1 /* $OpenBSD: auth2.c,v 1.149 2018/07/11 18:53:29 markus 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"
56 #include "blacklist_client.h"
61 #include "monitor_wrap.h"
66 extern ServerOptions options;
67 extern u_char *session_id2;
68 extern u_int session_id2_len;
69 extern struct sshbuf *loginmsg;
73 extern Authmethod method_none;
74 extern Authmethod method_pubkey;
75 extern Authmethod method_passwd;
76 extern Authmethod method_kbdint;
77 extern Authmethod method_hostbased;
79 extern Authmethod method_gssapi;
82 Authmethod *authmethods[] = {
96 static int input_service_request(int, u_int32_t, struct ssh *);
97 static int input_userauth_request(int, u_int32_t, struct ssh *);
100 static Authmethod *authmethod_lookup(Authctxt *, const char *);
101 static char *authmethods_get(Authctxt *authctxt);
103 #define MATCH_NONE 0 /* method or submethod mismatch */
104 #define MATCH_METHOD 1 /* method matches (no submethod specified) */
105 #define MATCH_BOTH 2 /* method and submethod match */
106 #define MATCH_PARTIAL 3 /* method matches, submethod can't be checked */
107 static int list_starts_with(const char *, const char *, const char *);
110 auth2_read_banner(void)
117 if ((fd = open(options.banner, O_RDONLY)) == -1)
119 if (fstat(fd, &st) == -1) {
123 if (st.st_size <= 0 || st.st_size > 1*1024*1024) {
128 len = (size_t)st.st_size; /* truncate */
129 banner = xmalloc(len + 1);
130 n = atomicio(read, fd, banner, len);
143 userauth_send_banner(const char *msg)
145 packet_start(SSH2_MSG_USERAUTH_BANNER);
146 packet_put_cstring(msg);
147 packet_put_cstring(""); /* language, unused */
149 debug("%s: sent", __func__);
153 userauth_banner(void)
157 if (options.banner == NULL)
160 if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
162 userauth_send_banner(banner);
169 * loop until authctxt->success == TRUE
172 do_authentication2(Authctxt *authctxt)
174 struct ssh *ssh = active_state; /* XXX */
175 ssh->authctxt = authctxt; /* XXX move to caller */
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;
184 input_service_request(int type, u_int32_t seq, struct ssh *ssh)
186 Authctxt *authctxt = ssh->authctxt;
189 char *service = packet_get_cstring(&len);
192 if (authctxt == NULL)
193 fatal("input_service_request: no authctxt");
195 if (strcmp(service, "ssh-userauth") == 0) {
196 if (!authctxt->success) {
198 /* now we can handle user-auth requests */
199 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
202 /* XXX all other service requests are denied */
205 packet_start(SSH2_MSG_SERVICE_ACCEPT);
206 packet_put_cstring(service);
210 debug("bad service request %s", service);
211 packet_disconnect("bad service request %s", service);
217 #define MIN_FAIL_DELAY_SECONDS 0.005
219 user_specific_delay(const char *user)
222 size_t len = ssh_digest_bytes(SSH_DIGEST_SHA512);
223 u_char *hash = xmalloc(len);
226 (void)snprintf(b, sizeof b, "%llu%s",
227 (unsigned long long)options.timing_secret, user);
228 if (ssh_digest_memory(SSH_DIGEST_SHA512, b, strlen(b), hash, len) != 0)
229 fatal("%s: ssh_digest_memory", __func__);
230 /* 0-4.2 ms of delay */
231 delay = (double)PEEK_U32(hash) / 1000 / 1000 / 1000 / 1000;
233 debug3("%s: user specific delay %0.3lfms", __func__, delay/1000);
234 return MIN_FAIL_DELAY_SECONDS + delay;
238 ensure_minimum_time_since(double start, double seconds)
241 double elapsed = monotime_double() - start, req = seconds, remain;
243 /* if we've already passed the requested time, scale up */
244 while ((remain = seconds - elapsed) < 0.0)
248 ts.tv_nsec = (remain - ts.tv_sec) * 1000000000;
249 debug3("%s: elapsed %0.3lfms, delaying %0.3lfms (requested %0.3lfms)",
250 __func__, elapsed*1000, remain*1000, req*1000);
251 nanosleep(&ts, NULL);
256 input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)
258 Authctxt *authctxt = ssh->authctxt;
259 Authmethod *m = NULL;
260 char *user, *service, *method, *style = NULL;
261 int authenticated = 0;
262 double tstart = monotime_double();
263 #ifdef HAVE_LOGIN_CAP
265 const char *from_host, *from_ip;
268 if (authctxt == NULL)
269 fatal("input_userauth_request: no authctxt");
271 user = packet_get_cstring(NULL);
272 service = packet_get_cstring(NULL);
273 method = packet_get_cstring(NULL);
274 debug("userauth-request for user %s service %s method %s", user, service, method);
275 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
277 if ((style = strchr(user, ':')) != NULL)
280 if (authctxt->attempt++ == 0) {
281 /* setup auth context */
282 authctxt->pw = PRIVSEP(getpwnamallow(user));
283 authctxt->user = xstrdup(user);
284 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
286 debug2("%s: setting up authctxt for %s",
289 /* Invalid user, fake password information */
290 authctxt->pw = fakepw();
291 #ifdef SSH_AUDIT_EVENTS
292 PRIVSEP(audit_event(SSH_INVALID_USER));
297 PRIVSEP(start_pam(authctxt));
299 ssh_packet_set_log_preamble(ssh, "%suser %s",
300 authctxt->valid ? "authenticating " : "invalid ", user);
301 setproctitle("%s%s", authctxt->valid ? user : "unknown",
302 use_privsep ? " [net]" : "");
303 authctxt->service = xstrdup(service);
304 authctxt->style = style ? xstrdup(style) : NULL;
306 mm_inform_authserv(service, style);
308 if (auth2_setup_methods_lists(authctxt) != 0)
309 packet_disconnect("no authentication methods enabled");
310 } else if (strcmp(user, authctxt->user) != 0 ||
311 strcmp(service, authctxt->service) != 0) {
312 packet_disconnect("Change of username or service not allowed: "
313 "(%s,%s) -> (%s,%s)",
314 authctxt->user, authctxt->service, user, service);
317 #ifdef HAVE_LOGIN_CAP
318 if (authctxt->pw != NULL &&
319 (lc = PRIVSEP(login_getpwclass(authctxt->pw))) != NULL) {
320 logit("user %s login class %s", authctxt->pw->pw_name,
321 authctxt->pw->pw_class);
322 from_host = auth_get_canonical_hostname(ssh, options.use_dns);
323 from_ip = ssh_remote_ipaddr(ssh);
324 if (!auth_hostok(lc, from_host, from_ip)) {
325 logit("Denied connection for %.200s from %.200s [%.200s].",
326 authctxt->pw->pw_name, from_host, from_ip);
327 packet_disconnect("Sorry, you are not allowed to connect.");
329 if (!auth_timeok(lc, time(NULL))) {
330 logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
331 authctxt->pw->pw_name, from_host);
332 packet_disconnect("Logins not available right now.");
334 PRIVSEP(login_close(lc));
336 #endif /* HAVE_LOGIN_CAP */
339 auth2_challenge_stop(ssh);
342 /* XXX move to auth2_gssapi_stop() */
343 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
344 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
347 auth2_authctxt_reset_info(authctxt);
348 authctxt->postponed = 0;
349 authctxt->server_caused_failure = 0;
351 /* try to authenticate user */
352 m = authmethod_lookup(authctxt, method);
353 if (m != NULL && authctxt->failures < options.max_authtries) {
354 debug2("input_userauth_request: try method %s", method);
355 authenticated = m->userauth(ssh);
357 if (!authctxt->authenticated)
358 ensure_minimum_time_since(tstart,
359 user_specific_delay(authctxt->user));
360 userauth_finish(ssh, authenticated, method, NULL);
369 userauth_finish(struct ssh *ssh, int authenticated, const char *method,
370 const char *submethod)
372 Authctxt *authctxt = ssh->authctxt;
376 if (!authctxt->valid && authenticated)
377 fatal("INTERNAL ERROR: authenticated invalid user %s",
379 if (authenticated && authctxt->postponed)
380 fatal("INTERNAL ERROR: authenticated and postponed");
382 /* Special handling for root */
383 if (authenticated && authctxt->pw->pw_uid == 0 &&
384 !auth_root_allowed(ssh, method)) {
386 #ifdef SSH_AUDIT_EVENTS
387 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
391 if (authenticated && options.num_auth_methods != 0) {
392 if (!auth2_update_methods_lists(authctxt, method, submethod)) {
398 /* Log before sending the reply */
399 auth_log(authctxt, authenticated, partial, method, submethod);
401 /* Update information exposed to session */
402 if (authenticated || partial)
403 auth2_update_session_info(authctxt, method, submethod);
405 if (authctxt->postponed)
409 if (options.use_pam && authenticated) {
412 if (!PRIVSEP(do_pam_account())) {
413 /* if PAM returned a message, send it to the user */
414 if (sshbuf_len(loginmsg) > 0) {
415 if ((r = sshbuf_put(loginmsg, "\0", 1)) != 0)
416 fatal("%s: buffer error: %s",
417 __func__, ssh_err(r));
418 userauth_send_banner(sshbuf_ptr(loginmsg));
421 fatal("Access denied for user %s by PAM account "
422 "configuration", authctxt->user);
427 if (authenticated == 1) {
428 /* turn off userauth */
429 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
430 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
433 /* now we can break out */
434 authctxt->success = 1;
435 ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
437 /* Allow initial try of "none" auth without failure penalty */
438 if (!partial && !authctxt->server_caused_failure &&
439 (authctxt->attempt > 1 || strcmp(method, "none") != 0)) {
440 authctxt->failures++;
441 BLACKLIST_NOTIFY(BLACKLIST_AUTH_FAIL, "ssh");
443 if (authctxt->failures >= options.max_authtries) {
444 #ifdef SSH_AUDIT_EVENTS
445 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
447 auth_maxtries_exceeded(authctxt);
449 methods = authmethods_get(authctxt);
450 debug3("%s: failure partial=%d next methods=\"%s\"", __func__,
452 packet_start(SSH2_MSG_USERAUTH_FAILURE);
453 packet_put_cstring(methods);
454 packet_put_char(partial);
462 * Checks whether method is allowed by at least one AuthenticationMethods
463 * methods list. Returns 1 if allowed, or no methods lists configured.
467 auth2_method_allowed(Authctxt *authctxt, const char *method,
468 const char *submethod)
473 * NB. authctxt->num_auth_methods might be zero as a result of
474 * auth2_setup_methods_lists(), so check the configuration.
476 if (options.num_auth_methods == 0)
478 for (i = 0; i < authctxt->num_auth_methods; i++) {
479 if (list_starts_with(authctxt->auth_methods[i], method,
480 submethod) != MATCH_NONE)
487 authmethods_get(Authctxt *authctxt)
493 if ((b = sshbuf_new()) == NULL)
494 fatal("%s: sshbuf_new failed", __func__);
495 for (i = 0; authmethods[i] != NULL; i++) {
496 if (strcmp(authmethods[i]->name, "none") == 0)
498 if (authmethods[i]->enabled == NULL ||
499 *(authmethods[i]->enabled) == 0)
501 if (!auth2_method_allowed(authctxt, authmethods[i]->name,
504 if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) ? "," : "",
505 authmethods[i]->name)) != 0)
506 fatal("%s: buffer error: %s", __func__, ssh_err(r));
508 if ((list = sshbuf_dup_string(b)) == NULL)
509 fatal("%s: sshbuf_dup_string failed", __func__);
515 authmethod_lookup(Authctxt *authctxt, const char *name)
520 for (i = 0; authmethods[i] != NULL; i++)
521 if (authmethods[i]->enabled != NULL &&
522 *(authmethods[i]->enabled) != 0 &&
523 strcmp(name, authmethods[i]->name) == 0 &&
524 auth2_method_allowed(authctxt,
525 authmethods[i]->name, NULL))
526 return authmethods[i];
527 debug2("Unrecognized authentication method name: %s",
528 name ? name : "NULL");
533 * Check a comma-separated list of methods for validity. Is need_enable is
534 * non-zero, then also require that the methods are enabled.
535 * Returns 0 on success or -1 if the methods list is invalid.
538 auth2_methods_valid(const char *_methods, int need_enable)
540 char *methods, *omethods, *method, *p;
544 if (*_methods == '\0') {
545 error("empty authentication method list");
548 omethods = methods = xstrdup(_methods);
549 while ((method = strsep(&methods, ",")) != NULL) {
550 for (found = i = 0; !found && authmethods[i] != NULL; i++) {
551 if ((p = strchr(method, ':')) != NULL)
553 if (strcmp(method, authmethods[i]->name) != 0)
556 if (authmethods[i]->enabled == NULL ||
557 *(authmethods[i]->enabled) == 0) {
558 error("Disabled method \"%s\" in "
559 "AuthenticationMethods list \"%s\"",
568 error("Unknown authentication method \"%s\" in list",
580 * Prune the AuthenticationMethods supplied in the configuration, removing
581 * any methods lists that include disabled methods. Note that this might
582 * leave authctxt->num_auth_methods == 0, even when multiple required auth
583 * has been requested. For this reason, all tests for whether multiple is
584 * enabled should consult options.num_auth_methods directly.
587 auth2_setup_methods_lists(Authctxt *authctxt)
591 if (options.num_auth_methods == 0)
593 debug3("%s: checking methods", __func__);
594 authctxt->auth_methods = xcalloc(options.num_auth_methods,
595 sizeof(*authctxt->auth_methods));
596 authctxt->num_auth_methods = 0;
597 for (i = 0; i < options.num_auth_methods; i++) {
598 if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {
599 logit("Authentication methods list \"%s\" contains "
600 "disabled method, skipping",
601 options.auth_methods[i]);
604 debug("authentication methods list %d: %s",
605 authctxt->num_auth_methods, options.auth_methods[i]);
606 authctxt->auth_methods[authctxt->num_auth_methods++] =
607 xstrdup(options.auth_methods[i]);
609 if (authctxt->num_auth_methods == 0) {
610 error("No AuthenticationMethods left after eliminating "
618 list_starts_with(const char *methods, const char *method,
619 const char *submethod)
621 size_t l = strlen(method);
625 if (strncmp(methods, method, l) != 0)
628 match = MATCH_METHOD;
631 return MATCH_PARTIAL;
632 l = strlen(submethod);
634 if (strncmp(submethod, p, l))
639 if (*p != ',' && *p != '\0')
645 * Remove method from the start of a comma-separated list of methods.
646 * Returns 0 if the list of methods did not start with that method or 1
650 remove_method(char **methods, const char *method, const char *submethod)
652 char *omethods = *methods, *p;
653 size_t l = strlen(method);
656 match = list_starts_with(omethods, method, submethod);
657 if (match != MATCH_METHOD && match != MATCH_BOTH)
660 if (submethod && match == MATCH_BOTH)
661 p += 1 + strlen(submethod); /* include colon */
664 *methods = xstrdup(p);
670 * Called after successful authentication. Will remove the successful method
671 * from the start of each list in which it occurs. If it was the last method
672 * in any list, then authentication is deemed successful.
673 * Returns 1 if the method completed any authentication list or 0 otherwise.
676 auth2_update_methods_lists(Authctxt *authctxt, const char *method,
677 const char *submethod)
681 debug3("%s: updating methods list after \"%s\"", __func__, method);
682 for (i = 0; i < authctxt->num_auth_methods; i++) {
683 if (!remove_method(&(authctxt->auth_methods[i]), method,
687 if (*authctxt->auth_methods[i] == '\0') {
688 debug2("authentication methods list %d complete", i);
691 debug3("authentication methods list %d remaining: \"%s\"",
692 i, authctxt->auth_methods[i]);
694 /* This should not happen, but would be bad if it did */
696 fatal("%s: method not in AuthenticationMethods", __func__);
700 /* Reset method-specific information */
701 void auth2_authctxt_reset_info(Authctxt *authctxt)
703 sshkey_free(authctxt->auth_method_key);
704 free(authctxt->auth_method_info);
705 authctxt->auth_method_key = NULL;
706 authctxt->auth_method_info = NULL;
709 /* Record auth method-specific information for logs */
711 auth2_record_info(Authctxt *authctxt, const char *fmt, ...)
716 free(authctxt->auth_method_info);
717 authctxt->auth_method_info = NULL;
720 i = vasprintf(&authctxt->auth_method_info, fmt, ap);
723 if (i < 0 || authctxt->auth_method_info == NULL)
724 fatal("%s: vasprintf failed", __func__);
728 * Records a public key used in authentication. This is used for logging
729 * and to ensure that the same key is not subsequently accepted again for
730 * multiple authentication.
733 auth2_record_key(Authctxt *authctxt, int authenticated,
734 const struct sshkey *key)
736 struct sshkey **tmp, *dup;
739 if ((r = sshkey_from_private(key, &dup)) != 0)
740 fatal("%s: copy key: %s", __func__, ssh_err(r));
741 sshkey_free(authctxt->auth_method_key);
742 authctxt->auth_method_key = dup;
747 /* If authenticated, make sure we don't accept this key again */
748 if ((r = sshkey_from_private(key, &dup)) != 0)
749 fatal("%s: copy key: %s", __func__, ssh_err(r));
750 if (authctxt->nprev_keys >= INT_MAX ||
751 (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,
752 authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)
753 fatal("%s: reallocarray failed", __func__);
754 authctxt->prev_keys = tmp;
755 authctxt->prev_keys[authctxt->nprev_keys] = dup;
756 authctxt->nprev_keys++;
760 /* Checks whether a key has already been previously used for authentication */
762 auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key)
767 for (i = 0; i < authctxt->nprev_keys; i++) {
768 if (sshkey_equal_public(key, authctxt->prev_keys[i])) {
769 fp = sshkey_fingerprint(authctxt->prev_keys[i],
770 options.fingerprint_hash, SSH_FP_DEFAULT);
771 debug3("%s: key already used: %s %s", __func__,
772 sshkey_type(authctxt->prev_keys[i]),
773 fp == NULL ? "UNKNOWN" : fp);
782 * Updates authctxt->session_info with details of authentication. Should be
783 * whenever an authentication method succeeds.
786 auth2_update_session_info(Authctxt *authctxt, const char *method,
787 const char *submethod)
791 if (authctxt->session_info == NULL) {
792 if ((authctxt->session_info = sshbuf_new()) == NULL)
793 fatal("%s: sshbuf_new", __func__);
796 /* Append method[/submethod] */
797 if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",
798 method, submethod == NULL ? "" : "/",
799 submethod == NULL ? "" : submethod)) != 0)
800 fatal("%s: append method: %s", __func__, ssh_err(r));
802 /* Append key if present */
803 if (authctxt->auth_method_key != NULL) {
804 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
805 (r = sshkey_format_text(authctxt->auth_method_key,
806 authctxt->session_info)) != 0)
807 fatal("%s: append key: %s", __func__, ssh_err(r));
810 if (authctxt->auth_method_info != NULL) {
811 /* Ensure no ambiguity here */
812 if (strchr(authctxt->auth_method_info, '\n') != NULL)
813 fatal("%s: auth_method_info contains \\n", __func__);
814 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
815 (r = sshbuf_putf(authctxt->session_info, "%s",
816 authctxt->auth_method_info)) != 0) {
817 fatal("%s: append method info: %s",
818 __func__, ssh_err(r));
821 if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)
822 fatal("%s: append: %s", __func__, ssh_err(r));