2023-08-30 17:31:07 +02:00
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# SPDX-License-Identifier: GPL-2.0
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config FS_VERITY
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bool "FS Verity (read-only file-based authenticity protection)"
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select CRYPTO
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select CRYPTO_HASH_INFO
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# SHA-256 is implied as it's intended to be the default hash algorithm.
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# To avoid bloat, other wanted algorithms must be selected explicitly.
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# Note that CRYPTO_SHA256 denotes the generic C implementation, but
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# some architectures provided optimized implementations of the same
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# algorithm that may be used instead. In this case, CRYPTO_SHA256 may
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# be omitted even if SHA-256 is being used.
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imply CRYPTO_SHA256
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help
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This option enables fs-verity. fs-verity is the dm-verity
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mechanism implemented at the file level. On supported
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filesystems (currently ext4, f2fs, and btrfs), userspace can
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use an ioctl to enable verity for a file, which causes the
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filesystem to build a Merkle tree for the file. The filesystem
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will then transparently verify any data read from the file
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against the Merkle tree. The file is also made read-only.
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This serves as an integrity check, but the availability of the
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Merkle tree root hash also allows efficiently supporting
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various use cases where normally the whole file would need to
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be hashed at once, such as: (a) auditing (logging the file's
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hash), or (b) authenticity verification (comparing the hash
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against a known good value, e.g. from a digital signature).
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fs-verity is especially useful on large files where not all
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the contents may actually be needed. Also, fs-verity verifies
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data each time it is paged back in, which provides better
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protection against malicious disks vs. an ahead-of-time hash.
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If unsure, say N.
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config FS_VERITY_BUILTIN_SIGNATURES
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bool "FS Verity builtin signature support"
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depends on FS_VERITY
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select SYSTEM_DATA_VERIFICATION
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help
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2023-10-24 12:59:35 +02:00
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This option adds support for in-kernel verification of
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fs-verity builtin signatures.
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2023-08-30 17:31:07 +02:00
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2023-10-24 12:59:35 +02:00
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Please take great care before using this feature. It is not
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the only way to do signatures with fs-verity, and the
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alternatives (such as userspace signature verification, and
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IMA appraisal) can be much better. For details about the
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limitations of this feature, see
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Documentation/filesystems/fsverity.rst.
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2023-08-30 17:31:07 +02:00
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If unsure, say N.
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