1671e67b4SEric Biggers# SPDX-License-Identifier: GPL-2.0 2671e67b4SEric Biggers 3671e67b4SEric Biggersconfig FS_VERITY 4671e67b4SEric Biggers bool "FS Verity (read-only file-based authenticity protection)" 5246d9216SMimi Zohar select CRYPTO_HASH_INFO 6*998646b3SEric Biggers select CRYPTO_LIB_SHA256 7*998646b3SEric Biggers select CRYPTO_LIB_SHA512 8671e67b4SEric Biggers help 9671e67b4SEric Biggers This option enables fs-verity. fs-verity is the dm-verity 10671e67b4SEric Biggers mechanism implemented at the file level. On supported 118da572c5SEric Biggers filesystems (currently ext4, f2fs, and btrfs), userspace can 128da572c5SEric Biggers use an ioctl to enable verity for a file, which causes the 138da572c5SEric Biggers filesystem to build a Merkle tree for the file. The filesystem 148da572c5SEric Biggers will then transparently verify any data read from the file 158da572c5SEric Biggers against the Merkle tree. The file is also made read-only. 16671e67b4SEric Biggers 17671e67b4SEric Biggers This serves as an integrity check, but the availability of the 18671e67b4SEric Biggers Merkle tree root hash also allows efficiently supporting 19671e67b4SEric Biggers various use cases where normally the whole file would need to 20671e67b4SEric Biggers be hashed at once, such as: (a) auditing (logging the file's 21671e67b4SEric Biggers hash), or (b) authenticity verification (comparing the hash 22671e67b4SEric Biggers against a known good value, e.g. from a digital signature). 23671e67b4SEric Biggers 24671e67b4SEric Biggers fs-verity is especially useful on large files where not all 25671e67b4SEric Biggers the contents may actually be needed. Also, fs-verity verifies 26671e67b4SEric Biggers data each time it is paged back in, which provides better 27671e67b4SEric Biggers protection against malicious disks vs. an ahead-of-time hash. 28671e67b4SEric Biggers 29671e67b4SEric Biggers If unsure, say N. 30671e67b4SEric Biggers 31432434c9SEric Biggersconfig FS_VERITY_BUILTIN_SIGNATURES 32432434c9SEric Biggers bool "FS Verity builtin signature support" 33432434c9SEric Biggers depends on FS_VERITY 34432434c9SEric Biggers select SYSTEM_DATA_VERIFICATION 35432434c9SEric Biggers help 36672d6ef4SEric Biggers This option adds support for in-kernel verification of 37672d6ef4SEric Biggers fs-verity builtin signatures. 38432434c9SEric Biggers 39672d6ef4SEric Biggers Please take great care before using this feature. It is not 40672d6ef4SEric Biggers the only way to do signatures with fs-verity, and the 41672d6ef4SEric Biggers alternatives (such as userspace signature verification, and 42672d6ef4SEric Biggers IMA appraisal) can be much better. For details about the 43672d6ef4SEric Biggers limitations of this feature, see 44672d6ef4SEric Biggers Documentation/filesystems/fsverity.rst. 45432434c9SEric Biggers 46432434c9SEric Biggers If unsure, say N. 47