xref: /openbmc/linux/security/keys/request_key.c (revision d5590152)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Request a key from userspace
3  *
4  * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
5  * Written by David Howells (dhowells@redhat.com)
6  *
7  * See Documentation/security/keys/request-key.rst
8  */
9 
10 #include <linux/export.h>
11 #include <linux/sched.h>
12 #include <linux/kmod.h>
13 #include <linux/err.h>
14 #include <linux/keyctl.h>
15 #include <linux/slab.h>
16 #include <net/net_namespace.h>
17 #include "internal.h"
18 #include <keys/request_key_auth-type.h>
19 
20 #define key_negative_timeout	60	/* default timeout on a negative key's existence */
21 
check_cached_key(struct keyring_search_context * ctx)22 static struct key *check_cached_key(struct keyring_search_context *ctx)
23 {
24 #ifdef CONFIG_KEYS_REQUEST_CACHE
25 	struct key *key = current->cached_requested_key;
26 
27 	if (key &&
28 	    ctx->match_data.cmp(key, &ctx->match_data) &&
29 	    !(key->flags & ((1 << KEY_FLAG_INVALIDATED) |
30 			    (1 << KEY_FLAG_REVOKED))))
31 		return key_get(key);
32 #endif
33 	return NULL;
34 }
35 
cache_requested_key(struct key * key)36 static void cache_requested_key(struct key *key)
37 {
38 #ifdef CONFIG_KEYS_REQUEST_CACHE
39 	struct task_struct *t = current;
40 
41 	/* Do not cache key if it is a kernel thread */
42 	if (!(t->flags & PF_KTHREAD)) {
43 		key_put(t->cached_requested_key);
44 		t->cached_requested_key = key_get(key);
45 		set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
46 	}
47 #endif
48 }
49 
50 /**
51  * complete_request_key - Complete the construction of a key.
52  * @authkey: The authorisation key.
53  * @error: The success or failute of the construction.
54  *
55  * Complete the attempt to construct a key.  The key will be negated
56  * if an error is indicated.  The authorisation key will be revoked
57  * unconditionally.
58  */
complete_request_key(struct key * authkey,int error)59 void complete_request_key(struct key *authkey, int error)
60 {
61 	struct request_key_auth *rka = get_request_key_auth(authkey);
62 	struct key *key = rka->target_key;
63 
64 	kenter("%d{%d},%d", authkey->serial, key->serial, error);
65 
66 	if (error < 0)
67 		key_negate_and_link(key, key_negative_timeout, NULL, authkey);
68 	else
69 		key_revoke(authkey);
70 }
71 EXPORT_SYMBOL(complete_request_key);
72 
73 /*
74  * Initialise a usermode helper that is going to have a specific session
75  * keyring.
76  *
77  * This is called in context of freshly forked kthread before kernel_execve(),
78  * so we can simply install the desired session_keyring at this point.
79  */
umh_keys_init(struct subprocess_info * info,struct cred * cred)80 static int umh_keys_init(struct subprocess_info *info, struct cred *cred)
81 {
82 	struct key *keyring = info->data;
83 
84 	return install_session_keyring_to_cred(cred, keyring);
85 }
86 
87 /*
88  * Clean up a usermode helper with session keyring.
89  */
umh_keys_cleanup(struct subprocess_info * info)90 static void umh_keys_cleanup(struct subprocess_info *info)
91 {
92 	struct key *keyring = info->data;
93 	key_put(keyring);
94 }
95 
96 /*
97  * Call a usermode helper with a specific session keyring.
98  */
call_usermodehelper_keys(const char * path,char ** argv,char ** envp,struct key * session_keyring,int wait)99 static int call_usermodehelper_keys(const char *path, char **argv, char **envp,
100 					struct key *session_keyring, int wait)
101 {
102 	struct subprocess_info *info;
103 
104 	info = call_usermodehelper_setup(path, argv, envp, GFP_KERNEL,
105 					  umh_keys_init, umh_keys_cleanup,
106 					  session_keyring);
107 	if (!info)
108 		return -ENOMEM;
109 
110 	key_get(session_keyring);
111 	return call_usermodehelper_exec(info, wait);
112 }
113 
114 /*
115  * Request userspace finish the construction of a key
116  * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
117  */
call_sbin_request_key(struct key * authkey,void * aux)118 static int call_sbin_request_key(struct key *authkey, void *aux)
119 {
120 	static char const request_key[] = "/sbin/request-key";
121 	struct request_key_auth *rka = get_request_key_auth(authkey);
122 	const struct cred *cred = current_cred();
123 	key_serial_t prkey, sskey;
124 	struct key *key = rka->target_key, *keyring, *session, *user_session;
125 	char *argv[9], *envp[3], uid_str[12], gid_str[12];
126 	char key_str[12], keyring_str[3][12];
127 	char desc[20];
128 	int ret, i;
129 
130 	kenter("{%d},{%d},%s", key->serial, authkey->serial, rka->op);
131 
132 	ret = look_up_user_keyrings(NULL, &user_session);
133 	if (ret < 0)
134 		goto error_us;
135 
136 	/* allocate a new session keyring */
137 	sprintf(desc, "_req.%u", key->serial);
138 
139 	cred = get_current_cred();
140 	keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred,
141 				KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ,
142 				KEY_ALLOC_QUOTA_OVERRUN, NULL, NULL);
143 	put_cred(cred);
144 	if (IS_ERR(keyring)) {
145 		ret = PTR_ERR(keyring);
146 		goto error_alloc;
147 	}
148 
149 	/* attach the auth key to the session keyring */
150 	ret = key_link(keyring, authkey);
151 	if (ret < 0)
152 		goto error_link;
153 
154 	/* record the UID and GID */
155 	sprintf(uid_str, "%d", from_kuid(&init_user_ns, cred->fsuid));
156 	sprintf(gid_str, "%d", from_kgid(&init_user_ns, cred->fsgid));
157 
158 	/* we say which key is under construction */
159 	sprintf(key_str, "%d", key->serial);
160 
161 	/* we specify the process's default keyrings */
162 	sprintf(keyring_str[0], "%d",
163 		cred->thread_keyring ? cred->thread_keyring->serial : 0);
164 
165 	prkey = 0;
166 	if (cred->process_keyring)
167 		prkey = cred->process_keyring->serial;
168 	sprintf(keyring_str[1], "%d", prkey);
169 
170 	session = cred->session_keyring;
171 	if (!session)
172 		session = user_session;
173 	sskey = session->serial;
174 
175 	sprintf(keyring_str[2], "%d", sskey);
176 
177 	/* set up a minimal environment */
178 	i = 0;
179 	envp[i++] = "HOME=/";
180 	envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
181 	envp[i] = NULL;
182 
183 	/* set up the argument list */
184 	i = 0;
185 	argv[i++] = (char *)request_key;
186 	argv[i++] = (char *)rka->op;
187 	argv[i++] = key_str;
188 	argv[i++] = uid_str;
189 	argv[i++] = gid_str;
190 	argv[i++] = keyring_str[0];
191 	argv[i++] = keyring_str[1];
192 	argv[i++] = keyring_str[2];
193 	argv[i] = NULL;
194 
195 	/* do it */
196 	ret = call_usermodehelper_keys(request_key, argv, envp, keyring,
197 				       UMH_WAIT_PROC);
198 	kdebug("usermode -> 0x%x", ret);
199 	if (ret >= 0) {
200 		/* ret is the exit/wait code */
201 		if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
202 		    key_validate(key) < 0)
203 			ret = -ENOKEY;
204 		else
205 			/* ignore any errors from userspace if the key was
206 			 * instantiated */
207 			ret = 0;
208 	}
209 
210 error_link:
211 	key_put(keyring);
212 
213 error_alloc:
214 	key_put(user_session);
215 error_us:
216 	complete_request_key(authkey, ret);
217 	kleave(" = %d", ret);
218 	return ret;
219 }
220 
221 /*
222  * Call out to userspace for key construction.
223  *
224  * Program failure is ignored in favour of key status.
225  */
construct_key(struct key * key,const void * callout_info,size_t callout_len,void * aux,struct key * dest_keyring)226 static int construct_key(struct key *key, const void *callout_info,
227 			 size_t callout_len, void *aux,
228 			 struct key *dest_keyring)
229 {
230 	request_key_actor_t actor;
231 	struct key *authkey;
232 	int ret;
233 
234 	kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux);
235 
236 	/* allocate an authorisation key */
237 	authkey = request_key_auth_new(key, "create", callout_info, callout_len,
238 				       dest_keyring);
239 	if (IS_ERR(authkey))
240 		return PTR_ERR(authkey);
241 
242 	/* Make the call */
243 	actor = call_sbin_request_key;
244 	if (key->type->request_key)
245 		actor = key->type->request_key;
246 
247 	ret = actor(authkey, aux);
248 
249 	/* check that the actor called complete_request_key() prior to
250 	 * returning an error */
251 	WARN_ON(ret < 0 &&
252 		!test_bit(KEY_FLAG_INVALIDATED, &authkey->flags));
253 
254 	key_put(authkey);
255 	kleave(" = %d", ret);
256 	return ret;
257 }
258 
259 /*
260  * Get the appropriate destination keyring for the request.
261  *
262  * The keyring selected is returned with an extra reference upon it which the
263  * caller must release.
264  */
construct_get_dest_keyring(struct key ** _dest_keyring)265 static int construct_get_dest_keyring(struct key **_dest_keyring)
266 {
267 	struct request_key_auth *rka;
268 	const struct cred *cred = current_cred();
269 	struct key *dest_keyring = *_dest_keyring, *authkey;
270 	int ret;
271 
272 	kenter("%p", dest_keyring);
273 
274 	/* find the appropriate keyring */
275 	if (dest_keyring) {
276 		/* the caller supplied one */
277 		key_get(dest_keyring);
278 	} else {
279 		bool do_perm_check = true;
280 
281 		/* use a default keyring; falling through the cases until we
282 		 * find one that we actually have */
283 		switch (cred->jit_keyring) {
284 		case KEY_REQKEY_DEFL_DEFAULT:
285 		case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
286 			if (cred->request_key_auth) {
287 				authkey = cred->request_key_auth;
288 				down_read(&authkey->sem);
289 				rka = get_request_key_auth(authkey);
290 				if (!test_bit(KEY_FLAG_REVOKED,
291 					      &authkey->flags))
292 					dest_keyring =
293 						key_get(rka->dest_keyring);
294 				up_read(&authkey->sem);
295 				if (dest_keyring) {
296 					do_perm_check = false;
297 					break;
298 				}
299 			}
300 
301 			fallthrough;
302 		case KEY_REQKEY_DEFL_THREAD_KEYRING:
303 			dest_keyring = key_get(cred->thread_keyring);
304 			if (dest_keyring)
305 				break;
306 
307 			fallthrough;
308 		case KEY_REQKEY_DEFL_PROCESS_KEYRING:
309 			dest_keyring = key_get(cred->process_keyring);
310 			if (dest_keyring)
311 				break;
312 
313 			fallthrough;
314 		case KEY_REQKEY_DEFL_SESSION_KEYRING:
315 			dest_keyring = key_get(cred->session_keyring);
316 
317 			if (dest_keyring)
318 				break;
319 
320 			fallthrough;
321 		case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
322 			ret = look_up_user_keyrings(NULL, &dest_keyring);
323 			if (ret < 0)
324 				return ret;
325 			break;
326 
327 		case KEY_REQKEY_DEFL_USER_KEYRING:
328 			ret = look_up_user_keyrings(&dest_keyring, NULL);
329 			if (ret < 0)
330 				return ret;
331 			break;
332 
333 		case KEY_REQKEY_DEFL_GROUP_KEYRING:
334 		default:
335 			BUG();
336 		}
337 
338 		/*
339 		 * Require Write permission on the keyring.  This is essential
340 		 * because the default keyring may be the session keyring, and
341 		 * joining a keyring only requires Search permission.
342 		 *
343 		 * However, this check is skipped for the "requestor keyring" so
344 		 * that /sbin/request-key can itself use request_key() to add
345 		 * keys to the original requestor's destination keyring.
346 		 */
347 		if (dest_keyring && do_perm_check) {
348 			ret = key_permission(make_key_ref(dest_keyring, 1),
349 					     KEY_NEED_WRITE);
350 			if (ret) {
351 				key_put(dest_keyring);
352 				return ret;
353 			}
354 		}
355 	}
356 
357 	*_dest_keyring = dest_keyring;
358 	kleave(" [dk %d]", key_serial(dest_keyring));
359 	return 0;
360 }
361 
362 /*
363  * Allocate a new key in under-construction state and attempt to link it in to
364  * the requested keyring.
365  *
366  * May return a key that's already under construction instead if there was a
367  * race between two thread calling request_key().
368  */
construct_alloc_key(struct keyring_search_context * ctx,struct key * dest_keyring,unsigned long flags,struct key_user * user,struct key ** _key)369 static int construct_alloc_key(struct keyring_search_context *ctx,
370 			       struct key *dest_keyring,
371 			       unsigned long flags,
372 			       struct key_user *user,
373 			       struct key **_key)
374 {
375 	struct assoc_array_edit *edit = NULL;
376 	struct key *key;
377 	key_perm_t perm;
378 	key_ref_t key_ref;
379 	int ret;
380 
381 	kenter("%s,%s,,,",
382 	       ctx->index_key.type->name, ctx->index_key.description);
383 
384 	*_key = NULL;
385 	mutex_lock(&user->cons_lock);
386 
387 	perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
388 	perm |= KEY_USR_VIEW;
389 	if (ctx->index_key.type->read)
390 		perm |= KEY_POS_READ;
391 	if (ctx->index_key.type == &key_type_keyring ||
392 	    ctx->index_key.type->update)
393 		perm |= KEY_POS_WRITE;
394 
395 	key = key_alloc(ctx->index_key.type, ctx->index_key.description,
396 			ctx->cred->fsuid, ctx->cred->fsgid, ctx->cred,
397 			perm, flags, NULL);
398 	if (IS_ERR(key))
399 		goto alloc_failed;
400 
401 	set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
402 
403 	if (dest_keyring) {
404 		ret = __key_link_lock(dest_keyring, &key->index_key);
405 		if (ret < 0)
406 			goto link_lock_failed;
407 	}
408 
409 	/*
410 	 * Attach the key to the destination keyring under lock, but we do need
411 	 * to do another check just in case someone beat us to it whilst we
412 	 * waited for locks.
413 	 *
414 	 * The caller might specify a comparison function which looks for keys
415 	 * that do not exactly match but are still equivalent from the caller's
416 	 * perspective. The __key_link_begin() operation must be done only after
417 	 * an actual key is determined.
418 	 */
419 	mutex_lock(&key_construction_mutex);
420 
421 	rcu_read_lock();
422 	key_ref = search_process_keyrings_rcu(ctx);
423 	rcu_read_unlock();
424 	if (!IS_ERR(key_ref))
425 		goto key_already_present;
426 
427 	if (dest_keyring) {
428 		ret = __key_link_begin(dest_keyring, &key->index_key, &edit);
429 		if (ret < 0)
430 			goto link_alloc_failed;
431 		__key_link(dest_keyring, key, &edit);
432 	}
433 
434 	mutex_unlock(&key_construction_mutex);
435 	if (dest_keyring)
436 		__key_link_end(dest_keyring, &key->index_key, edit);
437 	mutex_unlock(&user->cons_lock);
438 	*_key = key;
439 	kleave(" = 0 [%d]", key_serial(key));
440 	return 0;
441 
442 	/* the key is now present - we tell the caller that we found it by
443 	 * returning -EINPROGRESS  */
444 key_already_present:
445 	key_put(key);
446 	mutex_unlock(&key_construction_mutex);
447 	key = key_ref_to_ptr(key_ref);
448 	if (dest_keyring) {
449 		ret = __key_link_begin(dest_keyring, &key->index_key, &edit);
450 		if (ret < 0)
451 			goto link_alloc_failed_unlocked;
452 		ret = __key_link_check_live_key(dest_keyring, key);
453 		if (ret == 0)
454 			__key_link(dest_keyring, key, &edit);
455 		__key_link_end(dest_keyring, &key->index_key, edit);
456 		if (ret < 0)
457 			goto link_check_failed;
458 	}
459 	mutex_unlock(&user->cons_lock);
460 	*_key = key;
461 	kleave(" = -EINPROGRESS [%d]", key_serial(key));
462 	return -EINPROGRESS;
463 
464 link_check_failed:
465 	mutex_unlock(&user->cons_lock);
466 	key_put(key);
467 	kleave(" = %d [linkcheck]", ret);
468 	return ret;
469 
470 link_alloc_failed:
471 	mutex_unlock(&key_construction_mutex);
472 link_alloc_failed_unlocked:
473 	__key_link_end(dest_keyring, &key->index_key, edit);
474 link_lock_failed:
475 	mutex_unlock(&user->cons_lock);
476 	key_put(key);
477 	kleave(" = %d [prelink]", ret);
478 	return ret;
479 
480 alloc_failed:
481 	mutex_unlock(&user->cons_lock);
482 	kleave(" = %ld", PTR_ERR(key));
483 	return PTR_ERR(key);
484 }
485 
486 /*
487  * Commence key construction.
488  */
construct_key_and_link(struct keyring_search_context * ctx,const char * callout_info,size_t callout_len,void * aux,struct key * dest_keyring,unsigned long flags)489 static struct key *construct_key_and_link(struct keyring_search_context *ctx,
490 					  const char *callout_info,
491 					  size_t callout_len,
492 					  void *aux,
493 					  struct key *dest_keyring,
494 					  unsigned long flags)
495 {
496 	struct key_user *user;
497 	struct key *key;
498 	int ret;
499 
500 	kenter("");
501 
502 	if (ctx->index_key.type == &key_type_keyring)
503 		return ERR_PTR(-EPERM);
504 
505 	ret = construct_get_dest_keyring(&dest_keyring);
506 	if (ret)
507 		goto error;
508 
509 	user = key_user_lookup(current_fsuid());
510 	if (!user) {
511 		ret = -ENOMEM;
512 		goto error_put_dest_keyring;
513 	}
514 
515 	ret = construct_alloc_key(ctx, dest_keyring, flags, user, &key);
516 	key_user_put(user);
517 
518 	if (ret == 0) {
519 		ret = construct_key(key, callout_info, callout_len, aux,
520 				    dest_keyring);
521 		if (ret < 0) {
522 			kdebug("cons failed");
523 			goto construction_failed;
524 		}
525 	} else if (ret == -EINPROGRESS) {
526 		ret = 0;
527 	} else {
528 		goto error_put_dest_keyring;
529 	}
530 
531 	key_put(dest_keyring);
532 	kleave(" = key %d", key_serial(key));
533 	return key;
534 
535 construction_failed:
536 	key_negate_and_link(key, key_negative_timeout, NULL, NULL);
537 	key_put(key);
538 error_put_dest_keyring:
539 	key_put(dest_keyring);
540 error:
541 	kleave(" = %d", ret);
542 	return ERR_PTR(ret);
543 }
544 
545 /**
546  * request_key_and_link - Request a key and cache it in a keyring.
547  * @type: The type of key we want.
548  * @description: The searchable description of the key.
549  * @domain_tag: The domain in which the key operates.
550  * @callout_info: The data to pass to the instantiation upcall (or NULL).
551  * @callout_len: The length of callout_info.
552  * @aux: Auxiliary data for the upcall.
553  * @dest_keyring: Where to cache the key.
554  * @flags: Flags to key_alloc().
555  *
556  * A key matching the specified criteria (type, description, domain_tag) is
557  * searched for in the process's keyrings and returned with its usage count
558  * incremented if found.  Otherwise, if callout_info is not NULL, a key will be
559  * allocated and some service (probably in userspace) will be asked to
560  * instantiate it.
561  *
562  * If successfully found or created, the key will be linked to the destination
563  * keyring if one is provided.
564  *
565  * Returns a pointer to the key if successful; -EACCES, -ENOKEY, -EKEYREVOKED
566  * or -EKEYEXPIRED if an inaccessible, negative, revoked or expired key was
567  * found; -ENOKEY if no key was found and no @callout_info was given; -EDQUOT
568  * if insufficient key quota was available to create a new key; or -ENOMEM if
569  * insufficient memory was available.
570  *
571  * If the returned key was created, then it may still be under construction,
572  * and wait_for_key_construction() should be used to wait for that to complete.
573  */
request_key_and_link(struct key_type * type,const char * description,struct key_tag * domain_tag,const void * callout_info,size_t callout_len,void * aux,struct key * dest_keyring,unsigned long flags)574 struct key *request_key_and_link(struct key_type *type,
575 				 const char *description,
576 				 struct key_tag *domain_tag,
577 				 const void *callout_info,
578 				 size_t callout_len,
579 				 void *aux,
580 				 struct key *dest_keyring,
581 				 unsigned long flags)
582 {
583 	struct keyring_search_context ctx = {
584 		.index_key.type		= type,
585 		.index_key.domain_tag	= domain_tag,
586 		.index_key.description	= description,
587 		.index_key.desc_len	= strlen(description),
588 		.cred			= current_cred(),
589 		.match_data.cmp		= key_default_cmp,
590 		.match_data.raw_data	= description,
591 		.match_data.lookup_type	= KEYRING_SEARCH_LOOKUP_DIRECT,
592 		.flags			= (KEYRING_SEARCH_DO_STATE_CHECK |
593 					   KEYRING_SEARCH_SKIP_EXPIRED |
594 					   KEYRING_SEARCH_RECURSE),
595 	};
596 	struct key *key;
597 	key_ref_t key_ref;
598 	int ret;
599 
600 	kenter("%s,%s,%p,%zu,%p,%p,%lx",
601 	       ctx.index_key.type->name, ctx.index_key.description,
602 	       callout_info, callout_len, aux, dest_keyring, flags);
603 
604 	if (type->match_preparse) {
605 		ret = type->match_preparse(&ctx.match_data);
606 		if (ret < 0) {
607 			key = ERR_PTR(ret);
608 			goto error;
609 		}
610 	}
611 
612 	key = check_cached_key(&ctx);
613 	if (key)
614 		goto error_free;
615 
616 	/* search all the process keyrings for a key */
617 	rcu_read_lock();
618 	key_ref = search_process_keyrings_rcu(&ctx);
619 	rcu_read_unlock();
620 
621 	if (!IS_ERR(key_ref)) {
622 		if (dest_keyring) {
623 			ret = key_task_permission(key_ref, current_cred(),
624 						  KEY_NEED_LINK);
625 			if (ret < 0) {
626 				key_ref_put(key_ref);
627 				key = ERR_PTR(ret);
628 				goto error_free;
629 			}
630 		}
631 
632 		key = key_ref_to_ptr(key_ref);
633 		if (dest_keyring) {
634 			ret = key_link(dest_keyring, key);
635 			if (ret < 0) {
636 				key_put(key);
637 				key = ERR_PTR(ret);
638 				goto error_free;
639 			}
640 		}
641 
642 		/* Only cache the key on immediate success */
643 		cache_requested_key(key);
644 	} else if (PTR_ERR(key_ref) != -EAGAIN) {
645 		key = ERR_CAST(key_ref);
646 	} else  {
647 		/* the search failed, but the keyrings were searchable, so we
648 		 * should consult userspace if we can */
649 		key = ERR_PTR(-ENOKEY);
650 		if (!callout_info)
651 			goto error_free;
652 
653 		key = construct_key_and_link(&ctx, callout_info, callout_len,
654 					     aux, dest_keyring, flags);
655 	}
656 
657 error_free:
658 	if (type->match_free)
659 		type->match_free(&ctx.match_data);
660 error:
661 	kleave(" = %p", key);
662 	return key;
663 }
664 
665 /**
666  * wait_for_key_construction - Wait for construction of a key to complete
667  * @key: The key being waited for.
668  * @intr: Whether to wait interruptibly.
669  *
670  * Wait for a key to finish being constructed.
671  *
672  * Returns 0 if successful; -ERESTARTSYS if the wait was interrupted; -ENOKEY
673  * if the key was negated; or -EKEYREVOKED or -EKEYEXPIRED if the key was
674  * revoked or expired.
675  */
wait_for_key_construction(struct key * key,bool intr)676 int wait_for_key_construction(struct key *key, bool intr)
677 {
678 	int ret;
679 
680 	ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
681 			  intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
682 	if (ret)
683 		return -ERESTARTSYS;
684 	ret = key_read_state(key);
685 	if (ret < 0)
686 		return ret;
687 	return key_validate(key);
688 }
689 EXPORT_SYMBOL(wait_for_key_construction);
690 
691 /**
692  * request_key_tag - Request a key and wait for construction
693  * @type: Type of key.
694  * @description: The searchable description of the key.
695  * @domain_tag: The domain in which the key operates.
696  * @callout_info: The data to pass to the instantiation upcall (or NULL).
697  *
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,
700  * the callout_info must be a NUL-terminated string and no auxiliary data can
701  * be passed.
702  *
703  * Furthermore, it then works as wait_for_key_construction() to wait for the
704  * completion of keys undergoing construction with a non-interruptible wait.
705  */
request_key_tag(struct key_type * type,const char * description,struct key_tag * domain_tag,const char * callout_info)706 struct key *request_key_tag(struct key_type *type,
707 			    const char *description,
708 			    struct key_tag *domain_tag,
709 			    const char *callout_info)
710 {
711 	struct key *key;
712 	size_t callout_len = 0;
713 	int ret;
714 
715 	if (callout_info)
716 		callout_len = strlen(callout_info);
717 	key = request_key_and_link(type, description, domain_tag,
718 				   callout_info, callout_len,
719 				   NULL, NULL, KEY_ALLOC_IN_QUOTA);
720 	if (!IS_ERR(key)) {
721 		ret = wait_for_key_construction(key, false);
722 		if (ret < 0) {
723 			key_put(key);
724 			return ERR_PTR(ret);
725 		}
726 	}
727 	return key;
728 }
729 EXPORT_SYMBOL(request_key_tag);
730 
731 /**
732  * request_key_with_auxdata - Request a key with auxiliary data for the upcaller
733  * @type: The type of key we want.
734  * @description: The searchable description of the key.
735  * @domain_tag: The domain in which the key operates.
736  * @callout_info: The data to pass to the instantiation upcall (or NULL).
737  * @callout_len: The length of callout_info.
738  * @aux: Auxiliary data for the upcall.
739  *
740  * As for request_key_and_link() except that it does not add the returned key
741  * to a keyring if found and new keys are always allocated in the user's quota.
742  *
743  * Furthermore, it then works as wait_for_key_construction() to wait for the
744  * completion of keys undergoing construction with a non-interruptible wait.
745  */
request_key_with_auxdata(struct key_type * type,const char * description,struct key_tag * domain_tag,const void * callout_info,size_t callout_len,void * aux)746 struct key *request_key_with_auxdata(struct key_type *type,
747 				     const char *description,
748 				     struct key_tag *domain_tag,
749 				     const void *callout_info,
750 				     size_t callout_len,
751 				     void *aux)
752 {
753 	struct key *key;
754 	int ret;
755 
756 	key = request_key_and_link(type, description, domain_tag,
757 				   callout_info, callout_len,
758 				   aux, NULL, KEY_ALLOC_IN_QUOTA);
759 	if (!IS_ERR(key)) {
760 		ret = wait_for_key_construction(key, false);
761 		if (ret < 0) {
762 			key_put(key);
763 			return ERR_PTR(ret);
764 		}
765 	}
766 	return key;
767 }
768 EXPORT_SYMBOL(request_key_with_auxdata);
769 
770 /**
771  * request_key_rcu - Request key from RCU-read-locked context
772  * @type: The type of key we want.
773  * @description: The name of the key we want.
774  * @domain_tag: The domain in which the key operates.
775  *
776  * Request a key from a context that we may not sleep in (such as RCU-mode
777  * pathwalk).  Keys under construction are ignored.
778  *
779  * Return a pointer to the found key if successful, -ENOKEY if we couldn't find
780  * a key or some other error if the key found was unsuitable or inaccessible.
781  */
request_key_rcu(struct key_type * type,const char * description,struct key_tag * domain_tag)782 struct key *request_key_rcu(struct key_type *type,
783 			    const char *description,
784 			    struct key_tag *domain_tag)
785 {
786 	struct keyring_search_context ctx = {
787 		.index_key.type		= type,
788 		.index_key.domain_tag	= domain_tag,
789 		.index_key.description	= description,
790 		.index_key.desc_len	= strlen(description),
791 		.cred			= current_cred(),
792 		.match_data.cmp		= key_default_cmp,
793 		.match_data.raw_data	= description,
794 		.match_data.lookup_type	= KEYRING_SEARCH_LOOKUP_DIRECT,
795 		.flags			= (KEYRING_SEARCH_DO_STATE_CHECK |
796 					   KEYRING_SEARCH_SKIP_EXPIRED),
797 	};
798 	struct key *key;
799 	key_ref_t key_ref;
800 
801 	kenter("%s,%s", type->name, description);
802 
803 	key = check_cached_key(&ctx);
804 	if (key)
805 		return key;
806 
807 	/* search all the process keyrings for a key */
808 	key_ref = search_process_keyrings_rcu(&ctx);
809 	if (IS_ERR(key_ref)) {
810 		key = ERR_CAST(key_ref);
811 		if (PTR_ERR(key_ref) == -EAGAIN)
812 			key = ERR_PTR(-ENOKEY);
813 	} else {
814 		key = key_ref_to_ptr(key_ref);
815 		cache_requested_key(key);
816 	}
817 
818 	kleave(" = %p", key);
819 	return key;
820 }
821 EXPORT_SYMBOL(request_key_rcu);
822