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 */
64 extern ServerOptions options;
65 extern struct sshbuf *loginmsg;
66
67 /* methods */
68
69 extern Authmethod method_none;
70 extern Authmethod method_pubkey;
71 extern Authmethod method_passwd;
72 extern Authmethod method_kbdint;
73 extern Authmethod method_hostbased;
74 #ifdef GSSAPI
75 extern Authmethod method_gssapi;
76 #endif
77
78 Authmethod *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
92 static int input_service_request(int, u_int32_t, struct ssh *);
93 static int input_userauth_request(int, u_int32_t, struct ssh *);
94
95 /* helper */
96 static Authmethod *authmethod_byname(const char *);
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 *
auth2_read_banner(void)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
userauth_send_banner(struct ssh * ssh,const char * msg)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_fr(r, "send packet");
149 debug("%s: sent", __func__);
150 }
151
152 static void
userauth_banner(struct ssh * ssh)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
do_authentication2(struct ssh * ssh)172 do_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
184 static int
input_service_request(int type,u_int32_t seq,struct ssh * ssh)185 input_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
227 static double
user_specific_delay(const char * user)228 user_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
246 static void
ensure_minimum_time_since(double start,double seconds)247 ensure_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
269 static int
input_userauth_request(int type,u_int32_t seq,struct ssh * ssh)270 input_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
363 void
userauth_finish(struct ssh * ssh,int authenticated,const char * packet_method,const char * submethod)364 userauth_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 */
476 int
auth2_method_allowed(Authctxt * authctxt,const char * method,const char * submethod)477 auth2_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
496 static char *
authmethods_get(Authctxt * authctxt)497 authmethods_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
524 static Authmethod *
authmethod_byname(const char * name)525 authmethod_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
541 static Authmethod *
authmethod_lookup(Authctxt * authctxt,const char * name)542 authmethod_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 */
566 int
auth2_methods_valid(const char * _methods,int need_enable)567 auth2_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 */
615 int
auth2_setup_methods_lists(Authctxt * authctxt)616 auth2_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
654 static int
list_starts_with(const char * methods,const char * method,const char * submethod)655 list_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 */
686 static int
remove_method(char ** methods,const char * method,const char * submethod)687 remove_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 */
712 int
auth2_update_methods_lists(Authctxt * authctxt,const char * method,const char * submethod)713 auth2_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 */
auth2_authctxt_reset_info(Authctxt * authctxt)738 void 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 */
747 void
auth2_record_info(Authctxt * authctxt,const char * fmt,...)748 auth2_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 */
769 void
auth2_record_key(Authctxt * authctxt,int authenticated,const struct sshkey * key)770 auth2_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 */
798 int
auth2_key_already_used(Authctxt * authctxt,const struct sshkey * key)799 auth2_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 */
822 void
auth2_update_session_info(Authctxt * authctxt,const char * method,const char * submethod)823 auth2_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