1 /* $OpenBSD: auth.c,v 1.160 2023/03/05 05:34:09 dtucker Exp $ */
2 /*
3 * Copyright (c) 2000 Markus Friedl. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26 #include <sys/types.h>
27 #include <sys/stat.h>
28 #include <sys/socket.h>
29 #include <sys/wait.h>
30
31 #include <stdlib.h>
32 #include <errno.h>
33 #include <fcntl.h>
34 #include <login_cap.h>
35 #include <paths.h>
36 #include <pwd.h>
37 #include <stdarg.h>
38 #include <stdio.h>
39 #include <string.h>
40 #include <unistd.h>
41 #include <limits.h>
42 #include <netdb.h>
43 #include <time.h>
44
45 #include "xmalloc.h"
46 #include "match.h"
47 #include "groupaccess.h"
48 #include "log.h"
49 #include "sshbuf.h"
50 #include "misc.h"
51 #include "servconf.h"
52 #include "sshkey.h"
53 #include "hostfile.h"
54 #include "auth.h"
55 #include "auth-options.h"
56 #include "canohost.h"
57 #include "uidswap.h"
58 #include "packet.h"
59 #ifdef GSSAPI
60 #include "ssh-gss.h"
61 #endif
62 #include "authfile.h"
63 #include "monitor_wrap.h"
64 #include "ssherr.h"
65 #include "channels.h"
66
67 /* import */
68 extern ServerOptions options;
69 extern struct include_list includes;
70 extern int use_privsep;
71 extern struct sshauthopt *auth_opts;
72
73 /* Debugging messages */
74 static struct sshbuf *auth_debug;
75
76 /*
77 * Check if the user is allowed to log in via ssh. If user is listed
78 * in DenyUsers or one of user's groups is listed in DenyGroups, false
79 * will be returned. If AllowUsers isn't empty and user isn't listed
80 * there, or if AllowGroups isn't empty and one of user's groups isn't
81 * listed there, false will be returned.
82 * If the user's shell is not executable, false will be returned.
83 * Otherwise true is returned.
84 */
85 int
allowed_user(struct ssh * ssh,struct passwd * pw)86 allowed_user(struct ssh *ssh, struct passwd * pw)
87 {
88 struct stat st;
89 const char *hostname = NULL, *ipaddr = NULL;
90 int r;
91 u_int i;
92
93 /* Shouldn't be called if pw is NULL, but better safe than sorry... */
94 if (!pw || !pw->pw_name)
95 return 0;
96
97 /*
98 * Deny if shell does not exist or is not executable unless we
99 * are chrooting.
100 */
101 if (options.chroot_directory == NULL ||
102 strcasecmp(options.chroot_directory, "none") == 0) {
103 char *shell = xstrdup((pw->pw_shell[0] == '\0') ?
104 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */
105
106 if (stat(shell, &st) == -1) {
107 logit("User %.100s not allowed because shell %.100s "
108 "does not exist", pw->pw_name, shell);
109 free(shell);
110 return 0;
111 }
112 if (S_ISREG(st.st_mode) == 0 ||
113 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
114 logit("User %.100s not allowed because shell %.100s "
115 "is not executable", pw->pw_name, shell);
116 free(shell);
117 return 0;
118 }
119 free(shell);
120 }
121
122 if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
123 options.num_deny_groups > 0 || options.num_allow_groups > 0) {
124 hostname = auth_get_canonical_hostname(ssh, options.use_dns);
125 ipaddr = ssh_remote_ipaddr(ssh);
126 }
127
128 /* Return false if user is listed in DenyUsers */
129 if (options.num_deny_users > 0) {
130 for (i = 0; i < options.num_deny_users; i++) {
131 r = match_user(pw->pw_name, hostname, ipaddr,
132 options.deny_users[i]);
133 if (r < 0) {
134 fatal("Invalid DenyUsers pattern \"%.100s\"",
135 options.deny_users[i]);
136 } else if (r != 0) {
137 logit("User %.100s from %.100s not allowed "
138 "because listed in DenyUsers",
139 pw->pw_name, hostname);
140 return 0;
141 }
142 }
143 }
144 /* Return false if AllowUsers isn't empty and user isn't listed there */
145 if (options.num_allow_users > 0) {
146 for (i = 0; i < options.num_allow_users; i++) {
147 r = match_user(pw->pw_name, hostname, ipaddr,
148 options.allow_users[i]);
149 if (r < 0) {
150 fatal("Invalid AllowUsers pattern \"%.100s\"",
151 options.allow_users[i]);
152 } else if (r == 1)
153 break;
154 }
155 /* i < options.num_allow_users iff we break for loop */
156 if (i >= options.num_allow_users) {
157 logit("User %.100s from %.100s not allowed because "
158 "not listed in AllowUsers", pw->pw_name, hostname);
159 return 0;
160 }
161 }
162 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
163 /* Get the user's group access list (primary and supplementary) */
164 if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
165 logit("User %.100s from %.100s not allowed because "
166 "not in any group", pw->pw_name, hostname);
167 return 0;
168 }
169
170 /* Return false if one of user's groups is listed in DenyGroups */
171 if (options.num_deny_groups > 0)
172 if (ga_match(options.deny_groups,
173 options.num_deny_groups)) {
174 ga_free();
175 logit("User %.100s from %.100s not allowed "
176 "because a group is listed in DenyGroups",
177 pw->pw_name, hostname);
178 return 0;
179 }
180 /*
181 * Return false if AllowGroups isn't empty and one of user's groups
182 * isn't listed there
183 */
184 if (options.num_allow_groups > 0)
185 if (!ga_match(options.allow_groups,
186 options.num_allow_groups)) {
187 ga_free();
188 logit("User %.100s from %.100s not allowed "
189 "because none of user's groups are listed "
190 "in AllowGroups", pw->pw_name, hostname);
191 return 0;
192 }
193 ga_free();
194 }
195 /* We found no reason not to let this user try to log on... */
196 return 1;
197 }
198
199 /*
200 * Formats any key left in authctxt->auth_method_key for inclusion in
201 * auth_log()'s message. Also includes authxtct->auth_method_info if present.
202 */
203 static char *
format_method_key(Authctxt * authctxt)204 format_method_key(Authctxt *authctxt)
205 {
206 const struct sshkey *key = authctxt->auth_method_key;
207 const char *methinfo = authctxt->auth_method_info;
208 char *fp, *cafp, *ret = NULL;
209
210 if (key == NULL)
211 return NULL;
212
213 if (sshkey_is_cert(key)) {
214 fp = sshkey_fingerprint(key,
215 options.fingerprint_hash, SSH_FP_DEFAULT);
216 cafp = sshkey_fingerprint(key->cert->signature_key,
217 options.fingerprint_hash, SSH_FP_DEFAULT);
218 xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s",
219 sshkey_type(key), fp == NULL ? "(null)" : fp,
220 key->cert->key_id,
221 (unsigned long long)key->cert->serial,
222 sshkey_type(key->cert->signature_key),
223 cafp == NULL ? "(null)" : cafp,
224 methinfo == NULL ? "" : ", ",
225 methinfo == NULL ? "" : methinfo);
226 free(fp);
227 free(cafp);
228 } else {
229 fp = sshkey_fingerprint(key, options.fingerprint_hash,
230 SSH_FP_DEFAULT);
231 xasprintf(&ret, "%s %s%s%s", sshkey_type(key),
232 fp == NULL ? "(null)" : fp,
233 methinfo == NULL ? "" : ", ",
234 methinfo == NULL ? "" : methinfo);
235 free(fp);
236 }
237 return ret;
238 }
239
240 void
auth_log(struct ssh * ssh,int authenticated,int partial,const char * method,const char * submethod)241 auth_log(struct ssh *ssh, int authenticated, int partial,
242 const char *method, const char *submethod)
243 {
244 Authctxt *authctxt = (Authctxt *)ssh->authctxt;
245 int level = SYSLOG_LEVEL_VERBOSE;
246 const char *authmsg;
247 char *extra = NULL;
248
249 if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
250 return;
251
252 /* Raise logging level */
253 if (authenticated == 1 ||
254 !authctxt->valid ||
255 authctxt->failures >= options.max_authtries / 2 ||
256 strcmp(method, "password") == 0)
257 level = SYSLOG_LEVEL_INFO;
258
259 if (authctxt->postponed)
260 authmsg = "Postponed";
261 else if (partial)
262 authmsg = "Partial";
263 else
264 authmsg = authenticated ? "Accepted" : "Failed";
265
266 if ((extra = format_method_key(authctxt)) == NULL) {
267 if (authctxt->auth_method_info != NULL)
268 extra = xstrdup(authctxt->auth_method_info);
269 }
270
271 do_log2(level, "%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s",
272 authmsg,
273 method,
274 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
275 authctxt->valid ? "" : "invalid user ",
276 authctxt->user,
277 ssh_remote_ipaddr(ssh),
278 ssh_remote_port(ssh),
279 extra != NULL ? ": " : "",
280 extra != NULL ? extra : "");
281
282 free(extra);
283 }
284
285 void
auth_maxtries_exceeded(struct ssh * ssh)286 auth_maxtries_exceeded(struct ssh *ssh)
287 {
288 Authctxt *authctxt = (Authctxt *)ssh->authctxt;
289
290 error("maximum authentication attempts exceeded for "
291 "%s%.100s from %.200s port %d ssh2",
292 authctxt->valid ? "" : "invalid user ",
293 authctxt->user,
294 ssh_remote_ipaddr(ssh),
295 ssh_remote_port(ssh));
296 ssh_packet_disconnect(ssh, "Too many authentication failures");
297 /* NOTREACHED */
298 }
299
300 /*
301 * Check whether root logins are disallowed.
302 */
303 int
auth_root_allowed(struct ssh * ssh,const char * method)304 auth_root_allowed(struct ssh *ssh, const char *method)
305 {
306 switch (options.permit_root_login) {
307 case PERMIT_YES:
308 return 1;
309 case PERMIT_NO_PASSWD:
310 if (strcmp(method, "publickey") == 0 ||
311 strcmp(method, "hostbased") == 0 ||
312 strcmp(method, "gssapi-with-mic") == 0)
313 return 1;
314 break;
315 case PERMIT_FORCED_ONLY:
316 if (auth_opts->force_command != NULL) {
317 logit("Root login accepted for forced command.");
318 return 1;
319 }
320 break;
321 }
322 logit("ROOT LOGIN REFUSED FROM %.200s port %d",
323 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
324 return 0;
325 }
326
327
328 /*
329 * Given a template and a passwd structure, build a filename
330 * by substituting % tokenised options. Currently, %% becomes '%',
331 * %h becomes the home directory and %u the username.
332 *
333 * This returns a buffer allocated by xmalloc.
334 */
335 char *
expand_authorized_keys(const char * filename,struct passwd * pw)336 expand_authorized_keys(const char *filename, struct passwd *pw)
337 {
338 char *file, uidstr[32], ret[PATH_MAX];
339 int i;
340
341 snprintf(uidstr, sizeof(uidstr), "%llu",
342 (unsigned long long)pw->pw_uid);
343 file = percent_expand(filename, "h", pw->pw_dir,
344 "u", pw->pw_name, "U", uidstr, (char *)NULL);
345
346 /*
347 * Ensure that filename starts anchored. If not, be backward
348 * compatible and prepend the '%h/'
349 */
350 if (path_absolute(file))
351 return (file);
352
353 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
354 if (i < 0 || (size_t)i >= sizeof(ret))
355 fatal("expand_authorized_keys: path too long");
356 free(file);
357 return (xstrdup(ret));
358 }
359
360 char *
authorized_principals_file(struct passwd * pw)361 authorized_principals_file(struct passwd *pw)
362 {
363 if (options.authorized_principals_file == NULL)
364 return NULL;
365 return expand_authorized_keys(options.authorized_principals_file, pw);
366 }
367
368 /* return ok if key exists in sysfile or userfile */
369 HostStatus
check_key_in_hostfiles(struct passwd * pw,struct sshkey * key,const char * host,const char * sysfile,const char * userfile)370 check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host,
371 const char *sysfile, const char *userfile)
372 {
373 char *user_hostfile;
374 struct stat st;
375 HostStatus host_status;
376 struct hostkeys *hostkeys;
377 const struct hostkey_entry *found;
378
379 hostkeys = init_hostkeys();
380 load_hostkeys(hostkeys, host, sysfile, 0);
381 if (userfile != NULL) {
382 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
383 if (options.strict_modes &&
384 (stat(user_hostfile, &st) == 0) &&
385 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
386 (st.st_mode & 022) != 0)) {
387 logit("Authentication refused for %.100s: "
388 "bad owner or modes for %.200s",
389 pw->pw_name, user_hostfile);
390 auth_debug_add("Ignored %.200s: bad ownership or modes",
391 user_hostfile);
392 } else {
393 temporarily_use_uid(pw);
394 load_hostkeys(hostkeys, host, user_hostfile, 0);
395 restore_uid();
396 }
397 free(user_hostfile);
398 }
399 host_status = check_key_in_hostkeys(hostkeys, key, &found);
400 if (host_status == HOST_REVOKED)
401 error("WARNING: revoked key for %s attempted authentication",
402 host);
403 else if (host_status == HOST_OK)
404 debug_f("key for %s found at %s:%ld",
405 found->host, found->file, found->line);
406 else
407 debug_f("key for host %s not found", host);
408
409 free_hostkeys(hostkeys);
410
411 return host_status;
412 }
413
414 struct passwd *
getpwnamallow(struct ssh * ssh,const char * user)415 getpwnamallow(struct ssh *ssh, const char *user)
416 {
417 extern login_cap_t *lc;
418 auth_session_t *as;
419 struct passwd *pw;
420 struct connection_info *ci;
421 u_int i;
422
423 ci = get_connection_info(ssh, 1, options.use_dns);
424 ci->user = user;
425 parse_server_match_config(&options, &includes, ci);
426 log_change_level(options.log_level);
427 log_verbose_reset();
428 for (i = 0; i < options.num_log_verbose; i++)
429 log_verbose_add(options.log_verbose[i]);
430 process_permitopen(ssh, &options);
431
432 pw = getpwnam(user);
433 if (pw == NULL) {
434 logit("Invalid user %.100s from %.100s port %d",
435 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
436 return (NULL);
437 }
438 if (!allowed_user(ssh, pw))
439 return (NULL);
440 if ((lc = login_getclass(pw->pw_class)) == NULL) {
441 debug("unable to get login class: %s", user);
442 return (NULL);
443 }
444 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
445 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
446 debug("Approval failure for %s", user);
447 pw = NULL;
448 }
449 if (as != NULL)
450 auth_close(as);
451 if (pw != NULL)
452 return (pwcopy(pw));
453 return (NULL);
454 }
455
456 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
457 int
auth_key_is_revoked(struct sshkey * key)458 auth_key_is_revoked(struct sshkey *key)
459 {
460 char *fp = NULL;
461 int r;
462
463 if (options.revoked_keys_file == NULL)
464 return 0;
465 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
466 SSH_FP_DEFAULT)) == NULL) {
467 r = SSH_ERR_ALLOC_FAIL;
468 error_fr(r, "fingerprint key");
469 goto out;
470 }
471
472 r = sshkey_check_revoked(key, options.revoked_keys_file);
473 switch (r) {
474 case 0:
475 break; /* not revoked */
476 case SSH_ERR_KEY_REVOKED:
477 error("Authentication key %s %s revoked by file %s",
478 sshkey_type(key), fp, options.revoked_keys_file);
479 goto out;
480 default:
481 error_r(r, "Error checking authentication key %s %s in "
482 "revoked keys file %s", sshkey_type(key), fp,
483 options.revoked_keys_file);
484 goto out;
485 }
486
487 /* Success */
488 r = 0;
489
490 out:
491 free(fp);
492 return r == 0 ? 0 : 1;
493 }
494
495 void
auth_debug_add(const char * fmt,...)496 auth_debug_add(const char *fmt,...)
497 {
498 char buf[1024];
499 va_list args;
500 int r;
501
502 va_start(args, fmt);
503 vsnprintf(buf, sizeof(buf), fmt, args);
504 va_end(args);
505 debug3("%s", buf);
506 if (auth_debug != NULL)
507 if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0)
508 fatal_fr(r, "sshbuf_put_cstring");
509 }
510
511 void
auth_debug_send(struct ssh * ssh)512 auth_debug_send(struct ssh *ssh)
513 {
514 char *msg;
515 int r;
516
517 if (auth_debug == NULL)
518 return;
519 while (sshbuf_len(auth_debug) != 0) {
520 if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0)
521 fatal_fr(r, "sshbuf_get_cstring");
522 ssh_packet_send_debug(ssh, "%s", msg);
523 free(msg);
524 }
525 }
526
527 void
auth_debug_reset(void)528 auth_debug_reset(void)
529 {
530 if (auth_debug != NULL)
531 sshbuf_reset(auth_debug);
532 else if ((auth_debug = sshbuf_new()) == NULL)
533 fatal_f("sshbuf_new failed");
534 }
535
536 struct passwd *
fakepw(void)537 fakepw(void)
538 {
539 static int done = 0;
540 static struct passwd fake;
541 const char hashchars[] = "./ABCDEFGHIJKLMNOPQRSTUVWXYZ"
542 "abcdefghijklmnopqrstuvwxyz0123456789"; /* from bcrypt.c */
543 char *cp;
544
545 if (done)
546 return (&fake);
547
548 memset(&fake, 0, sizeof(fake));
549 fake.pw_name = "NOUSER";
550 fake.pw_passwd = xstrdup("$2a$10$"
551 "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx");
552 for (cp = fake.pw_passwd + 7; *cp != '\0'; cp++)
553 *cp = hashchars[arc4random_uniform(sizeof(hashchars) - 1)];
554 fake.pw_gecos = "NOUSER";
555 fake.pw_uid = (uid_t)-1;
556 fake.pw_gid = (gid_t)-1;
557 fake.pw_class = "";
558 fake.pw_dir = "/nonexist";
559 fake.pw_shell = "/nonexist";
560 done = 1;
561
562 return (&fake);
563 }
564
565 /*
566 * Returns the remote DNS hostname as a string. The returned string must not
567 * be freed. NB. this will usually trigger a DNS query the first time it is
568 * called.
569 * This function does additional checks on the hostname to mitigate some
570 * attacks on based on conflation of hostnames and IP addresses.
571 */
572
573 static char *
remote_hostname(struct ssh * ssh)574 remote_hostname(struct ssh *ssh)
575 {
576 struct sockaddr_storage from;
577 socklen_t fromlen;
578 struct addrinfo hints, *ai, *aitop;
579 char name[NI_MAXHOST], ntop2[NI_MAXHOST];
580 const char *ntop = ssh_remote_ipaddr(ssh);
581
582 /* Get IP address of client. */
583 fromlen = sizeof(from);
584 memset(&from, 0, sizeof(from));
585 if (getpeername(ssh_packet_get_connection_in(ssh),
586 (struct sockaddr *)&from, &fromlen) == -1) {
587 debug("getpeername failed: %.100s", strerror(errno));
588 return xstrdup(ntop);
589 }
590
591 debug3("Trying to reverse map address %.100s.", ntop);
592 /* Map the IP address to a host name. */
593 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
594 NULL, 0, NI_NAMEREQD) != 0) {
595 /* Host name not found. Use ip address. */
596 return xstrdup(ntop);
597 }
598
599 /*
600 * if reverse lookup result looks like a numeric hostname,
601 * someone is trying to trick us by PTR record like following:
602 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5
603 */
604 memset(&hints, 0, sizeof(hints));
605 hints.ai_socktype = SOCK_DGRAM; /*dummy*/
606 hints.ai_flags = AI_NUMERICHOST;
607 if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
608 logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
609 name, ntop);
610 freeaddrinfo(ai);
611 return xstrdup(ntop);
612 }
613
614 /* Names are stored in lowercase. */
615 lowercase(name);
616
617 /*
618 * Map it back to an IP address and check that the given
619 * address actually is an address of this host. This is
620 * necessary because anyone with access to a name server can
621 * define arbitrary names for an IP address. Mapping from
622 * name to IP address can be trusted better (but can still be
623 * fooled if the intruder has access to the name server of
624 * the domain).
625 */
626 memset(&hints, 0, sizeof(hints));
627 hints.ai_family = from.ss_family;
628 hints.ai_socktype = SOCK_STREAM;
629 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
630 logit("reverse mapping checking getaddrinfo for %.700s "
631 "[%s] failed.", name, ntop);
632 return xstrdup(ntop);
633 }
634 /* Look for the address from the list of addresses. */
635 for (ai = aitop; ai; ai = ai->ai_next) {
636 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
637 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
638 (strcmp(ntop, ntop2) == 0))
639 break;
640 }
641 freeaddrinfo(aitop);
642 /* If we reached the end of the list, the address was not there. */
643 if (ai == NULL) {
644 /* Address not found for the host name. */
645 logit("Address %.100s maps to %.600s, but this does not "
646 "map back to the address.", ntop, name);
647 return xstrdup(ntop);
648 }
649 return xstrdup(name);
650 }
651
652 /*
653 * Return the canonical name of the host in the other side of the current
654 * connection. The host name is cached, so it is efficient to call this
655 * several times.
656 */
657
658 const char *
auth_get_canonical_hostname(struct ssh * ssh,int use_dns)659 auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
660 {
661 static char *dnsname;
662
663 if (!use_dns)
664 return ssh_remote_ipaddr(ssh);
665 else if (dnsname != NULL)
666 return dnsname;
667 else {
668 dnsname = remote_hostname(ssh);
669 return dnsname;
670 }
671 }
672
673 /* These functions link key/cert options to the auth framework */
674
675 /* Log sshauthopt options locally and (optionally) for remote transmission */
676 void
auth_log_authopts(const char * loc,const struct sshauthopt * opts,int do_remote)677 auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote)
678 {
679 int do_env = options.permit_user_env && opts->nenv > 0;
680 int do_permitopen = opts->npermitopen > 0 &&
681 (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0;
682 int do_permitlisten = opts->npermitlisten > 0 &&
683 (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0;
684 size_t i;
685 char msg[1024], buf[64];
686
687 snprintf(buf, sizeof(buf), "%d", opts->force_tun_device);
688 /* Try to keep this alphabetically sorted */
689 snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
690 opts->permit_agent_forwarding_flag ? " agent-forwarding" : "",
691 opts->force_command == NULL ? "" : " command",
692 do_env ? " environment" : "",
693 opts->valid_before == 0 ? "" : "expires",
694 opts->no_require_user_presence ? " no-touch-required" : "",
695 do_permitopen ? " permitopen" : "",
696 do_permitlisten ? " permitlisten" : "",
697 opts->permit_port_forwarding_flag ? " port-forwarding" : "",
698 opts->cert_principals == NULL ? "" : " principals",
699 opts->permit_pty_flag ? " pty" : "",
700 opts->require_verify ? " uv" : "",
701 opts->force_tun_device == -1 ? "" : " tun=",
702 opts->force_tun_device == -1 ? "" : buf,
703 opts->permit_user_rc ? " user-rc" : "",
704 opts->permit_x11_forwarding_flag ? " x11-forwarding" : "");
705
706 debug("%s: %s", loc, msg);
707 if (do_remote)
708 auth_debug_add("%s: %s", loc, msg);
709
710 if (options.permit_user_env) {
711 for (i = 0; i < opts->nenv; i++) {
712 debug("%s: environment: %s", loc, opts->env[i]);
713 if (do_remote) {
714 auth_debug_add("%s: environment: %s",
715 loc, opts->env[i]);
716 }
717 }
718 }
719
720 /* Go into a little more details for the local logs. */
721 if (opts->valid_before != 0) {
722 format_absolute_time(opts->valid_before, buf, sizeof(buf));
723 debug("%s: expires at %s", loc, buf);
724 }
725 if (opts->cert_principals != NULL) {
726 debug("%s: authorized principals: \"%s\"",
727 loc, opts->cert_principals);
728 }
729 if (opts->force_command != NULL)
730 debug("%s: forced command: \"%s\"", loc, opts->force_command);
731 if (do_permitopen) {
732 for (i = 0; i < opts->npermitopen; i++) {
733 debug("%s: permitted open: %s",
734 loc, opts->permitopen[i]);
735 }
736 }
737 if (do_permitlisten) {
738 for (i = 0; i < opts->npermitlisten; i++) {
739 debug("%s: permitted listen: %s",
740 loc, opts->permitlisten[i]);
741 }
742 }
743 }
744
745 /* Activate a new set of key/cert options; merging with what is there. */
746 int
auth_activate_options(struct ssh * ssh,struct sshauthopt * opts)747 auth_activate_options(struct ssh *ssh, struct sshauthopt *opts)
748 {
749 struct sshauthopt *old = auth_opts;
750 const char *emsg = NULL;
751
752 debug_f("setting new authentication options");
753 if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) {
754 error("Inconsistent authentication options: %s", emsg);
755 return -1;
756 }
757 return 0;
758 }
759
760 /* Disable forwarding, etc for the session */
761 void
auth_restrict_session(struct ssh * ssh)762 auth_restrict_session(struct ssh *ssh)
763 {
764 struct sshauthopt *restricted;
765
766 debug_f("restricting session");
767
768 /* A blank sshauthopt defaults to permitting nothing */
769 if ((restricted = sshauthopt_new()) == NULL)
770 fatal_f("sshauthopt_new failed");
771 restricted->permit_pty_flag = 1;
772 restricted->restricted = 1;
773
774 if (auth_activate_options(ssh, restricted) != 0)
775 fatal_f("failed to restrict session");
776 sshauthopt_free(restricted);
777 }
778