1# SPDX-License-Identifier: GPL-2.0 2 3config FS_VERITY 4 bool "FS Verity (read-only file-based authenticity protection)" 5 select CRYPTO_HASH_INFO 6 select CRYPTO_LIB_SHA256 7 select CRYPTO_LIB_SHA512 8 help 9 This option enables fs-verity. fs-verity is the dm-verity 10 mechanism implemented at the file level. On supported 11 filesystems (currently ext4, f2fs, and btrfs), userspace can 12 use an ioctl to enable verity for a file, which causes the 13 filesystem to build a Merkle tree for the file. The filesystem 14 will then transparently verify any data read from the file 15 against the Merkle tree. The file is also made read-only. 16 17 This serves as an integrity check, but the availability of the 18 Merkle tree root hash also allows efficiently supporting 19 various use cases where normally the whole file would need to 20 be hashed at once, such as: (a) auditing (logging the file's 21 hash), or (b) authenticity verification (comparing the hash 22 against a known good value, e.g. from a digital signature). 23 24 fs-verity is especially useful on large files where not all 25 the contents may actually be needed. Also, fs-verity verifies 26 data each time it is paged back in, which provides better 27 protection against malicious disks vs. an ahead-of-time hash. 28 29 If unsure, say N. 30 31config FS_VERITY_BUILTIN_SIGNATURES 32 bool "FS Verity builtin signature support" 33 depends on FS_VERITY 34 select SYSTEM_DATA_VERIFICATION 35 help 36 This option adds support for in-kernel verification of 37 fs-verity builtin signatures. 38 39 Please take great care before using this feature. It is not 40 the only way to do signatures with fs-verity, and the 41 alternatives (such as userspace signature verification, and 42 IMA appraisal) can be much better. For details about the 43 limitations of this feature, see 44 Documentation/filesystems/fsverity.rst. 45 46 If unsure, say N. 47