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TOMOYO Linux Cross Reference
Linux/security/keys/keyctl.c

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  1 /* Userspace key control operations
  2  *
  3  * Copyright (C) 2004-5 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/sched/task.h>
 16 #include <linux/slab.h>
 17 #include <linux/syscalls.h>
 18 #include <linux/key.h>
 19 #include <linux/keyctl.h>
 20 #include <linux/fs.h>
 21 #include <linux/capability.h>
 22 #include <linux/cred.h>
 23 #include <linux/string.h>
 24 #include <linux/err.h>
 25 #include <linux/vmalloc.h>
 26 #include <linux/security.h>
 27 #include <linux/uio.h>
 28 #include <linux/uaccess.h>
 29 #include "internal.h"
 30 
 31 #define KEY_MAX_DESC_SIZE 4096
 32 
 33 static int key_get_type_from_user(char *type,
 34                                   const char __user *_type,
 35                                   unsigned len)
 36 {
 37         int ret;
 38 
 39         ret = strncpy_from_user(type, _type, len);
 40         if (ret < 0)
 41                 return ret;
 42         if (ret == 0 || ret >= len)
 43                 return -EINVAL;
 44         if (type[0] == '.')
 45                 return -EPERM;
 46         type[len - 1] = '\0';
 47         return 0;
 48 }
 49 
 50 /*
 51  * Extract the description of a new key from userspace and either add it as a
 52  * new key to the specified keyring or update a matching key in that keyring.
 53  *
 54  * If the description is NULL or an empty string, the key type is asked to
 55  * generate one from the payload.
 56  *
 57  * The keyring must be writable so that we can attach the key to it.
 58  *
 59  * If successful, the new key's serial number is returned, otherwise an error
 60  * code is returned.
 61  */
 62 SYSCALL_DEFINE5(add_key, const char __user *, _type,
 63                 const char __user *, _description,
 64                 const void __user *, _payload,
 65                 size_t, plen,
 66                 key_serial_t, ringid)
 67 {
 68         key_ref_t keyring_ref, key_ref;
 69         char type[32], *description;
 70         void *payload;
 71         long ret;
 72 
 73         ret = -EINVAL;
 74         if (plen > 1024 * 1024 - 1)
 75                 goto error;
 76 
 77         /* draw all the data into kernel space */
 78         ret = key_get_type_from_user(type, _type, sizeof(type));
 79         if (ret < 0)
 80                 goto error;
 81 
 82         description = NULL;
 83         if (_description) {
 84                 description = strndup_user(_description, KEY_MAX_DESC_SIZE);
 85                 if (IS_ERR(description)) {
 86                         ret = PTR_ERR(description);
 87                         goto error;
 88                 }
 89                 if (!*description) {
 90                         kfree(description);
 91                         description = NULL;
 92                 } else if ((description[0] == '.') &&
 93                            (strncmp(type, "keyring", 7) == 0)) {
 94                         ret = -EPERM;
 95                         goto error2;
 96                 }
 97         }
 98 
 99         /* pull the payload in if one was supplied */
100         payload = NULL;
101 
102         if (plen) {
103                 ret = -ENOMEM;
104                 payload = kvmalloc(plen, GFP_KERNEL);
105                 if (!payload)
106                         goto error2;
107 
108                 ret = -EFAULT;
109                 if (copy_from_user(payload, _payload, plen) != 0)
110                         goto error3;
111         }
112 
113         /* find the target keyring (which must be writable) */
114         keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
115         if (IS_ERR(keyring_ref)) {
116                 ret = PTR_ERR(keyring_ref);
117                 goto error3;
118         }
119 
120         /* create or update the requested key and add it to the target
121          * keyring */
122         key_ref = key_create_or_update(keyring_ref, type, description,
123                                        payload, plen, KEY_PERM_UNDEF,
124                                        KEY_ALLOC_IN_QUOTA);
125         if (!IS_ERR(key_ref)) {
126                 ret = key_ref_to_ptr(key_ref)->serial;
127                 key_ref_put(key_ref);
128         }
129         else {
130                 ret = PTR_ERR(key_ref);
131         }
132 
133         key_ref_put(keyring_ref);
134  error3:
135         if (payload) {
136                 memzero_explicit(payload, plen);
137                 kvfree(payload);
138         }
139  error2:
140         kfree(description);
141  error:
142         return ret;
143 }
144 
145 /*
146  * Search the process keyrings and keyring trees linked from those for a
147  * matching key.  Keyrings must have appropriate Search permission to be
148  * searched.
149  *
150  * If a key is found, it will be attached to the destination keyring if there's
151  * one specified and the serial number of the key will be returned.
152  *
153  * If no key is found, /sbin/request-key will be invoked if _callout_info is
154  * non-NULL in an attempt to create a key.  The _callout_info string will be
155  * passed to /sbin/request-key to aid with completing the request.  If the
156  * _callout_info string is "" then it will be changed to "-".
157  */
158 SYSCALL_DEFINE4(request_key, const char __user *, _type,
159                 const char __user *, _description,
160                 const char __user *, _callout_info,
161                 key_serial_t, destringid)
162 {
163         struct key_type *ktype;
164         struct key *key;
165         key_ref_t dest_ref;
166         size_t callout_len;
167         char type[32], *description, *callout_info;
168         long ret;
169 
170         /* pull the type into kernel space */
171         ret = key_get_type_from_user(type, _type, sizeof(type));
172         if (ret < 0)
173                 goto error;
174 
175         /* pull the description into kernel space */
176         description = strndup_user(_description, KEY_MAX_DESC_SIZE);
177         if (IS_ERR(description)) {
178                 ret = PTR_ERR(description);
179                 goto error;
180         }
181 
182         /* pull the callout info into kernel space */
183         callout_info = NULL;
184         callout_len = 0;
185         if (_callout_info) {
186                 callout_info = strndup_user(_callout_info, PAGE_SIZE);
187                 if (IS_ERR(callout_info)) {
188                         ret = PTR_ERR(callout_info);
189                         goto error2;
190                 }
191                 callout_len = strlen(callout_info);
192         }
193 
194         /* get the destination keyring if specified */
195         dest_ref = NULL;
196         if (destringid) {
197                 dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
198                                            KEY_NEED_WRITE);
199                 if (IS_ERR(dest_ref)) {
200                         ret = PTR_ERR(dest_ref);
201                         goto error3;
202                 }
203         }
204 
205         /* find the key type */
206         ktype = key_type_lookup(type);
207         if (IS_ERR(ktype)) {
208                 ret = PTR_ERR(ktype);
209                 goto error4;
210         }
211 
212         /* do the search */
213         key = request_key_and_link(ktype, description, callout_info,
214                                    callout_len, NULL, key_ref_to_ptr(dest_ref),
215                                    KEY_ALLOC_IN_QUOTA);
216         if (IS_ERR(key)) {
217                 ret = PTR_ERR(key);
218                 goto error5;
219         }
220 
221         /* wait for the key to finish being constructed */
222         ret = wait_for_key_construction(key, 1);
223         if (ret < 0)
224                 goto error6;
225 
226         ret = key->serial;
227 
228 error6:
229         key_put(key);
230 error5:
231         key_type_put(ktype);
232 error4:
233         key_ref_put(dest_ref);
234 error3:
235         kfree(callout_info);
236 error2:
237         kfree(description);
238 error:
239         return ret;
240 }
241 
242 /*
243  * Get the ID of the specified process keyring.
244  *
245  * The requested keyring must have search permission to be found.
246  *
247  * If successful, the ID of the requested keyring will be returned.
248  */
249 long keyctl_get_keyring_ID(key_serial_t id, int create)
250 {
251         key_ref_t key_ref;
252         unsigned long lflags;
253         long ret;
254 
255         lflags = create ? KEY_LOOKUP_CREATE : 0;
256         key_ref = lookup_user_key(id, lflags, KEY_NEED_SEARCH);
257         if (IS_ERR(key_ref)) {
258                 ret = PTR_ERR(key_ref);
259                 goto error;
260         }
261 
262         ret = key_ref_to_ptr(key_ref)->serial;
263         key_ref_put(key_ref);
264 error:
265         return ret;
266 }
267 
268 /*
269  * Join a (named) session keyring.
270  *
271  * Create and join an anonymous session keyring or join a named session
272  * keyring, creating it if necessary.  A named session keyring must have Search
273  * permission for it to be joined.  Session keyrings without this permit will
274  * be skipped over.  It is not permitted for userspace to create or join
275  * keyrings whose name begin with a dot.
276  *
277  * If successful, the ID of the joined session keyring will be returned.
278  */
279 long keyctl_join_session_keyring(const char __user *_name)
280 {
281         char *name;
282         long ret;
283 
284         /* fetch the name from userspace */
285         name = NULL;
286         if (_name) {
287                 name = strndup_user(_name, KEY_MAX_DESC_SIZE);
288                 if (IS_ERR(name)) {
289                         ret = PTR_ERR(name);
290                         goto error;
291                 }
292 
293                 ret = -EPERM;
294                 if (name[0] == '.')
295                         goto error_name;
296         }
297 
298         /* join the session */
299         ret = join_session_keyring(name);
300 error_name:
301         kfree(name);
302 error:
303         return ret;
304 }
305 
306 /*
307  * Update a key's data payload from the given data.
308  *
309  * The key must grant the caller Write permission and the key type must support
310  * updating for this to work.  A negative key can be positively instantiated
311  * with this call.
312  *
313  * If successful, 0 will be returned.  If the key type does not support
314  * updating, then -EOPNOTSUPP will be returned.
315  */
316 long keyctl_update_key(key_serial_t id,
317                        const void __user *_payload,
318                        size_t plen)
319 {
320         key_ref_t key_ref;
321         void *payload;
322         long ret;
323 
324         ret = -EINVAL;
325         if (plen > PAGE_SIZE)
326                 goto error;
327 
328         /* pull the payload in if one was supplied */
329         payload = NULL;
330         if (plen) {
331                 ret = -ENOMEM;
332                 payload = kmalloc(plen, GFP_KERNEL);
333                 if (!payload)
334                         goto error;
335 
336                 ret = -EFAULT;
337                 if (copy_from_user(payload, _payload, plen) != 0)
338                         goto error2;
339         }
340 
341         /* find the target key (which must be writable) */
342         key_ref = lookup_user_key(id, 0, KEY_NEED_WRITE);
343         if (IS_ERR(key_ref)) {
344                 ret = PTR_ERR(key_ref);
345                 goto error2;
346         }
347 
348         /* update the key */
349         ret = key_update(key_ref, payload, plen);
350 
351         key_ref_put(key_ref);
352 error2:
353         kzfree(payload);
354 error:
355         return ret;
356 }
357 
358 /*
359  * Revoke a key.
360  *
361  * The key must be grant the caller Write or Setattr permission for this to
362  * work.  The key type should give up its quota claim when revoked.  The key
363  * and any links to the key will be automatically garbage collected after a
364  * certain amount of time (/proc/sys/kernel/keys/gc_delay).
365  *
366  * Keys with KEY_FLAG_KEEP set should not be revoked.
367  *
368  * If successful, 0 is returned.
369  */
370 long keyctl_revoke_key(key_serial_t id)
371 {
372         key_ref_t key_ref;
373         struct key *key;
374         long ret;
375 
376         key_ref = lookup_user_key(id, 0, KEY_NEED_WRITE);
377         if (IS_ERR(key_ref)) {
378                 ret = PTR_ERR(key_ref);
379                 if (ret != -EACCES)
380                         goto error;
381                 key_ref = lookup_user_key(id, 0, KEY_NEED_SETATTR);
382                 if (IS_ERR(key_ref)) {
383                         ret = PTR_ERR(key_ref);
384                         goto error;
385                 }
386         }
387 
388         key = key_ref_to_ptr(key_ref);
389         ret = 0;
390         if (test_bit(KEY_FLAG_KEEP, &key->flags))
391                 ret = -EPERM;
392         else
393                 key_revoke(key);
394 
395         key_ref_put(key_ref);
396 error:
397         return ret;
398 }
399 
400 /*
401  * Invalidate a key.
402  *
403  * The key must be grant the caller Invalidate permission for this to work.
404  * The key and any links to the key will be automatically garbage collected
405  * immediately.
406  *
407  * Keys with KEY_FLAG_KEEP set should not be invalidated.
408  *
409  * If successful, 0 is returned.
410  */
411 long keyctl_invalidate_key(key_serial_t id)
412 {
413         key_ref_t key_ref;
414         struct key *key;
415         long ret;
416 
417         kenter("%d", id);
418 
419         key_ref = lookup_user_key(id, 0, KEY_NEED_SEARCH);
420         if (IS_ERR(key_ref)) {
421                 ret = PTR_ERR(key_ref);
422 
423                 /* Root is permitted to invalidate certain special keys */
424                 if (capable(CAP_SYS_ADMIN)) {
425                         key_ref = lookup_user_key(id, 0, 0);
426                         if (IS_ERR(key_ref))
427                                 goto error;
428                         if (test_bit(KEY_FLAG_ROOT_CAN_INVAL,
429                                      &key_ref_to_ptr(key_ref)->flags))
430                                 goto invalidate;
431                         goto error_put;
432                 }
433 
434                 goto error;
435         }
436 
437 invalidate:
438         key = key_ref_to_ptr(key_ref);
439         ret = 0;
440         if (test_bit(KEY_FLAG_KEEP, &key->flags))
441                 ret = -EPERM;
442         else
443                 key_invalidate(key);
444 error_put:
445         key_ref_put(key_ref);
446 error:
447         kleave(" = %ld", ret);
448         return ret;
449 }
450 
451 /*
452  * Clear the specified keyring, creating an empty process keyring if one of the
453  * special keyring IDs is used.
454  *
455  * The keyring must grant the caller Write permission and not have
456  * KEY_FLAG_KEEP set for this to work.  If successful, 0 will be returned.
457  */
458 long keyctl_keyring_clear(key_serial_t ringid)
459 {
460         key_ref_t keyring_ref;
461         struct key *keyring;
462         long ret;
463 
464         keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
465         if (IS_ERR(keyring_ref)) {
466                 ret = PTR_ERR(keyring_ref);
467 
468                 /* Root is permitted to invalidate certain special keyrings */
469                 if (capable(CAP_SYS_ADMIN)) {
470                         keyring_ref = lookup_user_key(ringid, 0, 0);
471                         if (IS_ERR(keyring_ref))
472                                 goto error;
473                         if (test_bit(KEY_FLAG_ROOT_CAN_CLEAR,
474                                      &key_ref_to_ptr(keyring_ref)->flags))
475                                 goto clear;
476                         goto error_put;
477                 }
478 
479                 goto error;
480         }
481 
482 clear:
483         keyring = key_ref_to_ptr(keyring_ref);
484         if (test_bit(KEY_FLAG_KEEP, &keyring->flags))
485                 ret = -EPERM;
486         else
487                 ret = keyring_clear(keyring);
488 error_put:
489         key_ref_put(keyring_ref);
490 error:
491         return ret;
492 }
493 
494 /*
495  * Create a link from a keyring to a key if there's no matching key in the
496  * keyring, otherwise replace the link to the matching key with a link to the
497  * new key.
498  *
499  * The key must grant the caller Link permission and the the keyring must grant
500  * the caller Write permission.  Furthermore, if an additional link is created,
501  * the keyring's quota will be extended.
502  *
503  * If successful, 0 will be returned.
504  */
505 long keyctl_keyring_link(key_serial_t id, key_serial_t ringid)
506 {
507         key_ref_t keyring_ref, key_ref;
508         long ret;
509 
510         keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
511         if (IS_ERR(keyring_ref)) {
512                 ret = PTR_ERR(keyring_ref);
513                 goto error;
514         }
515 
516         key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_NEED_LINK);
517         if (IS_ERR(key_ref)) {
518                 ret = PTR_ERR(key_ref);
519                 goto error2;
520         }
521 
522         ret = key_link(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));
523 
524         key_ref_put(key_ref);
525 error2:
526         key_ref_put(keyring_ref);
527 error:
528         return ret;
529 }
530 
531 /*
532  * Unlink a key from a keyring.
533  *
534  * The keyring must grant the caller Write permission for this to work; the key
535  * itself need not grant the caller anything.  If the last link to a key is
536  * removed then that key will be scheduled for destruction.
537  *
538  * Keys or keyrings with KEY_FLAG_KEEP set should not be unlinked.
539  *
540  * If successful, 0 will be returned.
541  */
542 long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)
543 {
544         key_ref_t keyring_ref, key_ref;
545         struct key *keyring, *key;
546         long ret;
547 
548         keyring_ref = lookup_user_key(ringid, 0, KEY_NEED_WRITE);
549         if (IS_ERR(keyring_ref)) {
550                 ret = PTR_ERR(keyring_ref);
551                 goto error;
552         }
553 
554         key_ref = lookup_user_key(id, KEY_LOOKUP_FOR_UNLINK, 0);
555         if (IS_ERR(key_ref)) {
556                 ret = PTR_ERR(key_ref);
557                 goto error2;
558         }
559 
560         keyring = key_ref_to_ptr(keyring_ref);
561         key = key_ref_to_ptr(key_ref);
562         if (test_bit(KEY_FLAG_KEEP, &keyring->flags) &&
563             test_bit(KEY_FLAG_KEEP, &key->flags))
564                 ret = -EPERM;
565         else
566                 ret = key_unlink(keyring, key);
567 
568         key_ref_put(key_ref);
569 error2:
570         key_ref_put(keyring_ref);
571 error:
572         return ret;
573 }
574 
575 /*
576  * Return a description of a key to userspace.
577  *
578  * The key must grant the caller View permission for this to work.
579  *
580  * If there's a buffer, we place up to buflen bytes of data into it formatted
581  * in the following way:
582  *
583  *      type;uid;gid;perm;description<NUL>
584  *
585  * If successful, we return the amount of description available, irrespective
586  * of how much we may have copied into the buffer.
587  */
588 long keyctl_describe_key(key_serial_t keyid,
589                          char __user *buffer,
590                          size_t buflen)
591 {
592         struct key *key, *instkey;
593         key_ref_t key_ref;
594         char *infobuf;
595         long ret;
596         int desclen, infolen;
597 
598         key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_NEED_VIEW);
599         if (IS_ERR(key_ref)) {
600                 /* viewing a key under construction is permitted if we have the
601                  * authorisation token handy */
602                 if (PTR_ERR(key_ref) == -EACCES) {
603                         instkey = key_get_instantiation_authkey(keyid);
604                         if (!IS_ERR(instkey)) {
605                                 key_put(instkey);
606                                 key_ref = lookup_user_key(keyid,
607                                                           KEY_LOOKUP_PARTIAL,
608                                                           0);
609                                 if (!IS_ERR(key_ref))
610                                         goto okay;
611                         }
612                 }
613 
614                 ret = PTR_ERR(key_ref);
615                 goto error;
616         }
617 
618 okay:
619         key = key_ref_to_ptr(key_ref);
620         desclen = strlen(key->description);
621 
622         /* calculate how much information we're going to return */
623         ret = -ENOMEM;
624         infobuf = kasprintf(GFP_KERNEL,
625                             "%s;%d;%d;%08x;",
626                             key->type->name,
627                             from_kuid_munged(current_user_ns(), key->uid),
628                             from_kgid_munged(current_user_ns(), key->gid),
629                             key->perm);
630         if (!infobuf)
631                 goto error2;
632         infolen = strlen(infobuf);
633         ret = infolen + desclen + 1;
634 
635         /* consider returning the data */
636         if (buffer && buflen >= ret) {
637                 if (copy_to_user(buffer, infobuf, infolen) != 0 ||
638                     copy_to_user(buffer + infolen, key->description,
639                                  desclen + 1) != 0)
640                         ret = -EFAULT;
641         }
642 
643         kfree(infobuf);
644 error2:
645         key_ref_put(key_ref);
646 error:
647         return ret;
648 }
649 
650 /*
651  * Search the specified keyring and any keyrings it links to for a matching
652  * key.  Only keyrings that grant the caller Search permission will be searched
653  * (this includes the starting keyring).  Only keys with Search permission can
654  * be found.
655  *
656  * If successful, the found key will be linked to the destination keyring if
657  * supplied and the key has Link permission, and the found key ID will be
658  * returned.
659  */
660 long keyctl_keyring_search(key_serial_t ringid,
661                            const char __user *_type,
662                            const char __user *_description,
663                            key_serial_t destringid)
664 {
665         struct key_type *ktype;
666         key_ref_t keyring_ref, key_ref, dest_ref;
667         char type[32], *description;
668         long ret;
669 
670         /* pull the type and description into kernel space */
671         ret = key_get_type_from_user(type, _type, sizeof(type));
672         if (ret < 0)
673                 goto error;
674 
675         description = strndup_user(_description, KEY_MAX_DESC_SIZE);
676         if (IS_ERR(description)) {
677                 ret = PTR_ERR(description);
678                 goto error;
679         }
680 
681         /* get the keyring at which to begin the search */
682         keyring_ref = lookup_user_key(ringid, 0, KEY_NEED_SEARCH);
683         if (IS_ERR(keyring_ref)) {
684                 ret = PTR_ERR(keyring_ref);
685                 goto error2;
686         }
687 
688         /* get the destination keyring if specified */
689         dest_ref = NULL;
690         if (destringid) {
691                 dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
692                                            KEY_NEED_WRITE);
693                 if (IS_ERR(dest_ref)) {
694                         ret = PTR_ERR(dest_ref);
695                         goto error3;
696                 }
697         }
698 
699         /* find the key type */
700         ktype = key_type_lookup(type);
701         if (IS_ERR(ktype)) {
702                 ret = PTR_ERR(ktype);
703                 goto error4;
704         }
705 
706         /* do the search */
707         key_ref = keyring_search(keyring_ref, ktype, description);
708         if (IS_ERR(key_ref)) {
709                 ret = PTR_ERR(key_ref);
710 
711                 /* treat lack or presence of a negative key the same */
712                 if (ret == -EAGAIN)
713                         ret = -ENOKEY;
714                 goto error5;
715         }
716 
717         /* link the resulting key to the destination keyring if we can */
718         if (dest_ref) {
719                 ret = key_permission(key_ref, KEY_NEED_LINK);
720                 if (ret < 0)
721                         goto error6;
722 
723                 ret = key_link(key_ref_to_ptr(dest_ref), key_ref_to_ptr(key_ref));
724                 if (ret < 0)
725                         goto error6;
726         }
727 
728         ret = key_ref_to_ptr(key_ref)->serial;
729 
730 error6:
731         key_ref_put(key_ref);
732 error5:
733         key_type_put(ktype);
734 error4:
735         key_ref_put(dest_ref);
736 error3:
737         key_ref_put(keyring_ref);
738 error2:
739         kfree(description);
740 error:
741         return ret;
742 }
743 
744 /*
745  * Read a key's payload.
746  *
747  * The key must either grant the caller Read permission, or it must grant the
748  * caller Search permission when searched for from the process keyrings.
749  *
750  * If successful, we place up to buflen bytes of data into the buffer, if one
751  * is provided, and return the amount of data that is available in the key,
752  * irrespective of how much we copied into the buffer.
753  */
754 long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
755 {
756         struct key *key;
757         key_ref_t key_ref;
758         long ret;
759 
760         /* find the key first */
761         key_ref = lookup_user_key(keyid, 0, 0);
762         if (IS_ERR(key_ref)) {
763                 ret = -ENOKEY;
764                 goto error;
765         }
766 
767         key = key_ref_to_ptr(key_ref);
768 
769         ret = key_read_state(key);
770         if (ret < 0)
771                 goto error2; /* Negatively instantiated */
772 
773         /* see if we can read it directly */
774         ret = key_permission(key_ref, KEY_NEED_READ);
775         if (ret == 0)
776                 goto can_read_key;
777         if (ret != -EACCES)
778                 goto error;
779 
780         /* we can't; see if it's searchable from this process's keyrings
781          * - we automatically take account of the fact that it may be
782          *   dangling off an instantiation key
783          */
784         if (!is_key_possessed(key_ref)) {
785                 ret = -EACCES;
786                 goto error2;
787         }
788 
789         /* the key is probably readable - now try to read it */
790 can_read_key:
791         ret = -EOPNOTSUPP;
792         if (key->type->read) {
793                 /* Read the data with the semaphore held (since we might sleep)
794                  * to protect against the key being updated or revoked.
795                  */
796                 down_read(&key->sem);
797                 ret = key_validate(key);
798                 if (ret == 0)
799                         ret = key->type->read(key, buffer, buflen);
800                 up_read(&key->sem);
801         }
802 
803 error2:
804         key_put(key);
805 error:
806         return ret;
807 }
808 
809 /*
810  * Change the ownership of a key
811  *
812  * The key must grant the caller Setattr permission for this to work, though
813  * the key need not be fully instantiated yet.  For the UID to be changed, or
814  * for the GID to be changed to a group the caller is not a member of, the
815  * caller must have sysadmin capability.  If either uid or gid is -1 then that
816  * attribute is not changed.
817  *
818  * If the UID is to be changed, the new user must have sufficient quota to
819  * accept the key.  The quota deduction will be removed from the old user to
820  * the new user should the attribute be changed.
821  *
822  * If successful, 0 will be returned.
823  */
824 long keyctl_chown_key(key_serial_t id, uid_t user, gid_t group)
825 {
826         struct key_user *newowner, *zapowner = NULL;
827         struct key *key;
828         key_ref_t key_ref;
829         long ret;
830         kuid_t uid;
831         kgid_t gid;
832 
833         uid = make_kuid(current_user_ns(), user);
834         gid = make_kgid(current_user_ns(), group);
835         ret = -EINVAL;
836         if ((user != (uid_t) -1) && !uid_valid(uid))
837                 goto error;
838         if ((group != (gid_t) -1) && !gid_valid(gid))
839                 goto error;
840 
841         ret = 0;
842         if (user == (uid_t) -1 && group == (gid_t) -1)
843                 goto error;
844 
845         key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
846                                   KEY_NEED_SETATTR);
847         if (IS_ERR(key_ref)) {
848                 ret = PTR_ERR(key_ref);
849                 goto error;
850         }
851 
852         key = key_ref_to_ptr(key_ref);
853 
854         /* make the changes with the locks held to prevent chown/chown races */
855         ret = -EACCES;
856         down_write(&key->sem);
857 
858         if (!capable(CAP_SYS_ADMIN)) {
859                 /* only the sysadmin can chown a key to some other UID */
860                 if (user != (uid_t) -1 && !uid_eq(key->uid, uid))
861                         goto error_put;
862 
863                 /* only the sysadmin can set the key's GID to a group other
864                  * than one of those that the current process subscribes to */
865                 if (group != (gid_t) -1 && !gid_eq(gid, key->gid) && !in_group_p(gid))
866                         goto error_put;
867         }
868 
869         /* change the UID */
870         if (user != (uid_t) -1 && !uid_eq(uid, key->uid)) {
871                 ret = -ENOMEM;
872                 newowner = key_user_lookup(uid);
873                 if (!newowner)
874                         goto error_put;
875 
876                 /* transfer the quota burden to the new user */
877                 if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
878                         unsigned maxkeys = uid_eq(uid, GLOBAL_ROOT_UID) ?
879                                 key_quota_root_maxkeys : key_quota_maxkeys;
880                         unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ?
881                                 key_quota_root_maxbytes : key_quota_maxbytes;
882 
883                         spin_lock(&newowner->lock);
884                         if (newowner->qnkeys + 1 >= maxkeys ||
885                             newowner->qnbytes + key->quotalen >= maxbytes ||
886                             newowner->qnbytes + key->quotalen <
887                             newowner->qnbytes)
888                                 goto quota_overrun;
889 
890                         newowner->qnkeys++;
891                         newowner->qnbytes += key->quotalen;
892                         spin_unlock(&newowner->lock);
893 
894                         spin_lock(&key->user->lock);
895                         key->user->qnkeys--;
896                         key->user->qnbytes -= key->quotalen;
897                         spin_unlock(&key->user->lock);
898                 }
899 
900                 atomic_dec(&key->user->nkeys);
901                 atomic_inc(&newowner->nkeys);
902 
903                 if (key->state != KEY_IS_UNINSTANTIATED) {
904                         atomic_dec(&key->user->nikeys);
905                         atomic_inc(&newowner->nikeys);
906                 }
907 
908                 zapowner = key->user;
909                 key->user = newowner;
910                 key->uid = uid;
911         }
912 
913         /* change the GID */
914         if (group != (gid_t) -1)
915                 key->gid = gid;
916 
917         ret = 0;
918 
919 error_put:
920         up_write(&key->sem);
921         key_put(key);
922         if (zapowner)
923                 key_user_put(zapowner);
924 error:
925         return ret;
926 
927 quota_overrun:
928         spin_unlock(&newowner->lock);
929         zapowner = newowner;
930         ret = -EDQUOT;
931         goto error_put;
932 }
933 
934 /*
935  * Change the permission mask on a key.
936  *
937  * The key must grant the caller Setattr permission for this to work, though
938  * the key need not be fully instantiated yet.  If the caller does not have
939  * sysadmin capability, it may only change the permission on keys that it owns.
940  */
941 long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
942 {
943         struct key *key;
944         key_ref_t key_ref;
945         long ret;
946 
947         ret = -EINVAL;
948         if (perm & ~(KEY_POS_ALL | KEY_USR_ALL | KEY_GRP_ALL | KEY_OTH_ALL))
949                 goto error;
950 
951         key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
952                                   KEY_NEED_SETATTR);
953         if (IS_ERR(key_ref)) {
954                 ret = PTR_ERR(key_ref);
955                 goto error;
956         }
957 
958         key = key_ref_to_ptr(key_ref);
959 
960         /* make the changes with the locks held to prevent chown/chmod races */
961         ret = -EACCES;
962         down_write(&key->sem);
963 
964         /* if we're not the sysadmin, we can only change a key that we own */
965         if (capable(CAP_SYS_ADMIN) || uid_eq(key->uid, current_fsuid())) {
966                 key->perm = perm;
967                 ret = 0;
968         }
969 
970         up_write(&key->sem);
971         key_put(key);
972 error:
973         return ret;
974 }
975 
976 /*
977  * Get the destination keyring for instantiation and check that the caller has
978  * Write permission on it.
979  */
980 static long get_instantiation_keyring(key_serial_t ringid,
981                                       struct request_key_auth *rka,
982                                       struct key **_dest_keyring)
983 {
984         key_ref_t dkref;
985 
986         *_dest_keyring = NULL;
987 
988         /* just return a NULL pointer if we weren't asked to make a link */
989         if (ringid == 0)
990                 return 0;
991 
992         /* if a specific keyring is nominated by ID, then use that */
993         if (ringid > 0) {
994                 dkref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
995                 if (IS_ERR(dkref))
996                         return PTR_ERR(dkref);
997                 *_dest_keyring = key_ref_to_ptr(dkref);
998                 return 0;
999         }
1000 
1001         if (ringid == KEY_SPEC_REQKEY_AUTH_KEY)
1002                 return -EINVAL;
1003 
1004         /* otherwise specify the destination keyring recorded in the
1005          * authorisation key (any KEY_SPEC_*_KEYRING) */
1006         if (ringid >= KEY_SPEC_REQUESTOR_KEYRING) {
1007                 *_dest_keyring = key_get(rka->dest_keyring);
1008                 return 0;
1009         }
1010 
1011         return -ENOKEY;
1012 }
1013 
1014 /*
1015  * Change the request_key authorisation key on the current process.
1016  */
1017 static int keyctl_change_reqkey_auth(struct key *key)
1018 {
1019         struct cred *new;
1020 
1021         new = prepare_creds();
1022         if (!new)
1023                 return -ENOMEM;
1024 
1025         key_put(new->request_key_auth);
1026         new->request_key_auth = key_get(key);
1027 
1028         return commit_creds(new);
1029 }
1030 
1031 /*
1032  * Instantiate a key with the specified payload and link the key into the
1033  * destination keyring if one is given.
1034  *
1035  * The caller must have the appropriate instantiation permit set for this to
1036  * work (see keyctl_assume_authority).  No other permissions are required.
1037  *
1038  * If successful, 0 will be returned.
1039  */
1040 long keyctl_instantiate_key_common(key_serial_t id,
1041                                    struct iov_iter *from,
1042                                    key_serial_t ringid)
1043 {
1044         const struct cred *cred = current_cred();
1045         struct request_key_auth *rka;
1046         struct key *instkey, *dest_keyring;
1047         size_t plen = from ? iov_iter_count(from) : 0;
1048         void *payload;
1049         long ret;
1050 
1051         kenter("%d,,%zu,%d", id, plen, ringid);
1052 
1053         if (!plen)
1054                 from = NULL;
1055 
1056         ret = -EINVAL;
1057         if (plen > 1024 * 1024 - 1)
1058                 goto error;
1059 
1060         /* the appropriate instantiation authorisation key must have been
1061          * assumed before calling this */
1062         ret = -EPERM;
1063         instkey = cred->request_key_auth;
1064         if (!instkey)
1065                 goto error;
1066 
1067         rka = instkey->payload.data[0];
1068         if (rka->target_key->serial != id)
1069                 goto error;
1070 
1071         /* pull the payload in if one was supplied */
1072         payload = NULL;
1073 
1074         if (from) {
1075                 ret = -ENOMEM;
1076                 payload = kvmalloc(plen, GFP_KERNEL);
1077                 if (!payload)
1078                         goto error;
1079 
1080                 ret = -EFAULT;
1081                 if (!copy_from_iter_full(payload, plen, from))
1082                         goto error2;
1083         }
1084 
1085         /* find the destination keyring amongst those belonging to the
1086          * requesting task */
1087         ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
1088         if (ret < 0)
1089                 goto error2;
1090 
1091         /* instantiate the key and link it into a keyring */
1092         ret = key_instantiate_and_link(rka->target_key, payload, plen,
1093                                        dest_keyring, instkey);
1094 
1095         key_put(dest_keyring);
1096 
1097         /* discard the assumed authority if it's just been disabled by
1098          * instantiation of the key */
1099         if (ret == 0)
1100                 keyctl_change_reqkey_auth(NULL);
1101 
1102 error2:
1103         if (payload) {
1104                 memzero_explicit(payload, plen);
1105                 kvfree(payload);
1106         }
1107 error:
1108         return ret;
1109 }
1110 
1111 /*
1112  * Instantiate a key with the specified payload and link the key into the
1113  * destination keyring if one is given.
1114  *
1115  * The caller must have the appropriate instantiation permit set for this to
1116  * work (see keyctl_assume_authority).  No other permissions are required.
1117  *
1118  * If successful, 0 will be returned.
1119  */
1120 long keyctl_instantiate_key(key_serial_t id,
1121                             const void __user *_payload,
1122                             size_t plen,
1123                             key_serial_t ringid)
1124 {
1125         if (_payload && plen) {
1126                 struct iovec iov;
1127                 struct iov_iter from;
1128                 int ret;
1129 
1130                 ret = import_single_range(WRITE, (void __user *)_payload, plen,
1131                                           &iov, &from);
1132                 if (unlikely(ret))
1133                         return ret;
1134 
1135                 return keyctl_instantiate_key_common(id, &from, ringid);
1136         }
1137 
1138         return keyctl_instantiate_key_common(id, NULL, ringid);
1139 }
1140 
1141 /*
1142  * Instantiate a key with the specified multipart payload and link the key into
1143  * the destination keyring if one is given.
1144  *
1145  * The caller must have the appropriate instantiation permit set for this to
1146  * work (see keyctl_assume_authority).  No other permissions are required.
1147  *
1148  * If successful, 0 will be returned.
1149  */
1150 long keyctl_instantiate_key_iov(key_serial_t id,
1151                                 const struct iovec __user *_payload_iov,
1152                                 unsigned ioc,
1153                                 key_serial_t ringid)
1154 {
1155         struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
1156         struct iov_iter from;
1157         long ret;
1158 
1159         if (!_payload_iov)
1160                 ioc = 0;
1161 
1162         ret = import_iovec(WRITE, _payload_iov, ioc,
1163                                     ARRAY_SIZE(iovstack), &iov, &from);
1164         if (ret < 0)
1165                 return ret;
1166         ret = keyctl_instantiate_key_common(id, &from, ringid);
1167         kfree(iov);
1168         return ret;
1169 }
1170 
1171 /*
1172  * Negatively instantiate the key with the given timeout (in seconds) and link
1173  * the key into the destination keyring if one is given.
1174  *
1175  * The caller must have the appropriate instantiation permit set for this to
1176  * work (see keyctl_assume_authority).  No other permissions are required.
1177  *
1178  * The key and any links to the key will be automatically garbage collected
1179  * after the timeout expires.
1180  *
1181  * Negative keys are used to rate limit repeated request_key() calls by causing
1182  * them to return -ENOKEY until the negative key expires.
1183  *
1184  * If successful, 0 will be returned.
1185  */
1186 long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
1187 {
1188         return keyctl_reject_key(id, timeout, ENOKEY, ringid);
1189 }
1190 
1191 /*
1192  * Negatively instantiate the key with the given timeout (in seconds) and error
1193  * code and link the key into the destination keyring if one is given.
1194  *
1195  * The caller must have the appropriate instantiation permit set for this to
1196  * work (see keyctl_assume_authority).  No other permissions are required.
1197  *
1198  * The key and any links to the key will be automatically garbage collected
1199  * after the timeout expires.
1200  *
1201  * Negative keys are used to rate limit repeated request_key() calls by causing
1202  * them to return the specified error code until the negative key expires.
1203  *
1204  * If successful, 0 will be returned.
1205  */
1206 long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error,
1207                        key_serial_t ringid)
1208 {
1209         const struct cred *cred = current_cred();
1210         struct request_key_auth *rka;
1211         struct key *instkey, *dest_keyring;
1212         long ret;
1213 
1214         kenter("%d,%u,%u,%d", id, timeout, error, ringid);
1215 
1216         /* must be a valid error code and mustn't be a kernel special */
1217         if (error <= 0 ||
1218             error >= MAX_ERRNO ||
1219             error == ERESTARTSYS ||
1220             error == ERESTARTNOINTR ||
1221             error == ERESTARTNOHAND ||
1222             error == ERESTART_RESTARTBLOCK)
1223                 return -EINVAL;
1224 
1225         /* the appropriate instantiation authorisation key must have been
1226          * assumed before calling this */
1227         ret = -EPERM;
1228         instkey = cred->request_key_auth;
1229         if (!instkey)
1230                 goto error;
1231 
1232         rka = instkey->payload.data[0];
1233         if (rka->target_key->serial != id)
1234                 goto error;
1235 
1236         /* find the destination keyring if present (which must also be
1237          * writable) */
1238         ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
1239         if (ret < 0)
1240                 goto error;
1241 
1242         /* instantiate the key and link it into a keyring */
1243         ret = key_reject_and_link(rka->target_key, timeout, error,
1244                                   dest_keyring, instkey);
1245 
1246         key_put(dest_keyring);
1247 
1248         /* discard the assumed authority if it's just been disabled by
1249          * instantiation of the key */
1250         if (ret == 0)
1251                 keyctl_change_reqkey_auth(NULL);
1252 
1253 error:
1254         return ret;
1255 }
1256 
1257 /*
1258  * Read or set the default keyring in which request_key() will cache keys and
1259  * return the old setting.
1260  *
1261  * If a thread or process keyring is specified then it will be created if it
1262  * doesn't yet exist.  The old setting will be returned if successful.
1263  */
1264 long keyctl_set_reqkey_keyring(int reqkey_defl)
1265 {
1266         struct cred *new;
1267         int ret, old_setting;
1268 
1269         old_setting = current_cred_xxx(jit_keyring);
1270 
1271         if (reqkey_defl == KEY_REQKEY_DEFL_NO_CHANGE)
1272                 return old_setting;
1273 
1274         new = prepare_creds();
1275         if (!new)
1276                 return -ENOMEM;
1277 
1278         switch (reqkey_defl) {
1279         case KEY_REQKEY_DEFL_THREAD_KEYRING:
1280                 ret = install_thread_keyring_to_cred(new);
1281                 if (ret < 0)
1282                         goto error;
1283                 goto set;
1284 
1285         case KEY_REQKEY_DEFL_PROCESS_KEYRING:
1286                 ret = install_process_keyring_to_cred(new);
1287                 if (ret < 0)
1288                         goto error;
1289                 goto set;
1290 
1291         case KEY_REQKEY_DEFL_DEFAULT:
1292         case KEY_REQKEY_DEFL_SESSION_KEYRING:
1293         case KEY_REQKEY_DEFL_USER_KEYRING:
1294         case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
1295         case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
1296                 goto set;
1297 
1298         case KEY_REQKEY_DEFL_NO_CHANGE:
1299         case KEY_REQKEY_DEFL_GROUP_KEYRING:
1300         default:
1301                 ret = -EINVAL;
1302                 goto error;
1303         }
1304 
1305 set:
1306         new->jit_keyring = reqkey_defl;
1307         commit_creds(new);
1308         return old_setting;
1309 error:
1310         abort_creds(new);
1311         return ret;
1312 }
1313 
1314 /*
1315  * Set or clear the timeout on a key.
1316  *
1317  * Either the key must grant the caller Setattr permission or else the caller
1318  * must hold an instantiation authorisation token for the key.
1319  *
1320  * The timeout is either 0 to clear the timeout, or a number of seconds from
1321  * the current time.  The key and any links to the key will be automatically
1322  * garbage collected after the timeout expires.
1323  *
1324  * Keys with KEY_FLAG_KEEP set should not be timed out.
1325  *
1326  * If successful, 0 is returned.
1327  */
1328 long keyctl_set_timeout(key_serial_t id, unsigned timeout)
1329 {
1330         struct key *key, *instkey;
1331         key_ref_t key_ref;
1332         long ret;
1333 
1334         key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
1335                                   KEY_NEED_SETATTR);
1336         if (IS_ERR(key_ref)) {
1337                 /* setting the timeout on a key under construction is permitted
1338                  * if we have the authorisation token handy */
1339                 if (PTR_ERR(key_ref) == -EACCES) {
1340                         instkey = key_get_instantiation_authkey(id);
1341                         if (!IS_ERR(instkey)) {
1342                                 key_put(instkey);
1343                                 key_ref = lookup_user_key(id,
1344                                                           KEY_LOOKUP_PARTIAL,
1345                                                           0);
1346                                 if (!IS_ERR(key_ref))
1347                                         goto okay;
1348                         }
1349                 }
1350 
1351                 ret = PTR_ERR(key_ref);
1352                 goto error;
1353         }
1354 
1355 okay:
1356         key = key_ref_to_ptr(key_ref);
1357         ret = 0;
1358         if (test_bit(KEY_FLAG_KEEP, &key->flags))
1359                 ret = -EPERM;
1360         else
1361                 key_set_timeout(key, timeout);
1362         key_put(key);
1363 
1364 error:
1365         return ret;
1366 }
1367 
1368 /*
1369  * Assume (or clear) the authority to instantiate the specified key.
1370  *
1371  * This sets the authoritative token currently in force for key instantiation.
1372  * This must be done for a key to be instantiated.  It has the effect of making
1373  * available all the keys from the caller of the request_key() that created a
1374  * key to request_key() calls made by the caller of this function.
1375  *
1376  * The caller must have the instantiation key in their process keyrings with a
1377  * Search permission grant available to the caller.
1378  *
1379  * If the ID given is 0, then the setting will be cleared and 0 returned.
1380  *
1381  * If the ID given has a matching an authorisation key, then that key will be
1382  * set and its ID will be returned.  The authorisation key can be read to get
1383  * the callout information passed to request_key().
1384  */
1385 long keyctl_assume_authority(key_serial_t id)
1386 {
1387         struct key *authkey;
1388         long ret;
1389 
1390         /* special key IDs aren't permitted */
1391         ret = -EINVAL;
1392         if (id < 0)
1393                 goto error;
1394 
1395         /* we divest ourselves of authority if given an ID of 0 */
1396         if (id == 0) {
1397                 ret = keyctl_change_reqkey_auth(NULL);
1398                 goto error;
1399         }
1400 
1401         /* attempt to assume the authority temporarily granted to us whilst we
1402          * instantiate the specified key
1403          * - the authorisation key must be in the current task's keyrings
1404          *   somewhere
1405          */
1406         authkey = key_get_instantiation_authkey(id);
1407         if (IS_ERR(authkey)) {
1408                 ret = PTR_ERR(authkey);
1409                 goto error;
1410         }
1411 
1412         ret = keyctl_change_reqkey_auth(authkey);
1413         if (ret < 0)
1414                 goto error;
1415         key_put(authkey);
1416 
1417         ret = authkey->serial;
1418 error:
1419         return ret;
1420 }
1421 
1422 /*
1423  * Get a key's the LSM security label.
1424  *
1425  * The key must grant the caller View permission for this to work.
1426  *
1427  * If there's a buffer, then up to buflen bytes of data will be placed into it.
1428  *
1429  * If successful, the amount of information available will be returned,
1430  * irrespective of how much was copied (including the terminal NUL).
1431  */
1432 long keyctl_get_security(key_serial_t keyid,
1433                          char __user *buffer,
1434                          size_t buflen)
1435 {
1436         struct key *key, *instkey;
1437         key_ref_t key_ref;
1438         char *context;
1439         long ret;
1440 
1441         key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_NEED_VIEW);
1442         if (IS_ERR(key_ref)) {
1443                 if (PTR_ERR(key_ref) != -EACCES)
1444                         return PTR_ERR(key_ref);
1445 
1446                 /* viewing a key under construction is also permitted if we
1447                  * have the authorisation token handy */
1448                 instkey = key_get_instantiation_authkey(keyid);
1449                 if (IS_ERR(instkey))
1450                         return PTR_ERR(instkey);
1451                 key_put(instkey);
1452 
1453                 key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, 0);
1454                 if (IS_ERR(key_ref))
1455                         return PTR_ERR(key_ref);
1456         }
1457 
1458         key = key_ref_to_ptr(key_ref);
1459         ret = security_key_getsecurity(key, &context);
1460         if (ret == 0) {
1461                 /* if no information was returned, give userspace an empty
1462                  * string */
1463                 ret = 1;
1464                 if (buffer && buflen > 0 &&
1465                     copy_to_user(buffer, "", 1) != 0)
1466                         ret = -EFAULT;
1467         } else if (ret > 0) {
1468                 /* return as much data as there's room for */
1469                 if (buffer && buflen > 0) {
1470                         if (buflen > ret)
1471                                 buflen = ret;
1472 
1473                         if (copy_to_user(buffer, context, buflen) != 0)
1474                                 ret = -EFAULT;
1475                 }
1476 
1477                 kfree(context);
1478         }
1479 
1480         key_ref_put(key_ref);
1481         return ret;
1482 }
1483 
1484 /*
1485  * Attempt to install the calling process's session keyring on the process's
1486  * parent process.
1487  *
1488  * The keyring must exist and must grant the caller LINK permission, and the
1489  * parent process must be single-threaded and must have the same effective
1490  * ownership as this process and mustn't be SUID/SGID.
1491  *
1492  * The keyring will be emplaced on the parent when it next resumes userspace.
1493  *
1494  * If successful, 0 will be returned.
1495  */
1496 long keyctl_session_to_parent(void)
1497 {
1498         struct task_struct *me, *parent;
1499         const struct cred *mycred, *pcred;
1500         struct callback_head *newwork, *oldwork;
1501         key_ref_t keyring_r;
1502         struct cred *cred;
1503         int ret;
1504 
1505         keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_NEED_LINK);
1506         if (IS_ERR(keyring_r))
1507                 return PTR_ERR(keyring_r);
1508 
1509         ret = -ENOMEM;
1510 
1511         /* our parent is going to need a new cred struct, a new tgcred struct
1512          * and new security data, so we allocate them here to prevent ENOMEM in
1513          * our parent */
1514         cred = cred_alloc_blank();
1515         if (!cred)
1516                 goto error_keyring;
1517         newwork = &cred->rcu;
1518 
1519         cred->session_keyring = key_ref_to_ptr(keyring_r);
1520         keyring_r = NULL;
1521         init_task_work(newwork, key_change_session_keyring);
1522 
1523         me = current;
1524         rcu_read_lock();
1525         write_lock_irq(&tasklist_lock);
1526 
1527         ret = -EPERM;
1528         oldwork = NULL;
1529         parent = me->real_parent;
1530 
1531         /* the parent mustn't be init and mustn't be a kernel thread */
1532         if (parent->pid <= 1 || !parent->mm)
1533                 goto unlock;
1534 
1535         /* the parent must be single threaded */
1536         if (!thread_group_empty(parent))
1537                 goto unlock;
1538 
1539         /* the parent and the child must have different session keyrings or
1540          * there's no point */
1541         mycred = current_cred();
1542         pcred = __task_cred(parent);
1543         if (mycred == pcred ||
1544             mycred->session_keyring == pcred->session_keyring) {
1545                 ret = 0;
1546                 goto unlock;
1547         }
1548 
1549         /* the parent must have the same effective ownership and mustn't be
1550          * SUID/SGID */
1551         if (!uid_eq(pcred->uid,  mycred->euid) ||
1552             !uid_eq(pcred->euid, mycred->euid) ||
1553             !uid_eq(pcred->suid, mycred->euid) ||
1554             !gid_eq(pcred->gid,  mycred->egid) ||
1555             !gid_eq(pcred->egid, mycred->egid) ||
1556             !gid_eq(pcred->sgid, mycred->egid))
1557                 goto unlock;
1558 
1559         /* the keyrings must have the same UID */
1560         if ((pcred->session_keyring &&
1561              !uid_eq(pcred->session_keyring->uid, mycred->euid)) ||
1562             !uid_eq(mycred->session_keyring->uid, mycred->euid))
1563                 goto unlock;
1564 
1565         /* cancel an already pending keyring replacement */
1566         oldwork = task_work_cancel(parent, key_change_session_keyring);
1567 
1568         /* the replacement session keyring is applied just prior to userspace
1569          * restarting */
1570         ret = task_work_add(parent, newwork, true);
1571         if (!ret)
1572                 newwork = NULL;
1573 unlock:
1574         write_unlock_irq(&tasklist_lock);
1575         rcu_read_unlock();
1576         if (oldwork)
1577                 put_cred(container_of(oldwork, struct cred, rcu));
1578         if (newwork)
1579                 put_cred(cred);
1580         return ret;
1581 
1582 error_keyring:
1583         key_ref_put(keyring_r);
1584         return ret;
1585 }
1586 
1587 /*
1588  * Apply a restriction to a given keyring.
1589  *
1590  * The caller must have Setattr permission to change keyring restrictions.
1591  *
1592  * The requested type name may be a NULL pointer to reject all attempts
1593  * to link to the keyring. If _type is non-NULL, _restriction can be
1594  * NULL or a pointer to a string describing the restriction. If _type is
1595  * NULL, _restriction must also be NULL.
1596  *
1597  * Returns 0 if successful.
1598  */
1599 long keyctl_restrict_keyring(key_serial_t id, const char __user *_type,
1600                              const char __user *_restriction)
1601 {
1602         key_ref_t key_ref;
1603         bool link_reject = !_type;
1604         char type[32];
1605         char *restriction = NULL;
1606         long ret;
1607 
1608         key_ref = lookup_user_key(id, 0, KEY_NEED_SETATTR);
1609         if (IS_ERR(key_ref))
1610                 return PTR_ERR(key_ref);
1611 
1612         if (_type) {
1613                 ret = key_get_type_from_user(type, _type, sizeof(type));
1614                 if (ret < 0)
1615                         goto error;
1616         }
1617 
1618         if (_restriction) {
1619                 if (!_type) {
1620                         ret = -EINVAL;
1621                         goto error;
1622                 }
1623 
1624                 restriction = strndup_user(_restriction, PAGE_SIZE);
1625                 if (IS_ERR(restriction)) {
1626                         ret = PTR_ERR(restriction);
1627                         goto error;
1628                 }
1629         }
1630 
1631         ret = keyring_restrict(key_ref, link_reject ? NULL : type, restriction);
1632         kfree(restriction);
1633 
1634 error:
1635         key_ref_put(key_ref);
1636 
1637         return ret;
1638 }
1639 
1640 /*
1641  * The key control system call
1642  */
1643 SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
1644                 unsigned long, arg4, unsigned long, arg5)
1645 {
1646         switch (option) {
1647         case KEYCTL_GET_KEYRING_ID:
1648                 return keyctl_get_keyring_ID((key_serial_t) arg2,
1649                                              (int) arg3);
1650 
1651         case KEYCTL_JOIN_SESSION_KEYRING:
1652                 return keyctl_join_session_keyring((const char __user *) arg2);
1653 
1654         case KEYCTL_UPDATE:
1655                 return keyctl_update_key((key_serial_t) arg2,
1656                                          (const void __user *) arg3,
1657                                          (size_t) arg4);
1658 
1659         case KEYCTL_REVOKE:
1660                 return keyctl_revoke_key((key_serial_t) arg2);
1661 
1662         case KEYCTL_DESCRIBE:
1663                 return keyctl_describe_key((key_serial_t) arg2,
1664                                            (char __user *) arg3,
1665                                            (unsigned) arg4);
1666 
1667         case KEYCTL_CLEAR:
1668                 return keyctl_keyring_clear((key_serial_t) arg2);
1669 
1670         case KEYCTL_LINK:
1671                 return keyctl_keyring_link((key_serial_t) arg2,
1672                                            (key_serial_t) arg3);
1673 
1674         case KEYCTL_UNLINK:
1675                 return keyctl_keyring_unlink((key_serial_t) arg2,
1676                                              (key_serial_t) arg3);
1677 
1678         case KEYCTL_SEARCH:
1679                 return keyctl_keyring_search((key_serial_t) arg2,
1680                                              (const char __user *) arg3,
1681                                              (const char __user *) arg4,
1682                                              (key_serial_t) arg5);
1683 
1684         case KEYCTL_READ:
1685                 return keyctl_read_key((key_serial_t) arg2,
1686                                        (char __user *) arg3,
1687                                        (size_t) arg4);
1688 
1689         case KEYCTL_CHOWN:
1690                 return keyctl_chown_key((key_serial_t) arg2,
1691                                         (uid_t) arg3,
1692                                         (gid_t) arg4);
1693 
1694         case KEYCTL_SETPERM:
1695                 return keyctl_setperm_key((key_serial_t) arg2,
1696                                           (key_perm_t) arg3);
1697 
1698         case KEYCTL_INSTANTIATE:
1699                 return keyctl_instantiate_key((key_serial_t) arg2,
1700                                               (const void __user *) arg3,
1701                                               (size_t) arg4,
1702                                               (key_serial_t) arg5);
1703 
1704         case KEYCTL_NEGATE:
1705                 return keyctl_negate_key((key_serial_t) arg2,
1706                                          (unsigned) arg3,
1707                                          (key_serial_t) arg4);
1708 
1709         case KEYCTL_SET_REQKEY_KEYRING:
1710                 return keyctl_set_reqkey_keyring(arg2);
1711 
1712         case KEYCTL_SET_TIMEOUT:
1713                 return keyctl_set_timeout((key_serial_t) arg2,
1714                                           (unsigned) arg3);
1715 
1716         case KEYCTL_ASSUME_AUTHORITY:
1717                 return keyctl_assume_authority((key_serial_t) arg2);
1718 
1719         case KEYCTL_GET_SECURITY:
1720                 return keyctl_get_security((key_serial_t) arg2,
1721                                            (char __user *) arg3,
1722                                            (size_t) arg4);
1723 
1724         case KEYCTL_SESSION_TO_PARENT:
1725                 return keyctl_session_to_parent();
1726 
1727         case KEYCTL_REJECT:
1728                 return keyctl_reject_key((key_serial_t) arg2,
1729                                          (unsigned) arg3,
1730                                          (unsigned) arg4,
1731                                          (key_serial_t) arg5);
1732 
1733         case KEYCTL_INSTANTIATE_IOV:
1734                 return keyctl_instantiate_key_iov(
1735                         (key_serial_t) arg2,
1736                         (const struct iovec __user *) arg3,
1737                         (unsigned) arg4,
1738                         (key_serial_t) arg5);
1739 
1740         case KEYCTL_INVALIDATE:
1741                 return keyctl_invalidate_key((key_serial_t) arg2);
1742 
1743         case KEYCTL_GET_PERSISTENT:
1744                 return keyctl_get_persistent((uid_t)arg2, (key_serial_t)arg3);
1745 
1746         case KEYCTL_DH_COMPUTE:
1747                 return keyctl_dh_compute((struct keyctl_dh_params __user *) arg2,
1748                                          (char __user *) arg3, (size_t) arg4,
1749                                          (struct keyctl_kdf_params __user *) arg5);
1750 
1751         case KEYCTL_RESTRICT_KEYRING:
1752                 return keyctl_restrict_keyring((key_serial_t) arg2,
1753                                                (const char __user *) arg3,
1754                                                (const char __user *) arg4);
1755 
1756         default:
1757                 return -EOPNOTSUPP;
1758         }
1759 }
1760 

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