1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2007 Casey Schaufler <casey@schaufler-ca.com>
4 *
5 * Author:
6 * Casey Schaufler <casey@schaufler-ca.com>
7 */
8
9 #include <linux/types.h>
10 #include <linux/slab.h>
11 #include <linux/fs.h>
12 #include <linux/sched.h>
13 #include "smack.h"
14
15 struct smack_known smack_known_huh = {
16 .smk_known = "?",
17 .smk_secid = 2,
18 };
19
20 struct smack_known smack_known_hat = {
21 .smk_known = "^",
22 .smk_secid = 3,
23 };
24
25 struct smack_known smack_known_star = {
26 .smk_known = "*",
27 .smk_secid = 4,
28 };
29
30 struct smack_known smack_known_floor = {
31 .smk_known = "_",
32 .smk_secid = 5,
33 };
34
35 struct smack_known smack_known_web = {
36 .smk_known = "@",
37 .smk_secid = 7,
38 };
39
40 LIST_HEAD(smack_known_list);
41
42 /*
43 * The initial value needs to be bigger than any of the
44 * known values above.
45 */
46 static u32 smack_next_secid = 10;
47
48 /*
49 * what events do we log
50 * can be overwritten at run-time by /smack/logging
51 */
52 int log_policy = SMACK_AUDIT_DENIED;
53
54 /**
55 * smk_access_entry - look up matching access rule
56 * @subject_label: a pointer to the subject's Smack label
57 * @object_label: a pointer to the object's Smack label
58 * @rule_list: the list of rules to search
59 *
60 * This function looks up the subject/object pair in the
61 * access rule list and returns the access mode. If no
62 * entry is found returns -ENOENT.
63 *
64 * NOTE:
65 *
66 * Earlier versions of this function allowed for labels that
67 * were not on the label list. This was done to allow for
68 * labels to come over the network that had never been seen
69 * before on this host. Unless the receiving socket has the
70 * star label this will always result in a failure check. The
71 * star labeled socket case is now handled in the networking
72 * hooks so there is no case where the label is not on the
73 * label list. Checking to see if the address of two labels
74 * is the same is now a reliable test.
75 *
76 * Do the object check first because that is more
77 * likely to differ.
78 *
79 * Allowing write access implies allowing locking.
80 */
81 int smk_access_entry(char *subject_label, char *object_label,
82 struct list_head *rule_list)
83 {
84 int may = -ENOENT;
85 struct smack_rule *srp;
86
87 list_for_each_entry_rcu(srp, rule_list, list) {
88 if (srp->smk_object->smk_known == object_label &&
89 srp->smk_subject->smk_known == subject_label) {
90 may = srp->smk_access;
91 break;
92 }
93 }
94
95 /*
96 * MAY_WRITE implies MAY_LOCK.
97 */
98 if ((may & MAY_WRITE) == MAY_WRITE)
99 may |= MAY_LOCK;
100 return may;
101 }
102
103 /**
104 * smk_access - determine if a subject has a specific access to an object
105 * @subject: a pointer to the subject's Smack label entry
106 * @object: a pointer to the object's Smack label entry
107 * @request: the access requested, in "MAY" format
108 * @a : a pointer to the audit data
109 *
110 * This function looks up the subject/object pair in the
111 * access rule list and returns 0 if the access is permitted,
112 * non zero otherwise.
113 *
114 * Smack labels are shared on smack_list
115 */
116 int smk_access(struct smack_known *subject, struct smack_known *object,
117 int request, struct smk_audit_info *a)
118 {
119 int may = MAY_NOT;
120 int rc = 0;
121
122 /*
123 * Hardcoded comparisons.
124 */
125 /*
126 * A star subject can't access any object.
127 */
128 if (subject == &smack_known_star) {
129 rc = -EACCES;
130 goto out_audit;
131 }
132 /*
133 * An internet object can be accessed by any subject.
134 * Tasks cannot be assigned the internet label.
135 * An internet subject can access any object.
136 */
137 if (object == &smack_known_web || subject == &smack_known_web)
138 goto out_audit;
139 /*
140 * A star object can be accessed by any subject.
141 */
142 if (object == &smack_known_star)
143 goto out_audit;
144 /*
145 * An object can be accessed in any way by a subject
146 * with the same label.
147 */
148 if (subject->smk_known == object->smk_known)
149 goto out_audit;
150 /*
151 * A hat subject can read or lock any object.
152 * A floor object can be read or locked by any subject.
153 */
154 if ((request & MAY_ANYREAD) == request ||
155 (request & MAY_LOCK) == request) {
156 if (object == &smack_known_floor)
157 goto out_audit;
158 if (subject == &smack_known_hat)
159 goto out_audit;
160 }
161 /*
162 * Beyond here an explicit relationship is required.
163 * If the requested access is contained in the available
164 * access (e.g. read is included in readwrite) it's
165 * good. A negative response from smk_access_entry()
166 * indicates there is no entry for this pair.
167 */
168 rcu_read_lock();
169 may = smk_access_entry(subject->smk_known, object->smk_known,
170 &subject->smk_rules);
171 rcu_read_unlock();
172
173 if (may <= 0 || (request & may) != request) {
174 rc = -EACCES;
175 goto out_audit;
176 }
177 #ifdef CONFIG_SECURITY_SMACK_BRINGUP
178 /*
179 * Return a positive value if using bringup mode.
180 * This allows the hooks to identify checks that
181 * succeed because of "b" rules.
182 */
183 if (may & MAY_BRINGUP)
184 rc = SMACK_BRINGUP_ALLOW;
185 #endif
186
187 out_audit:
188
189 #ifdef CONFIG_SECURITY_SMACK_BRINGUP
190 if (rc < 0) {
191 if (object == smack_unconfined)
192 rc = SMACK_UNCONFINED_OBJECT;
193 if (subject == smack_unconfined)
194 rc = SMACK_UNCONFINED_SUBJECT;
195 }
196 #endif
197
198 #ifdef CONFIG_AUDIT
199 if (a)
200 smack_log(subject->smk_known, object->smk_known,
201 request, rc, a);
202 #endif
203
204 return rc;
205 }
206
207 /**
208 * smk_tskacc - determine if a task has a specific access to an object
209 * @tsp: a pointer to the subject's task
210 * @obj_known: a pointer to the object's label entry
211 * @mode: the access requested, in "MAY" format
212 * @a : common audit data
213 *
214 * This function checks the subject task's label/object label pair
215 * in the access rule list and returns 0 if the access is permitted,
216 * non zero otherwise. It allows that the task may have the capability
217 * to override the rules.
218 */
219 int smk_tskacc(struct task_smack *tsp, struct smack_known *obj_known,
220 u32 mode, struct smk_audit_info *a)
221 {
222 struct smack_known *sbj_known = smk_of_task(tsp);
223 int may;
224 int rc;
225
226 /*
227 * Check the global rule list
228 */
229 rc = smk_access(sbj_known, obj_known, mode, NULL);
230 if (rc >= 0) {
231 /*
232 * If there is an entry in the task's rule list
233 * it can further restrict access.
234 */
235 may = smk_access_entry(sbj_known->smk_known,
236 obj_known->smk_known,
237 &tsp->smk_rules);
238 if (may < 0)
239 goto out_audit;
240 if ((mode & may) == mode)
241 goto out_audit;
242 rc = -EACCES;
243 }
244
245 /*
246 * Allow for priviliged to override policy.
247 */
248 if (rc != 0 && smack_privileged(CAP_MAC_OVERRIDE))
249 rc = 0;
250
251 out_audit:
252 #ifdef CONFIG_AUDIT
253 if (a)
254 smack_log(sbj_known->smk_known, obj_known->smk_known,
255 mode, rc, a);
256 #endif
257 return rc;
258 }
259
260 /**
261 * smk_curacc - determine if current has a specific access to an object
262 * @obj_known: a pointer to the object's Smack label entry
263 * @mode: the access requested, in "MAY" format
264 * @a : common audit data
265 *
266 * This function checks the current subject label/object label pair
267 * in the access rule list and returns 0 if the access is permitted,
268 * non zero otherwise. It allows that current may have the capability
269 * to override the rules.
270 */
271 int smk_curacc(struct smack_known *obj_known,
272 u32 mode, struct smk_audit_info *a)
273 {
274 struct task_smack *tsp = smack_cred(current_cred());
275
276 return smk_tskacc(tsp, obj_known, mode, a);
277 }
278
279 #ifdef CONFIG_AUDIT
280 /**
281 * smack_str_from_perm : helper to transalate an int to a
282 * readable string
283 * @string : the string to fill
284 * @access : the int
285 *
286 */
287 static inline void smack_str_from_perm(char *string, int access)
288 {
289 int i = 0;
290
291 if (access & MAY_READ)
292 string[i++] = 'r';
293 if (access & MAY_WRITE)
294 string[i++] = 'w';
295 if (access & MAY_EXEC)
296 string[i++] = 'x';
297 if (access & MAY_APPEND)
298 string[i++] = 'a';
299 if (access & MAY_TRANSMUTE)
300 string[i++] = 't';
301 if (access & MAY_LOCK)
302 string[i++] = 'l';
303 string[i] = '\0';
304 }
305 /**
306 * smack_log_callback - SMACK specific information
307 * will be called by generic audit code
308 * @ab : the audit_buffer
309 * @a : audit_data
310 *
311 */
312 static void smack_log_callback(struct audit_buffer *ab, void *a)
313 {
314 struct common_audit_data *ad = a;
315 struct smack_audit_data *sad = ad->smack_audit_data;
316 audit_log_format(ab, "lsm=SMACK fn=%s action=%s",
317 ad->smack_audit_data->function,
318 sad->result ? "denied" : "granted");
319 audit_log_format(ab, " subject=");
320 audit_log_untrustedstring(ab, sad->subject);
321 audit_log_format(ab, " object=");
322 audit_log_untrustedstring(ab, sad->object);
323 if (sad->request[0] == '\0')
324 audit_log_format(ab, " labels_differ");
325 else
326 audit_log_format(ab, " requested=%s", sad->request);
327 }
328
329 /**
330 * smack_log - Audit the granting or denial of permissions.
331 * @subject_label : smack label of the requester
332 * @object_label : smack label of the object being accessed
333 * @request: requested permissions
334 * @result: result from smk_access
335 * @a: auxiliary audit data
336 *
337 * Audit the granting or denial of permissions in accordance
338 * with the policy.
339 */
340 void smack_log(char *subject_label, char *object_label, int request,
341 int result, struct smk_audit_info *ad)
342 {
343 #ifdef CONFIG_SECURITY_SMACK_BRINGUP
344 char request_buffer[SMK_NUM_ACCESS_TYPE + 5];
345 #else
346 char request_buffer[SMK_NUM_ACCESS_TYPE + 1];
347 #endif
348 struct smack_audit_data *sad;
349 struct common_audit_data *a = &ad->a;
350
351 /* check if we have to log the current event */
352 if (result < 0 && (log_policy & SMACK_AUDIT_DENIED) == 0)
353 return;
354 if (result == 0 && (log_policy & SMACK_AUDIT_ACCEPT) == 0)
355 return;
356
357 sad = a->smack_audit_data;
358
359 if (sad->function == NULL)
360 sad->function = "unknown";
361
362 /* end preparing the audit data */
363 smack_str_from_perm(request_buffer, request);
364 sad->subject = subject_label;
365 sad->object = object_label;
366 #ifdef CONFIG_SECURITY_SMACK_BRINGUP
367 /*
368 * The result may be positive in bringup mode.
369 * A positive result is an allow, but not for normal reasons.
370 * Mark it as successful, but don't filter it out even if
371 * the logging policy says to do so.
372 */
373 if (result == SMACK_UNCONFINED_SUBJECT)
374 strcat(request_buffer, "(US)");
375 else if (result == SMACK_UNCONFINED_OBJECT)
376 strcat(request_buffer, "(UO)");
377
378 if (result > 0)
379 result = 0;
380 #endif
381 sad->request = request_buffer;
382 sad->result = result;
383
384 common_lsm_audit(a, smack_log_callback, NULL);
385 }
386 #else /* #ifdef CONFIG_AUDIT */
387 void smack_log(char *subject_label, char *object_label, int request,
388 int result, struct smk_audit_info *ad)
389 {
390 }
391 #endif
392
393 DEFINE_MUTEX(smack_known_lock);
394
395 struct hlist_head smack_known_hash[SMACK_HASH_SLOTS];
396
397 /**
398 * smk_insert_entry - insert a smack label into a hash map,
399 *
400 * this function must be called under smack_known_lock
401 */
402 void smk_insert_entry(struct smack_known *skp)
403 {
404 unsigned int hash;
405 struct hlist_head *head;
406
407 hash = full_name_hash(NULL, skp->smk_known, strlen(skp->smk_known));
408 head = &smack_known_hash[hash & (SMACK_HASH_SLOTS - 1)];
409
410 hlist_add_head_rcu(&skp->smk_hashed, head);
411 list_add_rcu(&skp->list, &smack_known_list);
412 }
413
414 /**
415 * smk_find_entry - find a label on the list, return the list entry
416 * @string: a text string that might be a Smack label
417 *
418 * Returns a pointer to the entry in the label list that
419 * matches the passed string or NULL if not found.
420 */
421 struct smack_known *smk_find_entry(const char *string)
422 {
423 unsigned int hash;
424 struct hlist_head *head;
425 struct smack_known *skp;
426
427 hash = full_name_hash(NULL, string, strlen(string));
428 head = &smack_known_hash[hash & (SMACK_HASH_SLOTS - 1)];
429
430 hlist_for_each_entry_rcu(skp, head, smk_hashed)
431 if (strcmp(skp->smk_known, string) == 0)
432 return skp;
433
434 return NULL;
435 }
436
437 /**
438 * smk_parse_smack - parse smack label from a text string
439 * @string: a text string that might contain a Smack label
440 * @len: the maximum size, or zero if it is NULL terminated.
441 *
442 * Returns a pointer to the clean label or an error code.
443 */
444 char *smk_parse_smack(const char *string, int len)
445 {
446 char *smack;
447 int i;
448
449 if (len <= 0)
450 len = strlen(string) + 1;
451
452 /*
453 * Reserve a leading '-' as an indicator that
454 * this isn't a label, but an option to interfaces
455 * including /smack/cipso and /smack/cipso2
456 */
457 if (string[0] == '-')
458 return ERR_PTR(-EINVAL);
459
460 for (i = 0; i < len; i++)
461 if (string[i] > '~' || string[i] <= ' ' || string[i] == '/' ||
462 string[i] == '"' || string[i] == '\\' || string[i] == '\'')
463 break;
464
465 if (i == 0 || i >= SMK_LONGLABEL)
466 return ERR_PTR(-EINVAL);
467
468 smack = kzalloc(i + 1, GFP_NOFS);
469 if (smack == NULL)
470 return ERR_PTR(-ENOMEM);
471
472 strncpy(smack, string, i);
473
474 return smack;
475 }
476
477 /**
478 * smk_netlbl_mls - convert a catset to netlabel mls categories
479 * @catset: the Smack categories
480 * @sap: where to put the netlabel categories
481 *
482 * Allocates and fills attr.mls
483 * Returns 0 on success, error code on failure.
484 */
485 int smk_netlbl_mls(int level, char *catset, struct netlbl_lsm_secattr *sap,
486 int len)
487 {
488 unsigned char *cp;
489 unsigned char m;
490 int cat;
491 int rc;
492 int byte;
493
494 sap->flags |= NETLBL_SECATTR_MLS_CAT;
495 sap->attr.mls.lvl = level;
496 sap->attr.mls.cat = NULL;
497
498 for (cat = 1, cp = catset, byte = 0; byte < len; cp++, byte++)
499 for (m = 0x80; m != 0; m >>= 1, cat++) {
500 if ((m & *cp) == 0)
501 continue;
502 rc = netlbl_catmap_setbit(&sap->attr.mls.cat,
503 cat, GFP_NOFS);
504 if (rc < 0) {
505 netlbl_catmap_free(sap->attr.mls.cat);
506 return rc;
507 }
508 }
509
510 return 0;
511 }
512
513 /**
514 * smk_import_entry - import a label, return the list entry
515 * @string: a text string that might be a Smack label
516 * @len: the maximum size, or zero if it is NULL terminated.
517 *
518 * Returns a pointer to the entry in the label list that
519 * matches the passed string, adding it if necessary,
520 * or an error code.
521 */
522 struct smack_known *smk_import_entry(const char *string, int len)
523 {
524 struct smack_known *skp;
525 char *smack;
526 int slen;
527 int rc;
528
529 smack = smk_parse_smack(string, len);
530 if (IS_ERR(smack))
531 return ERR_CAST(smack);
532
533 mutex_lock(&smack_known_lock);
534
535 skp = smk_find_entry(smack);
536 if (skp != NULL)
537 goto freeout;
538
539 skp = kzalloc(sizeof(*skp), GFP_NOFS);
540 if (skp == NULL) {
541 skp = ERR_PTR(-ENOMEM);
542 goto freeout;
543 }
544
545 skp->smk_known = smack;
546 skp->smk_secid = smack_next_secid++;
547 skp->smk_netlabel.domain = skp->smk_known;
548 skp->smk_netlabel.flags =
549 NETLBL_SECATTR_DOMAIN | NETLBL_SECATTR_MLS_LVL;
550 /*
551 * If direct labeling works use it.
552 * Otherwise use mapped labeling.
553 */
554 slen = strlen(smack);
555 if (slen < SMK_CIPSOLEN)
556 rc = smk_netlbl_mls(smack_cipso_direct, skp->smk_known,
557 &skp->smk_netlabel, slen);
558 else
559 rc = smk_netlbl_mls(smack_cipso_mapped, (char *)&skp->smk_secid,
560 &skp->smk_netlabel, sizeof(skp->smk_secid));
561
562 if (rc >= 0) {
563 INIT_LIST_HEAD(&skp->smk_rules);
564 mutex_init(&skp->smk_rules_lock);
565 /*
566 * Make sure that the entry is actually
567 * filled before putting it on the list.
568 */
569 smk_insert_entry(skp);
570 goto unlockout;
571 }
572 /*
573 * smk_netlbl_mls failed.
574 */
575 kfree(skp);
576 skp = ERR_PTR(rc);
577 freeout:
578 kfree(smack);
579 unlockout:
580 mutex_unlock(&smack_known_lock);
581
582 return skp;
583 }
584
585 /**
586 * smack_from_secid - find the Smack label associated with a secid
587 * @secid: an integer that might be associated with a Smack label
588 *
589 * Returns a pointer to the appropriate Smack label entry if there is one,
590 * otherwise a pointer to the invalid Smack label.
591 */
592 struct smack_known *smack_from_secid(const u32 secid)
593 {
594 struct smack_known *skp;
595
596 rcu_read_lock();
597 list_for_each_entry_rcu(skp, &smack_known_list, list) {
598 if (skp->smk_secid == secid) {
599 rcu_read_unlock();
600 return skp;
601 }
602 }
603
604 /*
605 * If we got this far someone asked for the translation
606 * of a secid that is not on the list.
607 */
608 rcu_read_unlock();
609 return &smack_known_huh;
610 }
611
612 /*
613 * Unless a process is running with one of these labels
614 * even having CAP_MAC_OVERRIDE isn't enough to grant
615 * privilege to violate MAC policy. If no labels are
616 * designated (the empty list case) capabilities apply to
617 * everyone.
618 */
619 LIST_HEAD(smack_onlycap_list);
620 DEFINE_MUTEX(smack_onlycap_lock);
621
622 /**
623 * smack_privileged_cred - are all privilege requirements met by cred
624 * @cap: The requested capability
625 * @cred: the credential to use
626 *
627 * Is the task privileged and allowed to be privileged
628 * by the onlycap rule.
629 *
630 * Returns true if the task is allowed to be privileged, false if it's not.
631 */
632 bool smack_privileged_cred(int cap, const struct cred *cred)
633 {
634 struct task_smack *tsp = smack_cred(cred);
635 struct smack_known *skp = tsp->smk_task;
636 struct smack_known_list_elem *sklep;
637 int rc;
638
639 rc = cap_capable(cred, &init_user_ns, cap, CAP_OPT_NONE);
640 if (rc)
641 return false;
642
643 rcu_read_lock();
644 if (list_empty(&smack_onlycap_list)) {
645 rcu_read_unlock();
646 return true;
647 }
648
649 list_for_each_entry_rcu(sklep, &smack_onlycap_list, list) {
650 if (sklep->smk_label == skp) {
651 rcu_read_unlock();
652 return true;
653 }
654 }
655 rcu_read_unlock();
656
657 return false;
658 }
659
660 /**
661 * smack_privileged - are all privilege requirements met
662 * @cap: The requested capability
663 *
664 * Is the task privileged and allowed to be privileged
665 * by the onlycap rule.
666 *
667 * Returns true if the task is allowed to be privileged, false if it's not.
668 */
669 bool smack_privileged(int cap)
670 {
671 /*
672 * All kernel tasks are privileged
673 */
674 if (unlikely(current->flags & PF_KTHREAD))
675 return true;
676
677 return smack_privileged_cred(cap, current_cred());
678 }