1 /* $NetBSD: ssh-agent.c,v 1.35 2023/07/26 17:58:15 christos Exp $ */
2 /* $OpenBSD: ssh-agent.c,v 1.297 2023/03/09 21:06:24 jcs Exp $ */
3 /*
4 * Author: Tatu Ylonen <ylo@cs.hut.fi>
5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * All rights reserved
7 * The authentication agent program.
8 *
9 * As far as I am concerned, the code I have written for this software
10 * can be used freely for any purpose. Any derived versions of this
11 * software must be clearly marked as such, and if the derived work is
12 * incompatible with the protocol description in the RFC file, it must be
13 * called by a name other than "ssh" or "Secure Shell".
14 *
15 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions
19 * are met:
20 * 1. Redistributions of source code must retain the above copyright
21 * notice, this list of conditions and the following disclaimer.
22 * 2. Redistributions in binary form must reproduce the above copyright
23 * notice, this list of conditions and the following disclaimer in the
24 * documentation and/or other materials provided with the distribution.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 */
37
38 #include "includes.h"
39 __RCSID("$NetBSD: ssh-agent.c,v 1.35 2023/07/26 17:58:15 christos Exp $");
40
41 #include <sys/param.h> /* MIN MAX */
42 #include <sys/types.h>
43 #include <sys/time.h>
44 #include <sys/queue.h>
45 #include <sys/resource.h>
46 #include <sys/socket.h>
47 #include <sys/stat.h>
48 #include <sys/un.h>
49 #include <sys/wait.h>
50
51 #ifdef WITH_OPENSSL
52 #include <openssl/evp.h>
53 #endif
54
55 #include <errno.h>
56 #include <fcntl.h>
57 #include <paths.h>
58 #include <poll.h>
59 #include <signal.h>
60 #include <stdlib.h>
61 #include <stdio.h>
62 #include <string.h>
63 #include <stdarg.h>
64 #include <limits.h>
65 #include <time.h>
66 #include <unistd.h>
67 #include <util.h>
68
69 #include "xmalloc.h"
70 #include "ssh.h"
71 #include "ssh2.h"
72 #include "sshbuf.h"
73 #include "sshkey.h"
74 #include "authfd.h"
75 #include "log.h"
76 #include "misc.h"
77 #include "getpeereid.h"
78 #include "digest.h"
79 #include "ssherr.h"
80 #include "match.h"
81 #include "msg.h"
82 #include "pathnames.h"
83 #include "ssh-pkcs11.h"
84 #include "sk-api.h"
85 #include "myproposal.h"
86
87 #ifndef DEFAULT_ALLOWED_PROVIDERS
88 # define DEFAULT_ALLOWED_PROVIDERS "/usr/lib*/*,/usr/pkg/lib*/*"
89 #endif
90
91 /* Maximum accepted message length */
92 #define AGENT_MAX_LEN (256*1024)
93 /* Maximum bytes to read from client socket */
94 #define AGENT_RBUF_LEN (4096)
95 /* Maximum number of recorded session IDs/hostkeys per connection */
96 #define AGENT_MAX_SESSION_IDS 16
97 /* Maximum size of session ID */
98 #define AGENT_MAX_SID_LEN 128
99 /* Maximum number of destination constraints to accept on a key */
100 #define AGENT_MAX_DEST_CONSTRAINTS 1024
101
102 /* XXX store hostkey_sid in a refcounted tree */
103
104 typedef enum {
105 AUTH_UNUSED = 0,
106 AUTH_SOCKET = 1,
107 AUTH_CONNECTION = 2,
108 } sock_type;
109
110 struct hostkey_sid {
111 struct sshkey *key;
112 struct sshbuf *sid;
113 int forwarded;
114 };
115
116 typedef struct socket_entry {
117 int fd;
118 sock_type type;
119 struct sshbuf *input;
120 struct sshbuf *output;
121 struct sshbuf *request;
122 size_t nsession_ids;
123 struct hostkey_sid *session_ids;
124 } SocketEntry;
125
126 u_int sockets_alloc = 0;
127 SocketEntry *sockets = NULL;
128
129 typedef struct identity {
130 TAILQ_ENTRY(identity) next;
131 struct sshkey *key;
132 char *comment;
133 char *provider;
134 time_t death;
135 u_int confirm;
136 char *sk_provider;
137 struct dest_constraint *dest_constraints;
138 size_t ndest_constraints;
139 } Identity;
140
141 struct idtable {
142 int nentries;
143 TAILQ_HEAD(idqueue, identity) idlist;
144 };
145
146 /* private key table */
147 struct idtable *idtab;
148
149 int max_fd = 0;
150
151 /* pid of shell == parent of agent */
152 pid_t parent_pid = -1;
153 time_t parent_alive_interval = 0;
154
155 /* pid of process for which cleanup_socket is applicable */
156 pid_t cleanup_pid = 0;
157
158 /* pathname and directory for AUTH_SOCKET */
159 char socket_name[PATH_MAX];
160 char socket_dir[PATH_MAX];
161
162 /* Pattern-list of allowed PKCS#11/Security key paths */
163 static char *allowed_providers;
164
165 /*
166 * Allows PKCS11 providers or SK keys that use non-internal providers to
167 * be added over a remote connection (identified by session-bind@openssh.com).
168 */
169 static int remote_add_provider;
170
171 /* locking */
172 #define LOCK_SIZE 32
173 #define LOCK_SALT_SIZE 16
174 #define LOCK_ROUNDS 1
175 int locked = 0;
176 u_char lock_pwhash[LOCK_SIZE];
177 u_char lock_salt[LOCK_SALT_SIZE];
178
179 extern char *__progname;
180
181 /* Default lifetime in seconds (0 == forever) */
182 static int lifetime = 0;
183
184 static int fingerprint_hash = SSH_FP_HASH_DEFAULT;
185
186 /* Refuse signing of non-SSH messages for web-origin FIDO keys */
187 static int restrict_websafe = 1;
188
189 static void
close_socket(SocketEntry * e)190 close_socket(SocketEntry *e)
191 {
192 size_t i;
193
194 close(e->fd);
195 sshbuf_free(e->input);
196 sshbuf_free(e->output);
197 sshbuf_free(e->request);
198 for (i = 0; i < e->nsession_ids; i++) {
199 sshkey_free(e->session_ids[i].key);
200 sshbuf_free(e->session_ids[i].sid);
201 }
202 free(e->session_ids);
203 memset(e, '\0', sizeof(*e));
204 e->fd = -1;
205 e->type = AUTH_UNUSED;
206 }
207
208 static void
idtab_init(void)209 idtab_init(void)
210 {
211 idtab = xcalloc(1, sizeof(*idtab));
212 TAILQ_INIT(&idtab->idlist);
213 idtab->nentries = 0;
214 }
215
216 static void
free_dest_constraint_hop(struct dest_constraint_hop * dch)217 free_dest_constraint_hop(struct dest_constraint_hop *dch)
218 {
219 u_int i;
220
221 if (dch == NULL)
222 return;
223 free(dch->user);
224 free(dch->hostname);
225 for (i = 0; i < dch->nkeys; i++)
226 sshkey_free(dch->keys[i]);
227 free(dch->keys);
228 free(dch->key_is_ca);
229 }
230
231 static void
free_dest_constraints(struct dest_constraint * dcs,size_t ndcs)232 free_dest_constraints(struct dest_constraint *dcs, size_t ndcs)
233 {
234 size_t i;
235
236 for (i = 0; i < ndcs; i++) {
237 free_dest_constraint_hop(&dcs[i].from);
238 free_dest_constraint_hop(&dcs[i].to);
239 }
240 free(dcs);
241 }
242
243 static void
free_identity(Identity * id)244 free_identity(Identity *id)
245 {
246 sshkey_free(id->key);
247 free(id->provider);
248 free(id->comment);
249 free(id->sk_provider);
250 free_dest_constraints(id->dest_constraints, id->ndest_constraints);
251 free(id);
252 }
253
254 /*
255 * Match 'key' against the key/CA list in a destination constraint hop
256 * Returns 0 on success or -1 otherwise.
257 */
258 static int
match_key_hop(const char * tag,const struct sshkey * key,const struct dest_constraint_hop * dch)259 match_key_hop(const char *tag, const struct sshkey *key,
260 const struct dest_constraint_hop *dch)
261 {
262 const char *reason = NULL;
263 const char *hostname = dch->hostname ? dch->hostname : "(ORIGIN)";
264 u_int i;
265 char *fp;
266
267 if (key == NULL)
268 return -1;
269 /* XXX logspam */
270 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
271 SSH_FP_DEFAULT)) == NULL)
272 fatal_f("fingerprint failed");
273 debug3_f("%s: entering hostname %s, requested key %s %s, %u keys avail",
274 tag, hostname, sshkey_type(key), fp, dch->nkeys);
275 free(fp);
276 for (i = 0; i < dch->nkeys; i++) {
277 if (dch->keys[i] == NULL)
278 return -1;
279 /* XXX logspam */
280 if ((fp = sshkey_fingerprint(dch->keys[i], SSH_FP_HASH_DEFAULT,
281 SSH_FP_DEFAULT)) == NULL)
282 fatal_f("fingerprint failed");
283 debug3_f("%s: key %u: %s%s %s", tag, i,
284 dch->key_is_ca[i] ? "CA " : "",
285 sshkey_type(dch->keys[i]), fp);
286 free(fp);
287 if (!sshkey_is_cert(key)) {
288 /* plain key */
289 if (dch->key_is_ca[i] ||
290 !sshkey_equal(key, dch->keys[i]))
291 continue;
292 return 0;
293 }
294 /* certificate */
295 if (!dch->key_is_ca[i])
296 continue;
297 if (key->cert == NULL || key->cert->signature_key == NULL)
298 return -1; /* shouldn't happen */
299 if (!sshkey_equal(key->cert->signature_key, dch->keys[i]))
300 continue;
301 if (sshkey_cert_check_host(key, hostname, 1,
302 SSH_ALLOWED_CA_SIGALGS, &reason) != 0) {
303 debug_f("cert %s / hostname %s rejected: %s",
304 key->cert->key_id, hostname, reason);
305 continue;
306 }
307 return 0;
308 }
309 return -1;
310 }
311
312 /* Check destination constraints on an identity against the hostkey/user */
313 static int
permitted_by_dest_constraints(const struct sshkey * fromkey,const struct sshkey * tokey,Identity * id,const char * user,const char ** hostnamep)314 permitted_by_dest_constraints(const struct sshkey *fromkey,
315 const struct sshkey *tokey, Identity *id, const char *user,
316 const char **hostnamep)
317 {
318 size_t i;
319 struct dest_constraint *d;
320
321 if (hostnamep != NULL)
322 *hostnamep = NULL;
323 for (i = 0; i < id->ndest_constraints; i++) {
324 d = id->dest_constraints + i;
325 /* XXX remove logspam */
326 debug2_f("constraint %zu %s%s%s (%u keys) > %s%s%s (%u keys)",
327 i, d->from.user ? d->from.user : "",
328 d->from.user ? "@" : "",
329 d->from.hostname ? d->from.hostname : "(ORIGIN)",
330 d->from.nkeys,
331 d->to.user ? d->to.user : "", d->to.user ? "@" : "",
332 d->to.hostname ? d->to.hostname : "(ANY)", d->to.nkeys);
333
334 /* Match 'from' key */
335 if (fromkey == NULL) {
336 /* We are matching the first hop */
337 if (d->from.hostname != NULL || d->from.nkeys != 0)
338 continue;
339 } else if (match_key_hop("from", fromkey, &d->from) != 0)
340 continue;
341
342 /* Match 'to' key */
343 if (tokey != NULL && match_key_hop("to", tokey, &d->to) != 0)
344 continue;
345
346 /* Match user if specified */
347 if (d->to.user != NULL && user != NULL &&
348 !match_pattern(user, d->to.user))
349 continue;
350
351 /* successfully matched this constraint */
352 if (hostnamep != NULL)
353 *hostnamep = d->to.hostname;
354 debug2_f("allowed for hostname %s",
355 d->to.hostname == NULL ? "*" : d->to.hostname);
356 return 0;
357 }
358 /* no match */
359 debug2_f("%s identity \"%s\" not permitted for this destination",
360 sshkey_type(id->key), id->comment);
361 return -1;
362 }
363
364 /*
365 * Check whether hostkeys on a SocketEntry and the optionally specified user
366 * are permitted by the destination constraints on the Identity.
367 * Returns 0 on success or -1 otherwise.
368 */
369 static int
identity_permitted(Identity * id,SocketEntry * e,char * user,const char ** forward_hostnamep,const char ** last_hostnamep)370 identity_permitted(Identity *id, SocketEntry *e, char *user,
371 const char **forward_hostnamep, const char **last_hostnamep)
372 {
373 size_t i;
374 const char **hp;
375 struct hostkey_sid *hks;
376 const struct sshkey *fromkey = NULL;
377 const char *test_user;
378 char *fp1, *fp2;
379
380 /* XXX remove logspam */
381 debug3_f("entering: key %s comment \"%s\", %zu socket bindings, "
382 "%zu constraints", sshkey_type(id->key), id->comment,
383 e->nsession_ids, id->ndest_constraints);
384 if (id->ndest_constraints == 0)
385 return 0; /* unconstrained */
386 if (e->nsession_ids == 0)
387 return 0; /* local use */
388 /*
389 * Walk through the hops recorded by session_id and try to find a
390 * constraint that satisfies each.
391 */
392 for (i = 0; i < e->nsession_ids; i++) {
393 hks = e->session_ids + i;
394 if (hks->key == NULL)
395 fatal_f("internal error: no bound key");
396 /* XXX remove logspam */
397 fp1 = fp2 = NULL;
398 if (fromkey != NULL &&
399 (fp1 = sshkey_fingerprint(fromkey, SSH_FP_HASH_DEFAULT,
400 SSH_FP_DEFAULT)) == NULL)
401 fatal_f("fingerprint failed");
402 if ((fp2 = sshkey_fingerprint(hks->key, SSH_FP_HASH_DEFAULT,
403 SSH_FP_DEFAULT)) == NULL)
404 fatal_f("fingerprint failed");
405 debug3_f("socketentry fd=%d, entry %zu %s, "
406 "from hostkey %s %s to user %s hostkey %s %s",
407 e->fd, i, hks->forwarded ? "FORWARD" : "AUTH",
408 fromkey ? sshkey_type(fromkey) : "(ORIGIN)",
409 fromkey ? fp1 : "", user ? user : "(ANY)",
410 sshkey_type(hks->key), fp2);
411 free(fp1);
412 free(fp2);
413 /*
414 * Record the hostnames for the initial forwarding and
415 * the final destination.
416 */
417 hp = NULL;
418 if (i == e->nsession_ids - 1)
419 hp = last_hostnamep;
420 else if (i == 0)
421 hp = forward_hostnamep;
422 /* Special handling for final recorded binding */
423 test_user = NULL;
424 if (i == e->nsession_ids - 1) {
425 /* Can only check user at final hop */
426 test_user = user;
427 /*
428 * user is only presented for signature requests.
429 * If this is the case, make sure last binding is not
430 * for a forwarding.
431 */
432 if (hks->forwarded && user != NULL) {
433 error_f("tried to sign on forwarding hop");
434 return -1;
435 }
436 } else if (!hks->forwarded) {
437 error_f("tried to forward though signing bind");
438 return -1;
439 }
440 if (permitted_by_dest_constraints(fromkey, hks->key, id,
441 test_user, hp) != 0)
442 return -1;
443 fromkey = hks->key;
444 }
445 /*
446 * Another special case: if the last bound session ID was for a
447 * forwarding, and this function is not being called to check a sign
448 * request (i.e. no 'user' supplied), then only permit the key if
449 * there is a permission that would allow it to be used at another
450 * destination. This hides keys that are allowed to be used to
451 * authenticate *to* a host but not permitted for *use* beyond it.
452 */
453 hks = &e->session_ids[e->nsession_ids - 1];
454 if (hks->forwarded && user == NULL &&
455 permitted_by_dest_constraints(hks->key, NULL, id,
456 NULL, NULL) != 0) {
457 debug3_f("key permitted at host but not after");
458 return -1;
459 }
460
461 /* success */
462 return 0;
463 }
464
465 /* return matching private key for given public key */
466 static Identity *
lookup_identity(struct sshkey * key)467 lookup_identity(struct sshkey *key)
468 {
469 Identity *id;
470
471 TAILQ_FOREACH(id, &idtab->idlist, next) {
472 if (sshkey_equal(key, id->key))
473 return (id);
474 }
475 return (NULL);
476 }
477
478 /* Check confirmation of keysign request */
479 static int
confirm_key(Identity * id,const char * extra)480 confirm_key(Identity *id, const char *extra)
481 {
482 char *p;
483 int ret = -1;
484
485 p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT);
486 if (p != NULL &&
487 ask_permission("Allow use of key %s?\nKey fingerprint %s.%s%s",
488 id->comment, p,
489 extra == NULL ? "" : "\n", extra == NULL ? "" : extra))
490 ret = 0;
491 free(p);
492
493 return (ret);
494 }
495
496 static void
send_status(SocketEntry * e,int success)497 send_status(SocketEntry *e, int success)
498 {
499 int r;
500
501 if ((r = sshbuf_put_u32(e->output, 1)) != 0 ||
502 (r = sshbuf_put_u8(e->output, success ?
503 SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
504 fatal_fr(r, "compose");
505 }
506
507 /* send list of supported public keys to 'client' */
508 static void
process_request_identities(SocketEntry * e)509 process_request_identities(SocketEntry *e)
510 {
511 Identity *id;
512 struct sshbuf *msg, *keys;
513 int r;
514 u_int nentries = 0;
515
516 debug2_f("entering");
517
518 if ((msg = sshbuf_new()) == NULL || (keys = sshbuf_new()) == NULL)
519 fatal_f("sshbuf_new failed");
520 TAILQ_FOREACH(id, &idtab->idlist, next) {
521 /* identity not visible, don't include in response */
522 if (identity_permitted(id, e, NULL, NULL, NULL) != 0)
523 continue;
524 if ((r = sshkey_puts_opts(id->key, keys,
525 SSHKEY_SERIALIZE_INFO)) != 0 ||
526 (r = sshbuf_put_cstring(keys, id->comment)) != 0) {
527 error_fr(r, "compose key/comment");
528 continue;
529 }
530 nentries++;
531 }
532 debug2_f("replying with %u allowed of %u available keys",
533 nentries, idtab->nentries);
534 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
535 (r = sshbuf_put_u32(msg, nentries)) != 0 ||
536 (r = sshbuf_putb(msg, keys)) != 0)
537 fatal_fr(r, "compose");
538 if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
539 fatal_fr(r, "enqueue");
540 sshbuf_free(msg);
541 sshbuf_free(keys);
542 }
543
544
545 static const char *
agent_decode_alg(struct sshkey * key,u_int flags)546 agent_decode_alg(struct sshkey *key, u_int flags)
547 {
548 if (key->type == KEY_RSA) {
549 if (flags & SSH_AGENT_RSA_SHA2_256)
550 return "rsa-sha2-256";
551 else if (flags & SSH_AGENT_RSA_SHA2_512)
552 return "rsa-sha2-512";
553 } else if (key->type == KEY_RSA_CERT) {
554 if (flags & SSH_AGENT_RSA_SHA2_256)
555 return "rsa-sha2-256-cert-v01@openssh.com";
556 else if (flags & SSH_AGENT_RSA_SHA2_512)
557 return "rsa-sha2-512-cert-v01@openssh.com";
558 }
559 return NULL;
560 }
561
562 /*
563 * Attempt to parse the contents of a buffer as a SSH publickey userauth
564 * request, checking its contents for consistency and matching the embedded
565 * key against the one that is being used for signing.
566 * Note: does not modify msg buffer.
567 * Optionally extract the username, session ID and/or hostkey from the request.
568 */
569 static int
parse_userauth_request(struct sshbuf * msg,const struct sshkey * expected_key,char ** userp,struct sshbuf ** sess_idp,struct sshkey ** hostkeyp)570 parse_userauth_request(struct sshbuf *msg, const struct sshkey *expected_key,
571 char **userp, struct sshbuf **sess_idp, struct sshkey **hostkeyp)
572 {
573 struct sshbuf *b = NULL, *sess_id = NULL;
574 char *user = NULL, *service = NULL, *method = NULL, *pkalg = NULL;
575 int r;
576 u_char t, sig_follows;
577 struct sshkey *mkey = NULL, *hostkey = NULL;
578
579 if (userp != NULL)
580 *userp = NULL;
581 if (sess_idp != NULL)
582 *sess_idp = NULL;
583 if (hostkeyp != NULL)
584 *hostkeyp = NULL;
585 if ((b = sshbuf_fromb(msg)) == NULL)
586 fatal_f("sshbuf_fromb");
587
588 /* SSH userauth request */
589 if ((r = sshbuf_froms(b, &sess_id)) != 0)
590 goto out;
591 if (sshbuf_len(sess_id) == 0) {
592 r = SSH_ERR_INVALID_FORMAT;
593 goto out;
594 }
595 if ((r = sshbuf_get_u8(b, &t)) != 0 || /* SSH2_MSG_USERAUTH_REQUEST */
596 (r = sshbuf_get_cstring(b, &user, NULL)) != 0 || /* server user */
597 (r = sshbuf_get_cstring(b, &service, NULL)) != 0 || /* service */
598 (r = sshbuf_get_cstring(b, &method, NULL)) != 0 || /* method */
599 (r = sshbuf_get_u8(b, &sig_follows)) != 0 || /* sig-follows */
600 (r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 || /* alg */
601 (r = sshkey_froms(b, &mkey)) != 0) /* key */
602 goto out;
603 if (t != SSH2_MSG_USERAUTH_REQUEST ||
604 sig_follows != 1 ||
605 strcmp(service, "ssh-connection") != 0 ||
606 !sshkey_equal(expected_key, mkey) ||
607 sshkey_type_from_name(pkalg) != expected_key->type) {
608 r = SSH_ERR_INVALID_FORMAT;
609 goto out;
610 }
611 if (strcmp(method, "publickey-hostbound-v00@openssh.com") == 0) {
612 if ((r = sshkey_froms(b, &hostkey)) != 0)
613 goto out;
614 } else if (strcmp(method, "publickey") != 0) {
615 r = SSH_ERR_INVALID_FORMAT;
616 goto out;
617 }
618 if (sshbuf_len(b) != 0) {
619 r = SSH_ERR_INVALID_FORMAT;
620 goto out;
621 }
622 /* success */
623 r = 0;
624 debug3_f("well formed userauth");
625 if (userp != NULL) {
626 *userp = user;
627 user = NULL;
628 }
629 if (sess_idp != NULL) {
630 *sess_idp = sess_id;
631 sess_id = NULL;
632 }
633 if (hostkeyp != NULL) {
634 *hostkeyp = hostkey;
635 hostkey = NULL;
636 }
637 out:
638 sshbuf_free(b);
639 sshbuf_free(sess_id);
640 free(user);
641 free(service);
642 free(method);
643 free(pkalg);
644 sshkey_free(mkey);
645 sshkey_free(hostkey);
646 return r;
647 }
648
649 /*
650 * Attempt to parse the contents of a buffer as a SSHSIG signature request.
651 * Note: does not modify buffer.
652 */
653 static int
parse_sshsig_request(struct sshbuf * msg)654 parse_sshsig_request(struct sshbuf *msg)
655 {
656 int r;
657 struct sshbuf *b;
658
659 if ((b = sshbuf_fromb(msg)) == NULL)
660 fatal_f("sshbuf_fromb");
661
662 if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) != 0 ||
663 (r = sshbuf_consume(b, 6)) != 0 ||
664 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* namespace */
665 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0 || /* reserved */
666 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* hashalg */
667 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0) /* H(msg) */
668 goto out;
669 if (sshbuf_len(b) != 0) {
670 r = SSH_ERR_INVALID_FORMAT;
671 goto out;
672 }
673 /* success */
674 r = 0;
675 out:
676 sshbuf_free(b);
677 return r;
678 }
679
680 /*
681 * This function inspects a message to be signed by a FIDO key that has a
682 * web-like application string (i.e. one that does not begin with "ssh:".
683 * It checks that the message is one of those expected for SSH operations
684 * (pubkey userauth, sshsig, CA key signing) to exclude signing challenges
685 * for the web.
686 */
687 static int
check_websafe_message_contents(struct sshkey * key,struct sshbuf * data)688 check_websafe_message_contents(struct sshkey *key, struct sshbuf *data)
689 {
690 if (parse_userauth_request(data, key, NULL, NULL, NULL) == 0) {
691 debug_f("signed data matches public key userauth request");
692 return 1;
693 }
694 if (parse_sshsig_request(data) == 0) {
695 debug_f("signed data matches SSHSIG signature request");
696 return 1;
697 }
698
699 /* XXX check CA signature operation */
700
701 error("web-origin key attempting to sign non-SSH message");
702 return 0;
703 }
704
705 static int
buf_equal(const struct sshbuf * a,const struct sshbuf * b)706 buf_equal(const struct sshbuf *a, const struct sshbuf *b)
707 {
708 if (sshbuf_ptr(a) == NULL || sshbuf_ptr(b) == NULL)
709 return SSH_ERR_INVALID_ARGUMENT;
710 if (sshbuf_len(a) != sshbuf_len(b))
711 return SSH_ERR_INVALID_FORMAT;
712 if (timingsafe_bcmp(sshbuf_ptr(a), sshbuf_ptr(b), sshbuf_len(a)) != 0)
713 return SSH_ERR_INVALID_FORMAT;
714 return 0;
715 }
716
717 /* ssh2 only */
718 static void
process_sign_request2(SocketEntry * e)719 process_sign_request2(SocketEntry *e)
720 {
721 u_char *signature = NULL;
722 size_t slen = 0;
723 u_int compat = 0, flags;
724 int r, ok = -1, retried = 0;
725 char *fp = NULL, *pin = NULL, *prompt = NULL;
726 char *user = NULL, *sig_dest = NULL;
727 const char *fwd_host = NULL, *dest_host = NULL;
728 struct sshbuf *msg = NULL, *data = NULL, *sid = NULL;
729 struct sshkey *key = NULL, *hostkey = NULL;
730 struct identity *id;
731 struct notifier_ctx *notifier = NULL;
732
733 debug_f("entering");
734
735 if ((msg = sshbuf_new()) == NULL || (data = sshbuf_new()) == NULL)
736 fatal_f("sshbuf_new failed");
737 if ((r = sshkey_froms(e->request, &key)) != 0 ||
738 (r = sshbuf_get_stringb(e->request, data)) != 0 ||
739 (r = sshbuf_get_u32(e->request, &flags)) != 0) {
740 error_fr(r, "parse");
741 goto send;
742 }
743
744 if ((id = lookup_identity(key)) == NULL) {
745 verbose_f("%s key not found", sshkey_type(key));
746 goto send;
747 }
748 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
749 SSH_FP_DEFAULT)) == NULL)
750 fatal_f("fingerprint failed");
751
752 if (id->ndest_constraints != 0) {
753 if (e->nsession_ids == 0) {
754 logit_f("refusing use of destination-constrained key "
755 "to sign on unbound connection");
756 goto send;
757 }
758 if (parse_userauth_request(data, key, &user, &sid,
759 &hostkey) != 0) {
760 logit_f("refusing use of destination-constrained key "
761 "to sign an unidentified signature");
762 goto send;
763 }
764 /* XXX logspam */
765 debug_f("user=%s", user);
766 if (identity_permitted(id, e, user, &fwd_host, &dest_host) != 0)
767 goto send;
768 /* XXX display fwd_host/dest_host in askpass UI */
769 /*
770 * Ensure that the session ID is the most recent one
771 * registered on the socket - it should have been bound by
772 * ssh immediately before userauth.
773 */
774 if (buf_equal(sid,
775 e->session_ids[e->nsession_ids - 1].sid) != 0) {
776 error_f("unexpected session ID (%zu listed) on "
777 "signature request for target user %s with "
778 "key %s %s", e->nsession_ids, user,
779 sshkey_type(id->key), fp);
780 goto send;
781 }
782 /*
783 * Ensure that the hostkey embedded in the signature matches
784 * the one most recently bound to the socket. An exception is
785 * made for the initial forwarding hop.
786 */
787 if (e->nsession_ids > 1 && hostkey == NULL) {
788 error_f("refusing use of destination-constrained key: "
789 "no hostkey recorded in signature for forwarded "
790 "connection");
791 goto send;
792 }
793 if (hostkey != NULL && !sshkey_equal(hostkey,
794 e->session_ids[e->nsession_ids - 1].key)) {
795 error_f("refusing use of destination-constrained key: "
796 "mismatch between hostkey in request and most "
797 "recently bound session");
798 goto send;
799 }
800 xasprintf(&sig_dest, "public key authentication request for "
801 "user \"%s\" to listed host", user);
802 }
803 if (id->confirm && confirm_key(id, sig_dest) != 0) {
804 verbose_f("user refused key");
805 goto send;
806 }
807 if (sshkey_is_sk(id->key)) {
808 if (restrict_websafe &&
809 strncmp(id->key->sk_application, "ssh:", 4) != 0 &&
810 !check_websafe_message_contents(key, data)) {
811 /* error already logged */
812 goto send;
813 }
814 if (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) {
815 notifier = notify_start(0,
816 "Confirm user presence for key %s %s%s%s",
817 sshkey_type(id->key), fp,
818 sig_dest == NULL ? "" : "\n",
819 sig_dest == NULL ? "" : sig_dest);
820 }
821 }
822 retry_pin:
823 if ((r = sshkey_sign(id->key, &signature, &slen,
824 sshbuf_ptr(data), sshbuf_len(data), agent_decode_alg(key, flags),
825 id->sk_provider, pin, compat)) != 0) {
826 debug_fr(r, "sshkey_sign");
827 if (pin == NULL && !retried && sshkey_is_sk(id->key) &&
828 r == SSH_ERR_KEY_WRONG_PASSPHRASE) {
829 notify_complete(notifier, NULL);
830 notifier = NULL;
831 /* XXX include sig_dest */
832 xasprintf(&prompt, "Enter PIN%sfor %s key %s: ",
833 (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) ?
834 " and confirm user presence " : " ",
835 sshkey_type(id->key), fp);
836 pin = read_passphrase(prompt, RP_USE_ASKPASS);
837 retried = 1;
838 goto retry_pin;
839 }
840 error_fr(r, "sshkey_sign");
841 goto send;
842 }
843 /* Success */
844 ok = 0;
845 send:
846 debug_f("good signature");
847 notify_complete(notifier, "User presence confirmed");
848
849 if (ok == 0) {
850 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
851 (r = sshbuf_put_string(msg, signature, slen)) != 0)
852 fatal_fr(r, "compose");
853 } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
854 fatal_fr(r, "compose failure");
855
856 if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
857 fatal_fr(r, "enqueue");
858
859 sshbuf_free(sid);
860 sshbuf_free(data);
861 sshbuf_free(msg);
862 sshkey_free(key);
863 sshkey_free(hostkey);
864 free(fp);
865 free(signature);
866 free(sig_dest);
867 free(user);
868 free(prompt);
869 if (pin != NULL)
870 freezero(pin, strlen(pin));
871 }
872
873 /* shared */
874 static void
process_remove_identity(SocketEntry * e)875 process_remove_identity(SocketEntry *e)
876 {
877 int r, success = 0;
878 struct sshkey *key = NULL;
879 Identity *id;
880
881 debug2_f("entering");
882 if ((r = sshkey_froms(e->request, &key)) != 0) {
883 error_fr(r, "parse key");
884 goto done;
885 }
886 if ((id = lookup_identity(key)) == NULL) {
887 debug_f("key not found");
888 goto done;
889 }
890 /* identity not visible, cannot be removed */
891 if (identity_permitted(id, e, NULL, NULL, NULL) != 0)
892 goto done; /* error already logged */
893 /* We have this key, free it. */
894 if (idtab->nentries < 1)
895 fatal_f("internal error: nentries %d", idtab->nentries);
896 TAILQ_REMOVE(&idtab->idlist, id, next);
897 free_identity(id);
898 idtab->nentries--;
899 success = 1;
900 done:
901 sshkey_free(key);
902 send_status(e, success);
903 }
904
905 static void
process_remove_all_identities(SocketEntry * e)906 process_remove_all_identities(SocketEntry *e)
907 {
908 Identity *id;
909
910 debug2_f("entering");
911 /* Loop over all identities and clear the keys. */
912 for (id = TAILQ_FIRST(&idtab->idlist); id;
913 id = TAILQ_FIRST(&idtab->idlist)) {
914 TAILQ_REMOVE(&idtab->idlist, id, next);
915 free_identity(id);
916 }
917
918 /* Mark that there are no identities. */
919 idtab->nentries = 0;
920
921 /* Send success. */
922 send_status(e, 1);
923 }
924
925 /* removes expired keys and returns number of seconds until the next expiry */
926 static time_t
reaper(void)927 reaper(void)
928 {
929 time_t deadline = 0, now = monotime();
930 Identity *id, *nxt;
931
932 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
933 nxt = TAILQ_NEXT(id, next);
934 if (id->death == 0)
935 continue;
936 if (now >= id->death) {
937 debug("expiring key '%s'", id->comment);
938 TAILQ_REMOVE(&idtab->idlist, id, next);
939 free_identity(id);
940 idtab->nentries--;
941 } else
942 deadline = (deadline == 0) ? id->death :
943 MINIMUM(deadline, id->death);
944 }
945 if (deadline == 0 || deadline <= now)
946 return 0;
947 else
948 return (deadline - now);
949 }
950
951 static int
parse_dest_constraint_hop(struct sshbuf * b,struct dest_constraint_hop * dch)952 parse_dest_constraint_hop(struct sshbuf *b, struct dest_constraint_hop *dch)
953 {
954 u_char key_is_ca;
955 size_t elen = 0;
956 int r;
957 struct sshkey *k = NULL;
958 char *fp;
959
960 memset(dch, '\0', sizeof(*dch));
961 if ((r = sshbuf_get_cstring(b, &dch->user, NULL)) != 0 ||
962 (r = sshbuf_get_cstring(b, &dch->hostname, NULL)) != 0 ||
963 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) {
964 error_fr(r, "parse");
965 goto out;
966 }
967 if (elen != 0) {
968 error_f("unsupported extensions (len %zu)", elen);
969 r = SSH_ERR_FEATURE_UNSUPPORTED;
970 goto out;
971 }
972 if (*dch->hostname == '\0') {
973 free(dch->hostname);
974 dch->hostname = NULL;
975 }
976 if (*dch->user == '\0') {
977 free(dch->user);
978 dch->user = NULL;
979 }
980 while (sshbuf_len(b) != 0) {
981 dch->keys = xrecallocarray(dch->keys, dch->nkeys,
982 dch->nkeys + 1, sizeof(*dch->keys));
983 dch->key_is_ca = xrecallocarray(dch->key_is_ca, dch->nkeys,
984 dch->nkeys + 1, sizeof(*dch->key_is_ca));
985 if ((r = sshkey_froms(b, &k)) != 0 ||
986 (r = sshbuf_get_u8(b, &key_is_ca)) != 0)
987 goto out;
988 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT,
989 SSH_FP_DEFAULT)) == NULL)
990 fatal_f("fingerprint failed");
991 debug3_f("%s%s%s: adding %skey %s %s",
992 dch->user == NULL ? "" : dch->user,
993 dch->user == NULL ? "" : "@",
994 dch->hostname, key_is_ca ? "CA " : "", sshkey_type(k), fp);
995 free(fp);
996 dch->keys[dch->nkeys] = k;
997 dch->key_is_ca[dch->nkeys] = key_is_ca != 0;
998 dch->nkeys++;
999 k = NULL; /* transferred */
1000 }
1001 /* success */
1002 r = 0;
1003 out:
1004 sshkey_free(k);
1005 return r;
1006 }
1007
1008 static int
parse_dest_constraint(struct sshbuf * m,struct dest_constraint * dc)1009 parse_dest_constraint(struct sshbuf *m, struct dest_constraint *dc)
1010 {
1011 struct sshbuf *b = NULL, *frombuf = NULL, *tobuf = NULL;
1012 int r;
1013 size_t elen = 0;
1014
1015 debug3_f("entering");
1016
1017 memset(dc, '\0', sizeof(*dc));
1018 if ((r = sshbuf_froms(m, &b)) != 0 ||
1019 (r = sshbuf_froms(b, &frombuf)) != 0 ||
1020 (r = sshbuf_froms(b, &tobuf)) != 0 ||
1021 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) {
1022 error_fr(r, "parse");
1023 goto out;
1024 }
1025 if ((r = parse_dest_constraint_hop(frombuf, &dc->from)) != 0 ||
1026 (r = parse_dest_constraint_hop(tobuf, &dc->to)) != 0)
1027 goto out; /* already logged */
1028 if (elen != 0) {
1029 error_f("unsupported extensions (len %zu)", elen);
1030 r = SSH_ERR_FEATURE_UNSUPPORTED;
1031 goto out;
1032 }
1033 debug2_f("parsed %s (%u keys) > %s%s%s (%u keys)",
1034 dc->from.hostname ? dc->from.hostname : "(ORIGIN)", dc->from.nkeys,
1035 dc->to.user ? dc->to.user : "", dc->to.user ? "@" : "",
1036 dc->to.hostname ? dc->to.hostname : "(ANY)", dc->to.nkeys);
1037 /* check consistency */
1038 if ((dc->from.hostname == NULL) != (dc->from.nkeys == 0) ||
1039 dc->from.user != NULL) {
1040 error_f("inconsistent \"from\" specification");
1041 r = SSH_ERR_INVALID_FORMAT;
1042 goto out;
1043 }
1044 if (dc->to.hostname == NULL || dc->to.nkeys == 0) {
1045 error_f("incomplete \"to\" specification");
1046 r = SSH_ERR_INVALID_FORMAT;
1047 goto out;
1048 }
1049 /* success */
1050 r = 0;
1051 out:
1052 sshbuf_free(b);
1053 sshbuf_free(frombuf);
1054 sshbuf_free(tobuf);
1055 return r;
1056 }
1057
1058 static int
parse_key_constraint_extension(struct sshbuf * m,char ** sk_providerp,struct dest_constraint ** dcsp,size_t * ndcsp)1059 parse_key_constraint_extension(struct sshbuf *m, char **sk_providerp,
1060 struct dest_constraint **dcsp, size_t *ndcsp)
1061 {
1062 char *ext_name = NULL;
1063 int r;
1064 struct sshbuf *b = NULL;
1065
1066 if ((r = sshbuf_get_cstring(m, &ext_name, NULL)) != 0) {
1067 error_fr(r, "parse constraint extension");
1068 goto out;
1069 }
1070 debug_f("constraint ext %s", ext_name);
1071 if (strcmp(ext_name, "sk-provider@openssh.com") == 0) {
1072 if (sk_providerp == NULL) {
1073 error_f("%s not valid here", ext_name);
1074 r = SSH_ERR_INVALID_FORMAT;
1075 goto out;
1076 }
1077 if (*sk_providerp != NULL) {
1078 error_f("%s already set", ext_name);
1079 r = SSH_ERR_INVALID_FORMAT;
1080 goto out;
1081 }
1082 if ((r = sshbuf_get_cstring(m, sk_providerp, NULL)) != 0) {
1083 error_fr(r, "parse %s", ext_name);
1084 goto out;
1085 }
1086 } else if (strcmp(ext_name,
1087 "restrict-destination-v00@openssh.com") == 0) {
1088 if (*dcsp != NULL) {
1089 error_f("%s already set", ext_name);
1090 goto out;
1091 }
1092 if ((r = sshbuf_froms(m, &b)) != 0) {
1093 error_fr(r, "parse %s outer", ext_name);
1094 goto out;
1095 }
1096 while (sshbuf_len(b) != 0) {
1097 if (*ndcsp >= AGENT_MAX_DEST_CONSTRAINTS) {
1098 error_f("too many %s constraints", ext_name);
1099 goto out;
1100 }
1101 *dcsp = xrecallocarray(*dcsp, *ndcsp, *ndcsp + 1,
1102 sizeof(**dcsp));
1103 if ((r = parse_dest_constraint(b,
1104 *dcsp + (*ndcsp)++)) != 0)
1105 goto out; /* error already logged */
1106 }
1107 } else {
1108 error_f("unsupported constraint \"%s\"", ext_name);
1109 r = SSH_ERR_FEATURE_UNSUPPORTED;
1110 goto out;
1111 }
1112 /* success */
1113 r = 0;
1114 out:
1115 free(ext_name);
1116 sshbuf_free(b);
1117 return r;
1118 }
1119
1120 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)1121 parse_key_constraints(struct sshbuf *m, struct sshkey *k, time_t *deathp,
1122 u_int *secondsp, int *confirmp, char **sk_providerp,
1123 struct dest_constraint **dcsp, size_t *ndcsp)
1124 {
1125 u_char ctype;
1126 int r;
1127 u_int seconds, maxsign = 0;
1128
1129 while (sshbuf_len(m)) {
1130 if ((r = sshbuf_get_u8(m, &ctype)) != 0) {
1131 error_fr(r, "parse constraint type");
1132 goto out;
1133 }
1134 switch (ctype) {
1135 case SSH_AGENT_CONSTRAIN_LIFETIME:
1136 if (*deathp != 0) {
1137 error_f("lifetime already set");
1138 r = SSH_ERR_INVALID_FORMAT;
1139 goto out;
1140 }
1141 if ((r = sshbuf_get_u32(m, &seconds)) != 0) {
1142 error_fr(r, "parse lifetime constraint");
1143 goto out;
1144 }
1145 *deathp = monotime() + seconds;
1146 *secondsp = seconds;
1147 break;
1148 case SSH_AGENT_CONSTRAIN_CONFIRM:
1149 if (*confirmp != 0) {
1150 error_f("confirm already set");
1151 r = SSH_ERR_INVALID_FORMAT;
1152 goto out;
1153 }
1154 *confirmp = 1;
1155 break;
1156 case SSH_AGENT_CONSTRAIN_MAXSIGN:
1157 if (k == NULL) {
1158 error_f("maxsign not valid here");
1159 r = SSH_ERR_INVALID_FORMAT;
1160 goto out;
1161 }
1162 if (maxsign != 0) {
1163 error_f("maxsign already set");
1164 r = SSH_ERR_INVALID_FORMAT;
1165 goto out;
1166 }
1167 if ((r = sshbuf_get_u32(m, &maxsign)) != 0) {
1168 error_fr(r, "parse maxsign constraint");
1169 goto out;
1170 }
1171 if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) {
1172 error_fr(r, "enable maxsign");
1173 goto out;
1174 }
1175 break;
1176 case SSH_AGENT_CONSTRAIN_EXTENSION:
1177 if ((r = parse_key_constraint_extension(m,
1178 sk_providerp, dcsp, ndcsp)) != 0)
1179 goto out; /* error already logged */
1180 break;
1181 default:
1182 error_f("Unknown constraint %d", ctype);
1183 r = SSH_ERR_FEATURE_UNSUPPORTED;
1184 goto out;
1185 }
1186 }
1187 /* success */
1188 r = 0;
1189 out:
1190 return r;
1191 }
1192
1193 static void
process_add_identity(SocketEntry * e)1194 process_add_identity(SocketEntry *e)
1195 {
1196 Identity *id;
1197 int success = 0, confirm = 0;
1198 char *fp, *comment = NULL, *sk_provider = NULL;
1199 char canonical_provider[PATH_MAX];
1200 time_t death = 0;
1201 u_int seconds = 0;
1202 struct dest_constraint *dest_constraints = NULL;
1203 size_t ndest_constraints = 0;
1204 struct sshkey *k = NULL;
1205 int r = SSH_ERR_INTERNAL_ERROR;
1206
1207 debug2_f("entering");
1208 if ((r = sshkey_private_deserialize(e->request, &k)) != 0 ||
1209 k == NULL ||
1210 (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) {
1211 error_fr(r, "parse");
1212 goto out;
1213 }
1214 if (parse_key_constraints(e->request, k, &death, &seconds, &confirm,
1215 &sk_provider, &dest_constraints, &ndest_constraints) != 0) {
1216 error_f("failed to parse constraints");
1217 sshbuf_reset(e->request);
1218 goto out;
1219 }
1220
1221 if (sk_provider != NULL) {
1222 if (!sshkey_is_sk(k)) {
1223 error("Cannot add provider: %s is not an "
1224 "authenticator-hosted key", sshkey_type(k));
1225 goto out;
1226 }
1227 if (strcasecmp(sk_provider, "internal") == 0) {
1228 debug_f("internal provider");
1229 } else {
1230 if (e->nsession_ids != 0 && !remote_add_provider) {
1231 verbose("failed add of SK provider \"%.100s\": "
1232 "remote addition of providers is disabled",
1233 sk_provider);
1234 goto out;
1235 }
1236 if (realpath(sk_provider, canonical_provider) == NULL) {
1237 verbose("failed provider \"%.100s\": "
1238 "realpath: %s", sk_provider,
1239 strerror(errno));
1240 goto out;
1241 }
1242 free(sk_provider);
1243 sk_provider = xstrdup(canonical_provider);
1244 if (match_pattern_list(sk_provider,
1245 allowed_providers, 0) != 1) {
1246 error("Refusing add key: "
1247 "provider %s not allowed", sk_provider);
1248 goto out;
1249 }
1250 }
1251 }
1252 if ((r = sshkey_shield_private(k)) != 0) {
1253 error_fr(r, "shield private");
1254 goto out;
1255 }
1256 if (lifetime && !death)
1257 death = monotime() + lifetime;
1258 if ((id = lookup_identity(k)) == NULL) {
1259 id = xcalloc(1, sizeof(Identity));
1260 TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
1261 /* Increment the number of identities. */
1262 idtab->nentries++;
1263 } else {
1264 /* identity not visible, do not update */
1265 if (identity_permitted(id, e, NULL, NULL, NULL) != 0)
1266 goto out; /* error already logged */
1267 /* key state might have been updated */
1268 sshkey_free(id->key);
1269 free(id->comment);
1270 free(id->sk_provider);
1271 free_dest_constraints(id->dest_constraints,
1272 id->ndest_constraints);
1273 }
1274 /* success */
1275 id->key = k;
1276 id->comment = comment;
1277 id->death = death;
1278 id->confirm = confirm;
1279 id->sk_provider = sk_provider;
1280 id->dest_constraints = dest_constraints;
1281 id->ndest_constraints = ndest_constraints;
1282
1283 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT,
1284 SSH_FP_DEFAULT)) == NULL)
1285 fatal_f("sshkey_fingerprint failed");
1286 debug_f("add %s %s \"%.100s\" (life: %u) (confirm: %u) "
1287 "(provider: %s) (destination constraints: %zu)",
1288 sshkey_ssh_name(k), fp, comment, seconds, confirm,
1289 sk_provider == NULL ? "none" : sk_provider, ndest_constraints);
1290 free(fp);
1291 /* transferred */
1292 k = NULL;
1293 comment = NULL;
1294 sk_provider = NULL;
1295 dest_constraints = NULL;
1296 ndest_constraints = 0;
1297 success = 1;
1298 out:
1299 free(sk_provider);
1300 free(comment);
1301 sshkey_free(k);
1302 free_dest_constraints(dest_constraints, ndest_constraints);
1303 send_status(e, success);
1304 }
1305
1306 /* XXX todo: encrypt sensitive data with passphrase */
1307 static void
process_lock_agent(SocketEntry * e,int lock)1308 process_lock_agent(SocketEntry *e, int lock)
1309 {
1310 int r, success = 0, delay;
1311 char *passwd;
1312 u_char passwdhash[LOCK_SIZE];
1313 static u_int fail_count = 0;
1314 size_t pwlen;
1315
1316 debug2_f("entering");
1317 /*
1318 * This is deliberately fatal: the user has requested that we lock,
1319 * but we can't parse their request properly. The only safe thing to
1320 * do is abort.
1321 */
1322 if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0)
1323 fatal_fr(r, "parse");
1324 if (pwlen == 0) {
1325 debug("empty password not supported");
1326 } else if (locked && !lock) {
1327 if (bcrypt_pbkdf(passwd, pwlen, (uint8_t *)lock_salt, sizeof(lock_salt),
1328 (uint8_t *)passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0)
1329 fatal("bcrypt_pbkdf");
1330 if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) {
1331 debug("agent unlocked");
1332 locked = 0;
1333 fail_count = 0;
1334 explicit_bzero(lock_pwhash, sizeof(lock_pwhash));
1335 success = 1;
1336 } else {
1337 /* delay in 0.1s increments up to 10s */
1338 if (fail_count < 100)
1339 fail_count++;
1340 delay = 100000 * fail_count;
1341 debug("unlock failed, delaying %0.1lf seconds",
1342 (double)delay/1000000);
1343 usleep(delay);
1344 }
1345 explicit_bzero(passwdhash, sizeof(passwdhash));
1346 } else if (!locked && lock) {
1347 debug("agent locked");
1348 locked = 1;
1349 arc4random_buf(lock_salt, sizeof(lock_salt));
1350 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
1351 lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0)
1352 fatal("bcrypt_pbkdf");
1353 success = 1;
1354 }
1355 freezero(passwd, pwlen);
1356 send_status(e, success);
1357 }
1358
1359 static void
no_identities(SocketEntry * e)1360 no_identities(SocketEntry *e)
1361 {
1362 struct sshbuf *msg;
1363 int r;
1364
1365 if ((msg = sshbuf_new()) == NULL)
1366 fatal_f("sshbuf_new failed");
1367 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
1368 (r = sshbuf_put_u32(msg, 0)) != 0 ||
1369 (r = sshbuf_put_stringb(e->output, msg)) != 0)
1370 fatal_fr(r, "compose");
1371 sshbuf_free(msg);
1372 }
1373
1374 #ifdef ENABLE_PKCS11
1375 static void
process_add_smartcard_key(SocketEntry * e)1376 process_add_smartcard_key(SocketEntry *e)
1377 {
1378 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
1379 char **comments = NULL;
1380 int r, i, count = 0, success = 0, confirm = 0;
1381 u_int seconds = 0;
1382 time_t death = 0;
1383 struct sshkey **keys = NULL, *k;
1384 Identity *id;
1385 struct dest_constraint *dest_constraints = NULL;
1386 size_t ndest_constraints = 0;
1387
1388 debug2_f("entering");
1389 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
1390 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
1391 error_fr(r, "parse");
1392 goto send;
1393 }
1394 if (parse_key_constraints(e->request, NULL, &death, &seconds, &confirm,
1395 NULL, &dest_constraints, &ndest_constraints) != 0) {
1396 error_f("failed to parse constraints");
1397 goto send;
1398 }
1399 if (e->nsession_ids != 0 && !remote_add_provider) {
1400 verbose("failed PKCS#11 add of \"%.100s\": remote addition of "
1401 "providers is disabled", provider);
1402 goto send;
1403 }
1404 if (realpath(provider, canonical_provider) == NULL) {
1405 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
1406 provider, strerror(errno));
1407 goto send;
1408 }
1409 if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) {
1410 verbose("refusing PKCS#11 add of \"%.100s\": "
1411 "provider not allowed", canonical_provider);
1412 goto send;
1413 }
1414 debug_f("add %.100s", canonical_provider);
1415 if (lifetime && !death)
1416 death = monotime() + lifetime;
1417
1418 count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments);
1419 for (i = 0; i < count; i++) {
1420 k = keys[i];
1421 if (lookup_identity(k) == NULL) {
1422 id = xcalloc(1, sizeof(Identity));
1423 id->key = k;
1424 keys[i] = NULL; /* transferred */
1425 id->provider = xstrdup(canonical_provider);
1426 if (*comments[i] != '\0') {
1427 id->comment = comments[i];
1428 comments[i] = NULL; /* transferred */
1429 } else {
1430 id->comment = xstrdup(canonical_provider);
1431 }
1432 id->death = death;
1433 id->confirm = confirm;
1434 id->dest_constraints = dest_constraints;
1435 id->ndest_constraints = ndest_constraints;
1436 dest_constraints = NULL; /* transferred */
1437 ndest_constraints = 0;
1438 TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
1439 idtab->nentries++;
1440 success = 1;
1441 }
1442 /* XXX update constraints for existing keys */
1443 sshkey_free(keys[i]);
1444 free(comments[i]);
1445 }
1446 send:
1447 free(pin);
1448 free(provider);
1449 free(keys);
1450 free(comments);
1451 free_dest_constraints(dest_constraints, ndest_constraints);
1452 send_status(e, success);
1453 }
1454
1455 static void
process_remove_smartcard_key(SocketEntry * e)1456 process_remove_smartcard_key(SocketEntry *e)
1457 {
1458 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
1459 int r, success = 0;
1460 Identity *id, *nxt;
1461
1462 debug2_f("entering");
1463 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
1464 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
1465 error_fr(r, "parse");
1466 goto send;
1467 }
1468 free(pin);
1469
1470 if (realpath(provider, canonical_provider) == NULL) {
1471 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
1472 provider, strerror(errno));
1473 goto send;
1474 }
1475
1476 debug_f("remove %.100s", canonical_provider);
1477 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
1478 nxt = TAILQ_NEXT(id, next);
1479 /* Skip file--based keys */
1480 if (id->provider == NULL)
1481 continue;
1482 if (!strcmp(canonical_provider, id->provider)) {
1483 TAILQ_REMOVE(&idtab->idlist, id, next);
1484 free_identity(id);
1485 idtab->nentries--;
1486 }
1487 }
1488 if (pkcs11_del_provider(canonical_provider) == 0)
1489 success = 1;
1490 else
1491 error_f("pkcs11_del_provider failed");
1492 send:
1493 free(provider);
1494 send_status(e, success);
1495 }
1496 #endif /* ENABLE_PKCS11 */
1497
1498 static int
process_ext_session_bind(SocketEntry * e)1499 process_ext_session_bind(SocketEntry *e)
1500 {
1501 int r, sid_match, key_match;
1502 struct sshkey *key = NULL;
1503 struct sshbuf *sid = NULL, *sig = NULL;
1504 char *fp = NULL;
1505 size_t i;
1506 u_char fwd = 0;
1507
1508 debug2_f("entering");
1509 if ((r = sshkey_froms(e->request, &key)) != 0 ||
1510 (r = sshbuf_froms(e->request, &sid)) != 0 ||
1511 (r = sshbuf_froms(e->request, &sig)) != 0 ||
1512 (r = sshbuf_get_u8(e->request, &fwd)) != 0) {
1513 error_fr(r, "parse");
1514 goto out;
1515 }
1516 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
1517 SSH_FP_DEFAULT)) == NULL)
1518 fatal_f("fingerprint failed");
1519 /* check signature with hostkey on session ID */
1520 if ((r = sshkey_verify(key, sshbuf_ptr(sig), sshbuf_len(sig),
1521 sshbuf_ptr(sid), sshbuf_len(sid), NULL, 0, NULL)) != 0) {
1522 error_fr(r, "sshkey_verify for %s %s", sshkey_type(key), fp);
1523 goto out;
1524 }
1525 /* check whether sid/key already recorded */
1526 for (i = 0; i < e->nsession_ids; i++) {
1527 if (!e->session_ids[i].forwarded) {
1528 error_f("attempt to bind session ID to socket "
1529 "previously bound for authentication attempt");
1530 r = -1;
1531 goto out;
1532 }
1533 sid_match = buf_equal(sid, e->session_ids[i].sid) == 0;
1534 key_match = sshkey_equal(key, e->session_ids[i].key);
1535 if (sid_match && key_match) {
1536 debug_f("session ID already recorded for %s %s",
1537 sshkey_type(key), fp);
1538 r = 0;
1539 goto out;
1540 } else if (sid_match) {
1541 error_f("session ID recorded against different key "
1542 "for %s %s", sshkey_type(key), fp);
1543 r = -1;
1544 goto out;
1545 }
1546 /*
1547 * new sid with previously-seen key can happen, e.g. multiple
1548 * connections to the same host.
1549 */
1550 }
1551 /* record new key/sid */
1552 if (e->nsession_ids >= AGENT_MAX_SESSION_IDS) {
1553 error_f("too many session IDs recorded");
1554 goto out;
1555 }
1556 e->session_ids = xrecallocarray(e->session_ids, e->nsession_ids,
1557 e->nsession_ids + 1, sizeof(*e->session_ids));
1558 i = e->nsession_ids++;
1559 debug_f("recorded %s %s (slot %zu of %d)", sshkey_type(key), fp, i,
1560 AGENT_MAX_SESSION_IDS);
1561 e->session_ids[i].key = key;
1562 e->session_ids[i].forwarded = fwd != 0;
1563 key = NULL; /* transferred */
1564 /* can't transfer sid; it's refcounted and scoped to request's life */
1565 if ((e->session_ids[i].sid = sshbuf_new()) == NULL)
1566 fatal_f("sshbuf_new");
1567 if ((r = sshbuf_putb(e->session_ids[i].sid, sid)) != 0)
1568 fatal_fr(r, "sshbuf_putb session ID");
1569 /* success */
1570 r = 0;
1571 out:
1572 free(fp);
1573 sshkey_free(key);
1574 sshbuf_free(sid);
1575 sshbuf_free(sig);
1576 return r == 0 ? 1 : 0;
1577 }
1578
1579 static void
process_extension(SocketEntry * e)1580 process_extension(SocketEntry *e)
1581 {
1582 int r, success = 0;
1583 char *name;
1584
1585 debug2_f("entering");
1586 if ((r = sshbuf_get_cstring(e->request, &name, NULL)) != 0) {
1587 error_fr(r, "parse");
1588 goto send;
1589 }
1590 if (strcmp(name, "session-bind@openssh.com") == 0)
1591 success = process_ext_session_bind(e);
1592 else
1593 debug_f("unsupported extension \"%s\"", name);
1594 free(name);
1595 send:
1596 send_status(e, success);
1597 }
1598 /*
1599 * dispatch incoming message.
1600 * returns 1 on success, 0 for incomplete messages or -1 on error.
1601 */
1602 static int
process_message(u_int socknum)1603 process_message(u_int socknum)
1604 {
1605 u_int msg_len;
1606 u_char type;
1607 const u_char *cp;
1608 int r;
1609 SocketEntry *e;
1610
1611 if (socknum >= sockets_alloc)
1612 fatal_f("sock %u >= allocated %u", socknum, sockets_alloc);
1613 e = &sockets[socknum];
1614
1615 if (sshbuf_len(e->input) < 5)
1616 return 0; /* Incomplete message header. */
1617 cp = sshbuf_ptr(e->input);
1618 msg_len = PEEK_U32(cp);
1619 if (msg_len > AGENT_MAX_LEN) {
1620 debug_f("socket %u (fd=%d) message too long %u > %u",
1621 socknum, e->fd, msg_len, AGENT_MAX_LEN);
1622 return -1;
1623 }
1624 if (sshbuf_len(e->input) < msg_len + 4)
1625 return 0; /* Incomplete message body. */
1626
1627 /* move the current input to e->request */
1628 sshbuf_reset(e->request);
1629 if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 ||
1630 (r = sshbuf_get_u8(e->request, &type)) != 0) {
1631 if (r == SSH_ERR_MESSAGE_INCOMPLETE ||
1632 r == SSH_ERR_STRING_TOO_LARGE) {
1633 error_fr(r, "parse");
1634 return -1;
1635 }
1636 fatal_fr(r, "parse");
1637 }
1638
1639 debug_f("socket %u (fd=%d) type %d", socknum, e->fd, type);
1640
1641 /* check whether agent is locked */
1642 if (locked && type != SSH_AGENTC_UNLOCK) {
1643 sshbuf_reset(e->request);
1644 switch (type) {
1645 case SSH2_AGENTC_REQUEST_IDENTITIES:
1646 /* send empty lists */
1647 no_identities(e);
1648 break;
1649 default:
1650 /* send a fail message for all other request types */
1651 send_status(e, 0);
1652 }
1653 return 1;
1654 }
1655
1656 switch (type) {
1657 case SSH_AGENTC_LOCK:
1658 case SSH_AGENTC_UNLOCK:
1659 process_lock_agent(e, type == SSH_AGENTC_LOCK);
1660 break;
1661 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
1662 process_remove_all_identities(e); /* safe for !WITH_SSH1 */
1663 break;
1664 /* ssh2 */
1665 case SSH2_AGENTC_SIGN_REQUEST:
1666 process_sign_request2(e);
1667 break;
1668 case SSH2_AGENTC_REQUEST_IDENTITIES:
1669 process_request_identities(e);
1670 break;
1671 case SSH2_AGENTC_ADD_IDENTITY:
1672 case SSH2_AGENTC_ADD_ID_CONSTRAINED:
1673 process_add_identity(e);
1674 break;
1675 case SSH2_AGENTC_REMOVE_IDENTITY:
1676 process_remove_identity(e);
1677 break;
1678 case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
1679 process_remove_all_identities(e);
1680 break;
1681 #ifdef ENABLE_PKCS11
1682 case SSH_AGENTC_ADD_SMARTCARD_KEY:
1683 case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
1684 process_add_smartcard_key(e);
1685 break;
1686 case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
1687 process_remove_smartcard_key(e);
1688 break;
1689 #endif /* ENABLE_PKCS11 */
1690 case SSH_AGENTC_EXTENSION:
1691 process_extension(e);
1692 break;
1693 default:
1694 /* Unknown message. Respond with failure. */
1695 error("Unknown message %d", type);
1696 sshbuf_reset(e->request);
1697 send_status(e, 0);
1698 break;
1699 }
1700 return 1;
1701 }
1702
1703 static void
new_socket(sock_type type,int fd)1704 new_socket(sock_type type, int fd)
1705 {
1706 u_int i, old_alloc, new_alloc;
1707
1708 debug_f("type = %s", type == AUTH_CONNECTION ? "CONNECTION" :
1709 (type == AUTH_SOCKET ? "SOCKET" : "UNKNOWN"));
1710 set_nonblock(fd);
1711
1712 if (fd > max_fd)
1713 max_fd = fd;
1714
1715 for (i = 0; i < sockets_alloc; i++)
1716 if (sockets[i].type == AUTH_UNUSED) {
1717 sockets[i].fd = fd;
1718 if ((sockets[i].input = sshbuf_new()) == NULL ||
1719 (sockets[i].output = sshbuf_new()) == NULL ||
1720 (sockets[i].request = sshbuf_new()) == NULL)
1721 fatal_f("sshbuf_new failed");
1722 sockets[i].type = type;
1723 return;
1724 }
1725 old_alloc = sockets_alloc;
1726 new_alloc = sockets_alloc + 10;
1727 sockets = xrecallocarray(sockets, old_alloc, new_alloc,
1728 sizeof(sockets[0]));
1729 for (i = old_alloc; i < new_alloc; i++)
1730 sockets[i].type = AUTH_UNUSED;
1731 sockets_alloc = new_alloc;
1732 sockets[old_alloc].fd = fd;
1733 if ((sockets[old_alloc].input = sshbuf_new()) == NULL ||
1734 (sockets[old_alloc].output = sshbuf_new()) == NULL ||
1735 (sockets[old_alloc].request = sshbuf_new()) == NULL)
1736 fatal_f("sshbuf_new failed");
1737 sockets[old_alloc].type = type;
1738 }
1739
1740 static int
handle_socket_read(u_int socknum)1741 handle_socket_read(u_int socknum)
1742 {
1743 struct sockaddr_un sunaddr;
1744 socklen_t slen;
1745 uid_t euid;
1746 gid_t egid;
1747 int fd;
1748
1749 slen = sizeof(sunaddr);
1750 fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen);
1751 if (fd == -1) {
1752 error("accept from AUTH_SOCKET: %s", strerror(errno));
1753 return -1;
1754 }
1755 if (getpeereid(fd, &euid, &egid) == -1) {
1756 error("getpeereid %d failed: %s", fd, strerror(errno));
1757 close(fd);
1758 return -1;
1759 }
1760 if ((euid != 0) && (getuid() != euid)) {
1761 error("uid mismatch: peer euid %u != uid %u",
1762 (u_int) euid, (u_int) getuid());
1763 close(fd);
1764 return -1;
1765 }
1766 new_socket(AUTH_CONNECTION, fd);
1767 return 0;
1768 }
1769
1770 static int
handle_conn_read(u_int socknum)1771 handle_conn_read(u_int socknum)
1772 {
1773 char buf[AGENT_RBUF_LEN];
1774 ssize_t len;
1775 int r;
1776
1777 if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) {
1778 if (len == -1) {
1779 if (errno == EAGAIN || errno == EINTR)
1780 return 0;
1781 error_f("read error on socket %u (fd %d): %s",
1782 socknum, sockets[socknum].fd, strerror(errno));
1783 }
1784 return -1;
1785 }
1786 if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0)
1787 fatal_fr(r, "compose");
1788 explicit_bzero(buf, sizeof(buf));
1789 for (;;) {
1790 if ((r = process_message(socknum)) == -1)
1791 return -1;
1792 else if (r == 0)
1793 break;
1794 }
1795 return 0;
1796 }
1797
1798 static int
handle_conn_write(u_int socknum)1799 handle_conn_write(u_int socknum)
1800 {
1801 ssize_t len;
1802 int r;
1803
1804 if (sshbuf_len(sockets[socknum].output) == 0)
1805 return 0; /* shouldn't happen */
1806 if ((len = write(sockets[socknum].fd,
1807 sshbuf_ptr(sockets[socknum].output),
1808 sshbuf_len(sockets[socknum].output))) <= 0) {
1809 if (len == -1) {
1810 if (errno == EAGAIN || errno == EINTR)
1811 return 0;
1812 error_f("read error on socket %u (fd %d): %s",
1813 socknum, sockets[socknum].fd, strerror(errno));
1814 }
1815 return -1;
1816 }
1817 if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0)
1818 fatal_fr(r, "consume");
1819 return 0;
1820 }
1821
1822 static void
after_poll(struct pollfd * pfd,size_t npfd,u_int maxfds)1823 after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds)
1824 {
1825 size_t i;
1826 u_int socknum, activefds = npfd;
1827
1828 for (i = 0; i < npfd; i++) {
1829 if (pfd[i].revents == 0)
1830 continue;
1831 /* Find sockets entry */
1832 for (socknum = 0; socknum < sockets_alloc; socknum++) {
1833 if (sockets[socknum].type != AUTH_SOCKET &&
1834 sockets[socknum].type != AUTH_CONNECTION)
1835 continue;
1836 if (pfd[i].fd == sockets[socknum].fd)
1837 break;
1838 }
1839 if (socknum >= sockets_alloc) {
1840 error_f("no socket for fd %d", pfd[i].fd);
1841 continue;
1842 }
1843 /* Process events */
1844 switch (sockets[socknum].type) {
1845 case AUTH_SOCKET:
1846 if ((pfd[i].revents & (POLLIN|POLLERR)) == 0)
1847 break;
1848 if (npfd > maxfds) {
1849 debug3("out of fds (active %u >= limit %u); "
1850 "skipping accept", activefds, maxfds);
1851 break;
1852 }
1853 if (handle_socket_read(socknum) == 0)
1854 activefds++;
1855 break;
1856 case AUTH_CONNECTION:
1857 if ((pfd[i].revents & (POLLIN|POLLHUP|POLLERR)) != 0 &&
1858 handle_conn_read(socknum) != 0)
1859 goto close_sock;
1860 if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 &&
1861 handle_conn_write(socknum) != 0) {
1862 close_sock:
1863 if (activefds == 0)
1864 fatal("activefds == 0 at close_sock");
1865 close_socket(&sockets[socknum]);
1866 activefds--;
1867 break;
1868 }
1869 break;
1870 default:
1871 break;
1872 }
1873 }
1874 }
1875
1876 static int
prepare_poll(struct pollfd ** pfdp,size_t * npfdp,int * timeoutp,u_int maxfds)1877 prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp, u_int maxfds)
1878 {
1879 struct pollfd *pfd = *pfdp;
1880 size_t i, j, npfd = 0;
1881 time_t deadline;
1882 int r;
1883
1884 /* Count active sockets */
1885 for (i = 0; i < sockets_alloc; i++) {
1886 switch (sockets[i].type) {
1887 case AUTH_SOCKET:
1888 case AUTH_CONNECTION:
1889 npfd++;
1890 break;
1891 case AUTH_UNUSED:
1892 break;
1893 default:
1894 fatal("Unknown socket type %d", sockets[i].type);
1895 break;
1896 }
1897 }
1898 if (npfd != *npfdp &&
1899 (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL)
1900 fatal_f("recallocarray failed");
1901 *pfdp = pfd;
1902 *npfdp = npfd;
1903
1904 for (i = j = 0; i < sockets_alloc; i++) {
1905 switch (sockets[i].type) {
1906 case AUTH_SOCKET:
1907 if (npfd > maxfds) {
1908 debug3("out of fds (active %zu >= limit %u); "
1909 "skipping arming listener", npfd, maxfds);
1910 break;
1911 }
1912 pfd[j].fd = sockets[i].fd;
1913 pfd[j].revents = 0;
1914 pfd[j].events = POLLIN;
1915 j++;
1916 break;
1917 case AUTH_CONNECTION:
1918 pfd[j].fd = sockets[i].fd;
1919 pfd[j].revents = 0;
1920 /*
1921 * Only prepare to read if we can handle a full-size
1922 * input read buffer and enqueue a max size reply..
1923 */
1924 if ((r = sshbuf_check_reserve(sockets[i].input,
1925 AGENT_RBUF_LEN)) == 0 &&
1926 (r = sshbuf_check_reserve(sockets[i].output,
1927 AGENT_MAX_LEN)) == 0)
1928 pfd[j].events = POLLIN;
1929 else if (r != SSH_ERR_NO_BUFFER_SPACE)
1930 fatal_fr(r, "reserve");
1931 if (sshbuf_len(sockets[i].output) > 0)
1932 pfd[j].events |= POLLOUT;
1933 j++;
1934 break;
1935 default:
1936 break;
1937 }
1938 }
1939 deadline = reaper();
1940 if (parent_alive_interval != 0)
1941 deadline = (deadline == 0) ? parent_alive_interval :
1942 MINIMUM(deadline, parent_alive_interval);
1943 if (deadline == 0) {
1944 *timeoutp = -1; /* INFTIM */
1945 } else {
1946 if (deadline > INT_MAX / 1000)
1947 *timeoutp = INT_MAX / 1000;
1948 else
1949 *timeoutp = deadline * 1000;
1950 }
1951 return (1);
1952 }
1953
1954 static void
cleanup_socket(void)1955 cleanup_socket(void)
1956 {
1957 if (cleanup_pid != 0 && getpid() != cleanup_pid)
1958 return;
1959 debug_f("cleanup");
1960 if (socket_name[0])
1961 unlink(socket_name);
1962 if (socket_dir[0])
1963 rmdir(socket_dir);
1964 }
1965
1966 void
cleanup_exit(int i)1967 cleanup_exit(int i)
1968 {
1969 cleanup_socket();
1970 _exit(i);
1971 }
1972
1973 /*ARGSUSED*/
1974 __dead static void
cleanup_handler(int sig)1975 cleanup_handler(int sig)
1976 {
1977 cleanup_socket();
1978 #ifdef ENABLE_PKCS11
1979 pkcs11_terminate();
1980 #endif
1981 _exit(2);
1982 }
1983
1984 static void
check_parent_exists(void)1985 check_parent_exists(void)
1986 {
1987 /*
1988 * If our parent has exited then getppid() will return (pid_t)1,
1989 * so testing for that should be safe.
1990 */
1991 if (parent_pid != -1 && getppid() != parent_pid) {
1992 /* printf("Parent has died - Authentication agent exiting.\n"); */
1993 cleanup_socket();
1994 _exit(2);
1995 }
1996 }
1997
1998 __dead static void
usage(void)1999 usage(void)
2000 {
2001 fprintf(stderr,
2002 "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n"
2003 " [-O option] [-P allowed_providers] [-t life]\n"
2004 " ssh-agent [-a bind_address] [-E fingerprint_hash] [-O option]\n"
2005 " [-P allowed_providers] [-t life] command [arg ...]\n"
2006 " ssh-agent [-c | -s] -k\n");
2007 exit(1);
2008 }
2009
2010 static void
csh_setenv(const char * name,const char * value)2011 csh_setenv(const char *name, const char *value)
2012 {
2013 printf("setenv %s %s;\n", name, value);
2014 }
2015
2016 static void
csh_unsetenv(const char * name)2017 csh_unsetenv(const char *name)
2018 {
2019 printf("unsetenv %s;\n", name);
2020 }
2021
2022 static void
sh_setenv(const char * name,const char * value)2023 sh_setenv(const char *name, const char *value)
2024 {
2025 printf("%s=%s; export %s;\n", name, value, name);
2026 }
2027
2028 static void
sh_unsetenv(const char * name)2029 sh_unsetenv(const char *name)
2030 {
2031 printf("unset %s;\n", name);
2032 }
2033 int
main(int ac,char ** av)2034 main(int ac, char **av)
2035 {
2036 int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0;
2037 int sock, ch, result, saved_errno;
2038 char *shell, *pidstr, *agentsocket = NULL;
2039 struct rlimit rlim;
2040 void (*f_setenv)(const char *, const char *);
2041 void (*f_unsetenv)(const char *);
2042 extern int optind;
2043 extern char *optarg;
2044 pid_t pid;
2045 char pidstrbuf[1 + 3 * sizeof pid];
2046 size_t len;
2047 mode_t prev_mask;
2048 int timeout = -1; /* INFTIM */
2049 struct pollfd *pfd = NULL;
2050 size_t npfd = 0;
2051 u_int maxfds;
2052
2053 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
2054 sanitise_stdfd();
2055
2056 /* drop */
2057 setegid(getgid());
2058 setgid(getgid());
2059
2060 if (getrlimit(RLIMIT_NOFILE, &rlim) == -1)
2061 fatal("%s: getrlimit: %s", __progname, strerror(errno));
2062
2063 #ifdef WITH_OPENSSL
2064 OpenSSL_add_all_algorithms();
2065 #endif
2066
2067 while ((ch = getopt(ac, av, "cDdksE:a:O:P:t:")) != -1) {
2068 switch (ch) {
2069 case 'E':
2070 fingerprint_hash = ssh_digest_alg_by_name(optarg);
2071 if (fingerprint_hash == -1)
2072 fatal("Invalid hash algorithm \"%s\"", optarg);
2073 break;
2074 case 'c':
2075 if (s_flag)
2076 usage();
2077 c_flag++;
2078 break;
2079 case 'k':
2080 k_flag++;
2081 break;
2082 case 'O':
2083 if (strcmp(optarg, "no-restrict-websafe") == 0)
2084 restrict_websafe = 0;
2085 else if (strcmp(optarg, "allow-remote-pkcs11") == 0)
2086 remote_add_provider = 1;
2087 else
2088 fatal("Unknown -O option");
2089 break;
2090 case 'P':
2091 if (allowed_providers != NULL)
2092 fatal("-P option already specified");
2093 allowed_providers = xstrdup(optarg);
2094 break;
2095 case 's':
2096 if (c_flag)
2097 usage();
2098 s_flag++;
2099 break;
2100 case 'd':
2101 if (d_flag || D_flag)
2102 usage();
2103 d_flag++;
2104 break;
2105 case 'D':
2106 if (d_flag || D_flag)
2107 usage();
2108 D_flag++;
2109 break;
2110 case 'a':
2111 agentsocket = optarg;
2112 break;
2113 case 't':
2114 if ((lifetime = convtime(optarg)) == -1) {
2115 fprintf(stderr, "Invalid lifetime\n");
2116 usage();
2117 }
2118 break;
2119 default:
2120 usage();
2121 }
2122 }
2123 ac -= optind;
2124 av += optind;
2125
2126 if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag))
2127 usage();
2128
2129 if (allowed_providers == NULL)
2130 allowed_providers = xstrdup(DEFAULT_ALLOWED_PROVIDERS);
2131
2132 if (ac == 0 && !c_flag && !s_flag) {
2133 shell = getenv("SHELL");
2134 if (shell != NULL && (len = strlen(shell)) > 2 &&
2135 strncmp(shell + len - 3, "csh", 3) == 0)
2136 c_flag = 1;
2137 }
2138 if (c_flag) {
2139 f_setenv = csh_setenv;
2140 f_unsetenv = csh_unsetenv;
2141 } else {
2142 f_setenv = sh_setenv;
2143 f_unsetenv = sh_unsetenv;
2144 }
2145 if (k_flag) {
2146 const char *errstr = NULL;
2147
2148 pidstr = getenv(SSH_AGENTPID_ENV_NAME);
2149 if (pidstr == NULL) {
2150 fprintf(stderr, "%s not set, cannot kill agent\n",
2151 SSH_AGENTPID_ENV_NAME);
2152 exit(1);
2153 }
2154 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr);
2155 if (errstr) {
2156 fprintf(stderr,
2157 "%s=\"%s\", which is not a good PID: %s\n",
2158 SSH_AGENTPID_ENV_NAME, pidstr, errstr);
2159 exit(1);
2160 }
2161 if (kill(pid, SIGTERM) == -1) {
2162 perror("kill");
2163 exit(1);
2164 }
2165 (*f_unsetenv)(SSH_AUTHSOCKET_ENV_NAME);
2166 (*f_unsetenv)(SSH_AGENTPID_ENV_NAME);
2167 printf("echo Agent pid %ld killed;\n", (long)pid);
2168 exit(0);
2169 }
2170
2171 /*
2172 * Minimum file descriptors:
2173 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) +
2174 * a few spare for libc / stack protectors / sanitisers, etc.
2175 */
2176 #define SSH_AGENT_MIN_FDS (3+1+1+1+4)
2177 if (rlim.rlim_cur < SSH_AGENT_MIN_FDS)
2178 fatal("%s: file descriptor rlimit %lld too low (minimum %u)",
2179 __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS);
2180 maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS;
2181
2182 parent_pid = getpid();
2183
2184 if (agentsocket == NULL) {
2185 /* Create private directory for agent socket */
2186 mktemp_proto(socket_dir, sizeof(socket_dir));
2187 if (mkdtemp(socket_dir) == NULL) {
2188 perror("mkdtemp: private socket dir");
2189 exit(1);
2190 }
2191 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
2192 (long)parent_pid);
2193 } else {
2194 /* Try to use specified agent socket */
2195 socket_dir[0] = '\0';
2196 strlcpy(socket_name, agentsocket, sizeof socket_name);
2197 }
2198
2199 /*
2200 * Create socket early so it will exist before command gets run from
2201 * the parent.
2202 */
2203 prev_mask = umask(0177);
2204 sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
2205 if (sock < 0) {
2206 /* XXX - unix_listener() calls error() not perror() */
2207 *socket_name = '\0'; /* Don't unlink any existing file */
2208 cleanup_exit(1);
2209 }
2210 umask(prev_mask);
2211
2212 /*
2213 * Fork, and have the parent execute the command, if any, or present
2214 * the socket data. The child continues as the authentication agent.
2215 */
2216 if (D_flag || d_flag) {
2217 log_init(__progname,
2218 d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO,
2219 SYSLOG_FACILITY_AUTH, 1);
2220 if (c_flag)
2221 printf("setenv %s %s;\n",
2222 SSH_AUTHSOCKET_ENV_NAME, socket_name);
2223 else
2224 printf("%s=%s; export %s;\n",
2225 SSH_AUTHSOCKET_ENV_NAME, socket_name,
2226 SSH_AUTHSOCKET_ENV_NAME);
2227 printf("echo Agent pid %ld;\n", (long)parent_pid);
2228 fflush(stdout);
2229 goto skip;
2230 }
2231 pid = fork();
2232 if (pid == -1) {
2233 perror("fork");
2234 cleanup_exit(1);
2235 }
2236 if (pid != 0) { /* Parent - execute the given command. */
2237 close(sock);
2238 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid);
2239 if (ac == 0) {
2240 (*f_setenv)(SSH_AUTHSOCKET_ENV_NAME, socket_name);
2241 (*f_setenv)(SSH_AGENTPID_ENV_NAME, pidstrbuf);
2242 printf("echo Agent pid %ld;\n", (long)pid);
2243 exit(0);
2244 }
2245 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
2246 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
2247 perror("setenv");
2248 exit(1);
2249 }
2250 execvp(av[0], av);
2251 perror(av[0]);
2252 exit(1);
2253 }
2254 /* child */
2255 log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0);
2256
2257 if (setsid() == -1) {
2258 error("setsid: %s", strerror(errno));
2259 cleanup_exit(1);
2260 }
2261
2262 (void)chdir("/");
2263 if (stdfd_devnull(1, 1, 1) == -1)
2264 error_f("stdfd_devnull failed");
2265
2266 /* deny core dumps, since memory contains unencrypted private keys */
2267 rlim.rlim_cur = rlim.rlim_max = 0;
2268 if (setrlimit(RLIMIT_CORE, &rlim) == -1) {
2269 error("setrlimit RLIMIT_CORE: %s", strerror(errno));
2270 cleanup_exit(1);
2271 }
2272
2273 skip:
2274
2275 cleanup_pid = getpid();
2276
2277 #ifdef ENABLE_PKCS11
2278 pkcs11_init(0);
2279 #endif
2280 new_socket(AUTH_SOCKET, sock);
2281 if (ac > 0)
2282 parent_alive_interval = 10;
2283 idtab_init();
2284 ssh_signal(SIGPIPE, SIG_IGN);
2285 ssh_signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN);
2286 ssh_signal(SIGHUP, cleanup_handler);
2287 ssh_signal(SIGTERM, cleanup_handler);
2288
2289 #ifdef __OpenBSD__
2290 if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1)
2291 fatal("%s: pledge: %s", __progname, strerror(errno));
2292 #endif
2293
2294 while (1) {
2295 prepare_poll(&pfd, &npfd, &timeout, maxfds);
2296 result = poll(pfd, npfd, timeout);
2297 saved_errno = errno;
2298 if (parent_alive_interval != 0)
2299 check_parent_exists();
2300 (void) reaper(); /* remove expired keys */
2301 if (result == -1) {
2302 if (saved_errno == EINTR)
2303 continue;
2304 fatal("poll: %s", strerror(saved_errno));
2305 } else if (result > 0)
2306 after_poll(pfd, npfd, maxfds);
2307 }
2308 /* NOTREACHED */
2309 }
2310