KEYS: Do preallocation for __key_link()
[linux-3.10.git] / security / keys / request_key.c
1 /* Request a key from userspace
2  *
3  * Copyright (C) 2004-2007 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  * See Documentation/keys-request-key.txt
12  */
13
14 #include <linux/module.h>
15 #include <linux/sched.h>
16 #include <linux/kmod.h>
17 #include <linux/err.h>
18 #include <linux/keyctl.h>
19 #include <linux/slab.h>
20 #include "internal.h"
21
22 #define key_negative_timeout    60      /* default timeout on a negative key's existence */
23
24 /*
25  * wait_on_bit() sleep function for uninterruptible waiting
26  */
27 static int key_wait_bit(void *flags)
28 {
29         schedule();
30         return 0;
31 }
32
33 /*
34  * wait_on_bit() sleep function for interruptible waiting
35  */
36 static int key_wait_bit_intr(void *flags)
37 {
38         schedule();
39         return signal_pending(current) ? -ERESTARTSYS : 0;
40 }
41
42 /*
43  * call to complete the construction of a key
44  */
45 void complete_request_key(struct key_construction *cons, int error)
46 {
47         kenter("{%d,%d},%d", cons->key->serial, cons->authkey->serial, error);
48
49         if (error < 0)
50                 key_negate_and_link(cons->key, key_negative_timeout, NULL,
51                                     cons->authkey);
52         else
53                 key_revoke(cons->authkey);
54
55         key_put(cons->key);
56         key_put(cons->authkey);
57         kfree(cons);
58 }
59 EXPORT_SYMBOL(complete_request_key);
60
61 /*
62  * request userspace finish the construction of a key
63  * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
64  */
65 static int call_sbin_request_key(struct key_construction *cons,
66                                  const char *op,
67                                  void *aux)
68 {
69         const struct cred *cred = current_cred();
70         key_serial_t prkey, sskey;
71         struct key *key = cons->key, *authkey = cons->authkey, *keyring,
72                 *session;
73         char *argv[9], *envp[3], uid_str[12], gid_str[12];
74         char key_str[12], keyring_str[3][12];
75         char desc[20];
76         int ret, i;
77
78         kenter("{%d},{%d},%s", key->serial, authkey->serial, op);
79
80         ret = install_user_keyrings();
81         if (ret < 0)
82                 goto error_alloc;
83
84         /* allocate a new session keyring */
85         sprintf(desc, "_req.%u", key->serial);
86
87         cred = get_current_cred();
88         keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred,
89                                 KEY_ALLOC_QUOTA_OVERRUN, NULL);
90         put_cred(cred);
91         if (IS_ERR(keyring)) {
92                 ret = PTR_ERR(keyring);
93                 goto error_alloc;
94         }
95
96         /* attach the auth key to the session keyring */
97         ret = key_link(keyring, authkey);
98         if (ret < 0)
99                 goto error_link;
100
101         /* record the UID and GID */
102         sprintf(uid_str, "%d", cred->fsuid);
103         sprintf(gid_str, "%d", cred->fsgid);
104
105         /* we say which key is under construction */
106         sprintf(key_str, "%d", key->serial);
107
108         /* we specify the process's default keyrings */
109         sprintf(keyring_str[0], "%d",
110                 cred->thread_keyring ? cred->thread_keyring->serial : 0);
111
112         prkey = 0;
113         if (cred->tgcred->process_keyring)
114                 prkey = cred->tgcred->process_keyring->serial;
115
116         rcu_read_lock();
117         session = rcu_dereference(cred->tgcred->session_keyring);
118         if (!session)
119                 session = cred->user->session_keyring;
120         sskey = session->serial;
121         rcu_read_unlock();
122
123         sprintf(keyring_str[2], "%d", sskey);
124
125         /* set up a minimal environment */
126         i = 0;
127         envp[i++] = "HOME=/";
128         envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
129         envp[i] = NULL;
130
131         /* set up the argument list */
132         i = 0;
133         argv[i++] = "/sbin/request-key";
134         argv[i++] = (char *) op;
135         argv[i++] = key_str;
136         argv[i++] = uid_str;
137         argv[i++] = gid_str;
138         argv[i++] = keyring_str[0];
139         argv[i++] = keyring_str[1];
140         argv[i++] = keyring_str[2];
141         argv[i] = NULL;
142
143         /* do it */
144         ret = call_usermodehelper_keys(argv[0], argv, envp, keyring,
145                                        UMH_WAIT_PROC);
146         kdebug("usermode -> 0x%x", ret);
147         if (ret >= 0) {
148                 /* ret is the exit/wait code */
149                 if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
150                     key_validate(key) < 0)
151                         ret = -ENOKEY;
152                 else
153                         /* ignore any errors from userspace if the key was
154                          * instantiated */
155                         ret = 0;
156         }
157
158 error_link:
159         key_put(keyring);
160
161 error_alloc:
162         complete_request_key(cons, ret);
163         kleave(" = %d", ret);
164         return ret;
165 }
166
167 /*
168  * call out to userspace for key construction
169  * - we ignore program failure and go on key status instead
170  */
171 static int construct_key(struct key *key, const void *callout_info,
172                          size_t callout_len, void *aux,
173                          struct key *dest_keyring)
174 {
175         struct key_construction *cons;
176         request_key_actor_t actor;
177         struct key *authkey;
178         int ret;
179
180         kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);
181
182         cons = kmalloc(sizeof(*cons), GFP_KERNEL);
183         if (!cons)
184                 return -ENOMEM;
185
186         /* allocate an authorisation key */
187         authkey = request_key_auth_new(key, callout_info, callout_len,
188                                        dest_keyring);
189         if (IS_ERR(authkey)) {
190                 kfree(cons);
191                 ret = PTR_ERR(authkey);
192                 authkey = NULL;
193         } else {
194                 cons->authkey = key_get(authkey);
195                 cons->key = key_get(key);
196
197                 /* make the call */
198                 actor = call_sbin_request_key;
199                 if (key->type->request_key)
200                         actor = key->type->request_key;
201
202                 ret = actor(cons, "create", aux);
203
204                 /* check that the actor called complete_request_key() prior to
205                  * returning an error */
206                 WARN_ON(ret < 0 &&
207                         !test_bit(KEY_FLAG_REVOKED, &authkey->flags));
208                 key_put(authkey);
209         }
210
211         kleave(" = %d", ret);
212         return ret;
213 }
214
215 /*
216  * get the appropriate destination keyring for the request
217  * - we return whatever keyring we select with an extra reference upon it which
218  *   the caller must release
219  */
220 static void construct_get_dest_keyring(struct key **_dest_keyring)
221 {
222         struct request_key_auth *rka;
223         const struct cred *cred = current_cred();
224         struct key *dest_keyring = *_dest_keyring, *authkey;
225
226         kenter("%p", dest_keyring);
227
228         /* find the appropriate keyring */
229         if (dest_keyring) {
230                 /* the caller supplied one */
231                 key_get(dest_keyring);
232         } else {
233                 /* use a default keyring; falling through the cases until we
234                  * find one that we actually have */
235                 switch (cred->jit_keyring) {
236                 case KEY_REQKEY_DEFL_DEFAULT:
237                 case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
238                         if (cred->request_key_auth) {
239                                 authkey = cred->request_key_auth;
240                                 down_read(&authkey->sem);
241                                 rka = authkey->payload.data;
242                                 if (!test_bit(KEY_FLAG_REVOKED,
243                                               &authkey->flags))
244                                         dest_keyring =
245                                                 key_get(rka->dest_keyring);
246                                 up_read(&authkey->sem);
247                                 if (dest_keyring)
248                                         break;
249                         }
250
251                 case KEY_REQKEY_DEFL_THREAD_KEYRING:
252                         dest_keyring = key_get(cred->thread_keyring);
253                         if (dest_keyring)
254                                 break;
255
256                 case KEY_REQKEY_DEFL_PROCESS_KEYRING:
257                         dest_keyring = key_get(cred->tgcred->process_keyring);
258                         if (dest_keyring)
259                                 break;
260
261                 case KEY_REQKEY_DEFL_SESSION_KEYRING:
262                         rcu_read_lock();
263                         dest_keyring = key_get(
264                                 rcu_dereference(cred->tgcred->session_keyring));
265                         rcu_read_unlock();
266
267                         if (dest_keyring)
268                                 break;
269
270                 case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
271                         dest_keyring =
272                                 key_get(cred->user->session_keyring);
273                         break;
274
275                 case KEY_REQKEY_DEFL_USER_KEYRING:
276                         dest_keyring = key_get(cred->user->uid_keyring);
277                         break;
278
279                 case KEY_REQKEY_DEFL_GROUP_KEYRING:
280                 default:
281                         BUG();
282                 }
283         }
284
285         *_dest_keyring = dest_keyring;
286         kleave(" [dk %d]", key_serial(dest_keyring));
287         return;
288 }
289
290 /*
291  * allocate a new key in under-construction state and attempt to link it in to
292  * the requested place
293  * - may return a key that's already under construction instead
294  */
295 static int construct_alloc_key(struct key_type *type,
296                                const char *description,
297                                struct key *dest_keyring,
298                                unsigned long flags,
299                                struct key_user *user,
300                                struct key **_key)
301 {
302         struct keyring_list *prealloc;
303         const struct cred *cred = current_cred();
304         struct key *key;
305         key_ref_t key_ref;
306         int ret;
307
308         kenter("%s,%s,,,", type->name, description);
309
310         *_key = NULL;
311         mutex_lock(&user->cons_lock);
312
313         key = key_alloc(type, description, cred->fsuid, cred->fsgid, cred,
314                         KEY_POS_ALL, flags);
315         if (IS_ERR(key))
316                 goto alloc_failed;
317
318         set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
319
320         if (dest_keyring) {
321                 ret = __key_link_begin(dest_keyring, type, description,
322                                        &prealloc);
323                 if (ret < 0)
324                         goto link_prealloc_failed;
325         }
326
327         /* attach the key to the destination keyring under lock, but we do need
328          * to do another check just in case someone beat us to it whilst we
329          * waited for locks */
330         mutex_lock(&key_construction_mutex);
331
332         key_ref = search_process_keyrings(type, description, type->match, cred);
333         if (!IS_ERR(key_ref))
334                 goto key_already_present;
335
336         if (dest_keyring)
337                 __key_link(dest_keyring, key, &prealloc);
338
339         mutex_unlock(&key_construction_mutex);
340         if (dest_keyring)
341                 __key_link_end(dest_keyring, type, prealloc);
342         mutex_unlock(&user->cons_lock);
343         *_key = key;
344         kleave(" = 0 [%d]", key_serial(key));
345         return 0;
346
347         /* the key is now present - we tell the caller that we found it by
348          * returning -EINPROGRESS  */
349 key_already_present:
350         key_put(key);
351         mutex_unlock(&key_construction_mutex);
352         key = key_ref_to_ptr(key_ref);
353         if (dest_keyring) {
354                 ret = __key_link_check_live_key(dest_keyring, key);
355                 if (ret == 0)
356                         __key_link(dest_keyring, key, &prealloc);
357                 __key_link_end(dest_keyring, type, prealloc);
358                 if (ret < 0)
359                         goto link_check_failed;
360         }
361         mutex_unlock(&user->cons_lock);
362         *_key = key;
363         kleave(" = -EINPROGRESS [%d]", key_serial(key));
364         return -EINPROGRESS;
365
366 link_check_failed:
367         mutex_unlock(&user->cons_lock);
368         key_put(key);
369         kleave(" = %d [linkcheck]", ret);
370         return ret;
371
372 link_prealloc_failed:
373         up_write(&dest_keyring->sem);
374         mutex_unlock(&user->cons_lock);
375         kleave(" = %d [prelink]", ret);
376         return ret;
377
378 alloc_failed:
379         mutex_unlock(&user->cons_lock);
380         kleave(" = %ld", PTR_ERR(key));
381         return PTR_ERR(key);
382 }
383
384 /*
385  * commence key construction
386  */
387 static struct key *construct_key_and_link(struct key_type *type,
388                                           const char *description,
389                                           const char *callout_info,
390                                           size_t callout_len,
391                                           void *aux,
392                                           struct key *dest_keyring,
393                                           unsigned long flags)
394 {
395         struct key_user *user;
396         struct key *key;
397         int ret;
398
399         kenter("");
400
401         user = key_user_lookup(current_fsuid(), current_user_ns());
402         if (!user)
403                 return ERR_PTR(-ENOMEM);
404
405         construct_get_dest_keyring(&dest_keyring);
406
407         ret = construct_alloc_key(type, description, dest_keyring, flags, user,
408                                   &key);
409         key_user_put(user);
410
411         if (ret == 0) {
412                 ret = construct_key(key, callout_info, callout_len, aux,
413                                     dest_keyring);
414                 if (ret < 0) {
415                         kdebug("cons failed");
416                         goto construction_failed;
417                 }
418         } else if (ret == -EINPROGRESS) {
419                 ret = 0;
420         } else {
421                 key = ERR_PTR(ret);
422         }
423
424         key_put(dest_keyring);
425         kleave(" = key %d", key_serial(key));
426         return key;
427
428 construction_failed:
429         key_negate_and_link(key, key_negative_timeout, NULL, NULL);
430         key_put(key);
431         key_put(dest_keyring);
432         kleave(" = %d", ret);
433         return ERR_PTR(ret);
434 }
435
436 /*
437  * request a key
438  * - search the process's keyrings
439  * - check the list of keys being created or updated
440  * - call out to userspace for a key if supplementary info was provided
441  * - cache the key in an appropriate keyring
442  */
443 struct key *request_key_and_link(struct key_type *type,
444                                  const char *description,
445                                  const void *callout_info,
446                                  size_t callout_len,
447                                  void *aux,
448                                  struct key *dest_keyring,
449                                  unsigned long flags)
450 {
451         const struct cred *cred = current_cred();
452         struct key *key;
453         key_ref_t key_ref;
454         int ret;
455
456         kenter("%s,%s,%p,%zu,%p,%p,%lx",
457                type->name, description, callout_info, callout_len, aux,
458                dest_keyring, flags);
459
460         /* search all the process keyrings for a key */
461         key_ref = search_process_keyrings(type, description, type->match,
462                                           cred);
463
464         if (!IS_ERR(key_ref)) {
465                 key = key_ref_to_ptr(key_ref);
466                 if (dest_keyring) {
467                         construct_get_dest_keyring(&dest_keyring);
468                         ret = key_link(dest_keyring, key);
469                         key_put(dest_keyring);
470                         if (ret < 0) {
471                                 key_put(key);
472                                 key = ERR_PTR(ret);
473                                 goto error;
474                         }
475                 }
476         } else if (PTR_ERR(key_ref) != -EAGAIN) {
477                 key = ERR_CAST(key_ref);
478         } else  {
479                 /* the search failed, but the keyrings were searchable, so we
480                  * should consult userspace if we can */
481                 key = ERR_PTR(-ENOKEY);
482                 if (!callout_info)
483                         goto error;
484
485                 key = construct_key_and_link(type, description, callout_info,
486                                              callout_len, aux, dest_keyring,
487                                              flags);
488         }
489
490 error:
491         kleave(" = %p", key);
492         return key;
493 }
494
495 /*
496  * wait for construction of a key to complete
497  */
498 int wait_for_key_construction(struct key *key, bool intr)
499 {
500         int ret;
501
502         ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
503                           intr ? key_wait_bit_intr : key_wait_bit,
504                           intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
505         if (ret < 0)
506                 return ret;
507         return key_validate(key);
508 }
509 EXPORT_SYMBOL(wait_for_key_construction);
510
511 /*
512  * request a key
513  * - search the process's keyrings
514  * - check the list of keys being created or updated
515  * - call out to userspace for a key if supplementary info was provided
516  * - waits uninterruptible for creation to complete
517  */
518 struct key *request_key(struct key_type *type,
519                         const char *description,
520                         const char *callout_info)
521 {
522         struct key *key;
523         size_t callout_len = 0;
524         int ret;
525
526         if (callout_info)
527                 callout_len = strlen(callout_info);
528         key = request_key_and_link(type, description, callout_info, callout_len,
529                                    NULL, NULL, KEY_ALLOC_IN_QUOTA);
530         if (!IS_ERR(key)) {
531                 ret = wait_for_key_construction(key, false);
532                 if (ret < 0) {
533                         key_put(key);
534                         return ERR_PTR(ret);
535                 }
536         }
537         return key;
538 }
539 EXPORT_SYMBOL(request_key);
540
541 /*
542  * request a key with auxiliary data for the upcaller
543  * - search the process's keyrings
544  * - check the list of keys being created or updated
545  * - call out to userspace for a key if supplementary info was provided
546  * - waits uninterruptible for creation to complete
547  */
548 struct key *request_key_with_auxdata(struct key_type *type,
549                                      const char *description,
550                                      const void *callout_info,
551                                      size_t callout_len,
552                                      void *aux)
553 {
554         struct key *key;
555         int ret;
556
557         key = request_key_and_link(type, description, callout_info, callout_len,
558                                    aux, NULL, KEY_ALLOC_IN_QUOTA);
559         if (!IS_ERR(key)) {
560                 ret = wait_for_key_construction(key, false);
561                 if (ret < 0) {
562                         key_put(key);
563                         return ERR_PTR(ret);
564                 }
565         }
566         return key;
567 }
568 EXPORT_SYMBOL(request_key_with_auxdata);
569
570 /*
571  * request a key (allow async construction)
572  * - search the process's keyrings
573  * - check the list of keys being created or updated
574  * - call out to userspace for a key if supplementary info was provided
575  */
576 struct key *request_key_async(struct key_type *type,
577                               const char *description,
578                               const void *callout_info,
579                               size_t callout_len)
580 {
581         return request_key_and_link(type, description, callout_info,
582                                     callout_len, NULL, NULL,
583                                     KEY_ALLOC_IN_QUOTA);
584 }
585 EXPORT_SYMBOL(request_key_async);
586
587 /*
588  * request a key with auxiliary data for the upcaller (allow async construction)
589  * - search the process's keyrings
590  * - check the list of keys being created or updated
591  * - call out to userspace for a key if supplementary info was provided
592  */
593 struct key *request_key_async_with_auxdata(struct key_type *type,
594                                            const char *description,
595                                            const void *callout_info,
596                                            size_t callout_len,
597                                            void *aux)
598 {
599         return request_key_and_link(type, description, callout_info,
600                                     callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
601 }
602 EXPORT_SYMBOL(request_key_async_with_auxdata);