1/*	$NetBSD: auth2.c,v 1.29 2023/12/20 17:15:20 christos Exp $	*/
2/* $OpenBSD: auth2.c,v 1.168 2023/12/18 14:45:49 djm Exp $ */
3
4/*
5 * Copyright (c) 2000 Markus Friedl.  All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28#include "includes.h"
29__RCSID("$NetBSD: auth2.c,v 1.29 2023/12/20 17:15:20 christos Exp $");
30
31#include <sys/types.h>
32#include <sys/stat.h>
33#include <sys/uio.h>
34
35#include <fcntl.h>
36#include <limits.h>
37#include <pwd.h>
38#include <stdarg.h>
39#include <string.h>
40#include <unistd.h>
41#include <time.h>
42
43#include "stdlib.h"
44#include "atomicio.h"
45#include "xmalloc.h"
46#include "ssh2.h"
47#include "packet.h"
48#include "log.h"
49#include "sshbuf.h"
50#include "misc.h"
51#include "servconf.h"
52#include "sshkey.h"
53#include "hostfile.h"
54#include "auth.h"
55#include "dispatch.h"
56#include "pathnames.h"
57#include "canohost.h"
58#include "pfilter.h"
59
60#ifdef GSSAPI
61#include "ssh-gss.h"
62#endif
63
64#include "monitor_wrap.h"
65#include "ssherr.h"
66#include "digest.h"
67#include "kex.h"
68
69/* import */
70extern ServerOptions options;
71extern struct sshbuf *loginmsg;
72
73/* methods */
74
75extern Authmethod method_none;
76extern Authmethod method_pubkey;
77extern Authmethod method_passwd;
78extern Authmethod method_kbdint;
79extern Authmethod method_hostbased;
80#ifdef KRB5
81extern Authmethod method_kerberos;
82#endif
83#ifdef GSSAPI
84extern Authmethod method_gssapi;
85#endif
86
87static int log_flag = 0;
88
89Authmethod *authmethods[] = {
90	&method_none,
91	&method_pubkey,
92#ifdef GSSAPI
93	&method_gssapi,
94#endif
95	&method_passwd,
96	&method_kbdint,
97	&method_hostbased,
98#ifdef KRB5
99	&method_kerberos,
100#endif
101	NULL
102};
103
104/* protocol */
105
106static int input_service_request(int, u_int32_t, struct ssh *);
107static int input_userauth_request(int, u_int32_t, struct ssh *);
108
109/* helper */
110static Authmethod *authmethod_byname(const char *);
111static Authmethod *authmethod_lookup(Authctxt *, const char *);
112static char *authmethods_get(Authctxt *authctxt);
113
114#define MATCH_NONE	0	/* method or submethod mismatch */
115#define MATCH_METHOD	1	/* method matches (no submethod specified) */
116#define MATCH_BOTH	2	/* method and submethod match */
117#define MATCH_PARTIAL	3	/* method matches, submethod can't be checked */
118static int list_starts_with(const char *, const char *, const char *);
119
120char *
121auth2_read_banner(void)
122{
123	struct stat st;
124	char *banner = NULL;
125	size_t len, n;
126	int fd;
127
128	if ((fd = open(options.banner, O_RDONLY)) == -1)
129		return (NULL);
130	if (fstat(fd, &st) == -1) {
131		close(fd);
132		return (NULL);
133	}
134	if (st.st_size <= 0 || st.st_size > 1*1024*1024) {
135		close(fd);
136		return (NULL);
137	}
138
139	len = (size_t)st.st_size;		/* truncate */
140	banner = xmalloc(len + 1);
141	n = atomicio(read, fd, banner, len);
142	close(fd);
143
144	if (n != len) {
145		free(banner);
146		return (NULL);
147	}
148	banner[n] = '\0';
149
150	return (banner);
151}
152
153static void
154userauth_send_banner(struct ssh *ssh, const char *msg)
155{
156	int r;
157
158	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_BANNER)) != 0 ||
159	    (r = sshpkt_put_cstring(ssh, msg)) != 0 ||
160	    (r = sshpkt_put_cstring(ssh, "")) != 0 ||	/* language, unused */
161	    (r = sshpkt_send(ssh)) != 0)
162		fatal_fr(r, "send packet");
163	debug("%s: sent", __func__);
164}
165
166static void
167userauth_banner(struct ssh *ssh)
168{
169	char *banner = NULL;
170
171	if (options.banner == NULL)
172		return;
173
174	if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
175		goto done;
176	userauth_send_banner(ssh, banner);
177
178done:
179	free(banner);
180}
181
182/*
183 * loop until authctxt->success == TRUE
184 */
185void
186do_authentication2(struct ssh *ssh)
187{
188	Authctxt *authctxt = ssh->authctxt;
189
190	ssh_dispatch_init(ssh, &dispatch_protocol_error);
191	if (ssh->kex->ext_info_c)
192		ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &kex_input_ext_info);
193	ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_REQUEST, &input_service_request);
194	ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt->success);
195	ssh->authctxt = NULL;
196}
197
198static int
199input_service_request(int type, u_int32_t seq, struct ssh *ssh)
200{
201	Authctxt *authctxt = ssh->authctxt;
202	char *service = NULL;
203	int r, acceptit = 0;
204
205	if ((r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 ||
206	    (r = sshpkt_get_end(ssh)) != 0)
207		goto out;
208
209	if (authctxt == NULL)
210		fatal("input_service_request: no authctxt");
211
212	if (strcmp(service, "ssh-userauth") == 0) {
213		if (!authctxt->success) {
214			acceptit = 1;
215			/* now we can handle user-auth requests */
216			ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST,
217			    &input_userauth_request);
218		}
219	}
220	/* XXX all other service requests are denied */
221
222	if (acceptit) {
223		if ((r = sshpkt_start(ssh, SSH2_MSG_SERVICE_ACCEPT)) != 0 ||
224		    (r = sshpkt_put_cstring(ssh, service)) != 0 ||
225		    (r = sshpkt_send(ssh)) != 0 ||
226		    (r = ssh_packet_write_wait(ssh)) < 0)
227			goto out;
228	} else {
229		debug("bad service request %s", service);
230		ssh_packet_disconnect(ssh, "bad service request %s", service);
231	}
232	ssh_dispatch_set(ssh, SSH2_MSG_EXT_INFO, &dispatch_protocol_error);
233	r = 0;
234 out:
235	free(service);
236	return r;
237}
238
239#define MIN_FAIL_DELAY_SECONDS 0.005
240#define MAX_FAIL_DELAY_SECONDS 5.0
241static double
242user_specific_delay(const char *user)
243{
244	char b[512];
245	size_t len = ssh_digest_bytes(SSH_DIGEST_SHA512);
246	u_char *hash = xmalloc(len);
247	double delay;
248
249	(void)snprintf(b, sizeof b, "%llu%s",
250	    (unsigned long long)options.timing_secret, user);
251	if (ssh_digest_memory(SSH_DIGEST_SHA512, b, strlen(b), hash, len) != 0)
252		fatal_f("ssh_digest_memory");
253	/* 0-4.2 ms of delay */
254	delay = (double)PEEK_U32(hash) / 1000 / 1000 / 1000 / 1000;
255	freezero(hash, len);
256	debug3_f("user specific delay %0.3lfms", delay/1000);
257	return MIN_FAIL_DELAY_SECONDS + delay;
258}
259
260static void
261ensure_minimum_time_since(double start, double seconds)
262{
263	struct timespec ts;
264	double elapsed = monotime_double() - start, req = seconds, remain;
265
266	if (elapsed > MAX_FAIL_DELAY_SECONDS) {
267		debug3_f("elapsed %0.3lfms exceeded the max delay "
268		    "requested %0.3lfms)", elapsed*1000, req*1000);
269		return;
270	}
271
272	/* if we've already passed the requested time, scale up */
273	while ((remain = seconds - elapsed) < 0.0)
274		seconds *= 2;
275
276	ts.tv_sec = remain;
277	ts.tv_nsec = (remain - ts.tv_sec) * 1000000000;
278	debug3_f("elapsed %0.3lfms, delaying %0.3lfms (requested %0.3lfms)",
279	    elapsed*1000, remain*1000, req*1000);
280	nanosleep(&ts, NULL);
281}
282
283static int
284input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)
285{
286	Authctxt *authctxt = ssh->authctxt;
287	Authmethod *m = NULL;
288	char *user = NULL, *service = NULL, *method = NULL, *style = NULL;
289	int r, authenticated = 0;
290	double tstart = monotime_double();
291
292	if (authctxt == NULL)
293		fatal("input_userauth_request: no authctxt");
294
295	if ((r = sshpkt_get_cstring(ssh, &user, NULL)) != 0 ||
296	    (r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 ||
297	    (r = sshpkt_get_cstring(ssh, &method, NULL)) != 0)
298		goto out;
299	debug("userauth-request for user %s service %s method %s", user, service, method);
300	if (!log_flag) {
301		logit("SSH: Server;Ltype: Authname;Remote: %s-%d;Name: %s",
302		      ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), user);
303		log_flag = 1;
304	}
305	debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
306
307	if ((style = strchr(user, ':')) != NULL)
308		*style++ = 0;
309
310	if (authctxt->attempt >= 1024)
311		auth_maxtries_exceeded(ssh);
312	if (authctxt->attempt++ == 0) {
313		/* setup auth context */
314		authctxt->pw = PRIVSEP(getpwnamallow(ssh, user));
315		authctxt->user = xstrdup(user);
316		if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
317			authctxt->valid = 1;
318			debug2_f("setting up authctxt for %s", user);
319		} else {
320			authctxt->valid = 0;
321			/* Invalid user, fake password information */
322			authctxt->pw = fakepw();
323			pfilter_notify(1);
324		}
325#ifdef USE_PAM
326		if (options.use_pam)
327			PRIVSEP(start_pam(ssh));
328#endif
329		ssh_packet_set_log_preamble(ssh, "%suser %s",
330		    authctxt->valid ? "authenticating " : "invalid ", user);
331		setproctitle("%s%s", authctxt->valid ? user : "unknown",
332		    use_privsep ? " [net]" : "");
333		authctxt->service = xstrdup(service);
334		authctxt->style = style ? xstrdup(style) : NULL;
335		if (use_privsep)
336			mm_inform_authserv(service, style);
337		userauth_banner(ssh);
338		if ((r = kex_server_update_ext_info(ssh)) != 0)
339			fatal_fr(r, "kex_server_update_ext_info failed");
340		if (auth2_setup_methods_lists(authctxt) != 0)
341			ssh_packet_disconnect(ssh,
342			    "no authentication methods enabled");
343	} else if (strcmp(user, authctxt->user) != 0 ||
344	    strcmp(service, authctxt->service) != 0) {
345		ssh_packet_disconnect(ssh, "Change of username or service "
346		    "not allowed: (%s,%s) -> (%s,%s)",
347		    authctxt->user, authctxt->service, user, service);
348	}
349	/* reset state */
350	auth2_challenge_stop(ssh);
351
352#ifdef GSSAPI
353	/* XXX move to auth2_gssapi_stop() */
354	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
355	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
356#endif
357
358	auth2_authctxt_reset_info(authctxt);
359	authctxt->postponed = 0;
360	authctxt->server_caused_failure = 0;
361
362	/* try to authenticate user */
363	m = authmethod_lookup(authctxt, method);
364	if (m != NULL && authctxt->failures < options.max_authtries) {
365		debug2("input_userauth_request: try method %s", method);
366		authenticated =	m->userauth(ssh, method);
367	}
368	if (!authctxt->authenticated && strcmp(method, "none") != 0)
369		ensure_minimum_time_since(tstart,
370		    user_specific_delay(authctxt->user));
371	userauth_finish(ssh, authenticated, method, NULL);
372	r = 0;
373 out:
374	free(service);
375	free(user);
376	free(method);
377	return r;
378}
379
380void
381userauth_finish(struct ssh *ssh, int authenticated, const char *packet_method,
382    const char *submethod)
383{
384	Authctxt *authctxt = ssh->authctxt;
385	Authmethod *m = NULL;
386	const char *method = packet_method;
387	char *methods;
388	int r, partial = 0;
389
390	if (authenticated) {
391		if (!authctxt->valid) {
392			fatal("INTERNAL ERROR: authenticated invalid user %s",
393			    authctxt->user);
394		}
395		if (authctxt->postponed)
396			fatal("INTERNAL ERROR: authenticated and postponed");
397		/* prefer primary authmethod name to possible synonym */
398		if ((m = authmethod_byname(method)) == NULL)
399			fatal("INTERNAL ERROR: bad method %s", method);
400		method = m->name;
401	}
402
403	/* Special handling for root */
404	if (authenticated && authctxt->pw->pw_uid == 0 &&
405	    !auth_root_allowed(ssh, method)) {
406		authenticated = 0;
407#ifdef SSH_AUDIT_EVENTS
408		PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
409#endif
410	}
411
412#ifdef USE_PAM
413	if (options.use_pam && authenticated) {
414		if (!PRIVSEP(do_pam_account())) {
415			/* if PAM returned a message, send it to the user */
416			if (sshbuf_len(loginmsg) > 0) {
417				if ((r = sshbuf_put(loginmsg, "\0", 1)) != 0)
418					fatal("%s: buffer error: %s",
419					    __func__, ssh_err(r));
420				userauth_send_banner(ssh,
421				    (const char *)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			fatal("Access denied for user %s by PAM account "
428			    "configuration", authctxt->user);
429		}
430	}
431#endif
432
433	if (authenticated && options.num_auth_methods != 0) {
434		if (!auth2_update_methods_lists(authctxt, method, submethod)) {
435			authenticated = 0;
436			partial = 1;
437		}
438	}
439
440	/* Log before sending the reply */
441	auth_log(ssh, authenticated, partial, method, submethod);
442
443	/* Update information exposed to session */
444	if (authenticated || partial)
445		auth2_update_session_info(authctxt, method, submethod);
446
447	if (authctxt->postponed)
448		return;
449
450	if (authenticated == 1) {
451		/* turn off userauth */
452		ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST,
453		    &dispatch_protocol_ignore);
454		if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_SUCCESS)) != 0 ||
455		    (r = sshpkt_send(ssh)) != 0 ||
456		    (r = ssh_packet_write_wait(ssh)) < 0)
457			fatal_fr(r, "send success packet");
458		/* now we can break out */
459		authctxt->success = 1;
460		ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
461	} else {
462		/* Allow initial try of "none" auth without failure penalty */
463		if (!partial && !authctxt->server_caused_failure &&
464		    (authctxt->attempt > 1 || strcmp(method, "none") != 0)) {
465			authctxt->failures++;
466			pfilter_notify(1);
467		}
468		if (authctxt->failures >= options.max_authtries)
469			auth_maxtries_exceeded(ssh);
470		methods = authmethods_get(authctxt);
471		debug3_f("failure partial=%d next methods=\"%s\"",
472		    partial, methods);
473		if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_FAILURE)) != 0 ||
474		    (r = sshpkt_put_cstring(ssh, methods)) != 0 ||
475		    (r = sshpkt_put_u8(ssh, partial)) != 0 ||
476		    (r = sshpkt_send(ssh)) != 0 ||
477		    (r = ssh_packet_write_wait(ssh)) < 0)
478			fatal_fr(r, "send failure packet");
479		free(methods);
480	}
481}
482
483/*
484 * Checks whether method is allowed by at least one AuthenticationMethods
485 * methods list. Returns 1 if allowed, or no methods lists configured.
486 * 0 otherwise.
487 */
488int
489auth2_method_allowed(Authctxt *authctxt, const char *method,
490    const char *submethod)
491{
492	u_int i;
493
494	/*
495	 * NB. authctxt->num_auth_methods might be zero as a result of
496	 * auth2_setup_methods_lists(), so check the configuration.
497	 */
498	if (options.num_auth_methods == 0)
499		return 1;
500	for (i = 0; i < authctxt->num_auth_methods; i++) {
501		if (list_starts_with(authctxt->auth_methods[i], method,
502		    submethod) != MATCH_NONE)
503			return 1;
504	}
505	return 0;
506}
507
508static char *
509authmethods_get(Authctxt *authctxt)
510{
511	struct sshbuf *b;
512	char *list;
513	int i, r;
514
515	if ((b = sshbuf_new()) == NULL)
516		fatal_f("sshbuf_new failed");
517	for (i = 0; authmethods[i] != NULL; i++) {
518		if (strcmp(authmethods[i]->name, "none") == 0)
519			continue;
520		if (authmethods[i]->enabled == NULL ||
521		    *(authmethods[i]->enabled) == 0)
522			continue;
523		if (!auth2_method_allowed(authctxt, authmethods[i]->name,
524		    NULL))
525			continue;
526		if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) ? "," : "",
527		    authmethods[i]->name)) != 0)
528			fatal_fr(r, "buffer error");
529	}
530	if ((list = sshbuf_dup_string(b)) == NULL)
531		fatal_f("sshbuf_dup_string failed");
532	sshbuf_free(b);
533	return list;
534}
535
536static Authmethod *
537authmethod_byname(const char *name)
538{
539	int i;
540
541	if (name == NULL)
542		fatal_f("NULL authentication method name");
543	for (i = 0; authmethods[i] != NULL; i++) {
544		if (strcmp(name, authmethods[i]->name) == 0 ||
545		    (authmethods[i]->synonym != NULL &&
546		    strcmp(name, authmethods[i]->synonym) == 0))
547			return authmethods[i];
548	}
549	debug_f("unrecognized authentication method name: %s", name);
550	return NULL;
551}
552
553static Authmethod *
554authmethod_lookup(Authctxt *authctxt, const char *name)
555{
556	Authmethod *method;
557
558	if ((method = authmethod_byname(name)) == NULL)
559		return NULL;
560
561	if (method->enabled == NULL || *(method->enabled) == 0) {
562		debug3_f("method %s not enabled", name);
563		return NULL;
564	}
565	if (!auth2_method_allowed(authctxt, method->name, NULL)) {
566		debug3_f("method %s not allowed "
567		    "by AuthenticationMethods", name);
568		return NULL;
569	}
570	return method;
571}
572
573/*
574 * Check a comma-separated list of methods for validity. Is need_enable is
575 * non-zero, then also require that the methods are enabled.
576 * Returns 0 on success or -1 if the methods list is invalid.
577 */
578int
579auth2_methods_valid(const char *_methods, int need_enable)
580{
581	char *methods, *omethods, *method, *p;
582	u_int i, found;
583	int ret = -1;
584
585	if (*_methods == '\0') {
586		error("empty authentication method list");
587		return -1;
588	}
589	omethods = methods = xstrdup(_methods);
590	while ((method = strsep(&methods, ",")) != NULL) {
591		for (found = i = 0; !found && authmethods[i] != NULL; i++) {
592			if ((p = strchr(method, ':')) != NULL)
593				*p = '\0';
594			if (strcmp(method, authmethods[i]->name) != 0)
595				continue;
596			if (need_enable) {
597				if (authmethods[i]->enabled == NULL ||
598				    *(authmethods[i]->enabled) == 0) {
599					error("Disabled method \"%s\" in "
600					    "AuthenticationMethods list \"%s\"",
601					    method, _methods);
602					goto out;
603				}
604			}
605			found = 1;
606			break;
607		}
608		if (!found) {
609			error("Unknown authentication method \"%s\" in list",
610			    method);
611			goto out;
612		}
613	}
614	ret = 0;
615 out:
616	free(omethods);
617	return ret;
618}
619
620/*
621 * Prune the AuthenticationMethods supplied in the configuration, removing
622 * any methods lists that include disabled methods. Note that this might
623 * leave authctxt->num_auth_methods == 0, even when multiple required auth
624 * has been requested. For this reason, all tests for whether multiple is
625 * enabled should consult options.num_auth_methods directly.
626 */
627int
628auth2_setup_methods_lists(Authctxt *authctxt)
629{
630	u_int i;
631
632	/* First, normalise away the "any" pseudo-method */
633	if (options.num_auth_methods == 1 &&
634	    strcmp(options.auth_methods[0], "any") == 0) {
635		free(options.auth_methods[0]);
636		options.auth_methods[0] = NULL;
637		options.num_auth_methods = 0;
638	}
639
640	if (options.num_auth_methods == 0)
641		return 0;
642	debug3_f("checking methods");
643	authctxt->auth_methods = xcalloc(options.num_auth_methods,
644	    sizeof(*authctxt->auth_methods));
645	authctxt->num_auth_methods = 0;
646	for (i = 0; i < options.num_auth_methods; i++) {
647		if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {
648			logit("Authentication methods list \"%s\" contains "
649			    "disabled method, skipping",
650			    options.auth_methods[i]);
651			continue;
652		}
653		debug("authentication methods list %d: %s",
654		    authctxt->num_auth_methods, options.auth_methods[i]);
655		authctxt->auth_methods[authctxt->num_auth_methods++] =
656		    xstrdup(options.auth_methods[i]);
657	}
658	if (authctxt->num_auth_methods == 0) {
659		error("No AuthenticationMethods left after eliminating "
660		    "disabled methods");
661		return -1;
662	}
663	return 0;
664}
665
666static int
667list_starts_with(const char *methods, const char *method,
668    const char *submethod)
669{
670	size_t l = strlen(method);
671	int match;
672	const char *p;
673
674	if (strncmp(methods, method, l) != 0)
675		return MATCH_NONE;
676	p = methods + l;
677	match = MATCH_METHOD;
678	if (*p == ':') {
679		if (!submethod)
680			return MATCH_PARTIAL;
681		l = strlen(submethod);
682		p += 1;
683		if (strncmp(submethod, p, l))
684			return MATCH_NONE;
685		p += l;
686		match = MATCH_BOTH;
687	}
688	if (*p != ',' && *p != '\0')
689		return MATCH_NONE;
690	return match;
691}
692
693/*
694 * Remove method from the start of a comma-separated list of methods.
695 * Returns 0 if the list of methods did not start with that method or 1
696 * if it did.
697 */
698static int
699remove_method(char **methods, const char *method, const char *submethod)
700{
701	char *omethods = *methods, *p;
702	size_t l = strlen(method);
703	int match;
704
705	match = list_starts_with(omethods, method, submethod);
706	if (match != MATCH_METHOD && match != MATCH_BOTH)
707		return 0;
708	p = omethods + l;
709	if (submethod && match == MATCH_BOTH)
710		p += 1 + strlen(submethod); /* include colon */
711	if (*p == ',')
712		p++;
713	*methods = xstrdup(p);
714	free(omethods);
715	return 1;
716}
717
718/*
719 * Called after successful authentication. Will remove the successful method
720 * from the start of each list in which it occurs. If it was the last method
721 * in any list, then authentication is deemed successful.
722 * Returns 1 if the method completed any authentication list or 0 otherwise.
723 */
724int
725auth2_update_methods_lists(Authctxt *authctxt, const char *method,
726    const char *submethod)
727{
728	u_int i, found = 0;
729
730	debug3_f("updating methods list after \"%s\"", method);
731	for (i = 0; i < authctxt->num_auth_methods; i++) {
732		if (!remove_method(&(authctxt->auth_methods[i]), method,
733		    submethod))
734			continue;
735		found = 1;
736		if (*authctxt->auth_methods[i] == '\0') {
737			debug2("authentication methods list %d complete", i);
738			return 1;
739		}
740		debug3("authentication methods list %d remaining: \"%s\"",
741		    i, authctxt->auth_methods[i]);
742	}
743	/* This should not happen, but would be bad if it did */
744	if (!found)
745		fatal_f("method not in AuthenticationMethods");
746	return 0;
747}
748
749/* Reset method-specific information */
750void auth2_authctxt_reset_info(Authctxt *authctxt)
751{
752	sshkey_free(authctxt->auth_method_key);
753	free(authctxt->auth_method_info);
754	authctxt->auth_method_key = NULL;
755	authctxt->auth_method_info = NULL;
756}
757
758/* Record auth method-specific information for logs */
759void
760auth2_record_info(Authctxt *authctxt, const char *fmt, ...)
761{
762	va_list ap;
763	int i;
764
765	free(authctxt->auth_method_info);
766	authctxt->auth_method_info = NULL;
767
768	va_start(ap, fmt);
769	i = vasprintf(&authctxt->auth_method_info, fmt, ap);
770	va_end(ap);
771
772	if (i == -1)
773		fatal_f("vasprintf failed");
774}
775
776/*
777 * Records a public key used in authentication. This is used for logging
778 * and to ensure that the same key is not subsequently accepted again for
779 * multiple authentication.
780 */
781void
782auth2_record_key(Authctxt *authctxt, int authenticated,
783    const struct sshkey *key)
784{
785	struct sshkey **tmp, *dup;
786	int r;
787
788	if ((r = sshkey_from_private(key, &dup)) != 0)
789		fatal_fr(r, "copy key");
790	sshkey_free(authctxt->auth_method_key);
791	authctxt->auth_method_key = dup;
792
793	if (!authenticated)
794		return;
795
796	/* If authenticated, make sure we don't accept this key again */
797	if ((r = sshkey_from_private(key, &dup)) != 0)
798		fatal_fr(r, "copy key");
799	if (authctxt->nprev_keys >= INT_MAX ||
800	    (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,
801	    authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)
802		fatal_f("reallocarray failed");
803	authctxt->prev_keys = tmp;
804	authctxt->prev_keys[authctxt->nprev_keys] = dup;
805	authctxt->nprev_keys++;
806
807}
808
809/* Checks whether a key has already been previously used for authentication */
810int
811auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key)
812{
813	u_int i;
814	char *fp;
815
816	for (i = 0; i < authctxt->nprev_keys; i++) {
817		if (sshkey_equal_public(key, authctxt->prev_keys[i])) {
818			fp = sshkey_fingerprint(authctxt->prev_keys[i],
819			    options.fingerprint_hash, SSH_FP_DEFAULT);
820			debug3_f("key already used: %s %s",
821			    sshkey_type(authctxt->prev_keys[i]),
822			    fp == NULL ? "UNKNOWN" : fp);
823			free(fp);
824			return 1;
825		}
826	}
827	return 0;
828}
829
830/*
831 * Updates authctxt->session_info with details of authentication. Should be
832 * whenever an authentication method succeeds.
833 */
834void
835auth2_update_session_info(Authctxt *authctxt, const char *method,
836    const char *submethod)
837{
838	int r;
839
840	if (authctxt->session_info == NULL) {
841		if ((authctxt->session_info = sshbuf_new()) == NULL)
842			fatal_f("sshbuf_new");
843	}
844
845	/* Append method[/submethod] */
846	if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",
847	    method, submethod == NULL ? "" : "/",
848	    submethod == NULL ? "" : submethod)) != 0)
849		fatal_fr(r, "append method");
850
851	/* Append key if present */
852	if (authctxt->auth_method_key != NULL) {
853		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
854		    (r = sshkey_format_text(authctxt->auth_method_key,
855		    authctxt->session_info)) != 0)
856			fatal_fr(r, "append key");
857	}
858
859	if (authctxt->auth_method_info != NULL) {
860		/* Ensure no ambiguity here */
861		if (strchr(authctxt->auth_method_info, '\n') != NULL)
862			fatal_f("auth_method_info contains \\n");
863		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
864		    (r = sshbuf_putf(authctxt->session_info, "%s",
865		    authctxt->auth_method_info)) != 0) {
866			fatal_fr(r, "append method info");
867		}
868	}
869	if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)
870		fatal_fr(r, "append");
871}
872
873