1 /* $OpenBSD: auth.c,v 1.146 2020/01/31 22:42:45 djm 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 "compat.h"
78 #include "channels.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, *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) == -1) {
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 /*
271 * Formats any key left in authctxt->auth_method_key for inclusion in
272 * auth_log()'s message. Also includes authxtct->auth_method_info if present.
273 */
274 static char *
format_method_key(Authctxt * authctxt)275 format_method_key(Authctxt *authctxt)
276 {
277 const struct sshkey *key = authctxt->auth_method_key;
278 const char *methinfo = authctxt->auth_method_info;
279 char *fp, *cafp, *ret = NULL;
280
281 if (key == NULL)
282 return NULL;
283
284 if (sshkey_is_cert(key)) {
285 fp = sshkey_fingerprint(key,
286 options.fingerprint_hash, SSH_FP_DEFAULT);
287 cafp = sshkey_fingerprint(key->cert->signature_key,
288 options.fingerprint_hash, SSH_FP_DEFAULT);
289 xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s",
290 sshkey_type(key), fp == NULL ? "(null)" : fp,
291 key->cert->key_id,
292 (unsigned long long)key->cert->serial,
293 sshkey_type(key->cert->signature_key),
294 cafp == NULL ? "(null)" : cafp,
295 methinfo == NULL ? "" : ", ",
296 methinfo == NULL ? "" : methinfo);
297 free(fp);
298 free(cafp);
299 } else {
300 fp = sshkey_fingerprint(key, options.fingerprint_hash,
301 SSH_FP_DEFAULT);
302 xasprintf(&ret, "%s %s%s%s", sshkey_type(key),
303 fp == NULL ? "(null)" : fp,
304 methinfo == NULL ? "" : ", ",
305 methinfo == NULL ? "" : methinfo);
306 free(fp);
307 }
308 return ret;
309 }
310
311 void
auth_log(struct ssh * ssh,int authenticated,int partial,const char * method,const char * submethod)312 auth_log(struct ssh *ssh, int authenticated, int partial,
313 const char *method, const char *submethod)
314 {
315 Authctxt *authctxt = (Authctxt *)ssh->authctxt;
316 int level = SYSLOG_LEVEL_VERBOSE;
317 const char *authmsg;
318 char *extra = NULL;
319
320 if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
321 return;
322
323 /* Raise logging level */
324 if (authenticated == 1 ||
325 !authctxt->valid ||
326 authctxt->failures >= options.max_authtries / 2 ||
327 strcmp(method, "password") == 0)
328 level = SYSLOG_LEVEL_INFO;
329
330 if (authctxt->postponed)
331 authmsg = "Postponed";
332 else if (partial)
333 authmsg = "Partial";
334 else
335 authmsg = authenticated ? "Accepted" : "Failed";
336
337 if ((extra = format_method_key(authctxt)) == NULL) {
338 if (authctxt->auth_method_info != NULL)
339 extra = xstrdup(authctxt->auth_method_info);
340 }
341
342 do_log2(level, "%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s",
343 authmsg,
344 method,
345 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
346 authctxt->valid ? "" : "invalid user ",
347 authctxt->user,
348 ssh_remote_ipaddr(ssh),
349 ssh_remote_port(ssh),
350 extra != NULL ? ": " : "",
351 extra != NULL ? extra : "");
352
353 free(extra);
354
355 #ifdef CUSTOM_FAILED_LOGIN
356 if (authenticated == 0 && !authctxt->postponed &&
357 (strcmp(method, "password") == 0 ||
358 strncmp(method, "keyboard-interactive", 20) == 0 ||
359 strcmp(method, "challenge-response") == 0))
360 record_failed_login(ssh, authctxt->user,
361 auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
362 # ifdef WITH_AIXAUTHENTICATE
363 if (authenticated)
364 sys_auth_record_login(authctxt->user,
365 auth_get_canonical_hostname(ssh, options.use_dns), "ssh",
366 loginmsg);
367 # endif
368 #endif
369 #ifdef SSH_AUDIT_EVENTS
370 if (authenticated == 0 && !authctxt->postponed)
371 audit_event(ssh, audit_classify_auth(method));
372 #endif
373 }
374
375
376 void
auth_maxtries_exceeded(struct ssh * ssh)377 auth_maxtries_exceeded(struct ssh *ssh)
378 {
379 Authctxt *authctxt = (Authctxt *)ssh->authctxt;
380
381 error("maximum authentication attempts exceeded for "
382 "%s%.100s from %.200s port %d ssh2",
383 authctxt->valid ? "" : "invalid user ",
384 authctxt->user,
385 ssh_remote_ipaddr(ssh),
386 ssh_remote_port(ssh));
387 ssh_packet_disconnect(ssh, "Too many authentication failures");
388 /* NOTREACHED */
389 }
390
391 /*
392 * Check whether root logins are disallowed.
393 */
394 int
auth_root_allowed(struct ssh * ssh,const char * method)395 auth_root_allowed(struct ssh *ssh, const char *method)
396 {
397 switch (options.permit_root_login) {
398 case PERMIT_YES:
399 return 1;
400 case PERMIT_NO_PASSWD:
401 if (strcmp(method, "publickey") == 0 ||
402 strcmp(method, "hostbased") == 0 ||
403 strcmp(method, "gssapi-with-mic") == 0)
404 return 1;
405 break;
406 case PERMIT_FORCED_ONLY:
407 if (auth_opts->force_command != NULL) {
408 logit("Root login accepted for forced command.");
409 return 1;
410 }
411 break;
412 }
413 logit("ROOT LOGIN REFUSED FROM %.200s port %d",
414 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
415 return 0;
416 }
417
418
419 /*
420 * Given a template and a passwd structure, build a filename
421 * by substituting % tokenised options. Currently, %% becomes '%',
422 * %h becomes the home directory and %u the username.
423 *
424 * This returns a buffer allocated by xmalloc.
425 */
426 char *
expand_authorized_keys(const char * filename,struct passwd * pw)427 expand_authorized_keys(const char *filename, struct passwd *pw)
428 {
429 char *file, uidstr[32], ret[PATH_MAX];
430 int i;
431
432 snprintf(uidstr, sizeof(uidstr), "%llu",
433 (unsigned long long)pw->pw_uid);
434 file = percent_expand(filename, "h", pw->pw_dir,
435 "u", pw->pw_name, "U", uidstr, (char *)NULL);
436
437 /*
438 * Ensure that filename starts anchored. If not, be backward
439 * compatible and prepend the '%h/'
440 */
441 if (path_absolute(file))
442 return (file);
443
444 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
445 if (i < 0 || (size_t)i >= sizeof(ret))
446 fatal("expand_authorized_keys: path too long");
447 free(file);
448 return (xstrdup(ret));
449 }
450
451 char *
authorized_principals_file(struct passwd * pw)452 authorized_principals_file(struct passwd *pw)
453 {
454 if (options.authorized_principals_file == NULL)
455 return NULL;
456 return expand_authorized_keys(options.authorized_principals_file, pw);
457 }
458
459 /* return ok if key exists in sysfile or userfile */
460 HostStatus
check_key_in_hostfiles(struct passwd * pw,struct sshkey * key,const char * host,const char * sysfile,const char * userfile)461 check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host,
462 const char *sysfile, const char *userfile)
463 {
464 char *user_hostfile;
465 struct stat st;
466 HostStatus host_status;
467 struct hostkeys *hostkeys;
468 const struct hostkey_entry *found;
469
470 hostkeys = init_hostkeys();
471 load_hostkeys(hostkeys, host, sysfile);
472 if (userfile != NULL) {
473 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
474 if (options.strict_modes &&
475 (stat(user_hostfile, &st) == 0) &&
476 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
477 (st.st_mode & 022) != 0)) {
478 logit("Authentication refused for %.100s: "
479 "bad owner or modes for %.200s",
480 pw->pw_name, user_hostfile);
481 auth_debug_add("Ignored %.200s: bad ownership or modes",
482 user_hostfile);
483 } else {
484 temporarily_use_uid(pw);
485 load_hostkeys(hostkeys, host, user_hostfile);
486 restore_uid();
487 }
488 free(user_hostfile);
489 }
490 host_status = check_key_in_hostkeys(hostkeys, key, &found);
491 if (host_status == HOST_REVOKED)
492 error("WARNING: revoked key for %s attempted authentication",
493 host);
494 else if (host_status == HOST_OK)
495 debug("%s: key for %s found at %s:%ld", __func__,
496 found->host, found->file, found->line);
497 else
498 debug("%s: key for host %s not found", __func__, host);
499
500 free_hostkeys(hostkeys);
501
502 return host_status;
503 }
504
505 static FILE *
auth_openfile(const char * file,struct passwd * pw,int strict_modes,int log_missing,char * file_type)506 auth_openfile(const char *file, struct passwd *pw, int strict_modes,
507 int log_missing, char *file_type)
508 {
509 char line[1024];
510 struct stat st;
511 int fd;
512 FILE *f;
513
514 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
515 if (log_missing || errno != ENOENT)
516 debug("Could not open %s '%s': %s", file_type, file,
517 strerror(errno));
518 return NULL;
519 }
520
521 if (fstat(fd, &st) == -1) {
522 close(fd);
523 return NULL;
524 }
525 if (!S_ISREG(st.st_mode)) {
526 logit("User %s %s %s is not a regular file",
527 pw->pw_name, file_type, file);
528 close(fd);
529 return NULL;
530 }
531 unset_nonblock(fd);
532 if ((f = fdopen(fd, "r")) == NULL) {
533 close(fd);
534 return NULL;
535 }
536 if (strict_modes &&
537 safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) {
538 fclose(f);
539 logit("Authentication refused: %s", line);
540 auth_debug_add("Ignored %s: %s", file_type, line);
541 return NULL;
542 }
543
544 return f;
545 }
546
547
548 FILE *
auth_openkeyfile(const char * file,struct passwd * pw,int strict_modes)549 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
550 {
551 return auth_openfile(file, pw, strict_modes, 1, "authorized keys");
552 }
553
554 FILE *
auth_openprincipals(const char * file,struct passwd * pw,int strict_modes)555 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
556 {
557 return auth_openfile(file, pw, strict_modes, 0,
558 "authorized principals");
559 }
560
561 struct passwd *
getpwnamallow(struct ssh * ssh,const char * user)562 getpwnamallow(struct ssh *ssh, const char *user)
563 {
564 #ifdef HAVE_LOGIN_CAP
565 extern login_cap_t *lc;
566 #ifdef BSD_AUTH
567 auth_session_t *as;
568 #endif
569 #endif
570 struct passwd *pw;
571 struct connection_info *ci;
572
573 ci = get_connection_info(ssh, 1, options.use_dns);
574 ci->user = user;
575 parse_server_match_config(&options, &includes, ci);
576 log_change_level(options.log_level);
577 process_permitopen(ssh, &options);
578
579 #if defined(_AIX) && defined(HAVE_SETAUTHDB)
580 aix_setauthdb(user);
581 #endif
582
583 #if defined(ANDROID)
584 // Android has a fixed set of users. Any incoming user that we can't
585 // identify should be authenticated as the shell user.
586 if (strcmp(user, "root") && strcmp(user, "shell")) {
587 logit("Login name %.100s forced to shell", user);
588 user = "shell";
589 }
590 #endif
591 pw = getpwnam(user);
592
593 #if defined(_AIX) && defined(HAVE_SETAUTHDB)
594 aix_restoreauthdb();
595 #endif
596 if (pw == NULL) {
597 logit("Invalid user %.100s from %.100s port %d",
598 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
599 #ifdef CUSTOM_FAILED_LOGIN
600 record_failed_login(ssh, user,
601 auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
602 #endif
603 #ifdef SSH_AUDIT_EVENTS
604 audit_event(ssh, SSH_INVALID_USER);
605 #endif /* SSH_AUDIT_EVENTS */
606 return (NULL);
607 }
608 if (!allowed_user(ssh, pw))
609 return (NULL);
610 #ifdef HAVE_LOGIN_CAP
611 if ((lc = login_getclass(pw->pw_class)) == NULL) {
612 debug("unable to get login class: %s", user);
613 return (NULL);
614 }
615 #ifdef BSD_AUTH
616 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
617 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
618 debug("Approval failure for %s", user);
619 pw = NULL;
620 }
621 if (as != NULL)
622 auth_close(as);
623 #endif
624 #endif
625 if (pw != NULL)
626 return (pwcopy(pw));
627 return (NULL);
628 }
629
630 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
631 int
auth_key_is_revoked(struct sshkey * key)632 auth_key_is_revoked(struct sshkey *key)
633 {
634 char *fp = NULL;
635 int r;
636
637 if (options.revoked_keys_file == NULL)
638 return 0;
639 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
640 SSH_FP_DEFAULT)) == NULL) {
641 r = SSH_ERR_ALLOC_FAIL;
642 error("%s: fingerprint key: %s", __func__, ssh_err(r));
643 goto out;
644 }
645
646 r = sshkey_check_revoked(key, options.revoked_keys_file);
647 switch (r) {
648 case 0:
649 break; /* not revoked */
650 case SSH_ERR_KEY_REVOKED:
651 error("Authentication key %s %s revoked by file %s",
652 sshkey_type(key), fp, options.revoked_keys_file);
653 goto out;
654 default:
655 error("Error checking authentication key %s %s in "
656 "revoked keys file %s: %s", sshkey_type(key), fp,
657 options.revoked_keys_file, ssh_err(r));
658 goto out;
659 }
660
661 /* Success */
662 r = 0;
663
664 out:
665 free(fp);
666 return r == 0 ? 0 : 1;
667 }
668
669 void
auth_debug_add(const char * fmt,...)670 auth_debug_add(const char *fmt,...)
671 {
672 char buf[1024];
673 va_list args;
674 int r;
675
676 if (auth_debug == NULL)
677 return;
678
679 va_start(args, fmt);
680 vsnprintf(buf, sizeof(buf), fmt, args);
681 va_end(args);
682 if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0)
683 fatal("%s: sshbuf_put_cstring: %s", __func__, ssh_err(r));
684 }
685
686 void
auth_debug_send(struct ssh * ssh)687 auth_debug_send(struct ssh *ssh)
688 {
689 char *msg;
690 int r;
691
692 if (auth_debug == NULL)
693 return;
694 while (sshbuf_len(auth_debug) != 0) {
695 if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0)
696 fatal("%s: sshbuf_get_cstring: %s",
697 __func__, ssh_err(r));
698 ssh_packet_send_debug(ssh, "%s", msg);
699 free(msg);
700 }
701 }
702
703 void
auth_debug_reset(void)704 auth_debug_reset(void)
705 {
706 if (auth_debug != NULL)
707 sshbuf_reset(auth_debug);
708 else if ((auth_debug = sshbuf_new()) == NULL)
709 fatal("%s: sshbuf_new failed", __func__);
710 }
711
712 struct passwd *
fakepw(void)713 fakepw(void)
714 {
715 static struct passwd fake;
716
717 memset(&fake, 0, sizeof(fake));
718 fake.pw_name = "NOUSER";
719 fake.pw_passwd =
720 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
721 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS
722 fake.pw_gecos = "NOUSER";
723 #endif
724 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid;
725 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid;
726 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS
727 fake.pw_class = "";
728 #endif
729 fake.pw_dir = "/nonexist";
730 fake.pw_shell = "/nonexist";
731
732 return (&fake);
733 }
734
735 /*
736 * Returns the remote DNS hostname as a string. The returned string must not
737 * be freed. NB. this will usually trigger a DNS query the first time it is
738 * called.
739 * This function does additional checks on the hostname to mitigate some
740 * attacks on legacy rhosts-style authentication.
741 * XXX is RhostsRSAAuthentication vulnerable to these?
742 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
743 */
744
745 static char *
remote_hostname(struct ssh * ssh)746 remote_hostname(struct ssh *ssh)
747 {
748 struct sockaddr_storage from;
749 socklen_t fromlen;
750 struct addrinfo hints, *ai, *aitop;
751 char name[NI_MAXHOST], ntop2[NI_MAXHOST];
752 const char *ntop = ssh_remote_ipaddr(ssh);
753
754 /* Get IP address of client. */
755 fromlen = sizeof(from);
756 memset(&from, 0, sizeof(from));
757 if (getpeername(ssh_packet_get_connection_in(ssh),
758 (struct sockaddr *)&from, &fromlen) == -1) {
759 debug("getpeername failed: %.100s", strerror(errno));
760 return xstrdup(ntop);
761 }
762
763 ipv64_normalise_mapped(&from, &fromlen);
764 if (from.ss_family == AF_INET6)
765 fromlen = sizeof(struct sockaddr_in6);
766
767 debug3("Trying to reverse map address %.100s.", ntop);
768 /* Map the IP address to a host name. */
769 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
770 NULL, 0, NI_NAMEREQD) != 0) {
771 /* Host name not found. Use ip address. */
772 return xstrdup(ntop);
773 }
774
775 /*
776 * if reverse lookup result looks like a numeric hostname,
777 * someone is trying to trick us by PTR record like following:
778 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
779 */
780 memset(&hints, 0, sizeof(hints));
781 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
782 hints.ai_flags = AI_NUMERICHOST;
783 if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
784 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
785 name, ntop);
786 freeaddrinfo(ai);
787 return xstrdup(ntop);
788 }
789
790 /* Names are stored in lowercase. */
791 lowercase(name);
792
793 /*
794 * Map it back to an IP address and check that the given
795 * address actually is an address of this host. This is
796 * necessary because anyone with access to a name server can
797 * define arbitrary names for an IP address. Mapping from
798 * name to IP address can be trusted better (but can still be
799 * fooled if the intruder has access to the name server of
800 * the domain).
801 */
802 memset(&hints, 0, sizeof(hints));
803 hints.ai_family = from.ss_family;
804 hints.ai_socktype = SOCK_STREAM;
805 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
806 logit("reverse mapping checking getaddrinfo for %.700s "
807 "[%s] failed.", name, ntop);
808 return xstrdup(ntop);
809 }
810 /* Look for the address from the list of addresses. */
811 for (ai = aitop; ai; ai = ai->ai_next) {
812 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
813 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
814 (strcmp(ntop, ntop2) == 0))
815 break;
816 }
817 freeaddrinfo(aitop);
818 /* If we reached the end of the list, the address was not there. */
819 if (ai == NULL) {
820 /* Address not found for the host name. */
821 logit("Address %.100s maps to %.600s, but this does not "
822 "map back to the address.", ntop, name);
823 return xstrdup(ntop);
824 }
825 return xstrdup(name);
826 }
827
828 /*
829 * Return the canonical name of the host in the other side of the current
830 * connection. The host name is cached, so it is efficient to call this
831 * several times.
832 */
833
834 const char *
auth_get_canonical_hostname(struct ssh * ssh,int use_dns)835 auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
836 {
837 static char *dnsname;
838
839 if (!use_dns)
840 return ssh_remote_ipaddr(ssh);
841 else if (dnsname != NULL)
842 return dnsname;
843 else {
844 dnsname = remote_hostname(ssh);
845 return dnsname;
846 }
847 }
848
849 /*
850 * Runs command in a subprocess with a minimal environment.
851 * Returns pid on success, 0 on failure.
852 * The child stdout and stderr maybe captured, left attached or sent to
853 * /dev/null depending on the contents of flags.
854 * "tag" is prepended to log messages.
855 * NB. "command" is only used for logging; the actual command executed is
856 * av[0].
857 */
858 pid_t
subprocess(const char * tag,struct passwd * pw,const char * command,int ac,char ** av,FILE ** child,u_int flags)859 subprocess(const char *tag, struct passwd *pw, const char *command,
860 int ac, char **av, FILE **child, u_int flags)
861 {
862 FILE *f = NULL;
863 struct stat st;
864 int fd, devnull, p[2], i;
865 pid_t pid;
866 char *cp, errmsg[512];
867 u_int envsize;
868 char **child_env;
869
870 if (child != NULL)
871 *child = NULL;
872
873 debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__,
874 tag, command, pw->pw_name, flags);
875
876 /* Check consistency */
877 if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
878 (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) {
879 error("%s: inconsistent flags", __func__);
880 return 0;
881 }
882 if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) {
883 error("%s: inconsistent flags/output", __func__);
884 return 0;
885 }
886
887 /*
888 * If executing an explicit binary, then verify the it exists
889 * and appears safe-ish to execute
890 */
891 if (!path_absolute(av[0])) {
892 error("%s path is not absolute", tag);
893 return 0;
894 }
895 temporarily_use_uid(pw);
896 if (stat(av[0], &st) == -1) {
897 error("Could not stat %s \"%s\": %s", tag,
898 av[0], strerror(errno));
899 restore_uid();
900 return 0;
901 }
902 if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) {
903 error("Unsafe %s \"%s\": %s", tag, av[0], errmsg);
904 restore_uid();
905 return 0;
906 }
907 /* Prepare to keep the child's stdout if requested */
908 if (pipe(p) == -1) {
909 error("%s: pipe: %s", tag, strerror(errno));
910 restore_uid();
911 return 0;
912 }
913 restore_uid();
914
915 switch ((pid = fork())) {
916 case -1: /* error */
917 error("%s: fork: %s", tag, strerror(errno));
918 close(p[0]);
919 close(p[1]);
920 return 0;
921 case 0: /* child */
922 /* Prepare a minimal environment for the child. */
923 envsize = 5;
924 child_env = xcalloc(sizeof(*child_env), envsize);
925 child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH);
926 child_set_env(&child_env, &envsize, "USER", pw->pw_name);
927 child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name);
928 child_set_env(&child_env, &envsize, "HOME", pw->pw_dir);
929 if ((cp = getenv("LANG")) != NULL)
930 child_set_env(&child_env, &envsize, "LANG", cp);
931
932 for (i = 0; i < NSIG; i++)
933 ssh_signal(i, SIG_DFL);
934
935 if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
936 error("%s: open %s: %s", tag, _PATH_DEVNULL,
937 strerror(errno));
938 _exit(1);
939 }
940 if (dup2(devnull, STDIN_FILENO) == -1) {
941 error("%s: dup2: %s", tag, strerror(errno));
942 _exit(1);
943 }
944
945 /* Set up stdout as requested; leave stderr in place for now. */
946 fd = -1;
947 if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0)
948 fd = p[1];
949 else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0)
950 fd = devnull;
951 if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) {
952 error("%s: dup2: %s", tag, strerror(errno));
953 _exit(1);
954 }
955 closefrom(STDERR_FILENO + 1);
956
957 /* Don't use permanently_set_uid() here to avoid fatal() */
958 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1) {
959 error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid,
960 strerror(errno));
961 _exit(1);
962 }
963 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1) {
964 error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid,
965 strerror(errno));
966 _exit(1);
967 }
968 /* stdin is pointed to /dev/null at this point */
969 if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
970 dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
971 error("%s: dup2: %s", tag, strerror(errno));
972 _exit(1);
973 }
974
975 execve(av[0], av, child_env);
976 error("%s exec \"%s\": %s", tag, command, strerror(errno));
977 _exit(127);
978 default: /* parent */
979 break;
980 }
981
982 close(p[1]);
983 if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0)
984 close(p[0]);
985 else if ((f = fdopen(p[0], "r")) == NULL) {
986 error("%s: fdopen: %s", tag, strerror(errno));
987 close(p[0]);
988 /* Don't leave zombie child */
989 kill(pid, SIGTERM);
990 while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
991 ;
992 return 0;
993 }
994 /* Success */
995 debug3("%s: %s pid %ld", __func__, tag, (long)pid);
996 if (child != NULL)
997 *child = f;
998 return pid;
999 }
1000
1001 /* These functions link key/cert options to the auth framework */
1002
1003 /* Log sshauthopt options locally and (optionally) for remote transmission */
1004 void
auth_log_authopts(const char * loc,const struct sshauthopt * opts,int do_remote)1005 auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote)
1006 {
1007 int do_env = options.permit_user_env && opts->nenv > 0;
1008 int do_permitopen = opts->npermitopen > 0 &&
1009 (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0;
1010 int do_permitlisten = opts->npermitlisten > 0 &&
1011 (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0;
1012 size_t i;
1013 char msg[1024], buf[64];
1014
1015 snprintf(buf, sizeof(buf), "%d", opts->force_tun_device);
1016 /* Try to keep this alphabetically sorted */
1017 snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
1018 opts->permit_agent_forwarding_flag ? " agent-forwarding" : "",
1019 opts->force_command == NULL ? "" : " command",
1020 do_env ? " environment" : "",
1021 opts->valid_before == 0 ? "" : "expires",
1022 do_permitopen ? " permitopen" : "",
1023 do_permitlisten ? " permitlisten" : "",
1024 opts->permit_port_forwarding_flag ? " port-forwarding" : "",
1025 opts->cert_principals == NULL ? "" : " principals",
1026 opts->permit_pty_flag ? " pty" : "",
1027 opts->force_tun_device == -1 ? "" : " tun=",
1028 opts->force_tun_device == -1 ? "" : buf,
1029 opts->permit_user_rc ? " user-rc" : "",
1030 opts->permit_x11_forwarding_flag ? " x11-forwarding" : "",
1031 opts->no_require_user_presence ? " no-touch-required" : "");
1032
1033 debug("%s: %s", loc, msg);
1034 if (do_remote)
1035 auth_debug_add("%s: %s", loc, msg);
1036
1037 if (options.permit_user_env) {
1038 for (i = 0; i < opts->nenv; i++) {
1039 debug("%s: environment: %s", loc, opts->env[i]);
1040 if (do_remote) {
1041 auth_debug_add("%s: environment: %s",
1042 loc, opts->env[i]);
1043 }
1044 }
1045 }
1046
1047 /* Go into a little more details for the local logs. */
1048 if (opts->valid_before != 0) {
1049 format_absolute_time(opts->valid_before, buf, sizeof(buf));
1050 debug("%s: expires at %s", loc, buf);
1051 }
1052 if (opts->cert_principals != NULL) {
1053 debug("%s: authorized principals: \"%s\"",
1054 loc, opts->cert_principals);
1055 }
1056 if (opts->force_command != NULL)
1057 debug("%s: forced command: \"%s\"", loc, opts->force_command);
1058 if (do_permitopen) {
1059 for (i = 0; i < opts->npermitopen; i++) {
1060 debug("%s: permitted open: %s",
1061 loc, opts->permitopen[i]);
1062 }
1063 }
1064 if (do_permitlisten) {
1065 for (i = 0; i < opts->npermitlisten; i++) {
1066 debug("%s: permitted listen: %s",
1067 loc, opts->permitlisten[i]);
1068 }
1069 }
1070 }
1071
1072 /* Activate a new set of key/cert options; merging with what is there. */
1073 int
auth_activate_options(struct ssh * ssh,struct sshauthopt * opts)1074 auth_activate_options(struct ssh *ssh, struct sshauthopt *opts)
1075 {
1076 struct sshauthopt *old = auth_opts;
1077 const char *emsg = NULL;
1078
1079 debug("%s: setting new authentication options", __func__);
1080 if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) {
1081 error("Inconsistent authentication options: %s", emsg);
1082 return -1;
1083 }
1084 return 0;
1085 }
1086
1087 /* Disable forwarding, etc for the session */
1088 void
auth_restrict_session(struct ssh * ssh)1089 auth_restrict_session(struct ssh *ssh)
1090 {
1091 struct sshauthopt *restricted;
1092
1093 debug("%s: restricting session", __func__);
1094
1095 /* A blank sshauthopt defaults to permitting nothing */
1096 restricted = sshauthopt_new();
1097 restricted->permit_pty_flag = 1;
1098 restricted->restricted = 1;
1099
1100 if (auth_activate_options(ssh, restricted) != 0)
1101 fatal("%s: failed to restrict session", __func__);
1102 sshauthopt_free(restricted);
1103 }
1104
1105 int
auth_authorise_keyopts(struct ssh * ssh,struct passwd * pw,struct sshauthopt * opts,int allow_cert_authority,const char * loc)1106 auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw,
1107 struct sshauthopt *opts, int allow_cert_authority, const char *loc)
1108 {
1109 const char *remote_ip = ssh_remote_ipaddr(ssh);
1110 const char *remote_host = auth_get_canonical_hostname(ssh,
1111 options.use_dns);
1112 time_t now = time(NULL);
1113 char buf[64];
1114
1115 /*
1116 * Check keys/principals file expiry time.
1117 * NB. validity interval in certificate is handled elsewhere.
1118 */
1119 if (opts->valid_before && now > 0 &&
1120 opts->valid_before < (uint64_t)now) {
1121 format_absolute_time(opts->valid_before, buf, sizeof(buf));
1122 debug("%s: entry expired at %s", loc, buf);
1123 auth_debug_add("%s: entry expired at %s", loc, buf);
1124 return -1;
1125 }
1126 /* Consistency checks */
1127 if (opts->cert_principals != NULL && !opts->cert_authority) {
1128 debug("%s: principals on non-CA key", loc);
1129 auth_debug_add("%s: principals on non-CA key", loc);
1130 /* deny access */
1131 return -1;
1132 }
1133 /* cert-authority flag isn't valid in authorized_principals files */
1134 if (!allow_cert_authority && opts->cert_authority) {
1135 debug("%s: cert-authority flag invalid here", loc);
1136 auth_debug_add("%s: cert-authority flag invalid here", loc);
1137 /* deny access */
1138 return -1;
1139 }
1140
1141 /* Perform from= checks */
1142 if (opts->required_from_host_keys != NULL) {
1143 switch (match_host_and_ip(remote_host, remote_ip,
1144 opts->required_from_host_keys )) {
1145 case 1:
1146 /* Host name matches. */
1147 break;
1148 case -1:
1149 default:
1150 debug("%s: invalid from criteria", loc);
1151 auth_debug_add("%s: invalid from criteria", loc);
1152 /* FALLTHROUGH */
1153 case 0:
1154 logit("%s: Authentication tried for %.100s with "
1155 "correct key but not from a permitted "
1156 "host (host=%.200s, ip=%.200s, required=%.200s).",
1157 loc, pw->pw_name, remote_host, remote_ip,
1158 opts->required_from_host_keys);
1159 auth_debug_add("%s: Your host '%.200s' is not "
1160 "permitted to use this key for login.",
1161 loc, remote_host);
1162 /* deny access */
1163 return -1;
1164 }
1165 }
1166 /* Check source-address restriction from certificate */
1167 if (opts->required_from_host_cert != NULL) {
1168 switch (addr_match_cidr_list(remote_ip,
1169 opts->required_from_host_cert)) {
1170 case 1:
1171 /* accepted */
1172 break;
1173 case -1:
1174 default:
1175 /* invalid */
1176 error("%s: Certificate source-address invalid",
1177 loc);
1178 /* FALLTHROUGH */
1179 case 0:
1180 logit("%s: Authentication tried for %.100s with valid "
1181 "certificate but not from a permitted source "
1182 "address (%.200s).", loc, pw->pw_name, remote_ip);
1183 auth_debug_add("%s: Your address '%.200s' is not "
1184 "permitted to use this certificate for login.",
1185 loc, remote_ip);
1186 return -1;
1187 }
1188 }
1189 /*
1190 *
1191 * XXX this is spammy. We should report remotely only for keys
1192 * that are successful in actual auth attempts, and not PK_OK
1193 * tests.
1194 */
1195 auth_log_authopts(loc, opts, 1);
1196
1197 return 0;
1198 }
1199