2 * Copyright (c) 2000 Markus Friedl. All rights reserved.
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 RCSID("$OpenBSD: auth2.c,v 1.72 2001/11/07 22:41:51 markus Exp $");
28 #include <openssl/evp.h>
47 #include "pathnames.h"
49 #include "auth-options.h"
56 extern ServerOptions options;
57 extern u_char *session_id2;
58 extern int session_id2_len;
60 static Authctxt *x_authctxt = NULL;
63 typedef struct Authmethod Authmethod;
66 int (*userauth)(Authctxt *authctxt);
72 static void input_service_request(int, int, void *);
73 static void input_userauth_request(int, int, void *);
74 static void protocol_error(int, int, void *);
77 static Authmethod *authmethod_lookup(const char *);
78 static char *authmethods_get(void);
79 static int user_key_allowed(struct passwd *, Key *);
80 static int hostbased_key_allowed(struct passwd *, const char *, char *, Key *);
83 static void userauth_banner(void);
84 static int userauth_none(Authctxt *);
85 static int userauth_passwd(Authctxt *);
86 static int userauth_pubkey(Authctxt *);
87 static int userauth_hostbased(Authctxt *);
88 static int userauth_kbdint(Authctxt *);
90 Authmethod authmethods[] = {
96 &options.pubkey_authentication},
99 &options.password_authentication},
100 {"keyboard-interactive",
102 &options.kbd_interactive_authentication},
105 &options.hostbased_authentication},
110 * loop until authctxt->success == TRUE
116 Authctxt *authctxt = authctxt_new();
118 x_authctxt = authctxt; /*XXX*/
120 /* challenge-response is implemented via keyboard interactive */
121 if (options.challenge_response_authentication)
122 options.kbd_interactive_authentication = 1;
123 if (options.pam_authentication_via_kbd_int)
124 options.kbd_interactive_authentication = 1;
126 dispatch_init(&protocol_error);
127 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
128 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
129 do_authenticated(authctxt);
133 protocol_error(int type, int plen, void *ctxt)
135 log("auth: protocol error: type %d plen %d", type, plen);
136 packet_start(SSH2_MSG_UNIMPLEMENTED);
143 input_service_request(int type, int plen, void *ctxt)
145 Authctxt *authctxt = ctxt;
148 char *service = packet_get_string(&len);
151 if (authctxt == NULL)
152 fatal("input_service_request: no authctxt");
154 if (strcmp(service, "ssh-userauth") == 0) {
155 if (!authctxt->success) {
157 /* now we can handle user-auth requests */
158 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
161 /* XXX all other service requests are denied */
164 packet_start(SSH2_MSG_SERVICE_ACCEPT);
165 packet_put_cstring(service);
169 debug("bad service request %s", service);
170 packet_disconnect("bad service request %s", service);
176 input_userauth_request(int type, int plen, void *ctxt)
178 Authctxt *authctxt = ctxt;
179 Authmethod *m = NULL;
180 char *user, *service, *method, *style = NULL;
181 int authenticated = 0;
183 if (authctxt == NULL)
184 fatal("input_userauth_request: no authctxt");
186 user = packet_get_string(NULL);
187 service = packet_get_string(NULL);
188 method = packet_get_string(NULL);
189 debug("userauth-request for user %s service %s method %s", user, service, method);
190 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
192 if ((style = strchr(user, ':')) != NULL)
195 if (authctxt->attempt++ == 0) {
196 /* setup auth context */
197 struct passwd *pw = NULL;
199 if (pw && allowed_user(pw) && strcmp(service, "ssh-connection")==0) {
200 authctxt->pw = pwcopy(pw);
202 debug2("input_userauth_request: setting up authctxt for %s", user);
204 start_pam(pw->pw_name);
207 log("input_userauth_request: illegal user %s", user);
212 setproctitle("%s", pw ? user : "unknown");
213 authctxt->user = xstrdup(user);
214 authctxt->service = xstrdup(service);
215 authctxt->style = style ? xstrdup(style) : NULL;
216 } else if (strcmp(user, authctxt->user) != 0 ||
217 strcmp(service, authctxt->service) != 0) {
218 packet_disconnect("Change of username or service not allowed: "
219 "(%s,%s) -> (%s,%s)",
220 authctxt->user, authctxt->service, user, service);
223 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, &protocol_error);
224 authctxt->postponed = 0;
227 auth_close(authctxt->as);
232 /* try to authenticate user */
233 m = authmethod_lookup(method);
235 debug2("input_userauth_request: try method %s", method);
236 authenticated = m->userauth(authctxt);
238 userauth_finish(authctxt, authenticated, method);
246 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
250 if (!authctxt->valid && authenticated)
251 fatal("INTERNAL ERROR: authenticated invalid user %s",
254 /* Special handling for root */
255 if (authenticated && authctxt->pw->pw_uid == 0 &&
256 !auth_root_allowed(method))
260 if (authenticated && authctxt->user && !do_pam_account(authctxt->user,
265 /* Log before sending the reply */
266 auth_log(authctxt, authenticated, method, " ssh2");
268 if (authctxt->postponed)
271 /* XXX todo: check if multiple auth methods are needed */
272 if (authenticated == 1) {
273 /* turn off userauth */
274 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &protocol_error);
275 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
278 /* now we can break out */
279 authctxt->success = 1;
281 if (authctxt->failures++ > AUTH_FAIL_MAX) {
282 #ifdef WITH_AIXAUTHENTICATE
283 loginfailed(authctxt->user,
284 get_canonical_hostname(options.reverse_mapping_check),
286 #endif /* WITH_AIXAUTHENTICATE */
287 packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
289 methods = authmethods_get();
290 packet_start(SSH2_MSG_USERAUTH_FAILURE);
291 packet_put_cstring(methods);
292 packet_put_char(0); /* XXX partial success, unused */
300 userauth_banner(void)
307 if (options.banner == NULL || (datafellows & SSH_BUG_BANNER))
309 if ((fd = open(options.banner, O_RDONLY)) < 0)
311 if (fstat(fd, &st) < 0)
314 banner = xmalloc(len + 1);
315 if ((n = read(fd, banner, len)) < 0)
318 packet_start(SSH2_MSG_USERAUTH_BANNER);
319 packet_put_cstring(banner);
320 packet_put_cstring(""); /* language, unused */
322 debug("userauth_banner: sent");
331 userauth_none(Authctxt *authctxt)
333 /* disable method "none", only allowed one time */
334 Authmethod *m = authmethod_lookup("none");
340 if (authctxt->valid == 0)
344 if (check_nt_auth(1, authctxt->pw->pw_uid) == 0)
348 return auth_pam_password(authctxt->pw, "");
349 #elif defined(HAVE_OSF_SIA)
351 #else /* !HAVE_OSF_SIA && !USE_PAM */
352 return auth_password(authctxt, "");
357 userauth_passwd(Authctxt *authctxt)
360 int authenticated = 0;
363 change = packet_get_char();
365 log("password change not supported");
366 password = packet_get_string(&len);
368 if (authctxt->valid &&
370 check_nt_auth(1, authctxt->pw->pw_uid) &&
373 auth_pam_password(authctxt->pw, password) == 1)
374 #elif defined(HAVE_OSF_SIA)
375 auth_sia_password(authctxt->user, password) == 1)
376 #else /* !USE_PAM && !HAVE_OSF_SIA */
377 auth_password(authctxt, password) == 1)
380 memset(password, 0, len);
382 return authenticated;
386 userauth_kbdint(Authctxt *authctxt)
388 int authenticated = 0;
391 lang = packet_get_string(NULL);
392 devs = packet_get_string(NULL);
395 debug("keyboard-interactive devs %s", devs);
397 if (options.challenge_response_authentication)
398 authenticated = auth2_challenge(authctxt, devs);
401 if (authenticated == 0 && options.pam_authentication_via_kbd_int)
402 authenticated = auth2_pam(authctxt);
407 if (check_nt_auth(0, authctxt->pw->pw_uid) == 0)
410 return authenticated;
414 userauth_pubkey(Authctxt *authctxt)
418 char *pkalg, *pkblob, *sig;
419 u_int alen, blen, slen;
420 int have_sig, pktype;
421 int authenticated = 0;
423 if (!authctxt->valid) {
424 debug2("userauth_pubkey: disabled because of invalid user");
427 have_sig = packet_get_char();
428 if (datafellows & SSH_BUG_PKAUTH) {
429 debug2("userauth_pubkey: SSH_BUG_PKAUTH");
430 /* no explicit pkalg given */
431 pkblob = packet_get_string(&blen);
433 buffer_append(&b, pkblob, blen);
434 /* so we have to extract the pkalg from the pkblob */
435 pkalg = buffer_get_string(&b, &alen);
438 pkalg = packet_get_string(&alen);
439 pkblob = packet_get_string(&blen);
441 pktype = key_type_from_name(pkalg);
442 if (pktype == KEY_UNSPEC) {
443 /* this is perfectly legal */
444 log("userauth_pubkey: unsupported public key algorithm: %s", pkalg);
449 key = key_from_blob(pkblob, blen);
452 sig = packet_get_string(&slen);
455 if (datafellows & SSH_OLD_SESSIONID) {
456 buffer_append(&b, session_id2, session_id2_len);
458 buffer_put_string(&b, session_id2, session_id2_len);
460 /* reconstruct packet */
461 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
462 buffer_put_cstring(&b, authctxt->user);
463 buffer_put_cstring(&b,
464 datafellows & SSH_BUG_PKSERVICE ?
467 if (datafellows & SSH_BUG_PKAUTH) {
468 buffer_put_char(&b, have_sig);
470 buffer_put_cstring(&b, "publickey");
471 buffer_put_char(&b, have_sig);
472 buffer_put_cstring(&b, pkalg);
474 buffer_put_string(&b, pkblob, blen);
478 /* test for correct signature */
479 if (user_key_allowed(authctxt->pw, key) &&
480 key_verify(key, sig, slen, buffer_ptr(&b), buffer_len(&b)) == 1)
485 debug("test whether pkalg/pkblob are acceptable");
488 /* XXX fake reply and always send PK_OK ? */
490 * XXX this allows testing whether a user is allowed
491 * to login: if you happen to have a valid pubkey this
492 * message is sent. the message is NEVER sent at all
493 * if a user is not allowed to login. is this an
496 if (user_key_allowed(authctxt->pw, key)) {
497 packet_start(SSH2_MSG_USERAUTH_PK_OK);
498 packet_put_string(pkalg, alen);
499 packet_put_string(pkblob, blen);
502 authctxt->postponed = 1;
505 if (authenticated != 1)
506 auth_clear_options();
509 debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
513 if (check_nt_auth(0, authctxt->pw->pw_uid) == 0)
516 return authenticated;
520 userauth_hostbased(Authctxt *authctxt)
524 char *pkalg, *pkblob, *sig, *cuser, *chost, *service;
525 u_int alen, blen, slen;
527 int authenticated = 0;
529 if (!authctxt->valid) {
530 debug2("userauth_hostbased: disabled because of invalid user");
533 pkalg = packet_get_string(&alen);
534 pkblob = packet_get_string(&blen);
535 chost = packet_get_string(NULL);
536 cuser = packet_get_string(NULL);
537 sig = packet_get_string(&slen);
539 debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d",
540 cuser, chost, pkalg, slen);
544 buffer_append(&b, sig, slen);
548 pktype = key_type_from_name(pkalg);
549 if (pktype == KEY_UNSPEC) {
550 /* this is perfectly legal */
551 log("userauth_hostbased: unsupported "
552 "public key algorithm: %s", pkalg);
555 key = key_from_blob(pkblob, blen);
557 debug("userauth_hostbased: cannot decode key: %s", pkalg);
560 service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
563 buffer_put_string(&b, session_id2, session_id2_len);
564 /* reconstruct packet */
565 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
566 buffer_put_cstring(&b, authctxt->user);
567 buffer_put_cstring(&b, service);
568 buffer_put_cstring(&b, "hostbased");
569 buffer_put_string(&b, pkalg, alen);
570 buffer_put_string(&b, pkblob, blen);
571 buffer_put_cstring(&b, chost);
572 buffer_put_cstring(&b, cuser);
576 /* test for allowed key and correct signature */
577 if (hostbased_key_allowed(authctxt->pw, cuser, chost, key) &&
578 key_verify(key, sig, slen, buffer_ptr(&b), buffer_len(&b)) == 1)
585 debug2("userauth_hostbased: authenticated %d", authenticated);
591 return authenticated;
594 /* get current user */
599 return (x_authctxt != NULL && x_authctxt->valid) ? x_authctxt->pw : NULL;
605 authmethods_get(void)
607 Authmethod *method = NULL;
611 for (method = authmethods; method->name != NULL; method++) {
612 if (strcmp(method->name, "none") == 0)
614 if (method->enabled != NULL && *(method->enabled) != 0) {
616 size += strlen(DELIM);
617 size += strlen(method->name);
620 size++; /* trailing '\0' */
621 list = xmalloc(size);
624 for (method = authmethods; method->name != NULL; method++) {
625 if (strcmp(method->name, "none") == 0)
627 if (method->enabled != NULL && *(method->enabled) != 0) {
629 strlcat(list, DELIM, size);
630 strlcat(list, method->name, size);
637 authmethod_lookup(const char *name)
639 Authmethod *method = NULL;
641 for (method = authmethods; method->name != NULL; method++)
642 if (method->enabled != NULL &&
643 *(method->enabled) != 0 &&
644 strcmp(name, method->name) == 0)
646 debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
650 /* return 1 if user allows given key */
652 user_key_allowed2(struct passwd *pw, Key *key, char *file)
664 /* Temporarily use the user's uid. */
665 temporarily_use_uid(pw);
667 debug("trying public key file %s", file);
669 /* Fail quietly if file does not exist */
670 if (stat(file, &st) < 0) {
671 /* Restore the privileged uid. */
675 /* Open the file containing the authorized keys. */
676 f = fopen(file, "r");
678 /* Restore the privileged uid. */
682 if (options.strict_modes &&
683 secure_filename(f, file, pw, line, sizeof(line)) != 0) {
685 log("Authentication refused: %s", line);
691 found = key_new(key->type);
693 while (fgets(line, sizeof(line), f)) {
694 char *cp, *options = NULL;
696 /* Skip leading whitespace, empty and comment lines. */
697 for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
699 if (!*cp || *cp == '\n' || *cp == '#')
702 if (key_read(found, &cp) != 1) {
703 /* no key? check if there are options for this key */
705 debug2("user_key_allowed: check options: '%s'", cp);
707 for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
708 if (*cp == '\\' && cp[1] == '"')
709 cp++; /* Skip both */
713 /* Skip remaining whitespace. */
714 for (; *cp == ' ' || *cp == '\t'; cp++)
716 if (key_read(found, &cp) != 1) {
717 debug2("user_key_allowed: advance: '%s'", cp);
718 /* still no key? advance to next line*/
722 if (key_equal(found, key) &&
723 auth_parse_options(pw, options, file, linenum) == 1) {
725 debug("matching key found: file %s, line %lu",
734 debug2("key not found");
738 /* check whether given key is in .ssh/authorized_keys* */
740 user_key_allowed(struct passwd *pw, Key *key)
745 file = authorized_keys_file(pw);
746 success = user_key_allowed2(pw, key, file);
751 /* try suffix "2" for backward compat, too */
752 file = authorized_keys_file2(pw);
753 success = user_key_allowed2(pw, key, file);
758 /* return 1 if given hostkey is allowed */
760 hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
763 const char *resolvedname, *ipaddr, *lookup;
764 int host_status, len;
766 resolvedname = get_canonical_hostname(options.reverse_mapping_check);
767 ipaddr = get_remote_ipaddr();
769 debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s",
770 chost, resolvedname, ipaddr);
772 if (options.hostbased_uses_name_from_packet_only) {
773 if (auth_rhosts2(pw, cuser, chost, chost) == 0)
777 if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
778 debug2("stripping trailing dot from chost %s", chost);
779 chost[len - 1] = '\0';
781 if (strcasecmp(resolvedname, chost) != 0)
782 log("userauth_hostbased mismatch: "
783 "client sends %s, but we resolve %s to %s",
784 chost, ipaddr, resolvedname);
785 if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0)
787 lookup = resolvedname;
789 debug2("userauth_hostbased: access allowed by auth_rhosts2");
791 host_status = check_key_in_hostfiles(pw, key, lookup,
792 _PATH_SSH_SYSTEM_HOSTFILE,
793 options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
795 /* backward compat if no key has been found. */
796 if (host_status == HOST_NEW)
797 host_status = check_key_in_hostfiles(pw, key, lookup,
798 _PATH_SSH_SYSTEM_HOSTFILE2,
799 options.ignore_user_known_hosts ? NULL :
800 _PATH_SSH_USER_HOSTFILE2);
802 return (host_status == HOST_OK);