1 /* $OpenBSD: auth2.c,v 1.145 2018/03/03 03:15:51 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.
29 #include <sys/types.h>
53 #include "pathnames.h"
55 #include "blacklist_client.h"
60 #include "monitor_wrap.h"
64 extern ServerOptions options;
65 extern u_char *session_id2;
66 extern u_int session_id2_len;
67 extern Buffer loginmsg;
71 extern Authmethod method_none;
72 extern Authmethod method_pubkey;
73 extern Authmethod method_passwd;
74 extern Authmethod method_kbdint;
75 extern Authmethod method_hostbased;
77 extern Authmethod method_gssapi;
80 Authmethod *authmethods[] = {
94 static int input_service_request(int, u_int32_t, struct ssh *);
95 static int input_userauth_request(int, u_int32_t, struct ssh *);
98 static Authmethod *authmethod_lookup(Authctxt *, const char *);
99 static char *authmethods_get(Authctxt *authctxt);
101 #define MATCH_NONE 0 /* method or submethod mismatch */
102 #define MATCH_METHOD 1 /* method matches (no submethod specified) */
103 #define MATCH_BOTH 2 /* method and submethod match */
104 #define MATCH_PARTIAL 3 /* method matches, submethod can't be checked */
105 static int list_starts_with(const char *, const char *, const char *);
108 auth2_read_banner(void)
115 if ((fd = open(options.banner, O_RDONLY)) == -1)
117 if (fstat(fd, &st) == -1) {
121 if (st.st_size <= 0 || st.st_size > 1*1024*1024) {
126 len = (size_t)st.st_size; /* truncate */
127 banner = xmalloc(len + 1);
128 n = atomicio(read, fd, banner, len);
141 userauth_send_banner(const char *msg)
143 packet_start(SSH2_MSG_USERAUTH_BANNER);
144 packet_put_cstring(msg);
145 packet_put_cstring(""); /* language, unused */
147 debug("%s: sent", __func__);
151 userauth_banner(void)
155 if (options.banner == NULL)
158 if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
160 userauth_send_banner(banner);
167 * loop until authctxt->success == TRUE
170 do_authentication2(Authctxt *authctxt)
172 struct ssh *ssh = active_state; /* XXX */
173 ssh->authctxt = authctxt; /* XXX move to caller */
174 ssh_dispatch_init(ssh, &dispatch_protocol_error);
175 ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_REQUEST, &input_service_request);
176 ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt->success);
177 ssh->authctxt = NULL;
182 input_service_request(int type, u_int32_t seq, struct ssh *ssh)
184 Authctxt *authctxt = ssh->authctxt;
187 char *service = packet_get_cstring(&len);
190 if (authctxt == NULL)
191 fatal("input_service_request: no authctxt");
193 if (strcmp(service, "ssh-userauth") == 0) {
194 if (!authctxt->success) {
196 /* now we can handle user-auth requests */
197 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
200 /* XXX all other service requests are denied */
203 packet_start(SSH2_MSG_SERVICE_ACCEPT);
204 packet_put_cstring(service);
208 debug("bad service request %s", service);
209 packet_disconnect("bad service request %s", service);
217 input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)
219 Authctxt *authctxt = ssh->authctxt;
220 Authmethod *m = NULL;
221 char *user, *service, *method, *style = NULL;
222 int authenticated = 0;
223 #ifdef HAVE_LOGIN_CAP
225 const char *from_host, *from_ip;
228 if (authctxt == NULL)
229 fatal("input_userauth_request: no authctxt");
231 user = packet_get_cstring(NULL);
232 service = packet_get_cstring(NULL);
233 method = packet_get_cstring(NULL);
234 debug("userauth-request for user %s service %s method %s", user, service, method);
235 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
237 if ((style = strchr(user, ':')) != NULL)
240 if (authctxt->attempt++ == 0) {
241 /* setup auth context */
242 authctxt->pw = PRIVSEP(getpwnamallow(user));
243 authctxt->user = xstrdup(user);
244 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
246 debug2("%s: setting up authctxt for %s",
249 /* Invalid user, fake password information */
250 authctxt->pw = fakepw();
251 #ifdef SSH_AUDIT_EVENTS
252 PRIVSEP(audit_event(SSH_INVALID_USER));
257 PRIVSEP(start_pam(authctxt));
259 ssh_packet_set_log_preamble(ssh, "%suser %s",
260 authctxt->valid ? "authenticating " : "invalid ", user);
261 setproctitle("%s%s", authctxt->valid ? user : "unknown",
262 use_privsep ? " [net]" : "");
263 authctxt->service = xstrdup(service);
264 authctxt->style = style ? xstrdup(style) : NULL;
266 mm_inform_authserv(service, style);
268 if (auth2_setup_methods_lists(authctxt) != 0)
269 packet_disconnect("no authentication methods enabled");
270 } else if (strcmp(user, authctxt->user) != 0 ||
271 strcmp(service, authctxt->service) != 0) {
272 packet_disconnect("Change of username or service not allowed: "
273 "(%s,%s) -> (%s,%s)",
274 authctxt->user, authctxt->service, user, service);
277 #ifdef HAVE_LOGIN_CAP
278 if (authctxt->pw != NULL &&
279 (lc = login_getpwclass(authctxt->pw)) != NULL) {
280 logit("user %s login class %s", authctxt->pw->pw_name,
281 authctxt->pw->pw_class);
282 from_host = auth_get_canonical_hostname(ssh, options.use_dns);
283 from_ip = ssh_remote_ipaddr(ssh);
284 if (!auth_hostok(lc, from_host, from_ip)) {
285 logit("Denied connection for %.200s from %.200s [%.200s].",
286 authctxt->pw->pw_name, from_host, from_ip);
287 packet_disconnect("Sorry, you are not allowed to connect.");
289 if (!auth_timeok(lc, time(NULL))) {
290 logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
291 authctxt->pw->pw_name, from_host);
292 packet_disconnect("Logins not available right now.");
296 #endif /* HAVE_LOGIN_CAP */
299 auth2_challenge_stop(ssh);
302 /* XXX move to auth2_gssapi_stop() */
303 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
304 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
307 auth2_authctxt_reset_info(authctxt);
308 authctxt->postponed = 0;
309 authctxt->server_caused_failure = 0;
311 /* try to authenticate user */
312 m = authmethod_lookup(authctxt, method);
313 if (m != NULL && authctxt->failures < options.max_authtries) {
314 debug2("input_userauth_request: try method %s", method);
315 authenticated = m->userauth(ssh);
317 userauth_finish(ssh, authenticated, method, NULL);
326 userauth_finish(struct ssh *ssh, int authenticated, const char *method,
327 const char *submethod)
329 Authctxt *authctxt = ssh->authctxt;
333 if (!authctxt->valid && authenticated)
334 fatal("INTERNAL ERROR: authenticated invalid user %s",
336 if (authenticated && authctxt->postponed)
337 fatal("INTERNAL ERROR: authenticated and postponed");
339 /* Special handling for root */
340 if (authenticated && authctxt->pw->pw_uid == 0 &&
341 !auth_root_allowed(ssh, method)) {
343 #ifdef SSH_AUDIT_EVENTS
344 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
348 if (authenticated && options.num_auth_methods != 0) {
349 if (!auth2_update_methods_lists(authctxt, method, submethod)) {
355 /* Log before sending the reply */
356 auth_log(authctxt, authenticated, partial, method, submethod);
358 /* Update information exposed to session */
359 if (authenticated || partial)
360 auth2_update_session_info(authctxt, method, submethod);
362 if (authctxt->postponed)
366 if (options.use_pam && authenticated) {
367 if (!PRIVSEP(do_pam_account())) {
368 /* if PAM returned a message, send it to the user */
369 if (buffer_len(&loginmsg) > 0) {
370 buffer_append(&loginmsg, "\0", 1);
371 userauth_send_banner(buffer_ptr(&loginmsg));
374 fatal("Access denied for user %s by PAM account "
375 "configuration", authctxt->user);
380 if (authenticated == 1) {
381 /* turn off userauth */
382 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
383 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
386 /* now we can break out */
387 authctxt->success = 1;
388 ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
390 /* Allow initial try of "none" auth without failure penalty */
391 if (!partial && !authctxt->server_caused_failure &&
392 (authctxt->attempt > 1 || strcmp(method, "none") != 0)) {
393 authctxt->failures++;
394 BLACKLIST_NOTIFY(BLACKLIST_AUTH_FAIL, "ssh");
396 if (authctxt->failures >= options.max_authtries) {
397 #ifdef SSH_AUDIT_EVENTS
398 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
400 auth_maxtries_exceeded(authctxt);
402 methods = authmethods_get(authctxt);
403 debug3("%s: failure partial=%d next methods=\"%s\"", __func__,
405 packet_start(SSH2_MSG_USERAUTH_FAILURE);
406 packet_put_cstring(methods);
407 packet_put_char(partial);
415 * Checks whether method is allowed by at least one AuthenticationMethods
416 * methods list. Returns 1 if allowed, or no methods lists configured.
420 auth2_method_allowed(Authctxt *authctxt, const char *method,
421 const char *submethod)
426 * NB. authctxt->num_auth_methods might be zero as a result of
427 * auth2_setup_methods_lists(), so check the configuration.
429 if (options.num_auth_methods == 0)
431 for (i = 0; i < authctxt->num_auth_methods; i++) {
432 if (list_starts_with(authctxt->auth_methods[i], method,
433 submethod) != MATCH_NONE)
440 authmethods_get(Authctxt *authctxt)
447 for (i = 0; authmethods[i] != NULL; i++) {
448 if (strcmp(authmethods[i]->name, "none") == 0)
450 if (authmethods[i]->enabled == NULL ||
451 *(authmethods[i]->enabled) == 0)
453 if (!auth2_method_allowed(authctxt, authmethods[i]->name,
456 if (buffer_len(&b) > 0)
457 buffer_append(&b, ",", 1);
458 buffer_append(&b, authmethods[i]->name,
459 strlen(authmethods[i]->name));
461 if ((list = sshbuf_dup_string(&b)) == NULL)
462 fatal("%s: sshbuf_dup_string failed", __func__);
468 authmethod_lookup(Authctxt *authctxt, const char *name)
473 for (i = 0; authmethods[i] != NULL; i++)
474 if (authmethods[i]->enabled != NULL &&
475 *(authmethods[i]->enabled) != 0 &&
476 strcmp(name, authmethods[i]->name) == 0 &&
477 auth2_method_allowed(authctxt,
478 authmethods[i]->name, NULL))
479 return authmethods[i];
480 debug2("Unrecognized authentication method name: %s",
481 name ? name : "NULL");
486 * Check a comma-separated list of methods for validity. Is need_enable is
487 * non-zero, then also require that the methods are enabled.
488 * Returns 0 on success or -1 if the methods list is invalid.
491 auth2_methods_valid(const char *_methods, int need_enable)
493 char *methods, *omethods, *method, *p;
497 if (*_methods == '\0') {
498 error("empty authentication method list");
501 omethods = methods = xstrdup(_methods);
502 while ((method = strsep(&methods, ",")) != NULL) {
503 for (found = i = 0; !found && authmethods[i] != NULL; i++) {
504 if ((p = strchr(method, ':')) != NULL)
506 if (strcmp(method, authmethods[i]->name) != 0)
509 if (authmethods[i]->enabled == NULL ||
510 *(authmethods[i]->enabled) == 0) {
511 error("Disabled method \"%s\" in "
512 "AuthenticationMethods list \"%s\"",
521 error("Unknown authentication method \"%s\" in list",
533 * Prune the AuthenticationMethods supplied in the configuration, removing
534 * any methods lists that include disabled methods. Note that this might
535 * leave authctxt->num_auth_methods == 0, even when multiple required auth
536 * has been requested. For this reason, all tests for whether multiple is
537 * enabled should consult options.num_auth_methods directly.
540 auth2_setup_methods_lists(Authctxt *authctxt)
544 if (options.num_auth_methods == 0)
546 debug3("%s: checking methods", __func__);
547 authctxt->auth_methods = xcalloc(options.num_auth_methods,
548 sizeof(*authctxt->auth_methods));
549 authctxt->num_auth_methods = 0;
550 for (i = 0; i < options.num_auth_methods; i++) {
551 if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {
552 logit("Authentication methods list \"%s\" contains "
553 "disabled method, skipping",
554 options.auth_methods[i]);
557 debug("authentication methods list %d: %s",
558 authctxt->num_auth_methods, options.auth_methods[i]);
559 authctxt->auth_methods[authctxt->num_auth_methods++] =
560 xstrdup(options.auth_methods[i]);
562 if (authctxt->num_auth_methods == 0) {
563 error("No AuthenticationMethods left after eliminating "
571 list_starts_with(const char *methods, const char *method,
572 const char *submethod)
574 size_t l = strlen(method);
578 if (strncmp(methods, method, l) != 0)
581 match = MATCH_METHOD;
584 return MATCH_PARTIAL;
585 l = strlen(submethod);
587 if (strncmp(submethod, p, l))
592 if (*p != ',' && *p != '\0')
598 * Remove method from the start of a comma-separated list of methods.
599 * Returns 0 if the list of methods did not start with that method or 1
603 remove_method(char **methods, const char *method, const char *submethod)
605 char *omethods = *methods, *p;
606 size_t l = strlen(method);
609 match = list_starts_with(omethods, method, submethod);
610 if (match != MATCH_METHOD && match != MATCH_BOTH)
613 if (submethod && match == MATCH_BOTH)
614 p += 1 + strlen(submethod); /* include colon */
617 *methods = xstrdup(p);
623 * Called after successful authentication. Will remove the successful method
624 * from the start of each list in which it occurs. If it was the last method
625 * in any list, then authentication is deemed successful.
626 * Returns 1 if the method completed any authentication list or 0 otherwise.
629 auth2_update_methods_lists(Authctxt *authctxt, const char *method,
630 const char *submethod)
634 debug3("%s: updating methods list after \"%s\"", __func__, method);
635 for (i = 0; i < authctxt->num_auth_methods; i++) {
636 if (!remove_method(&(authctxt->auth_methods[i]), method,
640 if (*authctxt->auth_methods[i] == '\0') {
641 debug2("authentication methods list %d complete", i);
644 debug3("authentication methods list %d remaining: \"%s\"",
645 i, authctxt->auth_methods[i]);
647 /* This should not happen, but would be bad if it did */
649 fatal("%s: method not in AuthenticationMethods", __func__);
653 /* Reset method-specific information */
654 void auth2_authctxt_reset_info(Authctxt *authctxt)
656 sshkey_free(authctxt->auth_method_key);
657 free(authctxt->auth_method_info);
658 authctxt->auth_method_key = NULL;
659 authctxt->auth_method_info = NULL;
662 /* Record auth method-specific information for logs */
664 auth2_record_info(Authctxt *authctxt, const char *fmt, ...)
669 free(authctxt->auth_method_info);
670 authctxt->auth_method_info = NULL;
673 i = vasprintf(&authctxt->auth_method_info, fmt, ap);
676 if (i < 0 || authctxt->auth_method_info == NULL)
677 fatal("%s: vasprintf failed", __func__);
681 * Records a public key used in authentication. This is used for logging
682 * and to ensure that the same key is not subsequently accepted again for
683 * multiple authentication.
686 auth2_record_key(Authctxt *authctxt, int authenticated,
687 const struct sshkey *key)
689 struct sshkey **tmp, *dup;
692 if ((r = sshkey_demote(key, &dup)) != 0)
693 fatal("%s: copy key: %s", __func__, ssh_err(r));
694 sshkey_free(authctxt->auth_method_key);
695 authctxt->auth_method_key = dup;
700 /* If authenticated, make sure we don't accept this key again */
701 if ((r = sshkey_demote(key, &dup)) != 0)
702 fatal("%s: copy key: %s", __func__, ssh_err(r));
703 if (authctxt->nprev_keys >= INT_MAX ||
704 (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,
705 authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)
706 fatal("%s: reallocarray failed", __func__);
707 authctxt->prev_keys = tmp;
708 authctxt->prev_keys[authctxt->nprev_keys] = dup;
709 authctxt->nprev_keys++;
713 /* Checks whether a key has already been previously used for authentication */
715 auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key)
720 for (i = 0; i < authctxt->nprev_keys; i++) {
721 if (sshkey_equal_public(key, authctxt->prev_keys[i])) {
722 fp = sshkey_fingerprint(authctxt->prev_keys[i],
723 options.fingerprint_hash, SSH_FP_DEFAULT);
724 debug3("%s: key already used: %s %s", __func__,
725 sshkey_type(authctxt->prev_keys[i]),
726 fp == NULL ? "UNKNOWN" : fp);
735 * Updates authctxt->session_info with details of authentication. Should be
736 * whenever an authentication method succeeds.
739 auth2_update_session_info(Authctxt *authctxt, const char *method,
740 const char *submethod)
744 if (authctxt->session_info == NULL) {
745 if ((authctxt->session_info = sshbuf_new()) == NULL)
746 fatal("%s: sshbuf_new", __func__);
749 /* Append method[/submethod] */
750 if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",
751 method, submethod == NULL ? "" : "/",
752 submethod == NULL ? "" : submethod)) != 0)
753 fatal("%s: append method: %s", __func__, ssh_err(r));
755 /* Append key if present */
756 if (authctxt->auth_method_key != NULL) {
757 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
758 (r = sshkey_format_text(authctxt->auth_method_key,
759 authctxt->session_info)) != 0)
760 fatal("%s: append key: %s", __func__, ssh_err(r));
763 if (authctxt->auth_method_info != NULL) {
764 /* Ensure no ambiguity here */
765 if (strchr(authctxt->auth_method_info, '\n') != NULL)
766 fatal("%s: auth_method_info contains \\n", __func__);
767 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
768 (r = sshbuf_putf(authctxt->session_info, "%s",
769 authctxt->auth_method_info)) != 0) {
770 fatal("%s: append method info: %s",
771 __func__, ssh_err(r));
774 if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)
775 fatal("%s: append: %s", __func__, ssh_err(r));