1 /* $OpenBSD: auth.c,v 1.160 2023/03/05 05:34:09 dtucker Exp $ */
2 /*
3 * Copyright (c) 2000 Markus Friedl. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
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.
13 *
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.
24 */
25
26 #include "includes.h"
27
28 #include <sys/types.h>
29 #include <sys/stat.h>
30 #include <sys/socket.h>
31 #include <sys/wait.h>
32
33 #include <netinet/in.h>
34
35 #include <stdlib.h>
36 #include <errno.h>
37 #include <fcntl.h>
38 #ifdef HAVE_PATHS_H
39 # include <paths.h>
40 #endif
41 #include <pwd.h>
42 #ifdef HAVE_LOGIN_H
43 #include <login.h>
44 #endif
45 #ifdef USE_SHADOW
46 #include <shadow.h>
47 #endif
48 #include <stdarg.h>
49 #include <stdio.h>
50 #include <string.h>
51 #include <unistd.h>
52 #include <limits.h>
53 #include <netdb.h>
54 #include <time.h>
55
56 #include "xmalloc.h"
57 #include "match.h"
58 #include "groupaccess.h"
59 #include "log.h"
60 #include "sshbuf.h"
61 #include "misc.h"
62 #include "servconf.h"
63 #include "sshkey.h"
64 #include "hostfile.h"
65 #include "auth.h"
66 #include "auth-options.h"
67 #include "canohost.h"
68 #include "uidswap.h"
69 #include "packet.h"
70 #include "loginrec.h"
71 #ifdef GSSAPI
72 #include "ssh-gss.h"
73 #endif
74 #include "authfile.h"
75 #include "monitor_wrap.h"
76 #include "ssherr.h"
77 #include "channels.h"
78 #include "blacklist_client.h"
79
80 /* import */
81 extern ServerOptions options;
82 extern struct include_list includes;
83 extern int use_privsep;
84 extern struct sshbuf *loginmsg;
85 extern struct passwd *privsep_pw;
86 extern struct sshauthopt *auth_opts;
87
88 /* Debugging messages */
89 static struct sshbuf *auth_debug;
90
91 /*
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.
99 */
100 int
allowed_user(struct ssh * ssh,struct passwd * pw)101 allowed_user(struct ssh *ssh, struct passwd * pw)
102 {
103 struct stat st;
104 const char *hostname = NULL, *ipaddr = NULL;
105 u_int i;
106 int r;
107
108 /* Shouldn't be called if pw is NULL, but better safe than sorry... */
109 if (!pw || !pw->pw_name)
110 return 0;
111
112 if (!options.use_pam && platform_locked_account(pw)) {
113 logit("User %.100s not allowed because account is locked",
114 pw->pw_name);
115 return 0;
116 }
117
118 /*
119 * Deny if shell does not exist or is not executable unless we
120 * are chrooting.
121 */
122 if (options.chroot_directory == NULL ||
123 strcasecmp(options.chroot_directory, "none") == 0) {
124 char *shell = xstrdup((pw->pw_shell[0] == '\0') ?
125 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */
126
127 if (stat(shell, &st) == -1) {
128 logit("User %.100s not allowed because shell %.100s "
129 "does not exist", pw->pw_name, shell);
130 free(shell);
131 return 0;
132 }
133 if (S_ISREG(st.st_mode) == 0 ||
134 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
135 logit("User %.100s not allowed because shell %.100s "
136 "is not executable", pw->pw_name, shell);
137 free(shell);
138 return 0;
139 }
140 free(shell);
141 }
142
143 if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
144 options.num_deny_groups > 0 || options.num_allow_groups > 0) {
145 hostname = auth_get_canonical_hostname(ssh, options.use_dns);
146 ipaddr = ssh_remote_ipaddr(ssh);
147 }
148
149 /* Return false if user is listed in DenyUsers */
150 if (options.num_deny_users > 0) {
151 for (i = 0; i < options.num_deny_users; i++) {
152 r = match_user(pw->pw_name, hostname, ipaddr,
153 options.deny_users[i]);
154 if (r < 0) {
155 fatal("Invalid DenyUsers pattern \"%.100s\"",
156 options.deny_users[i]);
157 } else if (r != 0) {
158 logit("User %.100s from %.100s not allowed "
159 "because listed in DenyUsers",
160 pw->pw_name, hostname);
161 return 0;
162 }
163 }
164 }
165 /* Return false if AllowUsers isn't empty and user isn't listed there */
166 if (options.num_allow_users > 0) {
167 for (i = 0; i < options.num_allow_users; i++) {
168 r = match_user(pw->pw_name, hostname, ipaddr,
169 options.allow_users[i]);
170 if (r < 0) {
171 fatal("Invalid AllowUsers pattern \"%.100s\"",
172 options.allow_users[i]);
173 } else if (r == 1)
174 break;
175 }
176 /* i < options.num_allow_users iff we break for loop */
177 if (i >= options.num_allow_users) {
178 logit("User %.100s from %.100s not allowed because "
179 "not listed in AllowUsers", pw->pw_name, hostname);
180 return 0;
181 }
182 }
183 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
184 /* Get the user's group access list (primary and supplementary) */
185 if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
186 logit("User %.100s from %.100s not allowed because "
187 "not in any group", pw->pw_name, hostname);
188 return 0;
189 }
190
191 /* Return false if one of user's groups is listed in DenyGroups */
192 if (options.num_deny_groups > 0)
193 if (ga_match(options.deny_groups,
194 options.num_deny_groups)) {
195 ga_free();
196 logit("User %.100s from %.100s not allowed "
197 "because a group is listed in DenyGroups",
198 pw->pw_name, hostname);
199 return 0;
200 }
201 /*
202 * Return false if AllowGroups isn't empty and one of user's groups
203 * isn't listed there
204 */
205 if (options.num_allow_groups > 0)
206 if (!ga_match(options.allow_groups,
207 options.num_allow_groups)) {
208 ga_free();
209 logit("User %.100s from %.100s not allowed "
210 "because none of user's groups are listed "
211 "in AllowGroups", pw->pw_name, hostname);
212 return 0;
213 }
214 ga_free();
215 }
216
217 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER
218 if (!sys_auth_allowed_user(pw, loginmsg))
219 return 0;
220 #endif
221
222 /* We found no reason not to let this user try to log on... */
223 return 1;
224 }
225
226 /*
227 * Formats any key left in authctxt->auth_method_key for inclusion in
228 * auth_log()'s message. Also includes authxtct->auth_method_info if present.
229 */
230 static char *
format_method_key(Authctxt * authctxt)231 format_method_key(Authctxt *authctxt)
232 {
233 const struct sshkey *key = authctxt->auth_method_key;
234 const char *methinfo = authctxt->auth_method_info;
235 char *fp, *cafp, *ret = NULL;
236
237 if (key == NULL)
238 return NULL;
239
240 if (sshkey_is_cert(key)) {
241 fp = sshkey_fingerprint(key,
242 options.fingerprint_hash, SSH_FP_DEFAULT);
243 cafp = sshkey_fingerprint(key->cert->signature_key,
244 options.fingerprint_hash, SSH_FP_DEFAULT);
245 xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s",
246 sshkey_type(key), fp == NULL ? "(null)" : fp,
247 key->cert->key_id,
248 (unsigned long long)key->cert->serial,
249 sshkey_type(key->cert->signature_key),
250 cafp == NULL ? "(null)" : cafp,
251 methinfo == NULL ? "" : ", ",
252 methinfo == NULL ? "" : methinfo);
253 free(fp);
254 free(cafp);
255 } else {
256 fp = sshkey_fingerprint(key, options.fingerprint_hash,
257 SSH_FP_DEFAULT);
258 xasprintf(&ret, "%s %s%s%s", sshkey_type(key),
259 fp == NULL ? "(null)" : fp,
260 methinfo == NULL ? "" : ", ",
261 methinfo == NULL ? "" : methinfo);
262 free(fp);
263 }
264 return ret;
265 }
266
267 void
auth_log(struct ssh * ssh,int authenticated,int partial,const char * method,const char * submethod)268 auth_log(struct ssh *ssh, int authenticated, int partial,
269 const char *method, const char *submethod)
270 {
271 Authctxt *authctxt = (Authctxt *)ssh->authctxt;
272 int level = SYSLOG_LEVEL_VERBOSE;
273 const char *authmsg;
274 char *extra = NULL;
275
276 if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
277 return;
278
279 /* Raise logging level */
280 if (authenticated == 1 ||
281 !authctxt->valid ||
282 authctxt->failures >= options.max_authtries / 2 ||
283 strcmp(method, "password") == 0)
284 level = SYSLOG_LEVEL_INFO;
285
286 if (authctxt->postponed)
287 authmsg = "Postponed";
288 else if (partial)
289 authmsg = "Partial";
290 else {
291 authmsg = authenticated ? "Accepted" : "Failed";
292 if (authenticated)
293 BLACKLIST_NOTIFY(ssh, BLACKLIST_AUTH_OK, "ssh");
294 }
295
296 if ((extra = format_method_key(authctxt)) == NULL) {
297 if (authctxt->auth_method_info != NULL)
298 extra = xstrdup(authctxt->auth_method_info);
299 }
300
301 do_log2(level, "%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s",
302 authmsg,
303 method,
304 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
305 authctxt->valid ? "" : "invalid user ",
306 authctxt->user,
307 ssh_remote_ipaddr(ssh),
308 ssh_remote_port(ssh),
309 extra != NULL ? ": " : "",
310 extra != NULL ? extra : "");
311
312 free(extra);
313
314 #if defined(CUSTOM_FAILED_LOGIN) || defined(SSH_AUDIT_EVENTS)
315 if (authenticated == 0 && !(authctxt->postponed || partial)) {
316 /* Log failed login attempt */
317 # ifdef CUSTOM_FAILED_LOGIN
318 if (strcmp(method, "password") == 0 ||
319 strncmp(method, "keyboard-interactive", 20) == 0 ||
320 strcmp(method, "challenge-response") == 0)
321 record_failed_login(ssh, authctxt->user,
322 auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
323 # endif
324 # ifdef SSH_AUDIT_EVENTS
325 audit_event(ssh, audit_classify_auth(method));
326 # endif
327 }
328 #endif
329 #if defined(CUSTOM_FAILED_LOGIN) && defined(WITH_AIXAUTHENTICATE)
330 if (authenticated)
331 sys_auth_record_login(authctxt->user,
332 auth_get_canonical_hostname(ssh, options.use_dns), "ssh",
333 loginmsg);
334 #endif
335 }
336
337 void
auth_maxtries_exceeded(struct ssh * ssh)338 auth_maxtries_exceeded(struct ssh *ssh)
339 {
340 Authctxt *authctxt = (Authctxt *)ssh->authctxt;
341
342 error("maximum authentication attempts exceeded for "
343 "%s%.100s from %.200s port %d ssh2",
344 authctxt->valid ? "" : "invalid user ",
345 authctxt->user,
346 ssh_remote_ipaddr(ssh),
347 ssh_remote_port(ssh));
348 ssh_packet_disconnect(ssh, "Too many authentication failures");
349 /* NOTREACHED */
350 }
351
352 /*
353 * Check whether root logins are disallowed.
354 */
355 int
auth_root_allowed(struct ssh * ssh,const char * method)356 auth_root_allowed(struct ssh *ssh, const char *method)
357 {
358 switch (options.permit_root_login) {
359 case PERMIT_YES:
360 return 1;
361 case PERMIT_NO_PASSWD:
362 if (strcmp(method, "publickey") == 0 ||
363 strcmp(method, "hostbased") == 0 ||
364 strcmp(method, "gssapi-with-mic") == 0)
365 return 1;
366 break;
367 case PERMIT_FORCED_ONLY:
368 if (auth_opts->force_command != NULL) {
369 logit("Root login accepted for forced command.");
370 return 1;
371 }
372 break;
373 }
374 logit("ROOT LOGIN REFUSED FROM %.200s port %d",
375 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
376 return 0;
377 }
378
379
380 /*
381 * Given a template and a passwd structure, build a filename
382 * by substituting % tokenised options. Currently, %% becomes '%',
383 * %h becomes the home directory and %u the username.
384 *
385 * This returns a buffer allocated by xmalloc.
386 */
387 char *
expand_authorized_keys(const char * filename,struct passwd * pw)388 expand_authorized_keys(const char *filename, struct passwd *pw)
389 {
390 char *file, uidstr[32], ret[PATH_MAX];
391 int i;
392
393 snprintf(uidstr, sizeof(uidstr), "%llu",
394 (unsigned long long)pw->pw_uid);
395 file = percent_expand(filename, "h", pw->pw_dir,
396 "u", pw->pw_name, "U", uidstr, (char *)NULL);
397
398 /*
399 * Ensure that filename starts anchored. If not, be backward
400 * compatible and prepend the '%h/'
401 */
402 if (path_absolute(file))
403 return (file);
404
405 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
406 if (i < 0 || (size_t)i >= sizeof(ret))
407 fatal("expand_authorized_keys: path too long");
408 free(file);
409 return (xstrdup(ret));
410 }
411
412 char *
authorized_principals_file(struct passwd * pw)413 authorized_principals_file(struct passwd *pw)
414 {
415 if (options.authorized_principals_file == NULL)
416 return NULL;
417 return expand_authorized_keys(options.authorized_principals_file, pw);
418 }
419
420 /* return ok if key exists in sysfile or userfile */
421 HostStatus
check_key_in_hostfiles(struct passwd * pw,struct sshkey * key,const char * host,const char * sysfile,const char * userfile)422 check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host,
423 const char *sysfile, const char *userfile)
424 {
425 char *user_hostfile;
426 struct stat st;
427 HostStatus host_status;
428 struct hostkeys *hostkeys;
429 const struct hostkey_entry *found;
430
431 hostkeys = init_hostkeys();
432 load_hostkeys(hostkeys, host, sysfile, 0);
433 if (userfile != NULL) {
434 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
435 if (options.strict_modes &&
436 (stat(user_hostfile, &st) == 0) &&
437 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
438 (st.st_mode & 022) != 0)) {
439 logit("Authentication refused for %.100s: "
440 "bad owner or modes for %.200s",
441 pw->pw_name, user_hostfile);
442 auth_debug_add("Ignored %.200s: bad ownership or modes",
443 user_hostfile);
444 } else {
445 temporarily_use_uid(pw);
446 load_hostkeys(hostkeys, host, user_hostfile, 0);
447 restore_uid();
448 }
449 free(user_hostfile);
450 }
451 host_status = check_key_in_hostkeys(hostkeys, key, &found);
452 if (host_status == HOST_REVOKED)
453 error("WARNING: revoked key for %s attempted authentication",
454 host);
455 else if (host_status == HOST_OK)
456 debug_f("key for %s found at %s:%ld",
457 found->host, found->file, found->line);
458 else
459 debug_f("key for host %s not found", host);
460
461 free_hostkeys(hostkeys);
462
463 return host_status;
464 }
465
466 struct passwd *
getpwnamallow(struct ssh * ssh,const char * user)467 getpwnamallow(struct ssh *ssh, const char *user)
468 {
469 #ifdef HAVE_LOGIN_CAP
470 extern login_cap_t *lc;
471 #ifdef HAVE_AUTH_HOSTOK
472 const char *from_host, *from_ip;
473 #endif
474 #ifdef BSD_AUTH
475 auth_session_t *as;
476 #endif
477 #endif
478 struct passwd *pw;
479 struct connection_info *ci;
480 u_int i;
481
482 ci = get_connection_info(ssh, 1, options.use_dns);
483 ci->user = user;
484 parse_server_match_config(&options, &includes, ci);
485 log_change_level(options.log_level);
486 log_verbose_reset();
487 for (i = 0; i < options.num_log_verbose; i++)
488 log_verbose_add(options.log_verbose[i]);
489 process_permitopen(ssh, &options);
490
491 #if defined(_AIX) && defined(HAVE_SETAUTHDB)
492 aix_setauthdb(user);
493 #endif
494
495 pw = getpwnam(user);
496
497 #if defined(_AIX) && defined(HAVE_SETAUTHDB)
498 aix_restoreauthdb();
499 #endif
500 if (pw == NULL) {
501 BLACKLIST_NOTIFY(ssh, BLACKLIST_BAD_USER, user);
502 logit("Invalid user %.100s from %.100s port %d",
503 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
504 #ifdef CUSTOM_FAILED_LOGIN
505 record_failed_login(ssh, user,
506 auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
507 #endif
508 #ifdef SSH_AUDIT_EVENTS
509 audit_event(ssh, SSH_INVALID_USER);
510 #endif /* SSH_AUDIT_EVENTS */
511 return (NULL);
512 }
513 if (!allowed_user(ssh, pw))
514 return (NULL);
515 #ifdef HAVE_LOGIN_CAP
516 if ((lc = login_getpwclass(pw)) == NULL) {
517 debug("unable to get login class: %s", user);
518 return (NULL);
519 }
520 #ifdef HAVE_AUTH_HOSTOK
521 from_host = auth_get_canonical_hostname(ssh, options.use_dns);
522 from_ip = ssh_remote_ipaddr(ssh);
523 if (!auth_hostok(lc, from_host, from_ip)) {
524 debug("Denied connection for %.200s from %.200s [%.200s].",
525 pw->pw_name, from_host, from_ip);
526 return (NULL);
527 }
528 #endif /* HAVE_AUTH_HOSTOK */
529 #ifdef HAVE_AUTH_TIMEOK
530 if (!auth_timeok(lc, time(NULL))) {
531 debug("LOGIN %.200s REFUSED (TIME)", pw->pw_name);
532 return (NULL);
533 }
534 #endif /* HAVE_AUTH_TIMEOK */
535 #ifdef BSD_AUTH
536 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
537 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
538 debug("Approval failure for %s", user);
539 pw = NULL;
540 }
541 if (as != NULL)
542 auth_close(as);
543 #endif
544 #endif
545 if (pw != NULL)
546 return (pwcopy(pw));
547 return (NULL);
548 }
549
550 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
551 int
auth_key_is_revoked(struct sshkey * key)552 auth_key_is_revoked(struct sshkey *key)
553 {
554 char *fp = NULL;
555 int r;
556
557 if (options.revoked_keys_file == NULL)
558 return 0;
559 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
560 SSH_FP_DEFAULT)) == NULL) {
561 r = SSH_ERR_ALLOC_FAIL;
562 error_fr(r, "fingerprint key");
563 goto out;
564 }
565
566 r = sshkey_check_revoked(key, options.revoked_keys_file);
567 switch (r) {
568 case 0:
569 break; /* not revoked */
570 case SSH_ERR_KEY_REVOKED:
571 error("Authentication key %s %s revoked by file %s",
572 sshkey_type(key), fp, options.revoked_keys_file);
573 goto out;
574 default:
575 error_r(r, "Error checking authentication key %s %s in "
576 "revoked keys file %s", sshkey_type(key), fp,
577 options.revoked_keys_file);
578 goto out;
579 }
580
581 /* Success */
582 r = 0;
583
584 out:
585 free(fp);
586 return r == 0 ? 0 : 1;
587 }
588
589 void
auth_debug_add(const char * fmt,...)590 auth_debug_add(const char *fmt,...)
591 {
592 char buf[1024];
593 va_list args;
594 int r;
595
596 va_start(args, fmt);
597 vsnprintf(buf, sizeof(buf), fmt, args);
598 va_end(args);
599 debug3("%s", buf);
600 if (auth_debug != NULL)
601 if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0)
602 fatal_fr(r, "sshbuf_put_cstring");
603 }
604
605 void
auth_debug_send(struct ssh * ssh)606 auth_debug_send(struct ssh *ssh)
607 {
608 char *msg;
609 int r;
610
611 if (auth_debug == NULL)
612 return;
613 while (sshbuf_len(auth_debug) != 0) {
614 if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0)
615 fatal_fr(r, "sshbuf_get_cstring");
616 ssh_packet_send_debug(ssh, "%s", msg);
617 free(msg);
618 }
619 }
620
621 void
auth_debug_reset(void)622 auth_debug_reset(void)
623 {
624 if (auth_debug != NULL)
625 sshbuf_reset(auth_debug);
626 else if ((auth_debug = sshbuf_new()) == NULL)
627 fatal_f("sshbuf_new failed");
628 }
629
630 struct passwd *
fakepw(void)631 fakepw(void)
632 {
633 static int done = 0;
634 static struct passwd fake;
635 const char hashchars[] = "./ABCDEFGHIJKLMNOPQRSTUVWXYZ"
636 "abcdefghijklmnopqrstuvwxyz0123456789"; /* from bcrypt.c */
637 char *cp;
638
639 if (done)
640 return (&fake);
641
642 memset(&fake, 0, sizeof(fake));
643 fake.pw_name = "NOUSER";
644 fake.pw_passwd = xstrdup("$2a$10$"
645 "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx");
646 for (cp = fake.pw_passwd + 7; *cp != '\0'; cp++)
647 *cp = hashchars[arc4random_uniform(sizeof(hashchars) - 1)];
648 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS
649 fake.pw_gecos = "NOUSER";
650 #endif
651 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid;
652 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid;
653 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS
654 fake.pw_class = "";
655 #endif
656 fake.pw_dir = "/nonexist";
657 fake.pw_shell = "/nonexist";
658 done = 1;
659
660 return (&fake);
661 }
662
663 /*
664 * Returns the remote DNS hostname as a string. The returned string must not
665 * be freed. NB. this will usually trigger a DNS query the first time it is
666 * called.
667 * This function does additional checks on the hostname to mitigate some
668 * attacks on based on conflation of hostnames and IP addresses.
669 */
670
671 static char *
remote_hostname(struct ssh * ssh)672 remote_hostname(struct ssh *ssh)
673 {
674 struct sockaddr_storage from;
675 socklen_t fromlen;
676 struct addrinfo hints, *ai, *aitop;
677 char name[NI_MAXHOST], ntop2[NI_MAXHOST];
678 const char *ntop = ssh_remote_ipaddr(ssh);
679
680 /* Get IP address of client. */
681 fromlen = sizeof(from);
682 memset(&from, 0, sizeof(from));
683 if (getpeername(ssh_packet_get_connection_in(ssh),
684 (struct sockaddr *)&from, &fromlen) == -1) {
685 debug("getpeername failed: %.100s", strerror(errno));
686 return xstrdup(ntop);
687 }
688
689 ipv64_normalise_mapped(&from, &fromlen);
690 if (from.ss_family == AF_INET6)
691 fromlen = sizeof(struct sockaddr_in6);
692
693 debug3("Trying to reverse map address %.100s.", ntop);
694 /* Map the IP address to a host name. */
695 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
696 NULL, 0, NI_NAMEREQD) != 0) {
697 /* Host name not found. Use ip address. */
698 return xstrdup(ntop);
699 }
700
701 /*
702 * if reverse lookup result looks like a numeric hostname,
703 * someone is trying to trick us by PTR record like following:
704 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
705 */
706 memset(&hints, 0, sizeof(hints));
707 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
708 hints.ai_flags = AI_NUMERICHOST;
709 if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
710 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
711 name, ntop);
712 freeaddrinfo(ai);
713 return xstrdup(ntop);
714 }
715
716 /* Names are stored in lowercase. */
717 lowercase(name);
718
719 /*
720 * Map it back to an IP address and check that the given
721 * address actually is an address of this host. This is
722 * necessary because anyone with access to a name server can
723 * define arbitrary names for an IP address. Mapping from
724 * name to IP address can be trusted better (but can still be
725 * fooled if the intruder has access to the name server of
726 * the domain).
727 */
728 memset(&hints, 0, sizeof(hints));
729 hints.ai_family = from.ss_family;
730 hints.ai_socktype = SOCK_STREAM;
731 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
732 logit("reverse mapping checking getaddrinfo for %.700s "
733 "[%s] failed.", name, ntop);
734 return xstrdup(ntop);
735 }
736 /* Look for the address from the list of addresses. */
737 for (ai = aitop; ai; ai = ai->ai_next) {
738 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
739 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
740 (strcmp(ntop, ntop2) == 0))
741 break;
742 }
743 freeaddrinfo(aitop);
744 /* If we reached the end of the list, the address was not there. */
745 if (ai == NULL) {
746 /* Address not found for the host name. */
747 logit("Address %.100s maps to %.600s, but this does not "
748 "map back to the address.", ntop, name);
749 return xstrdup(ntop);
750 }
751 return xstrdup(name);
752 }
753
754 /*
755 * Return the canonical name of the host in the other side of the current
756 * connection. The host name is cached, so it is efficient to call this
757 * several times.
758 */
759
760 const char *
auth_get_canonical_hostname(struct ssh * ssh,int use_dns)761 auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
762 {
763 static char *dnsname;
764
765 if (!use_dns)
766 return ssh_remote_ipaddr(ssh);
767 else if (dnsname != NULL)
768 return dnsname;
769 else {
770 dnsname = remote_hostname(ssh);
771 return dnsname;
772 }
773 }
774
775 /* These functions link key/cert options to the auth framework */
776
777 /* Log sshauthopt options locally and (optionally) for remote transmission */
778 void
auth_log_authopts(const char * loc,const struct sshauthopt * opts,int do_remote)779 auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote)
780 {
781 int do_env = options.permit_user_env && opts->nenv > 0;
782 int do_permitopen = opts->npermitopen > 0 &&
783 (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0;
784 int do_permitlisten = opts->npermitlisten > 0 &&
785 (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0;
786 size_t i;
787 char msg[1024], buf[64];
788
789 snprintf(buf, sizeof(buf), "%d", opts->force_tun_device);
790 /* Try to keep this alphabetically sorted */
791 snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
792 opts->permit_agent_forwarding_flag ? " agent-forwarding" : "",
793 opts->force_command == NULL ? "" : " command",
794 do_env ? " environment" : "",
795 opts->valid_before == 0 ? "" : "expires",
796 opts->no_require_user_presence ? " no-touch-required" : "",
797 do_permitopen ? " permitopen" : "",
798 do_permitlisten ? " permitlisten" : "",
799 opts->permit_port_forwarding_flag ? " port-forwarding" : "",
800 opts->cert_principals == NULL ? "" : " principals",
801 opts->permit_pty_flag ? " pty" : "",
802 opts->require_verify ? " uv" : "",
803 opts->force_tun_device == -1 ? "" : " tun=",
804 opts->force_tun_device == -1 ? "" : buf,
805 opts->permit_user_rc ? " user-rc" : "",
806 opts->permit_x11_forwarding_flag ? " x11-forwarding" : "");
807
808 debug("%s: %s", loc, msg);
809 if (do_remote)
810 auth_debug_add("%s: %s", loc, msg);
811
812 if (options.permit_user_env) {
813 for (i = 0; i < opts->nenv; i++) {
814 debug("%s: environment: %s", loc, opts->env[i]);
815 if (do_remote) {
816 auth_debug_add("%s: environment: %s",
817 loc, opts->env[i]);
818 }
819 }
820 }
821
822 /* Go into a little more details for the local logs. */
823 if (opts->valid_before != 0) {
824 format_absolute_time(opts->valid_before, buf, sizeof(buf));
825 debug("%s: expires at %s", loc, buf);
826 }
827 if (opts->cert_principals != NULL) {
828 debug("%s: authorized principals: \"%s\"",
829 loc, opts->cert_principals);
830 }
831 if (opts->force_command != NULL)
832 debug("%s: forced command: \"%s\"", loc, opts->force_command);
833 if (do_permitopen) {
834 for (i = 0; i < opts->npermitopen; i++) {
835 debug("%s: permitted open: %s",
836 loc, opts->permitopen[i]);
837 }
838 }
839 if (do_permitlisten) {
840 for (i = 0; i < opts->npermitlisten; i++) {
841 debug("%s: permitted listen: %s",
842 loc, opts->permitlisten[i]);
843 }
844 }
845 }
846
847 /* Activate a new set of key/cert options; merging with what is there. */
848 int
auth_activate_options(struct ssh * ssh,struct sshauthopt * opts)849 auth_activate_options(struct ssh *ssh, struct sshauthopt *opts)
850 {
851 struct sshauthopt *old = auth_opts;
852 const char *emsg = NULL;
853
854 debug_f("setting new authentication options");
855 if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) {
856 error("Inconsistent authentication options: %s", emsg);
857 return -1;
858 }
859 return 0;
860 }
861
862 /* Disable forwarding, etc for the session */
863 void
auth_restrict_session(struct ssh * ssh)864 auth_restrict_session(struct ssh *ssh)
865 {
866 struct sshauthopt *restricted;
867
868 debug_f("restricting session");
869
870 /* A blank sshauthopt defaults to permitting nothing */
871 if ((restricted = sshauthopt_new()) == NULL)
872 fatal_f("sshauthopt_new failed");
873 restricted->permit_pty_flag = 1;
874 restricted->restricted = 1;
875
876 if (auth_activate_options(ssh, restricted) != 0)
877 fatal_f("failed to restrict session");
878 sshauthopt_free(restricted);
879 }
880