1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Encryption policy functions for per-file encryption support.
4 *
5 * Copyright (C) 2015, Google, Inc.
6 * Copyright (C) 2015, Motorola Mobility.
7 *
8 * Originally written by Michael Halcrow, 2015.
9 * Modified by Jaegeuk Kim, 2015.
10 * Modified by Eric Biggers, 2019 for v2 policy support.
11 */
12
13 #include <linux/random.h>
14 #include <linux/seq_file.h>
15 #include <linux/string.h>
16 #include <linux/mount.h>
17 #include "fscrypt_private.h"
18
19 /**
20 * fscrypt_policies_equal() - check whether two encryption policies are the same
21 * @policy1: the first policy
22 * @policy2: the second policy
23 *
24 * Return: %true if equal, else %false
25 */
fscrypt_policies_equal(const union fscrypt_policy * policy1,const union fscrypt_policy * policy2)26 bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
27 const union fscrypt_policy *policy2)
28 {
29 if (policy1->version != policy2->version)
30 return false;
31
32 return !memcmp(policy1, policy2, fscrypt_policy_size(policy1));
33 }
34
fscrypt_valid_enc_modes(u32 contents_mode,u32 filenames_mode)35 static bool fscrypt_valid_enc_modes(u32 contents_mode, u32 filenames_mode)
36 {
37 if (contents_mode == FSCRYPT_MODE_AES_256_XTS &&
38 filenames_mode == FSCRYPT_MODE_AES_256_CTS)
39 return true;
40
41 if (contents_mode == FSCRYPT_MODE_AES_128_CBC &&
42 filenames_mode == FSCRYPT_MODE_AES_128_CTS)
43 return true;
44
45 if (contents_mode == FSCRYPT_MODE_ADIANTUM &&
46 filenames_mode == FSCRYPT_MODE_ADIANTUM)
47 return true;
48
49 return false;
50 }
51
supported_direct_key_modes(const struct inode * inode,u32 contents_mode,u32 filenames_mode)52 static bool supported_direct_key_modes(const struct inode *inode,
53 u32 contents_mode, u32 filenames_mode)
54 {
55 const struct fscrypt_mode *mode;
56
57 if (contents_mode != filenames_mode) {
58 fscrypt_warn(inode,
59 "Direct key flag not allowed with different contents and filenames modes");
60 return false;
61 }
62 mode = &fscrypt_modes[contents_mode];
63
64 if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) {
65 fscrypt_warn(inode, "Direct key flag not allowed with %s",
66 mode->friendly_name);
67 return false;
68 }
69 return true;
70 }
71
supported_iv_ino_lblk_policy(const struct fscrypt_policy_v2 * policy,const struct inode * inode,const char * type,int max_ino_bits,int max_lblk_bits)72 static bool supported_iv_ino_lblk_policy(const struct fscrypt_policy_v2 *policy,
73 const struct inode *inode,
74 const char *type,
75 int max_ino_bits, int max_lblk_bits)
76 {
77 struct super_block *sb = inode->i_sb;
78 int ino_bits = 64, lblk_bits = 64;
79
80 /*
81 * IV_INO_LBLK_* exist only because of hardware limitations, and
82 * currently the only known use case for them involves AES-256-XTS.
83 * That's also all we test currently. For these reasons, for now only
84 * allow AES-256-XTS here. This can be relaxed later if a use case for
85 * IV_INO_LBLK_* with other encryption modes arises.
86 */
87 if (policy->contents_encryption_mode != FSCRYPT_MODE_AES_256_XTS) {
88 fscrypt_warn(inode,
89 "Can't use %s policy with contents mode other than AES-256-XTS",
90 type);
91 return false;
92 }
93
94 /*
95 * It's unsafe to include inode numbers in the IVs if the filesystem can
96 * potentially renumber inodes, e.g. via filesystem shrinking.
97 */
98 if (!sb->s_cop->has_stable_inodes ||
99 !sb->s_cop->has_stable_inodes(sb)) {
100 fscrypt_warn(inode,
101 "Can't use %s policy on filesystem '%s' because it doesn't have stable inode numbers",
102 type, sb->s_id);
103 return false;
104 }
105 if (sb->s_cop->get_ino_and_lblk_bits)
106 sb->s_cop->get_ino_and_lblk_bits(sb, &ino_bits, &lblk_bits);
107 if (ino_bits > max_ino_bits) {
108 fscrypt_warn(inode,
109 "Can't use %s policy on filesystem '%s' because its inode numbers are too long",
110 type, sb->s_id);
111 return false;
112 }
113 if (lblk_bits > max_lblk_bits) {
114 fscrypt_warn(inode,
115 "Can't use %s policy on filesystem '%s' because its block numbers are too long",
116 type, sb->s_id);
117 return false;
118 }
119 return true;
120 }
121
fscrypt_supported_v1_policy(const struct fscrypt_policy_v1 * policy,const struct inode * inode)122 static bool fscrypt_supported_v1_policy(const struct fscrypt_policy_v1 *policy,
123 const struct inode *inode)
124 {
125 if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
126 policy->filenames_encryption_mode)) {
127 fscrypt_warn(inode,
128 "Unsupported encryption modes (contents %d, filenames %d)",
129 policy->contents_encryption_mode,
130 policy->filenames_encryption_mode);
131 return false;
132 }
133
134 if (policy->flags & ~(FSCRYPT_POLICY_FLAGS_PAD_MASK |
135 FSCRYPT_POLICY_FLAG_DIRECT_KEY)) {
136 fscrypt_warn(inode, "Unsupported encryption flags (0x%02x)",
137 policy->flags);
138 return false;
139 }
140
141 if ((policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) &&
142 !supported_direct_key_modes(inode, policy->contents_encryption_mode,
143 policy->filenames_encryption_mode))
144 return false;
145
146 if (IS_CASEFOLDED(inode)) {
147 /* With v1, there's no way to derive dirhash keys. */
148 fscrypt_warn(inode,
149 "v1 policies can't be used on casefolded directories");
150 return false;
151 }
152
153 return true;
154 }
155
fscrypt_supported_v2_policy(const struct fscrypt_policy_v2 * policy,const struct inode * inode)156 static bool fscrypt_supported_v2_policy(const struct fscrypt_policy_v2 *policy,
157 const struct inode *inode)
158 {
159 int count = 0;
160
161 if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
162 policy->filenames_encryption_mode)) {
163 fscrypt_warn(inode,
164 "Unsupported encryption modes (contents %d, filenames %d)",
165 policy->contents_encryption_mode,
166 policy->filenames_encryption_mode);
167 return false;
168 }
169
170 if (policy->flags & ~(FSCRYPT_POLICY_FLAGS_PAD_MASK |
171 FSCRYPT_POLICY_FLAG_DIRECT_KEY |
172 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64 |
173 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) {
174 fscrypt_warn(inode, "Unsupported encryption flags (0x%02x)",
175 policy->flags);
176 return false;
177 }
178
179 count += !!(policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY);
180 count += !!(policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64);
181 count += !!(policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32);
182 if (count > 1) {
183 fscrypt_warn(inode, "Mutually exclusive encryption flags (0x%02x)",
184 policy->flags);
185 return false;
186 }
187
188 if ((policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) &&
189 !supported_direct_key_modes(inode, policy->contents_encryption_mode,
190 policy->filenames_encryption_mode))
191 return false;
192
193 if ((policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) &&
194 !supported_iv_ino_lblk_policy(policy, inode, "IV_INO_LBLK_64",
195 32, 32))
196 return false;
197
198 /*
199 * IV_INO_LBLK_32 hashes the inode number, so in principle it can
200 * support any ino_bits. However, currently the inode number is gotten
201 * from inode::i_ino which is 'unsigned long'. So for now the
202 * implementation limit is 32 bits.
203 */
204 if ((policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) &&
205 !supported_iv_ino_lblk_policy(policy, inode, "IV_INO_LBLK_32",
206 32, 32))
207 return false;
208
209 if (memchr_inv(policy->__reserved, 0, sizeof(policy->__reserved))) {
210 fscrypt_warn(inode, "Reserved bits set in encryption policy");
211 return false;
212 }
213
214 return true;
215 }
216
217 /**
218 * fscrypt_supported_policy() - check whether an encryption policy is supported
219 * @policy_u: the encryption policy
220 * @inode: the inode on which the policy will be used
221 *
222 * Given an encryption policy, check whether all its encryption modes and other
223 * settings are supported by this kernel on the given inode. (But we don't
224 * currently don't check for crypto API support here, so attempting to use an
225 * algorithm not configured into the crypto API will still fail later.)
226 *
227 * Return: %true if supported, else %false
228 */
fscrypt_supported_policy(const union fscrypt_policy * policy_u,const struct inode * inode)229 bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
230 const struct inode *inode)
231 {
232 switch (policy_u->version) {
233 case FSCRYPT_POLICY_V1:
234 return fscrypt_supported_v1_policy(&policy_u->v1, inode);
235 case FSCRYPT_POLICY_V2:
236 return fscrypt_supported_v2_policy(&policy_u->v2, inode);
237 }
238 return false;
239 }
240
241 /**
242 * fscrypt_new_context_from_policy() - create a new fscrypt_context from
243 * an fscrypt_policy
244 * @ctx_u: output context
245 * @policy_u: input policy
246 *
247 * Create an fscrypt_context for an inode that is being assigned the given
248 * encryption policy. A new nonce is randomly generated.
249 *
250 * Return: the size of the new context in bytes.
251 */
fscrypt_new_context_from_policy(union fscrypt_context * ctx_u,const union fscrypt_policy * policy_u)252 static int fscrypt_new_context_from_policy(union fscrypt_context *ctx_u,
253 const union fscrypt_policy *policy_u)
254 {
255 memset(ctx_u, 0, sizeof(*ctx_u));
256
257 switch (policy_u->version) {
258 case FSCRYPT_POLICY_V1: {
259 const struct fscrypt_policy_v1 *policy = &policy_u->v1;
260 struct fscrypt_context_v1 *ctx = &ctx_u->v1;
261
262 ctx->version = FSCRYPT_CONTEXT_V1;
263 ctx->contents_encryption_mode =
264 policy->contents_encryption_mode;
265 ctx->filenames_encryption_mode =
266 policy->filenames_encryption_mode;
267 ctx->flags = policy->flags;
268 memcpy(ctx->master_key_descriptor,
269 policy->master_key_descriptor,
270 sizeof(ctx->master_key_descriptor));
271 get_random_bytes(ctx->nonce, sizeof(ctx->nonce));
272 return sizeof(*ctx);
273 }
274 case FSCRYPT_POLICY_V2: {
275 const struct fscrypt_policy_v2 *policy = &policy_u->v2;
276 struct fscrypt_context_v2 *ctx = &ctx_u->v2;
277
278 ctx->version = FSCRYPT_CONTEXT_V2;
279 ctx->contents_encryption_mode =
280 policy->contents_encryption_mode;
281 ctx->filenames_encryption_mode =
282 policy->filenames_encryption_mode;
283 ctx->flags = policy->flags;
284 memcpy(ctx->master_key_identifier,
285 policy->master_key_identifier,
286 sizeof(ctx->master_key_identifier));
287 get_random_bytes(ctx->nonce, sizeof(ctx->nonce));
288 return sizeof(*ctx);
289 }
290 }
291 BUG();
292 }
293
294 /**
295 * fscrypt_policy_from_context() - convert an fscrypt_context to
296 * an fscrypt_policy
297 * @policy_u: output policy
298 * @ctx_u: input context
299 * @ctx_size: size of input context in bytes
300 *
301 * Given an fscrypt_context, build the corresponding fscrypt_policy.
302 *
303 * Return: 0 on success, or -EINVAL if the fscrypt_context has an unrecognized
304 * version number or size.
305 *
306 * This does *not* validate the settings within the policy itself, e.g. the
307 * modes, flags, and reserved bits. Use fscrypt_supported_policy() for that.
308 */
fscrypt_policy_from_context(union fscrypt_policy * policy_u,const union fscrypt_context * ctx_u,int ctx_size)309 int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
310 const union fscrypt_context *ctx_u,
311 int ctx_size)
312 {
313 memset(policy_u, 0, sizeof(*policy_u));
314
315 if (!fscrypt_context_is_valid(ctx_u, ctx_size))
316 return -EINVAL;
317
318 switch (ctx_u->version) {
319 case FSCRYPT_CONTEXT_V1: {
320 const struct fscrypt_context_v1 *ctx = &ctx_u->v1;
321 struct fscrypt_policy_v1 *policy = &policy_u->v1;
322
323 policy->version = FSCRYPT_POLICY_V1;
324 policy->contents_encryption_mode =
325 ctx->contents_encryption_mode;
326 policy->filenames_encryption_mode =
327 ctx->filenames_encryption_mode;
328 policy->flags = ctx->flags;
329 memcpy(policy->master_key_descriptor,
330 ctx->master_key_descriptor,
331 sizeof(policy->master_key_descriptor));
332 return 0;
333 }
334 case FSCRYPT_CONTEXT_V2: {
335 const struct fscrypt_context_v2 *ctx = &ctx_u->v2;
336 struct fscrypt_policy_v2 *policy = &policy_u->v2;
337
338 policy->version = FSCRYPT_POLICY_V2;
339 policy->contents_encryption_mode =
340 ctx->contents_encryption_mode;
341 policy->filenames_encryption_mode =
342 ctx->filenames_encryption_mode;
343 policy->flags = ctx->flags;
344 memcpy(policy->__reserved, ctx->__reserved,
345 sizeof(policy->__reserved));
346 memcpy(policy->master_key_identifier,
347 ctx->master_key_identifier,
348 sizeof(policy->master_key_identifier));
349 return 0;
350 }
351 }
352 /* unreachable */
353 return -EINVAL;
354 }
355
356 /* Retrieve an inode's encryption policy */
fscrypt_get_policy(struct inode * inode,union fscrypt_policy * policy)357 static int fscrypt_get_policy(struct inode *inode, union fscrypt_policy *policy)
358 {
359 const struct fscrypt_info *ci;
360 union fscrypt_context ctx;
361 int ret;
362
363 ci = READ_ONCE(inode->i_crypt_info);
364 if (ci) {
365 /* key available, use the cached policy */
366 *policy = ci->ci_policy;
367 return 0;
368 }
369
370 if (!IS_ENCRYPTED(inode))
371 return -ENODATA;
372
373 ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
374 if (ret < 0)
375 return (ret == -ERANGE) ? -EINVAL : ret;
376
377 return fscrypt_policy_from_context(policy, &ctx, ret);
378 }
379
set_encryption_policy(struct inode * inode,const union fscrypt_policy * policy)380 static int set_encryption_policy(struct inode *inode,
381 const union fscrypt_policy *policy)
382 {
383 union fscrypt_context ctx;
384 int ctxsize;
385 int err;
386
387 if (!fscrypt_supported_policy(policy, inode))
388 return -EINVAL;
389
390 switch (policy->version) {
391 case FSCRYPT_POLICY_V1:
392 /*
393 * The original encryption policy version provided no way of
394 * verifying that the correct master key was supplied, which was
395 * insecure in scenarios where multiple users have access to the
396 * same encrypted files (even just read-only access). The new
397 * encryption policy version fixes this and also implies use of
398 * an improved key derivation function and allows non-root users
399 * to securely remove keys. So as long as compatibility with
400 * old kernels isn't required, it is recommended to use the new
401 * policy version for all new encrypted directories.
402 */
403 pr_warn_once("%s (pid %d) is setting deprecated v1 encryption policy; recommend upgrading to v2.\n",
404 current->comm, current->pid);
405 break;
406 case FSCRYPT_POLICY_V2:
407 err = fscrypt_verify_key_added(inode->i_sb,
408 policy->v2.master_key_identifier);
409 if (err)
410 return err;
411 if (policy->v2.flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)
412 pr_warn_once("%s (pid %d) is setting an IV_INO_LBLK_32 encryption policy. This should only be used if there are certain hardware limitations.\n",
413 current->comm, current->pid);
414 break;
415 default:
416 WARN_ON(1);
417 return -EINVAL;
418 }
419
420 ctxsize = fscrypt_new_context_from_policy(&ctx, policy);
421
422 return inode->i_sb->s_cop->set_context(inode, &ctx, ctxsize, NULL);
423 }
424
fscrypt_ioctl_set_policy(struct file * filp,const void __user * arg)425 int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
426 {
427 union fscrypt_policy policy;
428 union fscrypt_policy existing_policy;
429 struct inode *inode = file_inode(filp);
430 u8 version;
431 int size;
432 int ret;
433
434 if (get_user(policy.version, (const u8 __user *)arg))
435 return -EFAULT;
436
437 size = fscrypt_policy_size(&policy);
438 if (size <= 0)
439 return -EINVAL;
440
441 /*
442 * We should just copy the remaining 'size - 1' bytes here, but a
443 * bizarre bug in gcc 7 and earlier (fixed by gcc r255731) causes gcc to
444 * think that size can be 0 here (despite the check above!) *and* that
445 * it's a compile-time constant. Thus it would think copy_from_user()
446 * is passed compile-time constant ULONG_MAX, causing the compile-time
447 * buffer overflow check to fail, breaking the build. This only occurred
448 * when building an i386 kernel with -Os and branch profiling enabled.
449 *
450 * Work around it by just copying the first byte again...
451 */
452 version = policy.version;
453 if (copy_from_user(&policy, arg, size))
454 return -EFAULT;
455 policy.version = version;
456
457 if (!inode_owner_or_capable(inode))
458 return -EACCES;
459
460 ret = mnt_want_write_file(filp);
461 if (ret)
462 return ret;
463
464 inode_lock(inode);
465
466 ret = fscrypt_get_policy(inode, &existing_policy);
467 if (ret == -ENODATA) {
468 if (!S_ISDIR(inode->i_mode))
469 ret = -ENOTDIR;
470 else if (IS_DEADDIR(inode))
471 ret = -ENOENT;
472 else if (!inode->i_sb->s_cop->empty_dir(inode))
473 ret = -ENOTEMPTY;
474 else
475 ret = set_encryption_policy(inode, &policy);
476 } else if (ret == -EINVAL ||
477 (ret == 0 && !fscrypt_policies_equal(&policy,
478 &existing_policy))) {
479 /* The file already uses a different encryption policy. */
480 ret = -EEXIST;
481 }
482
483 inode_unlock(inode);
484
485 mnt_drop_write_file(filp);
486 return ret;
487 }
488 EXPORT_SYMBOL(fscrypt_ioctl_set_policy);
489
490 /* Original ioctl version; can only get the original policy version */
fscrypt_ioctl_get_policy(struct file * filp,void __user * arg)491 int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
492 {
493 union fscrypt_policy policy;
494 int err;
495
496 err = fscrypt_get_policy(file_inode(filp), &policy);
497 if (err)
498 return err;
499
500 if (policy.version != FSCRYPT_POLICY_V1)
501 return -EINVAL;
502
503 if (copy_to_user(arg, &policy, sizeof(policy.v1)))
504 return -EFAULT;
505 return 0;
506 }
507 EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
508
509 /* Extended ioctl version; can get policies of any version */
fscrypt_ioctl_get_policy_ex(struct file * filp,void __user * uarg)510 int fscrypt_ioctl_get_policy_ex(struct file *filp, void __user *uarg)
511 {
512 struct fscrypt_get_policy_ex_arg arg;
513 union fscrypt_policy *policy = (union fscrypt_policy *)&arg.policy;
514 size_t policy_size;
515 int err;
516
517 /* arg is policy_size, then policy */
518 BUILD_BUG_ON(offsetof(typeof(arg), policy_size) != 0);
519 BUILD_BUG_ON(offsetofend(typeof(arg), policy_size) !=
520 offsetof(typeof(arg), policy));
521 BUILD_BUG_ON(sizeof(arg.policy) != sizeof(*policy));
522
523 err = fscrypt_get_policy(file_inode(filp), policy);
524 if (err)
525 return err;
526 policy_size = fscrypt_policy_size(policy);
527
528 if (copy_from_user(&arg, uarg, sizeof(arg.policy_size)))
529 return -EFAULT;
530
531 if (policy_size > arg.policy_size)
532 return -EOVERFLOW;
533 arg.policy_size = policy_size;
534
535 if (copy_to_user(uarg, &arg, sizeof(arg.policy_size) + policy_size))
536 return -EFAULT;
537 return 0;
538 }
539 EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_policy_ex);
540
541 /* FS_IOC_GET_ENCRYPTION_NONCE: retrieve file's encryption nonce for testing */
fscrypt_ioctl_get_nonce(struct file * filp,void __user * arg)542 int fscrypt_ioctl_get_nonce(struct file *filp, void __user *arg)
543 {
544 struct inode *inode = file_inode(filp);
545 union fscrypt_context ctx;
546 int ret;
547
548 ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
549 if (ret < 0)
550 return ret;
551 if (!fscrypt_context_is_valid(&ctx, ret))
552 return -EINVAL;
553 if (copy_to_user(arg, fscrypt_context_nonce(&ctx),
554 FSCRYPT_FILE_NONCE_SIZE))
555 return -EFAULT;
556 return 0;
557 }
558 EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_nonce);
559
560 /**
561 * fscrypt_has_permitted_context() - is a file's encryption policy permitted
562 * within its directory?
563 *
564 * @parent: inode for parent directory
565 * @child: inode for file being looked up, opened, or linked into @parent
566 *
567 * Filesystems must call this before permitting access to an inode in a
568 * situation where the parent directory is encrypted (either before allowing
569 * ->lookup() to succeed, or for a regular file before allowing it to be opened)
570 * and before any operation that involves linking an inode into an encrypted
571 * directory, including link, rename, and cross rename. It enforces the
572 * constraint that within a given encrypted directory tree, all files use the
573 * same encryption policy. The pre-access check is needed to detect potentially
574 * malicious offline violations of this constraint, while the link and rename
575 * checks are needed to prevent online violations of this constraint.
576 *
577 * Return: 1 if permitted, 0 if forbidden.
578 */
fscrypt_has_permitted_context(struct inode * parent,struct inode * child)579 int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
580 {
581 union fscrypt_policy parent_policy, child_policy;
582 int err;
583
584 /* No restrictions on file types which are never encrypted */
585 if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
586 !S_ISLNK(child->i_mode))
587 return 1;
588
589 /* No restrictions if the parent directory is unencrypted */
590 if (!IS_ENCRYPTED(parent))
591 return 1;
592
593 /* Encrypted directories must not contain unencrypted files */
594 if (!IS_ENCRYPTED(child))
595 return 0;
596
597 /*
598 * Both parent and child are encrypted, so verify they use the same
599 * encryption policy. Compare the fscrypt_info structs if the keys are
600 * available, otherwise retrieve and compare the fscrypt_contexts.
601 *
602 * Note that the fscrypt_context retrieval will be required frequently
603 * when accessing an encrypted directory tree without the key.
604 * Performance-wise this is not a big deal because we already don't
605 * really optimize for file access without the key (to the extent that
606 * such access is even possible), given that any attempted access
607 * already causes a fscrypt_context retrieval and keyring search.
608 *
609 * In any case, if an unexpected error occurs, fall back to "forbidden".
610 */
611
612 err = fscrypt_get_encryption_info(parent);
613 if (err)
614 return 0;
615 err = fscrypt_get_encryption_info(child);
616 if (err)
617 return 0;
618
619 err = fscrypt_get_policy(parent, &parent_policy);
620 if (err)
621 return 0;
622
623 err = fscrypt_get_policy(child, &child_policy);
624 if (err)
625 return 0;
626
627 return fscrypt_policies_equal(&parent_policy, &child_policy);
628 }
629 EXPORT_SYMBOL(fscrypt_has_permitted_context);
630
631 /**
632 * fscrypt_inherit_context() - Sets a child context from its parent
633 * @parent: Parent inode from which the context is inherited.
634 * @child: Child inode that inherits the context from @parent.
635 * @fs_data: private data given by FS.
636 * @preload: preload child i_crypt_info if true
637 *
638 * Return: 0 on success, -errno on failure
639 */
fscrypt_inherit_context(struct inode * parent,struct inode * child,void * fs_data,bool preload)640 int fscrypt_inherit_context(struct inode *parent, struct inode *child,
641 void *fs_data, bool preload)
642 {
643 union fscrypt_context ctx;
644 int ctxsize;
645 struct fscrypt_info *ci;
646 int res;
647
648 res = fscrypt_get_encryption_info(parent);
649 if (res < 0)
650 return res;
651
652 ci = READ_ONCE(parent->i_crypt_info);
653 if (ci == NULL)
654 return -ENOKEY;
655
656 ctxsize = fscrypt_new_context_from_policy(&ctx, &ci->ci_policy);
657
658 BUILD_BUG_ON(sizeof(ctx) != FSCRYPT_SET_CONTEXT_MAX_SIZE);
659 res = parent->i_sb->s_cop->set_context(child, &ctx, ctxsize, fs_data);
660 if (res)
661 return res;
662 return preload ? fscrypt_get_encryption_info(child): 0;
663 }
664 EXPORT_SYMBOL(fscrypt_inherit_context);
665
666 /**
667 * fscrypt_set_test_dummy_encryption() - handle '-o test_dummy_encryption'
668 * @sb: the filesystem on which test_dummy_encryption is being specified
669 * @arg: the argument to the test_dummy_encryption option.
670 * If no argument was specified, then @arg->from == NULL.
671 * @dummy_ctx: the filesystem's current dummy context (input/output, see below)
672 *
673 * Handle the test_dummy_encryption mount option by creating a dummy encryption
674 * context, saving it in @dummy_ctx, and adding the corresponding dummy
675 * encryption key to the filesystem. If the @dummy_ctx is already set, then
676 * instead validate that it matches @arg. Don't support changing it via
677 * remount, as that is difficult to do safely.
678 *
679 * The reason we use an fscrypt_context rather than an fscrypt_policy is because
680 * we mustn't generate a new nonce each time we access a dummy-encrypted
681 * directory, as that would change the way filenames are encrypted.
682 *
683 * Return: 0 on success (dummy context set, or the same context is already set);
684 * -EEXIST if a different dummy context is already set;
685 * or another -errno value.
686 */
fscrypt_set_test_dummy_encryption(struct super_block * sb,const substring_t * arg,struct fscrypt_dummy_context * dummy_ctx)687 int fscrypt_set_test_dummy_encryption(struct super_block *sb,
688 const substring_t *arg,
689 struct fscrypt_dummy_context *dummy_ctx)
690 {
691 const char *argstr = "v2";
692 const char *argstr_to_free = NULL;
693 struct fscrypt_key_specifier key_spec = { 0 };
694 int version;
695 union fscrypt_context *ctx = NULL;
696 int err;
697
698 if (arg->from) {
699 argstr = argstr_to_free = match_strdup(arg);
700 if (!argstr)
701 return -ENOMEM;
702 }
703
704 if (!strcmp(argstr, "v1")) {
705 version = FSCRYPT_CONTEXT_V1;
706 key_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
707 memset(key_spec.u.descriptor, 0x42,
708 FSCRYPT_KEY_DESCRIPTOR_SIZE);
709 } else if (!strcmp(argstr, "v2")) {
710 version = FSCRYPT_CONTEXT_V2;
711 key_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
712 /* key_spec.u.identifier gets filled in when adding the key */
713 } else {
714 err = -EINVAL;
715 goto out;
716 }
717
718 if (dummy_ctx->ctx) {
719 /*
720 * Note: if we ever make test_dummy_encryption support
721 * specifying other encryption settings, such as the encryption
722 * modes, we'll need to compare those settings here.
723 */
724 if (dummy_ctx->ctx->version == version)
725 err = 0;
726 else
727 err = -EEXIST;
728 goto out;
729 }
730
731 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
732 if (!ctx) {
733 err = -ENOMEM;
734 goto out;
735 }
736
737 err = fscrypt_add_test_dummy_key(sb, &key_spec);
738 if (err)
739 goto out;
740
741 ctx->version = version;
742 switch (ctx->version) {
743 case FSCRYPT_CONTEXT_V1:
744 ctx->v1.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS;
745 ctx->v1.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS;
746 memcpy(ctx->v1.master_key_descriptor, key_spec.u.descriptor,
747 FSCRYPT_KEY_DESCRIPTOR_SIZE);
748 break;
749 case FSCRYPT_CONTEXT_V2:
750 ctx->v2.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS;
751 ctx->v2.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS;
752 memcpy(ctx->v2.master_key_identifier, key_spec.u.identifier,
753 FSCRYPT_KEY_IDENTIFIER_SIZE);
754 break;
755 default:
756 WARN_ON(1);
757 err = -EINVAL;
758 goto out;
759 }
760 dummy_ctx->ctx = ctx;
761 ctx = NULL;
762 err = 0;
763 out:
764 kfree(ctx);
765 kfree(argstr_to_free);
766 return err;
767 }
768 EXPORT_SYMBOL_GPL(fscrypt_set_test_dummy_encryption);
769
770 /**
771 * fscrypt_show_test_dummy_encryption() - show '-o test_dummy_encryption'
772 * @seq: the seq_file to print the option to
773 * @sep: the separator character to use
774 * @sb: the filesystem whose options are being shown
775 *
776 * Show the test_dummy_encryption mount option, if it was specified.
777 * This is mainly used for /proc/mounts.
778 */
fscrypt_show_test_dummy_encryption(struct seq_file * seq,char sep,struct super_block * sb)779 void fscrypt_show_test_dummy_encryption(struct seq_file *seq, char sep,
780 struct super_block *sb)
781 {
782 const union fscrypt_context *ctx = fscrypt_get_dummy_context(sb);
783
784 if (!ctx)
785 return;
786 seq_printf(seq, "%ctest_dummy_encryption=v%d", sep, ctx->version);
787 }
788 EXPORT_SYMBOL_GPL(fscrypt_show_test_dummy_encryption);
789