 #include <sys/wait.h>
45 #ifdef HAVE_SYS_TIME_H
46 # include <sys/time.h>
47 #endif
48 #ifdef HAVE_SYS_UN_H
49 # include <sys/un.h>
50 #endif
51 #include "openbsd-compat/sys-queue.h"
52
53 #ifdef WITH_OPENSSL
54 #include <openssl/evp.h>
55 #include "openbsd-compat/openssl-compat.h"
56 #endif
57
58 #include <errno.h>
59 #include <fcntl.h>
60 #include <limits.h>
61 #ifdef HAVE_PATHS_H
62 # include <paths.h>
63 #endif
64 #ifdef HAVE_POLL_H
65 # include <poll.h>
66 #endif
67 #include <signal.h>
68 #include <stdarg.h>
69 #include <stdio.h>
70 #include <stdlib.h>
71 #include <time.h>
72 #include <string.h>
73 #include <unistd.h>
74 #ifdef HAVE_UTIL_H
75 # include <util.h>
76 #endif
77
78 #include "xmalloc.h"
79 #include "ssh.h"
80 #include "ssh2.h"
81 #include "sshbuf.h"
82 #include "sshkey.h"
83 #include "authfd.h"
84 #include "compat.h"
85 #include "log.h"
86 #include "misc.h"
87 #include "digest.h"
88 #include "ssherr.h"
89 #include "match.h"
90 #include "msg.h"
91 #include "ssherr.h"
92 #include "pathnames.h"
93 #include "ssh-pkcs11.h"
94 #include "sk-api.h"
95
96 #ifndef DEFAULT_ALLOWED_PROVIDERS
97 # define DEFAULT_ALLOWED_PROVIDERS "/usr/lib*/*,/usr/local/lib*/*"
98 #endif
99
100 /* Maximum accepted message length */
101 #define AGENT_MAX_LEN (256*1024)
102 /* Maximum bytes to read from client socket */
103 #define AGENT_RBUF_LEN (4096)
104
105 typedef enum {
106 AUTH_UNUSED = 0,
107 AUTH_SOCKET = 1,
108 AUTH_CONNECTION = 2,
109 } sock_type;
110
111 typedef struct socket_entry {
112 int fd;
113 sock_type type;
114 struct sshbuf *input;
115 struct sshbuf *output;
116 struct sshbuf *request;
117 } SocketEntry;
118
119 u_int sockets_alloc = 0;
120 SocketEntry *sockets = NULL;
121
122 typedef struct identity {
123 TAILQ_ENTRY(identity) next;
124 struct sshkey *key;
125 char *comment;
126 char *provider;
127 time_t death;
128 u_int confirm;
129 char *sk_provider;
130 } Identity;
131
132 struct idtable {
133 int nentries;
134 TAILQ_HEAD(idqueue, identity) idlist;
135 };
136
137 /* private key table */
138 struct idtable *idtab;
139
140 int max_fd = 0;
141
142 /* pid of shell == parent of agent */
143 pid_t parent_pid = -1;
144 time_t parent_alive_interval = 0;
145
146 /* pid of process for which cleanup_socket is applicable */
147 pid_t cleanup_pid = 0;
148
149 /* pathname and directory for AUTH_SOCKET */
150 char socket_name[PATH_MAX];
151 char socket_dir[PATH_MAX];
152
153 /* Pattern-list of allowed PKCS#11/Security key paths */
154 static char *allowed_providers;
155
156 /* locking */
157 #define LOCK_SIZE 32
158 #define LOCK_SALT_SIZE 16
159 #define LOCK_ROUNDS 1
160 int locked = 0;
161 u_char lock_pwhash[LOCK_SIZE];
162 u_char lock_salt[LOCK_SALT_SIZE];
163
164 extern char *__progname;
165
166 /* Default lifetime in seconds (0 == forever) */
167 static int lifetime = 0;
168
169 static int fingerprint_hash = SSH_FP_HASH_DEFAULT;
170
171 /* Refuse signing of non-SSH messages for web-origin FIDO keys */
172 static int restrict_websafe = 1;
173
174 /*
175 * Client connection count; incremented in new_socket() and decremented in
176 * close_socket(). When it reaches 0, ssh-agent will exit. Since it is
177 * normally initialized to 1, it will never reach 0. However, if the -x
178 * option is specified, it is initialized to 0 in main(); in that case,
179 * ssh-agent will exit as soon as it has had at least one client but no
180 * longer has any.
181 */
182 static int xcount = 1;
183
184 static void
close_socket(SocketEntry * e)185 close_socket(SocketEntry *e)
186 {
187 int last = 0;
188
189 if (e->type == AUTH_CONNECTION) {
190 debug("xcount %d -> %d", xcount, xcount - 1);
191 if (--xcount == 0)
192 last = 1;
193 }
194 close(e->fd);
195 sshbuf_free(e->input);
196 sshbuf_free(e->output);
197 sshbuf_free(e->request);
198 memset(e, '\0', sizeof(*e));
199 e->fd = -1;
200 e->type = AUTH_UNUSED;
201 if (last)
202 cleanup_exit(0);
203 }
204
205 static void
idtab_init(void)206 idtab_init(void)
207 {
208 idtab = xcalloc(1, sizeof(*idtab));
209 TAILQ_INIT(&idtab->idlist);
210 idtab->nentries = 0;
211 }
212
213 static void
free_identity(Identity * id)214 free_identity(Identity *id)
215 {
216 sshkey_free(id->key);
217 free(id->provider);
218 free(id->comment);
219 free(id->sk_provider);
220 free(id);
221 }
222
223 /* return matching private key for given public key */
224 static Identity *
lookup_identity(struct sshkey * key)225 lookup_identity(struct sshkey *key)
226 {
227 Identity *id;
228
229 TAILQ_FOREACH(id, &idtab->idlist, next) {
230 if (sshkey_equal(key, id->key))
231 return (id);
232 }
233 return (NULL);
234 }
235
236 /* Check confirmation of keysign request */
237 static int
confirm_key(Identity * id,const char * extra)238 confirm_key(Identity *id, const char *extra)
239 {
240 char *p;
241 int ret = -1;
242
243 p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT);
244 if (p != NULL &&
245 ask_permission("Allow use of key %s?\nKey fingerprint %s.%s%s",
246 id->comment, p,
247 extra == NULL ? "" : "\n", extra == NULL ? "" : extra))
248 ret = 0;
249 free(p);
250
251 return (ret);
252 }
253
254 static void
send_status(SocketEntry * e,int success)255 send_status(SocketEntry *e, int success)
256 {
257 int r;
258
259 if ((r = sshbuf_put_u32(e->output, 1)) != 0 ||
260 (r = sshbuf_put_u8(e->output, success ?
261 SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
262 fatal_fr(r, "compose");
263 }
264
265 /* send list of supported public keys to 'client' */
266 static void
process_request_identities(SocketEntry * e)267 process_request_identities(SocketEntry *e)
268 {
269 Identity *id;
270 struct sshbuf *msg;
271 int r;
272
273 debug2_f("entering");
274
275 if ((msg = sshbuf_new()) == NULL)
276 fatal_f("sshbuf_new failed");
277 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
278 (r = sshbuf_put_u32(msg, idtab->nentries)) != 0)
279 fatal_fr(r, "compose");
280 TAILQ_FOREACH(id, &idtab->idlist, next) {
281 if ((r = sshkey_puts_opts(id->key, msg,
282 SSHKEY_SERIALIZE_INFO)) != 0 ||
283 (r = sshbuf_put_cstring(msg, id->comment)) != 0) {
284 error_fr(r, "compose key/comment");
285 continue;
286 }
287 }
288 if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
289 fatal_fr(r, "enqueue");
290 sshbuf_free(msg);
291 }
292
293
294 static char *
agent_decode_alg(struct sshkey * key,u_int flags)295 agent_decode_alg(struct sshkey *key, u_int flags)
296 {
297 if (key->type == KEY_RSA) {
298 if (flags & SSH_AGENT_RSA_SHA2_256)
299 return "rsa-sha2-256";
300 else if (flags & SSH_AGENT_RSA_SHA2_512)
301 return "rsa-sha2-512";
302 } else if (key->type == KEY_RSA_CERT) {
303 if (flags & SSH_AGENT_RSA_SHA2_256)
304 return "rsa-sha2-256-cert-v01@openssh.com";
305 else if (flags & SSH_AGENT_RSA_SHA2_512)
306 return "rsa-sha2-512-cert-v01@openssh.com";
307 }
308 return NULL;
309 }
310
311 /*
312 * Attempt to parse the contents of a buffer as a SSH publickey userauth
313 * request, checking its contents for consistency and matching the embedded
314 * key against the one that is being used for signing.
315 * Note: does not modify msg buffer.
316 * Optionally extract the username and session ID from the request.
317 */
318 static int
parse_userauth_request(struct sshbuf * msg,const struct sshkey * expected_key,char ** userp,struct sshbuf ** sess_idp)319 parse_userauth_request(struct sshbuf *msg, const struct sshkey *expected_key,
320 char **userp, struct sshbuf **sess_idp)
321 {
322 struct sshbuf *b = NULL, *sess_id = NULL;
323 char *user = NULL, *service = NULL, *method = NULL, *pkalg = NULL;
324 int r;
325 u_char t, sig_follows;
326 struct sshkey *mkey = NULL;
327
328 if (userp != NULL)
329 *userp = NULL;
330 if (sess_idp != NULL)
331 *sess_idp = NULL;
332 if ((b = sshbuf_fromb(msg)) == NULL)
333 fatal_f("sshbuf_fromb");
334
335 /* SSH userauth request */
336 if ((r = sshbuf_froms(b, &sess_id)) != 0)
337 goto out;
338 if (sshbuf_len(sess_id) == 0) {
339 r = SSH_ERR_INVALID_FORMAT;
340 goto out;
341 }
342 if ((r = sshbuf_get_u8(b, &t)) != 0 || /* SSH2_MSG_USERAUTH_REQUEST */
343 (r = sshbuf_get_cstring(b, &user, NULL)) != 0 || /* server user */
344 (r = sshbuf_get_cstring(b, &service, NULL)) != 0 || /* service */
345 (r = sshbuf_get_cstring(b, &method, NULL)) != 0 || /* method */
346 (r = sshbuf_get_u8(b, &sig_follows)) != 0 || /* sig-follows */
347 (r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 || /* alg */
348 (r = sshkey_froms(b, &mkey)) != 0) /* key */
349 goto out;
350 if (t != SSH2_MSG_USERAUTH_REQUEST ||
351 sig_follows != 1 ||
352 strcmp(service, "ssh-connection") != 0 ||
353 !sshkey_equal(expected_key, mkey) ||
354 sshkey_type_from_name(pkalg) != expected_key->type) {
355 r = SSH_ERR_INVALID_FORMAT;
356 goto out;
357 }
358 if (strcmp(method, "publickey") != 0) {
359 r = SSH_ERR_INVALID_FORMAT;
360 goto out;
361 }
362 if (sshbuf_len(b) != 0) {
363 r = SSH_ERR_INVALID_FORMAT;
364 goto out;
365 }
366 /* success */
367 r = 0;
368 debug3_f("well formed userauth");
369 if (userp != NULL) {
370 *userp = user;
371 user = NULL;
372 }
373 if (sess_idp != NULL) {
374 *sess_idp = sess_id;
375 sess_id = NULL;
376 }
377 out:
378 sshbuf_free(b);
379 sshbuf_free(sess_id);
380 free(user);
381 free(service);
382 free(method);
383 free(pkalg);
384 sshkey_free(mkey);
385 return r;
386 }
387
388 /*
389 * Attempt to parse the contents of a buffer as a SSHSIG signature request.
390 * Note: does not modify buffer.
391 */
392 static int
parse_sshsig_request(struct sshbuf * msg)393 parse_sshsig_request(struct sshbuf *msg)
394 {
395 int r;
396 struct sshbuf *b;
397
398 if ((b = sshbuf_fromb(msg)) == NULL)
399 fatal_f("sshbuf_fromb");
400
401 if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) != 0 ||
402 (r = sshbuf_consume(b, 6)) != 0 ||
403 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* namespace */
404 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0 || /* reserved */
405 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* hashalg */
406 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0) /* H(msg) */
407 goto out;
408 if (sshbuf_len(b) != 0) {
409 r = SSH_ERR_INVALID_FORMAT;
410 goto out;
411 }
412 /* success */
413 r = 0;
414 out:
415 sshbuf_free(b);
416 return r;
417 }
418
419 /*
420 * This function inspects a message to be signed by a FIDO key that has a
421 * web-like application string (i.e. one that does not begin with "ssh:".
422 * It checks that the message is one of those expected for SSH operations
423 * (pubkey userauth, sshsig, CA key signing) to exclude signing challenges
424 * for the web.
425 */
426 static int
check_websafe_message_contents(struct sshkey * key,struct sshbuf * data)427 check_websafe_message_contents(struct sshkey *key, struct sshbuf *data)
428 {
429 if (parse_userauth_request(data, key, NULL, NULL) == 0) {
430 debug_f("signed data matches public key userauth request");
431 return 1;
432 }
433 if (parse_sshsig_request(data) == 0) {
434 debug_f("signed data matches SSHSIG signature request");
435 return 1;
436 }
437
438 /* XXX check CA signature operation */
439
440 error("web-origin key attempting to sign non-SSH message");
441 return 0;
442 }
443
444 /* ssh2 only */
445 static void
process_sign_request2(SocketEntry * e)446 process_sign_request2(SocketEntry *e)
447 {
448 u_char *signature = NULL;
449 size_t slen = 0;
450 u_int compat = 0, flags;
451 int r, ok = -1;
452 char *fp = NULL;
453 struct sshbuf *msg = NULL, *data = NULL;
454 struct sshkey *key = NULL;
455 struct identity *id;
456 struct notifier_ctx *notifier = NULL;
457
458 debug_f("entering");
459
460 if ((msg = sshbuf_new()) == NULL || (data = sshbuf_new()) == NULL)
461 fatal_f("sshbuf_new failed");
462 if ((r = sshkey_froms(e->request, &key)) != 0 ||
463 (r = sshbuf_get_stringb(e->request, data)) != 0 ||
464 (r = sshbuf_get_u32(e->request, &flags)) != 0) {
465 error_fr(r, "parse");
466 goto send;
467 }
468
469 if ((id = lookup_identity(key)) == NULL) {
470 verbose_f("%s key not found", sshkey_type(key));
471 goto send;
472 }
473 if (id->confirm && confirm_key(id, NULL) != 0) {
474 verbose_f("user refused key");
475 goto send;
476 }
477 if (sshkey_is_sk(id->key)) {
478 if (strncmp(id->key->sk_application, "ssh:", 4) != 0 &&
479 !check_websafe_message_contents(key, data)) {
480 /* error already logged */
481 goto send;
482 }
483 if ((id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD)) {
484 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
485 SSH_FP_DEFAULT)) == NULL)
486 fatal_f("fingerprint failed");
487 notifier = notify_start(0,
488 "Confirm user presence for key %s %s",
489 sshkey_type(id->key), fp);
490 }
491 }
492 /* XXX support PIN required FIDO keys */
493 if ((r = sshkey_sign(id->key, &signature, &slen,
494 sshbuf_ptr(data), sshbuf_len(data), agent_decode_alg(key, flags),
495 id->sk_provider, NULL, compat)) != 0) {
496 error_fr(r, "sshkey_sign");
497 goto send;
498 }
499 /* Success */
500 ok = 0;
501 send:
502 notify_complete(notifier, "User presence confirmed");
503
504 if (ok == 0) {
505 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
506 (r = sshbuf_put_string(msg, signature, slen)) != 0)
507 fatal_fr(r, "compose");
508 } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
509 fatal_fr(r, "compose failure");
510
511 if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
512 fatal_fr(r, "enqueue");
513
514 sshbuf_free(data);
515 sshbuf_free(msg);
516 sshkey_free(key);
517 free(fp);
518 free(signature);
519 }
520
521 /* shared */
522 static void
process_remove_identity(SocketEntry * e)523 process_remove_identity(SocketEntry *e)
524 {
525 int r, success = 0;
526 struct sshkey *key = NULL;
527 Identity *id;
528
529 debug2_f("entering");
530 if ((r = sshkey_froms(e->request, &key)) != 0) {
531 error_fr(r, "parse key");
532 goto done;
533 }
534 if ((id = lookup_identity(key)) == NULL) {
535 debug_f("key not found");
536 goto done;
537 }
538 /* We have this key, free it. */
539 if (idtab->nentries < 1)
540 fatal_f("internal error: nentries %d", idtab->nentries);
541 TAILQ_REMOVE(&idtab->idlist, id, next);
542 free_identity(id);
543 idtab->nentries--;
544 success = 1;
545 done:
546 sshkey_free(key);
547 send_status(e, success);
548 }
549
550 static void
process_remove_all_identities(SocketEntry * e)551 process_remove_all_identities(SocketEntry *e)
552 {
553 Identity *id;
554
555 debug2_f("entering");
556 /* Loop over all identities and clear the keys. */
557 for (id = TAILQ_FIRST(&idtab->idlist); id;
558 id = TAILQ_FIRST(&idtab->idlist)) {
559 TAILQ_REMOVE(&idtab->idlist, id, next);
560 free_identity(id);
561 }
562
563 /* Mark that there are no identities. */
564 idtab->nentries = 0;
565
566 /* Send success. */
567 send_status(e, 1);
568 }
569
570 /* removes expired keys and returns number of seconds until the next expiry */
571 static time_t
reaper(void)572 reaper(void)
573 {
574 time_t deadline = 0, now = monotime();
575 Identity *id, *nxt;
576
577 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
578 nxt = TAILQ_NEXT(id, next);
579 if (id->death == 0)
580 continue;
581 if (now >= id->death) {
582 debug("expiring key '%s'", id->comment);
583 TAILQ_REMOVE(&idtab->idlist, id, next);
584 free_identity(id);
585 idtab->nentries--;
586 } else
587 deadline = (deadline == 0) ? id->death :
588 MINIMUM(deadline, id->death);
589 }
590 if (deadline == 0 || deadline <= now)
591 return 0;
592 else
593 return (deadline - now);
594 }
595
596 static int
parse_key_constraint_extension(struct sshbuf * m,char ** sk_providerp)597 parse_key_constraint_extension(struct sshbuf *m, char **sk_providerp)
598 {
599 char *ext_name = NULL;
600 int r;
601
602 if ((r = sshbuf_get_cstring(m, &ext_name, NULL)) != 0) {
603 error_fr(r, "parse constraint extension");
604 goto out;
605 }
606 debug_f("constraint ext %s", ext_name);
607 if (strcmp(ext_name, "sk-provider@openssh.com") == 0) {
608 if (sk_providerp == NULL) {
609 error_f("%s not valid here", ext_name);
610 r = SSH_ERR_INVALID_FORMAT;
611 goto out;
612 }
613 if (*sk_providerp != NULL) {
614 error_f("%s already set", ext_name);
615 r = SSH_ERR_INVALID_FORMAT;
616 goto out;
617 }
618 if ((r = sshbuf_get_cstring(m, sk_providerp, NULL)) != 0) {
619 error_fr(r, "parse %s", ext_name);
620 goto out;
621 }
622 } else {
623 error_f("unsupported constraint \"%s\"", ext_name);
624 r = SSH_ERR_FEATURE_UNSUPPORTED;
625 goto out;
626 }
627 /* success */
628 r = 0;
629 out:
630 free(ext_name);
631 return r;
632 }
633
634 static int
parse_key_constraints(struct sshbuf * m,struct sshkey * k,time_t * deathp,u_int * secondsp,int * confirmp,char ** sk_providerp)635 parse_key_constraints(struct sshbuf *m, struct sshkey *k, time_t *deathp,
636 u_int *secondsp, int *confirmp, char **sk_providerp)
637 {
638 u_char ctype;
639 int r;
640 u_int seconds, maxsign = 0;
641
642 while (sshbuf_len(m)) {
643 if ((r = sshbuf_get_u8(m, &ctype)) != 0) {
644 error_fr(r, "parse constraint type");
645 goto out;
646 }
647 switch (ctype) {
648 case SSH_AGENT_CONSTRAIN_LIFETIME:
649 if (*deathp != 0) {
650 error_f("lifetime already set");
651 r = SSH_ERR_INVALID_FORMAT;
652 goto out;
653 }
654 if ((r = sshbuf_get_u32(m, &seconds)) != 0) {
655 error_fr(r, "parse lifetime constraint");
656 goto out;
657 }
658 *deathp = monotime() + seconds;
659 *secondsp = seconds;
660 break;
661 case SSH_AGENT_CONSTRAIN_CONFIRM:
662 if (*confirmp != 0) {
663 error_f("confirm already set");
664 r = SSH_ERR_INVALID_FORMAT;
665 goto out;
666 }
667 *confirmp = 1;
668 break;
669 case SSH_AGENT_CONSTRAIN_MAXSIGN:
670 if (k == NULL) {
671 error_f("maxsign not valid here");
672 r = SSH_ERR_INVALID_FORMAT;
673 goto out;
674 }
675 if (maxsign != 0) {
676 error_f("maxsign already set");
677 r = SSH_ERR_INVALID_FORMAT;
678 goto out;
679 }
680 if ((r = sshbuf_get_u32(m, &maxsign)) != 0) {
681 error_fr(r, "parse maxsign constraint");
682 goto out;
683 }
684 if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) {
685 error_fr(r, "enable maxsign");
686 goto out;
687 }
688 break;
689 case SSH_AGENT_CONSTRAIN_EXTENSION:
690 if ((r = parse_key_constraint_extension(m,
691 sk_providerp)) != 0)
692 goto out; /* error already logged */
693 break;
694 default:
695 error_f("Unknown constraint %d", ctype);
696 r = SSH_ERR_FEATURE_UNSUPPORTED;
697 goto out;
698 }
699 }
700 /* success */
701 r = 0;
702 out:
703 return r;
704 }
705
706 static void
process_add_identity(SocketEntry * e)707 process_add_identity(SocketEntry *e)
708 {
709 Identity *id;
710 int success = 0, confirm = 0;
711 char *fp, *comment = NULL, *sk_provider = NULL;
712 char canonical_provider[PATH_MAX];
713 time_t death = 0;
714 u_int seconds = 0;
715 struct sshkey *k = NULL;
716 int r = SSH_ERR_INTERNAL_ERROR;
717
718 debug2_f("entering");
719 if ((r = sshkey_private_deserialize(e->request, &k)) != 0 ||
720 k == NULL ||
721 (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) {
722 error_fr(r, "parse");
723 goto out;
724 }
725 if (parse_key_constraints(e->request, k, &death, &seconds, &confirm,
726 &sk_provider) != 0) {
727 error_f("failed to parse constraints");
728 sshbuf_reset(e->request);
729 goto out;
730 }
731
732 if (sk_provider != NULL) {
733 if (!sshkey_is_sk(k)) {
734 error("Cannot add provider: %s is not an "
735 "authenticator-hosted key", sshkey_type(k));
736 goto out;
737 }
738 if (strcasecmp(sk_provider, "internal") == 0) {
739 debug_f("internal provider");
740 } else {
741 if (realpath(sk_provider, canonical_provider) == NULL) {
742 verbose("failed provider \"%.100s\": "
743 "realpath: %s", sk_provider,
744 strerror(errno));
745 goto out;
746 }
747 free(sk_provider);
748 sk_provider = xstrdup(canonical_provider);
749 if (match_pattern_list(sk_provider,
750 allowed_providers, 0) != 1) {
751 error("Refusing add key: "
752 "provider %s not allowed", sk_provider);
753 goto out;
754 }
755 }
756 }
757 if ((r = sshkey_shield_private(k)) != 0) {
758 error_fr(r, "shield private");
759 goto out;
760 }
761 if (lifetime && !death)
762 death = monotime() + lifetime;
763 if ((id = lookup_identity(k)) == NULL) {
764 id = xcalloc(1, sizeof(Identity));
765 TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
766 /* Increment the number of identities. */
767 idtab->nentries++;
768 } else {
769 /* key state might have been updated */
770 sshkey_free(id->key);
771 free(id->comment);
772 free(id->sk_provider);
773 }
774 /* success */
775 id->key = k;
776 id->comment = comment;
777 id->death = death;
778 id->confirm = confirm;
779 id->sk_provider = sk_provider;
780
781 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT,
782 SSH_FP_DEFAULT)) == NULL)
783 fatal_f("sshkey_fingerprint failed");
784 debug_f("add %s %s \"%.100s\" (life: %u) (confirm: %u) "
785 "(provider: %s)", sshkey_ssh_name(k), fp, comment, seconds,
786 confirm, sk_provider == NULL ? "none" : sk_provider);
787 free(fp);
788 /* transferred */
789 k = NULL;
790 comment = NULL;
791 sk_provider = NULL;
792 success = 1;
793 out:
794 free(sk_provider);
795 free(comment);
796 sshkey_free(k);
797 send_status(e, success);
798 }
799
800 /* XXX todo: encrypt sensitive data with passphrase */
801 static void
process_lock_agent(SocketEntry * e,int lock)802 process_lock_agent(SocketEntry *e, int lock)
803 {
804 int r, success = 0, delay;
805 char *passwd;
806 u_char passwdhash[LOCK_SIZE];
807 static u_int fail_count = 0;
808 size_t pwlen;
809
810 debug2_f("entering");
811 /*
812 * This is deliberately fatal: the user has requested that we lock,
813 * but we can't parse their request properly. The only safe thing to
814 * do is abort.
815 */
816 if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0)
817 fatal_fr(r, "parse");
818 if (pwlen == 0) {
819 debug("empty password not supported");
820 } else if (locked && !lock) {
821 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
822 passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0)
823 fatal("bcrypt_pbkdf");
824 if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) {
825 debug("agent unlocked");
826 locked = 0;
827 fail_count = 0;
828 explicit_bzero(lock_pwhash, sizeof(lock_pwhash));
829 success = 1;
830 } else {
831 /* delay in 0.1s increments up to 10s */
832 if (fail_count < 100)
833 fail_count++;
834 delay = 100000 * fail_count;
835 debug("unlock failed, delaying %0.1lf seconds",
836 (double)delay/1000000);
837 usleep(delay);
838 }
839 explicit_bzero(passwdhash, sizeof(passwdhash));
840 } else if (!locked && lock) {
841 debug("agent locked");
842 locked = 1;
843 arc4random_buf(lock_salt, sizeof(lock_salt));
844 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
845 lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0)
846 fatal("bcrypt_pbkdf");
847 success = 1;
848 }
849 freezero(passwd, pwlen);
850 send_status(e, success);
851 }
852
853 static void
no_identities(SocketEntry * e)854 no_identities(SocketEntry *e)
855 {
856 struct sshbuf *msg;
857 int r;
858
859 if ((msg = sshbuf_new()) == NULL)
860 fatal_f("sshbuf_new failed");
861 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
862 (r = sshbuf_put_u32(msg, 0)) != 0 ||
863 (r = sshbuf_put_stringb(e->output, msg)) != 0)
864 fatal_fr(r, "compose");
865 sshbuf_free(msg);
866 }
867
868 #ifdef ENABLE_PKCS11
869 static void
process_add_smartcard_key(SocketEntry * e)870 process_add_smartcard_key(SocketEntry *e)
871 {
872 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
873 char **comments = NULL;
874 int r, i, count = 0, success = 0, confirm = 0;
875 u_int seconds = 0;
876 time_t death = 0;
877 struct sshkey **keys = NULL, *k;
878 Identity *id;
879
880 debug2_f("entering");
881 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
882 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
883 error_fr(r, "parse");
884 goto send;
885 }
886 if (parse_key_constraints(e->request, NULL, &death, &seconds, &confirm,
887 NULL) != 0) {
888 error_f("failed to parse constraints");
889 goto send;
890 }
891 if (realpath(provider, canonical_provider) == NULL) {
892 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
893 provider, strerror(errno));
894 goto send;
895 }
896 if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) {
897 verbose("refusing PKCS#11 add of \"%.100s\": "
898 "provider not allowed", canonical_provider);
899 goto send;
900 }
901 debug_f("add %.100s", canonical_provider);
902 if (lifetime && !death)
903 death = monotime() + lifetime;
904
905 count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments);
906 for (i = 0; i < count; i++) {
907 k = keys[i];
908 if (lookup_identity(k) == NULL) {
909 id = xcalloc(1, sizeof(Identity));
910 id->key = k;
911 keys[i] = NULL; /* transferred */
912 id->provider = xstrdup(canonical_provider);
913 if (*comments[i] != '\0') {
914 id->comment = comments[i];
915 comments[i] = NULL; /* transferred */
916 } else {
917 id->comment = xstrdup(canonical_provider);
918 }
919 id->death = death;
920 id->confirm = confirm;
921 TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
922 idtab->nentries++;
923 success = 1;
924 }
925 /* XXX update constraints for existing keys */
926 sshkey_free(keys[i]);
927 free(comments[i]);
928 }
929 send:
930 free(pin);
931 free(provider);
932 free(keys);
933 free(comments);
934 send_status(e, success);
935 }
936
937 static void
process_remove_smartcard_key(SocketEntry * e)938 process_remove_smartcard_key(SocketEntry *e)
939 {
940 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
941 int r, success = 0;
942 Identity *id, *nxt;
943
944 debug2_f("entering");
945 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
946 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
947 error_fr(r, "parse");
948 goto send;
949 }
950 free(pin);
951
952 if (realpath(provider, canonical_provider) == NULL) {
953 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
954 provider, strerror(errno));
955 goto send;
956 }
957
958 debug_f("remove %.100s", canonical_provider);
959 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
960 nxt = TAILQ_NEXT(id, next);
961 /* Skip file--based keys */
962 if (id->provider == NULL)
963 continue;
964 if (!strcmp(canonical_provider, id->provider)) {
965 TAILQ_REMOVE(&idtab->idlist, id, next);
966 free_identity(id);
967 idtab->nentries--;
968 }
969 }
970 if (pkcs11_del_provider(canonical_provider) == 0)
971 success = 1;
972 else
973 error_f("pkcs11_del_provider failed");
974 send:
975 free(provider);
976 send_status(e, success);
977 }
978 #endif /* ENABLE_PKCS11 */
979
980 /*
981 * dispatch incoming message.
982 * returns 1 on success, 0 for incomplete messages or -1 on error.
983 */
984 static int
process_message(u_int socknum)985 process_message(u_int socknum)
986 {
987 u_int msg_len;
988 u_char type;
989 const u_char *cp;
990 int r;
991 SocketEntry *e;
992
993 if (socknum >= sockets_alloc)
994 fatal_f("sock %u >= allocated %u", socknum, sockets_alloc);
995 e = &sockets[socknum];
996
997 if (sshbuf_len(e->input) < 5)
998 return 0; /* Incomplete message header. */
999 cp = sshbuf_ptr(e->input);
1000 msg_len = PEEK_U32(cp);
1001 if (msg_len > AGENT_MAX_LEN) {
1002 debug_f("socket %u (fd=%d) message too long %u > %u",
1003 socknum, e->fd, msg_len, AGENT_MAX_LEN);
1004 return -1;
1005 }
1006 if (sshbuf_len(e->input) < msg_len + 4)
1007 return 0; /* Incomplete message body. */
1008
1009 /* move the current input to e->request */
1010 sshbuf_reset(e->request);
1011 if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 ||
1012 (r = sshbuf_get_u8(e->request, &type)) != 0) {
1013 if (r == SSH_ERR_MESSAGE_INCOMPLETE ||
1014 r == SSH_ERR_STRING_TOO_LARGE) {
1015 error_fr(r, "parse");
1016 return -1;
1017 }
1018 fatal_fr(r, "parse");
1019 }
1020
1021 debug_f("socket %u (fd=%d) type %d", socknum, e->fd, type);
1022
1023 /* check whether agent is locked */
1024 if (locked && type != SSH_AGENTC_UNLOCK) {
1025 sshbuf_reset(e->request);
1026 switch (type) {
1027 case SSH2_AGENTC_REQUEST_IDENTITIES:
1028 /* send empty lists */
1029 no_identities(e);
1030 break;
1031 default:
1032 /* send a fail message for all other request types */
1033 send_status(e, 0);
1034 }
1035 return 1;
1036 }
1037
1038 switch (type) {
1039 case SSH_AGENTC_LOCK:
1040 case SSH_AGENTC_UNLOCK:
1041 process_lock_agent(e, type == SSH_AGENTC_LOCK);
1042 break;
1043 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
1044 process_remove_all_identities(e); /* safe for !WITH_SSH1 */
1045 break;
1046 /* ssh2 */
1047 case SSH2_AGENTC_SIGN_REQUEST:
1048 process_sign_request2(e);
1049 break;
1050 case SSH2_AGENTC_REQUEST_IDENTITIES:
1051 process_request_identities(e);
1052 break;
1053 case SSH2_AGENTC_ADD_IDENTITY:
1054 case SSH2_AGENTC_ADD_ID_CONSTRAINED:
1055 process_add_identity(e);
1056 break;
1057 case SSH2_AGENTC_REMOVE_IDENTITY:
1058 process_remove_identity(e);
1059 break;
1060 case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
1061 process_remove_all_identities(e);
1062 break;
1063 #ifdef ENABLE_PKCS11
1064 case SSH_AGENTC_ADD_SMARTCARD_KEY:
1065 case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
1066 process_add_smartcard_key(e);
1067 break;
1068 case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
1069 process_remove_smartcard_key(e);
1070 break;
1071 #endif /* ENABLE_PKCS11 */
1072 default:
1073 /* Unknown message. Respond with failure. */
1074 error("Unknown message %d", type);
1075 sshbuf_reset(e->request);
1076 send_status(e, 0);
1077 break;
1078 }
1079 return 1;
1080 }
1081
1082 static void
new_socket(sock_type type,int fd)1083 new_socket(sock_type type, int fd)
1084 {
1085 u_int i, old_alloc, new_alloc;
1086
1087 debug_f("type = %s", type == AUTH_CONNECTION ? "CONNECTION" :
1088 (type == AUTH_SOCKET ? "SOCKET" : "UNKNOWN"));
1089 if (type == AUTH_CONNECTION) {
1090 debug("xcount %d -> %d", xcount, xcount + 1);
1091 ++xcount;
1092 }
1093 set_nonblock(fd);
1094
1095 if (fd > max_fd)
1096 max_fd = fd;
1097
1098 for (i = 0; i < sockets_alloc; i++)
1099 if (sockets[i].type == AUTH_UNUSED) {
1100 sockets[i].fd = fd;
1101 if ((sockets[i].input = sshbuf_new()) == NULL ||
1102 (sockets[i].output = sshbuf_new()) == NULL ||
1103 (sockets[i].request = sshbuf_new()) == NULL)
1104 fatal_f("sshbuf_new failed");
1105 sockets[i].type = type;
1106 return;
1107 }
1108 old_alloc = sockets_alloc;
1109 new_alloc = sockets_alloc + 10;
1110 sockets = xrecallocarray(sockets, old_alloc, new_alloc,
1111 sizeof(sockets[0]));
1112 for (i = old_alloc; i < new_alloc; i++)
1113 sockets[i].type = AUTH_UNUSED;
1114 sockets_alloc = new_alloc;
1115 sockets[old_alloc].fd = fd;
1116 if ((sockets[old_alloc].input = sshbuf_new()) == NULL ||
1117 (sockets[old_alloc].output = sshbuf_new()) == NULL ||
1118 (sockets[old_alloc].request = sshbuf_new()) == NULL)
1119 fatal_f("sshbuf_new failed");
1120 sockets[old_alloc].type = type;
1121 }
1122
1123 static int
handle_socket_read(u_int socknum)1124 handle_socket_read(u_int socknum)
1125 {
1126 struct sockaddr_un sunaddr;
1127 socklen_t slen;
1128 uid_t euid;
1129 gid_t egid;
1130 int fd;
1131
1132 slen = sizeof(sunaddr);
1133 fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen);
1134 if (fd == -1) {
1135 error("accept from AUTH_SOCKET: %s", strerror(errno));
1136 return -1;
1137 }
1138 if (getpeereid(fd, &euid, &egid) == -1) {
1139 error("getpeereid %d failed: %s", fd, strerror(errno));
1140 close(fd);
1141 return -1;
1142 }
1143 if ((euid != 0) && (getuid() != euid)) {
1144 error("uid mismatch: peer euid %u != uid %u",
1145 (u_int) euid, (u_int) getuid());
1146 close(fd);
1147 return -1;
1148 }
1149 new_socket(AUTH_CONNECTION, fd);
1150 return 0;
1151 }
1152
1153 static int
handle_conn_read(u_int socknum)1154 handle_conn_read(u_int socknum)
1155 {
1156 char buf[AGENT_RBUF_LEN];
1157 ssize_t len;
1158 int r;
1159
1160 if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) {
1161 if (len == -1) {
1162 if (errno == EAGAIN || errno == EINTR)
1163 return 0;
1164 error_f("read error on socket %u (fd %d): %s",
1165 socknum, sockets[socknum].fd, strerror(errno));
1166 }
1167 return -1;
1168 }
1169 if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0)
1170 fatal_fr(r, "compose");
1171 explicit_bzero(buf, sizeof(buf));
1172 for (;;) {
1173 if ((r = process_message(socknum)) == -1)
1174 return -1;
1175 else if (r == 0)
1176 break;
1177 }
1178 return 0;
1179 }
1180
1181 static int
handle_conn_write(u_int socknum)1182 handle_conn_write(u_int socknum)
1183 {
1184 ssize_t len;
1185 int r;
1186
1187 if (sshbuf_len(sockets[socknum].output) == 0)
1188 return 0; /* shouldn't happen */
1189 if ((len = write(sockets[socknum].fd,
1190 sshbuf_ptr(sockets[socknum].output),
1191 sshbuf_len(sockets[socknum].output))) <= 0) {
1192 if (len == -1) {
1193 if (errno == EAGAIN || errno == EINTR)
1194 return 0;
1195 error_f("read error on socket %u (fd %d): %s",
1196 socknum, sockets[socknum].fd, strerror(errno));
1197 }
1198 return -1;
1199 }
1200 if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0)
1201 fatal_fr(r, "consume");
1202 return 0;
1203 }
1204
1205 static void
after_poll(struct pollfd * pfd,size_t npfd,u_int maxfds)1206 after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds)
1207 {
1208 size_t i;
1209 u_int socknum, activefds = npfd;
1210
1211 for (i = 0; i < npfd; i++) {
1212 if (pfd[i].revents == 0)
1213 continue;
1214 /* Find sockets entry */
1215 for (socknum = 0; socknum < sockets_alloc; socknum++) {
1216 if (sockets[socknum].type != AUTH_SOCKET &&
1217 sockets[socknum].type != AUTH_CONNECTION)
1218 continue;
1219 if (pfd[i].fd == sockets[socknum].fd)
1220 break;
1221 }
1222 if (socknum >= sockets_alloc) {
1223 error_f("no socket for fd %d", pfd[i].fd);
1224 continue;
1225 }
1226 /* Process events */
1227 switch (sockets[socknum].type) {
1228 case AUTH_SOCKET:
1229 if ((pfd[i].revents & (POLLIN|POLLERR)) == 0)
1230 break;
1231 if (npfd > maxfds) {
1232 debug3("out of fds (active %u >= limit %u); "
1233 "skipping accept", activefds, maxfds);
1234 break;
1235 }
1236 if (handle_socket_read(socknum) == 0)
1237 activefds++;
1238 break;
1239 case AUTH_CONNECTION:
1240 if ((pfd[i].revents & (POLLIN|POLLERR)) != 0 &&
1241 handle_conn_read(socknum) != 0) {
1242 goto close_sock;
1243 }
1244 if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 &&
1245 handle_conn_write(socknum) != 0) {
1246 close_sock:
1247 if (activefds == 0)
1248 fatal("activefds == 0 at close_sock");
1249 close_socket(&sockets[socknum]);
1250 activefds--;
1251 break;
1252 }
1253 break;
1254 default:
1255 break;
1256 }
1257 }
1258 }
1259
1260 static int
prepare_poll(struct pollfd ** pfdp,size_t * npfdp,int * timeoutp,u_int maxfds)1261 prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp, u_int maxfds)
1262 {
1263 struct pollfd *pfd = *pfdp;
1264 size_t i, j, npfd = 0;
1265 time_t deadline;
1266 int r;
1267
1268 /* Count active sockets */
1269 for (i = 0; i < sockets_alloc; i++) {
1270 switch (sockets[i].type) {
1271 case AUTH_SOCKET:
1272 case AUTH_CONNECTION:
1273 npfd++;
1274 break;
1275 case AUTH_UNUSED:
1276 break;
1277 default:
1278 fatal("Unknown socket type %d", sockets[i].type);
1279 break;
1280 }
1281 }
1282 if (npfd != *npfdp &&
1283 (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL)
1284 fatal_f("recallocarray failed");
1285 *pfdp = pfd;
1286 *npfdp = npfd;
1287
1288 for (i = j = 0; i < sockets_alloc; i++) {
1289 switch (sockets[i].type) {
1290 case AUTH_SOCKET:
1291 if (npfd > maxfds) {
1292 debug3("out of fds (active %zu >= limit %u); "
1293 "skipping arming listener", npfd, maxfds);
1294 break;
1295 }
1296 pfd[j].fd = sockets[i].fd;
1297 pfd[j].revents = 0;
1298 pfd[j].events = POLLIN;
1299 j++;
1300 break;
1301 case AUTH_CONNECTION:
1302 pfd[j].fd = sockets[i].fd;
1303 pfd[j].revents = 0;
1304 /*
1305 * Only prepare to read if we can handle a full-size
1306 * input read buffer and enqueue a max size reply..
1307 */
1308 if ((r = sshbuf_check_reserve(sockets[i].input,
1309 AGENT_RBUF_LEN)) == 0 &&
1310 (r = sshbuf_check_reserve(sockets[i].output,
1311 AGENT_MAX_LEN)) == 0)
1312 pfd[j].events = POLLIN;
1313 else if (r != SSH_ERR_NO_BUFFER_SPACE)
1314 fatal_fr(r, "reserve");
1315 if (sshbuf_len(sockets[i].output) > 0)
1316 pfd[j].events |= POLLOUT;
1317 j++;
1318 break;
1319 default:
1320 break;
1321 }
1322 }
1323 deadline = reaper();
1324 if (parent_alive_interval != 0)
1325 deadline = (deadline == 0) ? parent_alive_interval :
1326 MINIMUM(deadline, parent_alive_interval);
1327 if (deadline == 0) {
1328 *timeoutp = -1; /* INFTIM */
1329 } else {
1330 if (deadline > INT_MAX / 1000)
1331 *timeoutp = INT_MAX / 1000;
1332 else
1333 *timeoutp = deadline * 1000;
1334 }
1335 return (1);
1336 }
1337
1338 static void
cleanup_socket(void)1339 cleanup_socket(void)
1340 {
1341 if (cleanup_pid != 0 && getpid() != cleanup_pid)
1342 return;
1343 debug_f("cleanup");
1344 if (socket_name[0])
1345 unlink(socket_name);
1346 if (socket_dir[0])
1347 rmdir(socket_dir);
1348 }
1349
1350 void
cleanup_exit(int i)1351 cleanup_exit(int i)
1352 {
1353 cleanup_socket();
1354 _exit(i);
1355 }
1356
1357 /*ARGSUSED*/
1358 static void
cleanup_handler(int sig)1359 cleanup_handler(int sig)
1360 {
1361 cleanup_socket();
1362 #ifdef ENABLE_PKCS11
1363 pkcs11_terminate();
1364 #endif
1365 _exit(2);
1366 }
1367
1368 static void
check_parent_exists(void)1369 check_parent_exists(void)
1370 {
1371 /*
1372 * If our parent has exited then getppid() will return (pid_t)1,
1373 * so testing for that should be safe.
1374 */
1375 if (parent_pid != -1 && getppid() != parent_pid) {
1376 /* printf("Parent has died - Authentication agent exiting.\n"); */
1377 cleanup_socket();
1378 _exit(2);
1379 }
1380 }
1381
1382 static void
usage(void)1383 usage(void)
1384 {
1385 fprintf(stderr,
1386 "usage: ssh-agent [-c | -s] [-Ddx] [-a bind_address] [-E fingerprint_hash]\n"
1387 " [-P allowed_providers] [-t life]\n"
1388 " ssh-agent [-a bind_address] [-E fingerprint_hash] [-P allowed_providers]\n"
1389 " [-t life] command [arg ...]\n"
1390 " ssh-agent [-c | -s] -k\n");
1391 exit(1);
1392 }
1393
1394 int
main(int ac,char ** av)1395 main(int ac, char **av)
1396 {
1397 int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0;
1398 int sock, ch, result, saved_errno;
1399 char *shell, *format, *pidstr, *agentsocket = NULL;
1400 #ifdef HAVE_SETRLIMIT
1401 struct rlimit rlim;
1402 #endif
1403 extern int optind;
1404 extern char *optarg;
1405 pid_t pid;
1406 char pidstrbuf[1 + 3 * sizeof pid];
1407 size_t len;
1408 mode_t prev_mask;
1409 int timeout = -1; /* INFTIM */
1410 struct pollfd *pfd = NULL;
1411 size_t npfd = 0;
1412 u_int maxfds;
1413
1414 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1415 sanitise_stdfd();
1416
1417 /* drop */
1418 setegid(getgid());
1419 setgid(getgid());
1420 setuid(geteuid());
1421
1422 platform_disable_tracing(0); /* strict=no */
1423
1424 #ifdef RLIMIT_NOFILE
1425 if (getrlimit(RLIMIT_NOFILE, &rlim) == -1)
1426 fatal("%s: getrlimit: %s", __progname, strerror(errno));
1427 #endif
1428
1429 __progname = ssh_get_progname(av[0]);
1430 seed_rng();
1431
1432 while ((ch = getopt(ac, av, "cDdksE:a:O:P:t:x")) != -1) {
1433 switch (ch) {
1434 case 'E':
1435 fingerprint_hash = ssh_digest_alg_by_name(optarg);
1436 if (fingerprint_hash == -1)
1437 fatal("Invalid hash algorithm \"%s\"", optarg);
1438 break;
1439 case 'c':
1440 if (s_flag)
1441 usage();
1442 c_flag++;
1443 break;
1444 case 'k':
1445 k_flag++;
1446 break;
1447 case 'O':
1448 if (strcmp(optarg, "no-restrict-websafe") == 0)
1449 restrict_websafe = 0;
1450 else
1451 fatal("Unknown -O option");
1452 break;
1453 case 'P':
1454 if (allowed_providers != NULL)
1455 fatal("-P option already specified");
1456 allowed_providers = xstrdup(optarg);
1457 break;
1458 case 's':
1459 if (c_flag)
1460 usage();
1461 s_flag++;
1462 break;
1463 case 'd':
1464 if (d_flag || D_flag)
1465 usage();
1466 d_flag++;
1467 break;
1468 case 'D':
1469 if (d_flag || D_flag)
1470 usage();
1471 D_flag++;
1472 break;
1473 case 'a':
1474 agentsocket = optarg;
1475 break;
1476 case 't':
1477 if ((lifetime = convtime(optarg)) == -1) {
1478 fprintf(stderr, "Invalid lifetime\n");
1479 usage();
1480 }
1481 break;
1482 case 'x':
1483 xcount = 0;
1484 break;
1485 default:
1486 usage();
1487 }
1488 }
1489 ac -= optind;
1490 av += optind;
1491
1492 if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag))
1493 usage();
1494
1495 if (allowed_providers == NULL)
1496 allowed_providers = xstrdup(DEFAULT_ALLOWED_PROVIDERS);
1497
1498 if (ac == 0 && !c_flag && !s_flag) {
1499 shell = getenv("SHELL");
1500 if (shell != NULL && (len = strlen(shell)) > 2 &&
1501 strncmp(shell + len - 3, "csh", 3) == 0)
1502 c_flag = 1;
1503 }
1504 if (k_flag) {
1505 const char *errstr = NULL;
1506
1507 pidstr = getenv(SSH_AGENTPID_ENV_NAME);
1508 if (pidstr == NULL) {
1509 fprintf(stderr, "%s not set, cannot kill agent\n",
1510 SSH_AGENTPID_ENV_NAME);
1511 exit(1);
1512 }
1513 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr);
1514 if (errstr) {
1515 fprintf(stderr,
1516 "%s=\"%s\", which is not a good PID: %s\n",
1517 SSH_AGENTPID_ENV_NAME, pidstr, errstr);
1518 exit(1);
1519 }
1520 if (kill(pid, SIGTERM) == -1) {
1521 perror("kill");
1522 exit(1);
1523 }
1524 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n";
1525 printf(format, SSH_AUTHSOCKET_ENV_NAME);
1526 printf(format, SSH_AGENTPID_ENV_NAME);
1527 printf("echo Agent pid %ld killed;\n", (long)pid);
1528 exit(0);
1529 }
1530
1531 /*
1532 * Minimum file descriptors:
1533 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) +
1534 * a few spare for libc / stack protectors / sanitisers, etc.
1535 */
1536 #define SSH_AGENT_MIN_FDS (3+1+1+1+4)
1537 if (rlim.rlim_cur < SSH_AGENT_MIN_FDS)
1538 fatal("%s: file descriptor rlimit %lld too low (minimum %u)",
1539 __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS);
1540 maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS;
1541
1542 parent_pid = getpid();
1543
1544 if (agentsocket == NULL) {
1545 /* Create private directory for agent socket */
1546 mktemp_proto(socket_dir, sizeof(socket_dir));
1547 if (mkdtemp(socket_dir) == NULL) {
1548 perror("mkdtemp: private socket dir");
1549 exit(1);
1550 }
1551 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
1552 (long)parent_pid);
1553 } else {
1554 /* Try to use specified agent socket */
1555 socket_dir[0] = '\0';
1556 strlcpy(socket_name, agentsocket, sizeof socket_name);
1557 }
1558
1559 /*
1560 * Create socket early so it will exist before command gets run from
1561 * the parent.
1562 */
1563 prev_mask = umask(0177);
1564 sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
1565 if (sock < 0) {
1566 /* XXX - unix_listener() calls error() not perror() */
1567 *socket_name = '\0'; /* Don't unlink any existing file */
1568 cleanup_exit(1);
1569 }
1570 umask(prev_mask);
1571
1572 /*
1573 * Fork, and have the parent execute the command, if any, or present
1574 * the socket data. The child continues as the authentication agent.
1575 */
1576 if (D_flag || d_flag) {
1577 log_init(__progname,
1578 d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO,
1579 SYSLOG_FACILITY_AUTH, 1);
1580 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
1581 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
1582 SSH_AUTHSOCKET_ENV_NAME);
1583 printf("echo Agent pid %ld;\n", (long)parent_pid);
1584 fflush(stdout);
1585 goto skip;
1586 }
1587 pid = fork();
1588 if (pid == -1) {
1589 perror("fork");
1590 cleanup_exit(1);
1591 }
1592 if (pid != 0) { /* Parent - execute the given command. */
1593 close(sock);
1594 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid);
1595 if (ac == 0) {
1596 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
1597 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
1598 SSH_AUTHSOCKET_ENV_NAME);
1599 printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf,
1600 SSH_AGENTPID_ENV_NAME);
1601 printf("echo Agent pid %ld;\n", (long)pid);
1602 exit(0);
1603 }
1604 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
1605 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
1606 perror("setenv");
1607 exit(1);
1608 }
1609 execvp(av[0], av);
1610 perror(av[0]);
1611 exit(1);
1612 }
1613 /* child */
1614 log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0);
1615
1616 if (setsid() == -1) {
1617 error("setsid: %s", strerror(errno));
1618 cleanup_exit(1);
1619 }
1620
1621 (void)chdir("/");
1622 if (stdfd_devnull(1, 1, 1) == -1)
1623 error_f("stdfd_devnull failed");
1624
1625 #ifdef HAVE_SETRLIMIT
1626 /* deny core dumps, since memory contains unencrypted private keys */
1627 rlim.rlim_cur = rlim.rlim_max = 0;
1628 if (setrlimit(RLIMIT_CORE, &rlim) == -1) {
1629 error("setrlimit RLIMIT_CORE: %s", strerror(errno));
1630 cleanup_exit(1);
1631 }
1632 #endif
1633
1634 skip:
1635
1636 cleanup_pid = getpid();
1637
1638 #ifdef ENABLE_PKCS11
1639 pkcs11_init(0);
1640 #endif
1641 new_socket(AUTH_SOCKET, sock);
1642 if (ac > 0)
1643 parent_alive_interval = 10;
1644 idtab_init();
1645 ssh_signal(SIGPIPE, SIG_IGN);
1646 ssh_signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN);
1647 ssh_signal(SIGHUP, cleanup_handler);
1648 ssh_signal(SIGTERM, cleanup_handler);
1649
1650 if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1)
1651 fatal("%s: pledge: %s", __progname, strerror(errno));
1652 platform_pledge_agent();
1653
1654 while (1) {
1655 prepare_poll(&pfd, &npfd, &timeout, maxfds);
1656 result = poll(pfd, npfd, timeout);
1657 saved_errno = errno;
1658 if (parent_alive_interval != 0)
1659 check_parent_exists();
1660 (void) reaper(); /* remove expired keys */
1661 if (result == -1) {
1662 if (saved_errno == EINTR)
1663 continue;
1664 fatal("poll: %s", strerror(saved_errno));
1665 } else if (result > 0)
1666 after_poll(pfd, npfd, maxfds);
1667 }
1668 /* NOTREACHED */
1669 }
1670