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 implied as it's intended to be the default hash algorithm. 7 # To avoid bloat, other wanted algorithms must be selected explicitly. 8 # Note that CRYPTO_SHA256 denotes the generic C implementation, but 9 # some architectures provided optimized implementations of the same 10 # algorithm that may be used instead. In this case, CRYPTO_SHA256 may 11 # be omitted even if SHA-256 is being used. 12 imply CRYPTO_SHA256 13 help 14 This option enables fs-verity. fs-verity is the dm-verity 15 mechanism implemented at the file level. On supported 16 filesystems (currently EXT4 and F2FS), userspace can use an 17 ioctl to enable verity for a file, which causes the filesystem 18 to build a Merkle tree for the file. The filesystem will then 19 transparently verify any data read from the file against the 20 Merkle tree. The file is also made read-only. 21 22 This serves as an integrity check, but the availability of the 23 Merkle tree root hash also allows efficiently supporting 24 various use cases where normally the whole file would need to 25 be hashed at once, such as: (a) auditing (logging the file's 26 hash), or (b) authenticity verification (comparing the hash 27 against a known good value, e.g. from a digital signature). 28 29 fs-verity is especially useful on large files where not all 30 the contents may actually be needed. Also, fs-verity verifies 31 data each time it is paged back in, which provides better 32 protection against malicious disks vs. an ahead-of-time hash. 33 34 If unsure, say N. 35 36config FS_VERITY_DEBUG 37 bool "FS Verity debugging" 38 depends on FS_VERITY 39 help 40 Enable debugging messages related to fs-verity by default. 41 42 Say N unless you are an fs-verity developer. 43 44config FS_VERITY_BUILTIN_SIGNATURES 45 bool "FS Verity builtin signature support" 46 depends on FS_VERITY 47 select SYSTEM_DATA_VERIFICATION 48 help 49 Support verifying signatures of verity files against the X.509 50 certificates that have been loaded into the ".fs-verity" 51 kernel keyring. 52 53 This is meant as a relatively simple mechanism that can be 54 used to provide an authenticity guarantee for verity files, as 55 an alternative to IMA appraisal. Userspace programs still 56 need to check that the verity bit is set in order to get an 57 authenticity guarantee. 58 59 If unsure, say N. 60