summaryrefslogtreecommitdiffstats
path: root/security/tomoyo/domain.c
blob: 229de1e71a38cc4f0bfd5ae0bb37b0ad18f2ae9e (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
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
/*
 * security/tomoyo/domain.c
 *
 * Implementation of the Domain-Based Mandatory Access Control.
 *
 * Copyright (C) 2005-2009  NTT DATA CORPORATION
 *
 * Version: 2.2.0   2009/04/01
 *
 */

#include "common.h"
#include "tomoyo.h"
#include "realpath.h"
#include <linux/binfmts.h>

/* Variables definitions.*/

/* The initial domain. */
struct tomoyo_domain_info tomoyo_kernel_domain;

/*
 * tomoyo_domain_list is used for holding list of domains.
 * The ->acl_info_list of "struct tomoyo_domain_info" is used for holding
 * permissions (e.g. "allow_read /lib/libc-2.5.so") given to each domain.
 *
 * An entry is added by
 *
 * # ( echo "<kernel>"; echo "allow_execute /sbin/init" ) > \
 *                                  /sys/kernel/security/tomoyo/domain_policy
 *
 * and is deleted by
 *
 * # ( echo "<kernel>"; echo "delete allow_execute /sbin/init" ) > \
 *                                  /sys/kernel/security/tomoyo/domain_policy
 *
 * and all entries are retrieved by
 *
 * # cat /sys/kernel/security/tomoyo/domain_policy
 *
 * A domain is added by
 *
 * # echo "<kernel>" > /sys/kernel/security/tomoyo/domain_policy
 *
 * and is deleted by
 *
 * # echo "delete <kernel>" > /sys/kernel/security/tomoyo/domain_policy
 *
 * and all domains are retrieved by
 *
 * # grep '^<kernel>' /sys/kernel/security/tomoyo/domain_policy
 *
 * Normally, a domainname is monotonically getting longer because a domainname
 * which the process will belong to if an execve() operation succeeds is
 * defined as a concatenation of "current domainname" + "pathname passed to
 * execve()".
 * See tomoyo_domain_initializer_list and tomoyo_domain_keeper_list for
 * exceptions.
 */
LIST_HEAD(tomoyo_domain_list);

/*
 * tomoyo_domain_initializer_entry is a structure which is used for holding
 * "initialize_domain" and "no_initialize_domain" entries.
 * It has following fields.
 *
 *  (1) "list" which is linked to tomoyo_domain_initializer_list .
 *  (2) "domainname" which is "a domainname" or "the last component of a
 *      domainname". This field is NULL if "from" clause is not specified.
 *  (3) "program" which is a program's pathname.
 *  (4) "is_deleted" is a bool which is true if marked as deleted, false
 *      otherwise.
 *  (5) "is_not" is a bool which is true if "no_initialize_domain", false
 *      otherwise.
 *  (6) "is_last_name" is a bool which is true if "domainname" is "the last
 *      component of a domainname", false otherwise.
 */
struct tomoyo_domain_initializer_entry {
	struct list_head list;
	const struct tomoyo_path_info *domainname;    /* This may be NULL */
	const struct tomoyo_path_info *program;
	bool is_deleted;
	bool is_not;       /* True if this entry is "no_initialize_domain".  */
	/* True if the domainname is tomoyo_get_last_name(). */
	bool is_last_name;
};

/*
 * tomoyo_domain_keeper_entry is a structure which is used for holding
 * "keep_domain" and "no_keep_domain" entries.
 * It has following fields.
 *
 *  (1) "list" which is linked to tomoyo_domain_keeper_list .
 *  (2) "domainname" which is "a domainname" or "the last component of a
 *      domainname".
 *  (3) "program" which is a program's pathname.
 *      This field is NULL if "from" clause is not specified.
 *  (4) "is_deleted" is a bool which is true if marked as deleted, false
 *      otherwise.
 *  (5) "is_not" is a bool which is true if "no_initialize_domain", false
 *      otherwise.
 *  (6) "is_last_name" is a bool which is true if "domainname" is "the last
 *      component of a domainname", false otherwise.
 */
struct tomoyo_domain_keeper_entry {
	struct list_head list;
	const struct tomoyo_path_info *domainname;
	const struct tomoyo_path_info *program;       /* This may be NULL */
	bool is_deleted;
	bool is_not;       /* True if this entry is "no_keep_domain".        */
	/* True if the domainname is tomoyo_get_last_name(). */
	bool is_last_name;
};

/*
 * tomoyo_alias_entry is a structure which is used for holding "alias" entries.
 * It has following fields.
 *
 *  (1) "list" which is linked to tomoyo_alias_list .
 *  (2) "original_name" which is a dereferenced pathname.
 *  (3) "aliased_name" which is a symlink's pathname.
 *  (4) "is_deleted" is a bool which is true if marked as deleted, false
 *      otherwise.
 */
struct tomoyo_alias_entry {
	struct list_head list;
	const struct tomoyo_path_info *original_name;
	const struct tomoyo_path_info *aliased_name;
	bool is_deleted;
};

/**
 * tomoyo_get_last_name - Get last component of a domainname.
 *
 * @domain: Pointer to "struct tomoyo_domain_info".
 *
 * Returns the last component of the domainname.
 */
const char *tomoyo_get_last_name(const struct tomoyo_domain_info *domain)
{
	const char *cp0 = domain->domainname->name;
	const char *cp1 = strrchr(cp0, ' ');

	if (cp1)
		return cp1 + 1;
	return cp0;
}

/*
 * tomoyo_domain_initializer_list is used for holding list of programs which
 * triggers reinitialization of domainname. Normally, a domainname is
 * monotonically getting longer. But sometimes, we restart daemon programs.
 * It would be convenient for us that "a daemon started upon system boot" and
 * "the daemon restarted from console" belong to the same domain. Thus, TOMOYO
 * provides a way to shorten domainnames.
 *
 * An entry is added by
 *
 * # echo 'initialize_domain /usr/sbin/httpd' > \
 *                               /sys/kernel/security/tomoyo/exception_policy
 *
 * and is deleted by
 *
 * # echo 'delete initialize_domain /usr/sbin/httpd' > \
 *                               /sys/kernel/security/tomoyo/exception_policy
 *
 * and all entries are retrieved by
 *
 * # grep ^initialize_domain /sys/kernel/security/tomoyo/exception_policy
 *
 * In the example above, /usr/sbin/httpd will belong to
 * "<kernel> /usr/sbin/httpd" domain.
 *
 * You may specify a domainname using "from" keyword.
 * "initialize_domain /usr/sbin/httpd from <kernel> /etc/rc.d/init.d/httpd"
 * will cause "/usr/sbin/httpd" executed from "<kernel> /etc/rc.d/init.d/httpd"
 * domain to belong to "<kernel> /usr/sbin/httpd" domain.
 *
 * You may add "no_" prefix to "initialize_domain".
 * "initialize_domain /usr/sbin/httpd" and
 * "no_initialize_domain /usr/sbin/httpd from <kernel> /etc/rc.d/init.d/httpd"
 * will cause "/usr/sbin/httpd" to belong to "<kernel> /usr/sbin/httpd" domain
 * unless executed from "<kernel> /etc/rc.d/init.d/httpd" domain.
 */
static LIST_HEAD(tomoyo_domain_initializer_list);

/**
 * tomoyo_update_domain_initializer_entry - Update "struct tomoyo_domain_initializer_entry" list.
 *
 * @domainname: The name of domain. May be NULL.
 * @program:    The name of program.
 * @is_not:     True if it is "no_initialize_domain" entry.
 * @is_delete:  True if it is a delete request.
 *
 * Returns 0 on success, negative value otherwise.
 *
 * Caller holds tomoyo_read_lock().
 */
static int tomoyo_update_domain_initializer_entry(const char *domainname,
						  const char *program,
						  const bool is_not,
						  const bool is_delete)
{
	struct tomoyo_domain_initializer_entry *entry = NULL;
	struct tomoyo_domain_initializer_entry *ptr;
	const struct tomoyo_path_info *saved_program;
	const struct tomoyo_path_info *saved_domainname = NULL;
	int error = is_delete ? -ENOENT : -ENOMEM;
	bool is_last_name = false;

	if (!tomoyo_is_correct_path(program, 1, -1, -1, __func__))
		return -EINVAL; /* No patterns allowed. */
	if (domainname) {
		if (!tomoyo_is_domain_def(domainname) &&
		    tomoyo_is_correct_path(domainname, 1, -1, -1, __func__))
			is_last_name = true;
		else if (!tomoyo_is_correct_domain(domainname, __func__))
			return -EINVAL;
		saved_domainname = tomoyo_save_name(domainname);
		if (!saved_domainname)
			goto out;
	}
	saved_program = tomoyo_save_name(program);
	if (!saved_program)
		goto out;
	if (!is_delete)
		entry = kmalloc(sizeof(*entry), GFP_KERNEL);
	mutex_lock(&tomoyo_policy_lock);
	list_for_each_entry_rcu(ptr, &tomoyo_domain_initializer_list, list) {
		if (ptr->is_not != is_not ||
		    ptr->domainname != saved_domainname ||
		    ptr->program != saved_program)
			continue;
		ptr->is_deleted = is_delete;
		error = 0;
		break;
	}
	if (!is_delete && error && tomoyo_memory_ok(entry)) {
		entry->domainname = saved_domainname;
		entry->program = saved_program;
		entry->is_not = is_not;
		entry->is_last_name = is_last_name;
		list_add_tail_rcu(&entry->list,
				  &tomoyo_domain_initializer_list);
		entry = NULL;
		error = 0;
	}
	mutex_unlock(&tomoyo_policy_lock);
 out:
	kfree(entry);
	return error;
}

/**
 * tomoyo_read_domain_initializer_policy - Read "struct tomoyo_domain_initializer_entry" list.
 *
 * @head: Pointer to "struct tomoyo_io_buffer".
 *
 * Returns true on success, false otherwise.
 *
 * Caller holds tomoyo_read_lock().
 */
bool tomoyo_read_domain_initializer_policy(struct tomoyo_io_buffer *head)
{
	struct list_head *pos;
	bool done = true;

	list_for_each_cookie(pos, head->read_var2,
			     &tomoyo_domain_initializer_list) {
		const char *no;
		const char *from = "";
		const char *domain = "";
		struct tomoyo_domain_initializer_entry *ptr;
		ptr = list_entry(pos, struct tomoyo_domain_initializer_entry,
				  list);
		if (ptr->is_deleted)
			continue;
		no = ptr->is_not ? "no_" : "";
		if (ptr->domainname) {
			from = " from ";
			domain = ptr->domainname->name;
		}
		done = tomoyo_io_printf(head,
					"%s" TOMOYO_KEYWORD_INITIALIZE_DOMAIN
					"%s%s%s\n", no, ptr->program->name,
					from, domain);
		if (!done)
			break;
	}
	return done;
}

/**
 * tomoyo_write_domain_initializer_policy - Write "struct tomoyo_domain_initializer_entry" list.
 *
 * @data:      String to parse.
 * @is_not:    True if it is "no_initialize_domain" entry.
 * @is_delete: True if it is a delete request.
 *
 * Returns 0 on success, negative value otherwise.
 *
 * Caller holds tomoyo_read_lock().
 */
int tomoyo_write_domain_initializer_policy(char *data, const bool is_not,
					   const bool is_delete)
{
	char *cp = strstr(data, " from ");

	if (cp) {
		*cp = '\0';
		return tomoyo_update_domain_initializer_entry(cp + 6, data,
							      is_not,
							      is_delete);
	}
	return tomoyo_update_domain_initializer_entry(NULL, data, is_not,
						      is_delete);
}

/**
 * tomoyo_is_domain_initializer - Check whether the given program causes domainname reinitialization.
 *
 * @domainname: The name of domain.
 * @program:    The name of program.
 * @last_name:  The last component of @domainname.
 *
 * Returns true if executing @program reinitializes domain transition,
 * false otherwise.
 *
 * Caller holds tomoyo_read_lock().
 */
static bool tomoyo_is_domain_initializer(const struct tomoyo_path_info *
					 domainname,
					 const struct tomoyo_path_info *program,
					 const struct tomoyo_path_info *
					 last_name)
{
	struct tomoyo_domain_initializer_entry *ptr;
	bool flag = false;

	list_for_each_entry_rcu(ptr, &tomoyo_domain_initializer_list, list) {
		if (ptr->is_deleted)
			continue;
		if (ptr->domainname) {
			if (!ptr->is_last_name) {
				if (ptr->domainname != domainname)
					continue;
			} else {
				if (tomoyo_pathcmp(ptr->domainname, last_name))
					continue;
			}
		}
		if (tomoyo_pathcmp(ptr->program, program))
			continue;
		if (ptr->is_not) {
			flag = false;
			break;
		}
		flag = true;
	}
	return flag;
}

/*
 * tomoyo_domain_keeper_list is used for holding list of domainnames which
 * suppresses domain transition. Normally, a domainname is monotonically
 * getting longer. But sometimes, we want to suppress domain transition.
 * It would be convenient for us that programs executed from a login session
 * belong to the same domain. Thus, TOMOYO provides a way to suppress domain
 * transition.
 *
 * An entry is added by
 *
 * # echo 'keep_domain <kernel> /usr/sbin/sshd /bin/bash' > \
 *                              /sys/kernel/security/tomoyo/exception_policy
 *
 * and is deleted by
 *
 * # echo 'delete keep_domain <kernel> /usr/sbin/sshd /bin/bash' > \
 *                              /sys/kernel/security/tomoyo/exception_policy
 *
 * and all entries are retrieved by
 *
 * # grep ^keep_domain /sys/kernel/security/tomoyo/exception_policy
 *
 * In the example above, any process which belongs to
 * "<kernel> /usr/sbin/sshd /bin/bash" domain will remain in that domain,
 * unless explicitly specified by "initialize_domain" or "no_keep_domain".
 *
 * You may specify a program using "from" keyword.
 * "keep_domain /bin/pwd from <kernel> /usr/sbin/sshd /bin/bash"
 * will cause "/bin/pwd" executed from "<kernel> /usr/sbin/sshd /bin/bash"
 * domain to remain in "<kernel> /usr/sbin/sshd /bin/bash" domain.
 *
 * You may add "no_" prefix to "keep_domain".
 * "keep_domain <kernel> /usr/sbin/sshd /bin/bash" and
 * "no_keep_domain /usr/bin/passwd from <kernel> /usr/sbin/sshd /bin/bash" will
 * cause "/usr/bin/passwd" to belong to
 * "<kernel> /usr/sbin/sshd /bin/bash /usr/bin/passwd" domain, unless
 * explicitly specified by "initialize_domain".
 */
static LIST_HEAD(tomoyo_domain_keeper_list);

/**
 * tomoyo_update_domain_keeper_entry - Update "struct tomoyo_domain_keeper_entry" list.
 *
 * @domainname: The name of domain.
 * @program:    The name of program. May be NULL.
 * @is_not:     True if it is "no_keep_domain" entry.
 * @is_delete:  True if it is a delete request.
 *
 * Returns 0 on success, negative value otherwise.
 *
 * Caller holds tomoyo_read_lock().
 */
static int tomoyo_update_domain_keeper_entry(const char *domainname,
					     const char *program,
					     const bool is_not,
					     const bool is_delete)
{
	struct tomoyo_domain_keeper_entry *entry = NULL;
	struct tomoyo_domain_keeper_entry *ptr;
	const struct tomoyo_path_info *saved_domainname;
	const struct tomoyo_path_info *saved_program = NULL;
	int error = is_delete ? -ENOENT : -ENOMEM;
	bool is_last_name = false;

	if (!tomoyo_is_domain_def(domainname) &&
	    tomoyo_is_correct_path(domainname, 1, -1, -1, __func__))
		is_last_name = true;
	else if (!tomoyo_is_correct_domain(domainname, __func__))
		return -EINVAL;
	if (program) {
		if (!tomoyo_is_correct_path(program, 1, -1, -1, __func__))
			return -EINVAL;
		saved_program = tomoyo_save_name(program);
		if (!saved_program)
			goto out;
	}
	saved_domainname = tomoyo_save_name(domainname);
	if (!saved_domainname)
		goto out;
	if (!is_delete)
		entry = kmalloc(sizeof(*entry), GFP_KERNEL);
	mutex_lock(&tomoyo_policy_lock);
	list_for_each_entry_rcu(ptr, &tomoyo_domain_keeper_list, list) {
		if (ptr->is_not != is_not ||
		    ptr->domainname != saved_domainname ||
		    ptr->program != saved_program)
			continue;
		ptr->is_deleted = is_delete;
		error = 0;
		break;
	}
	if (!is_delete && error && tomoyo_memory_ok(entry)) {
		entry->domainname = saved_domainname;
		entry->program = saved_program;
		entry->is_not = is_not;
		entry->is_last_name = is_last_name;
		list_add_tail_rcu(&entry->list, &tomoyo_domain_keeper_list);
		entry = NULL;
		error = 0;
	}
	mutex_unlock(&tomoyo_policy_lock);
 out:
	kfree(entry);
	return error;
}

/**
 * tomoyo_write_domain_keeper_policy - Write "struct tomoyo_domain_keeper_entry" list.
 *
 * @data:      String to parse.
 * @is_not:    True if it is "no_keep_domain" entry.
 * @is_delete: True if it is a delete request.
 *
 * Caller holds tomoyo_read_lock().
 */
int tomoyo_write_domain_keeper_policy(char *data, const bool is_not,
				      const bool is_delete)
{
	char *cp = strstr(data, " from ");

	if (cp) {
		*cp = '\0';
		return tomoyo_update_domain_keeper_entry(cp + 6, data, is_not,
							 is_delete);
	}
	return tomoyo_update_domain_keeper_entry(data, NULL, is_not, is_delete);
}

/**
 * tomoyo_read_domain_keeper_policy - Read "struct tomoyo_domain_keeper_entry" list.
 *
 * @head: Pointer to "struct tomoyo_io_buffer".
 *
 * Returns true on success, false otherwise.
 *
 * Caller holds tomoyo_read_lock().
 */
bool tomoyo_read_domain_keeper_policy(struct tomoyo_io_buffer *head)
{
	struct list_head *pos;
	bool done = true;

	list_for_each_cookie(pos, head->read_var2,
			     &tomoyo_domain_keeper_list) {
		struct tomoyo_domain_keeper_entry *ptr;
		const char *no;
		const char *from = "";
		const char *program = "";

		ptr = list_entry(pos, struct tomoyo_domain_keeper_entry, list);
		if (ptr->is_deleted)
			continue;
		no = ptr->is_not ? "no_" : "";
		if (ptr->program) {
			from = " from ";
			program = ptr->program->name;
		}
		done = tomoyo_io_printf(head,
					"%s" TOMOYO_KEYWORD_KEEP_DOMAIN
					"%s%s%s\n", no, program, from,
					ptr->domainname->name);
		if (!done)
			break;
	}
	return done;
}

/**
 * tomoyo_is_domain_keeper - Check whether the given program causes domain transition suppression.
 *
 * @domainname: The name of domain.
 * @program:    The name of program.
 * @last_name:  The last component of @domainname.
 *
 * Returns true if executing @program supresses domain transition,
 * false otherwise.
 *
 * Caller holds tomoyo_read_lock().
 */
static bool tomoyo_is_domain_keeper(const struct tomoyo_path_info *domainname,
				    const struct tomoyo_path_info *program,
				    const struct tomoyo_path_info *last_name)
{
	struct tomoyo_domain_keeper_entry *ptr;
	bool flag = false;

	list_for_each_entry_rcu(ptr, &tomoyo_domain_keeper_list, list) {
		if (ptr->is_deleted)
			continue;
		if (!ptr->is_last_name) {
			if (ptr->domainname != domainname)
				continue;
		} else {
			if (tomoyo_pathcmp(ptr->domainname, last_name))
				continue;
		}
		if (ptr->program && tomoyo_pathcmp(ptr->program, program))
			continue;
		if (ptr->is_not) {
			flag = false;
			break;
		}
		flag = true;
	}
	return flag;
}

/*
 * tomoyo_alias_list is used for holding list of symlink's pathnames which are
 * allowed to be passed to an execve() request. Normally, the domainname which
 * the current process will belong to after execve() succeeds is calculated
 * using dereferenced pathnames. But some programs behave differently depending
 * on the name passed to argv[0]. For busybox, calculating domainname using
 * dereferenced pathnames will cause all programs in the busybox to belong to
 * the same domain. Thus, TOMOYO provides a way to allow use of symlink's
 * pathname for checking execve()'s permission and calculating domainname which
 * the current process will belong to after execve() succeeds.
 *
 * An entry is added by
 *
 * # echo 'alias /bin/busybox /bin/cat' > \
 *                            /sys/kernel/security/tomoyo/exception_policy
 *
 * and is deleted by
 *
 * # echo 'delete alias /bin/busybox /bin/cat' > \
 *                            /sys/kernel/security/tomoyo/exception_policy
 *
 * and all entries are retrieved by
 *
 * # grep ^alias /sys/kernel/security/tomoyo/exception_policy
 *
 * In the example above, if /bin/cat is a symlink to /bin/busybox and execution
 * of /bin/cat is requested, permission is checked for /bin/cat rather than
 * /bin/busybox and domainname which the current process will belong to after
 * execve() succeeds is calculated using /bin/cat rather than /bin/busybox .
 */
static LIST_HEAD(tomoyo_alias_list);

/**
 * tomoyo_update_alias_entry - Update "struct tomoyo_alias_entry" list.
 *
 * @original_name: The original program's real name.
 * @aliased_name:  The symbolic program's symbolic link's name.
 * @is_delete:     True if it is a delete request.
 *
 * Returns 0 on success, negative value otherwise.
 *
 * Caller holds tomoyo_read_lock().
 */
static int tomoyo_update_alias_entry(const char *original_name,
				     const char *aliased_name,
				     const bool is_delete)
{
	struct tomoyo_alias_entry *entry = NULL;
	struct tomoyo_alias_entry *ptr;
	const struct tomoyo_path_info *saved_original_name;
	const struct tomoyo_path_info *saved_aliased_name;
	int error = is_delete ? -ENOENT : -ENOMEM;

	if (!tomoyo_is_correct_path(original_name, 1, -1, -1, __func__) ||
	    !tomoyo_is_correct_path(aliased_name, 1, -1, -1, __func__))
		return -EINVAL; /* No patterns allowed. */
	saved_original_name = tomoyo_save_name(original_name);
	saved_aliased_name = tomoyo_save_name(aliased_name);
	if (!saved_original_name || !saved_aliased_name)
		goto out;
	if (!is_delete)
		entry = kmalloc(sizeof(*entry), GFP_KERNEL);
	mutex_lock(&tomoyo_policy_lock);
	list_for_each_entry_rcu(ptr, &tomoyo_alias_list, list) {
		if (ptr->original_name != saved_original_name ||
		    ptr->aliased_name != saved_aliased_name)
			continue;
		ptr->is_deleted = is_delete;
		error = 0;
		break;
	}
	if (!is_delete && error && tomoyo_memory_ok(entry)) {
		entry->original_name = saved_original_name;
		entry->aliased_name = saved_aliased_name;
		list_add_tail_rcu(&entry->list, &tomoyo_alias_list);
		entry = NULL;
		error = 0;
	}
	mutex_unlock(&tomoyo_policy_lock);
 out:
	kfree(entry);
	return error;
}

/**
 * tomoyo_read_alias_policy - Read "struct tomoyo_alias_entry" list.
 *
 * @head: Pointer to "struct tomoyo_io_buffer".
 *
 * Returns true on success, false otherwise.
 *
 * Caller holds tomoyo_read_lock().
 */
bool tomoyo_read_alias_policy(struct tomoyo_io_buffer *head)
{
	struct list_head *pos;
	bool done = true;

	list_for_each_cookie(pos, head->read_var2, &tomoyo_alias_list) {
		struct tomoyo_alias_entry *ptr;

		ptr = list_entry(pos, struct tomoyo_alias_entry, list);
		if (ptr->is_deleted)
			continue;
		done = tomoyo_io_printf(head, TOMOYO_KEYWORD_ALIAS "%s %s\n",
					ptr->original_name->name,
					ptr->aliased_name->name);
		if (!done)
			break;
	}
	return done;
}

/**
 * tomoyo_write_alias_policy - Write "struct tomoyo_alias_entry" list.
 *
 * @data:      String to parse.
 * @is_delete: True if it is a delete request.
 *
 * Returns 0 on success, negative value otherwise.
 *
 * Caller holds tomoyo_read_lock().
 */
int tomoyo_write_alias_policy(char *data, const bool is_delete)
{
	char *cp = strchr(data, ' ');

	if (!cp)
		return -EINVAL;
	*cp++ = '\0';
	return tomoyo_update_alias_entry(data, cp, is_delete);
}

/**
 * tomoyo_find_or_assign_new_domain - Create a domain.
 *
 * @domainname: The name of domain.
 * @profile:    Profile number to assign if the domain was newly created.
 *
 * Returns pointer to "struct tomoyo_domain_info" on success, NULL otherwise.
 *
 * Caller holds tomoyo_read_lock().
 */
struct tomoyo_domain_info *tomoyo_find_or_assign_new_domain(const char *
							    domainname,
							    const u8 profile)
{
	struct tomoyo_domain_info *entry;
	struct tomoyo_domain_info *domain;
	const struct tomoyo_path_info *saved_domainname;
	bool found = false;

	if (!tomoyo_is_correct_domain(domainname, __func__))
		return NULL;
	saved_domainname = tomoyo_save_name(domainname);
	if (!saved_domainname)
		return NULL;
	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
	mutex_lock(&tomoyo_policy_lock);
	list_for_each_entry_rcu(domain, &tomoyo_domain_list, list) {
		if (domain->is_deleted ||
		    tomoyo_pathcmp(saved_domainname, domain->domainname))
			continue;
		found = true;
		break;
	}
	if (!found && tomoyo_memory_ok(entry)) {
		INIT_LIST_HEAD(&entry->acl_info_list);
		entry->domainname = saved_domainname;
		entry->profile = profile;
		list_add_tail_rcu(&entry->list, &tomoyo_domain_list);
		domain = entry;
		entry = NULL;
		found = true;
	}
	mutex_unlock(&tomoyo_policy_lock);
	kfree(entry);
	return found ? domain : NULL;
}

/**
 * tomoyo_find_next_domain - Find a domain.
 *
 * @bprm: Pointer to "struct linux_binprm".
 *
 * Returns 0 on success, negative value otherwise.
 *
 * Caller holds tomoyo_read_lock().
 */
int tomoyo_find_next_domain(struct linux_binprm *bprm)
{
	/*
	 * This function assumes that the size of buffer returned by
	 * tomoyo_realpath() = TOMOYO_MAX_PATHNAME_LEN.
	 */
	struct tomoyo_page_buffer *tmp = kzalloc(sizeof(*tmp), GFP_KERNEL);
	struct tomoyo_domain_info *old_domain = tomoyo_domain();
	struct tomoyo_domain_info *domain = NULL;
	const char *old_domain_name = old_domain->domainname->name;
	const char *original_name = bprm->filename;
	char *new_domain_name = NULL;
	char *real_program_name = NULL;
	char *symlink_program_name = NULL;
	const u8 mode = tomoyo_check_flags(old_domain, TOMOYO_MAC_FOR_FILE);
	const bool is_enforce = (mode == 3);
	int retval = -ENOMEM;
	struct tomoyo_path_info r; /* real name */
	struct tomoyo_path_info s; /* symlink name */
	struct tomoyo_path_info l; /* last name */
	static bool initialized;

	if (!tmp)
		goto out;

	if (!initialized) {
		/*
		 * Built-in initializers. This is needed because policies are
		 * not loaded until starting /sbin/init.
		 */
		tomoyo_update_domain_initializer_entry(NULL, "/sbin/hotplug",
						       false, false);
		tomoyo_update_domain_initializer_entry(NULL, "/sbin/modprobe",
						       false, false);
		initialized = true;
	}

	/* Get tomoyo_realpath of program. */
	retval = -ENOENT;
	/* I hope tomoyo_realpath() won't fail with -ENOMEM. */
	real_program_name = tomoyo_realpath(original_name);
	if (!real_program_name)
		goto out;
	/* Get tomoyo_realpath of symbolic link. */
	symlink_program_name = tomoyo_realpath_nofollow(original_name);
	if (!symlink_program_name)
		goto out;

	r.name = real_program_name;
	tomoyo_fill_path_info(&r);
	s.name = symlink_program_name;
	tomoyo_fill_path_info(&s);
	l.name = tomoyo_get_last_name(old_domain);
	tomoyo_fill_path_info(&l);

	/* Check 'alias' directive. */
	if (tomoyo_pathcmp(&r, &s)) {
		struct tomoyo_alias_entry *ptr;
		/* Is this program allowed to be called via symbolic links? */
		list_for_each_entry_rcu(ptr, &tomoyo_alias_list, list) {
			if (ptr->is_deleted ||
			    tomoyo_pathcmp(&r, ptr->original_name) ||
			    tomoyo_pathcmp(&s, ptr->aliased_name))
				continue;
			memset(real_program_name, 0, TOMOYO_MAX_PATHNAME_LEN);
			strncpy(real_program_name, ptr->aliased_name->name,
				TOMOYO_MAX_PATHNAME_LEN - 1);
			tomoyo_fill_path_info(&r);
			break;
		}
	}

	/* Check execute permission. */
	retval = tomoyo_check_exec_perm(old_domain, &r);
	if (retval < 0)
		goto out;

	new_domain_name = tmp->buffer;
	if (tomoyo_is_domain_initializer(old_domain->domainname, &r, &l)) {
		/* Transit to the child of tomoyo_kernel_domain domain. */
		snprintf(new_domain_name, TOMOYO_MAX_PATHNAME_LEN + 1,
			 TOMOYO_ROOT_NAME " " "%s", real_program_name);
	} else if (old_domain == &tomoyo_kernel_domain &&
		   !tomoyo_policy_loaded) {
		/*
		 * Needn't to transit from kernel domain before starting
		 * /sbin/init. But transit from kernel domain if executing
		 * initializers because they might start before /sbin/init.
		 */
		domain = old_domain;
	} else if (tomoyo_is_domain_keeper(old_domain->domainname, &r, &l)) {
		/* Keep current domain. */
		domain = old_domain;
	} else {
		/* Normal domain transition. */
		snprintf(new_domain_name, TOMOYO_MAX_PATHNAME_LEN + 1,
			 "%s %s", old_domain_name, real_program_name);
	}
	if (domain || strlen(new_domain_name) >= TOMOYO_MAX_PATHNAME_LEN)
		goto done;
	domain = tomoyo_find_domain(new_domain_name);
	if (domain)
		goto done;
	if (is_enforce)
		goto done;
	domain = tomoyo_find_or_assign_new_domain(new_domain_name,
						  old_domain->profile);
 done:
	if (domain)
		goto out;
	printk(KERN_WARNING "TOMOYO-ERROR: Domain '%s' not defined.\n",
	       new_domain_name);
	if (is_enforce)
		retval = -EPERM;
	else
		old_domain->transition_failed = true;
 out:
	if (!domain)
		domain = old_domain;
	bprm->cred->security = domain;
	kfree(real_program_name);
	kfree(symlink_program_name);
	kfree(tmp);
	return retval;
}