1 /* $OpenBSD: auth.c,v 1.119 2016/12/15 21:29:05 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
32 #include <netinet/in.h>
33
34 #include <errno.h>
35 #include <fcntl.h>
36 #ifdef HAVE_PATHS_H
37 # include <paths.h>
38 #endif
39 #include <pwd.h>
40 #ifdef HAVE_LOGIN_H
41 #include <login.h>
42 #endif
43 #ifdef USE_SHADOW
44 #include <shadow.h>
45 #endif
46 #ifdef HAVE_LIBGEN_H
47 #include <libgen.h>
48 #endif
49 #include <stdarg.h>
50 #include <stdio.h>
51 #include <string.h>
52 #include <unistd.h>
53 #include <limits.h>
54 #include <netdb.h>
55
56 #include "xmalloc.h"
57 #include "match.h"
58 #include "groupaccess.h"
59 #include "log.h"
60 #include "buffer.h"
61 #include "misc.h"
62 #include "servconf.h"
63 #include "key.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 "authfile.h"
77 #include "ssherr.h"
78 #include "compat.h"
79
80 /* import */
81 extern ServerOptions options;
82 extern int use_privsep;
83 extern Buffer loginmsg;
84 extern struct passwd *privsep_pw;
85
86 /* Debugging messages */
87 Buffer auth_debug;
88 int auth_debug_init;
89
90 /*
91 * Check if the user is allowed to log in via ssh. If user is listed
92 * in DenyUsers or one of user's groups is listed in DenyGroups, false
93 * will be returned. If AllowUsers isn't empty and user isn't listed
94 * there, or if AllowGroups isn't empty and one of user's groups isn't
95 * listed there, false will be returned.
96 * If the user's shell is not executable, false will be returned.
97 * Otherwise true is returned.
98 */
99 int
allowed_user(struct passwd * pw)100 allowed_user(struct passwd * pw)
101 {
102 struct ssh *ssh = active_state; /* XXX */
103 struct stat st;
104 const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL;
105 u_int i;
106 int r;
107 #ifdef USE_SHADOW
108 struct spwd *spw = NULL;
109 #endif
110
111 /* Shouldn't be called if pw is NULL, but better safe than sorry... */
112 if (!pw || !pw->pw_name)
113 return 0;
114
115 #ifdef USE_SHADOW
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))
120 return 0;
121 #endif /* HAS_SHADOW_EXPIRE */
122 #endif /* USE_SHADOW */
123
124 /* grab passwd field for locked account check */
125 passwd = pw->pw_passwd;
126 #ifdef USE_SHADOW
127 if (spw != NULL)
128 #ifdef USE_LIBIAF
129 passwd = get_iaf_password(pw);
130 #else
131 passwd = spw->sp_pwdp;
132 #endif /* USE_LIBIAF */
133 #endif
134
135 /* check for locked account */
136 if (!options.use_pam && passwd && *passwd) {
137 int locked = 0;
138
139 #ifdef LOCKED_PASSWD_STRING
140 if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0)
141 locked = 1;
142 #endif
143 #ifdef LOCKED_PASSWD_PREFIX
144 if (strncmp(passwd, LOCKED_PASSWD_PREFIX,
145 strlen(LOCKED_PASSWD_PREFIX)) == 0)
146 locked = 1;
147 #endif
148 #ifdef LOCKED_PASSWD_SUBSTR
149 if (strstr(passwd, LOCKED_PASSWD_SUBSTR))
150 locked = 1;
151 #endif
152 #ifdef USE_LIBIAF
153 free((void *) passwd);
154 #endif /* USE_LIBIAF */
155 if (locked) {
156 logit("User %.100s not allowed because account is locked",
157 pw->pw_name);
158 return 0;
159 }
160 }
161
162 /*
163 * Deny if shell does not exist or is not executable unless we
164 * are chrooting.
165 */
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 */
170
171 if (stat(shell, &st) != 0) {
172 logit("User %.100s not allowed because shell %.100s "
173 "does not exist", pw->pw_name, shell);
174 free(shell);
175 return 0;
176 }
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);
181 free(shell);
182 return 0;
183 }
184 free(shell);
185 }
186
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);
191 }
192
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 r = match_user(pw->pw_name, hostname, ipaddr,
197 options.deny_users[i]);
198 if (r < 0) {
199 fatal("Invalid DenyUsers pattern \"%.100s\"",
200 options.deny_users[i]);
201 } else if (r != 0) {
202 logit("User %.100s from %.100s not allowed "
203 "because listed in DenyUsers",
204 pw->pw_name, hostname);
205 return 0;
206 }
207 }
208 }
209 /* Return false if AllowUsers isn't empty and user isn't listed there */
210 if (options.num_allow_users > 0) {
211 for (i = 0; i < options.num_allow_users; i++) {
212 r = match_user(pw->pw_name, hostname, ipaddr,
213 options.allow_users[i]);
214 if (r < 0) {
215 fatal("Invalid AllowUsers pattern \"%.100s\"",
216 options.allow_users[i]);
217 } else if (r == 1)
218 break;
219 }
220 /* i < options.num_allow_users iff we break for loop */
221 if (i >= options.num_allow_users) {
222 logit("User %.100s from %.100s not allowed because "
223 "not listed in AllowUsers", pw->pw_name, hostname);
224 return 0;
225 }
226 }
227 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
228 /* Get the user's group access list (primary and supplementary) */
229 if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
230 logit("User %.100s from %.100s not allowed because "
231 "not in any group", pw->pw_name, hostname);
232 return 0;
233 }
234
235 /* Return false if one of user's groups is listed in DenyGroups */
236 if (options.num_deny_groups > 0)
237 if (ga_match(options.deny_groups,
238 options.num_deny_groups)) {
239 ga_free();
240 logit("User %.100s from %.100s not allowed "
241 "because a group is listed in DenyGroups",
242 pw->pw_name, hostname);
243 return 0;
244 }
245 /*
246 * Return false if AllowGroups isn't empty and one of user's groups
247 * isn't listed there
248 */
249 if (options.num_allow_groups > 0)
250 if (!ga_match(options.allow_groups,
251 options.num_allow_groups)) {
252 ga_free();
253 logit("User %.100s from %.100s not allowed "
254 "because none of user's groups are listed "
255 "in AllowGroups", pw->pw_name, hostname);
256 return 0;
257 }
258 ga_free();
259 }
260
261 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER
262 if (!sys_auth_allowed_user(pw, &loginmsg))
263 return 0;
264 #endif
265
266 /* We found no reason not to let this user try to log on... */
267 return 1;
268 }
269
270 void
auth_info(Authctxt * authctxt,const char * fmt,...)271 auth_info(Authctxt *authctxt, const char *fmt, ...)
272 {
273 va_list ap;
274 int i;
275
276 free(authctxt->info);
277 authctxt->info = NULL;
278
279 va_start(ap, fmt);
280 i = vasprintf(&authctxt->info, fmt, ap);
281 va_end(ap);
282
283 if (i < 0 || authctxt->info == NULL)
284 fatal("vasprintf failed");
285 }
286
287 void
auth_log(Authctxt * authctxt,int authenticated,int partial,const char * method,const char * submethod)288 auth_log(Authctxt *authctxt, int authenticated, int partial,
289 const char *method, const char *submethod)
290 {
291 struct ssh *ssh = active_state; /* XXX */
292 void (*authlog) (const char *fmt,...) = verbose;
293 char *authmsg;
294
295 if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
296 return;
297
298 /* Raise logging level */
299 if (authenticated == 1 ||
300 !authctxt->valid ||
301 authctxt->failures >= options.max_authtries / 2 ||
302 strcmp(method, "password") == 0)
303 authlog = logit;
304
305 if (authctxt->postponed)
306 authmsg = "Postponed";
307 else if (partial)
308 authmsg = "Partial";
309 else
310 authmsg = authenticated ? "Accepted" : "Failed";
311
312 authlog("%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s",
313 authmsg,
314 method,
315 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
316 authctxt->valid ? "" : "invalid user ",
317 authctxt->user,
318 ssh_remote_ipaddr(ssh),
319 ssh_remote_port(ssh),
320 authctxt->info != NULL ? ": " : "",
321 authctxt->info != NULL ? authctxt->info : "");
322 free(authctxt->info);
323 authctxt->info = NULL;
324
325 #ifdef CUSTOM_FAILED_LOGIN
326 if (authenticated == 0 && !authctxt->postponed &&
327 (strcmp(method, "password") == 0 ||
328 strncmp(method, "keyboard-interactive", 20) == 0 ||
329 strcmp(method, "challenge-response") == 0))
330 record_failed_login(authctxt->user,
331 auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
332 # ifdef WITH_AIXAUTHENTICATE
333 if (authenticated)
334 sys_auth_record_login(authctxt->user,
335 auth_get_canonical_hostname(ssh, options.use_dns), "ssh",
336 &loginmsg);
337 # endif
338 #endif
339 #ifdef SSH_AUDIT_EVENTS
340 if (authenticated == 0 && !authctxt->postponed)
341 audit_event(audit_classify_auth(method));
342 #endif
343 }
344
345
346 void
auth_maxtries_exceeded(Authctxt * authctxt)347 auth_maxtries_exceeded(Authctxt *authctxt)
348 {
349 struct ssh *ssh = active_state; /* XXX */
350
351 error("maximum authentication attempts exceeded for "
352 "%s%.100s from %.200s port %d ssh2",
353 authctxt->valid ? "" : "invalid user ",
354 authctxt->user,
355 ssh_remote_ipaddr(ssh),
356 ssh_remote_port(ssh));
357 packet_disconnect("Too many authentication failures");
358 /* NOTREACHED */
359 }
360
361 /*
362 * Check whether root logins are disallowed.
363 */
364 int
auth_root_allowed(const char * method)365 auth_root_allowed(const char *method)
366 {
367 struct ssh *ssh = active_state; /* XXX */
368
369 switch (options.permit_root_login) {
370 case PERMIT_YES:
371 return 1;
372 case PERMIT_NO_PASSWD:
373 if (strcmp(method, "publickey") == 0 ||
374 strcmp(method, "hostbased") == 0 ||
375 strcmp(method, "gssapi-with-mic") == 0)
376 return 1;
377 break;
378 case PERMIT_FORCED_ONLY:
379 if (forced_command) {
380 logit("Root login accepted for forced command.");
381 return 1;
382 }
383 break;
384 }
385 logit("ROOT LOGIN REFUSED FROM %.200s port %d",
386 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
387 return 0;
388 }
389
390
391 /*
392 * Given a template and a passwd structure, build a filename
393 * by substituting % tokenised options. Currently, %% becomes '%',
394 * %h becomes the home directory and %u the username.
395 *
396 * This returns a buffer allocated by xmalloc.
397 */
398 char *
expand_authorized_keys(const char * filename,struct passwd * pw)399 expand_authorized_keys(const char *filename, struct passwd *pw)
400 {
401 char *file, ret[PATH_MAX];
402 int i;
403
404 file = percent_expand(filename, "h", pw->pw_dir,
405 "u", pw->pw_name, (char *)NULL);
406
407 /*
408 * Ensure that filename starts anchored. If not, be backward
409 * compatible and prepend the '%h/'
410 */
411 if (*file == '/')
412 return (file);
413
414 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
415 if (i < 0 || (size_t)i >= sizeof(ret))
416 fatal("expand_authorized_keys: path too long");
417 free(file);
418 return (xstrdup(ret));
419 }
420
421 char *
authorized_principals_file(struct passwd * pw)422 authorized_principals_file(struct passwd *pw)
423 {
424 if (options.authorized_principals_file == NULL)
425 return NULL;
426 return expand_authorized_keys(options.authorized_principals_file, pw);
427 }
428
429 /* return ok if key exists in sysfile or userfile */
430 HostStatus
check_key_in_hostfiles(struct passwd * pw,Key * key,const char * host,const char * sysfile,const char * userfile)431 check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
432 const char *sysfile, const char *userfile)
433 {
434 char *user_hostfile;
435 struct stat st;
436 HostStatus host_status;
437 struct hostkeys *hostkeys;
438 const struct hostkey_entry *found;
439
440 hostkeys = init_hostkeys();
441 load_hostkeys(hostkeys, host, sysfile);
442 if (userfile != NULL) {
443 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
444 if (options.strict_modes &&
445 (stat(user_hostfile, &st) == 0) &&
446 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
447 (st.st_mode & 022) != 0)) {
448 logit("Authentication refused for %.100s: "
449 "bad owner or modes for %.200s",
450 pw->pw_name, user_hostfile);
451 auth_debug_add("Ignored %.200s: bad ownership or modes",
452 user_hostfile);
453 } else {
454 temporarily_use_uid(pw);
455 load_hostkeys(hostkeys, host, user_hostfile);
456 restore_uid();
457 }
458 free(user_hostfile);
459 }
460 host_status = check_key_in_hostkeys(hostkeys, key, &found);
461 if (host_status == HOST_REVOKED)
462 error("WARNING: revoked key for %s attempted authentication",
463 found->host);
464 else if (host_status == HOST_OK)
465 debug("%s: key for %s found at %s:%ld", __func__,
466 found->host, found->file, found->line);
467 else
468 debug("%s: key for host %s not found", __func__, host);
469
470 free_hostkeys(hostkeys);
471
472 return host_status;
473 }
474
475 /*
476 * Check a given path for security. This is defined as all components
477 * of the path to the file must be owned by either the owner of
478 * of the file or root and no directories must be group or world writable.
479 *
480 * XXX Should any specific check be done for sym links ?
481 *
482 * Takes a file name, its stat information (preferably from fstat() to
483 * avoid races), the uid of the expected owner, their home directory and an
484 * error buffer plus max size as arguments.
485 *
486 * Returns 0 on success and -1 on failure
487 */
488 int
auth_secure_path(const char * name,struct stat * stp,const char * pw_dir,uid_t uid,char * err,size_t errlen)489 auth_secure_path(const char *name, struct stat *stp, const char *pw_dir,
490 uid_t uid, char *err, size_t errlen)
491 {
492 char buf[PATH_MAX], homedir[PATH_MAX];
493 char *cp;
494 int comparehome = 0;
495 struct stat st;
496
497 if (realpath(name, buf) == NULL) {
498 snprintf(err, errlen, "realpath %s failed: %s", name,
499 strerror(errno));
500 return -1;
501 }
502 if (pw_dir != NULL && realpath(pw_dir, homedir) != NULL)
503 comparehome = 1;
504
505 if (!S_ISREG(stp->st_mode)) {
506 snprintf(err, errlen, "%s is not a regular file", buf);
507 return -1;
508 }
509 if ((!platform_sys_dir_uid(stp->st_uid) && stp->st_uid != uid) ||
510 (stp->st_mode & 022) != 0) {
511 #if defined(ANDROID)
512 /* needed to allow root login on Android. */
513 if (getuid() != 0)
514 #endif
515 {
516 snprintf(err, errlen, "bad ownership or modes for file %s",
517 buf);
518 return -1;
519 }
520 }
521
522 /* for each component of the canonical path, walking upwards */
523 for (;;) {
524 if ((cp = dirname(buf)) == NULL) {
525 snprintf(err, errlen, "dirname() failed");
526 return -1;
527 }
528 strlcpy(buf, cp, sizeof(buf));
529
530 #if !defined(ANDROID)
531 /* /data is owned by system user, which causes this check to fail */
532 if (stat(buf, &st) < 0 ||
533 (!platform_sys_dir_uid(st.st_uid) && st.st_uid != uid) ||
534 (st.st_mode & 022) != 0) {
535 snprintf(err, errlen,
536 "bad ownership or modes for directory %s", buf);
537 return -1;
538 }
539 #endif
540
541 /* If are past the homedir then we can stop */
542 if (comparehome && strcmp(homedir, buf) == 0)
543 break;
544
545 /*
546 * dirname should always complete with a "/" path,
547 * but we can be paranoid and check for "." too
548 */
549 if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
550 break;
551 }
552 return 0;
553 }
554
555 /*
556 * Version of secure_path() that accepts an open file descriptor to
557 * avoid races.
558 *
559 * Returns 0 on success and -1 on failure
560 */
561 static int
secure_filename(FILE * f,const char * file,struct passwd * pw,char * err,size_t errlen)562 secure_filename(FILE *f, const char *file, struct passwd *pw,
563 char *err, size_t errlen)
564 {
565 struct stat st;
566
567 /* check the open file to avoid races */
568 if (fstat(fileno(f), &st) < 0) {
569 snprintf(err, errlen, "cannot stat file %s: %s",
570 file, strerror(errno));
571 return -1;
572 }
573 return auth_secure_path(file, &st, pw->pw_dir, pw->pw_uid, err, errlen);
574 }
575
576 static FILE *
auth_openfile(const char * file,struct passwd * pw,int strict_modes,int log_missing,char * file_type)577 auth_openfile(const char *file, struct passwd *pw, int strict_modes,
578 int log_missing, char *file_type)
579 {
580 char line[1024];
581 struct stat st;
582 int fd;
583 FILE *f;
584
585 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
586 if (log_missing || errno != ENOENT)
587 debug("Could not open %s '%s': %s", file_type, file,
588 strerror(errno));
589 return NULL;
590 }
591
592 if (fstat(fd, &st) < 0) {
593 close(fd);
594 return NULL;
595 }
596 if (!S_ISREG(st.st_mode)) {
597 logit("User %s %s %s is not a regular file",
598 pw->pw_name, file_type, file);
599 close(fd);
600 return NULL;
601 }
602 unset_nonblock(fd);
603 if ((f = fdopen(fd, "r")) == NULL) {
604 close(fd);
605 return NULL;
606 }
607 if (strict_modes &&
608 secure_filename(f, file, pw, line, sizeof(line)) != 0) {
609 fclose(f);
610 logit("Authentication refused: %s", line);
611 auth_debug_add("Ignored %s: %s", file_type, line);
612 return NULL;
613 }
614
615 return f;
616 }
617
618
619 FILE *
auth_openkeyfile(const char * file,struct passwd * pw,int strict_modes)620 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
621 {
622 return auth_openfile(file, pw, strict_modes, 1, "authorized keys");
623 }
624
625 FILE *
auth_openprincipals(const char * file,struct passwd * pw,int strict_modes)626 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
627 {
628 return auth_openfile(file, pw, strict_modes, 0,
629 "authorized principals");
630 }
631
632 struct passwd *
getpwnamallow(const char * user)633 getpwnamallow(const char *user)
634 {
635 struct ssh *ssh = active_state; /* XXX */
636 #ifdef HAVE_LOGIN_CAP
637 extern login_cap_t *lc;
638 #ifdef BSD_AUTH
639 auth_session_t *as;
640 #endif
641 #endif
642 struct passwd *pw;
643 struct connection_info *ci = get_connection_info(1, options.use_dns);
644
645 ci->user = user;
646 parse_server_match_config(&options, ci);
647
648 #if defined(_AIX) && defined(HAVE_SETAUTHDB)
649 aix_setauthdb(user);
650 #endif
651
652 #if defined(ANDROID)
653 // Android has a fixed set of users. Any incoming user that we can't
654 // identify should be authenticated as the shell user.
655 if (strcmp(user, "root") && strcmp(user, "shell")) {
656 logit("Login name %.100s forced to shell", user);
657 user = "shell";
658 }
659 #endif
660 pw = getpwnam(user);
661
662 #if defined(_AIX) && defined(HAVE_SETAUTHDB)
663 aix_restoreauthdb();
664 #endif
665 #ifdef HAVE_CYGWIN
666 /*
667 * Windows usernames are case-insensitive. To avoid later problems
668 * when trying to match the username, the user is only allowed to
669 * login if the username is given in the same case as stored in the
670 * user database.
671 */
672 if (pw != NULL && strcmp(user, pw->pw_name) != 0) {
673 logit("Login name %.100s does not match stored username %.100s",
674 user, pw->pw_name);
675 pw = NULL;
676 }
677 #endif
678 if (pw == NULL) {
679 logit("Invalid user %.100s from %.100s port %d",
680 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
681 #ifdef CUSTOM_FAILED_LOGIN
682 record_failed_login(user,
683 auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
684 #endif
685 #ifdef SSH_AUDIT_EVENTS
686 audit_event(SSH_INVALID_USER);
687 #endif /* SSH_AUDIT_EVENTS */
688 return (NULL);
689 }
690 if (!allowed_user(pw))
691 return (NULL);
692 #ifdef HAVE_LOGIN_CAP
693 if ((lc = login_getclass(pw->pw_class)) == NULL) {
694 debug("unable to get login class: %s", user);
695 return (NULL);
696 }
697 #ifdef BSD_AUTH
698 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
699 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
700 debug("Approval failure for %s", user);
701 pw = NULL;
702 }
703 if (as != NULL)
704 auth_close(as);
705 #endif
706 #endif
707 if (pw != NULL)
708 return (pwcopy(pw));
709 return (NULL);
710 }
711
712 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
713 int
auth_key_is_revoked(Key * key)714 auth_key_is_revoked(Key *key)
715 {
716 char *fp = NULL;
717 int r;
718
719 if (options.revoked_keys_file == NULL)
720 return 0;
721 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
722 SSH_FP_DEFAULT)) == NULL) {
723 r = SSH_ERR_ALLOC_FAIL;
724 error("%s: fingerprint key: %s", __func__, ssh_err(r));
725 goto out;
726 }
727
728 r = sshkey_check_revoked(key, options.revoked_keys_file);
729 switch (r) {
730 case 0:
731 break; /* not revoked */
732 case SSH_ERR_KEY_REVOKED:
733 error("Authentication key %s %s revoked by file %s",
734 sshkey_type(key), fp, options.revoked_keys_file);
735 goto out;
736 default:
737 error("Error checking authentication key %s %s in "
738 "revoked keys file %s: %s", sshkey_type(key), fp,
739 options.revoked_keys_file, ssh_err(r));
740 goto out;
741 }
742
743 /* Success */
744 r = 0;
745
746 out:
747 free(fp);
748 return r == 0 ? 0 : 1;
749 }
750
751 void
auth_debug_add(const char * fmt,...)752 auth_debug_add(const char *fmt,...)
753 {
754 char buf[1024];
755 va_list args;
756
757 if (!auth_debug_init)
758 return;
759
760 va_start(args, fmt);
761 vsnprintf(buf, sizeof(buf), fmt, args);
762 va_end(args);
763 buffer_put_cstring(&auth_debug, buf);
764 }
765
766 void
auth_debug_send(void)767 auth_debug_send(void)
768 {
769 char *msg;
770
771 if (!auth_debug_init)
772 return;
773 while (buffer_len(&auth_debug)) {
774 msg = buffer_get_string(&auth_debug, NULL);
775 packet_send_debug("%s", msg);
776 free(msg);
777 }
778 }
779
780 void
auth_debug_reset(void)781 auth_debug_reset(void)
782 {
783 if (auth_debug_init)
784 buffer_clear(&auth_debug);
785 else {
786 buffer_init(&auth_debug);
787 auth_debug_init = 1;
788 }
789 }
790
791 struct passwd *
fakepw(void)792 fakepw(void)
793 {
794 static struct passwd fake;
795
796 memset(&fake, 0, sizeof(fake));
797 fake.pw_name = "NOUSER";
798 fake.pw_passwd =
799 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
800 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS
801 fake.pw_gecos = "NOUSER";
802 #endif
803 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid;
804 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid;
805 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS
806 fake.pw_class = "";
807 #endif
808 fake.pw_dir = "/nonexist";
809 fake.pw_shell = "/nonexist";
810
811 return (&fake);
812 }
813
814 /*
815 * Returns the remote DNS hostname as a string. The returned string must not
816 * be freed. NB. this will usually trigger a DNS query the first time it is
817 * called.
818 * This function does additional checks on the hostname to mitigate some
819 * attacks on legacy rhosts-style authentication.
820 * XXX is RhostsRSAAuthentication vulnerable to these?
821 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
822 */
823
824 static char *
remote_hostname(struct ssh * ssh)825 remote_hostname(struct ssh *ssh)
826 {
827 struct sockaddr_storage from;
828 socklen_t fromlen;
829 struct addrinfo hints, *ai, *aitop;
830 char name[NI_MAXHOST], ntop2[NI_MAXHOST];
831 const char *ntop = ssh_remote_ipaddr(ssh);
832
833 /* Get IP address of client. */
834 fromlen = sizeof(from);
835 memset(&from, 0, sizeof(from));
836 if (getpeername(ssh_packet_get_connection_in(ssh),
837 (struct sockaddr *)&from, &fromlen) < 0) {
838 debug("getpeername failed: %.100s", strerror(errno));
839 return strdup(ntop);
840 }
841
842 ipv64_normalise_mapped(&from, &fromlen);
843 if (from.ss_family == AF_INET6)
844 fromlen = sizeof(struct sockaddr_in6);
845
846 debug3("Trying to reverse map address %.100s.", ntop);
847 /* Map the IP address to a host name. */
848 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
849 NULL, 0, NI_NAMEREQD) != 0) {
850 /* Host name not found. Use ip address. */
851 return strdup(ntop);
852 }
853
854 /*
855 * if reverse lookup result looks like a numeric hostname,
856 * someone is trying to trick us by PTR record like following:
857 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
858 */
859 memset(&hints, 0, sizeof(hints));
860 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
861 hints.ai_flags = AI_NUMERICHOST;
862 if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
863 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
864 name, ntop);
865 freeaddrinfo(ai);
866 return strdup(ntop);
867 }
868
869 /* Names are stored in lowercase. */
870 lowercase(name);
871
872 /*
873 * Map it back to an IP address and check that the given
874 * address actually is an address of this host. This is
875 * necessary because anyone with access to a name server can
876 * define arbitrary names for an IP address. Mapping from
877 * name to IP address can be trusted better (but can still be
878 * fooled if the intruder has access to the name server of
879 * the domain).
880 */
881 memset(&hints, 0, sizeof(hints));
882 hints.ai_family = from.ss_family;
883 hints.ai_socktype = SOCK_STREAM;
884 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
885 logit("reverse mapping checking getaddrinfo for %.700s "
886 "[%s] failed.", name, ntop);
887 return strdup(ntop);
888 }
889 /* Look for the address from the list of addresses. */
890 for (ai = aitop; ai; ai = ai->ai_next) {
891 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
892 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
893 (strcmp(ntop, ntop2) == 0))
894 break;
895 }
896 freeaddrinfo(aitop);
897 /* If we reached the end of the list, the address was not there. */
898 if (ai == NULL) {
899 /* Address not found for the host name. */
900 logit("Address %.100s maps to %.600s, but this does not "
901 "map back to the address.", ntop, name);
902 return strdup(ntop);
903 }
904 return strdup(name);
905 }
906
907 /*
908 * Return the canonical name of the host in the other side of the current
909 * connection. The host name is cached, so it is efficient to call this
910 * several times.
911 */
912
913 const char *
auth_get_canonical_hostname(struct ssh * ssh,int use_dns)914 auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
915 {
916 static char *dnsname;
917
918 if (!use_dns)
919 return ssh_remote_ipaddr(ssh);
920 else if (dnsname != NULL)
921 return dnsname;
922 else {
923 dnsname = remote_hostname(ssh);
924 return dnsname;
925 }
926 }
927