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For the HKDF-SHA512 key derivation needed by fscrypt, just use the HMAC-SHA512 library functions directly. These functions were introduced in v6.17, and they provide simple and efficient direct support for HMAC-SHA512. This ends up being quite a bit simpler and more efficient than using crypto/hkdf.c, as it avoids the generic crypto layer: - The HMAC library can't fail, so callers don't need to handle errors - No inefficient indirect calls - No inefficient and error-prone dynamic allocations - No inefficient and error-prone loading of algorithm by name - Less stack usage Benchmarks on x86_64 show that deriving a per-file key gets about 30% faster, and FS_IOC_ADD_ENCRYPTION_KEY gets nearly twice as fast. The only small downside is the HKDF-Expand logic gets duplicated again. Then again, even considering that, the new fscrypt_hkdf_expand() is only 7 lines longer than the version that called hkdf_expand(). Later we could add HKDF support to lib/crypto/, but for now let's just do this. Link: https://lore.kernel.org/r/20250906035913.1141532-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@kernel.org>
41 lines
1.5 KiB
Plaintext
41 lines
1.5 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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config FS_ENCRYPTION
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bool "FS Encryption (Per-file encryption)"
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select CRYPTO
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select CRYPTO_SKCIPHER
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select CRYPTO_LIB_SHA256
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select CRYPTO_LIB_SHA512
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select KEYS
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help
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Enable encryption of files and directories. This
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feature is similar to ecryptfs, but it is more memory
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efficient since it avoids caching the encrypted and
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decrypted pages in the page cache. Currently Ext4,
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F2FS, UBIFS, and CephFS make use of this feature.
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# Filesystems supporting encryption must select this if FS_ENCRYPTION. This
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# allows the algorithms to be built as modules when all the filesystems are,
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# whereas selecting them from FS_ENCRYPTION would force them to be built-in.
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#
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# Note: this option only pulls in the algorithms that filesystem encryption
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# needs "by default". If userspace will use "non-default" encryption modes such
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# as Adiantum encryption, then those other modes need to be explicitly enabled
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# in the crypto API; see Documentation/filesystems/fscrypt.rst for details.
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#
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# Also note that this option only pulls in the generic implementations of the
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# algorithms, not any per-architecture optimized implementations. It is
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# strongly recommended to enable optimized implementations too.
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config FS_ENCRYPTION_ALGS
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tristate
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select CRYPTO_AES
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select CRYPTO_CBC
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select CRYPTO_CTS
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select CRYPTO_ECB
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select CRYPTO_XTS
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config FS_ENCRYPTION_INLINE_CRYPT
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bool "Enable fscrypt to use inline crypto"
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depends on FS_ENCRYPTION && BLK_INLINE_ENCRYPTION
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help
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Enable fscrypt to use inline encryption hardware if available.
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