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3c0ef626 | 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 1.29 2001/11/08 20:02:24 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 | ||
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 | return 0; | |
110 | if (!((st.st_mode & S_IFREG) && (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)))) | |
111 | return 0; | |
112 | ||
113 | if (options.num_deny_users > 0 || options.num_allow_users > 0) { | |
114 | hostname = get_canonical_hostname(options.reverse_mapping_check); | |
115 | ipaddr = get_remote_ipaddr(); | |
116 | } | |
117 | ||
118 | /* Return false if user is listed in DenyUsers */ | |
119 | if (options.num_deny_users > 0) { | |
120 | for (i = 0; i < options.num_deny_users; i++) | |
121 | if (match_user(pw->pw_name, hostname, ipaddr, | |
122 | options.deny_users[i])) | |
123 | return 0; | |
124 | } | |
125 | /* Return false if AllowUsers isn't empty and user isn't listed there */ | |
126 | if (options.num_allow_users > 0) { | |
127 | for (i = 0; i < options.num_allow_users; i++) | |
128 | if (match_user(pw->pw_name, hostname, ipaddr, | |
129 | options.allow_users[i])) | |
130 | break; | |
131 | /* i < options.num_allow_users iff we break for loop */ | |
132 | if (i >= options.num_allow_users) | |
133 | return 0; | |
134 | } | |
135 | if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { | |
136 | /* Get the user's group access list (primary and supplementary) */ | |
137 | if (ga_init(pw->pw_name, pw->pw_gid) == 0) | |
138 | return 0; | |
139 | ||
140 | /* Return false if one of user's groups is listed in DenyGroups */ | |
141 | if (options.num_deny_groups > 0) | |
142 | if (ga_match(options.deny_groups, | |
143 | options.num_deny_groups)) { | |
144 | ga_free(); | |
145 | return 0; | |
146 | } | |
147 | /* | |
148 | * Return false if AllowGroups isn't empty and one of user's groups | |
149 | * isn't listed there | |
150 | */ | |
151 | if (options.num_allow_groups > 0) | |
152 | if (!ga_match(options.allow_groups, | |
153 | options.num_allow_groups)) { | |
154 | ga_free(); | |
155 | return 0; | |
156 | } | |
157 | ga_free(); | |
158 | } | |
159 | ||
160 | #ifdef WITH_AIXAUTHENTICATE | |
161 | if (loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &loginmsg) != 0) { | |
162 | if (loginmsg && *loginmsg) { | |
163 | /* Remove embedded newlines (if any) */ | |
164 | char *p; | |
165 | for (p = loginmsg; *p; p++) { | |
166 | if (*p == '\n') | |
167 | *p = ' '; | |
168 | } | |
169 | /* Remove trailing newline */ | |
170 | *--p = '\0'; | |
171 | log("Login restricted for %s: %.100s", pw->pw_name, loginmsg); | |
172 | } | |
173 | return 0; | |
174 | } | |
175 | #endif /* WITH_AIXAUTHENTICATE */ | |
176 | ||
177 | /* We found no reason not to let this user try to log on... */ | |
178 | return 1; | |
179 | } | |
180 | ||
181 | Authctxt * | |
182 | authctxt_new(void) | |
183 | { | |
184 | Authctxt *authctxt = xmalloc(sizeof(*authctxt)); | |
185 | memset(authctxt, 0, sizeof(*authctxt)); | |
186 | return authctxt; | |
187 | } | |
188 | ||
189 | void | |
190 | auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) | |
191 | { | |
192 | void (*authlog) (const char *fmt,...) = verbose; | |
193 | char *authmsg; | |
194 | ||
195 | /* Raise logging level */ | |
196 | if (authenticated == 1 || | |
197 | !authctxt->valid || | |
198 | authctxt->failures >= AUTH_FAIL_LOG || | |
199 | strcmp(method, "password") == 0) | |
200 | authlog = log; | |
201 | ||
202 | if (authctxt->postponed) | |
203 | authmsg = "Postponed"; | |
204 | else | |
205 | authmsg = authenticated ? "Accepted" : "Failed"; | |
206 | ||
207 | authlog("%s %s for %s%.100s from %.200s port %d%s", | |
208 | authmsg, | |
209 | method, | |
210 | authctxt->valid ? "" : "illegal user ", | |
211 | authctxt->user, | |
212 | get_remote_ipaddr(), | |
213 | get_remote_port(), | |
214 | info); | |
215 | } | |
216 | ||
217 | /* | |
218 | * Check whether root logins are disallowed. | |
219 | */ | |
220 | int | |
221 | auth_root_allowed(char *method) | |
222 | { | |
223 | switch (options.permit_root_login) { | |
224 | case PERMIT_YES: | |
225 | return 1; | |
226 | break; | |
227 | case PERMIT_NO_PASSWD: | |
228 | if (strcmp(method, "password") != 0) | |
229 | return 1; | |
230 | break; | |
231 | case PERMIT_FORCED_ONLY: | |
232 | if (forced_command) { | |
233 | log("Root login accepted for forced command."); | |
234 | return 1; | |
235 | } | |
236 | break; | |
237 | } | |
238 | log("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); | |
239 | return 0; | |
240 | } | |
241 | ||
242 | ||
243 | /* | |
244 | * Given a template and a passwd structure, build a filename | |
245 | * by substituting % tokenised options. Currently, %% becomes '%', | |
246 | * %h becomes the home directory and %u the username. | |
247 | * | |
248 | * This returns a buffer allocated by xmalloc. | |
249 | */ | |
250 | char * | |
251 | expand_filename(const char *filename, struct passwd *pw) | |
252 | { | |
253 | Buffer buffer; | |
254 | char *file; | |
255 | const char *cp; | |
256 | ||
257 | /* | |
258 | * Build the filename string in the buffer by making the appropriate | |
259 | * substitutions to the given file name. | |
260 | */ | |
261 | buffer_init(&buffer); | |
262 | for (cp = filename; *cp; cp++) { | |
263 | if (cp[0] == '%' && cp[1] == '%') { | |
264 | buffer_append(&buffer, "%", 1); | |
265 | cp++; | |
266 | continue; | |
267 | } | |
268 | if (cp[0] == '%' && cp[1] == 'h') { | |
269 | buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir)); | |
270 | cp++; | |
271 | continue; | |
272 | } | |
273 | if (cp[0] == '%' && cp[1] == 'u') { | |
274 | buffer_append(&buffer, pw->pw_name, | |
275 | strlen(pw->pw_name)); | |
276 | cp++; | |
277 | continue; | |
278 | } | |
279 | buffer_append(&buffer, cp, 1); | |
280 | } | |
281 | buffer_append(&buffer, "\0", 1); | |
282 | ||
283 | /* | |
284 | * Ensure that filename starts anchored. If not, be backward | |
285 | * compatible and prepend the '%h/' | |
286 | */ | |
287 | file = xmalloc(MAXPATHLEN); | |
288 | cp = buffer_ptr(&buffer); | |
289 | if (*cp != '/') | |
290 | snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp); | |
291 | else | |
292 | strlcpy(file, cp, MAXPATHLEN); | |
293 | ||
294 | buffer_free(&buffer); | |
295 | return file; | |
296 | } | |
297 | ||
298 | char * | |
299 | authorized_keys_file(struct passwd *pw) | |
300 | { | |
301 | return expand_filename(options.authorized_keys_file, pw); | |
302 | } | |
303 | ||
304 | char * | |
305 | authorized_keys_file2(struct passwd *pw) | |
306 | { | |
307 | return expand_filename(options.authorized_keys_file2, pw); | |
308 | } | |
309 | ||
310 | /* return ok if key exists in sysfile or userfile */ | |
311 | HostStatus | |
312 | check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, | |
313 | const char *sysfile, const char *userfile) | |
314 | { | |
315 | Key *found; | |
316 | char *user_hostfile; | |
317 | struct stat st; | |
318 | int host_status; | |
319 | ||
320 | /* Check if we know the host and its host key. */ | |
321 | found = key_new(key->type); | |
322 | host_status = check_host_in_hostfile(sysfile, host, key, found, NULL); | |
323 | ||
324 | if (host_status != HOST_OK && userfile != NULL) { | |
325 | user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); | |
326 | if (options.strict_modes && | |
327 | (stat(user_hostfile, &st) == 0) && | |
328 | ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || | |
329 | (st.st_mode & 022) != 0)) { | |
330 | log("Authentication refused for %.100s: " | |
331 | "bad owner or modes for %.200s", | |
332 | pw->pw_name, user_hostfile); | |
333 | } else { | |
334 | temporarily_use_uid(pw); | |
335 | host_status = check_host_in_hostfile(user_hostfile, | |
336 | host, key, found, NULL); | |
337 | restore_uid(); | |
338 | } | |
339 | xfree(user_hostfile); | |
340 | } | |
341 | key_free(found); | |
342 | ||
343 | debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ? | |
344 | "ok" : "not found", host); | |
345 | return host_status; | |
346 | } | |
347 | ||
348 | ||
349 | /* | |
350 | * Check a given file for security. This is defined as all components | |
351 | * of the path to the file must either be owned by either the owner of | |
352 | * of the file or root and no directories must be group or world writable. | |
353 | * | |
354 | * XXX Should any specific check be done for sym links ? | |
355 | * | |
356 | * Takes an open file descriptor, the file name, a uid and and | |
357 | * error buffer plus max size as arguments. | |
358 | * | |
359 | * Returns 0 on success and -1 on failure | |
360 | */ | |
361 | int | |
362 | secure_filename(FILE *f, const char *file, struct passwd *pw, | |
363 | char *err, size_t errlen) | |
364 | { | |
365 | uid_t uid = pw->pw_uid; | |
366 | char buf[MAXPATHLEN], homedir[MAXPATHLEN]; | |
367 | char *cp; | |
368 | struct stat st; | |
369 | ||
370 | if (realpath(file, buf) == NULL) { | |
371 | snprintf(err, errlen, "realpath %s failed: %s", file, | |
372 | strerror(errno)); | |
373 | return -1; | |
374 | } | |
375 | if (realpath(pw->pw_dir, homedir) == NULL) { | |
376 | snprintf(err, errlen, "realpath %s failed: %s", pw->pw_dir, | |
377 | strerror(errno)); | |
378 | return -1; | |
379 | } | |
380 | ||
381 | /* check the open file to avoid races */ | |
382 | if (fstat(fileno(f), &st) < 0 || | |
383 | (st.st_uid != 0 && st.st_uid != uid) || | |
384 | (st.st_mode & 022) != 0) { | |
385 | snprintf(err, errlen, "bad ownership or modes for file %s", | |
386 | buf); | |
387 | return -1; | |
388 | } | |
389 | ||
390 | /* for each component of the canonical path, walking upwards */ | |
391 | for (;;) { | |
392 | if ((cp = dirname(buf)) == NULL) { | |
393 | snprintf(err, errlen, "dirname() failed"); | |
394 | return -1; | |
395 | } | |
396 | strlcpy(buf, cp, sizeof(buf)); | |
397 | ||
398 | debug3("secure_filename: checking '%s'", buf); | |
399 | if (stat(buf, &st) < 0 || | |
400 | (st.st_uid != 0 && st.st_uid != uid) || | |
401 | (st.st_mode & 022) != 0) { | |
402 | snprintf(err, errlen, | |
403 | "bad ownership or modes for directory %s", buf); | |
404 | return -1; | |
405 | } | |
406 | ||
407 | /* If are passed the homedir then we can stop */ | |
408 | if (strcmp(homedir, buf) == 0) { | |
409 | debug3("secure_filename: terminating check at '%s'", | |
410 | buf); | |
411 | break; | |
412 | } | |
413 | /* | |
414 | * dirname should always complete with a "/" path, | |
415 | * but we can be paranoid and check for "." too | |
416 | */ | |
417 | if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) | |
418 | break; | |
419 | } | |
420 | return 0; | |
421 | } |