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1 | /* |
2 | * Copyright (C) 2007 Casey Schaufler <casey@schaufler-ca.com> |
3 | * |
4 | * This program is free software; you can redistribute it and/or modify |
5 | * it under the terms of the GNU General Public License as published by |
6 | * the Free Software Foundation, version 2. |
7 | * |
8 | * Author: |
9 | * Casey Schaufler <casey@schaufler-ca.com> |
10 | * |
11 | */ |
12 | |
13 | #include <linux/types.h> |
14 | #include <linux/slab.h> |
15 | #include <linux/fs.h> |
16 | #include <linux/sched.h> |
17 | #include "smack.h" |
18 | |
19 | struct smack_known smack_known_huh = { |
20 | .smk_known = "?", |
21 | .smk_secid = 2, |
22 | .smk_cipso = NULL, |
23 | }; |
24 | |
25 | struct smack_known smack_known_hat = { |
26 | .smk_known = "^", |
27 | .smk_secid = 3, |
28 | .smk_cipso = NULL, |
29 | }; |
30 | |
31 | struct smack_known smack_known_star = { |
32 | .smk_known = "*", |
33 | .smk_secid = 4, |
34 | .smk_cipso = NULL, |
35 | }; |
36 | |
37 | struct smack_known smack_known_floor = { |
38 | .smk_known = "_", |
39 | .smk_secid = 5, |
40 | .smk_cipso = NULL, |
41 | }; |
42 | |
43 | struct smack_known smack_known_invalid = { |
44 | .smk_known = "", |
45 | .smk_secid = 6, |
46 | .smk_cipso = NULL, |
47 | }; |
48 | |
49 | struct smack_known smack_known_web = { |
50 | .smk_known = "@", |
51 | .smk_secid = 7, |
52 | .smk_cipso = NULL, |
53 | }; |
54 | |
55 | LIST_HEAD(smack_known_list); |
56 | |
57 | /* |
58 | * The initial value needs to be bigger than any of the |
59 | * known values above. |
60 | */ |
61 | static u32 smack_next_secid = 10; |
62 | |
63 | /* |
64 | * what events do we log |
65 | * can be overwritten at run-time by /smack/logging |
66 | */ |
67 | int log_policy = SMACK_AUDIT_DENIED; |
68 | |
69 | /** |
70 | * smk_access_entry - look up matching access rule |
71 | * @subject_label: a pointer to the subject's Smack label |
72 | * @object_label: a pointer to the object's Smack label |
73 | * @rule_list: the list of rules to search |
74 | * |
75 | * This function looks up the subject/object pair in the |
76 | * access rule list and returns the access mode. If no |
77 | * entry is found returns -ENOENT. |
78 | * |
79 | * NOTE: |
80 | * |
81 | * Earlier versions of this function allowed for labels that |
82 | * were not on the label list. This was done to allow for |
83 | * labels to come over the network that had never been seen |
84 | * before on this host. Unless the receiving socket has the |
85 | * star label this will always result in a failure check. The |
86 | * star labeled socket case is now handled in the networking |
87 | * hooks so there is no case where the label is not on the |
88 | * label list. Checking to see if the address of two labels |
89 | * is the same is now a reliable test. |
90 | * |
91 | * Do the object check first because that is more |
92 | * likely to differ. |
93 | */ |
94 | int smk_access_entry(char *subject_label, char *object_label, |
95 | struct list_head *rule_list) |
96 | { |
97 | int may = -ENOENT; |
98 | struct smack_rule *srp; |
99 | |
100 | list_for_each_entry_rcu(srp, rule_list, list) { |
101 | if (srp->smk_object == object_label && |
102 | srp->smk_subject == subject_label) { |
103 | may = srp->smk_access; |
104 | break; |
105 | } |
106 | } |
107 | |
108 | return may; |
109 | } |
110 | |
111 | /** |
112 | * smk_access - determine if a subject has a specific access to an object |
113 | * @subject_label: a pointer to the subject's Smack label |
114 | * @object_label: a pointer to the object's Smack label |
115 | * @request: the access requested, in "MAY" format |
116 | * @a : a pointer to the audit data |
117 | * |
118 | * This function looks up the subject/object pair in the |
119 | * access rule list and returns 0 if the access is permitted, |
120 | * non zero otherwise. |
121 | * |
122 | * Smack labels are shared on smack_list |
123 | */ |
124 | int smk_access(char *subject_label, char *object_label, int request, |
125 | struct smk_audit_info *a) |
126 | { |
127 | struct smack_known *skp; |
128 | int may = MAY_NOT; |
129 | int rc = 0; |
130 | |
131 | /* |
132 | * Hardcoded comparisons. |
133 | * |
134 | * A star subject can't access any object. |
135 | */ |
136 | if (subject_label == smack_known_star.smk_known) { |
137 | rc = -EACCES; |
138 | goto out_audit; |
139 | } |
140 | /* |
141 | * An internet object can be accessed by any subject. |
142 | * Tasks cannot be assigned the internet label. |
143 | * An internet subject can access any object. |
144 | */ |
145 | if (object_label == smack_known_web.smk_known || |
146 | subject_label == smack_known_web.smk_known) |
147 | goto out_audit; |
148 | /* |
149 | * A star object can be accessed by any subject. |
150 | */ |
151 | if (object_label == smack_known_star.smk_known) |
152 | goto out_audit; |
153 | /* |
154 | * An object can be accessed in any way by a subject |
155 | * with the same label. |
156 | */ |
157 | if (subject_label == object_label) |
158 | goto out_audit; |
159 | /* |
160 | * A hat subject can read any object. |
161 | * A floor object can be read by any subject. |
162 | */ |
163 | if ((request & MAY_ANYREAD) == request) { |
164 | if (object_label == smack_known_floor.smk_known) |
165 | goto out_audit; |
166 | if (subject_label == smack_known_hat.smk_known) |
167 | goto out_audit; |
168 | } |
169 | /* |
170 | * Beyond here an explicit relationship is required. |
171 | * If the requested access is contained in the available |
172 | * access (e.g. read is included in readwrite) it's |
173 | * good. A negative response from smk_access_entry() |
174 | * indicates there is no entry for this pair. |
175 | */ |
176 | skp = smk_find_entry(subject_label); |
177 | rcu_read_lock(); |
178 | may = smk_access_entry(subject_label, object_label, &skp->smk_rules); |
179 | rcu_read_unlock(); |
180 | |
181 | if (may > 0 && (request & may) == request) |
182 | goto out_audit; |
183 | |
184 | rc = -EACCES; |
185 | out_audit: |
186 | #ifdef CONFIG_AUDIT |
187 | if (a) |
188 | smack_log(subject_label, object_label, request, rc, a); |
189 | #endif |
190 | return rc; |
191 | } |
192 | |
193 | /** |
194 | * smk_curacc - determine if current has a specific access to an object |
195 | * @obj_label: a pointer to the object's Smack label |
196 | * @mode: the access requested, in "MAY" format |
197 | * @a : common audit data |
198 | * |
199 | * This function checks the current subject label/object label pair |
200 | * in the access rule list and returns 0 if the access is permitted, |
201 | * non zero otherwise. It allows that current may have the capability |
202 | * to override the rules. |
203 | */ |
204 | int smk_curacc(char *obj_label, u32 mode, struct smk_audit_info *a) |
205 | { |
206 | struct task_smack *tsp = current_security(); |
207 | char *sp = smk_of_task(tsp); |
208 | int may; |
209 | int rc; |
210 | |
211 | /* |
212 | * Check the global rule list |
213 | */ |
214 | rc = smk_access(sp, obj_label, mode, NULL); |
215 | if (rc == 0) { |
216 | /* |
217 | * If there is an entry in the task's rule list |
218 | * it can further restrict access. |
219 | */ |
220 | may = smk_access_entry(sp, obj_label, &tsp->smk_rules); |
221 | if (may < 0) |
222 | goto out_audit; |
223 | if ((mode & may) == mode) |
224 | goto out_audit; |
225 | rc = -EACCES; |
226 | } |
227 | |
228 | /* |
229 | * Return if a specific label has been designated as the |
230 | * only one that gets privilege and current does not |
231 | * have that label. |
232 | */ |
233 | if (smack_onlycap != NULL && smack_onlycap != sp) |
234 | goto out_audit; |
235 | |
236 | if (capable(CAP_MAC_OVERRIDE)) |
237 | rc = 0; |
238 | |
239 | out_audit: |
240 | #ifdef CONFIG_AUDIT |
241 | if (a) |
242 | smack_log(sp, obj_label, mode, rc, a); |
243 | #endif |
244 | return rc; |
245 | } |
246 | |
247 | #ifdef CONFIG_AUDIT |
248 | /** |
249 | * smack_str_from_perm : helper to transalate an int to a |
250 | * readable string |
251 | * @string : the string to fill |
252 | * @access : the int |
253 | * |
254 | */ |
255 | static inline void smack_str_from_perm(char *string, int access) |
256 | { |
257 | int i = 0; |
258 | if (access & MAY_READ) |
259 | string[i++] = 'r'; |
260 | if (access & MAY_WRITE) |
261 | string[i++] = 'w'; |
262 | if (access & MAY_EXEC) |
263 | string[i++] = 'x'; |
264 | if (access & MAY_APPEND) |
265 | string[i++] = 'a'; |
266 | string[i] = '\0'; |
267 | } |
268 | /** |
269 | * smack_log_callback - SMACK specific information |
270 | * will be called by generic audit code |
271 | * @ab : the audit_buffer |
272 | * @a : audit_data |
273 | * |
274 | */ |
275 | static void smack_log_callback(struct audit_buffer *ab, void *a) |
276 | { |
277 | struct common_audit_data *ad = a; |
278 | struct smack_audit_data *sad = ad->smack_audit_data; |
279 | audit_log_format(ab, "lsm=SMACK fn=%s action=%s", |
280 | ad->smack_audit_data->function, |
281 | sad->result ? "denied" : "granted"); |
282 | audit_log_format(ab, " subject="); |
283 | audit_log_untrustedstring(ab, sad->subject); |
284 | audit_log_format(ab, " object="); |
285 | audit_log_untrustedstring(ab, sad->object); |
286 | audit_log_format(ab, " requested=%s", sad->request); |
287 | } |
288 | |
289 | /** |
290 | * smack_log - Audit the granting or denial of permissions. |
291 | * @subject_label : smack label of the requester |
292 | * @object_label : smack label of the object being accessed |
293 | * @request: requested permissions |
294 | * @result: result from smk_access |
295 | * @a: auxiliary audit data |
296 | * |
297 | * Audit the granting or denial of permissions in accordance |
298 | * with the policy. |
299 | */ |
300 | void smack_log(char *subject_label, char *object_label, int request, |
301 | int result, struct smk_audit_info *ad) |
302 | { |
303 | char request_buffer[SMK_NUM_ACCESS_TYPE + 1]; |
304 | struct smack_audit_data *sad; |
305 | struct common_audit_data *a = &ad->a; |
306 | |
307 | /* check if we have to log the current event */ |
308 | if (result != 0 && (log_policy & SMACK_AUDIT_DENIED) == 0) |
309 | return; |
310 | if (result == 0 && (log_policy & SMACK_AUDIT_ACCEPT) == 0) |
311 | return; |
312 | |
313 | sad = a->smack_audit_data; |
314 | |
315 | if (sad->function == NULL) |
316 | sad->function = "unknown"; |
317 | |
318 | /* end preparing the audit data */ |
319 | smack_str_from_perm(request_buffer, request); |
320 | sad->subject = subject_label; |
321 | sad->object = object_label; |
322 | sad->request = request_buffer; |
323 | sad->result = result; |
324 | |
325 | common_lsm_audit(a, smack_log_callback, NULL); |
326 | } |
327 | #else /* #ifdef CONFIG_AUDIT */ |
328 | void smack_log(char *subject_label, char *object_label, int request, |
329 | int result, struct smk_audit_info *ad) |
330 | { |
331 | } |
332 | #endif |
333 | |
334 | static DEFINE_MUTEX(smack_known_lock); |
335 | |
336 | /** |
337 | * smk_find_entry - find a label on the list, return the list entry |
338 | * @string: a text string that might be a Smack label |
339 | * |
340 | * Returns a pointer to the entry in the label list that |
341 | * matches the passed string. |
342 | */ |
343 | struct smack_known *smk_find_entry(const char *string) |
344 | { |
345 | struct smack_known *skp; |
346 | |
347 | list_for_each_entry_rcu(skp, &smack_known_list, list) { |
348 | if (strncmp(skp->smk_known, string, SMK_MAXLEN) == 0) |
349 | return skp; |
350 | } |
351 | |
352 | return NULL; |
353 | } |
354 | |
355 | /** |
356 | * smk_parse_smack - parse smack label from a text string |
357 | * @string: a text string that might contain a Smack label |
358 | * @len: the maximum size, or zero if it is NULL terminated. |
359 | * @smack: parsed smack label, or NULL if parse error |
360 | */ |
361 | void smk_parse_smack(const char *string, int len, char *smack) |
362 | { |
363 | int found; |
364 | int i; |
365 | |
366 | if (len <= 0 || len > SMK_MAXLEN) |
367 | len = SMK_MAXLEN; |
368 | |
369 | for (i = 0, found = 0; i < SMK_LABELLEN; i++) { |
370 | if (found) |
371 | smack[i] = '\0'; |
372 | else if (i >= len || string[i] > '~' || string[i] <= ' ' || |
373 | string[i] == '/' || string[i] == '"' || |
374 | string[i] == '\\' || string[i] == '\'') { |
375 | smack[i] = '\0'; |
376 | found = 1; |
377 | } else |
378 | smack[i] = string[i]; |
379 | } |
380 | } |
381 | |
382 | /** |
383 | * smk_import_entry - import a label, return the list entry |
384 | * @string: a text string that might be a Smack label |
385 | * @len: the maximum size, or zero if it is NULL terminated. |
386 | * |
387 | * Returns a pointer to the entry in the label list that |
388 | * matches the passed string, adding it if necessary. |
389 | */ |
390 | struct smack_known *smk_import_entry(const char *string, int len) |
391 | { |
392 | struct smack_known *skp; |
393 | char smack[SMK_LABELLEN]; |
394 | |
395 | smk_parse_smack(string, len, smack); |
396 | if (smack[0] == '\0') |
397 | return NULL; |
398 | |
399 | mutex_lock(&smack_known_lock); |
400 | |
401 | skp = smk_find_entry(smack); |
402 | |
403 | if (skp == NULL) { |
404 | skp = kzalloc(sizeof(struct smack_known), GFP_KERNEL); |
405 | if (skp != NULL) { |
406 | strncpy(skp->smk_known, smack, SMK_MAXLEN); |
407 | skp->smk_secid = smack_next_secid++; |
408 | skp->smk_cipso = NULL; |
409 | INIT_LIST_HEAD(&skp->smk_rules); |
410 | spin_lock_init(&skp->smk_cipsolock); |
411 | mutex_init(&skp->smk_rules_lock); |
412 | /* |
413 | * Make sure that the entry is actually |
414 | * filled before putting it on the list. |
415 | */ |
416 | list_add_rcu(&skp->list, &smack_known_list); |
417 | } |
418 | } |
419 | |
420 | mutex_unlock(&smack_known_lock); |
421 | |
422 | return skp; |
423 | } |
424 | |
425 | /** |
426 | * smk_import - import a smack label |
427 | * @string: a text string that might be a Smack label |
428 | * @len: the maximum size, or zero if it is NULL terminated. |
429 | * |
430 | * Returns a pointer to the label in the label list that |
431 | * matches the passed string, adding it if necessary. |
432 | */ |
433 | char *smk_import(const char *string, int len) |
434 | { |
435 | struct smack_known *skp; |
436 | |
437 | /* labels cannot begin with a '-' */ |
438 | if (string[0] == '-') |
439 | return NULL; |
440 | skp = smk_import_entry(string, len); |
441 | if (skp == NULL) |
442 | return NULL; |
443 | return skp->smk_known; |
444 | } |
445 | |
446 | /** |
447 | * smack_from_secid - find the Smack label associated with a secid |
448 | * @secid: an integer that might be associated with a Smack label |
449 | * |
450 | * Returns a pointer to the appropriate Smack label if there is one, |
451 | * otherwise a pointer to the invalid Smack label. |
452 | */ |
453 | char *smack_from_secid(const u32 secid) |
454 | { |
455 | struct smack_known *skp; |
456 | |
457 | rcu_read_lock(); |
458 | list_for_each_entry_rcu(skp, &smack_known_list, list) { |
459 | if (skp->smk_secid == secid) { |
460 | rcu_read_unlock(); |
461 | return skp->smk_known; |
462 | } |
463 | } |
464 | |
465 | /* |
466 | * If we got this far someone asked for the translation |
467 | * of a secid that is not on the list. |
468 | */ |
469 | rcu_read_unlock(); |
470 | return smack_known_invalid.smk_known; |
471 | } |
472 | |
473 | /** |
474 | * smack_to_secid - find the secid associated with a Smack label |
475 | * @smack: the Smack label |
476 | * |
477 | * Returns the appropriate secid if there is one, |
478 | * otherwise 0 |
479 | */ |
480 | u32 smack_to_secid(const char *smack) |
481 | { |
482 | struct smack_known *skp; |
483 | |
484 | rcu_read_lock(); |
485 | list_for_each_entry_rcu(skp, &smack_known_list, list) { |
486 | if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0) { |
487 | rcu_read_unlock(); |
488 | return skp->smk_secid; |
489 | } |
490 | } |
491 | rcu_read_unlock(); |
492 | return 0; |
493 | } |
494 | |
495 | /** |
496 | * smack_from_cipso - find the Smack label associated with a CIPSO option |
497 | * @level: Bell & LaPadula level from the network |
498 | * @cp: Bell & LaPadula categories from the network |
499 | * |
500 | * This is a simple lookup in the label table. |
501 | * |
502 | * Return the matching label from the label list or NULL. |
503 | */ |
504 | char *smack_from_cipso(u32 level, char *cp) |
505 | { |
506 | struct smack_known *kp; |
507 | char *final = NULL; |
508 | |
509 | rcu_read_lock(); |
510 | list_for_each_entry(kp, &smack_known_list, list) { |
511 | if (kp->smk_cipso == NULL) |
512 | continue; |
513 | |
514 | spin_lock_bh(&kp->smk_cipsolock); |
515 | |
516 | if (kp->smk_cipso->smk_level == level && |
517 | memcmp(kp->smk_cipso->smk_catset, cp, SMK_LABELLEN) == 0) |
518 | final = kp->smk_known; |
519 | |
520 | spin_unlock_bh(&kp->smk_cipsolock); |
521 | |
522 | if (final != NULL) |
523 | break; |
524 | } |
525 | rcu_read_unlock(); |
526 | |
527 | return final; |
528 | } |
529 | |
530 | /** |
531 | * smack_to_cipso - find the CIPSO option to go with a Smack label |
532 | * @smack: a pointer to the smack label in question |
533 | * @cp: where to put the result |
534 | * |
535 | * Returns zero if a value is available, non-zero otherwise. |
536 | */ |
537 | int smack_to_cipso(const char *smack, struct smack_cipso *cp) |
538 | { |
539 | struct smack_known *kp; |
540 | int found = 0; |
541 | |
542 | rcu_read_lock(); |
543 | list_for_each_entry_rcu(kp, &smack_known_list, list) { |
544 | if (kp->smk_known == smack || |
545 | strcmp(kp->smk_known, smack) == 0) { |
546 | found = 1; |
547 | break; |
548 | } |
549 | } |
550 | rcu_read_unlock(); |
551 | |
552 | if (found == 0 || kp->smk_cipso == NULL) |
553 | return -ENOENT; |
554 | |
555 | memcpy(cp, kp->smk_cipso, sizeof(struct smack_cipso)); |
556 | return 0; |
557 | } |
558 |
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