2eb0e471cd40817a4ae548188dd82be73cbaca71
[linux-3.10.git] / security / keys / process_keys.c
1 /* process_keys.c: management of a process's keyrings
2  *
3  * Copyright (C) 2004 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 <asm/uaccess.h>
20 #include "internal.h"
21
22 /* session keyring create vs join semaphore */
23 static DECLARE_MUTEX(key_session_sem);
24
25 /* the root user's tracking struct */
26 struct key_user root_key_user = {
27         .usage          = ATOMIC_INIT(3),
28         .consq          = LIST_HEAD_INIT(root_key_user.consq),
29         .lock           = SPIN_LOCK_UNLOCKED,
30         .nkeys          = ATOMIC_INIT(2),
31         .nikeys         = ATOMIC_INIT(2),
32         .uid            = 0,
33 };
34
35 /* the root user's UID keyring */
36 struct key root_user_keyring = {
37         .usage          = ATOMIC_INIT(1),
38         .serial         = 2,
39         .type           = &key_type_keyring,
40         .user           = &root_key_user,
41         .lock           = RW_LOCK_UNLOCKED,
42         .sem            = __RWSEM_INITIALIZER(root_user_keyring.sem),
43         .perm           = KEY_USR_ALL,
44         .flags          = 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         .lock           = RW_LOCK_UNLOCKED,
58         .sem            = __RWSEM_INITIALIZER(root_session_keyring.sem),
59         .perm           = KEY_USR_ALL,
60         .flags          = KEY_FLAG_INSTANTIATED,
61         .description    = "_uid_ses.0",
62 #ifdef KEY_DEBUGGING
63         .magic          = KEY_DEBUG_MAGIC,
64 #endif
65 };
66
67 /*****************************************************************************/
68 /*
69  * allocate the keyrings to be associated with a UID
70  */
71 int alloc_uid_keyring(struct user_struct *user)
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, 0, NULL);
81         if (IS_ERR(session_keyring)) {
82                 ret = PTR_ERR(session_keyring);
83                 goto error;
84         }
85
86         /* and a UID specific keyring, pointed to by the default session
87          * keyring */
88         sprintf(buf, "_uid.%u", user->uid);
89
90         uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, 0,
91                                     session_keyring);
92         if (IS_ERR(uid_keyring)) {
93                 key_put(session_keyring);
94                 ret = PTR_ERR(uid_keyring);
95                 goto error;
96         }
97
98         /* install the keyrings */
99         user->uid_keyring = uid_keyring;
100         user->session_keyring = session_keyring;
101         ret = 0;
102
103  error:
104         return ret;
105
106 } /* end alloc_uid_keyring() */
107
108 /*****************************************************************************/
109 /*
110  * deal with the UID changing
111  */
112 void switch_uid_keyring(struct user_struct *new_user)
113 {
114 #if 0 /* do nothing for now */
115         struct key *old;
116
117         /* switch to the new user's session keyring if we were running under
118          * root's default session keyring */
119         if (new_user->uid != 0 &&
120             current->session_keyring == &root_session_keyring
121             ) {
122                 atomic_inc(&new_user->session_keyring->usage);
123
124                 task_lock(current);
125                 old = current->session_keyring;
126                 current->session_keyring = new_user->session_keyring;
127                 task_unlock(current);
128
129                 key_put(old);
130         }
131 #endif
132
133 } /* end switch_uid_keyring() */
134
135 /*****************************************************************************/
136 /*
137  * install a fresh thread keyring, discarding the old one
138  */
139 int install_thread_keyring(struct task_struct *tsk)
140 {
141         struct key *keyring, *old;
142         char buf[20];
143         int ret;
144
145         sprintf(buf, "_tid.%u", tsk->pid);
146
147         keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL);
148         if (IS_ERR(keyring)) {
149                 ret = PTR_ERR(keyring);
150                 goto error;
151         }
152
153         task_lock(tsk);
154         old = tsk->thread_keyring;
155         tsk->thread_keyring = keyring;
156         task_unlock(tsk);
157
158         ret = 0;
159
160         key_put(old);
161  error:
162         return ret;
163
164 } /* end install_thread_keyring() */
165
166 /*****************************************************************************/
167 /*
168  * make sure a process keyring is installed
169  */
170 static int install_process_keyring(struct task_struct *tsk)
171 {
172         unsigned long flags;
173         struct key *keyring;
174         char buf[20];
175         int ret;
176
177         if (!tsk->signal->process_keyring) {
178                 sprintf(buf, "_pid.%u", tsk->tgid);
179
180                 keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL);
181                 if (IS_ERR(keyring)) {
182                         ret = PTR_ERR(keyring);
183                         goto error;
184                 }
185
186                 /* attach or swap keyrings */
187                 spin_lock_irqsave(&tsk->sighand->siglock, flags);
188                 if (!tsk->signal->process_keyring) {
189                         tsk->signal->process_keyring = keyring;
190                         keyring = NULL;
191                 }
192                 spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
193
194                 key_put(keyring);
195         }
196
197         ret = 0;
198  error:
199         return ret;
200
201 } /* end install_process_keyring() */
202
203 /*****************************************************************************/
204 /*
205  * install a session keyring, discarding the old one
206  * - if a keyring is not supplied, an empty one is invented
207  */
208 static int install_session_keyring(struct task_struct *tsk,
209                                    struct key *keyring)
210 {
211         unsigned long flags;
212         struct key *old;
213         char buf[20];
214         int ret;
215
216         /* create an empty session keyring */
217         if (!keyring) {
218                 sprintf(buf, "_ses.%u", tsk->tgid);
219
220                 keyring = keyring_alloc(buf, tsk->uid, tsk->gid, 1, NULL);
221                 if (IS_ERR(keyring)) {
222                         ret = PTR_ERR(keyring);
223                         goto error;
224                 }
225         }
226         else {
227                 atomic_inc(&keyring->usage);
228         }
229
230         /* install the keyring */
231         spin_lock_irqsave(&tsk->sighand->siglock, flags);
232         old = tsk->signal->session_keyring;
233         tsk->signal->session_keyring = keyring;
234         spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
235
236         ret = 0;
237
238         key_put(old);
239  error:
240         return ret;
241
242 } /* end install_session_keyring() */
243
244 /*****************************************************************************/
245 /*
246  * copy the keys in a thread group for fork without CLONE_THREAD
247  */
248 int copy_thread_group_keys(struct task_struct *tsk)
249 {
250         unsigned long flags;
251
252         key_check(current->thread_group->session_keyring);
253         key_check(current->thread_group->process_keyring);
254
255         /* no process keyring yet */
256         tsk->signal->process_keyring = NULL;
257
258         /* same session keyring */
259         spin_lock_irqsave(&current->sighand->siglock, flags);
260         tsk->signal->session_keyring =
261                 key_get(current->signal->session_keyring);
262         spin_unlock_irqrestore(&current->sighand->siglock, flags);
263
264         return 0;
265
266 } /* end copy_thread_group_keys() */
267
268 /*****************************************************************************/
269 /*
270  * copy the keys for fork
271  */
272 int copy_keys(unsigned long clone_flags, struct task_struct *tsk)
273 {
274         key_check(tsk->thread_keyring);
275
276         /* no thread keyring yet */
277         tsk->thread_keyring = NULL;
278         return 0;
279
280 } /* end copy_keys() */
281
282 /*****************************************************************************/
283 /*
284  * dispose of thread group keys upon thread group destruction
285  */
286 void exit_thread_group_keys(struct signal_struct *tg)
287 {
288         key_put(tg->session_keyring);
289         key_put(tg->process_keyring);
290
291 } /* end exit_thread_group_keys() */
292
293 /*****************************************************************************/
294 /*
295  * dispose of keys upon thread exit
296  */
297 void exit_keys(struct task_struct *tsk)
298 {
299         key_put(tsk->thread_keyring);
300
301 } /* end exit_keys() */
302
303 /*****************************************************************************/
304 /*
305  * deal with execve()
306  */
307 int exec_keys(struct task_struct *tsk)
308 {
309         unsigned long flags;
310         struct key *old;
311
312         /* newly exec'd tasks don't get a thread keyring */
313         task_lock(tsk);
314         old = tsk->thread_keyring;
315         tsk->thread_keyring = NULL;
316         task_unlock(tsk);
317
318         key_put(old);
319
320         /* discard the process keyring from a newly exec'd task */
321         spin_lock_irqsave(&tsk->sighand->siglock, flags);
322         old = tsk->signal->process_keyring;
323         tsk->signal->process_keyring = NULL;
324         spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
325
326         key_put(old);
327
328         return 0;
329
330 } /* end exec_keys() */
331
332 /*****************************************************************************/
333 /*
334  * deal with SUID programs
335  * - we might want to make this invent a new session keyring
336  */
337 int suid_keys(struct task_struct *tsk)
338 {
339         return 0;
340
341 } /* end suid_keys() */
342
343 /*****************************************************************************/
344 /*
345  * the filesystem user ID changed
346  */
347 void key_fsuid_changed(struct task_struct *tsk)
348 {
349         /* update the ownership of the thread keyring */
350         if (tsk->thread_keyring) {
351                 down_write(&tsk->thread_keyring->sem);
352                 write_lock(&tsk->thread_keyring->lock);
353                 tsk->thread_keyring->uid = tsk->fsuid;
354                 write_unlock(&tsk->thread_keyring->lock);
355                 up_write(&tsk->thread_keyring->sem);
356         }
357
358 } /* end key_fsuid_changed() */
359
360 /*****************************************************************************/
361 /*
362  * the filesystem group ID changed
363  */
364 void key_fsgid_changed(struct task_struct *tsk)
365 {
366         /* update the ownership of the thread keyring */
367         if (tsk->thread_keyring) {
368                 down_write(&tsk->thread_keyring->sem);
369                 write_lock(&tsk->thread_keyring->lock);
370                 tsk->thread_keyring->gid = tsk->fsgid;
371                 write_unlock(&tsk->thread_keyring->lock);
372                 up_write(&tsk->thread_keyring->sem);
373         }
374
375 } /* end key_fsgid_changed() */
376
377 /*****************************************************************************/
378 /*
379  * search the process keyrings for the first matching key
380  * - we use the supplied match function to see if the description (or other
381  *   feature of interest) matches
382  * - we return -EAGAIN if we didn't find any matching key
383  * - we return -ENOKEY if we found only negative matching keys
384  */
385 struct key *search_process_keyrings_aux(struct key_type *type,
386                                         const void *description,
387                                         key_match_func_t match)
388 {
389         struct task_struct *tsk = current;
390         unsigned long flags;
391         struct key *key, *ret, *err, *tmp;
392
393         /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were
394          * searchable, but we failed to find a key or we found a negative key;
395          * otherwise we want to return a sample error (probably -EACCES) if
396          * none of the keyrings were searchable
397          *
398          * in terms of priority: success > -ENOKEY > -EAGAIN > other error
399          */
400         key = NULL;
401         ret = NULL;
402         err = ERR_PTR(-EAGAIN);
403
404         /* search the thread keyring first */
405         if (tsk->thread_keyring) {
406                 key = keyring_search_aux(tsk->thread_keyring, type,
407                                          description, match);
408                 if (!IS_ERR(key))
409                         goto found;
410
411                 switch (PTR_ERR(key)) {
412                 case -EAGAIN: /* no key */
413                         if (ret)
414                                 break;
415                 case -ENOKEY: /* negative key */
416                         ret = key;
417                         break;
418                 default:
419                         err = key;
420                         break;
421                 }
422         }
423
424         /* search the process keyring second */
425         if (tsk->signal->process_keyring) {
426                 key = keyring_search_aux(tsk->signal->process_keyring,
427                                          type, description, match);
428                 if (!IS_ERR(key))
429                         goto found;
430
431                 switch (PTR_ERR(key)) {
432                 case -EAGAIN: /* no key */
433                         if (ret)
434                                 break;
435                 case -ENOKEY: /* negative key */
436                         ret = key;
437                         break;
438                 default:
439                         err = key;
440                         break;
441                 }
442         }
443
444         /* search the session keyring last */
445         spin_lock_irqsave(&tsk->sighand->siglock, flags);
446
447         tmp = tsk->signal->session_keyring;
448         if (!tmp)
449                 tmp = tsk->user->session_keyring;
450         atomic_inc(&tmp->usage);
451
452         spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
453
454         key = keyring_search_aux(tmp, type, description, match);
455         key_put(tmp);
456         if (!IS_ERR(key))
457                 goto found;
458
459         switch (PTR_ERR(key)) {
460         case -EAGAIN: /* no key */
461                 if (ret)
462                         break;
463         case -ENOKEY: /* negative key */
464                 ret = key;
465                 break;
466         default:
467                 err = key;
468                 break;
469         }
470
471         /* no key - decide on the error we're going to go for */
472         key = ret ? ret : err;
473
474  found:
475         return key;
476
477 } /* end search_process_keyrings_aux() */
478
479 /*****************************************************************************/
480 /*
481  * search the process keyrings for the first matching key
482  * - we return -EAGAIN if we didn't find any matching key
483  * - we return -ENOKEY if we found only negative matching keys
484  */
485 struct key *search_process_keyrings(struct key_type *type,
486                                     const char *description)
487 {
488         return search_process_keyrings_aux(type, description, type->match);
489
490 } /* end search_process_keyrings() */
491
492 /*****************************************************************************/
493 /*
494  * lookup a key given a key ID from userspace with a given permissions mask
495  * - don't create special keyrings unless so requested
496  * - partially constructed keys aren't found unless requested
497  */
498 struct key *lookup_user_key(key_serial_t id, int create, int partial,
499                             key_perm_t perm)
500 {
501         struct task_struct *tsk = current;
502         unsigned long flags;
503         struct key *key;
504         int ret;
505
506         key = ERR_PTR(-ENOKEY);
507
508         switch (id) {
509         case KEY_SPEC_THREAD_KEYRING:
510                 if (!tsk->thread_keyring) {
511                         if (!create)
512                                 goto error;
513
514                         ret = install_thread_keyring(tsk);
515                         if (ret < 0) {
516                                 key = ERR_PTR(ret);
517                                 goto error;
518                         }
519                 }
520
521                 key = tsk->thread_keyring;
522                 atomic_inc(&key->usage);
523                 break;
524
525         case KEY_SPEC_PROCESS_KEYRING:
526                 if (!tsk->signal->process_keyring) {
527                         if (!create)
528                                 goto error;
529
530                         ret = install_process_keyring(tsk);
531                         if (ret < 0) {
532                                 key = ERR_PTR(ret);
533                                 goto error;
534                         }
535                 }
536
537                 key = tsk->signal->process_keyring;
538                 atomic_inc(&key->usage);
539                 break;
540
541         case KEY_SPEC_SESSION_KEYRING:
542                 if (!tsk->signal->session_keyring) {
543                         /* always install a session keyring upon access if one
544                          * doesn't exist yet */
545                         ret = install_session_keyring(
546                                tsk, tsk->user->session_keyring);
547                         if (ret < 0)
548                                 goto error;
549                 }
550
551                 spin_lock_irqsave(&tsk->sighand->siglock, flags);
552                 key = tsk->signal->session_keyring;
553                 atomic_inc(&key->usage);
554                 spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
555                 break;
556
557         case KEY_SPEC_USER_KEYRING:
558                 key = tsk->user->uid_keyring;
559                 atomic_inc(&key->usage);
560                 break;
561
562         case KEY_SPEC_USER_SESSION_KEYRING:
563                 key = tsk->user->session_keyring;
564                 atomic_inc(&key->usage);
565                 break;
566
567         case KEY_SPEC_GROUP_KEYRING:
568                 /* group keyrings are not yet supported */
569                 key = ERR_PTR(-EINVAL);
570                 goto error;
571
572         default:
573                 key = ERR_PTR(-EINVAL);
574                 if (id < 1)
575                         goto error;
576
577                 key = key_lookup(id);
578                 if (IS_ERR(key))
579                         goto error;
580                 break;
581         }
582
583         /* check the status and permissions */
584         if (perm) {
585                 ret = key_validate(key);
586                 if (ret < 0)
587                         goto invalid_key;
588         }
589
590         ret = -EIO;
591         if (!partial && !(key->flags & KEY_FLAG_INSTANTIATED))
592                 goto invalid_key;
593
594         ret = -EACCES;
595         if (!key_permission(key, perm))
596                 goto invalid_key;
597
598  error:
599         return key;
600
601  invalid_key:
602         key_put(key);
603         key = ERR_PTR(ret);
604         goto error;
605
606 } /* end lookup_user_key() */
607
608 /*****************************************************************************/
609 /*
610  * join the named keyring as the session keyring if possible, or attempt to
611  * create a new one of that name if not
612  * - if the name is NULL, an empty anonymous keyring is installed instead
613  * - named session keyring joining is done with a semaphore held
614  */
615 long join_session_keyring(const char *name)
616 {
617         struct task_struct *tsk = current;
618         unsigned long flags;
619         struct key *keyring;
620         long ret;
621
622         /* if no name is provided, install an anonymous keyring */
623         if (!name) {
624                 ret = install_session_keyring(tsk, NULL);
625                 if (ret < 0)
626                         goto error;
627
628                 spin_lock_irqsave(&tsk->sighand->siglock, flags);
629                 ret = tsk->signal->session_keyring->serial;
630                 spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
631                 goto error;
632         }
633
634         /* allow the user to join or create a named keyring */
635         down(&key_session_sem);
636
637         /* look for an existing keyring of this name */
638         keyring = find_keyring_by_name(name, 0);
639         if (PTR_ERR(keyring) == -ENOKEY) {
640                 /* not found - try and create a new one */
641                 keyring = keyring_alloc(name, tsk->uid, tsk->gid, 0, NULL);
642                 if (IS_ERR(keyring)) {
643                         ret = PTR_ERR(keyring);
644                         goto error;
645                 }
646         }
647         else if (IS_ERR(keyring)) {
648                 ret = PTR_ERR(keyring);
649                 goto error2;
650         }
651
652         /* we've got a keyring - now to install it */
653         ret = install_session_keyring(tsk, keyring);
654         if (ret < 0)
655                 goto error2;
656
657         ret = keyring->serial;
658         key_put(keyring);
659
660  error2:
661         up(&key_session_sem);
662  error:
663         return ret;
664
665 } /* end join_session_keyring() */