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1 : : // SPDX-License-Identifier: GPL-2.0
2 : : /*
3 : : * Filesystem-level keyring for fscrypt
4 : : *
5 : : * Copyright 2019 Google LLC
6 : : */
7 : :
8 : : /*
9 : : * This file implements management of fscrypt master keys in the
10 : : * filesystem-level keyring, including the ioctls:
11 : : *
12 : : * - FS_IOC_ADD_ENCRYPTION_KEY
13 : : * - FS_IOC_REMOVE_ENCRYPTION_KEY
14 : : * - FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS
15 : : * - FS_IOC_GET_ENCRYPTION_KEY_STATUS
16 : : *
17 : : * See the "User API" section of Documentation/filesystems/fscrypt.rst for more
18 : : * information about these ioctls.
19 : : */
20 : :
21 : : #include <crypto/skcipher.h>
22 : : #include <linux/key-type.h>
23 : : #include <linux/seq_file.h>
24 : :
25 : : #include "fscrypt_private.h"
26 : :
27 : 0 : static void wipe_master_key_secret(struct fscrypt_master_key_secret *secret)
28 : : {
29 : 0 : fscrypt_destroy_hkdf(&secret->hkdf);
30 : : memzero_explicit(secret, sizeof(*secret));
31 : 0 : }
32 : :
33 : 0 : static void move_master_key_secret(struct fscrypt_master_key_secret *dst,
34 : : struct fscrypt_master_key_secret *src)
35 : : {
36 : 0 : memcpy(dst, src, sizeof(*dst));
37 : : memzero_explicit(src, sizeof(*src));
38 : 0 : }
39 : :
40 : 0 : static void free_master_key(struct fscrypt_master_key *mk)
41 : : {
42 : : size_t i;
43 : :
44 : 0 : wipe_master_key_secret(&mk->mk_secret);
45 : :
46 [ # # ]: 0 : for (i = 0; i < ARRAY_SIZE(mk->mk_mode_keys); i++)
47 : 0 : crypto_free_skcipher(mk->mk_mode_keys[i]);
48 : :
49 : 0 : key_put(mk->mk_users);
50 : 0 : kzfree(mk);
51 : 0 : }
52 : :
53 : : static inline bool valid_key_spec(const struct fscrypt_key_specifier *spec)
54 : : {
55 [ # # # # : 0 : if (spec->__reserved)
# # ]
56 : : return false;
57 : 0 : return master_key_spec_len(spec) != 0;
58 : : }
59 : :
60 : 0 : static int fscrypt_key_instantiate(struct key *key,
61 : : struct key_preparsed_payload *prep)
62 : : {
63 : 0 : key->payload.data[0] = (struct fscrypt_master_key *)prep->data;
64 : 0 : return 0;
65 : : }
66 : :
67 : 0 : static void fscrypt_key_destroy(struct key *key)
68 : : {
69 : 0 : free_master_key(key->payload.data[0]);
70 : 0 : }
71 : :
72 : 0 : static void fscrypt_key_describe(const struct key *key, struct seq_file *m)
73 : : {
74 : 0 : seq_puts(m, key->description);
75 : :
76 [ # # ]: 0 : if (key_is_positive(key)) {
77 : 0 : const struct fscrypt_master_key *mk = key->payload.data[0];
78 : :
79 [ # # ]: 0 : if (!is_master_key_secret_present(&mk->mk_secret))
80 : 0 : seq_puts(m, ": secret removed");
81 : : }
82 : 0 : }
83 : :
84 : : /*
85 : : * Type of key in ->s_master_keys. Each key of this type represents a master
86 : : * key which has been added to the filesystem. Its payload is a
87 : : * 'struct fscrypt_master_key'. The "." prefix in the key type name prevents
88 : : * users from adding keys of this type via the keyrings syscalls rather than via
89 : : * the intended method of FS_IOC_ADD_ENCRYPTION_KEY.
90 : : */
91 : : static struct key_type key_type_fscrypt = {
92 : : .name = "._fscrypt",
93 : : .instantiate = fscrypt_key_instantiate,
94 : : .destroy = fscrypt_key_destroy,
95 : : .describe = fscrypt_key_describe,
96 : : };
97 : :
98 : 0 : static int fscrypt_user_key_instantiate(struct key *key,
99 : : struct key_preparsed_payload *prep)
100 : : {
101 : : /*
102 : : * We just charge FSCRYPT_MAX_KEY_SIZE bytes to the user's key quota for
103 : : * each key, regardless of the exact key size. The amount of memory
104 : : * actually used is greater than the size of the raw key anyway.
105 : : */
106 : 0 : return key_payload_reserve(key, FSCRYPT_MAX_KEY_SIZE);
107 : : }
108 : :
109 : 0 : static void fscrypt_user_key_describe(const struct key *key, struct seq_file *m)
110 : : {
111 : 0 : seq_puts(m, key->description);
112 : 0 : }
113 : :
114 : : /*
115 : : * Type of key in ->mk_users. Each key of this type represents a particular
116 : : * user who has added a particular master key.
117 : : *
118 : : * Note that the name of this key type really should be something like
119 : : * ".fscrypt-user" instead of simply ".fscrypt". But the shorter name is chosen
120 : : * mainly for simplicity of presentation in /proc/keys when read by a non-root
121 : : * user. And it is expected to be rare that a key is actually added by multiple
122 : : * users, since users should keep their encryption keys confidential.
123 : : */
124 : : static struct key_type key_type_fscrypt_user = {
125 : : .name = ".fscrypt",
126 : : .instantiate = fscrypt_user_key_instantiate,
127 : : .describe = fscrypt_user_key_describe,
128 : : };
129 : :
130 : : /* Search ->s_master_keys or ->mk_users */
131 : 0 : static struct key *search_fscrypt_keyring(struct key *keyring,
132 : : struct key_type *type,
133 : : const char *description)
134 : : {
135 : : /*
136 : : * We need to mark the keyring reference as "possessed" so that we
137 : : * acquire permission to search it, via the KEY_POS_SEARCH permission.
138 : : */
139 : : key_ref_t keyref = make_key_ref(keyring, true /* possessed */);
140 : :
141 : 0 : keyref = keyring_search(keyref, type, description, false);
142 [ # # ]: 0 : if (IS_ERR(keyref)) {
143 [ # # # # ]: 0 : if (PTR_ERR(keyref) == -EAGAIN || /* not found */
144 : : PTR_ERR(keyref) == -EKEYREVOKED) /* recently invalidated */
145 : : keyref = ERR_PTR(-ENOKEY);
146 : 0 : return ERR_CAST(keyref);
147 : : }
148 : 0 : return key_ref_to_ptr(keyref);
149 : : }
150 : :
151 : : #define FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE \
152 : : (CONST_STRLEN("fscrypt-") + FIELD_SIZEOF(struct super_block, s_id))
153 : :
154 : : #define FSCRYPT_MK_DESCRIPTION_SIZE (2 * FSCRYPT_KEY_IDENTIFIER_SIZE + 1)
155 : :
156 : : #define FSCRYPT_MK_USERS_DESCRIPTION_SIZE \
157 : : (CONST_STRLEN("fscrypt-") + 2 * FSCRYPT_KEY_IDENTIFIER_SIZE + \
158 : : CONST_STRLEN("-users") + 1)
159 : :
160 : : #define FSCRYPT_MK_USER_DESCRIPTION_SIZE \
161 : : (2 * FSCRYPT_KEY_IDENTIFIER_SIZE + CONST_STRLEN(".uid.") + 10 + 1)
162 : :
163 : : static void format_fs_keyring_description(
164 : : char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE],
165 : : const struct super_block *sb)
166 : : {
167 : 0 : sprintf(description, "fscrypt-%s", sb->s_id);
168 : : }
169 : :
170 : 0 : static void format_mk_description(
171 : : char description[FSCRYPT_MK_DESCRIPTION_SIZE],
172 : : const struct fscrypt_key_specifier *mk_spec)
173 : : {
174 : 0 : sprintf(description, "%*phN",
175 : 0 : master_key_spec_len(mk_spec), (u8 *)&mk_spec->u);
176 : 0 : }
177 : :
178 : : static void format_mk_users_keyring_description(
179 : : char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE],
180 : : const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
181 : : {
182 : 0 : sprintf(description, "fscrypt-%*phN-users",
183 : : FSCRYPT_KEY_IDENTIFIER_SIZE, mk_identifier);
184 : : }
185 : :
186 : 0 : static void format_mk_user_description(
187 : : char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE],
188 : : const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
189 : : {
190 : :
191 : 0 : sprintf(description, "%*phN.uid.%u", FSCRYPT_KEY_IDENTIFIER_SIZE,
192 : 0 : mk_identifier, __kuid_val(current_fsuid()));
193 : 0 : }
194 : :
195 : : /* Create ->s_master_keys if needed. Synchronized by fscrypt_add_key_mutex. */
196 : 0 : static int allocate_filesystem_keyring(struct super_block *sb)
197 : : {
198 : : char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE];
199 : : struct key *keyring;
200 : :
201 [ # # ]: 0 : if (sb->s_master_keys)
202 : : return 0;
203 : :
204 : : format_fs_keyring_description(description, sb);
205 : 0 : keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
206 : 0 : current_cred(), KEY_POS_SEARCH |
207 : : KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW,
208 : : KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
209 [ # # ]: 0 : if (IS_ERR(keyring))
210 : 0 : return PTR_ERR(keyring);
211 : :
212 : : /* Pairs with READ_ONCE() in fscrypt_find_master_key() */
213 : 0 : smp_store_release(&sb->s_master_keys, keyring);
214 : 0 : return 0;
215 : : }
216 : :
217 : 808 : void fscrypt_sb_free(struct super_block *sb)
218 : : {
219 : 808 : key_put(sb->s_master_keys);
220 : 808 : sb->s_master_keys = NULL;
221 : 808 : }
222 : :
223 : : /*
224 : : * Find the specified master key in ->s_master_keys.
225 : : * Returns ERR_PTR(-ENOKEY) if not found.
226 : : */
227 : 0 : struct key *fscrypt_find_master_key(struct super_block *sb,
228 : : const struct fscrypt_key_specifier *mk_spec)
229 : : {
230 : : struct key *keyring;
231 : : char description[FSCRYPT_MK_DESCRIPTION_SIZE];
232 : :
233 : : /* pairs with smp_store_release() in allocate_filesystem_keyring() */
234 : 0 : keyring = READ_ONCE(sb->s_master_keys);
235 [ # # ]: 0 : if (keyring == NULL)
236 : : return ERR_PTR(-ENOKEY); /* No keyring yet, so no keys yet. */
237 : :
238 : 0 : format_mk_description(description, mk_spec);
239 : 0 : return search_fscrypt_keyring(keyring, &key_type_fscrypt, description);
240 : : }
241 : :
242 : 0 : static int allocate_master_key_users_keyring(struct fscrypt_master_key *mk)
243 : : {
244 : : char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE];
245 : : struct key *keyring;
246 : :
247 : : format_mk_users_keyring_description(description,
248 : 0 : mk->mk_spec.u.identifier);
249 : 0 : keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
250 : 0 : current_cred(), KEY_POS_SEARCH |
251 : : KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW,
252 : : KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
253 [ # # ]: 0 : if (IS_ERR(keyring))
254 : 0 : return PTR_ERR(keyring);
255 : :
256 : 0 : mk->mk_users = keyring;
257 : 0 : return 0;
258 : : }
259 : :
260 : : /*
261 : : * Find the current user's "key" in the master key's ->mk_users.
262 : : * Returns ERR_PTR(-ENOKEY) if not found.
263 : : */
264 : 0 : static struct key *find_master_key_user(struct fscrypt_master_key *mk)
265 : : {
266 : : char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE];
267 : :
268 : 0 : format_mk_user_description(description, mk->mk_spec.u.identifier);
269 : 0 : return search_fscrypt_keyring(mk->mk_users, &key_type_fscrypt_user,
270 : : description);
271 : : }
272 : :
273 : : /*
274 : : * Give the current user a "key" in ->mk_users. This charges the user's quota
275 : : * and marks the master key as added by the current user, so that it cannot be
276 : : * removed by another user with the key. Either the master key's key->sem must
277 : : * be held for write, or the master key must be still undergoing initialization.
278 : : */
279 : 0 : static int add_master_key_user(struct fscrypt_master_key *mk)
280 : : {
281 : : char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE];
282 : : struct key *mk_user;
283 : : int err;
284 : :
285 : 0 : format_mk_user_description(description, mk->mk_spec.u.identifier);
286 : 0 : mk_user = key_alloc(&key_type_fscrypt_user, description,
287 : 0 : current_fsuid(), current_gid(), current_cred(),
288 : : KEY_POS_SEARCH | KEY_USR_VIEW, 0, NULL);
289 [ # # ]: 0 : if (IS_ERR(mk_user))
290 : 0 : return PTR_ERR(mk_user);
291 : :
292 : 0 : err = key_instantiate_and_link(mk_user, NULL, 0, mk->mk_users, NULL);
293 : 0 : key_put(mk_user);
294 : 0 : return err;
295 : : }
296 : :
297 : : /*
298 : : * Remove the current user's "key" from ->mk_users.
299 : : * The master key's key->sem must be held for write.
300 : : *
301 : : * Returns 0 if removed, -ENOKEY if not found, or another -errno code.
302 : : */
303 : 0 : static int remove_master_key_user(struct fscrypt_master_key *mk)
304 : : {
305 : : struct key *mk_user;
306 : : int err;
307 : :
308 : 0 : mk_user = find_master_key_user(mk);
309 [ # # ]: 0 : if (IS_ERR(mk_user))
310 : 0 : return PTR_ERR(mk_user);
311 : 0 : err = key_unlink(mk->mk_users, mk_user);
312 : 0 : key_put(mk_user);
313 : 0 : return err;
314 : : }
315 : :
316 : : /*
317 : : * Allocate a new fscrypt_master_key which contains the given secret, set it as
318 : : * the payload of a new 'struct key' of type fscrypt, and link the 'struct key'
319 : : * into the given keyring. Synchronized by fscrypt_add_key_mutex.
320 : : */
321 : 0 : static int add_new_master_key(struct fscrypt_master_key_secret *secret,
322 : : const struct fscrypt_key_specifier *mk_spec,
323 : : struct key *keyring)
324 : : {
325 : : struct fscrypt_master_key *mk;
326 : : char description[FSCRYPT_MK_DESCRIPTION_SIZE];
327 : : struct key *key;
328 : : int err;
329 : :
330 : 0 : mk = kzalloc(sizeof(*mk), GFP_KERNEL);
331 [ # # ]: 0 : if (!mk)
332 : : return -ENOMEM;
333 : :
334 : 0 : mk->mk_spec = *mk_spec;
335 : :
336 : 0 : move_master_key_secret(&mk->mk_secret, secret);
337 : 0 : init_rwsem(&mk->mk_secret_sem);
338 : :
339 : : refcount_set(&mk->mk_refcount, 1); /* secret is present */
340 : 0 : INIT_LIST_HEAD(&mk->mk_decrypted_inodes);
341 : 0 : spin_lock_init(&mk->mk_decrypted_inodes_lock);
342 : :
343 [ # # ]: 0 : if (mk_spec->type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) {
344 : 0 : err = allocate_master_key_users_keyring(mk);
345 [ # # ]: 0 : if (err)
346 : : goto out_free_mk;
347 : 0 : err = add_master_key_user(mk);
348 [ # # ]: 0 : if (err)
349 : : goto out_free_mk;
350 : : }
351 : :
352 : : /*
353 : : * Note that we don't charge this key to anyone's quota, since when
354 : : * ->mk_users is in use those keys are charged instead, and otherwise
355 : : * (when ->mk_users isn't in use) only root can add these keys.
356 : : */
357 : 0 : format_mk_description(description, mk_spec);
358 : 0 : key = key_alloc(&key_type_fscrypt, description,
359 : 0 : GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
360 : : KEY_POS_SEARCH | KEY_USR_SEARCH | KEY_USR_VIEW,
361 : : KEY_ALLOC_NOT_IN_QUOTA, NULL);
362 [ # # ]: 0 : if (IS_ERR(key)) {
363 : : err = PTR_ERR(key);
364 : 0 : goto out_free_mk;
365 : : }
366 : 0 : err = key_instantiate_and_link(key, mk, sizeof(*mk), keyring, NULL);
367 : 0 : key_put(key);
368 [ # # ]: 0 : if (err)
369 : : goto out_free_mk;
370 : :
371 : : return 0;
372 : :
373 : : out_free_mk:
374 : 0 : free_master_key(mk);
375 : 0 : return err;
376 : : }
377 : :
378 : : #define KEY_DEAD 1
379 : :
380 : 0 : static int add_existing_master_key(struct fscrypt_master_key *mk,
381 : : struct fscrypt_master_key_secret *secret)
382 : : {
383 : : struct key *mk_user;
384 : : bool rekey;
385 : : int err;
386 : :
387 : : /*
388 : : * If the current user is already in ->mk_users, then there's nothing to
389 : : * do. (Not applicable for v1 policy keys, which have NULL ->mk_users.)
390 : : */
391 [ # # ]: 0 : if (mk->mk_users) {
392 : 0 : mk_user = find_master_key_user(mk);
393 [ # # ]: 0 : if (mk_user != ERR_PTR(-ENOKEY)) {
394 [ # # ]: 0 : if (IS_ERR(mk_user))
395 : 0 : return PTR_ERR(mk_user);
396 : 0 : key_put(mk_user);
397 : 0 : return 0;
398 : : }
399 : : }
400 : :
401 : : /* If we'll be re-adding ->mk_secret, try to take the reference. */
402 : 0 : rekey = !is_master_key_secret_present(&mk->mk_secret);
403 [ # # # # ]: 0 : if (rekey && !refcount_inc_not_zero(&mk->mk_refcount))
404 : : return KEY_DEAD;
405 : :
406 : : /* Add the current user to ->mk_users, if applicable. */
407 [ # # ]: 0 : if (mk->mk_users) {
408 : 0 : err = add_master_key_user(mk);
409 [ # # ]: 0 : if (err) {
410 [ # # # # ]: 0 : if (rekey && refcount_dec_and_test(&mk->mk_refcount))
411 : : return KEY_DEAD;
412 : 0 : return err;
413 : : }
414 : : }
415 : :
416 : : /* Re-add the secret if needed. */
417 [ # # ]: 0 : if (rekey) {
418 : 0 : down_write(&mk->mk_secret_sem);
419 : 0 : move_master_key_secret(&mk->mk_secret, secret);
420 : 0 : up_write(&mk->mk_secret_sem);
421 : : }
422 : : return 0;
423 : : }
424 : :
425 : 0 : static int add_master_key(struct super_block *sb,
426 : : struct fscrypt_master_key_secret *secret,
427 : : const struct fscrypt_key_specifier *mk_spec)
428 : : {
429 : : static DEFINE_MUTEX(fscrypt_add_key_mutex);
430 : : struct key *key;
431 : : int err;
432 : :
433 : 0 : mutex_lock(&fscrypt_add_key_mutex); /* serialize find + link */
434 : : retry:
435 : 0 : key = fscrypt_find_master_key(sb, mk_spec);
436 [ # # ]: 0 : if (IS_ERR(key)) {
437 : : err = PTR_ERR(key);
438 [ # # ]: 0 : if (err != -ENOKEY)
439 : : goto out_unlock;
440 : : /* Didn't find the key in ->s_master_keys. Add it. */
441 : 0 : err = allocate_filesystem_keyring(sb);
442 [ # # ]: 0 : if (err)
443 : : goto out_unlock;
444 : 0 : err = add_new_master_key(secret, mk_spec, sb->s_master_keys);
445 : : } else {
446 : : /*
447 : : * Found the key in ->s_master_keys. Re-add the secret if
448 : : * needed, and add the user to ->mk_users if needed.
449 : : */
450 : 0 : down_write(&key->sem);
451 : 0 : err = add_existing_master_key(key->payload.data[0], secret);
452 : 0 : up_write(&key->sem);
453 [ # # ]: 0 : if (err == KEY_DEAD) {
454 : : /* Key being removed or needs to be removed */
455 : 0 : key_invalidate(key);
456 : 0 : key_put(key);
457 : 0 : goto retry;
458 : : }
459 : 0 : key_put(key);
460 : : }
461 : : out_unlock:
462 : 0 : mutex_unlock(&fscrypt_add_key_mutex);
463 : 0 : return err;
464 : : }
465 : :
466 : : /*
467 : : * Add a master encryption key to the filesystem, causing all files which were
468 : : * encrypted with it to appear "unlocked" (decrypted) when accessed.
469 : : *
470 : : * When adding a key for use by v1 encryption policies, this ioctl is
471 : : * privileged, and userspace must provide the 'key_descriptor'.
472 : : *
473 : : * When adding a key for use by v2+ encryption policies, this ioctl is
474 : : * unprivileged. This is needed, in general, to allow non-root users to use
475 : : * encryption without encountering the visibility problems of process-subscribed
476 : : * keyrings and the inability to properly remove keys. This works by having
477 : : * each key identified by its cryptographically secure hash --- the
478 : : * 'key_identifier'. The cryptographic hash ensures that a malicious user
479 : : * cannot add the wrong key for a given identifier. Furthermore, each added key
480 : : * is charged to the appropriate user's quota for the keyrings service, which
481 : : * prevents a malicious user from adding too many keys. Finally, we forbid a
482 : : * user from removing a key while other users have added it too, which prevents
483 : : * a user who knows another user's key from causing a denial-of-service by
484 : : * removing it at an inopportune time. (We tolerate that a user who knows a key
485 : : * can prevent other users from removing it.)
486 : : *
487 : : * For more details, see the "FS_IOC_ADD_ENCRYPTION_KEY" section of
488 : : * Documentation/filesystems/fscrypt.rst.
489 : : */
490 : 0 : int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg)
491 : : {
492 : 0 : struct super_block *sb = file_inode(filp)->i_sb;
493 : : struct fscrypt_add_key_arg __user *uarg = _uarg;
494 : : struct fscrypt_add_key_arg arg;
495 : : struct fscrypt_master_key_secret secret;
496 : : int err;
497 : :
498 [ # # ]: 0 : if (copy_from_user(&arg, uarg, sizeof(arg)))
499 : : return -EFAULT;
500 : :
501 [ # # ]: 0 : if (!valid_key_spec(&arg.key_spec))
502 : : return -EINVAL;
503 : :
504 [ # # ]: 0 : if (arg.raw_size < FSCRYPT_MIN_KEY_SIZE ||
505 : : arg.raw_size > FSCRYPT_MAX_KEY_SIZE)
506 : : return -EINVAL;
507 : :
508 [ # # ]: 0 : if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
509 : : return -EINVAL;
510 : :
511 : 0 : memset(&secret, 0, sizeof(secret));
512 : 0 : secret.size = arg.raw_size;
513 : : err = -EFAULT;
514 [ # # ]: 0 : if (copy_from_user(secret.raw, uarg->raw, secret.size))
515 : : goto out_wipe_secret;
516 : :
517 [ # # # ]: 0 : switch (arg.key_spec.type) {
518 : : case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
519 : : /*
520 : : * Only root can add keys that are identified by an arbitrary
521 : : * descriptor rather than by a cryptographic hash --- since
522 : : * otherwise a malicious user could add the wrong key.
523 : : */
524 : : err = -EACCES;
525 [ # # ]: 0 : if (!capable(CAP_SYS_ADMIN))
526 : : goto out_wipe_secret;
527 : : break;
528 : : case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
529 : 0 : err = fscrypt_init_hkdf(&secret.hkdf, secret.raw, secret.size);
530 [ # # ]: 0 : if (err)
531 : : goto out_wipe_secret;
532 : :
533 : : /*
534 : : * Now that the HKDF context is initialized, the raw key is no
535 : : * longer needed.
536 : : */
537 : 0 : memzero_explicit(secret.raw, secret.size);
538 : :
539 : : /* Calculate the key identifier and return it to userspace. */
540 : 0 : err = fscrypt_hkdf_expand(&secret.hkdf,
541 : : HKDF_CONTEXT_KEY_IDENTIFIER,
542 : : NULL, 0, arg.key_spec.u.identifier,
543 : : FSCRYPT_KEY_IDENTIFIER_SIZE);
544 [ # # ]: 0 : if (err)
545 : : goto out_wipe_secret;
546 : : err = -EFAULT;
547 [ # # ]: 0 : if (copy_to_user(uarg->key_spec.u.identifier,
548 : : arg.key_spec.u.identifier,
549 : : FSCRYPT_KEY_IDENTIFIER_SIZE))
550 : : goto out_wipe_secret;
551 : : break;
552 : : default:
553 : 0 : WARN_ON(1);
554 : : err = -EINVAL;
555 : 0 : goto out_wipe_secret;
556 : : }
557 : :
558 : 0 : err = add_master_key(sb, &secret, &arg.key_spec);
559 : : out_wipe_secret:
560 : 0 : wipe_master_key_secret(&secret);
561 : 0 : return err;
562 : : }
563 : : EXPORT_SYMBOL_GPL(fscrypt_ioctl_add_key);
564 : :
565 : : /*
566 : : * Verify that the current user has added a master key with the given identifier
567 : : * (returns -ENOKEY if not). This is needed to prevent a user from encrypting
568 : : * their files using some other user's key which they don't actually know.
569 : : * Cryptographically this isn't much of a problem, but the semantics of this
570 : : * would be a bit weird, so it's best to just forbid it.
571 : : *
572 : : * The system administrator (CAP_FOWNER) can override this, which should be
573 : : * enough for any use cases where encryption policies are being set using keys
574 : : * that were chosen ahead of time but aren't available at the moment.
575 : : *
576 : : * Note that the key may have already removed by the time this returns, but
577 : : * that's okay; we just care whether the key was there at some point.
578 : : *
579 : : * Return: 0 if the key is added, -ENOKEY if it isn't, or another -errno code
580 : : */
581 : 0 : int fscrypt_verify_key_added(struct super_block *sb,
582 : : const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
583 : : {
584 : : struct fscrypt_key_specifier mk_spec;
585 : : struct key *key, *mk_user;
586 : : struct fscrypt_master_key *mk;
587 : : int err;
588 : :
589 : 0 : mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
590 : 0 : memcpy(mk_spec.u.identifier, identifier, FSCRYPT_KEY_IDENTIFIER_SIZE);
591 : :
592 : 0 : key = fscrypt_find_master_key(sb, &mk_spec);
593 [ # # ]: 0 : if (IS_ERR(key)) {
594 : : err = PTR_ERR(key);
595 : 0 : goto out;
596 : : }
597 : 0 : mk = key->payload.data[0];
598 : 0 : mk_user = find_master_key_user(mk);
599 [ # # ]: 0 : if (IS_ERR(mk_user)) {
600 : : err = PTR_ERR(mk_user);
601 : : } else {
602 : 0 : key_put(mk_user);
603 : : err = 0;
604 : : }
605 : 0 : key_put(key);
606 : : out:
607 [ # # # # ]: 0 : if (err == -ENOKEY && capable(CAP_FOWNER))
608 : : err = 0;
609 : 0 : return err;
610 : : }
611 : :
612 : : /*
613 : : * Try to evict the inode's dentries from the dentry cache. If the inode is a
614 : : * directory, then it can have at most one dentry; however, that dentry may be
615 : : * pinned by child dentries, so first try to evict the children too.
616 : : */
617 : 0 : static void shrink_dcache_inode(struct inode *inode)
618 : : {
619 : : struct dentry *dentry;
620 : :
621 [ # # ]: 0 : if (S_ISDIR(inode->i_mode)) {
622 : 0 : dentry = d_find_any_alias(inode);
623 [ # # ]: 0 : if (dentry) {
624 : 0 : shrink_dcache_parent(dentry);
625 : 0 : dput(dentry);
626 : : }
627 : : }
628 : 0 : d_prune_aliases(inode);
629 : 0 : }
630 : :
631 : 0 : static void evict_dentries_for_decrypted_inodes(struct fscrypt_master_key *mk)
632 : : {
633 : : struct fscrypt_info *ci;
634 : : struct inode *inode;
635 : : struct inode *toput_inode = NULL;
636 : :
637 : : spin_lock(&mk->mk_decrypted_inodes_lock);
638 : :
639 [ # # ]: 0 : list_for_each_entry(ci, &mk->mk_decrypted_inodes, ci_master_key_link) {
640 : 0 : inode = ci->ci_inode;
641 : : spin_lock(&inode->i_lock);
642 [ # # ]: 0 : if (inode->i_state & (I_FREEING | I_WILL_FREE | I_NEW)) {
643 : : spin_unlock(&inode->i_lock);
644 : 0 : continue;
645 : : }
646 : 0 : __iget(inode);
647 : : spin_unlock(&inode->i_lock);
648 : : spin_unlock(&mk->mk_decrypted_inodes_lock);
649 : :
650 : 0 : shrink_dcache_inode(inode);
651 : 0 : iput(toput_inode);
652 : : toput_inode = inode;
653 : :
654 : : spin_lock(&mk->mk_decrypted_inodes_lock);
655 : : }
656 : :
657 : : spin_unlock(&mk->mk_decrypted_inodes_lock);
658 : 0 : iput(toput_inode);
659 : 0 : }
660 : :
661 : 0 : static int check_for_busy_inodes(struct super_block *sb,
662 : : struct fscrypt_master_key *mk)
663 : : {
664 : : struct list_head *pos;
665 : : size_t busy_count = 0;
666 : : unsigned long ino;
667 : :
668 : : spin_lock(&mk->mk_decrypted_inodes_lock);
669 : :
670 [ # # ]: 0 : list_for_each(pos, &mk->mk_decrypted_inodes)
671 : 0 : busy_count++;
672 : :
673 [ # # ]: 0 : if (busy_count == 0) {
674 : : spin_unlock(&mk->mk_decrypted_inodes_lock);
675 : 0 : return 0;
676 : : }
677 : :
678 : : {
679 : : /* select an example file to show for debugging purposes */
680 : 0 : struct inode *inode =
681 : : list_first_entry(&mk->mk_decrypted_inodes,
682 : : struct fscrypt_info,
683 : : ci_master_key_link)->ci_inode;
684 : 0 : ino = inode->i_ino;
685 : : }
686 : : spin_unlock(&mk->mk_decrypted_inodes_lock);
687 : :
688 : 0 : fscrypt_warn(NULL,
689 : : "%s: %zu inode(s) still busy after removing key with %s %*phN, including ino %lu",
690 : : sb->s_id, busy_count, master_key_spec_type(&mk->mk_spec),
691 : : master_key_spec_len(&mk->mk_spec), (u8 *)&mk->mk_spec.u,
692 : : ino);
693 : 0 : return -EBUSY;
694 : : }
695 : :
696 : 0 : static int try_to_lock_encrypted_files(struct super_block *sb,
697 : : struct fscrypt_master_key *mk)
698 : : {
699 : : int err1;
700 : : int err2;
701 : :
702 : : /*
703 : : * An inode can't be evicted while it is dirty or has dirty pages.
704 : : * Thus, we first have to clean the inodes in ->mk_decrypted_inodes.
705 : : *
706 : : * Just do it the easy way: call sync_filesystem(). It's overkill, but
707 : : * it works, and it's more important to minimize the amount of caches we
708 : : * drop than the amount of data we sync. Also, unprivileged users can
709 : : * already call sync_filesystem() via sys_syncfs() or sys_sync().
710 : : */
711 : 0 : down_read(&sb->s_umount);
712 : 0 : err1 = sync_filesystem(sb);
713 : 0 : up_read(&sb->s_umount);
714 : : /* If a sync error occurs, still try to evict as much as possible. */
715 : :
716 : : /*
717 : : * Inodes are pinned by their dentries, so we have to evict their
718 : : * dentries. shrink_dcache_sb() would suffice, but would be overkill
719 : : * and inappropriate for use by unprivileged users. So instead go
720 : : * through the inodes' alias lists and try to evict each dentry.
721 : : */
722 : 0 : evict_dentries_for_decrypted_inodes(mk);
723 : :
724 : : /*
725 : : * evict_dentries_for_decrypted_inodes() already iput() each inode in
726 : : * the list; any inodes for which that dropped the last reference will
727 : : * have been evicted due to fscrypt_drop_inode() detecting the key
728 : : * removal and telling the VFS to evict the inode. So to finish, we
729 : : * just need to check whether any inodes couldn't be evicted.
730 : : */
731 : 0 : err2 = check_for_busy_inodes(sb, mk);
732 : :
733 [ # # ]: 0 : return err1 ?: err2;
734 : : }
735 : :
736 : : /*
737 : : * Try to remove an fscrypt master encryption key.
738 : : *
739 : : * FS_IOC_REMOVE_ENCRYPTION_KEY (all_users=false) removes the current user's
740 : : * claim to the key, then removes the key itself if no other users have claims.
741 : : * FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS (all_users=true) always removes the
742 : : * key itself.
743 : : *
744 : : * To "remove the key itself", first we wipe the actual master key secret, so
745 : : * that no more inodes can be unlocked with it. Then we try to evict all cached
746 : : * inodes that had been unlocked with the key.
747 : : *
748 : : * If all inodes were evicted, then we unlink the fscrypt_master_key from the
749 : : * keyring. Otherwise it remains in the keyring in the "incompletely removed"
750 : : * state (without the actual secret key) where it tracks the list of remaining
751 : : * inodes. Userspace can execute the ioctl again later to retry eviction, or
752 : : * alternatively can re-add the secret key again.
753 : : *
754 : : * For more details, see the "Removing keys" section of
755 : : * Documentation/filesystems/fscrypt.rst.
756 : : */
757 : 0 : static int do_remove_key(struct file *filp, void __user *_uarg, bool all_users)
758 : : {
759 : 0 : struct super_block *sb = file_inode(filp)->i_sb;
760 : : struct fscrypt_remove_key_arg __user *uarg = _uarg;
761 : : struct fscrypt_remove_key_arg arg;
762 : : struct key *key;
763 : : struct fscrypt_master_key *mk;
764 : : u32 status_flags = 0;
765 : : int err;
766 : : bool dead;
767 : :
768 [ # # ]: 0 : if (copy_from_user(&arg, uarg, sizeof(arg)))
769 : : return -EFAULT;
770 : :
771 [ # # ]: 0 : if (!valid_key_spec(&arg.key_spec))
772 : : return -EINVAL;
773 : :
774 [ # # ]: 0 : if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
775 : : return -EINVAL;
776 : :
777 : : /*
778 : : * Only root can add and remove keys that are identified by an arbitrary
779 : : * descriptor rather than by a cryptographic hash.
780 : : */
781 [ # # # # ]: 0 : if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR &&
782 : 0 : !capable(CAP_SYS_ADMIN))
783 : : return -EACCES;
784 : :
785 : : /* Find the key being removed. */
786 : 0 : key = fscrypt_find_master_key(sb, &arg.key_spec);
787 [ # # ]: 0 : if (IS_ERR(key))
788 : 0 : return PTR_ERR(key);
789 : 0 : mk = key->payload.data[0];
790 : :
791 : 0 : down_write(&key->sem);
792 : :
793 : : /* If relevant, remove current user's (or all users) claim to the key */
794 [ # # # # ]: 0 : if (mk->mk_users && mk->mk_users->keys.nr_leaves_on_tree != 0) {
795 [ # # ]: 0 : if (all_users)
796 : 0 : err = keyring_clear(mk->mk_users);
797 : : else
798 : 0 : err = remove_master_key_user(mk);
799 [ # # ]: 0 : if (err) {
800 : 0 : up_write(&key->sem);
801 : 0 : goto out_put_key;
802 : : }
803 [ # # ]: 0 : if (mk->mk_users->keys.nr_leaves_on_tree != 0) {
804 : : /*
805 : : * Other users have still added the key too. We removed
806 : : * the current user's claim to the key, but we still
807 : : * can't remove the key itself.
808 : : */
809 : : status_flags |=
810 : : FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS;
811 : : err = 0;
812 : 0 : up_write(&key->sem);
813 : 0 : goto out_put_key;
814 : : }
815 : : }
816 : :
817 : : /* No user claims remaining. Go ahead and wipe the secret. */
818 : : dead = false;
819 [ # # ]: 0 : if (is_master_key_secret_present(&mk->mk_secret)) {
820 : 0 : down_write(&mk->mk_secret_sem);
821 : 0 : wipe_master_key_secret(&mk->mk_secret);
822 : 0 : dead = refcount_dec_and_test(&mk->mk_refcount);
823 : 0 : up_write(&mk->mk_secret_sem);
824 : : }
825 : 0 : up_write(&key->sem);
826 [ # # ]: 0 : if (dead) {
827 : : /*
828 : : * No inodes reference the key, and we wiped the secret, so the
829 : : * key object is free to be removed from the keyring.
830 : : */
831 : 0 : key_invalidate(key);
832 : : err = 0;
833 : : } else {
834 : : /* Some inodes still reference this key; try to evict them. */
835 : 0 : err = try_to_lock_encrypted_files(sb, mk);
836 [ # # ]: 0 : if (err == -EBUSY) {
837 : : status_flags |=
838 : : FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY;
839 : : err = 0;
840 : : }
841 : : }
842 : : /*
843 : : * We return 0 if we successfully did something: removed a claim to the
844 : : * key, wiped the secret, or tried locking the files again. Users need
845 : : * to check the informational status flags if they care whether the key
846 : : * has been fully removed including all files locked.
847 : : */
848 : : out_put_key:
849 : 0 : key_put(key);
850 [ # # ]: 0 : if (err == 0)
851 : 0 : err = put_user(status_flags, &uarg->removal_status_flags);
852 : 0 : return err;
853 : : }
854 : :
855 : 0 : int fscrypt_ioctl_remove_key(struct file *filp, void __user *uarg)
856 : : {
857 : 0 : return do_remove_key(filp, uarg, false);
858 : : }
859 : : EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key);
860 : :
861 : 0 : int fscrypt_ioctl_remove_key_all_users(struct file *filp, void __user *uarg)
862 : : {
863 [ # # ]: 0 : if (!capable(CAP_SYS_ADMIN))
864 : : return -EACCES;
865 : 0 : return do_remove_key(filp, uarg, true);
866 : : }
867 : : EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key_all_users);
868 : :
869 : : /*
870 : : * Retrieve the status of an fscrypt master encryption key.
871 : : *
872 : : * We set ->status to indicate whether the key is absent, present, or
873 : : * incompletely removed. "Incompletely removed" means that the master key
874 : : * secret has been removed, but some files which had been unlocked with it are
875 : : * still in use. This field allows applications to easily determine the state
876 : : * of an encrypted directory without using a hack such as trying to open a
877 : : * regular file in it (which can confuse the "incompletely removed" state with
878 : : * absent or present).
879 : : *
880 : : * In addition, for v2 policy keys we allow applications to determine, via
881 : : * ->status_flags and ->user_count, whether the key has been added by the
882 : : * current user, by other users, or by both. Most applications should not need
883 : : * this, since ordinarily only one user should know a given key. However, if a
884 : : * secret key is shared by multiple users, applications may wish to add an
885 : : * already-present key to prevent other users from removing it. This ioctl can
886 : : * be used to check whether that really is the case before the work is done to
887 : : * add the key --- which might e.g. require prompting the user for a passphrase.
888 : : *
889 : : * For more details, see the "FS_IOC_GET_ENCRYPTION_KEY_STATUS" section of
890 : : * Documentation/filesystems/fscrypt.rst.
891 : : */
892 : 0 : int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg)
893 : : {
894 : 0 : struct super_block *sb = file_inode(filp)->i_sb;
895 : : struct fscrypt_get_key_status_arg arg;
896 : : struct key *key;
897 : : struct fscrypt_master_key *mk;
898 : : int err;
899 : :
900 [ # # ]: 0 : if (copy_from_user(&arg, uarg, sizeof(arg)))
901 : : return -EFAULT;
902 : :
903 [ # # ]: 0 : if (!valid_key_spec(&arg.key_spec))
904 : : return -EINVAL;
905 : :
906 [ # # ]: 0 : if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
907 : : return -EINVAL;
908 : :
909 : 0 : arg.status_flags = 0;
910 : 0 : arg.user_count = 0;
911 : 0 : memset(arg.__out_reserved, 0, sizeof(arg.__out_reserved));
912 : :
913 : 0 : key = fscrypt_find_master_key(sb, &arg.key_spec);
914 [ # # ]: 0 : if (IS_ERR(key)) {
915 [ # # ]: 0 : if (key != ERR_PTR(-ENOKEY))
916 : 0 : return PTR_ERR(key);
917 : 0 : arg.status = FSCRYPT_KEY_STATUS_ABSENT;
918 : : err = 0;
919 : 0 : goto out;
920 : : }
921 : 0 : mk = key->payload.data[0];
922 : 0 : down_read(&key->sem);
923 : :
924 [ # # ]: 0 : if (!is_master_key_secret_present(&mk->mk_secret)) {
925 : 0 : arg.status = FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED;
926 : : err = 0;
927 : 0 : goto out_release_key;
928 : : }
929 : :
930 : 0 : arg.status = FSCRYPT_KEY_STATUS_PRESENT;
931 [ # # ]: 0 : if (mk->mk_users) {
932 : : struct key *mk_user;
933 : :
934 : 0 : arg.user_count = mk->mk_users->keys.nr_leaves_on_tree;
935 : 0 : mk_user = find_master_key_user(mk);
936 [ # # ]: 0 : if (!IS_ERR(mk_user)) {
937 : 0 : arg.status_flags |=
938 : : FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF;
939 : 0 : key_put(mk_user);
940 [ # # ]: 0 : } else if (mk_user != ERR_PTR(-ENOKEY)) {
941 : : err = PTR_ERR(mk_user);
942 : 0 : goto out_release_key;
943 : : }
944 : : }
945 : : err = 0;
946 : : out_release_key:
947 : 0 : up_read(&key->sem);
948 : 0 : key_put(key);
949 : : out:
950 [ # # # # ]: 0 : if (!err && copy_to_user(uarg, &arg, sizeof(arg)))
951 : : err = -EFAULT;
952 : 0 : return err;
953 : : }
954 : : EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_key_status);
955 : :
956 : 404 : int __init fscrypt_init_keyring(void)
957 : : {
958 : : int err;
959 : :
960 : 404 : err = register_key_type(&key_type_fscrypt);
961 [ + - ]: 404 : if (err)
962 : : return err;
963 : :
964 : 404 : err = register_key_type(&key_type_fscrypt_user);
965 [ - + ]: 404 : if (err)
966 : : goto err_unregister_fscrypt;
967 : :
968 : : return 0;
969 : :
970 : : err_unregister_fscrypt:
971 : 0 : unregister_key_type(&key_type_fscrypt);
972 : 0 : return err;
973 : : }
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