xref: /openssh-portable/auth2.c (revision 5467fbcb)
1 /* $OpenBSD: auth2.c,v 1.149 2018/07/11 18:53:29 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 "sshkey.h"
49 #include "hostfile.h"
50 #include "auth.h"
51 #include "dispatch.h"
52 #include "pathnames.h"
53 #include "sshbuf.h"
54 #include "ssherr.h"
55 
56 #ifdef GSSAPI
57 #include "ssh-gss.h"
58 #endif
59 #include "monitor_wrap.h"
60 #include "ssherr.h"
61 #include "digest.h"
62 
63 /* import */
64 extern ServerOptions options;
65 extern u_char *session_id2;
66 extern u_int session_id2_len;
67 extern struct sshbuf *loginmsg;
68 
69 /* methods */
70 
71 extern Authmethod method_none;
72 extern Authmethod method_pubkey;
73 extern Authmethod method_passwd;
74 extern Authmethod method_kbdint;
75 extern Authmethod method_hostbased;
76 #ifdef GSSAPI
77 extern Authmethod method_gssapi;
78 #endif
79 
80 Authmethod *authmethods[] = {
81 	&method_none,
82 	&method_pubkey,
83 #ifdef GSSAPI
84 	&method_gssapi,
85 #endif
86 	&method_passwd,
87 	&method_kbdint,
88 	&method_hostbased,
89 	NULL
90 };
91 
92 /* protocol */
93 
94 static int input_service_request(int, u_int32_t, struct ssh *);
95 static int input_userauth_request(int, u_int32_t, struct ssh *);
96 
97 /* helper */
98 static Authmethod *authmethod_lookup(Authctxt *, const char *);
99 static char *authmethods_get(Authctxt *authctxt);
100 
101 #define MATCH_NONE	0	/* method or submethod mismatch */
102 #define MATCH_METHOD	1	/* method matches (no submethod specified) */
103 #define MATCH_BOTH	2	/* method and submethod match */
104 #define MATCH_PARTIAL	3	/* method matches, submethod can't be checked */
105 static int list_starts_with(const char *, const char *, const char *);
106 
107 char *
108 auth2_read_banner(void)
109 {
110 	struct stat st;
111 	char *banner = NULL;
112 	size_t len, n;
113 	int fd;
114 
115 	if ((fd = open(options.banner, O_RDONLY)) == -1)
116 		return (NULL);
117 	if (fstat(fd, &st) == -1) {
118 		close(fd);
119 		return (NULL);
120 	}
121 	if (st.st_size <= 0 || st.st_size > 1*1024*1024) {
122 		close(fd);
123 		return (NULL);
124 	}
125 
126 	len = (size_t)st.st_size;		/* truncate */
127 	banner = xmalloc(len + 1);
128 	n = atomicio(read, fd, banner, len);
129 	close(fd);
130 
131 	if (n != len) {
132 		free(banner);
133 		return (NULL);
134 	}
135 	banner[n] = '\0';
136 
137 	return (banner);
138 }
139 
140 void
141 userauth_send_banner(const char *msg)
142 {
143 	packet_start(SSH2_MSG_USERAUTH_BANNER);
144 	packet_put_cstring(msg);
145 	packet_put_cstring("");		/* language, unused */
146 	packet_send();
147 	debug("%s: sent", __func__);
148 }
149 
150 static void
151 userauth_banner(void)
152 {
153 	char *banner = NULL;
154 
155 	if (options.banner == NULL)
156 		return;
157 
158 	if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
159 		goto done;
160 	userauth_send_banner(banner);
161 
162 done:
163 	free(banner);
164 }
165 
166 /*
167  * loop until authctxt->success == TRUE
168  */
169 void
170 do_authentication2(Authctxt *authctxt)
171 {
172 	struct ssh *ssh = active_state;		/* XXX */
173 	ssh->authctxt = authctxt;		/* XXX move to caller */
174 	ssh_dispatch_init(ssh, &dispatch_protocol_error);
175 	ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_REQUEST, &input_service_request);
176 	ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt->success);
177 	ssh->authctxt = NULL;
178 }
179 
180 /*ARGSUSED*/
181 static int
182 input_service_request(int type, u_int32_t seq, struct ssh *ssh)
183 {
184 	Authctxt *authctxt = ssh->authctxt;
185 	u_int len;
186 	int acceptit = 0;
187 	char *service = packet_get_cstring(&len);
188 	packet_check_eom();
189 
190 	if (authctxt == NULL)
191 		fatal("input_service_request: no authctxt");
192 
193 	if (strcmp(service, "ssh-userauth") == 0) {
194 		if (!authctxt->success) {
195 			acceptit = 1;
196 			/* now we can handle user-auth requests */
197 			ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
198 		}
199 	}
200 	/* XXX all other service requests are denied */
201 
202 	if (acceptit) {
203 		packet_start(SSH2_MSG_SERVICE_ACCEPT);
204 		packet_put_cstring(service);
205 		packet_send();
206 		packet_write_wait();
207 	} else {
208 		debug("bad service request %s", service);
209 		packet_disconnect("bad service request %s", service);
210 	}
211 	free(service);
212 	return 0;
213 }
214 
215 #define MIN_FAIL_DELAY_SECONDS 0.005
216 static double
217 user_specific_delay(const char *user)
218 {
219 	char b[512];
220 	size_t len = ssh_digest_bytes(SSH_DIGEST_SHA512);
221 	u_char *hash = xmalloc(len);
222 	double delay;
223 
224 	(void)snprintf(b, sizeof b, "%llu%s",
225 	     (unsigned long long)options.timing_secret, user);
226 	if (ssh_digest_memory(SSH_DIGEST_SHA512, b, strlen(b), hash, len) != 0)
227 		fatal("%s: ssh_digest_memory", __func__);
228 	/* 0-4.2 ms of delay */
229 	delay = (double)PEEK_U32(hash) / 1000 / 1000 / 1000 / 1000;
230 	freezero(hash, len);
231 	debug3("%s: user specific delay %0.3lfms", __func__, delay/1000);
232 	return MIN_FAIL_DELAY_SECONDS + delay;
233 }
234 
235 static void
236 ensure_minimum_time_since(double start, double seconds)
237 {
238 	struct timespec ts;
239 	double elapsed = monotime_double() - start, req = seconds, remain;
240 
241 	/* if we've already passed the requested time, scale up */
242 	while ((remain = seconds - elapsed) < 0.0)
243 		seconds *= 2;
244 
245 	ts.tv_sec = remain;
246 	ts.tv_nsec = (remain - ts.tv_sec) * 1000000000;
247 	debug3("%s: elapsed %0.3lfms, delaying %0.3lfms (requested %0.3lfms)",
248 	    __func__, elapsed*1000, remain*1000, req*1000);
249 	nanosleep(&ts, NULL);
250 }
251 
252 /*ARGSUSED*/
253 static int
254 input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)
255 {
256 	Authctxt *authctxt = ssh->authctxt;
257 	Authmethod *m = NULL;
258 	char *user, *service, *method, *style = NULL;
259 	int authenticated = 0;
260 	double tstart = monotime_double();
261 
262 	if (authctxt == NULL)
263 		fatal("input_userauth_request: no authctxt");
264 
265 	user = packet_get_cstring(NULL);
266 	service = packet_get_cstring(NULL);
267 	method = packet_get_cstring(NULL);
268 	debug("userauth-request for user %s service %s method %s", user, service, method);
269 	debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
270 
271 	if ((style = strchr(user, ':')) != NULL)
272 		*style++ = 0;
273 
274 	if (authctxt->attempt++ == 0) {
275 		/* setup auth context */
276 		authctxt->pw = PRIVSEP(getpwnamallow(user));
277 		authctxt->user = xstrdup(user);
278 		if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
279 			authctxt->valid = 1;
280 			debug2("%s: setting up authctxt for %s",
281 			    __func__, user);
282 		} else {
283 			/* Invalid user, fake password information */
284 			authctxt->pw = fakepw();
285 #ifdef SSH_AUDIT_EVENTS
286 			PRIVSEP(audit_event(SSH_INVALID_USER));
287 #endif
288 		}
289 #ifdef USE_PAM
290 		if (options.use_pam)
291 			PRIVSEP(start_pam(authctxt));
292 #endif
293 		ssh_packet_set_log_preamble(ssh, "%suser %s",
294 		    authctxt->valid ? "authenticating " : "invalid ", user);
295 		setproctitle("%s%s", authctxt->valid ? user : "unknown",
296 		    use_privsep ? " [net]" : "");
297 		authctxt->service = xstrdup(service);
298 		authctxt->style = style ? xstrdup(style) : NULL;
299 		if (use_privsep)
300 			mm_inform_authserv(service, style);
301 		userauth_banner();
302 		if (auth2_setup_methods_lists(authctxt) != 0)
303 			packet_disconnect("no authentication methods enabled");
304 	} else if (strcmp(user, authctxt->user) != 0 ||
305 	    strcmp(service, authctxt->service) != 0) {
306 		packet_disconnect("Change of username or service not allowed: "
307 		    "(%s,%s) -> (%s,%s)",
308 		    authctxt->user, authctxt->service, user, service);
309 	}
310 	/* reset state */
311 	auth2_challenge_stop(ssh);
312 
313 #ifdef GSSAPI
314 	/* XXX move to auth2_gssapi_stop() */
315 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
316 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
317 #endif
318 
319 	auth2_authctxt_reset_info(authctxt);
320 	authctxt->postponed = 0;
321 	authctxt->server_caused_failure = 0;
322 
323 	/* try to authenticate user */
324 	m = authmethod_lookup(authctxt, method);
325 	if (m != NULL && authctxt->failures < options.max_authtries) {
326 		debug2("input_userauth_request: try method %s", method);
327 		authenticated =	m->userauth(ssh);
328 	}
329 	if (!authctxt->authenticated)
330 		ensure_minimum_time_since(tstart,
331 		    user_specific_delay(authctxt->user));
332 	userauth_finish(ssh, authenticated, method, NULL);
333 
334 	free(service);
335 	free(user);
336 	free(method);
337 	return 0;
338 }
339 
340 void
341 userauth_finish(struct ssh *ssh, int authenticated, const char *method,
342     const char *submethod)
343 {
344 	Authctxt *authctxt = ssh->authctxt;
345 	char *methods;
346 	int partial = 0;
347 
348 	if (!authctxt->valid && authenticated)
349 		fatal("INTERNAL ERROR: authenticated invalid user %s",
350 		    authctxt->user);
351 	if (authenticated && authctxt->postponed)
352 		fatal("INTERNAL ERROR: authenticated and postponed");
353 
354 	/* Special handling for root */
355 	if (authenticated && authctxt->pw->pw_uid == 0 &&
356 	    !auth_root_allowed(ssh, method)) {
357 		authenticated = 0;
358 #ifdef SSH_AUDIT_EVENTS
359 		PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
360 #endif
361 	}
362 
363 	if (authenticated && options.num_auth_methods != 0) {
364 		if (!auth2_update_methods_lists(authctxt, method, submethod)) {
365 			authenticated = 0;
366 			partial = 1;
367 		}
368 	}
369 
370 	/* Log before sending the reply */
371 	auth_log(authctxt, authenticated, partial, method, submethod);
372 
373 	/* Update information exposed to session */
374 	if (authenticated || partial)
375 		auth2_update_session_info(authctxt, method, submethod);
376 
377 	if (authctxt->postponed)
378 		return;
379 
380 #ifdef USE_PAM
381 	if (options.use_pam && authenticated) {
382 		int r;
383 
384 		if (!PRIVSEP(do_pam_account())) {
385 			/* if PAM returned a message, send it to the user */
386 			if (sshbuf_len(loginmsg) > 0) {
387 				if ((r = sshbuf_put(loginmsg, "\0", 1)) != 0)
388 					fatal("%s: buffer error: %s",
389 					    __func__, ssh_err(r));
390 				userauth_send_banner(sshbuf_ptr(loginmsg));
391 				packet_write_wait();
392 			}
393 			fatal("Access denied for user %s by PAM account "
394 			    "configuration", authctxt->user);
395 		}
396 	}
397 #endif
398 
399 	if (authenticated == 1) {
400 		/* turn off userauth */
401 		ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
402 		packet_start(SSH2_MSG_USERAUTH_SUCCESS);
403 		packet_send();
404 		packet_write_wait();
405 		/* now we can break out */
406 		authctxt->success = 1;
407 		ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
408 	} else {
409 		/* Allow initial try of "none" auth without failure penalty */
410 		if (!partial && !authctxt->server_caused_failure &&
411 		    (authctxt->attempt > 1 || strcmp(method, "none") != 0))
412 			authctxt->failures++;
413 		if (authctxt->failures >= options.max_authtries) {
414 #ifdef SSH_AUDIT_EVENTS
415 			PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
416 #endif
417 			auth_maxtries_exceeded(authctxt);
418 		}
419 		methods = authmethods_get(authctxt);
420 		debug3("%s: failure partial=%d next methods=\"%s\"", __func__,
421 		    partial, methods);
422 		packet_start(SSH2_MSG_USERAUTH_FAILURE);
423 		packet_put_cstring(methods);
424 		packet_put_char(partial);
425 		packet_send();
426 		packet_write_wait();
427 		free(methods);
428 	}
429 }
430 
431 /*
432  * Checks whether method is allowed by at least one AuthenticationMethods
433  * methods list. Returns 1 if allowed, or no methods lists configured.
434  * 0 otherwise.
435  */
436 int
437 auth2_method_allowed(Authctxt *authctxt, const char *method,
438     const char *submethod)
439 {
440 	u_int i;
441 
442 	/*
443 	 * NB. authctxt->num_auth_methods might be zero as a result of
444 	 * auth2_setup_methods_lists(), so check the configuration.
445 	 */
446 	if (options.num_auth_methods == 0)
447 		return 1;
448 	for (i = 0; i < authctxt->num_auth_methods; i++) {
449 		if (list_starts_with(authctxt->auth_methods[i], method,
450 		    submethod) != MATCH_NONE)
451 			return 1;
452 	}
453 	return 0;
454 }
455 
456 static char *
457 authmethods_get(Authctxt *authctxt)
458 {
459 	struct sshbuf *b;
460 	char *list;
461 	int i, r;
462 
463 	if ((b = sshbuf_new()) == NULL)
464 		fatal("%s: sshbuf_new failed", __func__);
465 	for (i = 0; authmethods[i] != NULL; i++) {
466 		if (strcmp(authmethods[i]->name, "none") == 0)
467 			continue;
468 		if (authmethods[i]->enabled == NULL ||
469 		    *(authmethods[i]->enabled) == 0)
470 			continue;
471 		if (!auth2_method_allowed(authctxt, authmethods[i]->name,
472 		    NULL))
473 			continue;
474 		if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) ? "," : "",
475 		    authmethods[i]->name)) != 0)
476 			fatal("%s: buffer error: %s", __func__, ssh_err(r));
477 	}
478 	if ((list = sshbuf_dup_string(b)) == NULL)
479 		fatal("%s: sshbuf_dup_string failed", __func__);
480 	sshbuf_free(b);
481 	return list;
482 }
483 
484 static Authmethod *
485 authmethod_lookup(Authctxt *authctxt, const char *name)
486 {
487 	int i;
488 
489 	if (name != NULL)
490 		for (i = 0; authmethods[i] != NULL; i++)
491 			if (authmethods[i]->enabled != NULL &&
492 			    *(authmethods[i]->enabled) != 0 &&
493 			    strcmp(name, authmethods[i]->name) == 0 &&
494 			    auth2_method_allowed(authctxt,
495 			    authmethods[i]->name, NULL))
496 				return authmethods[i];
497 	debug2("Unrecognized authentication method name: %s",
498 	    name ? name : "NULL");
499 	return NULL;
500 }
501 
502 /*
503  * Check a comma-separated list of methods for validity. Is need_enable is
504  * non-zero, then also require that the methods are enabled.
505  * Returns 0 on success or -1 if the methods list is invalid.
506  */
507 int
508 auth2_methods_valid(const char *_methods, int need_enable)
509 {
510 	char *methods, *omethods, *method, *p;
511 	u_int i, found;
512 	int ret = -1;
513 
514 	if (*_methods == '\0') {
515 		error("empty authentication method list");
516 		return -1;
517 	}
518 	omethods = methods = xstrdup(_methods);
519 	while ((method = strsep(&methods, ",")) != NULL) {
520 		for (found = i = 0; !found && authmethods[i] != NULL; i++) {
521 			if ((p = strchr(method, ':')) != NULL)
522 				*p = '\0';
523 			if (strcmp(method, authmethods[i]->name) != 0)
524 				continue;
525 			if (need_enable) {
526 				if (authmethods[i]->enabled == NULL ||
527 				    *(authmethods[i]->enabled) == 0) {
528 					error("Disabled method \"%s\" in "
529 					    "AuthenticationMethods list \"%s\"",
530 					    method, _methods);
531 					goto out;
532 				}
533 			}
534 			found = 1;
535 			break;
536 		}
537 		if (!found) {
538 			error("Unknown authentication method \"%s\" in list",
539 			    method);
540 			goto out;
541 		}
542 	}
543 	ret = 0;
544  out:
545 	free(omethods);
546 	return ret;
547 }
548 
549 /*
550  * Prune the AuthenticationMethods supplied in the configuration, removing
551  * any methods lists that include disabled methods. Note that this might
552  * leave authctxt->num_auth_methods == 0, even when multiple required auth
553  * has been requested. For this reason, all tests for whether multiple is
554  * enabled should consult options.num_auth_methods directly.
555  */
556 int
557 auth2_setup_methods_lists(Authctxt *authctxt)
558 {
559 	u_int i;
560 
561 	if (options.num_auth_methods == 0)
562 		return 0;
563 	debug3("%s: checking methods", __func__);
564 	authctxt->auth_methods = xcalloc(options.num_auth_methods,
565 	    sizeof(*authctxt->auth_methods));
566 	authctxt->num_auth_methods = 0;
567 	for (i = 0; i < options.num_auth_methods; i++) {
568 		if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {
569 			logit("Authentication methods list \"%s\" contains "
570 			    "disabled method, skipping",
571 			    options.auth_methods[i]);
572 			continue;
573 		}
574 		debug("authentication methods list %d: %s",
575 		    authctxt->num_auth_methods, options.auth_methods[i]);
576 		authctxt->auth_methods[authctxt->num_auth_methods++] =
577 		    xstrdup(options.auth_methods[i]);
578 	}
579 	if (authctxt->num_auth_methods == 0) {
580 		error("No AuthenticationMethods left after eliminating "
581 		    "disabled methods");
582 		return -1;
583 	}
584 	return 0;
585 }
586 
587 static int
588 list_starts_with(const char *methods, const char *method,
589     const char *submethod)
590 {
591 	size_t l = strlen(method);
592 	int match;
593 	const char *p;
594 
595 	if (strncmp(methods, method, l) != 0)
596 		return MATCH_NONE;
597 	p = methods + l;
598 	match = MATCH_METHOD;
599 	if (*p == ':') {
600 		if (!submethod)
601 			return MATCH_PARTIAL;
602 		l = strlen(submethod);
603 		p += 1;
604 		if (strncmp(submethod, p, l))
605 			return MATCH_NONE;
606 		p += l;
607 		match = MATCH_BOTH;
608 	}
609 	if (*p != ',' && *p != '\0')
610 		return MATCH_NONE;
611 	return match;
612 }
613 
614 /*
615  * Remove method from the start of a comma-separated list of methods.
616  * Returns 0 if the list of methods did not start with that method or 1
617  * if it did.
618  */
619 static int
620 remove_method(char **methods, const char *method, const char *submethod)
621 {
622 	char *omethods = *methods, *p;
623 	size_t l = strlen(method);
624 	int match;
625 
626 	match = list_starts_with(omethods, method, submethod);
627 	if (match != MATCH_METHOD && match != MATCH_BOTH)
628 		return 0;
629 	p = omethods + l;
630 	if (submethod && match == MATCH_BOTH)
631 		p += 1 + strlen(submethod); /* include colon */
632 	if (*p == ',')
633 		p++;
634 	*methods = xstrdup(p);
635 	free(omethods);
636 	return 1;
637 }
638 
639 /*
640  * Called after successful authentication. Will remove the successful method
641  * from the start of each list in which it occurs. If it was the last method
642  * in any list, then authentication is deemed successful.
643  * Returns 1 if the method completed any authentication list or 0 otherwise.
644  */
645 int
646 auth2_update_methods_lists(Authctxt *authctxt, const char *method,
647     const char *submethod)
648 {
649 	u_int i, found = 0;
650 
651 	debug3("%s: updating methods list after \"%s\"", __func__, method);
652 	for (i = 0; i < authctxt->num_auth_methods; i++) {
653 		if (!remove_method(&(authctxt->auth_methods[i]), method,
654 		    submethod))
655 			continue;
656 		found = 1;
657 		if (*authctxt->auth_methods[i] == '\0') {
658 			debug2("authentication methods list %d complete", i);
659 			return 1;
660 		}
661 		debug3("authentication methods list %d remaining: \"%s\"",
662 		    i, authctxt->auth_methods[i]);
663 	}
664 	/* This should not happen, but would be bad if it did */
665 	if (!found)
666 		fatal("%s: method not in AuthenticationMethods", __func__);
667 	return 0;
668 }
669 
670 /* Reset method-specific information */
671 void auth2_authctxt_reset_info(Authctxt *authctxt)
672 {
673 	sshkey_free(authctxt->auth_method_key);
674 	free(authctxt->auth_method_info);
675 	authctxt->auth_method_key = NULL;
676 	authctxt->auth_method_info = NULL;
677 }
678 
679 /* Record auth method-specific information for logs */
680 void
681 auth2_record_info(Authctxt *authctxt, const char *fmt, ...)
682 {
683 	va_list ap;
684         int i;
685 
686 	free(authctxt->auth_method_info);
687 	authctxt->auth_method_info = NULL;
688 
689 	va_start(ap, fmt);
690 	i = vasprintf(&authctxt->auth_method_info, fmt, ap);
691 	va_end(ap);
692 
693 	if (i < 0 || authctxt->auth_method_info == NULL)
694 		fatal("%s: vasprintf failed", __func__);
695 }
696 
697 /*
698  * Records a public key used in authentication. This is used for logging
699  * and to ensure that the same key is not subsequently accepted again for
700  * multiple authentication.
701  */
702 void
703 auth2_record_key(Authctxt *authctxt, int authenticated,
704     const struct sshkey *key)
705 {
706 	struct sshkey **tmp, *dup;
707 	int r;
708 
709 	if ((r = sshkey_demote(key, &dup)) != 0)
710 		fatal("%s: copy key: %s", __func__, ssh_err(r));
711 	sshkey_free(authctxt->auth_method_key);
712 	authctxt->auth_method_key = dup;
713 
714 	if (!authenticated)
715 		return;
716 
717 	/* If authenticated, make sure we don't accept this key again */
718 	if ((r = sshkey_demote(key, &dup)) != 0)
719 		fatal("%s: copy key: %s", __func__, ssh_err(r));
720 	if (authctxt->nprev_keys >= INT_MAX ||
721 	    (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,
722 	    authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)
723 		fatal("%s: reallocarray failed", __func__);
724 	authctxt->prev_keys = tmp;
725 	authctxt->prev_keys[authctxt->nprev_keys] = dup;
726 	authctxt->nprev_keys++;
727 
728 }
729 
730 /* Checks whether a key has already been previously used for authentication */
731 int
732 auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key)
733 {
734 	u_int i;
735 	char *fp;
736 
737 	for (i = 0; i < authctxt->nprev_keys; i++) {
738 		if (sshkey_equal_public(key, authctxt->prev_keys[i])) {
739 			fp = sshkey_fingerprint(authctxt->prev_keys[i],
740 			    options.fingerprint_hash, SSH_FP_DEFAULT);
741 			debug3("%s: key already used: %s %s", __func__,
742 			    sshkey_type(authctxt->prev_keys[i]),
743 			    fp == NULL ? "UNKNOWN" : fp);
744 			free(fp);
745 			return 1;
746 		}
747 	}
748 	return 0;
749 }
750 
751 /*
752  * Updates authctxt->session_info with details of authentication. Should be
753  * whenever an authentication method succeeds.
754  */
755 void
756 auth2_update_session_info(Authctxt *authctxt, const char *method,
757     const char *submethod)
758 {
759 	int r;
760 
761 	if (authctxt->session_info == NULL) {
762 		if ((authctxt->session_info = sshbuf_new()) == NULL)
763 			fatal("%s: sshbuf_new", __func__);
764 	}
765 
766 	/* Append method[/submethod] */
767 	if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",
768 	    method, submethod == NULL ? "" : "/",
769 	    submethod == NULL ? "" : submethod)) != 0)
770 		fatal("%s: append method: %s", __func__, ssh_err(r));
771 
772 	/* Append key if present */
773 	if (authctxt->auth_method_key != NULL) {
774 		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
775 		    (r = sshkey_format_text(authctxt->auth_method_key,
776 		    authctxt->session_info)) != 0)
777 			fatal("%s: append key: %s", __func__, ssh_err(r));
778 	}
779 
780 	if (authctxt->auth_method_info != NULL) {
781 		/* Ensure no ambiguity here */
782 		if (strchr(authctxt->auth_method_info, '\n') != NULL)
783 			fatal("%s: auth_method_info contains \\n", __func__);
784 		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
785 		    (r = sshbuf_putf(authctxt->session_info, "%s",
786 		    authctxt->auth_method_info)) != 0) {
787 			fatal("%s: append method info: %s",
788 			    __func__, ssh_err(r));
789 		}
790 	}
791 	if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)
792 		fatal("%s: append: %s", __func__, ssh_err(r));
793 }
794 
795