aboutsummaryrefslogtreecommitdiffstats
path: root/security/keys/process_keys.c
blob: 2eb0e471cd40817a4ae548188dd82be73cbaca71 (plain) (blame)
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
/* process_keys.c: management of a process's keyrings
 *
 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/keyctl.h>
#include <linux/fs.h>
#include <linux/err.h>
#include <asm/uaccess.h>
#include "internal.h"

/* session keyring create vs join semaphore */
static DECLARE_MUTEX(key_session_sem);

/* the root user's tracking struct */
struct key_user root_key_user = {
	.usage		= ATOMIC_INIT(3),
	.consq		= LIST_HEAD_INIT(root_key_user.consq),
	.lock		= SPIN_LOCK_UNLOCKED,
	.nkeys		= ATOMIC_INIT(2),
	.nikeys		= ATOMIC_INIT(2),
	.uid		= 0,
};

/* the root user's UID keyring */
struct key root_user_keyring = {
	.usage		= ATOMIC_INIT(1),
	.serial		= 2,
	.type		= &key_type_keyring,
	.user		= &root_key_user,
	.lock		= RW_LOCK_UNLOCKED,
	.sem		= __RWSEM_INITIALIZER(root_user_keyring.sem),
	.perm		= KEY_USR_ALL,
	.flags		= KEY_FLAG_INSTANTIATED,
	.description	= "_uid.0",
#ifdef KEY_DEBUGGING
	.magic		= KEY_DEBUG_MAGIC,
#endif
};

/* the root user's default session keyring */
struct key root_session_keyring = {
	.usage		= ATOMIC_INIT(1),
	.serial		= 1,
	.type		= &key_type_keyring,
	.user		= &root_key_user,
	.lock		= RW_LOCK_UNLOCKED,
	.sem		= __RWSEM_INITIALIZER(root_session_keyring.sem),
	.perm		= KEY_USR_ALL,
	.flags		= KEY_FLAG_INSTANTIATED,
	.description	= "_uid_ses.0",
#ifdef KEY_DEBUGGING
	.magic		= KEY_DEBUG_MAGIC,
#endif
};

/*****************************************************************************/
/*
 * allocate the keyrings to be associated with a UID
 */
int alloc_uid_keyring(struct user_struct *user)
{
	struct key *uid_keyring, *session_keyring;
	char buf[20];
	int ret;

	/* concoct a default session keyring */
	sprintf(buf, "_uid_ses.%u", user->uid);

	session_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, 0, NULL);
	if (IS_ERR(session_keyring)) {
		ret = PTR_ERR(session_keyring);
		goto error;
	}

	/* and a UID specific keyring, pointed to by the default session
	 * keyring */
	sprintf(buf, "_uid.%u", user->uid);

	uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, 0,
				    session_keyring);
	if (IS_ERR(uid_keyring)) {
		key_put(session_keyring);
		ret = PTR_ERR(uid_keyring);
		goto error;
	}

	/* install the keyrings */
	user->uid_keyring = uid_keyring;
	user->session_keyring = session_keyring;
	ret = 0;

 error:
	return ret;

} /* end alloc_uid_keyring() */

/*****************************************************************************/
/*
 * deal with the UID changing
 */
void switch_uid_keyring(struct user_struct *new_user)
{
#if 0 /* do nothing for now */
	struct key *old;

	/* switch to the new user's session keyring if we were running under
	 * root's default session keyring */
	if (new_user->uid != 0 &&
	    current->session_keyring == &root_session_keyring
	    ) {
		atomic_inc(&new_user->session_keyring->usage);

		task_lock(current);
		old = current->session_keyring;
		current->session_keyring = new_user->session_keyring;
		task_unlock(current);

		key_put(old);
	}
#endif

} /* end switch_uid_keyring() */

/*****************************************************************************/
/*
 * install a fresh thread keyring, discarding the old one
 */
int install_thread_keyring(struct task_struct *tsk)
{
	struct key *keyring, *old;
	char buf[20];
	int ret;

	sprintf(buf, "_tid.%u", tsk->pid);

	keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL);
	if (IS_ERR(keyring)) {
		ret = PTR_ERR(keyring);
		goto error;
	}

	task_lock(tsk);
	old = tsk->thread_keyring;
	tsk->thread_keyring = keyring;
	task_unlock(tsk);

	ret = 0;

	key_put(old);
 error:
	return ret;

} /* end install_thread_keyring() */

/*****************************************************************************/
/*
 * make sure a process keyring is installed
 */
static int install_process_keyring(struct task_struct *tsk)
{
	unsigned long flags;
	struct key *keyring;
	char buf[20];
	int ret;

	if (!tsk->signal->process_keyring) {
		sprintf(buf, "_pid.%u", tsk->tgid);

		keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL);
		if (IS_ERR(keyring)) {
			ret = PTR_ERR(keyring);
			goto error;
		}

		/* attach or swap keyrings */
		spin_lock_irqsave(&tsk->sighand->siglock, flags);
		if (!tsk->signal->process_keyring) {
			tsk->signal->process_keyring = keyring;
			keyring = NULL;
		}
		spin_unlock_irqrestore(&tsk->sighand->siglock, flags);

		key_put(keyring);
	}

	ret = 0;
 error:
	return ret;

} /* end install_process_keyring() */

/*****************************************************************************/
/*
 * install a session keyring, discarding the old one
 * - if a keyring is not supplied, an empty one is invented
 */
static int install_session_keyring(struct task_struct *tsk,
				   struct key *keyring)
{
	unsigned long flags;
	struct key *old;
	char buf[20];
	int ret;

	/* create an empty session keyring */
	if (!keyring) {
		sprintf(buf, "_ses.%u", tsk->tgid);

		keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL);
		if (IS_ERR(keyring)) {
			ret = PTR_ERR(keyring);
			goto error;
		}
	}
	else {
		atomic_inc(&keyring->usage);
	}

	/* install the keyring */
	spin_lock_irqsave(&tsk->sighand->siglock, flags);
	old = tsk->signal->session_keyring;
	tsk->signal->session_keyring = keyring;
	spin_unlock_irqrestore(&tsk->sighand->siglock, flags);

	ret = 0;

	key_put(old);
 error:
	return ret;

} /* end install_session_keyring() */

/*****************************************************************************/
/*
 * copy the keys in a thread group for fork without CLONE_THREAD
 */
int copy_thread_group_keys(struct task_struct *tsk)
{
	unsigned long flags;

	key_check(current->thread_group->session_keyring);
	key_check(current->thread_group->process_keyring);

	/* no process keyring yet */
	tsk->signal->process_keyring = NULL;

	/* same session keyring */
	spin_lock_irqsave(&current->sighand->siglock, flags);
	tsk->signal->session_keyring =
		key_get(current->signal->session_keyring);
	spin_unlock_irqrestore(&current->sighand->siglock, flags);

	return 0;

} /* end copy_thread_group_keys() */

/*****************************************************************************/
/*
 * copy the keys for fork
 */
int copy_keys(unsigned long clone_flags, struct task_struct *tsk)
{
	key_check(tsk->thread_keyring);

	/* no thread keyring yet */
	tsk->thread_keyring = NULL;
	return 0;

} /* end copy_keys() */

/*****************************************************************************/
/*
 * dispose of thread group keys upon thread group destruction
 */
void exit_thread_group_keys(struct signal_struct *tg)
{
	key_put(tg->session_keyring);
	key_put(tg->process_keyring);

} /* end exit_thread_group_keys() */

/*****************************************************************************/
/*
 * dispose of keys upon thread exit
 */
void exit_keys(struct task_struct *tsk)
{
	key_put(tsk->thread_keyring);

} /* end exit_keys() */

/*****************************************************************************/
/*
 * deal with execve()
 */
int exec_keys(struct task_struct *tsk)
{
	unsigned long flags;
	struct key *old;

	/* newly exec'd tasks don't get a thread keyring */
	task_lock(tsk);
	old = tsk->thread_keyring;
	tsk->thread_keyring = NULL;
	task_unlock(tsk);

	key_put(old);

	/* discard the process keyring from a newly exec'd task */
	spin_lock_irqsave(&tsk->sighand->siglock, flags);
	old = tsk->signal->process_keyring;
	tsk->signal->process_keyring = NULL;
	spin_unlock_irqrestore(&tsk->sighand->siglock, flags);

	key_put(old);

	return 0;

} /* end exec_keys() */

/*****************************************************************************/
/*
 * deal with SUID programs
 * - we might want to make this invent a new session keyring
 */
int suid_keys(struct task_struct *tsk)
{
	return 0;

} /* end suid_keys() */

/*****************************************************************************/
/*
 * the filesystem user ID changed
 */
void key_fsuid_changed(struct task_struct *tsk)
{
	/* update the ownership of the thread keyring */
	if (tsk->thread_keyring) {
		down_write(&tsk->thread_keyring->sem);
		write_lock(&tsk->thread_keyring->lock);
		tsk->thread_keyring->uid = tsk->fsuid;
		write_unlock(&tsk->thread_keyring->lock);
		up_write(&tsk->thread_keyring->sem);
	}

} /* end key_fsuid_changed() */

/*****************************************************************************/
/*
 * the filesystem group ID changed
 */
void key_fsgid_changed(struct task_struct *tsk)
{
	/* update the ownership of the thread keyring */
	if (tsk->thread_keyring) {
		down_write(&tsk->thread_keyring->sem);
		write_lock(&tsk->thread_keyring->lock);
		tsk->thread_keyring->gid = tsk->fsgid;
		write_unlock(&tsk->thread_keyring->lock);
		up_write(&tsk->thread_keyring->sem);
	}

} /* end key_fsgid_changed() */

/*****************************************************************************/
/*
 * search the process keyrings for the first matching key
 * - we use the supplied match function to see if the description (or other
 *   feature of interest) matches
 * - we return -EAGAIN if we didn't find any matching key
 * - we return -ENOKEY if we found only negative matching keys
 */
struct key *search_process_keyrings_aux(struct key_type *type,
					const void *description,
					key_match_func_t match)
{
	struct task_struct *tsk = current;
	unsigned long flags;
	struct key *key, *ret, *err, *tmp;

	/* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
	 * searchable, but we failed to find a key or we found a negative key;
	 * otherwise we want to return a sample error (probably -EACCES) if
	 * none of the keyrings were searchable
	 *
	 * in terms of priority: success > -ENOKEY > -EAGAIN > other error
	 */
	key = NULL;
	ret = NULL;
	err = ERR_PTR(-EAGAIN);

	/* search the thread keyring first */
	if (tsk->thread_keyring) {
		key = keyring_search_aux(tsk->thread_keyring, type,
					 description, match);
		if (!IS_ERR(key))
			goto found;

		switch (PTR_ERR(key)) {
		case -EAGAIN: /* no key */
			if (ret)
				break;
		case -ENOKEY: /* negative key */
			ret = key;
			break;
		default:
			err = key;
			break;
		}
	}

	/* search the process keyring second */
	if (tsk->signal->process_keyring) {
		key = keyring_search_aux(tsk->signal->process_keyring,
					 type, description, match);
		if (!IS_ERR(key))
			goto found;

		switch (PTR_ERR(key)) {
		case -EAGAIN: /* no key */
			if (ret)
				break;
		case -ENOKEY: /* negative key */
			ret = key;
			break;
		default:
			err = key;
			break;
		}
	}

	/* search the session keyring last */
	spin_lock_irqsave(&tsk->sighand->siglock, flags);

	tmp = tsk->signal->session_keyring;
	if (!tmp)
		tmp = tsk->user->session_keyring;
	atomic_inc(&tmp->usage);

	spin_unlock_irqrestore(&tsk->sighand->siglock, flags);

	key = keyring_search_aux(tmp, type, description, match);
	key_put(tmp);
	if (!IS_ERR(key))
		goto found;

	switch (PTR_ERR(key)) {
	case -EAGAIN: /* no key */
		if (ret)
			break;
	case -ENOKEY: /* negative key */
		ret = key;
		break;
	default:
		err = key;
		break;
	}

	/* no key - decide on the error we're going to go for */
	key = ret ? ret : err;

 found:
	return key;

} /* end search_process_keyrings_aux() */

/*****************************************************************************/
/*
 * search the process keyrings for the first matching key
 * - we return -EAGAIN if we didn't find any matching key
 * - we return -ENOKEY if we found only negative matching keys
 */
struct key *search_process_keyrings(struct key_type *type,
				    const char *description)
{
	return search_process_keyrings_aux(type, description, type->match);

} /* end search_process_keyrings() */

/*****************************************************************************/
/*
 * lookup a key given a key ID from userspace with a given permissions mask
 * - don't create special keyrings unless so requested
 * - partially constructed keys aren't found unless requested
 */
struct key *lookup_user_key(key_serial_t id, int create, int partial,
			    key_perm_t perm)
{
	struct task_struct *tsk = current;
	unsigned long flags;
	struct key *key;
	int ret;

	key = ERR_PTR(-ENOKEY);

	switch (id) {
	case KEY_SPEC_THREAD_KEYRING:
		if (!tsk->thread_keyring) {
			if (!create)
				goto error;

			ret = install_thread_keyring(tsk);
			if (ret < 0) {
				key = ERR_PTR(ret);
				goto error;
			}
		}

		key = tsk->thread_keyring;
		atomic_inc(&key->usage);
		break;

	case KEY_SPEC_PROCESS_KEYRING:
		if (!tsk->signal->process_keyring) {
			if (!create)
				goto error;

			ret = install_process_keyring(tsk);
			if (ret < 0) {
				key = ERR_PTR(ret);
				goto error;
			}
		}

		key = tsk->signal->process_keyring;
		atomic_inc(&key->usage);
		break;

	case KEY_SPEC_SESSION_KEYRING:
		if (!tsk->signal->session_keyring) {
			/* always install a session keyring upon access if one
			 * doesn't exist yet */
			ret = install_session_keyring(
			       tsk, tsk->user->session_keyring);
			if (ret < 0)
				goto error;
		}

		spin_lock_irqsave(&tsk->sighand->siglock, flags);
		key = tsk->signal->session_keyring;
		atomic_inc(&key->usage);
		spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
		break;

	case KEY_SPEC_USER_KEYRING:
		key = tsk->user->uid_keyring;
		atomic_inc(&key->usage);
		break;

	case KEY_SPEC_USER_SESSION_KEYRING:
		key = tsk->user->session_keyring;
		atomic_inc(&key->usage);
		break;

	case KEY_SPEC_GROUP_KEYRING:
		/* group keyrings are not yet supported */
		key = ERR_PTR(-EINVAL);
		goto error;

	default:
		key = ERR_PTR(-EINVAL);
		if (id < 1)
			goto error;

		key = key_lookup(id);
		if (IS_ERR(key))
			goto error;
		break;
	}

	/* check the status and permissions */
	if (perm) {
		ret = key_validate(key);
		if (ret < 0)
			goto invalid_key;
	}

	ret = -EIO;
	if (!partial && !(key->flags & KEY_FLAG_INSTANTIATED))
		goto invalid_key;

	ret = -EACCES;
	if (!key_permission(key, perm))
		goto invalid_key;

 error:
	return key;

 invalid_key:
	key_put(key);
	key = ERR_PTR(ret);
	goto error;

} /* end lookup_user_key() */

/*****************************************************************************/
/*
 * join the named keyring as the session keyring if possible, or attempt to
 * create a new one of that name if not
 * - if the name is NULL, an empty anonymous keyring is installed instead
 * - named session keyring joining is done with a semaphore held
 */
long join_session_keyring(const char *name)
{
	struct task_struct *tsk = current;
	unsigned long flags;
	struct key *keyring;
	long ret;

	/* if no name is provided, install an anonymous keyring */
	if (!name) {
		ret = install_session_keyring(tsk, NULL);
		if (ret < 0)
			goto error;

		spin_lock_irqsave(&tsk->sighand->siglock, flags);
		ret = tsk->signal->session_keyring->serial;
		spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
		goto error;
	}

	/* allow the user to join or create a named keyring */
	down(&key_session_sem);

	/* look for an existing keyring of this name */
	keyring = find_keyring_by_name(name, 0);
	if (PTR_ERR(keyring) == -ENOKEY) {
		/* not found - try and create a new one */
		keyring = keyring_alloc(name, tsk->uid, tsk->gid, 0, NULL);
		if (IS_ERR(keyring)) {
			ret = PTR_ERR(keyring);
			goto error;
		}
	}
	else if (IS_ERR(keyring)) {
		ret = PTR_ERR(keyring);
		goto error2;
	}

	/* we've got a keyring - now to install it */
	ret = install_session_keyring(tsk, keyring);
	if (ret < 0)
		goto error2;

	ret = keyring->serial;
	key_put(keyring);

 error2:
	up(&key_session_sem);
 error:
	return ret;

} /* end join_session_keyring() */