1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
|
# 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_BUILTIN_SIGNATURES
bool "FS Verity builtin signature support"
depends on FS_VERITY
select SYSTEM_DATA_VERIFICATION
help
This option adds support for in-kernel verification of
fs-verity builtin signatures.
Please take great care before using this feature. It is not
the only way to do signatures with fs-verity, and the
alternatives (such as userspace signature verification, and
IMA appraisal) can be much better. For details about the
limitations of this feature, see
Documentation/filesystems/fsverity.rst.
If unsure, say N.
|
