blob: 96f528071bed3f8ea401e38b90ae622d7a261745 [file] [log] [blame]
Greg Kroah-Hartmanb2441312017-11-01 15:07:57 +01001// SPDX-License-Identifier: GPL-2.0
Jaegeuk Kim0b81d072015-05-15 16:26:10 -07002/*
3 * Encryption policy functions for per-file encryption support.
4 *
5 * Copyright (C) 2015, Google, Inc.
6 * Copyright (C) 2015, Motorola Mobility.
7 *
Eric Biggers5dae4602019-08-04 19:35:47 -07008 * Originally written by Michael Halcrow, 2015.
Jaegeuk Kim0b81d072015-05-15 16:26:10 -07009 * Modified by Jaegeuk Kim, 2015.
Eric Biggers5dae4602019-08-04 19:35:47 -070010 * Modified by Eric Biggers, 2019 for v2 policy support.
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070011 */
12
13#include <linux/random.h>
14#include <linux/string.h>
Eric Biggersba63f232016-09-08 14:20:38 -070015#include <linux/mount.h>
Theodore Ts'occ4e0df2016-11-26 22:05:18 -050016#include "fscrypt_private.h"
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070017
Eric Biggers5dae4602019-08-04 19:35:47 -070018/**
19 * fscrypt_policies_equal - check whether two encryption policies are the same
20 *
21 * Return: %true if equal, else %false
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070022 */
Eric Biggers5dae4602019-08-04 19:35:47 -070023bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
24 const union fscrypt_policy *policy2)
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070025{
Eric Biggers5dae4602019-08-04 19:35:47 -070026 if (policy1->version != policy2->version)
27 return false;
28
29 return !memcmp(policy1, policy2, fscrypt_policy_size(policy1));
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070030}
31
Eric Biggersb103fb72019-10-24 14:54:36 -070032static bool supported_iv_ino_lblk_64_policy(
33 const struct fscrypt_policy_v2 *policy,
34 const struct inode *inode)
35{
36 struct super_block *sb = inode->i_sb;
37 int ino_bits = 64, lblk_bits = 64;
38
39 if (policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
40 fscrypt_warn(inode,
41 "The DIRECT_KEY and IV_INO_LBLK_64 flags are mutually exclusive");
42 return false;
43 }
44 /*
45 * It's unsafe to include inode numbers in the IVs if the filesystem can
46 * potentially renumber inodes, e.g. via filesystem shrinking.
47 */
48 if (!sb->s_cop->has_stable_inodes ||
49 !sb->s_cop->has_stable_inodes(sb)) {
50 fscrypt_warn(inode,
51 "Can't use IV_INO_LBLK_64 policy on filesystem '%s' because it doesn't have stable inode numbers",
52 sb->s_id);
53 return false;
54 }
55 if (sb->s_cop->get_ino_and_lblk_bits)
56 sb->s_cop->get_ino_and_lblk_bits(sb, &ino_bits, &lblk_bits);
57 if (ino_bits > 32 || lblk_bits > 32) {
58 fscrypt_warn(inode,
59 "Can't use IV_INO_LBLK_64 policy on filesystem '%s' because it doesn't use 32-bit inode and block numbers",
60 sb->s_id);
61 return false;
62 }
63 return true;
64}
65
Eric Biggers5dae4602019-08-04 19:35:47 -070066/**
67 * fscrypt_supported_policy - check whether an encryption policy is supported
68 *
69 * Given an encryption policy, check whether all its encryption modes and other
70 * settings are supported by this kernel. (But we don't currently don't check
71 * for crypto API support here, so attempting to use an algorithm not configured
72 * into the crypto API will still fail later.)
73 *
74 * Return: %true if supported, else %false
75 */
76bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
77 const struct inode *inode)
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070078{
Eric Biggers5dae4602019-08-04 19:35:47 -070079 switch (policy_u->version) {
80 case FSCRYPT_POLICY_V1: {
81 const struct fscrypt_policy_v1 *policy = &policy_u->v1;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070082
Eric Biggers5dae4602019-08-04 19:35:47 -070083 if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
84 policy->filenames_encryption_mode)) {
85 fscrypt_warn(inode,
86 "Unsupported encryption modes (contents %d, filenames %d)",
87 policy->contents_encryption_mode,
88 policy->filenames_encryption_mode);
89 return false;
90 }
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070091
Eric Biggersb103fb72019-10-24 14:54:36 -070092 if (policy->flags & ~(FSCRYPT_POLICY_FLAGS_PAD_MASK |
93 FSCRYPT_POLICY_FLAG_DIRECT_KEY)) {
Eric Biggers5dae4602019-08-04 19:35:47 -070094 fscrypt_warn(inode,
95 "Unsupported encryption flags (0x%02x)",
96 policy->flags);
97 return false;
98 }
99
100 return true;
101 }
102 case FSCRYPT_POLICY_V2: {
103 const struct fscrypt_policy_v2 *policy = &policy_u->v2;
104
105 if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
106 policy->filenames_encryption_mode)) {
107 fscrypt_warn(inode,
108 "Unsupported encryption modes (contents %d, filenames %d)",
109 policy->contents_encryption_mode,
110 policy->filenames_encryption_mode);
111 return false;
112 }
113
114 if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) {
115 fscrypt_warn(inode,
116 "Unsupported encryption flags (0x%02x)",
117 policy->flags);
118 return false;
119 }
120
Eric Biggersb103fb72019-10-24 14:54:36 -0700121 if ((policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) &&
122 !supported_iv_ino_lblk_64_policy(policy, inode))
123 return false;
124
Eric Biggers5dae4602019-08-04 19:35:47 -0700125 if (memchr_inv(policy->__reserved, 0,
126 sizeof(policy->__reserved))) {
127 fscrypt_warn(inode,
128 "Reserved bits set in encryption policy");
129 return false;
130 }
131
132 return true;
133 }
134 }
135 return false;
136}
137
138/**
139 * fscrypt_new_context_from_policy - create a new fscrypt_context from a policy
140 *
141 * Create an fscrypt_context for an inode that is being assigned the given
142 * encryption policy. A new nonce is randomly generated.
143 *
144 * Return: the size of the new context in bytes.
145 */
146static int fscrypt_new_context_from_policy(union fscrypt_context *ctx_u,
147 const union fscrypt_policy *policy_u)
148{
149 memset(ctx_u, 0, sizeof(*ctx_u));
150
151 switch (policy_u->version) {
152 case FSCRYPT_POLICY_V1: {
153 const struct fscrypt_policy_v1 *policy = &policy_u->v1;
154 struct fscrypt_context_v1 *ctx = &ctx_u->v1;
155
156 ctx->version = FSCRYPT_CONTEXT_V1;
157 ctx->contents_encryption_mode =
158 policy->contents_encryption_mode;
159 ctx->filenames_encryption_mode =
160 policy->filenames_encryption_mode;
161 ctx->flags = policy->flags;
162 memcpy(ctx->master_key_descriptor,
163 policy->master_key_descriptor,
164 sizeof(ctx->master_key_descriptor));
165 get_random_bytes(ctx->nonce, sizeof(ctx->nonce));
166 return sizeof(*ctx);
167 }
168 case FSCRYPT_POLICY_V2: {
169 const struct fscrypt_policy_v2 *policy = &policy_u->v2;
170 struct fscrypt_context_v2 *ctx = &ctx_u->v2;
171
172 ctx->version = FSCRYPT_CONTEXT_V2;
173 ctx->contents_encryption_mode =
174 policy->contents_encryption_mode;
175 ctx->filenames_encryption_mode =
176 policy->filenames_encryption_mode;
177 ctx->flags = policy->flags;
178 memcpy(ctx->master_key_identifier,
179 policy->master_key_identifier,
180 sizeof(ctx->master_key_identifier));
181 get_random_bytes(ctx->nonce, sizeof(ctx->nonce));
182 return sizeof(*ctx);
183 }
184 }
185 BUG();
186}
187
188/**
189 * fscrypt_policy_from_context - convert an fscrypt_context to an fscrypt_policy
190 *
191 * Given an fscrypt_context, build the corresponding fscrypt_policy.
192 *
193 * Return: 0 on success, or -EINVAL if the fscrypt_context has an unrecognized
194 * version number or size.
195 *
196 * This does *not* validate the settings within the policy itself, e.g. the
197 * modes, flags, and reserved bits. Use fscrypt_supported_policy() for that.
198 */
199int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
200 const union fscrypt_context *ctx_u,
201 int ctx_size)
202{
203 memset(policy_u, 0, sizeof(*policy_u));
204
205 if (ctx_size <= 0 || ctx_size != fscrypt_context_size(ctx_u))
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700206 return -EINVAL;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700207
Eric Biggers5dae4602019-08-04 19:35:47 -0700208 switch (ctx_u->version) {
209 case FSCRYPT_CONTEXT_V1: {
210 const struct fscrypt_context_v1 *ctx = &ctx_u->v1;
211 struct fscrypt_policy_v1 *policy = &policy_u->v1;
212
213 policy->version = FSCRYPT_POLICY_V1;
214 policy->contents_encryption_mode =
215 ctx->contents_encryption_mode;
216 policy->filenames_encryption_mode =
217 ctx->filenames_encryption_mode;
218 policy->flags = ctx->flags;
219 memcpy(policy->master_key_descriptor,
220 ctx->master_key_descriptor,
221 sizeof(policy->master_key_descriptor));
222 return 0;
223 }
224 case FSCRYPT_CONTEXT_V2: {
225 const struct fscrypt_context_v2 *ctx = &ctx_u->v2;
226 struct fscrypt_policy_v2 *policy = &policy_u->v2;
227
228 policy->version = FSCRYPT_POLICY_V2;
229 policy->contents_encryption_mode =
230 ctx->contents_encryption_mode;
231 policy->filenames_encryption_mode =
232 ctx->filenames_encryption_mode;
233 policy->flags = ctx->flags;
234 memcpy(policy->__reserved, ctx->__reserved,
235 sizeof(policy->__reserved));
236 memcpy(policy->master_key_identifier,
237 ctx->master_key_identifier,
238 sizeof(policy->master_key_identifier));
239 return 0;
240 }
241 }
242 /* unreachable */
243 return -EINVAL;
244}
245
246/* Retrieve an inode's encryption policy */
247static int fscrypt_get_policy(struct inode *inode, union fscrypt_policy *policy)
248{
249 const struct fscrypt_info *ci;
250 union fscrypt_context ctx;
251 int ret;
252
253 ci = READ_ONCE(inode->i_crypt_info);
254 if (ci) {
255 /* key available, use the cached policy */
256 *policy = ci->ci_policy;
257 return 0;
258 }
259
260 if (!IS_ENCRYPTED(inode))
261 return -ENODATA;
262
263 ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
264 if (ret < 0)
265 return (ret == -ERANGE) ? -EINVAL : ret;
266
267 return fscrypt_policy_from_context(policy, &ctx, ret);
268}
269
270static int set_encryption_policy(struct inode *inode,
271 const union fscrypt_policy *policy)
272{
273 union fscrypt_context ctx;
274 int ctxsize;
Eric Biggers5ab71892019-08-04 19:35:48 -0700275 int err;
Eric Biggers5dae4602019-08-04 19:35:47 -0700276
277 if (!fscrypt_supported_policy(policy, inode))
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700278 return -EINVAL;
279
Eric Biggers5ab71892019-08-04 19:35:48 -0700280 switch (policy->version) {
281 case FSCRYPT_POLICY_V1:
Eric Biggers5dae4602019-08-04 19:35:47 -0700282 /*
283 * The original encryption policy version provided no way of
284 * verifying that the correct master key was supplied, which was
285 * insecure in scenarios where multiple users have access to the
286 * same encrypted files (even just read-only access). The new
287 * encryption policy version fixes this and also implies use of
288 * an improved key derivation function and allows non-root users
289 * to securely remove keys. So as long as compatibility with
290 * old kernels isn't required, it is recommended to use the new
291 * policy version for all new encrypted directories.
292 */
293 pr_warn_once("%s (pid %d) is setting deprecated v1 encryption policy; recommend upgrading to v2.\n",
294 current->comm, current->pid);
Eric Biggers5ab71892019-08-04 19:35:48 -0700295 break;
296 case FSCRYPT_POLICY_V2:
297 err = fscrypt_verify_key_added(inode->i_sb,
298 policy->v2.master_key_identifier);
299 if (err)
300 return err;
301 break;
302 default:
303 WARN_ON(1);
304 return -EINVAL;
Eric Biggers5dae4602019-08-04 19:35:47 -0700305 }
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700306
Eric Biggers5dae4602019-08-04 19:35:47 -0700307 ctxsize = fscrypt_new_context_from_policy(&ctx, policy);
308
309 return inode->i_sb->s_cop->set_context(inode, &ctx, ctxsize, NULL);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700310}
311
Eric Biggersdb717d82016-11-26 19:07:49 -0500312int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700313{
Eric Biggers5dae4602019-08-04 19:35:47 -0700314 union fscrypt_policy policy;
315 union fscrypt_policy existing_policy;
Eric Biggersba63f232016-09-08 14:20:38 -0700316 struct inode *inode = file_inode(filp);
Eric Biggers5dae4602019-08-04 19:35:47 -0700317 u8 version;
318 int size;
Eric Biggersba63f232016-09-08 14:20:38 -0700319 int ret;
320
Eric Biggers5dae4602019-08-04 19:35:47 -0700321 if (get_user(policy.version, (const u8 __user *)arg))
Eric Biggersdb717d82016-11-26 19:07:49 -0500322 return -EFAULT;
323
Eric Biggers5dae4602019-08-04 19:35:47 -0700324 size = fscrypt_policy_size(&policy);
325 if (size <= 0)
326 return -EINVAL;
327
328 /*
329 * We should just copy the remaining 'size - 1' bytes here, but a
330 * bizarre bug in gcc 7 and earlier (fixed by gcc r255731) causes gcc to
331 * think that size can be 0 here (despite the check above!) *and* that
332 * it's a compile-time constant. Thus it would think copy_from_user()
333 * is passed compile-time constant ULONG_MAX, causing the compile-time
334 * buffer overflow check to fail, breaking the build. This only occurred
335 * when building an i386 kernel with -Os and branch profiling enabled.
336 *
337 * Work around it by just copying the first byte again...
338 */
339 version = policy.version;
340 if (copy_from_user(&policy, arg, size))
341 return -EFAULT;
342 policy.version = version;
343
Eric Biggers163ae1c2016-09-08 10:57:08 -0700344 if (!inode_owner_or_capable(inode))
345 return -EACCES;
346
Eric Biggersba63f232016-09-08 14:20:38 -0700347 ret = mnt_want_write_file(filp);
348 if (ret)
349 return ret;
350
Eric Biggers8906a822016-10-15 09:48:50 -0400351 inode_lock(inode);
352
Eric Biggers5dae4602019-08-04 19:35:47 -0700353 ret = fscrypt_get_policy(inode, &existing_policy);
Eric Biggersefee590e2016-12-05 11:12:48 -0800354 if (ret == -ENODATA) {
Eric Biggers002ced42016-09-08 11:36:39 -0700355 if (!S_ISDIR(inode->i_mode))
Eric Biggersdffd0cf2016-12-05 11:12:45 -0800356 ret = -ENOTDIR;
Hongjie Fang5858bda2019-05-22 10:02:53 +0800357 else if (IS_DEADDIR(inode))
358 ret = -ENOENT;
Eric Biggersba63f232016-09-08 14:20:38 -0700359 else if (!inode->i_sb->s_cop->empty_dir(inode))
360 ret = -ENOTEMPTY;
361 else
Eric Biggers5dae4602019-08-04 19:35:47 -0700362 ret = set_encryption_policy(inode, &policy);
363 } else if (ret == -EINVAL ||
364 (ret == 0 && !fscrypt_policies_equal(&policy,
365 &existing_policy))) {
Eric Biggersefee590e2016-12-05 11:12:48 -0800366 /* The file already uses a different encryption policy. */
Eric Biggers8488cd92016-12-05 11:12:46 -0800367 ret = -EEXIST;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700368 }
369
Eric Biggers8906a822016-10-15 09:48:50 -0400370 inode_unlock(inode);
371
Eric Biggersba63f232016-09-08 14:20:38 -0700372 mnt_drop_write_file(filp);
373 return ret;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700374}
Eric Biggersdb717d82016-11-26 19:07:49 -0500375EXPORT_SYMBOL(fscrypt_ioctl_set_policy);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700376
Eric Biggers5dae4602019-08-04 19:35:47 -0700377/* Original ioctl version; can only get the original policy version */
Eric Biggersdb717d82016-11-26 19:07:49 -0500378int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700379{
Eric Biggers5dae4602019-08-04 19:35:47 -0700380 union fscrypt_policy policy;
381 int err;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700382
Eric Biggers5dae4602019-08-04 19:35:47 -0700383 err = fscrypt_get_policy(file_inode(filp), &policy);
384 if (err)
385 return err;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700386
Eric Biggers5dae4602019-08-04 19:35:47 -0700387 if (policy.version != FSCRYPT_POLICY_V1)
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700388 return -EINVAL;
389
Eric Biggers5dae4602019-08-04 19:35:47 -0700390 if (copy_to_user(arg, &policy, sizeof(policy.v1)))
Eric Biggersdb717d82016-11-26 19:07:49 -0500391 return -EFAULT;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700392 return 0;
393}
Eric Biggersdb717d82016-11-26 19:07:49 -0500394EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700395
Eric Biggers5dae4602019-08-04 19:35:47 -0700396/* Extended ioctl version; can get policies of any version */
397int fscrypt_ioctl_get_policy_ex(struct file *filp, void __user *uarg)
398{
399 struct fscrypt_get_policy_ex_arg arg;
400 union fscrypt_policy *policy = (union fscrypt_policy *)&arg.policy;
401 size_t policy_size;
402 int err;
403
404 /* arg is policy_size, then policy */
405 BUILD_BUG_ON(offsetof(typeof(arg), policy_size) != 0);
406 BUILD_BUG_ON(offsetofend(typeof(arg), policy_size) !=
407 offsetof(typeof(arg), policy));
408 BUILD_BUG_ON(sizeof(arg.policy) != sizeof(*policy));
409
410 err = fscrypt_get_policy(file_inode(filp), policy);
411 if (err)
412 return err;
413 policy_size = fscrypt_policy_size(policy);
414
415 if (copy_from_user(&arg, uarg, sizeof(arg.policy_size)))
416 return -EFAULT;
417
418 if (policy_size > arg.policy_size)
419 return -EOVERFLOW;
420 arg.policy_size = policy_size;
421
422 if (copy_to_user(uarg, &arg, sizeof(arg.policy_size) + policy_size))
423 return -EFAULT;
424 return 0;
425}
426EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_policy_ex);
427
Eric Biggers272f98f2017-04-07 10:58:37 -0700428/**
429 * fscrypt_has_permitted_context() - is a file's encryption policy permitted
430 * within its directory?
431 *
432 * @parent: inode for parent directory
433 * @child: inode for file being looked up, opened, or linked into @parent
434 *
435 * Filesystems must call this before permitting access to an inode in a
436 * situation where the parent directory is encrypted (either before allowing
437 * ->lookup() to succeed, or for a regular file before allowing it to be opened)
438 * and before any operation that involves linking an inode into an encrypted
439 * directory, including link, rename, and cross rename. It enforces the
440 * constraint that within a given encrypted directory tree, all files use the
441 * same encryption policy. The pre-access check is needed to detect potentially
442 * malicious offline violations of this constraint, while the link and rename
443 * checks are needed to prevent online violations of this constraint.
444 *
Eric Biggersf5e55e72019-01-22 16:20:21 -0800445 * Return: 1 if permitted, 0 if forbidden.
Eric Biggers272f98f2017-04-07 10:58:37 -0700446 */
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700447int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
448{
Eric Biggers5dae4602019-08-04 19:35:47 -0700449 union fscrypt_policy parent_policy, child_policy;
450 int err;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700451
Eric Biggers42d97eb2016-12-19 14:20:13 -0800452 /* No restrictions on file types which are never encrypted */
453 if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
454 !S_ISLNK(child->i_mode))
455 return 1;
456
Eric Biggers272f98f2017-04-07 10:58:37 -0700457 /* No restrictions if the parent directory is unencrypted */
Eric Biggerse0428a22017-10-09 12:15:36 -0700458 if (!IS_ENCRYPTED(parent))
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700459 return 1;
Eric Biggers272f98f2017-04-07 10:58:37 -0700460
461 /* Encrypted directories must not contain unencrypted files */
Eric Biggerse0428a22017-10-09 12:15:36 -0700462 if (!IS_ENCRYPTED(child))
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700463 return 0;
Eric Biggers272f98f2017-04-07 10:58:37 -0700464
465 /*
466 * Both parent and child are encrypted, so verify they use the same
467 * encryption policy. Compare the fscrypt_info structs if the keys are
468 * available, otherwise retrieve and compare the fscrypt_contexts.
469 *
470 * Note that the fscrypt_context retrieval will be required frequently
471 * when accessing an encrypted directory tree without the key.
472 * Performance-wise this is not a big deal because we already don't
473 * really optimize for file access without the key (to the extent that
474 * such access is even possible), given that any attempted access
475 * already causes a fscrypt_context retrieval and keyring search.
476 *
477 * In any case, if an unexpected error occurs, fall back to "forbidden".
478 */
479
Eric Biggers5dae4602019-08-04 19:35:47 -0700480 err = fscrypt_get_encryption_info(parent);
481 if (err)
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700482 return 0;
Eric Biggers5dae4602019-08-04 19:35:47 -0700483 err = fscrypt_get_encryption_info(child);
484 if (err)
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700485 return 0;
486
Eric Biggers5dae4602019-08-04 19:35:47 -0700487 err = fscrypt_get_policy(parent, &parent_policy);
488 if (err)
Eric Biggers272f98f2017-04-07 10:58:37 -0700489 return 0;
490
Eric Biggers5dae4602019-08-04 19:35:47 -0700491 err = fscrypt_get_policy(child, &child_policy);
492 if (err)
493 return 0;
494
495 return fscrypt_policies_equal(&parent_policy, &child_policy);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700496}
497EXPORT_SYMBOL(fscrypt_has_permitted_context);
498
499/**
500 * fscrypt_inherit_context() - Sets a child context from its parent
501 * @parent: Parent inode from which the context is inherited.
502 * @child: Child inode that inherits the context from @parent.
503 * @fs_data: private data given by FS.
Theodore Ts'o5bbdcbb2017-01-02 15:12:17 -0500504 * @preload: preload child i_crypt_info if true
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700505 *
Theodore Ts'o5bbdcbb2017-01-02 15:12:17 -0500506 * Return: 0 on success, -errno on failure
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700507 */
508int fscrypt_inherit_context(struct inode *parent, struct inode *child,
509 void *fs_data, bool preload)
510{
Eric Biggers5dae4602019-08-04 19:35:47 -0700511 union fscrypt_context ctx;
512 int ctxsize;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700513 struct fscrypt_info *ci;
514 int res;
515
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700516 res = fscrypt_get_encryption_info(parent);
517 if (res < 0)
518 return res;
519
Eric Biggerse37a7842019-04-11 14:32:15 -0700520 ci = READ_ONCE(parent->i_crypt_info);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700521 if (ci == NULL)
522 return -ENOKEY;
523
Eric Biggers5dae4602019-08-04 19:35:47 -0700524 ctxsize = fscrypt_new_context_from_policy(&ctx, &ci->ci_policy);
525
Tahsin Erdoganaf652072017-07-06 00:01:59 -0400526 BUILD_BUG_ON(sizeof(ctx) != FSCRYPT_SET_CONTEXT_MAX_SIZE);
Eric Biggers5dae4602019-08-04 19:35:47 -0700527 res = parent->i_sb->s_cop->set_context(child, &ctx, ctxsize, fs_data);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700528 if (res)
529 return res;
530 return preload ? fscrypt_get_encryption_info(child): 0;
531}
532EXPORT_SYMBOL(fscrypt_inherit_context);