xref: /openssh-portable/auth2.c (revision 16d4f996)
1 /* $OpenBSD: auth2.c,v 1.158 2020/03/06 18:16:21 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 #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 "compat.h"
50 #include "sshkey.h"
51 #include "hostfile.h"
52 #include "auth.h"
53 #include "dispatch.h"
54 #include "pathnames.h"
55 #include "ssherr.h"
56 #ifdef GSSAPI
57 #include "ssh-gss.h"
58 #endif
59 #include "monitor_wrap.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 struct sshbuf *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 static void
140 userauth_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("%s: %s", __func__, ssh_err(r));
149 	debug("%s: sent", __func__);
150 }
151 
152 static void
153 userauth_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 
164 done:
165 	free(banner);
166 }
167 
168 /*
169  * loop until authctxt->success == TRUE
170  */
171 void
172 do_authentication2(struct ssh *ssh)
173 {
174 	Authctxt *authctxt = ssh->authctxt;
175 
176 	ssh_dispatch_init(ssh, &dispatch_protocol_error);
177 	ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_REQUEST, &input_service_request);
178 	ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt->success);
179 	ssh->authctxt = NULL;
180 }
181 
182 /*ARGSUSED*/
183 static int
184 input_service_request(int type, u_int32_t seq, struct ssh *ssh)
185 {
186 	Authctxt *authctxt = ssh->authctxt;
187 	char *service = NULL;
188 	int r, acceptit = 0;
189 
190 	if ((r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 ||
191 	    (r = sshpkt_get_end(ssh)) != 0)
192 		goto out;
193 
194 	if (authctxt == NULL)
195 		fatal("input_service_request: no authctxt");
196 
197 	if (strcmp(service, "ssh-userauth") == 0) {
198 		if (!authctxt->success) {
199 			acceptit = 1;
200 			/* now we can handle user-auth requests */
201 			ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST,
202 			    &input_userauth_request);
203 		}
204 	}
205 	/* XXX all other service requests are denied */
206 
207 	if (acceptit) {
208 		if ((r = sshpkt_start(ssh, SSH2_MSG_SERVICE_ACCEPT)) != 0 ||
209 		    (r = sshpkt_put_cstring(ssh, service)) != 0 ||
210 		    (r = sshpkt_send(ssh)) != 0 ||
211 		    (r = ssh_packet_write_wait(ssh)) != 0)
212 			goto out;
213 	} else {
214 		debug("bad service request %s", service);
215 		ssh_packet_disconnect(ssh, "bad service request %s", service);
216 	}
217 	r = 0;
218  out:
219 	free(service);
220 	return r;
221 }
222 
223 #define MIN_FAIL_DELAY_SECONDS 0.005
224 static double
225 user_specific_delay(const char *user)
226 {
227 	char b[512];
228 	size_t len = ssh_digest_bytes(SSH_DIGEST_SHA512);
229 	u_char *hash = xmalloc(len);
230 	double delay;
231 
232 	(void)snprintf(b, sizeof b, "%llu%s",
233 	     (unsigned long long)options.timing_secret, user);
234 	if (ssh_digest_memory(SSH_DIGEST_SHA512, b, strlen(b), hash, len) != 0)
235 		fatal("%s: ssh_digest_memory", __func__);
236 	/* 0-4.2 ms of delay */
237 	delay = (double)PEEK_U32(hash) / 1000 / 1000 / 1000 / 1000;
238 	freezero(hash, len);
239 	debug3("%s: user specific delay %0.3lfms", __func__, delay/1000);
240 	return MIN_FAIL_DELAY_SECONDS + delay;
241 }
242 
243 static void
244 ensure_minimum_time_since(double start, double seconds)
245 {
246 	struct timespec ts;
247 	double elapsed = monotime_double() - start, req = seconds, remain;
248 
249 	/* if we've already passed the requested time, scale up */
250 	while ((remain = seconds - elapsed) < 0.0)
251 		seconds *= 2;
252 
253 	ts.tv_sec = remain;
254 	ts.tv_nsec = (remain - ts.tv_sec) * 1000000000;
255 	debug3("%s: elapsed %0.3lfms, delaying %0.3lfms (requested %0.3lfms)",
256 	    __func__, elapsed*1000, remain*1000, req*1000);
257 	nanosleep(&ts, NULL);
258 }
259 
260 /*ARGSUSED*/
261 static int
262 input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)
263 {
264 	Authctxt *authctxt = ssh->authctxt;
265 	Authmethod *m = NULL;
266 	char *user = NULL, *service = NULL, *method = NULL, *style = NULL;
267 	int r, authenticated = 0;
268 	double tstart = monotime_double();
269 
270 	if (authctxt == NULL)
271 		fatal("input_userauth_request: no authctxt");
272 
273 	if ((r = sshpkt_get_cstring(ssh, &user, NULL)) != 0 ||
274 	    (r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 ||
275 	    (r = sshpkt_get_cstring(ssh, &method, NULL)) != 0)
276 		goto out;
277 	debug("userauth-request for user %s service %s method %s", user, service, method);
278 	debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
279 
280 	if ((style = strchr(user, ':')) != NULL)
281 		*style++ = 0;
282 
283 	if (authctxt->attempt++ == 0) {
284 		/* setup auth context */
285 		authctxt->pw = PRIVSEP(getpwnamallow(ssh, user));
286 		authctxt->user = xstrdup(user);
287 		if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
288 			authctxt->valid = 1;
289 			debug2("%s: setting up authctxt for %s",
290 			    __func__, user);
291 		} else {
292 			/* Invalid user, fake password information */
293 			authctxt->pw = fakepw();
294 #ifdef SSH_AUDIT_EVENTS
295 			PRIVSEP(audit_event(ssh, SSH_INVALID_USER));
296 #endif
297 		}
298 #ifdef USE_PAM
299 		if (options.use_pam)
300 			PRIVSEP(start_pam(ssh));
301 #endif
302 		ssh_packet_set_log_preamble(ssh, "%suser %s",
303 		    authctxt->valid ? "authenticating " : "invalid ", user);
304 		setproctitle("%s%s", authctxt->valid ? user : "unknown",
305 		    use_privsep ? " [net]" : "");
306 		authctxt->service = xstrdup(service);
307 		authctxt->style = style ? xstrdup(style) : NULL;
308 		if (use_privsep)
309 			mm_inform_authserv(service, style);
310 		userauth_banner(ssh);
311 		if (auth2_setup_methods_lists(authctxt) != 0)
312 			ssh_packet_disconnect(ssh,
313 			    "no authentication methods enabled");
314 	} else if (strcmp(user, authctxt->user) != 0 ||
315 	    strcmp(service, authctxt->service) != 0) {
316 		ssh_packet_disconnect(ssh, "Change of username or service "
317 		    "not allowed: (%s,%s) -> (%s,%s)",
318 		    authctxt->user, authctxt->service, user, service);
319 	}
320 	/* reset state */
321 	auth2_challenge_stop(ssh);
322 
323 #ifdef GSSAPI
324 	/* XXX move to auth2_gssapi_stop() */
325 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
326 	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
327 #endif
328 
329 	auth2_authctxt_reset_info(authctxt);
330 	authctxt->postponed = 0;
331 	authctxt->server_caused_failure = 0;
332 
333 	/* try to authenticate user */
334 	m = authmethod_lookup(authctxt, method);
335 	if (m != NULL && authctxt->failures < options.max_authtries) {
336 		debug2("input_userauth_request: try method %s", method);
337 		authenticated =	m->userauth(ssh);
338 	}
339 	if (!authctxt->authenticated)
340 		ensure_minimum_time_since(tstart,
341 		    user_specific_delay(authctxt->user));
342 	userauth_finish(ssh, authenticated, method, NULL);
343 	r = 0;
344  out:
345 	free(service);
346 	free(user);
347 	free(method);
348 	return r;
349 }
350 
351 void
352 userauth_finish(struct ssh *ssh, int authenticated, const char *method,
353     const char *submethod)
354 {
355 	Authctxt *authctxt = ssh->authctxt;
356 	char *methods;
357 	int r, partial = 0;
358 
359 	if (!authctxt->valid && authenticated)
360 		fatal("INTERNAL ERROR: authenticated invalid user %s",
361 		    authctxt->user);
362 	if (authenticated && authctxt->postponed)
363 		fatal("INTERNAL ERROR: authenticated and postponed");
364 
365 	/* Special handling for root */
366 	if (authenticated && authctxt->pw->pw_uid == 0 &&
367 	    !auth_root_allowed(ssh, method)) {
368 		authenticated = 0;
369 #ifdef SSH_AUDIT_EVENTS
370 		PRIVSEP(audit_event(ssh, SSH_LOGIN_ROOT_DENIED));
371 #endif
372 	}
373 
374 	if (authenticated && options.num_auth_methods != 0) {
375 		if (!auth2_update_methods_lists(authctxt, method, submethod)) {
376 			authenticated = 0;
377 			partial = 1;
378 		}
379 	}
380 
381 	/* Log before sending the reply */
382 	auth_log(ssh, authenticated, partial, method, submethod);
383 
384 	/* Update information exposed to session */
385 	if (authenticated || partial)
386 		auth2_update_session_info(authctxt, method, submethod);
387 
388 	if (authctxt->postponed)
389 		return;
390 
391 #ifdef USE_PAM
392 	if (options.use_pam && authenticated) {
393 		int r;
394 
395 		if (!PRIVSEP(do_pam_account())) {
396 			/* if PAM returned a message, send it to the user */
397 			if (sshbuf_len(loginmsg) > 0) {
398 				if ((r = sshbuf_put(loginmsg, "\0", 1)) != 0)
399 					fatal("%s: buffer error: %s",
400 					    __func__, ssh_err(r));
401 				userauth_send_banner(ssh, sshbuf_ptr(loginmsg));
402 				if ((r = ssh_packet_write_wait(ssh)) != 0) {
403 					sshpkt_fatal(ssh, r,
404 					    "%s: send PAM banner", __func__);
405 				}
406 			}
407 			fatal("Access denied for user %s by PAM account "
408 			    "configuration", authctxt->user);
409 		}
410 	}
411 #endif
412 
413 	if (authenticated == 1) {
414 		/* turn off userauth */
415 		ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST,
416 		    &dispatch_protocol_ignore);
417 		if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_SUCCESS)) != 0 ||
418 		    (r = sshpkt_send(ssh)) != 0 ||
419 		    (r = ssh_packet_write_wait(ssh)) != 0)
420 			fatal("%s: %s", __func__, ssh_err(r));
421 		/* now we can break out */
422 		authctxt->success = 1;
423 		ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
424 	} else {
425 		/* Allow initial try of "none" auth without failure penalty */
426 		if (!partial && !authctxt->server_caused_failure &&
427 		    (authctxt->attempt > 1 || strcmp(method, "none") != 0))
428 			authctxt->failures++;
429 		if (authctxt->failures >= options.max_authtries) {
430 #ifdef SSH_AUDIT_EVENTS
431 			PRIVSEP(audit_event(ssh, SSH_LOGIN_EXCEED_MAXTRIES));
432 #endif
433 			auth_maxtries_exceeded(ssh);
434 		}
435 		methods = authmethods_get(authctxt);
436 		debug3("%s: failure partial=%d next methods=\"%s\"", __func__,
437 		    partial, methods);
438 		if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_FAILURE)) != 0 ||
439 		    (r = sshpkt_put_cstring(ssh, methods)) != 0 ||
440 		    (r = sshpkt_put_u8(ssh, partial)) != 0 ||
441 		    (r = sshpkt_send(ssh)) != 0 ||
442 		    (r = ssh_packet_write_wait(ssh)) != 0)
443 			fatal("%s: %s", __func__, ssh_err(r));
444 		free(methods);
445 	}
446 }
447 
448 /*
449  * Checks whether method is allowed by at least one AuthenticationMethods
450  * methods list. Returns 1 if allowed, or no methods lists configured.
451  * 0 otherwise.
452  */
453 int
454 auth2_method_allowed(Authctxt *authctxt, const char *method,
455     const char *submethod)
456 {
457 	u_int i;
458 
459 	/*
460 	 * NB. authctxt->num_auth_methods might be zero as a result of
461 	 * auth2_setup_methods_lists(), so check the configuration.
462 	 */
463 	if (options.num_auth_methods == 0)
464 		return 1;
465 	for (i = 0; i < authctxt->num_auth_methods; i++) {
466 		if (list_starts_with(authctxt->auth_methods[i], method,
467 		    submethod) != MATCH_NONE)
468 			return 1;
469 	}
470 	return 0;
471 }
472 
473 static char *
474 authmethods_get(Authctxt *authctxt)
475 {
476 	struct sshbuf *b;
477 	char *list;
478 	int i, r;
479 
480 	if ((b = sshbuf_new()) == NULL)
481 		fatal("%s: sshbuf_new failed", __func__);
482 	for (i = 0; authmethods[i] != NULL; i++) {
483 		if (strcmp(authmethods[i]->name, "none") == 0)
484 			continue;
485 		if (authmethods[i]->enabled == NULL ||
486 		    *(authmethods[i]->enabled) == 0)
487 			continue;
488 		if (!auth2_method_allowed(authctxt, authmethods[i]->name,
489 		    NULL))
490 			continue;
491 		if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) ? "," : "",
492 		    authmethods[i]->name)) != 0)
493 			fatal("%s: buffer error: %s", __func__, ssh_err(r));
494 	}
495 	if ((list = sshbuf_dup_string(b)) == NULL)
496 		fatal("%s: sshbuf_dup_string failed", __func__);
497 	sshbuf_free(b);
498 	return list;
499 }
500 
501 static Authmethod *
502 authmethod_lookup(Authctxt *authctxt, const char *name)
503 {
504 	int i;
505 
506 	if (name != NULL)
507 		for (i = 0; authmethods[i] != NULL; i++)
508 			if (authmethods[i]->enabled != NULL &&
509 			    *(authmethods[i]->enabled) != 0 &&
510 			    strcmp(name, authmethods[i]->name) == 0 &&
511 			    auth2_method_allowed(authctxt,
512 			    authmethods[i]->name, NULL))
513 				return authmethods[i];
514 	debug2("Unrecognized authentication method name: %s",
515 	    name ? name : "NULL");
516 	return NULL;
517 }
518 
519 /*
520  * Check a comma-separated list of methods for validity. Is need_enable is
521  * non-zero, then also require that the methods are enabled.
522  * Returns 0 on success or -1 if the methods list is invalid.
523  */
524 int
525 auth2_methods_valid(const char *_methods, int need_enable)
526 {
527 	char *methods, *omethods, *method, *p;
528 	u_int i, found;
529 	int ret = -1;
530 
531 	if (*_methods == '\0') {
532 		error("empty authentication method list");
533 		return -1;
534 	}
535 	omethods = methods = xstrdup(_methods);
536 	while ((method = strsep(&methods, ",")) != NULL) {
537 		for (found = i = 0; !found && authmethods[i] != NULL; i++) {
538 			if ((p = strchr(method, ':')) != NULL)
539 				*p = '\0';
540 			if (strcmp(method, authmethods[i]->name) != 0)
541 				continue;
542 			if (need_enable) {
543 				if (authmethods[i]->enabled == NULL ||
544 				    *(authmethods[i]->enabled) == 0) {
545 					error("Disabled method \"%s\" in "
546 					    "AuthenticationMethods list \"%s\"",
547 					    method, _methods);
548 					goto out;
549 				}
550 			}
551 			found = 1;
552 			break;
553 		}
554 		if (!found) {
555 			error("Unknown authentication method \"%s\" in list",
556 			    method);
557 			goto out;
558 		}
559 	}
560 	ret = 0;
561  out:
562 	free(omethods);
563 	return ret;
564 }
565 
566 /*
567  * Prune the AuthenticationMethods supplied in the configuration, removing
568  * any methods lists that include disabled methods. Note that this might
569  * leave authctxt->num_auth_methods == 0, even when multiple required auth
570  * has been requested. For this reason, all tests for whether multiple is
571  * enabled should consult options.num_auth_methods directly.
572  */
573 int
574 auth2_setup_methods_lists(Authctxt *authctxt)
575 {
576 	u_int i;
577 
578 	/* First, normalise away the "any" pseudo-method */
579 	if (options.num_auth_methods == 1 &&
580 	    strcmp(options.auth_methods[0], "any") == 0) {
581 		free(options.auth_methods[0]);
582 		options.auth_methods[0] = NULL;
583 		options.num_auth_methods = 0;
584 	}
585 
586 	if (options.num_auth_methods == 0)
587 		return 0;
588 	debug3("%s: checking methods", __func__);
589 	authctxt->auth_methods = xcalloc(options.num_auth_methods,
590 	    sizeof(*authctxt->auth_methods));
591 	authctxt->num_auth_methods = 0;
592 	for (i = 0; i < options.num_auth_methods; i++) {
593 		if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {
594 			logit("Authentication methods list \"%s\" contains "
595 			    "disabled method, skipping",
596 			    options.auth_methods[i]);
597 			continue;
598 		}
599 		debug("authentication methods list %d: %s",
600 		    authctxt->num_auth_methods, options.auth_methods[i]);
601 		authctxt->auth_methods[authctxt->num_auth_methods++] =
602 		    xstrdup(options.auth_methods[i]);
603 	}
604 	if (authctxt->num_auth_methods == 0) {
605 		error("No AuthenticationMethods left after eliminating "
606 		    "disabled methods");
607 		return -1;
608 	}
609 	return 0;
610 }
611 
612 static int
613 list_starts_with(const char *methods, const char *method,
614     const char *submethod)
615 {
616 	size_t l = strlen(method);
617 	int match;
618 	const char *p;
619 
620 	if (strncmp(methods, method, l) != 0)
621 		return MATCH_NONE;
622 	p = methods + l;
623 	match = MATCH_METHOD;
624 	if (*p == ':') {
625 		if (!submethod)
626 			return MATCH_PARTIAL;
627 		l = strlen(submethod);
628 		p += 1;
629 		if (strncmp(submethod, p, l))
630 			return MATCH_NONE;
631 		p += l;
632 		match = MATCH_BOTH;
633 	}
634 	if (*p != ',' && *p != '\0')
635 		return MATCH_NONE;
636 	return match;
637 }
638 
639 /*
640  * Remove method from the start of a comma-separated list of methods.
641  * Returns 0 if the list of methods did not start with that method or 1
642  * if it did.
643  */
644 static int
645 remove_method(char **methods, const char *method, const char *submethod)
646 {
647 	char *omethods = *methods, *p;
648 	size_t l = strlen(method);
649 	int match;
650 
651 	match = list_starts_with(omethods, method, submethod);
652 	if (match != MATCH_METHOD && match != MATCH_BOTH)
653 		return 0;
654 	p = omethods + l;
655 	if (submethod && match == MATCH_BOTH)
656 		p += 1 + strlen(submethod); /* include colon */
657 	if (*p == ',')
658 		p++;
659 	*methods = xstrdup(p);
660 	free(omethods);
661 	return 1;
662 }
663 
664 /*
665  * Called after successful authentication. Will remove the successful method
666  * from the start of each list in which it occurs. If it was the last method
667  * in any list, then authentication is deemed successful.
668  * Returns 1 if the method completed any authentication list or 0 otherwise.
669  */
670 int
671 auth2_update_methods_lists(Authctxt *authctxt, const char *method,
672     const char *submethod)
673 {
674 	u_int i, found = 0;
675 
676 	debug3("%s: updating methods list after \"%s\"", __func__, method);
677 	for (i = 0; i < authctxt->num_auth_methods; i++) {
678 		if (!remove_method(&(authctxt->auth_methods[i]), method,
679 		    submethod))
680 			continue;
681 		found = 1;
682 		if (*authctxt->auth_methods[i] == '\0') {
683 			debug2("authentication methods list %d complete", i);
684 			return 1;
685 		}
686 		debug3("authentication methods list %d remaining: \"%s\"",
687 		    i, authctxt->auth_methods[i]);
688 	}
689 	/* This should not happen, but would be bad if it did */
690 	if (!found)
691 		fatal("%s: method not in AuthenticationMethods", __func__);
692 	return 0;
693 }
694 
695 /* Reset method-specific information */
696 void auth2_authctxt_reset_info(Authctxt *authctxt)
697 {
698 	sshkey_free(authctxt->auth_method_key);
699 	free(authctxt->auth_method_info);
700 	authctxt->auth_method_key = NULL;
701 	authctxt->auth_method_info = NULL;
702 }
703 
704 /* Record auth method-specific information for logs */
705 void
706 auth2_record_info(Authctxt *authctxt, const char *fmt, ...)
707 {
708 	va_list ap;
709         int i;
710 
711 	free(authctxt->auth_method_info);
712 	authctxt->auth_method_info = NULL;
713 
714 	va_start(ap, fmt);
715 	i = vasprintf(&authctxt->auth_method_info, fmt, ap);
716 	va_end(ap);
717 
718 	if (i == -1)
719 		fatal("%s: vasprintf failed", __func__);
720 }
721 
722 /*
723  * Records a public key used in authentication. This is used for logging
724  * and to ensure that the same key is not subsequently accepted again for
725  * multiple authentication.
726  */
727 void
728 auth2_record_key(Authctxt *authctxt, int authenticated,
729     const struct sshkey *key)
730 {
731 	struct sshkey **tmp, *dup;
732 	int r;
733 
734 	if ((r = sshkey_from_private(key, &dup)) != 0)
735 		fatal("%s: copy key: %s", __func__, ssh_err(r));
736 	sshkey_free(authctxt->auth_method_key);
737 	authctxt->auth_method_key = dup;
738 
739 	if (!authenticated)
740 		return;
741 
742 	/* If authenticated, make sure we don't accept this key again */
743 	if ((r = sshkey_from_private(key, &dup)) != 0)
744 		fatal("%s: copy key: %s", __func__, ssh_err(r));
745 	if (authctxt->nprev_keys >= INT_MAX ||
746 	    (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,
747 	    authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)
748 		fatal("%s: reallocarray failed", __func__);
749 	authctxt->prev_keys = tmp;
750 	authctxt->prev_keys[authctxt->nprev_keys] = dup;
751 	authctxt->nprev_keys++;
752 
753 }
754 
755 /* Checks whether a key has already been previously used for authentication */
756 int
757 auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key)
758 {
759 	u_int i;
760 	char *fp;
761 
762 	for (i = 0; i < authctxt->nprev_keys; i++) {
763 		if (sshkey_equal_public(key, authctxt->prev_keys[i])) {
764 			fp = sshkey_fingerprint(authctxt->prev_keys[i],
765 			    options.fingerprint_hash, SSH_FP_DEFAULT);
766 			debug3("%s: key already used: %s %s", __func__,
767 			    sshkey_type(authctxt->prev_keys[i]),
768 			    fp == NULL ? "UNKNOWN" : fp);
769 			free(fp);
770 			return 1;
771 		}
772 	}
773 	return 0;
774 }
775 
776 /*
777  * Updates authctxt->session_info with details of authentication. Should be
778  * whenever an authentication method succeeds.
779  */
780 void
781 auth2_update_session_info(Authctxt *authctxt, const char *method,
782     const char *submethod)
783 {
784 	int r;
785 
786 	if (authctxt->session_info == NULL) {
787 		if ((authctxt->session_info = sshbuf_new()) == NULL)
788 			fatal("%s: sshbuf_new", __func__);
789 	}
790 
791 	/* Append method[/submethod] */
792 	if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",
793 	    method, submethod == NULL ? "" : "/",
794 	    submethod == NULL ? "" : submethod)) != 0)
795 		fatal("%s: append method: %s", __func__, ssh_err(r));
796 
797 	/* Append key if present */
798 	if (authctxt->auth_method_key != NULL) {
799 		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
800 		    (r = sshkey_format_text(authctxt->auth_method_key,
801 		    authctxt->session_info)) != 0)
802 			fatal("%s: append key: %s", __func__, ssh_err(r));
803 	}
804 
805 	if (authctxt->auth_method_info != NULL) {
806 		/* Ensure no ambiguity here */
807 		if (strchr(authctxt->auth_method_info, '\n') != NULL)
808 			fatal("%s: auth_method_info contains \\n", __func__);
809 		if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
810 		    (r = sshbuf_putf(authctxt->session_info, "%s",
811 		    authctxt->auth_method_info)) != 0) {
812 			fatal("%s: append method info: %s",
813 			    __func__, ssh_err(r));
814 		}
815 	}
816 	if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)
817 		fatal("%s: append: %s", __func__, ssh_err(r));
818 }
819 
820