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1 | /* $OpenBSD: auth.c,v 1.72 2006/07/22 20:48:22 stevesk 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 | ||
31 | #include <errno.h> | |
32 | #ifdef HAVE_PATHS_H | |
33 | # include <paths.h> | |
34 | #endif | |
35 | #include <pwd.h> | |
36 | #ifdef HAVE_LOGIN_H | |
37 | #include <login.h> | |
38 | #endif | |
39 | #ifdef USE_SHADOW | |
40 | #include <shadow.h> | |
41 | #endif | |
42 | #ifdef HAVE_LIBGEN_H | |
43 | #include <libgen.h> | |
44 | #endif | |
45 | #include <stdarg.h> | |
46 | #include <string.h> | |
47 | ||
48 | #include "xmalloc.h" | |
49 | #include "match.h" | |
50 | #include "groupaccess.h" | |
51 | #include "log.h" | |
52 | #include "servconf.h" | |
53 | #include "auth.h" | |
54 | #include "auth-options.h" | |
55 | #include "canohost.h" | |
56 | #include "buffer.h" | |
57 | #include "bufaux.h" | |
58 | #include "uidswap.h" | |
59 | #include "misc.h" | |
60 | #include "bufaux.h" | |
61 | #include "packet.h" | |
62 | #include "loginrec.h" | |
63 | #include "monitor_wrap.h" | |
64 | ||
65 | /* import */ | |
66 | extern ServerOptions options; | |
67 | extern int use_privsep; | |
68 | extern Buffer loginmsg; | |
69 | ||
70 | /* Debugging messages */ | |
71 | Buffer auth_debug; | |
72 | int auth_debug_init; | |
73 | ||
74 | /* | |
75 | * Check if the user is allowed to log in via ssh. If user is listed | |
76 | * in DenyUsers or one of user's groups is listed in DenyGroups, false | |
77 | * will be returned. If AllowUsers isn't empty and user isn't listed | |
78 | * there, or if AllowGroups isn't empty and one of user's groups isn't | |
79 | * listed there, false will be returned. | |
80 | * If the user's shell is not executable, false will be returned. | |
81 | * Otherwise true is returned. | |
82 | */ | |
83 | int | |
84 | allowed_user(struct passwd * pw) | |
85 | { | |
86 | struct stat st; | |
87 | const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; | |
88 | char *shell; | |
89 | u_int i; | |
90 | #ifdef USE_SHADOW | |
91 | struct spwd *spw = NULL; | |
92 | #endif | |
93 | ||
94 | /* Shouldn't be called if pw is NULL, but better safe than sorry... */ | |
95 | if (!pw || !pw->pw_name) | |
96 | return 0; | |
97 | ||
98 | #ifdef USE_SHADOW | |
99 | if (!options.use_pam) | |
100 | spw = getspnam(pw->pw_name); | |
101 | #ifdef HAS_SHADOW_EXPIRE | |
102 | if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw)) | |
103 | return 0; | |
104 | #endif /* HAS_SHADOW_EXPIRE */ | |
105 | #endif /* USE_SHADOW */ | |
106 | ||
107 | /* grab passwd field for locked account check */ | |
108 | #ifdef USE_SHADOW | |
109 | if (spw != NULL) | |
110 | #if defined(HAVE_LIBIAF) && !defined(BROKEN_LIBIAF) | |
111 | passwd = get_iaf_password(pw); | |
112 | #else | |
113 | passwd = spw->sp_pwdp; | |
114 | #endif /* HAVE_LIBIAF && !BROKEN_LIBIAF */ | |
115 | #else | |
116 | passwd = pw->pw_passwd; | |
117 | #endif | |
118 | ||
119 | /* check for locked account */ | |
120 | if (!options.use_pam && passwd && *passwd) { | |
121 | int locked = 0; | |
122 | ||
123 | #ifdef LOCKED_PASSWD_STRING | |
124 | if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0) | |
125 | locked = 1; | |
126 | #endif | |
127 | #ifdef LOCKED_PASSWD_PREFIX | |
128 | if (strncmp(passwd, LOCKED_PASSWD_PREFIX, | |
129 | strlen(LOCKED_PASSWD_PREFIX)) == 0) | |
130 | locked = 1; | |
131 | #endif | |
132 | #ifdef LOCKED_PASSWD_SUBSTR | |
133 | if (strstr(passwd, LOCKED_PASSWD_SUBSTR)) | |
134 | locked = 1; | |
135 | #endif | |
136 | #if defined(HAVE_LIBIAF) && !defined(BROKEN_LIBIAF) | |
137 | free(passwd); | |
138 | #endif /* HAVE_LIBIAF && !BROKEN_LIBIAF */ | |
139 | if (locked) { | |
140 | logit("User %.100s not allowed because account is locked", | |
141 | pw->pw_name); | |
142 | return 0; | |
143 | } | |
144 | } | |
145 | ||
146 | /* | |
147 | * Get the shell from the password data. An empty shell field is | |
148 | * legal, and means /bin/sh. | |
149 | */ | |
150 | shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell; | |
151 | ||
152 | /* deny if shell does not exists or is not executable */ | |
153 | if (stat(shell, &st) != 0) { | |
154 | logit("User %.100s not allowed because shell %.100s does not exist", | |
155 | pw->pw_name, shell); | |
156 | return 0; | |
157 | } | |
158 | if (S_ISREG(st.st_mode) == 0 || | |
159 | (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { | |
160 | logit("User %.100s not allowed because shell %.100s is not executable", | |
161 | pw->pw_name, shell); | |
162 | return 0; | |
163 | } | |
164 | ||
165 | if (options.num_deny_users > 0 || options.num_allow_users > 0 || | |
166 | options.num_deny_groups > 0 || options.num_allow_groups > 0) { | |
167 | hostname = get_canonical_hostname(options.use_dns); | |
168 | ipaddr = get_remote_ipaddr(); | |
169 | } | |
170 | ||
171 | /* Return false if user is listed in DenyUsers */ | |
172 | if (options.num_deny_users > 0) { | |
173 | for (i = 0; i < options.num_deny_users; i++) | |
174 | if (match_user(pw->pw_name, hostname, ipaddr, | |
175 | options.deny_users[i])) { | |
176 | logit("User %.100s from %.100s not allowed " | |
177 | "because listed in DenyUsers", | |
178 | pw->pw_name, hostname); | |
179 | return 0; | |
180 | } | |
181 | } | |
182 | /* Return false if AllowUsers isn't empty and user isn't listed there */ | |
183 | if (options.num_allow_users > 0) { | |
184 | for (i = 0; i < options.num_allow_users; i++) | |
185 | if (match_user(pw->pw_name, hostname, ipaddr, | |
186 | options.allow_users[i])) | |
187 | break; | |
188 | /* i < options.num_allow_users iff we break for loop */ | |
189 | if (i >= options.num_allow_users) { | |
190 | logit("User %.100s from %.100s not allowed because " | |
191 | "not listed in AllowUsers", pw->pw_name, hostname); | |
192 | return 0; | |
193 | } | |
194 | } | |
195 | if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { | |
196 | /* Get the user's group access list (primary and supplementary) */ | |
197 | if (ga_init(pw->pw_name, pw->pw_gid) == 0) { | |
198 | logit("User %.100s from %.100s not allowed because " | |
199 | "not in any group", pw->pw_name, hostname); | |
200 | return 0; | |
201 | } | |
202 | ||
203 | /* Return false if one of user's groups is listed in DenyGroups */ | |
204 | if (options.num_deny_groups > 0) | |
205 | if (ga_match(options.deny_groups, | |
206 | options.num_deny_groups)) { | |
207 | ga_free(); | |
208 | logit("User %.100s from %.100s not allowed " | |
209 | "because a group is listed in DenyGroups", | |
210 | pw->pw_name, hostname); | |
211 | return 0; | |
212 | } | |
213 | /* | |
214 | * Return false if AllowGroups isn't empty and one of user's groups | |
215 | * isn't listed there | |
216 | */ | |
217 | if (options.num_allow_groups > 0) | |
218 | if (!ga_match(options.allow_groups, | |
219 | options.num_allow_groups)) { | |
220 | ga_free(); | |
221 | logit("User %.100s from %.100s not allowed " | |
222 | "because none of user's groups are listed " | |
223 | "in AllowGroups", pw->pw_name, hostname); | |
224 | return 0; | |
225 | } | |
226 | ga_free(); | |
227 | } | |
228 | ||
229 | #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER | |
230 | if (!sys_auth_allowed_user(pw, &loginmsg)) | |
231 | return 0; | |
232 | #endif | |
233 | ||
234 | /* We found no reason not to let this user try to log on... */ | |
235 | return 1; | |
236 | } | |
237 | ||
238 | void | |
239 | auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) | |
240 | { | |
241 | void (*authlog) (const char *fmt,...) = verbose; | |
242 | char *authmsg; | |
243 | ||
244 | if (use_privsep && !mm_is_monitor() && !authctxt->postponed) | |
245 | return; | |
246 | ||
247 | /* Raise logging level */ | |
248 | if (authenticated == 1 || | |
249 | !authctxt->valid || | |
250 | authctxt->failures >= options.max_authtries / 2 || | |
251 | strcmp(method, "password") == 0) | |
252 | authlog = logit; | |
253 | ||
254 | if (authctxt->postponed) | |
255 | authmsg = "Postponed"; | |
256 | else | |
257 | authmsg = authenticated ? "Accepted" : "Failed"; | |
258 | ||
259 | authlog("%s %s for %s%.100s from %.200s port %d%s", | |
260 | authmsg, | |
261 | method, | |
262 | authctxt->valid ? "" : "invalid user ", | |
263 | authctxt->user, | |
264 | get_remote_ipaddr(), | |
265 | get_remote_port(), | |
266 | info); | |
267 | ||
268 | #ifdef CUSTOM_FAILED_LOGIN | |
269 | if (authenticated == 0 && !authctxt->postponed && | |
270 | (strcmp(method, "password") == 0 || | |
271 | strncmp(method, "keyboard-interactive", 20) == 0 || | |
272 | strcmp(method, "challenge-response") == 0)) | |
273 | record_failed_login(authctxt->user, | |
274 | get_canonical_hostname(options.use_dns), "ssh"); | |
275 | #endif | |
276 | #ifdef SSH_AUDIT_EVENTS | |
277 | if (authenticated == 0 && !authctxt->postponed) | |
278 | audit_event(audit_classify_auth(method)); | |
279 | #endif | |
280 | } | |
281 | ||
282 | /* | |
283 | * Check whether root logins are disallowed. | |
284 | */ | |
285 | int | |
286 | auth_root_allowed(char *method) | |
287 | { | |
288 | switch (options.permit_root_login) { | |
289 | case PERMIT_YES: | |
290 | return 1; | |
291 | case PERMIT_NO_PASSWD: | |
292 | if (strcmp(method, "password") != 0) | |
293 | return 1; | |
294 | break; | |
295 | case PERMIT_FORCED_ONLY: | |
296 | if (forced_command) { | |
297 | logit("Root login accepted for forced command."); | |
298 | return 1; | |
299 | } | |
300 | break; | |
301 | } | |
302 | logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); | |
303 | return 0; | |
304 | } | |
305 | ||
306 | ||
307 | /* | |
308 | * Given a template and a passwd structure, build a filename | |
309 | * by substituting % tokenised options. Currently, %% becomes '%', | |
310 | * %h becomes the home directory and %u the username. | |
311 | * | |
312 | * This returns a buffer allocated by xmalloc. | |
313 | */ | |
314 | static char * | |
315 | expand_authorized_keys(const char *filename, struct passwd *pw) | |
316 | { | |
317 | char *file, ret[MAXPATHLEN]; | |
318 | int i; | |
319 | ||
320 | file = percent_expand(filename, "h", pw->pw_dir, | |
321 | "u", pw->pw_name, (char *)NULL); | |
322 | ||
323 | /* | |
324 | * Ensure that filename starts anchored. If not, be backward | |
325 | * compatible and prepend the '%h/' | |
326 | */ | |
327 | if (*file == '/') | |
328 | return (file); | |
329 | ||
330 | i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); | |
331 | if (i < 0 || (size_t)i >= sizeof(ret)) | |
332 | fatal("expand_authorized_keys: path too long"); | |
333 | xfree(file); | |
334 | return (xstrdup(ret)); | |
335 | } | |
336 | ||
337 | char * | |
338 | authorized_keys_file(struct passwd *pw) | |
339 | { | |
340 | return expand_authorized_keys(options.authorized_keys_file, pw); | |
341 | } | |
342 | ||
343 | char * | |
344 | authorized_keys_file2(struct passwd *pw) | |
345 | { | |
346 | return expand_authorized_keys(options.authorized_keys_file2, pw); | |
347 | } | |
348 | ||
349 | /* return ok if key exists in sysfile or userfile */ | |
350 | HostStatus | |
351 | check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, | |
352 | const char *sysfile, const char *userfile) | |
353 | { | |
354 | Key *found; | |
355 | char *user_hostfile; | |
356 | struct stat st; | |
357 | HostStatus host_status; | |
358 | ||
359 | /* Check if we know the host and its host key. */ | |
360 | found = key_new(key->type); | |
361 | host_status = check_host_in_hostfile(sysfile, host, key, found, NULL); | |
362 | ||
363 | if (host_status != HOST_OK && userfile != NULL) { | |
364 | user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); | |
365 | if (options.strict_modes && | |
366 | (stat(user_hostfile, &st) == 0) && | |
367 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
368 | (st.st_mode & 022) != 0)) { | |
369 | logit("Authentication refused for %.100s: " | |
370 | "bad owner or modes for %.200s", | |
371 | pw->pw_name, user_hostfile); | |
372 | } else { | |
373 | temporarily_use_uid(pw); | |
374 | host_status = check_host_in_hostfile(user_hostfile, | |
375 | host, key, found, NULL); | |
376 | restore_uid(); | |
377 | } | |
378 | xfree(user_hostfile); | |
379 | } | |
380 | key_free(found); | |
381 | ||
382 | debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ? | |
383 | "ok" : "not found", host); | |
384 | return host_status; | |
385 | } | |
386 | ||
387 | ||
388 | /* | |
389 | * Check a given file for security. This is defined as all components | |
390 | * of the path to the file must be owned by either the owner of | |
391 | * of the file or root and no directories must be group or world writable. | |
392 | * | |
393 | * XXX Should any specific check be done for sym links ? | |
394 | * | |
395 | * Takes an open file descriptor, the file name, a uid and and | |
396 | * error buffer plus max size as arguments. | |
397 | * | |
398 | * Returns 0 on success and -1 on failure | |
399 | */ | |
400 | int | |
401 | secure_filename(FILE *f, const char *file, struct passwd *pw, | |
402 | char *err, size_t errlen) | |
403 | { | |
404 | uid_t uid = pw->pw_uid; | |
405 | char buf[MAXPATHLEN], homedir[MAXPATHLEN]; | |
406 | char *cp; | |
407 | int comparehome = 0; | |
408 | struct stat st; | |
409 | ||
410 | if (realpath(file, buf) == NULL) { | |
411 | snprintf(err, errlen, "realpath %s failed: %s", file, | |
412 | strerror(errno)); | |
413 | return -1; | |
414 | } | |
415 | if (realpath(pw->pw_dir, homedir) != NULL) | |
416 | comparehome = 1; | |
417 | ||
418 | /* check the open file to avoid races */ | |
419 | if (fstat(fileno(f), &st) < 0 || | |
420 | (st.st_uid != 0 && st.st_uid != uid) || | |
421 | (st.st_mode & 022) != 0) { | |
422 | snprintf(err, errlen, "bad ownership or modes for file %s", | |
423 | buf); | |
424 | return -1; | |
425 | } | |
426 | ||
427 | /* for each component of the canonical path, walking upwards */ | |
428 | for (;;) { | |
429 | if ((cp = dirname(buf)) == NULL) { | |
430 | snprintf(err, errlen, "dirname() failed"); | |
431 | return -1; | |
432 | } | |
433 | strlcpy(buf, cp, sizeof(buf)); | |
434 | ||
435 | debug3("secure_filename: checking '%s'", buf); | |
436 | if (stat(buf, &st) < 0 || | |
437 | (st.st_uid != 0 && st.st_uid != uid) || | |
438 | (st.st_mode & 022) != 0) { | |
439 | snprintf(err, errlen, | |
440 | "bad ownership or modes for directory %s", buf); | |
441 | return -1; | |
442 | } | |
443 | ||
444 | /* If are passed the homedir then we can stop */ | |
445 | if (comparehome && strcmp(homedir, buf) == 0) { | |
446 | debug3("secure_filename: terminating check at '%s'", | |
447 | buf); | |
448 | break; | |
449 | } | |
450 | /* | |
451 | * dirname should always complete with a "/" path, | |
452 | * but we can be paranoid and check for "." too | |
453 | */ | |
454 | if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) | |
455 | break; | |
456 | } | |
457 | return 0; | |
458 | } | |
459 | ||
460 | struct passwd * | |
461 | getpwnamallow(const char *user) | |
462 | { | |
463 | #ifdef HAVE_LOGIN_CAP | |
464 | extern login_cap_t *lc; | |
465 | #ifdef BSD_AUTH | |
466 | auth_session_t *as; | |
467 | #endif | |
468 | #endif | |
469 | struct passwd *pw; | |
470 | ||
471 | parse_server_match_config(&options, user, | |
472 | get_canonical_hostname(options.use_dns), get_remote_ipaddr()); | |
473 | ||
474 | pw = getpwnam(user); | |
475 | if (pw == NULL) { | |
476 | logit("Invalid user %.100s from %.100s", | |
477 | user, get_remote_ipaddr()); | |
478 | #ifdef CUSTOM_FAILED_LOGIN | |
479 | record_failed_login(user, | |
480 | get_canonical_hostname(options.use_dns), "ssh"); | |
481 | #endif | |
482 | #ifdef SSH_AUDIT_EVENTS | |
483 | audit_event(SSH_INVALID_USER); | |
484 | #endif /* SSH_AUDIT_EVENTS */ | |
485 | return (NULL); | |
486 | } | |
487 | if (!allowed_user(pw)) | |
488 | return (NULL); | |
489 | #ifdef HAVE_LOGIN_CAP | |
490 | if ((lc = login_getclass(pw->pw_class)) == NULL) { | |
491 | debug("unable to get login class: %s", user); | |
492 | return (NULL); | |
493 | } | |
494 | #ifdef BSD_AUTH | |
495 | if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || | |
496 | auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { | |
497 | debug("Approval failure for %s", user); | |
498 | pw = NULL; | |
499 | } | |
500 | if (as != NULL) | |
501 | auth_close(as); | |
502 | #endif | |
503 | #endif | |
504 | if (pw != NULL) | |
505 | return (pwcopy(pw)); | |
506 | return (NULL); | |
507 | } | |
508 | ||
509 | void | |
510 | auth_debug_add(const char *fmt,...) | |
511 | { | |
512 | char buf[1024]; | |
513 | va_list args; | |
514 | ||
515 | if (!auth_debug_init) | |
516 | return; | |
517 | ||
518 | va_start(args, fmt); | |
519 | vsnprintf(buf, sizeof(buf), fmt, args); | |
520 | va_end(args); | |
521 | buffer_put_cstring(&auth_debug, buf); | |
522 | } | |
523 | ||
524 | void | |
525 | auth_debug_send(void) | |
526 | { | |
527 | char *msg; | |
528 | ||
529 | if (!auth_debug_init) | |
530 | return; | |
531 | while (buffer_len(&auth_debug)) { | |
532 | msg = buffer_get_string(&auth_debug, NULL); | |
533 | packet_send_debug("%s", msg); | |
534 | xfree(msg); | |
535 | } | |
536 | } | |
537 | ||
538 | void | |
539 | auth_debug_reset(void) | |
540 | { | |
541 | if (auth_debug_init) | |
542 | buffer_clear(&auth_debug); | |
543 | else { | |
544 | buffer_init(&auth_debug); | |
545 | auth_debug_init = 1; | |
546 | } | |
547 | } | |
548 | ||
549 | struct passwd * | |
550 | fakepw(void) | |
551 | { | |
552 | static struct passwd fake; | |
553 | ||
554 | memset(&fake, 0, sizeof(fake)); | |
555 | fake.pw_name = "NOUSER"; | |
556 | fake.pw_passwd = | |
557 | "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; | |
558 | fake.pw_gecos = "NOUSER"; | |
559 | fake.pw_uid = (uid_t)-1; | |
560 | fake.pw_gid = (gid_t)-1; | |
561 | #ifdef HAVE_PW_CLASS_IN_PASSWD | |
562 | fake.pw_class = ""; | |
563 | #endif | |
564 | fake.pw_dir = "/nonexist"; | |
565 | fake.pw_shell = "/nonexist"; | |
566 | ||
567 | return (&fake); | |
568 | } |