xref: /openbmc/linux/fs/crypto/policy.c (revision 41b2ad80)
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_ONCE(1);
52 		return -EINVAL;
53 	}
54 }
55 
fscrypt_get_dummy_policy(struct super_block * sb)56 const union fscrypt_policy *fscrypt_get_dummy_policy(struct super_block *sb)
57 {
58 	if (!sb->s_cop->get_dummy_policy)
59 		return NULL;
60 	return sb->s_cop->get_dummy_policy(sb);
61 }
62 
63 /*
64  * Return %true if the given combination of encryption modes is supported for v1
65  * (and later) encryption policies.
66  *
67  * Do *not* add anything new here, since v1 encryption policies are deprecated.
68  * New combinations of modes should go in fscrypt_valid_enc_modes_v2() only.
69  */
fscrypt_valid_enc_modes_v1(u32 contents_mode,u32 filenames_mode)70 static bool fscrypt_valid_enc_modes_v1(u32 contents_mode, u32 filenames_mode)
71 {
72 	if (contents_mode == FSCRYPT_MODE_AES_256_XTS &&
73 	    filenames_mode == FSCRYPT_MODE_AES_256_CTS)
74 		return true;
75 
76 	if (contents_mode == FSCRYPT_MODE_AES_128_CBC &&
77 	    filenames_mode == FSCRYPT_MODE_AES_128_CTS)
78 		return true;
79 
80 	if (contents_mode == FSCRYPT_MODE_ADIANTUM &&
81 	    filenames_mode == FSCRYPT_MODE_ADIANTUM)
82 		return true;
83 
84 	return false;
85 }
86 
fscrypt_valid_enc_modes_v2(u32 contents_mode,u32 filenames_mode)87 static bool fscrypt_valid_enc_modes_v2(u32 contents_mode, u32 filenames_mode)
88 {
89 	if (contents_mode == FSCRYPT_MODE_AES_256_XTS &&
90 	    filenames_mode == FSCRYPT_MODE_AES_256_HCTR2)
91 		return true;
92 
93 	if (contents_mode == FSCRYPT_MODE_SM4_XTS &&
94 	    filenames_mode == FSCRYPT_MODE_SM4_CTS)
95 		return true;
96 
97 	return fscrypt_valid_enc_modes_v1(contents_mode, filenames_mode);
98 }
99 
supported_direct_key_modes(const struct inode * inode,u32 contents_mode,u32 filenames_mode)100 static bool supported_direct_key_modes(const struct inode *inode,
101 				       u32 contents_mode, u32 filenames_mode)
102 {
103 	const struct fscrypt_mode *mode;
104 
105 	if (contents_mode != filenames_mode) {
106 		fscrypt_warn(inode,
107 			     "Direct key flag not allowed with different contents and filenames modes");
108 		return false;
109 	}
110 	mode = &fscrypt_modes[contents_mode];
111 
112 	if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) {
113 		fscrypt_warn(inode, "Direct key flag not allowed with %s",
114 			     mode->friendly_name);
115 		return false;
116 	}
117 	return true;
118 }
119 
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)120 static bool supported_iv_ino_lblk_policy(const struct fscrypt_policy_v2 *policy,
121 					 const struct inode *inode,
122 					 const char *type,
123 					 int max_ino_bits, int max_lblk_bits)
124 {
125 	struct super_block *sb = inode->i_sb;
126 	int ino_bits = 64, lblk_bits = 64;
127 
128 	/*
129 	 * IV_INO_LBLK_* exist only because of hardware limitations, and
130 	 * currently the only known use case for them involves AES-256-XTS.
131 	 * That's also all we test currently.  For these reasons, for now only
132 	 * allow AES-256-XTS here.  This can be relaxed later if a use case for
133 	 * IV_INO_LBLK_* with other encryption modes arises.
134 	 */
135 	if (policy->contents_encryption_mode != FSCRYPT_MODE_AES_256_XTS) {
136 		fscrypt_warn(inode,
137 			     "Can't use %s policy with contents mode other than AES-256-XTS",
138 			     type);
139 		return false;
140 	}
141 
142 	/*
143 	 * It's unsafe to include inode numbers in the IVs if the filesystem can
144 	 * potentially renumber inodes, e.g. via filesystem shrinking.
145 	 */
146 	if (!sb->s_cop->has_stable_inodes ||
147 	    !sb->s_cop->has_stable_inodes(sb)) {
148 		fscrypt_warn(inode,
149 			     "Can't use %s policy on filesystem '%s' because it doesn't have stable inode numbers",
150 			     type, sb->s_id);
151 		return false;
152 	}
153 	if (sb->s_cop->get_ino_and_lblk_bits)
154 		sb->s_cop->get_ino_and_lblk_bits(sb, &ino_bits, &lblk_bits);
155 	if (ino_bits > max_ino_bits) {
156 		fscrypt_warn(inode,
157 			     "Can't use %s policy on filesystem '%s' because its inode numbers are too long",
158 			     type, sb->s_id);
159 		return false;
160 	}
161 	if (lblk_bits > max_lblk_bits) {
162 		fscrypt_warn(inode,
163 			     "Can't use %s policy on filesystem '%s' because its block numbers are too long",
164 			     type, sb->s_id);
165 		return false;
166 	}
167 	return true;
168 }
169 
fscrypt_supported_v1_policy(const struct fscrypt_policy_v1 * policy,const struct inode * inode)170 static bool fscrypt_supported_v1_policy(const struct fscrypt_policy_v1 *policy,
171 					const struct inode *inode)
172 {
173 	if (!fscrypt_valid_enc_modes_v1(policy->contents_encryption_mode,
174 				     policy->filenames_encryption_mode)) {
175 		fscrypt_warn(inode,
176 			     "Unsupported encryption modes (contents %d, filenames %d)",
177 			     policy->contents_encryption_mode,
178 			     policy->filenames_encryption_mode);
179 		return false;
180 	}
181 
182 	if (policy->flags & ~(FSCRYPT_POLICY_FLAGS_PAD_MASK |
183 			      FSCRYPT_POLICY_FLAG_DIRECT_KEY)) {
184 		fscrypt_warn(inode, "Unsupported encryption flags (0x%02x)",
185 			     policy->flags);
186 		return false;
187 	}
188 
189 	if ((policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) &&
190 	    !supported_direct_key_modes(inode, policy->contents_encryption_mode,
191 					policy->filenames_encryption_mode))
192 		return false;
193 
194 	if (IS_CASEFOLDED(inode)) {
195 		/* With v1, there's no way to derive dirhash keys. */
196 		fscrypt_warn(inode,
197 			     "v1 policies can't be used on casefolded directories");
198 		return false;
199 	}
200 
201 	return true;
202 }
203 
fscrypt_supported_v2_policy(const struct fscrypt_policy_v2 * policy,const struct inode * inode)204 static bool fscrypt_supported_v2_policy(const struct fscrypt_policy_v2 *policy,
205 					const struct inode *inode)
206 {
207 	int count = 0;
208 
209 	if (!fscrypt_valid_enc_modes_v2(policy->contents_encryption_mode,
210 				     policy->filenames_encryption_mode)) {
211 		fscrypt_warn(inode,
212 			     "Unsupported encryption modes (contents %d, filenames %d)",
213 			     policy->contents_encryption_mode,
214 			     policy->filenames_encryption_mode);
215 		return false;
216 	}
217 
218 	if (policy->flags & ~(FSCRYPT_POLICY_FLAGS_PAD_MASK |
219 			      FSCRYPT_POLICY_FLAG_DIRECT_KEY |
220 			      FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64 |
221 			      FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) {
222 		fscrypt_warn(inode, "Unsupported encryption flags (0x%02x)",
223 			     policy->flags);
224 		return false;
225 	}
226 
227 	count += !!(policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY);
228 	count += !!(policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64);
229 	count += !!(policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32);
230 	if (count > 1) {
231 		fscrypt_warn(inode, "Mutually exclusive encryption flags (0x%02x)",
232 			     policy->flags);
233 		return false;
234 	}
235 
236 	if ((policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) &&
237 	    !supported_direct_key_modes(inode, policy->contents_encryption_mode,
238 					policy->filenames_encryption_mode))
239 		return false;
240 
241 	if ((policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) &&
242 	    !supported_iv_ino_lblk_policy(policy, inode, "IV_INO_LBLK_64",
243 					  32, 32))
244 		return false;
245 
246 	/*
247 	 * IV_INO_LBLK_32 hashes the inode number, so in principle it can
248 	 * support any ino_bits.  However, currently the inode number is gotten
249 	 * from inode::i_ino which is 'unsigned long'.  So for now the
250 	 * implementation limit is 32 bits.
251 	 */
252 	if ((policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) &&
253 	    !supported_iv_ino_lblk_policy(policy, inode, "IV_INO_LBLK_32",
254 					  32, 32))
255 		return false;
256 
257 	if (memchr_inv(policy->__reserved, 0, sizeof(policy->__reserved))) {
258 		fscrypt_warn(inode, "Reserved bits set in encryption policy");
259 		return false;
260 	}
261 
262 	return true;
263 }
264 
265 /**
266  * fscrypt_supported_policy() - check whether an encryption policy is supported
267  * @policy_u: the encryption policy
268  * @inode: the inode on which the policy will be used
269  *
270  * Given an encryption policy, check whether all its encryption modes and other
271  * settings are supported by this kernel on the given inode.  (But we don't
272  * currently don't check for crypto API support here, so attempting to use an
273  * algorithm not configured into the crypto API will still fail later.)
274  *
275  * Return: %true if supported, else %false
276  */
fscrypt_supported_policy(const union fscrypt_policy * policy_u,const struct inode * inode)277 bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
278 			      const struct inode *inode)
279 {
280 	switch (policy_u->version) {
281 	case FSCRYPT_POLICY_V1:
282 		return fscrypt_supported_v1_policy(&policy_u->v1, inode);
283 	case FSCRYPT_POLICY_V2:
284 		return fscrypt_supported_v2_policy(&policy_u->v2, inode);
285 	}
286 	return false;
287 }
288 
289 /**
290  * fscrypt_new_context() - create a new fscrypt_context
291  * @ctx_u: output context
292  * @policy_u: input policy
293  * @nonce: nonce to use
294  *
295  * Create an fscrypt_context for an inode that is being assigned the given
296  * encryption policy.  @nonce must be a new random nonce.
297  *
298  * Return: the size of the new context in bytes.
299  */
fscrypt_new_context(union fscrypt_context * ctx_u,const union fscrypt_policy * policy_u,const u8 nonce[FSCRYPT_FILE_NONCE_SIZE])300 static int fscrypt_new_context(union fscrypt_context *ctx_u,
301 			       const union fscrypt_policy *policy_u,
302 			       const u8 nonce[FSCRYPT_FILE_NONCE_SIZE])
303 {
304 	memset(ctx_u, 0, sizeof(*ctx_u));
305 
306 	switch (policy_u->version) {
307 	case FSCRYPT_POLICY_V1: {
308 		const struct fscrypt_policy_v1 *policy = &policy_u->v1;
309 		struct fscrypt_context_v1 *ctx = &ctx_u->v1;
310 
311 		ctx->version = FSCRYPT_CONTEXT_V1;
312 		ctx->contents_encryption_mode =
313 			policy->contents_encryption_mode;
314 		ctx->filenames_encryption_mode =
315 			policy->filenames_encryption_mode;
316 		ctx->flags = policy->flags;
317 		memcpy(ctx->master_key_descriptor,
318 		       policy->master_key_descriptor,
319 		       sizeof(ctx->master_key_descriptor));
320 		memcpy(ctx->nonce, nonce, FSCRYPT_FILE_NONCE_SIZE);
321 		return sizeof(*ctx);
322 	}
323 	case FSCRYPT_POLICY_V2: {
324 		const struct fscrypt_policy_v2 *policy = &policy_u->v2;
325 		struct fscrypt_context_v2 *ctx = &ctx_u->v2;
326 
327 		ctx->version = FSCRYPT_CONTEXT_V2;
328 		ctx->contents_encryption_mode =
329 			policy->contents_encryption_mode;
330 		ctx->filenames_encryption_mode =
331 			policy->filenames_encryption_mode;
332 		ctx->flags = policy->flags;
333 		memcpy(ctx->master_key_identifier,
334 		       policy->master_key_identifier,
335 		       sizeof(ctx->master_key_identifier));
336 		memcpy(ctx->nonce, nonce, FSCRYPT_FILE_NONCE_SIZE);
337 		return sizeof(*ctx);
338 	}
339 	}
340 	BUG();
341 }
342 
343 /**
344  * fscrypt_policy_from_context() - convert an fscrypt_context to
345  *				   an fscrypt_policy
346  * @policy_u: output policy
347  * @ctx_u: input context
348  * @ctx_size: size of input context in bytes
349  *
350  * Given an fscrypt_context, build the corresponding fscrypt_policy.
351  *
352  * Return: 0 on success, or -EINVAL if the fscrypt_context has an unrecognized
353  * version number or size.
354  *
355  * This does *not* validate the settings within the policy itself, e.g. the
356  * modes, flags, and reserved bits.  Use fscrypt_supported_policy() for that.
357  */
fscrypt_policy_from_context(union fscrypt_policy * policy_u,const union fscrypt_context * ctx_u,int ctx_size)358 int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
359 				const union fscrypt_context *ctx_u,
360 				int ctx_size)
361 {
362 	memset(policy_u, 0, sizeof(*policy_u));
363 
364 	if (!fscrypt_context_is_valid(ctx_u, ctx_size))
365 		return -EINVAL;
366 
367 	switch (ctx_u->version) {
368 	case FSCRYPT_CONTEXT_V1: {
369 		const struct fscrypt_context_v1 *ctx = &ctx_u->v1;
370 		struct fscrypt_policy_v1 *policy = &policy_u->v1;
371 
372 		policy->version = FSCRYPT_POLICY_V1;
373 		policy->contents_encryption_mode =
374 			ctx->contents_encryption_mode;
375 		policy->filenames_encryption_mode =
376 			ctx->filenames_encryption_mode;
377 		policy->flags = ctx->flags;
378 		memcpy(policy->master_key_descriptor,
379 		       ctx->master_key_descriptor,
380 		       sizeof(policy->master_key_descriptor));
381 		return 0;
382 	}
383 	case FSCRYPT_CONTEXT_V2: {
384 		const struct fscrypt_context_v2 *ctx = &ctx_u->v2;
385 		struct fscrypt_policy_v2 *policy = &policy_u->v2;
386 
387 		policy->version = FSCRYPT_POLICY_V2;
388 		policy->contents_encryption_mode =
389 			ctx->contents_encryption_mode;
390 		policy->filenames_encryption_mode =
391 			ctx->filenames_encryption_mode;
392 		policy->flags = ctx->flags;
393 		memcpy(policy->__reserved, ctx->__reserved,
394 		       sizeof(policy->__reserved));
395 		memcpy(policy->master_key_identifier,
396 		       ctx->master_key_identifier,
397 		       sizeof(policy->master_key_identifier));
398 		return 0;
399 	}
400 	}
401 	/* unreachable */
402 	return -EINVAL;
403 }
404 
405 /* Retrieve an inode's encryption policy */
fscrypt_get_policy(struct inode * inode,union fscrypt_policy * policy)406 static int fscrypt_get_policy(struct inode *inode, union fscrypt_policy *policy)
407 {
408 	const struct fscrypt_info *ci;
409 	union fscrypt_context ctx;
410 	int ret;
411 
412 	ci = fscrypt_get_info(inode);
413 	if (ci) {
414 		/* key available, use the cached policy */
415 		*policy = ci->ci_policy;
416 		return 0;
417 	}
418 
419 	if (!IS_ENCRYPTED(inode))
420 		return -ENODATA;
421 
422 	ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
423 	if (ret < 0)
424 		return (ret == -ERANGE) ? -EINVAL : ret;
425 
426 	return fscrypt_policy_from_context(policy, &ctx, ret);
427 }
428 
set_encryption_policy(struct inode * inode,const union fscrypt_policy * policy)429 static int set_encryption_policy(struct inode *inode,
430 				 const union fscrypt_policy *policy)
431 {
432 	u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
433 	union fscrypt_context ctx;
434 	int ctxsize;
435 	int err;
436 
437 	if (!fscrypt_supported_policy(policy, inode))
438 		return -EINVAL;
439 
440 	switch (policy->version) {
441 	case FSCRYPT_POLICY_V1:
442 		/*
443 		 * The original encryption policy version provided no way of
444 		 * verifying that the correct master key was supplied, which was
445 		 * insecure in scenarios where multiple users have access to the
446 		 * same encrypted files (even just read-only access).  The new
447 		 * encryption policy version fixes this and also implies use of
448 		 * an improved key derivation function and allows non-root users
449 		 * to securely remove keys.  So as long as compatibility with
450 		 * old kernels isn't required, it is recommended to use the new
451 		 * policy version for all new encrypted directories.
452 		 */
453 		pr_warn_once("%s (pid %d) is setting deprecated v1 encryption policy; recommend upgrading to v2.\n",
454 			     current->comm, current->pid);
455 		break;
456 	case FSCRYPT_POLICY_V2:
457 		err = fscrypt_verify_key_added(inode->i_sb,
458 					       policy->v2.master_key_identifier);
459 		if (err)
460 			return err;
461 		if (policy->v2.flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)
462 			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",
463 				     current->comm, current->pid);
464 		break;
465 	default:
466 		WARN_ON_ONCE(1);
467 		return -EINVAL;
468 	}
469 
470 	get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE);
471 	ctxsize = fscrypt_new_context(&ctx, policy, nonce);
472 
473 	return inode->i_sb->s_cop->set_context(inode, &ctx, ctxsize, NULL);
474 }
475 
fscrypt_ioctl_set_policy(struct file * filp,const void __user * arg)476 int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
477 {
478 	union fscrypt_policy policy;
479 	union fscrypt_policy existing_policy;
480 	struct inode *inode = file_inode(filp);
481 	u8 version;
482 	int size;
483 	int ret;
484 
485 	if (get_user(policy.version, (const u8 __user *)arg))
486 		return -EFAULT;
487 
488 	size = fscrypt_policy_size(&policy);
489 	if (size <= 0)
490 		return -EINVAL;
491 
492 	/*
493 	 * We should just copy the remaining 'size - 1' bytes here, but a
494 	 * bizarre bug in gcc 7 and earlier (fixed by gcc r255731) causes gcc to
495 	 * think that size can be 0 here (despite the check above!) *and* that
496 	 * it's a compile-time constant.  Thus it would think copy_from_user()
497 	 * is passed compile-time constant ULONG_MAX, causing the compile-time
498 	 * buffer overflow check to fail, breaking the build. This only occurred
499 	 * when building an i386 kernel with -Os and branch profiling enabled.
500 	 *
501 	 * Work around it by just copying the first byte again...
502 	 */
503 	version = policy.version;
504 	if (copy_from_user(&policy, arg, size))
505 		return -EFAULT;
506 	policy.version = version;
507 
508 	if (!inode_owner_or_capable(&nop_mnt_idmap, inode))
509 		return -EACCES;
510 
511 	ret = mnt_want_write_file(filp);
512 	if (ret)
513 		return ret;
514 
515 	inode_lock(inode);
516 
517 	ret = fscrypt_get_policy(inode, &existing_policy);
518 	if (ret == -ENODATA) {
519 		if (!S_ISDIR(inode->i_mode))
520 			ret = -ENOTDIR;
521 		else if (IS_DEADDIR(inode))
522 			ret = -ENOENT;
523 		else if (!inode->i_sb->s_cop->empty_dir(inode))
524 			ret = -ENOTEMPTY;
525 		else
526 			ret = set_encryption_policy(inode, &policy);
527 	} else if (ret == -EINVAL ||
528 		   (ret == 0 && !fscrypt_policies_equal(&policy,
529 							&existing_policy))) {
530 		/* The file already uses a different encryption policy. */
531 		ret = -EEXIST;
532 	}
533 
534 	inode_unlock(inode);
535 
536 	mnt_drop_write_file(filp);
537 	return ret;
538 }
539 EXPORT_SYMBOL(fscrypt_ioctl_set_policy);
540 
541 /* Original ioctl version; can only get the original policy version */
fscrypt_ioctl_get_policy(struct file * filp,void __user * arg)542 int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
543 {
544 	union fscrypt_policy policy;
545 	int err;
546 
547 	err = fscrypt_get_policy(file_inode(filp), &policy);
548 	if (err)
549 		return err;
550 
551 	if (policy.version != FSCRYPT_POLICY_V1)
552 		return -EINVAL;
553 
554 	if (copy_to_user(arg, &policy, sizeof(policy.v1)))
555 		return -EFAULT;
556 	return 0;
557 }
558 EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
559 
560 /* Extended ioctl version; can get policies of any version */
fscrypt_ioctl_get_policy_ex(struct file * filp,void __user * uarg)561 int fscrypt_ioctl_get_policy_ex(struct file *filp, void __user *uarg)
562 {
563 	struct fscrypt_get_policy_ex_arg arg;
564 	union fscrypt_policy *policy = (union fscrypt_policy *)&arg.policy;
565 	size_t policy_size;
566 	int err;
567 
568 	/* arg is policy_size, then policy */
569 	BUILD_BUG_ON(offsetof(typeof(arg), policy_size) != 0);
570 	BUILD_BUG_ON(offsetofend(typeof(arg), policy_size) !=
571 		     offsetof(typeof(arg), policy));
572 	BUILD_BUG_ON(sizeof(arg.policy) != sizeof(*policy));
573 
574 	err = fscrypt_get_policy(file_inode(filp), policy);
575 	if (err)
576 		return err;
577 	policy_size = fscrypt_policy_size(policy);
578 
579 	if (copy_from_user(&arg, uarg, sizeof(arg.policy_size)))
580 		return -EFAULT;
581 
582 	if (policy_size > arg.policy_size)
583 		return -EOVERFLOW;
584 	arg.policy_size = policy_size;
585 
586 	if (copy_to_user(uarg, &arg, sizeof(arg.policy_size) + policy_size))
587 		return -EFAULT;
588 	return 0;
589 }
590 EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_policy_ex);
591 
592 /* FS_IOC_GET_ENCRYPTION_NONCE: retrieve file's encryption nonce for testing */
fscrypt_ioctl_get_nonce(struct file * filp,void __user * arg)593 int fscrypt_ioctl_get_nonce(struct file *filp, void __user *arg)
594 {
595 	struct inode *inode = file_inode(filp);
596 	union fscrypt_context ctx;
597 	int ret;
598 
599 	ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
600 	if (ret < 0)
601 		return ret;
602 	if (!fscrypt_context_is_valid(&ctx, ret))
603 		return -EINVAL;
604 	if (copy_to_user(arg, fscrypt_context_nonce(&ctx),
605 			 FSCRYPT_FILE_NONCE_SIZE))
606 		return -EFAULT;
607 	return 0;
608 }
609 EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_nonce);
610 
611 /**
612  * fscrypt_has_permitted_context() - is a file's encryption policy permitted
613  *				     within its directory?
614  *
615  * @parent: inode for parent directory
616  * @child: inode for file being looked up, opened, or linked into @parent
617  *
618  * Filesystems must call this before permitting access to an inode in a
619  * situation where the parent directory is encrypted (either before allowing
620  * ->lookup() to succeed, or for a regular file before allowing it to be opened)
621  * and before any operation that involves linking an inode into an encrypted
622  * directory, including link, rename, and cross rename.  It enforces the
623  * constraint that within a given encrypted directory tree, all files use the
624  * same encryption policy.  The pre-access check is needed to detect potentially
625  * malicious offline violations of this constraint, while the link and rename
626  * checks are needed to prevent online violations of this constraint.
627  *
628  * Return: 1 if permitted, 0 if forbidden.
629  */
fscrypt_has_permitted_context(struct inode * parent,struct inode * child)630 int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
631 {
632 	union fscrypt_policy parent_policy, child_policy;
633 	int err, err1, err2;
634 
635 	/* No restrictions on file types which are never encrypted */
636 	if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
637 	    !S_ISLNK(child->i_mode))
638 		return 1;
639 
640 	/* No restrictions if the parent directory is unencrypted */
641 	if (!IS_ENCRYPTED(parent))
642 		return 1;
643 
644 	/* Encrypted directories must not contain unencrypted files */
645 	if (!IS_ENCRYPTED(child))
646 		return 0;
647 
648 	/*
649 	 * Both parent and child are encrypted, so verify they use the same
650 	 * encryption policy.  Compare the fscrypt_info structs if the keys are
651 	 * available, otherwise retrieve and compare the fscrypt_contexts.
652 	 *
653 	 * Note that the fscrypt_context retrieval will be required frequently
654 	 * when accessing an encrypted directory tree without the key.
655 	 * Performance-wise this is not a big deal because we already don't
656 	 * really optimize for file access without the key (to the extent that
657 	 * such access is even possible), given that any attempted access
658 	 * already causes a fscrypt_context retrieval and keyring search.
659 	 *
660 	 * In any case, if an unexpected error occurs, fall back to "forbidden".
661 	 */
662 
663 	err = fscrypt_get_encryption_info(parent, true);
664 	if (err)
665 		return 0;
666 	err = fscrypt_get_encryption_info(child, true);
667 	if (err)
668 		return 0;
669 
670 	err1 = fscrypt_get_policy(parent, &parent_policy);
671 	err2 = fscrypt_get_policy(child, &child_policy);
672 
673 	/*
674 	 * Allow the case where the parent and child both have an unrecognized
675 	 * encryption policy, so that files with an unrecognized encryption
676 	 * policy can be deleted.
677 	 */
678 	if (err1 == -EINVAL && err2 == -EINVAL)
679 		return 1;
680 
681 	if (err1 || err2)
682 		return 0;
683 
684 	return fscrypt_policies_equal(&parent_policy, &child_policy);
685 }
686 EXPORT_SYMBOL(fscrypt_has_permitted_context);
687 
688 /*
689  * Return the encryption policy that new files in the directory will inherit, or
690  * NULL if none, or an ERR_PTR() on error.  If the directory is encrypted, also
691  * ensure that its key is set up, so that the new filename can be encrypted.
692  */
fscrypt_policy_to_inherit(struct inode * dir)693 const union fscrypt_policy *fscrypt_policy_to_inherit(struct inode *dir)
694 {
695 	int err;
696 
697 	if (IS_ENCRYPTED(dir)) {
698 		err = fscrypt_require_key(dir);
699 		if (err)
700 			return ERR_PTR(err);
701 		return &dir->i_crypt_info->ci_policy;
702 	}
703 
704 	return fscrypt_get_dummy_policy(dir->i_sb);
705 }
706 
707 /**
708  * fscrypt_context_for_new_inode() - create an encryption context for a new inode
709  * @ctx: where context should be written
710  * @inode: inode from which to fetch policy and nonce
711  *
712  * Given an in-core "prepared" (via fscrypt_prepare_new_inode) inode,
713  * generate a new context and write it to ctx. ctx _must_ be at least
714  * FSCRYPT_SET_CONTEXT_MAX_SIZE bytes.
715  *
716  * Return: size of the resulting context or a negative error code.
717  */
fscrypt_context_for_new_inode(void * ctx,struct inode * inode)718 int fscrypt_context_for_new_inode(void *ctx, struct inode *inode)
719 {
720 	struct fscrypt_info *ci = inode->i_crypt_info;
721 
722 	BUILD_BUG_ON(sizeof(union fscrypt_context) !=
723 			FSCRYPT_SET_CONTEXT_MAX_SIZE);
724 
725 	/* fscrypt_prepare_new_inode() should have set up the key already. */
726 	if (WARN_ON_ONCE(!ci))
727 		return -ENOKEY;
728 
729 	return fscrypt_new_context(ctx, &ci->ci_policy, ci->ci_nonce);
730 }
731 EXPORT_SYMBOL_GPL(fscrypt_context_for_new_inode);
732 
733 /**
734  * fscrypt_set_context() - Set the fscrypt context of a new inode
735  * @inode: a new inode
736  * @fs_data: private data given by FS and passed to ->set_context()
737  *
738  * This should be called after fscrypt_prepare_new_inode(), generally during a
739  * filesystem transaction.  Everything here must be %GFP_NOFS-safe.
740  *
741  * Return: 0 on success, -errno on failure
742  */
fscrypt_set_context(struct inode * inode,void * fs_data)743 int fscrypt_set_context(struct inode *inode, void *fs_data)
744 {
745 	struct fscrypt_info *ci = inode->i_crypt_info;
746 	union fscrypt_context ctx;
747 	int ctxsize;
748 
749 	ctxsize = fscrypt_context_for_new_inode(&ctx, inode);
750 	if (ctxsize < 0)
751 		return ctxsize;
752 
753 	/*
754 	 * This may be the first time the inode number is available, so do any
755 	 * delayed key setup that requires the inode number.
756 	 */
757 	if (ci->ci_policy.version == FSCRYPT_POLICY_V2 &&
758 	    (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32))
759 		fscrypt_hash_inode_number(ci, ci->ci_master_key);
760 
761 	return inode->i_sb->s_cop->set_context(inode, &ctx, ctxsize, fs_data);
762 }
763 EXPORT_SYMBOL_GPL(fscrypt_set_context);
764 
765 /**
766  * fscrypt_parse_test_dummy_encryption() - parse the test_dummy_encryption mount option
767  * @param: the mount option
768  * @dummy_policy: (input/output) the place to write the dummy policy that will
769  *	result from parsing the option.  Zero-initialize this.  If a policy is
770  *	already set here (due to test_dummy_encryption being given multiple
771  *	times), then this function will verify that the policies are the same.
772  *
773  * Return: 0 on success; -EINVAL if the argument is invalid; -EEXIST if the
774  *	   argument conflicts with one already specified; or -ENOMEM.
775  */
fscrypt_parse_test_dummy_encryption(const struct fs_parameter * param,struct fscrypt_dummy_policy * dummy_policy)776 int fscrypt_parse_test_dummy_encryption(const struct fs_parameter *param,
777 				struct fscrypt_dummy_policy *dummy_policy)
778 {
779 	const char *arg = "v2";
780 	union fscrypt_policy *policy;
781 	int err;
782 
783 	if (param->type == fs_value_is_string && *param->string)
784 		arg = param->string;
785 
786 	policy = kzalloc(sizeof(*policy), GFP_KERNEL);
787 	if (!policy)
788 		return -ENOMEM;
789 
790 	if (!strcmp(arg, "v1")) {
791 		policy->version = FSCRYPT_POLICY_V1;
792 		policy->v1.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS;
793 		policy->v1.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS;
794 		memset(policy->v1.master_key_descriptor, 0x42,
795 		       FSCRYPT_KEY_DESCRIPTOR_SIZE);
796 	} else if (!strcmp(arg, "v2")) {
797 		policy->version = FSCRYPT_POLICY_V2;
798 		policy->v2.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS;
799 		policy->v2.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS;
800 		err = fscrypt_get_test_dummy_key_identifier(
801 				policy->v2.master_key_identifier);
802 		if (err)
803 			goto out;
804 	} else {
805 		err = -EINVAL;
806 		goto out;
807 	}
808 
809 	if (dummy_policy->policy) {
810 		if (fscrypt_policies_equal(policy, dummy_policy->policy))
811 			err = 0;
812 		else
813 			err = -EEXIST;
814 		goto out;
815 	}
816 	dummy_policy->policy = policy;
817 	policy = NULL;
818 	err = 0;
819 out:
820 	kfree(policy);
821 	return err;
822 }
823 EXPORT_SYMBOL_GPL(fscrypt_parse_test_dummy_encryption);
824 
825 /**
826  * fscrypt_dummy_policies_equal() - check whether two dummy policies are equal
827  * @p1: the first test dummy policy (may be unset)
828  * @p2: the second test dummy policy (may be unset)
829  *
830  * Return: %true if the dummy policies are both set and equal, or both unset.
831  */
fscrypt_dummy_policies_equal(const struct fscrypt_dummy_policy * p1,const struct fscrypt_dummy_policy * p2)832 bool fscrypt_dummy_policies_equal(const struct fscrypt_dummy_policy *p1,
833 				  const struct fscrypt_dummy_policy *p2)
834 {
835 	if (!p1->policy && !p2->policy)
836 		return true;
837 	if (!p1->policy || !p2->policy)
838 		return false;
839 	return fscrypt_policies_equal(p1->policy, p2->policy);
840 }
841 EXPORT_SYMBOL_GPL(fscrypt_dummy_policies_equal);
842 
843 /**
844  * fscrypt_show_test_dummy_encryption() - show '-o test_dummy_encryption'
845  * @seq: the seq_file to print the option to
846  * @sep: the separator character to use
847  * @sb: the filesystem whose options are being shown
848  *
849  * Show the test_dummy_encryption mount option, if it was specified.
850  * This is mainly used for /proc/mounts.
851  */
fscrypt_show_test_dummy_encryption(struct seq_file * seq,char sep,struct super_block * sb)852 void fscrypt_show_test_dummy_encryption(struct seq_file *seq, char sep,
853 					struct super_block *sb)
854 {
855 	const union fscrypt_policy *policy = fscrypt_get_dummy_policy(sb);
856 	int vers;
857 
858 	if (!policy)
859 		return;
860 
861 	vers = policy->version;
862 	if (vers == FSCRYPT_POLICY_V1) /* Handle numbering quirk */
863 		vers = 1;
864 
865 	seq_printf(seq, "%ctest_dummy_encryption=v%d", sep, vers);
866 }
867 EXPORT_SYMBOL_GPL(fscrypt_show_test_dummy_encryption);
868