linux/fs/crypto/Kconfig

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# SPDX-License-Identifier: GPL-2.0-only
config FS_ENCRYPTION
bool "FS Encryption (Per-file encryption)"
select CRYPTO
select CRYPTO_HASH
select CRYPTO_SKCIPHER
select KEYS
help
Enable encryption of files and directories. This
feature is similar to ecryptfs, but it is more memory
efficient since it avoids caching the encrypted and
decrypted pages in the page cache. Currently Ext4,
F2FS and UBIFS make use of this feature.
# Filesystems supporting encryption must select this if FS_ENCRYPTION. This
# allows the algorithms to be built as modules when all the filesystems are.
config FS_ENCRYPTION_ALGS
tristate
select CRYPTO_AES
select CRYPTO_CBC
select CRYPTO_CTS
select CRYPTO_ECB
select CRYPTO_HMAC
fscrypt: improve format of no-key names When an encrypted directory is listed without the key, the filesystem must show "no-key names" that uniquely identify directory entries, are at most 255 (NAME_MAX) bytes long, and don't contain '/' or '\0'. Currently, for short names the no-key name is the base64 encoding of the ciphertext filename, while for long names it's the base64 encoding of the ciphertext filename's dirhash and second-to-last 16-byte block. This format has the following problems: - Since it doesn't always include the dirhash, it's incompatible with directories that will use a secret-keyed dirhash over the plaintext filenames. In this case, the dirhash won't be computable from the ciphertext name without the key, so it instead must be retrieved from the directory entry and always included in the no-key name. Casefolded encrypted directories will use this type of dirhash. - It's ambiguous: it's possible to craft two filenames that map to the same no-key name, since the method used to abbreviate long filenames doesn't use a proper cryptographic hash function. Solve both these problems by switching to a new no-key name format that is the base64 encoding of a variable-length structure that contains the dirhash, up to 149 bytes of the ciphertext filename, and (if any bytes remain) the SHA-256 of the remaining bytes of the ciphertext filename. This ensures that each no-key name contains everything needed to find the directory entry again, contains only legal characters, doesn't exceed NAME_MAX, is unambiguous unless there's a SHA-256 collision, and that we only take the performance hit of SHA-256 on very long filenames. Note: this change does *not* address the existing issue where users can modify the 'dirhash' part of a no-key name and the filesystem may still accept the name. Signed-off-by: Daniel Rosenberg <drosen@google.com> [EB: improved comments and commit message, fixed checking return value of base64_decode(), check for SHA-256 error, continue to set disk_name for short names to keep matching simpler, and many other cleanups] Link: https://lore.kernel.org/r/20200120223201.241390-7-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-01-21 01:32:01 +03:00
select CRYPTO_SHA256
select CRYPTO_SHA512
select CRYPTO_XTS
fscrypt: add inline encryption support Add support for inline encryption to fs/crypto/. With "inline encryption", the block layer handles the decryption/encryption as part of the bio, instead of the filesystem doing the crypto itself via Linux's crypto API. This model is needed in order to take advantage of the inline encryption hardware present on most modern mobile SoCs. To use inline encryption, the filesystem needs to be mounted with '-o inlinecrypt'. Blk-crypto will then be used instead of the traditional filesystem-layer crypto whenever possible to encrypt the contents of any encrypted files in that filesystem. Fscrypt still provides the key and IV to use, and the actual ciphertext on-disk is still the same; therefore it's testable using the existing fscrypt ciphertext verification tests. Note that since blk-crypto has a fallback to Linux's crypto API, and also supports all the encryption modes currently supported by fscrypt, this feature is usable and testable even without actual inline encryption hardware. Per-filesystem changes will be needed to set encryption contexts when submitting bios and to implement the 'inlinecrypt' mount option. This patch just adds the common code. Signed-off-by: Satya Tangirala <satyat@google.com> Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org> Reviewed-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Theodore Ts'o <tytso@mit.edu> Link: https://lore.kernel.org/r/20200702015607.1215430-3-satyat@google.com Co-developed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Eric Biggers <ebiggers@google.com>
2020-07-02 04:56:05 +03:00
config FS_ENCRYPTION_INLINE_CRYPT
bool "Enable fscrypt to use inline crypto"
depends on FS_ENCRYPTION && BLK_INLINE_ENCRYPTION
help
Enable fscrypt to use inline encryption hardware if available.