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1 | /* | |
2 | * Copyright (c) 2000 Markus Friedl. All rights reserved. | |
3 | * | |
4 | * Redistribution and use in source and binary forms, with or without | |
5 | * modification, are permitted provided that the following conditions | |
6 | * are met: | |
7 | * 1. Redistributions of source code must retain the above copyright | |
8 | * notice, this list of conditions and the following disclaimer. | |
9 | * 2. Redistributions in binary form must reproduce the above copyright | |
10 | * notice, this list of conditions and the following disclaimer in the | |
11 | * documentation and/or other materials provided with the distribution. | |
12 | * | |
13 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR | |
14 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
15 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
16 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
17 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
18 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
19 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
20 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
21 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
22 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
23 | */ | |
24 | ||
25 | #include "includes.h" | |
26 | RCSID("$OpenBSD: auth.c,v 1.56 2004/07/28 09:40:29 markus Exp $"); | |
27 | ||
28 | #ifdef HAVE_LOGIN_H | |
29 | #include <login.h> | |
30 | #endif | |
31 | #ifdef USE_SHADOW | |
32 | #include <shadow.h> | |
33 | #endif | |
34 | ||
35 | #ifdef HAVE_LIBGEN_H | |
36 | #include <libgen.h> | |
37 | #endif | |
38 | ||
39 | #include "xmalloc.h" | |
40 | #include "match.h" | |
41 | #include "groupaccess.h" | |
42 | #include "log.h" | |
43 | #include "servconf.h" | |
44 | #include "auth.h" | |
45 | #include "auth-options.h" | |
46 | #include "canohost.h" | |
47 | #include "buffer.h" | |
48 | #include "bufaux.h" | |
49 | #include "uidswap.h" | |
50 | #include "misc.h" | |
51 | #include "bufaux.h" | |
52 | #include "packet.h" | |
53 | ||
54 | /* import */ | |
55 | extern ServerOptions options; | |
56 | extern Buffer loginmsg; | |
57 | ||
58 | /* Debugging messages */ | |
59 | Buffer auth_debug; | |
60 | int auth_debug_init; | |
61 | ||
62 | /* | |
63 | * Check if the user is allowed to log in via ssh. If user is listed | |
64 | * in DenyUsers or one of user's groups is listed in DenyGroups, false | |
65 | * will be returned. If AllowUsers isn't empty and user isn't listed | |
66 | * there, or if AllowGroups isn't empty and one of user's groups isn't | |
67 | * listed there, false will be returned. | |
68 | * If the user's shell is not executable, false will be returned. | |
69 | * Otherwise true is returned. | |
70 | */ | |
71 | int | |
72 | allowed_user(struct passwd * pw) | |
73 | { | |
74 | struct stat st; | |
75 | const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; | |
76 | char *shell; | |
77 | int i; | |
78 | #ifdef USE_SHADOW | |
79 | struct spwd *spw = NULL; | |
80 | #endif | |
81 | ||
82 | /* Shouldn't be called if pw is NULL, but better safe than sorry... */ | |
83 | if (!pw || !pw->pw_name) | |
84 | return 0; | |
85 | ||
86 | #ifdef USE_SHADOW | |
87 | if (!options.use_pam) | |
88 | spw = getspnam(pw->pw_name); | |
89 | #ifdef HAS_SHADOW_EXPIRE | |
90 | if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw)) | |
91 | return 0; | |
92 | #endif /* HAS_SHADOW_EXPIRE */ | |
93 | #endif /* USE_SHADOW */ | |
94 | ||
95 | /* grab passwd field for locked account check */ | |
96 | #ifdef USE_SHADOW | |
97 | if (spw != NULL) | |
98 | passwd = spw->sp_pwdp; | |
99 | #else | |
100 | passwd = pw->pw_passwd; | |
101 | #endif | |
102 | ||
103 | /* check for locked account */ | |
104 | if (!options.use_pam && passwd && *passwd) { | |
105 | int locked = 0; | |
106 | ||
107 | #ifdef LOCKED_PASSWD_STRING | |
108 | if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0) | |
109 | locked = 1; | |
110 | #endif | |
111 | #ifdef LOCKED_PASSWD_PREFIX | |
112 | if (strncmp(passwd, LOCKED_PASSWD_PREFIX, | |
113 | strlen(LOCKED_PASSWD_PREFIX)) == 0) | |
114 | locked = 1; | |
115 | #endif | |
116 | #ifdef LOCKED_PASSWD_SUBSTR | |
117 | if (strstr(passwd, LOCKED_PASSWD_SUBSTR)) | |
118 | locked = 1; | |
119 | #endif | |
120 | if (locked) { | |
121 | logit("User %.100s not allowed because account is locked", | |
122 | pw->pw_name); | |
123 | return 0; | |
124 | } | |
125 | } | |
126 | ||
127 | /* | |
128 | * Get the shell from the password data. An empty shell field is | |
129 | * legal, and means /bin/sh. | |
130 | */ | |
131 | shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell; | |
132 | ||
133 | /* deny if shell does not exists or is not executable */ | |
134 | if (stat(shell, &st) != 0) { | |
135 | logit("User %.100s not allowed because shell %.100s does not exist", | |
136 | pw->pw_name, shell); | |
137 | return 0; | |
138 | } | |
139 | if (S_ISREG(st.st_mode) == 0 || | |
140 | (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { | |
141 | logit("User %.100s not allowed because shell %.100s is not executable", | |
142 | pw->pw_name, shell); | |
143 | return 0; | |
144 | } | |
145 | ||
146 | if (options.num_deny_users > 0 || options.num_allow_users > 0) { | |
147 | hostname = get_canonical_hostname(options.use_dns); | |
148 | ipaddr = get_remote_ipaddr(); | |
149 | } | |
150 | ||
151 | /* Return false if user is listed in DenyUsers */ | |
152 | if (options.num_deny_users > 0) { | |
153 | for (i = 0; i < options.num_deny_users; i++) | |
154 | if (match_user(pw->pw_name, hostname, ipaddr, | |
155 | options.deny_users[i])) { | |
156 | logit("User %.100s not allowed because listed in DenyUsers", | |
157 | pw->pw_name); | |
158 | return 0; | |
159 | } | |
160 | } | |
161 | /* Return false if AllowUsers isn't empty and user isn't listed there */ | |
162 | if (options.num_allow_users > 0) { | |
163 | for (i = 0; i < options.num_allow_users; i++) | |
164 | if (match_user(pw->pw_name, hostname, ipaddr, | |
165 | options.allow_users[i])) | |
166 | break; | |
167 | /* i < options.num_allow_users iff we break for loop */ | |
168 | if (i >= options.num_allow_users) { | |
169 | logit("User %.100s not allowed because not listed in AllowUsers", | |
170 | pw->pw_name); | |
171 | return 0; | |
172 | } | |
173 | } | |
174 | if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { | |
175 | /* Get the user's group access list (primary and supplementary) */ | |
176 | if (ga_init(pw->pw_name, pw->pw_gid) == 0) { | |
177 | logit("User %.100s not allowed because not in any group", | |
178 | pw->pw_name); | |
179 | return 0; | |
180 | } | |
181 | ||
182 | /* Return false if one of user's groups is listed in DenyGroups */ | |
183 | if (options.num_deny_groups > 0) | |
184 | if (ga_match(options.deny_groups, | |
185 | options.num_deny_groups)) { | |
186 | ga_free(); | |
187 | logit("User %.100s not allowed because a group is listed in DenyGroups", | |
188 | pw->pw_name); | |
189 | return 0; | |
190 | } | |
191 | /* | |
192 | * Return false if AllowGroups isn't empty and one of user's groups | |
193 | * isn't listed there | |
194 | */ | |
195 | if (options.num_allow_groups > 0) | |
196 | if (!ga_match(options.allow_groups, | |
197 | options.num_allow_groups)) { | |
198 | ga_free(); | |
199 | logit("User %.100s not allowed because none of user's groups are listed in AllowGroups", | |
200 | pw->pw_name); | |
201 | return 0; | |
202 | } | |
203 | ga_free(); | |
204 | } | |
205 | ||
206 | #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER | |
207 | if (!sys_auth_allowed_user(pw)) | |
208 | return 0; | |
209 | #endif | |
210 | ||
211 | /* We found no reason not to let this user try to log on... */ | |
212 | return 1; | |
213 | } | |
214 | ||
215 | void | |
216 | auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) | |
217 | { | |
218 | void (*authlog) (const char *fmt,...) = verbose; | |
219 | char *authmsg; | |
220 | ||
221 | /* Raise logging level */ | |
222 | if (authenticated == 1 || | |
223 | !authctxt->valid || | |
224 | authctxt->failures >= options.max_authtries / 2 || | |
225 | strcmp(method, "password") == 0) | |
226 | authlog = logit; | |
227 | ||
228 | if (authctxt->postponed) | |
229 | authmsg = "Postponed"; | |
230 | else | |
231 | authmsg = authenticated ? "Accepted" : "Failed"; | |
232 | ||
233 | authlog("%s %s for %s%.100s from %.200s port %d%s", | |
234 | authmsg, | |
235 | method, | |
236 | authctxt->valid ? "" : "invalid user ", | |
237 | authctxt->user, | |
238 | get_remote_ipaddr(), | |
239 | get_remote_port(), | |
240 | info); | |
241 | ||
242 | #ifdef CUSTOM_FAILED_LOGIN | |
243 | if (authenticated == 0 && strcmp(method, "password") == 0) | |
244 | record_failed_login(authctxt->user, "ssh"); | |
245 | #endif | |
246 | } | |
247 | ||
248 | /* | |
249 | * Check whether root logins are disallowed. | |
250 | */ | |
251 | int | |
252 | auth_root_allowed(char *method) | |
253 | { | |
254 | switch (options.permit_root_login) { | |
255 | case PERMIT_YES: | |
256 | return 1; | |
257 | break; | |
258 | case PERMIT_NO_PASSWD: | |
259 | if (strcmp(method, "password") != 0) | |
260 | return 1; | |
261 | break; | |
262 | case PERMIT_FORCED_ONLY: | |
263 | if (forced_command) { | |
264 | logit("Root login accepted for forced command."); | |
265 | return 1; | |
266 | } | |
267 | break; | |
268 | } | |
269 | logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); | |
270 | return 0; | |
271 | } | |
272 | ||
273 | ||
274 | /* | |
275 | * Given a template and a passwd structure, build a filename | |
276 | * by substituting % tokenised options. Currently, %% becomes '%', | |
277 | * %h becomes the home directory and %u the username. | |
278 | * | |
279 | * This returns a buffer allocated by xmalloc. | |
280 | */ | |
281 | char * | |
282 | expand_filename(const char *filename, struct passwd *pw) | |
283 | { | |
284 | Buffer buffer; | |
285 | char *file; | |
286 | const char *cp; | |
287 | ||
288 | /* | |
289 | * Build the filename string in the buffer by making the appropriate | |
290 | * substitutions to the given file name. | |
291 | */ | |
292 | buffer_init(&buffer); | |
293 | for (cp = filename; *cp; cp++) { | |
294 | if (cp[0] == '%' && cp[1] == '%') { | |
295 | buffer_append(&buffer, "%", 1); | |
296 | cp++; | |
297 | continue; | |
298 | } | |
299 | if (cp[0] == '%' && cp[1] == 'h') { | |
300 | buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir)); | |
301 | cp++; | |
302 | continue; | |
303 | } | |
304 | if (cp[0] == '%' && cp[1] == 'u') { | |
305 | buffer_append(&buffer, pw->pw_name, | |
306 | strlen(pw->pw_name)); | |
307 | cp++; | |
308 | continue; | |
309 | } | |
310 | buffer_append(&buffer, cp, 1); | |
311 | } | |
312 | buffer_append(&buffer, "\0", 1); | |
313 | ||
314 | /* | |
315 | * Ensure that filename starts anchored. If not, be backward | |
316 | * compatible and prepend the '%h/' | |
317 | */ | |
318 | file = xmalloc(MAXPATHLEN); | |
319 | cp = buffer_ptr(&buffer); | |
320 | if (*cp != '/') | |
321 | snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp); | |
322 | else | |
323 | strlcpy(file, cp, MAXPATHLEN); | |
324 | ||
325 | buffer_free(&buffer); | |
326 | return file; | |
327 | } | |
328 | ||
329 | char * | |
330 | authorized_keys_file(struct passwd *pw) | |
331 | { | |
332 | return expand_filename(options.authorized_keys_file, pw); | |
333 | } | |
334 | ||
335 | char * | |
336 | authorized_keys_file2(struct passwd *pw) | |
337 | { | |
338 | return expand_filename(options.authorized_keys_file2, pw); | |
339 | } | |
340 | ||
341 | /* return ok if key exists in sysfile or userfile */ | |
342 | HostStatus | |
343 | check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, | |
344 | const char *sysfile, const char *userfile) | |
345 | { | |
346 | Key *found; | |
347 | char *user_hostfile; | |
348 | struct stat st; | |
349 | HostStatus host_status; | |
350 | ||
351 | /* Check if we know the host and its host key. */ | |
352 | found = key_new(key->type); | |
353 | host_status = check_host_in_hostfile(sysfile, host, key, found, NULL); | |
354 | ||
355 | if (host_status != HOST_OK && userfile != NULL) { | |
356 | user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); | |
357 | if (options.strict_modes && | |
358 | (stat(user_hostfile, &st) == 0) && | |
359 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
360 | (st.st_mode & 022) != 0)) { | |
361 | logit("Authentication refused for %.100s: " | |
362 | "bad owner or modes for %.200s", | |
363 | pw->pw_name, user_hostfile); | |
364 | } else { | |
365 | temporarily_use_uid(pw); | |
366 | host_status = check_host_in_hostfile(user_hostfile, | |
367 | host, key, found, NULL); | |
368 | restore_uid(); | |
369 | } | |
370 | xfree(user_hostfile); | |
371 | } | |
372 | key_free(found); | |
373 | ||
374 | debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ? | |
375 | "ok" : "not found", host); | |
376 | return host_status; | |
377 | } | |
378 | ||
379 | ||
380 | /* | |
381 | * Check a given file for security. This is defined as all components | |
382 | * of the path to the file must be owned by either the owner of | |
383 | * of the file or root and no directories must be group or world writable. | |
384 | * | |
385 | * XXX Should any specific check be done for sym links ? | |
386 | * | |
387 | * Takes an open file descriptor, the file name, a uid and and | |
388 | * error buffer plus max size as arguments. | |
389 | * | |
390 | * Returns 0 on success and -1 on failure | |
391 | */ | |
392 | int | |
393 | secure_filename(FILE *f, const char *file, struct passwd *pw, | |
394 | char *err, size_t errlen) | |
395 | { | |
396 | uid_t uid = pw->pw_uid; | |
397 | char buf[MAXPATHLEN], homedir[MAXPATHLEN]; | |
398 | char *cp; | |
399 | int comparehome = 0; | |
400 | struct stat st; | |
401 | ||
402 | if (realpath(file, buf) == NULL) { | |
403 | snprintf(err, errlen, "realpath %s failed: %s", file, | |
404 | strerror(errno)); | |
405 | return -1; | |
406 | } | |
407 | if (realpath(pw->pw_dir, homedir) != NULL) | |
408 | comparehome = 1; | |
409 | ||
410 | /* check the open file to avoid races */ | |
411 | if (fstat(fileno(f), &st) < 0 || | |
412 | (st.st_uid != 0 && st.st_uid != uid) || | |
413 | (st.st_mode & 022) != 0) { | |
414 | snprintf(err, errlen, "bad ownership or modes for file %s", | |
415 | buf); | |
416 | return -1; | |
417 | } | |
418 | ||
419 | /* for each component of the canonical path, walking upwards */ | |
420 | for (;;) { | |
421 | if ((cp = dirname(buf)) == NULL) { | |
422 | snprintf(err, errlen, "dirname() failed"); | |
423 | return -1; | |
424 | } | |
425 | strlcpy(buf, cp, sizeof(buf)); | |
426 | ||
427 | debug3("secure_filename: checking '%s'", buf); | |
428 | if (stat(buf, &st) < 0 || | |
429 | (st.st_uid != 0 && st.st_uid != uid) || | |
430 | (st.st_mode & 022) != 0) { | |
431 | snprintf(err, errlen, | |
432 | "bad ownership or modes for directory %s", buf); | |
433 | return -1; | |
434 | } | |
435 | ||
436 | /* If are passed the homedir then we can stop */ | |
437 | if (comparehome && strcmp(homedir, buf) == 0) { | |
438 | debug3("secure_filename: terminating check at '%s'", | |
439 | buf); | |
440 | break; | |
441 | } | |
442 | /* | |
443 | * dirname should always complete with a "/" path, | |
444 | * but we can be paranoid and check for "." too | |
445 | */ | |
446 | if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) | |
447 | break; | |
448 | } | |
449 | return 0; | |
450 | } | |
451 | ||
452 | struct passwd * | |
453 | getpwnamallow(const char *user) | |
454 | { | |
455 | #ifdef HAVE_LOGIN_CAP | |
456 | extern login_cap_t *lc; | |
457 | #ifdef BSD_AUTH | |
458 | auth_session_t *as; | |
459 | #endif | |
460 | #endif | |
461 | struct passwd *pw; | |
462 | ||
463 | pw = getpwnam(user); | |
464 | if (pw == NULL) { | |
465 | logit("Invalid user %.100s from %.100s", | |
466 | user, get_remote_ipaddr()); | |
467 | #ifdef CUSTOM_FAILED_LOGIN | |
468 | record_failed_login(user, "ssh"); | |
469 | #endif | |
470 | return (NULL); | |
471 | } | |
472 | if (!allowed_user(pw)) | |
473 | return (NULL); | |
474 | #ifdef HAVE_LOGIN_CAP | |
475 | if ((lc = login_getclass(pw->pw_class)) == NULL) { | |
476 | debug("unable to get login class: %s", user); | |
477 | return (NULL); | |
478 | } | |
479 | #ifdef BSD_AUTH | |
480 | if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || | |
481 | auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { | |
482 | debug("Approval failure for %s", user); | |
483 | pw = NULL; | |
484 | } | |
485 | if (as != NULL) | |
486 | auth_close(as); | |
487 | #endif | |
488 | #endif | |
489 | if (pw != NULL) | |
490 | return (pwcopy(pw)); | |
491 | return (NULL); | |
492 | } | |
493 | ||
494 | void | |
495 | auth_debug_add(const char *fmt,...) | |
496 | { | |
497 | char buf[1024]; | |
498 | va_list args; | |
499 | ||
500 | if (!auth_debug_init) | |
501 | return; | |
502 | ||
503 | va_start(args, fmt); | |
504 | vsnprintf(buf, sizeof(buf), fmt, args); | |
505 | va_end(args); | |
506 | buffer_put_cstring(&auth_debug, buf); | |
507 | } | |
508 | ||
509 | void | |
510 | auth_debug_send(void) | |
511 | { | |
512 | char *msg; | |
513 | ||
514 | if (!auth_debug_init) | |
515 | return; | |
516 | while (buffer_len(&auth_debug)) { | |
517 | msg = buffer_get_string(&auth_debug, NULL); | |
518 | packet_send_debug("%s", msg); | |
519 | xfree(msg); | |
520 | } | |
521 | } | |
522 | ||
523 | void | |
524 | auth_debug_reset(void) | |
525 | { | |
526 | if (auth_debug_init) | |
527 | buffer_clear(&auth_debug); | |
528 | else { | |
529 | buffer_init(&auth_debug); | |
530 | auth_debug_init = 1; | |
531 | } | |
532 | } | |
533 | ||
534 | struct passwd * | |
535 | fakepw(void) | |
536 | { | |
537 | static struct passwd fake; | |
538 | ||
539 | memset(&fake, 0, sizeof(fake)); | |
540 | fake.pw_name = "NOUSER"; | |
541 | fake.pw_passwd = | |
542 | "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; | |
543 | fake.pw_gecos = "NOUSER"; | |
544 | fake.pw_uid = (uid_t)-1; | |
545 | fake.pw_gid = (gid_t)-1; | |
546 | #ifdef HAVE_PW_CLASS_IN_PASSWD | |
547 | fake.pw_class = ""; | |
548 | #endif | |
549 | fake.pw_dir = "/nonexist"; | |
550 | fake.pw_shell = "/nonexist"; | |
551 | ||
552 | return (&fake); | |
553 | } |