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 */
24 static DEFINE_MUTEX(key_session_mutex);
25
26 /* the root user's tracking struct */
27 struct key_user root_key_user = {
28 .usage = ATOMIC_INIT(3),
29 .cons_lock = __MUTEX_INITIALIZER(root_key_user.cons_lock),
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 */
37 struct 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 */
52 struct 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 */
70 int 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
104 error:
105 return ret;
106
107 } /* end alloc_uid_keyring() */
108
109 /*****************************************************************************/
110 /*
111 * deal with the UID changing
112 */
113 void switch_uid_keyring(struct user_struct *new_user)
114 {
115 #if 0 /* do nothing for now */
116 struct key *old;
117
118 /* switch to the new user's session keyring if we were running under
119 * root's default session keyring */
120 if (new_user->uid != 0 &&
121 current->session_keyring == &root_session_keyring
122 ) {
123 atomic_inc(&new_user->session_keyring->usage);
124
125 task_lock(current);
126 old = current->session_keyring;
127 current->session_keyring = new_user->session_keyring;
128 task_unlock(current);
129
130 key_put(old);
131 }
132 #endif
133
134 } /* end switch_uid_keyring() */
135
136 /*****************************************************************************/
137 /*
138 * install a fresh thread keyring, discarding the old one
139 */
140 int install_thread_keyring(struct task_struct *tsk)
141 {
142 struct key *keyring, *old;
143 char buf[20];
144 int ret;
145
146 sprintf(buf, "_tid.%u", tsk->pid);
147
148 keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk,
149 KEY_ALLOC_QUOTA_OVERRUN, NULL);
150 if (IS_ERR(keyring)) {
151 ret = PTR_ERR(keyring);
152 goto error;
153 }
154
155 task_lock(tsk);
156 old = tsk->thread_keyring;
157 tsk->thread_keyring = keyring;
158 task_unlock(tsk);
159
160 ret = 0;
161
162 key_put(old);
163 error:
164 return ret;
165
166 } /* end install_thread_keyring() */
167
168 /*****************************************************************************/
169 /*
170 * make sure a process keyring is installed
171 */
172 int install_process_keyring(struct task_struct *tsk)
173 {
174 struct key *keyring;
175 char buf[20];
176 int ret;
177
178 might_sleep();
179
180 if (!tsk->signal->process_keyring) {
181 sprintf(buf, "_pid.%u", tsk->tgid);
182
183 keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk,
184 KEY_ALLOC_QUOTA_OVERRUN, NULL);
185 if (IS_ERR(keyring)) {
186 ret = PTR_ERR(keyring);
187 goto error;
188 }
189
190 /* attach keyring */
191 spin_lock_irq(&tsk->sighand->siglock);
192 if (!tsk->signal->process_keyring) {
193 tsk->signal->process_keyring = keyring;
194 keyring = NULL;
195 }
196 spin_unlock_irq(&tsk->sighand->siglock);
197
198 key_put(keyring);
199 }
200
201 ret = 0;
202 error:
203 return ret;
204
205 } /* end install_process_keyring() */
206
207 /*****************************************************************************/
208 /*
209 * install a session keyring, discarding the old one
210 * - if a keyring is not supplied, an empty one is invented
211 */
212 static int install_session_keyring(struct task_struct *tsk,
213 struct key *keyring)
214 {
215 unsigned long flags;
216 struct key *old;
217 char buf[20];
218
219 might_sleep();
220
221 /* create an empty session keyring */
222 if (!keyring) {
223 sprintf(buf, "_ses.%u", tsk->tgid);
224
225 flags = KEY_ALLOC_QUOTA_OVERRUN;
226 if (tsk->signal->session_keyring)
227 flags = KEY_ALLOC_IN_QUOTA;
228
229 keyring = keyring_alloc(buf, tsk->uid, tsk->gid, tsk,
230 flags, NULL);
231 if (IS_ERR(keyring))
232 return PTR_ERR(keyring);
233 }
234 else {
235 atomic_inc(&keyring->usage);
236 }
237
238 /* install the keyring */
239 spin_lock_irq(&tsk->sighand->siglock);
240 old = tsk->signal->session_keyring;
241 rcu_assign_pointer(tsk->signal->session_keyring, keyring);
242 spin_unlock_irq(&tsk->sighand->siglock);
243
244 /* we're using RCU on the pointer, but there's no point synchronising
245 * on it if it didn't previously point to anything */
246 if (old) {
247 synchronize_rcu();
248 key_put(old);
249 }
250
251 return 0;
252
253 } /* end install_session_keyring() */
254
255 /*****************************************************************************/
256 /*
257 * copy the keys in a thread group for fork without CLONE_THREAD
258 */
259 int copy_thread_group_keys(struct task_struct *tsk)
260 {
261 key_check(current->thread_group->session_keyring);
262 key_check(current->thread_group->process_keyring);
263
264 /* no process keyring yet */
265 tsk->signal->process_keyring = NULL;
266
267 /* same session keyring */
268 rcu_read_lock();
269 tsk->signal->session_keyring =
270 key_get(rcu_dereference(current->signal->session_keyring));
271 rcu_read_unlock();
272
273 return 0;
274
275 } /* end copy_thread_group_keys() */
276
277 /*****************************************************************************/
278 /*
279 * copy the keys for fork
280 */
281 int copy_keys(unsigned long clone_flags, struct task_struct *tsk)
282 {
283 key_check(tsk->thread_keyring);
284 key_check(tsk->request_key_auth);
285
286 /* no thread keyring yet */
287 tsk->thread_keyring = NULL;
288
289 /* copy the request_key() authorisation for this thread */
290 key_get(tsk->request_key_auth);
291
292 return 0;
293
294 } /* end copy_keys() */
295
296 /*****************************************************************************/
297 /*
298 * dispose of thread group keys upon thread group destruction
299 */
300 void exit_thread_group_keys(struct signal_struct *tg)
301 {
302 key_put(tg->session_keyring);
303 key_put(tg->process_keyring);
304
305 } /* end exit_thread_group_keys() */
306
307 /*****************************************************************************/
308 /*
309 * dispose of per-thread keys upon thread exit
310 */
311 void exit_keys(struct task_struct *tsk)
312 {
313 key_put(tsk->thread_keyring);
314 key_put(tsk->request_key_auth);
315
316 } /* end exit_keys() */
317
318 /*****************************************************************************/
319 /*
320 * deal with execve()
321 */
322 int exec_keys(struct task_struct *tsk)
323 {
324 struct key *old;
325
326 /* newly exec'd tasks don't get a thread keyring */
327 task_lock(tsk);
328 old = tsk->thread_keyring;
329 tsk->thread_keyring = NULL;
330 task_unlock(tsk);
331
332 key_put(old);
333
334 /* discard the process keyring from a newly exec'd task */
335 spin_lock_irq(&tsk->sighand->siglock);
336 old = tsk->signal->process_keyring;
337 tsk->signal->process_keyring = NULL;
338 spin_unlock_irq(&tsk->sighand->siglock);
339
340 key_put(old);
341
342 return 0;
343
344 } /* end exec_keys() */
345
346 /*****************************************************************************/
347 /*
348 * deal with SUID programs
349 * - we might want to make this invent a new session keyring
350 */
351 int suid_keys(struct task_struct *tsk)
352 {
353 return 0;
354
355 } /* end suid_keys() */
356
357 /*****************************************************************************/
358 /*
359 * the filesystem user ID changed
360 */
361 void key_fsuid_changed(struct task_struct *tsk)
362 {
363 /* update the ownership of the thread keyring */
364 if (tsk->thread_keyring) {
365 down_write(&tsk->thread_keyring->sem);
366 tsk->thread_keyring->uid = tsk->fsuid;
367 up_write(&tsk->thread_keyring->sem);
368 }
369
370 } /* end key_fsuid_changed() */
371
372 /*****************************************************************************/
373 /*
374 * the filesystem group ID changed
375 */
376 void key_fsgid_changed(struct task_struct *tsk)
377 {
378 /* update the ownership of the thread keyring */
379 if (tsk->thread_keyring) {
380 down_write(&tsk->thread_keyring->sem);
381 tsk->thread_keyring->gid = tsk->fsgid;
382 up_write(&tsk->thread_keyring->sem);
383 }
384
385 } /* end key_fsgid_changed() */
386
387 /*****************************************************************************/
388 /*
389 * search the process keyrings for the first matching key
390 * - we use the supplied match function to see if the description (or other
391 * feature of interest) matches
392 * - we return -EAGAIN if we didn't find any matching key
393 * - we return -ENOKEY if we found only negative matching keys
394 */
395 key_ref_t search_process_keyrings(struct key_type *type,
396 const void *description,
397 key_match_func_t match,
398 struct task_struct *context)
399 {
400 struct request_key_auth *rka;
401 key_ref_t key_ref, ret, err;
402
403 might_sleep();
404
405 /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
406 * searchable, but we failed to find a key or we found a negative key;
407 * otherwise we want to return a sample error (probably -EACCES) if
408 * none of the keyrings were searchable
409 *
410 * in terms of priority: success > -ENOKEY > -EAGAIN > other error
411 */
412 key_ref = NULL;
413 ret = NULL;
414 err = ERR_PTR(-EAGAIN);
415
416 /* search the thread keyring first */
417 if (context->thread_keyring) {
418 key_ref = keyring_search_aux(
419 make_key_ref(context->thread_keyring, 1),
420 context, type, description, match);
421 if (!IS_ERR(key_ref))
422 goto found;
423
424 switch (PTR_ERR(key_ref)) {
425 case -EAGAIN: /* no key */
426 if (ret)
427 break;
428 case -ENOKEY: /* negative key */
429 ret = key_ref;
430 break;
431 default:
432 err = key_ref;
433 break;
434 }
435 }
436
437 /* search the process keyring second */
438 if (context->signal->process_keyring) {
439 key_ref = keyring_search_aux(
440 make_key_ref(context->signal->process_keyring, 1),
441 context, type, description, match);
442 if (!IS_ERR(key_ref))
443 goto found;
444
445 switch (PTR_ERR(key_ref)) {
446 case -EAGAIN: /* no key */
447 if (ret)
448 break;
449 case -ENOKEY: /* negative key */
450 ret = key_ref;
451 break;
452 default:
453 err = key_ref;
454 break;
455 }
456 }
457
458 /* search the session keyring */
459 if (context->signal->session_keyring) {
460 rcu_read_lock();
461 key_ref = keyring_search_aux(
462 make_key_ref(rcu_dereference(
463 context->signal->session_keyring),
464 1),
465 context, type, description, match);
466 rcu_read_unlock();
467
468 if (!IS_ERR(key_ref))
469 goto found;
470
471 switch (PTR_ERR(key_ref)) {
472 case -EAGAIN: /* no key */
473 if (ret)
474 break;
475 case -ENOKEY: /* negative key */
476 ret = key_ref;
477 break;
478 default:
479 err = key_ref;
480 break;
481 }
482 }
483 /* or search the user-session keyring */
484 else {
485 key_ref = keyring_search_aux(
486 make_key_ref(context->user->session_keyring, 1),
487 context, type, description, match);
488 if (!IS_ERR(key_ref))
489 goto found;
490
491 switch (PTR_ERR(key_ref)) {
492 case -EAGAIN: /* no key */
493 if (ret)
494 break;
495 case -ENOKEY: /* negative key */
496 ret = key_ref;
497 break;
498 default:
499 err = key_ref;
500 break;
501 }
502 }
503
504 /* if this process has an instantiation authorisation key, then we also
505 * search the keyrings of the process mentioned there
506 * - we don't permit access to request_key auth keys via this method
507 */
508 if (context->request_key_auth &&
509 context == current &&
510 type != &key_type_request_key_auth
511 ) {
512 /* defend against the auth key being revoked */
513 down_read(&context->request_key_auth->sem);
514
515 if (key_validate(context->request_key_auth) == 0) {
516 rka = context->request_key_auth->payload.data;
517
518 key_ref = search_process_keyrings(type, description,
519 match, rka->context);
520
521 up_read(&context->request_key_auth->sem);
522
523 if (!IS_ERR(key_ref))
524 goto found;
525
526 switch (PTR_ERR(key_ref)) {
527 case -EAGAIN: /* no key */
528 if (ret)
529 break;
530 case -ENOKEY: /* negative key */
531 ret = key_ref;
532 break;
533 default:
534 err = key_ref;
535 break;
536 }
537 } else {
538 up_read(&context->request_key_auth->sem);
539 }
540 }
541
542 /* no key - decide on the error we're going to go for */
543 key_ref = ret ? ret : err;
544
545 found:
546 return key_ref;
547
548 } /* end search_process_keyrings() */
549
550 /*****************************************************************************/
551 /*
552 * see if the key we're looking at is the target key
553 */
554 static int lookup_user_key_possessed(const struct key *key, const void *target)
555 {
556 return key == target;
557
558 } /* end lookup_user_key_possessed() */
559
560 /*****************************************************************************/
561 /*
562 * lookup a key given a key ID from userspace with a given permissions mask
563 * - don't create special keyrings unless so requested
564 * - partially constructed keys aren't found unless requested
565 */
566 key_ref_t lookup_user_key(struct task_struct *context, key_serial_t id,
567 int create, int partial, key_perm_t perm)
568 {
569 key_ref_t key_ref, skey_ref;
570 struct key *key;
571 int ret;
572
573 if (!context)
574 context = current;
575
576 key_ref = ERR_PTR(-ENOKEY);
577
578 switch (id) {
579 case KEY_SPEC_THREAD_KEYRING:
580 if (!context->thread_keyring) {
581 if (!create)
582 goto error;
583
584 ret = install_thread_keyring(context);
585 if (ret < 0) {
586 key = ERR_PTR(ret);
587 goto error;
588 }
589 }
590
591 key = context->thread_keyring;
592 atomic_inc(&key->usage);
593 key_ref = make_key_ref(key, 1);
594 break;
595
596 case KEY_SPEC_PROCESS_KEYRING:
597 if (!context->signal->process_keyring) {
598 if (!create)
599 goto error;
600
601 ret = install_process_keyring(context);
602 if (ret < 0) {
603 key = ERR_PTR(ret);
604 goto error;
605 }
606 }
607
608 key = context->signal->process_keyring;
609 atomic_inc(&key->usage);
610 key_ref = make_key_ref(key, 1);
611 break;
612
613 case KEY_SPEC_SESSION_KEYRING:
614 if (!context->signal->session_keyring) {
615 /* always install a session keyring upon access if one
616 * doesn't exist yet */
617 ret = install_session_keyring(
618 context, context->user->session_keyring);
619 if (ret < 0)
620 goto error;
621 }
622
623 rcu_read_lock();
624 key = rcu_dereference(context->signal->session_keyring);
625 atomic_inc(&key->usage);
626 rcu_read_unlock();
627 key_ref = make_key_ref(key, 1);
628 break;
629
630 case KEY_SPEC_USER_KEYRING:
631 key = context->user->uid_keyring;
632 atomic_inc(&key->usage);
633 key_ref = make_key_ref(key, 1);
634 break;
635
636 case KEY_SPEC_USER_SESSION_KEYRING:
637 key = context->user->session_keyring;
638 atomic_inc(&key->usage);
639 key_ref = make_key_ref(key, 1);
640 break;
641
642 case KEY_SPEC_GROUP_KEYRING:
643 /* group keyrings are not yet supported */
644 key = ERR_PTR(-EINVAL);
645 goto error;
646
647 case KEY_SPEC_REQKEY_AUTH_KEY:
648 key = context->request_key_auth;
649 if (!key)
650 goto error;
651
652 atomic_inc(&key->usage);
653 key_ref = make_key_ref(key, 1);
654 break;
655
656 default:
657 key_ref = ERR_PTR(-EINVAL);
658 if (id < 1)
659 goto error;
660
661 key = key_lookup(id);
662 if (IS_ERR(key)) {
663 key_ref = ERR_CAST(key);
664 goto error;
665 }
666
667 key_ref = make_key_ref(key, 0);
668
669 /* check to see if we possess the key */
670 skey_ref = search_process_keyrings(key->type, key,
671 lookup_user_key_possessed,
672 current);
673
674 if (!IS_ERR(skey_ref)) {
675 key_put(key);
676 key_ref = skey_ref;
677 }
678
679 break;
680 }
681
682 if (!partial) {
683 ret = wait_for_key_construction(key, true);
684 switch (ret) {
685 case -ERESTARTSYS:
686 goto invalid_key;
687 default:
688 if (perm)
689 goto invalid_key;
690 case 0:
691 break;
692 }
693 } else if (perm) {
694 ret = key_validate(key);
695 if (ret < 0)
696 goto invalid_key;
697 }
698
699 ret = -EIO;
700 if (!partial && !test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
701 goto invalid_key;
702
703 /* check the permissions */
704 ret = key_task_permission(key_ref, context, perm);
705 if (ret < 0)
706 goto invalid_key;
707
708 error:
709 return key_ref;
710
711 invalid_key:
712 key_ref_put(key_ref);
713 key_ref = ERR_PTR(ret);
714 goto error;
715
716 } /* end lookup_user_key() */
717
718 /*****************************************************************************/
719 /*
720 * join the named keyring as the session keyring if possible, or attempt to
721 * create a new one of that name if not
722 * - if the name is NULL, an empty anonymous keyring is installed instead
723 * - named session keyring joining is done with a semaphore held
724 */
725 long join_session_keyring(const char *name)
726 {
727 struct task_struct *tsk = current;
728 struct key *keyring;
729 long ret;
730
731 /* if no name is provided, install an anonymous keyring */
732 if (!name) {
733 ret = install_session_keyring(tsk, NULL);
734 if (ret < 0)
735 goto error;
736
737 rcu_read_lock();
738 ret = rcu_dereference(tsk->signal->session_keyring)->serial;
739 rcu_read_unlock();
740 goto error;
741 }
742
743 /* allow the user to join or create a named keyring */
744 mutex_lock(&key_session_mutex);
745
746 /* look for an existing keyring of this name */
747 keyring = find_keyring_by_name(name, 0);
748 if (PTR_ERR(keyring) == -ENOKEY) {
749 /* not found - try and create a new one */
750 keyring = keyring_alloc(name, tsk->uid, tsk->gid, tsk,
751 KEY_ALLOC_IN_QUOTA, NULL);
752 if (IS_ERR(keyring)) {
753 ret = PTR_ERR(keyring);
754 goto error2;
755 }
756 }
757 else if (IS_ERR(keyring)) {
758 ret = PTR_ERR(keyring);
759 goto error2;
760 }
761
762 /* we've got a keyring - now to install it */
763 ret = install_session_keyring(tsk, keyring);
764 if (ret < 0)
765 goto error2;
766
767 ret = keyring->serial;
768 key_put(keyring);
769
770 error2:
771 mutex_unlock(&key_session_mutex);
772 error:
773 return ret;
774
775 } /* end join_session_keyring() */
776
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