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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 1.37 2002/03/17 20:25:56 provos 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 | ||
52 | /* import */ | |
53 | extern ServerOptions options; | |
54 | ||
55 | /* | |
56 | * Check if the user is allowed to log in via ssh. If user is listed | |
57 | * in DenyUsers or one of user's groups is listed in DenyGroups, false | |
58 | * will be returned. If AllowUsers isn't empty and user isn't listed | |
59 | * there, or if AllowGroups isn't empty and one of user's groups isn't | |
60 | * listed there, false will be returned. | |
61 | * If the user's shell is not executable, false will be returned. | |
62 | * Otherwise true is returned. | |
63 | */ | |
64 | int | |
65 | allowed_user(struct passwd * pw) | |
66 | { | |
67 | struct stat st; | |
68 | const char *hostname = NULL, *ipaddr = NULL; | |
69 | char *shell; | |
70 | int i; | |
71 | #ifdef WITH_AIXAUTHENTICATE | |
72 | char *loginmsg; | |
73 | #endif /* WITH_AIXAUTHENTICATE */ | |
74 | #if !defined(USE_PAM) && defined(HAVE_SHADOW_H) && \ | |
75 | !defined(DISABLE_SHADOW) && defined(HAS_SHADOW_EXPIRE) | |
76 | struct spwd *spw; | |
77 | ||
78 | /* Shouldn't be called if pw is NULL, but better safe than sorry... */ | |
79 | if (!pw || !pw->pw_name) | |
80 | return 0; | |
81 | ||
82 | spw = getspnam(pw->pw_name); | |
83 | if (spw != NULL) { | |
84 | int days = time(NULL) / 86400; | |
85 | ||
86 | /* Check account expiry */ | |
87 | if ((spw->sp_expire >= 0) && (days > spw->sp_expire)) | |
88 | return 0; | |
89 | ||
90 | /* Check password expiry */ | |
91 | if ((spw->sp_lstchg >= 0) && (spw->sp_max >= 0) && | |
92 | (days > (spw->sp_lstchg + spw->sp_max))) | |
93 | return 0; | |
94 | } | |
95 | #else | |
96 | /* Shouldn't be called if pw is NULL, but better safe than sorry... */ | |
97 | if (!pw || !pw->pw_name) | |
98 | return 0; | |
99 | #endif | |
100 | ||
101 | /* | |
102 | * Get the shell from the password data. An empty shell field is | |
103 | * legal, and means /bin/sh. | |
104 | */ | |
105 | shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell; | |
106 | ||
107 | /* deny if shell does not exists or is not executable */ | |
108 | if (stat(shell, &st) != 0) { | |
109 | log("User %.100s not allowed because shell %.100s does not exist", | |
110 | pw->pw_name, shell); | |
111 | return 0; | |
112 | } | |
113 | if (S_ISREG(st.st_mode) == 0 || | |
114 | (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { | |
115 | log("User %.100s not allowed because shell %.100s is not executable", | |
116 | pw->pw_name, shell); | |
117 | return 0; | |
118 | } | |
119 | ||
120 | if (options.num_deny_users > 0 || options.num_allow_users > 0) { | |
121 | hostname = get_canonical_hostname(options.verify_reverse_mapping); | |
122 | ipaddr = get_remote_ipaddr(); | |
123 | } | |
124 | ||
125 | /* Return false if user is listed in DenyUsers */ | |
126 | if (options.num_deny_users > 0) { | |
127 | for (i = 0; i < options.num_deny_users; i++) | |
128 | if (match_user(pw->pw_name, hostname, ipaddr, | |
129 | options.deny_users[i])) { | |
130 | log("User %.100s not allowed because listed in DenyUsers", | |
131 | pw->pw_name); | |
132 | return 0; | |
133 | } | |
134 | } | |
135 | /* Return false if AllowUsers isn't empty and user isn't listed there */ | |
136 | if (options.num_allow_users > 0) { | |
137 | for (i = 0; i < options.num_allow_users; i++) | |
138 | if (match_user(pw->pw_name, hostname, ipaddr, | |
139 | options.allow_users[i])) | |
140 | break; | |
141 | /* i < options.num_allow_users iff we break for loop */ | |
142 | if (i >= options.num_allow_users) { | |
143 | log("User %.100s not allowed because not listed in AllowUsers", | |
144 | pw->pw_name); | |
145 | return 0; | |
146 | } | |
147 | } | |
148 | if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { | |
149 | /* Get the user's group access list (primary and supplementary) */ | |
150 | if (ga_init(pw->pw_name, pw->pw_gid) == 0) { | |
151 | log("User %.100s not allowed because not in any group", | |
152 | pw->pw_name); | |
153 | return 0; | |
154 | } | |
155 | ||
156 | /* Return false if one of user's groups is listed in DenyGroups */ | |
157 | if (options.num_deny_groups > 0) | |
158 | if (ga_match(options.deny_groups, | |
159 | options.num_deny_groups)) { | |
160 | ga_free(); | |
161 | log("User %.100s not allowed because a group is listed in DenyGroups", | |
162 | pw->pw_name); | |
163 | return 0; | |
164 | } | |
165 | /* | |
166 | * Return false if AllowGroups isn't empty and one of user's groups | |
167 | * isn't listed there | |
168 | */ | |
169 | if (options.num_allow_groups > 0) | |
170 | if (!ga_match(options.allow_groups, | |
171 | options.num_allow_groups)) { | |
172 | ga_free(); | |
173 | log("User %.100s not allowed because none of user's groups are listed in AllowGroups", | |
174 | pw->pw_name); | |
175 | return 0; | |
176 | } | |
177 | ga_free(); | |
178 | } | |
179 | ||
180 | #ifdef WITH_AIXAUTHENTICATE | |
181 | if (loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &loginmsg) != 0) { | |
182 | if (loginmsg && *loginmsg) { | |
183 | /* Remove embedded newlines (if any) */ | |
184 | char *p; | |
185 | for (p = loginmsg; *p; p++) { | |
186 | if (*p == '\n') | |
187 | *p = ' '; | |
188 | } | |
189 | /* Remove trailing newline */ | |
190 | *--p = '\0'; | |
191 | log("Login restricted for %s: %.100s", pw->pw_name, loginmsg); | |
192 | } | |
193 | return 0; | |
194 | } | |
195 | #endif /* WITH_AIXAUTHENTICATE */ | |
196 | ||
197 | /* We found no reason not to let this user try to log on... */ | |
198 | return 1; | |
199 | } | |
200 | ||
201 | Authctxt * | |
202 | authctxt_new(void) | |
203 | { | |
204 | Authctxt *authctxt = xmalloc(sizeof(*authctxt)); | |
205 | memset(authctxt, 0, sizeof(*authctxt)); | |
206 | return authctxt; | |
207 | } | |
208 | ||
209 | void | |
210 | auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) | |
211 | { | |
212 | void (*authlog) (const char *fmt,...) = verbose; | |
213 | char *authmsg; | |
214 | ||
215 | /* Raise logging level */ | |
216 | if (authenticated == 1 || | |
217 | !authctxt->valid || | |
218 | authctxt->failures >= AUTH_FAIL_LOG || | |
219 | strcmp(method, "password") == 0) | |
220 | authlog = log; | |
221 | ||
222 | if (authctxt->postponed) | |
223 | authmsg = "Postponed"; | |
224 | else | |
225 | authmsg = authenticated ? "Accepted" : "Failed"; | |
226 | ||
227 | authlog("%s %s for %s%.100s from %.200s port %d%s", | |
228 | authmsg, | |
229 | method, | |
230 | authctxt->valid ? "" : "illegal user ", | |
231 | authctxt->user, | |
232 | get_remote_ipaddr(), | |
233 | get_remote_port(), | |
234 | info); | |
235 | } | |
236 | ||
237 | /* | |
238 | * Check whether root logins are disallowed. | |
239 | */ | |
240 | int | |
241 | auth_root_allowed(char *method) | |
242 | { | |
243 | switch (options.permit_root_login) { | |
244 | case PERMIT_YES: | |
245 | return 1; | |
246 | break; | |
247 | case PERMIT_NO_PASSWD: | |
248 | if (strcmp(method, "password") != 0) | |
249 | return 1; | |
250 | break; | |
251 | case PERMIT_FORCED_ONLY: | |
252 | if (forced_command) { | |
253 | log("Root login accepted for forced command."); | |
254 | return 1; | |
255 | } | |
256 | break; | |
257 | } | |
258 | log("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); | |
259 | return 0; | |
260 | } | |
261 | ||
262 | ||
263 | /* | |
264 | * Given a template and a passwd structure, build a filename | |
265 | * by substituting % tokenised options. Currently, %% becomes '%', | |
266 | * %h becomes the home directory and %u the username. | |
267 | * | |
268 | * This returns a buffer allocated by xmalloc. | |
269 | */ | |
270 | char * | |
271 | expand_filename(const char *filename, struct passwd *pw) | |
272 | { | |
273 | Buffer buffer; | |
274 | char *file; | |
275 | const char *cp; | |
276 | ||
277 | /* | |
278 | * Build the filename string in the buffer by making the appropriate | |
279 | * substitutions to the given file name. | |
280 | */ | |
281 | buffer_init(&buffer); | |
282 | for (cp = filename; *cp; cp++) { | |
283 | if (cp[0] == '%' && cp[1] == '%') { | |
284 | buffer_append(&buffer, "%", 1); | |
285 | cp++; | |
286 | continue; | |
287 | } | |
288 | if (cp[0] == '%' && cp[1] == 'h') { | |
289 | buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir)); | |
290 | cp++; | |
291 | continue; | |
292 | } | |
293 | if (cp[0] == '%' && cp[1] == 'u') { | |
294 | buffer_append(&buffer, pw->pw_name, | |
295 | strlen(pw->pw_name)); | |
296 | cp++; | |
297 | continue; | |
298 | } | |
299 | buffer_append(&buffer, cp, 1); | |
300 | } | |
301 | buffer_append(&buffer, "\0", 1); | |
302 | ||
303 | /* | |
304 | * Ensure that filename starts anchored. If not, be backward | |
305 | * compatible and prepend the '%h/' | |
306 | */ | |
307 | file = xmalloc(MAXPATHLEN); | |
308 | cp = buffer_ptr(&buffer); | |
309 | if (*cp != '/') | |
310 | snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp); | |
311 | else | |
312 | strlcpy(file, cp, MAXPATHLEN); | |
313 | ||
314 | buffer_free(&buffer); | |
315 | return file; | |
316 | } | |
317 | ||
318 | char * | |
319 | authorized_keys_file(struct passwd *pw) | |
320 | { | |
321 | return expand_filename(options.authorized_keys_file, pw); | |
322 | } | |
323 | ||
324 | char * | |
325 | authorized_keys_file2(struct passwd *pw) | |
326 | { | |
327 | return expand_filename(options.authorized_keys_file2, pw); | |
328 | } | |
329 | ||
330 | /* return ok if key exists in sysfile or userfile */ | |
331 | HostStatus | |
332 | check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, | |
333 | const char *sysfile, const char *userfile) | |
334 | { | |
335 | Key *found; | |
336 | char *user_hostfile; | |
337 | struct stat st; | |
338 | HostStatus host_status; | |
339 | ||
340 | /* Check if we know the host and its host key. */ | |
341 | found = key_new(key->type); | |
342 | host_status = check_host_in_hostfile(sysfile, host, key, found, NULL); | |
343 | ||
344 | if (host_status != HOST_OK && userfile != NULL) { | |
345 | user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); | |
346 | if (options.strict_modes && | |
347 | (stat(user_hostfile, &st) == 0) && | |
348 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
349 | (st.st_mode & 022) != 0)) { | |
350 | log("Authentication refused for %.100s: " | |
351 | "bad owner or modes for %.200s", | |
352 | pw->pw_name, user_hostfile); | |
353 | } else { | |
354 | temporarily_use_uid(pw); | |
355 | host_status = check_host_in_hostfile(user_hostfile, | |
356 | host, key, found, NULL); | |
357 | restore_uid(); | |
358 | } | |
359 | xfree(user_hostfile); | |
360 | } | |
361 | key_free(found); | |
362 | ||
363 | debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ? | |
364 | "ok" : "not found", host); | |
365 | return host_status; | |
366 | } | |
367 | ||
368 | ||
369 | /* | |
370 | * Check a given file for security. This is defined as all components | |
371 | * of the path to the file must either be owned by either the owner of | |
372 | * of the file or root and no directories must be group or world writable. | |
373 | * | |
374 | * XXX Should any specific check be done for sym links ? | |
375 | * | |
376 | * Takes an open file descriptor, the file name, a uid and and | |
377 | * error buffer plus max size as arguments. | |
378 | * | |
379 | * Returns 0 on success and -1 on failure | |
380 | */ | |
381 | int | |
382 | secure_filename(FILE *f, const char *file, struct passwd *pw, | |
383 | char *err, size_t errlen) | |
384 | { | |
385 | uid_t uid = pw->pw_uid; | |
386 | char buf[MAXPATHLEN], homedir[MAXPATHLEN]; | |
387 | char *cp; | |
388 | struct stat st; | |
389 | ||
390 | if (realpath(file, buf) == NULL) { | |
391 | snprintf(err, errlen, "realpath %s failed: %s", file, | |
392 | strerror(errno)); | |
393 | return -1; | |
394 | } | |
395 | if (realpath(pw->pw_dir, homedir) == NULL) { | |
396 | snprintf(err, errlen, "realpath %s failed: %s", pw->pw_dir, | |
397 | strerror(errno)); | |
398 | return -1; | |
399 | } | |
400 | ||
401 | /* check the open file to avoid races */ | |
402 | if (fstat(fileno(f), &st) < 0 || | |
403 | (st.st_uid != 0 && st.st_uid != uid) || | |
404 | (st.st_mode & 022) != 0) { | |
405 | snprintf(err, errlen, "bad ownership or modes for file %s", | |
406 | buf); | |
407 | return -1; | |
408 | } | |
409 | ||
410 | /* for each component of the canonical path, walking upwards */ | |
411 | for (;;) { | |
412 | if ((cp = dirname(buf)) == NULL) { | |
413 | snprintf(err, errlen, "dirname() failed"); | |
414 | return -1; | |
415 | } | |
416 | strlcpy(buf, cp, sizeof(buf)); | |
417 | ||
418 | debug3("secure_filename: checking '%s'", buf); | |
419 | if (stat(buf, &st) < 0 || | |
420 | (st.st_uid != 0 && st.st_uid != uid) || | |
421 | (st.st_mode & 022) != 0) { | |
422 | snprintf(err, errlen, | |
423 | "bad ownership or modes for directory %s", buf); | |
424 | return -1; | |
425 | } | |
426 | ||
427 | /* If are passed the homedir then we can stop */ | |
428 | if (strcmp(homedir, buf) == 0) { | |
429 | debug3("secure_filename: terminating check at '%s'", | |
430 | buf); | |
431 | break; | |
432 | } | |
433 | /* | |
434 | * dirname should always complete with a "/" path, | |
435 | * but we can be paranoid and check for "." too | |
436 | */ | |
437 | if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) | |
438 | break; | |
439 | } | |
440 | return 0; | |
441 | } | |
442 | ||
443 | struct passwd * | |
444 | getpwnamallow(const char *user) | |
445 | { | |
446 | struct passwd *pw; | |
447 | ||
448 | pw = getpwnam(user); | |
449 | if (pw != NULL && !allowed_user(pw)) | |
450 | pw = NULL; | |
451 | ||
452 | return (pw); | |
453 | } |