1/* $OpenBSD: auth2.c,v 1.168 2023/12/18 14:45:49 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 "stdlib.h"
41#include "atomicio.h"
42#include "xmalloc.h"
43#include "ssh2.h"
44#include "packet.h"
45#include "log.h"
46#include "sshbuf.h"
47#include "misc.h"
48#include "servconf.h"
49#include "sshkey.h"
50#include "hostfile.h"
51#include "auth.h"
52#include "dispatch.h"
53#include "pathnames.h"
54#include "ssherr.h"
55#include "blacklist_client.h"
56#ifdef GSSAPI
57#include "ssh-gss.h"
58#endif
59#include "monitor_wrap.h"
60#include "digest.h"
61#include "kex.h"
62
63/* import */
64extern ServerOptions options;
65extern struct sshbuf *loginmsg;
66
67/* methods */
68
69extern Authmethod method_none;
70extern Authmethod method_pubkey;
71extern Authmethod method_passwd;
72extern Authmethod method_kbdint;
73extern Authmethod method_hostbased;
74#ifdef GSSAPI
75extern Authmethod method_gssapi;
76#endif
77
78Authmethod *authmethods[] = {
79	&method_none,
80	&method_pubkey,
81#ifdef GSSAPI
82	&method_gssapi,
83#endif
84	&method_passwd,
85	&method_kbdint,
86	&method_hostbased,
87	NULL
88};
89
90/* protocol */
91
92static int input_service_request(int, u_int32_t, struct ssh *);
93static int input_userauth_request(int, u_int32_t, struct ssh *);
94
95/* helper */
96static Authmethod *authmethod_byname(const char *);
97static Authmethod *authmethod_lookup(Authctxt *, const char *);
98static 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 */
104static int list_starts_with(const char *, const char *, const char *);
105
106char *
107auth2_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
139static void
140userauth_send_banner(struct ssh *ssh, const char *msg)
141{
142	int r;
143
144	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_BANNER)) != 0 ||
145	    (r = sshpkt_put_cstring(ssh, msg)) != 0 ||
146	    (r = sshpkt_put_cstring(ssh, "")) != 0 ||	/* language, unused */
147	    (r = sshpkt_send(ssh)) != 0)
148		fatal_fr(r, "send packet");
149	debug("%s: sent", __func__);
150}
151
152static void
153userauth_banner(struct ssh *ssh)
154{
155	char *banner = NULL;
156
157	if (options.banner == NULL)
158		return;
159
160	if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
161		goto done;
162	userauth_send_banner(ssh, banner);
163
164done:
165	free(banner);
166}
167
168/*
169 * loop until authctxt->success == TRUE
170 */
171void
172do_authentication2(struct ssh *ssh)
173{
174	Authctxt *authctxt = ssh->authctxt;
175
176	ssh_dispatch_init(ssh, &dispatch_protocol_error);
177	if (ssh->kex->ext_info_c)
178		ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_input_ext_info);
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
184static int
185input_service_request(int type, u_int32_t seq, struct ssh *ssh)
186{
187	Authctxt *authctxt = ssh->authctxt;
188	char *service = NULL;
189	int r, acceptit = 0;
190
191	if ((r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 ||
192	    (r = sshpkt_get_end(ssh)) != 0)
193		goto out;
194
195	if (authctxt == NULL)
196		fatal("input_service_request: no authctxt");
197
198	if (strcmp(service, "ssh-userauth") == 0) {
199		if (!authctxt->success) {
200			acceptit = 1;
201			/* now we can handle user-auth requests */
202			ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST,
203			    &input_userauth_request);
204		}
205	}
206	/* XXX all other service requests are denied */
207
208	if (acceptit) {
209		if ((r = sshpkt_start(ssh, SSH2_MSG_SERVICE_ACCEPT)) != 0 ||
210		    (r = sshpkt_put_cstring(ssh, service)) != 0 ||
211		    (r = sshpkt_send(ssh)) != 0 ||
212		    (r = ssh_packet_write_wait(ssh)) != 0)
213			goto out;
214	} else {
215		debug("bad service request %s", service);
216		ssh_packet_disconnect(ssh, "bad service request %s", service);
217	}
218	ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &dispatch_protocol_error);
219	r = 0;
220 out:
221	free(service);
222	return r;
223}
224
225#define MIN_FAIL_DELAY_SECONDS 0.005
226#define MAX_FAIL_DELAY_SECONDS 5.0
227static double
228user_specific_delay(const char *user)
229{
230	char b[512];
231	size_t len = ssh_digest_bytes(SSH_DIGEST_SHA512);
232	u_char *hash = xmalloc(len);
233	double delay;
234
235	(void)snprintf(b, sizeof b, "%llu%s",
236	    (unsigned long long)options.timing_secret, user);
237	if (ssh_digest_memory(SSH_DIGEST_SHA512, b, strlen(b), hash, len) != 0)
238		fatal_f("ssh_digest_memory");
239	/* 0-4.2 ms of delay */
240	delay = (double)PEEK_U32(hash) / 1000 / 1000 / 1000 / 1000;
241	freezero(hash, len);
242	debug3_f("user specific delay %0.3lfms", delay/1000);
243	return MIN_FAIL_DELAY_SECONDS + delay;
244}
245
246static void
247ensure_minimum_time_since(double start, double seconds)
248{
249	struct timespec ts;
250	double elapsed = monotime_double() - start, req = seconds, remain;
251
252	if (elapsed > MAX_FAIL_DELAY_SECONDS) {
253		debug3_f("elapsed %0.3lfms exceeded the max delay "
254		    "requested %0.3lfms)", elapsed*1000, req*1000);
255		return;
256	}
257
258	/* if we've already passed the requested time, scale up */
259	while ((remain = seconds - elapsed) < 0.0)
260		seconds *= 2;
261
262	ts.tv_sec = remain;
263	ts.tv_nsec = (remain - ts.tv_sec) * 1000000000;
264	debug3_f("elapsed %0.3lfms, delaying %0.3lfms (requested %0.3lfms)",
265	    elapsed*1000, remain*1000, req*1000);
266	nanosleep(&ts, NULL);
267}
268
269static int
270input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)
271{
272	Authctxt *authctxt = ssh->authctxt;
273	Authmethod *m = NULL;
274	char *user = NULL, *service = NULL, *method = NULL, *style = NULL;
275	int r, authenticated = 0;
276	double tstart = monotime_double();
277
278	if (authctxt == NULL)
279		fatal("input_userauth_request: no authctxt");
280
281	if ((r = sshpkt_get_cstring(ssh, &user, NULL)) != 0 ||
282	    (r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 ||
283	    (r = sshpkt_get_cstring(ssh, &method, NULL)) != 0)
284		goto out;
285	debug("userauth-request for user %s service %s method %s", user, service, method);
286	debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
287
288	if ((style = strchr(user, ':')) != NULL)
289		*style++ = 0;
290
291	if (authctxt->attempt >= 1024)
292		auth_maxtries_exceeded(ssh);
293	if (authctxt->attempt++ == 0) {
294		/* setup auth context */
295		authctxt->pw = PRIVSEP(getpwnamallow(ssh, user));
296		authctxt->user = xstrdup(user);
297		if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
298			authctxt->valid = 1;
299			debug2_f("setting up authctxt for %s", user);
300		} else {
301			authctxt->valid = 0;
302			/* Invalid user, fake password information */
303			authctxt->pw = fakepw();
304#ifdef SSH_AUDIT_EVENTS
305			PRIVSEP(audit_event(ssh, SSH_INVALID_USER));
306#endif
307		}
308#ifdef USE_PAM
309		if (options.use_pam)
310			PRIVSEP(start_pam(ssh));
311#endif
312		ssh_packet_set_log_preamble(ssh, "%suser %s",
313		    authctxt->valid ? "authenticating " : "invalid ", user);
314		setproctitle("%s%s", authctxt->valid ? user : "unknown",
315		    use_privsep ? " [net]" : "");
316		authctxt->service = xstrdup(service);
317		authctxt->style = style ? xstrdup(style) : NULL;
318		if (use_privsep)
319			mm_inform_authserv(service, style);
320		userauth_banner(ssh);
321		if ((r = kex_server_update_ext_info(ssh)) != 0)
322			fatal_fr(r, "kex_server_update_ext_info failed");
323		if (auth2_setup_methods_lists(authctxt) != 0)
324			ssh_packet_disconnect(ssh,
325			    "no authentication methods enabled");
326	} else if (strcmp(user, authctxt->user) != 0 ||
327	    strcmp(service, authctxt->service) != 0) {
328		ssh_packet_disconnect(ssh, "Change of username or service "
329		    "not allowed: (%s,%s) -> (%s,%s)",
330		    authctxt->user, authctxt->service, user, service);
331	}
332	/* reset state */
333	auth2_challenge_stop(ssh);
334
335#ifdef GSSAPI
336	/* XXX move to auth2_gssapi_stop() */
337	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
338	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
339#endif
340
341	auth2_authctxt_reset_info(authctxt);
342	authctxt->postponed = 0;
343	authctxt->server_caused_failure = 0;
344
345	/* try to authenticate user */
346	m = authmethod_lookup(authctxt, method);
347	if (m != NULL && authctxt->failures < options.max_authtries) {
348		debug2("input_userauth_request: try method %s", method);
349		authenticated =	m->userauth(ssh, method);
350	}
351	if (!authctxt->authenticated && strcmp(method, "none") != 0)
352		ensure_minimum_time_since(tstart,
353		    user_specific_delay(authctxt->user));
354	userauth_finish(ssh, authenticated, method, NULL);
355	r = 0;
356 out:
357	free(service);
358	free(user);
359	free(method);
360	return r;
361}
362
363void
364userauth_finish(struct ssh *ssh, int authenticated, const char *packet_method,
365    const char *submethod)
366{
367	Authctxt *authctxt = ssh->authctxt;
368	Authmethod *m = NULL;
369	const char *method = packet_method;
370	char *methods;
371	int r, partial = 0;
372
373	if (authenticated) {
374		if (!authctxt->valid) {
375			fatal("INTERNAL ERROR: authenticated invalid user %s",
376			    authctxt->user);
377		}
378		if (authctxt->postponed)
379			fatal("INTERNAL ERROR: authenticated and postponed");
380		/* prefer primary authmethod name to possible synonym */
381		if ((m = authmethod_byname(method)) == NULL)
382			fatal("INTERNAL ERROR: bad method %s", method);
383		method = m->name;
384	}
385
386	/* Special handling for root */
387	if (authenticated && authctxt->pw->pw_uid == 0 &&
388	    !auth_root_allowed(ssh, method)) {
389		authenticated = 0;
390#ifdef SSH_AUDIT_EVENTS
391		PRIVSEP(audit_event(ssh, SSH_LOGIN_ROOT_DENIED));
392#endif
393	}
394
395	if (authenticated && options.num_auth_methods != 0) {
396		if (!auth2_update_methods_lists(authctxt, method, submethod)) {
397			authenticated = 0;
398			partial = 1;
399		}
400	}
401
402	/* Log before sending the reply */
403	auth_log(ssh, authenticated, partial, method, submethod);
404
405	/* Update information exposed to session */
406	if (authenticated || partial)
407		auth2_update_session_info(authctxt, method, submethod);
408
409	if (authctxt->postponed)
410		return;
411
412#ifdef USE_PAM
413	if (options.use_pam && authenticated) {
414		int r, success = PRIVSEP(do_pam_account());
415
416		/* If PAM returned a message, send it to the user. */
417		if (sshbuf_len(loginmsg) > 0) {
418			if ((r = sshbuf_put(loginmsg, "\0", 1)) != 0)
419				fatal("%s: buffer error: %s",
420				    __func__, ssh_err(r));
421			userauth_send_banner(ssh, sshbuf_ptr(loginmsg));
422			if ((r = ssh_packet_write_wait(ssh)) != 0) {
423				sshpkt_fatal(ssh, r,
424				    "%s: send PAM banner", __func__);
425			}
426		}
427		if (!success) {
428			fatal("Access denied for user %s by PAM account "
429			    "configuration", authctxt->user);
430		}
431	}
432#endif
433
434	if (authenticated == 1) {
435		/* turn off userauth */
436		ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST,
437		    &dispatch_protocol_ignore);
438		if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_SUCCESS)) != 0 ||
439		    (r = sshpkt_send(ssh)) != 0 ||
440		    (r = ssh_packet_write_wait(ssh)) != 0)
441			fatal_fr(r, "send success packet");
442		/* now we can break out */
443		authctxt->success = 1;
444		ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
445	} else {
446		/* Allow initial try of "none" auth without failure penalty */
447		if (!partial && !authctxt->server_caused_failure &&
448		    (authctxt->attempt > 1 || strcmp(method, "none") != 0)) {
449			authctxt->failures++;
450			BLACKLIST_NOTIFY(ssh, BLACKLIST_AUTH_FAIL, "ssh");
451		}
452		if (authctxt->failures >= options.max_authtries) {
453#ifdef SSH_AUDIT_EVENTS
454			PRIVSEP(audit_event(ssh, SSH_LOGIN_EXCEED_MAXTRIES));
455#endif
456			auth_maxtries_exceeded(ssh);
457		}
458		methods = authmethods_get(authctxt);
459		debug3_f("failure partial=%d next methods=\"%s\"",
460		    partial, methods);
461		if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_FAILURE)) != 0 ||
462		    (r = sshpkt_put_cstring(ssh, methods)) != 0 ||
463		    (r = sshpkt_put_u8(ssh, partial)) != 0 ||
464		    (r = sshpkt_send(ssh)) != 0 ||
465		    (r = ssh_packet_write_wait(ssh)) != 0)
466			fatal_fr(r, "send failure packet");
467		free(methods);
468	}
469}
470
471/*
472 * Checks whether method is allowed by at least one AuthenticationMethods
473 * methods list. Returns 1 if allowed, or no methods lists configured.
474 * 0 otherwise.
475 */
476int
477auth2_method_allowed(Authctxt *authctxt, const char *method,
478    const char *submethod)
479{
480	u_int i;
481
482	/*
483	 * NB. authctxt->num_auth_methods might be zero as a result of
484	 * auth2_setup_methods_lists(), so check the configuration.
485	 */
486	if (options.num_auth_methods == 0)
487		return 1;
488	for (i = 0; i < authctxt->num_auth_methods; i++) {
489		if (list_starts_with(authctxt->auth_methods[i], method,
490		    submethod) != MATCH_NONE)
491			return 1;
492	}
493	return 0;
494}
495
496static char *
497authmethods_get(Authctxt *authctxt)
498{
499	struct sshbuf *b;
500	char *list;
501	int i, r;
502
503	if ((b = sshbuf_new()) == NULL)
504		fatal_f("sshbuf_new failed");
505	for (i = 0; authmethods[i] != NULL; i++) {
506		if (strcmp(authmethods[i]->name, "none") == 0)
507			continue;
508		if (authmethods[i]->enabled == NULL ||
509		    *(authmethods[i]->enabled) == 0)
510			continue;
511		if (!auth2_method_allowed(authctxt, authmethods[i]->name,
512		    NULL))
513			continue;
514		if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) ? "," : "",
515		    authmethods[i]->name)) != 0)
516			fatal_fr(r, "buffer error");
517	}
518	if ((list = sshbuf_dup_string(b)) == NULL)
519		fatal_f("sshbuf_dup_string failed");
520	sshbuf_free(b);
521	return list;
522}
523
524static Authmethod *
525authmethod_byname(const char *name)
526{
527	int i;
528
529	if (name == NULL)
530		fatal_f("NULL authentication method name");
531	for (i = 0; authmethods[i] != NULL; i++) {
532		if (strcmp(name, authmethods[i]->name) == 0 ||
533		    (authmethods[i]->synonym != NULL &&
534		    strcmp(name, authmethods[i]->synonym) == 0))
535			return authmethods[i];
536	}
537	debug_f("unrecognized authentication method name: %s", name);
538	return NULL;
539}
540
541static Authmethod *
542authmethod_lookup(Authctxt *authctxt, const char *name)
543{
544	Authmethod *method;
545
546	if ((method = authmethod_byname(name)) == NULL)
547		return NULL;
548
549	if (method->enabled == NULL || *(method->enabled) == 0) {
550		debug3_f("method %s not enabled", name);
551		return NULL;
552	}
553	if (!auth2_method_allowed(authctxt, method->name, NULL)) {
554		debug3_f("method %s not allowed "
555		    "by AuthenticationMethods", name);
556		return NULL;
557	}
558	return method;
559}
560
561/*
562 * Check a comma-separated list of methods for validity. Is need_enable is
563 * non-zero, then also require that the methods are enabled.
564 * Returns 0 on success or -1 if the methods list is invalid.
565 */
566int
567auth2_methods_valid(const char *_methods, int need_enable)
568{
569	char *methods, *omethods, *method, *p;
570	u_int i, found;
571	int ret = -1;
572
573	if (*_methods == '\0') {
574		error("empty authentication method list");
575		return -1;
576	}
577	omethods = methods = xstrdup(_methods);
578	while ((method = strsep(&methods, ",")) != NULL) {
579		for (found = i = 0; !found && authmethods[i] != NULL; i++) {
580			if ((p = strchr(method, ':')) != NULL)
581				*p = '\0';
582			if (strcmp(method, authmethods[i]->name) != 0)
583				continue;
584			if (need_enable) {
585				if (authmethods[i]->enabled == NULL ||
586				    *(authmethods[i]->enabled) == 0) {
587					error("Disabled method \"%s\" in "
588					    "AuthenticationMethods list \"%s\"",
589					    method, _methods);
590					goto out;
591				}
592			}
593			found = 1;
594			break;
595		}
596		if (!found) {
597			error("Unknown authentication method \"%s\" in list",
598			    method);
599			goto out;
600		}
601	}
602	ret = 0;
603 out:
604	free(omethods);
605	return ret;
606}
607
608/*
609 * Prune the AuthenticationMethods supplied in the configuration, removing
610 * any methods lists that include disabled methods. Note that this might
611 * leave authctxt->num_auth_methods == 0, even when multiple required auth
612 * has been requested. For this reason, all tests for whether multiple is
613 * enabled should consult options.num_auth_methods directly.
614 */
615int
616auth2_setup_methods_lists(Authctxt *authctxt)
617{
618	u_int i;
619
620	/* First, normalise away the "any" pseudo-method */
621	if (options.num_auth_methods == 1 &&
622	    strcmp(options.auth_methods[0], "any") == 0) {
623		free(options.auth_methods[0]);
624		options.auth_methods[0] = NULL;
625		options.num_auth_methods = 0;
626	}
627
628	if (options.num_auth_methods == 0)
629		return 0;
630	debug3_f("checking methods");
631	authctxt->auth_methods = xcalloc(options.num_auth_methods,
632	    sizeof(*authctxt->auth_methods));
633	authctxt->num_auth_methods = 0;
634	for (i = 0; i < options.num_auth_methods; i++) {
635		if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {
636			logit("Authentication methods list \"%s\" contains "
637			    "disabled method, skipping",
638			    options.auth_methods[i]);
639			continue;
640		}
641		debug("authentication methods list %d: %s",
642		    authctxt->num_auth_methods, options.auth_methods[i]);
643		authctxt->auth_methods[authctxt->num_auth_methods++] =
644		    xstrdup(options.auth_methods[i]);
645	}
646	if (authctxt->num_auth_methods == 0) {
647		error("No AuthenticationMethods left after eliminating "
648		    "disabled methods");
649		return -1;
650	}
651	return 0;
652}
653
654static int
655list_starts_with(const char *methods, const char *method,
656    const char *submethod)
657{
658	size_t l = strlen(method);
659	int match;
660	const char *p;
661
662	if (strncmp(methods, method, l) != 0)
663		return MATCH_NONE;
664	p = methods + l;
665	match = MATCH_METHOD;
666	if (*p == ':') {
667		if (!submethod)
668			return MATCH_PARTIAL;
669		l = strlen(submethod);
670		p += 1;
671		if (strncmp(submethod, p, l))
672			return MATCH_NONE;
673		p += l;
674		match = MATCH_BOTH;
675	}
676	if (*p != ',' && *p != '\0')
677		return MATCH_NONE;
678	return match;
679}
680
681/*
682 * Remove method from the start of a comma-separated list of methods.
683 * Returns 0 if the list of methods did not start with that method or 1
684 * if it did.
685 */
686static int
687remove_method(char **methods, const char *method, const char *submethod)
688{
689	char *omethods = *methods, *p;
690	size_t l = strlen(method);
691	int match;
692
693	match = list_starts_with(omethods, method, submethod);
694	if (match != MATCH_METHOD && match != MATCH_BOTH)
695		return 0;
696	p = omethods + l;
697	if (submethod && match == MATCH_BOTH)
698		p += 1 + strlen(submethod); /* include colon */
699	if (*p == ',')
700		p++;
701	*methods = xstrdup(p);
702	free(omethods);
703	return 1;
704}
705
706/*
707 * Called after successful authentication. Will remove the successful method
708 * from the start of each list in which it occurs. If it was the last method
709 * in any list, then authentication is deemed successful.
710 * Returns 1 if the method completed any authentication list or 0 otherwise.
711 */
712int
713auth2_update_methods_lists(Authctxt *authctxt, const char *method,
714    const char *submethod)
715{
716	u_int i, found = 0;
717
718	debug3_f("updating methods list after \"%s\"", method);
719	for (i = 0; i < authctxt->num_auth_methods; i++) {
720		if (!remove_method(&(authctxt->auth_methods[i]), method,
721		    submethod))
722			continue;
723		found = 1;
724		if (*authctxt->auth_methods[i] == '\0') {
725			debug2("authentication methods list %d complete", i);
726			return 1;
727		}
728		debug3("authentication methods list %d remaining: \"%s\"",
729		    i, authctxt->auth_methods[i]);
730	}
731	/* This should not happen, but would be bad if it did */
732	if (!found)
733		fatal_f("method not in AuthenticationMethods");
734	return 0;
735}
736
737/* Reset method-specific information */
738void auth2_authctxt_reset_info(Authctxt *authctxt)
739{
740	sshkey_free(authctxt->auth_method_key);
741	free(authctxt->auth_method_info);
742	authctxt->auth_method_key = NULL;
743	authctxt->auth_method_info = NULL;
744}
745
746/* Record auth method-specific information for logs */
747void
748auth2_record_info(Authctxt *authctxt, const char *fmt, ...)
749{
750	va_list ap;
751	int i;
752
753	free(authctxt->auth_method_info);
754	authctxt->auth_method_info = NULL;
755
756	va_start(ap, fmt);
757	i = vasprintf(&authctxt->auth_method_info, fmt, ap);
758	va_end(ap);
759
760	if (i == -1)
761		fatal_f("vasprintf failed");
762}
763
764/*
765 * Records a public key used in authentication. This is used for logging
766 * and to ensure that the same key is not subsequently accepted again for
767 * multiple authentication.
768 */
769void
770auth2_record_key(Authctxt *authctxt, int authenticated,
771    const struct sshkey *key)
772{
773	struct sshkey **tmp, *dup;
774	int r;
775
776	if ((r = sshkey_from_private(key, &dup)) != 0)
777		fatal_fr(r, "copy key");
778	sshkey_free(authctxt->auth_method_key);
779	authctxt->auth_method_key = dup;
780
781	if (!authenticated)
782		return;
783
784	/* If authenticated, make sure we don't accept this key again */
785	if ((r = sshkey_from_private(key, &dup)) != 0)
786		fatal_fr(r, "copy key");
787	if (authctxt->nprev_keys >= INT_MAX ||
788	    (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,
789	    authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)
790		fatal_f("reallocarray failed");
791	authctxt->prev_keys = tmp;
792	authctxt->prev_keys[authctxt->nprev_keys] = dup;
793	authctxt->nprev_keys++;
794
795}
796
797/* Checks whether a key has already been previously used for authentication */
798int
799auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key)
800{
801	u_int i;
802	char *fp;
803
804	for (i = 0; i < authctxt->nprev_keys; i++) {
805		if (sshkey_equal_public(key, authctxt->prev_keys[i])) {
806			fp = sshkey_fingerprint(authctxt->prev_keys[i],
807			    options.fingerprint_hash, SSH_FP_DEFAULT);
808			debug3_f("key already used: %s %s",
809			    sshkey_type(authctxt->prev_keys[i]),
810			    fp == NULL ? "UNKNOWN" : fp);
811			free(fp);
812			return 1;
813		}
814	}
815	return 0;
816}
817
818/*
819 * Updates authctxt->session_info with details of authentication. Should be
820 * whenever an authentication method succeeds.
821 */
822void
823auth2_update_session_info(Authctxt *authctxt, const char *method,
824    const char *submethod)
825{
826	int r;
827
828	if (authctxt->session_info == NULL) {
829		if ((authctxt->session_info = sshbuf_new()) == NULL)
830			fatal_f("sshbuf_new");
831	}
832
833	/* Append method[/submethod] */
834	if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",
835	    method, submethod == NULL ? "" : "/",
836	    submethod == NULL ? "" : submethod)) != 0)
837		fatal_fr(r, "append method");
838
839	/* Append key if present */
840	if (authctxt->auth_method_key != NULL) {
841		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
842		    (r = sshkey_format_text(authctxt->auth_method_key,
843		    authctxt->session_info)) != 0)
844			fatal_fr(r, "append key");
845	}
846
847	if (authctxt->auth_method_info != NULL) {
848		/* Ensure no ambiguity here */
849		if (strchr(authctxt->auth_method_info, '\n') != NULL)
850			fatal_f("auth_method_info contains \\n");
851		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
852		    (r = sshbuf_putf(authctxt->session_info, "%s",
853		    authctxt->auth_method_info)) != 0) {
854			fatal_fr(r, "append method info");
855		}
856	}
857	if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)
858		fatal_fr(r, "append");
859}
860
861