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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 1.51 2003/11/21 11:57:02 djm 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 "tildexpand.h" | |
51 | #include "misc.h" | |
52 | #include "bufaux.h" | |
53 | #include "packet.h" | |
54 | ||
55 | /* import */ | |
56 | extern ServerOptions options; | |
57 | extern Buffer loginmsg; | |
58 | ||
59 | /* Debugging messages */ | |
60 | Buffer auth_debug; | |
61 | int auth_debug_init; | |
62 | ||
63 | /* | |
64 | * Check if the user is allowed to log in via ssh. If user is listed | |
65 | * in DenyUsers or one of user's groups is listed in DenyGroups, false | |
66 | * will be returned. If AllowUsers isn't empty and user isn't listed | |
67 | * there, or if AllowGroups isn't empty and one of user's groups isn't | |
68 | * listed there, false will be returned. | |
69 | * If the user's shell is not executable, false will be returned. | |
70 | * Otherwise true is returned. | |
71 | */ | |
72 | int | |
73 | allowed_user(struct passwd * pw) | |
74 | { | |
75 | struct stat st; | |
76 | const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; | |
77 | char *shell; | |
78 | int i; | |
79 | #ifdef USE_SHADOW | |
80 | struct spwd *spw = NULL; | |
81 | #endif | |
82 | ||
83 | /* Shouldn't be called if pw is NULL, but better safe than sorry... */ | |
84 | if (!pw || !pw->pw_name) | |
85 | return 0; | |
86 | ||
87 | #ifdef USE_SHADOW | |
88 | if (!options.use_pam) | |
89 | spw = getspnam(pw->pw_name); | |
90 | #ifdef HAS_SHADOW_EXPIRE | |
91 | if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw)) | |
92 | return 0; | |
93 | #endif /* HAS_SHADOW_EXPIRE */ | |
94 | #endif /* USE_SHADOW */ | |
95 | ||
96 | /* grab passwd field for locked account check */ | |
97 | #ifdef USE_SHADOW | |
98 | if (spw != NULL) | |
99 | passwd = spw->sp_pwdp; | |
100 | #else | |
101 | passwd = pw->pw_passwd; | |
102 | #endif | |
103 | ||
104 | /* check for locked account */ | |
105 | if (!options.use_pam && passwd && *passwd) { | |
106 | int locked = 0; | |
107 | ||
108 | #ifdef LOCKED_PASSWD_STRING | |
109 | if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0) | |
110 | locked = 1; | |
111 | #endif | |
112 | #ifdef LOCKED_PASSWD_PREFIX | |
113 | if (strncmp(passwd, LOCKED_PASSWD_PREFIX, | |
114 | strlen(LOCKED_PASSWD_PREFIX)) == 0) | |
115 | locked = 1; | |
116 | #endif | |
117 | #ifdef LOCKED_PASSWD_SUBSTR | |
118 | if (strstr(passwd, LOCKED_PASSWD_SUBSTR)) | |
119 | locked = 1; | |
120 | #endif | |
121 | if (locked) { | |
122 | logit("User %.100s not allowed because account is locked", | |
123 | pw->pw_name); | |
124 | return 0; | |
125 | } | |
126 | } | |
127 | ||
128 | /* | |
129 | * Get the shell from the password data. An empty shell field is | |
130 | * legal, and means /bin/sh. | |
131 | */ | |
132 | shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell; | |
133 | ||
134 | /* deny if shell does not exists or is not executable */ | |
135 | if (stat(shell, &st) != 0) { | |
136 | logit("User %.100s not allowed because shell %.100s does not exist", | |
137 | pw->pw_name, shell); | |
138 | return 0; | |
139 | } | |
140 | if (S_ISREG(st.st_mode) == 0 || | |
141 | (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { | |
142 | logit("User %.100s not allowed because shell %.100s is not executable", | |
143 | pw->pw_name, shell); | |
144 | return 0; | |
145 | } | |
146 | ||
147 | if (options.num_deny_users > 0 || options.num_allow_users > 0) { | |
148 | hostname = get_canonical_hostname(options.use_dns); | |
149 | ipaddr = get_remote_ipaddr(); | |
150 | } | |
151 | ||
152 | /* Return false if user is listed in DenyUsers */ | |
153 | if (options.num_deny_users > 0) { | |
154 | for (i = 0; i < options.num_deny_users; i++) | |
155 | if (match_user(pw->pw_name, hostname, ipaddr, | |
156 | options.deny_users[i])) { | |
157 | logit("User %.100s not allowed because listed in DenyUsers", | |
158 | pw->pw_name); | |
159 | return 0; | |
160 | } | |
161 | } | |
162 | /* Return false if AllowUsers isn't empty and user isn't listed there */ | |
163 | if (options.num_allow_users > 0) { | |
164 | for (i = 0; i < options.num_allow_users; i++) | |
165 | if (match_user(pw->pw_name, hostname, ipaddr, | |
166 | options.allow_users[i])) | |
167 | break; | |
168 | /* i < options.num_allow_users iff we break for loop */ | |
169 | if (i >= options.num_allow_users) { | |
170 | logit("User %.100s not allowed because not listed in AllowUsers", | |
171 | pw->pw_name); | |
172 | return 0; | |
173 | } | |
174 | } | |
175 | if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { | |
176 | /* Get the user's group access list (primary and supplementary) */ | |
177 | if (ga_init(pw->pw_name, pw->pw_gid) == 0) { | |
178 | logit("User %.100s not allowed because not in any group", | |
179 | pw->pw_name); | |
180 | return 0; | |
181 | } | |
182 | ||
183 | /* Return false if one of user's groups is listed in DenyGroups */ | |
184 | if (options.num_deny_groups > 0) | |
185 | if (ga_match(options.deny_groups, | |
186 | options.num_deny_groups)) { | |
187 | ga_free(); | |
188 | logit("User %.100s not allowed because a group is listed in DenyGroups", | |
189 | pw->pw_name); | |
190 | return 0; | |
191 | } | |
192 | /* | |
193 | * Return false if AllowGroups isn't empty and one of user's groups | |
194 | * isn't listed there | |
195 | */ | |
196 | if (options.num_allow_groups > 0) | |
197 | if (!ga_match(options.allow_groups, | |
198 | options.num_allow_groups)) { | |
199 | ga_free(); | |
200 | logit("User %.100s not allowed because none of user's groups are listed in AllowGroups", | |
201 | pw->pw_name); | |
202 | return 0; | |
203 | } | |
204 | ga_free(); | |
205 | } | |
206 | ||
207 | #ifdef WITH_AIXAUTHENTICATE | |
208 | /* | |
209 | * Don't check loginrestrictions() for root account (use | |
210 | * PermitRootLogin to control logins via ssh), or if running as | |
211 | * non-root user (since loginrestrictions will always fail). | |
212 | */ | |
213 | if ((pw->pw_uid != 0) && (geteuid() == 0)) { | |
214 | char *msg; | |
215 | ||
216 | if (loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &msg) != 0) { | |
217 | int loginrestrict_errno = errno; | |
218 | ||
219 | if (msg && *msg) { | |
220 | buffer_append(&loginmsg, msg, strlen(msg)); | |
221 | aix_remove_embedded_newlines(msg); | |
222 | logit("Login restricted for %s: %.100s", | |
223 | pw->pw_name, msg); | |
224 | } | |
225 | /* Don't fail if /etc/nologin set */ | |
226 | if (!(loginrestrict_errno == EPERM && | |
227 | stat(_PATH_NOLOGIN, &st) == 0)) | |
228 | return 0; | |
229 | } | |
230 | } | |
231 | #endif /* WITH_AIXAUTHENTICATE */ | |
232 | ||
233 | /* We found no reason not to let this user try to log on... */ | |
234 | return 1; | |
235 | } | |
236 | ||
237 | void | |
238 | auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) | |
239 | { | |
240 | void (*authlog) (const char *fmt,...) = verbose; | |
241 | char *authmsg; | |
242 | ||
243 | /* Raise logging level */ | |
244 | if (authenticated == 1 || | |
245 | !authctxt->valid || | |
246 | authctxt->failures >= AUTH_FAIL_LOG || | |
247 | strcmp(method, "password") == 0) | |
248 | authlog = logit; | |
249 | ||
250 | if (authctxt->postponed) | |
251 | authmsg = "Postponed"; | |
252 | else | |
253 | authmsg = authenticated ? "Accepted" : "Failed"; | |
254 | ||
255 | authlog("%s %s for %s%.100s from %.200s port %d%s", | |
256 | authmsg, | |
257 | method, | |
258 | authctxt->valid ? "" : "illegal user ", | |
259 | authctxt->user, | |
260 | get_remote_ipaddr(), | |
261 | get_remote_port(), | |
262 | info); | |
263 | ||
264 | #ifdef CUSTOM_FAILED_LOGIN | |
265 | if (authenticated == 0 && strcmp(method, "password") == 0) | |
266 | record_failed_login(authctxt->user, "ssh"); | |
267 | #endif | |
268 | } | |
269 | ||
270 | /* | |
271 | * Check whether root logins are disallowed. | |
272 | */ | |
273 | int | |
274 | auth_root_allowed(char *method) | |
275 | { | |
276 | switch (options.permit_root_login) { | |
277 | case PERMIT_YES: | |
278 | return 1; | |
279 | break; | |
280 | case PERMIT_NO_PASSWD: | |
281 | if (strcmp(method, "password") != 0) | |
282 | return 1; | |
283 | break; | |
284 | case PERMIT_FORCED_ONLY: | |
285 | if (forced_command) { | |
286 | logit("Root login accepted for forced command."); | |
287 | return 1; | |
288 | } | |
289 | break; | |
290 | } | |
291 | logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); | |
292 | return 0; | |
293 | } | |
294 | ||
295 | ||
296 | /* | |
297 | * Given a template and a passwd structure, build a filename | |
298 | * by substituting % tokenised options. Currently, %% becomes '%', | |
299 | * %h becomes the home directory and %u the username. | |
300 | * | |
301 | * This returns a buffer allocated by xmalloc. | |
302 | */ | |
303 | char * | |
304 | expand_filename(const char *filename, struct passwd *pw) | |
305 | { | |
306 | Buffer buffer; | |
307 | char *file; | |
308 | const char *cp; | |
309 | ||
310 | /* | |
311 | * Build the filename string in the buffer by making the appropriate | |
312 | * substitutions to the given file name. | |
313 | */ | |
314 | buffer_init(&buffer); | |
315 | for (cp = filename; *cp; cp++) { | |
316 | if (cp[0] == '%' && cp[1] == '%') { | |
317 | buffer_append(&buffer, "%", 1); | |
318 | cp++; | |
319 | continue; | |
320 | } | |
321 | if (cp[0] == '%' && cp[1] == 'h') { | |
322 | buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir)); | |
323 | cp++; | |
324 | continue; | |
325 | } | |
326 | if (cp[0] == '%' && cp[1] == 'u') { | |
327 | buffer_append(&buffer, pw->pw_name, | |
328 | strlen(pw->pw_name)); | |
329 | cp++; | |
330 | continue; | |
331 | } | |
332 | buffer_append(&buffer, cp, 1); | |
333 | } | |
334 | buffer_append(&buffer, "\0", 1); | |
335 | ||
336 | /* | |
337 | * Ensure that filename starts anchored. If not, be backward | |
338 | * compatible and prepend the '%h/' | |
339 | */ | |
340 | file = xmalloc(MAXPATHLEN); | |
341 | cp = buffer_ptr(&buffer); | |
342 | if (*cp != '/') | |
343 | snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp); | |
344 | else | |
345 | strlcpy(file, cp, MAXPATHLEN); | |
346 | ||
347 | buffer_free(&buffer); | |
348 | return file; | |
349 | } | |
350 | ||
351 | char * | |
352 | authorized_keys_file(struct passwd *pw) | |
353 | { | |
354 | return expand_filename(options.authorized_keys_file, pw); | |
355 | } | |
356 | ||
357 | char * | |
358 | authorized_keys_file2(struct passwd *pw) | |
359 | { | |
360 | return expand_filename(options.authorized_keys_file2, pw); | |
361 | } | |
362 | ||
363 | /* return ok if key exists in sysfile or userfile */ | |
364 | HostStatus | |
365 | check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, | |
366 | const char *sysfile, const char *userfile) | |
367 | { | |
368 | Key *found; | |
369 | char *user_hostfile; | |
370 | struct stat st; | |
371 | HostStatus host_status; | |
372 | ||
373 | /* Check if we know the host and its host key. */ | |
374 | found = key_new(key->type); | |
375 | host_status = check_host_in_hostfile(sysfile, host, key, found, NULL); | |
376 | ||
377 | if (host_status != HOST_OK && userfile != NULL) { | |
378 | user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); | |
379 | if (options.strict_modes && | |
380 | (stat(user_hostfile, &st) == 0) && | |
381 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
382 | (st.st_mode & 022) != 0)) { | |
383 | logit("Authentication refused for %.100s: " | |
384 | "bad owner or modes for %.200s", | |
385 | pw->pw_name, user_hostfile); | |
386 | } else { | |
387 | temporarily_use_uid(pw); | |
388 | host_status = check_host_in_hostfile(user_hostfile, | |
389 | host, key, found, NULL); | |
390 | restore_uid(); | |
391 | } | |
392 | xfree(user_hostfile); | |
393 | } | |
394 | key_free(found); | |
395 | ||
396 | debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ? | |
397 | "ok" : "not found", host); | |
398 | return host_status; | |
399 | } | |
400 | ||
401 | ||
402 | /* | |
403 | * Check a given file for security. This is defined as all components | |
404 | * of the path to the file must be owned by either the owner of | |
405 | * of the file or root and no directories must be group or world writable. | |
406 | * | |
407 | * XXX Should any specific check be done for sym links ? | |
408 | * | |
409 | * Takes an open file descriptor, the file name, a uid and and | |
410 | * error buffer plus max size as arguments. | |
411 | * | |
412 | * Returns 0 on success and -1 on failure | |
413 | */ | |
414 | int | |
415 | secure_filename(FILE *f, const char *file, struct passwd *pw, | |
416 | char *err, size_t errlen) | |
417 | { | |
418 | uid_t uid = pw->pw_uid; | |
419 | char buf[MAXPATHLEN], homedir[MAXPATHLEN]; | |
420 | char *cp; | |
421 | int comparehome = 0; | |
422 | struct stat st; | |
423 | ||
424 | if (realpath(file, buf) == NULL) { | |
425 | snprintf(err, errlen, "realpath %s failed: %s", file, | |
426 | strerror(errno)); | |
427 | return -1; | |
428 | } | |
429 | if (realpath(pw->pw_dir, homedir) != NULL) | |
430 | comparehome = 1; | |
431 | ||
432 | /* check the open file to avoid races */ | |
433 | if (fstat(fileno(f), &st) < 0 || | |
434 | (st.st_uid != 0 && st.st_uid != uid) || | |
435 | (st.st_mode & 022) != 0) { | |
436 | snprintf(err, errlen, "bad ownership or modes for file %s", | |
437 | buf); | |
438 | return -1; | |
439 | } | |
440 | ||
441 | /* for each component of the canonical path, walking upwards */ | |
442 | for (;;) { | |
443 | if ((cp = dirname(buf)) == NULL) { | |
444 | snprintf(err, errlen, "dirname() failed"); | |
445 | return -1; | |
446 | } | |
447 | strlcpy(buf, cp, sizeof(buf)); | |
448 | ||
449 | debug3("secure_filename: checking '%s'", buf); | |
450 | if (stat(buf, &st) < 0 || | |
451 | (st.st_uid != 0 && st.st_uid != uid) || | |
452 | (st.st_mode & 022) != 0) { | |
453 | snprintf(err, errlen, | |
454 | "bad ownership or modes for directory %s", buf); | |
455 | return -1; | |
456 | } | |
457 | ||
458 | /* If are passed the homedir then we can stop */ | |
459 | if (comparehome && strcmp(homedir, buf) == 0) { | |
460 | debug3("secure_filename: terminating check at '%s'", | |
461 | buf); | |
462 | break; | |
463 | } | |
464 | /* | |
465 | * dirname should always complete with a "/" path, | |
466 | * but we can be paranoid and check for "." too | |
467 | */ | |
468 | if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) | |
469 | break; | |
470 | } | |
471 | return 0; | |
472 | } | |
473 | ||
474 | struct passwd * | |
475 | getpwnamallow(const char *user) | |
476 | { | |
477 | #ifdef HAVE_LOGIN_CAP | |
478 | extern login_cap_t *lc; | |
479 | #ifdef BSD_AUTH | |
480 | auth_session_t *as; | |
481 | #endif | |
482 | #endif | |
483 | struct passwd *pw; | |
484 | ||
485 | pw = getpwnam(user); | |
486 | if (pw == NULL) { | |
487 | logit("Illegal user %.100s from %.100s", | |
488 | user, get_remote_ipaddr()); | |
489 | #ifdef CUSTOM_FAILED_LOGIN | |
490 | record_failed_login(user, "ssh"); | |
491 | #endif | |
492 | return (NULL); | |
493 | } | |
494 | if (!allowed_user(pw)) | |
495 | return (NULL); | |
496 | #ifdef HAVE_LOGIN_CAP | |
497 | if ((lc = login_getclass(pw->pw_class)) == NULL) { | |
498 | debug("unable to get login class: %s", user); | |
499 | return (NULL); | |
500 | } | |
501 | #ifdef BSD_AUTH | |
502 | if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || | |
503 | auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { | |
504 | debug("Approval failure for %s", user); | |
505 | pw = NULL; | |
506 | } | |
507 | if (as != NULL) | |
508 | auth_close(as); | |
509 | #endif | |
510 | #endif | |
511 | if (pw != NULL) | |
512 | return (pwcopy(pw)); | |
513 | return (NULL); | |
514 | } | |
515 | ||
516 | void | |
517 | auth_debug_add(const char *fmt,...) | |
518 | { | |
519 | char buf[1024]; | |
520 | va_list args; | |
521 | ||
522 | if (!auth_debug_init) | |
523 | return; | |
524 | ||
525 | va_start(args, fmt); | |
526 | vsnprintf(buf, sizeof(buf), fmt, args); | |
527 | va_end(args); | |
528 | buffer_put_cstring(&auth_debug, buf); | |
529 | } | |
530 | ||
531 | void | |
532 | auth_debug_send(void) | |
533 | { | |
534 | char *msg; | |
535 | ||
536 | if (!auth_debug_init) | |
537 | return; | |
538 | while (buffer_len(&auth_debug)) { | |
539 | msg = buffer_get_string(&auth_debug, NULL); | |
540 | packet_send_debug("%s", msg); | |
541 | xfree(msg); | |
542 | } | |
543 | } | |
544 | ||
545 | void | |
546 | auth_debug_reset(void) | |
547 | { | |
548 | if (auth_debug_init) | |
549 | buffer_clear(&auth_debug); | |
550 | else { | |
551 | buffer_init(&auth_debug); | |
552 | auth_debug_init = 1; | |
553 | } | |
554 | } | |
555 | ||
556 | struct passwd * | |
557 | fakepw(void) | |
558 | { | |
559 | static struct passwd fake; | |
560 | ||
561 | memset(&fake, 0, sizeof(fake)); | |
562 | fake.pw_name = "NOUSER"; | |
563 | fake.pw_passwd = | |
564 | "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; | |
565 | fake.pw_gecos = "NOUSER"; | |
566 | fake.pw_uid = -1; | |
567 | fake.pw_gid = -1; | |
568 | #ifdef HAVE_PW_CLASS_IN_PASSWD | |
569 | fake.pw_class = ""; | |
570 | #endif | |
571 | fake.pw_dir = "/nonexist"; | |
572 | fake.pw_shell = "/nonexist"; | |
573 | ||
574 | return (&fake); | |
575 | } |