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upstream: Improve description of KbdInteractiveAuthentication.
[openssh.git] / ssh-agent.c
blob96c25b9d5718134230c5ba8a86ea765dfd4879e1
1 /* $OpenBSD: ssh-agent.c,v 1.309 2024/11/06 22:51:26 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/resource.h>
41 #include <sys/stat.h>
42 #include <sys/socket.h>
43 #include <sys/wait.h>
44 #ifdef HAVE_SYS_TIME_H
45 # include <sys/time.h>
46 #endif
47 #ifdef HAVE_SYS_UN_H
48 # include <sys/un.h>
49 #endif
50 #include "openbsd-compat/sys-queue.h"
51
52 #ifdef WITH_OPENSSL
53 #include <openssl/evp.h>
54 #include "openbsd-compat/openssl-compat.h"
55 #endif
56
57 #include <errno.h>
58 #include <fcntl.h>
59 #include <limits.h>
60 #ifdef HAVE_PATHS_H
61 # include <paths.h>
62 #endif
63 #ifdef HAVE_POLL_H
64 # include <poll.h>
65 #endif
66 #include <signal.h>
67 #include <stdarg.h>
68 #include <stdio.h>
69 #include <stdlib.h>
70 #include <time.h>
71 #include <string.h>
72 #include <unistd.h>
73 #ifdef HAVE_UTIL_H
74 # include <util.h>
75 #endif
76
77 #include "xmalloc.h"
78 #include "ssh.h"
79 #include "ssh2.h"
80 #include "sshbuf.h"
81 #include "sshkey.h"
82 #include "authfd.h"
83 #include "log.h"
84 #include "misc.h"
85 #include "digest.h"
86 #include "ssherr.h"
87 #include "match.h"
88 #include "msg.h"
89 #include "pathnames.h"
90 #include "ssh-pkcs11.h"
91 #include "sk-api.h"
92 #include "myproposal.h"
93
94 #ifndef DEFAULT_ALLOWED_PROVIDERS
95 # define DEFAULT_ALLOWED_PROVIDERS "/usr/lib*/*,/usr/local/lib*/*"
96 #endif
97 #ifndef DEFAULT_WEBSAFE_ALLOWLIST
98 # define DEFAULT_WEBSAFE_ALLOWLIST "ssh:*"
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 /* Maximum number of recorded session IDs/hostkeys per connection */
106 #define AGENT_MAX_SESSION_IDS 16
107 /* Maximum size of session ID */
108 #define AGENT_MAX_SID_LEN 128
109 /* Maximum number of destination constraints to accept on a key */
110 #define AGENT_MAX_DEST_CONSTRAINTS 1024
111 /* Maximum number of associated certificate constraints to accept on a key */
112 #define AGENT_MAX_EXT_CERTS 1024
113
114 /* XXX store hostkey_sid in a refcounted tree */
115
116 typedef enum {
117 AUTH_UNUSED = 0,
118 AUTH_SOCKET = 1,
119 AUTH_CONNECTION = 2,
120 } sock_type;
121
122 struct hostkey_sid {
123 struct sshkey *key;
124 struct sshbuf *sid;
125 int forwarded;
126 };
127
128 typedef struct socket_entry {
129 int fd;
130 sock_type type;
131 struct sshbuf *input;
132 struct sshbuf *output;
133 struct sshbuf *request;
134 size_t nsession_ids;
135 struct hostkey_sid *session_ids;
136 int session_bind_attempted;
137 } SocketEntry;
138
139 u_int sockets_alloc = 0;
140 SocketEntry *sockets = NULL;
141
142 typedef struct identity {
143 TAILQ_ENTRY(identity) next;
144 struct sshkey *key;
145 char *comment;
146 char *provider;
147 time_t death;
148 u_int confirm;
149 char *sk_provider;
150 struct dest_constraint *dest_constraints;
151 size_t ndest_constraints;
152 } Identity;
153
154 struct idtable {
155 int nentries;
156 TAILQ_HEAD(idqueue, identity) idlist;
157 };
158
159 /* private key table */
160 struct idtable *idtab;
161
162 int max_fd = 0;
163
164 /* pid of shell == parent of agent */
165 pid_t parent_pid = -1;
166 time_t parent_alive_interval = 0;
167
168 static sig_atomic_t signalled_exit;
169 static sig_atomic_t signalled_keydrop;
170
171 /* pid of process for which cleanup_socket is applicable */
172 pid_t cleanup_pid = 0;
173
174 /* pathname and directory for AUTH_SOCKET */
175 char socket_name[PATH_MAX];
176 char socket_dir[PATH_MAX];
177
178 /* Pattern-list of allowed PKCS#11/Security key paths */
179 static char *allowed_providers;
180
181 /*
182 * Allows PKCS11 providers or SK keys that use non-internal providers to
183 * be added over a remote connection (identified by session-bind@openssh.com).
184 */
185 static int remote_add_provider;
186
187 /* locking */
188 #define LOCK_SIZE 32
189 #define LOCK_SALT_SIZE 16
190 #define LOCK_ROUNDS 1
191 int locked = 0;
192 u_char lock_pwhash[LOCK_SIZE];
193 u_char lock_salt[LOCK_SALT_SIZE];
194
195 extern char *__progname;
196
197 /* Default lifetime in seconds (0 == forever) */
198 static int lifetime = 0;
199
200 static int fingerprint_hash = SSH_FP_HASH_DEFAULT;
201
202 /* Refuse signing of non-SSH messages for web-origin FIDO keys */
203 static int restrict_websafe = 1;
204 static char *websafe_allowlist;
205
206 static void
207 close_socket(SocketEntry *e)
208 {
209 size_t i;
210
211 close(e->fd);
212 sshbuf_free(e->input);
213 sshbuf_free(e->output);
214 sshbuf_free(e->request);
215 for (i = 0; i < e->nsession_ids; i++) {
216 sshkey_free(e->session_ids[i].key);
217 sshbuf_free(e->session_ids[i].sid);
218 }
219 free(e->session_ids);
220 memset(e, '\0', sizeof(*e));
221 e->fd = -1;
222 e->type = AUTH_UNUSED;
223 }
224
225 static void
226 idtab_init(void)
227 {
228 idtab = xcalloc(1, sizeof(*idtab));
229 TAILQ_INIT(&idtab->idlist);
230 idtab->nentries = 0;
231 }
232
233 static void
234 free_dest_constraint_hop(struct dest_constraint_hop *dch)
235 {
236 u_int i;
237
238 if (dch == NULL)
239 return;
240 free(dch->user);
241 free(dch->hostname);
242 for (i = 0; i < dch->nkeys; i++)
243 sshkey_free(dch->keys[i]);
244 free(dch->keys);
245 free(dch->key_is_ca);
246 }
247
248 static void
249 free_dest_constraints(struct dest_constraint *dcs, size_t ndcs)
250 {
251 size_t i;
252
253 for (i = 0; i < ndcs; i++) {
254 free_dest_constraint_hop(&dcs[i].from);
255 free_dest_constraint_hop(&dcs[i].to);
256 }
257 free(dcs);
258 }
259
260 #ifdef ENABLE_PKCS11
261 static void
262 dup_dest_constraint_hop(const struct dest_constraint_hop *dch,
263 struct dest_constraint_hop *out)
264 {
265 u_int i;
266 int r;
267
268 out->user = dch->user == NULL ? NULL : xstrdup(dch->user);
269 out->hostname = dch->hostname == NULL ? NULL : xstrdup(dch->hostname);
270 out->is_ca = dch->is_ca;
271 out->nkeys = dch->nkeys;
272 out->keys = out->nkeys == 0 ? NULL :
273 xcalloc(out->nkeys, sizeof(*out->keys));
274 out->key_is_ca = out->nkeys == 0 ? NULL :
275 xcalloc(out->nkeys, sizeof(*out->key_is_ca));
276 for (i = 0; i < dch->nkeys; i++) {
277 if (dch->keys[i] != NULL &&
278 (r = sshkey_from_private(dch->keys[i],
279 &(out->keys[i]))) != 0)
280 fatal_fr(r, "copy key");
281 out->key_is_ca[i] = dch->key_is_ca[i];
282 }
283 }
284
285 static struct dest_constraint *
286 dup_dest_constraints(const struct dest_constraint *dcs, size_t ndcs)
287 {
288 size_t i;
289 struct dest_constraint *ret;
290
291 if (ndcs == 0)
292 return NULL;
293 ret = xcalloc(ndcs, sizeof(*ret));
294 for (i = 0; i < ndcs; i++) {
295 dup_dest_constraint_hop(&dcs[i].from, &ret[i].from);
296 dup_dest_constraint_hop(&dcs[i].to, &ret[i].to);
297 }
298 return ret;
299 }
300 #endif /* ENABLE_PKCS11 */
301
302 #ifdef DEBUG_CONSTRAINTS
303 static void
304 dump_dest_constraint_hop(const struct dest_constraint_hop *dch)
305 {
306 u_int i;
307 char *fp;
308
309 debug_f("user %s hostname %s is_ca %d nkeys %u",
310 dch->user == NULL ? "(null)" : dch->user,
311 dch->hostname == NULL ? "(null)" : dch->hostname,
312 dch->is_ca, dch->nkeys);
313 for (i = 0; i < dch->nkeys; i++) {
314 fp = NULL;
315 if (dch->keys[i] != NULL &&
316 (fp = sshkey_fingerprint(dch->keys[i],
317 SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL)
318 fatal_f("fingerprint failed");
319 debug_f("key %u/%u: %s%s%s key_is_ca %d", i, dch->nkeys,
320 dch->keys[i] == NULL ? "" : sshkey_ssh_name(dch->keys[i]),
321 dch->keys[i] == NULL ? "" : " ",
322 dch->keys[i] == NULL ? "none" : fp,
323 dch->key_is_ca[i]);
324 free(fp);
325 }
326 }
327 #endif /* DEBUG_CONSTRAINTS */
328
329 static void
330 dump_dest_constraints(const char *context,
331 const struct dest_constraint *dcs, size_t ndcs)
332 {
333 #ifdef DEBUG_CONSTRAINTS
334 size_t i;
335
336 debug_f("%s: %zu constraints", context, ndcs);
337 for (i = 0; i < ndcs; i++) {
338 debug_f("constraint %zu / %zu: from: ", i, ndcs);
339 dump_dest_constraint_hop(&dcs[i].from);
340 debug_f("constraint %zu / %zu: to: ", i, ndcs);
341 dump_dest_constraint_hop(&dcs[i].to);
342 }
343 debug_f("done for %s", context);
344 #endif /* DEBUG_CONSTRAINTS */
345 }
346
347 static void
348 free_identity(Identity *id)
349 {
350 sshkey_free(id->key);
351 free(id->provider);
352 free(id->comment);
353 free(id->sk_provider);
354 free_dest_constraints(id->dest_constraints, id->ndest_constraints);
355 free(id);
356 }
357
358 /*
359 * Match 'key' against the key/CA list in a destination constraint hop
360 * Returns 0 on success or -1 otherwise.
361 */
362 static int
363 match_key_hop(const char *tag, const struct sshkey *key,
364 const struct dest_constraint_hop *dch)
365 {
366 const char *reason = NULL;
367 const char *hostname = dch->hostname ? dch->hostname : "(ORIGIN)";
368 u_int i;
369 char *fp;
370
371 if (key == NULL)
372 return -1;
373 /* XXX logspam */
374 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
375 SSH_FP_DEFAULT)) == NULL)
376 fatal_f("fingerprint failed");
377 debug3_f("%s: entering hostname %s, requested key %s %s, %u keys avail",
378 tag, hostname, sshkey_type(key), fp, dch->nkeys);
379 free(fp);
380 for (i = 0; i < dch->nkeys; i++) {
381 if (dch->keys[i] == NULL)
382 return -1;
383 /* XXX logspam */
384 if ((fp = sshkey_fingerprint(dch->keys[i], SSH_FP_HASH_DEFAULT,
385 SSH_FP_DEFAULT)) == NULL)
386 fatal_f("fingerprint failed");
387 debug3_f("%s: key %u: %s%s %s", tag, i,
388 dch->key_is_ca[i] ? "CA " : "",
389 sshkey_type(dch->keys[i]), fp);
390 free(fp);
391 if (!sshkey_is_cert(key)) {
392 /* plain key */
393 if (dch->key_is_ca[i] ||
394 !sshkey_equal(key, dch->keys[i]))
395 continue;
396 return 0;
397 }
398 /* certificate */
399 if (!dch->key_is_ca[i])
400 continue;
401 if (key->cert == NULL || key->cert->signature_key == NULL)
402 return -1; /* shouldn't happen */
403 if (!sshkey_equal(key->cert->signature_key, dch->keys[i]))
404 continue;
405 if (sshkey_cert_check_host(key, hostname, 1,
406 SSH_ALLOWED_CA_SIGALGS, &reason) != 0) {
407 debug_f("cert %s / hostname %s rejected: %s",
408 key->cert->key_id, hostname, reason);
409 continue;
410 }
411 return 0;
412 }
413 return -1;
414 }
415
416 /* Check destination constraints on an identity against the hostkey/user */
417 static int
418 permitted_by_dest_constraints(const struct sshkey *fromkey,
419 const struct sshkey *tokey, Identity *id, const char *user,
420 const char **hostnamep)
421 {
422 size_t i;
423 struct dest_constraint *d;
424
425 if (hostnamep != NULL)
426 *hostnamep = NULL;
427 for (i = 0; i < id->ndest_constraints; i++) {
428 d = id->dest_constraints + i;
429 /* XXX remove logspam */
430 debug2_f("constraint %zu %s%s%s (%u keys) > %s%s%s (%u keys)",
431 i, d->from.user ? d->from.user : "",
432 d->from.user ? "@" : "",
433 d->from.hostname ? d->from.hostname : "(ORIGIN)",
434 d->from.nkeys,
435 d->to.user ? d->to.user : "", d->to.user ? "@" : "",
436 d->to.hostname ? d->to.hostname : "(ANY)", d->to.nkeys);
437
438 /* Match 'from' key */
439 if (fromkey == NULL) {
440 /* We are matching the first hop */
441 if (d->from.hostname != NULL || d->from.nkeys != 0)
442 continue;
443 } else if (match_key_hop("from", fromkey, &d->from) != 0)
444 continue;
445
446 /* Match 'to' key */
447 if (tokey != NULL && match_key_hop("to", tokey, &d->to) != 0)
448 continue;
449
450 /* Match user if specified */
451 if (d->to.user != NULL && user != NULL &&
452 !match_pattern(user, d->to.user))
453 continue;
454
455 /* successfully matched this constraint */
456 if (hostnamep != NULL)
457 *hostnamep = d->to.hostname;
458 debug2_f("allowed for hostname %s",
459 d->to.hostname == NULL ? "*" : d->to.hostname);
460 return 0;
461 }
462 /* no match */
463 debug2_f("%s identity \"%s\" not permitted for this destination",
464 sshkey_type(id->key), id->comment);
465 return -1;
466 }
467
468 /*
469 * Check whether hostkeys on a SocketEntry and the optionally specified user
470 * are permitted by the destination constraints on the Identity.
471 * Returns 0 on success or -1 otherwise.
472 */
473 static int
474 identity_permitted(Identity *id, SocketEntry *e, char *user,
475 const char **forward_hostnamep, const char **last_hostnamep)
476 {
477 size_t i;
478 const char **hp;
479 struct hostkey_sid *hks;
480 const struct sshkey *fromkey = NULL;
481 const char *test_user;
482 char *fp1, *fp2;
483
484 /* XXX remove logspam */
485 debug3_f("entering: key %s comment \"%s\", %zu socket bindings, "
486 "%zu constraints", sshkey_type(id->key), id->comment,
487 e->nsession_ids, id->ndest_constraints);
488 if (id->ndest_constraints == 0)
489 return 0; /* unconstrained */
490 if (e->session_bind_attempted && e->nsession_ids == 0) {
491 error_f("previous session bind failed on socket");
492 return -1;
493 }
494 if (e->nsession_ids == 0)
495 return 0; /* local use */
496 /*
497 * Walk through the hops recorded by session_id and try to find a
498 * constraint that satisfies each.
499 */
500 for (i = 0; i < e->nsession_ids; i++) {
501 hks = e->session_ids + i;
502 if (hks->key == NULL)
503 fatal_f("internal error: no bound key");
504 /* XXX remove logspam */
505 fp1 = fp2 = NULL;
506 if (fromkey != NULL &&
507 (fp1 = sshkey_fingerprint(fromkey, SSH_FP_HASH_DEFAULT,
508 SSH_FP_DEFAULT)) == NULL)
509 fatal_f("fingerprint failed");
510 if ((fp2 = sshkey_fingerprint(hks->key, SSH_FP_HASH_DEFAULT,
511 SSH_FP_DEFAULT)) == NULL)
512 fatal_f("fingerprint failed");
513 debug3_f("socketentry fd=%d, entry %zu %s, "
514 "from hostkey %s %s to user %s hostkey %s %s",
515 e->fd, i, hks->forwarded ? "FORWARD" : "AUTH",
516 fromkey ? sshkey_type(fromkey) : "(ORIGIN)",
517 fromkey ? fp1 : "", user ? user : "(ANY)",
518 sshkey_type(hks->key), fp2);
519 free(fp1);
520 free(fp2);
521 /*
522 * Record the hostnames for the initial forwarding and
523 * the final destination.
524 */
525 hp = NULL;
526 if (i == e->nsession_ids - 1)
527 hp = last_hostnamep;
528 else if (i == 0)
529 hp = forward_hostnamep;
530 /* Special handling for final recorded binding */
531 test_user = NULL;
532 if (i == e->nsession_ids - 1) {
533 /* Can only check user at final hop */
534 test_user = user;
535 /*
536 * user is only presented for signature requests.
537 * If this is the case, make sure last binding is not
538 * for a forwarding.
539 */
540 if (hks->forwarded && user != NULL) {
541 error_f("tried to sign on forwarding hop");
542 return -1;
543 }
544 } else if (!hks->forwarded) {
545 error_f("tried to forward though signing bind");
546 return -1;
547 }
548 if (permitted_by_dest_constraints(fromkey, hks->key, id,
549 test_user, hp) != 0)
550 return -1;
551 fromkey = hks->key;
552 }
553 /*
554 * Another special case: if the last bound session ID was for a
555 * forwarding, and this function is not being called to check a sign
556 * request (i.e. no 'user' supplied), then only permit the key if
557 * there is a permission that would allow it to be used at another
558 * destination. This hides keys that are allowed to be used to
559 * authenticate *to* a host but not permitted for *use* beyond it.
560 */
561 hks = &e->session_ids[e->nsession_ids - 1];
562 if (hks->forwarded && user == NULL &&
563 permitted_by_dest_constraints(hks->key, NULL, id,
564 NULL, NULL) != 0) {
565 debug3_f("key permitted at host but not after");
566 return -1;
567 }
568
569 /* success */
570 return 0;
571 }
572
573 static int
574 socket_is_remote(SocketEntry *e)
575 {
576 return e->session_bind_attempted || (e->nsession_ids != 0);
577 }
578
579 /* return matching private key for given public key */
580 static Identity *
581 lookup_identity(struct sshkey *key)
582 {
583 Identity *id;
584
585 TAILQ_FOREACH(id, &idtab->idlist, next) {
586 if (sshkey_equal(key, id->key))
587 return (id);
588 }
589 return (NULL);
590 }
591
592 /* Check confirmation of keysign request */
593 static int
594 confirm_key(Identity *id, const char *extra)
595 {
596 char *p;
597 int ret = -1;
598
599 p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT);
600 if (p != NULL &&
601 ask_permission("Allow use of key %s?\nKey fingerprint %s.%s%s",
602 id->comment, p,
603 extra == NULL ? "" : "\n", extra == NULL ? "" : extra))
604 ret = 0;
605 free(p);
606
607 return (ret);
608 }
609
610 static void
611 send_status(SocketEntry *e, int success)
612 {
613 int r;
614
615 if ((r = sshbuf_put_u32(e->output, 1)) != 0 ||
616 (r = sshbuf_put_u8(e->output, success ?
617 SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
618 fatal_fr(r, "compose");
619 }
620
621 /* send list of supported public keys to 'client' */
622 static void
623 process_request_identities(SocketEntry *e)
624 {
625 Identity *id;
626 struct sshbuf *msg, *keys;
627 int r;
628 u_int i = 0, nentries = 0;
629 char *fp;
630
631 debug2_f("entering");
632
633 if ((msg = sshbuf_new()) == NULL || (keys = sshbuf_new()) == NULL)
634 fatal_f("sshbuf_new failed");
635 TAILQ_FOREACH(id, &idtab->idlist, next) {
636 if ((fp = sshkey_fingerprint(id->key, SSH_FP_HASH_DEFAULT,
637 SSH_FP_DEFAULT)) == NULL)
638 fatal_f("fingerprint failed");
639 debug_f("key %u / %u: %s %s", i++, idtab->nentries,
640 sshkey_ssh_name(id->key), fp);
641 dump_dest_constraints(__func__,
642 id->dest_constraints, id->ndest_constraints);
643 free(fp);
644 /* identity not visible, don't include in response */
645 if (identity_permitted(id, e, NULL, NULL, NULL) != 0)
646 continue;
647 if ((r = sshkey_puts_opts(id->key, keys,
648 SSHKEY_SERIALIZE_INFO)) != 0 ||
649 (r = sshbuf_put_cstring(keys, id->comment)) != 0) {
650 error_fr(r, "compose key/comment");
651 continue;
652 }
653 nentries++;
654 }
655 debug2_f("replying with %u allowed of %u available keys",
656 nentries, idtab->nentries);
657 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
658 (r = sshbuf_put_u32(msg, nentries)) != 0 ||
659 (r = sshbuf_putb(msg, keys)) != 0)
660 fatal_fr(r, "compose");
661 if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
662 fatal_fr(r, "enqueue");
663 sshbuf_free(msg);
664 sshbuf_free(keys);
665 }
666
667
668 static char *
669 agent_decode_alg(struct sshkey *key, u_int flags)
670 {
671 if (key->type == KEY_RSA) {
672 if (flags & SSH_AGENT_RSA_SHA2_256)
673 return "rsa-sha2-256";
674 else if (flags & SSH_AGENT_RSA_SHA2_512)
675 return "rsa-sha2-512";
676 } else if (key->type == KEY_RSA_CERT) {
677 if (flags & SSH_AGENT_RSA_SHA2_256)
678 return "rsa-sha2-256-cert-v01@openssh.com";
679 else if (flags & SSH_AGENT_RSA_SHA2_512)
680 return "rsa-sha2-512-cert-v01@openssh.com";
681 }
682 return NULL;
683 }
684
685 /*
686 * Attempt to parse the contents of a buffer as a SSH publickey userauth
687 * request, checking its contents for consistency and matching the embedded
688 * key against the one that is being used for signing.
689 * Note: does not modify msg buffer.
690 * Optionally extract the username, session ID and/or hostkey from the request.
691 */
692 static int
693 parse_userauth_request(struct sshbuf *msg, const struct sshkey *expected_key,
694 char **userp, struct sshbuf **sess_idp, struct sshkey **hostkeyp)
695 {
696 struct sshbuf *b = NULL, *sess_id = NULL;
697 char *user = NULL, *service = NULL, *method = NULL, *pkalg = NULL;
698 int r;
699 u_char t, sig_follows;
700 struct sshkey *mkey = NULL, *hostkey = NULL;
701
702 if (userp != NULL)
703 *userp = NULL;
704 if (sess_idp != NULL)
705 *sess_idp = NULL;
706 if (hostkeyp != NULL)
707 *hostkeyp = NULL;
708 if ((b = sshbuf_fromb(msg)) == NULL)
709 fatal_f("sshbuf_fromb");
710
711 /* SSH userauth request */
712 if ((r = sshbuf_froms(b, &sess_id)) != 0)
713 goto out;
714 if (sshbuf_len(sess_id) == 0) {
715 r = SSH_ERR_INVALID_FORMAT;
716 goto out;
717 }
718 if ((r = sshbuf_get_u8(b, &t)) != 0 || /* SSH2_MSG_USERAUTH_REQUEST */
719 (r = sshbuf_get_cstring(b, &user, NULL)) != 0 || /* server user */
720 (r = sshbuf_get_cstring(b, &service, NULL)) != 0 || /* service */
721 (r = sshbuf_get_cstring(b, &method, NULL)) != 0 || /* method */
722 (r = sshbuf_get_u8(b, &sig_follows)) != 0 || /* sig-follows */
723 (r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 || /* alg */
724 (r = sshkey_froms(b, &mkey)) != 0) /* key */
725 goto out;
726 if (t != SSH2_MSG_USERAUTH_REQUEST ||
727 sig_follows != 1 ||
728 strcmp(service, "ssh-connection") != 0 ||
729 !sshkey_equal(expected_key, mkey) ||
730 sshkey_type_from_name(pkalg) != expected_key->type) {
731 r = SSH_ERR_INVALID_FORMAT;
732 goto out;
733 }
734 if (strcmp(method, "publickey-hostbound-v00@openssh.com") == 0) {
735 if ((r = sshkey_froms(b, &hostkey)) != 0)
736 goto out;
737 } else if (strcmp(method, "publickey") != 0) {
738 r = SSH_ERR_INVALID_FORMAT;
739 goto out;
740 }
741 if (sshbuf_len(b) != 0) {
742 r = SSH_ERR_INVALID_FORMAT;
743 goto out;
744 }
745 /* success */
746 r = 0;
747 debug3_f("well formed userauth");
748 if (userp != NULL) {
749 *userp = user;
750 user = NULL;
751 }
752 if (sess_idp != NULL) {
753 *sess_idp = sess_id;
754 sess_id = NULL;
755 }
756 if (hostkeyp != NULL) {
757 *hostkeyp = hostkey;
758 hostkey = NULL;
759 }
760 out:
761 sshbuf_free(b);
762 sshbuf_free(sess_id);
763 free(user);
764 free(service);
765 free(method);
766 free(pkalg);
767 sshkey_free(mkey);
768 sshkey_free(hostkey);
769 return r;
770 }
771
772 /*
773 * Attempt to parse the contents of a buffer as a SSHSIG signature request.
774 * Note: does not modify buffer.
775 */
776 static int
777 parse_sshsig_request(struct sshbuf *msg)
778 {
779 int r;
780 struct sshbuf *b;
781
782 if ((b = sshbuf_fromb(msg)) == NULL)
783 fatal_f("sshbuf_fromb");
784
785 if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) != 0 ||
786 (r = sshbuf_consume(b, 6)) != 0 ||
787 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* namespace */
788 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0 || /* reserved */
789 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* hashalg */
790 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0) /* H(msg) */
791 goto out;
792 if (sshbuf_len(b) != 0) {
793 r = SSH_ERR_INVALID_FORMAT;
794 goto out;
795 }
796 /* success */
797 r = 0;
798 out:
799 sshbuf_free(b);
800 return r;
801 }
802
803 /*
804 * This function inspects a message to be signed by a FIDO key that has a
805 * web-like application string (i.e. one that does not begin with "ssh:".
806 * It checks that the message is one of those expected for SSH operations
807 * (pubkey userauth, sshsig, CA key signing) to exclude signing challenges
808 * for the web.
809 */
810 static int
811 check_websafe_message_contents(struct sshkey *key, struct sshbuf *data)
812 {
813 if (parse_userauth_request(data, key, NULL, NULL, NULL) == 0) {
814 debug_f("signed data matches public key userauth request");
815 return 1;
816 }
817 if (parse_sshsig_request(data) == 0) {
818 debug_f("signed data matches SSHSIG signature request");
819 return 1;
820 }
821
822 /* XXX check CA signature operation */
823
824 error("web-origin key attempting to sign non-SSH message");
825 return 0;
826 }
827
828 static int
829 buf_equal(const struct sshbuf *a, const struct sshbuf *b)
830 {
831 if (sshbuf_ptr(a) == NULL || sshbuf_ptr(b) == NULL)
832 return SSH_ERR_INVALID_ARGUMENT;
833 if (sshbuf_len(a) != sshbuf_len(b))
834 return SSH_ERR_INVALID_FORMAT;
835 if (timingsafe_bcmp(sshbuf_ptr(a), sshbuf_ptr(b), sshbuf_len(a)) != 0)
836 return SSH_ERR_INVALID_FORMAT;
837 return 0;
838 }
839
840 /* ssh2 only */
841 static void
842 process_sign_request2(SocketEntry *e)
843 {
844 u_char *signature = NULL;
845 size_t slen = 0;
846 u_int compat = 0, flags;
847 int r, ok = -1, retried = 0;
848 char *fp = NULL, *pin = NULL, *prompt = NULL;
849 char *user = NULL, *sig_dest = NULL;
850 const char *fwd_host = NULL, *dest_host = NULL;
851 struct sshbuf *msg = NULL, *data = NULL, *sid = NULL;
852 struct sshkey *key = NULL, *hostkey = NULL;
853 struct identity *id;
854 struct notifier_ctx *notifier = NULL;
855
856 debug_f("entering");
857
858 if ((msg = sshbuf_new()) == NULL || (data = sshbuf_new()) == NULL)
859 fatal_f("sshbuf_new failed");
860 if ((r = sshkey_froms(e->request, &key)) != 0 ||
861 (r = sshbuf_get_stringb(e->request, data)) != 0 ||
862 (r = sshbuf_get_u32(e->request, &flags)) != 0) {
863 error_fr(r, "parse");
864 goto send;
865 }
866
867 if ((id = lookup_identity(key)) == NULL) {
868 verbose_f("%s key not found", sshkey_type(key));
869 goto send;
870 }
871 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
872 SSH_FP_DEFAULT)) == NULL)
873 fatal_f("fingerprint failed");
874
875 if (id->ndest_constraints != 0) {
876 if (e->nsession_ids == 0) {
877 logit_f("refusing use of destination-constrained key "
878 "to sign on unbound connection");
879 goto send;
880 }
881 if (parse_userauth_request(data, key, &user, &sid,
882 &hostkey) != 0) {
883 logit_f("refusing use of destination-constrained key "
884 "to sign an unidentified signature");
885 goto send;
886 }
887 /* XXX logspam */
888 debug_f("user=%s", user);
889 if (identity_permitted(id, e, user, &fwd_host, &dest_host) != 0)
890 goto send;
891 /* XXX display fwd_host/dest_host in askpass UI */
892 /*
893 * Ensure that the session ID is the most recent one
894 * registered on the socket - it should have been bound by
895 * ssh immediately before userauth.
896 */
897 if (buf_equal(sid,
898 e->session_ids[e->nsession_ids - 1].sid) != 0) {
899 error_f("unexpected session ID (%zu listed) on "
900 "signature request for target user %s with "
901 "key %s %s", e->nsession_ids, user,
902 sshkey_type(id->key), fp);
903 goto send;
904 }
905 /*
906 * Ensure that the hostkey embedded in the signature matches
907 * the one most recently bound to the socket. An exception is
908 * made for the initial forwarding hop.
909 */
910 if (e->nsession_ids > 1 && hostkey == NULL) {
911 error_f("refusing use of destination-constrained key: "
912 "no hostkey recorded in signature for forwarded "
913 "connection");
914 goto send;
915 }
916 if (hostkey != NULL && !sshkey_equal(hostkey,
917 e->session_ids[e->nsession_ids - 1].key)) {
918 error_f("refusing use of destination-constrained key: "
919 "mismatch between hostkey in request and most "
920 "recently bound session");
921 goto send;
922 }
923 xasprintf(&sig_dest, "public key authentication request for "
924 "user \"%s\" to listed host", user);
925 }
926 if (id->confirm && confirm_key(id, sig_dest) != 0) {
927 verbose_f("user refused key");
928 goto send;
929 }
930 if (sshkey_is_sk(id->key)) {
931 if (restrict_websafe &&
932 match_pattern_list(id->key->sk_application,
933 websafe_allowlist, 0) != 1 &&
934 !check_websafe_message_contents(key, data)) {
935 /* error already logged */
936 goto send;
937 }
938 if (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) {
939 notifier = notify_start(0,
940 "Confirm user presence for key %s %s%s%s",
941 sshkey_type(id->key), fp,
942 sig_dest == NULL ? "" : "\n",
943 sig_dest == NULL ? "" : sig_dest);
944 }
945 }
946 retry_pin:
947 if ((r = sshkey_sign(id->key, &signature, &slen,
948 sshbuf_ptr(data), sshbuf_len(data), agent_decode_alg(key, flags),
949 id->sk_provider, pin, compat)) != 0) {
950 debug_fr(r, "sshkey_sign");
951 if (pin == NULL && !retried && sshkey_is_sk(id->key) &&
952 r == SSH_ERR_KEY_WRONG_PASSPHRASE) {
953 notify_complete(notifier, NULL);
954 notifier = NULL;
955 /* XXX include sig_dest */
956 xasprintf(&prompt, "Enter PIN%sfor %s key %s: ",
957 (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) ?
958 " and confirm user presence " : " ",
959 sshkey_type(id->key), fp);
960 pin = read_passphrase(prompt, RP_USE_ASKPASS);
961 retried = 1;
962 goto retry_pin;
963 }
964 error_fr(r, "sshkey_sign");
965 goto send;
966 }
967 /* Success */
968 ok = 0;
969 debug_f("good signature");
970 send:
971 notify_complete(notifier, "User presence confirmed");
972
973 if (ok == 0) {
974 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
975 (r = sshbuf_put_string(msg, signature, slen)) != 0)
976 fatal_fr(r, "compose");
977 } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
978 fatal_fr(r, "compose failure");
979
980 if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
981 fatal_fr(r, "enqueue");
982
983 sshbuf_free(sid);
984 sshbuf_free(data);
985 sshbuf_free(msg);
986 sshkey_free(key);
987 sshkey_free(hostkey);
988 free(fp);
989 free(signature);
990 free(sig_dest);
991 free(user);
992 free(prompt);
993 if (pin != NULL)
994 freezero(pin, strlen(pin));
995 }
996
997 /* shared */
998 static void
999 process_remove_identity(SocketEntry *e)
1000 {
1001 int r, success = 0;
1002 struct sshkey *key = NULL;
1003 Identity *id;
1004
1005 debug2_f("entering");
1006 if ((r = sshkey_froms(e->request, &key)) != 0) {
1007 error_fr(r, "parse key");
1008 goto done;
1009 }
1010 if ((id = lookup_identity(key)) == NULL) {
1011 debug_f("key not found");
1012 goto done;
1013 }
1014 /* identity not visible, cannot be removed */
1015 if (identity_permitted(id, e, NULL, NULL, NULL) != 0)
1016 goto done; /* error already logged */
1017 /* We have this key, free it. */
1018 if (idtab->nentries < 1)
1019 fatal_f("internal error: nentries %d", idtab->nentries);
1020 TAILQ_REMOVE(&idtab->idlist, id, next);
1021 free_identity(id);
1022 idtab->nentries--;
1023 success = 1;
1024 done:
1025 sshkey_free(key);
1026 send_status(e, success);
1027 }
1028
1029 static void
1030 remove_all_identities(void)
1031 {
1032 Identity *id;
1033
1034 debug2_f("entering");
1035 /* Loop over all identities and clear the keys. */
1036 for (id = TAILQ_FIRST(&idtab->idlist); id;
1037 id = TAILQ_FIRST(&idtab->idlist)) {
1038 TAILQ_REMOVE(&idtab->idlist, id, next);
1039 free_identity(id);
1040 }
1041
1042 /* Mark that there are no identities. */
1043 idtab->nentries = 0;
1044 }
1045
1046 static void
1047 process_remove_all_identities(SocketEntry *e)
1048 {
1049 remove_all_identities();
1050
1051 /* Send success. */
1052 send_status(e, 1);
1053 }
1054
1055 /* removes expired keys and returns number of seconds until the next expiry */
1056 static time_t
1057 reaper(void)
1058 {
1059 time_t deadline = 0, now = monotime();
1060 Identity *id, *nxt;
1061
1062 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
1063 nxt = TAILQ_NEXT(id, next);
1064 if (id->death == 0)
1065 continue;
1066 if (now >= id->death) {
1067 debug("expiring key '%s'", id->comment);
1068 TAILQ_REMOVE(&idtab->idlist, id, next);
1069 free_identity(id);
1070 idtab->nentries--;
1071 } else
1072 deadline = (deadline == 0) ? id->death :
1073 MINIMUM(deadline, id->death);
1074 }
1075 if (deadline == 0 || deadline <= now)
1076 return 0;
1077 else
1078 return (deadline - now);
1079 }
1080
1081 static int
1082 parse_dest_constraint_hop(struct sshbuf *b, struct dest_constraint_hop *dch)
1083 {
1084 u_char key_is_ca;
1085 size_t elen = 0;
1086 int r;
1087 struct sshkey *k = NULL;
1088 char *fp;
1089
1090 memset(dch, '\0', sizeof(*dch));
1091 if ((r = sshbuf_get_cstring(b, &dch->user, NULL)) != 0 ||
1092 (r = sshbuf_get_cstring(b, &dch->hostname, NULL)) != 0 ||
1093 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) {
1094 error_fr(r, "parse");
1095 goto out;
1096 }
1097 if (elen != 0) {
1098 error_f("unsupported extensions (len %zu)", elen);
1099 r = SSH_ERR_FEATURE_UNSUPPORTED;
1100 goto out;
1101 }
1102 if (*dch->hostname == '\0') {
1103 free(dch->hostname);
1104 dch->hostname = NULL;
1105 }
1106 if (*dch->user == '\0') {
1107 free(dch->user);
1108 dch->user = NULL;
1109 }
1110 while (sshbuf_len(b) != 0) {
1111 dch->keys = xrecallocarray(dch->keys, dch->nkeys,
1112 dch->nkeys + 1, sizeof(*dch->keys));
1113 dch->key_is_ca = xrecallocarray(dch->key_is_ca, dch->nkeys,
1114 dch->nkeys + 1, sizeof(*dch->key_is_ca));
1115 if ((r = sshkey_froms(b, &k)) != 0 ||
1116 (r = sshbuf_get_u8(b, &key_is_ca)) != 0)
1117 goto out;
1118 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT,
1119 SSH_FP_DEFAULT)) == NULL)
1120 fatal_f("fingerprint failed");
1121 debug3_f("%s%s%s: adding %skey %s %s",
1122 dch->user == NULL ? "" : dch->user,
1123 dch->user == NULL ? "" : "@",
1124 dch->hostname, key_is_ca ? "CA " : "", sshkey_type(k), fp);
1125 free(fp);
1126 dch->keys[dch->nkeys] = k;
1127 dch->key_is_ca[dch->nkeys] = key_is_ca != 0;
1128 dch->nkeys++;
1129 k = NULL; /* transferred */
1130 }
1131 /* success */
1132 r = 0;
1133 out:
1134 sshkey_free(k);
1135 return r;
1136 }
1137
1138 static int
1139 parse_dest_constraint(struct sshbuf *m, struct dest_constraint *dc)
1140 {
1141 struct sshbuf *b = NULL, *frombuf = NULL, *tobuf = NULL;
1142 int r;
1143 size_t elen = 0;
1144
1145 debug3_f("entering");
1146
1147 memset(dc, '\0', sizeof(*dc));
1148 if ((r = sshbuf_froms(m, &b)) != 0 ||
1149 (r = sshbuf_froms(b, &frombuf)) != 0 ||
1150 (r = sshbuf_froms(b, &tobuf)) != 0 ||
1151 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) {
1152 error_fr(r, "parse");
1153 goto out;
1154 }
1155 if ((r = parse_dest_constraint_hop(frombuf, &dc->from)) != 0 ||
1156 (r = parse_dest_constraint_hop(tobuf, &dc->to)) != 0)
1157 goto out; /* already logged */
1158 if (elen != 0) {
1159 error_f("unsupported extensions (len %zu)", elen);
1160 r = SSH_ERR_FEATURE_UNSUPPORTED;
1161 goto out;
1162 }
1163 debug2_f("parsed %s (%u keys) > %s%s%s (%u keys)",
1164 dc->from.hostname ? dc->from.hostname : "(ORIGIN)", dc->from.nkeys,
1165 dc->to.user ? dc->to.user : "", dc->to.user ? "@" : "",
1166 dc->to.hostname ? dc->to.hostname : "(ANY)", dc->to.nkeys);
1167 /* check consistency */
1168 if ((dc->from.hostname == NULL) != (dc->from.nkeys == 0) ||
1169 dc->from.user != NULL) {
1170 error_f("inconsistent \"from\" specification");
1171 r = SSH_ERR_INVALID_FORMAT;
1172 goto out;
1173 }
1174 if (dc->to.hostname == NULL || dc->to.nkeys == 0) {
1175 error_f("incomplete \"to\" specification");
1176 r = SSH_ERR_INVALID_FORMAT;
1177 goto out;
1178 }
1179 /* success */
1180 r = 0;
1181 out:
1182 sshbuf_free(b);
1183 sshbuf_free(frombuf);
1184 sshbuf_free(tobuf);
1185 return r;
1186 }
1187
1188 static int
1189 parse_key_constraint_extension(struct sshbuf *m, char **sk_providerp,
1190 struct dest_constraint **dcsp, size_t *ndcsp, int *cert_onlyp,
1191 struct sshkey ***certs, size_t *ncerts)
1192 {
1193 char *ext_name = NULL;
1194 int r;
1195 struct sshbuf *b = NULL;
1196 u_char v;
1197 struct sshkey *k;
1198
1199 if ((r = sshbuf_get_cstring(m, &ext_name, NULL)) != 0) {
1200 error_fr(r, "parse constraint extension");
1201 goto out;
1202 }
1203 debug_f("constraint ext %s", ext_name);
1204 if (strcmp(ext_name, "sk-provider@openssh.com") == 0) {
1205 if (sk_providerp == NULL) {
1206 error_f("%s not valid here", ext_name);
1207 r = SSH_ERR_INVALID_FORMAT;
1208 goto out;
1209 }
1210 if (*sk_providerp != NULL) {
1211 error_f("%s already set", ext_name);
1212 r = SSH_ERR_INVALID_FORMAT;
1213 goto out;
1214 }
1215 if ((r = sshbuf_get_cstring(m, sk_providerp, NULL)) != 0) {
1216 error_fr(r, "parse %s", ext_name);
1217 goto out;
1218 }
1219 } else if (strcmp(ext_name,
1220 "restrict-destination-v00@openssh.com") == 0) {
1221 if (*dcsp != NULL) {
1222 error_f("%s already set", ext_name);
1223 goto out;
1224 }
1225 if ((r = sshbuf_froms(m, &b)) != 0) {
1226 error_fr(r, "parse %s outer", ext_name);
1227 goto out;
1228 }
1229 while (sshbuf_len(b) != 0) {
1230 if (*ndcsp >= AGENT_MAX_DEST_CONSTRAINTS) {
1231 error_f("too many %s constraints", ext_name);
1232 goto out;
1233 }
1234 *dcsp = xrecallocarray(*dcsp, *ndcsp, *ndcsp + 1,
1235 sizeof(**dcsp));
1236 if ((r = parse_dest_constraint(b,
1237 *dcsp + (*ndcsp)++)) != 0)
1238 goto out; /* error already logged */
1239 }
1240 } else if (strcmp(ext_name,
1241 "associated-certs-v00@openssh.com") == 0) {
1242 if (certs == NULL || ncerts == NULL || cert_onlyp == NULL) {
1243 error_f("%s not valid here", ext_name);
1244 r = SSH_ERR_INVALID_FORMAT;
1245 goto out;
1246 }
1247 if (*certs != NULL) {
1248 error_f("%s already set", ext_name);
1249 goto out;
1250 }
1251 if ((r = sshbuf_get_u8(m, &v)) != 0 ||
1252 (r = sshbuf_froms(m, &b)) != 0) {
1253 error_fr(r, "parse %s", ext_name);
1254 goto out;
1255 }
1256 *cert_onlyp = v != 0;
1257 while (sshbuf_len(b) != 0) {
1258 if (*ncerts >= AGENT_MAX_EXT_CERTS) {
1259 error_f("too many %s constraints", ext_name);
1260 goto out;
1261 }
1262 *certs = xrecallocarray(*certs, *ncerts, *ncerts + 1,
1263 sizeof(**certs));
1264 if ((r = sshkey_froms(b, &k)) != 0) {
1265 error_fr(r, "parse key");
1266 goto out;
1267 }
1268 (*certs)[(*ncerts)++] = k;
1269 }
1270 } else {
1271 error_f("unsupported constraint \"%s\"", ext_name);
1272 r = SSH_ERR_FEATURE_UNSUPPORTED;
1273 goto out;
1274 }
1275 /* success */
1276 r = 0;
1277 out:
1278 free(ext_name);
1279 sshbuf_free(b);
1280 return r;
1281 }
1282
1283 static int
1284 parse_key_constraints(struct sshbuf *m, struct sshkey *k, time_t *deathp,
1285 u_int *secondsp, int *confirmp, char **sk_providerp,
1286 struct dest_constraint **dcsp, size_t *ndcsp,
1287 int *cert_onlyp, size_t *ncerts, struct sshkey ***certs)
1288 {
1289 u_char ctype;
1290 int r;
1291 u_int seconds, maxsign = 0;
1292
1293 while (sshbuf_len(m)) {
1294 if ((r = sshbuf_get_u8(m, &ctype)) != 0) {
1295 error_fr(r, "parse constraint type");
1296 goto out;
1297 }
1298 switch (ctype) {
1299 case SSH_AGENT_CONSTRAIN_LIFETIME:
1300 if (*deathp != 0) {
1301 error_f("lifetime already set");
1302 r = SSH_ERR_INVALID_FORMAT;
1303 goto out;
1304 }
1305 if ((r = sshbuf_get_u32(m, &seconds)) != 0) {
1306 error_fr(r, "parse lifetime constraint");
1307 goto out;
1308 }
1309 *deathp = monotime() + seconds;
1310 *secondsp = seconds;
1311 break;
1312 case SSH_AGENT_CONSTRAIN_CONFIRM:
1313 if (*confirmp != 0) {
1314 error_f("confirm already set");
1315 r = SSH_ERR_INVALID_FORMAT;
1316 goto out;
1317 }
1318 *confirmp = 1;
1319 break;
1320 case SSH_AGENT_CONSTRAIN_MAXSIGN:
1321 if (k == NULL) {
1322 error_f("maxsign not valid here");
1323 r = SSH_ERR_INVALID_FORMAT;
1324 goto out;
1325 }
1326 if (maxsign != 0) {
1327 error_f("maxsign already set");
1328 r = SSH_ERR_INVALID_FORMAT;
1329 goto out;
1330 }
1331 if ((r = sshbuf_get_u32(m, &maxsign)) != 0) {
1332 error_fr(r, "parse maxsign constraint");
1333 goto out;
1334 }
1335 if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) {
1336 error_fr(r, "enable maxsign");
1337 goto out;
1338 }
1339 break;
1340 case SSH_AGENT_CONSTRAIN_EXTENSION:
1341 if ((r = parse_key_constraint_extension(m,
1342 sk_providerp, dcsp, ndcsp,
1343 cert_onlyp, certs, ncerts)) != 0)
1344 goto out; /* error already logged */
1345 break;
1346 default:
1347 error_f("Unknown constraint %d", ctype);
1348 r = SSH_ERR_FEATURE_UNSUPPORTED;
1349 goto out;
1350 }
1351 }
1352 /* success */
1353 r = 0;
1354 out:
1355 return r;
1356 }
1357
1358 static void
1359 process_add_identity(SocketEntry *e)
1360 {
1361 Identity *id;
1362 int success = 0, confirm = 0;
1363 char *fp, *comment = NULL, *sk_provider = NULL;
1364 char canonical_provider[PATH_MAX];
1365 time_t death = 0;
1366 u_int seconds = 0;
1367 struct dest_constraint *dest_constraints = NULL;
1368 size_t ndest_constraints = 0;
1369 struct sshkey *k = NULL;
1370 int r = SSH_ERR_INTERNAL_ERROR;
1371
1372 debug2_f("entering");
1373 if ((r = sshkey_private_deserialize(e->request, &k)) != 0 ||
1374 k == NULL ||
1375 (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) {
1376 error_fr(r, "parse");
1377 goto out;
1378 }
1379 if (parse_key_constraints(e->request, k, &death, &seconds, &confirm,
1380 &sk_provider, &dest_constraints, &ndest_constraints,
1381 NULL, NULL, NULL) != 0) {
1382 error_f("failed to parse constraints");
1383 sshbuf_reset(e->request);
1384 goto out;
1385 }
1386 dump_dest_constraints(__func__, dest_constraints, ndest_constraints);
1387
1388 if (sk_provider != NULL) {
1389 if (!sshkey_is_sk(k)) {
1390 error("Cannot add provider: %s is not an "
1391 "authenticator-hosted key", sshkey_type(k));
1392 goto out;
1393 }
1394 if (strcasecmp(sk_provider, "internal") == 0) {
1395 debug_f("internal provider");
1396 } else {
1397 if (socket_is_remote(e) && !remote_add_provider) {
1398 verbose("failed add of SK provider \"%.100s\": "
1399 "remote addition of providers is disabled",
1400 sk_provider);
1401 goto out;
1402 }
1403 if (realpath(sk_provider, canonical_provider) == NULL) {
1404 verbose("failed provider \"%.100s\": "
1405 "realpath: %s", sk_provider,
1406 strerror(errno));
1407 goto out;
1408 }
1409 free(sk_provider);
1410 sk_provider = xstrdup(canonical_provider);
1411 if (match_pattern_list(sk_provider,
1412 allowed_providers, 0) != 1) {
1413 error("Refusing add key: "
1414 "provider %s not allowed", sk_provider);
1415 goto out;
1416 }
1417 }
1418 }
1419 if ((r = sshkey_shield_private(k)) != 0) {
1420 error_fr(r, "shield private");
1421 goto out;
1422 }
1423 if (lifetime && !death)
1424 death = monotime() + lifetime;
1425 if ((id = lookup_identity(k)) == NULL) {
1426 id = xcalloc(1, sizeof(Identity));
1427 TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
1428 /* Increment the number of identities. */
1429 idtab->nentries++;
1430 } else {
1431 /* identity not visible, do not update */
1432 if (identity_permitted(id, e, NULL, NULL, NULL) != 0)
1433 goto out; /* error already logged */
1434 /* key state might have been updated */
1435 sshkey_free(id->key);
1436 free(id->comment);
1437 free(id->sk_provider);
1438 free_dest_constraints(id->dest_constraints,
1439 id->ndest_constraints);
1440 }
1441 /* success */
1442 id->key = k;
1443 id->comment = comment;
1444 id->death = death;
1445 id->confirm = confirm;
1446 id->sk_provider = sk_provider;
1447 id->dest_constraints = dest_constraints;
1448 id->ndest_constraints = ndest_constraints;
1449
1450 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT,
1451 SSH_FP_DEFAULT)) == NULL)
1452 fatal_f("sshkey_fingerprint failed");
1453 debug_f("add %s %s \"%.100s\" (life: %u) (confirm: %u) "
1454 "(provider: %s) (destination constraints: %zu)",
1455 sshkey_ssh_name(k), fp, comment, seconds, confirm,
1456 sk_provider == NULL ? "none" : sk_provider, ndest_constraints);
1457 free(fp);
1458 /* transferred */
1459 k = NULL;
1460 comment = NULL;
1461 sk_provider = NULL;
1462 dest_constraints = NULL;
1463 ndest_constraints = 0;
1464 success = 1;
1465 out:
1466 free(sk_provider);
1467 free(comment);
1468 sshkey_free(k);
1469 free_dest_constraints(dest_constraints, ndest_constraints);
1470 send_status(e, success);
1471 }
1472
1473 /* XXX todo: encrypt sensitive data with passphrase */
1474 static void
1475 process_lock_agent(SocketEntry *e, int lock)
1476 {
1477 int r, success = 0, delay;
1478 char *passwd;
1479 u_char passwdhash[LOCK_SIZE];
1480 static u_int fail_count = 0;
1481 size_t pwlen;
1482
1483 debug2_f("entering");
1484 /*
1485 * This is deliberately fatal: the user has requested that we lock,
1486 * but we can't parse their request properly. The only safe thing to
1487 * do is abort.
1488 */
1489 if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0)
1490 fatal_fr(r, "parse");
1491 if (pwlen == 0) {
1492 debug("empty password not supported");
1493 } else if (locked && !lock) {
1494 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
1495 passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0)
1496 fatal("bcrypt_pbkdf");
1497 if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) {
1498 debug("agent unlocked");
1499 locked = 0;
1500 fail_count = 0;
1501 explicit_bzero(lock_pwhash, sizeof(lock_pwhash));
1502 success = 1;
1503 } else {
1504 /* delay in 0.1s increments up to 10s */
1505 if (fail_count < 100)
1506 fail_count++;
1507 delay = 100000 * fail_count;
1508 debug("unlock failed, delaying %0.1lf seconds",
1509 (double)delay/1000000);
1510 usleep(delay);
1511 }
1512 explicit_bzero(passwdhash, sizeof(passwdhash));
1513 } else if (!locked && lock) {
1514 debug("agent locked");
1515 locked = 1;
1516 arc4random_buf(lock_salt, sizeof(lock_salt));
1517 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
1518 lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0)
1519 fatal("bcrypt_pbkdf");
1520 success = 1;
1521 }
1522 freezero(passwd, pwlen);
1523 send_status(e, success);
1524 }
1525
1526 static void
1527 no_identities(SocketEntry *e)
1528 {
1529 struct sshbuf *msg;
1530 int r;
1531
1532 if ((msg = sshbuf_new()) == NULL)
1533 fatal_f("sshbuf_new failed");
1534 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
1535 (r = sshbuf_put_u32(msg, 0)) != 0 ||
1536 (r = sshbuf_put_stringb(e->output, msg)) != 0)
1537 fatal_fr(r, "compose");
1538 sshbuf_free(msg);
1539 }
1540
1541 #ifdef ENABLE_PKCS11
1542 /* Add an identity to idlist; takes ownership of 'key' and 'comment' */
1543 static void
1544 add_p11_identity(struct sshkey *key, char *comment, const char *provider,
1545 time_t death, u_int confirm, struct dest_constraint *dest_constraints,
1546 size_t ndest_constraints)
1547 {
1548 Identity *id;
1549
1550 if (lookup_identity(key) != NULL) {
1551 sshkey_free(key);
1552 free(comment);
1553 return;
1554 }
1555 id = xcalloc(1, sizeof(Identity));
1556 id->key = key;
1557 id->comment = comment;
1558 id->provider = xstrdup(provider);
1559 id->death = death;
1560 id->confirm = confirm;
1561 id->dest_constraints = dup_dest_constraints(dest_constraints,
1562 ndest_constraints);
1563 id->ndest_constraints = ndest_constraints;
1564 TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
1565 idtab->nentries++;
1566 }
1567
1568 static void
1569 process_add_smartcard_key(SocketEntry *e)
1570 {
1571 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
1572 char **comments = NULL;
1573 int r, i, count = 0, success = 0, confirm = 0;
1574 u_int seconds = 0;
1575 time_t death = 0;
1576 struct sshkey **keys = NULL, *k;
1577 struct dest_constraint *dest_constraints = NULL;
1578 size_t j, ndest_constraints = 0, ncerts = 0;
1579 struct sshkey **certs = NULL;
1580 int cert_only = 0;
1581
1582 debug2_f("entering");
1583 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
1584 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
1585 error_fr(r, "parse");
1586 goto send;
1587 }
1588 if (parse_key_constraints(e->request, NULL, &death, &seconds, &confirm,
1589 NULL, &dest_constraints, &ndest_constraints, &cert_only,
1590 &ncerts, &certs) != 0) {
1591 error_f("failed to parse constraints");
1592 goto send;
1593 }
1594 dump_dest_constraints(__func__, dest_constraints, ndest_constraints);
1595 if (socket_is_remote(e) && !remote_add_provider) {
1596 verbose("failed PKCS#11 add of \"%.100s\": remote addition of "
1597 "providers is disabled", provider);
1598 goto send;
1599 }
1600 if (realpath(provider, canonical_provider) == NULL) {
1601 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
1602 provider, strerror(errno));
1603 goto send;
1604 }
1605 if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) {
1606 verbose("refusing PKCS#11 add of \"%.100s\": "
1607 "provider not allowed", canonical_provider);
1608 goto send;
1609 }
1610 debug_f("add %.100s", canonical_provider);
1611 if (lifetime && !death)
1612 death = monotime() + lifetime;
1613
1614 count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments);
1615 for (i = 0; i < count; i++) {
1616 if (comments[i] == NULL || comments[i][0] == '\0') {
1617 free(comments[i]);
1618 comments[i] = xstrdup(canonical_provider);
1619 }
1620 for (j = 0; j < ncerts; j++) {
1621 if (!sshkey_is_cert(certs[j]))
1622 continue;
1623 if (!sshkey_equal_public(keys[i], certs[j]))
1624 continue;
1625 if (pkcs11_make_cert(keys[i], certs[j], &k) != 0)
1626 continue;
1627 add_p11_identity(k, xstrdup(comments[i]),
1628 canonical_provider, death, confirm,
1629 dest_constraints, ndest_constraints);
1630 success = 1;
1631 }
1632 if (!cert_only && lookup_identity(keys[i]) == NULL) {
1633 add_p11_identity(keys[i], comments[i],
1634 canonical_provider, death, confirm,
1635 dest_constraints, ndest_constraints);
1636 keys[i] = NULL; /* transferred */
1637 comments[i] = NULL; /* transferred */
1638 success = 1;
1639 }
1640 /* XXX update constraints for existing keys */
1641 sshkey_free(keys[i]);
1642 free(comments[i]);
1643 }
1644 send:
1645 free(pin);
1646 free(provider);
1647 free(keys);
1648 free(comments);
1649 free_dest_constraints(dest_constraints, ndest_constraints);
1650 for (j = 0; j < ncerts; j++)
1651 sshkey_free(certs[j]);
1652 free(certs);
1653 send_status(e, success);
1654 }
1655
1656 static void
1657 process_remove_smartcard_key(SocketEntry *e)
1658 {
1659 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
1660 int r, success = 0;
1661 Identity *id, *nxt;
1662
1663 debug2_f("entering");
1664 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
1665 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
1666 error_fr(r, "parse");
1667 goto send;
1668 }
1669 free(pin);
1670
1671 if (realpath(provider, canonical_provider) == NULL) {
1672 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
1673 provider, strerror(errno));
1674 goto send;
1675 }
1676
1677 debug_f("remove %.100s", canonical_provider);
1678 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
1679 nxt = TAILQ_NEXT(id, next);
1680 /* Skip file--based keys */
1681 if (id->provider == NULL)
1682 continue;
1683 if (!strcmp(canonical_provider, id->provider)) {
1684 TAILQ_REMOVE(&idtab->idlist, id, next);
1685 free_identity(id);
1686 idtab->nentries--;
1687 }
1688 }
1689 if (pkcs11_del_provider(canonical_provider) == 0)
1690 success = 1;
1691 else
1692 error_f("pkcs11_del_provider failed");
1693 send:
1694 free(provider);
1695 send_status(e, success);
1696 }
1697 #endif /* ENABLE_PKCS11 */
1698
1699 static int
1700 process_ext_session_bind(SocketEntry *e)
1701 {
1702 int r, sid_match, key_match;
1703 struct sshkey *key = NULL;
1704 struct sshbuf *sid = NULL, *sig = NULL;
1705 char *fp = NULL;
1706 size_t i;
1707 u_char fwd = 0;
1708
1709 debug2_f("entering");
1710 e->session_bind_attempted = 1;
1711 if ((r = sshkey_froms(e->request, &key)) != 0 ||
1712 (r = sshbuf_froms(e->request, &sid)) != 0 ||
1713 (r = sshbuf_froms(e->request, &sig)) != 0 ||
1714 (r = sshbuf_get_u8(e->request, &fwd)) != 0) {
1715 error_fr(r, "parse");
1716 goto out;
1717 }
1718 if (sshbuf_len(sid) > AGENT_MAX_SID_LEN) {
1719 error_f("session ID too long");
1720 goto out;
1721 }
1722 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
1723 SSH_FP_DEFAULT)) == NULL)
1724 fatal_f("fingerprint failed");
1725 /* check signature with hostkey on session ID */
1726 if ((r = sshkey_verify(key, sshbuf_ptr(sig), sshbuf_len(sig),
1727 sshbuf_ptr(sid), sshbuf_len(sid), NULL, 0, NULL)) != 0) {
1728 error_fr(r, "sshkey_verify for %s %s", sshkey_type(key), fp);
1729 goto out;
1730 }
1731 /* check whether sid/key already recorded */
1732 for (i = 0; i < e->nsession_ids; i++) {
1733 if (!e->session_ids[i].forwarded) {
1734 error_f("attempt to bind session ID to socket "
1735 "previously bound for authentication attempt");
1736 r = -1;
1737 goto out;
1738 }
1739 sid_match = buf_equal(sid, e->session_ids[i].sid) == 0;
1740 key_match = sshkey_equal(key, e->session_ids[i].key);
1741 if (sid_match && key_match) {
1742 debug_f("session ID already recorded for %s %s",
1743 sshkey_type(key), fp);
1744 r = 0;
1745 goto out;
1746 } else if (sid_match) {
1747 error_f("session ID recorded against different key "
1748 "for %s %s", sshkey_type(key), fp);
1749 r = -1;
1750 goto out;
1751 }
1752 /*
1753 * new sid with previously-seen key can happen, e.g. multiple
1754 * connections to the same host.
1755 */
1756 }
1757 /* record new key/sid */
1758 if (e->nsession_ids >= AGENT_MAX_SESSION_IDS) {
1759 error_f("too many session IDs recorded");
1760 goto out;
1761 }
1762 e->session_ids = xrecallocarray(e->session_ids, e->nsession_ids,
1763 e->nsession_ids + 1, sizeof(*e->session_ids));
1764 i = e->nsession_ids++;
1765 debug_f("recorded %s %s (slot %zu of %d)", sshkey_type(key), fp, i,
1766 AGENT_MAX_SESSION_IDS);
1767 e->session_ids[i].key = key;
1768 e->session_ids[i].forwarded = fwd != 0;
1769 key = NULL; /* transferred */
1770 /* can't transfer sid; it's refcounted and scoped to request's life */
1771 if ((e->session_ids[i].sid = sshbuf_new()) == NULL)
1772 fatal_f("sshbuf_new");
1773 if ((r = sshbuf_putb(e->session_ids[i].sid, sid)) != 0)
1774 fatal_fr(r, "sshbuf_putb session ID");
1775 /* success */
1776 r = 0;
1777 out:
1778 free(fp);
1779 sshkey_free(key);
1780 sshbuf_free(sid);
1781 sshbuf_free(sig);
1782 return r == 0 ? 1 : 0;
1783 }
1784
1785 static void
1786 process_extension(SocketEntry *e)
1787 {
1788 int r, success = 0;
1789 char *name;
1790
1791 debug2_f("entering");
1792 if ((r = sshbuf_get_cstring(e->request, &name, NULL)) != 0) {
1793 error_fr(r, "parse");
1794 goto send;
1795 }
1796 if (strcmp(name, "session-bind@openssh.com") == 0)
1797 success = process_ext_session_bind(e);
1798 else
1799 debug_f("unsupported extension \"%s\"", name);
1800 free(name);
1801 send:
1802 send_status(e, success);
1803 }
1804 /*
1805 * dispatch incoming message.
1806 * returns 1 on success, 0 for incomplete messages or -1 on error.
1807 */
1808 static int
1809 process_message(u_int socknum)
1810 {
1811 u_int msg_len;
1812 u_char type;
1813 const u_char *cp;
1814 int r;
1815 SocketEntry *e;
1816
1817 if (socknum >= sockets_alloc)
1818 fatal_f("sock %u >= allocated %u", socknum, sockets_alloc);
1819 e = &sockets[socknum];
1820
1821 if (sshbuf_len(e->input) < 5)
1822 return 0; /* Incomplete message header. */
1823 cp = sshbuf_ptr(e->input);
1824 msg_len = PEEK_U32(cp);
1825 if (msg_len > AGENT_MAX_LEN) {
1826 debug_f("socket %u (fd=%d) message too long %u > %u",
1827 socknum, e->fd, msg_len, AGENT_MAX_LEN);
1828 return -1;
1829 }
1830 if (sshbuf_len(e->input) < msg_len + 4)
1831 return 0; /* Incomplete message body. */
1832
1833 /* move the current input to e->request */
1834 sshbuf_reset(e->request);
1835 if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 ||
1836 (r = sshbuf_get_u8(e->request, &type)) != 0) {
1837 if (r == SSH_ERR_MESSAGE_INCOMPLETE ||
1838 r == SSH_ERR_STRING_TOO_LARGE) {
1839 error_fr(r, "parse");
1840 return -1;
1841 }
1842 fatal_fr(r, "parse");
1843 }
1844
1845 debug_f("socket %u (fd=%d) type %d", socknum, e->fd, type);
1846
1847 /* check whether agent is locked */
1848 if (locked && type != SSH_AGENTC_UNLOCK) {
1849 sshbuf_reset(e->request);
1850 switch (type) {
1851 case SSH2_AGENTC_REQUEST_IDENTITIES:
1852 /* send empty lists */
1853 no_identities(e);
1854 break;
1855 default:
1856 /* send a fail message for all other request types */
1857 send_status(e, 0);
1858 }
1859 return 1;
1860 }
1861
1862 switch (type) {
1863 case SSH_AGENTC_LOCK:
1864 case SSH_AGENTC_UNLOCK:
1865 process_lock_agent(e, type == SSH_AGENTC_LOCK);
1866 break;
1867 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
1868 process_remove_all_identities(e); /* safe for !WITH_SSH1 */
1869 break;
1870 /* ssh2 */
1871 case SSH2_AGENTC_SIGN_REQUEST:
1872 process_sign_request2(e);
1873 break;
1874 case SSH2_AGENTC_REQUEST_IDENTITIES:
1875 process_request_identities(e);
1876 break;
1877 case SSH2_AGENTC_ADD_IDENTITY:
1878 case SSH2_AGENTC_ADD_ID_CONSTRAINED:
1879 process_add_identity(e);
1880 break;
1881 case SSH2_AGENTC_REMOVE_IDENTITY:
1882 process_remove_identity(e);
1883 break;
1884 case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
1885 process_remove_all_identities(e);
1886 break;
1887 #ifdef ENABLE_PKCS11
1888 case SSH_AGENTC_ADD_SMARTCARD_KEY:
1889 case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
1890 process_add_smartcard_key(e);
1891 break;
1892 case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
1893 process_remove_smartcard_key(e);
1894 break;
1895 #endif /* ENABLE_PKCS11 */
1896 case SSH_AGENTC_EXTENSION:
1897 process_extension(e);
1898 break;
1899 default:
1900 /* Unknown message. Respond with failure. */
1901 error("Unknown message %d", type);
1902 sshbuf_reset(e->request);
1903 send_status(e, 0);
1904 break;
1905 }
1906 return 1;
1907 }
1908
1909 static void
1910 new_socket(sock_type type, int fd)
1911 {
1912 u_int i, old_alloc, new_alloc;
1913
1914 debug_f("type = %s", type == AUTH_CONNECTION ? "CONNECTION" :
1915 (type == AUTH_SOCKET ? "SOCKET" : "UNKNOWN"));
1916 set_nonblock(fd);
1917
1918 if (fd > max_fd)
1919 max_fd = fd;
1920
1921 for (i = 0; i < sockets_alloc; i++)
1922 if (sockets[i].type == AUTH_UNUSED) {
1923 sockets[i].fd = fd;
1924 if ((sockets[i].input = sshbuf_new()) == NULL ||
1925 (sockets[i].output = sshbuf_new()) == NULL ||
1926 (sockets[i].request = sshbuf_new()) == NULL)
1927 fatal_f("sshbuf_new failed");
1928 sockets[i].type = type;
1929 return;
1930 }
1931 old_alloc = sockets_alloc;
1932 new_alloc = sockets_alloc + 10;
1933 sockets = xrecallocarray(sockets, old_alloc, new_alloc,
1934 sizeof(sockets[0]));
1935 for (i = old_alloc; i < new_alloc; i++)
1936 sockets[i].type = AUTH_UNUSED;
1937 sockets_alloc = new_alloc;
1938 sockets[old_alloc].fd = fd;
1939 if ((sockets[old_alloc].input = sshbuf_new()) == NULL ||
1940 (sockets[old_alloc].output = sshbuf_new()) == NULL ||
1941 (sockets[old_alloc].request = sshbuf_new()) == NULL)
1942 fatal_f("sshbuf_new failed");
1943 sockets[old_alloc].type = type;
1944 }
1945
1946 static int
1947 handle_socket_read(u_int socknum)
1948 {
1949 struct sockaddr_un sunaddr;
1950 socklen_t slen;
1951 uid_t euid;
1952 gid_t egid;
1953 int fd;
1954
1955 slen = sizeof(sunaddr);
1956 fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen);
1957 if (fd == -1) {
1958 error("accept from AUTH_SOCKET: %s", strerror(errno));
1959 return -1;
1960 }
1961 if (getpeereid(fd, &euid, &egid) == -1) {
1962 error("getpeereid %d failed: %s", fd, strerror(errno));
1963 close(fd);
1964 return -1;
1965 }
1966 if ((euid != 0) && (getuid() != euid)) {
1967 error("uid mismatch: peer euid %u != uid %u",
1968 (u_int) euid, (u_int) getuid());
1969 close(fd);
1970 return -1;
1971 }
1972 new_socket(AUTH_CONNECTION, fd);
1973 return 0;
1974 }
1975
1976 static int
1977 handle_conn_read(u_int socknum)
1978 {
1979 char buf[AGENT_RBUF_LEN];
1980 ssize_t len;
1981 int r;
1982
1983 if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) {
1984 if (len == -1) {
1985 if (errno == EAGAIN || errno == EINTR)
1986 return 0;
1987 error_f("read error on socket %u (fd %d): %s",
1988 socknum, sockets[socknum].fd, strerror(errno));
1989 }
1990 return -1;
1991 }
1992 if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0)
1993 fatal_fr(r, "compose");
1994 explicit_bzero(buf, sizeof(buf));
1995 for (;;) {
1996 if ((r = process_message(socknum)) == -1)
1997 return -1;
1998 else if (r == 0)
1999 break;
2000 }
2001 return 0;
2002 }
2003
2004 static int
2005 handle_conn_write(u_int socknum)
2006 {
2007 ssize_t len;
2008 int r;
2009
2010 if (sshbuf_len(sockets[socknum].output) == 0)
2011 return 0; /* shouldn't happen */
2012 if ((len = write(sockets[socknum].fd,
2013 sshbuf_ptr(sockets[socknum].output),
2014 sshbuf_len(sockets[socknum].output))) <= 0) {
2015 if (len == -1) {
2016 if (errno == EAGAIN || errno == EINTR)
2017 return 0;
2018 error_f("read error on socket %u (fd %d): %s",
2019 socknum, sockets[socknum].fd, strerror(errno));
2020 }
2021 return -1;
2022 }
2023 if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0)
2024 fatal_fr(r, "consume");
2025 return 0;
2026 }
2027
2028 static void
2029 after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds)
2030 {
2031 size_t i;
2032 u_int socknum, activefds = npfd;
2033
2034 for (i = 0; i < npfd; i++) {
2035 if (pfd[i].revents == 0)
2036 continue;
2037 /* Find sockets entry */
2038 for (socknum = 0; socknum < sockets_alloc; socknum++) {
2039 if (sockets[socknum].type != AUTH_SOCKET &&
2040 sockets[socknum].type != AUTH_CONNECTION)
2041 continue;
2042 if (pfd[i].fd == sockets[socknum].fd)
2043 break;
2044 }
2045 if (socknum >= sockets_alloc) {
2046 error_f("no socket for fd %d", pfd[i].fd);
2047 continue;
2048 }
2049 /* Process events */
2050 switch (sockets[socknum].type) {
2051 case AUTH_SOCKET:
2052 if ((pfd[i].revents & (POLLIN|POLLERR)) == 0)
2053 break;
2054 if (npfd > maxfds) {
2055 debug3("out of fds (active %u >= limit %u); "
2056 "skipping accept", activefds, maxfds);
2057 break;
2058 }
2059 if (handle_socket_read(socknum) == 0)
2060 activefds++;
2061 break;
2062 case AUTH_CONNECTION:
2063 if ((pfd[i].revents & (POLLIN|POLLHUP|POLLERR)) != 0 &&
2064 handle_conn_read(socknum) != 0)
2065 goto close_sock;
2066 if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 &&
2067 handle_conn_write(socknum) != 0) {
2068 close_sock:
2069 if (activefds == 0)
2070 fatal("activefds == 0 at close_sock");
2071 close_socket(&sockets[socknum]);
2072 activefds--;
2073 break;
2074 }
2075 break;
2076 default:
2077 break;
2078 }
2079 }
2080 }
2081
2082 static int
2083 prepare_poll(struct pollfd **pfdp, size_t *npfdp, struct timespec *timeoutp, u_int maxfds)
2084 {
2085 struct pollfd *pfd = *pfdp;
2086 size_t i, j, npfd = 0;
2087 time_t deadline;
2088 int r;
2089
2090 /* Count active sockets */
2091 for (i = 0; i < sockets_alloc; i++) {
2092 switch (sockets[i].type) {
2093 case AUTH_SOCKET:
2094 case AUTH_CONNECTION:
2095 npfd++;
2096 break;
2097 case AUTH_UNUSED:
2098 break;
2099 default:
2100 fatal("Unknown socket type %d", sockets[i].type);
2101 break;
2102 }
2103 }
2104 if (npfd != *npfdp &&
2105 (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL)
2106 fatal_f("recallocarray failed");
2107 *pfdp = pfd;
2108 *npfdp = npfd;
2109
2110 for (i = j = 0; i < sockets_alloc; i++) {
2111 switch (sockets[i].type) {
2112 case AUTH_SOCKET:
2113 if (npfd > maxfds) {
2114 debug3("out of fds (active %zu >= limit %u); "
2115 "skipping arming listener", npfd, maxfds);
2116 break;
2117 }
2118 pfd[j].fd = sockets[i].fd;
2119 pfd[j].revents = 0;
2120 pfd[j].events = POLLIN;
2121 j++;
2122 break;
2123 case AUTH_CONNECTION:
2124 pfd[j].fd = sockets[i].fd;
2125 pfd[j].revents = 0;
2126 /*
2127 * Only prepare to read if we can handle a full-size
2128 * input read buffer and enqueue a max size reply..
2129 */
2130 if ((r = sshbuf_check_reserve(sockets[i].input,
2131 AGENT_RBUF_LEN)) == 0 &&
2132 (r = sshbuf_check_reserve(sockets[i].output,
2133 AGENT_MAX_LEN)) == 0)
2134 pfd[j].events = POLLIN;
2135 else if (r != SSH_ERR_NO_BUFFER_SPACE)
2136 fatal_fr(r, "reserve");
2137 if (sshbuf_len(sockets[i].output) > 0)
2138 pfd[j].events |= POLLOUT;
2139 j++;
2140 break;
2141 default:
2142 break;
2143 }
2144 }
2145 deadline = reaper();
2146 if (parent_alive_interval != 0)
2147 deadline = (deadline == 0) ? parent_alive_interval :
2148 MINIMUM(deadline, parent_alive_interval);
2149 if (deadline != 0)
2150 ptimeout_deadline_sec(timeoutp, deadline);
2151 return (1);
2152 }
2153
2154 static void
2155 cleanup_socket(void)
2156 {
2157 if (cleanup_pid != 0 && getpid() != cleanup_pid)
2158 return;
2159 debug_f("cleanup");
2160 if (socket_name[0])
2161 unlink(socket_name);
2162 if (socket_dir[0])
2163 rmdir(socket_dir);
2164 }
2165
2166 void
2167 cleanup_exit(int i)
2168 {
2169 cleanup_socket();
2170 #ifdef ENABLE_PKCS11
2171 pkcs11_terminate();
2172 #endif
2173 _exit(i);
2174 }
2175
2176 static void
2177 cleanup_handler(int sig)
2178 {
2179 signalled_exit = sig;
2180 }
2181
2182 static void
2183 keydrop_handler(int sig)
2184 {
2185 signalled_keydrop = sig;
2186 }
2187
2188 static void
2189 check_parent_exists(void)
2190 {
2191 /*
2192 * If our parent has exited then getppid() will return (pid_t)1,
2193 * so testing for that should be safe.
2194 */
2195 if (parent_pid != -1 && getppid() != parent_pid) {
2196 /* printf("Parent has died - Authentication agent exiting.\n"); */
2197 cleanup_socket();
2198 _exit(2);
2199 }
2200 }
2201
2202 static void
2203 usage(void)
2204 {
2205 fprintf(stderr,
2206 "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n"
2207 " [-O option] [-P allowed_providers] [-t life]\n"
2208 " ssh-agent [-a bind_address] [-E fingerprint_hash] [-O option]\n"
2209 " [-P allowed_providers] [-t life] command [arg ...]\n"
2210 " ssh-agent [-c | -s] -k\n");
2211 exit(1);
2212 }
2213
2214 int
2215 main(int ac, char **av)
2216 {
2217 int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0;
2218 int sock, ch, result, saved_errno;
2219 char *shell, *format, *pidstr, *agentsocket = NULL;
2220 const char *ccp;
2221 #ifdef HAVE_SETRLIMIT
2222 struct rlimit rlim;
2223 #endif
2224 extern int optind;
2225 extern char *optarg;
2226 pid_t pid;
2227 char pidstrbuf[1 + 3 * sizeof pid];
2228 size_t len;
2229 mode_t prev_mask;
2230 struct timespec timeout;
2231 struct pollfd *pfd = NULL;
2232 size_t npfd = 0;
2233 u_int maxfds;
2234 sigset_t nsigset, osigset;
2235
2236 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
2237 sanitise_stdfd();
2238
2239 /* drop */
2240 (void)setegid(getgid());
2241 (void)setgid(getgid());
2242
2243 platform_disable_tracing(0); /* strict=no */
2244
2245 #ifdef RLIMIT_NOFILE
2246 if (getrlimit(RLIMIT_NOFILE, &rlim) == -1)
2247 fatal("%s: getrlimit: %s", __progname, strerror(errno));
2248 #endif
2249
2250 __progname = ssh_get_progname(av[0]);
2251 seed_rng();
2252
2253 while ((ch = getopt(ac, av, "cDdksE:a:O:P:t:")) != -1) {
2254 switch (ch) {
2255 case 'E':
2256 fingerprint_hash = ssh_digest_alg_by_name(optarg);
2257 if (fingerprint_hash == -1)
2258 fatal("Invalid hash algorithm \"%s\"", optarg);
2259 break;
2260 case 'c':
2261 if (s_flag)
2262 usage();
2263 c_flag++;
2264 break;
2265 case 'k':
2266 k_flag++;
2267 break;
2268 case 'O':
2269 if (strcmp(optarg, "no-restrict-websafe") == 0)
2270 restrict_websafe = 0;
2271 else if (strcmp(optarg, "allow-remote-pkcs11") == 0)
2272 remote_add_provider = 1;
2273 else if ((ccp = strprefix(optarg,
2274 "websafe-allow=", 0)) != NULL) {
2275 if (websafe_allowlist != NULL)
2276 fatal("websafe-allow already set");
2277 websafe_allowlist = xstrdup(ccp);
2278 } else
2279 fatal("Unknown -O option");
2280 break;
2281 case 'P':
2282 if (allowed_providers != NULL)
2283 fatal("-P option already specified");
2284 allowed_providers = xstrdup(optarg);
2285 break;
2286 case 's':
2287 if (c_flag)
2288 usage();
2289 s_flag++;
2290 break;
2291 case 'd':
2292 if (d_flag || D_flag)
2293 usage();
2294 d_flag++;
2295 break;
2296 case 'D':
2297 if (d_flag || D_flag)
2298 usage();
2299 D_flag++;
2300 break;
2301 case 'a':
2302 agentsocket = optarg;
2303 break;
2304 case 't':
2305 if ((lifetime = convtime(optarg)) == -1) {
2306 fprintf(stderr, "Invalid lifetime\n");
2307 usage();
2308 }
2309 break;
2310 default:
2311 usage();
2312 }
2313 }
2314 ac -= optind;
2315 av += optind;
2316
2317 if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag))
2318 usage();
2319
2320 if (allowed_providers == NULL)
2321 allowed_providers = xstrdup(DEFAULT_ALLOWED_PROVIDERS);
2322 if (websafe_allowlist == NULL)
2323 websafe_allowlist = xstrdup(DEFAULT_WEBSAFE_ALLOWLIST);
2324
2325 if (ac == 0 && !c_flag && !s_flag) {
2326 shell = getenv("SHELL");
2327 if (shell != NULL && (len = strlen(shell)) > 2 &&
2328 strncmp(shell + len - 3, "csh", 3) == 0)
2329 c_flag = 1;
2330 }
2331 if (k_flag) {
2332 const char *errstr = NULL;
2333
2334 pidstr = getenv(SSH_AGENTPID_ENV_NAME);
2335 if (pidstr == NULL) {
2336 fprintf(stderr, "%s not set, cannot kill agent\n",
2337 SSH_AGENTPID_ENV_NAME);
2338 exit(1);
2339 }
2340 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr);
2341 if (errstr) {
2342 fprintf(stderr,
2343 "%s=\"%s\", which is not a good PID: %s\n",
2344 SSH_AGENTPID_ENV_NAME, pidstr, errstr);
2345 exit(1);
2346 }
2347 if (kill(pid, SIGTERM) == -1) {
2348 perror("kill");
2349 exit(1);
2350 }
2351 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n";
2352 printf(format, SSH_AUTHSOCKET_ENV_NAME);
2353 printf(format, SSH_AGENTPID_ENV_NAME);
2354 printf("echo Agent pid %ld killed;\n", (long)pid);
2355 exit(0);
2356 }
2357
2358 /*
2359 * Minimum file descriptors:
2360 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) +
2361 * a few spare for libc / stack protectors / sanitisers, etc.
2362 */
2363 #define SSH_AGENT_MIN_FDS (3+1+1+1+4)
2364 if (rlim.rlim_cur < SSH_AGENT_MIN_FDS)
2365 fatal("%s: file descriptor rlimit %lld too low (minimum %u)",
2366 __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS);
2367 maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS;
2368
2369 parent_pid = getpid();
2370
2371 if (agentsocket == NULL) {
2372 /* Create private directory for agent socket */
2373 mktemp_proto(socket_dir, sizeof(socket_dir));
2374 if (mkdtemp(socket_dir) == NULL) {
2375 perror("mkdtemp: private socket dir");
2376 exit(1);
2377 }
2378 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
2379 (long)parent_pid);
2380 } else {
2381 /* Try to use specified agent socket */
2382 socket_dir[0] = '\0';
2383 strlcpy(socket_name, agentsocket, sizeof socket_name);
2384 }
2385
2386 /*
2387 * Create socket early so it will exist before command gets run from
2388 * the parent.
2389 */
2390 prev_mask = umask(0177);
2391 sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
2392 if (sock < 0) {
2393 /* XXX - unix_listener() calls error() not perror() */
2394 *socket_name = '\0'; /* Don't unlink any existing file */
2395 cleanup_exit(1);
2396 }
2397 umask(prev_mask);
2398
2399 /*
2400 * Fork, and have the parent execute the command, if any, or present
2401 * the socket data. The child continues as the authentication agent.
2402 */
2403 if (D_flag || d_flag) {
2404 log_init(__progname,
2405 d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO,
2406 SYSLOG_FACILITY_AUTH, 1);
2407 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
2408 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
2409 SSH_AUTHSOCKET_ENV_NAME);
2410 printf("echo Agent pid %ld;\n", (long)parent_pid);
2411 fflush(stdout);
2412 goto skip;
2413 }
2414 pid = fork();
2415 if (pid == -1) {
2416 perror("fork");
2417 cleanup_exit(1);
2418 }
2419 if (pid != 0) { /* Parent - execute the given command. */
2420 close(sock);
2421 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid);
2422 if (ac == 0) {
2423 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
2424 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
2425 SSH_AUTHSOCKET_ENV_NAME);
2426 printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf,
2427 SSH_AGENTPID_ENV_NAME);
2428 printf("echo Agent pid %ld;\n", (long)pid);
2429 exit(0);
2430 }
2431 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
2432 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
2433 perror("setenv");
2434 exit(1);
2435 }
2436 execvp(av[0], av);
2437 perror(av[0]);
2438 exit(1);
2439 }
2440 /* child */
2441 log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0);
2442
2443 if (setsid() == -1) {
2444 error("setsid: %s", strerror(errno));
2445 cleanup_exit(1);
2446 }
2447
2448 (void)chdir("/");
2449 if (stdfd_devnull(1, 1, 1) == -1)
2450 error_f("stdfd_devnull failed");
2451
2452 #ifdef HAVE_SETRLIMIT
2453 /* deny core dumps, since memory contains unencrypted private keys */
2454 rlim.rlim_cur = rlim.rlim_max = 0;
2455 if (setrlimit(RLIMIT_CORE, &rlim) == -1) {
2456 error("setrlimit RLIMIT_CORE: %s", strerror(errno));
2457 cleanup_exit(1);
2458 }
2459 #endif
2460
2461 skip:
2462
2463 cleanup_pid = getpid();
2464
2465 #ifdef ENABLE_PKCS11
2466 pkcs11_init(0);
2467 #endif
2468 new_socket(AUTH_SOCKET, sock);
2469 if (ac > 0)
2470 parent_alive_interval = 10;
2471 idtab_init();
2472 ssh_signal(SIGPIPE, SIG_IGN);
2473 ssh_signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN);
2474 ssh_signal(SIGHUP, cleanup_handler);
2475 ssh_signal(SIGTERM, cleanup_handler);
2476 ssh_signal(SIGUSR1, keydrop_handler);
2477
2478 sigemptyset(&nsigset);
2479 sigaddset(&nsigset, SIGINT);
2480 sigaddset(&nsigset, SIGHUP);
2481 sigaddset(&nsigset, SIGTERM);
2482 sigaddset(&nsigset, SIGUSR1);
2483
2484 if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1)
2485 fatal("%s: pledge: %s", __progname, strerror(errno));
2486 platform_pledge_agent();
2487
2488 while (1) {
2489 sigprocmask(SIG_BLOCK, &nsigset, &osigset);
2490 if (signalled_exit != 0) {
2491 logit("exiting on signal %d", (int)signalled_exit);
2492 cleanup_exit(2);
2493 }
2494 if (signalled_keydrop) {
2495 logit("signal %d received; removing all keys",
2496 signalled_keydrop);
2497 remove_all_identities();
2498 signalled_keydrop = 0;
2499 }
2500 ptimeout_init(&timeout);
2501 prepare_poll(&pfd, &npfd, &timeout, maxfds);
2502 result = ppoll(pfd, npfd, ptimeout_get_tsp(&timeout), &osigset);
2503 sigprocmask(SIG_SETMASK, &osigset, NULL);
2504 saved_errno = errno;
2505 if (parent_alive_interval != 0)
2506 check_parent_exists();
2507 (void) reaper(); /* remove expired keys */
2508 if (result == -1) {
2509 if (saved_errno == EINTR)
2510 continue;
2511 fatal("poll: %s", strerror(saved_errno));
2512 } else if (result > 0)
2513 after_poll(pfd, npfd, maxfds);
2514 }
2515 /* NOTREACHED */
2516 }
Portable OpenSSH is a multi-platform compatible version of OpenBSD's OpenSSH