summaryrefslogtreecommitdiffstats
path: root/security/apparmor/file.c
blob: cb3d3060d1049b24e4f948e182ee0258991f4a34 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
// SPDX-License-Identifier: GPL-2.0-only
/*
 * AppArmor security module
 *
 * This file contains AppArmor mediation of files
 *
 * Copyright (C) 1998-2008 Novell/SUSE
 * Copyright 2009-2010 Canonical Ltd.
 */

#include <linux/tty.h>
#include <linux/fdtable.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/mount.h>

#include "include/apparmor.h"
#include "include/audit.h"
#include "include/cred.h"
#include "include/file.h"
#include "include/match.h"
#include "include/net.h"
#include "include/path.h"
#include "include/policy.h"
#include "include/label.h"

static u32 map_mask_to_chr_mask(u32 mask)
{
	u32 m = mask & PERMS_CHRS_MASK;

	if (mask & AA_MAY_GETATTR)
		m |= MAY_READ;
	if (mask & (AA_MAY_SETATTR | AA_MAY_CHMOD | AA_MAY_CHOWN))
		m |= MAY_WRITE;

	return m;
}

/**
 * file_audit_cb - call back for file specific audit fields
 * @ab: audit_buffer  (NOT NULL)
 * @va: audit struct to audit values of  (NOT NULL)
 */
static void file_audit_cb(struct audit_buffer *ab, void *va)
{
	struct common_audit_data *sa = va;
	kuid_t fsuid = current_fsuid();
	char str[10];

	if (aad(sa)->request & AA_AUDIT_FILE_MASK) {
		aa_perm_mask_to_str(str, sizeof(str), aa_file_perm_chrs,
				    map_mask_to_chr_mask(aad(sa)->request));
		audit_log_format(ab, " requested_mask=\"%s\"", str);
	}
	if (aad(sa)->denied & AA_AUDIT_FILE_MASK) {
		aa_perm_mask_to_str(str, sizeof(str), aa_file_perm_chrs,
				    map_mask_to_chr_mask(aad(sa)->denied));
		audit_log_format(ab, " denied_mask=\"%s\"", str);
	}
	if (aad(sa)->request & AA_AUDIT_FILE_MASK) {
		audit_log_format(ab, " fsuid=%d",
				 from_kuid(&init_user_ns, fsuid));
		audit_log_format(ab, " ouid=%d",
				 from_kuid(&init_user_ns, aad(sa)->fs.ouid));
	}

	if (aad(sa)->peer) {
		audit_log_format(ab, " target=");
		aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
				FLAG_VIEW_SUBNS, GFP_KERNEL);
	} else if (aad(sa)->fs.target) {
		audit_log_format(ab, " target=");
		audit_log_untrustedstring(ab, aad(sa)->fs.target);
	}
}

/**
 * aa_audit_file - handle the auditing of file operations
 * @profile: the profile being enforced  (NOT NULL)
 * @perms: the permissions computed for the request (NOT NULL)
 * @op: operation being mediated
 * @request: permissions requested
 * @name: name of object being mediated (MAYBE NULL)
 * @target: name of target (MAYBE NULL)
 * @tlabel: target label (MAY BE NULL)
 * @ouid: object uid
 * @info: extra information message (MAYBE NULL)
 * @error: 0 if operation allowed else failure error code
 *
 * Returns: %0 or error on failure
 */
int aa_audit_file(struct aa_profile *profile, struct aa_perms *perms,
		  const char *op, u32 request, const char *name,
		  const char *target, struct aa_label *tlabel,
		  kuid_t ouid, const char *info, int error)
{
	int type = AUDIT_APPARMOR_AUTO;
	DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_TASK, AA_CLASS_FILE, op);

	sa.u.tsk = NULL;
	aad(&sa)->request = request;
	aad(&sa)->name = name;
	aad(&sa)->fs.target = target;
	aad(&sa)->peer = tlabel;
	aad(&sa)->fs.ouid = ouid;
	aad(&sa)->info = info;
	aad(&sa)->error = error;
	sa.u.tsk = NULL;

	if (likely(!aad(&sa)->error)) {
		u32 mask = perms->audit;

		if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
			mask = 0xffff;

		/* mask off perms that are not being force audited */
		aad(&sa)->request &= mask;

		if (likely(!aad(&sa)->request))
			return 0;
		type = AUDIT_APPARMOR_AUDIT;
	} else {
		/* only report permissions that were denied */
		aad(&sa)->request = aad(&sa)->request & ~perms->allow;
		AA_BUG(!aad(&sa)->request);

		if (aad(&sa)->request & perms->kill)
			type = AUDIT_APPARMOR_KILL;

		/* quiet known rejects, assumes quiet and kill do not overlap */
		if ((aad(&sa)->request & perms->quiet) &&
		    AUDIT_MODE(profile) != AUDIT_NOQUIET &&
		    AUDIT_MODE(profile) != AUDIT_ALL)
			aad(&sa)->request &= ~perms->quiet;

		if (!aad(&sa)->request)
			return aad(&sa)->error;
	}

	aad(&sa)->denied = aad(&sa)->request & ~perms->allow;
	return aa_audit(type, profile, &sa, file_audit_cb);
}

static int path_name(const char *op, struct aa_label *label,
		     const struct path *path, int flags, char *buffer,
		     const char **name, struct path_cond *cond, u32 request)
{
	struct aa_profile *profile;
	const char *info = NULL;
	int error;

	error = aa_path_name(path, flags, buffer, name, &info,
			     labels_profile(label)->disconnected);
	if (error) {
		fn_for_each_confined(label, profile,
			aa_audit_file(profile, &nullperms, op, request, *name,
				      NULL, NULL, cond->uid, info, error));
		return error;
	}

	return 0;
}

/**
 * aa_lookup_fperms - convert dfa compressed perms to internal perms
 * @dfa: dfa to lookup perms for   (NOT NULL)
 * @state: state in dfa
 * @cond:  conditions to consider  (NOT NULL)
 *
 * TODO: convert from dfa + state to permission entry
 *
 * Returns: a pointer to a file permission set
 */
struct aa_perms default_perms = {};
struct aa_perms *aa_lookup_fperms(struct aa_policydb *file_rules,
				 aa_state_t state, struct path_cond *cond)
{
	unsigned int index = ACCEPT_TABLE(file_rules->dfa)[state];

	if (!(file_rules->perms))
		return &default_perms;

	if (uid_eq(current_fsuid(), cond->uid))
		return &(file_rules->perms[index]);

	return &(file_rules->perms[index + 1]);
}

/**
 * aa_str_perms - find permission that match @name
 * @dfa: to match against  (MAYBE NULL)
 * @state: state to start matching in
 * @name: string to match against dfa  (NOT NULL)
 * @cond: conditions to consider for permission set computation  (NOT NULL)
 * @perms: Returns - the permissions found when matching @name
 *
 * Returns: the final state in @dfa when beginning @start and walking @name
 */
aa_state_t aa_str_perms(struct aa_policydb *file_rules, aa_state_t start,
			const char *name, struct path_cond *cond,
			struct aa_perms *perms)
{
	aa_state_t state;
	state = aa_dfa_match(file_rules->dfa, start, name);
	*perms = *(aa_lookup_fperms(file_rules, state, cond));

	return state;
}

static int __aa_path_perm(const char *op, struct aa_profile *profile,
			  const char *name, u32 request,
			  struct path_cond *cond, int flags,
			  struct aa_perms *perms)
{
	struct aa_ruleset *rules = list_first_entry(&profile->rules,
						    typeof(*rules), list);
	int e = 0;

	if (profile_unconfined(profile))
		return 0;
	aa_str_perms(&(rules->file), rules->file.start[AA_CLASS_FILE],
		     name, cond, perms);
	if (request & ~perms->allow)
		e = -EACCES;
	return aa_audit_file(profile, perms, op, request, name, NULL, NULL,
			     cond->uid, NULL, e);
}


static int profile_path_perm(const char *op, struct aa_profile *profile,
			     const struct path *path, char *buffer, u32 request,
			     struct path_cond *cond, int flags,
			     struct aa_perms *perms)
{
	const char *name;
	int error;

	if (profile_unconfined(profile))
		return 0;

	error = path_name(op, &profile->label, path,
			  flags | profile->path_flags, buffer, &name, cond,
			  request);
	if (error)
		return error;
	return __aa_path_perm(op, profile, name, request, cond, flags,
			      perms);
}

/**
 * aa_path_perm - do permissions check & audit for @path
 * @op: operation being checked
 * @label: profile being enforced  (NOT NULL)
 * @path: path to check permissions of  (NOT NULL)
 * @flags: any additional path flags beyond what the profile specifies
 * @request: requested permissions
 * @cond: conditional info for this request  (NOT NULL)
 *
 * Returns: %0 else error if access denied or other error
 */
int aa_path_perm(const char *op, struct aa_label *label,
		 const struct path *path, int flags, u32 request,
		 struct path_cond *cond)
{
	struct aa_perms perms = {};
	struct aa_profile *profile;
	char *buffer = NULL;
	int error;

	flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR :
								0);
	buffer = aa_get_buffer(false);
	if (!buffer)
		return -ENOMEM;
	error = fn_for_each_confined(label, profile,
			profile_path_perm(op, profile, path, buffer, request,
					  cond, flags, &perms));

	aa_put_buffer(buffer);

	return error;
}

/**
 * xindex_is_subset - helper for aa_path_link
 * @link: link permission set
 * @target: target permission set
 *
 * test target x permissions are equal OR a subset of link x permissions
 * this is done as part of the subset test, where a hardlink must have
 * a subset of permissions that the target has.
 *
 * Returns: true if subset else false
 */
static inline bool xindex_is_subset(u32 link, u32 target)
{
	if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
	    ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
		return false;

	return true;
}

static int profile_path_link(struct aa_profile *profile,
			     const struct path *link, char *buffer,
			     const struct path *target, char *buffer2,
			     struct path_cond *cond)
{
	struct aa_ruleset *rules = list_first_entry(&profile->rules,
						    typeof(*rules), list);
	const char *lname, *tname = NULL;
	struct aa_perms lperms = {}, perms;
	const char *info = NULL;
	u32 request = AA_MAY_LINK;
	aa_state_t state;
	int error;

	error = path_name(OP_LINK, &profile->label, link, profile->path_flags,
			  buffer, &lname, cond, AA_MAY_LINK);
	if (error)
		goto audit;

	/* buffer2 freed below, tname is pointer in buffer2 */
	error = path_name(OP_LINK, &profile->label, target, profile->path_flags,
			  buffer2, &tname, cond, AA_MAY_LINK);
	if (error)
		goto audit;

	error = -EACCES;
	/* aa_str_perms - handles the case of the dfa being NULL */
	state = aa_str_perms(&(rules->file),
			     rules->file.start[AA_CLASS_FILE], lname,
			     cond, &lperms);

	if (!(lperms.allow & AA_MAY_LINK))
		goto audit;

	/* test to see if target can be paired with link */
	state = aa_dfa_null_transition(rules->file.dfa, state);
	aa_str_perms(&(rules->file), state, tname, cond, &perms);

	/* force audit/quiet masks for link are stored in the second entry
	 * in the link pair.
	 */
	lperms.audit = perms.audit;
	lperms.quiet = perms.quiet;
	lperms.kill = perms.kill;

	if (!(perms.allow & AA_MAY_LINK)) {
		info = "target restricted";
		lperms = perms;
		goto audit;
	}

	/* done if link subset test is not required */
	if (!(perms.allow & AA_LINK_SUBSET))
		goto done_tests;

	/* Do link perm subset test requiring allowed permission on link are
	 * a subset of the allowed permissions on target.
	 */
	aa_str_perms(&(rules->file), rules->file.start[AA_CLASS_FILE],
		     tname, cond, &perms);

	/* AA_MAY_LINK is not considered in the subset test */
	request = lperms.allow & ~AA_MAY_LINK;
	lperms.allow &= perms.allow | AA_MAY_LINK;

	request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
	if (request & ~lperms.allow) {
		goto audit;
	} else if ((lperms.allow & MAY_EXEC) &&
		   !xindex_is_subset(lperms.xindex, perms.xindex)) {
		lperms.allow &= ~MAY_EXEC;
		request |= MAY_EXEC;
		info = "link not subset of target";
		goto audit;
	}

done_tests:
	error = 0;

audit:
	return aa_audit_file(profile, &lperms, OP_LINK, request, lname, tname,
			     NULL, cond->uid, info, error);
}

/**
 * aa_path_link - Handle hard link permission check
 * @label: the label being enforced  (NOT NULL)
 * @old_dentry: the target dentry  (NOT NULL)
 * @new_dir: directory the new link will be created in  (NOT NULL)
 * @new_dentry: the link being created  (NOT NULL)
 *
 * Handle the permission test for a link & target pair.  Permission
 * is encoded as a pair where the link permission is determined
 * first, and if allowed, the target is tested.  The target test
 * is done from the point of the link match (not start of DFA)
 * making the target permission dependent on the link permission match.
 *
 * The subset test if required forces that permissions granted
 * on link are a subset of the permission granted to target.
 *
 * Returns: %0 if allowed else error
 */
int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
		 const struct path *new_dir, struct dentry *new_dentry)
{
	struct path link = { .mnt = new_dir->mnt, .dentry = new_dentry };
	struct path target = { .mnt = new_dir->mnt, .dentry = old_dentry };
	struct path_cond cond = {
		d_backing_inode(old_dentry)->i_uid,
		d_backing_inode(old_dentry)->i_mode
	};
	char *buffer = NULL, *buffer2 = NULL;
	struct aa_profile *profile;
	int error;

	/* buffer freed below, lname is pointer in buffer */
	buffer = aa_get_buffer(false);
	buffer2 = aa_get_buffer(false);
	error = -ENOMEM;
	if (!buffer || !buffer2)
		goto out;

	error = fn_for_each_confined(label, profile,
			profile_path_link(profile, &link, buffer, &target,
					  buffer2, &cond));
out:
	aa_put_buffer(buffer);
	aa_put_buffer(buffer2);
	return error;
}

static void update_file_ctx(struct aa_file_ctx *fctx, struct aa_label *label,
			    u32 request)
{
	struct aa_label *l, *old;

	/* update caching of label on file_ctx */
	spin_lock(&fctx->lock);
	old = rcu_dereference_protected(fctx->label,
					lockdep_is_held(&fctx->lock));
	l = aa_label_merge(old, label, GFP_ATOMIC);
	if (l) {
		if (l != old) {
			rcu_assign_pointer(fctx->label, l);
			aa_put_label(old);
		} else
			aa_put_label(l);
		fctx->allow |= request;
	}
	spin_unlock(&fctx->lock);
}

static int __file_path_perm(const char *op, struct aa_label *label,
			    struct aa_label *flabel, struct file *file,
			    u32 request, u32 denied, bool in_atomic)
{
	struct aa_profile *profile;
	struct aa_perms perms = {};
	vfsuid_t vfsuid = i_uid_into_vfsuid(file_mnt_user_ns(file),
					    file_inode(file));
	struct path_cond cond = {
		.uid = vfsuid_into_kuid(vfsuid),
		.mode = file_inode(file)->i_mode
	};
	char *buffer;
	int flags, error;

	/* revalidation due to label out of date. No revocation at this time */
	if (!denied && aa_label_is_subset(flabel, label))
		/* TODO: check for revocation on stale profiles */
		return 0;

	flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
	buffer = aa_get_buffer(in_atomic);
	if (!buffer)
		return -ENOMEM;

	/* check every profile in task label not in current cache */
	error = fn_for_each_not_in_set(flabel, label, profile,
			profile_path_perm(op, profile, &file->f_path, buffer,
					  request, &cond, flags, &perms));
	if (denied && !error) {
		/*
		 * check every profile in file label that was not tested
		 * in the initial check above.
		 *
		 * TODO: cache full perms so this only happens because of
		 * conditionals
		 * TODO: don't audit here
		 */
		if (label == flabel)
			error = fn_for_each(label, profile,
				profile_path_perm(op, profile, &file->f_path,
						  buffer, request, &cond, flags,
						  &perms));
		else
			error = fn_for_each_not_in_set(label, flabel, profile,
				profile_path_perm(op, profile, &file->f_path,
						  buffer, request, &cond, flags,
						  &perms));
	}
	if (!error)
		update_file_ctx(file_ctx(file), label, request);

	aa_put_buffer(buffer);

	return error;
}

static int __file_sock_perm(const char *op, struct aa_label *label,
			    struct aa_label *flabel, struct file *file,
			    u32 request, u32 denied)
{
	struct socket *sock = (struct socket *) file->private_data;
	int error;

	AA_BUG(!sock);

	/* revalidation due to label out of date. No revocation at this time */
	if (!denied && aa_label_is_subset(flabel, label))
		return 0;

	/* TODO: improve to skip profiles cached in flabel */
	error = aa_sock_file_perm(label, op, request, sock);
	if (denied) {
		/* TODO: improve to skip profiles checked above */
		/* check every profile in file label to is cached */
		last_error(error, aa_sock_file_perm(flabel, op, request, sock));
	}
	if (!error)
		update_file_ctx(file_ctx(file), label, request);

	return error;
}

/**
 * aa_file_perm - do permission revalidation check & audit for @file
 * @op: operation being checked
 * @label: label being enforced   (NOT NULL)
 * @file: file to revalidate access permissions on  (NOT NULL)
 * @request: requested permissions
 * @in_atomic: whether allocations need to be done in atomic context
 *
 * Returns: %0 if access allowed else error
 */
int aa_file_perm(const char *op, struct aa_label *label, struct file *file,
		 u32 request, bool in_atomic)
{
	struct aa_file_ctx *fctx;
	struct aa_label *flabel;
	u32 denied;
	int error = 0;

	AA_BUG(!label);
	AA_BUG(!file);

	fctx = file_ctx(file);

	rcu_read_lock();
	flabel  = rcu_dereference(fctx->label);
	AA_BUG(!flabel);

	/* revalidate access, if task is unconfined, or the cached cred
	 * doesn't match or if the request is for more permissions than
	 * was granted.
	 *
	 * Note: the test for !unconfined(flabel) is to handle file
	 *       delegation from unconfined tasks
	 */
	denied = request & ~fctx->allow;
	if (unconfined(label) || unconfined(flabel) ||
	    (!denied && aa_label_is_subset(flabel, label))) {
		rcu_read_unlock();
		goto done;
	}

	flabel  = aa_get_newest_label(flabel);
	rcu_read_unlock();
	/* TODO: label cross check */

	if (file->f_path.mnt && path_mediated_fs(file->f_path.dentry))
		error = __file_path_perm(op, label, flabel, file, request,
					 denied, in_atomic);

	else if (S_ISSOCK(file_inode(file)->i_mode))
		error = __file_sock_perm(op, label, flabel, file, request,
					 denied);
	aa_put_label(flabel);

done:
	return error;
}

static void revalidate_tty(struct aa_label *label)
{
	struct tty_struct *tty;
	int drop_tty = 0;

	tty = get_current_tty();
	if (!tty)
		return;

	spin_lock(&tty->files_lock);
	if (!list_empty(&tty->tty_files)) {
		struct tty_file_private *file_priv;
		struct file *file;
		/* TODO: Revalidate access to controlling tty. */
		file_priv = list_first_entry(&tty->tty_files,
					     struct tty_file_private, list);
		file = file_priv->file;

		if (aa_file_perm(OP_INHERIT, label, file, MAY_READ | MAY_WRITE,
				 IN_ATOMIC))
			drop_tty = 1;
	}
	spin_unlock(&tty->files_lock);
	tty_kref_put(tty);

	if (drop_tty)
		no_tty();
}

static int match_file(const void *p, struct file *file, unsigned int fd)
{
	struct aa_label *label = (struct aa_label *)p;

	if (aa_file_perm(OP_INHERIT, label, file, aa_map_file_to_perms(file),
			 IN_ATOMIC))
		return fd + 1;
	return 0;
}


/* based on selinux's flush_unauthorized_files */
void aa_inherit_files(const struct cred *cred, struct files_struct *files)
{
	struct aa_label *label = aa_get_newest_cred_label(cred);
	struct file *devnull = NULL;
	unsigned int n;

	revalidate_tty(label);

	/* Revalidate access to inherited open files. */
	n = iterate_fd(files, 0, match_file, label);
	if (!n) /* none found? */
		goto out;

	devnull = dentry_open(&aa_null, O_RDWR, cred);
	if (IS_ERR(devnull))
		devnull = NULL;
	/* replace all the matching ones with this */
	do {
		replace_fd(n - 1, devnull, 0);
	} while ((n = iterate_fd(files, n, match_file, label)) != 0);
	if (devnull)
		fput(devnull);
out:
	aa_put_label(label);
}