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.
28 #include <sys/types.h>
52 #include "pathnames.h"
58 #include "monitor_wrap.h"
62 extern ServerOptions options;
63 extern u_char *session_id2;
64 extern u_int session_id2_len;
65 extern Buffer loginmsg;
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;
75 extern Authmethod method_gssapi;
78 Authmethod *authmethods[] = {
92 static int input_service_request(int, u_int32_t, struct ssh *);
93 static int input_userauth_request(int, u_int32_t, struct ssh *);
96 static Authmethod *authmethod_lookup(Authctxt *, const char *);
97 static char *authmethods_get(Authctxt *authctxt);
99 #define MATCH_NONE 0 /* method or submethod mismatch */
100 #define MATCH_METHOD 1 /* method matches (no submethod specified) */
101 #define MATCH_BOTH 2 /* method and submethod match */
102 #define MATCH_PARTIAL 3 /* method matches, submethod can't be checked */
103 static int list_starts_with(const char *, const char *, const char *);
106 auth2_read_banner(void)
113 if ((fd = open(options.banner, O_RDONLY)) == -1)
115 if (fstat(fd, &st) == -1) {
119 if (st.st_size <= 0 || st.st_size > 1*1024*1024) {
124 len = (size_t)st.st_size; /* truncate */
125 banner = xmalloc(len + 1);
126 n = atomicio(read, fd, banner, len);
139 userauth_send_banner(const char *msg)
141 packet_start(SSH2_MSG_USERAUTH_BANNER);
142 packet_put_cstring(msg);
143 packet_put_cstring(""); /* language, unused */
145 debug("%s: sent", __func__);
149 userauth_banner(void)
153 if (options.banner == NULL)
156 if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
158 userauth_send_banner(banner);
165 * loop until authctxt->success == TRUE
168 do_authentication2(Authctxt *authctxt)
170 struct ssh *ssh = active_state; /* XXX */
171 ssh->authctxt = authctxt; /* XXX move to caller */
172 ssh_dispatch_init(ssh, &dispatch_protocol_error);
173 ssh_dispatch_set(ssh, SSH2_MSG_SERVICE_REQUEST, &input_service_request);
174 ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &authctxt->success);
175 ssh->authctxt = NULL;
180 input_service_request(int type, u_int32_t seq, struct ssh *ssh)
182 Authctxt *authctxt = ssh->authctxt;
185 char *service = packet_get_cstring(&len);
188 if (authctxt == NULL)
189 fatal("input_service_request: no authctxt");
191 if (strcmp(service, "ssh-userauth") == 0) {
192 if (!authctxt->success) {
194 /* now we can handle user-auth requests */
195 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
198 /* XXX all other service requests are denied */
201 packet_start(SSH2_MSG_SERVICE_ACCEPT);
202 packet_put_cstring(service);
206 debug("bad service request %s", service);
207 packet_disconnect("bad service request %s", service);
215 input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)
217 Authctxt *authctxt = ssh->authctxt;
218 Authmethod *m = NULL;
219 char *user, *service, *method, *style = NULL;
220 int authenticated = 0;
222 if (authctxt == NULL)
223 fatal("input_userauth_request: no authctxt");
225 user = packet_get_cstring(NULL);
226 service = packet_get_cstring(NULL);
227 method = packet_get_cstring(NULL);
228 debug("userauth-request for user %s service %s method %s", user, service, method);
229 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
231 if ((style = strchr(user, ':')) != NULL)
234 if (authctxt->attempt++ == 0) {
235 /* setup auth context */
236 authctxt->pw = PRIVSEP(getpwnamallow(user));
237 authctxt->user = xstrdup(user);
238 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
240 debug2("%s: setting up authctxt for %s",
243 /* Invalid user, fake password information */
244 authctxt->pw = fakepw();
245 #ifdef SSH_AUDIT_EVENTS
246 PRIVSEP(audit_event(SSH_INVALID_USER));
251 PRIVSEP(start_pam(authctxt));
253 ssh_packet_set_log_preamble(ssh, "%suser %s",
254 authctxt->valid ? "authenticating " : "invalid ", user);
255 setproctitle("%s%s", authctxt->valid ? user : "unknown",
256 use_privsep ? " [net]" : "");
257 authctxt->service = xstrdup(service);
258 authctxt->style = style ? xstrdup(style) : NULL;
260 mm_inform_authserv(service, style);
262 if (auth2_setup_methods_lists(authctxt) != 0)
263 packet_disconnect("no authentication methods enabled");
264 } else if (strcmp(user, authctxt->user) != 0 ||
265 strcmp(service, authctxt->service) != 0) {
266 packet_disconnect("Change of username or service not allowed: "
267 "(%s,%s) -> (%s,%s)",
268 authctxt->user, authctxt->service, user, service);
271 auth2_challenge_stop(ssh);
274 /* XXX move to auth2_gssapi_stop() */
275 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
276 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
279 auth2_authctxt_reset_info(authctxt);
280 authctxt->postponed = 0;
281 authctxt->server_caused_failure = 0;
283 /* try to authenticate user */
284 m = authmethod_lookup(authctxt, method);
285 if (m != NULL && authctxt->failures < options.max_authtries) {
286 debug2("input_userauth_request: try method %s", method);
287 authenticated = m->userauth(ssh);
289 userauth_finish(ssh, authenticated, method, NULL);
298 userauth_finish(struct ssh *ssh, int authenticated, const char *method,
299 const char *submethod)
301 Authctxt *authctxt = ssh->authctxt;
305 if (!authctxt->valid && authenticated)
306 fatal("INTERNAL ERROR: authenticated invalid user %s",
308 if (authenticated && authctxt->postponed)
309 fatal("INTERNAL ERROR: authenticated and postponed");
311 /* Special handling for root */
312 if (authenticated && authctxt->pw->pw_uid == 0 &&
313 !auth_root_allowed(ssh, method)) {
315 #ifdef SSH_AUDIT_EVENTS
316 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
320 if (authenticated && options.num_auth_methods != 0) {
321 if (!auth2_update_methods_lists(authctxt, method, submethod)) {
327 /* Log before sending the reply */
328 auth_log(authctxt, authenticated, partial, method, submethod);
330 /* Update information exposed to session */
331 if (authenticated || partial)
332 auth2_update_session_info(authctxt, method, submethod);
334 if (authctxt->postponed)
338 if (options.use_pam && authenticated) {
339 if (!PRIVSEP(do_pam_account())) {
340 /* if PAM returned a message, send it to the user */
341 if (buffer_len(&loginmsg) > 0) {
342 buffer_append(&loginmsg, "\0", 1);
343 userauth_send_banner(buffer_ptr(&loginmsg));
346 fatal("Access denied for user %s by PAM account "
347 "configuration", authctxt->user);
352 if (authenticated == 1) {
353 /* turn off userauth */
354 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
355 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
358 /* now we can break out */
359 authctxt->success = 1;
360 ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
362 /* Allow initial try of "none" auth without failure penalty */
363 if (!partial && !authctxt->server_caused_failure &&
364 (authctxt->attempt > 1 || strcmp(method, "none") != 0))
365 authctxt->failures++;
366 if (authctxt->failures >= options.max_authtries) {
367 #ifdef SSH_AUDIT_EVENTS
368 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
370 auth_maxtries_exceeded(authctxt);
372 methods = authmethods_get(authctxt);
373 debug3("%s: failure partial=%d next methods=\"%s\"", __func__,
375 packet_start(SSH2_MSG_USERAUTH_FAILURE);
376 packet_put_cstring(methods);
377 packet_put_char(partial);
385 * Checks whether method is allowed by at least one AuthenticationMethods
386 * methods list. Returns 1 if allowed, or no methods lists configured.
390 auth2_method_allowed(Authctxt *authctxt, const char *method,
391 const char *submethod)
396 * NB. authctxt->num_auth_methods might be zero as a result of
397 * auth2_setup_methods_lists(), so check the configuration.
399 if (options.num_auth_methods == 0)
401 for (i = 0; i < authctxt->num_auth_methods; i++) {
402 if (list_starts_with(authctxt->auth_methods[i], method,
403 submethod) != MATCH_NONE)
410 authmethods_get(Authctxt *authctxt)
417 for (i = 0; authmethods[i] != NULL; i++) {
418 if (strcmp(authmethods[i]->name, "none") == 0)
420 if (authmethods[i]->enabled == NULL ||
421 *(authmethods[i]->enabled) == 0)
423 if (!auth2_method_allowed(authctxt, authmethods[i]->name,
426 if (buffer_len(&b) > 0)
427 buffer_append(&b, ",", 1);
428 buffer_append(&b, authmethods[i]->name,
429 strlen(authmethods[i]->name));
431 if ((list = sshbuf_dup_string(&b)) == NULL)
432 fatal("%s: sshbuf_dup_string failed", __func__);
438 authmethod_lookup(Authctxt *authctxt, const char *name)
443 for (i = 0; authmethods[i] != NULL; i++)
444 if (authmethods[i]->enabled != NULL &&
445 *(authmethods[i]->enabled) != 0 &&
446 strcmp(name, authmethods[i]->name) == 0 &&
447 auth2_method_allowed(authctxt,
448 authmethods[i]->name, NULL))
449 return authmethods[i];
450 debug2("Unrecognized authentication method name: %s",
451 name ? name : "NULL");
456 * Check a comma-separated list of methods for validity. Is need_enable is
457 * non-zero, then also require that the methods are enabled.
458 * Returns 0 on success or -1 if the methods list is invalid.
461 auth2_methods_valid(const char *_methods, int need_enable)
463 char *methods, *omethods, *method, *p;
467 if (*_methods == '\0') {
468 error("empty authentication method list");
471 omethods = methods = xstrdup(_methods);
472 while ((method = strsep(&methods, ",")) != NULL) {
473 for (found = i = 0; !found && authmethods[i] != NULL; i++) {
474 if ((p = strchr(method, ':')) != NULL)
476 if (strcmp(method, authmethods[i]->name) != 0)
479 if (authmethods[i]->enabled == NULL ||
480 *(authmethods[i]->enabled) == 0) {
481 error("Disabled method \"%s\" in "
482 "AuthenticationMethods list \"%s\"",
491 error("Unknown authentication method \"%s\" in list",
503 * Prune the AuthenticationMethods supplied in the configuration, removing
504 * any methods lists that include disabled methods. Note that this might
505 * leave authctxt->num_auth_methods == 0, even when multiple required auth
506 * has been requested. For this reason, all tests for whether multiple is
507 * enabled should consult options.num_auth_methods directly.
510 auth2_setup_methods_lists(Authctxt *authctxt)
514 if (options.num_auth_methods == 0)
516 debug3("%s: checking methods", __func__);
517 authctxt->auth_methods = xcalloc(options.num_auth_methods,
518 sizeof(*authctxt->auth_methods));
519 authctxt->num_auth_methods = 0;
520 for (i = 0; i < options.num_auth_methods; i++) {
521 if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {
522 logit("Authentication methods list \"%s\" contains "
523 "disabled method, skipping",
524 options.auth_methods[i]);
527 debug("authentication methods list %d: %s",
528 authctxt->num_auth_methods, options.auth_methods[i]);
529 authctxt->auth_methods[authctxt->num_auth_methods++] =
530 xstrdup(options.auth_methods[i]);
532 if (authctxt->num_auth_methods == 0) {
533 error("No AuthenticationMethods left after eliminating "
541 list_starts_with(const char *methods, const char *method,
542 const char *submethod)
544 size_t l = strlen(method);
548 if (strncmp(methods, method, l) != 0)
551 match = MATCH_METHOD;
554 return MATCH_PARTIAL;
555 l = strlen(submethod);
557 if (strncmp(submethod, p, l))
562 if (*p != ',' && *p != '\0')
568 * Remove method from the start of a comma-separated list of methods.
569 * Returns 0 if the list of methods did not start with that method or 1
573 remove_method(char **methods, const char *method, const char *submethod)
575 char *omethods = *methods, *p;
576 size_t l = strlen(method);
579 match = list_starts_with(omethods, method, submethod);
580 if (match != MATCH_METHOD && match != MATCH_BOTH)
583 if (submethod && match == MATCH_BOTH)
584 p += 1 + strlen(submethod); /* include colon */
587 *methods = xstrdup(p);
593 * Called after successful authentication. Will remove the successful method
594 * from the start of each list in which it occurs. If it was the last method
595 * in any list, then authentication is deemed successful.
596 * Returns 1 if the method completed any authentication list or 0 otherwise.
599 auth2_update_methods_lists(Authctxt *authctxt, const char *method,
600 const char *submethod)
604 debug3("%s: updating methods list after \"%s\"", __func__, method);
605 for (i = 0; i < authctxt->num_auth_methods; i++) {
606 if (!remove_method(&(authctxt->auth_methods[i]), method,
610 if (*authctxt->auth_methods[i] == '\0') {
611 debug2("authentication methods list %d complete", i);
614 debug3("authentication methods list %d remaining: \"%s\"",
615 i, authctxt->auth_methods[i]);
617 /* This should not happen, but would be bad if it did */
619 fatal("%s: method not in AuthenticationMethods", __func__);
623 /* Reset method-specific information */
624 void auth2_authctxt_reset_info(Authctxt *authctxt)
626 sshkey_free(authctxt->auth_method_key);
627 free(authctxt->auth_method_info);
628 authctxt->auth_method_key = NULL;
629 authctxt->auth_method_info = NULL;
632 /* Record auth method-specific information for logs */
634 auth2_record_info(Authctxt *authctxt, const char *fmt, ...)
639 free(authctxt->auth_method_info);
640 authctxt->auth_method_info = NULL;
643 i = vasprintf(&authctxt->auth_method_info, fmt, ap);
646 if (i < 0 || authctxt->auth_method_info == NULL)
647 fatal("%s: vasprintf failed", __func__);
651 * Records a public key used in authentication. This is used for logging
652 * and to ensure that the same key is not subsequently accepted again for
653 * multiple authentication.
656 auth2_record_key(Authctxt *authctxt, int authenticated,
657 const struct sshkey *key)
659 struct sshkey **tmp, *dup;
662 if ((r = sshkey_demote(key, &dup)) != 0)
663 fatal("%s: copy key: %s", __func__, ssh_err(r));
664 sshkey_free(authctxt->auth_method_key);
665 authctxt->auth_method_key = dup;
670 /* If authenticated, make sure we don't accept this key again */
671 if ((r = sshkey_demote(key, &dup)) != 0)
672 fatal("%s: copy key: %s", __func__, ssh_err(r));
673 if (authctxt->nprev_keys >= INT_MAX ||
674 (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,
675 authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)
676 fatal("%s: reallocarray failed", __func__);
677 authctxt->prev_keys = tmp;
678 authctxt->prev_keys[authctxt->nprev_keys] = dup;
679 authctxt->nprev_keys++;
683 /* Checks whether a key has already been previously used for authentication */
685 auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key)
690 for (i = 0; i < authctxt->nprev_keys; i++) {
691 if (sshkey_equal_public(key, authctxt->prev_keys[i])) {
692 fp = sshkey_fingerprint(authctxt->prev_keys[i],
693 options.fingerprint_hash, SSH_FP_DEFAULT);
694 debug3("%s: key already used: %s %s", __func__,
695 sshkey_type(authctxt->prev_keys[i]),
696 fp == NULL ? "UNKNOWN" : fp);
705 * Updates authctxt->session_info with details of authentication. Should be
706 * whenever an authentication method succeeds.
709 auth2_update_session_info(Authctxt *authctxt, const char *method,
710 const char *submethod)
714 if (authctxt->session_info == NULL) {
715 if ((authctxt->session_info = sshbuf_new()) == NULL)
716 fatal("%s: sshbuf_new", __func__);
719 /* Append method[/submethod] */
720 if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",
721 method, submethod == NULL ? "" : "/",
722 submethod == NULL ? "" : submethod)) != 0)
723 fatal("%s: append method: %s", __func__, ssh_err(r));
725 /* Append key if present */
726 if (authctxt->auth_method_key != NULL) {
727 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
728 (r = sshkey_format_text(authctxt->auth_method_key,
729 authctxt->session_info)) != 0)
730 fatal("%s: append key: %s", __func__, ssh_err(r));
733 if (authctxt->auth_method_info != NULL) {
734 /* Ensure no ambiguity here */
735 if (strchr(authctxt->auth_method_info, '\n') != NULL)
736 fatal("%s: auth_method_info contains \\n", __func__);
737 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
738 (r = sshbuf_putf(authctxt->session_info, "%s",
739 authctxt->auth_method_info)) != 0) {
740 fatal("%s: append method info: %s",
741 __func__, ssh_err(r));
744 if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)
745 fatal("%s: append: %s", __func__, ssh_err(r));