aboutsummaryrefslogtreecommitdiffstats
path: root/security/keys/request_key.c
blob: 90c1506d007cc219c17ebd9c571d94b9c6a58ed9 (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
/* request_key.c: request a key from userspace
 *
 * Copyright (C) 2004-5 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/sched.h>
#include <linux/kmod.h>
#include <linux/err.h>
#include <linux/keyctl.h>
#include "internal.h"

struct key_construction {
	struct list_head	link;	/* link in construction queue */
	struct key		*key;	/* key being constructed */
};

/* when waiting for someone else's keys, you get added to this */
DECLARE_WAIT_QUEUE_HEAD(request_key_conswq);

/*****************************************************************************/
/*
 * request userspace finish the construction of a key
 * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring> <info>"
 */
static int call_request_key(struct key *key,
			    const char *op,
			    const char *callout_info)
{
	struct task_struct *tsk = current;
	key_serial_t prkey, sskey;
	struct key *session_keyring, *rkakey;
	char *argv[10], *envp[3], uid_str[12], gid_str[12];
	char key_str[12], keyring_str[3][12];
	int ret, i;

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

	/* generate a new session keyring with an auth key in it */
	session_keyring = request_key_auth_new(key, &rkakey);
	if (IS_ERR(session_keyring)) {
		ret = PTR_ERR(session_keyring);
		goto error;
	}

	/* record the UID and GID */
	sprintf(uid_str, "%d", current->fsuid);
	sprintf(gid_str, "%d", current->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",
		tsk->thread_keyring ? tsk->thread_keyring->serial : 0);

	prkey = 0;
	if (tsk->signal->process_keyring)
		prkey = tsk->signal->process_keyring->serial;

	sprintf(keyring_str[1], "%d", prkey);

	if (tsk->signal->session_keyring) {
		rcu_read_lock();
		sskey = rcu_dereference(tsk->signal->session_keyring)->serial;
		rcu_read_unlock();
	}
	else {
		sskey = tsk->user->session_keyring->serial;
	}

	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++] = (char *) callout_info;
	argv[i] = NULL;

	/* do it */
	ret = call_usermodehelper_keys(argv[0], argv, envp, session_keyring, 1);

	/* dispose of the special keys */
	key_revoke(rkakey);
	key_put(rkakey);
	key_put(session_keyring);

 error:
	kleave(" = %d", ret);
	return ret;

} /* end call_request_key() */

/*****************************************************************************/
/*
 * call out to userspace for the key
 * - called with the construction sem held, but the sem is dropped here
 * - we ignore program failure and go on key status instead
 */
static struct key *__request_key_construction(struct key_type *type,
					      const char *description,
					      const char *callout_info)
{
	struct key_construction cons;
	struct timespec now;
	struct key *key;
	int ret, negated;

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

	/* create a key and add it to the queue */
	key = key_alloc(type, description,
			current->fsuid, current->fsgid, KEY_USR_ALL, 0);
	if (IS_ERR(key))
		goto alloc_failed;

	set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);

	cons.key = key;
	list_add_tail(&cons.link, &key->user->consq);

	/* we drop the construction sem here on behalf of the caller */
	up_write(&key_construction_sem);

	/* make the call */
	ret = call_request_key(key, "create", callout_info);
	if (ret < 0)
		goto request_failed;

	/* if the key wasn't instantiated, then we want to give an error */
	ret = -ENOKEY;
	if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
		goto request_failed;

	down_write(&key_construction_sem);
	list_del(&cons.link);
	up_write(&key_construction_sem);

	/* also give an error if the key was negatively instantiated */
 check_not_negative:
	if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
		key_put(key);
		key = ERR_PTR(-ENOKEY);
	}

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

 request_failed:
	/* it wasn't instantiated
	 * - remove from construction queue
	 * - mark the key as dead
	 */
	negated = 0;
	down_write(&key_construction_sem);

	list_del(&cons.link);

	/* check it didn't get instantiated between the check and the down */
	if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
		set_bit(KEY_FLAG_NEGATIVE, &key->flags);
		set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
		negated = 1;
	}

	clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);

	up_write(&key_construction_sem);

	if (!negated)
		goto check_not_negative; /* surprisingly, the key got
					  * instantiated */

	/* set the timeout and store in the session keyring if we can */
	now = current_kernel_time();
	key->expiry = now.tv_sec + key_negative_timeout;

	if (current->signal->session_keyring) {
		struct key *keyring;

		rcu_read_lock();
		keyring = rcu_dereference(current->signal->session_keyring);
		atomic_inc(&keyring->usage);
		rcu_read_unlock();

		key_link(keyring, key);
		key_put(keyring);
	}

	key_put(key);

	/* notify anyone who was waiting */
	wake_up_all(&request_key_conswq);

	key = ERR_PTR(ret);
	goto out;

 alloc_failed:
	up_write(&key_construction_sem);
	goto out;

} /* end __request_key_construction() */

/*****************************************************************************/
/*
 * call out to userspace to request the key
 * - we check the construction queue first to see if an appropriate key is
 *   already being constructed by userspace
 */
static struct key *request_key_construction(struct key_type *type,
					    const char *description,
					    struct key_user *user,
					    const char *callout_info)
{
	struct key_construction *pcons;
	struct key *key, *ckey;

	DECLARE_WAITQUEUE(myself, current);

	kenter("%s,%s,{%d},%s",
	       type->name, description, user->uid, callout_info);

	/* see if there's such a key under construction already */
	down_write(&key_construction_sem);

	list_for_each_entry(pcons, &user->consq, link) {
		ckey = pcons->key;

		if (ckey->type != type)
			continue;

		if (type->match(ckey, description))
			goto found_key_under_construction;
	}

	/* see about getting userspace to construct the key */
	key = __request_key_construction(type, description, callout_info);
 error:
	kleave(" = %p", key);
	return key;

	/* someone else has the same key under construction
	 * - we want to keep an eye on their key
	 */
 found_key_under_construction:
	atomic_inc(&ckey->usage);
	up_write(&key_construction_sem);

	/* wait for the key to be completed one way or another */
	add_wait_queue(&request_key_conswq, &myself);

	for (;;) {
		set_current_state(TASK_INTERRUPTIBLE);
		if (!test_bit(KEY_FLAG_USER_CONSTRUCT, &ckey->flags))
			break;
		if (signal_pending(current))
			break;
		schedule();
	}

	set_current_state(TASK_RUNNING);
	remove_wait_queue(&request_key_conswq, &myself);

	/* we'll need to search this process's keyrings to see if the key is
	 * now there since we can't automatically assume it's also available
	 * there */
	key_put(ckey);
	ckey = NULL;

	key = NULL; /* request a retry */
	goto error;

} /* end request_key_construction() */

/*****************************************************************************/
/*
 * link a freshly minted key to an appropriate destination keyring
 */
static void request_key_link(struct key *key, struct key *dest_keyring)
{
	struct task_struct *tsk = current;
	struct key *drop = NULL;

	kenter("{%d},%p", key->serial, dest_keyring);

	/* find the appropriate keyring */
	if (!dest_keyring) {
		switch (tsk->jit_keyring) {
		case KEY_REQKEY_DEFL_DEFAULT:
		case KEY_REQKEY_DEFL_THREAD_KEYRING:
			dest_keyring = tsk->thread_keyring;
			if (dest_keyring)
				break;

		case KEY_REQKEY_DEFL_PROCESS_KEYRING:
			dest_keyring = tsk->signal->process_keyring;
			if (dest_keyring)
				break;

		case KEY_REQKEY_DEFL_SESSION_KEYRING:
			rcu_read_lock();
			dest_keyring = key_get(
				rcu_dereference(tsk->signal->session_keyring));
			rcu_read_unlock();
			drop = dest_keyring;

			if (dest_keyring)
				break;

		case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
			dest_keyring = current->user->session_keyring;
			break;

		case KEY_REQKEY_DEFL_USER_KEYRING:
			dest_keyring = current->user->uid_keyring;
			break;

		case KEY_REQKEY_DEFL_GROUP_KEYRING:
		default:
			BUG();
		}
	}

	/* and attach the key to it */
	key_link(dest_keyring, key);

	key_put(drop);

	kleave("");

} /* end request_key_link() */

/*****************************************************************************/
/*
 * 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 char *callout_info,
				 struct key *dest_keyring)
{
	struct key_user *user;
	struct key *key;

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

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

	if (PTR_ERR(key) == -EAGAIN) {
		/* 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;

		/* - get hold of the user's construction queue */
		user = key_user_lookup(current->fsuid);
		if (!user)
			goto nomem;

		do {
			if (signal_pending(current))
				goto interrupted;

			/* ask userspace (returns NULL if it waited on a key
			 * being constructed) */
			key = request_key_construction(type, description,
						       user, callout_info);
			if (key)
				break;

			/* someone else made the key we want, so we need to
			 * search again as it might now be available to us */
			key = search_process_keyrings(type, description,
						      type->match, current);

		} while (PTR_ERR(key) == -EAGAIN);

		key_user_put(user);

		/* link the new key into the appropriate keyring */
		if (!IS_ERR(key))
			request_key_link(key, dest_keyring);
	}

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

nomem:
	key = ERR_PTR(-ENOMEM);
	goto error;

interrupted:
	key_user_put(user);
	key = ERR_PTR(-EINTR);
	goto error;

} /* end request_key_and_link() */

/*****************************************************************************/
/*
 * 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
 */
struct key *request_key(struct key_type *type,
			const char *description,
			const char *callout_info)
{
	return request_key_and_link(type, description, callout_info, NULL);

} /* end request_key() */

EXPORT_SYMBOL(request_key);

/*****************************************************************************/
/*
 * validate a key
 */
int key_validate(struct key *key)
{
	struct timespec now;
	int ret = 0;

	if (key) {
		/* check it's still accessible */
		ret = -EKEYREVOKED;
		if (test_bit(KEY_FLAG_REVOKED, &key->flags) ||
		    test_bit(KEY_FLAG_DEAD, &key->flags))
			goto error;

		/* check it hasn't expired */
		ret = 0;
		if (key->expiry) {
			now = current_kernel_time();
			if (now.tv_sec >= key->expiry)
				ret = -EKEYEXPIRED;
		}
	}

 error:
	return ret;

} /* end key_validate() */

EXPORT_SYMBOL(key_validate);