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- # SPDX-License-Identifier: GPL-2.0
- config FS_VERITY
- bool "FS Verity (read-only file-based authenticity protection)"
- select CRYPTO
- select CRYPTO_HASH_INFO
- # SHA-256 is implied as it's intended to be the default hash algorithm.
- # To avoid bloat, other wanted algorithms must be selected explicitly.
- # Note that CRYPTO_SHA256 denotes the generic C implementation, but
- # some architectures provided optimized implementations of the same
- # algorithm that may be used instead. In this case, CRYPTO_SHA256 may
- # be omitted even if SHA-256 is being used.
- imply CRYPTO_SHA256
- help
- This option enables fs-verity. fs-verity is the dm-verity
- mechanism implemented at the file level. On supported
- filesystems (currently ext4, f2fs, and btrfs), userspace can
- use an ioctl to enable verity for a file, which causes the
- filesystem to build a Merkle tree for the file. The filesystem
- will then transparently verify any data read from the file
- against the Merkle tree. The file is also made read-only.
- This serves as an integrity check, but the availability of the
- Merkle tree root hash also allows efficiently supporting
- various use cases where normally the whole file would need to
- be hashed at once, such as: (a) auditing (logging the file's
- hash), or (b) authenticity verification (comparing the hash
- against a known good value, e.g. from a digital signature).
- fs-verity is especially useful on large files where not all
- the contents may actually be needed. Also, fs-verity verifies
- data each time it is paged back in, which provides better
- protection against malicious disks vs. an ahead-of-time hash.
- If unsure, say N.
- config FS_VERITY_BUILTIN_SIGNATURES
- bool "FS Verity builtin signature support"
- depends on FS_VERITY
- select SYSTEM_DATA_VERIFICATION
- help
- This option adds support for in-kernel verification of
- fs-verity builtin signatures.
- Please take great care before using this feature. It is not
- the only way to do signatures with fs-verity, and the
- alternatives (such as userspace signature verification, and
- IMA appraisal) can be much better. For details about the
- limitations of this feature, see
- Documentation/filesystems/fsverity.rst.
- If unsure, say N.
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