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 struct smack_rule *srp;
85
86 list_for_each_entry_rcu(srp, rule_list, list) {
87 if (srp->smk_object->smk_known == object_label &&
88 srp->smk_subject->smk_known == subject_label) {
89 int may = srp->smk_access;
90 /*
91 * MAY_WRITE implies MAY_LOCK.
92 */
93 if ((may & MAY_WRITE) == MAY_WRITE)
94 may |= MAY_LOCK;
95 return may;
96 }
97 }
98
99 return -ENOENT;
100 }
101
102 /**
103 * smk_access - determine if a subject has a specific access to an object
104 * @subject: a pointer to the subject's Smack label entry
105 * @object: a pointer to the object's Smack label entry
106 * @request: the access requested, in "MAY" format
107 * @a : a pointer to the audit data
108 *
109 * This function looks up the subject/object pair in the
110 * access rule list and returns 0 if the access is permitted,
111 * non zero otherwise.
112 *
113 * Smack labels are shared on smack_list
114 */
115 int smk_access(struct smack_known *subject, struct smack_known *object,
116 int request, struct smk_audit_info *a)
117 {
118 int may = MAY_NOT;
119 int rc = 0;
120
121 /*
122 * Hardcoded comparisons.
123 */
124 /*
125 * A star subject can't access any object.
126 */
127 if (subject == &smack_known_star) {
128 rc = -EACCES;
129 goto out_audit;
130 }
131 /*
132 * An internet object can be accessed by any subject.
133 * Tasks cannot be assigned the internet label.
134 * An internet subject can access any object.
135 */
136 if (object == &smack_known_web || subject == &smack_known_web)
137 goto out_audit;
138 /*
139 * A star object can be accessed by any subject.
140 */
141 if (object == &smack_known_star)
142 goto out_audit;
143 /*
144 * An object can be accessed in any way by a subject
145 * with the same label.
146 */
147 if (subject->smk_known == object->smk_known)
148 goto out_audit;
149 /*
150 * A hat subject can read or lock any object.
151 * A floor object can be read or locked by any subject.
152 */
153 if ((request & MAY_ANYREAD) == request ||
154 (request & MAY_LOCK) == request) {
155 if (object == &smack_known_floor)
156 goto out_audit;
157 if (subject == &smack_known_hat)
158 goto out_audit;
159 }
160 /*
161 * Beyond here an explicit relationship is required.
162 * If the requested access is contained in the available
163 * access (e.g. read is included in readwrite) it's
164 * good. A negative response from smk_access_entry()
165 * indicates there is no entry for this pair.
166 */
167 rcu_read_lock();
168 may = smk_access_entry(subject->smk_known, object->smk_known,
169 &subject->smk_rules);
170 rcu_read_unlock();
171
172 if (may <= 0 || (request & may) != request) {
173 rc = -EACCES;
174 goto out_audit;
175 }
176 #ifdef CONFIG_SECURITY_SMACK_BRINGUP
177 /*
178 * Return a positive value if using bringup mode.
179 * This allows the hooks to identify checks that
180 * succeed because of "b" rules.
181 */
182 if (may & MAY_BRINGUP)
183 rc = SMACK_BRINGUP_ALLOW;
184 #endif
185
186 out_audit:
187
188 #ifdef CONFIG_SECURITY_SMACK_BRINGUP
189 if (rc < 0) {
190 if (object == smack_unconfined)
191 rc = SMACK_UNCONFINED_OBJECT;
192 if (subject == smack_unconfined)
193 rc = SMACK_UNCONFINED_SUBJECT;
194 }
195 #endif
196
197 #ifdef CONFIG_AUDIT
198 if (a)
199 smack_log(subject->smk_known, object->smk_known,
200 request, rc, a);
201 #endif
202
203 return rc;
204 }
205
206 /**
207 * smk_tskacc - determine if a task has a specific access to an object
208 * @tsp: a pointer to the subject's task
209 * @obj_known: a pointer to the object's label entry
210 * @mode: the access requested, in "MAY" format
211 * @a : common audit data
212 *
213 * This function checks the subject task's label/object label pair
214 * in the access rule list and returns 0 if the access is permitted,
215 * non zero otherwise. It allows that the task may have the capability
216 * to override the rules.
217 */
218 int smk_tskacc(struct task_smack *tsp, struct smack_known *obj_known,
219 u32 mode, struct smk_audit_info *a)
220 {
221 struct smack_known *sbj_known = smk_of_task(tsp);
222 int may;
223 int rc;
224
225 /*
226 * Check the global rule list
227 */
228 rc = smk_access(sbj_known, obj_known, mode, NULL);
229 if (rc >= 0) {
230 /*
231 * If there is an entry in the task's rule list
232 * it can further restrict access.
233 */
234 may = smk_access_entry(sbj_known->smk_known,
235 obj_known->smk_known,
236 &tsp->smk_rules);
237 if (may < 0)
238 goto out_audit;
239 if ((mode & may) == mode)
240 goto out_audit;
241 rc = -EACCES;
242 }
243
244 /*
245 * Allow for priviliged to override policy.
246 */
247 if (rc != 0 && smack_privileged(CAP_MAC_OVERRIDE))
248 rc = 0;
249
250 out_audit:
251 #ifdef CONFIG_AUDIT
252 if (a)
253 smack_log(sbj_known->smk_known, obj_known->smk_known,
254 mode, rc, a);
255 #endif
256 return rc;
257 }
258
259 /**
260 * smk_curacc - determine if current has a specific access to an object
261 * @obj_known: a pointer to the object's Smack label entry
262 * @mode: the access requested, in "MAY" format
263 * @a : common audit data
264 *
265 * This function checks the current subject label/object label pair
266 * in the access rule list and returns 0 if the access is permitted,
267 * non zero otherwise. It allows that current may have the capability
268 * to override the rules.
269 */
270 int smk_curacc(struct smack_known *obj_known,
271 u32 mode, struct smk_audit_info *a)
272 {
273 struct task_smack *tsp = smack_cred(current_cred());
274
275 return smk_tskacc(tsp, obj_known, mode, a);
276 }
277
278 #ifdef CONFIG_AUDIT
279 /**
280 * smack_str_from_perm : helper to transalate an int to a
281 * readable string
282 * @string : the string to fill
283 * @access : the int
284 *
285 */
286 static inline void smack_str_from_perm(char *string, int access)
287 {
288 int i = 0;
289
290 if (access & MAY_READ)
291 string[i++] = 'r';
292 if (access & MAY_WRITE)
293 string[i++] = 'w';
294 if (access & MAY_EXEC)
295 string[i++] = 'x';
296 if (access & MAY_APPEND)
297 string[i++] = 'a';
298 if (access & MAY_TRANSMUTE)
299 string[i++] = 't';
300 if (access & MAY_LOCK)
301 string[i++] = 'l';
302 string[i] = '\0';
303 }
304 /**
305 * smack_log_callback - SMACK specific information
306 * will be called by generic audit code
307 * @ab : the audit_buffer
308 * @a : audit_data
309 *
310 */
311 static void smack_log_callback(struct audit_buffer *ab, void *a)
312 {
313 struct common_audit_data *ad = a;
314 struct smack_audit_data *sad = ad->smack_audit_data;
315 audit_log_format(ab, "lsm=SMACK fn=%s action=%s",
316 ad->smack_audit_data->function,
317 sad->result ? "denied" : "granted");
318 audit_log_format(ab, " subject=");
319 audit_log_untrustedstring(ab, sad->subject);
320 audit_log_format(ab, " object=");
321 audit_log_untrustedstring(ab, sad->object);
322 if (sad->request[0] == '\0')
323 audit_log_format(ab, " labels_differ");
324 else
325 audit_log_format(ab, " requested=%s", sad->request);
326 }
327
328 /**
329 * smack_log - Audit the granting or denial of permissions.
330 * @subject_label : smack label of the requester
331 * @object_label : smack label of the object being accessed
332 * @request: requested permissions
333 * @result: result from smk_access
334 * @ad: auxiliary audit data
335 *
336 * Audit the granting or denial of permissions in accordance
337 * with the policy.
338 */
339 void smack_log(char *subject_label, char *object_label, int request,
340 int result, struct smk_audit_info *ad)
341 {
342 #ifdef CONFIG_SECURITY_SMACK_BRINGUP
343 char request_buffer[SMK_NUM_ACCESS_TYPE + 5];
344 #else
345 char request_buffer[SMK_NUM_ACCESS_TYPE + 1];
346 #endif
347 struct smack_audit_data *sad;
348 struct common_audit_data *a = &ad->a;
349
350 /* check if we have to log the current event */
351 if (result < 0 && (log_policy & SMACK_AUDIT_DENIED) == 0)
352 return;
353 if (result == 0 && (log_policy & SMACK_AUDIT_ACCEPT) == 0)
354 return;
355
356 sad = a->smack_audit_data;
357
358 if (sad->function == NULL)
359 sad->function = "unknown";
360
361 /* end preparing the audit data */
362 smack_str_from_perm(request_buffer, request);
363 sad->subject = subject_label;
364 sad->object = object_label;
365 #ifdef CONFIG_SECURITY_SMACK_BRINGUP
366 /*
367 * The result may be positive in bringup mode.
368 * A positive result is an allow, but not for normal reasons.
369 * Mark it as successful, but don't filter it out even if
370 * the logging policy says to do so.
371 */
372 if (result == SMACK_UNCONFINED_SUBJECT)
373 strcat(request_buffer, "(US)");
374 else if (result == SMACK_UNCONFINED_OBJECT)
375 strcat(request_buffer, "(UO)");
376
377 if (result > 0)
378 result = 0;
379 #endif
380 sad->request = request_buffer;
381 sad->result = result;
382
383 common_lsm_audit(a, smack_log_callback, NULL);
384 }
385 #else /* #ifdef CONFIG_AUDIT */
386 void smack_log(char *subject_label, char *object_label, int request,
387 int result, struct smk_audit_info *ad)
388 {
389 }
390 #endif
391
392 DEFINE_MUTEX(smack_known_lock);
393
394 struct hlist_head smack_known_hash[SMACK_HASH_SLOTS];
395
396 /**
397 * smk_insert_entry - insert a smack label into a hash map,
398 * @skp: smack label
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 = kstrndup(string, i, GFP_NOFS);
469 if (!smack)
470 return ERR_PTR(-ENOMEM);
471 return smack;
472 }
473
474 /**
475 * smk_netlbl_mls - convert a catset to netlabel mls categories
476 * @level: MLS sensitivity level
477 * @catset: the Smack categories
478 * @sap: where to put the netlabel categories
479 * @len: number of bytes for the levels in a CIPSO IP option
480 *
481 * Allocates and fills attr.mls
482 * Returns 0 on success, error code on failure.
483 */
484 int smk_netlbl_mls(int level, char *catset, struct netlbl_lsm_secattr *sap,
485 int len)
486 {
487 unsigned char *cp;
488 unsigned char m;
489 int cat;
490 int rc;
491 int byte;
492
493 sap->flags |= NETLBL_SECATTR_MLS_CAT;
494 sap->attr.mls.lvl = level;
495 sap->attr.mls.cat = NULL;
496
497 for (cat = 1, cp = catset, byte = 0; byte < len; cp++, byte++)
498 for (m = 0x80; m != 0; m >>= 1, cat++) {
499 if ((m & *cp) == 0)
500 continue;
501 rc = netlbl_catmap_setbit(&sap->attr.mls.cat,
502 cat, GFP_NOFS);
503 if (rc < 0) {
504 netlbl_catmap_free(sap->attr.mls.cat);
505 return rc;
506 }
507 }
508
509 return 0;
510 }
511
512 /**
513 * smack_populate_secattr - fill in the smack_known netlabel information
514 * @skp: pointer to the structure to fill
515 *
516 * Populate the netlabel secattr structure for a Smack label.
517 *
518 * Returns 0 unless creating the category mapping fails
519 */
520 int smack_populate_secattr(struct smack_known *skp)
521 {
522 int slen;
523
524 skp->smk_netlabel.attr.secid = skp->smk_secid;
525 skp->smk_netlabel.domain = skp->smk_known;
526 skp->smk_netlabel.cache = netlbl_secattr_cache_alloc(GFP_ATOMIC);
527 if (skp->smk_netlabel.cache != NULL) {
528 skp->smk_netlabel.flags |= NETLBL_SECATTR_CACHE;
529 skp->smk_netlabel.cache->free = NULL;
530 skp->smk_netlabel.cache->data = skp;
531 }
532 skp->smk_netlabel.flags |= NETLBL_SECATTR_SECID |
533 NETLBL_SECATTR_MLS_LVL |
534 NETLBL_SECATTR_DOMAIN;
535 /*
536 * If direct labeling works use it.
537 * Otherwise use mapped labeling.
538 */
539 slen = strlen(skp->smk_known);
540 if (slen < SMK_CIPSOLEN)
541 return smk_netlbl_mls(smack_cipso_direct, skp->smk_known,
542 &skp->smk_netlabel, slen);
543
544 return smk_netlbl_mls(smack_cipso_mapped, (char *)&skp->smk_secid,
545 &skp->smk_netlabel, sizeof(skp->smk_secid));
546 }
547
548 /**
549 * smk_import_entry - import a label, return the list entry
550 * @string: a text string that might be a Smack label
551 * @len: the maximum size, or zero if it is NULL terminated.
552 *
553 * Returns a pointer to the entry in the label list that
554 * matches the passed string, adding it if necessary,
555 * or an error code.
556 */
557 struct smack_known *smk_import_entry(const char *string, int len)
558 {
559 struct smack_known *skp;
560 char *smack;
561 int rc;
562
563 smack = smk_parse_smack(string, len);
564 if (IS_ERR(smack))
565 return ERR_CAST(smack);
566
567 mutex_lock(&smack_known_lock);
568
569 skp = smk_find_entry(smack);
570 if (skp != NULL)
571 goto freeout;
572
573 skp = kzalloc(sizeof(*skp), GFP_NOFS);
574 if (skp == NULL) {
575 skp = ERR_PTR(-ENOMEM);
576 goto freeout;
577 }
578
579 skp->smk_known = smack;
580 skp->smk_secid = smack_next_secid++;
581
582 rc = smack_populate_secattr(skp);
583 if (rc >= 0) {
584 INIT_LIST_HEAD(&skp->smk_rules);
585 mutex_init(&skp->smk_rules_lock);
586 /*
587 * Make sure that the entry is actually
588 * filled before putting it on the list.
589 */
590 smk_insert_entry(skp);
591 goto unlockout;
592 }
593 kfree(skp);
594 skp = ERR_PTR(rc);
595 freeout:
596 kfree(smack);
597 unlockout:
598 mutex_unlock(&smack_known_lock);
599
600 return skp;
601 }
602
603 /**
604 * smack_from_secid - find the Smack label associated with a secid
605 * @secid: an integer that might be associated with a Smack label
606 *
607 * Returns a pointer to the appropriate Smack label entry if there is one,
608 * otherwise a pointer to the invalid Smack label.
609 */
610 struct smack_known *smack_from_secid(const u32 secid)
611 {
612 struct smack_known *skp;
613
614 rcu_read_lock();
615 list_for_each_entry_rcu(skp, &smack_known_list, list) {
616 if (skp->smk_secid == secid) {
617 rcu_read_unlock();
618 return skp;
619 }
620 }
621
622 /*
623 * If we got this far someone asked for the translation
624 * of a secid that is not on the list.
625 */
626 rcu_read_unlock();
627 return &smack_known_huh;
628 }
629
630 /*
631 * Unless a process is running with one of these labels
632 * even having CAP_MAC_OVERRIDE isn't enough to grant
633 * privilege to violate MAC policy. If no labels are
634 * designated (the empty list case) capabilities apply to
635 * everyone.
636 */
637 LIST_HEAD(smack_onlycap_list);
638 DEFINE_MUTEX(smack_onlycap_lock);
639
640 /**
641 * smack_privileged_cred - are all privilege requirements met by cred
642 * @cap: The requested capability
643 * @cred: the credential to use
644 *
645 * Is the task privileged and allowed to be privileged
646 * by the onlycap rule.
647 *
648 * Returns true if the task is allowed to be privileged, false if it's not.
649 */
650 bool smack_privileged_cred(int cap, const struct cred *cred)
651 {
652 struct task_smack *tsp = smack_cred(cred);
653 struct smack_known *skp = tsp->smk_task;
654 struct smack_known_list_elem *sklep;
655 int rc;
656
657 rc = cap_capable(cred, &init_user_ns, cap, CAP_OPT_NONE);
658 if (rc)
659 return false;
660
661 rcu_read_lock();
662 if (list_empty(&smack_onlycap_list)) {
663 rcu_read_unlock();
664 return true;
665 }
666
667 list_for_each_entry_rcu(sklep, &smack_onlycap_list, list) {
668 if (sklep->smk_label == skp) {
669 rcu_read_unlock();
670 return true;
671 }
672 }
673 rcu_read_unlock();
674
675 return false;
676 }
677
678 /**
679 * smack_privileged - are all privilege requirements met
680 * @cap: The requested capability
681 *
682 * Is the task privileged and allowed to be privileged
683 * by the onlycap rule.
684 *
685 * Returns true if the task is allowed to be privileged, false if it's not.
686 */
687 bool smack_privileged(int cap)
688 {
689 /*
690 * All kernel tasks are privileged
691 */
692 if (unlikely(current->flags & PF_KTHREAD))
693 return true;
694
695 return smack_privileged_cred(cap, current_cred());
696 }
697
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