xref: /openssh-portable/auth.c (revision 0fa174eb)
1 /* $OpenBSD: auth.c,v 1.136 2019/01/19 21:31:32 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 <errno.h>
36 #include <fcntl.h>
37 #ifdef HAVE_PATHS_H
38 # include <paths.h>
39 #endif
40 #include <pwd.h>
41 #ifdef HAVE_LOGIN_H
42 #include <login.h>
43 #endif
44 #ifdef USE_SHADOW
45 #include <shadow.h>
46 #endif
47 #include <stdarg.h>
48 #include <stdio.h>
49 #include <string.h>
50 #include <unistd.h>
51 #include <limits.h>
52 #include <netdb.h>
53 #include <time.h>
54 
55 #include "xmalloc.h"
56 #include "match.h"
57 #include "groupaccess.h"
58 #include "log.h"
59 #include "sshbuf.h"
60 #include "misc.h"
61 #include "servconf.h"
62 #include "sshkey.h"
63 #include "hostfile.h"
64 #include "auth.h"
65 #include "auth-options.h"
66 #include "canohost.h"
67 #include "uidswap.h"
68 #include "packet.h"
69 #include "loginrec.h"
70 #ifdef GSSAPI
71 #include "ssh-gss.h"
72 #endif
73 #include "authfile.h"
74 #include "monitor_wrap.h"
75 #include "authfile.h"
76 #include "ssherr.h"
77 #include "compat.h"
78 #include "channels.h"
79 
80 #include "opacket.h" /* XXX */
81 extern struct ssh *active_state; /* XXX */
82 
83 /* import */
84 extern ServerOptions options;
85 extern int use_privsep;
86 extern struct sshbuf *loginmsg;
87 extern struct passwd *privsep_pw;
88 extern struct sshauthopt *auth_opts;
89 
90 /* Debugging messages */
91 static struct sshbuf *auth_debug;
92 
93 /*
94  * Check if the user is allowed to log in via ssh. If user is listed
95  * in DenyUsers or one of user's groups is listed in DenyGroups, false
96  * will be returned. If AllowUsers isn't empty and user isn't listed
97  * there, or if AllowGroups isn't empty and one of user's groups isn't
98  * listed there, false will be returned.
99  * If the user's shell is not executable, false will be returned.
100  * Otherwise true is returned.
101  */
102 int
103 allowed_user(struct passwd * pw)
104 {
105 	struct ssh *ssh = active_state; /* XXX */
106 	struct stat st;
107 	const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL;
108 	u_int i;
109 	int r;
110 #ifdef USE_SHADOW
111 	struct spwd *spw = NULL;
112 #endif
113 
114 	/* Shouldn't be called if pw is NULL, but better safe than sorry... */
115 	if (!pw || !pw->pw_name)
116 		return 0;
117 
118 #ifdef USE_SHADOW
119 	if (!options.use_pam)
120 		spw = getspnam(pw->pw_name);
121 #ifdef HAS_SHADOW_EXPIRE
122 	if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw))
123 		return 0;
124 #endif /* HAS_SHADOW_EXPIRE */
125 #endif /* USE_SHADOW */
126 
127 	/* grab passwd field for locked account check */
128 	passwd = pw->pw_passwd;
129 #ifdef USE_SHADOW
130 	if (spw != NULL)
131 #ifdef USE_LIBIAF
132 		passwd = get_iaf_password(pw);
133 #else
134 		passwd = spw->sp_pwdp;
135 #endif /* USE_LIBIAF */
136 #endif
137 
138 	/* check for locked account */
139 	if (!options.use_pam && passwd && *passwd) {
140 		int locked = 0;
141 
142 #ifdef LOCKED_PASSWD_STRING
143 		if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0)
144 			 locked = 1;
145 #endif
146 #ifdef LOCKED_PASSWD_PREFIX
147 		if (strncmp(passwd, LOCKED_PASSWD_PREFIX,
148 		    strlen(LOCKED_PASSWD_PREFIX)) == 0)
149 			 locked = 1;
150 #endif
151 #ifdef LOCKED_PASSWD_SUBSTR
152 		if (strstr(passwd, LOCKED_PASSWD_SUBSTR))
153 			locked = 1;
154 #endif
155 #ifdef USE_LIBIAF
156 		free((void *) passwd);
157 #endif /* USE_LIBIAF */
158 		if (locked) {
159 			logit("User %.100s not allowed because account is locked",
160 			    pw->pw_name);
161 			return 0;
162 		}
163 	}
164 
165 	/*
166 	 * Deny if shell does not exist or is not executable unless we
167 	 * are chrooting.
168 	 */
169 	if (options.chroot_directory == NULL ||
170 	    strcasecmp(options.chroot_directory, "none") == 0) {
171 		char *shell = xstrdup((pw->pw_shell[0] == '\0') ?
172 		    _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */
173 
174 		if (stat(shell, &st) != 0) {
175 			logit("User %.100s not allowed because shell %.100s "
176 			    "does not exist", pw->pw_name, shell);
177 			free(shell);
178 			return 0;
179 		}
180 		if (S_ISREG(st.st_mode) == 0 ||
181 		    (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) {
182 			logit("User %.100s not allowed because shell %.100s "
183 			    "is not executable", pw->pw_name, shell);
184 			free(shell);
185 			return 0;
186 		}
187 		free(shell);
188 	}
189 
190 	if (options.num_deny_users > 0 || options.num_allow_users > 0 ||
191 	    options.num_deny_groups > 0 || options.num_allow_groups > 0) {
192 		hostname = auth_get_canonical_hostname(ssh, options.use_dns);
193 		ipaddr = ssh_remote_ipaddr(ssh);
194 	}
195 
196 	/* Return false if user is listed in DenyUsers */
197 	if (options.num_deny_users > 0) {
198 		for (i = 0; i < options.num_deny_users; i++) {
199 			r = match_user(pw->pw_name, hostname, ipaddr,
200 			    options.deny_users[i]);
201 			if (r < 0) {
202 				fatal("Invalid DenyUsers pattern \"%.100s\"",
203 				    options.deny_users[i]);
204 			} else if (r != 0) {
205 				logit("User %.100s from %.100s not allowed "
206 				    "because listed in DenyUsers",
207 				    pw->pw_name, hostname);
208 				return 0;
209 			}
210 		}
211 	}
212 	/* Return false if AllowUsers isn't empty and user isn't listed there */
213 	if (options.num_allow_users > 0) {
214 		for (i = 0; i < options.num_allow_users; i++) {
215 			r = match_user(pw->pw_name, hostname, ipaddr,
216 			    options.allow_users[i]);
217 			if (r < 0) {
218 				fatal("Invalid AllowUsers pattern \"%.100s\"",
219 				    options.allow_users[i]);
220 			} else if (r == 1)
221 				break;
222 		}
223 		/* i < options.num_allow_users iff we break for loop */
224 		if (i >= options.num_allow_users) {
225 			logit("User %.100s from %.100s not allowed because "
226 			    "not listed in AllowUsers", pw->pw_name, hostname);
227 			return 0;
228 		}
229 	}
230 	if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
231 		/* Get the user's group access list (primary and supplementary) */
232 		if (ga_init(pw->pw_name, pw->pw_gid) == 0) {
233 			logit("User %.100s from %.100s not allowed because "
234 			    "not in any group", pw->pw_name, hostname);
235 			return 0;
236 		}
237 
238 		/* Return false if one of user's groups is listed in DenyGroups */
239 		if (options.num_deny_groups > 0)
240 			if (ga_match(options.deny_groups,
241 			    options.num_deny_groups)) {
242 				ga_free();
243 				logit("User %.100s from %.100s not allowed "
244 				    "because a group is listed in DenyGroups",
245 				    pw->pw_name, hostname);
246 				return 0;
247 			}
248 		/*
249 		 * Return false if AllowGroups isn't empty and one of user's groups
250 		 * isn't listed there
251 		 */
252 		if (options.num_allow_groups > 0)
253 			if (!ga_match(options.allow_groups,
254 			    options.num_allow_groups)) {
255 				ga_free();
256 				logit("User %.100s from %.100s not allowed "
257 				    "because none of user's groups are listed "
258 				    "in AllowGroups", pw->pw_name, hostname);
259 				return 0;
260 			}
261 		ga_free();
262 	}
263 
264 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER
265 	if (!sys_auth_allowed_user(pw, loginmsg))
266 		return 0;
267 #endif
268 
269 	/* We found no reason not to let this user try to log on... */
270 	return 1;
271 }
272 
273 /*
274  * Formats any key left in authctxt->auth_method_key for inclusion in
275  * auth_log()'s message. Also includes authxtct->auth_method_info if present.
276  */
277 static char *
278 format_method_key(Authctxt *authctxt)
279 {
280 	const struct sshkey *key = authctxt->auth_method_key;
281 	const char *methinfo = authctxt->auth_method_info;
282 	char *fp, *cafp, *ret = NULL;
283 
284 	if (key == NULL)
285 		return NULL;
286 
287 	if (sshkey_is_cert(key)) {
288 		fp = sshkey_fingerprint(key,
289 		    options.fingerprint_hash, SSH_FP_DEFAULT);
290 		cafp = sshkey_fingerprint(key->cert->signature_key,
291 		    options.fingerprint_hash, SSH_FP_DEFAULT);
292 		xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s",
293 		    sshkey_type(key), fp == NULL ? "(null)" : fp,
294 		    key->cert->key_id,
295 		    (unsigned long long)key->cert->serial,
296 		    sshkey_type(key->cert->signature_key),
297 		    cafp == NULL ? "(null)" : cafp,
298 		    methinfo == NULL ? "" : ", ",
299 		    methinfo == NULL ? "" : methinfo);
300 		free(fp);
301 		free(cafp);
302 	} else {
303 		fp = sshkey_fingerprint(key, options.fingerprint_hash,
304 		    SSH_FP_DEFAULT);
305 		xasprintf(&ret, "%s %s%s%s", sshkey_type(key),
306 		    fp == NULL ? "(null)" : fp,
307 		    methinfo == NULL ? "" : ", ",
308 		    methinfo == NULL ? "" : methinfo);
309 		free(fp);
310 	}
311 	return ret;
312 }
313 
314 void
315 auth_log(Authctxt *authctxt, int authenticated, int partial,
316     const char *method, const char *submethod)
317 {
318 	struct ssh *ssh = active_state; /* XXX */
319 	int level = SYSLOG_LEVEL_VERBOSE;
320 	const char *authmsg;
321 	char *extra = NULL;
322 
323 	if (use_privsep && !mm_is_monitor() && !authctxt->postponed)
324 		return;
325 
326 	/* Raise logging level */
327 	if (authenticated == 1 ||
328 	    !authctxt->valid ||
329 	    authctxt->failures >= options.max_authtries / 2 ||
330 	    strcmp(method, "password") == 0)
331 		level = SYSLOG_LEVEL_INFO;
332 
333 	if (authctxt->postponed)
334 		authmsg = "Postponed";
335 	else if (partial)
336 		authmsg = "Partial";
337 	else
338 		authmsg = authenticated ? "Accepted" : "Failed";
339 
340 	if ((extra = format_method_key(authctxt)) == NULL) {
341 		if (authctxt->auth_method_info != NULL)
342 			extra = xstrdup(authctxt->auth_method_info);
343 	}
344 
345 	do_log2(level, "%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s",
346 	    authmsg,
347 	    method,
348 	    submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod,
349 	    authctxt->valid ? "" : "invalid user ",
350 	    authctxt->user,
351 	    ssh_remote_ipaddr(ssh),
352 	    ssh_remote_port(ssh),
353 	    extra != NULL ? ": " : "",
354 	    extra != NULL ? extra : "");
355 
356 	free(extra);
357 
358 #ifdef CUSTOM_FAILED_LOGIN
359 	if (authenticated == 0 && !authctxt->postponed &&
360 	    (strcmp(method, "password") == 0 ||
361 	    strncmp(method, "keyboard-interactive", 20) == 0 ||
362 	    strcmp(method, "challenge-response") == 0))
363 		record_failed_login(authctxt->user,
364 		    auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
365 # ifdef WITH_AIXAUTHENTICATE
366 	if (authenticated)
367 		sys_auth_record_login(authctxt->user,
368 		    auth_get_canonical_hostname(ssh, options.use_dns), "ssh",
369 		    loginmsg);
370 # endif
371 #endif
372 #ifdef SSH_AUDIT_EVENTS
373 	if (authenticated == 0 && !authctxt->postponed)
374 		audit_event(audit_classify_auth(method));
375 #endif
376 }
377 
378 
379 void
380 auth_maxtries_exceeded(Authctxt *authctxt)
381 {
382 	struct ssh *ssh = active_state; /* XXX */
383 
384 	error("maximum authentication attempts exceeded for "
385 	    "%s%.100s from %.200s port %d ssh2",
386 	    authctxt->valid ? "" : "invalid user ",
387 	    authctxt->user,
388 	    ssh_remote_ipaddr(ssh),
389 	    ssh_remote_port(ssh));
390 	packet_disconnect("Too many authentication failures");
391 	/* NOTREACHED */
392 }
393 
394 /*
395  * Check whether root logins are disallowed.
396  */
397 int
398 auth_root_allowed(struct ssh *ssh, const char *method)
399 {
400 	switch (options.permit_root_login) {
401 	case PERMIT_YES:
402 		return 1;
403 	case PERMIT_NO_PASSWD:
404 		if (strcmp(method, "publickey") == 0 ||
405 		    strcmp(method, "hostbased") == 0 ||
406 		    strcmp(method, "gssapi-with-mic") == 0)
407 			return 1;
408 		break;
409 	case PERMIT_FORCED_ONLY:
410 		if (auth_opts->force_command != NULL) {
411 			logit("Root login accepted for forced command.");
412 			return 1;
413 		}
414 		break;
415 	}
416 	logit("ROOT LOGIN REFUSED FROM %.200s port %d",
417 	    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
418 	return 0;
419 }
420 
421 
422 /*
423  * Given a template and a passwd structure, build a filename
424  * by substituting % tokenised options. Currently, %% becomes '%',
425  * %h becomes the home directory and %u the username.
426  *
427  * This returns a buffer allocated by xmalloc.
428  */
429 char *
430 expand_authorized_keys(const char *filename, struct passwd *pw)
431 {
432 	char *file, uidstr[32], ret[PATH_MAX];
433 	int i;
434 
435 	snprintf(uidstr, sizeof(uidstr), "%llu",
436 	    (unsigned long long)pw->pw_uid);
437 	file = percent_expand(filename, "h", pw->pw_dir,
438 	    "u", pw->pw_name, "U", uidstr, (char *)NULL);
439 
440 	/*
441 	 * Ensure that filename starts anchored. If not, be backward
442 	 * compatible and prepend the '%h/'
443 	 */
444 	if (path_absolute(file))
445 		return (file);
446 
447 	i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file);
448 	if (i < 0 || (size_t)i >= sizeof(ret))
449 		fatal("expand_authorized_keys: path too long");
450 	free(file);
451 	return (xstrdup(ret));
452 }
453 
454 char *
455 authorized_principals_file(struct passwd *pw)
456 {
457 	if (options.authorized_principals_file == NULL)
458 		return NULL;
459 	return expand_authorized_keys(options.authorized_principals_file, pw);
460 }
461 
462 /* return ok if key exists in sysfile or userfile */
463 HostStatus
464 check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host,
465     const char *sysfile, const char *userfile)
466 {
467 	char *user_hostfile;
468 	struct stat st;
469 	HostStatus host_status;
470 	struct hostkeys *hostkeys;
471 	const struct hostkey_entry *found;
472 
473 	hostkeys = init_hostkeys();
474 	load_hostkeys(hostkeys, host, sysfile);
475 	if (userfile != NULL) {
476 		user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
477 		if (options.strict_modes &&
478 		    (stat(user_hostfile, &st) == 0) &&
479 		    ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
480 		    (st.st_mode & 022) != 0)) {
481 			logit("Authentication refused for %.100s: "
482 			    "bad owner or modes for %.200s",
483 			    pw->pw_name, user_hostfile);
484 			auth_debug_add("Ignored %.200s: bad ownership or modes",
485 			    user_hostfile);
486 		} else {
487 			temporarily_use_uid(pw);
488 			load_hostkeys(hostkeys, host, user_hostfile);
489 			restore_uid();
490 		}
491 		free(user_hostfile);
492 	}
493 	host_status = check_key_in_hostkeys(hostkeys, key, &found);
494 	if (host_status == HOST_REVOKED)
495 		error("WARNING: revoked key for %s attempted authentication",
496 		    found->host);
497 	else if (host_status == HOST_OK)
498 		debug("%s: key for %s found at %s:%ld", __func__,
499 		    found->host, found->file, found->line);
500 	else
501 		debug("%s: key for host %s not found", __func__, host);
502 
503 	free_hostkeys(hostkeys);
504 
505 	return host_status;
506 }
507 
508 static FILE *
509 auth_openfile(const char *file, struct passwd *pw, int strict_modes,
510     int log_missing, char *file_type)
511 {
512 	char line[1024];
513 	struct stat st;
514 	int fd;
515 	FILE *f;
516 
517 	if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) {
518 		if (log_missing || errno != ENOENT)
519 			debug("Could not open %s '%s': %s", file_type, file,
520 			   strerror(errno));
521 		return NULL;
522 	}
523 
524 	if (fstat(fd, &st) < 0) {
525 		close(fd);
526 		return NULL;
527 	}
528 	if (!S_ISREG(st.st_mode)) {
529 		logit("User %s %s %s is not a regular file",
530 		    pw->pw_name, file_type, file);
531 		close(fd);
532 		return NULL;
533 	}
534 	unset_nonblock(fd);
535 	if ((f = fdopen(fd, "r")) == NULL) {
536 		close(fd);
537 		return NULL;
538 	}
539 	if (strict_modes &&
540 	    safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) {
541 		fclose(f);
542 		logit("Authentication refused: %s", line);
543 		auth_debug_add("Ignored %s: %s", file_type, line);
544 		return NULL;
545 	}
546 
547 	return f;
548 }
549 
550 
551 FILE *
552 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes)
553 {
554 	return auth_openfile(file, pw, strict_modes, 1, "authorized keys");
555 }
556 
557 FILE *
558 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes)
559 {
560 	return auth_openfile(file, pw, strict_modes, 0,
561 	    "authorized principals");
562 }
563 
564 struct passwd *
565 getpwnamallow(const char *user)
566 {
567 	struct ssh *ssh = active_state; /* XXX */
568 #ifdef HAVE_LOGIN_CAP
569 	extern login_cap_t *lc;
570 #ifdef BSD_AUTH
571 	auth_session_t *as;
572 #endif
573 #endif
574 	struct passwd *pw;
575 	struct connection_info *ci = get_connection_info(1, options.use_dns);
576 
577 	ci->user = user;
578 	parse_server_match_config(&options, ci);
579 	log_change_level(options.log_level);
580 	process_permitopen(ssh, &options);
581 
582 #if defined(_AIX) && defined(HAVE_SETAUTHDB)
583 	aix_setauthdb(user);
584 #endif
585 
586 	pw = getpwnam(user);
587 
588 #if defined(_AIX) && defined(HAVE_SETAUTHDB)
589 	aix_restoreauthdb();
590 #endif
591 #ifdef HAVE_CYGWIN
592 	/*
593 	 * Windows usernames are case-insensitive.  To avoid later problems
594 	 * when trying to match the username, the user is only allowed to
595 	 * login if the username is given in the same case as stored in the
596 	 * user database.
597 	 */
598 	if (pw != NULL && strcmp(user, pw->pw_name) != 0) {
599 		logit("Login name %.100s does not match stored username %.100s",
600 		    user, pw->pw_name);
601 		pw = NULL;
602 	}
603 #endif
604 	if (pw == NULL) {
605 		logit("Invalid user %.100s from %.100s port %d",
606 		    user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
607 #ifdef CUSTOM_FAILED_LOGIN
608 		record_failed_login(user,
609 		    auth_get_canonical_hostname(ssh, options.use_dns), "ssh");
610 #endif
611 #ifdef SSH_AUDIT_EVENTS
612 		audit_event(SSH_INVALID_USER);
613 #endif /* SSH_AUDIT_EVENTS */
614 		return (NULL);
615 	}
616 	if (!allowed_user(pw))
617 		return (NULL);
618 #ifdef HAVE_LOGIN_CAP
619 	if ((lc = login_getclass(pw->pw_class)) == NULL) {
620 		debug("unable to get login class: %s", user);
621 		return (NULL);
622 	}
623 #ifdef BSD_AUTH
624 	if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 ||
625 	    auth_approval(as, lc, pw->pw_name, "ssh") <= 0) {
626 		debug("Approval failure for %s", user);
627 		pw = NULL;
628 	}
629 	if (as != NULL)
630 		auth_close(as);
631 #endif
632 #endif
633 	if (pw != NULL)
634 		return (pwcopy(pw));
635 	return (NULL);
636 }
637 
638 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */
639 int
640 auth_key_is_revoked(struct sshkey *key)
641 {
642 	char *fp = NULL;
643 	int r;
644 
645 	if (options.revoked_keys_file == NULL)
646 		return 0;
647 	if ((fp = sshkey_fingerprint(key, options.fingerprint_hash,
648 	    SSH_FP_DEFAULT)) == NULL) {
649 		r = SSH_ERR_ALLOC_FAIL;
650 		error("%s: fingerprint key: %s", __func__, ssh_err(r));
651 		goto out;
652 	}
653 
654 	r = sshkey_check_revoked(key, options.revoked_keys_file);
655 	switch (r) {
656 	case 0:
657 		break; /* not revoked */
658 	case SSH_ERR_KEY_REVOKED:
659 		error("Authentication key %s %s revoked by file %s",
660 		    sshkey_type(key), fp, options.revoked_keys_file);
661 		goto out;
662 	default:
663 		error("Error checking authentication key %s %s in "
664 		    "revoked keys file %s: %s", sshkey_type(key), fp,
665 		    options.revoked_keys_file, ssh_err(r));
666 		goto out;
667 	}
668 
669 	/* Success */
670 	r = 0;
671 
672  out:
673 	free(fp);
674 	return r == 0 ? 0 : 1;
675 }
676 
677 void
678 auth_debug_add(const char *fmt,...)
679 {
680 	char buf[1024];
681 	va_list args;
682 	int r;
683 
684 	if (auth_debug == NULL)
685 		return;
686 
687 	va_start(args, fmt);
688 	vsnprintf(buf, sizeof(buf), fmt, args);
689 	va_end(args);
690 	if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0)
691 		fatal("%s: sshbuf_put_cstring: %s", __func__, ssh_err(r));
692 }
693 
694 void
695 auth_debug_send(void)
696 {
697 	struct ssh *ssh = active_state;		/* XXX */
698 	char *msg;
699 	int r;
700 
701 	if (auth_debug == NULL)
702 		return;
703 	while (sshbuf_len(auth_debug) != 0) {
704 		if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0)
705 			fatal("%s: sshbuf_get_cstring: %s",
706 			    __func__, ssh_err(r));
707 		ssh_packet_send_debug(ssh, "%s", msg);
708 		free(msg);
709 	}
710 }
711 
712 void
713 auth_debug_reset(void)
714 {
715 	if (auth_debug != NULL)
716 		sshbuf_reset(auth_debug);
717 	else if ((auth_debug = sshbuf_new()) == NULL)
718 		fatal("%s: sshbuf_new failed", __func__);
719 }
720 
721 struct passwd *
722 fakepw(void)
723 {
724 	static struct passwd fake;
725 
726 	memset(&fake, 0, sizeof(fake));
727 	fake.pw_name = "NOUSER";
728 	fake.pw_passwd =
729 	    "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK";
730 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS
731 	fake.pw_gecos = "NOUSER";
732 #endif
733 	fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid;
734 	fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid;
735 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS
736 	fake.pw_class = "";
737 #endif
738 	fake.pw_dir = "/nonexist";
739 	fake.pw_shell = "/nonexist";
740 
741 	return (&fake);
742 }
743 
744 /*
745  * Returns the remote DNS hostname as a string. The returned string must not
746  * be freed. NB. this will usually trigger a DNS query the first time it is
747  * called.
748  * This function does additional checks on the hostname to mitigate some
749  * attacks on legacy rhosts-style authentication.
750  * XXX is RhostsRSAAuthentication vulnerable to these?
751  * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?)
752  */
753 
754 static char *
755 remote_hostname(struct ssh *ssh)
756 {
757 	struct sockaddr_storage from;
758 	socklen_t fromlen;
759 	struct addrinfo hints, *ai, *aitop;
760 	char name[NI_MAXHOST], ntop2[NI_MAXHOST];
761 	const char *ntop = ssh_remote_ipaddr(ssh);
762 
763 	/* Get IP address of client. */
764 	fromlen = sizeof(from);
765 	memset(&from, 0, sizeof(from));
766 	if (getpeername(ssh_packet_get_connection_in(ssh),
767 	    (struct sockaddr *)&from, &fromlen) < 0) {
768 		debug("getpeername failed: %.100s", strerror(errno));
769 		return strdup(ntop);
770 	}
771 
772 	ipv64_normalise_mapped(&from, &fromlen);
773 	if (from.ss_family == AF_INET6)
774 		fromlen = sizeof(struct sockaddr_in6);
775 
776 	debug3("Trying to reverse map address %.100s.", ntop);
777 	/* Map the IP address to a host name. */
778 	if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
779 	    NULL, 0, NI_NAMEREQD) != 0) {
780 		/* Host name not found.  Use ip address. */
781 		return strdup(ntop);
782 	}
783 
784 	/*
785 	 * if reverse lookup result looks like a numeric hostname,
786 	 * someone is trying to trick us by PTR record like following:
787 	 *	1.1.1.10.in-addr.arpa.	IN PTR	2.3.4.5
788 	 */
789 	memset(&hints, 0, sizeof(hints));
790 	hints.ai_socktype = SOCK_DGRAM;	/*dummy*/
791 	hints.ai_flags = AI_NUMERICHOST;
792 	if (getaddrinfo(name, NULL, &hints, &ai) == 0) {
793 		logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
794 		    name, ntop);
795 		freeaddrinfo(ai);
796 		return strdup(ntop);
797 	}
798 
799 	/* Names are stored in lowercase. */
800 	lowercase(name);
801 
802 	/*
803 	 * Map it back to an IP address and check that the given
804 	 * address actually is an address of this host.  This is
805 	 * necessary because anyone with access to a name server can
806 	 * define arbitrary names for an IP address. Mapping from
807 	 * name to IP address can be trusted better (but can still be
808 	 * fooled if the intruder has access to the name server of
809 	 * the domain).
810 	 */
811 	memset(&hints, 0, sizeof(hints));
812 	hints.ai_family = from.ss_family;
813 	hints.ai_socktype = SOCK_STREAM;
814 	if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
815 		logit("reverse mapping checking getaddrinfo for %.700s "
816 		    "[%s] failed.", name, ntop);
817 		return strdup(ntop);
818 	}
819 	/* Look for the address from the list of addresses. */
820 	for (ai = aitop; ai; ai = ai->ai_next) {
821 		if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
822 		    sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
823 		    (strcmp(ntop, ntop2) == 0))
824 				break;
825 	}
826 	freeaddrinfo(aitop);
827 	/* If we reached the end of the list, the address was not there. */
828 	if (ai == NULL) {
829 		/* Address not found for the host name. */
830 		logit("Address %.100s maps to %.600s, but this does not "
831 		    "map back to the address.", ntop, name);
832 		return strdup(ntop);
833 	}
834 	return strdup(name);
835 }
836 
837 /*
838  * Return the canonical name of the host in the other side of the current
839  * connection.  The host name is cached, so it is efficient to call this
840  * several times.
841  */
842 
843 const char *
844 auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
845 {
846 	static char *dnsname;
847 
848 	if (!use_dns)
849 		return ssh_remote_ipaddr(ssh);
850 	else if (dnsname != NULL)
851 		return dnsname;
852 	else {
853 		dnsname = remote_hostname(ssh);
854 		return dnsname;
855 	}
856 }
857 
858 /*
859  * Runs command in a subprocess with a minimal environment.
860  * Returns pid on success, 0 on failure.
861  * The child stdout and stderr maybe captured, left attached or sent to
862  * /dev/null depending on the contents of flags.
863  * "tag" is prepended to log messages.
864  * NB. "command" is only used for logging; the actual command executed is
865  * av[0].
866  */
867 pid_t
868 subprocess(const char *tag, struct passwd *pw, const char *command,
869     int ac, char **av, FILE **child, u_int flags)
870 {
871 	FILE *f = NULL;
872 	struct stat st;
873 	int fd, devnull, p[2], i;
874 	pid_t pid;
875 	char *cp, errmsg[512];
876 	u_int envsize;
877 	char **child_env;
878 
879 	if (child != NULL)
880 		*child = NULL;
881 
882 	debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__,
883 	    tag, command, pw->pw_name, flags);
884 
885 	/* Check consistency */
886 	if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
887 	    (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) {
888 		error("%s: inconsistent flags", __func__);
889 		return 0;
890 	}
891 	if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) {
892 		error("%s: inconsistent flags/output", __func__);
893 		return 0;
894 	}
895 
896 	/*
897 	 * If executing an explicit binary, then verify the it exists
898 	 * and appears safe-ish to execute
899 	 */
900 	if (!path_absolute(av[0])) {
901 		error("%s path is not absolute", tag);
902 		return 0;
903 	}
904 	temporarily_use_uid(pw);
905 	if (stat(av[0], &st) < 0) {
906 		error("Could not stat %s \"%s\": %s", tag,
907 		    av[0], strerror(errno));
908 		restore_uid();
909 		return 0;
910 	}
911 	if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) {
912 		error("Unsafe %s \"%s\": %s", tag, av[0], errmsg);
913 		restore_uid();
914 		return 0;
915 	}
916 	/* Prepare to keep the child's stdout if requested */
917 	if (pipe(p) != 0) {
918 		error("%s: pipe: %s", tag, strerror(errno));
919 		restore_uid();
920 		return 0;
921 	}
922 	restore_uid();
923 
924 	switch ((pid = fork())) {
925 	case -1: /* error */
926 		error("%s: fork: %s", tag, strerror(errno));
927 		close(p[0]);
928 		close(p[1]);
929 		return 0;
930 	case 0: /* child */
931 		/* Prepare a minimal environment for the child. */
932 		envsize = 5;
933 		child_env = xcalloc(sizeof(*child_env), envsize);
934 		child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH);
935 		child_set_env(&child_env, &envsize, "USER", pw->pw_name);
936 		child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name);
937 		child_set_env(&child_env, &envsize, "HOME", pw->pw_dir);
938 		if ((cp = getenv("LANG")) != NULL)
939 			child_set_env(&child_env, &envsize, "LANG", cp);
940 
941 		for (i = 0; i < NSIG; i++)
942 			signal(i, SIG_DFL);
943 
944 		if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
945 			error("%s: open %s: %s", tag, _PATH_DEVNULL,
946 			    strerror(errno));
947 			_exit(1);
948 		}
949 		if (dup2(devnull, STDIN_FILENO) == -1) {
950 			error("%s: dup2: %s", tag, strerror(errno));
951 			_exit(1);
952 		}
953 
954 		/* Set up stdout as requested; leave stderr in place for now. */
955 		fd = -1;
956 		if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0)
957 			fd = p[1];
958 		else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0)
959 			fd = devnull;
960 		if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) {
961 			error("%s: dup2: %s", tag, strerror(errno));
962 			_exit(1);
963 		}
964 		closefrom(STDERR_FILENO + 1);
965 
966 		/* Don't use permanently_set_uid() here to avoid fatal() */
967 		if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
968 			error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid,
969 			    strerror(errno));
970 			_exit(1);
971 		}
972 		if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) {
973 			error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid,
974 			    strerror(errno));
975 			_exit(1);
976 		}
977 		/* stdin is pointed to /dev/null at this point */
978 		if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
979 		    dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
980 			error("%s: dup2: %s", tag, strerror(errno));
981 			_exit(1);
982 		}
983 
984 		execve(av[0], av, child_env);
985 		error("%s exec \"%s\": %s", tag, command, strerror(errno));
986 		_exit(127);
987 	default: /* parent */
988 		break;
989 	}
990 
991 	close(p[1]);
992 	if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0)
993 		close(p[0]);
994 	else if ((f = fdopen(p[0], "r")) == NULL) {
995 		error("%s: fdopen: %s", tag, strerror(errno));
996 		close(p[0]);
997 		/* Don't leave zombie child */
998 		kill(pid, SIGTERM);
999 		while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
1000 			;
1001 		return 0;
1002 	}
1003 	/* Success */
1004 	debug3("%s: %s pid %ld", __func__, tag, (long)pid);
1005 	if (child != NULL)
1006 		*child = f;
1007 	return pid;
1008 }
1009 
1010 /* These functions link key/cert options to the auth framework */
1011 
1012 /* Log sshauthopt options locally and (optionally) for remote transmission */
1013 void
1014 auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote)
1015 {
1016 	int do_env = options.permit_user_env && opts->nenv > 0;
1017 	int do_permitopen = opts->npermitopen > 0 &&
1018 	    (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0;
1019 	int do_permitlisten = opts->npermitlisten > 0 &&
1020 	    (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0;
1021 	size_t i;
1022 	char msg[1024], buf[64];
1023 
1024 	snprintf(buf, sizeof(buf), "%d", opts->force_tun_device);
1025 	/* Try to keep this alphabetically sorted */
1026 	snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s",
1027 	    opts->permit_agent_forwarding_flag ? " agent-forwarding" : "",
1028 	    opts->force_command == NULL ? "" : " command",
1029 	    do_env ?  " environment" : "",
1030 	    opts->valid_before == 0 ? "" : "expires",
1031 	    do_permitopen ?  " permitopen" : "",
1032 	    do_permitlisten ?  " permitlisten" : "",
1033 	    opts->permit_port_forwarding_flag ? " port-forwarding" : "",
1034 	    opts->cert_principals == NULL ? "" : " principals",
1035 	    opts->permit_pty_flag ? " pty" : "",
1036 	    opts->force_tun_device == -1 ? "" : " tun=",
1037 	    opts->force_tun_device == -1 ? "" : buf,
1038 	    opts->permit_user_rc ? " user-rc" : "",
1039 	    opts->permit_x11_forwarding_flag ? " x11-forwarding" : "");
1040 
1041 	debug("%s: %s", loc, msg);
1042 	if (do_remote)
1043 		auth_debug_add("%s: %s", loc, msg);
1044 
1045 	if (options.permit_user_env) {
1046 		for (i = 0; i < opts->nenv; i++) {
1047 			debug("%s: environment: %s", loc, opts->env[i]);
1048 			if (do_remote) {
1049 				auth_debug_add("%s: environment: %s",
1050 				    loc, opts->env[i]);
1051 			}
1052 		}
1053 	}
1054 
1055 	/* Go into a little more details for the local logs. */
1056 	if (opts->valid_before != 0) {
1057 		format_absolute_time(opts->valid_before, buf, sizeof(buf));
1058 		debug("%s: expires at %s", loc, buf);
1059 	}
1060 	if (opts->cert_principals != NULL) {
1061 		debug("%s: authorized principals: \"%s\"",
1062 		    loc, opts->cert_principals);
1063 	}
1064 	if (opts->force_command != NULL)
1065 		debug("%s: forced command: \"%s\"", loc, opts->force_command);
1066 	if (do_permitopen) {
1067 		for (i = 0; i < opts->npermitopen; i++) {
1068 			debug("%s: permitted open: %s",
1069 			    loc, opts->permitopen[i]);
1070 		}
1071 	}
1072 	if (do_permitlisten) {
1073 		for (i = 0; i < opts->npermitlisten; i++) {
1074 			debug("%s: permitted listen: %s",
1075 			    loc, opts->permitlisten[i]);
1076 		}
1077 	}
1078 }
1079 
1080 /* Activate a new set of key/cert options; merging with what is there. */
1081 int
1082 auth_activate_options(struct ssh *ssh, struct sshauthopt *opts)
1083 {
1084 	struct sshauthopt *old = auth_opts;
1085 	const char *emsg = NULL;
1086 
1087 	debug("%s: setting new authentication options", __func__);
1088 	if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) {
1089 		error("Inconsistent authentication options: %s", emsg);
1090 		return -1;
1091 	}
1092 	return 0;
1093 }
1094 
1095 /* Disable forwarding, etc for the session */
1096 void
1097 auth_restrict_session(struct ssh *ssh)
1098 {
1099 	struct sshauthopt *restricted;
1100 
1101 	debug("%s: restricting session", __func__);
1102 
1103 	/* A blank sshauthopt defaults to permitting nothing */
1104 	restricted = sshauthopt_new();
1105 	restricted->permit_pty_flag = 1;
1106 	restricted->restricted = 1;
1107 
1108 	if (auth_activate_options(ssh, restricted) != 0)
1109 		fatal("%s: failed to restrict session", __func__);
1110 	sshauthopt_free(restricted);
1111 }
1112 
1113 int
1114 auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw,
1115     struct sshauthopt *opts, int allow_cert_authority, const char *loc)
1116 {
1117 	const char *remote_ip = ssh_remote_ipaddr(ssh);
1118 	const char *remote_host = auth_get_canonical_hostname(ssh,
1119 	    options.use_dns);
1120 	time_t now = time(NULL);
1121 	char buf[64];
1122 
1123 	/*
1124 	 * Check keys/principals file expiry time.
1125 	 * NB. validity interval in certificate is handled elsewhere.
1126 	 */
1127 	if (opts->valid_before && now > 0 &&
1128 	    opts->valid_before < (uint64_t)now) {
1129 		format_absolute_time(opts->valid_before, buf, sizeof(buf));
1130 		debug("%s: entry expired at %s", loc, buf);
1131 		auth_debug_add("%s: entry expired at %s", loc, buf);
1132 		return -1;
1133 	}
1134 	/* Consistency checks */
1135 	if (opts->cert_principals != NULL && !opts->cert_authority) {
1136 		debug("%s: principals on non-CA key", loc);
1137 		auth_debug_add("%s: principals on non-CA key", loc);
1138 		/* deny access */
1139 		return -1;
1140 	}
1141 	/* cert-authority flag isn't valid in authorized_principals files */
1142 	if (!allow_cert_authority && opts->cert_authority) {
1143 		debug("%s: cert-authority flag invalid here", loc);
1144 		auth_debug_add("%s: cert-authority flag invalid here", loc);
1145 		/* deny access */
1146 		return -1;
1147 	}
1148 
1149 	/* Perform from= checks */
1150 	if (opts->required_from_host_keys != NULL) {
1151 		switch (match_host_and_ip(remote_host, remote_ip,
1152 		    opts->required_from_host_keys )) {
1153 		case 1:
1154 			/* Host name matches. */
1155 			break;
1156 		case -1:
1157 		default:
1158 			debug("%s: invalid from criteria", loc);
1159 			auth_debug_add("%s: invalid from criteria", loc);
1160 			/* FALLTHROUGH */
1161 		case 0:
1162 			logit("%s: Authentication tried for %.100s with "
1163 			    "correct key but not from a permitted "
1164 			    "host (host=%.200s, ip=%.200s, required=%.200s).",
1165 			    loc, pw->pw_name, remote_host, remote_ip,
1166 			    opts->required_from_host_keys);
1167 			auth_debug_add("%s: Your host '%.200s' is not "
1168 			    "permitted to use this key for login.",
1169 			    loc, remote_host);
1170 			/* deny access */
1171 			return -1;
1172 		}
1173 	}
1174 	/* Check source-address restriction from certificate */
1175 	if (opts->required_from_host_cert != NULL) {
1176 		switch (addr_match_cidr_list(remote_ip,
1177 		    opts->required_from_host_cert)) {
1178 		case 1:
1179 			/* accepted */
1180 			break;
1181 		case -1:
1182 		default:
1183 			/* invalid */
1184 			error("%s: Certificate source-address invalid",
1185 			    loc);
1186 			/* FALLTHROUGH */
1187 		case 0:
1188 			logit("%s: Authentication tried for %.100s with valid "
1189 			    "certificate but not from a permitted source "
1190 			    "address (%.200s).", loc, pw->pw_name, remote_ip);
1191 			auth_debug_add("%s: Your address '%.200s' is not "
1192 			    "permitted to use this certificate for login.",
1193 			    loc, remote_ip);
1194 			return -1;
1195 		}
1196 	}
1197 	/*
1198 	 *
1199 	 * XXX this is spammy. We should report remotely only for keys
1200 	 *     that are successful in actual auth attempts, and not PK_OK
1201 	 *     tests.
1202 	 */
1203 	auth_log_authopts(loc, opts, 1);
1204 
1205 	return 0;
1206 }
1207