1 /* $OpenBSD: auth2.c,v 1.155 2019/03/25 22:34:52 djm Exp $ */
3 * Copyright (c) 2000 Markus Friedl. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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.
28 #include <sys/types.h>
53 #include "pathnames.h"
60 #include "monitor_wrap.h"
65 extern ServerOptions options;
66 extern u_char *session_id2;
67 extern u_int session_id2_len;
68 extern struct sshbuf *loginmsg;
72 extern Authmethod method_none;
73 extern Authmethod method_pubkey;
74 extern Authmethod method_passwd;
75 extern Authmethod method_kbdint;
76 extern Authmethod method_hostbased;
78 extern Authmethod method_gssapi;
81 Authmethod *authmethods[] = {
95 static int input_service_request(int, u_int32_t, struct ssh *);
96 static int input_userauth_request(int, u_int32_t, struct ssh *);
99 static Authmethod *authmethod_lookup(Authctxt *, const char *);
100 static char *authmethods_get(Authctxt *authctxt);
102 #define MATCH_NONE 0 /* method or submethod mismatch */
103 #define MATCH_METHOD 1 /* method matches (no submethod specified) */
104 #define MATCH_BOTH 2 /* method and submethod match */
105 #define MATCH_PARTIAL 3 /* method matches, submethod can't be checked */
106 static int list_starts_with(const char *, const char *, const char *);
109 auth2_read_banner(void)
116 if ((fd = open(options.banner, O_RDONLY)) == -1)
118 if (fstat(fd, &st) == -1) {
122 if (st.st_size <= 0 || st.st_size > 1*1024*1024) {
127 len = (size_t)st.st_size; /* truncate */
128 banner = xmalloc(len + 1);
129 n = atomicio(read, fd, banner, len);
142 userauth_send_banner(struct ssh *ssh, const char *msg)
146 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_BANNER)) != 0 ||
147 (r = sshpkt_put_cstring(ssh, msg)) != 0 ||
148 (r = sshpkt_put_cstring(ssh, "")) != 0 || /* language, unused */
149 (r = sshpkt_send(ssh)) != 0)
150 fatal("%s: %s", __func__, ssh_err(r));
151 debug("%s: sent", __func__);
155 userauth_banner(struct ssh *ssh)
159 if (options.banner == NULL)
162 if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
164 userauth_send_banner(ssh, banner);
171 * loop until authctxt->success == TRUE
174 do_authentication2(struct ssh *ssh)
176 Authctxt *authctxt = ssh->authctxt;
178 ssh_dispatch_init(ssh, &dispatch_protocol_error);
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;
186 input_service_request(int type, u_int32_t seq, struct ssh *ssh)
188 Authctxt *authctxt = ssh->authctxt;
189 char *service = NULL;
192 if ((r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 ||
193 (r = sshpkt_get_end(ssh)) != 0)
196 if (authctxt == NULL)
197 fatal("input_service_request: no authctxt");
199 if (strcmp(service, "ssh-userauth") == 0) {
200 if (!authctxt->success) {
202 /* now we can handle user-auth requests */
203 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST,
204 &input_userauth_request);
207 /* XXX all other service requests are denied */
210 if ((r = sshpkt_start(ssh, SSH2_MSG_SERVICE_ACCEPT)) != 0 ||
211 (r = sshpkt_put_cstring(ssh, service)) != 0 ||
212 (r = sshpkt_send(ssh)) != 0 ||
213 (r = ssh_packet_write_wait(ssh)) != 0)
216 debug("bad service request %s", service);
217 ssh_packet_disconnect(ssh, "bad service request %s", service);
225 #define MIN_FAIL_DELAY_SECONDS 0.005
227 user_specific_delay(const char *user)
230 size_t len = ssh_digest_bytes(SSH_DIGEST_SHA512);
231 u_char *hash = xmalloc(len);
234 (void)snprintf(b, sizeof b, "%llu%s",
235 (unsigned long long)options.timing_secret, user);
236 if (ssh_digest_memory(SSH_DIGEST_SHA512, b, strlen(b), hash, len) != 0)
237 fatal("%s: ssh_digest_memory", __func__);
238 /* 0-4.2 ms of delay */
239 delay = (double)PEEK_U32(hash) / 1000 / 1000 / 1000 / 1000;
241 debug3("%s: user specific delay %0.3lfms", __func__, delay/1000);
242 return MIN_FAIL_DELAY_SECONDS + delay;
246 ensure_minimum_time_since(double start, double seconds)
249 double elapsed = monotime_double() - start, req = seconds, remain;
251 /* if we've already passed the requested time, scale up */
252 while ((remain = seconds - elapsed) < 0.0)
256 ts.tv_nsec = (remain - ts.tv_sec) * 1000000000;
257 debug3("%s: elapsed %0.3lfms, delaying %0.3lfms (requested %0.3lfms)",
258 __func__, elapsed*1000, remain*1000, req*1000);
259 nanosleep(&ts, NULL);
264 input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)
266 Authctxt *authctxt = ssh->authctxt;
267 Authmethod *m = NULL;
268 char *user = NULL, *service = NULL, *method = NULL, *style = NULL;
269 int r, authenticated = 0;
270 double tstart = monotime_double();
272 if (authctxt == NULL)
273 fatal("input_userauth_request: no authctxt");
275 if ((r = sshpkt_get_cstring(ssh, &user, NULL)) != 0 ||
276 (r = sshpkt_get_cstring(ssh, &service, NULL)) != 0 ||
277 (r = sshpkt_get_cstring(ssh, &method, NULL)) != 0)
279 debug("userauth-request for user %s service %s method %s", user, service, method);
280 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
282 if ((style = strchr(user, ':')) != NULL)
285 if (authctxt->attempt++ == 0) {
286 /* setup auth context */
287 authctxt->pw = PRIVSEP(getpwnamallow(ssh, user));
288 authctxt->user = xstrdup(user);
289 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
291 debug2("%s: setting up authctxt for %s",
294 /* Invalid user, fake password information */
295 authctxt->pw = fakepw();
296 #ifdef SSH_AUDIT_EVENTS
297 PRIVSEP(audit_event(ssh, SSH_INVALID_USER));
302 PRIVSEP(start_pam(ssh));
304 ssh_packet_set_log_preamble(ssh, "%suser %s",
305 authctxt->valid ? "authenticating " : "invalid ", user);
306 setproctitle("%s%s", authctxt->valid ? user : "unknown",
307 use_privsep ? " [net]" : "");
308 authctxt->service = xstrdup(service);
309 authctxt->style = style ? xstrdup(style) : NULL;
311 mm_inform_authserv(service, style);
312 userauth_banner(ssh);
313 if (auth2_setup_methods_lists(authctxt) != 0)
314 ssh_packet_disconnect(ssh,
315 "no authentication methods enabled");
316 } else if (strcmp(user, authctxt->user) != 0 ||
317 strcmp(service, authctxt->service) != 0) {
318 ssh_packet_disconnect(ssh, "Change of username or service "
319 "not allowed: (%s,%s) -> (%s,%s)",
320 authctxt->user, authctxt->service, user, service);
323 auth2_challenge_stop(ssh);
326 /* XXX move to auth2_gssapi_stop() */
327 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
328 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
331 auth2_authctxt_reset_info(authctxt);
332 authctxt->postponed = 0;
333 authctxt->server_caused_failure = 0;
335 /* try to authenticate user */
336 m = authmethod_lookup(authctxt, method);
337 if (m != NULL && authctxt->failures < options.max_authtries) {
338 debug2("input_userauth_request: try method %s", method);
339 authenticated = m->userauth(ssh);
341 if (!authctxt->authenticated)
342 ensure_minimum_time_since(tstart,
343 user_specific_delay(authctxt->user));
344 userauth_finish(ssh, authenticated, method, NULL);
354 userauth_finish(struct ssh *ssh, int authenticated, const char *method,
355 const char *submethod)
357 Authctxt *authctxt = ssh->authctxt;
361 if (!authctxt->valid && authenticated)
362 fatal("INTERNAL ERROR: authenticated invalid user %s",
364 if (authenticated && authctxt->postponed)
365 fatal("INTERNAL ERROR: authenticated and postponed");
367 /* Special handling for root */
368 if (authenticated && authctxt->pw->pw_uid == 0 &&
369 !auth_root_allowed(ssh, method)) {
371 #ifdef SSH_AUDIT_EVENTS
372 PRIVSEP(audit_event(ssh, SSH_LOGIN_ROOT_DENIED));
376 if (authenticated && options.num_auth_methods != 0) {
377 if (!auth2_update_methods_lists(authctxt, method, submethod)) {
383 /* Log before sending the reply */
384 auth_log(ssh, authenticated, partial, method, submethod);
386 /* Update information exposed to session */
387 if (authenticated || partial)
388 auth2_update_session_info(authctxt, method, submethod);
390 if (authctxt->postponed)
394 if (options.use_pam && authenticated) {
397 if (!PRIVSEP(do_pam_account())) {
398 /* if PAM returned a message, send it to the user */
399 if (sshbuf_len(loginmsg) > 0) {
400 if ((r = sshbuf_put(loginmsg, "\0", 1)) != 0)
401 fatal("%s: buffer error: %s",
402 __func__, ssh_err(r));
403 userauth_send_banner(ssh, sshbuf_ptr(loginmsg));
404 if ((r = ssh_packet_write_wait(ssh)) != 0) {
406 "%s: send PAM banner", __func__);
409 fatal("Access denied for user %s by PAM account "
410 "configuration", authctxt->user);
415 if (authenticated == 1) {
416 /* turn off userauth */
417 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST,
418 &dispatch_protocol_ignore);
419 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_SUCCESS)) != 0 ||
420 (r = sshpkt_send(ssh)) != 0 ||
421 (r = ssh_packet_write_wait(ssh)) != 0)
422 fatal("%s: %s", __func__, ssh_err(r));
423 /* now we can break out */
424 authctxt->success = 1;
425 ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
427 /* Allow initial try of "none" auth without failure penalty */
428 if (!partial && !authctxt->server_caused_failure &&
429 (authctxt->attempt > 1 || strcmp(method, "none") != 0))
430 authctxt->failures++;
431 if (authctxt->failures >= options.max_authtries) {
432 #ifdef SSH_AUDIT_EVENTS
433 PRIVSEP(audit_event(ssh, SSH_LOGIN_EXCEED_MAXTRIES));
435 auth_maxtries_exceeded(ssh);
437 methods = authmethods_get(authctxt);
438 debug3("%s: failure partial=%d next methods=\"%s\"", __func__,
440 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_FAILURE)) != 0 ||
441 (r = sshpkt_put_cstring(ssh, methods)) != 0 ||
442 (r = sshpkt_put_u8(ssh, partial)) != 0 ||
443 (r = sshpkt_send(ssh)) != 0 ||
444 (r = ssh_packet_write_wait(ssh)) != 0)
445 fatal("%s: %s", __func__, ssh_err(r));
451 * Checks whether method is allowed by at least one AuthenticationMethods
452 * methods list. Returns 1 if allowed, or no methods lists configured.
456 auth2_method_allowed(Authctxt *authctxt, const char *method,
457 const char *submethod)
462 * NB. authctxt->num_auth_methods might be zero as a result of
463 * auth2_setup_methods_lists(), so check the configuration.
465 if (options.num_auth_methods == 0)
467 for (i = 0; i < authctxt->num_auth_methods; i++) {
468 if (list_starts_with(authctxt->auth_methods[i], method,
469 submethod) != MATCH_NONE)
476 authmethods_get(Authctxt *authctxt)
482 if ((b = sshbuf_new()) == NULL)
483 fatal("%s: sshbuf_new failed", __func__);
484 for (i = 0; authmethods[i] != NULL; i++) {
485 if (strcmp(authmethods[i]->name, "none") == 0)
487 if (authmethods[i]->enabled == NULL ||
488 *(authmethods[i]->enabled) == 0)
490 if (!auth2_method_allowed(authctxt, authmethods[i]->name,
493 if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) ? "," : "",
494 authmethods[i]->name)) != 0)
495 fatal("%s: buffer error: %s", __func__, ssh_err(r));
497 if ((list = sshbuf_dup_string(b)) == NULL)
498 fatal("%s: sshbuf_dup_string failed", __func__);
504 authmethod_lookup(Authctxt *authctxt, const char *name)
509 for (i = 0; authmethods[i] != NULL; i++)
510 if (authmethods[i]->enabled != NULL &&
511 *(authmethods[i]->enabled) != 0 &&
512 strcmp(name, authmethods[i]->name) == 0 &&
513 auth2_method_allowed(authctxt,
514 authmethods[i]->name, NULL))
515 return authmethods[i];
516 debug2("Unrecognized authentication method name: %s",
517 name ? name : "NULL");
522 * Check a comma-separated list of methods for validity. Is need_enable is
523 * non-zero, then also require that the methods are enabled.
524 * Returns 0 on success or -1 if the methods list is invalid.
527 auth2_methods_valid(const char *_methods, int need_enable)
529 char *methods, *omethods, *method, *p;
533 if (*_methods == '\0') {
534 error("empty authentication method list");
537 omethods = methods = xstrdup(_methods);
538 while ((method = strsep(&methods, ",")) != NULL) {
539 for (found = i = 0; !found && authmethods[i] != NULL; i++) {
540 if ((p = strchr(method, ':')) != NULL)
542 if (strcmp(method, authmethods[i]->name) != 0)
545 if (authmethods[i]->enabled == NULL ||
546 *(authmethods[i]->enabled) == 0) {
547 error("Disabled method \"%s\" in "
548 "AuthenticationMethods list \"%s\"",
557 error("Unknown authentication method \"%s\" in list",
569 * Prune the AuthenticationMethods supplied in the configuration, removing
570 * any methods lists that include disabled methods. Note that this might
571 * leave authctxt->num_auth_methods == 0, even when multiple required auth
572 * has been requested. For this reason, all tests for whether multiple is
573 * enabled should consult options.num_auth_methods directly.
576 auth2_setup_methods_lists(Authctxt *authctxt)
580 /* First, normalise away the "any" pseudo-method */
581 if (options.num_auth_methods == 1 &&
582 strcmp(options.auth_methods[0], "any") == 0) {
583 free(options.auth_methods[0]);
584 options.auth_methods[0] = NULL;
585 options.num_auth_methods = 0;
588 if (options.num_auth_methods == 0)
590 debug3("%s: checking methods", __func__);
591 authctxt->auth_methods = xcalloc(options.num_auth_methods,
592 sizeof(*authctxt->auth_methods));
593 authctxt->num_auth_methods = 0;
594 for (i = 0; i < options.num_auth_methods; i++) {
595 if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {
596 logit("Authentication methods list \"%s\" contains "
597 "disabled method, skipping",
598 options.auth_methods[i]);
601 debug("authentication methods list %d: %s",
602 authctxt->num_auth_methods, options.auth_methods[i]);
603 authctxt->auth_methods[authctxt->num_auth_methods++] =
604 xstrdup(options.auth_methods[i]);
606 if (authctxt->num_auth_methods == 0) {
607 error("No AuthenticationMethods left after eliminating "
615 list_starts_with(const char *methods, const char *method,
616 const char *submethod)
618 size_t l = strlen(method);
622 if (strncmp(methods, method, l) != 0)
625 match = MATCH_METHOD;
628 return MATCH_PARTIAL;
629 l = strlen(submethod);
631 if (strncmp(submethod, p, l))
636 if (*p != ',' && *p != '\0')
642 * Remove method from the start of a comma-separated list of methods.
643 * Returns 0 if the list of methods did not start with that method or 1
647 remove_method(char **methods, const char *method, const char *submethod)
649 char *omethods = *methods, *p;
650 size_t l = strlen(method);
653 match = list_starts_with(omethods, method, submethod);
654 if (match != MATCH_METHOD && match != MATCH_BOTH)
657 if (submethod && match == MATCH_BOTH)
658 p += 1 + strlen(submethod); /* include colon */
661 *methods = xstrdup(p);
667 * Called after successful authentication. Will remove the successful method
668 * from the start of each list in which it occurs. If it was the last method
669 * in any list, then authentication is deemed successful.
670 * Returns 1 if the method completed any authentication list or 0 otherwise.
673 auth2_update_methods_lists(Authctxt *authctxt, const char *method,
674 const char *submethod)
678 debug3("%s: updating methods list after \"%s\"", __func__, method);
679 for (i = 0; i < authctxt->num_auth_methods; i++) {
680 if (!remove_method(&(authctxt->auth_methods[i]), method,
684 if (*authctxt->auth_methods[i] == '\0') {
685 debug2("authentication methods list %d complete", i);
688 debug3("authentication methods list %d remaining: \"%s\"",
689 i, authctxt->auth_methods[i]);
691 /* This should not happen, but would be bad if it did */
693 fatal("%s: method not in AuthenticationMethods", __func__);
697 /* Reset method-specific information */
698 void auth2_authctxt_reset_info(Authctxt *authctxt)
700 sshkey_free(authctxt->auth_method_key);
701 free(authctxt->auth_method_info);
702 authctxt->auth_method_key = NULL;
703 authctxt->auth_method_info = NULL;
706 /* Record auth method-specific information for logs */
708 auth2_record_info(Authctxt *authctxt, const char *fmt, ...)
713 free(authctxt->auth_method_info);
714 authctxt->auth_method_info = NULL;
717 i = vasprintf(&authctxt->auth_method_info, fmt, ap);
720 if (i < 0 || authctxt->auth_method_info == NULL)
721 fatal("%s: vasprintf failed", __func__);
725 * Records a public key used in authentication. This is used for logging
726 * and to ensure that the same key is not subsequently accepted again for
727 * multiple authentication.
730 auth2_record_key(Authctxt *authctxt, int authenticated,
731 const struct sshkey *key)
733 struct sshkey **tmp, *dup;
736 if ((r = sshkey_from_private(key, &dup)) != 0)
737 fatal("%s: copy key: %s", __func__, ssh_err(r));
738 sshkey_free(authctxt->auth_method_key);
739 authctxt->auth_method_key = dup;
744 /* If authenticated, make sure we don't accept this key again */
745 if ((r = sshkey_from_private(key, &dup)) != 0)
746 fatal("%s: copy key: %s", __func__, ssh_err(r));
747 if (authctxt->nprev_keys >= INT_MAX ||
748 (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,
749 authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)
750 fatal("%s: reallocarray failed", __func__);
751 authctxt->prev_keys = tmp;
752 authctxt->prev_keys[authctxt->nprev_keys] = dup;
753 authctxt->nprev_keys++;
757 /* Checks whether a key has already been previously used for authentication */
759 auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key)
764 for (i = 0; i < authctxt->nprev_keys; i++) {
765 if (sshkey_equal_public(key, authctxt->prev_keys[i])) {
766 fp = sshkey_fingerprint(authctxt->prev_keys[i],
767 options.fingerprint_hash, SSH_FP_DEFAULT);
768 debug3("%s: key already used: %s %s", __func__,
769 sshkey_type(authctxt->prev_keys[i]),
770 fp == NULL ? "UNKNOWN" : fp);
779 * Updates authctxt->session_info with details of authentication. Should be
780 * whenever an authentication method succeeds.
783 auth2_update_session_info(Authctxt *authctxt, const char *method,
784 const char *submethod)
788 if (authctxt->session_info == NULL) {
789 if ((authctxt->session_info = sshbuf_new()) == NULL)
790 fatal("%s: sshbuf_new", __func__);
793 /* Append method[/submethod] */
794 if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",
795 method, submethod == NULL ? "" : "/",
796 submethod == NULL ? "" : submethod)) != 0)
797 fatal("%s: append method: %s", __func__, ssh_err(r));
799 /* Append key if present */
800 if (authctxt->auth_method_key != NULL) {
801 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
802 (r = sshkey_format_text(authctxt->auth_method_key,
803 authctxt->session_info)) != 0)
804 fatal("%s: append key: %s", __func__, ssh_err(r));
807 if (authctxt->auth_method_info != NULL) {
808 /* Ensure no ambiguity here */
809 if (strchr(authctxt->auth_method_info, '\n') != NULL)
810 fatal("%s: auth_method_info contains \\n", __func__);
811 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
812 (r = sshbuf_putf(authctxt->session_info, "%s",
813 authctxt->auth_method_info)) != 0) {
814 fatal("%s: append method info: %s",
815 __func__, ssh_err(r));
818 if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)
819 fatal("%s: append: %s", __func__, ssh_err(r));