xref: /freebsd/crypto/openssh/sshconnect2.c (revision 188408da9f7c19f476c1afe9becb0d373088da31)
1 /* $OpenBSD: sshconnect2.c,v 1.367 2023/08/01 08:15:04 dtucker Exp $ */
2 /*
3  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
4  * Copyright (c) 2008 Damien Miller.  All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25  */
26 
27 #include "includes.h"
28 
29 #include <sys/types.h>
30 #include <sys/socket.h>
31 #include <sys/wait.h>
32 #include <sys/stat.h>
33 
34 #include <errno.h>
35 #include <fcntl.h>
36 #include <limits.h>
37 #include <netdb.h>
38 #include <pwd.h>
39 #include <signal.h>
40 #include <stdio.h>
41 #include <string.h>
42 #include <stdarg.h>
43 #include <unistd.h>
44 #if defined(HAVE_STRNVIS) && defined(HAVE_VIS_H) && !defined(BROKEN_STRNVIS)
45 #include <vis.h>
46 #endif
47 
48 #include "openbsd-compat/sys-queue.h"
49 
50 #include "xmalloc.h"
51 #include "ssh.h"
52 #include "ssh2.h"
53 #include "sshbuf.h"
54 #include "packet.h"
55 #include "compat.h"
56 #include "cipher.h"
57 #include "sshkey.h"
58 #include "kex.h"
59 #include "sshconnect.h"
60 #include "authfile.h"
61 #include "dh.h"
62 #include "authfd.h"
63 #include "log.h"
64 #include "misc.h"
65 #include "readconf.h"
66 #include "match.h"
67 #include "dispatch.h"
68 #include "canohost.h"
69 #include "msg.h"
70 #include "pathnames.h"
71 #include "uidswap.h"
72 #include "hostfile.h"
73 #include "ssherr.h"
74 #include "utf8.h"
75 #include "ssh-sk.h"
76 #include "sk-api.h"
77 
78 #ifdef GSSAPI
79 #include "ssh-gss.h"
80 #endif
81 
82 /* import */
83 extern char *client_version_string;
84 extern char *server_version_string;
85 extern Options options;
86 
87 /*
88  * SSH2 key exchange
89  */
90 
91 static char *xxx_host;
92 static struct sockaddr *xxx_hostaddr;
93 static const struct ssh_conn_info *xxx_conn_info;
94 
95 static int
96 verify_host_key_callback(struct sshkey *hostkey, struct ssh *ssh)
97 {
98 	int r;
99 
100 	if ((r = sshkey_check_rsa_length(hostkey,
101 	    options.required_rsa_size)) != 0)
102 		fatal_r(r, "Bad server host key");
103 	if (verify_host_key(xxx_host, xxx_hostaddr, hostkey,
104 	    xxx_conn_info) == -1)
105 		fatal("Host key verification failed.");
106 	return 0;
107 }
108 
109 /* Returns the first item from a comma-separated algorithm list */
110 static char *
111 first_alg(const char *algs)
112 {
113 	char *ret, *cp;
114 
115 	ret = xstrdup(algs);
116 	if ((cp = strchr(ret, ',')) != NULL)
117 		*cp = '\0';
118 	return ret;
119 }
120 
121 static char *
122 order_hostkeyalgs(char *host, struct sockaddr *hostaddr, u_short port,
123     const struct ssh_conn_info *cinfo)
124 {
125 	char *oavail = NULL, *avail = NULL, *first = NULL, *last = NULL;
126 	char *alg = NULL, *hostname = NULL, *ret = NULL, *best = NULL;
127 	size_t maxlen;
128 	struct hostkeys *hostkeys = NULL;
129 	int ktype;
130 	u_int i;
131 
132 	/* Find all hostkeys for this hostname */
133 	get_hostfile_hostname_ipaddr(host, hostaddr, port, &hostname, NULL);
134 	hostkeys = init_hostkeys();
135 	for (i = 0; i < options.num_user_hostfiles; i++)
136 		load_hostkeys(hostkeys, hostname, options.user_hostfiles[i], 0);
137 	for (i = 0; i < options.num_system_hostfiles; i++) {
138 		load_hostkeys(hostkeys, hostname,
139 		    options.system_hostfiles[i], 0);
140 	}
141 	if (options.known_hosts_command != NULL) {
142 		load_hostkeys_command(hostkeys, options.known_hosts_command,
143 		    "ORDER", cinfo, NULL, host);
144 	}
145 	/*
146 	 * If a plain public key exists that matches the type of the best
147 	 * preference HostkeyAlgorithms, then use the whole list as is.
148 	 * Note that we ignore whether the best preference algorithm is a
149 	 * certificate type, as sshconnect.c will downgrade certs to
150 	 * plain keys if necessary.
151 	 */
152 	best = first_alg(options.hostkeyalgorithms);
153 	if (lookup_key_in_hostkeys_by_type(hostkeys,
154 	    sshkey_type_plain(sshkey_type_from_name(best)),
155 	    sshkey_ecdsa_nid_from_name(best), NULL)) {
156 		debug3_f("have matching best-preference key type %s, "
157 		    "using HostkeyAlgorithms verbatim", best);
158 		ret = xstrdup(options.hostkeyalgorithms);
159 		goto out;
160 	}
161 
162 	/*
163 	 * Otherwise, prefer the host key algorithms that match known keys
164 	 * while keeping the ordering of HostkeyAlgorithms as much as possible.
165 	 */
166 	oavail = avail = xstrdup(options.hostkeyalgorithms);
167 	maxlen = strlen(avail) + 1;
168 	first = xmalloc(maxlen);
169 	last = xmalloc(maxlen);
170 	*first = *last = '\0';
171 
172 #define ALG_APPEND(to, from) \
173 	do { \
174 		if (*to != '\0') \
175 			strlcat(to, ",", maxlen); \
176 		strlcat(to, from, maxlen); \
177 	} while (0)
178 
179 	while ((alg = strsep(&avail, ",")) && *alg != '\0') {
180 		if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
181 			fatal_f("unknown alg %s", alg);
182 		/*
183 		 * If we have a @cert-authority marker in known_hosts then
184 		 * prefer all certificate algorithms.
185 		 */
186 		if (sshkey_type_is_cert(ktype) &&
187 		    lookup_marker_in_hostkeys(hostkeys, MRK_CA)) {
188 			ALG_APPEND(first, alg);
189 			continue;
190 		}
191 		/* If the key appears in known_hosts then prefer it */
192 		if (lookup_key_in_hostkeys_by_type(hostkeys,
193 		    sshkey_type_plain(ktype),
194 		    sshkey_ecdsa_nid_from_name(alg), NULL)) {
195 			ALG_APPEND(first, alg);
196 			continue;
197 		}
198 		/* Otherwise, put it last */
199 		ALG_APPEND(last, alg);
200 	}
201 #undef ALG_APPEND
202 	xasprintf(&ret, "%s%s%s", first,
203 	    (*first == '\0' || *last == '\0') ? "" : ",", last);
204 	if (*first != '\0')
205 		debug3_f("prefer hostkeyalgs: %s", first);
206 	else
207 		debug3_f("no algorithms matched; accept original");
208  out:
209 	free(best);
210 	free(first);
211 	free(last);
212 	free(hostname);
213 	free(oavail);
214 	free_hostkeys(hostkeys);
215 
216 	return ret;
217 }
218 
219 void
220 ssh_kex2(struct ssh *ssh, char *host, struct sockaddr *hostaddr, u_short port,
221     const struct ssh_conn_info *cinfo)
222 {
223 	char *myproposal[PROPOSAL_MAX];
224 	char *s, *all_key, *hkalgs = NULL;
225 	int r, use_known_hosts_order = 0;
226 
227 	xxx_host = host;
228 	xxx_hostaddr = hostaddr;
229 	xxx_conn_info = cinfo;
230 
231 	if (options.rekey_limit || options.rekey_interval)
232 		ssh_packet_set_rekey_limits(ssh, options.rekey_limit,
233 		    options.rekey_interval);
234 
235 	/*
236 	 * If the user has not specified HostkeyAlgorithms, or has only
237 	 * appended or removed algorithms from that list then prefer algorithms
238 	 * that are in the list that are supported by known_hosts keys.
239 	 */
240 	if (options.hostkeyalgorithms == NULL ||
241 	    options.hostkeyalgorithms[0] == '-' ||
242 	    options.hostkeyalgorithms[0] == '+')
243 		use_known_hosts_order = 1;
244 
245 	/* Expand or fill in HostkeyAlgorithms */
246 	all_key = sshkey_alg_list(0, 0, 1, ',');
247 	if ((r = kex_assemble_names(&options.hostkeyalgorithms,
248 	    kex_default_pk_alg(), all_key)) != 0)
249 		fatal_fr(r, "kex_assemble_namelist");
250 	free(all_key);
251 
252 	if ((s = kex_names_cat(options.kex_algorithms, "ext-info-c")) == NULL)
253 		fatal_f("kex_names_cat");
254 
255 	if (use_known_hosts_order)
256 		hkalgs = order_hostkeyalgs(host, hostaddr, port, cinfo);
257 
258 	kex_proposal_populate_entries(ssh, myproposal, s, options.ciphers,
259 	    options.macs, compression_alg_list(options.compression),
260 	    hkalgs ? hkalgs : options.hostkeyalgorithms);
261 
262 	free(hkalgs);
263 
264 	/* start key exchange */
265 	if ((r = kex_setup(ssh, myproposal)) != 0)
266 		fatal_r(r, "kex_setup");
267 #ifdef WITH_OPENSSL
268 	ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client;
269 	ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client;
270 	ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client;
271 	ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client;
272 	ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client;
273 	ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
274 	ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
275 # ifdef OPENSSL_HAS_ECC
276 	ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client;
277 # endif
278 #endif
279 	ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client;
280 	ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_client;
281 	ssh->kex->verify_host_key=&verify_host_key_callback;
282 
283 	ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &ssh->kex->done);
284 
285 	/* remove ext-info from the KEX proposals for rekeying */
286 	free(myproposal[PROPOSAL_KEX_ALGS]);
287 	myproposal[PROPOSAL_KEX_ALGS] =
288 	    compat_kex_proposal(ssh, options.kex_algorithms);
289 	if ((r = kex_prop2buf(ssh->kex->my, myproposal)) != 0)
290 		fatal_r(r, "kex_prop2buf");
291 
292 #ifdef DEBUG_KEXDH
293 	/* send 1st encrypted/maced/compressed message */
294 	if ((r = sshpkt_start(ssh, SSH2_MSG_IGNORE)) != 0 ||
295 	    (r = sshpkt_put_cstring(ssh, "markus")) != 0 ||
296 	    (r = sshpkt_send(ssh)) != 0 ||
297 	    (r = ssh_packet_write_wait(ssh)) != 0)
298 		fatal_fr(r, "send packet");
299 #endif
300 	kex_proposal_free_entries(myproposal);
301 }
302 
303 /*
304  * Authenticate user
305  */
306 
307 typedef struct cauthctxt Authctxt;
308 typedef struct cauthmethod Authmethod;
309 typedef struct identity Identity;
310 typedef struct idlist Idlist;
311 
312 struct identity {
313 	TAILQ_ENTRY(identity) next;
314 	int	agent_fd;		/* >=0 if agent supports key */
315 	struct sshkey	*key;		/* public/private key */
316 	char	*filename;		/* comment for agent-only keys */
317 	int	tried;
318 	int	isprivate;		/* key points to the private key */
319 	int	userprovided;
320 };
321 TAILQ_HEAD(idlist, identity);
322 
323 struct cauthctxt {
324 	const char *server_user;
325 	const char *local_user;
326 	const char *host;
327 	const char *service;
328 	struct cauthmethod *method;
329 	sig_atomic_t success;
330 	char *authlist;
331 #ifdef GSSAPI
332 	/* gssapi */
333 	gss_OID_set gss_supported_mechs;
334 	u_int mech_tried;
335 #endif
336 	/* pubkey */
337 	struct idlist keys;
338 	int agent_fd;
339 	/* hostbased */
340 	Sensitive *sensitive;
341 	char *oktypes, *ktypes;
342 	const char *active_ktype;
343 	/* kbd-interactive */
344 	int info_req_seen;
345 	int attempt_kbdint;
346 	/* password */
347 	int attempt_passwd;
348 	/* generic */
349 	void *methoddata;
350 };
351 
352 struct cauthmethod {
353 	char	*name;		/* string to compare against server's list */
354 	int	(*userauth)(struct ssh *ssh);
355 	void	(*cleanup)(struct ssh *ssh);
356 	int	*enabled;	/* flag in option struct that enables method */
357 	int	*batch_flag;	/* flag in option struct that disables method */
358 };
359 
360 static int input_userauth_service_accept(int, u_int32_t, struct ssh *);
361 static int input_userauth_success(int, u_int32_t, struct ssh *);
362 static int input_userauth_failure(int, u_int32_t, struct ssh *);
363 static int input_userauth_banner(int, u_int32_t, struct ssh *);
364 static int input_userauth_error(int, u_int32_t, struct ssh *);
365 static int input_userauth_info_req(int, u_int32_t, struct ssh *);
366 static int input_userauth_pk_ok(int, u_int32_t, struct ssh *);
367 static int input_userauth_passwd_changereq(int, u_int32_t, struct ssh *);
368 
369 static int userauth_none(struct ssh *);
370 static int userauth_pubkey(struct ssh *);
371 static int userauth_passwd(struct ssh *);
372 static int userauth_kbdint(struct ssh *);
373 static int userauth_hostbased(struct ssh *);
374 
375 #ifdef GSSAPI
376 static int userauth_gssapi(struct ssh *);
377 static void userauth_gssapi_cleanup(struct ssh *);
378 static int input_gssapi_response(int type, u_int32_t, struct ssh *);
379 static int input_gssapi_token(int type, u_int32_t, struct ssh *);
380 static int input_gssapi_error(int, u_int32_t, struct ssh *);
381 static int input_gssapi_errtok(int, u_int32_t, struct ssh *);
382 #endif
383 
384 void	userauth(struct ssh *, char *);
385 
386 static void pubkey_cleanup(struct ssh *);
387 static int sign_and_send_pubkey(struct ssh *ssh, Identity *);
388 static void pubkey_prepare(struct ssh *, Authctxt *);
389 static void pubkey_reset(Authctxt *);
390 static struct sshkey *load_identity_file(Identity *);
391 
392 static Authmethod *authmethod_get(char *authlist);
393 static Authmethod *authmethod_lookup(const char *name);
394 static char *authmethods_get(void);
395 
396 Authmethod authmethods[] = {
397 #ifdef GSSAPI
398 	{"gssapi-with-mic",
399 		userauth_gssapi,
400 		userauth_gssapi_cleanup,
401 		&options.gss_authentication,
402 		NULL},
403 #endif
404 	{"hostbased",
405 		userauth_hostbased,
406 		NULL,
407 		&options.hostbased_authentication,
408 		NULL},
409 	{"publickey",
410 		userauth_pubkey,
411 		NULL,
412 		&options.pubkey_authentication,
413 		NULL},
414 	{"keyboard-interactive",
415 		userauth_kbdint,
416 		NULL,
417 		&options.kbd_interactive_authentication,
418 		&options.batch_mode},
419 	{"password",
420 		userauth_passwd,
421 		NULL,
422 		&options.password_authentication,
423 		&options.batch_mode},
424 	{"none",
425 		userauth_none,
426 		NULL,
427 		NULL,
428 		NULL},
429 	{NULL, NULL, NULL, NULL, NULL}
430 };
431 
432 void
433 ssh_userauth2(struct ssh *ssh, const char *local_user,
434     const char *server_user, char *host, Sensitive *sensitive)
435 {
436 	Authctxt authctxt;
437 	int r;
438 
439 	if (options.preferred_authentications == NULL)
440 		options.preferred_authentications = authmethods_get();
441 
442 	/* setup authentication context */
443 	memset(&authctxt, 0, sizeof(authctxt));
444 	authctxt.server_user = server_user;
445 	authctxt.local_user = local_user;
446 	authctxt.host = host;
447 	authctxt.service = "ssh-connection";		/* service name */
448 	authctxt.success = 0;
449 	authctxt.method = authmethod_lookup("none");
450 	authctxt.authlist = NULL;
451 	authctxt.methoddata = NULL;
452 	authctxt.sensitive = sensitive;
453 	authctxt.active_ktype = authctxt.oktypes = authctxt.ktypes = NULL;
454 	authctxt.info_req_seen = 0;
455 	authctxt.attempt_kbdint = 0;
456 	authctxt.attempt_passwd = 0;
457 #if GSSAPI
458 	authctxt.gss_supported_mechs = NULL;
459 	authctxt.mech_tried = 0;
460 #endif
461 	authctxt.agent_fd = -1;
462 	pubkey_prepare(ssh, &authctxt);
463 	if (authctxt.method == NULL) {
464 		fatal_f("internal error: cannot send userauth none request");
465 	}
466 
467 	if ((r = sshpkt_start(ssh, SSH2_MSG_SERVICE_REQUEST)) != 0 ||
468 	    (r = sshpkt_put_cstring(ssh, "ssh-userauth")) != 0 ||
469 	    (r = sshpkt_send(ssh)) != 0)
470 		fatal_fr(r, "send packet");
471 
472 	ssh->authctxt = &authctxt;
473 	ssh_dispatch_init(ssh, &input_userauth_error);
474 	ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, kex_input_ext_info);
475 	ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_ACCEPT, &input_userauth_service_accept);
476 	ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt.success);	/* loop until success */
477 	pubkey_cleanup(ssh);
478 	ssh->authctxt = NULL;
479 
480 	ssh_dispatch_range(ssh, SSH2_MSG_USERAUTH_MIN, SSH2_MSG_USERAUTH_MAX, NULL);
481 
482 	if (!authctxt.success)
483 		fatal("Authentication failed.");
484 	if (ssh_packet_connection_is_on_socket(ssh)) {
485 		verbose("Authenticated to %s ([%s]:%d) using \"%s\".", host,
486 		    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
487 		    authctxt.method->name);
488 	} else {
489 		verbose("Authenticated to %s (via proxy) using \"%s\".", host,
490 		    authctxt.method->name);
491 	}
492 }
493 
494 static int
495 input_userauth_service_accept(int type, u_int32_t seq, struct ssh *ssh)
496 {
497 	int r;
498 
499 	if (ssh_packet_remaining(ssh) > 0) {
500 		char *reply;
501 
502 		if ((r = sshpkt_get_cstring(ssh, &reply, NULL)) != 0)
503 			goto out;
504 		debug2("service_accept: %s", reply);
505 		free(reply);
506 	} else {
507 		debug2("buggy server: service_accept w/o service");
508 	}
509 	if ((r = sshpkt_get_end(ssh)) != 0)
510 		goto out;
511 	debug("SSH2_MSG_SERVICE_ACCEPT received");
512 
513 	/* initial userauth request */
514 	userauth_none(ssh);
515 
516 	ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &input_userauth_error);
517 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_SUCCESS, &input_userauth_success);
518 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_FAILURE, &input_userauth_failure);
519 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_BANNER, &input_userauth_banner);
520 	r = 0;
521  out:
522 	return r;
523 }
524 
525 void
526 userauth(struct ssh *ssh, char *authlist)
527 {
528 	Authctxt *authctxt = (Authctxt *)ssh->authctxt;
529 
530 	if (authctxt->method != NULL && authctxt->method->cleanup != NULL)
531 		authctxt->method->cleanup(ssh);
532 
533 	free(authctxt->methoddata);
534 	authctxt->methoddata = NULL;
535 	if (authlist == NULL) {
536 		authlist = authctxt->authlist;
537 	} else {
538 		free(authctxt->authlist);
539 		authctxt->authlist = authlist;
540 	}
541 	for (;;) {
542 		Authmethod *method = authmethod_get(authlist);
543 		if (method == NULL)
544 			fatal("%s@%s: Permission denied (%s).",
545 			    authctxt->server_user, authctxt->host, authlist);
546 		authctxt->method = method;
547 
548 		/* reset the per method handler */
549 		ssh_dispatch_range(ssh, SSH2_MSG_USERAUTH_PER_METHOD_MIN,
550 		    SSH2_MSG_USERAUTH_PER_METHOD_MAX, NULL);
551 
552 		/* and try new method */
553 		if (method->userauth(ssh) != 0) {
554 			debug2("we sent a %s packet, wait for reply", method->name);
555 			break;
556 		} else {
557 			debug2("we did not send a packet, disable method");
558 			method->enabled = NULL;
559 		}
560 	}
561 }
562 
563 static int
564 input_userauth_error(int type, u_int32_t seq, struct ssh *ssh)
565 {
566 	fatal_f("bad message during authentication: type %d", type);
567 	return 0;
568 }
569 
570 static int
571 input_userauth_banner(int type, u_int32_t seq, struct ssh *ssh)
572 {
573 	char *msg = NULL;
574 	size_t len;
575 	int r;
576 
577 	debug3_f("entering");
578 	if ((r = sshpkt_get_cstring(ssh, &msg, &len)) != 0 ||
579 	    (r = sshpkt_get_cstring(ssh, NULL, NULL)) != 0)
580 		goto out;
581 	if (len > 0 && options.log_level >= SYSLOG_LEVEL_INFO)
582 		fmprintf(stderr, "%s", msg);
583 	r = 0;
584  out:
585 	free(msg);
586 	return r;
587 }
588 
589 static int
590 input_userauth_success(int type, u_int32_t seq, struct ssh *ssh)
591 {
592 	Authctxt *authctxt = ssh->authctxt;
593 
594 	if (authctxt == NULL)
595 		fatal_f("no authentication context");
596 	free(authctxt->authlist);
597 	authctxt->authlist = NULL;
598 	if (authctxt->method != NULL && authctxt->method->cleanup != NULL)
599 		authctxt->method->cleanup(ssh);
600 	free(authctxt->methoddata);
601 	authctxt->methoddata = NULL;
602 	authctxt->success = 1;			/* break out */
603 	ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, dispatch_protocol_error);
604 	return 0;
605 }
606 
607 #if 0
608 static int
609 input_userauth_success_unexpected(int type, u_int32_t seq, struct ssh *ssh)
610 {
611 	Authctxt *authctxt = ssh->authctxt;
612 
613 	if (authctxt == NULL)
614 		fatal_f("no authentication context");
615 
616 	fatal("Unexpected authentication success during %s.",
617 	    authctxt->method->name);
618 	return 0;
619 }
620 #endif
621 
622 static int
623 input_userauth_failure(int type, u_int32_t seq, struct ssh *ssh)
624 {
625 	Authctxt *authctxt = ssh->authctxt;
626 	char *authlist = NULL;
627 	u_char partial;
628 
629 	if (authctxt == NULL)
630 		fatal("input_userauth_failure: no authentication context");
631 
632 	if (sshpkt_get_cstring(ssh, &authlist, NULL) != 0 ||
633 	    sshpkt_get_u8(ssh, &partial) != 0 ||
634 	    sshpkt_get_end(ssh) != 0)
635 		goto out;
636 
637 	if (partial != 0) {
638 		verbose("Authenticated using \"%s\" with partial success.",
639 		    authctxt->method->name);
640 		/* reset state */
641 		pubkey_reset(authctxt);
642 	}
643 	debug("Authentications that can continue: %s", authlist);
644 
645 	userauth(ssh, authlist);
646 	authlist = NULL;
647  out:
648 	free(authlist);
649 	return 0;
650 }
651 
652 /*
653  * Format an identity for logging including filename, key type, fingerprint
654  * and location (agent, etc.). Caller must free.
655  */
656 static char *
657 format_identity(Identity *id)
658 {
659 	char *fp = NULL, *ret = NULL;
660 	const char *note = "";
661 
662 	if (id->key != NULL) {
663 		fp = sshkey_fingerprint(id->key, options.fingerprint_hash,
664 		    SSH_FP_DEFAULT);
665 	}
666 	if (id->key) {
667 		if ((id->key->flags & SSHKEY_FLAG_EXT) != 0)
668 			note = " token";
669 		else if (sshkey_is_sk(id->key))
670 			note = " authenticator";
671 	}
672 	xasprintf(&ret, "%s %s%s%s%s%s%s",
673 	    id->filename,
674 	    id->key ? sshkey_type(id->key) : "", id->key ? " " : "",
675 	    fp ? fp : "",
676 	    id->userprovided ? " explicit" : "", note,
677 	    id->agent_fd != -1 ? " agent" : "");
678 	free(fp);
679 	return ret;
680 }
681 
682 static int
683 input_userauth_pk_ok(int type, u_int32_t seq, struct ssh *ssh)
684 {
685 	Authctxt *authctxt = ssh->authctxt;
686 	struct sshkey *key = NULL;
687 	Identity *id = NULL;
688 	int pktype, found = 0, sent = 0;
689 	size_t blen;
690 	char *pkalg = NULL, *fp = NULL, *ident = NULL;
691 	u_char *pkblob = NULL;
692 	int r;
693 
694 	if (authctxt == NULL)
695 		fatal("input_userauth_pk_ok: no authentication context");
696 
697 	if ((r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
698 	    (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0 ||
699 	    (r = sshpkt_get_end(ssh)) != 0)
700 		goto done;
701 
702 	if ((pktype = sshkey_type_from_name(pkalg)) == KEY_UNSPEC) {
703 		debug_f("server sent unknown pkalg %s", pkalg);
704 		goto done;
705 	}
706 	if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
707 		debug_r(r, "no key from blob. pkalg %s", pkalg);
708 		goto done;
709 	}
710 	if (key->type != pktype) {
711 		error("input_userauth_pk_ok: type mismatch "
712 		    "for decoded key (received %d, expected %d)",
713 		    key->type, pktype);
714 		goto done;
715 	}
716 
717 	/*
718 	 * search keys in the reverse order, because last candidate has been
719 	 * moved to the end of the queue.  this also avoids confusion by
720 	 * duplicate keys
721 	 */
722 	TAILQ_FOREACH_REVERSE(id, &authctxt->keys, idlist, next) {
723 		if (sshkey_equal(key, id->key)) {
724 			found = 1;
725 			break;
726 		}
727 	}
728 	if (!found || id == NULL) {
729 		fp = sshkey_fingerprint(key, options.fingerprint_hash,
730 		    SSH_FP_DEFAULT);
731 		error_f("server replied with unknown key: %s %s",
732 		    sshkey_type(key), fp == NULL ? "<ERROR>" : fp);
733 		goto done;
734 	}
735 	ident = format_identity(id);
736 	debug("Server accepts key: %s", ident);
737 	sent = sign_and_send_pubkey(ssh, id);
738 	r = 0;
739  done:
740 	sshkey_free(key);
741 	free(ident);
742 	free(fp);
743 	free(pkalg);
744 	free(pkblob);
745 
746 	/* try another method if we did not send a packet */
747 	if (r == 0 && sent == 0)
748 		userauth(ssh, NULL);
749 	return r;
750 }
751 
752 #ifdef GSSAPI
753 static int
754 userauth_gssapi(struct ssh *ssh)
755 {
756 	Authctxt *authctxt = (Authctxt *)ssh->authctxt;
757 	Gssctxt *gssctxt = NULL;
758 	OM_uint32 min;
759 	int r, ok = 0;
760 	gss_OID mech = NULL;
761 
762 	/* Try one GSSAPI method at a time, rather than sending them all at
763 	 * once. */
764 
765 	if (authctxt->gss_supported_mechs == NULL)
766 		gss_indicate_mechs(&min, &authctxt->gss_supported_mechs);
767 
768 	/* Check to see whether the mechanism is usable before we offer it */
769 	while (authctxt->mech_tried < authctxt->gss_supported_mechs->count &&
770 	    !ok) {
771 		mech = &authctxt->gss_supported_mechs->
772 		    elements[authctxt->mech_tried];
773 		/* My DER encoding requires length<128 */
774 		if (mech->length < 128 && ssh_gssapi_check_mechanism(&gssctxt,
775 		    mech, authctxt->host)) {
776 			ok = 1; /* Mechanism works */
777 		} else {
778 			authctxt->mech_tried++;
779 		}
780 	}
781 
782 	if (!ok || mech == NULL)
783 		return 0;
784 
785 	authctxt->methoddata=(void *)gssctxt;
786 
787 	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
788 	    (r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
789 	    (r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
790 	    (r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
791 	    (r = sshpkt_put_u32(ssh, 1)) != 0 ||
792 	    (r = sshpkt_put_u32(ssh, (mech->length) + 2)) != 0 ||
793 	    (r = sshpkt_put_u8(ssh, SSH_GSS_OIDTYPE)) != 0 ||
794 	    (r = sshpkt_put_u8(ssh, mech->length)) != 0 ||
795 	    (r = sshpkt_put(ssh, mech->elements, mech->length)) != 0 ||
796 	    (r = sshpkt_send(ssh)) != 0)
797 		fatal_fr(r, "send packet");
798 
799 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_RESPONSE, &input_gssapi_response);
800 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
801 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERROR, &input_gssapi_error);
802 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
803 
804 	authctxt->mech_tried++; /* Move along to next candidate */
805 
806 	return 1;
807 }
808 
809 static void
810 userauth_gssapi_cleanup(struct ssh *ssh)
811 {
812 	Authctxt *authctxt = (Authctxt *)ssh->authctxt;
813 	Gssctxt *gssctxt = (Gssctxt *)authctxt->methoddata;
814 
815 	ssh_gssapi_delete_ctx(&gssctxt);
816 	authctxt->methoddata = NULL;
817 
818 	free(authctxt->gss_supported_mechs);
819 	authctxt->gss_supported_mechs = NULL;
820 }
821 
822 static OM_uint32
823 process_gssapi_token(struct ssh *ssh, gss_buffer_t recv_tok)
824 {
825 	Authctxt *authctxt = ssh->authctxt;
826 	Gssctxt *gssctxt = authctxt->methoddata;
827 	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
828 	gss_buffer_desc mic = GSS_C_EMPTY_BUFFER;
829 	gss_buffer_desc gssbuf;
830 	OM_uint32 status, ms, flags;
831 	int r;
832 
833 	status = ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
834 	    recv_tok, &send_tok, &flags);
835 
836 	if (send_tok.length > 0) {
837 		u_char type = GSS_ERROR(status) ?
838 		    SSH2_MSG_USERAUTH_GSSAPI_ERRTOK :
839 		    SSH2_MSG_USERAUTH_GSSAPI_TOKEN;
840 
841 		if ((r = sshpkt_start(ssh, type)) != 0 ||
842 		    (r = sshpkt_put_string(ssh, send_tok.value,
843 		    send_tok.length)) != 0 ||
844 		    (r = sshpkt_send(ssh)) != 0)
845 			fatal_fr(r, "send %u packet", type);
846 
847 		gss_release_buffer(&ms, &send_tok);
848 	}
849 
850 	if (status == GSS_S_COMPLETE) {
851 		/* send either complete or MIC, depending on mechanism */
852 		if (!(flags & GSS_C_INTEG_FLAG)) {
853 			if ((r = sshpkt_start(ssh,
854 			    SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE)) != 0 ||
855 			    (r = sshpkt_send(ssh)) != 0)
856 				fatal_fr(r, "send completion");
857 		} else {
858 			struct sshbuf *b;
859 
860 			if ((b = sshbuf_new()) == NULL)
861 				fatal_f("sshbuf_new failed");
862 			ssh_gssapi_buildmic(b, authctxt->server_user,
863 			    authctxt->service, "gssapi-with-mic",
864 			    ssh->kex->session_id);
865 
866 			if ((gssbuf.value = sshbuf_mutable_ptr(b)) == NULL)
867 				fatal_f("sshbuf_mutable_ptr failed");
868 			gssbuf.length = sshbuf_len(b);
869 
870 			status = ssh_gssapi_sign(gssctxt, &gssbuf, &mic);
871 
872 			if (!GSS_ERROR(status)) {
873 				if ((r = sshpkt_start(ssh,
874 				    SSH2_MSG_USERAUTH_GSSAPI_MIC)) != 0 ||
875 				    (r = sshpkt_put_string(ssh, mic.value,
876 				    mic.length)) != 0 ||
877 				    (r = sshpkt_send(ssh)) != 0)
878 					fatal_fr(r, "send MIC");
879 			}
880 
881 			sshbuf_free(b);
882 			gss_release_buffer(&ms, &mic);
883 		}
884 	}
885 
886 	return status;
887 }
888 
889 static int
890 input_gssapi_response(int type, u_int32_t plen, struct ssh *ssh)
891 {
892 	Authctxt *authctxt = ssh->authctxt;
893 	Gssctxt *gssctxt;
894 	size_t oidlen;
895 	u_char *oidv = NULL;
896 	int r;
897 
898 	if (authctxt == NULL)
899 		fatal("input_gssapi_response: no authentication context");
900 	gssctxt = authctxt->methoddata;
901 
902 	/* Setup our OID */
903 	if ((r = sshpkt_get_string(ssh, &oidv, &oidlen)) != 0)
904 		goto done;
905 
906 	if (oidlen <= 2 ||
907 	    oidv[0] != SSH_GSS_OIDTYPE ||
908 	    oidv[1] != oidlen - 2) {
909 		debug("Badly encoded mechanism OID received");
910 		userauth(ssh, NULL);
911 		goto ok;
912 	}
913 
914 	if (!ssh_gssapi_check_oid(gssctxt, oidv + 2, oidlen - 2))
915 		fatal("Server returned different OID than expected");
916 
917 	if ((r = sshpkt_get_end(ssh)) != 0)
918 		goto done;
919 
920 	if (GSS_ERROR(process_gssapi_token(ssh, GSS_C_NO_BUFFER))) {
921 		/* Start again with next method on list */
922 		debug("Trying to start again");
923 		userauth(ssh, NULL);
924 		goto ok;
925 	}
926  ok:
927 	r = 0;
928  done:
929 	free(oidv);
930 	return r;
931 }
932 
933 static int
934 input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh)
935 {
936 	Authctxt *authctxt = ssh->authctxt;
937 	gss_buffer_desc recv_tok;
938 	u_char *p = NULL;
939 	size_t len;
940 	OM_uint32 status;
941 	int r;
942 
943 	if (authctxt == NULL)
944 		fatal("input_gssapi_response: no authentication context");
945 
946 	if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 ||
947 	    (r = sshpkt_get_end(ssh)) != 0)
948 		goto out;
949 
950 	recv_tok.value = p;
951 	recv_tok.length = len;
952 	status = process_gssapi_token(ssh, &recv_tok);
953 
954 	/* Start again with the next method in the list */
955 	if (GSS_ERROR(status)) {
956 		userauth(ssh, NULL);
957 		/* ok */
958 	}
959 	r = 0;
960  out:
961 	free(p);
962 	return r;
963 }
964 
965 static int
966 input_gssapi_errtok(int type, u_int32_t plen, struct ssh *ssh)
967 {
968 	Authctxt *authctxt = ssh->authctxt;
969 	Gssctxt *gssctxt;
970 	gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
971 	gss_buffer_desc recv_tok;
972 	OM_uint32 ms;
973 	u_char *p = NULL;
974 	size_t len;
975 	int r;
976 
977 	if (authctxt == NULL)
978 		fatal("input_gssapi_response: no authentication context");
979 	gssctxt = authctxt->methoddata;
980 
981 	if ((r = sshpkt_get_string(ssh, &p, &len)) != 0 ||
982 	    (r = sshpkt_get_end(ssh)) != 0) {
983 		free(p);
984 		return r;
985 	}
986 
987 	/* Stick it into GSSAPI and see what it says */
988 	recv_tok.value = p;
989 	recv_tok.length = len;
990 	(void)ssh_gssapi_init_ctx(gssctxt, options.gss_deleg_creds,
991 	    &recv_tok, &send_tok, NULL);
992 	free(p);
993 	gss_release_buffer(&ms, &send_tok);
994 
995 	/* Server will be returning a failed packet after this one */
996 	return 0;
997 }
998 
999 static int
1000 input_gssapi_error(int type, u_int32_t plen, struct ssh *ssh)
1001 {
1002 	char *msg = NULL;
1003 	char *lang = NULL;
1004 	int r;
1005 
1006 	if ((r = sshpkt_get_u32(ssh, NULL)) != 0 ||	/* maj */
1007 	    (r = sshpkt_get_u32(ssh, NULL)) != 0 ||	/* min */
1008 	    (r = sshpkt_get_cstring(ssh, &msg, NULL)) != 0 ||
1009 	    (r = sshpkt_get_cstring(ssh, &lang, NULL)) != 0)
1010 		goto out;
1011 	r = sshpkt_get_end(ssh);
1012 	debug("Server GSSAPI Error:\n%s", msg);
1013  out:
1014 	free(msg);
1015 	free(lang);
1016 	return r;
1017 }
1018 #endif /* GSSAPI */
1019 
1020 static int
1021 userauth_none(struct ssh *ssh)
1022 {
1023 	Authctxt *authctxt = (Authctxt *)ssh->authctxt;
1024 	int r;
1025 
1026 	/* initial userauth request */
1027 	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
1028 	    (r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
1029 	    (r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
1030 	    (r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
1031 	    (r = sshpkt_send(ssh)) != 0)
1032 		fatal_fr(r, "send packet");
1033 	return 1;
1034 }
1035 
1036 static int
1037 userauth_passwd(struct ssh *ssh)
1038 {
1039 	Authctxt *authctxt = (Authctxt *)ssh->authctxt;
1040 	char *password, *prompt = NULL;
1041 	const char *host = options.host_key_alias ?  options.host_key_alias :
1042 	    authctxt->host;
1043 	int r;
1044 
1045 	if (authctxt->attempt_passwd++ >= options.number_of_password_prompts)
1046 		return 0;
1047 
1048 	if (authctxt->attempt_passwd != 1)
1049 		error("Permission denied, please try again.");
1050 
1051 	xasprintf(&prompt, "%s@%s's password: ", authctxt->server_user, host);
1052 	password = read_passphrase(prompt, 0);
1053 	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
1054 	    (r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
1055 	    (r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
1056 	    (r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
1057 	    (r = sshpkt_put_u8(ssh, 0)) != 0 ||
1058 	    (r = sshpkt_put_cstring(ssh, password)) != 0 ||
1059 	    (r = sshpkt_add_padding(ssh, 64)) != 0 ||
1060 	    (r = sshpkt_send(ssh)) != 0)
1061 		fatal_fr(r, "send packet");
1062 
1063 	free(prompt);
1064 	if (password != NULL)
1065 		freezero(password, strlen(password));
1066 
1067 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
1068 	    &input_userauth_passwd_changereq);
1069 
1070 	return 1;
1071 }
1072 
1073 /*
1074  * parse PASSWD_CHANGEREQ, prompt user and send SSH2_MSG_USERAUTH_REQUEST
1075  */
1076 static int
1077 input_userauth_passwd_changereq(int type, u_int32_t seqnr, struct ssh *ssh)
1078 {
1079 	Authctxt *authctxt = ssh->authctxt;
1080 	char *info = NULL, *lang = NULL, *password = NULL, *retype = NULL;
1081 	char prompt[256];
1082 	const char *host;
1083 	int r;
1084 
1085 	debug2("input_userauth_passwd_changereq");
1086 
1087 	if (authctxt == NULL)
1088 		fatal("input_userauth_passwd_changereq: "
1089 		    "no authentication context");
1090 	host = options.host_key_alias ? options.host_key_alias : authctxt->host;
1091 
1092 	if ((r = sshpkt_get_cstring(ssh, &info, NULL)) != 0 ||
1093 	    (r = sshpkt_get_cstring(ssh, &lang, NULL)) != 0)
1094 		goto out;
1095 	if (strlen(info) > 0)
1096 		logit("%s", info);
1097 	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
1098 	    (r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
1099 	    (r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
1100 	    (r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
1101 	    (r = sshpkt_put_u8(ssh, 1)) != 0)	/* additional info */
1102 		goto out;
1103 
1104 	snprintf(prompt, sizeof(prompt),
1105 	    "Enter %.30s@%.128s's old password: ",
1106 	    authctxt->server_user, host);
1107 	password = read_passphrase(prompt, 0);
1108 	if ((r = sshpkt_put_cstring(ssh, password)) != 0)
1109 		goto out;
1110 
1111 	freezero(password, strlen(password));
1112 	password = NULL;
1113 	while (password == NULL) {
1114 		snprintf(prompt, sizeof(prompt),
1115 		    "Enter %.30s@%.128s's new password: ",
1116 		    authctxt->server_user, host);
1117 		password = read_passphrase(prompt, RP_ALLOW_EOF);
1118 		if (password == NULL) {
1119 			/* bail out */
1120 			r = 0;
1121 			goto out;
1122 		}
1123 		snprintf(prompt, sizeof(prompt),
1124 		    "Retype %.30s@%.128s's new password: ",
1125 		    authctxt->server_user, host);
1126 		retype = read_passphrase(prompt, 0);
1127 		if (strcmp(password, retype) != 0) {
1128 			freezero(password, strlen(password));
1129 			logit("Mismatch; try again, EOF to quit.");
1130 			password = NULL;
1131 		}
1132 		freezero(retype, strlen(retype));
1133 	}
1134 	if ((r = sshpkt_put_cstring(ssh, password)) != 0 ||
1135 	    (r = sshpkt_add_padding(ssh, 64)) != 0 ||
1136 	    (r = sshpkt_send(ssh)) != 0)
1137 		goto out;
1138 
1139 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ,
1140 	    &input_userauth_passwd_changereq);
1141 	r = 0;
1142  out:
1143 	if (password)
1144 		freezero(password, strlen(password));
1145 	free(info);
1146 	free(lang);
1147 	return r;
1148 }
1149 
1150 /*
1151  * Select an algorithm for publickey signatures.
1152  * Returns algorithm (caller must free) or NULL if no mutual algorithm found.
1153  *
1154  * Call with ssh==NULL to ignore server-sig-algs extension list and
1155  * only attempt with the key's base signature type.
1156  */
1157 static char *
1158 key_sig_algorithm(struct ssh *ssh, const struct sshkey *key)
1159 {
1160 	char *allowed, *oallowed, *cp, *tmp, *alg = NULL;
1161 	const char *server_sig_algs;
1162 
1163 	/*
1164 	 * The signature algorithm will only differ from the key algorithm
1165 	 * for RSA keys/certs and when the server advertises support for
1166 	 * newer (SHA2) algorithms.
1167 	 */
1168 	if (ssh == NULL || ssh->kex->server_sig_algs == NULL ||
1169 	    (key->type != KEY_RSA && key->type != KEY_RSA_CERT) ||
1170 	    (key->type == KEY_RSA_CERT && (ssh->compat & SSH_BUG_SIGTYPE))) {
1171 		/* Filter base key signature alg against our configuration */
1172 		return match_list(sshkey_ssh_name(key),
1173 		    options.pubkey_accepted_algos, NULL);
1174 	}
1175 
1176 	/*
1177 	 * Workaround OpenSSH 7.4 bug: this version supports RSA/SHA-2 but
1178 	 * fails to advertise it via SSH2_MSG_EXT_INFO.
1179 	 */
1180 	server_sig_algs = ssh->kex->server_sig_algs;
1181 	if (key->type == KEY_RSA && (ssh->compat & SSH_BUG_SIGTYPE74))
1182 		server_sig_algs = "rsa-sha2-256,rsa-sha2-512";
1183 
1184 	/*
1185 	 * For RSA keys/certs, since these might have a different sig type:
1186 	 * find the first entry in PubkeyAcceptedAlgorithms of the right type
1187 	 * that also appears in the supported signature algorithms list from
1188 	 * the server.
1189 	 */
1190 	oallowed = allowed = xstrdup(options.pubkey_accepted_algos);
1191 	while ((cp = strsep(&allowed, ",")) != NULL) {
1192 		if (sshkey_type_from_name(cp) != key->type)
1193 			continue;
1194 		tmp = match_list(sshkey_sigalg_by_name(cp),
1195 		    server_sig_algs, NULL);
1196 		if (tmp != NULL)
1197 			alg = xstrdup(cp);
1198 		free(tmp);
1199 		if (alg != NULL)
1200 			break;
1201 	}
1202 	free(oallowed);
1203 	return alg;
1204 }
1205 
1206 static int
1207 identity_sign(struct identity *id, u_char **sigp, size_t *lenp,
1208     const u_char *data, size_t datalen, u_int compat, const char *alg)
1209 {
1210 	struct sshkey *sign_key = NULL, *prv = NULL;
1211 	int is_agent = 0, retried = 0, r = SSH_ERR_INTERNAL_ERROR;
1212 	struct notifier_ctx *notifier = NULL;
1213 	char *fp = NULL, *pin = NULL, *prompt = NULL;
1214 
1215 	*sigp = NULL;
1216 	*lenp = 0;
1217 
1218 	/* The agent supports this key. */
1219 	if (id->key != NULL && id->agent_fd != -1) {
1220 		return ssh_agent_sign(id->agent_fd, id->key, sigp, lenp,
1221 		    data, datalen, alg, compat);
1222 	}
1223 
1224 	/*
1225 	 * We have already loaded the private key or the private key is
1226 	 * stored in external hardware.
1227 	 */
1228 	if (id->key != NULL &&
1229 	    (id->isprivate || (id->key->flags & SSHKEY_FLAG_EXT))) {
1230 		sign_key = id->key;
1231 		is_agent = 1;
1232 	} else {
1233 		/* Load the private key from the file. */
1234 		if ((prv = load_identity_file(id)) == NULL)
1235 			return SSH_ERR_KEY_NOT_FOUND;
1236 		if (id->key != NULL && !sshkey_equal_public(prv, id->key)) {
1237 			error_f("private key %s contents do not match public",
1238 			    id->filename);
1239 			r = SSH_ERR_KEY_NOT_FOUND;
1240 			goto out;
1241 		}
1242 		sign_key = prv;
1243 	}
1244  retry_pin:
1245 	/* Prompt for touch for non-agent FIDO keys that request UP */
1246 	if (!is_agent && sshkey_is_sk(sign_key) &&
1247 	    (sign_key->sk_flags & SSH_SK_USER_PRESENCE_REQD)) {
1248 		/* XXX should batch mode just skip these? */
1249 		if ((fp = sshkey_fingerprint(sign_key,
1250 		    options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
1251 			fatal_f("fingerprint failed");
1252 		notifier = notify_start(options.batch_mode,
1253 		    "Confirm user presence for key %s %s",
1254 		    sshkey_type(sign_key), fp);
1255 		free(fp);
1256 	}
1257 	if ((r = sshkey_sign(sign_key, sigp, lenp, data, datalen,
1258 	    alg, options.sk_provider, pin, compat)) != 0) {
1259 		debug_fr(r, "sshkey_sign");
1260 		if (!retried && pin == NULL && !is_agent &&
1261 		    sshkey_is_sk(sign_key) &&
1262 		    r == SSH_ERR_KEY_WRONG_PASSPHRASE) {
1263 			notify_complete(notifier, NULL);
1264 			notifier = NULL;
1265 			xasprintf(&prompt, "Enter PIN for %s key %s: ",
1266 			    sshkey_type(sign_key), id->filename);
1267 			pin = read_passphrase(prompt, 0);
1268 			retried = 1;
1269 			goto retry_pin;
1270 		}
1271 		goto out;
1272 	}
1273 
1274 	/*
1275 	 * PKCS#11 tokens may not support all signature algorithms,
1276 	 * so check what we get back.
1277 	 */
1278 	if ((r = sshkey_check_sigtype(*sigp, *lenp, alg)) != 0) {
1279 		debug_fr(r, "sshkey_check_sigtype");
1280 		goto out;
1281 	}
1282 	/* success */
1283 	r = 0;
1284  out:
1285 	free(prompt);
1286 	if (pin != NULL)
1287 		freezero(pin, strlen(pin));
1288 	notify_complete(notifier, r == 0 ? "User presence confirmed" : NULL);
1289 	sshkey_free(prv);
1290 	return r;
1291 }
1292 
1293 static int
1294 id_filename_matches(Identity *id, Identity *private_id)
1295 {
1296 	static const char * const suffixes[] = { ".pub", "-cert.pub", NULL };
1297 	size_t len = strlen(id->filename), plen = strlen(private_id->filename);
1298 	size_t i, slen;
1299 
1300 	if (strcmp(id->filename, private_id->filename) == 0)
1301 		return 1;
1302 	for (i = 0; suffixes[i]; i++) {
1303 		slen = strlen(suffixes[i]);
1304 		if (len > slen && plen == len - slen &&
1305 		    strcmp(id->filename + (len - slen), suffixes[i]) == 0 &&
1306 		    memcmp(id->filename, private_id->filename, plen) == 0)
1307 			return 1;
1308 	}
1309 	return 0;
1310 }
1311 
1312 static int
1313 sign_and_send_pubkey(struct ssh *ssh, Identity *id)
1314 {
1315 	Authctxt *authctxt = (Authctxt *)ssh->authctxt;
1316 	struct sshbuf *b = NULL;
1317 	Identity *private_id, *sign_id = NULL;
1318 	u_char *signature = NULL;
1319 	size_t slen = 0, skip = 0;
1320 	int r, fallback_sigtype, sent = 0;
1321 	char *alg = NULL, *fp = NULL;
1322 	const char *loc = "", *method = "publickey";
1323 	int hostbound = 0;
1324 
1325 	/* prefer host-bound pubkey signatures if supported by server */
1326 	if ((ssh->kex->flags & KEX_HAS_PUBKEY_HOSTBOUND) != 0 &&
1327 	    (options.pubkey_authentication & SSH_PUBKEY_AUTH_HBOUND) != 0) {
1328 		hostbound = 1;
1329 		method = "publickey-hostbound-v00@openssh.com";
1330 	}
1331 
1332 	if ((fp = sshkey_fingerprint(id->key, options.fingerprint_hash,
1333 	    SSH_FP_DEFAULT)) == NULL)
1334 		return 0;
1335 
1336 	debug3_f("using %s with %s %s", method, sshkey_type(id->key), fp);
1337 
1338 	/*
1339 	 * If the key is an certificate, try to find a matching private key
1340 	 * and use it to complete the signature.
1341 	 * If no such private key exists, fall back to trying the certificate
1342 	 * key itself in case it has a private half already loaded.
1343 	 * This will try to set sign_id to the private key that will perform
1344 	 * the signature.
1345 	 */
1346 	if (sshkey_is_cert(id->key)) {
1347 		TAILQ_FOREACH(private_id, &authctxt->keys, next) {
1348 			if (sshkey_equal_public(id->key, private_id->key) &&
1349 			    id->key->type != private_id->key->type) {
1350 				sign_id = private_id;
1351 				break;
1352 			}
1353 		}
1354 		/*
1355 		 * Exact key matches are preferred, but also allow
1356 		 * filename matches for non-PKCS#11/agent keys that
1357 		 * didn't load public keys. This supports the case
1358 		 * of keeping just a private key file and public
1359 		 * certificate on disk.
1360 		 */
1361 		if (sign_id == NULL &&
1362 		    !id->isprivate && id->agent_fd == -1 &&
1363 		    (id->key->flags & SSHKEY_FLAG_EXT) == 0) {
1364 			TAILQ_FOREACH(private_id, &authctxt->keys, next) {
1365 				if (private_id->key == NULL &&
1366 				    id_filename_matches(id, private_id)) {
1367 					sign_id = private_id;
1368 					break;
1369 				}
1370 			}
1371 		}
1372 		if (sign_id != NULL) {
1373 			debug2_f("using private key \"%s\"%s for "
1374 			    "certificate", sign_id->filename,
1375 			    sign_id->agent_fd != -1 ? " from agent" : "");
1376 		} else {
1377 			debug_f("no separate private key for certificate "
1378 			    "\"%s\"", id->filename);
1379 		}
1380 	}
1381 
1382 	/*
1383 	 * If the above didn't select another identity to do the signing
1384 	 * then default to the one we started with.
1385 	 */
1386 	if (sign_id == NULL)
1387 		sign_id = id;
1388 
1389 	/* assemble and sign data */
1390 	for (fallback_sigtype = 0; fallback_sigtype <= 1; fallback_sigtype++) {
1391 		free(alg);
1392 		slen = 0;
1393 		signature = NULL;
1394 		if ((alg = key_sig_algorithm(fallback_sigtype ? NULL : ssh,
1395 		    id->key)) == NULL) {
1396 			error_f("no mutual signature supported");
1397 			goto out;
1398 		}
1399 		debug3_f("signing using %s %s", alg, fp);
1400 
1401 		sshbuf_free(b);
1402 		if ((b = sshbuf_new()) == NULL)
1403 			fatal_f("sshbuf_new failed");
1404 		if (ssh->compat & SSH_OLD_SESSIONID) {
1405 			if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0)
1406 				fatal_fr(r, "sshbuf_putb");
1407 		} else {
1408 			if ((r = sshbuf_put_stringb(b,
1409 			    ssh->kex->session_id)) != 0)
1410 				fatal_fr(r, "sshbuf_put_stringb");
1411 		}
1412 		skip = sshbuf_len(b);
1413 		if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
1414 		    (r = sshbuf_put_cstring(b, authctxt->server_user)) != 0 ||
1415 		    (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
1416 		    (r = sshbuf_put_cstring(b, method)) != 0 ||
1417 		    (r = sshbuf_put_u8(b, 1)) != 0 ||
1418 		    (r = sshbuf_put_cstring(b, alg)) != 0 ||
1419 		    (r = sshkey_puts(id->key, b)) != 0) {
1420 			fatal_fr(r, "assemble signed data");
1421 		}
1422 		if (hostbound) {
1423 			if (ssh->kex->initial_hostkey == NULL) {
1424 				fatal_f("internal error: initial hostkey "
1425 				    "not recorded");
1426 			}
1427 			if ((r = sshkey_puts(ssh->kex->initial_hostkey, b)) != 0)
1428 				fatal_fr(r, "assemble %s hostkey", method);
1429 		}
1430 		/* generate signature */
1431 		r = identity_sign(sign_id, &signature, &slen,
1432 		    sshbuf_ptr(b), sshbuf_len(b), ssh->compat, alg);
1433 		if (r == 0)
1434 			break;
1435 		else if (r == SSH_ERR_KEY_NOT_FOUND)
1436 			goto out; /* soft failure */
1437 		else if (r == SSH_ERR_SIGN_ALG_UNSUPPORTED &&
1438 		    !fallback_sigtype) {
1439 			if (sign_id->agent_fd != -1)
1440 				loc = "agent ";
1441 			else if ((sign_id->key->flags & SSHKEY_FLAG_EXT) != 0)
1442 				loc = "token ";
1443 			logit("%skey %s %s returned incorrect signature type",
1444 			    loc, sshkey_type(id->key), fp);
1445 			continue;
1446 		}
1447 		error_fr(r, "signing failed for %s \"%s\"%s",
1448 		    sshkey_type(sign_id->key), sign_id->filename,
1449 		    id->agent_fd != -1 ? " from agent" : "");
1450 		goto out;
1451 	}
1452 	if (slen == 0 || signature == NULL) /* shouldn't happen */
1453 		fatal_f("no signature");
1454 
1455 	/* append signature */
1456 	if ((r = sshbuf_put_string(b, signature, slen)) != 0)
1457 		fatal_fr(r, "append signature");
1458 
1459 #ifdef DEBUG_PK
1460 	sshbuf_dump(b, stderr);
1461 #endif
1462 	/* skip session id and packet type */
1463 	if ((r = sshbuf_consume(b, skip + 1)) != 0)
1464 		fatal_fr(r, "consume");
1465 
1466 	/* put remaining data from buffer into packet */
1467 	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
1468 	    (r = sshpkt_putb(ssh, b)) != 0 ||
1469 	    (r = sshpkt_send(ssh)) != 0)
1470 		fatal_fr(r, "enqueue request");
1471 
1472 	/* success */
1473 	sent = 1;
1474 
1475  out:
1476 	free(fp);
1477 	free(alg);
1478 	sshbuf_free(b);
1479 	freezero(signature, slen);
1480 	return sent;
1481 }
1482 
1483 static int
1484 send_pubkey_test(struct ssh *ssh, Identity *id)
1485 {
1486 	Authctxt *authctxt = (Authctxt *)ssh->authctxt;
1487 	u_char *blob = NULL;
1488 	char *alg = NULL;
1489 	size_t bloblen;
1490 	u_int have_sig = 0;
1491 	int sent = 0, r;
1492 
1493 	if ((alg = key_sig_algorithm(ssh, id->key)) == NULL) {
1494 		debug_f("no mutual signature algorithm");
1495 		goto out;
1496 	}
1497 
1498 	if ((r = sshkey_to_blob(id->key, &blob, &bloblen)) != 0) {
1499 		/* we cannot handle this key */
1500 		debug3_f("cannot handle key");
1501 		goto out;
1502 	}
1503 	/* register callback for USERAUTH_PK_OK message */
1504 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_PK_OK, &input_userauth_pk_ok);
1505 
1506 	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
1507 	    (r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
1508 	    (r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
1509 	    (r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
1510 	    (r = sshpkt_put_u8(ssh, have_sig)) != 0 ||
1511 	    (r = sshpkt_put_cstring(ssh, alg)) != 0 ||
1512 	    (r = sshpkt_put_string(ssh, blob, bloblen)) != 0 ||
1513 	    (r = sshpkt_send(ssh)) != 0)
1514 		fatal_fr(r, "send packet");
1515 	sent = 1;
1516 
1517  out:
1518 	free(alg);
1519 	free(blob);
1520 	return sent;
1521 }
1522 
1523 static struct sshkey *
1524 load_identity_file(Identity *id)
1525 {
1526 	struct sshkey *private = NULL;
1527 	char prompt[300], *passphrase, *comment;
1528 	int r, quit = 0, i;
1529 	struct stat st;
1530 
1531 	if (stat(id->filename, &st) == -1) {
1532 		do_log2(id->userprovided ?
1533 		    SYSLOG_LEVEL_INFO : SYSLOG_LEVEL_DEBUG3,
1534 		    "no such identity: %s: %s", id->filename, strerror(errno));
1535 		return NULL;
1536 	}
1537 	snprintf(prompt, sizeof prompt,
1538 	    "Enter passphrase for key '%.100s': ", id->filename);
1539 	for (i = 0; i <= options.number_of_password_prompts; i++) {
1540 		if (i == 0)
1541 			passphrase = "";
1542 		else {
1543 			passphrase = read_passphrase(prompt, 0);
1544 			if (*passphrase == '\0') {
1545 				debug2("no passphrase given, try next key");
1546 				free(passphrase);
1547 				break;
1548 			}
1549 		}
1550 		switch ((r = sshkey_load_private_type(KEY_UNSPEC, id->filename,
1551 		    passphrase, &private, &comment))) {
1552 		case 0:
1553 			break;
1554 		case SSH_ERR_KEY_WRONG_PASSPHRASE:
1555 			if (options.batch_mode) {
1556 				quit = 1;
1557 				break;
1558 			}
1559 			if (i != 0)
1560 				debug2("bad passphrase given, try again...");
1561 			break;
1562 		case SSH_ERR_SYSTEM_ERROR:
1563 			if (errno == ENOENT) {
1564 				debug2_r(r, "Load key \"%s\"", id->filename);
1565 				quit = 1;
1566 				break;
1567 			}
1568 			/* FALLTHROUGH */
1569 		default:
1570 			error_r(r, "Load key \"%s\"", id->filename);
1571 			quit = 1;
1572 			break;
1573 		}
1574 		if (private != NULL && sshkey_is_sk(private) &&
1575 		    options.sk_provider == NULL) {
1576 			debug("key \"%s\" is an authenticator-hosted key, "
1577 			    "but no provider specified", id->filename);
1578 			sshkey_free(private);
1579 			private = NULL;
1580 			quit = 1;
1581 		}
1582 		if (!quit && (r = sshkey_check_rsa_length(private,
1583 		    options.required_rsa_size)) != 0) {
1584 			debug_fr(r, "Skipping key %s", id->filename);
1585 			sshkey_free(private);
1586 			private = NULL;
1587 			quit = 1;
1588 		}
1589 		if (!quit && private != NULL && id->agent_fd == -1 &&
1590 		    !(id->key && id->isprivate))
1591 			maybe_add_key_to_agent(id->filename, private, comment,
1592 			    passphrase);
1593 		if (i > 0)
1594 			freezero(passphrase, strlen(passphrase));
1595 		free(comment);
1596 		if (private != NULL || quit)
1597 			break;
1598 	}
1599 	return private;
1600 }
1601 
1602 static int
1603 key_type_allowed_by_config(struct sshkey *key)
1604 {
1605 	if (match_pattern_list(sshkey_ssh_name(key),
1606 	    options.pubkey_accepted_algos, 0) == 1)
1607 		return 1;
1608 
1609 	/* RSA keys/certs might be allowed by alternate signature types */
1610 	switch (key->type) {
1611 	case KEY_RSA:
1612 		if (match_pattern_list("rsa-sha2-512",
1613 		    options.pubkey_accepted_algos, 0) == 1)
1614 			return 1;
1615 		if (match_pattern_list("rsa-sha2-256",
1616 		    options.pubkey_accepted_algos, 0) == 1)
1617 			return 1;
1618 		break;
1619 	case KEY_RSA_CERT:
1620 		if (match_pattern_list("rsa-sha2-512-cert-v01@openssh.com",
1621 		    options.pubkey_accepted_algos, 0) == 1)
1622 			return 1;
1623 		if (match_pattern_list("rsa-sha2-256-cert-v01@openssh.com",
1624 		    options.pubkey_accepted_algos, 0) == 1)
1625 			return 1;
1626 		break;
1627 	}
1628 	return 0;
1629 }
1630 
1631 /* obtain a list of keys from the agent */
1632 static int
1633 get_agent_identities(struct ssh *ssh, int *agent_fdp,
1634     struct ssh_identitylist **idlistp)
1635 {
1636 	int r, agent_fd;
1637 	struct ssh_identitylist *idlist;
1638 
1639 	if ((r = ssh_get_authentication_socket(&agent_fd)) != 0) {
1640 		if (r != SSH_ERR_AGENT_NOT_PRESENT)
1641 			debug_fr(r, "ssh_get_authentication_socket");
1642 		return r;
1643 	}
1644 	if ((r = ssh_agent_bind_hostkey(agent_fd, ssh->kex->initial_hostkey,
1645 	    ssh->kex->session_id, ssh->kex->initial_sig, 0)) == 0)
1646 		debug_f("bound agent to hostkey");
1647 	else
1648 		debug2_fr(r, "ssh_agent_bind_hostkey");
1649 
1650 	if ((r = ssh_fetch_identitylist(agent_fd, &idlist)) != 0) {
1651 		debug_fr(r, "ssh_fetch_identitylist");
1652 		close(agent_fd);
1653 		return r;
1654 	}
1655 	/* success */
1656 	*agent_fdp = agent_fd;
1657 	*idlistp = idlist;
1658 	debug_f("agent returned %zu keys", idlist->nkeys);
1659 	return 0;
1660 }
1661 
1662 /*
1663  * try keys in the following order:
1664  *	1. certificates listed in the config file
1665  *	2. other input certificates
1666  *	3. agent keys that are found in the config file
1667  *	4. other agent keys
1668  *	5. keys that are only listed in the config file
1669  */
1670 static void
1671 pubkey_prepare(struct ssh *ssh, Authctxt *authctxt)
1672 {
1673 	struct identity *id, *id2, *tmp;
1674 	struct idlist agent, files, *preferred;
1675 	struct sshkey *key;
1676 	int agent_fd = -1, i, r, found;
1677 	size_t j;
1678 	struct ssh_identitylist *idlist;
1679 	char *ident;
1680 
1681 	TAILQ_INIT(&agent);	/* keys from the agent */
1682 	TAILQ_INIT(&files);	/* keys from the config file */
1683 	preferred = &authctxt->keys;
1684 	TAILQ_INIT(preferred);	/* preferred order of keys */
1685 
1686 	/* list of keys stored in the filesystem and PKCS#11 */
1687 	for (i = 0; i < options.num_identity_files; i++) {
1688 		key = options.identity_keys[i];
1689 		if (key && key->cert &&
1690 		    key->cert->type != SSH2_CERT_TYPE_USER) {
1691 			debug_f("ignoring certificate %s: not a user "
1692 			    "certificate", options.identity_files[i]);
1693 			continue;
1694 		}
1695 		if (key && sshkey_is_sk(key) && options.sk_provider == NULL) {
1696 			debug_f("ignoring authenticator-hosted key %s as no "
1697 			    "SecurityKeyProvider has been specified",
1698 			    options.identity_files[i]);
1699 			continue;
1700 		}
1701 		options.identity_keys[i] = NULL;
1702 		id = xcalloc(1, sizeof(*id));
1703 		id->agent_fd = -1;
1704 		id->key = key;
1705 		id->filename = xstrdup(options.identity_files[i]);
1706 		id->userprovided = options.identity_file_userprovided[i];
1707 		TAILQ_INSERT_TAIL(&files, id, next);
1708 	}
1709 	/* list of certificates specified by user */
1710 	for (i = 0; i < options.num_certificate_files; i++) {
1711 		key = options.certificates[i];
1712 		if (!sshkey_is_cert(key) || key->cert == NULL ||
1713 		    key->cert->type != SSH2_CERT_TYPE_USER) {
1714 			debug_f("ignoring certificate %s: not a user "
1715 			    "certificate", options.identity_files[i]);
1716 			continue;
1717 		}
1718 		if (key && sshkey_is_sk(key) && options.sk_provider == NULL) {
1719 			debug_f("ignoring authenticator-hosted key "
1720 			    "certificate %s as no "
1721 			    "SecurityKeyProvider has been specified",
1722 			    options.identity_files[i]);
1723 			continue;
1724 		}
1725 		id = xcalloc(1, sizeof(*id));
1726 		id->agent_fd = -1;
1727 		id->key = key;
1728 		id->filename = xstrdup(options.certificate_files[i]);
1729 		id->userprovided = options.certificate_file_userprovided[i];
1730 		TAILQ_INSERT_TAIL(preferred, id, next);
1731 	}
1732 	/* list of keys supported by the agent */
1733 	if ((r = get_agent_identities(ssh, &agent_fd, &idlist)) == 0) {
1734 		for (j = 0; j < idlist->nkeys; j++) {
1735 			if ((r = sshkey_check_rsa_length(idlist->keys[j],
1736 			    options.required_rsa_size)) != 0) {
1737 				debug_fr(r, "ignoring %s agent key",
1738 				    sshkey_ssh_name(idlist->keys[j]));
1739 				continue;
1740 			}
1741 			found = 0;
1742 			TAILQ_FOREACH(id, &files, next) {
1743 				/*
1744 				 * agent keys from the config file are
1745 				 * preferred
1746 				 */
1747 				if (sshkey_equal(idlist->keys[j], id->key)) {
1748 					TAILQ_REMOVE(&files, id, next);
1749 					TAILQ_INSERT_TAIL(preferred, id, next);
1750 					id->agent_fd = agent_fd;
1751 					found = 1;
1752 					break;
1753 				}
1754 			}
1755 			if (!found && !options.identities_only) {
1756 				id = xcalloc(1, sizeof(*id));
1757 				/* XXX "steals" key/comment from idlist */
1758 				id->key = idlist->keys[j];
1759 				id->filename = idlist->comments[j];
1760 				idlist->keys[j] = NULL;
1761 				idlist->comments[j] = NULL;
1762 				id->agent_fd = agent_fd;
1763 				TAILQ_INSERT_TAIL(&agent, id, next);
1764 			}
1765 		}
1766 		ssh_free_identitylist(idlist);
1767 		/* append remaining agent keys */
1768 		TAILQ_CONCAT(preferred, &agent, next);
1769 		authctxt->agent_fd = agent_fd;
1770 	}
1771 	/* Prefer PKCS11 keys that are explicitly listed */
1772 	TAILQ_FOREACH_SAFE(id, &files, next, tmp) {
1773 		if (id->key == NULL || (id->key->flags & SSHKEY_FLAG_EXT) == 0)
1774 			continue;
1775 		found = 0;
1776 		TAILQ_FOREACH(id2, &files, next) {
1777 			if (id2->key == NULL ||
1778 			    (id2->key->flags & SSHKEY_FLAG_EXT) != 0)
1779 				continue;
1780 			if (sshkey_equal(id->key, id2->key)) {
1781 				TAILQ_REMOVE(&files, id, next);
1782 				TAILQ_INSERT_TAIL(preferred, id, next);
1783 				found = 1;
1784 				break;
1785 			}
1786 		}
1787 		/* If IdentitiesOnly set and key not found then don't use it */
1788 		if (!found && options.identities_only) {
1789 			TAILQ_REMOVE(&files, id, next);
1790 			freezero(id, sizeof(*id));
1791 		}
1792 	}
1793 	/* append remaining keys from the config file */
1794 	TAILQ_CONCAT(preferred, &files, next);
1795 	/* finally, filter by PubkeyAcceptedAlgorithms */
1796 	TAILQ_FOREACH_SAFE(id, preferred, next, id2) {
1797 		if (id->key != NULL && !key_type_allowed_by_config(id->key)) {
1798 			debug("Skipping %s key %s - "
1799 			    "corresponding algo not in PubkeyAcceptedAlgorithms",
1800 			    sshkey_ssh_name(id->key), id->filename);
1801 			TAILQ_REMOVE(preferred, id, next);
1802 			sshkey_free(id->key);
1803 			free(id->filename);
1804 			memset(id, 0, sizeof(*id));
1805 			continue;
1806 		}
1807 	}
1808 	/* List the keys we plan on using */
1809 	TAILQ_FOREACH_SAFE(id, preferred, next, id2) {
1810 		ident = format_identity(id);
1811 		debug("Will attempt key: %s", ident);
1812 		free(ident);
1813 	}
1814 	debug2_f("done");
1815 }
1816 
1817 static void
1818 pubkey_cleanup(struct ssh *ssh)
1819 {
1820 	Authctxt *authctxt = (Authctxt *)ssh->authctxt;
1821 	Identity *id;
1822 
1823 	if (authctxt->agent_fd != -1) {
1824 		ssh_close_authentication_socket(authctxt->agent_fd);
1825 		authctxt->agent_fd = -1;
1826 	}
1827 	for (id = TAILQ_FIRST(&authctxt->keys); id;
1828 	    id = TAILQ_FIRST(&authctxt->keys)) {
1829 		TAILQ_REMOVE(&authctxt->keys, id, next);
1830 		sshkey_free(id->key);
1831 		free(id->filename);
1832 		free(id);
1833 	}
1834 }
1835 
1836 static void
1837 pubkey_reset(Authctxt *authctxt)
1838 {
1839 	Identity *id;
1840 
1841 	TAILQ_FOREACH(id, &authctxt->keys, next)
1842 		id->tried = 0;
1843 }
1844 
1845 static int
1846 userauth_pubkey(struct ssh *ssh)
1847 {
1848 	Authctxt *authctxt = (Authctxt *)ssh->authctxt;
1849 	Identity *id;
1850 	int sent = 0;
1851 	char *ident;
1852 
1853 	while ((id = TAILQ_FIRST(&authctxt->keys))) {
1854 		if (id->tried++)
1855 			return (0);
1856 		/* move key to the end of the queue */
1857 		TAILQ_REMOVE(&authctxt->keys, id, next);
1858 		TAILQ_INSERT_TAIL(&authctxt->keys, id, next);
1859 		/*
1860 		 * send a test message if we have the public key. for
1861 		 * encrypted keys we cannot do this and have to load the
1862 		 * private key instead
1863 		 */
1864 		if (id->key != NULL) {
1865 			ident = format_identity(id);
1866 			debug("Offering public key: %s", ident);
1867 			free(ident);
1868 			sent = send_pubkey_test(ssh, id);
1869 		} else {
1870 			debug("Trying private key: %s", id->filename);
1871 			id->key = load_identity_file(id);
1872 			if (id->key != NULL) {
1873 				if (id->key != NULL) {
1874 					id->isprivate = 1;
1875 					sent = sign_and_send_pubkey(ssh, id);
1876 				}
1877 				sshkey_free(id->key);
1878 				id->key = NULL;
1879 				id->isprivate = 0;
1880 			}
1881 		}
1882 		if (sent)
1883 			return (sent);
1884 	}
1885 	return (0);
1886 }
1887 
1888 /*
1889  * Send userauth request message specifying keyboard-interactive method.
1890  */
1891 static int
1892 userauth_kbdint(struct ssh *ssh)
1893 {
1894 	Authctxt *authctxt = (Authctxt *)ssh->authctxt;
1895 	int r;
1896 
1897 	if (authctxt->attempt_kbdint++ >= options.number_of_password_prompts)
1898 		return 0;
1899 	/* disable if no SSH2_MSG_USERAUTH_INFO_REQUEST has been seen */
1900 	if (authctxt->attempt_kbdint > 1 && !authctxt->info_req_seen) {
1901 		debug3("userauth_kbdint: disable: no info_req_seen");
1902 		ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_REQUEST, NULL);
1903 		return 0;
1904 	}
1905 
1906 	debug2("userauth_kbdint");
1907 	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
1908 	    (r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
1909 	    (r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
1910 	    (r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
1911 	    (r = sshpkt_put_cstring(ssh, "")) != 0 ||		/* lang */
1912 	    (r = sshpkt_put_cstring(ssh, options.kbd_interactive_devices ?
1913 	    options.kbd_interactive_devices : "")) != 0 ||
1914 	    (r = sshpkt_send(ssh)) != 0)
1915 		fatal_fr(r, "send packet");
1916 
1917 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_REQUEST, &input_userauth_info_req);
1918 	return 1;
1919 }
1920 
1921 /*
1922  * parse INFO_REQUEST, prompt user and send INFO_RESPONSE
1923  */
1924 static int
1925 input_userauth_info_req(int type, u_int32_t seq, struct ssh *ssh)
1926 {
1927 	Authctxt *authctxt = ssh->authctxt;
1928 	char *name = NULL, *inst = NULL, *lang = NULL, *prompt = NULL;
1929 	char *display_prompt = NULL, *response = NULL;
1930 	u_char echo = 0;
1931 	u_int num_prompts, i;
1932 	int r;
1933 
1934 	debug2_f("entering");
1935 
1936 	if (authctxt == NULL)
1937 		fatal_f("no authentication context");
1938 
1939 	authctxt->info_req_seen = 1;
1940 
1941 	if ((r = sshpkt_get_cstring(ssh, &name, NULL)) != 0 ||
1942 	    (r = sshpkt_get_cstring(ssh, &inst, NULL)) != 0 ||
1943 	    (r = sshpkt_get_cstring(ssh, &lang, NULL)) != 0)
1944 		goto out;
1945 	if (strlen(name) > 0)
1946 		logit("%s", name);
1947 	if (strlen(inst) > 0)
1948 		logit("%s", inst);
1949 
1950 	if ((r = sshpkt_get_u32(ssh, &num_prompts)) != 0)
1951 		goto out;
1952 	/*
1953 	 * Begin to build info response packet based on prompts requested.
1954 	 * We commit to providing the correct number of responses, so if
1955 	 * further on we run into a problem that prevents this, we have to
1956 	 * be sure and clean this up and send a correct error response.
1957 	 */
1958 	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE)) != 0 ||
1959 	    (r = sshpkt_put_u32(ssh, num_prompts)) != 0)
1960 		goto out;
1961 
1962 	debug2_f("num_prompts %d", num_prompts);
1963 	for (i = 0; i < num_prompts; i++) {
1964 		if ((r = sshpkt_get_cstring(ssh, &prompt, NULL)) != 0 ||
1965 		    (r = sshpkt_get_u8(ssh, &echo)) != 0)
1966 			goto out;
1967 		if (asmprintf(&display_prompt, INT_MAX, NULL, "(%s@%s) %s",
1968 		    authctxt->server_user, options.host_key_alias ?
1969 		    options.host_key_alias : authctxt->host, prompt) == -1)
1970 			fatal_f("asmprintf failed");
1971 		response = read_passphrase(display_prompt, echo ? RP_ECHO : 0);
1972 		if ((r = sshpkt_put_cstring(ssh, response)) != 0)
1973 			goto out;
1974 		freezero(response, strlen(response));
1975 		free(prompt);
1976 		free(display_prompt);
1977 		display_prompt = response = prompt = NULL;
1978 	}
1979 	/* done with parsing incoming message. */
1980 	if ((r = sshpkt_get_end(ssh)) != 0 ||
1981 	    (r = sshpkt_add_padding(ssh, 64)) != 0)
1982 		goto out;
1983 	r = sshpkt_send(ssh);
1984  out:
1985 	if (response)
1986 		freezero(response, strlen(response));
1987 	free(prompt);
1988 	free(display_prompt);
1989 	free(name);
1990 	free(inst);
1991 	free(lang);
1992 	return r;
1993 }
1994 
1995 static int
1996 ssh_keysign(struct ssh *ssh, struct sshkey *key, u_char **sigp, size_t *lenp,
1997     const u_char *data, size_t datalen)
1998 {
1999 	struct sshbuf *b;
2000 	struct stat st;
2001 	pid_t pid;
2002 	int r, to[2], from[2], status;
2003 	int sock = ssh_packet_get_connection_in(ssh);
2004 	u_char rversion = 0, version = 2;
2005 	void (*osigchld)(int);
2006 
2007 	*sigp = NULL;
2008 	*lenp = 0;
2009 
2010 	if (stat(_PATH_SSH_KEY_SIGN, &st) == -1) {
2011 		error_f("not installed: %s", strerror(errno));
2012 		return -1;
2013 	}
2014 	if (fflush(stdout) != 0) {
2015 		error_f("fflush: %s", strerror(errno));
2016 		return -1;
2017 	}
2018 	if (pipe(to) == -1) {
2019 		error_f("pipe: %s", strerror(errno));
2020 		return -1;
2021 	}
2022 	if (pipe(from) == -1) {
2023 		error_f("pipe: %s", strerror(errno));
2024 		return -1;
2025 	}
2026 	if ((pid = fork()) == -1) {
2027 		error_f("fork: %s", strerror(errno));
2028 		return -1;
2029 	}
2030 	osigchld = ssh_signal(SIGCHLD, SIG_DFL);
2031 	if (pid == 0) {
2032 		close(from[0]);
2033 		if (dup2(from[1], STDOUT_FILENO) == -1)
2034 			fatal_f("dup2: %s", strerror(errno));
2035 		close(to[1]);
2036 		if (dup2(to[0], STDIN_FILENO) == -1)
2037 			fatal_f("dup2: %s", strerror(errno));
2038 		close(from[1]);
2039 		close(to[0]);
2040 
2041 		if (dup2(sock, STDERR_FILENO + 1) == -1)
2042 			fatal_f("dup2: %s", strerror(errno));
2043 		sock = STDERR_FILENO + 1;
2044 		if (fcntl(sock, F_SETFD, 0) == -1) /* keep the socket on exec */
2045 			debug3_f("fcntl F_SETFD: %s", strerror(errno));
2046 		closefrom(sock + 1);
2047 
2048 		debug3_f("[child] pid=%ld, exec %s",
2049 		    (long)getpid(), _PATH_SSH_KEY_SIGN);
2050 		execl(_PATH_SSH_KEY_SIGN, _PATH_SSH_KEY_SIGN, (char *)NULL);
2051 		fatal_f("exec(%s): %s", _PATH_SSH_KEY_SIGN,
2052 		    strerror(errno));
2053 	}
2054 	close(from[1]);
2055 	close(to[0]);
2056 	sock = STDERR_FILENO + 1;
2057 
2058 	if ((b = sshbuf_new()) == NULL)
2059 		fatal_f("sshbuf_new failed");
2060 	/* send # of sock, data to be signed */
2061 	if ((r = sshbuf_put_u32(b, sock)) != 0 ||
2062 	    (r = sshbuf_put_string(b, data, datalen)) != 0)
2063 		fatal_fr(r, "buffer error");
2064 	if (ssh_msg_send(to[1], version, b) == -1)
2065 		fatal_f("couldn't send request");
2066 	sshbuf_reset(b);
2067 	r = ssh_msg_recv(from[0], b);
2068 	close(from[0]);
2069 	close(to[1]);
2070 	if (r < 0) {
2071 		error_f("no reply");
2072 		goto fail;
2073 	}
2074 
2075 	errno = 0;
2076 	while (waitpid(pid, &status, 0) == -1) {
2077 		if (errno != EINTR) {
2078 			error_f("waitpid %ld: %s", (long)pid, strerror(errno));
2079 			goto fail;
2080 		}
2081 	}
2082 	if (!WIFEXITED(status)) {
2083 		error_f("exited abnormally");
2084 		goto fail;
2085 	}
2086 	if (WEXITSTATUS(status) != 0) {
2087 		error_f("exited with status %d", WEXITSTATUS(status));
2088 		goto fail;
2089 	}
2090 	if ((r = sshbuf_get_u8(b, &rversion)) != 0) {
2091 		error_fr(r, "buffer error");
2092 		goto fail;
2093 	}
2094 	if (rversion != version) {
2095 		error_f("bad version");
2096 		goto fail;
2097 	}
2098 	if ((r = sshbuf_get_string(b, sigp, lenp)) != 0) {
2099 		error_fr(r, "buffer error");
2100  fail:
2101 		ssh_signal(SIGCHLD, osigchld);
2102 		sshbuf_free(b);
2103 		return -1;
2104 	}
2105 	ssh_signal(SIGCHLD, osigchld);
2106 	sshbuf_free(b);
2107 
2108 	return 0;
2109 }
2110 
2111 static int
2112 userauth_hostbased(struct ssh *ssh)
2113 {
2114 	Authctxt *authctxt = (Authctxt *)ssh->authctxt;
2115 	struct sshkey *private = NULL;
2116 	struct sshbuf *b = NULL;
2117 	u_char *sig = NULL, *keyblob = NULL;
2118 	char *fp = NULL, *chost = NULL, *lname = NULL;
2119 	size_t siglen = 0, keylen = 0;
2120 	int i, r, success = 0;
2121 
2122 	if (authctxt->ktypes == NULL) {
2123 		authctxt->oktypes = xstrdup(options.hostbased_accepted_algos);
2124 		authctxt->ktypes = authctxt->oktypes;
2125 	}
2126 
2127 	/*
2128 	 * Work through each listed type pattern in HostbasedAcceptedAlgorithms,
2129 	 * trying each hostkey that matches the type in turn.
2130 	 */
2131 	for (;;) {
2132 		if (authctxt->active_ktype == NULL)
2133 			authctxt->active_ktype = strsep(&authctxt->ktypes, ",");
2134 		if (authctxt->active_ktype == NULL ||
2135 		    *authctxt->active_ktype == '\0')
2136 			break;
2137 		debug3_f("trying key type %s", authctxt->active_ktype);
2138 
2139 		/* check for a useful key */
2140 		private = NULL;
2141 		for (i = 0; i < authctxt->sensitive->nkeys; i++) {
2142 			if (authctxt->sensitive->keys[i] == NULL ||
2143 			    authctxt->sensitive->keys[i]->type == KEY_UNSPEC)
2144 				continue;
2145 			if (!sshkey_match_keyname_to_sigalgs(
2146 			    sshkey_ssh_name(authctxt->sensitive->keys[i]),
2147 			    authctxt->active_ktype))
2148 				continue;
2149 			/* we take and free the key */
2150 			private = authctxt->sensitive->keys[i];
2151 			authctxt->sensitive->keys[i] = NULL;
2152 			break;
2153 		}
2154 		/* Found one */
2155 		if (private != NULL)
2156 			break;
2157 		/* No more keys of this type; advance */
2158 		authctxt->active_ktype = NULL;
2159 	}
2160 	if (private == NULL) {
2161 		free(authctxt->oktypes);
2162 		authctxt->oktypes = authctxt->ktypes = NULL;
2163 		authctxt->active_ktype = NULL;
2164 		debug("No more client hostkeys for hostbased authentication.");
2165 		goto out;
2166 	}
2167 
2168 	if ((fp = sshkey_fingerprint(private, options.fingerprint_hash,
2169 	    SSH_FP_DEFAULT)) == NULL) {
2170 		error_f("sshkey_fingerprint failed");
2171 		goto out;
2172 	}
2173 	debug_f("trying hostkey %s %s using sigalg %s",
2174 	    sshkey_ssh_name(private), fp, authctxt->active_ktype);
2175 
2176 	/* figure out a name for the client host */
2177 	lname = get_local_name(ssh_packet_get_connection_in(ssh));
2178 	if (lname == NULL) {
2179 		error_f("cannot get local ipaddr/name");
2180 		goto out;
2181 	}
2182 
2183 	/* XXX sshbuf_put_stringf? */
2184 	xasprintf(&chost, "%s.", lname);
2185 	debug2_f("chost %s", chost);
2186 
2187 	/* construct data */
2188 	if ((b = sshbuf_new()) == NULL) {
2189 		error_f("sshbuf_new failed");
2190 		goto out;
2191 	}
2192 	if ((r = sshkey_to_blob(private, &keyblob, &keylen)) != 0) {
2193 		error_fr(r, "sshkey_to_blob");
2194 		goto out;
2195 	}
2196 	if ((r = sshbuf_put_stringb(b, ssh->kex->session_id)) != 0 ||
2197 	    (r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
2198 	    (r = sshbuf_put_cstring(b, authctxt->server_user)) != 0 ||
2199 	    (r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
2200 	    (r = sshbuf_put_cstring(b, authctxt->method->name)) != 0 ||
2201 	    (r = sshbuf_put_cstring(b, authctxt->active_ktype)) != 0 ||
2202 	    (r = sshbuf_put_string(b, keyblob, keylen)) != 0 ||
2203 	    (r = sshbuf_put_cstring(b, chost)) != 0 ||
2204 	    (r = sshbuf_put_cstring(b, authctxt->local_user)) != 0) {
2205 		error_fr(r, "buffer error");
2206 		goto out;
2207 	}
2208 
2209 #ifdef DEBUG_PK
2210 	sshbuf_dump(b, stderr);
2211 #endif
2212 	if ((r = ssh_keysign(ssh, private, &sig, &siglen,
2213 	    sshbuf_ptr(b), sshbuf_len(b))) != 0) {
2214 		error("sign using hostkey %s %s failed",
2215 		    sshkey_ssh_name(private), fp);
2216 		goto out;
2217 	}
2218 	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
2219 	    (r = sshpkt_put_cstring(ssh, authctxt->server_user)) != 0 ||
2220 	    (r = sshpkt_put_cstring(ssh, authctxt->service)) != 0 ||
2221 	    (r = sshpkt_put_cstring(ssh, authctxt->method->name)) != 0 ||
2222 	    (r = sshpkt_put_cstring(ssh, authctxt->active_ktype)) != 0 ||
2223 	    (r = sshpkt_put_string(ssh, keyblob, keylen)) != 0 ||
2224 	    (r = sshpkt_put_cstring(ssh, chost)) != 0 ||
2225 	    (r = sshpkt_put_cstring(ssh, authctxt->local_user)) != 0 ||
2226 	    (r = sshpkt_put_string(ssh, sig, siglen)) != 0 ||
2227 	    (r = sshpkt_send(ssh)) != 0) {
2228 		error_fr(r, "packet error");
2229 		goto out;
2230 	}
2231 	success = 1;
2232 
2233  out:
2234 	if (sig != NULL)
2235 		freezero(sig, siglen);
2236 	free(keyblob);
2237 	free(lname);
2238 	free(fp);
2239 	free(chost);
2240 	sshkey_free(private);
2241 	sshbuf_free(b);
2242 
2243 	return success;
2244 }
2245 
2246 /* find auth method */
2247 
2248 /*
2249  * given auth method name, if configurable options permit this method fill
2250  * in auth_ident field and return true, otherwise return false.
2251  */
2252 static int
2253 authmethod_is_enabled(Authmethod *method)
2254 {
2255 	if (method == NULL)
2256 		return 0;
2257 	/* return false if options indicate this method is disabled */
2258 	if  (method->enabled == NULL || *method->enabled == 0)
2259 		return 0;
2260 	/* return false if batch mode is enabled but method needs interactive mode */
2261 	if  (method->batch_flag != NULL && *method->batch_flag != 0)
2262 		return 0;
2263 	return 1;
2264 }
2265 
2266 static Authmethod *
2267 authmethod_lookup(const char *name)
2268 {
2269 	Authmethod *method = NULL;
2270 	if (name != NULL)
2271 		for (method = authmethods; method->name != NULL; method++)
2272 			if (strcmp(name, method->name) == 0)
2273 				return method;
2274 	debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
2275 	return NULL;
2276 }
2277 
2278 /* XXX internal state */
2279 static Authmethod *current = NULL;
2280 static char *supported = NULL;
2281 static char *preferred = NULL;
2282 
2283 /*
2284  * Given the authentication method list sent by the server, return the
2285  * next method we should try.  If the server initially sends a nil list,
2286  * use a built-in default list.
2287  */
2288 static Authmethod *
2289 authmethod_get(char *authlist)
2290 {
2291 	char *name = NULL;
2292 	u_int next;
2293 
2294 	/* Use a suitable default if we're passed a nil list.  */
2295 	if (authlist == NULL || strlen(authlist) == 0)
2296 		authlist = options.preferred_authentications;
2297 
2298 	if (supported == NULL || strcmp(authlist, supported) != 0) {
2299 		debug3("start over, passed a different list %s", authlist);
2300 		free(supported);
2301 		supported = xstrdup(authlist);
2302 		preferred = options.preferred_authentications;
2303 		debug3("preferred %s", preferred);
2304 		current = NULL;
2305 	} else if (current != NULL && authmethod_is_enabled(current))
2306 		return current;
2307 
2308 	for (;;) {
2309 		if ((name = match_list(preferred, supported, &next)) == NULL) {
2310 			debug("No more authentication methods to try.");
2311 			current = NULL;
2312 			return NULL;
2313 		}
2314 		preferred += next;
2315 		debug3("authmethod_lookup %s", name);
2316 		debug3("remaining preferred: %s", preferred);
2317 		if ((current = authmethod_lookup(name)) != NULL &&
2318 		    authmethod_is_enabled(current)) {
2319 			debug3("authmethod_is_enabled %s", name);
2320 			debug("Next authentication method: %s", name);
2321 			free(name);
2322 			return current;
2323 		}
2324 		free(name);
2325 	}
2326 }
2327 
2328 static char *
2329 authmethods_get(void)
2330 {
2331 	Authmethod *method = NULL;
2332 	struct sshbuf *b;
2333 	char *list;
2334 	int r;
2335 
2336 	if ((b = sshbuf_new()) == NULL)
2337 		fatal_f("sshbuf_new failed");
2338 	for (method = authmethods; method->name != NULL; method++) {
2339 		if (authmethod_is_enabled(method)) {
2340 			if ((r = sshbuf_putf(b, "%s%s",
2341 			    sshbuf_len(b) ? "," : "", method->name)) != 0)
2342 				fatal_fr(r, "buffer error");
2343 		}
2344 	}
2345 	if ((list = sshbuf_dup_string(b)) == NULL)
2346 		fatal_f("sshbuf_dup_string failed");
2347 	sshbuf_free(b);
2348 	return list;
2349 }
2350