| # SPDX-License-Identifier: GPL-2.0 |
| |
| config FS_VERITY |
| bool "FS Verity (read-only file-based authenticity protection)" |
| select CRYPTO |
| select CRYPTO_HASH_INFO |
| # SHA-256 is implied as it's intended to be the default hash algorithm. |
| # To avoid bloat, other wanted algorithms must be selected explicitly. |
| # Note that CRYPTO_SHA256 denotes the generic C implementation, but |
| # some architectures provided optimized implementations of the same |
| # algorithm that may be used instead. In this case, CRYPTO_SHA256 may |
| # be omitted even if SHA-256 is being used. |
| imply CRYPTO_SHA256 |
| help |
| This option enables fs-verity. fs-verity is the dm-verity |
| mechanism implemented at the file level. On supported |
| filesystems (currently ext4, f2fs, and btrfs), userspace can |
| use an ioctl to enable verity for a file, which causes the |
| filesystem to build a Merkle tree for the file. The filesystem |
| will then transparently verify any data read from the file |
| against the Merkle tree. The file is also made read-only. |
| |
| This serves as an integrity check, but the availability of the |
| Merkle tree root hash also allows efficiently supporting |
| various use cases where normally the whole file would need to |
| be hashed at once, such as: (a) auditing (logging the file's |
| hash), or (b) authenticity verification (comparing the hash |
| against a known good value, e.g. from a digital signature). |
| |
| fs-verity is especially useful on large files where not all |
| the contents may actually be needed. Also, fs-verity verifies |
| data each time it is paged back in, which provides better |
| protection against malicious disks vs. an ahead-of-time hash. |
| |
| If unsure, say N. |
| |
| config FS_VERITY_DEBUG |
| bool "FS Verity debugging" |
| depends on FS_VERITY |
| help |
| Enable debugging messages related to fs-verity by default. |
| |
| Say N unless you are an fs-verity developer. |
| |
| config FS_VERITY_BUILTIN_SIGNATURES |
| bool "FS Verity builtin signature support" |
| depends on FS_VERITY |
| select SYSTEM_DATA_VERIFICATION |
| help |
| Support verifying signatures of verity files against the X.509 |
| certificates that have been loaded into the ".fs-verity" |
| kernel keyring. |
| |
| This is meant as a relatively simple mechanism that can be |
| used to provide an authenticity guarantee for verity files, as |
| an alternative to IMA appraisal. Userspace programs still |
| need to check that the verity bit is set in order to get an |
| authenticity guarantee. |
| |
| If unsure, say N. |
