1 /* Request a key from userspace
3 * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
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.
11 * See Documentation/security/keys/request-key.rst
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>
21 #include <keys/request_key_auth-type.h>
23 #define key_negative_timeout 60 /* default timeout on a negative key's existence */
26 * complete_request_key - Complete the construction of a key.
27 * @auth_key: The authorisation key.
28 * @error: The success or failute of the construction.
30 * Complete the attempt to construct a key. The key will be negated
31 * if an error is indicated. The authorisation key will be revoked
34 void complete_request_key(struct key
*authkey
, int error
)
36 struct request_key_auth
*rka
= get_request_key_auth(authkey
);
37 struct key
*key
= rka
->target_key
;
39 kenter("%d{%d},%d", authkey
->serial
, key
->serial
, error
);
42 key_negate_and_link(key
, key_negative_timeout
, NULL
, authkey
);
46 EXPORT_SYMBOL(complete_request_key
);
49 * Initialise a usermode helper that is going to have a specific session
52 * This is called in context of freshly forked kthread before kernel_execve(),
53 * so we can simply install the desired session_keyring at this point.
55 static int umh_keys_init(struct subprocess_info
*info
, struct cred
*cred
)
57 struct key
*keyring
= info
->data
;
59 return install_session_keyring_to_cred(cred
, keyring
);
63 * Clean up a usermode helper with session keyring.
65 static void umh_keys_cleanup(struct subprocess_info
*info
)
67 struct key
*keyring
= info
->data
;
72 * Call a usermode helper with a specific session keyring.
74 static int call_usermodehelper_keys(const char *path
, char **argv
, char **envp
,
75 struct key
*session_keyring
, int wait
)
77 struct subprocess_info
*info
;
79 info
= call_usermodehelper_setup(path
, argv
, envp
, GFP_KERNEL
,
80 umh_keys_init
, umh_keys_cleanup
,
85 key_get(session_keyring
);
86 return call_usermodehelper_exec(info
, wait
);
90 * Request userspace finish the construction of a key
91 * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
93 static int call_sbin_request_key(struct key
*authkey
, void *aux
)
95 static char const request_key
[] = "/sbin/request-key";
96 struct request_key_auth
*rka
= get_request_key_auth(authkey
);
97 const struct cred
*cred
= current_cred();
98 key_serial_t prkey
, sskey
;
99 struct key
*key
= rka
->target_key
, *keyring
, *session
;
100 char *argv
[9], *envp
[3], uid_str
[12], gid_str
[12];
101 char key_str
[12], keyring_str
[3][12];
105 kenter("{%d},{%d},%s", key
->serial
, authkey
->serial
, rka
->op
);
107 ret
= install_user_keyrings();
111 /* allocate a new session keyring */
112 sprintf(desc
, "_req.%u", key
->serial
);
114 cred
= get_current_cred();
115 keyring
= keyring_alloc(desc
, cred
->fsuid
, cred
->fsgid
, cred
,
116 KEY_POS_ALL
| KEY_USR_VIEW
| KEY_USR_READ
,
117 KEY_ALLOC_QUOTA_OVERRUN
, NULL
, NULL
);
119 if (IS_ERR(keyring
)) {
120 ret
= PTR_ERR(keyring
);
124 /* attach the auth key to the session keyring */
125 ret
= key_link(keyring
, authkey
);
129 /* record the UID and GID */
130 sprintf(uid_str
, "%d", from_kuid(&init_user_ns
, cred
->fsuid
));
131 sprintf(gid_str
, "%d", from_kgid(&init_user_ns
, cred
->fsgid
));
133 /* we say which key is under construction */
134 sprintf(key_str
, "%d", key
->serial
);
136 /* we specify the process's default keyrings */
137 sprintf(keyring_str
[0], "%d",
138 cred
->thread_keyring
? cred
->thread_keyring
->serial
: 0);
141 if (cred
->process_keyring
)
142 prkey
= cred
->process_keyring
->serial
;
143 sprintf(keyring_str
[1], "%d", prkey
);
146 session
= rcu_dereference(cred
->session_keyring
);
148 session
= cred
->user
->session_keyring
;
149 sskey
= session
->serial
;
152 sprintf(keyring_str
[2], "%d", sskey
);
154 /* set up a minimal environment */
156 envp
[i
++] = "HOME=/";
157 envp
[i
++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
160 /* set up the argument list */
162 argv
[i
++] = (char *)request_key
;
163 argv
[i
++] = (char *)rka
->op
;
167 argv
[i
++] = keyring_str
[0];
168 argv
[i
++] = keyring_str
[1];
169 argv
[i
++] = keyring_str
[2];
173 ret
= call_usermodehelper_keys(request_key
, argv
, envp
, keyring
,
175 kdebug("usermode -> 0x%x", ret
);
177 /* ret is the exit/wait code */
178 if (test_bit(KEY_FLAG_USER_CONSTRUCT
, &key
->flags
) ||
179 key_validate(key
) < 0)
182 /* ignore any errors from userspace if the key was
191 complete_request_key(authkey
, ret
);
192 kleave(" = %d", ret
);
197 * Call out to userspace for key construction.
199 * Program failure is ignored in favour of key status.
201 static int construct_key(struct key
*key
, const void *callout_info
,
202 size_t callout_len
, void *aux
,
203 struct key
*dest_keyring
)
205 request_key_actor_t actor
;
209 kenter("%d,%p,%zu,%p", key
->serial
, callout_info
, callout_len
, aux
);
211 /* allocate an authorisation key */
212 authkey
= request_key_auth_new(key
, "create", callout_info
, callout_len
,
215 return PTR_ERR(authkey
);
218 actor
= call_sbin_request_key
;
219 if (key
->type
->request_key
)
220 actor
= key
->type
->request_key
;
222 ret
= actor(authkey
, aux
);
224 /* check that the actor called complete_request_key() prior to
225 * returning an error */
227 !test_bit(KEY_FLAG_REVOKED
, &authkey
->flags
));
230 kleave(" = %d", ret
);
235 * Get the appropriate destination keyring for the request.
237 * The keyring selected is returned with an extra reference upon it which the
238 * caller must release.
240 static int construct_get_dest_keyring(struct key
**_dest_keyring
)
242 struct request_key_auth
*rka
;
243 const struct cred
*cred
= current_cred();
244 struct key
*dest_keyring
= *_dest_keyring
, *authkey
;
247 kenter("%p", dest_keyring
);
249 /* find the appropriate keyring */
251 /* the caller supplied one */
252 key_get(dest_keyring
);
254 bool do_perm_check
= true;
256 /* use a default keyring; falling through the cases until we
257 * find one that we actually have */
258 switch (cred
->jit_keyring
) {
259 case KEY_REQKEY_DEFL_DEFAULT
:
260 case KEY_REQKEY_DEFL_REQUESTOR_KEYRING
:
261 if (cred
->request_key_auth
) {
262 authkey
= cred
->request_key_auth
;
263 down_read(&authkey
->sem
);
264 rka
= get_request_key_auth(authkey
);
265 if (!test_bit(KEY_FLAG_REVOKED
,
268 key_get(rka
->dest_keyring
);
269 up_read(&authkey
->sem
);
271 do_perm_check
= false;
276 case KEY_REQKEY_DEFL_THREAD_KEYRING
:
277 dest_keyring
= key_get(cred
->thread_keyring
);
281 case KEY_REQKEY_DEFL_PROCESS_KEYRING
:
282 dest_keyring
= key_get(cred
->process_keyring
);
286 case KEY_REQKEY_DEFL_SESSION_KEYRING
:
288 dest_keyring
= key_get(
289 rcu_dereference(cred
->session_keyring
));
295 case KEY_REQKEY_DEFL_USER_SESSION_KEYRING
:
297 key_get(cred
->user
->session_keyring
);
300 case KEY_REQKEY_DEFL_USER_KEYRING
:
301 dest_keyring
= key_get(cred
->user
->uid_keyring
);
304 case KEY_REQKEY_DEFL_GROUP_KEYRING
:
310 * Require Write permission on the keyring. This is essential
311 * because the default keyring may be the session keyring, and
312 * joining a keyring only requires Search permission.
314 * However, this check is skipped for the "requestor keyring" so
315 * that /sbin/request-key can itself use request_key() to add
316 * keys to the original requestor's destination keyring.
318 if (dest_keyring
&& do_perm_check
) {
319 ret
= key_permission(make_key_ref(dest_keyring
, 1),
322 key_put(dest_keyring
);
328 *_dest_keyring
= dest_keyring
;
329 kleave(" [dk %d]", key_serial(dest_keyring
));
334 * Allocate a new key in under-construction state and attempt to link it in to
335 * the requested keyring.
337 * May return a key that's already under construction instead if there was a
338 * race between two thread calling request_key().
340 static int construct_alloc_key(struct keyring_search_context
*ctx
,
341 struct key
*dest_keyring
,
343 struct key_user
*user
,
346 struct assoc_array_edit
*edit
;
353 ctx
->index_key
.type
->name
, ctx
->index_key
.description
);
356 mutex_lock(&user
->cons_lock
);
358 perm
= KEY_POS_VIEW
| KEY_POS_SEARCH
| KEY_POS_LINK
| KEY_POS_SETATTR
;
359 perm
|= KEY_USR_VIEW
;
360 if (ctx
->index_key
.type
->read
)
361 perm
|= KEY_POS_READ
;
362 if (ctx
->index_key
.type
== &key_type_keyring
||
363 ctx
->index_key
.type
->update
)
364 perm
|= KEY_POS_WRITE
;
366 key
= key_alloc(ctx
->index_key
.type
, ctx
->index_key
.description
,
367 ctx
->cred
->fsuid
, ctx
->cred
->fsgid
, ctx
->cred
,
372 set_bit(KEY_FLAG_USER_CONSTRUCT
, &key
->flags
);
375 ret
= __key_link_begin(dest_keyring
, &ctx
->index_key
, &edit
);
377 goto link_prealloc_failed
;
380 /* attach the key to the destination keyring under lock, but we do need
381 * to do another check just in case someone beat us to it whilst we
382 * waited for locks */
383 mutex_lock(&key_construction_mutex
);
385 key_ref
= search_process_keyrings(ctx
);
386 if (!IS_ERR(key_ref
))
387 goto key_already_present
;
390 __key_link(key
, &edit
);
392 mutex_unlock(&key_construction_mutex
);
394 __key_link_end(dest_keyring
, &ctx
->index_key
, edit
);
395 mutex_unlock(&user
->cons_lock
);
397 kleave(" = 0 [%d]", key_serial(key
));
400 /* the key is now present - we tell the caller that we found it by
401 * returning -EINPROGRESS */
404 mutex_unlock(&key_construction_mutex
);
405 key
= key_ref_to_ptr(key_ref
);
407 ret
= __key_link_check_live_key(dest_keyring
, key
);
409 __key_link(key
, &edit
);
410 __key_link_end(dest_keyring
, &ctx
->index_key
, edit
);
412 goto link_check_failed
;
414 mutex_unlock(&user
->cons_lock
);
416 kleave(" = -EINPROGRESS [%d]", key_serial(key
));
420 mutex_unlock(&user
->cons_lock
);
422 kleave(" = %d [linkcheck]", ret
);
425 link_prealloc_failed
:
426 mutex_unlock(&user
->cons_lock
);
428 kleave(" = %d [prelink]", ret
);
432 mutex_unlock(&user
->cons_lock
);
433 kleave(" = %ld", PTR_ERR(key
));
438 * Commence key construction.
440 static struct key
*construct_key_and_link(struct keyring_search_context
*ctx
,
441 const char *callout_info
,
444 struct key
*dest_keyring
,
447 struct key_user
*user
;
453 if (ctx
->index_key
.type
== &key_type_keyring
)
454 return ERR_PTR(-EPERM
);
456 ret
= construct_get_dest_keyring(&dest_keyring
);
460 user
= key_user_lookup(current_fsuid());
463 goto error_put_dest_keyring
;
466 ret
= construct_alloc_key(ctx
, dest_keyring
, flags
, user
, &key
);
470 ret
= construct_key(key
, callout_info
, callout_len
, aux
,
473 kdebug("cons failed");
474 goto construction_failed
;
476 } else if (ret
== -EINPROGRESS
) {
479 goto error_put_dest_keyring
;
482 key_put(dest_keyring
);
483 kleave(" = key %d", key_serial(key
));
487 key_negate_and_link(key
, key_negative_timeout
, NULL
, NULL
);
489 error_put_dest_keyring
:
490 key_put(dest_keyring
);
492 kleave(" = %d", ret
);
497 * request_key_and_link - Request a key and cache it in a keyring.
498 * @type: The type of key we want.
499 * @description: The searchable description of the key.
500 * @callout_info: The data to pass to the instantiation upcall (or NULL).
501 * @callout_len: The length of callout_info.
502 * @aux: Auxiliary data for the upcall.
503 * @dest_keyring: Where to cache the key.
504 * @flags: Flags to key_alloc().
506 * A key matching the specified criteria is searched for in the process's
507 * keyrings and returned with its usage count incremented if found. Otherwise,
508 * if callout_info is not NULL, a key will be allocated and some service
509 * (probably in userspace) will be asked to instantiate it.
511 * If successfully found or created, the key will be linked to the destination
512 * keyring if one is provided.
514 * Returns a pointer to the key if successful; -EACCES, -ENOKEY, -EKEYREVOKED
515 * or -EKEYEXPIRED if an inaccessible, negative, revoked or expired key was
516 * found; -ENOKEY if no key was found and no @callout_info was given; -EDQUOT
517 * if insufficient key quota was available to create a new key; or -ENOMEM if
518 * insufficient memory was available.
520 * If the returned key was created, then it may still be under construction,
521 * and wait_for_key_construction() should be used to wait for that to complete.
523 struct key
*request_key_and_link(struct key_type
*type
,
524 const char *description
,
525 const void *callout_info
,
528 struct key
*dest_keyring
,
531 struct keyring_search_context ctx
= {
532 .index_key
.type
= type
,
533 .index_key
.description
= description
,
534 .index_key
.desc_len
= strlen(description
),
535 .cred
= current_cred(),
536 .match_data
.cmp
= key_default_cmp
,
537 .match_data
.raw_data
= description
,
538 .match_data
.lookup_type
= KEYRING_SEARCH_LOOKUP_DIRECT
,
539 .flags
= (KEYRING_SEARCH_DO_STATE_CHECK
|
540 KEYRING_SEARCH_SKIP_EXPIRED
),
546 kenter("%s,%s,%p,%zu,%p,%p,%lx",
547 ctx
.index_key
.type
->name
, ctx
.index_key
.description
,
548 callout_info
, callout_len
, aux
, dest_keyring
, flags
);
550 if (type
->match_preparse
) {
551 ret
= type
->match_preparse(&ctx
.match_data
);
558 /* search all the process keyrings for a key */
559 key_ref
= search_process_keyrings(&ctx
);
561 if (!IS_ERR(key_ref
)) {
562 key
= key_ref_to_ptr(key_ref
);
564 ret
= key_link(dest_keyring
, key
);
571 } else if (PTR_ERR(key_ref
) != -EAGAIN
) {
572 key
= ERR_CAST(key_ref
);
574 /* the search failed, but the keyrings were searchable, so we
575 * should consult userspace if we can */
576 key
= ERR_PTR(-ENOKEY
);
580 key
= construct_key_and_link(&ctx
, callout_info
, callout_len
,
581 aux
, dest_keyring
, flags
);
585 if (type
->match_free
)
586 type
->match_free(&ctx
.match_data
);
588 kleave(" = %p", key
);
593 * wait_for_key_construction - Wait for construction of a key to complete
594 * @key: The key being waited for.
595 * @intr: Whether to wait interruptibly.
597 * Wait for a key to finish being constructed.
599 * Returns 0 if successful; -ERESTARTSYS if the wait was interrupted; -ENOKEY
600 * if the key was negated; or -EKEYREVOKED or -EKEYEXPIRED if the key was
601 * revoked or expired.
603 int wait_for_key_construction(struct key
*key
, bool intr
)
607 ret
= wait_on_bit(&key
->flags
, KEY_FLAG_USER_CONSTRUCT
,
608 intr
? TASK_INTERRUPTIBLE
: TASK_UNINTERRUPTIBLE
);
611 ret
= key_read_state(key
);
614 return key_validate(key
);
616 EXPORT_SYMBOL(wait_for_key_construction
);
619 * request_key - Request a key and wait for construction
620 * @type: Type of key.
621 * @description: The searchable description of the key.
622 * @callout_info: The data to pass to the instantiation upcall (or NULL).
624 * As for request_key_and_link() except that it does not add the returned key
625 * to a keyring if found, new keys are always allocated in the user's quota,
626 * the callout_info must be a NUL-terminated string and no auxiliary data can
629 * Furthermore, it then works as wait_for_key_construction() to wait for the
630 * completion of keys undergoing construction with a non-interruptible wait.
632 struct key
*request_key(struct key_type
*type
,
633 const char *description
,
634 const char *callout_info
)
637 size_t callout_len
= 0;
641 callout_len
= strlen(callout_info
);
642 key
= request_key_and_link(type
, description
, callout_info
, callout_len
,
643 NULL
, NULL
, KEY_ALLOC_IN_QUOTA
);
645 ret
= wait_for_key_construction(key
, false);
653 EXPORT_SYMBOL(request_key
);
656 * request_key_with_auxdata - Request a key with auxiliary data for the upcaller
657 * @type: The type of key we want.
658 * @description: The searchable description of the key.
659 * @callout_info: The data to pass to the instantiation upcall (or NULL).
660 * @callout_len: The length of callout_info.
661 * @aux: Auxiliary data for the upcall.
663 * As for request_key_and_link() except that it does not add the returned key
664 * to a keyring if found and new keys are always allocated in the user's quota.
666 * Furthermore, it then works as wait_for_key_construction() to wait for the
667 * completion of keys undergoing construction with a non-interruptible wait.
669 struct key
*request_key_with_auxdata(struct key_type
*type
,
670 const char *description
,
671 const void *callout_info
,
678 key
= request_key_and_link(type
, description
, callout_info
, callout_len
,
679 aux
, NULL
, KEY_ALLOC_IN_QUOTA
);
681 ret
= wait_for_key_construction(key
, false);
689 EXPORT_SYMBOL(request_key_with_auxdata
);
692 * request_key_async - Request a key (allow async construction)
693 * @type: Type of key.
694 * @description: The searchable description of the key.
695 * @callout_info: The data to pass to the instantiation upcall (or NULL).
696 * @callout_len: The length of callout_info.
698 * As for request_key_and_link() except that it does not add the returned key
699 * to a keyring if found, new keys are always allocated in the user's quota and
700 * no auxiliary data can be passed.
702 * The caller should call wait_for_key_construction() to wait for the
703 * completion of the returned key if it is still undergoing construction.
705 struct key
*request_key_async(struct key_type
*type
,
706 const char *description
,
707 const void *callout_info
,
710 return request_key_and_link(type
, description
, callout_info
,
711 callout_len
, NULL
, NULL
,
714 EXPORT_SYMBOL(request_key_async
);
717 * request a key with auxiliary data for the upcaller (allow async construction)
718 * @type: Type of key.
719 * @description: The searchable description of the key.
720 * @callout_info: The data to pass to the instantiation upcall (or NULL).
721 * @callout_len: The length of callout_info.
722 * @aux: Auxiliary data for the upcall.
724 * As for request_key_and_link() except that it does not add the returned key
725 * to a keyring if found and new keys are always allocated in the user's quota.
727 * The caller should call wait_for_key_construction() to wait for the
728 * completion of the returned key if it is still undergoing construction.
730 struct key
*request_key_async_with_auxdata(struct key_type
*type
,
731 const char *description
,
732 const void *callout_info
,
736 return request_key_and_link(type
, description
, callout_info
,
737 callout_len
, aux
, NULL
, KEY_ALLOC_IN_QUOTA
);
739 EXPORT_SYMBOL(request_key_async_with_auxdata
);