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