1/* process_keys.c: management of a process's keyrings
2 *
3 * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12#include <linux/module.h>
13#include <linux/init.h>
14#include <linux/sched.h>
15#include <linux/slab.h>
16#include <linux/keyctl.h>
17#include <linux/fs.h>
18#include <linux/err.h>
19#include <linux/mutex.h>
20#include <asm/uaccess.h>
21#include "internal.h"
22
23/* session keyring create vs join semaphore */
24static DEFINE_MUTEX(key_session_mutex);
25
26/* the root user's tracking struct */
27struct key_user root_key_user = {
28	.usage		= ATOMIC_INIT(3),
29	.consq		= LIST_HEAD_INIT(root_key_user.consq),
30	.lock		= __SPIN_LOCK_UNLOCKED(root_key_user.lock),
31	.nkeys		= ATOMIC_INIT(2),
32	.nikeys		= ATOMIC_INIT(2),
33	.uid		= 0,
34};
35
36/* the root user's UID keyring */
37struct key root_user_keyring = {
38	.usage		= ATOMIC_INIT(1),
39	.serial		= 2,
40	.type		= &key_type_keyring,
41	.user		= &root_key_user,
42	.sem		= __RWSEM_INITIALIZER(root_user_keyring.sem),
43	.perm		= (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
44	.flags		= 1 << KEY_FLAG_INSTANTIATED,
45	.description	= "_uid.0",
46#ifdef KEY_DEBUGGING
47	.magic		= KEY_DEBUG_MAGIC,
48#endif
49};
50
51/* the root user's default session keyring */
52struct key root_session_keyring = {
53	.usage		= ATOMIC_INIT(1),
54	.serial		= 1,
55	.type		= &key_type_keyring,
56	.user		= &root_key_user,
57	.sem		= __RWSEM_INITIALIZER(root_session_keyring.sem),
58	.perm		= (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
59	.flags		= 1 << KEY_FLAG_INSTANTIATED,
60	.description	= "_uid_ses.0",
61#ifdef KEY_DEBUGGING
62	.magic		= KEY_DEBUG_MAGIC,
63#endif
64};
65
66/*****************************************************************************/
67/*
68 * allocate the keyrings to be associated with a UID
69 */
70int alloc_uid_keyring(struct user_struct *user,
71		      struct task_struct *ctx)
72{
73	struct key *uid_keyring, *session_keyring;
74	char buf[20];
75	int ret;
76
77	/* concoct a default session keyring */
78	sprintf(buf, "_uid_ses.%u", user->uid);
79
80	session_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, ctx,
81					KEY_ALLOC_IN_QUOTA, NULL);
82	if (IS_ERR(session_keyring)) {
83		ret = PTR_ERR(session_keyring);
84		goto error;
85	}
86
87	/* and a UID specific keyring, pointed to by the default session
88	 * keyring */
89	sprintf(buf, "_uid.%u", user->uid);
90
91	uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, ctx,
92				    KEY_ALLOC_IN_QUOTA, session_keyring);
93	if (IS_ERR(uid_keyring)) {
94		key_put(session_keyring);
95		ret = PTR_ERR(uid_keyring);
96		goto error;
97	}
98
99	/* install the keyrings */
100	user->uid_keyring = uid_keyring;
101	user->session_keyring = session_keyring;
102	ret = 0;
103
104error:
105	return ret;
106
107} /* end alloc_uid_keyring() */
108
109/*****************************************************************************/
110/*
111 * deal with the UID changing
112 */
113void switch_uid_keyring(struct user_struct *new_user)
114{
115
116} /* end switch_uid_keyring() */
117
118/*****************************************************************************/
119/*
120 * install a fresh thread keyring, discarding the old one
121 */
122int install_thread_keyring(struct task_struct *tsk)
123{
124	struct key *keyring, *old;
125	char buf[20];
126	int ret;
127
128	sprintf(buf, "_tid.%u", tsk->pid);
129
130	keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk,
131				KEY_ALLOC_QUOTA_OVERRUN, NULL);
132	if (IS_ERR(keyring)) {
133		ret = PTR_ERR(keyring);
134		goto error;
135	}
136
137	task_lock(tsk);
138	old = tsk->thread_keyring;
139	tsk->thread_keyring = keyring;
140	task_unlock(tsk);
141
142	ret = 0;
143
144	key_put(old);
145error:
146	return ret;
147
148} /* end install_thread_keyring() */
149
150/*****************************************************************************/
151/*
152 * make sure a process keyring is installed
153 */
154int install_process_keyring(struct task_struct *tsk)
155{
156	struct key *keyring;
157	char buf[20];
158	int ret;
159
160	might_sleep();
161
162	if (!tsk->signal->process_keyring) {
163		sprintf(buf, "_pid.%u", tsk->tgid);
164
165		keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk,
166					KEY_ALLOC_QUOTA_OVERRUN, NULL);
167		if (IS_ERR(keyring)) {
168			ret = PTR_ERR(keyring);
169			goto error;
170		}
171
172		/* attach keyring */
173		spin_lock_irq(&tsk->sighand->siglock);
174		if (!tsk->signal->process_keyring) {
175			tsk->signal->process_keyring = keyring;
176			keyring = NULL;
177		}
178		spin_unlock_irq(&tsk->sighand->siglock);
179
180		key_put(keyring);
181	}
182
183	ret = 0;
184error:
185	return ret;
186
187} /* end install_process_keyring() */
188
189/*****************************************************************************/
190/*
191 * install a session keyring, discarding the old one
192 * - if a keyring is not supplied, an empty one is invented
193 */
194static int install_session_keyring(struct task_struct *tsk,
195				   struct key *keyring)
196{
197	unsigned long flags;
198	struct key *old;
199	char buf[20];
200
201	might_sleep();
202
203	/* create an empty session keyring */
204	if (!keyring) {
205		sprintf(buf, "_ses.%u", tsk->tgid);
206
207		flags = KEY_ALLOC_QUOTA_OVERRUN;
208		if (tsk->signal->session_keyring)
209			flags = KEY_ALLOC_IN_QUOTA;
210
211		keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk,
212					flags, NULL);
213		if (IS_ERR(keyring))
214			return PTR_ERR(keyring);
215	}
216	else {
217		atomic_inc(&keyring->usage);
218	}
219
220	/* install the keyring */
221	spin_lock_irq(&tsk->sighand->siglock);
222	old = tsk->signal->session_keyring;
223	rcu_assign_pointer(tsk->signal->session_keyring, keyring);
224	spin_unlock_irq(&tsk->sighand->siglock);
225
226	/* we're using RCU on the pointer, but there's no point synchronising
227	 * on it if it didn't previously point to anything */
228	if (old) {
229		synchronize_rcu();
230		key_put(old);
231	}
232
233	return 0;
234
235} /* end install_session_keyring() */
236
237/*****************************************************************************/
238/*
239 * copy the keys in a thread group for fork without CLONE_THREAD
240 */
241int copy_thread_group_keys(struct task_struct *tsk)
242{
243	key_check(current->thread_group->session_keyring);
244	key_check(current->thread_group->process_keyring);
245
246	/* no process keyring yet */
247	tsk->signal->process_keyring = NULL;
248
249	/* same session keyring */
250	rcu_read_lock();
251	tsk->signal->session_keyring =
252		key_get(rcu_dereference(current->signal->session_keyring));
253	rcu_read_unlock();
254
255	return 0;
256
257} /* end copy_thread_group_keys() */
258
259/*****************************************************************************/
260/*
261 * copy the keys for fork
262 */
263int copy_keys(unsigned long clone_flags, struct task_struct *tsk)
264{
265	key_check(tsk->thread_keyring);
266	key_check(tsk->request_key_auth);
267
268	/* no thread keyring yet */
269	tsk->thread_keyring = NULL;
270
271	/* copy the request_key() authorisation for this thread */
272	key_get(tsk->request_key_auth);
273
274	return 0;
275
276} /* end copy_keys() */
277
278/*****************************************************************************/
279/*
280 * dispose of thread group keys upon thread group destruction
281 */
282void exit_thread_group_keys(struct signal_struct *tg)
283{
284	key_put(tg->session_keyring);
285	key_put(tg->process_keyring);
286
287} /* end exit_thread_group_keys() */
288
289/*****************************************************************************/
290/*
291 * dispose of per-thread keys upon thread exit
292 */
293void exit_keys(struct task_struct *tsk)
294{
295	key_put(tsk->thread_keyring);
296	key_put(tsk->request_key_auth);
297
298} /* end exit_keys() */
299
300/*****************************************************************************/
301/*
302 * deal with execve()
303 */
304int exec_keys(struct task_struct *tsk)
305{
306	struct key *old;
307
308	/* newly exec'd tasks don't get a thread keyring */
309	task_lock(tsk);
310	old = tsk->thread_keyring;
311	tsk->thread_keyring = NULL;
312	task_unlock(tsk);
313
314	key_put(old);
315
316	/* discard the process keyring from a newly exec'd task */
317	spin_lock_irq(&tsk->sighand->siglock);
318	old = tsk->signal->process_keyring;
319	tsk->signal->process_keyring = NULL;
320	spin_unlock_irq(&tsk->sighand->siglock);
321
322	key_put(old);
323
324	return 0;
325
326} /* end exec_keys() */
327
328/*****************************************************************************/
329/*
330 * deal with SUID programs
331 * - we might want to make this invent a new session keyring
332 */
333int suid_keys(struct task_struct *tsk)
334{
335	return 0;
336
337} /* end suid_keys() */
338
339/*****************************************************************************/
340/*
341 * the filesystem user ID changed
342 */
343void key_fsuid_changed(struct task_struct *tsk)
344{
345	/* update the ownership of the thread keyring */
346	if (tsk->thread_keyring) {
347		down_write(&tsk->thread_keyring->sem);
348		tsk->thread_keyring->uid = tsk->fsuid;
349		up_write(&tsk->thread_keyring->sem);
350	}
351
352} /* end key_fsuid_changed() */
353
354/*****************************************************************************/
355/*
356 * the filesystem group ID changed
357 */
358void key_fsgid_changed(struct task_struct *tsk)
359{
360	/* update the ownership of the thread keyring */
361	if (tsk->thread_keyring) {
362		down_write(&tsk->thread_keyring->sem);
363		tsk->thread_keyring->gid = tsk->fsgid;
364		up_write(&tsk->thread_keyring->sem);
365	}
366
367} /* end key_fsgid_changed() */
368
369/*****************************************************************************/
370/*
371 * search the process keyrings for the first matching key
372 * - we use the supplied match function to see if the description (or other
373 *   feature of interest) matches
374 * - we return -EAGAIN if we didn't find any matching key
375 * - we return -ENOKEY if we found only negative matching keys
376 */
377key_ref_t search_process_keyrings(struct key_type *type,
378				  const void *description,
379				  key_match_func_t match,
380				  struct task_struct *context)
381{
382	struct request_key_auth *rka;
383	key_ref_t key_ref, ret, err;
384
385	might_sleep();
386
387	/* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
388	 * searchable, but we failed to find a key or we found a negative key;
389	 * otherwise we want to return a sample error (probably -EACCES) if
390	 * none of the keyrings were searchable
391	 *
392	 * in terms of priority: success > -ENOKEY > -EAGAIN > other error
393	 */
394	key_ref = NULL;
395	ret = NULL;
396	err = ERR_PTR(-EAGAIN);
397
398	/* search the thread keyring first */
399	if (context->thread_keyring) {
400		key_ref = keyring_search_aux(
401			make_key_ref(context->thread_keyring, 1),
402			context, type, description, match);
403		if (!IS_ERR(key_ref))
404			goto found;
405
406		switch (PTR_ERR(key_ref)) {
407		case -EAGAIN: /* no key */
408			if (ret)
409				break;
410		case -ENOKEY: /* negative key */
411			ret = key_ref;
412			break;
413		default:
414			err = key_ref;
415			break;
416		}
417	}
418
419	/* search the process keyring second */
420	if (context->signal->process_keyring) {
421		key_ref = keyring_search_aux(
422			make_key_ref(context->signal->process_keyring, 1),
423			context, type, description, match);
424		if (!IS_ERR(key_ref))
425			goto found;
426
427		switch (PTR_ERR(key_ref)) {
428		case -EAGAIN: /* no key */
429			if (ret)
430				break;
431		case -ENOKEY: /* negative key */
432			ret = key_ref;
433			break;
434		default:
435			err = key_ref;
436			break;
437		}
438	}
439
440	/* search the session keyring */
441	if (context->signal->session_keyring) {
442		rcu_read_lock();
443		key_ref = keyring_search_aux(
444			make_key_ref(rcu_dereference(
445					     context->signal->session_keyring),
446				     1),
447			context, type, description, match);
448		rcu_read_unlock();
449
450		if (!IS_ERR(key_ref))
451			goto found;
452
453		switch (PTR_ERR(key_ref)) {
454		case -EAGAIN: /* no key */
455			if (ret)
456				break;
457		case -ENOKEY: /* negative key */
458			ret = key_ref;
459			break;
460		default:
461			err = key_ref;
462			break;
463		}
464	}
465	/* or search the user-session keyring */
466	else {
467		key_ref = keyring_search_aux(
468			make_key_ref(context->user->session_keyring, 1),
469			context, type, description, match);
470		if (!IS_ERR(key_ref))
471			goto found;
472
473		switch (PTR_ERR(key_ref)) {
474		case -EAGAIN: /* no key */
475			if (ret)
476				break;
477		case -ENOKEY: /* negative key */
478			ret = key_ref;
479			break;
480		default:
481			err = key_ref;
482			break;
483		}
484	}
485
486	/* if this process has an instantiation authorisation key, then we also
487	 * search the keyrings of the process mentioned there
488	 * - we don't permit access to request_key auth keys via this method
489	 */
490	if (context->request_key_auth &&
491	    context == current &&
492	    type != &key_type_request_key_auth
493	    ) {
494		/* defend against the auth key being revoked */
495		down_read(&context->request_key_auth->sem);
496
497		if (key_validate(context->request_key_auth) == 0) {
498			rka = context->request_key_auth->payload.data;
499
500			key_ref = search_process_keyrings(type, description,
501							  match, rka->context);
502
503			up_read(&context->request_key_auth->sem);
504
505			if (!IS_ERR(key_ref))
506				goto found;
507
508			switch (PTR_ERR(key_ref)) {
509			case -EAGAIN: /* no key */
510				if (ret)
511					break;
512			case -ENOKEY: /* negative key */
513				ret = key_ref;
514				break;
515			default:
516				err = key_ref;
517				break;
518			}
519		} else {
520			up_read(&context->request_key_auth->sem);
521		}
522	}
523
524	/* no key - decide on the error we're going to go for */
525	key_ref = ret ? ret : err;
526
527found:
528	return key_ref;
529
530} /* end search_process_keyrings() */
531
532/*****************************************************************************/
533/*
534 * see if the key we're looking at is the target key
535 */
536static int lookup_user_key_possessed(const struct key *key, const void *target)
537{
538	return key == target;
539
540} /* end lookup_user_key_possessed() */
541
542/*****************************************************************************/
543/*
544 * lookup a key given a key ID from userspace with a given permissions mask
545 * - don't create special keyrings unless so requested
546 * - partially constructed keys aren't found unless requested
547 */
548key_ref_t lookup_user_key(struct task_struct *context, key_serial_t id,
549			  int create, int partial, key_perm_t perm)
550{
551	key_ref_t key_ref, skey_ref;
552	struct key *key;
553	int ret;
554
555	if (!context)
556		context = current;
557
558	key_ref = ERR_PTR(-ENOKEY);
559
560	switch (id) {
561	case KEY_SPEC_THREAD_KEYRING:
562		if (!context->thread_keyring) {
563			if (!create)
564				goto error;
565
566			ret = install_thread_keyring(context);
567			if (ret < 0) {
568				key = ERR_PTR(ret);
569				goto error;
570			}
571		}
572
573		key = context->thread_keyring;
574		atomic_inc(&key->usage);
575		key_ref = make_key_ref(key, 1);
576		break;
577
578	case KEY_SPEC_PROCESS_KEYRING:
579		if (!context->signal->process_keyring) {
580			if (!create)
581				goto error;
582
583			ret = install_process_keyring(context);
584			if (ret < 0) {
585				key = ERR_PTR(ret);
586				goto error;
587			}
588		}
589
590		key = context->signal->process_keyring;
591		atomic_inc(&key->usage);
592		key_ref = make_key_ref(key, 1);
593		break;
594
595	case KEY_SPEC_SESSION_KEYRING:
596		if (!context->signal->session_keyring) {
597			/* always install a session keyring upon access if one
598			 * doesn't exist yet */
599			ret = install_session_keyring(
600				context, context->user->session_keyring);
601			if (ret < 0)
602				goto error;
603		}
604
605		rcu_read_lock();
606		key = rcu_dereference(context->signal->session_keyring);
607		atomic_inc(&key->usage);
608		rcu_read_unlock();
609		key_ref = make_key_ref(key, 1);
610		break;
611
612	case KEY_SPEC_USER_KEYRING:
613		key = context->user->uid_keyring;
614		atomic_inc(&key->usage);
615		key_ref = make_key_ref(key, 1);
616		break;
617
618	case KEY_SPEC_USER_SESSION_KEYRING:
619		key = context->user->session_keyring;
620		atomic_inc(&key->usage);
621		key_ref = make_key_ref(key, 1);
622		break;
623
624	case KEY_SPEC_GROUP_KEYRING:
625		/* group keyrings are not yet supported */
626		key = ERR_PTR(-EINVAL);
627		goto error;
628
629	case KEY_SPEC_REQKEY_AUTH_KEY:
630		key = context->request_key_auth;
631		if (!key)
632			goto error;
633
634		atomic_inc(&key->usage);
635		key_ref = make_key_ref(key, 1);
636		break;
637
638	default:
639		key_ref = ERR_PTR(-EINVAL);
640		if (id < 1)
641			goto error;
642
643		key = key_lookup(id);
644		if (IS_ERR(key)) {
645			key_ref = ERR_PTR(PTR_ERR(key));
646			goto error;
647		}
648
649		key_ref = make_key_ref(key, 0);
650
651		/* check to see if we possess the key */
652		skey_ref = search_process_keyrings(key->type, key,
653						   lookup_user_key_possessed,
654						   current);
655
656		if (!IS_ERR(skey_ref)) {
657			key_put(key);
658			key_ref = skey_ref;
659		}
660
661		break;
662	}
663
664	/* check the status */
665	if (perm) {
666		ret = key_validate(key);
667		if (ret < 0)
668			goto invalid_key;
669	}
670
671	ret = -EIO;
672	if (!partial && !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
673		goto invalid_key;
674
675	/* check the permissions */
676	ret = key_task_permission(key_ref, context, perm);
677	if (ret < 0)
678		goto invalid_key;
679
680error:
681	return key_ref;
682
683invalid_key:
684	key_ref_put(key_ref);
685	key_ref = ERR_PTR(ret);
686	goto error;
687
688} /* end lookup_user_key() */
689
690/*****************************************************************************/
691/*
692 * join the named keyring as the session keyring if possible, or attempt to
693 * create a new one of that name if not
694 * - if the name is NULL, an empty anonymous keyring is installed instead
695 * - named session keyring joining is done with a semaphore held
696 */
697long join_session_keyring(const char *name)
698{
699	struct task_struct *tsk = current;
700	struct key *keyring;
701	long ret;
702
703	/* if no name is provided, install an anonymous keyring */
704	if (!name) {
705		ret = install_session_keyring(tsk, NULL);
706		if (ret < 0)
707			goto error;
708
709		rcu_read_lock();
710		ret = rcu_dereference(tsk->signal->session_keyring)->serial;
711		rcu_read_unlock();
712		goto error;
713	}
714
715	/* allow the user to join or create a named keyring */
716	mutex_lock(&key_session_mutex);
717
718	/* look for an existing keyring of this name */
719	keyring = find_keyring_by_name(name, 0);
720	if (PTR_ERR(keyring) == -ENOKEY) {
721		/* not found - try and create a new one */
722		keyring = keyring_alloc(name, tsk->uid, tsk->gid, tsk,
723					KEY_ALLOC_IN_QUOTA, NULL);
724		if (IS_ERR(keyring)) {
725			ret = PTR_ERR(keyring);
726			goto error2;
727		}
728	}
729	else if (IS_ERR(keyring)) {
730		ret = PTR_ERR(keyring);
731		goto error2;
732	}
733
734	/* we've got a keyring - now to install it */
735	ret = install_session_keyring(tsk, keyring);
736	if (ret < 0)
737		goto error2;
738
739	ret = keyring->serial;
740	key_put(keyring);
741
742error2:
743	mutex_unlock(&key_session_mutex);
744error:
745	return ret;
746
747} /* end join_session_keyring() */
748