1# SPDX-License-Identifier: GPL-2.0 2 3config FS_VERITY 4 bool "FS Verity (read-only file-based authenticity protection)" 5 select CRYPTO 6 # SHA-256 is selected as it's intended to be the default hash algorithm. 7 # To avoid bloat, other wanted algorithms must be selected explicitly. 8 select CRYPTO_SHA256 9 help 10 This option enables fs-verity. fs-verity is the dm-verity 11 mechanism implemented at the file level. On supported 12 filesystems (currently EXT4 and F2FS), userspace can use an 13 ioctl to enable verity for a file, which causes the filesystem 14 to build a Merkle tree for the file. The filesystem will then 15 transparently verify any data read from the file against the 16 Merkle tree. The file is also made read-only. 17 18 This serves as an integrity check, but the availability of the 19 Merkle tree root hash also allows efficiently supporting 20 various use cases where normally the whole file would need to 21 be hashed at once, such as: (a) auditing (logging the file's 22 hash), or (b) authenticity verification (comparing the hash 23 against a known good value, e.g. from a digital signature). 24 25 fs-verity is especially useful on large files where not all 26 the contents may actually be needed. Also, fs-verity verifies 27 data each time it is paged back in, which provides better 28 protection against malicious disks vs. an ahead-of-time hash. 29 30 If unsure, say N. 31 32config FS_VERITY_DEBUG 33 bool "FS Verity debugging" 34 depends on FS_VERITY 35 help 36 Enable debugging messages related to fs-verity by default. 37 38 Say N unless you are an fs-verity developer. 39 40config FS_VERITY_BUILTIN_SIGNATURES 41 bool "FS Verity builtin signature support" 42 depends on FS_VERITY 43 select SYSTEM_DATA_VERIFICATION 44 help 45 Support verifying signatures of verity files against the X.509 46 certificates that have been loaded into the ".fs-verity" 47 kernel keyring. 48 49 This is meant as a relatively simple mechanism that can be 50 used to provide an authenticity guarantee for verity files, as 51 an alternative to IMA appraisal. Userspace programs still 52 need to check that the verity bit is set in order to get an 53 authenticity guarantee. 54 55 If unsure, say N. 56