xref: /openssh-portable/auth2.c (revision 0fa174eb)
1 /* $OpenBSD: auth2.c,v 1.152 2019/01/19 21:31:32 djm Exp $ */
2 /*
3  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24  */
25 
26 #include "includes.h"
27 
28 #include <sys/types.h>
29 #include <sys/stat.h>
30 #include <sys/uio.h>
31 
32 #include <fcntl.h>
33 #include <limits.h>
34 #include <pwd.h>
35 #include <stdarg.h>
36 #include <string.h>
37 #include <unistd.h>
38 #include <time.h>
39 
40 #include "atomicio.h"
41 #include "xmalloc.h"
42 #include "ssh2.h"
43 #include "packet.h"
44 #include "log.h"
45 #include "sshbuf.h"
46 #include "misc.h"
47 #include "servconf.h"
48 #include "compat.h"
49 #include "sshkey.h"
50 #include "hostfile.h"
51 #include "auth.h"
52 #include "dispatch.h"
53 #include "pathnames.h"
54 #include "sshbuf.h"
55 #include "ssherr.h"
56 
57 #ifdef GSSAPI
58 #include "ssh-gss.h"
59 #endif
60 #include "monitor_wrap.h"
61 #include "ssherr.h"
62 #include "digest.h"
63 
64 #include "opacket.h" /* XXX */
65 extern struct ssh *active_state; /* XXX */
66 
67 /* import */
68 extern ServerOptions options;
69 extern u_char *session_id2;
70 extern u_int session_id2_len;
71 extern struct sshbuf *loginmsg;
72 
73 /* methods */
74 
75 extern Authmethod method_none;
76 extern Authmethod method_pubkey;
77 extern Authmethod method_passwd;
78 extern Authmethod method_kbdint;
79 extern Authmethod method_hostbased;
80 #ifdef GSSAPI
81 extern Authmethod method_gssapi;
82 #endif
83 
84 Authmethod *authmethods[] = {
85 	&method_none,
86 	&method_pubkey,
87 #ifdef GSSAPI
88 	&method_gssapi,
89 #endif
90 	&method_passwd,
91 	&method_kbdint,
92 	&method_hostbased,
93 	NULL
94 };
95 
96 /* protocol */
97 
98 static int input_service_request(int, u_int32_t, struct ssh *);
99 static int input_userauth_request(int, u_int32_t, struct ssh *);
100 
101 /* helper */
102 static Authmethod *authmethod_lookup(Authctxt *, const char *);
103 static char *authmethods_get(Authctxt *authctxt);
104 
105 #define MATCH_NONE	0	/* method or submethod mismatch */
106 #define MATCH_METHOD	1	/* method matches (no submethod specified) */
107 #define MATCH_BOTH	2	/* method and submethod match */
108 #define MATCH_PARTIAL	3	/* method matches, submethod can't be checked */
109 static int list_starts_with(const char *, const char *, const char *);
110 
111 char *
112 auth2_read_banner(void)
113 {
114 	struct stat st;
115 	char *banner = NULL;
116 	size_t len, n;
117 	int fd;
118 
119 	if ((fd = open(options.banner, O_RDONLY)) == -1)
120 		return (NULL);
121 	if (fstat(fd, &st) == -1) {
122 		close(fd);
123 		return (NULL);
124 	}
125 	if (st.st_size <= 0 || st.st_size > 1*1024*1024) {
126 		close(fd);
127 		return (NULL);
128 	}
129 
130 	len = (size_t)st.st_size;		/* truncate */
131 	banner = xmalloc(len + 1);
132 	n = atomicio(read, fd, banner, len);
133 	close(fd);
134 
135 	if (n != len) {
136 		free(banner);
137 		return (NULL);
138 	}
139 	banner[n] = '\0';
140 
141 	return (banner);
142 }
143 
144 void
145 userauth_send_banner(const char *msg)
146 {
147 	packet_start(SSH2_MSG_USERAUTH_BANNER);
148 	packet_put_cstring(msg);
149 	packet_put_cstring("");		/* language, unused */
150 	packet_send();
151 	debug("%s: sent", __func__);
152 }
153 
154 static void
155 userauth_banner(void)
156 {
157 	char *banner = NULL;
158 
159 	if (options.banner == NULL)
160 		return;
161 
162 	if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
163 		goto done;
164 	userauth_send_banner(banner);
165 
166 done:
167 	free(banner);
168 }
169 
170 /*
171  * loop until authctxt->success == TRUE
172  */
173 void
174 do_authentication2(Authctxt *authctxt)
175 {
176 	struct ssh *ssh = active_state;		/* XXX */
177 	ssh->authctxt = authctxt;		/* XXX move to caller */
178 	ssh_dispatch_init(ssh, &dispatch_protocol_error);
179 	ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_REQUEST, &input_service_request);
180 	ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt->success);
181 	ssh->authctxt = NULL;
182 }
183 
184 /*ARGSUSED*/
185 static int
186 input_service_request(int type, u_int32_t seq, struct ssh *ssh)
187 {
188 	Authctxt *authctxt = ssh->authctxt;
189 	u_int len;
190 	int acceptit = 0;
191 	char *service = packet_get_cstring(&len);
192 	packet_check_eom();
193 
194 	if (authctxt == NULL)
195 		fatal("input_service_request: no authctxt");
196 
197 	if (strcmp(service, "ssh-userauth") == 0) {
198 		if (!authctxt->success) {
199 			acceptit = 1;
200 			/* now we can handle user-auth requests */
201 			ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
202 		}
203 	}
204 	/* XXX all other service requests are denied */
205 
206 	if (acceptit) {
207 		packet_start(SSH2_MSG_SERVICE_ACCEPT);
208 		packet_put_cstring(service);
209 		packet_send();
210 		packet_write_wait();
211 	} else {
212 		debug("bad service request %s", service);
213 		packet_disconnect("bad service request %s", service);
214 	}
215 	free(service);
216 	return 0;
217 }
218 
219 #define MIN_FAIL_DELAY_SECONDS 0.005
220 static double
221 user_specific_delay(const char *user)
222 {
223 	char b[512];
224 	size_t len = ssh_digest_bytes(SSH_DIGEST_SHA512);
225 	u_char *hash = xmalloc(len);
226 	double delay;
227 
228 	(void)snprintf(b, sizeof b, "%llu%s",
229 	     (unsigned long long)options.timing_secret, user);
230 	if (ssh_digest_memory(SSH_DIGEST_SHA512, b, strlen(b), hash, len) != 0)
231 		fatal("%s: ssh_digest_memory", __func__);
232 	/* 0-4.2 ms of delay */
233 	delay = (double)PEEK_U32(hash) / 1000 / 1000 / 1000 / 1000;
234 	freezero(hash, len);
235 	debug3("%s: user specific delay %0.3lfms", __func__, delay/1000);
236 	return MIN_FAIL_DELAY_SECONDS + delay;
237 }
238 
239 static void
240 ensure_minimum_time_since(double start, double seconds)
241 {
242 	struct timespec ts;
243 	double elapsed = monotime_double() - start, req = seconds, remain;
244 
245 	/* if we've already passed the requested time, scale up */
246 	while ((remain = seconds - elapsed) < 0.0)
247 		seconds *= 2;
248 
249 	ts.tv_sec = remain;
250 	ts.tv_nsec = (remain - ts.tv_sec) * 1000000000;
251 	debug3("%s: elapsed %0.3lfms, delaying %0.3lfms (requested %0.3lfms)",
252 	    __func__, elapsed*1000, remain*1000, req*1000);
253 	nanosleep(&ts, NULL);
254 }
255 
256 /*ARGSUSED*/
257 static int
258 input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)
259 {
260 	Authctxt *authctxt = ssh->authctxt;
261 	Authmethod *m = NULL;
262 	char *user, *service, *method, *style = NULL;
263 	int authenticated = 0;
264 	double tstart = monotime_double();
265 
266 	if (authctxt == NULL)
267 		fatal("input_userauth_request: no authctxt");
268 
269 	user = packet_get_cstring(NULL);
270 	service = packet_get_cstring(NULL);
271 	method = packet_get_cstring(NULL);
272 	debug("userauth-request for user %s service %s method %s", user, service, method);
273 	debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
274 
275 	if ((style = strchr(user, ':')) != NULL)
276 		*style++ = 0;
277 
278 	if (authctxt->attempt++ == 0) {
279 		/* setup auth context */
280 		authctxt->pw = PRIVSEP(getpwnamallow(user));
281 		authctxt->user = xstrdup(user);
282 		if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
283 			authctxt->valid = 1;
284 			debug2("%s: setting up authctxt for %s",
285 			    __func__, user);
286 		} else {
287 			/* Invalid user, fake password information */
288 			authctxt->pw = fakepw();
289 #ifdef SSH_AUDIT_EVENTS
290 			PRIVSEP(audit_event(SSH_INVALID_USER));
291 #endif
292 		}
293 #ifdef USE_PAM
294 		if (options.use_pam)
295 			PRIVSEP(start_pam(authctxt));
296 #endif
297 		ssh_packet_set_log_preamble(ssh, "%suser %s",
298 		    authctxt->valid ? "authenticating " : "invalid ", user);
299 		setproctitle("%s%s", authctxt->valid ? user : "unknown",
300 		    use_privsep ? " [net]" : "");
301 		authctxt->service = xstrdup(service);
302 		authctxt->style = style ? xstrdup(style) : NULL;
303 		if (use_privsep)
304 			mm_inform_authserv(service, style);
305 		userauth_banner();
306 		if (auth2_setup_methods_lists(authctxt) != 0)
307 			packet_disconnect("no authentication methods enabled");
308 	} else if (strcmp(user, authctxt->user) != 0 ||
309 	    strcmp(service, authctxt->service) != 0) {
310 		packet_disconnect("Change of username or service not allowed: "
311 		    "(%s,%s) -> (%s,%s)",
312 		    authctxt->user, authctxt->service, user, service);
313 	}
314 	/* reset state */
315 	auth2_challenge_stop(ssh);
316 
317 #ifdef GSSAPI
318 	/* XXX move to auth2_gssapi_stop() */
319 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
320 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
321 #endif
322 
323 	auth2_authctxt_reset_info(authctxt);
324 	authctxt->postponed = 0;
325 	authctxt->server_caused_failure = 0;
326 
327 	/* try to authenticate user */
328 	m = authmethod_lookup(authctxt, method);
329 	if (m != NULL && authctxt->failures < options.max_authtries) {
330 		debug2("input_userauth_request: try method %s", method);
331 		authenticated =	m->userauth(ssh);
332 	}
333 	if (!authctxt->authenticated)
334 		ensure_minimum_time_since(tstart,
335 		    user_specific_delay(authctxt->user));
336 	userauth_finish(ssh, authenticated, method, NULL);
337 
338 	free(service);
339 	free(user);
340 	free(method);
341 	return 0;
342 }
343 
344 void
345 userauth_finish(struct ssh *ssh, int authenticated, const char *method,
346     const char *submethod)
347 {
348 	Authctxt *authctxt = ssh->authctxt;
349 	char *methods;
350 	int partial = 0;
351 
352 	if (!authctxt->valid && authenticated)
353 		fatal("INTERNAL ERROR: authenticated invalid user %s",
354 		    authctxt->user);
355 	if (authenticated && authctxt->postponed)
356 		fatal("INTERNAL ERROR: authenticated and postponed");
357 
358 	/* Special handling for root */
359 	if (authenticated && authctxt->pw->pw_uid == 0 &&
360 	    !auth_root_allowed(ssh, method)) {
361 		authenticated = 0;
362 #ifdef SSH_AUDIT_EVENTS
363 		PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
364 #endif
365 	}
366 
367 	if (authenticated && options.num_auth_methods != 0) {
368 		if (!auth2_update_methods_lists(authctxt, method, submethod)) {
369 			authenticated = 0;
370 			partial = 1;
371 		}
372 	}
373 
374 	/* Log before sending the reply */
375 	auth_log(authctxt, authenticated, partial, method, submethod);
376 
377 	/* Update information exposed to session */
378 	if (authenticated || partial)
379 		auth2_update_session_info(authctxt, method, submethod);
380 
381 	if (authctxt->postponed)
382 		return;
383 
384 #ifdef USE_PAM
385 	if (options.use_pam && authenticated) {
386 		int r;
387 
388 		if (!PRIVSEP(do_pam_account())) {
389 			/* if PAM returned a message, send it to the user */
390 			if (sshbuf_len(loginmsg) > 0) {
391 				if ((r = sshbuf_put(loginmsg, "\0", 1)) != 0)
392 					fatal("%s: buffer error: %s",
393 					    __func__, ssh_err(r));
394 				userauth_send_banner(sshbuf_ptr(loginmsg));
395 				packet_write_wait();
396 			}
397 			fatal("Access denied for user %s by PAM account "
398 			    "configuration", authctxt->user);
399 		}
400 	}
401 #endif
402 
403 	if (authenticated == 1) {
404 		/* turn off userauth */
405 		ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
406 		packet_start(SSH2_MSG_USERAUTH_SUCCESS);
407 		packet_send();
408 		packet_write_wait();
409 		/* now we can break out */
410 		authctxt->success = 1;
411 		ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
412 	} else {
413 		/* Allow initial try of "none" auth without failure penalty */
414 		if (!partial && !authctxt->server_caused_failure &&
415 		    (authctxt->attempt > 1 || strcmp(method, "none") != 0))
416 			authctxt->failures++;
417 		if (authctxt->failures >= options.max_authtries) {
418 #ifdef SSH_AUDIT_EVENTS
419 			PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
420 #endif
421 			auth_maxtries_exceeded(authctxt);
422 		}
423 		methods = authmethods_get(authctxt);
424 		debug3("%s: failure partial=%d next methods=\"%s\"", __func__,
425 		    partial, methods);
426 		packet_start(SSH2_MSG_USERAUTH_FAILURE);
427 		packet_put_cstring(methods);
428 		packet_put_char(partial);
429 		packet_send();
430 		packet_write_wait();
431 		free(methods);
432 	}
433 }
434 
435 /*
436  * Checks whether method is allowed by at least one AuthenticationMethods
437  * methods list. Returns 1 if allowed, or no methods lists configured.
438  * 0 otherwise.
439  */
440 int
441 auth2_method_allowed(Authctxt *authctxt, const char *method,
442     const char *submethod)
443 {
444 	u_int i;
445 
446 	/*
447 	 * NB. authctxt->num_auth_methods might be zero as a result of
448 	 * auth2_setup_methods_lists(), so check the configuration.
449 	 */
450 	if (options.num_auth_methods == 0)
451 		return 1;
452 	for (i = 0; i < authctxt->num_auth_methods; i++) {
453 		if (list_starts_with(authctxt->auth_methods[i], method,
454 		    submethod) != MATCH_NONE)
455 			return 1;
456 	}
457 	return 0;
458 }
459 
460 static char *
461 authmethods_get(Authctxt *authctxt)
462 {
463 	struct sshbuf *b;
464 	char *list;
465 	int i, r;
466 
467 	if ((b = sshbuf_new()) == NULL)
468 		fatal("%s: sshbuf_new failed", __func__);
469 	for (i = 0; authmethods[i] != NULL; i++) {
470 		if (strcmp(authmethods[i]->name, "none") == 0)
471 			continue;
472 		if (authmethods[i]->enabled == NULL ||
473 		    *(authmethods[i]->enabled) == 0)
474 			continue;
475 		if (!auth2_method_allowed(authctxt, authmethods[i]->name,
476 		    NULL))
477 			continue;
478 		if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) ? "," : "",
479 		    authmethods[i]->name)) != 0)
480 			fatal("%s: buffer error: %s", __func__, ssh_err(r));
481 	}
482 	if ((list = sshbuf_dup_string(b)) == NULL)
483 		fatal("%s: sshbuf_dup_string failed", __func__);
484 	sshbuf_free(b);
485 	return list;
486 }
487 
488 static Authmethod *
489 authmethod_lookup(Authctxt *authctxt, const char *name)
490 {
491 	int i;
492 
493 	if (name != NULL)
494 		for (i = 0; authmethods[i] != NULL; i++)
495 			if (authmethods[i]->enabled != NULL &&
496 			    *(authmethods[i]->enabled) != 0 &&
497 			    strcmp(name, authmethods[i]->name) == 0 &&
498 			    auth2_method_allowed(authctxt,
499 			    authmethods[i]->name, NULL))
500 				return authmethods[i];
501 	debug2("Unrecognized authentication method name: %s",
502 	    name ? name : "NULL");
503 	return NULL;
504 }
505 
506 /*
507  * Check a comma-separated list of methods for validity. Is need_enable is
508  * non-zero, then also require that the methods are enabled.
509  * Returns 0 on success or -1 if the methods list is invalid.
510  */
511 int
512 auth2_methods_valid(const char *_methods, int need_enable)
513 {
514 	char *methods, *omethods, *method, *p;
515 	u_int i, found;
516 	int ret = -1;
517 
518 	if (*_methods == '\0') {
519 		error("empty authentication method list");
520 		return -1;
521 	}
522 	omethods = methods = xstrdup(_methods);
523 	while ((method = strsep(&methods, ",")) != NULL) {
524 		for (found = i = 0; !found && authmethods[i] != NULL; i++) {
525 			if ((p = strchr(method, ':')) != NULL)
526 				*p = '\0';
527 			if (strcmp(method, authmethods[i]->name) != 0)
528 				continue;
529 			if (need_enable) {
530 				if (authmethods[i]->enabled == NULL ||
531 				    *(authmethods[i]->enabled) == 0) {
532 					error("Disabled method \"%s\" in "
533 					    "AuthenticationMethods list \"%s\"",
534 					    method, _methods);
535 					goto out;
536 				}
537 			}
538 			found = 1;
539 			break;
540 		}
541 		if (!found) {
542 			error("Unknown authentication method \"%s\" in list",
543 			    method);
544 			goto out;
545 		}
546 	}
547 	ret = 0;
548  out:
549 	free(omethods);
550 	return ret;
551 }
552 
553 /*
554  * Prune the AuthenticationMethods supplied in the configuration, removing
555  * any methods lists that include disabled methods. Note that this might
556  * leave authctxt->num_auth_methods == 0, even when multiple required auth
557  * has been requested. For this reason, all tests for whether multiple is
558  * enabled should consult options.num_auth_methods directly.
559  */
560 int
561 auth2_setup_methods_lists(Authctxt *authctxt)
562 {
563 	u_int i;
564 
565 	if (options.num_auth_methods == 0)
566 		return 0;
567 	debug3("%s: checking methods", __func__);
568 	authctxt->auth_methods = xcalloc(options.num_auth_methods,
569 	    sizeof(*authctxt->auth_methods));
570 	authctxt->num_auth_methods = 0;
571 	for (i = 0; i < options.num_auth_methods; i++) {
572 		if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {
573 			logit("Authentication methods list \"%s\" contains "
574 			    "disabled method, skipping",
575 			    options.auth_methods[i]);
576 			continue;
577 		}
578 		debug("authentication methods list %d: %s",
579 		    authctxt->num_auth_methods, options.auth_methods[i]);
580 		authctxt->auth_methods[authctxt->num_auth_methods++] =
581 		    xstrdup(options.auth_methods[i]);
582 	}
583 	if (authctxt->num_auth_methods == 0) {
584 		error("No AuthenticationMethods left after eliminating "
585 		    "disabled methods");
586 		return -1;
587 	}
588 	return 0;
589 }
590 
591 static int
592 list_starts_with(const char *methods, const char *method,
593     const char *submethod)
594 {
595 	size_t l = strlen(method);
596 	int match;
597 	const char *p;
598 
599 	if (strncmp(methods, method, l) != 0)
600 		return MATCH_NONE;
601 	p = methods + l;
602 	match = MATCH_METHOD;
603 	if (*p == ':') {
604 		if (!submethod)
605 			return MATCH_PARTIAL;
606 		l = strlen(submethod);
607 		p += 1;
608 		if (strncmp(submethod, p, l))
609 			return MATCH_NONE;
610 		p += l;
611 		match = MATCH_BOTH;
612 	}
613 	if (*p != ',' && *p != '\0')
614 		return MATCH_NONE;
615 	return match;
616 }
617 
618 /*
619  * Remove method from the start of a comma-separated list of methods.
620  * Returns 0 if the list of methods did not start with that method or 1
621  * if it did.
622  */
623 static int
624 remove_method(char **methods, const char *method, const char *submethod)
625 {
626 	char *omethods = *methods, *p;
627 	size_t l = strlen(method);
628 	int match;
629 
630 	match = list_starts_with(omethods, method, submethod);
631 	if (match != MATCH_METHOD && match != MATCH_BOTH)
632 		return 0;
633 	p = omethods + l;
634 	if (submethod && match == MATCH_BOTH)
635 		p += 1 + strlen(submethod); /* include colon */
636 	if (*p == ',')
637 		p++;
638 	*methods = xstrdup(p);
639 	free(omethods);
640 	return 1;
641 }
642 
643 /*
644  * Called after successful authentication. Will remove the successful method
645  * from the start of each list in which it occurs. If it was the last method
646  * in any list, then authentication is deemed successful.
647  * Returns 1 if the method completed any authentication list or 0 otherwise.
648  */
649 int
650 auth2_update_methods_lists(Authctxt *authctxt, const char *method,
651     const char *submethod)
652 {
653 	u_int i, found = 0;
654 
655 	debug3("%s: updating methods list after \"%s\"", __func__, method);
656 	for (i = 0; i < authctxt->num_auth_methods; i++) {
657 		if (!remove_method(&(authctxt->auth_methods[i]), method,
658 		    submethod))
659 			continue;
660 		found = 1;
661 		if (*authctxt->auth_methods[i] == '\0') {
662 			debug2("authentication methods list %d complete", i);
663 			return 1;
664 		}
665 		debug3("authentication methods list %d remaining: \"%s\"",
666 		    i, authctxt->auth_methods[i]);
667 	}
668 	/* This should not happen, but would be bad if it did */
669 	if (!found)
670 		fatal("%s: method not in AuthenticationMethods", __func__);
671 	return 0;
672 }
673 
674 /* Reset method-specific information */
675 void auth2_authctxt_reset_info(Authctxt *authctxt)
676 {
677 	sshkey_free(authctxt->auth_method_key);
678 	free(authctxt->auth_method_info);
679 	authctxt->auth_method_key = NULL;
680 	authctxt->auth_method_info = NULL;
681 }
682 
683 /* Record auth method-specific information for logs */
684 void
685 auth2_record_info(Authctxt *authctxt, const char *fmt, ...)
686 {
687 	va_list ap;
688         int i;
689 
690 	free(authctxt->auth_method_info);
691 	authctxt->auth_method_info = NULL;
692 
693 	va_start(ap, fmt);
694 	i = vasprintf(&authctxt->auth_method_info, fmt, ap);
695 	va_end(ap);
696 
697 	if (i < 0 || authctxt->auth_method_info == NULL)
698 		fatal("%s: vasprintf failed", __func__);
699 }
700 
701 /*
702  * Records a public key used in authentication. This is used for logging
703  * and to ensure that the same key is not subsequently accepted again for
704  * multiple authentication.
705  */
706 void
707 auth2_record_key(Authctxt *authctxt, int authenticated,
708     const struct sshkey *key)
709 {
710 	struct sshkey **tmp, *dup;
711 	int r;
712 
713 	if ((r = sshkey_from_private(key, &dup)) != 0)
714 		fatal("%s: copy key: %s", __func__, ssh_err(r));
715 	sshkey_free(authctxt->auth_method_key);
716 	authctxt->auth_method_key = dup;
717 
718 	if (!authenticated)
719 		return;
720 
721 	/* If authenticated, make sure we don't accept this key again */
722 	if ((r = sshkey_from_private(key, &dup)) != 0)
723 		fatal("%s: copy key: %s", __func__, ssh_err(r));
724 	if (authctxt->nprev_keys >= INT_MAX ||
725 	    (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,
726 	    authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)
727 		fatal("%s: reallocarray failed", __func__);
728 	authctxt->prev_keys = tmp;
729 	authctxt->prev_keys[authctxt->nprev_keys] = dup;
730 	authctxt->nprev_keys++;
731 
732 }
733 
734 /* Checks whether a key has already been previously used for authentication */
735 int
736 auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key)
737 {
738 	u_int i;
739 	char *fp;
740 
741 	for (i = 0; i < authctxt->nprev_keys; i++) {
742 		if (sshkey_equal_public(key, authctxt->prev_keys[i])) {
743 			fp = sshkey_fingerprint(authctxt->prev_keys[i],
744 			    options.fingerprint_hash, SSH_FP_DEFAULT);
745 			debug3("%s: key already used: %s %s", __func__,
746 			    sshkey_type(authctxt->prev_keys[i]),
747 			    fp == NULL ? "UNKNOWN" : fp);
748 			free(fp);
749 			return 1;
750 		}
751 	}
752 	return 0;
753 }
754 
755 /*
756  * Updates authctxt->session_info with details of authentication. Should be
757  * whenever an authentication method succeeds.
758  */
759 void
760 auth2_update_session_info(Authctxt *authctxt, const char *method,
761     const char *submethod)
762 {
763 	int r;
764 
765 	if (authctxt->session_info == NULL) {
766 		if ((authctxt->session_info = sshbuf_new()) == NULL)
767 			fatal("%s: sshbuf_new", __func__);
768 	}
769 
770 	/* Append method[/submethod] */
771 	if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",
772 	    method, submethod == NULL ? "" : "/",
773 	    submethod == NULL ? "" : submethod)) != 0)
774 		fatal("%s: append method: %s", __func__, ssh_err(r));
775 
776 	/* Append key if present */
777 	if (authctxt->auth_method_key != NULL) {
778 		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
779 		    (r = sshkey_format_text(authctxt->auth_method_key,
780 		    authctxt->session_info)) != 0)
781 			fatal("%s: append key: %s", __func__, ssh_err(r));
782 	}
783 
784 	if (authctxt->auth_method_info != NULL) {
785 		/* Ensure no ambiguity here */
786 		if (strchr(authctxt->auth_method_info, '\n') != NULL)
787 			fatal("%s: auth_method_info contains \\n", __func__);
788 		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
789 		    (r = sshbuf_putf(authctxt->session_info, "%s",
790 		    authctxt->auth_method_info)) != 0) {
791 			fatal("%s: append method info: %s",
792 			    __func__, ssh_err(r));
793 		}
794 	}
795 	if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)
796 		fatal("%s: append: %s", __func__, ssh_err(r));
797 }
798 
799