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.
28 #include <sys/types.h>
52 #include "pathnames.h"
59 #include "monitor_wrap.h"
64 extern ServerOptions options;
65 extern u_char *session_id2;
66 extern u_int session_id2_len;
67 extern struct sshbuf *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);
215 #define MIN_FAIL_DELAY_SECONDS 0.005
217 user_specific_delay(const char *user)
220 size_t len = ssh_digest_bytes(SSH_DIGEST_SHA512);
221 u_char *hash = xmalloc(len);
224 (void)snprintf(b, sizeof b, "%llu%s",
225 (unsigned long long)options.timing_secret, user);
226 if (ssh_digest_memory(SSH_DIGEST_SHA512, b, strlen(b), hash, len) != 0)
227 fatal("%s: ssh_digest_memory", __func__);
228 /* 0-4.2 ms of delay */
229 delay = (double)PEEK_U32(hash) / 1000 / 1000 / 1000 / 1000;
231 debug3("%s: user specific delay %0.3lfms", __func__, delay/1000);
232 return MIN_FAIL_DELAY_SECONDS + delay;
236 ensure_minimum_time_since(double start, double seconds)
239 double elapsed = monotime_double() - start, req = seconds, remain;
241 /* if we've already passed the requested time, scale up */
242 while ((remain = seconds - elapsed) < 0.0)
246 ts.tv_nsec = (remain - ts.tv_sec) * 1000000000;
247 debug3("%s: elapsed %0.3lfms, delaying %0.3lfms (requested %0.3lfms)",
248 __func__, elapsed*1000, remain*1000, req*1000);
249 nanosleep(&ts, NULL);
254 input_userauth_request(int type, u_int32_t seq, struct ssh *ssh)
256 Authctxt *authctxt = ssh->authctxt;
257 Authmethod *m = NULL;
258 char *user, *service, *method, *style = NULL;
259 int authenticated = 0;
260 double tstart = monotime_double();
262 if (authctxt == NULL)
263 fatal("input_userauth_request: no authctxt");
265 user = packet_get_cstring(NULL);
266 service = packet_get_cstring(NULL);
267 method = packet_get_cstring(NULL);
268 debug("userauth-request for user %s service %s method %s", user, service, method);
269 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
271 if ((style = strchr(user, ':')) != NULL)
274 if (authctxt->attempt++ == 0) {
275 /* setup auth context */
276 authctxt->pw = PRIVSEP(getpwnamallow(user));
277 authctxt->user = xstrdup(user);
278 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
280 debug2("%s: setting up authctxt for %s",
283 /* Invalid user, fake password information */
284 authctxt->pw = fakepw();
285 #ifdef SSH_AUDIT_EVENTS
286 PRIVSEP(audit_event(SSH_INVALID_USER));
291 PRIVSEP(start_pam(authctxt));
293 ssh_packet_set_log_preamble(ssh, "%suser %s",
294 authctxt->valid ? "authenticating " : "invalid ", user);
295 setproctitle("%s%s", authctxt->valid ? user : "unknown",
296 use_privsep ? " [net]" : "");
297 authctxt->service = xstrdup(service);
298 authctxt->style = style ? xstrdup(style) : NULL;
300 mm_inform_authserv(service, style);
302 if (auth2_setup_methods_lists(authctxt) != 0)
303 packet_disconnect("no authentication methods enabled");
304 } else if (strcmp(user, authctxt->user) != 0 ||
305 strcmp(service, authctxt->service) != 0) {
306 packet_disconnect("Change of username or service not allowed: "
307 "(%s,%s) -> (%s,%s)",
308 authctxt->user, authctxt->service, user, service);
311 auth2_challenge_stop(ssh);
314 /* XXX move to auth2_gssapi_stop() */
315 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
316 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
319 auth2_authctxt_reset_info(authctxt);
320 authctxt->postponed = 0;
321 authctxt->server_caused_failure = 0;
323 /* try to authenticate user */
324 m = authmethod_lookup(authctxt, method);
325 if (m != NULL && authctxt->failures < options.max_authtries) {
326 debug2("input_userauth_request: try method %s", method);
327 authenticated = m->userauth(ssh);
329 if (!authctxt->authenticated)
330 ensure_minimum_time_since(tstart,
331 user_specific_delay(authctxt->user));
332 userauth_finish(ssh, authenticated, method, NULL);
341 userauth_finish(struct ssh *ssh, int authenticated, const char *method,
342 const char *submethod)
344 Authctxt *authctxt = ssh->authctxt;
348 if (!authctxt->valid && authenticated)
349 fatal("INTERNAL ERROR: authenticated invalid user %s",
351 if (authenticated && authctxt->postponed)
352 fatal("INTERNAL ERROR: authenticated and postponed");
354 /* Special handling for root */
355 if (authenticated && authctxt->pw->pw_uid == 0 &&
356 !auth_root_allowed(ssh, method)) {
358 #ifdef SSH_AUDIT_EVENTS
359 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
363 if (authenticated && options.num_auth_methods != 0) {
364 if (!auth2_update_methods_lists(authctxt, method, submethod)) {
370 /* Log before sending the reply */
371 auth_log(authctxt, authenticated, partial, method, submethod);
373 /* Update information exposed to session */
374 if (authenticated || partial)
375 auth2_update_session_info(authctxt, method, submethod);
377 if (authctxt->postponed)
381 if (options.use_pam && authenticated) {
384 if (!PRIVSEP(do_pam_account())) {
385 /* if PAM returned a message, send it to the user */
386 if (sshbuf_len(loginmsg) > 0) {
387 if ((r = sshbuf_put(loginmsg, "\0", 1)) != 0)
388 fatal("%s: buffer error: %s",
389 __func__, ssh_err(r));
390 userauth_send_banner(sshbuf_ptr(loginmsg));
393 fatal("Access denied for user %s by PAM account "
394 "configuration", authctxt->user);
399 if (authenticated == 1) {
400 /* turn off userauth */
401 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
402 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
405 /* now we can break out */
406 authctxt->success = 1;
407 ssh_packet_set_log_preamble(ssh, "user %s", authctxt->user);
409 /* Allow initial try of "none" auth without failure penalty */
410 if (!partial && !authctxt->server_caused_failure &&
411 (authctxt->attempt > 1 || strcmp(method, "none") != 0))
412 authctxt->failures++;
413 if (authctxt->failures >= options.max_authtries) {
414 #ifdef SSH_AUDIT_EVENTS
415 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
417 auth_maxtries_exceeded(authctxt);
419 methods = authmethods_get(authctxt);
420 debug3("%s: failure partial=%d next methods=\"%s\"", __func__,
422 packet_start(SSH2_MSG_USERAUTH_FAILURE);
423 packet_put_cstring(methods);
424 packet_put_char(partial);
432 * Checks whether method is allowed by at least one AuthenticationMethods
433 * methods list. Returns 1 if allowed, or no methods lists configured.
437 auth2_method_allowed(Authctxt *authctxt, const char *method,
438 const char *submethod)
443 * NB. authctxt->num_auth_methods might be zero as a result of
444 * auth2_setup_methods_lists(), so check the configuration.
446 if (options.num_auth_methods == 0)
448 for (i = 0; i < authctxt->num_auth_methods; i++) {
449 if (list_starts_with(authctxt->auth_methods[i], method,
450 submethod) != MATCH_NONE)
457 authmethods_get(Authctxt *authctxt)
463 if ((b = sshbuf_new()) == NULL)
464 fatal("%s: sshbuf_new failed", __func__);
465 for (i = 0; authmethods[i] != NULL; i++) {
466 if (strcmp(authmethods[i]->name, "none") == 0)
468 if (authmethods[i]->enabled == NULL ||
469 *(authmethods[i]->enabled) == 0)
471 if (!auth2_method_allowed(authctxt, authmethods[i]->name,
474 if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) ? "," : "",
475 authmethods[i]->name)) != 0)
476 fatal("%s: buffer error: %s", __func__, ssh_err(r));
478 if ((list = sshbuf_dup_string(b)) == NULL)
479 fatal("%s: sshbuf_dup_string failed", __func__);
485 authmethod_lookup(Authctxt *authctxt, const char *name)
490 for (i = 0; authmethods[i] != NULL; i++)
491 if (authmethods[i]->enabled != NULL &&
492 *(authmethods[i]->enabled) != 0 &&
493 strcmp(name, authmethods[i]->name) == 0 &&
494 auth2_method_allowed(authctxt,
495 authmethods[i]->name, NULL))
496 return authmethods[i];
497 debug2("Unrecognized authentication method name: %s",
498 name ? name : "NULL");
503 * Check a comma-separated list of methods for validity. Is need_enable is
504 * non-zero, then also require that the methods are enabled.
505 * Returns 0 on success or -1 if the methods list is invalid.
508 auth2_methods_valid(const char *_methods, int need_enable)
510 char *methods, *omethods, *method, *p;
514 if (*_methods == '\0') {
515 error("empty authentication method list");
518 omethods = methods = xstrdup(_methods);
519 while ((method = strsep(&methods, ",")) != NULL) {
520 for (found = i = 0; !found && authmethods[i] != NULL; i++) {
521 if ((p = strchr(method, ':')) != NULL)
523 if (strcmp(method, authmethods[i]->name) != 0)
526 if (authmethods[i]->enabled == NULL ||
527 *(authmethods[i]->enabled) == 0) {
528 error("Disabled method \"%s\" in "
529 "AuthenticationMethods list \"%s\"",
538 error("Unknown authentication method \"%s\" in list",
550 * Prune the AuthenticationMethods supplied in the configuration, removing
551 * any methods lists that include disabled methods. Note that this might
552 * leave authctxt->num_auth_methods == 0, even when multiple required auth
553 * has been requested. For this reason, all tests for whether multiple is
554 * enabled should consult options.num_auth_methods directly.
557 auth2_setup_methods_lists(Authctxt *authctxt)
561 if (options.num_auth_methods == 0)
563 debug3("%s: checking methods", __func__);
564 authctxt->auth_methods = xcalloc(options.num_auth_methods,
565 sizeof(*authctxt->auth_methods));
566 authctxt->num_auth_methods = 0;
567 for (i = 0; i < options.num_auth_methods; i++) {
568 if (auth2_methods_valid(options.auth_methods[i], 1) != 0) {
569 logit("Authentication methods list \"%s\" contains "
570 "disabled method, skipping",
571 options.auth_methods[i]);
574 debug("authentication methods list %d: %s",
575 authctxt->num_auth_methods, options.auth_methods[i]);
576 authctxt->auth_methods[authctxt->num_auth_methods++] =
577 xstrdup(options.auth_methods[i]);
579 if (authctxt->num_auth_methods == 0) {
580 error("No AuthenticationMethods left after eliminating "
588 list_starts_with(const char *methods, const char *method,
589 const char *submethod)
591 size_t l = strlen(method);
595 if (strncmp(methods, method, l) != 0)
598 match = MATCH_METHOD;
601 return MATCH_PARTIAL;
602 l = strlen(submethod);
604 if (strncmp(submethod, p, l))
609 if (*p != ',' && *p != '\0')
615 * Remove method from the start of a comma-separated list of methods.
616 * Returns 0 if the list of methods did not start with that method or 1
620 remove_method(char **methods, const char *method, const char *submethod)
622 char *omethods = *methods, *p;
623 size_t l = strlen(method);
626 match = list_starts_with(omethods, method, submethod);
627 if (match != MATCH_METHOD && match != MATCH_BOTH)
630 if (submethod && match == MATCH_BOTH)
631 p += 1 + strlen(submethod); /* include colon */
634 *methods = xstrdup(p);
640 * Called after successful authentication. Will remove the successful method
641 * from the start of each list in which it occurs. If it was the last method
642 * in any list, then authentication is deemed successful.
643 * Returns 1 if the method completed any authentication list or 0 otherwise.
646 auth2_update_methods_lists(Authctxt *authctxt, const char *method,
647 const char *submethod)
651 debug3("%s: updating methods list after \"%s\"", __func__, method);
652 for (i = 0; i < authctxt->num_auth_methods; i++) {
653 if (!remove_method(&(authctxt->auth_methods[i]), method,
657 if (*authctxt->auth_methods[i] == '\0') {
658 debug2("authentication methods list %d complete", i);
661 debug3("authentication methods list %d remaining: \"%s\"",
662 i, authctxt->auth_methods[i]);
664 /* This should not happen, but would be bad if it did */
666 fatal("%s: method not in AuthenticationMethods", __func__);
670 /* Reset method-specific information */
671 void auth2_authctxt_reset_info(Authctxt *authctxt)
673 sshkey_free(authctxt->auth_method_key);
674 free(authctxt->auth_method_info);
675 authctxt->auth_method_key = NULL;
676 authctxt->auth_method_info = NULL;
679 /* Record auth method-specific information for logs */
681 auth2_record_info(Authctxt *authctxt, const char *fmt, ...)
686 free(authctxt->auth_method_info);
687 authctxt->auth_method_info = NULL;
690 i = vasprintf(&authctxt->auth_method_info, fmt, ap);
693 if (i < 0 || authctxt->auth_method_info == NULL)
694 fatal("%s: vasprintf failed", __func__);
698 * Records a public key used in authentication. This is used for logging
699 * and to ensure that the same key is not subsequently accepted again for
700 * multiple authentication.
703 auth2_record_key(Authctxt *authctxt, int authenticated,
704 const struct sshkey *key)
706 struct sshkey **tmp, *dup;
709 if ((r = sshkey_demote(key, &dup)) != 0)
710 fatal("%s: copy key: %s", __func__, ssh_err(r));
711 sshkey_free(authctxt->auth_method_key);
712 authctxt->auth_method_key = dup;
717 /* If authenticated, make sure we don't accept this key again */
718 if ((r = sshkey_demote(key, &dup)) != 0)
719 fatal("%s: copy key: %s", __func__, ssh_err(r));
720 if (authctxt->nprev_keys >= INT_MAX ||
721 (tmp = recallocarray(authctxt->prev_keys, authctxt->nprev_keys,
722 authctxt->nprev_keys + 1, sizeof(*authctxt->prev_keys))) == NULL)
723 fatal("%s: reallocarray failed", __func__);
724 authctxt->prev_keys = tmp;
725 authctxt->prev_keys[authctxt->nprev_keys] = dup;
726 authctxt->nprev_keys++;
730 /* Checks whether a key has already been previously used for authentication */
732 auth2_key_already_used(Authctxt *authctxt, const struct sshkey *key)
737 for (i = 0; i < authctxt->nprev_keys; i++) {
738 if (sshkey_equal_public(key, authctxt->prev_keys[i])) {
739 fp = sshkey_fingerprint(authctxt->prev_keys[i],
740 options.fingerprint_hash, SSH_FP_DEFAULT);
741 debug3("%s: key already used: %s %s", __func__,
742 sshkey_type(authctxt->prev_keys[i]),
743 fp == NULL ? "UNKNOWN" : fp);
752 * Updates authctxt->session_info with details of authentication. Should be
753 * whenever an authentication method succeeds.
756 auth2_update_session_info(Authctxt *authctxt, const char *method,
757 const char *submethod)
761 if (authctxt->session_info == NULL) {
762 if ((authctxt->session_info = sshbuf_new()) == NULL)
763 fatal("%s: sshbuf_new", __func__);
766 /* Append method[/submethod] */
767 if ((r = sshbuf_putf(authctxt->session_info, "%s%s%s",
768 method, submethod == NULL ? "" : "/",
769 submethod == NULL ? "" : submethod)) != 0)
770 fatal("%s: append method: %s", __func__, ssh_err(r));
772 /* Append key if present */
773 if (authctxt->auth_method_key != NULL) {
774 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
775 (r = sshkey_format_text(authctxt->auth_method_key,
776 authctxt->session_info)) != 0)
777 fatal("%s: append key: %s", __func__, ssh_err(r));
780 if (authctxt->auth_method_info != NULL) {
781 /* Ensure no ambiguity here */
782 if (strchr(authctxt->auth_method_info, '\n') != NULL)
783 fatal("%s: auth_method_info contains \\n", __func__);
784 if ((r = sshbuf_put_u8(authctxt->session_info, ' ')) != 0 ||
785 (r = sshbuf_putf(authctxt->session_info, "%s",
786 authctxt->auth_method_info)) != 0) {
787 fatal("%s: append method info: %s",
788 __func__, ssh_err(r));
791 if ((r = sshbuf_put_u8(authctxt->session_info, '\n')) != 0)
792 fatal("%s: append: %s", __func__, ssh_err(r));