1 /* $OpenBSD: ssh-agent.c,v 1.306 2024/03/09 05:12:13 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
98 /* Maximum accepted message length */
99 #define AGENT_MAX_LEN (256*1024)
100 /* Maximum bytes to read from client socket */
101 #define AGENT_RBUF_LEN (4096)
102 /* Maximum number of recorded session IDs/hostkeys per connection */
103 #define AGENT_MAX_SESSION_IDS 16
104 /* Maximum size of session ID */
105 #define AGENT_MAX_SID_LEN 128
106 /* Maximum number of destination constraints to accept on a key */
107 #define AGENT_MAX_DEST_CONSTRAINTS 1024
108 /* Maximum number of associated certificate constraints to accept on a key */
109 #define AGENT_MAX_EXT_CERTS 1024
110
111 /* XXX store hostkey_sid in a refcounted tree */
112
113 typedef enum {
114 AUTH_UNUSED = 0,
115 AUTH_SOCKET = 1,
116 AUTH_CONNECTION = 2,
117 } sock_type;
118
119 struct hostkey_sid {
120 struct sshkey *key;
121 struct sshbuf *sid;
122 int forwarded;
123 };
124
125 typedef struct socket_entry {
126 int fd;
127 sock_type type;
128 struct sshbuf *input;
129 struct sshbuf *output;
130 struct sshbuf *request;
131 size_t nsession_ids;
132 struct hostkey_sid *session_ids;
133 int session_bind_attempted;
134 } SocketEntry;
135
136 u_int sockets_alloc = 0;
137 SocketEntry *sockets = NULL;
138
139 typedef struct identity {
140 TAILQ_ENTRY(identity) next;
141 struct sshkey *key;
142 char *comment;
143 char *provider;
144 time_t death;
145 u_int confirm;
146 char *sk_provider;
147 struct dest_constraint *dest_constraints;
148 size_t ndest_constraints;
149 } Identity;
150
151 struct idtable {
152 int nentries;
153 TAILQ_HEAD(idqueue, identity) idlist;
154 };
155
156 /* private key table */
157 struct idtable *idtab;
158
159 int max_fd = 0;
160
161 /* pid of shell == parent of agent */
162 pid_t parent_pid = -1;
163 time_t parent_alive_interval = 0;
164
165 sig_atomic_t signalled = 0;
166
167 /* pid of process for which cleanup_socket is applicable */
168 pid_t cleanup_pid = 0;
169
170 /* pathname and directory for AUTH_SOCKET */
171 char socket_name[PATH_MAX];
172 char socket_dir[PATH_MAX];
173
174 /* Pattern-list of allowed PKCS#11/Security key paths */
175 static char *allowed_providers;
176
177 /*
178 * Allows PKCS11 providers or SK keys that use non-internal providers to
179 * be added over a remote connection (identified by session-bind@openssh.com).
180 */
181 static int remote_add_provider;
182
183 /* locking */
184 #define LOCK_SIZE 32
185 #define LOCK_SALT_SIZE 16
186 #define LOCK_ROUNDS 1
187 int locked = 0;
188 u_char lock_pwhash[LOCK_SIZE];
189 u_char lock_salt[LOCK_SALT_SIZE];
190
191 extern char *__progname;
192
193 /* Default lifetime in seconds (0 == forever) */
194 static int lifetime = 0;
195
196 static int fingerprint_hash = SSH_FP_HASH_DEFAULT;
197
198 /* Refuse signing of non-SSH messages for web-origin FIDO keys */
199 static int restrict_websafe = 1;
200
201 static void
close_socket(SocketEntry * e)202 close_socket(SocketEntry *e)
203 {
204 size_t i;
205
206 close(e->fd);
207 sshbuf_free(e->input);
208 sshbuf_free(e->output);
209 sshbuf_free(e->request);
210 for (i = 0; i < e->nsession_ids; i++) {
211 sshkey_free(e->session_ids[i].key);
212 sshbuf_free(e->session_ids[i].sid);
213 }
214 free(e->session_ids);
215 memset(e, '\0', sizeof(*e));
216 e->fd = -1;
217 e->type = AUTH_UNUSED;
218 }
219
220 static void
idtab_init(void)221 idtab_init(void)
222 {
223 idtab = xcalloc(1, sizeof(*idtab));
224 TAILQ_INIT(&idtab->idlist);
225 idtab->nentries = 0;
226 }
227
228 static void
free_dest_constraint_hop(struct dest_constraint_hop * dch)229 free_dest_constraint_hop(struct dest_constraint_hop *dch)
230 {
231 u_int i;
232
233 if (dch == NULL)
234 return;
235 free(dch->user);
236 free(dch->hostname);
237 for (i = 0; i < dch->nkeys; i++)
238 sshkey_free(dch->keys[i]);
239 free(dch->keys);
240 free(dch->key_is_ca);
241 }
242
243 static void
free_dest_constraints(struct dest_constraint * dcs,size_t ndcs)244 free_dest_constraints(struct dest_constraint *dcs, size_t ndcs)
245 {
246 size_t i;
247
248 for (i = 0; i < ndcs; i++) {
249 free_dest_constraint_hop(&dcs[i].from);
250 free_dest_constraint_hop(&dcs[i].to);
251 }
252 free(dcs);
253 }
254
255 #ifdef ENABLE_PKCS11
256 static void
dup_dest_constraint_hop(const struct dest_constraint_hop * dch,struct dest_constraint_hop * out)257 dup_dest_constraint_hop(const struct dest_constraint_hop *dch,
258 struct dest_constraint_hop *out)
259 {
260 u_int i;
261 int r;
262
263 out->user = dch->user == NULL ? NULL : xstrdup(dch->user);
264 out->hostname = dch->hostname == NULL ? NULL : xstrdup(dch->hostname);
265 out->is_ca = dch->is_ca;
266 out->nkeys = dch->nkeys;
267 out->keys = out->nkeys == 0 ? NULL :
268 xcalloc(out->nkeys, sizeof(*out->keys));
269 out->key_is_ca = out->nkeys == 0 ? NULL :
270 xcalloc(out->nkeys, sizeof(*out->key_is_ca));
271 for (i = 0; i < dch->nkeys; i++) {
272 if (dch->keys[i] != NULL &&
273 (r = sshkey_from_private(dch->keys[i],
274 &(out->keys[i]))) != 0)
275 fatal_fr(r, "copy key");
276 out->key_is_ca[i] = dch->key_is_ca[i];
277 }
278 }
279
280 static struct dest_constraint *
dup_dest_constraints(const struct dest_constraint * dcs,size_t ndcs)281 dup_dest_constraints(const struct dest_constraint *dcs, size_t ndcs)
282 {
283 size_t i;
284 struct dest_constraint *ret;
285
286 if (ndcs == 0)
287 return NULL;
288 ret = xcalloc(ndcs, sizeof(*ret));
289 for (i = 0; i < ndcs; i++) {
290 dup_dest_constraint_hop(&dcs[i].from, &ret[i].from);
291 dup_dest_constraint_hop(&dcs[i].to, &ret[i].to);
292 }
293 return ret;
294 }
295 #endif /* ENABLE_PKCS11 */
296
297 #ifdef DEBUG_CONSTRAINTS
298 static void
dump_dest_constraint_hop(const struct dest_constraint_hop * dch)299 dump_dest_constraint_hop(const struct dest_constraint_hop *dch)
300 {
301 u_int i;
302 char *fp;
303
304 debug_f("user %s hostname %s is_ca %d nkeys %u",
305 dch->user == NULL ? "(null)" : dch->user,
306 dch->hostname == NULL ? "(null)" : dch->hostname,
307 dch->is_ca, dch->nkeys);
308 for (i = 0; i < dch->nkeys; i++) {
309 fp = NULL;
310 if (dch->keys[i] != NULL &&
311 (fp = sshkey_fingerprint(dch->keys[i],
312 SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL)
313 fatal_f("fingerprint failed");
314 debug_f("key %u/%u: %s%s%s key_is_ca %d", i, dch->nkeys,
315 dch->keys[i] == NULL ? "" : sshkey_ssh_name(dch->keys[i]),
316 dch->keys[i] == NULL ? "" : " ",
317 dch->keys[i] == NULL ? "none" : fp,
318 dch->key_is_ca[i]);
319 free(fp);
320 }
321 }
322 #endif /* DEBUG_CONSTRAINTS */
323
324 static void
dump_dest_constraints(const char * context,const struct dest_constraint * dcs,size_t ndcs)325 dump_dest_constraints(const char *context,
326 const struct dest_constraint *dcs, size_t ndcs)
327 {
328 #ifdef DEBUG_CONSTRAINTS
329 size_t i;
330
331 debug_f("%s: %zu constraints", context, ndcs);
332 for (i = 0; i < ndcs; i++) {
333 debug_f("constraint %zu / %zu: from: ", i, ndcs);
334 dump_dest_constraint_hop(&dcs[i].from);
335 debug_f("constraint %zu / %zu: to: ", i, ndcs);
336 dump_dest_constraint_hop(&dcs[i].to);
337 }
338 debug_f("done for %s", context);
339 #endif /* DEBUG_CONSTRAINTS */
340 }
341
342 static void
free_identity(Identity * id)343 free_identity(Identity *id)
344 {
345 sshkey_free(id->key);
346 free(id->provider);
347 free(id->comment);
348 free(id->sk_provider);
349 free_dest_constraints(id->dest_constraints, id->ndest_constraints);
350 free(id);
351 }
352
353 /*
354 * Match 'key' against the key/CA list in a destination constraint hop
355 * Returns 0 on success or -1 otherwise.
356 */
357 static int
match_key_hop(const char * tag,const struct sshkey * key,const struct dest_constraint_hop * dch)358 match_key_hop(const char *tag, const struct sshkey *key,
359 const struct dest_constraint_hop *dch)
360 {
361 const char *reason = NULL;
362 const char *hostname = dch->hostname ? dch->hostname : "(ORIGIN)";
363 u_int i;
364 char *fp;
365
366 if (key == NULL)
367 return -1;
368 /* XXX logspam */
369 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
370 SSH_FP_DEFAULT)) == NULL)
371 fatal_f("fingerprint failed");
372 debug3_f("%s: entering hostname %s, requested key %s %s, %u keys avail",
373 tag, hostname, sshkey_type(key), fp, dch->nkeys);
374 free(fp);
375 for (i = 0; i < dch->nkeys; i++) {
376 if (dch->keys[i] == NULL)
377 return -1;
378 /* XXX logspam */
379 if ((fp = sshkey_fingerprint(dch->keys[i], SSH_FP_HASH_DEFAULT,
380 SSH_FP_DEFAULT)) == NULL)
381 fatal_f("fingerprint failed");
382 debug3_f("%s: key %u: %s%s %s", tag, i,
383 dch->key_is_ca[i] ? "CA " : "",
384 sshkey_type(dch->keys[i]), fp);
385 free(fp);
386 if (!sshkey_is_cert(key)) {
387 /* plain key */
388 if (dch->key_is_ca[i] ||
389 !sshkey_equal(key, dch->keys[i]))
390 continue;
391 return 0;
392 }
393 /* certificate */
394 if (!dch->key_is_ca[i])
395 continue;
396 if (key->cert == NULL || key->cert->signature_key == NULL)
397 return -1; /* shouldn't happen */
398 if (!sshkey_equal(key->cert->signature_key, dch->keys[i]))
399 continue;
400 if (sshkey_cert_check_host(key, hostname, 1,
401 SSH_ALLOWED_CA_SIGALGS, &reason) != 0) {
402 debug_f("cert %s / hostname %s rejected: %s",
403 key->cert->key_id, hostname, reason);
404 continue;
405 }
406 return 0;
407 }
408 return -1;
409 }
410
411 /* Check destination constraints on an identity against the hostkey/user */
412 static int
permitted_by_dest_constraints(const struct sshkey * fromkey,const struct sshkey * tokey,Identity * id,const char * user,const char ** hostnamep)413 permitted_by_dest_constraints(const struct sshkey *fromkey,
414 const struct sshkey *tokey, Identity *id, const char *user,
415 const char **hostnamep)
416 {
417 size_t i;
418 struct dest_constraint *d;
419
420 if (hostnamep != NULL)
421 *hostnamep = NULL;
422 for (i = 0; i < id->ndest_constraints; i++) {
423 d = id->dest_constraints + i;
424 /* XXX remove logspam */
425 debug2_f("constraint %zu %s%s%s (%u keys) > %s%s%s (%u keys)",
426 i, d->from.user ? d->from.user : "",
427 d->from.user ? "@" : "",
428 d->from.hostname ? d->from.hostname : "(ORIGIN)",
429 d->from.nkeys,
430 d->to.user ? d->to.user : "", d->to.user ? "@" : "",
431 d->to.hostname ? d->to.hostname : "(ANY)", d->to.nkeys);
432
433 /* Match 'from' key */
434 if (fromkey == NULL) {
435 /* We are matching the first hop */
436 if (d->from.hostname != NULL || d->from.nkeys != 0)
437 continue;
438 } else if (match_key_hop("from", fromkey, &d->from) != 0)
439 continue;
440
441 /* Match 'to' key */
442 if (tokey != NULL && match_key_hop("to", tokey, &d->to) != 0)
443 continue;
444
445 /* Match user if specified */
446 if (d->to.user != NULL && user != NULL &&
447 !match_pattern(user, d->to.user))
448 continue;
449
450 /* successfully matched this constraint */
451 if (hostnamep != NULL)
452 *hostnamep = d->to.hostname;
453 debug2_f("allowed for hostname %s",
454 d->to.hostname == NULL ? "*" : d->to.hostname);
455 return 0;
456 }
457 /* no match */
458 debug2_f("%s identity \"%s\" not permitted for this destination",
459 sshkey_type(id->key), id->comment);
460 return -1;
461 }
462
463 /*
464 * Check whether hostkeys on a SocketEntry and the optionally specified user
465 * are permitted by the destination constraints on the Identity.
466 * Returns 0 on success or -1 otherwise.
467 */
468 static int
identity_permitted(Identity * id,SocketEntry * e,char * user,const char ** forward_hostnamep,const char ** last_hostnamep)469 identity_permitted(Identity *id, SocketEntry *e, char *user,
470 const char **forward_hostnamep, const char **last_hostnamep)
471 {
472 size_t i;
473 const char **hp;
474 struct hostkey_sid *hks;
475 const struct sshkey *fromkey = NULL;
476 const char *test_user;
477 char *fp1, *fp2;
478
479 /* XXX remove logspam */
480 debug3_f("entering: key %s comment \"%s\", %zu socket bindings, "
481 "%zu constraints", sshkey_type(id->key), id->comment,
482 e->nsession_ids, id->ndest_constraints);
483 if (id->ndest_constraints == 0)
484 return 0; /* unconstrained */
485 if (e->session_bind_attempted && e->nsession_ids == 0) {
486 error_f("previous session bind failed on socket");
487 return -1;
488 }
489 if (e->nsession_ids == 0)
490 return 0; /* local use */
491 /*
492 * Walk through the hops recorded by session_id and try to find a
493 * constraint that satisfies each.
494 */
495 for (i = 0; i < e->nsession_ids; i++) {
496 hks = e->session_ids + i;
497 if (hks->key == NULL)
498 fatal_f("internal error: no bound key");
499 /* XXX remove logspam */
500 fp1 = fp2 = NULL;
501 if (fromkey != NULL &&
502 (fp1 = sshkey_fingerprint(fromkey, SSH_FP_HASH_DEFAULT,
503 SSH_FP_DEFAULT)) == NULL)
504 fatal_f("fingerprint failed");
505 if ((fp2 = sshkey_fingerprint(hks->key, SSH_FP_HASH_DEFAULT,
506 SSH_FP_DEFAULT)) == NULL)
507 fatal_f("fingerprint failed");
508 debug3_f("socketentry fd=%d, entry %zu %s, "
509 "from hostkey %s %s to user %s hostkey %s %s",
510 e->fd, i, hks->forwarded ? "FORWARD" : "AUTH",
511 fromkey ? sshkey_type(fromkey) : "(ORIGIN)",
512 fromkey ? fp1 : "", user ? user : "(ANY)",
513 sshkey_type(hks->key), fp2);
514 free(fp1);
515 free(fp2);
516 /*
517 * Record the hostnames for the initial forwarding and
518 * the final destination.
519 */
520 hp = NULL;
521 if (i == e->nsession_ids - 1)
522 hp = last_hostnamep;
523 else if (i == 0)
524 hp = forward_hostnamep;
525 /* Special handling for final recorded binding */
526 test_user = NULL;
527 if (i == e->nsession_ids - 1) {
528 /* Can only check user at final hop */
529 test_user = user;
530 /*
531 * user is only presented for signature requests.
532 * If this is the case, make sure last binding is not
533 * for a forwarding.
534 */
535 if (hks->forwarded && user != NULL) {
536 error_f("tried to sign on forwarding hop");
537 return -1;
538 }
539 } else if (!hks->forwarded) {
540 error_f("tried to forward though signing bind");
541 return -1;
542 }
543 if (permitted_by_dest_constraints(fromkey, hks->key, id,
544 test_user, hp) != 0)
545 return -1;
546 fromkey = hks->key;
547 }
548 /*
549 * Another special case: if the last bound session ID was for a
550 * forwarding, and this function is not being called to check a sign
551 * request (i.e. no 'user' supplied), then only permit the key if
552 * there is a permission that would allow it to be used at another
553 * destination. This hides keys that are allowed to be used to
554 * authenticate *to* a host but not permitted for *use* beyond it.
555 */
556 hks = &e->session_ids[e->nsession_ids - 1];
557 if (hks->forwarded && user == NULL &&
558 permitted_by_dest_constraints(hks->key, NULL, id,
559 NULL, NULL) != 0) {
560 debug3_f("key permitted at host but not after");
561 return -1;
562 }
563
564 /* success */
565 return 0;
566 }
567
568 static int
socket_is_remote(SocketEntry * e)569 socket_is_remote(SocketEntry *e)
570 {
571 return e->session_bind_attempted || (e->nsession_ids != 0);
572 }
573
574 /* return matching private key for given public key */
575 static Identity *
lookup_identity(struct sshkey * key)576 lookup_identity(struct sshkey *key)
577 {
578 Identity *id;
579
580 TAILQ_FOREACH(id, &idtab->idlist, next) {
581 if (sshkey_equal(key, id->key))
582 return (id);
583 }
584 return (NULL);
585 }
586
587 /* Check confirmation of keysign request */
588 static int
confirm_key(Identity * id,const char * extra)589 confirm_key(Identity *id, const char *extra)
590 {
591 char *p;
592 int ret = -1;
593
594 p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT);
595 if (p != NULL &&
596 ask_permission("Allow use of key %s?\nKey fingerprint %s.%s%s",
597 id->comment, p,
598 extra == NULL ? "" : "\n", extra == NULL ? "" : extra))
599 ret = 0;
600 free(p);
601
602 return (ret);
603 }
604
605 static void
send_status(SocketEntry * e,int success)606 send_status(SocketEntry *e, int success)
607 {
608 int r;
609
610 if ((r = sshbuf_put_u32(e->output, 1)) != 0 ||
611 (r = sshbuf_put_u8(e->output, success ?
612 SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
613 fatal_fr(r, "compose");
614 }
615
616 /* send list of supported public keys to 'client' */
617 static void
process_request_identities(SocketEntry * e)618 process_request_identities(SocketEntry *e)
619 {
620 Identity *id;
621 struct sshbuf *msg, *keys;
622 int r;
623 u_int i = 0, nentries = 0;
624 char *fp;
625
626 debug2_f("entering");
627
628 if ((msg = sshbuf_new()) == NULL || (keys = sshbuf_new()) == NULL)
629 fatal_f("sshbuf_new failed");
630 TAILQ_FOREACH(id, &idtab->idlist, next) {
631 if ((fp = sshkey_fingerprint(id->key, SSH_FP_HASH_DEFAULT,
632 SSH_FP_DEFAULT)) == NULL)
633 fatal_f("fingerprint failed");
634 debug_f("key %u / %u: %s %s", i++, idtab->nentries,
635 sshkey_ssh_name(id->key), fp);
636 dump_dest_constraints(__func__,
637 id->dest_constraints, id->ndest_constraints);
638 free(fp);
639 /* identity not visible, don't include in response */
640 if (identity_permitted(id, e, NULL, NULL, NULL) != 0)
641 continue;
642 if ((r = sshkey_puts_opts(id->key, keys,
643 SSHKEY_SERIALIZE_INFO)) != 0 ||
644 (r = sshbuf_put_cstring(keys, id->comment)) != 0) {
645 error_fr(r, "compose key/comment");
646 continue;
647 }
648 nentries++;
649 }
650 debug2_f("replying with %u allowed of %u available keys",
651 nentries, idtab->nentries);
652 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
653 (r = sshbuf_put_u32(msg, nentries)) != 0 ||
654 (r = sshbuf_putb(msg, keys)) != 0)
655 fatal_fr(r, "compose");
656 if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
657 fatal_fr(r, "enqueue");
658 sshbuf_free(msg);
659 sshbuf_free(keys);
660 }
661
662
663 static char *
agent_decode_alg(struct sshkey * key,u_int flags)664 agent_decode_alg(struct sshkey *key, u_int flags)
665 {
666 if (key->type == KEY_RSA) {
667 if (flags & SSH_AGENT_RSA_SHA2_256)
668 return "rsa-sha2-256";
669 else if (flags & SSH_AGENT_RSA_SHA2_512)
670 return "rsa-sha2-512";
671 } else if (key->type == KEY_RSA_CERT) {
672 if (flags & SSH_AGENT_RSA_SHA2_256)
673 return "rsa-sha2-256-cert-v01@openssh.com";
674 else if (flags & SSH_AGENT_RSA_SHA2_512)
675 return "rsa-sha2-512-cert-v01@openssh.com";
676 }
677 return NULL;
678 }
679
680 /*
681 * Attempt to parse the contents of a buffer as a SSH publickey userauth
682 * request, checking its contents for consistency and matching the embedded
683 * key against the one that is being used for signing.
684 * Note: does not modify msg buffer.
685 * Optionally extract the username, session ID and/or hostkey from the request.
686 */
687 static int
parse_userauth_request(struct sshbuf * msg,const struct sshkey * expected_key,char ** userp,struct sshbuf ** sess_idp,struct sshkey ** hostkeyp)688 parse_userauth_request(struct sshbuf *msg, const struct sshkey *expected_key,
689 char **userp, struct sshbuf **sess_idp, struct sshkey **hostkeyp)
690 {
691 struct sshbuf *b = NULL, *sess_id = NULL;
692 char *user = NULL, *service = NULL, *method = NULL, *pkalg = NULL;
693 int r;
694 u_char t, sig_follows;
695 struct sshkey *mkey = NULL, *hostkey = NULL;
696
697 if (userp != NULL)
698 *userp = NULL;
699 if (sess_idp != NULL)
700 *sess_idp = NULL;
701 if (hostkeyp != NULL)
702 *hostkeyp = NULL;
703 if ((b = sshbuf_fromb(msg)) == NULL)
704 fatal_f("sshbuf_fromb");
705
706 /* SSH userauth request */
707 if ((r = sshbuf_froms(b, &sess_id)) != 0)
708 goto out;
709 if (sshbuf_len(sess_id) == 0) {
710 r = SSH_ERR_INVALID_FORMAT;
711 goto out;
712 }
713 if ((r = sshbuf_get_u8(b, &t)) != 0 || /* SSH2_MSG_USERAUTH_REQUEST */
714 (r = sshbuf_get_cstring(b, &user, NULL)) != 0 || /* server user */
715 (r = sshbuf_get_cstring(b, &service, NULL)) != 0 || /* service */
716 (r = sshbuf_get_cstring(b, &method, NULL)) != 0 || /* method */
717 (r = sshbuf_get_u8(b, &sig_follows)) != 0 || /* sig-follows */
718 (r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 || /* alg */
719 (r = sshkey_froms(b, &mkey)) != 0) /* key */
720 goto out;
721 if (t != SSH2_MSG_USERAUTH_REQUEST ||
722 sig_follows != 1 ||
723 strcmp(service, "ssh-connection") != 0 ||
724 !sshkey_equal(expected_key, mkey) ||
725 sshkey_type_from_name(pkalg) != expected_key->type) {
726 r = SSH_ERR_INVALID_FORMAT;
727 goto out;
728 }
729 if (strcmp(method, "publickey-hostbound-v00@openssh.com") == 0) {
730 if ((r = sshkey_froms(b, &hostkey)) != 0)
731 goto out;
732 } else if (strcmp(method, "publickey") != 0) {
733 r = SSH_ERR_INVALID_FORMAT;
734 goto out;
735 }
736 if (sshbuf_len(b) != 0) {
737 r = SSH_ERR_INVALID_FORMAT;
738 goto out;
739 }
740 /* success */
741 r = 0;
742 debug3_f("well formed userauth");
743 if (userp != NULL) {
744 *userp = user;
745 user = NULL;
746 }
747 if (sess_idp != NULL) {
748 *sess_idp = sess_id;
749 sess_id = NULL;
750 }
751 if (hostkeyp != NULL) {
752 *hostkeyp = hostkey;
753 hostkey = NULL;
754 }
755 out:
756 sshbuf_free(b);
757 sshbuf_free(sess_id);
758 free(user);
759 free(service);
760 free(method);
761 free(pkalg);
762 sshkey_free(mkey);
763 sshkey_free(hostkey);
764 return r;
765 }
766
767 /*
768 * Attempt to parse the contents of a buffer as a SSHSIG signature request.
769 * Note: does not modify buffer.
770 */
771 static int
parse_sshsig_request(struct sshbuf * msg)772 parse_sshsig_request(struct sshbuf *msg)
773 {
774 int r;
775 struct sshbuf *b;
776
777 if ((b = sshbuf_fromb(msg)) == NULL)
778 fatal_f("sshbuf_fromb");
779
780 if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) != 0 ||
781 (r = sshbuf_consume(b, 6)) != 0 ||
782 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* namespace */
783 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0 || /* reserved */
784 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* hashalg */
785 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0) /* H(msg) */
786 goto out;
787 if (sshbuf_len(b) != 0) {
788 r = SSH_ERR_INVALID_FORMAT;
789 goto out;
790 }
791 /* success */
792 r = 0;
793 out:
794 sshbuf_free(b);
795 return r;
796 }
797
798 /*
799 * This function inspects a message to be signed by a FIDO key that has a
800 * web-like application string (i.e. one that does not begin with "ssh:".
801 * It checks that the message is one of those expected for SSH operations
802 * (pubkey userauth, sshsig, CA key signing) to exclude signing challenges
803 * for the web.
804 */
805 static int
check_websafe_message_contents(struct sshkey * key,struct sshbuf * data)806 check_websafe_message_contents(struct sshkey *key, struct sshbuf *data)
807 {
808 if (parse_userauth_request(data, key, NULL, NULL, NULL) == 0) {
809 debug_f("signed data matches public key userauth request");
810 return 1;
811 }
812 if (parse_sshsig_request(data) == 0) {
813 debug_f("signed data matches SSHSIG signature request");
814 return 1;
815 }
816
817 /* XXX check CA signature operation */
818
819 error("web-origin key attempting to sign non-SSH message");
820 return 0;
821 }
822
823 static int
buf_equal(const struct sshbuf * a,const struct sshbuf * b)824 buf_equal(const struct sshbuf *a, const struct sshbuf *b)
825 {
826 if (sshbuf_ptr(a) == NULL || sshbuf_ptr(b) == NULL)
827 return SSH_ERR_INVALID_ARGUMENT;
828 if (sshbuf_len(a) != sshbuf_len(b))
829 return SSH_ERR_INVALID_FORMAT;
830 if (timingsafe_bcmp(sshbuf_ptr(a), sshbuf_ptr(b), sshbuf_len(a)) != 0)
831 return SSH_ERR_INVALID_FORMAT;
832 return 0;
833 }
834
835 /* ssh2 only */
836 static void
process_sign_request2(SocketEntry * e)837 process_sign_request2(SocketEntry *e)
838 {
839 u_char *signature = NULL;
840 size_t slen = 0;
841 u_int compat = 0, flags;
842 int r, ok = -1, retried = 0;
843 char *fp = NULL, *pin = NULL, *prompt = NULL;
844 char *user = NULL, *sig_dest = NULL;
845 const char *fwd_host = NULL, *dest_host = NULL;
846 struct sshbuf *msg = NULL, *data = NULL, *sid = NULL;
847 struct sshkey *key = NULL, *hostkey = NULL;
848 struct identity *id;
849 struct notifier_ctx *notifier = NULL;
850
851 debug_f("entering");
852
853 if ((msg = sshbuf_new()) == NULL || (data = sshbuf_new()) == NULL)
854 fatal_f("sshbuf_new failed");
855 if ((r = sshkey_froms(e->request, &key)) != 0 ||
856 (r = sshbuf_get_stringb(e->request, data)) != 0 ||
857 (r = sshbuf_get_u32(e->request, &flags)) != 0) {
858 error_fr(r, "parse");
859 goto send;
860 }
861
862 if ((id = lookup_identity(key)) == NULL) {
863 verbose_f("%s key not found", sshkey_type(key));
864 goto send;
865 }
866 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
867 SSH_FP_DEFAULT)) == NULL)
868 fatal_f("fingerprint failed");
869
870 if (id->ndest_constraints != 0) {
871 if (e->nsession_ids == 0) {
872 logit_f("refusing use of destination-constrained key "
873 "to sign on unbound connection");
874 goto send;
875 }
876 if (parse_userauth_request(data, key, &user, &sid,
877 &hostkey) != 0) {
878 logit_f("refusing use of destination-constrained key "
879 "to sign an unidentified signature");
880 goto send;
881 }
882 /* XXX logspam */
883 debug_f("user=%s", user);
884 if (identity_permitted(id, e, user, &fwd_host, &dest_host) != 0)
885 goto send;
886 /* XXX display fwd_host/dest_host in askpass UI */
887 /*
888 * Ensure that the session ID is the most recent one
889 * registered on the socket - it should have been bound by
890 * ssh immediately before userauth.
891 */
892 if (buf_equal(sid,
893 e->session_ids[e->nsession_ids - 1].sid) != 0) {
894 error_f("unexpected session ID (%zu listed) on "
895 "signature request for target user %s with "
896 "key %s %s", e->nsession_ids, user,
897 sshkey_type(id->key), fp);
898 goto send;
899 }
900 /*
901 * Ensure that the hostkey embedded in the signature matches
902 * the one most recently bound to the socket. An exception is
903 * made for the initial forwarding hop.
904 */
905 if (e->nsession_ids > 1 && hostkey == NULL) {
906 error_f("refusing use of destination-constrained key: "
907 "no hostkey recorded in signature for forwarded "
908 "connection");
909 goto send;
910 }
911 if (hostkey != NULL && !sshkey_equal(hostkey,
912 e->session_ids[e->nsession_ids - 1].key)) {
913 error_f("refusing use of destination-constrained key: "
914 "mismatch between hostkey in request and most "
915 "recently bound session");
916 goto send;
917 }
918 xasprintf(&sig_dest, "public key authentication request for "
919 "user \"%s\" to listed host", user);
920 }
921 if (id->confirm && confirm_key(id, sig_dest) != 0) {
922 verbose_f("user refused key");
923 goto send;
924 }
925 if (sshkey_is_sk(id->key)) {
926 if (restrict_websafe &&
927 strncmp(id->key->sk_application, "ssh:", 4) != 0 &&
928 !check_websafe_message_contents(key, data)) {
929 /* error already logged */
930 goto send;
931 }
932 if (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) {
933 notifier = notify_start(0,
934 "Confirm user presence for key %s %s%s%s",
935 sshkey_type(id->key), fp,
936 sig_dest == NULL ? "" : "\n",
937 sig_dest == NULL ? "" : sig_dest);
938 }
939 }
940 retry_pin:
941 if ((r = sshkey_sign(id->key, &signature, &slen,
942 sshbuf_ptr(data), sshbuf_len(data), agent_decode_alg(key, flags),
943 id->sk_provider, pin, compat)) != 0) {
944 debug_fr(r, "sshkey_sign");
945 if (pin == NULL && !retried && sshkey_is_sk(id->key) &&
946 r == SSH_ERR_KEY_WRONG_PASSPHRASE) {
947 notify_complete(notifier, NULL);
948 notifier = NULL;
949 /* XXX include sig_dest */
950 xasprintf(&prompt, "Enter PIN%sfor %s key %s: ",
951 (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) ?
952 " and confirm user presence " : " ",
953 sshkey_type(id->key), fp);
954 pin = read_passphrase(prompt, RP_USE_ASKPASS);
955 retried = 1;
956 goto retry_pin;
957 }
958 error_fr(r, "sshkey_sign");
959 goto send;
960 }
961 /* Success */
962 ok = 0;
963 debug_f("good signature");
964 send:
965 notify_complete(notifier, "User presence confirmed");
966
967 if (ok == 0) {
968 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
969 (r = sshbuf_put_string(msg, signature, slen)) != 0)
970 fatal_fr(r, "compose");
971 } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
972 fatal_fr(r, "compose failure");
973
974 if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
975 fatal_fr(r, "enqueue");
976
977 sshbuf_free(sid);
978 sshbuf_free(data);
979 sshbuf_free(msg);
980 sshkey_free(key);
981 sshkey_free(hostkey);
982 free(fp);
983 free(signature);
984 free(sig_dest);
985 free(user);
986 free(prompt);
987 if (pin != NULL)
988 freezero(pin, strlen(pin));
989 }
990
991 /* shared */
992 static void
process_remove_identity(SocketEntry * e)993 process_remove_identity(SocketEntry *e)
994 {
995 int r, success = 0;
996 struct sshkey *key = NULL;
997 Identity *id;
998
999 debug2_f("entering");
1000 if ((r = sshkey_froms(e->request, &key)) != 0) {
1001 error_fr(r, "parse key");
1002 goto done;
1003 }
1004 if ((id = lookup_identity(key)) == NULL) {
1005 debug_f("key not found");
1006 goto done;
1007 }
1008 /* identity not visible, cannot be removed */
1009 if (identity_permitted(id, e, NULL, NULL, NULL) != 0)
1010 goto done; /* error already logged */
1011 /* We have this key, free it. */
1012 if (idtab->nentries < 1)
1013 fatal_f("internal error: nentries %d", idtab->nentries);
1014 TAILQ_REMOVE(&idtab->idlist, id, next);
1015 free_identity(id);
1016 idtab->nentries--;
1017 success = 1;
1018 done:
1019 sshkey_free(key);
1020 send_status(e, success);
1021 }
1022
1023 static void
process_remove_all_identities(SocketEntry * e)1024 process_remove_all_identities(SocketEntry *e)
1025 {
1026 Identity *id;
1027
1028 debug2_f("entering");
1029 /* Loop over all identities and clear the keys. */
1030 for (id = TAILQ_FIRST(&idtab->idlist); id;
1031 id = TAILQ_FIRST(&idtab->idlist)) {
1032 TAILQ_REMOVE(&idtab->idlist, id, next);
1033 free_identity(id);
1034 }
1035
1036 /* Mark that there are no identities. */
1037 idtab->nentries = 0;
1038
1039 /* Send success. */
1040 send_status(e, 1);
1041 }
1042
1043 /* removes expired keys and returns number of seconds until the next expiry */
1044 static time_t
reaper(void)1045 reaper(void)
1046 {
1047 time_t deadline = 0, now = monotime();
1048 Identity *id, *nxt;
1049
1050 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
1051 nxt = TAILQ_NEXT(id, next);
1052 if (id->death == 0)
1053 continue;
1054 if (now >= id->death) {
1055 debug("expiring key '%s'", id->comment);
1056 TAILQ_REMOVE(&idtab->idlist, id, next);
1057 free_identity(id);
1058 idtab->nentries--;
1059 } else
1060 deadline = (deadline == 0) ? id->death :
1061 MINIMUM(deadline, id->death);
1062 }
1063 if (deadline == 0 || deadline <= now)
1064 return 0;
1065 else
1066 return (deadline - now);
1067 }
1068
1069 static int
parse_dest_constraint_hop(struct sshbuf * b,struct dest_constraint_hop * dch)1070 parse_dest_constraint_hop(struct sshbuf *b, struct dest_constraint_hop *dch)
1071 {
1072 u_char key_is_ca;
1073 size_t elen = 0;
1074 int r;
1075 struct sshkey *k = NULL;
1076 char *fp;
1077
1078 memset(dch, '\0', sizeof(*dch));
1079 if ((r = sshbuf_get_cstring(b, &dch->user, NULL)) != 0 ||
1080 (r = sshbuf_get_cstring(b, &dch->hostname, NULL)) != 0 ||
1081 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) {
1082 error_fr(r, "parse");
1083 goto out;
1084 }
1085 if (elen != 0) {
1086 error_f("unsupported extensions (len %zu)", elen);
1087 r = SSH_ERR_FEATURE_UNSUPPORTED;
1088 goto out;
1089 }
1090 if (*dch->hostname == '\0') {
1091 free(dch->hostname);
1092 dch->hostname = NULL;
1093 }
1094 if (*dch->user == '\0') {
1095 free(dch->user);
1096 dch->user = NULL;
1097 }
1098 while (sshbuf_len(b) != 0) {
1099 dch->keys = xrecallocarray(dch->keys, dch->nkeys,
1100 dch->nkeys + 1, sizeof(*dch->keys));
1101 dch->key_is_ca = xrecallocarray(dch->key_is_ca, dch->nkeys,
1102 dch->nkeys + 1, sizeof(*dch->key_is_ca));
1103 if ((r = sshkey_froms(b, &k)) != 0 ||
1104 (r = sshbuf_get_u8(b, &key_is_ca)) != 0)
1105 goto out;
1106 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT,
1107 SSH_FP_DEFAULT)) == NULL)
1108 fatal_f("fingerprint failed");
1109 debug3_f("%s%s%s: adding %skey %s %s",
1110 dch->user == NULL ? "" : dch->user,
1111 dch->user == NULL ? "" : "@",
1112 dch->hostname, key_is_ca ? "CA " : "", sshkey_type(k), fp);
1113 free(fp);
1114 dch->keys[dch->nkeys] = k;
1115 dch->key_is_ca[dch->nkeys] = key_is_ca != 0;
1116 dch->nkeys++;
1117 k = NULL; /* transferred */
1118 }
1119 /* success */
1120 r = 0;
1121 out:
1122 sshkey_free(k);
1123 return r;
1124 }
1125
1126 static int
parse_dest_constraint(struct sshbuf * m,struct dest_constraint * dc)1127 parse_dest_constraint(struct sshbuf *m, struct dest_constraint *dc)
1128 {
1129 struct sshbuf *b = NULL, *frombuf = NULL, *tobuf = NULL;
1130 int r;
1131 size_t elen = 0;
1132
1133 debug3_f("entering");
1134
1135 memset(dc, '\0', sizeof(*dc));
1136 if ((r = sshbuf_froms(m, &b)) != 0 ||
1137 (r = sshbuf_froms(b, &frombuf)) != 0 ||
1138 (r = sshbuf_froms(b, &tobuf)) != 0 ||
1139 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) {
1140 error_fr(r, "parse");
1141 goto out;
1142 }
1143 if ((r = parse_dest_constraint_hop(frombuf, &dc->from)) != 0 ||
1144 (r = parse_dest_constraint_hop(tobuf, &dc->to)) != 0)
1145 goto out; /* already logged */
1146 if (elen != 0) {
1147 error_f("unsupported extensions (len %zu)", elen);
1148 r = SSH_ERR_FEATURE_UNSUPPORTED;
1149 goto out;
1150 }
1151 debug2_f("parsed %s (%u keys) > %s%s%s (%u keys)",
1152 dc->from.hostname ? dc->from.hostname : "(ORIGIN)", dc->from.nkeys,
1153 dc->to.user ? dc->to.user : "", dc->to.user ? "@" : "",
1154 dc->to.hostname ? dc->to.hostname : "(ANY)", dc->to.nkeys);
1155 /* check consistency */
1156 if ((dc->from.hostname == NULL) != (dc->from.nkeys == 0) ||
1157 dc->from.user != NULL) {
1158 error_f("inconsistent \"from\" specification");
1159 r = SSH_ERR_INVALID_FORMAT;
1160 goto out;
1161 }
1162 if (dc->to.hostname == NULL || dc->to.nkeys == 0) {
1163 error_f("incomplete \"to\" specification");
1164 r = SSH_ERR_INVALID_FORMAT;
1165 goto out;
1166 }
1167 /* success */
1168 r = 0;
1169 out:
1170 sshbuf_free(b);
1171 sshbuf_free(frombuf);
1172 sshbuf_free(tobuf);
1173 return r;
1174 }
1175
1176 static int
parse_key_constraint_extension(struct sshbuf * m,char ** sk_providerp,struct dest_constraint ** dcsp,size_t * ndcsp,int * cert_onlyp,struct sshkey *** certs,size_t * ncerts)1177 parse_key_constraint_extension(struct sshbuf *m, char **sk_providerp,
1178 struct dest_constraint **dcsp, size_t *ndcsp, int *cert_onlyp,
1179 struct sshkey ***certs, size_t *ncerts)
1180 {
1181 char *ext_name = NULL;
1182 int r;
1183 struct sshbuf *b = NULL;
1184 u_char v;
1185 struct sshkey *k;
1186
1187 if ((r = sshbuf_get_cstring(m, &ext_name, NULL)) != 0) {
1188 error_fr(r, "parse constraint extension");
1189 goto out;
1190 }
1191 debug_f("constraint ext %s", ext_name);
1192 if (strcmp(ext_name, "sk-provider@openssh.com") == 0) {
1193 if (sk_providerp == NULL) {
1194 error_f("%s not valid here", ext_name);
1195 r = SSH_ERR_INVALID_FORMAT;
1196 goto out;
1197 }
1198 if (*sk_providerp != NULL) {
1199 error_f("%s already set", ext_name);
1200 r = SSH_ERR_INVALID_FORMAT;
1201 goto out;
1202 }
1203 if ((r = sshbuf_get_cstring(m, sk_providerp, NULL)) != 0) {
1204 error_fr(r, "parse %s", ext_name);
1205 goto out;
1206 }
1207 } else if (strcmp(ext_name,
1208 "restrict-destination-v00@openssh.com") == 0) {
1209 if (*dcsp != NULL) {
1210 error_f("%s already set", ext_name);
1211 goto out;
1212 }
1213 if ((r = sshbuf_froms(m, &b)) != 0) {
1214 error_fr(r, "parse %s outer", ext_name);
1215 goto out;
1216 }
1217 while (sshbuf_len(b) != 0) {
1218 if (*ndcsp >= AGENT_MAX_DEST_CONSTRAINTS) {
1219 error_f("too many %s constraints", ext_name);
1220 goto out;
1221 }
1222 *dcsp = xrecallocarray(*dcsp, *ndcsp, *ndcsp + 1,
1223 sizeof(**dcsp));
1224 if ((r = parse_dest_constraint(b,
1225 *dcsp + (*ndcsp)++)) != 0)
1226 goto out; /* error already logged */
1227 }
1228 } else if (strcmp(ext_name,
1229 "associated-certs-v00@openssh.com") == 0) {
1230 if (certs == NULL || ncerts == NULL || cert_onlyp == NULL) {
1231 error_f("%s not valid here", ext_name);
1232 r = SSH_ERR_INVALID_FORMAT;
1233 goto out;
1234 }
1235 if (*certs != NULL) {
1236 error_f("%s already set", ext_name);
1237 goto out;
1238 }
1239 if ((r = sshbuf_get_u8(m, &v)) != 0 ||
1240 (r = sshbuf_froms(m, &b)) != 0) {
1241 error_fr(r, "parse %s", ext_name);
1242 goto out;
1243 }
1244 *cert_onlyp = v != 0;
1245 while (sshbuf_len(b) != 0) {
1246 if (*ncerts >= AGENT_MAX_EXT_CERTS) {
1247 error_f("too many %s constraints", ext_name);
1248 goto out;
1249 }
1250 *certs = xrecallocarray(*certs, *ncerts, *ncerts + 1,
1251 sizeof(**certs));
1252 if ((r = sshkey_froms(b, &k)) != 0) {
1253 error_fr(r, "parse key");
1254 goto out;
1255 }
1256 (*certs)[(*ncerts)++] = k;
1257 }
1258 } else {
1259 error_f("unsupported constraint \"%s\"", ext_name);
1260 r = SSH_ERR_FEATURE_UNSUPPORTED;
1261 goto out;
1262 }
1263 /* success */
1264 r = 0;
1265 out:
1266 free(ext_name);
1267 sshbuf_free(b);
1268 return r;
1269 }
1270
1271 static int
parse_key_constraints(struct sshbuf * m,struct sshkey * k,time_t * deathp,u_int * secondsp,int * confirmp,char ** sk_providerp,struct dest_constraint ** dcsp,size_t * ndcsp,int * cert_onlyp,size_t * ncerts,struct sshkey *** certs)1272 parse_key_constraints(struct sshbuf *m, struct sshkey *k, time_t *deathp,
1273 u_int *secondsp, int *confirmp, char **sk_providerp,
1274 struct dest_constraint **dcsp, size_t *ndcsp,
1275 int *cert_onlyp, size_t *ncerts, struct sshkey ***certs)
1276 {
1277 u_char ctype;
1278 int r;
1279 u_int seconds, maxsign = 0;
1280
1281 while (sshbuf_len(m)) {
1282 if ((r = sshbuf_get_u8(m, &ctype)) != 0) {
1283 error_fr(r, "parse constraint type");
1284 goto out;
1285 }
1286 switch (ctype) {
1287 case SSH_AGENT_CONSTRAIN_LIFETIME:
1288 if (*deathp != 0) {
1289 error_f("lifetime already set");
1290 r = SSH_ERR_INVALID_FORMAT;
1291 goto out;
1292 }
1293 if ((r = sshbuf_get_u32(m, &seconds)) != 0) {
1294 error_fr(r, "parse lifetime constraint");
1295 goto out;
1296 }
1297 *deathp = monotime() + seconds;
1298 *secondsp = seconds;
1299 break;
1300 case SSH_AGENT_CONSTRAIN_CONFIRM:
1301 if (*confirmp != 0) {
1302 error_f("confirm already set");
1303 r = SSH_ERR_INVALID_FORMAT;
1304 goto out;
1305 }
1306 *confirmp = 1;
1307 break;
1308 case SSH_AGENT_CONSTRAIN_MAXSIGN:
1309 if (k == NULL) {
1310 error_f("maxsign not valid here");
1311 r = SSH_ERR_INVALID_FORMAT;
1312 goto out;
1313 }
1314 if (maxsign != 0) {
1315 error_f("maxsign already set");
1316 r = SSH_ERR_INVALID_FORMAT;
1317 goto out;
1318 }
1319 if ((r = sshbuf_get_u32(m, &maxsign)) != 0) {
1320 error_fr(r, "parse maxsign constraint");
1321 goto out;
1322 }
1323 if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) {
1324 error_fr(r, "enable maxsign");
1325 goto out;
1326 }
1327 break;
1328 case SSH_AGENT_CONSTRAIN_EXTENSION:
1329 if ((r = parse_key_constraint_extension(m,
1330 sk_providerp, dcsp, ndcsp,
1331 cert_onlyp, certs, ncerts)) != 0)
1332 goto out; /* error already logged */
1333 break;
1334 default:
1335 error_f("Unknown constraint %d", ctype);
1336 r = SSH_ERR_FEATURE_UNSUPPORTED;
1337 goto out;
1338 }
1339 }
1340 /* success */
1341 r = 0;
1342 out:
1343 return r;
1344 }
1345
1346 static void
process_add_identity(SocketEntry * e)1347 process_add_identity(SocketEntry *e)
1348 {
1349 Identity *id;
1350 int success = 0, confirm = 0;
1351 char *fp, *comment = NULL, *sk_provider = NULL;
1352 char canonical_provider[PATH_MAX];
1353 time_t death = 0;
1354 u_int seconds = 0;
1355 struct dest_constraint *dest_constraints = NULL;
1356 size_t ndest_constraints = 0;
1357 struct sshkey *k = NULL;
1358 int r = SSH_ERR_INTERNAL_ERROR;
1359
1360 debug2_f("entering");
1361 if ((r = sshkey_private_deserialize(e->request, &k)) != 0 ||
1362 k == NULL ||
1363 (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) {
1364 error_fr(r, "parse");
1365 goto out;
1366 }
1367 if (parse_key_constraints(e->request, k, &death, &seconds, &confirm,
1368 &sk_provider, &dest_constraints, &ndest_constraints,
1369 NULL, NULL, NULL) != 0) {
1370 error_f("failed to parse constraints");
1371 sshbuf_reset(e->request);
1372 goto out;
1373 }
1374 dump_dest_constraints(__func__, dest_constraints, ndest_constraints);
1375
1376 if (sk_provider != NULL) {
1377 if (!sshkey_is_sk(k)) {
1378 error("Cannot add provider: %s is not an "
1379 "authenticator-hosted key", sshkey_type(k));
1380 goto out;
1381 }
1382 if (strcasecmp(sk_provider, "internal") == 0) {
1383 debug_f("internal provider");
1384 } else {
1385 if (socket_is_remote(e) && !remote_add_provider) {
1386 verbose("failed add of SK provider \"%.100s\": "
1387 "remote addition of providers is disabled",
1388 sk_provider);
1389 goto out;
1390 }
1391 if (realpath(sk_provider, canonical_provider) == NULL) {
1392 verbose("failed provider \"%.100s\": "
1393 "realpath: %s", sk_provider,
1394 strerror(errno));
1395 goto out;
1396 }
1397 free(sk_provider);
1398 sk_provider = xstrdup(canonical_provider);
1399 if (match_pattern_list(sk_provider,
1400 allowed_providers, 0) != 1) {
1401 error("Refusing add key: "
1402 "provider %s not allowed", sk_provider);
1403 goto out;
1404 }
1405 }
1406 }
1407 if ((r = sshkey_shield_private(k)) != 0) {
1408 error_fr(r, "shield private");
1409 goto out;
1410 }
1411 if (lifetime && !death)
1412 death = monotime() + lifetime;
1413 if ((id = lookup_identity(k)) == NULL) {
1414 id = xcalloc(1, sizeof(Identity));
1415 TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
1416 /* Increment the number of identities. */
1417 idtab->nentries++;
1418 } else {
1419 /* identity not visible, do not update */
1420 if (identity_permitted(id, e, NULL, NULL, NULL) != 0)
1421 goto out; /* error already logged */
1422 /* key state might have been updated */
1423 sshkey_free(id->key);
1424 free(id->comment);
1425 free(id->sk_provider);
1426 free_dest_constraints(id->dest_constraints,
1427 id->ndest_constraints);
1428 }
1429 /* success */
1430 id->key = k;
1431 id->comment = comment;
1432 id->death = death;
1433 id->confirm = confirm;
1434 id->sk_provider = sk_provider;
1435 id->dest_constraints = dest_constraints;
1436 id->ndest_constraints = ndest_constraints;
1437
1438 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT,
1439 SSH_FP_DEFAULT)) == NULL)
1440 fatal_f("sshkey_fingerprint failed");
1441 debug_f("add %s %s \"%.100s\" (life: %u) (confirm: %u) "
1442 "(provider: %s) (destination constraints: %zu)",
1443 sshkey_ssh_name(k), fp, comment, seconds, confirm,
1444 sk_provider == NULL ? "none" : sk_provider, ndest_constraints);
1445 free(fp);
1446 /* transferred */
1447 k = NULL;
1448 comment = NULL;
1449 sk_provider = NULL;
1450 dest_constraints = NULL;
1451 ndest_constraints = 0;
1452 success = 1;
1453 out:
1454 free(sk_provider);
1455 free(comment);
1456 sshkey_free(k);
1457 free_dest_constraints(dest_constraints, ndest_constraints);
1458 send_status(e, success);
1459 }
1460
1461 /* XXX todo: encrypt sensitive data with passphrase */
1462 static void
process_lock_agent(SocketEntry * e,int lock)1463 process_lock_agent(SocketEntry *e, int lock)
1464 {
1465 int r, success = 0, delay;
1466 char *passwd;
1467 u_char passwdhash[LOCK_SIZE];
1468 static u_int fail_count = 0;
1469 size_t pwlen;
1470
1471 debug2_f("entering");
1472 /*
1473 * This is deliberately fatal: the user has requested that we lock,
1474 * but we can't parse their request properly. The only safe thing to
1475 * do is abort.
1476 */
1477 if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0)
1478 fatal_fr(r, "parse");
1479 if (pwlen == 0) {
1480 debug("empty password not supported");
1481 } else if (locked && !lock) {
1482 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
1483 passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0)
1484 fatal("bcrypt_pbkdf");
1485 if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) {
1486 debug("agent unlocked");
1487 locked = 0;
1488 fail_count = 0;
1489 explicit_bzero(lock_pwhash, sizeof(lock_pwhash));
1490 success = 1;
1491 } else {
1492 /* delay in 0.1s increments up to 10s */
1493 if (fail_count < 100)
1494 fail_count++;
1495 delay = 100000 * fail_count;
1496 debug("unlock failed, delaying %0.1lf seconds",
1497 (double)delay/1000000);
1498 usleep(delay);
1499 }
1500 explicit_bzero(passwdhash, sizeof(passwdhash));
1501 } else if (!locked && lock) {
1502 debug("agent locked");
1503 locked = 1;
1504 arc4random_buf(lock_salt, sizeof(lock_salt));
1505 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
1506 lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0)
1507 fatal("bcrypt_pbkdf");
1508 success = 1;
1509 }
1510 freezero(passwd, pwlen);
1511 send_status(e, success);
1512 }
1513
1514 static void
no_identities(SocketEntry * e)1515 no_identities(SocketEntry *e)
1516 {
1517 struct sshbuf *msg;
1518 int r;
1519
1520 if ((msg = sshbuf_new()) == NULL)
1521 fatal_f("sshbuf_new failed");
1522 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
1523 (r = sshbuf_put_u32(msg, 0)) != 0 ||
1524 (r = sshbuf_put_stringb(e->output, msg)) != 0)
1525 fatal_fr(r, "compose");
1526 sshbuf_free(msg);
1527 }
1528
1529 #ifdef ENABLE_PKCS11
1530 /* Add an identity to idlist; takes ownership of 'key' and 'comment' */
1531 static void
add_p11_identity(struct sshkey * key,char * comment,const char * provider,time_t death,u_int confirm,struct dest_constraint * dest_constraints,size_t ndest_constraints)1532 add_p11_identity(struct sshkey *key, char *comment, const char *provider,
1533 time_t death, u_int confirm, struct dest_constraint *dest_constraints,
1534 size_t ndest_constraints)
1535 {
1536 Identity *id;
1537
1538 if (lookup_identity(key) != NULL) {
1539 sshkey_free(key);
1540 free(comment);
1541 return;
1542 }
1543 id = xcalloc(1, sizeof(Identity));
1544 id->key = key;
1545 id->comment = comment;
1546 id->provider = xstrdup(provider);
1547 id->death = death;
1548 id->confirm = confirm;
1549 id->dest_constraints = dup_dest_constraints(dest_constraints,
1550 ndest_constraints);
1551 id->ndest_constraints = ndest_constraints;
1552 TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
1553 idtab->nentries++;
1554 }
1555
1556 static void
process_add_smartcard_key(SocketEntry * e)1557 process_add_smartcard_key(SocketEntry *e)
1558 {
1559 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
1560 char **comments = NULL;
1561 int r, i, count = 0, success = 0, confirm = 0;
1562 u_int seconds = 0;
1563 time_t death = 0;
1564 struct sshkey **keys = NULL, *k;
1565 struct dest_constraint *dest_constraints = NULL;
1566 size_t j, ndest_constraints = 0, ncerts = 0;
1567 struct sshkey **certs = NULL;
1568 int cert_only = 0;
1569
1570 debug2_f("entering");
1571 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
1572 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
1573 error_fr(r, "parse");
1574 goto send;
1575 }
1576 if (parse_key_constraints(e->request, NULL, &death, &seconds, &confirm,
1577 NULL, &dest_constraints, &ndest_constraints, &cert_only,
1578 &ncerts, &certs) != 0) {
1579 error_f("failed to parse constraints");
1580 goto send;
1581 }
1582 dump_dest_constraints(__func__, dest_constraints, ndest_constraints);
1583 if (socket_is_remote(e) && !remote_add_provider) {
1584 verbose("failed PKCS#11 add of \"%.100s\": remote addition of "
1585 "providers is disabled", provider);
1586 goto send;
1587 }
1588 if (realpath(provider, canonical_provider) == NULL) {
1589 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
1590 provider, strerror(errno));
1591 goto send;
1592 }
1593 if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) {
1594 verbose("refusing PKCS#11 add of \"%.100s\": "
1595 "provider not allowed", canonical_provider);
1596 goto send;
1597 }
1598 debug_f("add %.100s", canonical_provider);
1599 if (lifetime && !death)
1600 death = monotime() + lifetime;
1601
1602 count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments);
1603 for (i = 0; i < count; i++) {
1604 if (comments[i] == NULL || comments[i][0] == '\0') {
1605 free(comments[i]);
1606 comments[i] = xstrdup(canonical_provider);
1607 }
1608 for (j = 0; j < ncerts; j++) {
1609 if (!sshkey_is_cert(certs[j]))
1610 continue;
1611 if (!sshkey_equal_public(keys[i], certs[j]))
1612 continue;
1613 if (pkcs11_make_cert(keys[i], certs[j], &k) != 0)
1614 continue;
1615 add_p11_identity(k, xstrdup(comments[i]),
1616 canonical_provider, death, confirm,
1617 dest_constraints, ndest_constraints);
1618 success = 1;
1619 }
1620 if (!cert_only && lookup_identity(keys[i]) == NULL) {
1621 add_p11_identity(keys[i], comments[i],
1622 canonical_provider, death, confirm,
1623 dest_constraints, ndest_constraints);
1624 keys[i] = NULL; /* transferred */
1625 comments[i] = NULL; /* transferred */
1626 success = 1;
1627 }
1628 /* XXX update constraints for existing keys */
1629 sshkey_free(keys[i]);
1630 free(comments[i]);
1631 }
1632 send:
1633 free(pin);
1634 free(provider);
1635 free(keys);
1636 free(comments);
1637 free_dest_constraints(dest_constraints, ndest_constraints);
1638 for (j = 0; j < ncerts; j++)
1639 sshkey_free(certs[j]);
1640 free(certs);
1641 send_status(e, success);
1642 }
1643
1644 static void
process_remove_smartcard_key(SocketEntry * e)1645 process_remove_smartcard_key(SocketEntry *e)
1646 {
1647 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
1648 int r, success = 0;
1649 Identity *id, *nxt;
1650
1651 debug2_f("entering");
1652 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
1653 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
1654 error_fr(r, "parse");
1655 goto send;
1656 }
1657 free(pin);
1658
1659 if (realpath(provider, canonical_provider) == NULL) {
1660 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
1661 provider, strerror(errno));
1662 goto send;
1663 }
1664
1665 debug_f("remove %.100s", canonical_provider);
1666 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
1667 nxt = TAILQ_NEXT(id, next);
1668 /* Skip file--based keys */
1669 if (id->provider == NULL)
1670 continue;
1671 if (!strcmp(canonical_provider, id->provider)) {
1672 TAILQ_REMOVE(&idtab->idlist, id, next);
1673 free_identity(id);
1674 idtab->nentries--;
1675 }
1676 }
1677 if (pkcs11_del_provider(canonical_provider) == 0)
1678 success = 1;
1679 else
1680 error_f("pkcs11_del_provider failed");
1681 send:
1682 free(provider);
1683 send_status(e, success);
1684 }
1685 #endif /* ENABLE_PKCS11 */
1686
1687 static int
process_ext_session_bind(SocketEntry * e)1688 process_ext_session_bind(SocketEntry *e)
1689 {
1690 int r, sid_match, key_match;
1691 struct sshkey *key = NULL;
1692 struct sshbuf *sid = NULL, *sig = NULL;
1693 char *fp = NULL;
1694 size_t i;
1695 u_char fwd = 0;
1696
1697 debug2_f("entering");
1698 e->session_bind_attempted = 1;
1699 if ((r = sshkey_froms(e->request, &key)) != 0 ||
1700 (r = sshbuf_froms(e->request, &sid)) != 0 ||
1701 (r = sshbuf_froms(e->request, &sig)) != 0 ||
1702 (r = sshbuf_get_u8(e->request, &fwd)) != 0) {
1703 error_fr(r, "parse");
1704 goto out;
1705 }
1706 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
1707 SSH_FP_DEFAULT)) == NULL)
1708 fatal_f("fingerprint failed");
1709 /* check signature with hostkey on session ID */
1710 if ((r = sshkey_verify(key, sshbuf_ptr(sig), sshbuf_len(sig),
1711 sshbuf_ptr(sid), sshbuf_len(sid), NULL, 0, NULL)) != 0) {
1712 error_fr(r, "sshkey_verify for %s %s", sshkey_type(key), fp);
1713 goto out;
1714 }
1715 /* check whether sid/key already recorded */
1716 for (i = 0; i < e->nsession_ids; i++) {
1717 if (!e->session_ids[i].forwarded) {
1718 error_f("attempt to bind session ID to socket "
1719 "previously bound for authentication attempt");
1720 r = -1;
1721 goto out;
1722 }
1723 sid_match = buf_equal(sid, e->session_ids[i].sid) == 0;
1724 key_match = sshkey_equal(key, e->session_ids[i].key);
1725 if (sid_match && key_match) {
1726 debug_f("session ID already recorded for %s %s",
1727 sshkey_type(key), fp);
1728 r = 0;
1729 goto out;
1730 } else if (sid_match) {
1731 error_f("session ID recorded against different key "
1732 "for %s %s", sshkey_type(key), fp);
1733 r = -1;
1734 goto out;
1735 }
1736 /*
1737 * new sid with previously-seen key can happen, e.g. multiple
1738 * connections to the same host.
1739 */
1740 }
1741 /* record new key/sid */
1742 if (e->nsession_ids >= AGENT_MAX_SESSION_IDS) {
1743 error_f("too many session IDs recorded");
1744 goto out;
1745 }
1746 e->session_ids = xrecallocarray(e->session_ids, e->nsession_ids,
1747 e->nsession_ids + 1, sizeof(*e->session_ids));
1748 i = e->nsession_ids++;
1749 debug_f("recorded %s %s (slot %zu of %d)", sshkey_type(key), fp, i,
1750 AGENT_MAX_SESSION_IDS);
1751 e->session_ids[i].key = key;
1752 e->session_ids[i].forwarded = fwd != 0;
1753 key = NULL; /* transferred */
1754 /* can't transfer sid; it's refcounted and scoped to request's life */
1755 if ((e->session_ids[i].sid = sshbuf_new()) == NULL)
1756 fatal_f("sshbuf_new");
1757 if ((r = sshbuf_putb(e->session_ids[i].sid, sid)) != 0)
1758 fatal_fr(r, "sshbuf_putb session ID");
1759 /* success */
1760 r = 0;
1761 out:
1762 free(fp);
1763 sshkey_free(key);
1764 sshbuf_free(sid);
1765 sshbuf_free(sig);
1766 return r == 0 ? 1 : 0;
1767 }
1768
1769 static void
process_extension(SocketEntry * e)1770 process_extension(SocketEntry *e)
1771 {
1772 int r, success = 0;
1773 char *name;
1774
1775 debug2_f("entering");
1776 if ((r = sshbuf_get_cstring(e->request, &name, NULL)) != 0) {
1777 error_fr(r, "parse");
1778 goto send;
1779 }
1780 if (strcmp(name, "session-bind@openssh.com") == 0)
1781 success = process_ext_session_bind(e);
1782 else
1783 debug_f("unsupported extension \"%s\"", name);
1784 free(name);
1785 send:
1786 send_status(e, success);
1787 }
1788 /*
1789 * dispatch incoming message.
1790 * returns 1 on success, 0 for incomplete messages or -1 on error.
1791 */
1792 static int
process_message(u_int socknum)1793 process_message(u_int socknum)
1794 {
1795 u_int msg_len;
1796 u_char type;
1797 const u_char *cp;
1798 int r;
1799 SocketEntry *e;
1800
1801 if (socknum >= sockets_alloc)
1802 fatal_f("sock %u >= allocated %u", socknum, sockets_alloc);
1803 e = &sockets[socknum];
1804
1805 if (sshbuf_len(e->input) < 5)
1806 return 0; /* Incomplete message header. */
1807 cp = sshbuf_ptr(e->input);
1808 msg_len = PEEK_U32(cp);
1809 if (msg_len > AGENT_MAX_LEN) {
1810 debug_f("socket %u (fd=%d) message too long %u > %u",
1811 socknum, e->fd, msg_len, AGENT_MAX_LEN);
1812 return -1;
1813 }
1814 if (sshbuf_len(e->input) < msg_len + 4)
1815 return 0; /* Incomplete message body. */
1816
1817 /* move the current input to e->request */
1818 sshbuf_reset(e->request);
1819 if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 ||
1820 (r = sshbuf_get_u8(e->request, &type)) != 0) {
1821 if (r == SSH_ERR_MESSAGE_INCOMPLETE ||
1822 r == SSH_ERR_STRING_TOO_LARGE) {
1823 error_fr(r, "parse");
1824 return -1;
1825 }
1826 fatal_fr(r, "parse");
1827 }
1828
1829 debug_f("socket %u (fd=%d) type %d", socknum, e->fd, type);
1830
1831 /* check whether agent is locked */
1832 if (locked && type != SSH_AGENTC_UNLOCK) {
1833 sshbuf_reset(e->request);
1834 switch (type) {
1835 case SSH2_AGENTC_REQUEST_IDENTITIES:
1836 /* send empty lists */
1837 no_identities(e);
1838 break;
1839 default:
1840 /* send a fail message for all other request types */
1841 send_status(e, 0);
1842 }
1843 return 1;
1844 }
1845
1846 switch (type) {
1847 case SSH_AGENTC_LOCK:
1848 case SSH_AGENTC_UNLOCK:
1849 process_lock_agent(e, type == SSH_AGENTC_LOCK);
1850 break;
1851 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
1852 process_remove_all_identities(e); /* safe for !WITH_SSH1 */
1853 break;
1854 /* ssh2 */
1855 case SSH2_AGENTC_SIGN_REQUEST:
1856 process_sign_request2(e);
1857 break;
1858 case SSH2_AGENTC_REQUEST_IDENTITIES:
1859 process_request_identities(e);
1860 break;
1861 case SSH2_AGENTC_ADD_IDENTITY:
1862 case SSH2_AGENTC_ADD_ID_CONSTRAINED:
1863 process_add_identity(e);
1864 break;
1865 case SSH2_AGENTC_REMOVE_IDENTITY:
1866 process_remove_identity(e);
1867 break;
1868 case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
1869 process_remove_all_identities(e);
1870 break;
1871 #ifdef ENABLE_PKCS11
1872 case SSH_AGENTC_ADD_SMARTCARD_KEY:
1873 case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
1874 process_add_smartcard_key(e);
1875 break;
1876 case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
1877 process_remove_smartcard_key(e);
1878 break;
1879 #endif /* ENABLE_PKCS11 */
1880 case SSH_AGENTC_EXTENSION:
1881 process_extension(e);
1882 break;
1883 default:
1884 /* Unknown message. Respond with failure. */
1885 error("Unknown message %d", type);
1886 sshbuf_reset(e->request);
1887 send_status(e, 0);
1888 break;
1889 }
1890 return 1;
1891 }
1892
1893 static void
new_socket(sock_type type,int fd)1894 new_socket(sock_type type, int fd)
1895 {
1896 u_int i, old_alloc, new_alloc;
1897
1898 debug_f("type = %s", type == AUTH_CONNECTION ? "CONNECTION" :
1899 (type == AUTH_SOCKET ? "SOCKET" : "UNKNOWN"));
1900 set_nonblock(fd);
1901
1902 if (fd > max_fd)
1903 max_fd = fd;
1904
1905 for (i = 0; i < sockets_alloc; i++)
1906 if (sockets[i].type == AUTH_UNUSED) {
1907 sockets[i].fd = fd;
1908 if ((sockets[i].input = sshbuf_new()) == NULL ||
1909 (sockets[i].output = sshbuf_new()) == NULL ||
1910 (sockets[i].request = sshbuf_new()) == NULL)
1911 fatal_f("sshbuf_new failed");
1912 sockets[i].type = type;
1913 return;
1914 }
1915 old_alloc = sockets_alloc;
1916 new_alloc = sockets_alloc + 10;
1917 sockets = xrecallocarray(sockets, old_alloc, new_alloc,
1918 sizeof(sockets[0]));
1919 for (i = old_alloc; i < new_alloc; i++)
1920 sockets[i].type = AUTH_UNUSED;
1921 sockets_alloc = new_alloc;
1922 sockets[old_alloc].fd = fd;
1923 if ((sockets[old_alloc].input = sshbuf_new()) == NULL ||
1924 (sockets[old_alloc].output = sshbuf_new()) == NULL ||
1925 (sockets[old_alloc].request = sshbuf_new()) == NULL)
1926 fatal_f("sshbuf_new failed");
1927 sockets[old_alloc].type = type;
1928 }
1929
1930 static int
handle_socket_read(u_int socknum)1931 handle_socket_read(u_int socknum)
1932 {
1933 struct sockaddr_un sunaddr;
1934 socklen_t slen;
1935 uid_t euid;
1936 gid_t egid;
1937 int fd;
1938
1939 slen = sizeof(sunaddr);
1940 fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen);
1941 if (fd == -1) {
1942 error("accept from AUTH_SOCKET: %s", strerror(errno));
1943 return -1;
1944 }
1945 if (getpeereid(fd, &euid, &egid) == -1) {
1946 error("getpeereid %d failed: %s", fd, strerror(errno));
1947 close(fd);
1948 return -1;
1949 }
1950 if ((euid != 0) && (getuid() != euid)) {
1951 error("uid mismatch: peer euid %u != uid %u",
1952 (u_int) euid, (u_int) getuid());
1953 close(fd);
1954 return -1;
1955 }
1956 new_socket(AUTH_CONNECTION, fd);
1957 return 0;
1958 }
1959
1960 static int
handle_conn_read(u_int socknum)1961 handle_conn_read(u_int socknum)
1962 {
1963 char buf[AGENT_RBUF_LEN];
1964 ssize_t len;
1965 int r;
1966
1967 if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) {
1968 if (len == -1) {
1969 if (errno == EAGAIN || errno == EINTR)
1970 return 0;
1971 error_f("read error on socket %u (fd %d): %s",
1972 socknum, sockets[socknum].fd, strerror(errno));
1973 }
1974 return -1;
1975 }
1976 if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0)
1977 fatal_fr(r, "compose");
1978 explicit_bzero(buf, sizeof(buf));
1979 for (;;) {
1980 if ((r = process_message(socknum)) == -1)
1981 return -1;
1982 else if (r == 0)
1983 break;
1984 }
1985 return 0;
1986 }
1987
1988 static int
handle_conn_write(u_int socknum)1989 handle_conn_write(u_int socknum)
1990 {
1991 ssize_t len;
1992 int r;
1993
1994 if (sshbuf_len(sockets[socknum].output) == 0)
1995 return 0; /* shouldn't happen */
1996 if ((len = write(sockets[socknum].fd,
1997 sshbuf_ptr(sockets[socknum].output),
1998 sshbuf_len(sockets[socknum].output))) <= 0) {
1999 if (len == -1) {
2000 if (errno == EAGAIN || errno == EINTR)
2001 return 0;
2002 error_f("read error on socket %u (fd %d): %s",
2003 socknum, sockets[socknum].fd, strerror(errno));
2004 }
2005 return -1;
2006 }
2007 if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0)
2008 fatal_fr(r, "consume");
2009 return 0;
2010 }
2011
2012 static void
after_poll(struct pollfd * pfd,size_t npfd,u_int maxfds)2013 after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds)
2014 {
2015 size_t i;
2016 u_int socknum, activefds = npfd;
2017
2018 for (i = 0; i < npfd; i++) {
2019 if (pfd[i].revents == 0)
2020 continue;
2021 /* Find sockets entry */
2022 for (socknum = 0; socknum < sockets_alloc; socknum++) {
2023 if (sockets[socknum].type != AUTH_SOCKET &&
2024 sockets[socknum].type != AUTH_CONNECTION)
2025 continue;
2026 if (pfd[i].fd == sockets[socknum].fd)
2027 break;
2028 }
2029 if (socknum >= sockets_alloc) {
2030 error_f("no socket for fd %d", pfd[i].fd);
2031 continue;
2032 }
2033 /* Process events */
2034 switch (sockets[socknum].type) {
2035 case AUTH_SOCKET:
2036 if ((pfd[i].revents & (POLLIN|POLLERR)) == 0)
2037 break;
2038 if (npfd > maxfds) {
2039 debug3("out of fds (active %u >= limit %u); "
2040 "skipping accept", activefds, maxfds);
2041 break;
2042 }
2043 if (handle_socket_read(socknum) == 0)
2044 activefds++;
2045 break;
2046 case AUTH_CONNECTION:
2047 if ((pfd[i].revents & (POLLIN|POLLHUP|POLLERR)) != 0 &&
2048 handle_conn_read(socknum) != 0)
2049 goto close_sock;
2050 if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 &&
2051 handle_conn_write(socknum) != 0) {
2052 close_sock:
2053 if (activefds == 0)
2054 fatal("activefds == 0 at close_sock");
2055 close_socket(&sockets[socknum]);
2056 activefds--;
2057 break;
2058 }
2059 break;
2060 default:
2061 break;
2062 }
2063 }
2064 }
2065
2066 static int
prepare_poll(struct pollfd ** pfdp,size_t * npfdp,struct timespec * timeoutp,u_int maxfds)2067 prepare_poll(struct pollfd **pfdp, size_t *npfdp, struct timespec *timeoutp, u_int maxfds)
2068 {
2069 struct pollfd *pfd = *pfdp;
2070 size_t i, j, npfd = 0;
2071 time_t deadline;
2072 int r;
2073
2074 /* Count active sockets */
2075 for (i = 0; i < sockets_alloc; i++) {
2076 switch (sockets[i].type) {
2077 case AUTH_SOCKET:
2078 case AUTH_CONNECTION:
2079 npfd++;
2080 break;
2081 case AUTH_UNUSED:
2082 break;
2083 default:
2084 fatal("Unknown socket type %d", sockets[i].type);
2085 break;
2086 }
2087 }
2088 if (npfd != *npfdp &&
2089 (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL)
2090 fatal_f("recallocarray failed");
2091 *pfdp = pfd;
2092 *npfdp = npfd;
2093
2094 for (i = j = 0; i < sockets_alloc; i++) {
2095 switch (sockets[i].type) {
2096 case AUTH_SOCKET:
2097 if (npfd > maxfds) {
2098 debug3("out of fds (active %zu >= limit %u); "
2099 "skipping arming listener", npfd, maxfds);
2100 break;
2101 }
2102 pfd[j].fd = sockets[i].fd;
2103 pfd[j].revents = 0;
2104 pfd[j].events = POLLIN;
2105 j++;
2106 break;
2107 case AUTH_CONNECTION:
2108 pfd[j].fd = sockets[i].fd;
2109 pfd[j].revents = 0;
2110 /*
2111 * Only prepare to read if we can handle a full-size
2112 * input read buffer and enqueue a max size reply..
2113 */
2114 if ((r = sshbuf_check_reserve(sockets[i].input,
2115 AGENT_RBUF_LEN)) == 0 &&
2116 (r = sshbuf_check_reserve(sockets[i].output,
2117 AGENT_MAX_LEN)) == 0)
2118 pfd[j].events = POLLIN;
2119 else if (r != SSH_ERR_NO_BUFFER_SPACE)
2120 fatal_fr(r, "reserve");
2121 if (sshbuf_len(sockets[i].output) > 0)
2122 pfd[j].events |= POLLOUT;
2123 j++;
2124 break;
2125 default:
2126 break;
2127 }
2128 }
2129 deadline = reaper();
2130 if (parent_alive_interval != 0)
2131 deadline = (deadline == 0) ? parent_alive_interval :
2132 MINIMUM(deadline, parent_alive_interval);
2133 if (deadline != 0)
2134 ptimeout_deadline_sec(timeoutp, deadline);
2135 return (1);
2136 }
2137
2138 static void
cleanup_socket(void)2139 cleanup_socket(void)
2140 {
2141 if (cleanup_pid != 0 && getpid() != cleanup_pid)
2142 return;
2143 debug_f("cleanup");
2144 if (socket_name[0])
2145 unlink(socket_name);
2146 if (socket_dir[0])
2147 rmdir(socket_dir);
2148 }
2149
2150 void
cleanup_exit(int i)2151 cleanup_exit(int i)
2152 {
2153 cleanup_socket();
2154 #ifdef ENABLE_PKCS11
2155 pkcs11_terminate();
2156 #endif
2157 _exit(i);
2158 }
2159
2160 static void
cleanup_handler(int sig)2161 cleanup_handler(int sig)
2162 {
2163 signalled = sig;
2164 }
2165
2166 static void
check_parent_exists(void)2167 check_parent_exists(void)
2168 {
2169 /*
2170 * If our parent has exited then getppid() will return (pid_t)1,
2171 * so testing for that should be safe.
2172 */
2173 if (parent_pid != -1 && getppid() != parent_pid) {
2174 /* printf("Parent has died - Authentication agent exiting.\n"); */
2175 cleanup_socket();
2176 _exit(2);
2177 }
2178 }
2179
2180 static void
usage(void)2181 usage(void)
2182 {
2183 fprintf(stderr,
2184 "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n"
2185 " [-O option] [-P allowed_providers] [-t life]\n"
2186 " ssh-agent [-a bind_address] [-E fingerprint_hash] [-O option]\n"
2187 " [-P allowed_providers] [-t life] command [arg ...]\n"
2188 " ssh-agent [-c | -s] -k\n");
2189 exit(1);
2190 }
2191
2192 int
main(int ac,char ** av)2193 main(int ac, char **av)
2194 {
2195 int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0;
2196 int sock, ch, result, saved_errno;
2197 char *shell, *format, *pidstr, *agentsocket = NULL;
2198 #ifdef HAVE_SETRLIMIT
2199 struct rlimit rlim;
2200 #endif
2201 extern int optind;
2202 extern char *optarg;
2203 pid_t pid;
2204 char pidstrbuf[1 + 3 * sizeof pid];
2205 size_t len;
2206 mode_t prev_mask;
2207 struct timespec timeout;
2208 struct pollfd *pfd = NULL;
2209 size_t npfd = 0;
2210 u_int maxfds;
2211 sigset_t nsigset, osigset;
2212
2213 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
2214 sanitise_stdfd();
2215
2216 /* drop */
2217 (void)setegid(getgid());
2218 (void)setgid(getgid());
2219
2220 platform_disable_tracing(0); /* strict=no */
2221
2222 #ifdef RLIMIT_NOFILE
2223 if (getrlimit(RLIMIT_NOFILE, &rlim) == -1)
2224 fatal("%s: getrlimit: %s", __progname, strerror(errno));
2225 #endif
2226
2227 __progname = ssh_get_progname(av[0]);
2228 seed_rng();
2229
2230 while ((ch = getopt(ac, av, "cDdksE:a:O:P:t:")) != -1) {
2231 switch (ch) {
2232 case 'E':
2233 fingerprint_hash = ssh_digest_alg_by_name(optarg);
2234 if (fingerprint_hash == -1)
2235 fatal("Invalid hash algorithm \"%s\"", optarg);
2236 break;
2237 case 'c':
2238 if (s_flag)
2239 usage();
2240 c_flag++;
2241 break;
2242 case 'k':
2243 k_flag++;
2244 break;
2245 case 'O':
2246 if (strcmp(optarg, "no-restrict-websafe") == 0)
2247 restrict_websafe = 0;
2248 else if (strcmp(optarg, "allow-remote-pkcs11") == 0)
2249 remote_add_provider = 1;
2250 else
2251 fatal("Unknown -O option");
2252 break;
2253 case 'P':
2254 if (allowed_providers != NULL)
2255 fatal("-P option already specified");
2256 allowed_providers = xstrdup(optarg);
2257 break;
2258 case 's':
2259 if (c_flag)
2260 usage();
2261 s_flag++;
2262 break;
2263 case 'd':
2264 if (d_flag || D_flag)
2265 usage();
2266 d_flag++;
2267 break;
2268 case 'D':
2269 if (d_flag || D_flag)
2270 usage();
2271 D_flag++;
2272 break;
2273 case 'a':
2274 agentsocket = optarg;
2275 break;
2276 case 't':
2277 if ((lifetime = convtime(optarg)) == -1) {
2278 fprintf(stderr, "Invalid lifetime\n");
2279 usage();
2280 }
2281 break;
2282 default:
2283 usage();
2284 }
2285 }
2286 ac -= optind;
2287 av += optind;
2288
2289 if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag))
2290 usage();
2291
2292 if (allowed_providers == NULL)
2293 allowed_providers = xstrdup(DEFAULT_ALLOWED_PROVIDERS);
2294
2295 if (ac == 0 && !c_flag && !s_flag) {
2296 shell = getenv("SHELL");
2297 if (shell != NULL && (len = strlen(shell)) > 2 &&
2298 strncmp(shell + len - 3, "csh", 3) == 0)
2299 c_flag = 1;
2300 }
2301 if (k_flag) {
2302 const char *errstr = NULL;
2303
2304 pidstr = getenv(SSH_AGENTPID_ENV_NAME);
2305 if (pidstr == NULL) {
2306 fprintf(stderr, "%s not set, cannot kill agent\n",
2307 SSH_AGENTPID_ENV_NAME);
2308 exit(1);
2309 }
2310 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr);
2311 if (errstr) {
2312 fprintf(stderr,
2313 "%s=\"%s\", which is not a good PID: %s\n",
2314 SSH_AGENTPID_ENV_NAME, pidstr, errstr);
2315 exit(1);
2316 }
2317 if (kill(pid, SIGTERM) == -1) {
2318 perror("kill");
2319 exit(1);
2320 }
2321 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n";
2322 printf(format, SSH_AUTHSOCKET_ENV_NAME);
2323 printf(format, SSH_AGENTPID_ENV_NAME);
2324 printf("echo Agent pid %ld killed;\n", (long)pid);
2325 exit(0);
2326 }
2327
2328 /*
2329 * Minimum file descriptors:
2330 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) +
2331 * a few spare for libc / stack protectors / sanitisers, etc.
2332 */
2333 #define SSH_AGENT_MIN_FDS (3+1+1+1+4)
2334 if (rlim.rlim_cur < SSH_AGENT_MIN_FDS)
2335 fatal("%s: file descriptor rlimit %lld too low (minimum %u)",
2336 __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS);
2337 maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS;
2338
2339 parent_pid = getpid();
2340
2341 if (agentsocket == NULL) {
2342 /* Create private directory for agent socket */
2343 mktemp_proto(socket_dir, sizeof(socket_dir));
2344 if (mkdtemp(socket_dir) == NULL) {
2345 perror("mkdtemp: private socket dir");
2346 exit(1);
2347 }
2348 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
2349 (long)parent_pid);
2350 } else {
2351 /* Try to use specified agent socket */
2352 socket_dir[0] = '\0';
2353 strlcpy(socket_name, agentsocket, sizeof socket_name);
2354 }
2355
2356 /*
2357 * Create socket early so it will exist before command gets run from
2358 * the parent.
2359 */
2360 prev_mask = umask(0177);
2361 sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
2362 if (sock < 0) {
2363 /* XXX - unix_listener() calls error() not perror() */
2364 *socket_name = '\0'; /* Don't unlink any existing file */
2365 cleanup_exit(1);
2366 }
2367 umask(prev_mask);
2368
2369 /*
2370 * Fork, and have the parent execute the command, if any, or present
2371 * the socket data. The child continues as the authentication agent.
2372 */
2373 if (D_flag || d_flag) {
2374 log_init(__progname,
2375 d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO,
2376 SYSLOG_FACILITY_AUTH, 1);
2377 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
2378 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
2379 SSH_AUTHSOCKET_ENV_NAME);
2380 printf("echo Agent pid %ld;\n", (long)parent_pid);
2381 fflush(stdout);
2382 goto skip;
2383 }
2384 pid = fork();
2385 if (pid == -1) {
2386 perror("fork");
2387 cleanup_exit(1);
2388 }
2389 if (pid != 0) { /* Parent - execute the given command. */
2390 close(sock);
2391 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid);
2392 if (ac == 0) {
2393 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
2394 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
2395 SSH_AUTHSOCKET_ENV_NAME);
2396 printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf,
2397 SSH_AGENTPID_ENV_NAME);
2398 printf("echo Agent pid %ld;\n", (long)pid);
2399 exit(0);
2400 }
2401 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
2402 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
2403 perror("setenv");
2404 exit(1);
2405 }
2406 execvp(av[0], av);
2407 perror(av[0]);
2408 exit(1);
2409 }
2410 /* child */
2411 log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0);
2412
2413 if (setsid() == -1) {
2414 error("setsid: %s", strerror(errno));
2415 cleanup_exit(1);
2416 }
2417
2418 (void)chdir("/");
2419 if (stdfd_devnull(1, 1, 1) == -1)
2420 error_f("stdfd_devnull failed");
2421
2422 #ifdef HAVE_SETRLIMIT
2423 /* deny core dumps, since memory contains unencrypted private keys */
2424 rlim.rlim_cur = rlim.rlim_max = 0;
2425 if (setrlimit(RLIMIT_CORE, &rlim) == -1) {
2426 error("setrlimit RLIMIT_CORE: %s", strerror(errno));
2427 cleanup_exit(1);
2428 }
2429 #endif
2430
2431 skip:
2432
2433 cleanup_pid = getpid();
2434
2435 #ifdef ENABLE_PKCS11
2436 pkcs11_init(0);
2437 #endif
2438 new_socket(AUTH_SOCKET, sock);
2439 if (ac > 0)
2440 parent_alive_interval = 10;
2441 idtab_init();
2442 ssh_signal(SIGPIPE, SIG_IGN);
2443 ssh_signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN);
2444 ssh_signal(SIGHUP, cleanup_handler);
2445 ssh_signal(SIGTERM, cleanup_handler);
2446
2447 sigemptyset(&nsigset);
2448 sigaddset(&nsigset, SIGINT);
2449 sigaddset(&nsigset, SIGHUP);
2450 sigaddset(&nsigset, SIGTERM);
2451
2452 if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1)
2453 fatal("%s: pledge: %s", __progname, strerror(errno));
2454 platform_pledge_agent();
2455
2456 while (1) {
2457 sigprocmask(SIG_BLOCK, &nsigset, &osigset);
2458 if (signalled != 0) {
2459 logit("exiting on signal %d", (int)signalled);
2460 cleanup_exit(2);
2461 }
2462 ptimeout_init(&timeout);
2463 prepare_poll(&pfd, &npfd, &timeout, maxfds);
2464 result = ppoll(pfd, npfd, ptimeout_get_tsp(&timeout), &osigset);
2465 sigprocmask(SIG_SETMASK, &osigset, NULL);
2466 saved_errno = errno;
2467 if (parent_alive_interval != 0)
2468 check_parent_exists();
2469 (void) reaper(); /* remove expired keys */
2470 if (result == -1) {
2471 if (saved_errno == EINTR)
2472 continue;
2473 fatal("poll: %s", strerror(saved_errno));
2474 } else if (result > 0)
2475 after_poll(pfd, npfd, maxfds);
2476 }
2477 /* NOTREACHED */
2478 }
2479