1 // SPDX-License-Identifier: GPL-2.0
3  * Key setup facility for FS encryption support.
18 		.friendly_name = "AES-256-XTS",
26 		.friendly_name = "AES-256-CTS-CBC",
33 		.friendly_name = "AES-128-CBC-ESSIV",
41 		.friendly_name = "AES-128-CTS-CBC",
48 		.friendly_name = "SM4-XTS",
56 		.friendly_name = "SM4-CTS-CBC",
71 		.friendly_name = "AES-256-HCTR2",
87 	if (S_ISREG(inode->i_mode))  in select_encryption_mode()
90 	if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))  in select_encryption_mode()
94 		  inode->i_ino, (inode->i_mode & S_IFMT));  in select_encryption_mode()
95 	return ERR_PTR(-EINVAL);  in select_encryption_mode()
98 /* Create a symmetric cipher object for the given encryption mode and key */
106 	tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);  in fscrypt_allocate_skcipher()
108 		if (PTR_ERR(tfm) == -ENOENT) {  in fscrypt_allocate_skcipher()
111 				     mode->friendly_name, mode->cipher_str);  in fscrypt_allocate_skcipher()
112 			return ERR_PTR(-ENOPKG);  in fscrypt_allocate_skcipher()
115 			    mode->cipher_str, PTR_ERR(tfm));  in fscrypt_allocate_skcipher()
118 	if (!xchg(&mode->logged_cryptoapi_impl, 1)) {  in fscrypt_allocate_skcipher()
122 		 * performance problems by logging the ->cra_driver_name the  in fscrypt_allocate_skcipher()
126 			mode->friendly_name, crypto_skcipher_driver_name(tfm));  in fscrypt_allocate_skcipher()
128 	if (WARN_ON_ONCE(crypto_skcipher_ivsize(tfm) != mode->ivsize)) {  in fscrypt_allocate_skcipher()
129 		err = -EINVAL;  in fscrypt_allocate_skcipher()
133 	err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize);  in fscrypt_allocate_skcipher()
145  * Prepare the crypto transform object or blk-crypto key in @prep_key, given the
146  * raw key, encryption mode (@ci->ci_mode), flag indicating which encryption
147  * implementation (fs-layer or blk-crypto) will be used (@ci->ci_inlinecrypt),
148  * and IV generation method (@ci->ci_policy.flags).
158 	tfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, ci->ci_inode);  in fscrypt_prepare_key()
163 	 * I.e., here we publish ->tfm with a RELEASE barrier so that  in fscrypt_prepare_key()
165 	 * possible for per-mode keys, not for per-file keys.  in fscrypt_prepare_key()
167 	smp_store_release(&prep_key->tfm, tfm);  in fscrypt_prepare_key()
171 /* Destroy a crypto transform object and/or blk-crypto key. */
175 	crypto_free_skcipher(prep_key->tfm);  in fscrypt_destroy_prepared_key()
180 /* Given a per-file encryption key, set up the file's crypto transform object */
183 	ci->ci_owns_key = true;  in fscrypt_set_per_file_enc_key()
184 	return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci);  in fscrypt_set_per_file_enc_key()
192 	const struct inode *inode = ci->ci_inode;  in setup_per_mode_enc_key()
193 	const struct super_block *sb = inode->i_sb;  in setup_per_mode_enc_key()
194 	struct fscrypt_mode *mode = ci->ci_mode;  in setup_per_mode_enc_key()
195 	const u8 mode_num = mode - fscrypt_modes;  in setup_per_mode_enc_key()
198 	u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)];  in setup_per_mode_enc_key()
203 		return -EINVAL;  in setup_per_mode_enc_key()
207 		ci->ci_enc_key = *prep_key;  in setup_per_mode_enc_key()
217 	BUILD_BUG_ON(sizeof(sb->s_uuid) != 16);  in setup_per_mode_enc_key()
221 		memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid,  in setup_per_mode_enc_key()
222 		       sizeof(sb->s_uuid));  in setup_per_mode_enc_key()
223 		hkdf_infolen += sizeof(sb->s_uuid);  in setup_per_mode_enc_key()
225 	err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,  in setup_per_mode_enc_key()
227 				  mode_key, mode->keysize);  in setup_per_mode_enc_key()
231 	memzero_explicit(mode_key, mode->keysize);  in setup_per_mode_enc_key()
235 	ci->ci_enc_key = *prep_key;  in setup_per_mode_enc_key()
243  * Derive a SipHash key from the given fscrypt master key and the given
244  * application-specific information string.
246  * Note that the KDF produces a byte array, but the SipHash APIs expect the key
247  * as a pair of 64-bit words.  Therefore, on big endian CPUs we have to do an
252 				      unsigned int infolen, siphash_key_t *key)  in fscrypt_derive_siphash_key()  argument
256 	err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, context, info, infolen,  in fscrypt_derive_siphash_key()
257 				  (u8 *)key, sizeof(*key));  in fscrypt_derive_siphash_key()
261 	BUILD_BUG_ON(sizeof(*key) != 16);  in fscrypt_derive_siphash_key()
262 	BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2);  in fscrypt_derive_siphash_key()
263 	le64_to_cpus(&key->key[0]);  in fscrypt_derive_siphash_key()
264 	le64_to_cpus(&key->key[1]);  in fscrypt_derive_siphash_key()
274 					 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE,  in fscrypt_derive_dirhash_key()
275 					 &ci->ci_dirhash_key);  in fscrypt_derive_dirhash_key()
278 	ci->ci_dirhash_key_initialized = true;  in fscrypt_derive_dirhash_key()
285 	WARN_ON_ONCE(ci->ci_inode->i_ino == 0);  in fscrypt_hash_inode_number()
286 	WARN_ON_ONCE(!mk->mk_ino_hash_key_initialized);  in fscrypt_hash_inode_number()
288 	ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino,  in fscrypt_hash_inode_number()
289 					      &mk->mk_ino_hash_key);  in fscrypt_hash_inode_number()
297 	err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys,  in fscrypt_setup_iv_ino_lblk_32_key()
303 	if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) {  in fscrypt_setup_iv_ino_lblk_32_key()
307 		if (mk->mk_ino_hash_key_initialized)  in fscrypt_setup_iv_ino_lblk_32_key()
312 						 NULL, 0, &mk->mk_ino_hash_key);  in fscrypt_setup_iv_ino_lblk_32_key()
316 		smp_store_release(&mk->mk_ino_hash_key_initialized, true);  in fscrypt_setup_iv_ino_lblk_32_key()
327 	if (ci->ci_inode->i_ino)  in fscrypt_setup_iv_ino_lblk_32_key()
338 	if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {  in fscrypt_setup_v2_file_key()
340 		 * DIRECT_KEY: instead of deriving per-file encryption keys, the  in fscrypt_setup_v2_file_key()
341 		 * per-file nonce will be included in all the IVs.  But unlike  in fscrypt_setup_v2_file_key()
343 		 * with the master key directly but rather derive a per-mode  in fscrypt_setup_v2_file_key()
344 		 * encryption key.  This ensures that the master key is  in fscrypt_setup_v2_file_key()
345 		 * consistently used only for HKDF, avoiding key reuse issues.  in fscrypt_setup_v2_file_key()
347 		err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys,  in fscrypt_setup_v2_file_key()
349 	} else if (ci->ci_policy.v2.flags &  in fscrypt_setup_v2_file_key()
357 		err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys,  in fscrypt_setup_v2_file_key()
360 	} else if (ci->ci_policy.v2.flags &  in fscrypt_setup_v2_file_key()
366 		err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,  in fscrypt_setup_v2_file_key()
368 					  ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE,  in fscrypt_setup_v2_file_key()
369 					  derived_key, ci->ci_mode->keysize);  in fscrypt_setup_v2_file_key()
374 		memzero_explicit(derived_key, ci->ci_mode->keysize);  in fscrypt_setup_v2_file_key()
379 	/* Derive a secret dirhash key for directories that need it. */  in fscrypt_setup_v2_file_key()
390  * Check whether the size of the given master key (@mk) is appropriate for the
393  * If the file uses a v1 encryption policy, then the master key must be at least
394  * as long as the derived key, as this is a requirement of the v1 KDF.
396  * Otherwise, the KDF can accept any size key, so we enforce a slightly looser
397  * requirement: we require that the size of the master key be at least the
398  * maximum security strength of any algorithm whose key will be derived from it
399  * (but in practice we only need to consider @ci->ci_mode, since any other
401  * required key size over @ci->ci_mode).  This allows AES-256-XTS keys to be
402  * derived from a 256-bit master key, which is cryptographically sufficient,
403  * rather than requiring a 512-bit master key which is unnecessarily long.  (We
404  * still allow 512-bit master keys if the user chooses to use them, though.)
411 	if (ci->ci_policy.version == FSCRYPT_POLICY_V1)  in fscrypt_valid_master_key_size()
412 		min_keysize = ci->ci_mode->keysize;  in fscrypt_valid_master_key_size()
414 		min_keysize = ci->ci_mode->security_strength;  in fscrypt_valid_master_key_size()
416 	if (mk->mk_secret.size < min_keysize) {  in fscrypt_valid_master_key_size()
418 			     "key with %s %*phN is too short (got %u bytes, need %u+ bytes)",  in fscrypt_valid_master_key_size()
419 			     master_key_spec_type(&mk->mk_spec),  in fscrypt_valid_master_key_size()
420 			     master_key_spec_len(&mk->mk_spec),  in fscrypt_valid_master_key_size()
421 			     (u8 *)&mk->mk_spec.u,  in fscrypt_valid_master_key_size()
422 			     mk->mk_secret.size, min_keysize);  in fscrypt_valid_master_key_size()
429  * Find the master key, then set up the inode's actual encryption key.
431  * If the master key is found in the filesystem-level keyring, then it is
432  * returned in *mk_ret with its semaphore read-locked.  This is needed to ensure
433  * that only one task links the fscrypt_info into ->mk_decrypted_inodes (as
435  * synchronize the master key being removed with a new inode starting to use it.
441 	struct super_block *sb = ci->ci_inode->i_sb;  in setup_file_encryption_key()
450 	err = fscrypt_policy_to_key_spec(&ci->ci_policy, &mk_spec);  in setup_file_encryption_key()
460 		 * Add the test_dummy_encryption key on-demand.  In principle,  in setup_file_encryption_key()
463 		 * this key at mount time and cleaning up on mount failure.  in setup_file_encryption_key()
466 		    fscrypt_policies_equal(dummy_policy, &ci->ci_policy)) {  in setup_file_encryption_key()
474 		if (ci->ci_policy.version != FSCRYPT_POLICY_V1)  in setup_file_encryption_key()
475 			return -ENOKEY;  in setup_file_encryption_key()
478 		 * As a legacy fallback for v1 policies, search for the key in  in setup_file_encryption_key()
480 		 * to before the search of ->s_master_keys, since users  in setup_file_encryption_key()
481 		 * shouldn't be able to override filesystem-level keys.  in setup_file_encryption_key()
485 	down_read(&mk->mk_sem);  in setup_file_encryption_key()
488 	if (!is_master_key_secret_present(&mk->mk_secret)) {  in setup_file_encryption_key()
489 		err = -ENOKEY;  in setup_file_encryption_key()
494 		err = -ENOKEY;  in setup_file_encryption_key()
498 	switch (ci->ci_policy.version) {  in setup_file_encryption_key()
500 		err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);  in setup_file_encryption_key()
507 		err = -EINVAL;  in setup_file_encryption_key()
517 	up_read(&mk->mk_sem);  in setup_file_encryption_key()
529 	if (ci->ci_direct_key)  in put_crypt_info()
530 		fscrypt_put_direct_key(ci->ci_direct_key);  in put_crypt_info()
531 	else if (ci->ci_owns_key)  in put_crypt_info()
532 		fscrypt_destroy_prepared_key(ci->ci_inode->i_sb,  in put_crypt_info()
533 					     &ci->ci_enc_key);  in put_crypt_info()
535 	mk = ci->ci_master_key;  in put_crypt_info()
539 		 * with the master key.  In addition, if we're removing the last  in put_crypt_info()
540 		 * inode from a master key struct that already had its secret  in put_crypt_info()
543 		spin_lock(&mk->mk_decrypted_inodes_lock);  in put_crypt_info()
544 		list_del(&ci->ci_master_key_link);  in put_crypt_info()
545 		spin_unlock(&mk->mk_decrypted_inodes_lock);  in put_crypt_info()
546 		fscrypt_put_master_key_activeref(ci->ci_inode->i_sb, mk);  in put_crypt_info()
563 	res = fscrypt_initialize(inode->i_sb);  in fscrypt_setup_encryption_info()
569 		return -ENOMEM;  in fscrypt_setup_encryption_info()
571 	crypt_info->ci_inode = inode;  in fscrypt_setup_encryption_info()
572 	crypt_info->ci_policy = *policy;  in fscrypt_setup_encryption_info()
573 	memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE);  in fscrypt_setup_encryption_info()
575 	mode = select_encryption_mode(&crypt_info->ci_policy, inode);  in fscrypt_setup_encryption_info()
580 	WARN_ON_ONCE(mode->ivsize > FSCRYPT_MAX_IV_SIZE);  in fscrypt_setup_encryption_info()
581 	crypt_info->ci_mode = mode;  in fscrypt_setup_encryption_info()
588 	 * For existing inodes, multiple tasks may race to set ->i_crypt_info.  in fscrypt_setup_encryption_info()
590 	 * fscrypt_get_info().  I.e., here we publish ->i_crypt_info with a  in fscrypt_setup_encryption_info()
593 	if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) {  in fscrypt_setup_encryption_info()
595 		 * We won the race and set ->i_crypt_info to our crypt_info.  in fscrypt_setup_encryption_info()
596 		 * Now link it into the master key's inode list.  in fscrypt_setup_encryption_info()
599 			crypt_info->ci_master_key = mk;  in fscrypt_setup_encryption_info()
600 			refcount_inc(&mk->mk_active_refs);  in fscrypt_setup_encryption_info()
601 			spin_lock(&mk->mk_decrypted_inodes_lock);  in fscrypt_setup_encryption_info()
602 			list_add(&crypt_info->ci_master_key_link,  in fscrypt_setup_encryption_info()
603 				 &mk->mk_decrypted_inodes);  in fscrypt_setup_encryption_info()
604 			spin_unlock(&mk->mk_decrypted_inodes_lock);  in fscrypt_setup_encryption_info()
611 		up_read(&mk->mk_sem);  in fscrypt_setup_encryption_info()
619  * fscrypt_get_encryption_info() - set up an inode's encryption key
620  * @inode: the inode to set up the key for.  Must be encrypted.
622  *		       unrecognized encryption context) the same way as the key
627  * Set up ->i_crypt_info, if it hasn't already been done.
629  * Note: unless ->i_crypt_info is already set, this isn't %GFP_NOFS-safe.  So
632  * Return: 0 if ->i_crypt_info was set or was already set, *or* if the
633  *	   encryption key is unavailable.  (Use fscrypt_has_encryption_key() to
634  *	   distinguish these cases.)  Also can return another -errno code.
645 	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));  in fscrypt_get_encryption_info()
647 		if (res == -ERANGE && allow_unsupported)  in fscrypt_get_encryption_info()
665 		return -EINVAL;  in fscrypt_get_encryption_info()
671 					    S_ISDIR(inode->i_mode));  in fscrypt_get_encryption_info()
673 	if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */  in fscrypt_get_encryption_info()
675 	if (res == -ENOKEY)  in fscrypt_get_encryption_info()
681  * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory
682  * @dir: a possibly-encrypted directory
683  * @inode: the new inode.  ->i_mode must be set already.
684  *	   ->i_ino doesn't need to be set yet.
687  * If the directory is encrypted, set up its ->i_crypt_info in preparation for
689  * encrypted, set up its ->i_crypt_info and set *encrypt_ret=true.
691  * This isn't %GFP_NOFS-safe, and therefore it should be called before starting
692  * any filesystem transaction to create the inode.  For this reason, ->i_ino
698  * Return: 0 on success, -ENOKEY if the encryption key is missing, or another
699  *	   -errno code
713 	if (WARN_ON_ONCE(inode->i_mode == 0))  in fscrypt_prepare_new_inode()
714 		return -EINVAL;  in fscrypt_prepare_new_inode()
720 	if (!S_ISREG(inode->i_mode) &&  in fscrypt_prepare_new_inode()
721 	    !S_ISDIR(inode->i_mode) &&  in fscrypt_prepare_new_inode()
722 	    !S_ISLNK(inode->i_mode))  in fscrypt_prepare_new_inode()
730 					     S_ISDIR(inode->i_mode));  in fscrypt_prepare_new_inode()
735  * fscrypt_put_encryption_info() - free most of an inode's fscrypt data
743 	put_crypt_info(inode->i_crypt_info);  in fscrypt_put_encryption_info()
744 	inode->i_crypt_info = NULL;  in fscrypt_put_encryption_info()
749  * fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay
757 	if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) {  in fscrypt_free_inode()
758 		kfree(inode->i_link);  in fscrypt_free_inode()
759 		inode->i_link = NULL;  in fscrypt_free_inode()
765  * fscrypt_drop_inode() - check whether the inode's master key has been removed
768  * Filesystems supporting fscrypt must call this from their ->drop_inode()
770  * use and their master key has been removed.
779 	 * If ci is NULL, then the inode doesn't have an encryption key set up  in fscrypt_drop_inode()
780 	 * so it's irrelevant.  If ci_master_key is NULL, then the master key  in fscrypt_drop_inode()
781 	 * was provided via the legacy mechanism of the process-subscribed  in fscrypt_drop_inode()
784 	if (!ci || !ci->ci_master_key)  in fscrypt_drop_inode()
788 	 * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes  in fscrypt_drop_inode()
789 	 * protected by the key were cleaned by sync_filesystem().  But if  in fscrypt_drop_inode()
793 	if (inode->i_state & I_DIRTY_ALL)  in fscrypt_drop_inode()
797 	 * Note: since we aren't holding the key semaphore, the result here can  in fscrypt_drop_inode()
800 	 * evicting while iput() is racing with the key being removed, since  in fscrypt_drop_inode()
801 	 * then the thread removing the key will either evict the inode itself  in fscrypt_drop_inode()
804 	return !is_master_key_secret_present(&ci->ci_master_key->mk_secret);  in fscrypt_drop_inode()