xref: /openssh-portable/auth2.c (revision c7d39ac8)
1 /* $OpenBSD: auth2.c,v 1.148 2018/07/09 21:35:50 markus 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 
39 #include "atomicio.h"
40 #include "xmalloc.h"
41 #include "ssh2.h"
42 #include "packet.h"
43 #include "log.h"
44 #include "sshbuf.h"
45 #include "misc.h"
46 #include "servconf.h"
47 #include "compat.h"
48 #include "key.h"
49 #include "hostfile.h"
50 #include "auth.h"
51 #include "dispatch.h"
52 #include "pathnames.h"
53 #include "buffer.h"
54 
55 #ifdef GSSAPI
56 #include "ssh-gss.h"
57 #endif
58 #include "monitor_wrap.h"
59 #include "ssherr.h"
60 #include "digest.h"
61 
62 /* import */
63 extern ServerOptions options;
64 extern u_char *session_id2;
65 extern u_int session_id2_len;
66 extern Buffer loginmsg;
67 
68 /* methods */
69 
70 extern Authmethod method_none;
71 extern Authmethod method_pubkey;
72 extern Authmethod method_passwd;
73 extern Authmethod method_kbdint;
74 extern Authmethod method_hostbased;
75 #ifdef GSSAPI
76 extern Authmethod method_gssapi;
77 #endif
78 
79 Authmethod *authmethods[] = {
80 	&method_none,
81 	&method_pubkey,
82 #ifdef GSSAPI
83 	&method_gssapi,
84 #endif
85 	&method_passwd,
86 	&method_kbdint,
87 	&method_hostbased,
88 	NULL
89 };
90 
91 /* protocol */
92 
93 static int input_service_request(int, u_int32_t, struct ssh *);
94 static int input_userauth_request(int, u_int32_t, struct ssh *);
95 
96 /* helper */
97 static Authmethod *authmethod_lookup(Authctxt *, const char *);
98 static char *authmethods_get(Authctxt *authctxt);
99 
100 #define MATCH_NONE	0	/* method or submethod mismatch */
101 #define MATCH_METHOD	1	/* method matches (no submethod specified) */
102 #define MATCH_BOTH	2	/* method and submethod match */
103 #define MATCH_PARTIAL	3	/* method matches, submethod can't be checked */
104 static int list_starts_with(const char *, const char *, const char *);
105 
106 char *
107 auth2_read_banner(void)
108 {
109 	struct stat st;
110 	char *banner = NULL;
111 	size_t len, n;
112 	int fd;
113 
114 	if ((fd = open(options.banner, O_RDONLY)) == -1)
115 		return (NULL);
116 	if (fstat(fd, &st) == -1) {
117 		close(fd);
118 		return (NULL);
119 	}
120 	if (st.st_size <= 0 || st.st_size > 1*1024*1024) {
121 		close(fd);
122 		return (NULL);
123 	}
124 
125 	len = (size_t)st.st_size;		/* truncate */
126 	banner = xmalloc(len + 1);
127 	n = atomicio(read, fd, banner, len);
128 	close(fd);
129 
130 	if (n != len) {
131 		free(banner);
132 		return (NULL);
133 	}
134 	banner[n] = '\0';
135 
136 	return (banner);
137 }
138 
139 void
140 userauth_send_banner(const char *msg)
141 {
142 	packet_start(SSH2_MSG_USERAUTH_BANNER);
143 	packet_put_cstring(msg);
144 	packet_put_cstring("");		/* language, unused */
145 	packet_send();
146 	debug("%s: sent", __func__);
147 }
148 
149 static void
150 userauth_banner(void)
151 {
152 	char *banner = NULL;
153 
154 	if (options.banner == NULL)
155 		return;
156 
157 	if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
158 		goto done;
159 	userauth_send_banner(banner);
160 
161 done:
162 	free(banner);
163 }
164 
165 /*
166  * loop until authctxt->success == TRUE
167  */
168 void
169 do_authentication2(Authctxt *authctxt)
170 {
171 	struct ssh *ssh = active_state;		/* XXX */
172 	ssh->authctxt = authctxt;		/* XXX move to caller */
173 	ssh_dispatch_init(ssh, &dispatch_protocol_error);
174 	ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_REQUEST, &input_service_request);
175 	ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt->success);
176 	ssh->authctxt = NULL;
177 }
178 
179 /*ARGSUSED*/
180 static int
181 input_service_request(int type, u_int32_t seq, struct ssh *ssh)
182 {
183 	Authctxt *authctxt = ssh->authctxt;
184 	u_int len;
185 	int acceptit = 0;
186 	char *service = packet_get_cstring(&len);
187 	packet_check_eom();
188 
189 	if (authctxt == NULL)
190 		fatal("input_service_request: no authctxt");
191 
192 	if (strcmp(service, "ssh-userauth") == 0) {
193 		if (!authctxt->success) {
194 			acceptit = 1;
195 			/* now we can handle user-auth requests */
196 			ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
197 		}
198 	}
199 	/* XXX all other service requests are denied */
200 
201 	if (acceptit) {
202 		packet_start(SSH2_MSG_SERVICE_ACCEPT);
203 		packet_put_cstring(service);
204 		packet_send();
205 		packet_write_wait();
206 	} else {
207 		debug("bad service request %s", service);
208 		packet_disconnect("bad service request %s", service);
209 	}
210 	free(service);
211 	return 0;
212 }
213 
214 #define MIN_FAIL_DELAY_SECONDS 0.005
215 static double
216 user_specific_delay(const char *user)
217 {
218 	char b[512];
219 	size_t len = ssh_digest_bytes(SSH_DIGEST_SHA512);
220 	u_char *hash = xmalloc(len);
221 	double delay;
222 
223 	(void)snprintf(b, sizeof b, "%llu%s",
224 	     (unsigned long long)options.timing_secret, user);
225 	if (ssh_digest_memory(SSH_DIGEST_SHA512, b, strlen(b), hash, len) != 0)
226 		fatal("%s: ssh_digest_memory", __func__);
227 	/* 0-4.2 ms of delay */
228 	delay = (double)PEEK_U32(hash) / 1000 / 1000 / 1000 / 1000;
229 	freezero(hash, len);
230 	debug3("%s: user specific delay %0.3lfms", __func__, delay/1000);
231 	return MIN_FAIL_DELAY_SECONDS + delay;
232 }
233 
234 static void
235 ensure_minimum_time_since(double start, double seconds)
236 {
237 	struct timespec ts;
238 	double elapsed = monotime_double() - start, req = seconds, remain;
239 
240 	/* if we've already passed the requested time, scale up */
241 	while ((remain = seconds - elapsed) < 0.0)
242 		seconds *= 2;
243 
244 	ts.tv_sec = remain;
245 	ts.tv_nsec = (remain - ts.tv_sec) * 1000000000;
246 	debug3("%s: elapsed %0.3lfms, delaying %0.3lfms (requested %0.3lfms)",
247 	    __func__, elapsed*1000, remain*1000, req*1000);
248 	nanosleep(&ts, NULL);
249 }
250 
251 /*ARGSUSED*/
252 static int
253 input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)
254 {
255 	Authctxt *authctxt = ssh->authctxt;
256 	Authmethod *m = NULL;
257 	char *user, *service, *method, *style = NULL;
258 	int authenticated = 0;
259 	double tstart = monotime_double();
260 
261 	if (authctxt == NULL)
262 		fatal("input_userauth_request: no authctxt");
263 
264 	user = packet_get_cstring(NULL);
265 	service = packet_get_cstring(NULL);
266 	method = packet_get_cstring(NULL);
267 	debug("userauth-request for user %s service %s method %s", user, service, method);
268 	debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
269 
270 	if ((style = strchr(user, ':')) != NULL)
271 		*style++ = 0;
272 
273 	if (authctxt->attempt++ == 0) {
274 		/* setup auth context */
275 		authctxt->pw = PRIVSEP(getpwnamallow(user));
276 		authctxt->user = xstrdup(user);
277 		if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
278 			authctxt->valid = 1;
279 			debug2("%s: setting up authctxt for %s",
280 			    __func__, user);
281 		} else {
282 			/* Invalid user, fake password information */
283 			authctxt->pw = fakepw();
284 #ifdef SSH_AUDIT_EVENTS
285 			PRIVSEP(audit_event(SSH_INVALID_USER));
286 #endif
287 		}
288 #ifdef USE_PAM
289 		if (options.use_pam)
290 			PRIVSEP(start_pam(authctxt));
291 #endif
292 		ssh_packet_set_log_preamble(ssh, "%suser %s",
293 		    authctxt->valid ? "authenticating " : "invalid ", user);
294 		setproctitle("%s%s", authctxt->valid ? user : "unknown",
295 		    use_privsep ? " [net]" : "");
296 		authctxt->service = xstrdup(service);
297 		authctxt->style = style ? xstrdup(style) : NULL;
298 		if (use_privsep)
299 			mm_inform_authserv(service, style);
300 		userauth_banner();
301 		if (auth2_setup_methods_lists(authctxt) != 0)
302 			packet_disconnect("no authentication methods enabled");
303 	} else if (strcmp(user, authctxt->user) != 0 ||
304 	    strcmp(service, authctxt->service) != 0) {
305 		packet_disconnect("Change of username or service not allowed: "
306 		    "(%s,%s) -> (%s,%s)",
307 		    authctxt->user, authctxt->service, user, service);
308 	}
309 	/* reset state */
310 	auth2_challenge_stop(ssh);
311 
312 #ifdef GSSAPI
313 	/* XXX move to auth2_gssapi_stop() */
314 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
315 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
316 #endif
317 
318 	auth2_authctxt_reset_info(authctxt);
319 	authctxt->postponed = 0;
320 	authctxt->server_caused_failure = 0;
321 
322 	/* try to authenticate user */
323 	m = authmethod_lookup(authctxt, method);
324 	if (m != NULL && authctxt->failures < options.max_authtries) {
325 		debug2("input_userauth_request: try method %s", method);
326 		authenticated =	m->userauth(ssh);
327 	}
328 	if (!authctxt->authenticated)
329 		ensure_minimum_time_since(tstart,
330 		    user_specific_delay(authctxt->user));
331 	userauth_finish(ssh, authenticated, method, NULL);
332 
333 	free(service);
334 	free(user);
335 	free(method);
336 	return 0;
337 }
338 
339 void
340 userauth_finish(struct ssh *ssh, int authenticated, const char *method,
341     const char *submethod)
342 {
343 	Authctxt *authctxt = ssh->authctxt;
344 	char *methods;
345 	int partial = 0;
346 
347 	if (!authctxt->valid && authenticated)
348 		fatal("INTERNAL ERROR: authenticated invalid user %s",
349 		    authctxt->user);
350 	if (authenticated && authctxt->postponed)
351 		fatal("INTERNAL ERROR: authenticated and postponed");
352 
353 	/* Special handling for root */
354 	if (authenticated && authctxt->pw->pw_uid == 0 &&
355 	    !auth_root_allowed(ssh, method)) {
356 		authenticated = 0;
357 #ifdef SSH_AUDIT_EVENTS
358 		PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
359 #endif
360 	}
361 
362 	if (authenticated && options.num_auth_methods != 0) {
363 		if (!auth2_update_methods_lists(authctxt, method, submethod)) {
364 			authenticated = 0;
365 			partial = 1;
366 		}
367 	}
368 
369 	/* Log before sending the reply */
370 	auth_log(authctxt, authenticated, partial, method, submethod);
371 
372 	/* Update information exposed to session */
373 	if (authenticated || partial)
374 		auth2_update_session_info(authctxt, method, submethod);
375 
376 	if (authctxt->postponed)
377 		return;
378 
379 #ifdef USE_PAM
380 	if (options.use_pam && authenticated) {
381 		if (!PRIVSEP(do_pam_account())) {
382 			/* if PAM returned a message, send it to the user */
383 			if (buffer_len(&loginmsg) > 0) {
384 				buffer_append(&loginmsg, "\0", 1);
385 				userauth_send_banner(buffer_ptr(&loginmsg));
386 				packet_write_wait();
387 			}
388 			fatal("Access denied for user %s by PAM account "
389 			    "configuration", authctxt->user);
390 		}
391 	}
392 #endif
393 
394 	if (authenticated == 1) {
395 		/* turn off userauth */
396 		ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
397 		packet_start(SSH2_MSG_USERAUTH_SUCCESS);
398 		packet_send();
399 		packet_write_wait();
400 		/* now we can break out */
401 		authctxt->success = 1;
402 		ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
403 	} else {
404 		/* Allow initial try of "none" auth without failure penalty */
405 		if (!partial && !authctxt->server_caused_failure &&
406 		    (authctxt->attempt > 1 || strcmp(method, "none") != 0))
407 			authctxt->failures++;
408 		if (authctxt->failures >= options.max_authtries) {
409 #ifdef SSH_AUDIT_EVENTS
410 			PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
411 #endif
412 			auth_maxtries_exceeded(authctxt);
413 		}
414 		methods = authmethods_get(authctxt);
415 		debug3("%s: failure partial=%d next methods=\"%s\"", __func__,
416 		    partial, methods);
417 		packet_start(SSH2_MSG_USERAUTH_FAILURE);
418 		packet_put_cstring(methods);
419 		packet_put_char(partial);
420 		packet_send();
421 		packet_write_wait();
422 		free(methods);
423 	}
424 }
425 
426 /*
427  * Checks whether method is allowed by at least one AuthenticationMethods
428  * methods list. Returns 1 if allowed, or no methods lists configured.
429  * 0 otherwise.
430  */
431 int
432 auth2_method_allowed(Authctxt *authctxt, const char *method,
433     const char *submethod)
434 {
435 	u_int i;
436 
437 	/*
438 	 * NB. authctxt->num_auth_methods might be zero as a result of
439 	 * auth2_setup_methods_lists(), so check the configuration.
440 	 */
441 	if (options.num_auth_methods == 0)
442 		return 1;
443 	for (i = 0; i < authctxt->num_auth_methods; i++) {
444 		if (list_starts_with(authctxt->auth_methods[i], method,
445 		    submethod) != MATCH_NONE)
446 			return 1;
447 	}
448 	return 0;
449 }
450 
451 static char *
452 authmethods_get(Authctxt *authctxt)
453 {
454 	struct sshbuf *b;
455 	char *list;
456 	int i, r;
457 
458 	if ((b = sshbuf_new()) == NULL)
459 		fatal("%s: sshbuf_new failed", __func__);
460 	for (i = 0; authmethods[i] != NULL; i++) {
461 		if (strcmp(authmethods[i]->name, "none") == 0)
462 			continue;
463 		if (authmethods[i]->enabled == NULL ||
464 		    *(authmethods[i]->enabled) == 0)
465 			continue;
466 		if (!auth2_method_allowed(authctxt, authmethods[i]->name,
467 		    NULL))
468 			continue;
469 		if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) ? "," : "",
470 		    authmethods[i]->name)) != 0)
471 			fatal("%s: buffer error: %s", __func__, ssh_err(r));
472 	}
473 	if ((list = sshbuf_dup_string(b)) == NULL)
474 		fatal("%s: sshbuf_dup_string failed", __func__);
475 	sshbuf_free(b);
476 	return list;
477 }
478 
479 static Authmethod *
480 authmethod_lookup(Authctxt *authctxt, const char *name)
481 {
482 	int i;
483 
484 	if (name != NULL)
485 		for (i = 0; authmethods[i] != NULL; i++)
486 			if (authmethods[i]->enabled != NULL &&
487 			    *(authmethods[i]->enabled) != 0 &&
488 			    strcmp(name, authmethods[i]->name) == 0 &&
489 			    auth2_method_allowed(authctxt,
490 			    authmethods[i]->name, NULL))
491 				return authmethods[i];
492 	debug2("Unrecognized authentication method name: %s",
493 	    name ? name : "NULL");
494 	return NULL;
495 }
496 
497 /*
498  * Check a comma-separated list of methods for validity. Is need_enable is
499  * non-zero, then also require that the methods are enabled.
500  * Returns 0 on success or -1 if the methods list is invalid.
501  */
502 int
503 auth2_methods_valid(const char *_methods, int need_enable)
504 {
505 	char *methods, *omethods, *method, *p;
506 	u_int i, found;
507 	int ret = -1;
508 
509 	if (*_methods == '\0') {
510 		error("empty authentication method list");
511 		return -1;
512 	}
513 	omethods = methods = xstrdup(_methods);
514 	while ((method = strsep(&methods, ",")) != NULL) {
515 		for (found = i = 0; !found && authmethods[i] != NULL; i++) {
516 			if ((p = strchr(method, ':')) != NULL)
517 				*p = '\0';
518 			if (strcmp(method, authmethods[i]->name) != 0)
519 				continue;
520 			if (need_enable) {
521 				if (authmethods[i]->enabled == NULL ||
522 				    *(authmethods[i]->enabled) == 0) {
523 					error("Disabled method \"%s\" in "
524 					    "AuthenticationMethods list \"%s\"",
525 					    method, _methods);
526 					goto out;
527 				}
528 			}
529 			found = 1;
530 			break;
531 		}
532 		if (!found) {
533 			error("Unknown authentication method \"%s\" in list",
534 			    method);
535 			goto out;
536 		}
537 	}
538 	ret = 0;
539  out:
540 	free(omethods);
541 	return ret;
542 }
543 
544 /*
545  * Prune the AuthenticationMethods supplied in the configuration, removing
546  * any methods lists that include disabled methods. Note that this might
547  * leave authctxt->num_auth_methods == 0, even when multiple required auth
548  * has been requested. For this reason, all tests for whether multiple is
549  * enabled should consult options.num_auth_methods directly.
550  */
551 int
552 auth2_setup_methods_lists(Authctxt *authctxt)
553 {
554 	u_int i;
555 
556 	if (options.num_auth_methods == 0)
557 		return 0;
558 	debug3("%s: checking methods", __func__);
559 	authctxt->auth_methods = xcalloc(options.num_auth_methods,
560 	    sizeof(*authctxt->auth_methods));
561 	authctxt->num_auth_methods = 0;
562 	for (i = 0; i < options.num_auth_methods; i++) {
563 		if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {
564 			logit("Authentication methods list \"%s\" contains "
565 			    "disabled method, skipping",
566 			    options.auth_methods[i]);
567 			continue;
568 		}
569 		debug("authentication methods list %d: %s",
570 		    authctxt->num_auth_methods, options.auth_methods[i]);
571 		authctxt->auth_methods[authctxt->num_auth_methods++] =
572 		    xstrdup(options.auth_methods[i]);
573 	}
574 	if (authctxt->num_auth_methods == 0) {
575 		error("No AuthenticationMethods left after eliminating "
576 		    "disabled methods");
577 		return -1;
578 	}
579 	return 0;
580 }
581 
582 static int
583 list_starts_with(const char *methods, const char *method,
584     const char *submethod)
585 {
586 	size_t l = strlen(method);
587 	int match;
588 	const char *p;
589 
590 	if (strncmp(methods, method, l) != 0)
591 		return MATCH_NONE;
592 	p = methods + l;
593 	match = MATCH_METHOD;
594 	if (*p == ':') {
595 		if (!submethod)
596 			return MATCH_PARTIAL;
597 		l = strlen(submethod);
598 		p += 1;
599 		if (strncmp(submethod, p, l))
600 			return MATCH_NONE;
601 		p += l;
602 		match = MATCH_BOTH;
603 	}
604 	if (*p != ',' && *p != '\0')
605 		return MATCH_NONE;
606 	return match;
607 }
608 
609 /*
610  * Remove method from the start of a comma-separated list of methods.
611  * Returns 0 if the list of methods did not start with that method or 1
612  * if it did.
613  */
614 static int
615 remove_method(char **methods, const char *method, const char *submethod)
616 {
617 	char *omethods = *methods, *p;
618 	size_t l = strlen(method);
619 	int match;
620 
621 	match = list_starts_with(omethods, method, submethod);
622 	if (match != MATCH_METHOD && match != MATCH_BOTH)
623 		return 0;
624 	p = omethods + l;
625 	if (submethod && match == MATCH_BOTH)
626 		p += 1 + strlen(submethod); /* include colon */
627 	if (*p == ',')
628 		p++;
629 	*methods = xstrdup(p);
630 	free(omethods);
631 	return 1;
632 }
633 
634 /*
635  * Called after successful authentication. Will remove the successful method
636  * from the start of each list in which it occurs. If it was the last method
637  * in any list, then authentication is deemed successful.
638  * Returns 1 if the method completed any authentication list or 0 otherwise.
639  */
640 int
641 auth2_update_methods_lists(Authctxt *authctxt, const char *method,
642     const char *submethod)
643 {
644 	u_int i, found = 0;
645 
646 	debug3("%s: updating methods list after \"%s\"", __func__, method);
647 	for (i = 0; i < authctxt->num_auth_methods; i++) {
648 		if (!remove_method(&(authctxt->auth_methods[i]), method,
649 		    submethod))
650 			continue;
651 		found = 1;
652 		if (*authctxt->auth_methods[i] == '\0') {
653 			debug2("authentication methods list %d complete", i);
654 			return 1;
655 		}
656 		debug3("authentication methods list %d remaining: \"%s\"",
657 		    i, authctxt->auth_methods[i]);
658 	}
659 	/* This should not happen, but would be bad if it did */
660 	if (!found)
661 		fatal("%s: method not in AuthenticationMethods", __func__);
662 	return 0;
663 }
664 
665 /* Reset method-specific information */
666 void auth2_authctxt_reset_info(Authctxt *authctxt)
667 {
668 	sshkey_free(authctxt->auth_method_key);
669 	free(authctxt->auth_method_info);
670 	authctxt->auth_method_key = NULL;
671 	authctxt->auth_method_info = NULL;
672 }
673 
674 /* Record auth method-specific information for logs */
675 void
676 auth2_record_info(Authctxt *authctxt, const char *fmt, ...)
677 {
678 	va_list ap;
679         int i;
680 
681 	free(authctxt->auth_method_info);
682 	authctxt->auth_method_info = NULL;
683 
684 	va_start(ap, fmt);
685 	i = vasprintf(&authctxt->auth_method_info, fmt, ap);
686 	va_end(ap);
687 
688 	if (i < 0 || authctxt->auth_method_info == NULL)
689 		fatal("%s: vasprintf failed", __func__);
690 }
691 
692 /*
693  * Records a public key used in authentication. This is used for logging
694  * and to ensure that the same key is not subsequently accepted again for
695  * multiple authentication.
696  */
697 void
698 auth2_record_key(Authctxt *authctxt, int authenticated,
699     const struct sshkey *key)
700 {
701 	struct sshkey **tmp, *dup;
702 	int r;
703 
704 	if ((r = sshkey_demote(key, &dup)) != 0)
705 		fatal("%s: copy key: %s", __func__, ssh_err(r));
706 	sshkey_free(authctxt->auth_method_key);
707 	authctxt->auth_method_key = dup;
708 
709 	if (!authenticated)
710 		return;
711 
712 	/* If authenticated, make sure we don't accept this key again */
713 	if ((r = sshkey_demote(key, &dup)) != 0)
714 		fatal("%s: copy key: %s", __func__, ssh_err(r));
715 	if (authctxt->nprev_keys >= INT_MAX ||
716 	    (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,
717 	    authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)
718 		fatal("%s: reallocarray failed", __func__);
719 	authctxt->prev_keys = tmp;
720 	authctxt->prev_keys[authctxt->nprev_keys] = dup;
721 	authctxt->nprev_keys++;
722 
723 }
724 
725 /* Checks whether a key has already been previously used for authentication */
726 int
727 auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key)
728 {
729 	u_int i;
730 	char *fp;
731 
732 	for (i = 0; i < authctxt->nprev_keys; i++) {
733 		if (sshkey_equal_public(key, authctxt->prev_keys[i])) {
734 			fp = sshkey_fingerprint(authctxt->prev_keys[i],
735 			    options.fingerprint_hash, SSH_FP_DEFAULT);
736 			debug3("%s: key already used: %s %s", __func__,
737 			    sshkey_type(authctxt->prev_keys[i]),
738 			    fp == NULL ? "UNKNOWN" : fp);
739 			free(fp);
740 			return 1;
741 		}
742 	}
743 	return 0;
744 }
745 
746 /*
747  * Updates authctxt->session_info with details of authentication. Should be
748  * whenever an authentication method succeeds.
749  */
750 void
751 auth2_update_session_info(Authctxt *authctxt, const char *method,
752     const char *submethod)
753 {
754 	int r;
755 
756 	if (authctxt->session_info == NULL) {
757 		if ((authctxt->session_info = sshbuf_new()) == NULL)
758 			fatal("%s: sshbuf_new", __func__);
759 	}
760 
761 	/* Append method[/submethod] */
762 	if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",
763 	    method, submethod == NULL ? "" : "/",
764 	    submethod == NULL ? "" : submethod)) != 0)
765 		fatal("%s: append method: %s", __func__, ssh_err(r));
766 
767 	/* Append key if present */
768 	if (authctxt->auth_method_key != NULL) {
769 		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
770 		    (r = sshkey_format_text(authctxt->auth_method_key,
771 		    authctxt->session_info)) != 0)
772 			fatal("%s: append key: %s", __func__, ssh_err(r));
773 	}
774 
775 	if (authctxt->auth_method_info != NULL) {
776 		/* Ensure no ambiguity here */
777 		if (strchr(authctxt->auth_method_info, '\n') != NULL)
778 			fatal("%s: auth_method_info contains \\n", __func__);
779 		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
780 		    (r = sshbuf_putf(authctxt->session_info, "%s",
781 		    authctxt->auth_method_info)) != 0) {
782 			fatal("%s: append method info: %s",
783 			    __func__, ssh_err(r));
784 		}
785 	}
786 	if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)
787 		fatal("%s: append: %s", __func__, ssh_err(r));
788 }
789 
790