KEYS: keyring_serialise_link_sem is only needed for keyring->keyring links
[linux-2.6.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         const struct cred *cred = current_cred();
303         struct key *key;
304         key_ref_t key_ref;
305
306         kenter("%s,%s,,,", type->name, description);
307
308         mutex_lock(&user->cons_lock);
309
310         key = key_alloc(type, description, cred->fsuid, cred->fsgid, cred,
311                         KEY_POS_ALL, flags);
312         if (IS_ERR(key))
313                 goto alloc_failed;
314
315         set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
316
317         if (dest_keyring)
318                 down_write(&dest_keyring->sem);
319
320         /* attach the key to the destination keyring under lock, but we do need
321          * to do another check just in case someone beat us to it whilst we
322          * waited for locks */
323         mutex_lock(&key_construction_mutex);
324
325         key_ref = search_process_keyrings(type, description, type->match, cred);
326         if (!IS_ERR(key_ref))
327                 goto key_already_present;
328
329         if (dest_keyring)
330                 __key_link(dest_keyring, key);
331
332         mutex_unlock(&key_construction_mutex);
333         if (dest_keyring)
334                 up_write(&dest_keyring->sem);
335         mutex_unlock(&user->cons_lock);
336         *_key = key;
337         kleave(" = 0 [%d]", key_serial(key));
338         return 0;
339
340 key_already_present:
341         mutex_unlock(&key_construction_mutex);
342         if (dest_keyring) {
343                 __key_link(dest_keyring, key_ref_to_ptr(key_ref));
344                 up_write(&dest_keyring->sem);
345         }
346         mutex_unlock(&user->cons_lock);
347         key_put(key);
348         *_key = key = key_ref_to_ptr(key_ref);
349         kleave(" = -EINPROGRESS [%d]", key_serial(key));
350         return -EINPROGRESS;
351
352 alloc_failed:
353         mutex_unlock(&user->cons_lock);
354         *_key = NULL;
355         kleave(" = %ld", PTR_ERR(key));
356         return PTR_ERR(key);
357 }
358
359 /*
360  * commence key construction
361  */
362 static struct key *construct_key_and_link(struct key_type *type,
363                                           const char *description,
364                                           const char *callout_info,
365                                           size_t callout_len,
366                                           void *aux,
367                                           struct key *dest_keyring,
368                                           unsigned long flags)
369 {
370         struct key_user *user;
371         struct key *key;
372         int ret;
373
374         kenter("");
375
376         user = key_user_lookup(current_fsuid(), current_user_ns());
377         if (!user)
378                 return ERR_PTR(-ENOMEM);
379
380         construct_get_dest_keyring(&dest_keyring);
381
382         ret = construct_alloc_key(type, description, dest_keyring, flags, user,
383                                   &key);
384         key_user_put(user);
385
386         if (ret == 0) {
387                 ret = construct_key(key, callout_info, callout_len, aux,
388                                     dest_keyring);
389                 if (ret < 0) {
390                         kdebug("cons failed");
391                         goto construction_failed;
392                 }
393         }
394
395         key_put(dest_keyring);
396         kleave(" = key %d", key_serial(key));
397         return key;
398
399 construction_failed:
400         key_negate_and_link(key, key_negative_timeout, NULL, NULL);
401         key_put(key);
402         key_put(dest_keyring);
403         kleave(" = %d", ret);
404         return ERR_PTR(ret);
405 }
406
407 /*
408  * request a key
409  * - search the process's keyrings
410  * - check the list of keys being created or updated
411  * - call out to userspace for a key if supplementary info was provided
412  * - cache the key in an appropriate keyring
413  */
414 struct key *request_key_and_link(struct key_type *type,
415                                  const char *description,
416                                  const void *callout_info,
417                                  size_t callout_len,
418                                  void *aux,
419                                  struct key *dest_keyring,
420                                  unsigned long flags)
421 {
422         const struct cred *cred = current_cred();
423         struct key *key;
424         key_ref_t key_ref;
425
426         kenter("%s,%s,%p,%zu,%p,%p,%lx",
427                type->name, description, callout_info, callout_len, aux,
428                dest_keyring, flags);
429
430         /* search all the process keyrings for a key */
431         key_ref = search_process_keyrings(type, description, type->match,
432                                           cred);
433
434         if (!IS_ERR(key_ref)) {
435                 key = key_ref_to_ptr(key_ref);
436                 if (dest_keyring) {
437                         construct_get_dest_keyring(&dest_keyring);
438                         key_link(dest_keyring, key);
439                         key_put(dest_keyring);
440                 }
441         } else if (PTR_ERR(key_ref) != -EAGAIN) {
442                 key = ERR_CAST(key_ref);
443         } else  {
444                 /* the search failed, but the keyrings were searchable, so we
445                  * should consult userspace if we can */
446                 key = ERR_PTR(-ENOKEY);
447                 if (!callout_info)
448                         goto error;
449
450                 key = construct_key_and_link(type, description, callout_info,
451                                              callout_len, aux, dest_keyring,
452                                              flags);
453         }
454
455 error:
456         kleave(" = %p", key);
457         return key;
458 }
459
460 /*
461  * wait for construction of a key to complete
462  */
463 int wait_for_key_construction(struct key *key, bool intr)
464 {
465         int ret;
466
467         ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
468                           intr ? key_wait_bit_intr : key_wait_bit,
469                           intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
470         if (ret < 0)
471                 return ret;
472         return key_validate(key);
473 }
474 EXPORT_SYMBOL(wait_for_key_construction);
475
476 /*
477  * request a key
478  * - search the process's keyrings
479  * - check the list of keys being created or updated
480  * - call out to userspace for a key if supplementary info was provided
481  * - waits uninterruptible for creation to complete
482  */
483 struct key *request_key(struct key_type *type,
484                         const char *description,
485                         const char *callout_info)
486 {
487         struct key *key;
488         size_t callout_len = 0;
489         int ret;
490
491         if (callout_info)
492                 callout_len = strlen(callout_info);
493         key = request_key_and_link(type, description, callout_info, callout_len,
494                                    NULL, NULL, KEY_ALLOC_IN_QUOTA);
495         if (!IS_ERR(key)) {
496                 ret = wait_for_key_construction(key, false);
497                 if (ret < 0) {
498                         key_put(key);
499                         return ERR_PTR(ret);
500                 }
501         }
502         return key;
503 }
504 EXPORT_SYMBOL(request_key);
505
506 /*
507  * request a key with auxiliary data for the upcaller
508  * - search the process's keyrings
509  * - check the list of keys being created or updated
510  * - call out to userspace for a key if supplementary info was provided
511  * - waits uninterruptible for creation to complete
512  */
513 struct key *request_key_with_auxdata(struct key_type *type,
514                                      const char *description,
515                                      const void *callout_info,
516                                      size_t callout_len,
517                                      void *aux)
518 {
519         struct key *key;
520         int ret;
521
522         key = request_key_and_link(type, description, callout_info, callout_len,
523                                    aux, NULL, KEY_ALLOC_IN_QUOTA);
524         if (!IS_ERR(key)) {
525                 ret = wait_for_key_construction(key, false);
526                 if (ret < 0) {
527                         key_put(key);
528                         return ERR_PTR(ret);
529                 }
530         }
531         return key;
532 }
533 EXPORT_SYMBOL(request_key_with_auxdata);
534
535 /*
536  * request a key (allow async construction)
537  * - search the process's keyrings
538  * - check the list of keys being created or updated
539  * - call out to userspace for a key if supplementary info was provided
540  */
541 struct key *request_key_async(struct key_type *type,
542                               const char *description,
543                               const void *callout_info,
544                               size_t callout_len)
545 {
546         return request_key_and_link(type, description, callout_info,
547                                     callout_len, NULL, NULL,
548                                     KEY_ALLOC_IN_QUOTA);
549 }
550 EXPORT_SYMBOL(request_key_async);
551
552 /*
553  * request a key with auxiliary data for the upcaller (allow async construction)
554  * - search the process's keyrings
555  * - check the list of keys being created or updated
556  * - call out to userspace for a key if supplementary info was provided
557  */
558 struct key *request_key_async_with_auxdata(struct key_type *type,
559                                            const char *description,
560                                            const void *callout_info,
561                                            size_t callout_len,
562                                            void *aux)
563 {
564         return request_key_and_link(type, description, callout_info,
565                                     callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA);
566 }
567 EXPORT_SYMBOL(request_key_async_with_auxdata);