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/fs_context.h>
14 #include <linux/random.h>
15 #include <linux/seq_file.h>
16 #include <linux/string.h>
17 #include <linux/mount.h>
18 #include "fscrypt_private.h"
19
20 /**
21 * fscrypt_policies_equal() - check whether two encryption policies are the same
22 * @policy1: the first policy
23 * @policy2: the second policy
24 *
25 * Return: %true if equal, else %false
26 */
27 bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
28 const union fscrypt_policy *policy2)
29 {
30 if (policy1->version != policy2->version)
31 return false;
32
33 return !memcmp(policy1, policy2, fscrypt_policy_size(policy1));
34 }
35
36 int fscrypt_policy_to_key_spec(const union fscrypt_policy *policy,
37 struct fscrypt_key_specifier *key_spec)
38 {
39 switch (policy->version) {
40 case FSCRYPT_POLICY_V1:
41 key_spec->type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
42 memcpy(key_spec->u.descriptor, policy->v1.master_key_descriptor,
43 FSCRYPT_KEY_DESCRIPTOR_SIZE);
44 return 0;
45 case FSCRYPT_POLICY_V2:
46 key_spec->type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
47 memcpy(key_spec->u.identifier, policy->v2.master_key_identifier,
48 FSCRYPT_KEY_IDENTIFIER_SIZE);
49 return 0;
50 default:
51 WARN_ON_ONCE(1);
52 return -EINVAL;
53 }
54 }
55
56 const union fscrypt_policy *fscrypt_get_dummy_policy(struct super_block *sb)
57 {
58 if (!sb->s_cop->get_dummy_policy)
59 return NULL;
60 return sb->s_cop->get_dummy_policy(sb);
61 }
62
63 /*
64 * Return %true if the given combination of encryption modes is supported for v1
65 * (and later) encryption policies.
66 *
67 * Do *not* add anything new here, since v1 encryption policies are deprecated.
68 * New combinations of modes should go in fscrypt_valid_enc_modes_v2() only.
69 */
70 static bool fscrypt_valid_enc_modes_v1(u32 contents_mode, u32 filenames_mode)
71 {
72 if (contents_mode == FSCRYPT_MODE_AES_256_XTS &&
73 filenames_mode == FSCRYPT_MODE_AES_256_CTS)
74 return true;
75
76 if (contents_mode == FSCRYPT_MODE_AES_128_CBC &&
77 filenames_mode == FSCRYPT_MODE_AES_128_CTS)
78 return true;
79
80 if (contents_mode == FSCRYPT_MODE_ADIANTUM &&
81 filenames_mode == FSCRYPT_MODE_ADIANTUM)
82 return true;
83
84 return false;
85 }
86
87 static bool fscrypt_valid_enc_modes_v2(u32 contents_mode, u32 filenames_mode)
88 {
89 if (contents_mode == FSCRYPT_MODE_AES_256_XTS &&
90 filenames_mode == FSCRYPT_MODE_AES_256_HCTR2)
91 return true;
92
93 if (contents_mode == FSCRYPT_MODE_SM4_XTS &&
94 filenames_mode == FSCRYPT_MODE_SM4_CTS)
95 return true;
96
97 return fscrypt_valid_enc_modes_v1(contents_mode, filenames_mode);
98 }
99
100 static bool supported_direct_key_modes(const struct inode *inode,
101 u32 contents_mode, u32 filenames_mode)
102 {
103 const struct fscrypt_mode *mode;
104
105 if (contents_mode != filenames_mode) {
106 fscrypt_warn(inode,
107 "Direct key flag not allowed with different contents and filenames modes");
108 return false;
109 }
110 mode = &fscrypt_modes[contents_mode];
111
112 if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) {
113 fscrypt_warn(inode, "Direct key flag not allowed with %s",
114 mode->friendly_name);
115 return false;
116 }
117 return true;
118 }
119
120 static bool supported_iv_ino_lblk_policy(const struct fscrypt_policy_v2 *policy,
121 const struct inode *inode)
122 {
123 const char *type = (policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64)
124 ? "IV_INO_LBLK_64" : "IV_INO_LBLK_32";
125 struct super_block *sb = inode->i_sb;
126
127 /*
128 * IV_INO_LBLK_* exist only because of hardware limitations, and
129 * currently the only known use case for them involves AES-256-XTS.
130 * That's also all we test currently. For these reasons, for now only
131 * allow AES-256-XTS here. This can be relaxed later if a use case for
132 * IV_INO_LBLK_* with other encryption modes arises.
133 */
134 if (policy->contents_encryption_mode != FSCRYPT_MODE_AES_256_XTS) {
135 fscrypt_warn(inode,
136 "Can't use %s policy with contents mode other than AES-256-XTS",
137 type);
138 return false;
139 }
140
141 /*
142 * It's unsafe to include inode numbers in the IVs if the filesystem can
143 * potentially renumber inodes, e.g. via filesystem shrinking.
144 */
145 if (!sb->s_cop->has_stable_inodes ||
146 !sb->s_cop->has_stable_inodes(sb)) {
147 fscrypt_warn(inode,
148 "Can't use %s policy on filesystem '%s' because it doesn't have stable inode numbers",
149 type, sb->s_id);
150 return false;
151 }
152
153 /*
154 * IV_INO_LBLK_64 and IV_INO_LBLK_32 both require that inode numbers fit
155 * in 32 bits. In principle, IV_INO_LBLK_32 could support longer inode
156 * numbers because it hashes the inode number; however, currently the
157 * inode number is gotten from inode::i_ino which is 'unsigned long'.
158 * So for now the implementation limit is 32 bits.
159 */
160 if (!sb->s_cop->has_32bit_inodes) {
161 fscrypt_warn(inode,
162 "Can't use %s policy on filesystem '%s' because its inode numbers are too long",
163 type, sb->s_id);
164 return false;
165 }
166
167 /*
168 * IV_INO_LBLK_64 and IV_INO_LBLK_32 both require that file data unit
169 * indices fit in 32 bits.
170 */
171 if (fscrypt_max_file_dun_bits(sb,
172 fscrypt_policy_v2_du_bits(policy, inode)) > 32) {
173 fscrypt_warn(inode,
174 "Can't use %s policy on filesystem '%s' because its maximum file size is too large",
175 type, sb->s_id);
176 return false;
177 }
178 return true;
179 }
180
181 static bool fscrypt_supported_v1_policy(const struct fscrypt_policy_v1 *policy,
182 const struct inode *inode)
183 {
184 if (!fscrypt_valid_enc_modes_v1(policy->contents_encryption_mode,
185 policy->filenames_encryption_mode)) {
186 fscrypt_warn(inode,
187 "Unsupported encryption modes (contents %d, filenames %d)",
188 policy->contents_encryption_mode,
189 policy->filenames_encryption_mode);
190 return false;
191 }
192
193 if (policy->flags & ~(FSCRYPT_POLICY_FLAGS_PAD_MASK |
194 FSCRYPT_POLICY_FLAG_DIRECT_KEY)) {
195 fscrypt_warn(inode, "Unsupported encryption flags (0x%02x)",
196 policy->flags);
197 return false;
198 }
199
200 if ((policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) &&
201 !supported_direct_key_modes(inode, policy->contents_encryption_mode,
202 policy->filenames_encryption_mode))
203 return false;
204
205 if (IS_CASEFOLDED(inode)) {
206 /* With v1, there's no way to derive dirhash keys. */
207 fscrypt_warn(inode,
208 "v1 policies can't be used on casefolded directories");
209 return false;
210 }
211
212 return true;
213 }
214
215 static bool fscrypt_supported_v2_policy(const struct fscrypt_policy_v2 *policy,
216 const struct inode *inode)
217 {
218 int count = 0;
219
220 if (!fscrypt_valid_enc_modes_v2(policy->contents_encryption_mode,
221 policy->filenames_encryption_mode)) {
222 fscrypt_warn(inode,
223 "Unsupported encryption modes (contents %d, filenames %d)",
224 policy->contents_encryption_mode,
225 policy->filenames_encryption_mode);
226 return false;
227 }
228
229 if (policy->flags & ~(FSCRYPT_POLICY_FLAGS_PAD_MASK |
230 FSCRYPT_POLICY_FLAG_DIRECT_KEY |
231 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64 |
232 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) {
233 fscrypt_warn(inode, "Unsupported encryption flags (0x%02x)",
234 policy->flags);
235 return false;
236 }
237
238 count += !!(policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY);
239 count += !!(policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64);
240 count += !!(policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32);
241 if (count > 1) {
242 fscrypt_warn(inode, "Mutually exclusive encryption flags (0x%02x)",
243 policy->flags);
244 return false;
245 }
246
247 if (policy->log2_data_unit_size) {
248 if (!inode->i_sb->s_cop->supports_subblock_data_units) {
249 fscrypt_warn(inode,
250 "Filesystem does not support configuring crypto data unit size");
251 return false;
252 }
253 if (policy->log2_data_unit_size > inode->i_blkbits ||
254 policy->log2_data_unit_size < SECTOR_SHIFT /* 9 */) {
255 fscrypt_warn(inode,
256 "Unsupported log2_data_unit_size in encryption policy: %d",
257 policy->log2_data_unit_size);
258 return false;
259 }
260 if (policy->log2_data_unit_size != inode->i_blkbits &&
261 (policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) {
262 /*
263 * Not safe to enable yet, as we need to ensure that DUN
264 * wraparound can only occur on a FS block boundary.
265 */
266 fscrypt_warn(inode,
267 "Sub-block data units not yet supported with IV_INO_LBLK_32");
268 return false;
269 }
270 }
271
272 if ((policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) &&
273 !supported_direct_key_modes(inode, policy->contents_encryption_mode,
274 policy->filenames_encryption_mode))
275 return false;
276
277 if ((policy->flags & (FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64 |
278 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) &&
279 !supported_iv_ino_lblk_policy(policy, inode))
280 return false;
281
282 if (memchr_inv(policy->__reserved, 0, sizeof(policy->__reserved))) {
283 fscrypt_warn(inode, "Reserved bits set in encryption policy");
284 return false;
285 }
286
287 return true;
288 }
289
290 /**
291 * fscrypt_supported_policy() - check whether an encryption policy is supported
292 * @policy_u: the encryption policy
293 * @inode: the inode on which the policy will be used
294 *
295 * Given an encryption policy, check whether all its encryption modes and other
296 * settings are supported by this kernel on the given inode. (But we don't
297 * currently don't check for crypto API support here, so attempting to use an
298 * algorithm not configured into the crypto API will still fail later.)
299 *
300 * Return: %true if supported, else %false
301 */
302 bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
303 const struct inode *inode)
304 {
305 switch (policy_u->version) {
306 case FSCRYPT_POLICY_V1:
307 return fscrypt_supported_v1_policy(&policy_u->v1, inode);
308 case FSCRYPT_POLICY_V2:
309 return fscrypt_supported_v2_policy(&policy_u->v2, inode);
310 }
311 return false;
312 }
313
314 /**
315 * fscrypt_new_context() - create a new fscrypt_context
316 * @ctx_u: output context
317 * @policy_u: input policy
318 * @nonce: nonce to use
319 *
320 * Create an fscrypt_context for an inode that is being assigned the given
321 * encryption policy. @nonce must be a new random nonce.
322 *
323 * Return: the size of the new context in bytes.
324 */
325 static int fscrypt_new_context(union fscrypt_context *ctx_u,
326 const union fscrypt_policy *policy_u,
327 const u8 nonce[FSCRYPT_FILE_NONCE_SIZE])
328 {
329 memset(ctx_u, 0, sizeof(*ctx_u));
330
331 switch (policy_u->version) {
332 case FSCRYPT_POLICY_V1: {
333 const struct fscrypt_policy_v1 *policy = &policy_u->v1;
334 struct fscrypt_context_v1 *ctx = &ctx_u->v1;
335
336 ctx->version = FSCRYPT_CONTEXT_V1;
337 ctx->contents_encryption_mode =
338 policy->contents_encryption_mode;
339 ctx->filenames_encryption_mode =
340 policy->filenames_encryption_mode;
341 ctx->flags = policy->flags;
342 memcpy(ctx->master_key_descriptor,
343 policy->master_key_descriptor,
344 sizeof(ctx->master_key_descriptor));
345 memcpy(ctx->nonce, nonce, FSCRYPT_FILE_NONCE_SIZE);
346 return sizeof(*ctx);
347 }
348 case FSCRYPT_POLICY_V2: {
349 const struct fscrypt_policy_v2 *policy = &policy_u->v2;
350 struct fscrypt_context_v2 *ctx = &ctx_u->v2;
351
352 ctx->version = FSCRYPT_CONTEXT_V2;
353 ctx->contents_encryption_mode =
354 policy->contents_encryption_mode;
355 ctx->filenames_encryption_mode =
356 policy->filenames_encryption_mode;
357 ctx->flags = policy->flags;
358 ctx->log2_data_unit_size = policy->log2_data_unit_size;
359 memcpy(ctx->master_key_identifier,
360 policy->master_key_identifier,
361 sizeof(ctx->master_key_identifier));
362 memcpy(ctx->nonce, nonce, FSCRYPT_FILE_NONCE_SIZE);
363 return sizeof(*ctx);
364 }
365 }
366 BUG();
367 }
368
369 /**
370 * fscrypt_policy_from_context() - convert an fscrypt_context to
371 * an fscrypt_policy
372 * @policy_u: output policy
373 * @ctx_u: input context
374 * @ctx_size: size of input context in bytes
375 *
376 * Given an fscrypt_context, build the corresponding fscrypt_policy.
377 *
378 * Return: 0 on success, or -EINVAL if the fscrypt_context has an unrecognized
379 * version number or size.
380 *
381 * This does *not* validate the settings within the policy itself, e.g. the
382 * modes, flags, and reserved bits. Use fscrypt_supported_policy() for that.
383 */
384 int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
385 const union fscrypt_context *ctx_u,
386 int ctx_size)
387 {
388 memset(policy_u, 0, sizeof(*policy_u));
389
390 if (!fscrypt_context_is_valid(ctx_u, ctx_size))
391 return -EINVAL;
392
393 switch (ctx_u->version) {
394 case FSCRYPT_CONTEXT_V1: {
395 const struct fscrypt_context_v1 *ctx = &ctx_u->v1;
396 struct fscrypt_policy_v1 *policy = &policy_u->v1;
397
398 policy->version = FSCRYPT_POLICY_V1;
399 policy->contents_encryption_mode =
400 ctx->contents_encryption_mode;
401 policy->filenames_encryption_mode =
402 ctx->filenames_encryption_mode;
403 policy->flags = ctx->flags;
404 memcpy(policy->master_key_descriptor,
405 ctx->master_key_descriptor,
406 sizeof(policy->master_key_descriptor));
407 return 0;
408 }
409 case FSCRYPT_CONTEXT_V2: {
410 const struct fscrypt_context_v2 *ctx = &ctx_u->v2;
411 struct fscrypt_policy_v2 *policy = &policy_u->v2;
412
413 policy->version = FSCRYPT_POLICY_V2;
414 policy->contents_encryption_mode =
415 ctx->contents_encryption_mode;
416 policy->filenames_encryption_mode =
417 ctx->filenames_encryption_mode;
418 policy->flags = ctx->flags;
419 policy->log2_data_unit_size = ctx->log2_data_unit_size;
420 memcpy(policy->__reserved, ctx->__reserved,
421 sizeof(policy->__reserved));
422 memcpy(policy->master_key_identifier,
423 ctx->master_key_identifier,
424 sizeof(policy->master_key_identifier));
425 return 0;
426 }
427 }
428 /* unreachable */
429 return -EINVAL;
430 }
431
432 /* Retrieve an inode's encryption policy */
433 static int fscrypt_get_policy(struct inode *inode, union fscrypt_policy *policy)
434 {
435 const struct fscrypt_inode_info *ci;
436 union fscrypt_context ctx;
437 int ret;
438
439 ci = fscrypt_get_inode_info(inode);
440 if (ci) {
441 /* key available, use the cached policy */
442 *policy = ci->ci_policy;
443 return 0;
444 }
445
446 if (!IS_ENCRYPTED(inode))
447 return -ENODATA;
448
449 ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
450 if (ret < 0)
451 return (ret == -ERANGE) ? -EINVAL : ret;
452
453 return fscrypt_policy_from_context(policy, &ctx, ret);
454 }
455
456 static int set_encryption_policy(struct inode *inode,
457 const union fscrypt_policy *policy)
458 {
459 u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
460 union fscrypt_context ctx;
461 int ctxsize;
462 int err;
463
464 if (!fscrypt_supported_policy(policy, inode))
465 return -EINVAL;
466
467 switch (policy->version) {
468 case FSCRYPT_POLICY_V1:
469 /*
470 * The original encryption policy version provided no way of
471 * verifying that the correct master key was supplied, which was
472 * insecure in scenarios where multiple users have access to the
473 * same encrypted files (even just read-only access). The new
474 * encryption policy version fixes this and also implies use of
475 * an improved key derivation function and allows non-root users
476 * to securely remove keys. So as long as compatibility with
477 * old kernels isn't required, it is recommended to use the new
478 * policy version for all new encrypted directories.
479 */
480 pr_warn_once("%s (pid %d) is setting deprecated v1 encryption policy; recommend upgrading to v2.\n",
481 current->comm, current->pid);
482 break;
483 case FSCRYPT_POLICY_V2:
484 err = fscrypt_verify_key_added(inode->i_sb,
485 policy->v2.master_key_identifier);
486 if (err)
487 return err;
488 if (policy->v2.flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)
489 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",
490 current->comm, current->pid);
491 break;
492 default:
493 WARN_ON_ONCE(1);
494 return -EINVAL;
495 }
496
497 get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE);
498 ctxsize = fscrypt_new_context(&ctx, policy, nonce);
499
500 return inode->i_sb->s_cop->set_context(inode, &ctx, ctxsize, NULL);
501 }
502
503 int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
504 {
505 union fscrypt_policy policy;
506 union fscrypt_policy existing_policy;
507 struct inode *inode = file_inode(filp);
508 u8 version;
509 int size;
510 int ret;
511
512 if (get_user(policy.version, (const u8 __user *)arg))
513 return -EFAULT;
514
515 size = fscrypt_policy_size(&policy);
516 if (size <= 0)
517 return -EINVAL;
518
519 /*
520 * We should just copy the remaining 'size - 1' bytes here, but a
521 * bizarre bug in gcc 7 and earlier (fixed by gcc r255731) causes gcc to
522 * think that size can be 0 here (despite the check above!) *and* that
523 * it's a compile-time constant. Thus it would think copy_from_user()
524 * is passed compile-time constant ULONG_MAX, causing the compile-time
525 * buffer overflow check to fail, breaking the build. This only occurred
526 * when building an i386 kernel with -Os and branch profiling enabled.
527 *
528 * Work around it by just copying the first byte again...
529 */
530 version = policy.version;
531 if (copy_from_user(&policy, arg, size))
532 return -EFAULT;
533 policy.version = version;
534
535 if (!inode_owner_or_capable(&nop_mnt_idmap, inode))
536 return -EACCES;
537
538 ret = mnt_want_write_file(filp);
539 if (ret)
540 return ret;
541
542 inode_lock(inode);
543
544 ret = fscrypt_get_policy(inode, &existing_policy);
545 if (ret == -ENODATA) {
546 if (!S_ISDIR(inode->i_mode))
547 ret = -ENOTDIR;
548 else if (IS_DEADDIR(inode))
549 ret = -ENOENT;
550 else if (!inode->i_sb->s_cop->empty_dir(inode))
551 ret = -ENOTEMPTY;
552 else
553 ret = set_encryption_policy(inode, &policy);
554 } else if (ret == -EINVAL ||
555 (ret == 0 && !fscrypt_policies_equal(&policy,
556 &existing_policy))) {
557 /* The file already uses a different encryption policy. */
558 ret = -EEXIST;
559 }
560
561 inode_unlock(inode);
562
563 mnt_drop_write_file(filp);
564 return ret;
565 }
566 EXPORT_SYMBOL(fscrypt_ioctl_set_policy);
567
568 /* Original ioctl version; can only get the original policy version */
569 int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
570 {
571 union fscrypt_policy policy;
572 int err;
573
574 err = fscrypt_get_policy(file_inode(filp), &policy);
575 if (err)
576 return err;
577
578 if (policy.version != FSCRYPT_POLICY_V1)
579 return -EINVAL;
580
581 if (copy_to_user(arg, &policy, sizeof(policy.v1)))
582 return -EFAULT;
583 return 0;
584 }
585 EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
586
587 /* Extended ioctl version; can get policies of any version */
588 int fscrypt_ioctl_get_policy_ex(struct file *filp, void __user *uarg)
589 {
590 struct fscrypt_get_policy_ex_arg arg;
591 union fscrypt_policy *policy = (union fscrypt_policy *)&arg.policy;
592 size_t policy_size;
593 int err;
594
595 /* arg is policy_size, then policy */
596 BUILD_BUG_ON(offsetof(typeof(arg), policy_size) != 0);
597 BUILD_BUG_ON(offsetofend(typeof(arg), policy_size) !=
598 offsetof(typeof(arg), policy));
599 BUILD_BUG_ON(sizeof(arg.policy) != sizeof(*policy));
600
601 err = fscrypt_get_policy(file_inode(filp), policy);
602 if (err)
603 return err;
604 policy_size = fscrypt_policy_size(policy);
605
606 if (copy_from_user(&arg, uarg, sizeof(arg.policy_size)))
607 return -EFAULT;
608
609 if (policy_size > arg.policy_size)
610 return -EOVERFLOW;
611 arg.policy_size = policy_size;
612
613 if (copy_to_user(uarg, &arg, sizeof(arg.policy_size) + policy_size))
614 return -EFAULT;
615 return 0;
616 }
617 EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_policy_ex);
618
619 /* FS_IOC_GET_ENCRYPTION_NONCE: retrieve file's encryption nonce for testing */
620 int fscrypt_ioctl_get_nonce(struct file *filp, void __user *arg)
621 {
622 struct inode *inode = file_inode(filp);
623 union fscrypt_context ctx;
624 int ret;
625
626 ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
627 if (ret < 0)
628 return ret;
629 if (!fscrypt_context_is_valid(&ctx, ret))
630 return -EINVAL;
631 if (copy_to_user(arg, fscrypt_context_nonce(&ctx),
632 FSCRYPT_FILE_NONCE_SIZE))
633 return -EFAULT;
634 return 0;
635 }
636 EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_nonce);
637
638 /**
639 * fscrypt_has_permitted_context() - is a file's encryption policy permitted
640 * within its directory?
641 *
642 * @parent: inode for parent directory
643 * @child: inode for file being looked up, opened, or linked into @parent
644 *
645 * Filesystems must call this before permitting access to an inode in a
646 * situation where the parent directory is encrypted (either before allowing
647 * ->lookup() to succeed, or for a regular file before allowing it to be opened)
648 * and before any operation that involves linking an inode into an encrypted
649 * directory, including link, rename, and cross rename. It enforces the
650 * constraint that within a given encrypted directory tree, all files use the
651 * same encryption policy. The pre-access check is needed to detect potentially
652 * malicious offline violations of this constraint, while the link and rename
653 * checks are needed to prevent online violations of this constraint.
654 *
655 * Return: 1 if permitted, 0 if forbidden.
656 */
657 int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
658 {
659 union fscrypt_policy parent_policy, child_policy;
660 int err, err1, err2;
661
662 /* No restrictions on file types which are never encrypted */
663 if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
664 !S_ISLNK(child->i_mode))
665 return 1;
666
667 /* No restrictions if the parent directory is unencrypted */
668 if (!IS_ENCRYPTED(parent))
669 return 1;
670
671 /* Encrypted directories must not contain unencrypted files */
672 if (!IS_ENCRYPTED(child))
673 return 0;
674
675 /*
676 * Both parent and child are encrypted, so verify they use the same
677 * encryption policy. Compare the cached policies if the keys are
678 * available, otherwise retrieve and compare the fscrypt_contexts.
679 *
680 * Note that the fscrypt_context retrieval will be required frequently
681 * when accessing an encrypted directory tree without the key.
682 * Performance-wise this is not a big deal because we already don't
683 * really optimize for file access without the key (to the extent that
684 * such access is even possible), given that any attempted access
685 * already causes a fscrypt_context retrieval and keyring search.
686 *
687 * In any case, if an unexpected error occurs, fall back to "forbidden".
688 */
689
690 err = fscrypt_get_encryption_info(parent, true);
691 if (err)
692 return 0;
693 err = fscrypt_get_encryption_info(child, true);
694 if (err)
695 return 0;
696
697 err1 = fscrypt_get_policy(parent, &parent_policy);
698 err2 = fscrypt_get_policy(child, &child_policy);
699
700 /*
701 * Allow the case where the parent and child both have an unrecognized
702 * encryption policy, so that files with an unrecognized encryption
703 * policy can be deleted.
704 */
705 if (err1 == -EINVAL && err2 == -EINVAL)
706 return 1;
707
708 if (err1 || err2)
709 return 0;
710
711 return fscrypt_policies_equal(&parent_policy, &child_policy);
712 }
713 EXPORT_SYMBOL(fscrypt_has_permitted_context);
714
715 /*
716 * Return the encryption policy that new files in the directory will inherit, or
717 * NULL if none, or an ERR_PTR() on error. If the directory is encrypted, also
718 * ensure that its key is set up, so that the new filename can be encrypted.
719 */
720 const union fscrypt_policy *fscrypt_policy_to_inherit(struct inode *dir)
721 {
722 int err;
723
724 if (IS_ENCRYPTED(dir)) {
725 err = fscrypt_require_key(dir);
726 if (err)
727 return ERR_PTR(err);
728 return &dir->i_crypt_info->ci_policy;
729 }
730
731 return fscrypt_get_dummy_policy(dir->i_sb);
732 }
733
734 /**
735 * fscrypt_context_for_new_inode() - create an encryption context for a new inode
736 * @ctx: where context should be written
737 * @inode: inode from which to fetch policy and nonce
738 *
739 * Given an in-core "prepared" (via fscrypt_prepare_new_inode) inode,
740 * generate a new context and write it to ctx. ctx _must_ be at least
741 * FSCRYPT_SET_CONTEXT_MAX_SIZE bytes.
742 *
743 * Return: size of the resulting context or a negative error code.
744 */
745 int fscrypt_context_for_new_inode(void *ctx, struct inode *inode)
746 {
747 struct fscrypt_inode_info *ci = inode->i_crypt_info;
748
749 BUILD_BUG_ON(sizeof(union fscrypt_context) !=
750 FSCRYPT_SET_CONTEXT_MAX_SIZE);
751
752 /* fscrypt_prepare_new_inode() should have set up the key already. */
753 if (WARN_ON_ONCE(!ci))
754 return -ENOKEY;
755
756 return fscrypt_new_context(ctx, &ci->ci_policy, ci->ci_nonce);
757 }
758 EXPORT_SYMBOL_GPL(fscrypt_context_for_new_inode);
759
760 /**
761 * fscrypt_set_context() - Set the fscrypt context of a new inode
762 * @inode: a new inode
763 * @fs_data: private data given by FS and passed to ->set_context()
764 *
765 * This should be called after fscrypt_prepare_new_inode(), generally during a
766 * filesystem transaction. Everything here must be %GFP_NOFS-safe.
767 *
768 * Return: 0 on success, -errno on failure
769 */
770 int fscrypt_set_context(struct inode *inode, void *fs_data)
771 {
772 struct fscrypt_inode_info *ci = inode->i_crypt_info;
773 union fscrypt_context ctx;
774 int ctxsize;
775
776 ctxsize = fscrypt_context_for_new_inode(&ctx, inode);
777 if (ctxsize < 0)
778 return ctxsize;
779
780 /*
781 * This may be the first time the inode number is available, so do any
782 * delayed key setup that requires the inode number.
783 */
784 if (ci->ci_policy.version == FSCRYPT_POLICY_V2 &&
785 (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32))
786 fscrypt_hash_inode_number(ci, ci->ci_master_key);
787
788 return inode->i_sb->s_cop->set_context(inode, &ctx, ctxsize, fs_data);
789 }
790 EXPORT_SYMBOL_GPL(fscrypt_set_context);
791
792 /**
793 * fscrypt_parse_test_dummy_encryption() - parse the test_dummy_encryption mount option
794 * @param: the mount option
795 * @dummy_policy: (input/output) the place to write the dummy policy that will
796 * result from parsing the option. Zero-initialize this. If a policy is
797 * already set here (due to test_dummy_encryption being given multiple
798 * times), then this function will verify that the policies are the same.
799 *
800 * Return: 0 on success; -EINVAL if the argument is invalid; -EEXIST if the
801 * argument conflicts with one already specified; or -ENOMEM.
802 */
803 int fscrypt_parse_test_dummy_encryption(const struct fs_parameter *param,
804 struct fscrypt_dummy_policy *dummy_policy)
805 {
806 const char *arg = "v2";
807 union fscrypt_policy *policy;
808 int err;
809
810 if (param->type == fs_value_is_string && *param->string)
811 arg = param->string;
812
813 policy = kzalloc(sizeof(*policy), GFP_KERNEL);
814 if (!policy)
815 return -ENOMEM;
816
817 if (!strcmp(arg, "v1")) {
818 policy->version = FSCRYPT_POLICY_V1;
819 policy->v1.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS;
820 policy->v1.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS;
821 memset(policy->v1.master_key_descriptor, 0x42,
822 FSCRYPT_KEY_DESCRIPTOR_SIZE);
823 } else if (!strcmp(arg, "v2")) {
824 policy->version = FSCRYPT_POLICY_V2;
825 policy->v2.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS;
826 policy->v2.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS;
827 err = fscrypt_get_test_dummy_key_identifier(
828 policy->v2.master_key_identifier);
829 if (err)
830 goto out;
831 } else {
832 err = -EINVAL;
833 goto out;
834 }
835
836 if (dummy_policy->policy) {
837 if (fscrypt_policies_equal(policy, dummy_policy->policy))
838 err = 0;
839 else
840 err = -EEXIST;
841 goto out;
842 }
843 dummy_policy->policy = policy;
844 policy = NULL;
845 err = 0;
846 out:
847 kfree(policy);
848 return err;
849 }
850 EXPORT_SYMBOL_GPL(fscrypt_parse_test_dummy_encryption);
851
852 /**
853 * fscrypt_dummy_policies_equal() - check whether two dummy policies are equal
854 * @p1: the first test dummy policy (may be unset)
855 * @p2: the second test dummy policy (may be unset)
856 *
857 * Return: %true if the dummy policies are both set and equal, or both unset.
858 */
859 bool fscrypt_dummy_policies_equal(const struct fscrypt_dummy_policy *p1,
860 const struct fscrypt_dummy_policy *p2)
861 {
862 if (!p1->policy && !p2->policy)
863 return true;
864 if (!p1->policy || !p2->policy)
865 return false;
866 return fscrypt_policies_equal(p1->policy, p2->policy);
867 }
868 EXPORT_SYMBOL_GPL(fscrypt_dummy_policies_equal);
869
870 /**
871 * fscrypt_show_test_dummy_encryption() - show '-o test_dummy_encryption'
872 * @seq: the seq_file to print the option to
873 * @sep: the separator character to use
874 * @sb: the filesystem whose options are being shown
875 *
876 * Show the test_dummy_encryption mount option, if it was specified.
877 * This is mainly used for /proc/mounts.
878 */
879 void fscrypt_show_test_dummy_encryption(struct seq_file *seq, char sep,
880 struct super_block *sb)
881 {
882 const union fscrypt_policy *policy = fscrypt_get_dummy_policy(sb);
883 int vers;
884
885 if (!policy)
886 return;
887
888 vers = policy->version;
889 if (vers == FSCRYPT_POLICY_V1) /* Handle numbering quirk */
890 vers = 1;
891
892 seq_printf(seq, "%ctest_dummy_encryption=v%d", sep, vers);
893 }
894 EXPORT_SYMBOL_GPL(fscrypt_show_test_dummy_encryption);
895
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