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.

 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	select CRYPTO_HASH_INFO
 7	# SHA-256 is implied as it's intended to be the default hash algorithm.
 8	# To avoid bloat, other wanted algorithms must be selected explicitly.
 9	# Note that CRYPTO_SHA256 denotes the generic C implementation, but
10	# some architectures provided optimized implementations of the same
11	# algorithm that may be used instead. In this case, CRYPTO_SHA256 may
12	# be omitted even if SHA-256 is being used.
13	imply CRYPTO_SHA256
14	help
15	  This option enables fs-verity.  fs-verity is the dm-verity
16	  mechanism implemented at the file level.  On supported
17	  filesystems (currently ext4, f2fs, and btrfs), userspace can
18	  use an ioctl to enable verity for a file, which causes the
19	  filesystem to build a Merkle tree for the file.  The filesystem
20	  will then transparently verify any data read from the file
21	  against the Merkle tree.  The file is also made read-only.
22
23	  This serves as an integrity check, but the availability of the
24	  Merkle tree root hash also allows efficiently supporting
25	  various use cases where normally the whole file would need to
26	  be hashed at once, such as: (a) auditing (logging the file's
27	  hash), or (b) authenticity verification (comparing the hash
28	  against a known good value, e.g. from a digital signature).
29
30	  fs-verity is especially useful on large files where not all
31	  the contents may actually be needed.  Also, fs-verity verifies
32	  data each time it is paged back in, which provides better
33	  protection against malicious disks vs. an ahead-of-time hash.
34
35	  If unsure, say N.
36
 
 
 
 
 
 
 
 
37config FS_VERITY_BUILTIN_SIGNATURES
38	bool "FS Verity builtin signature support"
39	depends on FS_VERITY
40	select SYSTEM_DATA_VERIFICATION
41	help
42	  This option adds support for in-kernel verification of
43	  fs-verity builtin signatures.
 
44
45	  Please take great care before using this feature.  It is not
46	  the only way to do signatures with fs-verity, and the
47	  alternatives (such as userspace signature verification, and
48	  IMA appraisal) can be much better.  For details about the
49	  limitations of this feature, see
50	  Documentation/filesystems/fsverity.rst.
51
52	  If unsure, say N.