From 671e67b47e9fffd12c8f69eda853a202cb5b3fc5 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Mon, 22 Jul 2019 09:26:21 -0700 Subject: fs-verity: add Kconfig and the helper functions for hashing Add the beginnings of the fs/verity/ support layer, including the Kconfig option and various helper functions for hashing. To start, only SHA-256 is supported, but other hash algorithms can easily be added. Reviewed-by: Theodore Ts'o Reviewed-by: Jaegeuk Kim Signed-off-by: Eric Biggers --- fs/verity/Kconfig | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) create mode 100644 fs/verity/Kconfig (limited to 'fs/verity/Kconfig') diff --git a/fs/verity/Kconfig b/fs/verity/Kconfig new file mode 100644 index 000000000000..c2bca0b01ecf --- /dev/null +++ b/fs/verity/Kconfig @@ -0,0 +1,38 @@ +# SPDX-License-Identifier: GPL-2.0 + +config FS_VERITY + bool "FS Verity (read-only file-based authenticity protection)" + select CRYPTO + # SHA-256 is selected as it's intended to be the default hash algorithm. + # To avoid bloat, other wanted algorithms must be selected explicitly. + select 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 and F2FS), 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. -- cgit v1.2.3-70-g09d2