1 /* $OpenBSD: auth.c,v 1.115 2016/06/15 00:40:40 dtucker 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>
31 #include <sys/socket.h>
33 #include <netinet/in.h>
59 #include "groupaccess.h"
67 #include "auth-options.h"
76 #include "monitor_wrap.h"
82 extern ServerOptions options;
83 extern int use_privsep;
84 extern Buffer loginmsg;
85 extern struct passwd *privsep_pw;
87 /* Debugging messages */
92 * Check if the user is allowed to log in via ssh. If user is listed
93 * in DenyUsers or one of user's groups is listed in DenyGroups, false
94 * will be returned. If AllowUsers isn't empty and user isn't listed
95 * there, or if AllowGroups isn't empty and one of user's groups isn't
96 * listed there, false will be returned.
97 * If the user's shell is not executable, false will be returned.
98 * Otherwise true is returned.
101 allowed_user(struct passwd * pw)
103 struct ssh *ssh = active_state; /* XXX */
105 const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL;
108 struct spwd *spw = NULL;
111 /* Shouldn't be called if pw is NULL, but better safe than sorry... */
112 if (!pw || !pw->pw_name)
116 if (!options.use_pam)
117 spw = getspnam(pw->pw_name);
118 #ifdef HAS_SHADOW_EXPIRE
119 if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw))
121 #endif /* HAS_SHADOW_EXPIRE */
122 #endif /* USE_SHADOW */
124 /* grab passwd field for locked account check */
125 passwd = pw->pw_passwd;
129 passwd = get_iaf_password(pw);
131 passwd = spw->sp_pwdp;
132 #endif /* USE_LIBIAF */
135 /* check for locked account */
136 if (!options.use_pam && passwd && *passwd) {
139 #ifdef LOCKED_PASSWD_STRING
140 if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0)
143 #ifdef LOCKED_PASSWD_PREFIX
144 if (strncmp(passwd, LOCKED_PASSWD_PREFIX,
145 strlen(LOCKED_PASSWD_PREFIX)) == 0)
148 #ifdef LOCKED_PASSWD_SUBSTR
149 if (strstr(passwd, LOCKED_PASSWD_SUBSTR))
153 free((void *) passwd);
154 #endif /* USE_LIBIAF */
156 logit("User %.100s not allowed because account is locked",
163 * Deny if shell does not exist or is not executable unless we
166 if (options.chroot_directory == NULL ||
167 strcasecmp(options.chroot_directory, "none") == 0) {
168 char *shell = xstrdup((pw->pw_shell[0] == '\0') ?
169 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */
171 if (stat(shell, &st) != 0) {
172 logit("User %.100s not allowed because shell %.100s "
173 "does not exist", pw->pw_name, shell);
177 if (S_ISREG(st.st_mode) == 0 ||
178 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
179 logit("User %.100s not allowed because shell %.100s "
180 "is not executable", pw->pw_name, shell);
187 if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
188 options.num_deny_groups > 0 || options.num_allow_groups > 0) {
189 hostname = auth_get_canonical_hostname(ssh, options.use_dns);
190 ipaddr = ssh_remote_ipaddr(ssh);
193 /* Return false if user is listed in DenyUsers */
194 if (options.num_deny_users > 0) {
195 for (i = 0; i < options.num_deny_users; i++)
196 if (match_user(pw->pw_name, hostname, ipaddr,
197 options.deny_users[i])) {
198 logit("User %.100s from %.100s not allowed "
199 "because listed in DenyUsers",
200 pw->pw_name, hostname);
204 /* Return false if AllowUsers isn't empty and user isn't listed there */
205 if (options.num_allow_users > 0) {
206 for (i = 0; i < options.num_allow_users; i++)
207 if (match_user(pw->pw_name, hostname, ipaddr,
208 options.allow_users[i]))
210 /* i < options.num_allow_users iff we break for loop */
211 if (i >= options.num_allow_users) {
212 logit("User %.100s from %.100s not allowed because "
213 "not listed in AllowUsers", pw->pw_name, hostname);
217 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
218 /* Get the user's group access list (primary and supplementary) */
219 if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
220 logit("User %.100s from %.100s not allowed because "
221 "not in any group", pw->pw_name, hostname);
225 /* Return false if one of user's groups is listed in DenyGroups */
226 if (options.num_deny_groups > 0)
227 if (ga_match(options.deny_groups,
228 options.num_deny_groups)) {
230 logit("User %.100s from %.100s not allowed "
231 "because a group is listed in DenyGroups",
232 pw->pw_name, hostname);
236 * Return false if AllowGroups isn't empty and one of user's groups
239 if (options.num_allow_groups > 0)
240 if (!ga_match(options.allow_groups,
241 options.num_allow_groups)) {
243 logit("User %.100s from %.100s not allowed "
244 "because none of user's groups are listed "
245 "in AllowGroups", pw->pw_name, hostname);
251 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER
252 if (!sys_auth_allowed_user(pw, &loginmsg))
256 /* We found no reason not to let this user try to log on... */
261 auth_info(Authctxt *authctxt, const char *fmt, ...)
266 free(authctxt->info);
267 authctxt->info = NULL;
270 i = vasprintf(&authctxt->info, fmt, ap);
273 if (i < 0 || authctxt->info == NULL)
274 fatal("vasprintf failed");
278 auth_log(Authctxt *authctxt, int authenticated, int partial,
279 const char *method, const char *submethod)
281 struct ssh *ssh = active_state; /* XXX */
282 void (*authlog) (const char *fmt,...) = verbose;
285 if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
288 /* Raise logging level */
289 if (authenticated == 1 ||
291 authctxt->failures >= options.max_authtries / 2 ||
292 strcmp(method, "password") == 0)
295 if (authctxt->postponed)
296 authmsg = "Postponed";
300 authmsg = authenticated ? "Accepted" : "Failed";
302 authlog("%s %s%s%s for %s%.100s from %.200s port %d %s%s%s",
305 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
306 authctxt->valid ? "" : "invalid user ",
308 ssh_remote_ipaddr(ssh),
309 ssh_remote_port(ssh),
310 compat20 ? "ssh2" : "ssh1",
311 authctxt->info != NULL ? ": " : "",
312 authctxt->info != NULL ? authctxt->info : "");
313 free(authctxt->info);
314 authctxt->info = NULL;
316 #ifdef CUSTOM_FAILED_LOGIN
317 if (authenticated == 0 && !authctxt->postponed &&
318 (strcmp(method, "password") == 0 ||
319 strncmp(method, "keyboard-interactive", 20) == 0 ||
320 strcmp(method, "challenge-response") == 0))
321 record_failed_login(authctxt->user,
322 auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
323 # ifdef WITH_AIXAUTHENTICATE
325 sys_auth_record_login(authctxt->user,
326 auth_get_canonical_hostname(ssh, options.use_dns), "ssh",
330 #ifdef SSH_AUDIT_EVENTS
331 if (authenticated == 0 && !authctxt->postponed)
332 audit_event(audit_classify_auth(method));
338 auth_maxtries_exceeded(Authctxt *authctxt)
340 struct ssh *ssh = active_state; /* XXX */
342 error("maximum authentication attempts exceeded for "
343 "%s%.100s from %.200s port %d %s",
344 authctxt->valid ? "" : "invalid user ",
346 ssh_remote_ipaddr(ssh),
347 ssh_remote_port(ssh),
348 compat20 ? "ssh2" : "ssh1");
349 packet_disconnect("Too many authentication failures");
354 * Check whether root logins are disallowed.
357 auth_root_allowed(const char *method)
359 struct ssh *ssh = active_state; /* XXX */
361 switch (options.permit_root_login) {
364 case PERMIT_NO_PASSWD:
365 if (strcmp(method, "publickey") == 0 ||
366 strcmp(method, "hostbased") == 0 ||
367 strcmp(method, "gssapi-with-mic") == 0)
370 case PERMIT_FORCED_ONLY:
371 if (forced_command) {
372 logit("Root login accepted for forced command.");
377 logit("ROOT LOGIN REFUSED FROM %.200s port %d",
378 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
384 * Given a template and a passwd structure, build a filename
385 * by substituting % tokenised options. Currently, %% becomes '%',
386 * %h becomes the home directory and %u the username.
388 * This returns a buffer allocated by xmalloc.
391 expand_authorized_keys(const char *filename, struct passwd *pw)
393 char *file, ret[PATH_MAX];
396 file = percent_expand(filename, "h", pw->pw_dir,
397 "u", pw->pw_name, (char *)NULL);
400 * Ensure that filename starts anchored. If not, be backward
401 * compatible and prepend the '%h/'
406 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
407 if (i < 0 || (size_t)i >= sizeof(ret))
408 fatal("expand_authorized_keys: path too long");
410 return (xstrdup(ret));
414 authorized_principals_file(struct passwd *pw)
416 if (options.authorized_principals_file == NULL)
418 return expand_authorized_keys(options.authorized_principals_file, pw);
421 /* return ok if key exists in sysfile or userfile */
423 check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
424 const char *sysfile, const char *userfile)
428 HostStatus host_status;
429 struct hostkeys *hostkeys;
430 const struct hostkey_entry *found;
432 hostkeys = init_hostkeys();
433 load_hostkeys(hostkeys, host, sysfile);
434 if (userfile != NULL) {
435 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
436 if (options.strict_modes &&
437 (stat(user_hostfile, &st) == 0) &&
438 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
439 (st.st_mode & 022) != 0)) {
440 logit("Authentication refused for %.100s: "
441 "bad owner or modes for %.200s",
442 pw->pw_name, user_hostfile);
443 auth_debug_add("Ignored %.200s: bad ownership or modes",
446 temporarily_use_uid(pw);
447 load_hostkeys(hostkeys, host, user_hostfile);
452 host_status = check_key_in_hostkeys(hostkeys, key, &found);
453 if (host_status == HOST_REVOKED)
454 error("WARNING: revoked key for %s attempted authentication",
456 else if (host_status == HOST_OK)
457 debug("%s: key for %s found at %s:%ld", __func__,
458 found->host, found->file, found->line);
460 debug("%s: key for host %s not found", __func__, host);
462 free_hostkeys(hostkeys);
468 * Check a given path for security. This is defined as all components
469 * of the path to the file must be owned by either the owner of
470 * of the file or root and no directories must be group or world writable.
472 * XXX Should any specific check be done for sym links ?
474 * Takes a file name, its stat information (preferably from fstat() to
475 * avoid races), the uid of the expected owner, their home directory and an
476 * error buffer plus max size as arguments.
478 * Returns 0 on success and -1 on failure
481 auth_secure_path(const char *name, struct stat *stp, const char *pw_dir,
482 uid_t uid, char *err, size_t errlen)
484 char buf[PATH_MAX], homedir[PATH_MAX];
489 if (realpath(name, buf) == NULL) {
490 snprintf(err, errlen, "realpath %s failed: %s", name,
494 if (pw_dir != NULL && realpath(pw_dir, homedir) != NULL)
497 if (!S_ISREG(stp->st_mode)) {
498 snprintf(err, errlen, "%s is not a regular file", buf);
501 if ((!platform_sys_dir_uid(stp->st_uid) && stp->st_uid != uid) ||
502 (stp->st_mode & 022) != 0) {
503 snprintf(err, errlen, "bad ownership or modes for file %s",
508 /* for each component of the canonical path, walking upwards */
510 if ((cp = dirname(buf)) == NULL) {
511 snprintf(err, errlen, "dirname() failed");
514 strlcpy(buf, cp, sizeof(buf));
516 if (stat(buf, &st) < 0 ||
517 (!platform_sys_dir_uid(st.st_uid) && st.st_uid != uid) ||
518 (st.st_mode & 022) != 0) {
519 snprintf(err, errlen,
520 "bad ownership or modes for directory %s", buf);
524 /* If are past the homedir then we can stop */
525 if (comparehome && strcmp(homedir, buf) == 0)
529 * dirname should always complete with a "/" path,
530 * but we can be paranoid and check for "." too
532 if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
539 * Version of secure_path() that accepts an open file descriptor to
542 * Returns 0 on success and -1 on failure
545 secure_filename(FILE *f, const char *file, struct passwd *pw,
546 char *err, size_t errlen)
550 /* check the open file to avoid races */
551 if (fstat(fileno(f), &st) < 0) {
552 snprintf(err, errlen, "cannot stat file %s: %s",
553 file, strerror(errno));
556 return auth_secure_path(file, &st, pw->pw_dir, pw->pw_uid, err, errlen);
560 auth_openfile(const char *file, struct passwd *pw, int strict_modes,
561 int log_missing, char *file_type)
568 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
569 if (log_missing || errno != ENOENT)
570 debug("Could not open %s '%s': %s", file_type, file,
575 if (fstat(fd, &st) < 0) {
579 if (!S_ISREG(st.st_mode)) {
580 logit("User %s %s %s is not a regular file",
581 pw->pw_name, file_type, file);
586 if ((f = fdopen(fd, "r")) == NULL) {
591 secure_filename(f, file, pw, line, sizeof(line)) != 0) {
593 logit("Authentication refused: %s", line);
594 auth_debug_add("Ignored %s: %s", file_type, line);
603 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
605 return auth_openfile(file, pw, strict_modes, 1, "authorized keys");
609 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
611 return auth_openfile(file, pw, strict_modes, 0,
612 "authorized principals");
616 getpwnamallow(const char *user)
618 struct ssh *ssh = active_state; /* XXX */
619 #ifdef HAVE_LOGIN_CAP
620 extern login_cap_t *lc;
626 struct connection_info *ci = get_connection_info(1, options.use_dns);
629 parse_server_match_config(&options, ci);
631 #if defined(_AIX) && defined(HAVE_SETAUTHDB)
637 #if defined(_AIX) && defined(HAVE_SETAUTHDB)
642 * Windows usernames are case-insensitive. To avoid later problems
643 * when trying to match the username, the user is only allowed to
644 * login if the username is given in the same case as stored in the
647 if (pw != NULL && strcmp(user, pw->pw_name) != 0) {
648 logit("Login name %.100s does not match stored username %.100s",
654 logit("Invalid user %.100s from %.100s port %d",
655 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
656 #ifdef CUSTOM_FAILED_LOGIN
657 record_failed_login(user,
658 auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
660 #ifdef SSH_AUDIT_EVENTS
661 audit_event(SSH_INVALID_USER);
662 #endif /* SSH_AUDIT_EVENTS */
665 if (!allowed_user(pw))
667 #ifdef HAVE_LOGIN_CAP
668 if ((lc = login_getpwclass(pw)) == NULL) {
669 debug("unable to get login class: %s", user);
673 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
674 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
675 debug("Approval failure for %s", user);
687 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
689 auth_key_is_revoked(Key *key)
694 if (options.revoked_keys_file == NULL)
696 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
697 SSH_FP_DEFAULT)) == NULL) {
698 r = SSH_ERR_ALLOC_FAIL;
699 error("%s: fingerprint key: %s", __func__, ssh_err(r));
703 r = sshkey_check_revoked(key, options.revoked_keys_file);
706 break; /* not revoked */
707 case SSH_ERR_KEY_REVOKED:
708 error("Authentication key %s %s revoked by file %s",
709 sshkey_type(key), fp, options.revoked_keys_file);
712 error("Error checking authentication key %s %s in "
713 "revoked keys file %s: %s", sshkey_type(key), fp,
714 options.revoked_keys_file, ssh_err(r));
723 return r == 0 ? 0 : 1;
727 auth_debug_add(const char *fmt,...)
732 if (!auth_debug_init)
736 vsnprintf(buf, sizeof(buf), fmt, args);
738 buffer_put_cstring(&auth_debug, buf);
742 auth_debug_send(void)
746 if (!auth_debug_init)
748 while (buffer_len(&auth_debug)) {
749 msg = buffer_get_string(&auth_debug, NULL);
750 packet_send_debug("%s", msg);
756 auth_debug_reset(void)
759 buffer_clear(&auth_debug);
761 buffer_init(&auth_debug);
769 static struct passwd fake;
771 memset(&fake, 0, sizeof(fake));
772 fake.pw_name = "NOUSER";
774 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
775 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS
776 fake.pw_gecos = "NOUSER";
778 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid;
779 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid;
780 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS
783 fake.pw_dir = "/nonexist";
784 fake.pw_shell = "/nonexist";
790 * Returns the remote DNS hostname as a string. The returned string must not
791 * be freed. NB. this will usually trigger a DNS query the first time it is
793 * This function does additional checks on the hostname to mitigate some
794 * attacks on legacy rhosts-style authentication.
795 * XXX is RhostsRSAAuthentication vulnerable to these?
796 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
800 remote_hostname(struct ssh *ssh)
802 struct sockaddr_storage from;
804 struct addrinfo hints, *ai, *aitop;
805 char name[NI_MAXHOST], ntop2[NI_MAXHOST];
806 const char *ntop = ssh_remote_ipaddr(ssh);
808 /* Get IP address of client. */
809 fromlen = sizeof(from);
810 memset(&from, 0, sizeof(from));
811 if (getpeername(ssh_packet_get_connection_in(ssh),
812 (struct sockaddr *)&from, &fromlen) < 0) {
813 debug("getpeername failed: %.100s", strerror(errno));
817 ipv64_normalise_mapped(&from, &fromlen);
818 if (from.ss_family == AF_INET6)
819 fromlen = sizeof(struct sockaddr_in6);
821 debug3("Trying to reverse map address %.100s.", ntop);
822 /* Map the IP address to a host name. */
823 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
824 NULL, 0, NI_NAMEREQD) != 0) {
825 /* Host name not found. Use ip address. */
830 * if reverse lookup result looks like a numeric hostname,
831 * someone is trying to trick us by PTR record like following:
832 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
834 memset(&hints, 0, sizeof(hints));
835 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
836 hints.ai_flags = AI_NUMERICHOST;
837 if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
838 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
844 /* Names are stored in lowercase. */
848 * Map it back to an IP address and check that the given
849 * address actually is an address of this host. This is
850 * necessary because anyone with access to a name server can
851 * define arbitrary names for an IP address. Mapping from
852 * name to IP address can be trusted better (but can still be
853 * fooled if the intruder has access to the name server of
856 memset(&hints, 0, sizeof(hints));
857 hints.ai_family = from.ss_family;
858 hints.ai_socktype = SOCK_STREAM;
859 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
860 logit("reverse mapping checking getaddrinfo for %.700s "
861 "[%s] failed.", name, ntop);
864 /* Look for the address from the list of addresses. */
865 for (ai = aitop; ai; ai = ai->ai_next) {
866 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
867 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
868 (strcmp(ntop, ntop2) == 0))
872 /* If we reached the end of the list, the address was not there. */
874 /* Address not found for the host name. */
875 logit("Address %.100s maps to %.600s, but this does not "
876 "map back to the address.", ntop, name);
883 * Return the canonical name of the host in the other side of the current
884 * connection. The host name is cached, so it is efficient to call this
889 auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
891 static char *dnsname;
894 return ssh_remote_ipaddr(ssh);
895 else if (dnsname != NULL)
898 dnsname = remote_hostname(ssh);