1 /* $OpenBSD: auth.c,v 1.119 2016/12/15 21:29:05 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"
80 #include "blacklist_client.h"
83 extern ServerOptions options;
84 extern int use_privsep;
85 extern Buffer loginmsg;
86 extern struct passwd *privsep_pw;
88 /* Debugging messages */
93 * Check if the user is allowed to log in via ssh. If user is listed
94 * in DenyUsers or one of user's groups is listed in DenyGroups, false
95 * will be returned. If AllowUsers isn't empty and user isn't listed
96 * there, or if AllowGroups isn't empty and one of user's groups isn't
97 * listed there, false will be returned.
98 * If the user's shell is not executable, false will be returned.
99 * Otherwise true is returned.
102 allowed_user(struct passwd * pw)
104 struct ssh *ssh = active_state; /* XXX */
106 const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL;
110 struct spwd *spw = NULL;
113 /* Shouldn't be called if pw is NULL, but better safe than sorry... */
114 if (!pw || !pw->pw_name)
118 if (!options.use_pam)
119 spw = getspnam(pw->pw_name);
120 #ifdef HAS_SHADOW_EXPIRE
121 if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw))
123 #endif /* HAS_SHADOW_EXPIRE */
124 #endif /* USE_SHADOW */
126 /* grab passwd field for locked account check */
127 passwd = pw->pw_passwd;
131 passwd = get_iaf_password(pw);
133 passwd = spw->sp_pwdp;
134 #endif /* USE_LIBIAF */
137 /* check for locked account */
138 if (!options.use_pam && passwd && *passwd) {
141 #ifdef LOCKED_PASSWD_STRING
142 if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0)
145 #ifdef LOCKED_PASSWD_PREFIX
146 if (strncmp(passwd, LOCKED_PASSWD_PREFIX,
147 strlen(LOCKED_PASSWD_PREFIX)) == 0)
150 #ifdef LOCKED_PASSWD_SUBSTR
151 if (strstr(passwd, LOCKED_PASSWD_SUBSTR))
155 free((void *) passwd);
156 #endif /* USE_LIBIAF */
158 logit("User %.100s not allowed because account is locked",
165 * Deny if shell does not exist or is not executable unless we
168 if (options.chroot_directory == NULL ||
169 strcasecmp(options.chroot_directory, "none") == 0) {
170 char *shell = xstrdup((pw->pw_shell[0] == '\0') ?
171 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */
173 if (stat(shell, &st) != 0) {
174 logit("User %.100s not allowed because shell %.100s "
175 "does not exist", pw->pw_name, shell);
179 if (S_ISREG(st.st_mode) == 0 ||
180 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
181 logit("User %.100s not allowed because shell %.100s "
182 "is not executable", pw->pw_name, shell);
189 if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
190 options.num_deny_groups > 0 || options.num_allow_groups > 0) {
191 hostname = auth_get_canonical_hostname(ssh, options.use_dns);
192 ipaddr = ssh_remote_ipaddr(ssh);
195 /* Return false if user is listed in DenyUsers */
196 if (options.num_deny_users > 0) {
197 for (i = 0; i < options.num_deny_users; i++) {
198 r = match_user(pw->pw_name, hostname, ipaddr,
199 options.deny_users[i]);
201 fatal("Invalid DenyUsers pattern \"%.100s\"",
202 options.deny_users[i]);
204 logit("User %.100s from %.100s not allowed "
205 "because listed in DenyUsers",
206 pw->pw_name, hostname);
211 /* Return false if AllowUsers isn't empty and user isn't listed there */
212 if (options.num_allow_users > 0) {
213 for (i = 0; i < options.num_allow_users; i++) {
214 r = match_user(pw->pw_name, hostname, ipaddr,
215 options.allow_users[i]);
217 fatal("Invalid AllowUsers pattern \"%.100s\"",
218 options.allow_users[i]);
222 /* i < options.num_allow_users iff we break for loop */
223 if (i >= options.num_allow_users) {
224 logit("User %.100s from %.100s not allowed because "
225 "not listed in AllowUsers", pw->pw_name, hostname);
229 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
230 /* Get the user's group access list (primary and supplementary) */
231 if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
232 logit("User %.100s from %.100s not allowed because "
233 "not in any group", pw->pw_name, hostname);
237 /* Return false if one of user's groups is listed in DenyGroups */
238 if (options.num_deny_groups > 0)
239 if (ga_match(options.deny_groups,
240 options.num_deny_groups)) {
242 logit("User %.100s from %.100s not allowed "
243 "because a group is listed in DenyGroups",
244 pw->pw_name, hostname);
248 * Return false if AllowGroups isn't empty and one of user's groups
251 if (options.num_allow_groups > 0)
252 if (!ga_match(options.allow_groups,
253 options.num_allow_groups)) {
255 logit("User %.100s from %.100s not allowed "
256 "because none of user's groups are listed "
257 "in AllowGroups", pw->pw_name, hostname);
263 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER
264 if (!sys_auth_allowed_user(pw, &loginmsg))
268 /* We found no reason not to let this user try to log on... */
273 auth_info(Authctxt *authctxt, const char *fmt, ...)
278 free(authctxt->info);
279 authctxt->info = NULL;
282 i = vasprintf(&authctxt->info, fmt, ap);
285 if (i < 0 || authctxt->info == NULL)
286 fatal("vasprintf failed");
290 auth_log(Authctxt *authctxt, int authenticated, int partial,
291 const char *method, const char *submethod)
293 struct ssh *ssh = active_state; /* XXX */
294 void (*authlog) (const char *fmt,...) = verbose;
297 if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
300 /* Raise logging level */
301 if (authenticated == 1 ||
303 authctxt->failures >= options.max_authtries / 2 ||
304 strcmp(method, "password") == 0)
307 if (authctxt->postponed)
308 authmsg = "Postponed";
312 authmsg = authenticated ? "Accepted" : "Failed";
314 BLACKLIST_NOTIFY(BLACKLIST_AUTH_OK, "ssh");
317 authlog("%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s",
320 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
321 authctxt->valid ? "" : "invalid user ",
323 ssh_remote_ipaddr(ssh),
324 ssh_remote_port(ssh),
325 authctxt->info != NULL ? ": " : "",
326 authctxt->info != NULL ? authctxt->info : "");
327 free(authctxt->info);
328 authctxt->info = NULL;
330 #ifdef CUSTOM_FAILED_LOGIN
331 if (authenticated == 0 && !authctxt->postponed &&
332 (strcmp(method, "password") == 0 ||
333 strncmp(method, "keyboard-interactive", 20) == 0 ||
334 strcmp(method, "challenge-response") == 0))
335 record_failed_login(authctxt->user,
336 auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
337 # ifdef WITH_AIXAUTHENTICATE
339 sys_auth_record_login(authctxt->user,
340 auth_get_canonical_hostname(ssh, options.use_dns), "ssh",
344 #ifdef SSH_AUDIT_EVENTS
345 if (authenticated == 0 && !authctxt->postponed)
346 audit_event(audit_classify_auth(method));
352 auth_maxtries_exceeded(Authctxt *authctxt)
354 struct ssh *ssh = active_state; /* XXX */
356 error("maximum authentication attempts exceeded for "
357 "%s%.100s from %.200s port %d ssh2",
358 authctxt->valid ? "" : "invalid user ",
360 ssh_remote_ipaddr(ssh),
361 ssh_remote_port(ssh));
362 packet_disconnect("Too many authentication failures");
367 * Check whether root logins are disallowed.
370 auth_root_allowed(const char *method)
372 struct ssh *ssh = active_state; /* XXX */
374 switch (options.permit_root_login) {
377 case PERMIT_NO_PASSWD:
378 if (strcmp(method, "publickey") == 0 ||
379 strcmp(method, "hostbased") == 0 ||
380 strcmp(method, "gssapi-with-mic") == 0)
383 case PERMIT_FORCED_ONLY:
384 if (forced_command) {
385 logit("Root login accepted for forced command.");
390 logit("ROOT LOGIN REFUSED FROM %.200s port %d",
391 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
397 * Given a template and a passwd structure, build a filename
398 * by substituting % tokenised options. Currently, %% becomes '%',
399 * %h becomes the home directory and %u the username.
401 * This returns a buffer allocated by xmalloc.
404 expand_authorized_keys(const char *filename, struct passwd *pw)
406 char *file, ret[PATH_MAX];
409 file = percent_expand(filename, "h", pw->pw_dir,
410 "u", pw->pw_name, (char *)NULL);
413 * Ensure that filename starts anchored. If not, be backward
414 * compatible and prepend the '%h/'
419 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
420 if (i < 0 || (size_t)i >= sizeof(ret))
421 fatal("expand_authorized_keys: path too long");
423 return (xstrdup(ret));
427 authorized_principals_file(struct passwd *pw)
429 if (options.authorized_principals_file == NULL)
431 return expand_authorized_keys(options.authorized_principals_file, pw);
434 /* return ok if key exists in sysfile or userfile */
436 check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
437 const char *sysfile, const char *userfile)
441 HostStatus host_status;
442 struct hostkeys *hostkeys;
443 const struct hostkey_entry *found;
445 hostkeys = init_hostkeys();
446 load_hostkeys(hostkeys, host, sysfile);
447 if (userfile != NULL) {
448 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
449 if (options.strict_modes &&
450 (stat(user_hostfile, &st) == 0) &&
451 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
452 (st.st_mode & 022) != 0)) {
453 logit("Authentication refused for %.100s: "
454 "bad owner or modes for %.200s",
455 pw->pw_name, user_hostfile);
456 auth_debug_add("Ignored %.200s: bad ownership or modes",
459 temporarily_use_uid(pw);
460 load_hostkeys(hostkeys, host, user_hostfile);
465 host_status = check_key_in_hostkeys(hostkeys, key, &found);
466 if (host_status == HOST_REVOKED)
467 error("WARNING: revoked key for %s attempted authentication",
469 else if (host_status == HOST_OK)
470 debug("%s: key for %s found at %s:%ld", __func__,
471 found->host, found->file, found->line);
473 debug("%s: key for host %s not found", __func__, host);
475 free_hostkeys(hostkeys);
481 * Check a given path for security. This is defined as all components
482 * of the path to the file must be owned by either the owner of
483 * of the file or root and no directories must be group or world writable.
485 * XXX Should any specific check be done for sym links ?
487 * Takes a file name, its stat information (preferably from fstat() to
488 * avoid races), the uid of the expected owner, their home directory and an
489 * error buffer plus max size as arguments.
491 * Returns 0 on success and -1 on failure
494 auth_secure_path(const char *name, struct stat *stp, const char *pw_dir,
495 uid_t uid, char *err, size_t errlen)
497 char buf[PATH_MAX], homedir[PATH_MAX];
502 if (realpath(name, buf) == NULL) {
503 snprintf(err, errlen, "realpath %s failed: %s", name,
507 if (pw_dir != NULL && realpath(pw_dir, homedir) != NULL)
510 if (!S_ISREG(stp->st_mode)) {
511 snprintf(err, errlen, "%s is not a regular file", buf);
514 if ((!platform_sys_dir_uid(stp->st_uid) && stp->st_uid != uid) ||
515 (stp->st_mode & 022) != 0) {
516 snprintf(err, errlen, "bad ownership or modes for file %s",
521 /* for each component of the canonical path, walking upwards */
523 if ((cp = dirname(buf)) == NULL) {
524 snprintf(err, errlen, "dirname() failed");
527 strlcpy(buf, cp, sizeof(buf));
529 if (stat(buf, &st) < 0 ||
530 (!platform_sys_dir_uid(st.st_uid) && st.st_uid != uid) ||
531 (st.st_mode & 022) != 0) {
532 snprintf(err, errlen,
533 "bad ownership or modes for directory %s", buf);
537 /* If are past the homedir then we can stop */
538 if (comparehome && strcmp(homedir, buf) == 0)
542 * dirname should always complete with a "/" path,
543 * but we can be paranoid and check for "." too
545 if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
552 * Version of secure_path() that accepts an open file descriptor to
555 * Returns 0 on success and -1 on failure
558 secure_filename(FILE *f, const char *file, struct passwd *pw,
559 char *err, size_t errlen)
563 /* check the open file to avoid races */
564 if (fstat(fileno(f), &st) < 0) {
565 snprintf(err, errlen, "cannot stat file %s: %s",
566 file, strerror(errno));
569 return auth_secure_path(file, &st, pw->pw_dir, pw->pw_uid, err, errlen);
573 auth_openfile(const char *file, struct passwd *pw, int strict_modes,
574 int log_missing, char *file_type)
581 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
582 if (log_missing || errno != ENOENT)
583 debug("Could not open %s '%s': %s", file_type, file,
588 if (fstat(fd, &st) < 0) {
592 if (!S_ISREG(st.st_mode)) {
593 logit("User %s %s %s is not a regular file",
594 pw->pw_name, file_type, file);
599 if ((f = fdopen(fd, "r")) == NULL) {
604 secure_filename(f, file, pw, line, sizeof(line)) != 0) {
606 logit("Authentication refused: %s", line);
607 auth_debug_add("Ignored %s: %s", file_type, line);
616 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
618 return auth_openfile(file, pw, strict_modes, 1, "authorized keys");
622 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
624 return auth_openfile(file, pw, strict_modes, 0,
625 "authorized principals");
629 getpwnamallow(const char *user)
631 struct ssh *ssh = active_state; /* XXX */
632 #ifdef HAVE_LOGIN_CAP
633 extern login_cap_t *lc;
639 struct connection_info *ci = get_connection_info(1, options.use_dns);
642 parse_server_match_config(&options, ci);
644 #if defined(_AIX) && defined(HAVE_SETAUTHDB)
650 #if defined(_AIX) && defined(HAVE_SETAUTHDB)
655 * Windows usernames are case-insensitive. To avoid later problems
656 * when trying to match the username, the user is only allowed to
657 * login if the username is given in the same case as stored in the
660 if (pw != NULL && strcmp(user, pw->pw_name) != 0) {
661 logit("Login name %.100s does not match stored username %.100s",
667 BLACKLIST_NOTIFY(BLACKLIST_BAD_USER, user);
668 logit("Invalid user %.100s from %.100s port %d",
669 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
670 #ifdef CUSTOM_FAILED_LOGIN
671 record_failed_login(user,
672 auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
674 #ifdef SSH_AUDIT_EVENTS
675 audit_event(SSH_INVALID_USER);
676 #endif /* SSH_AUDIT_EVENTS */
679 if (!allowed_user(pw))
681 #ifdef HAVE_LOGIN_CAP
682 if ((lc = login_getpwclass(pw)) == NULL) {
683 debug("unable to get login class: %s", user);
687 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
688 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
689 debug("Approval failure for %s", user);
701 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
703 auth_key_is_revoked(Key *key)
708 if (options.revoked_keys_file == NULL)
710 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
711 SSH_FP_DEFAULT)) == NULL) {
712 r = SSH_ERR_ALLOC_FAIL;
713 error("%s: fingerprint key: %s", __func__, ssh_err(r));
717 r = sshkey_check_revoked(key, options.revoked_keys_file);
720 break; /* not revoked */
721 case SSH_ERR_KEY_REVOKED:
722 error("Authentication key %s %s revoked by file %s",
723 sshkey_type(key), fp, options.revoked_keys_file);
726 error("Error checking authentication key %s %s in "
727 "revoked keys file %s: %s", sshkey_type(key), fp,
728 options.revoked_keys_file, ssh_err(r));
737 return r == 0 ? 0 : 1;
741 auth_debug_add(const char *fmt,...)
746 if (!auth_debug_init)
750 vsnprintf(buf, sizeof(buf), fmt, args);
752 buffer_put_cstring(&auth_debug, buf);
756 auth_debug_send(void)
760 if (!auth_debug_init)
762 while (buffer_len(&auth_debug)) {
763 msg = buffer_get_string(&auth_debug, NULL);
764 packet_send_debug("%s", msg);
770 auth_debug_reset(void)
773 buffer_clear(&auth_debug);
775 buffer_init(&auth_debug);
783 static struct passwd fake;
785 memset(&fake, 0, sizeof(fake));
786 fake.pw_name = "NOUSER";
788 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
789 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS
790 fake.pw_gecos = "NOUSER";
792 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid;
793 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid;
794 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS
797 fake.pw_dir = "/nonexist";
798 fake.pw_shell = "/nonexist";
804 * Returns the remote DNS hostname as a string. The returned string must not
805 * be freed. NB. this will usually trigger a DNS query the first time it is
807 * This function does additional checks on the hostname to mitigate some
808 * attacks on legacy rhosts-style authentication.
809 * XXX is RhostsRSAAuthentication vulnerable to these?
810 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
814 remote_hostname(struct ssh *ssh)
816 struct sockaddr_storage from;
818 struct addrinfo hints, *ai, *aitop;
819 char name[NI_MAXHOST], ntop2[NI_MAXHOST];
820 const char *ntop = ssh_remote_ipaddr(ssh);
822 /* Get IP address of client. */
823 fromlen = sizeof(from);
824 memset(&from, 0, sizeof(from));
825 if (getpeername(ssh_packet_get_connection_in(ssh),
826 (struct sockaddr *)&from, &fromlen) < 0) {
827 debug("getpeername failed: %.100s", strerror(errno));
831 ipv64_normalise_mapped(&from, &fromlen);
832 if (from.ss_family == AF_INET6)
833 fromlen = sizeof(struct sockaddr_in6);
835 debug3("Trying to reverse map address %.100s.", ntop);
836 /* Map the IP address to a host name. */
837 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
838 NULL, 0, NI_NAMEREQD) != 0) {
839 /* Host name not found. Use ip address. */
844 * if reverse lookup result looks like a numeric hostname,
845 * someone is trying to trick us by PTR record like following:
846 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
848 memset(&hints, 0, sizeof(hints));
849 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
850 hints.ai_flags = AI_NUMERICHOST;
851 if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
852 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
858 /* Names are stored in lowercase. */
862 * Map it back to an IP address and check that the given
863 * address actually is an address of this host. This is
864 * necessary because anyone with access to a name server can
865 * define arbitrary names for an IP address. Mapping from
866 * name to IP address can be trusted better (but can still be
867 * fooled if the intruder has access to the name server of
870 memset(&hints, 0, sizeof(hints));
871 hints.ai_family = from.ss_family;
872 hints.ai_socktype = SOCK_STREAM;
873 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
874 logit("reverse mapping checking getaddrinfo for %.700s "
875 "[%s] failed.", name, ntop);
878 /* Look for the address from the list of addresses. */
879 for (ai = aitop; ai; ai = ai->ai_next) {
880 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
881 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
882 (strcmp(ntop, ntop2) == 0))
886 /* If we reached the end of the list, the address was not there. */
888 /* Address not found for the host name. */
889 logit("Address %.100s maps to %.600s, but this does not "
890 "map back to the address.", ntop, name);
897 * Return the canonical name of the host in the other side of the current
898 * connection. The host name is cached, so it is efficient to call this
903 auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
905 static char *dnsname;
908 return ssh_remote_ipaddr(ssh);
909 else if (dnsname != NULL)
912 dnsname = remote_hostname(ssh);