aboutsummaryrefslogtreecommitdiffstats
path: root/security/keys/request_key.c
blob: 0088dd8bf68a77b29637527733ff0b8985b8ecb7 (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
/* Request a key from userspace
 *
 * Copyright (C) 2004-2007 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.
 *
 * See Documentation/keys-request-key.txt
 */

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kmod.h>
#include <linux/err.h>
#include <linux/keyctl.h>
#include <linux/slab.h>
#include "internal.h"

#define key_negative_timeout	60	/* default timeout on a negative key's existence */

/*
 * wait_on_bit() sleep function for uninterruptible waiting
 */
static int key_wait_bit(void *flags)
{
	schedule();
	return 0;
}

/*
 * wait_on_bit() sleep function for interruptible waiting
 */
static int key_wait_bit_intr(void *flags)
{
	schedule();
	return signal_pending(current) ? -ERESTARTSYS : 0;
}

/*
 * call to complete the construction of a key
 */
void complete_request_key(struct key_construction *cons, int error)
{
	kenter("{%d,%d},%d", cons->key->serial, cons->authkey->serial, error);

	if (error < 0)
		key_negate_and_link(cons->key, key_negative_timeout, NULL,
				    cons->authkey);
	else
		key_revoke(cons->authkey);

	key_put(cons->key);
	key_put(cons->authkey);
	kfree(cons);
}
EXPORT_SYMBOL(complete_request_key);

static int umh_keys_init(struct subprocess_info *info)
{
	struct cred *cred = (struct cred*)current_cred();
	struct key *keyring = info->data;
	/*
	 * This is called in context of freshly forked kthread before
	 * kernel_execve(), we can just change our ->session_keyring.
	 */
	return install_session_keyring_to_cred(cred, keyring);
}

static void umh_keys_cleanup(struct subprocess_info *info)
{
	struct key *keyring = info->data;
	key_put(keyring);
}

static int call_usermodehelper_keys(char *path, char **argv, char **envp,
			 struct key *session_keyring, enum umh_wait wait)
{
	gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
	struct subprocess_info *info =
		call_usermodehelper_setup(path, argv, envp, gfp_mask);

	if (!info)
		return -ENOMEM;

	call_usermodehelper_setfns(info, umh_keys_init, umh_keys_cleanup,
					key_get(session_keyring));
	return call_usermodehelper_exec(info, wait);
}

/*
 * request userspace finish the construction of a key
 * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
 */
static int call_sbin_request_key(struct key_construction *cons,
				 const char *op,
				 void *aux)
{
	const struct cred *cred = current_cred();
	key_serial_t prkey, sskey;
	struct key *key = cons->key, *authkey = cons->authkey, *keyring,
		*session;
	char *argv[9], *envp[3], uid_str[12], gid_str[12];
	char key_str[12], keyring_str[3][12];
	char desc[20];
	int ret, i;

	kenter("{%d},{%d},%s", key->serial, authkey->serial, op);

	ret = install_user_keyrings();
	if (ret < 0)
		goto error_alloc;

	/* allocate a new session keyring */
	sprintf(desc, "_req.%u", key->serial);

	cred = get_current_cred();
	keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred,
				KEY_ALLOC_QUOTA_OVERRUN, NULL);
	put_cred(cred);
	if (IS_ERR(keyring)) {
		ret = PTR_ERR(keyring);
		goto error_alloc;
	}

	/* attach the auth key to the session keyring */
	ret = key_link(keyring, authkey);
	if (ret < 0)
		goto error_link;

	/* record the UID and GID */
	sprintf(uid_str, "%d", cred->fsuid);
	sprintf(gid_str, "%d", cred->fsgid);

	/* we say which key is under construction */
	sprintf(key_str, "%d", key->serial);

	/* we specify the process's default keyrings */
	sprintf(keyring_str[0], "%d",
		cred->thread_keyring ? cred->thread_keyring->serial : 0);

	prkey = 0;
	if (cred->tgcred->process_keyring)
		prkey = cred->tgcred->process_keyring->serial;
	sprintf(keyring_str[1], "%d", prkey);

	rcu_read_lock();
	session = rcu_dereference(cred->tgcred->session_keyring);
	if (!session)
		session = cred->user->session_keyring;
	sskey = session->serial;
	rcu_read_unlock();

	sprintf(keyring_str[2], "%d", sskey);

	/* set up a minimal environment */
	i = 0;
	envp[i++] = "HOME=/";
	envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
	envp[i] = NULL;

	/* set up the argument list */
	i = 0;
	argv[i++] = "/sbin/request-key";
	argv[i++] = (char *) op;
	argv[i++] = key_str;
	argv[i++] = uid_str;
	argv[i++] = gid_str;
	argv[i++] = keyring_str[0];
	argv[i++] = keyring_str[1];
	argv[i++] = keyring_str[2];
	argv[i] = NULL;

	/* do it */
	ret = call_usermodehelper_keys(argv[0], argv, envp, keyring,
				       UMH_WAIT_PROC);
	kdebug("usermode -> 0x%x", ret);
	if (ret >= 0) {
		/* ret is the exit/wait code */
		if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
		    key_validate(key) < 0)
			ret = -ENOKEY;
		else
			/* ignore any errors from userspace if the key was
			 * instantiated */
			ret = 0;
	}

error_link:
	key_put(keyring);

error_alloc:
	complete_request_key(cons, ret);
	kleave(" = %d", ret);
	return ret;
}

/*
 * call out to userspace for key construction
 * - we ignore program failure and go on key status instead
 */
static int construct_key(struct key *key, const void *callout_info,
			 size_t callout_len, void *aux,
			 struct key *dest_keyring)
{
	struct key_construction *cons;
	request_key_actor_t actor;
	struct key *authkey;
	int ret;

	kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);

	cons = kmalloc(sizeof(*cons), GFP_KERNEL);
	if (!cons)
		return -ENOMEM;

	/* allocate an authorisation key */
	authkey = request_key_auth_new(key, callout_info, callout_len,
				       dest_keyring);
	if (IS_ERR(authkey)) {
		kfree(cons);
		ret = PTR_ERR(authkey);
		authkey = NULL;
	} else {
		cons->authkey = key_get(authkey);
		cons->key = key_get(key);

		/* make the call */
		actor = call_sbin_request_key;
		if (key->type->request_key)
			actor = key->type->request_key;

		ret = actor(cons, "create", aux);

		/* check that the actor called complete_request_key() prior to
		 * returning an error */
		WARN_ON(ret < 0 &&
			!test_bit(KEY_FLAG_REVOKED, &authkey->flags));
		key_put(authkey);
	}

	kleave(" = %d", ret);
	return ret;
}

/*
 * get the appropriate destination keyring for the request
 * - we return whatever keyring we select with an extra reference upon it which
 *   the caller must release
 */
static void construct_get_dest_keyring(struct key **_dest_keyring)
{
	struct request_key_auth *rka;
	const struct cred *cred = current_cred();
	struct key *dest_keyring = *_dest_keyring, *authkey;

	kenter("%p", dest_keyring);

	/* find the appropriate keyring */
	if (dest_keyring) {
		/* the caller supplied one */
		key_get(dest_keyring);
	} else {
		/* use a default keyring; falling through the cases until we
		 * find one that we actually have */
		switch (cred->jit_keyring) {
		case KEY_REQKEY_DEFL_DEFAULT:
		case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
			if (cred->request_key_auth) {
				authkey = cred->request_key_auth;
				down_read(&authkey->sem);
				rka = authkey->payload.data;
				if (!test_bit(KEY_FLAG_REVOKED,
					      &authkey->flags))
					dest_keyring =
						key_get(rka->dest_keyring);
				up_read(&authkey->sem);
				if (dest_keyring)
					break;
			}

		case KEY_REQKEY_DEFL_THREAD_KEYRING:
			dest_keyring = key_get(cred->thread_keyring);
			if (dest_keyring)
				break;

		case KEY_REQKEY_DEFL_PROCESS_KEYRING:
			dest_keyring = key_get(cred->tgcred->process_keyring);
			if (dest_keyring)
				break;

		case KEY_REQKEY_DEFL_SESSION_KEYRING:
			rcu_read_lock();
			dest_keyring = key_get(
				rcu_dereference(cred->tgcred->session_keyring));
			rcu_read_unlock();

			if (dest_keyring)
				break;

		case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
			dest_keyring =
				key_get(cred->user->session_keyring);
			break;

		case KEY_REQKEY_DEFL_USER_KEYRING:
			dest_keyring = key_get(cred->user->uid_keyring);
			break;

		case KEY_REQKEY_DEFL_GROUP_KEYRING:
		default:
			BUG();
		}
	}

	*_dest_keyring = dest_keyring;
	kleave(" [dk %d]", key_serial(dest_keyring));
	return;
}

/*
 * allocate a new key in under-construction state and attempt to link it in to
 * the requested place
 * - may return a key that's already under construction instead
 */
static int construct_alloc_key(struct key_type *type,
			       const char *description,
			       struct key *dest_keyring,
			       unsigned long flags,
			       struct key_user *user,
			       struct key **_key)
{
	struct keyring_list *prealloc;
	const struct cred *cred = current_cred();
	struct key *key;
	key_ref_t key_ref;
	int ret;

	kenter("%s,%s,,,", type->name, description);

	*_key = NULL;
	mutex_lock(&user->cons_lock);

	key = key_alloc(type, description, cred->fsuid, cred->fsgid, cred,
			KEY_POS_ALL, flags);
	if (IS_ERR(key))
		goto alloc_failed;

	set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);

	if (dest_keyring) {
		ret = __key_link_begin(dest_keyring, type, description,
				       &prealloc);
		if (ret < 0)
			goto link_prealloc_failed;
	}

	/* attach the key to the destination keyring under lock, but we do need
	 * to do another check just in case someone beat us to it whilst we
	 * waited for locks */
	mutex_lock(&key_construction_mutex);

	key_ref = search_process_keyrings(type, description, type->match, cred);
	if (!IS_ERR(key_ref))
		goto key_already_present;

	if (dest_keyring)
		__key_link(dest_keyring, key, &prealloc);

	mutex_unlock(&key_construction_mutex);
	if (dest_keyring)
		__key_link_end(dest_keyring, type, prealloc);
	mutex_unlock(&user->cons_lock);
	*_key = key;
	kleave(" = 0 [%d]", key_serial(key));
	return 0;

	/* the key is now present - we tell the caller that we found it by
	 * returning -EINPROGRESS  */
key_already_present:
	key_put(key);
	mutex_unlock(&key_construction_mutex);
	key = key_ref_to_ptr(key_ref);
	if (dest_keyring) {
		ret = __key_link_check_live_key(dest_keyring, key);
		if (ret == 0)
			__key_link(dest_keyring, key, &prealloc);
		__key_link_end(dest_keyring, type, prealloc);
		if (ret < 0)
			goto link_check_failed;
	}
	mutex_unlock(&user->cons_lock);
	*_key = key;
	kleave(" = -EINPROGRESS [%d]", key_serial(key));
	return -EINPROGRESS;

link_check_failed:
	mutex_unlock(&user->cons_lock);
	key_put(key);
	kleave(" = %d [linkcheck]", ret);
	return ret;

link_prealloc_failed:
	up_write(&dest_keyring->sem);
	mutex_unlock(&user->cons_lock);
	kleave(" = %d [prelink]", ret);
	return ret;

alloc_failed:
	mutex_unlock(&user->cons_lock);
	kleave(" = %ld", PTR_ERR(key));
	return PTR_ERR(key);
}

/*
 * commence key construction
 */
static struct key *construct_key_and_link(struct key_type *type,
					  const char *description,
					  const char *callout_info,
					  size_t callout_len,
					  void *aux,
					  struct key *dest_keyring,
					  unsigned long flags)
{
	struct key_user *user;
	struct key *key;
	int ret;

	kenter("");

	user = key_user_lookup(current_fsuid(), current_user_ns());
	if (!user)
		return ERR_PTR(-ENOMEM);

	construct_get_dest_keyring(&dest_keyring);

	ret = construct_alloc_key(type, description, dest_keyring, flags, user,
				  &key);
	key_user_put(user);

	if (ret == 0) {
		ret = construct_key(key, callout_info, callout_len, aux,
				    dest_keyring);
		if (ret < 0) {
			kdebug("cons failed");
			goto construction_failed;
		}
	} else if (ret == -EINPROGRESS) {
		ret = 0;
	} else {
		key = ERR_PTR(ret);
	}

	key_put(dest_keyring);
	kleave(" = key %d", key_serial(key));
	return key;

construction_failed:
	key_negate_and_link(key, key_negative_timeout, NULL, NULL);
	key_put(key);
	key_put(dest_keyring);
	kleave(" = %d", ret);
	return ERR_PTR(ret);
}

/*
 * request a key
 * - search the process's keyrings
 * - check the list of keys being created or updated
 * - call out to userspace for a key if supplementary info was provided
 * - cache the key in an appropriate keyring
 */
struct key *request_key_and_link(struct key_type *type,
				 const char *description,
				 const void *callout_info,
				 size_t callout_len,
				 void *aux,
				 struct key *dest_keyring,
				 unsigned long flags)
{
	const struct cred *cred = current_cred();
	struct key *key;
	key_ref_t key_ref;
	int ret;

	kenter("%s,%s,%p,%zu,%p,%p,%lx",
	       type->name, description, callout_info, callout_len, aux,
	       dest_keyring, flags);

	/* search all the process keyrings for a key */
	key_ref = search_process_keyrings(type, description, type->match,
					  cred);

	if (!IS_ERR(key_ref)) {
		key = key_ref_to_ptr(key_ref);
		if (dest_keyring) {
			construct_get_dest_keyring(&dest_keyring);
			ret = key_link(dest_keyring, key);
			key_put(dest_keyring);
			if (ret < 0) {
				key_put(key);
				key = ERR_PTR(ret);
				goto error;
			}
		}
	} else if (PTR_ERR(key_ref) != -EAGAIN) {
		key = ERR_CAST(key_ref);
	} else  {
		/* the search failed, but the keyrings were searchable, so we
		 * should consult userspace if we can */
		key = ERR_PTR(-ENOKEY);
		if (!callout_info)
			goto error;

		key = construct_key_and_link(type, description, callout_info,
					     callout_len, aux, dest_keyring,
					     flags);
	}

error:
	kleave(" = %p", key);
	return key;
}

/*
 * wait for construction of a key to complete
 */
int wait_for_key_construction(struct key *key, bool intr)
{
	int ret;

	ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
			  intr ? key_wait_bit_intr : key_wait_bit,
			  intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
	if (ret < 0)
		return ret;
	if (test_bit(KEY_FLAG_NEGATIVE, &key->flags))
		return -ENOKEY;
	return key_validate(key);
}
EXPORT_SYMBOL(wait_for_key_construction);

/*
 * request a key
 * - search the process's keyrings
 * - check the list of keys being created or updated
 * - call out to userspace for a key if supplementary info was provided
 * - waits uninterruptible for creation to complete
 */
struct key *request_key(struct key_type *type,
			const char *description,
			const char *callout_info)
{
	struct key *key;
	size_t callout_len = 0;
	int ret;

	if (callout_info)
		callout_len = strlen(callout_info);
	key = request_key_and_link(type, description, callout_info, callout_len,
				   NULL, NULL, KEY_ALLOC_IN_QUOTA);
	if (!IS_ERR(key)) {
		ret = wait_for_key_construction(key, false);
		if (ret < 0) {
			key_put(key);
			return ERR_PTR(ret);
		}
	}
	return key;
}
EXPORT_SYMBOL(request_key);

/*
 * request a key with auxiliary data for the upcaller
 * - search the process's keyrings
 * - check the list of keys being created or updated
 * - call out to userspace for a key if supplementary info was provided
 * - waits uninterruptible for creation to complete
 */
struct key *request_key_with_auxdata(struct key_type *type,
				     const char *description,
				     const void *callout_info,
				     size_t callout_len,
				     void *aux)
{
	struct key *key;
	int ret;

	key = request_key_and_link(type, description, callout_info, callout_len,
				   aux, NULL, KEY_ALLOC_IN_QUOTA);
	if (!IS_ERR(key)) {
		ret = wait_for_key_construction(key, false);
		if (ret < 0) {
			key_put(key);
			return ERR_PTR(ret);
		}
	}
	return key;
}
EXPORT_SYMBOL(request_key_with_auxdata);

/*
 * request a key (allow async construction)
 * - search the process's keyrings
 * - check the list of keys being created or updated
 * - call out to userspace for a key if supplementary info was provided
 */
struct key *request_key_async(struct key_type *type,
			      const char *description,
			      const void *callout_info,
			      size_t callout_len)
{
	return request_key_and_link(type, description, callout_info,
				    callout_len, NULL, NULL,
				    KEY_ALLOC_IN_QUOTA);
}
EXPORT_SYMBOL(request_key_async);

/*
 * request a key with auxiliary data for the upcaller (allow async construction)
 * - search the process's keyrings
 * - check the list of keys being created or updated
 * - call out to userspace for a key if supplementary info was provided
 */
struct key *request_key_async_with_auxdata(struct key_type *type,
					   const char *description,
					   const void *callout_info,
					   size_t callout_len,
					   void *aux)
{
	return request_key_and_link(type, description, callout_info,
				    callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
}
EXPORT_SYMBOL(request_key_async_with_auxdata);