1 /* $OpenBSD: auth.c,v 1.151 2020/12/22 00:12:22 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, 0);
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, 0);
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_f("key for %s found at %s:%ld",
496 found->host, found->file, found->line);
497 else
498 debug_f("key for host %s not found", 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 u_int i;
573
574 ci = get_connection_info(ssh, 1, options.use_dns);
575 ci->user = user;
576 parse_server_match_config(&options, &includes, ci);
577 log_change_level(options.log_level);
578 log_verbose_reset();
579 for (i = 0; i < options.num_log_verbose; i++)
580 log_verbose_add(options.log_verbose[i]);
581 process_permitopen(ssh, &options);
582
583 #if defined(_AIX) && defined(HAVE_SETAUTHDB)
584 aix_setauthdb(user);
585 #endif
586
587 pw = getpwnam(user);
588
589 #if defined(_AIX) && defined(HAVE_SETAUTHDB)
590 aix_restoreauthdb();
591 #endif
592 if (pw == NULL) {
593 logit("Invalid user %.100s from %.100s port %d",
594 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
595 #ifdef CUSTOM_FAILED_LOGIN
596 record_failed_login(ssh, user,
597 auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
598 #endif
599 #ifdef SSH_AUDIT_EVENTS
600 audit_event(ssh, SSH_INVALID_USER);
601 #endif /* SSH_AUDIT_EVENTS */
602 return (NULL);
603 }
604 if (!allowed_user(ssh, pw))
605 return (NULL);
606 #ifdef HAVE_LOGIN_CAP
607 if ((lc = login_getclass(pw->pw_class)) == NULL) {
608 debug("unable to get login class: %s", user);
609 return (NULL);
610 }
611 #ifdef BSD_AUTH
612 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
613 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
614 debug("Approval failure for %s", user);
615 pw = NULL;
616 }
617 if (as != NULL)
618 auth_close(as);
619 #endif
620 #endif
621 if (pw != NULL)
622 return (pwcopy(pw));
623 return (NULL);
624 }
625
626 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
627 int
auth_key_is_revoked(struct sshkey * key)628 auth_key_is_revoked(struct sshkey *key)
629 {
630 char *fp = NULL;
631 int r;
632
633 if (options.revoked_keys_file == NULL)
634 return 0;
635 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
636 SSH_FP_DEFAULT)) == NULL) {
637 r = SSH_ERR_ALLOC_FAIL;
638 error_fr(r, "fingerprint key");
639 goto out;
640 }
641
642 r = sshkey_check_revoked(key, options.revoked_keys_file);
643 switch (r) {
644 case 0:
645 break; /* not revoked */
646 case SSH_ERR_KEY_REVOKED:
647 error("Authentication key %s %s revoked by file %s",
648 sshkey_type(key), fp, options.revoked_keys_file);
649 goto out;
650 default:
651 error_r(r, "Error checking authentication key %s %s in "
652 "revoked keys file %s", sshkey_type(key), fp,
653 options.revoked_keys_file);
654 goto out;
655 }
656
657 /* Success */
658 r = 0;
659
660 out:
661 free(fp);
662 return r == 0 ? 0 : 1;
663 }
664
665 void
auth_debug_add(const char * fmt,...)666 auth_debug_add(const char *fmt,...)
667 {
668 char buf[1024];
669 va_list args;
670 int r;
671
672 if (auth_debug == NULL)
673 return;
674
675 va_start(args, fmt);
676 vsnprintf(buf, sizeof(buf), fmt, args);
677 va_end(args);
678 if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0)
679 fatal_fr(r, "sshbuf_put_cstring");
680 }
681
682 void
auth_debug_send(struct ssh * ssh)683 auth_debug_send(struct ssh *ssh)
684 {
685 char *msg;
686 int r;
687
688 if (auth_debug == NULL)
689 return;
690 while (sshbuf_len(auth_debug) != 0) {
691 if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0)
692 fatal_fr(r, "sshbuf_get_cstring");
693 ssh_packet_send_debug(ssh, "%s", msg);
694 free(msg);
695 }
696 }
697
698 void
auth_debug_reset(void)699 auth_debug_reset(void)
700 {
701 if (auth_debug != NULL)
702 sshbuf_reset(auth_debug);
703 else if ((auth_debug = sshbuf_new()) == NULL)
704 fatal_f("sshbuf_new failed");
705 }
706
707 struct passwd *
fakepw(void)708 fakepw(void)
709 {
710 static struct passwd fake;
711
712 memset(&fake, 0, sizeof(fake));
713 fake.pw_name = "NOUSER";
714 fake.pw_passwd =
715 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
716 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS
717 fake.pw_gecos = "NOUSER";
718 #endif
719 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid;
720 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid;
721 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS
722 fake.pw_class = "";
723 #endif
724 fake.pw_dir = "/nonexist";
725 fake.pw_shell = "/nonexist";
726
727 return (&fake);
728 }
729
730 /*
731 * Returns the remote DNS hostname as a string. The returned string must not
732 * be freed. NB. this will usually trigger a DNS query the first time it is
733 * called.
734 * This function does additional checks on the hostname to mitigate some
735 * attacks on legacy rhosts-style authentication.
736 * XXX is RhostsRSAAuthentication vulnerable to these?
737 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
738 */
739
740 static char *
remote_hostname(struct ssh * ssh)741 remote_hostname(struct ssh *ssh)
742 {
743 struct sockaddr_storage from;
744 socklen_t fromlen;
745 struct addrinfo hints, *ai, *aitop;
746 char name[NI_MAXHOST], ntop2[NI_MAXHOST];
747 const char *ntop = ssh_remote_ipaddr(ssh);
748
749 /* Get IP address of client. */
750 fromlen = sizeof(from);
751 memset(&from, 0, sizeof(from));
752 if (getpeername(ssh_packet_get_connection_in(ssh),
753 (struct sockaddr *)&from, &fromlen) == -1) {
754 debug("getpeername failed: %.100s", strerror(errno));
755 return xstrdup(ntop);
756 }
757
758 ipv64_normalise_mapped(&from, &fromlen);
759 if (from.ss_family == AF_INET6)
760 fromlen = sizeof(struct sockaddr_in6);
761
762 debug3("Trying to reverse map address %.100s.", ntop);
763 /* Map the IP address to a host name. */
764 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
765 NULL, 0, NI_NAMEREQD) != 0) {
766 /* Host name not found. Use ip address. */
767 return xstrdup(ntop);
768 }
769
770 /*
771 * if reverse lookup result looks like a numeric hostname,
772 * someone is trying to trick us by PTR record like following:
773 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
774 */
775 memset(&hints, 0, sizeof(hints));
776 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
777 hints.ai_flags = AI_NUMERICHOST;
778 if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
779 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
780 name, ntop);
781 freeaddrinfo(ai);
782 return xstrdup(ntop);
783 }
784
785 /* Names are stored in lowercase. */
786 lowercase(name);
787
788 /*
789 * Map it back to an IP address and check that the given
790 * address actually is an address of this host. This is
791 * necessary because anyone with access to a name server can
792 * define arbitrary names for an IP address. Mapping from
793 * name to IP address can be trusted better (but can still be
794 * fooled if the intruder has access to the name server of
795 * the domain).
796 */
797 memset(&hints, 0, sizeof(hints));
798 hints.ai_family = from.ss_family;
799 hints.ai_socktype = SOCK_STREAM;
800 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
801 logit("reverse mapping checking getaddrinfo for %.700s "
802 "[%s] failed.", name, ntop);
803 return xstrdup(ntop);
804 }
805 /* Look for the address from the list of addresses. */
806 for (ai = aitop; ai; ai = ai->ai_next) {
807 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
808 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
809 (strcmp(ntop, ntop2) == 0))
810 break;
811 }
812 freeaddrinfo(aitop);
813 /* If we reached the end of the list, the address was not there. */
814 if (ai == NULL) {
815 /* Address not found for the host name. */
816 logit("Address %.100s maps to %.600s, but this does not "
817 "map back to the address.", ntop, name);
818 return xstrdup(ntop);
819 }
820 return xstrdup(name);
821 }
822
823 /*
824 * Return the canonical name of the host in the other side of the current
825 * connection. The host name is cached, so it is efficient to call this
826 * several times.
827 */
828
829 const char *
auth_get_canonical_hostname(struct ssh * ssh,int use_dns)830 auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
831 {
832 static char *dnsname;
833
834 if (!use_dns)
835 return ssh_remote_ipaddr(ssh);
836 else if (dnsname != NULL)
837 return dnsname;
838 else {
839 dnsname = remote_hostname(ssh);
840 return dnsname;
841 }
842 }
843
844 /* These functions link key/cert options to the auth framework */
845
846 /* Log sshauthopt options locally and (optionally) for remote transmission */
847 void
auth_log_authopts(const char * loc,const struct sshauthopt * opts,int do_remote)848 auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote)
849 {
850 int do_env = options.permit_user_env && opts->nenv > 0;
851 int do_permitopen = opts->npermitopen > 0 &&
852 (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0;
853 int do_permitlisten = opts->npermitlisten > 0 &&
854 (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0;
855 size_t i;
856 char msg[1024], buf[64];
857
858 snprintf(buf, sizeof(buf), "%d", opts->force_tun_device);
859 /* Try to keep this alphabetically sorted */
860 snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
861 opts->permit_agent_forwarding_flag ? " agent-forwarding" : "",
862 opts->force_command == NULL ? "" : " command",
863 do_env ? " environment" : "",
864 opts->valid_before == 0 ? "" : "expires",
865 opts->no_require_user_presence ? " no-touch-required" : "",
866 do_permitopen ? " permitopen" : "",
867 do_permitlisten ? " permitlisten" : "",
868 opts->permit_port_forwarding_flag ? " port-forwarding" : "",
869 opts->cert_principals == NULL ? "" : " principals",
870 opts->permit_pty_flag ? " pty" : "",
871 opts->require_verify ? " uv" : "",
872 opts->force_tun_device == -1 ? "" : " tun=",
873 opts->force_tun_device == -1 ? "" : buf,
874 opts->permit_user_rc ? " user-rc" : "",
875 opts->permit_x11_forwarding_flag ? " x11-forwarding" : "");
876
877 debug("%s: %s", loc, msg);
878 if (do_remote)
879 auth_debug_add("%s: %s", loc, msg);
880
881 if (options.permit_user_env) {
882 for (i = 0; i < opts->nenv; i++) {
883 debug("%s: environment: %s", loc, opts->env[i]);
884 if (do_remote) {
885 auth_debug_add("%s: environment: %s",
886 loc, opts->env[i]);
887 }
888 }
889 }
890
891 /* Go into a little more details for the local logs. */
892 if (opts->valid_before != 0) {
893 format_absolute_time(opts->valid_before, buf, sizeof(buf));
894 debug("%s: expires at %s", loc, buf);
895 }
896 if (opts->cert_principals != NULL) {
897 debug("%s: authorized principals: \"%s\"",
898 loc, opts->cert_principals);
899 }
900 if (opts->force_command != NULL)
901 debug("%s: forced command: \"%s\"", loc, opts->force_command);
902 if (do_permitopen) {
903 for (i = 0; i < opts->npermitopen; i++) {
904 debug("%s: permitted open: %s",
905 loc, opts->permitopen[i]);
906 }
907 }
908 if (do_permitlisten) {
909 for (i = 0; i < opts->npermitlisten; i++) {
910 debug("%s: permitted listen: %s",
911 loc, opts->permitlisten[i]);
912 }
913 }
914 }
915
916 /* Activate a new set of key/cert options; merging with what is there. */
917 int
auth_activate_options(struct ssh * ssh,struct sshauthopt * opts)918 auth_activate_options(struct ssh *ssh, struct sshauthopt *opts)
919 {
920 struct sshauthopt *old = auth_opts;
921 const char *emsg = NULL;
922
923 debug_f("setting new authentication options");
924 if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) {
925 error("Inconsistent authentication options: %s", emsg);
926 return -1;
927 }
928 return 0;
929 }
930
931 /* Disable forwarding, etc for the session */
932 void
auth_restrict_session(struct ssh * ssh)933 auth_restrict_session(struct ssh *ssh)
934 {
935 struct sshauthopt *restricted;
936
937 debug_f("restricting session");
938
939 /* A blank sshauthopt defaults to permitting nothing */
940 restricted = sshauthopt_new();
941 restricted->permit_pty_flag = 1;
942 restricted->restricted = 1;
943
944 if (auth_activate_options(ssh, restricted) != 0)
945 fatal_f("failed to restrict session");
946 sshauthopt_free(restricted);
947 }
948
949 int
auth_authorise_keyopts(struct ssh * ssh,struct passwd * pw,struct sshauthopt * opts,int allow_cert_authority,const char * loc)950 auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw,
951 struct sshauthopt *opts, int allow_cert_authority, const char *loc)
952 {
953 const char *remote_ip = ssh_remote_ipaddr(ssh);
954 const char *remote_host = auth_get_canonical_hostname(ssh,
955 options.use_dns);
956 time_t now = time(NULL);
957 char buf[64];
958
959 /*
960 * Check keys/principals file expiry time.
961 * NB. validity interval in certificate is handled elsewhere.
962 */
963 if (opts->valid_before && now > 0 &&
964 opts->valid_before < (uint64_t)now) {
965 format_absolute_time(opts->valid_before, buf, sizeof(buf));
966 debug("%s: entry expired at %s", loc, buf);
967 auth_debug_add("%s: entry expired at %s", loc, buf);
968 return -1;
969 }
970 /* Consistency checks */
971 if (opts->cert_principals != NULL && !opts->cert_authority) {
972 debug("%s: principals on non-CA key", loc);
973 auth_debug_add("%s: principals on non-CA key", loc);
974 /* deny access */
975 return -1;
976 }
977 /* cert-authority flag isn't valid in authorized_principals files */
978 if (!allow_cert_authority && opts->cert_authority) {
979 debug("%s: cert-authority flag invalid here", loc);
980 auth_debug_add("%s: cert-authority flag invalid here", loc);
981 /* deny access */
982 return -1;
983 }
984
985 /* Perform from= checks */
986 if (opts->required_from_host_keys != NULL) {
987 switch (match_host_and_ip(remote_host, remote_ip,
988 opts->required_from_host_keys )) {
989 case 1:
990 /* Host name matches. */
991 break;
992 case -1:
993 default:
994 debug("%s: invalid from criteria", loc);
995 auth_debug_add("%s: invalid from criteria", loc);
996 /* FALLTHROUGH */
997 case 0:
998 logit("%s: Authentication tried for %.100s with "
999 "correct key but not from a permitted "
1000 "host (host=%.200s, ip=%.200s, required=%.200s).",
1001 loc, pw->pw_name, remote_host, remote_ip,
1002 opts->required_from_host_keys);
1003 auth_debug_add("%s: Your host '%.200s' is not "
1004 "permitted to use this key for login.",
1005 loc, remote_host);
1006 /* deny access */
1007 return -1;
1008 }
1009 }
1010 /* Check source-address restriction from certificate */
1011 if (opts->required_from_host_cert != NULL) {
1012 switch (addr_match_cidr_list(remote_ip,
1013 opts->required_from_host_cert)) {
1014 case 1:
1015 /* accepted */
1016 break;
1017 case -1:
1018 default:
1019 /* invalid */
1020 error("%s: Certificate source-address invalid", loc);
1021 /* FALLTHROUGH */
1022 case 0:
1023 logit("%s: Authentication tried for %.100s with valid "
1024 "certificate but not from a permitted source "
1025 "address (%.200s).", loc, pw->pw_name, remote_ip);
1026 auth_debug_add("%s: Your address '%.200s' is not "
1027 "permitted to use this certificate for login.",
1028 loc, remote_ip);
1029 return -1;
1030 }
1031 }
1032 /*
1033 *
1034 * XXX this is spammy. We should report remotely only for keys
1035 * that are successful in actual auth attempts, and not PK_OK
1036 * tests.
1037 */
1038 auth_log_authopts(loc, opts, 1);
1039
1040 return 0;
1041 }
1042