1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * AppArmor security module
4 *
5 * This file contains AppArmor mediation of files
6 *
7 * Copyright (C) 1998-2008 Novell/SUSE
8 * Copyright 2009-2010 Canonical Ltd.
9 */
10
11#include <linux/tty.h>
12#include <linux/fdtable.h>
13#include <linux/file.h>
14#include <linux/fs.h>
15#include <linux/mount.h>
16
17#include "include/apparmor.h"
18#include "include/audit.h"
19#include "include/cred.h"
20#include "include/file.h"
21#include "include/match.h"
22#include "include/net.h"
23#include "include/path.h"
24#include "include/policy.h"
25#include "include/label.h"
26
27static u32 map_mask_to_chr_mask(u32 mask)
28{
29 u32 m = mask & PERMS_CHRS_MASK;
30
31 if (mask & AA_MAY_GETATTR)
32 m |= MAY_READ;
33 if (mask & (AA_MAY_SETATTR | AA_MAY_CHMOD | AA_MAY_CHOWN))
34 m |= MAY_WRITE;
35
36 return m;
37}
38
39/**
40 * file_audit_cb - call back for file specific audit fields
41 * @ab: audit_buffer (NOT NULL)
42 * @va: audit struct to audit values of (NOT NULL)
43 */
44static void file_audit_cb(struct audit_buffer *ab, void *va)
45{
46 struct common_audit_data *sa = va;
47 struct apparmor_audit_data *ad = aad(sa);
48 kuid_t fsuid = ad->subj_cred ? ad->subj_cred->fsuid : current_fsuid();
49 char str[10];
50
51 if (ad->request & AA_AUDIT_FILE_MASK) {
52 aa_perm_mask_to_str(str, str_size: sizeof(str), chrs: aa_file_perm_chrs,
53 mask: map_mask_to_chr_mask(mask: ad->request));
54 audit_log_format(ab, fmt: " requested_mask=\"%s\"", str);
55 }
56 if (ad->denied & AA_AUDIT_FILE_MASK) {
57 aa_perm_mask_to_str(str, str_size: sizeof(str), chrs: aa_file_perm_chrs,
58 mask: map_mask_to_chr_mask(mask: ad->denied));
59 audit_log_format(ab, fmt: " denied_mask=\"%s\"", str);
60 }
61 if (ad->request & AA_AUDIT_FILE_MASK) {
62 audit_log_format(ab, fmt: " fsuid=%d",
63 from_kuid(to: &init_user_ns, uid: fsuid));
64 audit_log_format(ab, fmt: " ouid=%d",
65 from_kuid(to: &init_user_ns, uid: ad->fs.ouid));
66 }
67
68 if (ad->peer) {
69 audit_log_format(ab, fmt: " target=");
70 aa_label_xaudit(ab, labels_ns(ad->subj_label), label: ad->peer,
71 FLAG_VIEW_SUBNS, GFP_KERNEL);
72 } else if (ad->fs.target) {
73 audit_log_format(ab, fmt: " target=");
74 audit_log_untrustedstring(ab, string: ad->fs.target);
75 }
76}
77
78/**
79 * aa_audit_file - handle the auditing of file operations
80 * @subj_cred: cred of the subject
81 * @profile: the profile being enforced (NOT NULL)
82 * @perms: the permissions computed for the request (NOT NULL)
83 * @op: operation being mediated
84 * @request: permissions requested
85 * @name: name of object being mediated (MAYBE NULL)
86 * @target: name of target (MAYBE NULL)
87 * @tlabel: target label (MAY BE NULL)
88 * @ouid: object uid
89 * @info: extra information message (MAYBE NULL)
90 * @error: 0 if operation allowed else failure error code
91 *
92 * Returns: %0 or error on failure
93 */
94int aa_audit_file(const struct cred *subj_cred,
95 struct aa_profile *profile, struct aa_perms *perms,
96 const char *op, u32 request, const char *name,
97 const char *target, struct aa_label *tlabel,
98 kuid_t ouid, const char *info, int error)
99{
100 int type = AUDIT_APPARMOR_AUTO;
101 DEFINE_AUDIT_DATA(ad, LSM_AUDIT_DATA_TASK, AA_CLASS_FILE, op);
102
103 ad.subj_cred = subj_cred;
104 ad.request = request;
105 ad.name = name;
106 ad.fs.target = target;
107 ad.peer = tlabel;
108 ad.fs.ouid = ouid;
109 ad.info = info;
110 ad.error = error;
111 ad.common.u.tsk = NULL;
112
113 if (likely(!ad.error)) {
114 u32 mask = perms->audit;
115
116 if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
117 mask = 0xffff;
118
119 /* mask off perms that are not being force audited */
120 ad.request &= mask;
121
122 if (likely(!ad.request))
123 return 0;
124 type = AUDIT_APPARMOR_AUDIT;
125 } else {
126 /* only report permissions that were denied */
127 ad.request = ad.request & ~perms->allow;
128 AA_BUG(!ad.request);
129
130 if (ad.request & perms->kill)
131 type = AUDIT_APPARMOR_KILL;
132
133 /* quiet known rejects, assumes quiet and kill do not overlap */
134 if ((ad.request & perms->quiet) &&
135 AUDIT_MODE(profile) != AUDIT_NOQUIET &&
136 AUDIT_MODE(profile) != AUDIT_ALL)
137 ad.request &= ~perms->quiet;
138
139 if (!ad.request)
140 return ad.error;
141 }
142
143 ad.denied = ad.request & ~perms->allow;
144 return aa_audit(type, profile, ad: &ad, cb: file_audit_cb);
145}
146
147static int path_name(const char *op, const struct cred *subj_cred,
148 struct aa_label *label,
149 const struct path *path, int flags, char *buffer,
150 const char **name, struct path_cond *cond, u32 request)
151{
152 struct aa_profile *profile;
153 const char *info = NULL;
154 int error;
155
156 error = aa_path_name(path, flags, buffer, name, info: &info,
157 labels_profile(label)->disconnected);
158 if (error) {
159 fn_for_each_confined(label, profile,
160 aa_audit_file(subj_cred,
161 profile, &nullperms, op, request, *name,
162 NULL, NULL, cond->uid, info, error));
163 return error;
164 }
165
166 return 0;
167}
168
169struct aa_perms default_perms = {};
170/**
171 * aa_lookup_fperms - convert dfa compressed perms to internal perms
172 * @file_rules: the aa_policydb to lookup perms for (NOT NULL)
173 * @state: state in dfa
174 * @cond: conditions to consider (NOT NULL)
175 *
176 * TODO: convert from dfa + state to permission entry
177 *
178 * Returns: a pointer to a file permission set
179 */
180struct aa_perms *aa_lookup_fperms(struct aa_policydb *file_rules,
181 aa_state_t state, struct path_cond *cond)
182{
183 unsigned int index = ACCEPT_TABLE(file_rules->dfa)[state];
184
185 if (!(file_rules->perms))
186 return &default_perms;
187
188 if (uid_eq(current_fsuid(), right: cond->uid))
189 return &(file_rules->perms[index]);
190
191 return &(file_rules->perms[index + 1]);
192}
193
194/**
195 * aa_str_perms - find permission that match @name
196 * @file_rules: the aa_policydb to match against (NOT NULL)
197 * @start: state to start matching in
198 * @name: string to match against dfa (NOT NULL)
199 * @cond: conditions to consider for permission set computation (NOT NULL)
200 * @perms: Returns - the permissions found when matching @name
201 *
202 * Returns: the final state in @dfa when beginning @start and walking @name
203 */
204aa_state_t aa_str_perms(struct aa_policydb *file_rules, aa_state_t start,
205 const char *name, struct path_cond *cond,
206 struct aa_perms *perms)
207{
208 aa_state_t state;
209 state = aa_dfa_match(dfa: file_rules->dfa, start, str: name);
210 *perms = *(aa_lookup_fperms(file_rules, state, cond));
211
212 return state;
213}
214
215static int __aa_path_perm(const char *op, const struct cred *subj_cred,
216 struct aa_profile *profile, const char *name,
217 u32 request, struct path_cond *cond, int flags,
218 struct aa_perms *perms)
219{
220 struct aa_ruleset *rules = list_first_entry(&profile->rules,
221 typeof(*rules), list);
222 int e = 0;
223
224 if (profile_unconfined(profile))
225 return 0;
226 aa_str_perms(file_rules: rules->file, start: rules->file->start[AA_CLASS_FILE],
227 name, cond, perms);
228 if (request & ~perms->allow)
229 e = -EACCES;
230 return aa_audit_file(subj_cred,
231 profile, perms, op, request, name, NULL, NULL,
232 ouid: cond->uid, NULL, error: e);
233}
234
235
236static int profile_path_perm(const char *op, const struct cred *subj_cred,
237 struct aa_profile *profile,
238 const struct path *path, char *buffer, u32 request,
239 struct path_cond *cond, int flags,
240 struct aa_perms *perms)
241{
242 const char *name;
243 int error;
244
245 if (profile_unconfined(profile))
246 return 0;
247
248 error = path_name(op, subj_cred, label: &profile->label, path,
249 flags: flags | profile->path_flags, buffer, name: &name, cond,
250 request);
251 if (error)
252 return error;
253 return __aa_path_perm(op, subj_cred, profile, name, request, cond,
254 flags, perms);
255}
256
257/**
258 * aa_path_perm - do permissions check & audit for @path
259 * @op: operation being checked
260 * @subj_cred: subject cred
261 * @label: profile being enforced (NOT NULL)
262 * @path: path to check permissions of (NOT NULL)
263 * @flags: any additional path flags beyond what the profile specifies
264 * @request: requested permissions
265 * @cond: conditional info for this request (NOT NULL)
266 *
267 * Returns: %0 else error if access denied or other error
268 */
269int aa_path_perm(const char *op, const struct cred *subj_cred,
270 struct aa_label *label,
271 const struct path *path, int flags, u32 request,
272 struct path_cond *cond)
273{
274 struct aa_perms perms = {};
275 struct aa_profile *profile;
276 char *buffer = NULL;
277 int error;
278
279 flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR :
280 0);
281 buffer = aa_get_buffer(in_atomic: false);
282 if (!buffer)
283 return -ENOMEM;
284 error = fn_for_each_confined(label, profile,
285 profile_path_perm(op, subj_cred, profile, path, buffer,
286 request, cond, flags, &perms));
287
288 aa_put_buffer(buf: buffer);
289
290 return error;
291}
292
293/**
294 * xindex_is_subset - helper for aa_path_link
295 * @link: link permission set
296 * @target: target permission set
297 *
298 * test target x permissions are equal OR a subset of link x permissions
299 * this is done as part of the subset test, where a hardlink must have
300 * a subset of permissions that the target has.
301 *
302 * Returns: true if subset else false
303 */
304static inline bool xindex_is_subset(u32 link, u32 target)
305{
306 if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
307 ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
308 return false;
309
310 return true;
311}
312
313static int profile_path_link(const struct cred *subj_cred,
314 struct aa_profile *profile,
315 const struct path *link, char *buffer,
316 const struct path *target, char *buffer2,
317 struct path_cond *cond)
318{
319 struct aa_ruleset *rules = list_first_entry(&profile->rules,
320 typeof(*rules), list);
321 const char *lname, *tname = NULL;
322 struct aa_perms lperms = {}, perms;
323 const char *info = NULL;
324 u32 request = AA_MAY_LINK;
325 aa_state_t state;
326 int error;
327
328 error = path_name(OP_LINK, subj_cred, label: &profile->label, path: link,
329 flags: profile->path_flags,
330 buffer, name: &lname, cond, AA_MAY_LINK);
331 if (error)
332 goto audit;
333
334 /* buffer2 freed below, tname is pointer in buffer2 */
335 error = path_name(OP_LINK, subj_cred, label: &profile->label, path: target,
336 flags: profile->path_flags,
337 buffer: buffer2, name: &tname, cond, AA_MAY_LINK);
338 if (error)
339 goto audit;
340
341 error = -EACCES;
342 /* aa_str_perms - handles the case of the dfa being NULL */
343 state = aa_str_perms(file_rules: rules->file,
344 start: rules->file->start[AA_CLASS_FILE], name: lname,
345 cond, perms: &lperms);
346
347 if (!(lperms.allow & AA_MAY_LINK))
348 goto audit;
349
350 /* test to see if target can be paired with link */
351 state = aa_dfa_null_transition(dfa: rules->file->dfa, start: state);
352 aa_str_perms(file_rules: rules->file, start: state, name: tname, cond, perms: &perms);
353
354 /* force audit/quiet masks for link are stored in the second entry
355 * in the link pair.
356 */
357 lperms.audit = perms.audit;
358 lperms.quiet = perms.quiet;
359 lperms.kill = perms.kill;
360
361 if (!(perms.allow & AA_MAY_LINK)) {
362 info = "target restricted";
363 lperms = perms;
364 goto audit;
365 }
366
367 /* done if link subset test is not required */
368 if (!(perms.allow & AA_LINK_SUBSET))
369 goto done_tests;
370
371 /* Do link perm subset test requiring allowed permission on link are
372 * a subset of the allowed permissions on target.
373 */
374 aa_str_perms(file_rules: rules->file, start: rules->file->start[AA_CLASS_FILE],
375 name: tname, cond, perms: &perms);
376
377 /* AA_MAY_LINK is not considered in the subset test */
378 request = lperms.allow & ~AA_MAY_LINK;
379 lperms.allow &= perms.allow | AA_MAY_LINK;
380
381 request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
382 if (request & ~lperms.allow) {
383 goto audit;
384 } else if ((lperms.allow & MAY_EXEC) &&
385 !xindex_is_subset(link: lperms.xindex, target: perms.xindex)) {
386 lperms.allow &= ~MAY_EXEC;
387 request |= MAY_EXEC;
388 info = "link not subset of target";
389 goto audit;
390 }
391
392done_tests:
393 error = 0;
394
395audit:
396 return aa_audit_file(subj_cred,
397 profile, perms: &lperms, OP_LINK, request, name: lname, target: tname,
398 NULL, ouid: cond->uid, info, error);
399}
400
401/**
402 * aa_path_link - Handle hard link permission check
403 * @subj_cred: subject cred
404 * @label: the label being enforced (NOT NULL)
405 * @old_dentry: the target dentry (NOT NULL)
406 * @new_dir: directory the new link will be created in (NOT NULL)
407 * @new_dentry: the link being created (NOT NULL)
408 *
409 * Handle the permission test for a link & target pair. Permission
410 * is encoded as a pair where the link permission is determined
411 * first, and if allowed, the target is tested. The target test
412 * is done from the point of the link match (not start of DFA)
413 * making the target permission dependent on the link permission match.
414 *
415 * The subset test if required forces that permissions granted
416 * on link are a subset of the permission granted to target.
417 *
418 * Returns: %0 if allowed else error
419 */
420int aa_path_link(const struct cred *subj_cred,
421 struct aa_label *label, struct dentry *old_dentry,
422 const struct path *new_dir, struct dentry *new_dentry)
423{
424 struct path link = { .mnt = new_dir->mnt, .dentry = new_dentry };
425 struct path target = { .mnt = new_dir->mnt, .dentry = old_dentry };
426 struct path_cond cond = {
427 d_backing_inode(upper: old_dentry)->i_uid,
428 d_backing_inode(upper: old_dentry)->i_mode
429 };
430 char *buffer = NULL, *buffer2 = NULL;
431 struct aa_profile *profile;
432 int error;
433
434 /* buffer freed below, lname is pointer in buffer */
435 buffer = aa_get_buffer(in_atomic: false);
436 buffer2 = aa_get_buffer(in_atomic: false);
437 error = -ENOMEM;
438 if (!buffer || !buffer2)
439 goto out;
440
441 error = fn_for_each_confined(label, profile,
442 profile_path_link(subj_cred, profile, &link, buffer,
443 &target, buffer2, &cond));
444out:
445 aa_put_buffer(buf: buffer);
446 aa_put_buffer(buf: buffer2);
447 return error;
448}
449
450static void update_file_ctx(struct aa_file_ctx *fctx, struct aa_label *label,
451 u32 request)
452{
453 struct aa_label *l, *old;
454
455 /* update caching of label on file_ctx */
456 spin_lock(lock: &fctx->lock);
457 old = rcu_dereference_protected(fctx->label,
458 lockdep_is_held(&fctx->lock));
459 l = aa_label_merge(a: old, b: label, GFP_ATOMIC);
460 if (l) {
461 if (l != old) {
462 rcu_assign_pointer(fctx->label, l);
463 aa_put_label(l: old);
464 } else
465 aa_put_label(l);
466 fctx->allow |= request;
467 }
468 spin_unlock(lock: &fctx->lock);
469}
470
471static int __file_path_perm(const char *op, const struct cred *subj_cred,
472 struct aa_label *label,
473 struct aa_label *flabel, struct file *file,
474 u32 request, u32 denied, bool in_atomic)
475{
476 struct aa_profile *profile;
477 struct aa_perms perms = {};
478 vfsuid_t vfsuid = i_uid_into_vfsuid(idmap: file_mnt_idmap(file),
479 inode: file_inode(f: file));
480 struct path_cond cond = {
481 .uid = vfsuid_into_kuid(vfsuid),
482 .mode = file_inode(f: file)->i_mode
483 };
484 char *buffer;
485 int flags, error;
486
487 /* revalidation due to label out of date. No revocation at this time */
488 if (!denied && aa_label_is_subset(set: flabel, sub: label))
489 /* TODO: check for revocation on stale profiles */
490 return 0;
491
492 flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
493 buffer = aa_get_buffer(in_atomic);
494 if (!buffer)
495 return -ENOMEM;
496
497 /* check every profile in task label not in current cache */
498 error = fn_for_each_not_in_set(flabel, label, profile,
499 profile_path_perm(op, subj_cred, profile,
500 &file->f_path, buffer,
501 request, &cond, flags, &perms));
502 if (denied && !error) {
503 /*
504 * check every profile in file label that was not tested
505 * in the initial check above.
506 *
507 * TODO: cache full perms so this only happens because of
508 * conditionals
509 * TODO: don't audit here
510 */
511 if (label == flabel)
512 error = fn_for_each(label, profile,
513 profile_path_perm(op, subj_cred,
514 profile, &file->f_path,
515 buffer, request, &cond, flags,
516 &perms));
517 else
518 error = fn_for_each_not_in_set(label, flabel, profile,
519 profile_path_perm(op, subj_cred,
520 profile, &file->f_path,
521 buffer, request, &cond, flags,
522 &perms));
523 }
524 if (!error)
525 update_file_ctx(fctx: file_ctx(file), label, request);
526
527 aa_put_buffer(buf: buffer);
528
529 return error;
530}
531
532static int __file_sock_perm(const char *op, const struct cred *subj_cred,
533 struct aa_label *label,
534 struct aa_label *flabel, struct file *file,
535 u32 request, u32 denied)
536{
537 struct socket *sock = (struct socket *) file->private_data;
538 int error;
539
540 AA_BUG(!sock);
541
542 /* revalidation due to label out of date. No revocation at this time */
543 if (!denied && aa_label_is_subset(set: flabel, sub: label))
544 return 0;
545
546 /* TODO: improve to skip profiles cached in flabel */
547 error = aa_sock_file_perm(subj_cred, label, op, request, sock);
548 if (denied) {
549 /* TODO: improve to skip profiles checked above */
550 /* check every profile in file label to is cached */
551 last_error(error, aa_sock_file_perm(subj_cred, flabel, op,
552 request, sock));
553 }
554 if (!error)
555 update_file_ctx(fctx: file_ctx(file), label, request);
556
557 return error;
558}
559
560/**
561 * aa_file_perm - do permission revalidation check & audit for @file
562 * @op: operation being checked
563 * @subj_cred: subject cred
564 * @label: label being enforced (NOT NULL)
565 * @file: file to revalidate access permissions on (NOT NULL)
566 * @request: requested permissions
567 * @in_atomic: whether allocations need to be done in atomic context
568 *
569 * Returns: %0 if access allowed else error
570 */
571int aa_file_perm(const char *op, const struct cred *subj_cred,
572 struct aa_label *label, struct file *file,
573 u32 request, bool in_atomic)
574{
575 struct aa_file_ctx *fctx;
576 struct aa_label *flabel;
577 u32 denied;
578 int error = 0;
579
580 AA_BUG(!label);
581 AA_BUG(!file);
582
583 fctx = file_ctx(file);
584
585 rcu_read_lock();
586 flabel = rcu_dereference(fctx->label);
587 AA_BUG(!flabel);
588
589 /* revalidate access, if task is unconfined, or the cached cred
590 * doesn't match or if the request is for more permissions than
591 * was granted.
592 *
593 * Note: the test for !unconfined(flabel) is to handle file
594 * delegation from unconfined tasks
595 */
596 denied = request & ~fctx->allow;
597 if (unconfined(label) || unconfined(flabel) ||
598 (!denied && aa_label_is_subset(set: flabel, sub: label))) {
599 rcu_read_unlock();
600 goto done;
601 }
602
603 flabel = aa_get_newest_label(l: flabel);
604 rcu_read_unlock();
605 /* TODO: label cross check */
606
607 if (file->f_path.mnt && path_mediated_fs(dentry: file->f_path.dentry))
608 error = __file_path_perm(op, subj_cred, label, flabel, file,
609 request, denied, in_atomic);
610
611 else if (S_ISSOCK(file_inode(file)->i_mode))
612 error = __file_sock_perm(op, subj_cred, label, flabel, file,
613 request, denied);
614 aa_put_label(l: flabel);
615
616done:
617 return error;
618}
619
620static void revalidate_tty(const struct cred *subj_cred, struct aa_label *label)
621{
622 struct tty_struct *tty;
623 int drop_tty = 0;
624
625 tty = get_current_tty();
626 if (!tty)
627 return;
628
629 spin_lock(lock: &tty->files_lock);
630 if (!list_empty(head: &tty->tty_files)) {
631 struct tty_file_private *file_priv;
632 struct file *file;
633 /* TODO: Revalidate access to controlling tty. */
634 file_priv = list_first_entry(&tty->tty_files,
635 struct tty_file_private, list);
636 file = file_priv->file;
637
638 if (aa_file_perm(OP_INHERIT, subj_cred, label, file,
639 MAY_READ | MAY_WRITE, IN_ATOMIC))
640 drop_tty = 1;
641 }
642 spin_unlock(lock: &tty->files_lock);
643 tty_kref_put(tty);
644
645 if (drop_tty)
646 no_tty();
647}
648
649struct cred_label {
650 const struct cred *cred;
651 struct aa_label *label;
652};
653
654static int match_file(const void *p, struct file *file, unsigned int fd)
655{
656 struct cred_label *cl = (struct cred_label *)p;
657
658 if (aa_file_perm(OP_INHERIT, subj_cred: cl->cred, label: cl->label, file,
659 request: aa_map_file_to_perms(file), IN_ATOMIC))
660 return fd + 1;
661 return 0;
662}
663
664
665/* based on selinux's flush_unauthorized_files */
666void aa_inherit_files(const struct cred *cred, struct files_struct *files)
667{
668 struct aa_label *label = aa_get_newest_cred_label(cred);
669 struct cred_label cl = {
670 .cred = cred,
671 .label = label,
672 };
673 struct file *devnull = NULL;
674 unsigned int n;
675
676 revalidate_tty(subj_cred: cred, label);
677
678 /* Revalidate access to inherited open files. */
679 n = iterate_fd(files, 0, match_file, &cl);
680 if (!n) /* none found? */
681 goto out;
682
683 devnull = dentry_open(path: &aa_null, O_RDWR, creds: cred);
684 if (IS_ERR(ptr: devnull))
685 devnull = NULL;
686 /* replace all the matching ones with this */
687 do {
688 replace_fd(fd: n - 1, file: devnull, flags: 0);
689 } while ((n = iterate_fd(files, n, match_file, &cl)) != 0);
690 if (devnull)
691 fput(devnull);
692out:
693 aa_put_label(l: label);
694}
695

source code of linux/security/apparmor/file.c