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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 1.41 2002/03/19 15:31:47 markus Exp $"); | |
27 | ||
28 | #ifdef HAVE_LOGIN_H | |
29 | #include <login.h> | |
30 | #endif | |
31 | #if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) | |
32 | #include <shadow.h> | |
33 | #endif /* defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) */ | |
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 | ||
53 | /* import */ | |
54 | extern ServerOptions options; | |
55 | ||
56 | /* | |
57 | * Check if the user is allowed to log in via ssh. If user is listed | |
58 | * in DenyUsers or one of user's groups is listed in DenyGroups, false | |
59 | * will be returned. If AllowUsers isn't empty and user isn't listed | |
60 | * there, or if AllowGroups isn't empty and one of user's groups isn't | |
61 | * listed there, false will be returned. | |
62 | * If the user's shell is not executable, false will be returned. | |
63 | * Otherwise true is returned. | |
64 | */ | |
65 | int | |
66 | allowed_user(struct passwd * pw) | |
67 | { | |
68 | struct stat st; | |
69 | const char *hostname = NULL, *ipaddr = NULL; | |
70 | char *shell; | |
71 | int i; | |
72 | #ifdef WITH_AIXAUTHENTICATE | |
73 | char *loginmsg; | |
74 | #endif /* WITH_AIXAUTHENTICATE */ | |
75 | #if !defined(USE_PAM) && defined(HAVE_SHADOW_H) && \ | |
76 | !defined(DISABLE_SHADOW) && defined(HAS_SHADOW_EXPIRE) | |
77 | struct spwd *spw; | |
78 | ||
79 | /* Shouldn't be called if pw is NULL, but better safe than sorry... */ | |
80 | if (!pw || !pw->pw_name) | |
81 | return 0; | |
82 | ||
83 | spw = getspnam(pw->pw_name); | |
84 | if (spw != NULL) { | |
85 | int days = time(NULL) / 86400; | |
86 | ||
87 | /* Check account expiry */ | |
88 | if ((spw->sp_expire >= 0) && (days > spw->sp_expire)) | |
89 | return 0; | |
90 | ||
91 | /* Check password expiry */ | |
92 | if ((spw->sp_lstchg >= 0) && (spw->sp_max >= 0) && | |
93 | (days > (spw->sp_lstchg + spw->sp_max))) | |
94 | return 0; | |
95 | } | |
96 | #else | |
97 | /* Shouldn't be called if pw is NULL, but better safe than sorry... */ | |
98 | if (!pw || !pw->pw_name) | |
99 | return 0; | |
100 | #endif | |
101 | ||
102 | /* | |
103 | * Get the shell from the password data. An empty shell field is | |
104 | * legal, and means /bin/sh. | |
105 | */ | |
106 | shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell; | |
107 | ||
108 | /* deny if shell does not exists or is not executable */ | |
109 | if (stat(shell, &st) != 0) { | |
110 | log("User %.100s not allowed because shell %.100s does not exist", | |
111 | pw->pw_name, shell); | |
112 | return 0; | |
113 | } | |
114 | if (S_ISREG(st.st_mode) == 0 || | |
115 | (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { | |
116 | log("User %.100s not allowed because shell %.100s is not executable", | |
117 | pw->pw_name, shell); | |
118 | return 0; | |
119 | } | |
120 | ||
121 | if (options.num_deny_users > 0 || options.num_allow_users > 0) { | |
122 | hostname = get_canonical_hostname(options.verify_reverse_mapping); | |
123 | ipaddr = get_remote_ipaddr(); | |
124 | } | |
125 | ||
126 | /* Return false if user is listed in DenyUsers */ | |
127 | if (options.num_deny_users > 0) { | |
128 | for (i = 0; i < options.num_deny_users; i++) | |
129 | if (match_user(pw->pw_name, hostname, ipaddr, | |
130 | options.deny_users[i])) { | |
131 | log("User %.100s not allowed because listed in DenyUsers", | |
132 | pw->pw_name); | |
133 | return 0; | |
134 | } | |
135 | } | |
136 | /* Return false if AllowUsers isn't empty and user isn't listed there */ | |
137 | if (options.num_allow_users > 0) { | |
138 | for (i = 0; i < options.num_allow_users; i++) | |
139 | if (match_user(pw->pw_name, hostname, ipaddr, | |
140 | options.allow_users[i])) | |
141 | break; | |
142 | /* i < options.num_allow_users iff we break for loop */ | |
143 | if (i >= options.num_allow_users) { | |
144 | log("User %.100s not allowed because not listed in AllowUsers", | |
145 | pw->pw_name); | |
146 | return 0; | |
147 | } | |
148 | } | |
149 | if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { | |
150 | /* Get the user's group access list (primary and supplementary) */ | |
151 | if (ga_init(pw->pw_name, pw->pw_gid) == 0) { | |
152 | log("User %.100s not allowed because not in any group", | |
153 | pw->pw_name); | |
154 | return 0; | |
155 | } | |
156 | ||
157 | /* Return false if one of user's groups is listed in DenyGroups */ | |
158 | if (options.num_deny_groups > 0) | |
159 | if (ga_match(options.deny_groups, | |
160 | options.num_deny_groups)) { | |
161 | ga_free(); | |
162 | log("User %.100s not allowed because a group is listed in DenyGroups", | |
163 | pw->pw_name); | |
164 | return 0; | |
165 | } | |
166 | /* | |
167 | * Return false if AllowGroups isn't empty and one of user's groups | |
168 | * isn't listed there | |
169 | */ | |
170 | if (options.num_allow_groups > 0) | |
171 | if (!ga_match(options.allow_groups, | |
172 | options.num_allow_groups)) { | |
173 | ga_free(); | |
174 | log("User %.100s not allowed because none of user's groups are listed in AllowGroups", | |
175 | pw->pw_name); | |
176 | return 0; | |
177 | } | |
178 | ga_free(); | |
179 | } | |
180 | ||
181 | #ifdef WITH_AIXAUTHENTICATE | |
182 | if (loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &loginmsg) != 0) { | |
183 | if (loginmsg && *loginmsg) { | |
184 | /* Remove embedded newlines (if any) */ | |
185 | char *p; | |
186 | for (p = loginmsg; *p; p++) { | |
187 | if (*p == '\n') | |
188 | *p = ' '; | |
189 | } | |
190 | /* Remove trailing newline */ | |
191 | *--p = '\0'; | |
192 | log("Login restricted for %s: %.100s", pw->pw_name, loginmsg); | |
193 | } | |
194 | return 0; | |
195 | } | |
196 | #endif /* WITH_AIXAUTHENTICATE */ | |
197 | ||
198 | /* We found no reason not to let this user try to log on... */ | |
199 | return 1; | |
200 | } | |
201 | ||
202 | Authctxt * | |
203 | authctxt_new(void) | |
204 | { | |
205 | Authctxt *authctxt = xmalloc(sizeof(*authctxt)); | |
206 | memset(authctxt, 0, sizeof(*authctxt)); | |
207 | return authctxt; | |
208 | } | |
209 | ||
210 | void | |
211 | auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) | |
212 | { | |
213 | void (*authlog) (const char *fmt,...) = verbose; | |
214 | char *authmsg; | |
215 | ||
216 | /* Raise logging level */ | |
217 | if (authenticated == 1 || | |
218 | !authctxt->valid || | |
219 | authctxt->failures >= AUTH_FAIL_LOG || | |
220 | strcmp(method, "password") == 0) | |
221 | authlog = log; | |
222 | ||
223 | if (authctxt->postponed) | |
224 | authmsg = "Postponed"; | |
225 | else | |
226 | authmsg = authenticated ? "Accepted" : "Failed"; | |
227 | ||
228 | authlog("%s %s for %s%.100s from %.200s port %d%s", | |
229 | authmsg, | |
230 | method, | |
231 | authctxt->valid ? "" : "illegal user ", | |
232 | authctxt->user, | |
233 | get_remote_ipaddr(), | |
234 | get_remote_port(), | |
235 | info); | |
236 | } | |
237 | ||
238 | /* | |
239 | * Check whether root logins are disallowed. | |
240 | */ | |
241 | int | |
242 | auth_root_allowed(char *method) | |
243 | { | |
244 | switch (options.permit_root_login) { | |
245 | case PERMIT_YES: | |
246 | return 1; | |
247 | break; | |
248 | case PERMIT_NO_PASSWD: | |
249 | if (strcmp(method, "password") != 0) | |
250 | return 1; | |
251 | break; | |
252 | case PERMIT_FORCED_ONLY: | |
253 | if (forced_command) { | |
254 | log("Root login accepted for forced command."); | |
255 | return 1; | |
256 | } | |
257 | break; | |
258 | } | |
259 | log("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); | |
260 | return 0; | |
261 | } | |
262 | ||
263 | ||
264 | /* | |
265 | * Given a template and a passwd structure, build a filename | |
266 | * by substituting % tokenised options. Currently, %% becomes '%', | |
267 | * %h becomes the home directory and %u the username. | |
268 | * | |
269 | * This returns a buffer allocated by xmalloc. | |
270 | */ | |
271 | char * | |
272 | expand_filename(const char *filename, struct passwd *pw) | |
273 | { | |
274 | Buffer buffer; | |
275 | char *file; | |
276 | const char *cp; | |
277 | ||
278 | /* | |
279 | * Build the filename string in the buffer by making the appropriate | |
280 | * substitutions to the given file name. | |
281 | */ | |
282 | buffer_init(&buffer); | |
283 | for (cp = filename; *cp; cp++) { | |
284 | if (cp[0] == '%' && cp[1] == '%') { | |
285 | buffer_append(&buffer, "%", 1); | |
286 | cp++; | |
287 | continue; | |
288 | } | |
289 | if (cp[0] == '%' && cp[1] == 'h') { | |
290 | buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir)); | |
291 | cp++; | |
292 | continue; | |
293 | } | |
294 | if (cp[0] == '%' && cp[1] == 'u') { | |
295 | buffer_append(&buffer, pw->pw_name, | |
296 | strlen(pw->pw_name)); | |
297 | cp++; | |
298 | continue; | |
299 | } | |
300 | buffer_append(&buffer, cp, 1); | |
301 | } | |
302 | buffer_append(&buffer, "\0", 1); | |
303 | ||
304 | /* | |
305 | * Ensure that filename starts anchored. If not, be backward | |
306 | * compatible and prepend the '%h/' | |
307 | */ | |
308 | file = xmalloc(MAXPATHLEN); | |
309 | cp = buffer_ptr(&buffer); | |
310 | if (*cp != '/') | |
311 | snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp); | |
312 | else | |
313 | strlcpy(file, cp, MAXPATHLEN); | |
314 | ||
315 | buffer_free(&buffer); | |
316 | return file; | |
317 | } | |
318 | ||
319 | char * | |
320 | authorized_keys_file(struct passwd *pw) | |
321 | { | |
322 | return expand_filename(options.authorized_keys_file, pw); | |
323 | } | |
324 | ||
325 | char * | |
326 | authorized_keys_file2(struct passwd *pw) | |
327 | { | |
328 | return expand_filename(options.authorized_keys_file2, pw); | |
329 | } | |
330 | ||
331 | /* return ok if key exists in sysfile or userfile */ | |
332 | HostStatus | |
333 | check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, | |
334 | const char *sysfile, const char *userfile) | |
335 | { | |
336 | Key *found; | |
337 | char *user_hostfile; | |
338 | struct stat st; | |
339 | HostStatus host_status; | |
340 | ||
341 | /* Check if we know the host and its host key. */ | |
342 | found = key_new(key->type); | |
343 | host_status = check_host_in_hostfile(sysfile, host, key, found, NULL); | |
344 | ||
345 | if (host_status != HOST_OK && userfile != NULL) { | |
346 | user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); | |
347 | if (options.strict_modes && | |
348 | (stat(user_hostfile, &st) == 0) && | |
349 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
350 | (st.st_mode & 022) != 0)) { | |
351 | log("Authentication refused for %.100s: " | |
352 | "bad owner or modes for %.200s", | |
353 | pw->pw_name, user_hostfile); | |
354 | } else { | |
355 | temporarily_use_uid(pw); | |
356 | host_status = check_host_in_hostfile(user_hostfile, | |
357 | host, key, found, NULL); | |
358 | restore_uid(); | |
359 | } | |
360 | xfree(user_hostfile); | |
361 | } | |
362 | key_free(found); | |
363 | ||
364 | debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ? | |
365 | "ok" : "not found", host); | |
366 | return host_status; | |
367 | } | |
368 | ||
369 | ||
370 | /* | |
371 | * Check a given file for security. This is defined as all components | |
372 | * of the path to the file must either be owned by either the owner of | |
373 | * of the file or root and no directories must be group or world writable. | |
374 | * | |
375 | * XXX Should any specific check be done for sym links ? | |
376 | * | |
377 | * Takes an open file descriptor, the file name, a uid and and | |
378 | * error buffer plus max size as arguments. | |
379 | * | |
380 | * Returns 0 on success and -1 on failure | |
381 | */ | |
382 | int | |
383 | secure_filename(FILE *f, const char *file, struct passwd *pw, | |
384 | char *err, size_t errlen) | |
385 | { | |
386 | uid_t uid = pw->pw_uid; | |
387 | char buf[MAXPATHLEN], homedir[MAXPATHLEN]; | |
388 | char *cp; | |
389 | struct stat st; | |
390 | ||
391 | if (realpath(file, buf) == NULL) { | |
392 | snprintf(err, errlen, "realpath %s failed: %s", file, | |
393 | strerror(errno)); | |
394 | return -1; | |
395 | } | |
396 | if (realpath(pw->pw_dir, homedir) == NULL) { | |
397 | snprintf(err, errlen, "realpath %s failed: %s", pw->pw_dir, | |
398 | strerror(errno)); | |
399 | return -1; | |
400 | } | |
401 | ||
402 | /* check the open file to avoid races */ | |
403 | if (fstat(fileno(f), &st) < 0 || | |
404 | (st.st_uid != 0 && st.st_uid != uid) || | |
405 | (st.st_mode & 022) != 0) { | |
406 | snprintf(err, errlen, "bad ownership or modes for file %s", | |
407 | buf); | |
408 | return -1; | |
409 | } | |
410 | ||
411 | /* for each component of the canonical path, walking upwards */ | |
412 | for (;;) { | |
413 | if ((cp = dirname(buf)) == NULL) { | |
414 | snprintf(err, errlen, "dirname() failed"); | |
415 | return -1; | |
416 | } | |
417 | strlcpy(buf, cp, sizeof(buf)); | |
418 | ||
419 | debug3("secure_filename: checking '%s'", buf); | |
420 | if (stat(buf, &st) < 0 || | |
421 | (st.st_uid != 0 && st.st_uid != uid) || | |
422 | (st.st_mode & 022) != 0) { | |
423 | snprintf(err, errlen, | |
424 | "bad ownership or modes for directory %s", buf); | |
425 | return -1; | |
426 | } | |
427 | ||
428 | /* If are passed the homedir then we can stop */ | |
429 | if (strcmp(homedir, buf) == 0) { | |
430 | debug3("secure_filename: terminating check at '%s'", | |
431 | buf); | |
432 | break; | |
433 | } | |
434 | /* | |
435 | * dirname should always complete with a "/" path, | |
436 | * but we can be paranoid and check for "." too | |
437 | */ | |
438 | if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) | |
439 | break; | |
440 | } | |
441 | return 0; | |
442 | } | |
443 | ||
444 | struct passwd * | |
445 | getpwnamallow(const char *user) | |
446 | { | |
447 | #ifdef HAVE_LOGIN_CAP | |
448 | extern login_cap_t *lc; | |
449 | #ifdef BSD_AUTH | |
450 | auth_session_t *as; | |
451 | #endif | |
452 | #endif | |
453 | struct passwd *pw; | |
454 | ||
455 | pw = getpwnam(user); | |
456 | if (pw == NULL || !allowed_user(pw)) | |
457 | return (NULL); | |
458 | #ifdef HAVE_LOGIN_CAP | |
459 | if ((lc = login_getclass(pw->pw_class)) == NULL) { | |
460 | debug("unable to get login class: %s", user); | |
461 | return (NULL); | |
462 | } | |
463 | #ifdef BSD_AUTH | |
464 | if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || | |
465 | auth_approval(NULL, lc, pw->pw_name, "ssh") <= 0) { | |
466 | debug("Approval failure for %s", user); | |
467 | pw = NULL; | |
468 | } | |
469 | if (as != NULL) | |
470 | auth_close(as); | |
471 | #endif | |
472 | #endif | |
473 | if (pw != NULL) | |
474 | return (pwcopy(pw)); | |
475 | return (NULL); | |
476 | } |