53 lines · plain
1# SPDX-License-Identifier: GPL-2.02 3config FS_VERITY4 bool "FS Verity (read-only file-based authenticity protection)"5 select CRYPTO6 select CRYPTO_HASH_INFO7 # SHA-256 is implied as it's intended to be the default hash algorithm.8 # To avoid bloat, other wanted algorithms must be selected explicitly.9 # Note that CRYPTO_SHA256 denotes the generic C implementation, but10 # some architectures provided optimized implementations of the same11 # algorithm that may be used instead. In this case, CRYPTO_SHA256 may12 # be omitted even if SHA-256 is being used.13 imply CRYPTO_SHA25614 help15 This option enables fs-verity. fs-verity is the dm-verity16 mechanism implemented at the file level. On supported17 filesystems (currently ext4, f2fs, and btrfs), userspace can18 use an ioctl to enable verity for a file, which causes the19 filesystem to build a Merkle tree for the file. The filesystem20 will then transparently verify any data read from the file21 against the Merkle tree. The file is also made read-only.22 23 This serves as an integrity check, but the availability of the24 Merkle tree root hash also allows efficiently supporting25 various use cases where normally the whole file would need to26 be hashed at once, such as: (a) auditing (logging the file's27 hash), or (b) authenticity verification (comparing the hash28 against a known good value, e.g. from a digital signature).29 30 fs-verity is especially useful on large files where not all31 the contents may actually be needed. Also, fs-verity verifies32 data each time it is paged back in, which provides better33 protection against malicious disks vs. an ahead-of-time hash.34 35 If unsure, say N.36 37config FS_VERITY_BUILTIN_SIGNATURES38 bool "FS Verity builtin signature support"39 depends on FS_VERITY40 select SYSTEM_DATA_VERIFICATION41 help42 This option adds support for in-kernel verification of43 fs-verity builtin signatures.44 45 Please take great care before using this feature. It is not46 the only way to do signatures with fs-verity, and the47 alternatives (such as userspace signature verification, and48 IMA appraisal) can be much better. For details about the49 limitations of this feature, see50 Documentation/filesystems/fsverity.rst.51 52 If unsure, say N.53