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