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a19bcde499
This reverts commit e3a606f2c544b231f6079c8c5fea451e772e1139 because it allows people to create broken configurations that enable FS_VERITY but not SHA-256 support. The commit did allow people to disable the generic SHA-256 implementation when it's not needed. But that at best allowed saving a bit of code. In the real world people are unlikely to intentionally and correctly make such a tweak anyway, as they tend to just be confused by what all the different crypto kconfig options mean. Of course we really need the crypto API to enable the correct implementations automatically, but that's for a later fix. Acked-by: Ard Biesheuvel <ardb@kernel.org> Cc: Herbert Xu <herbert@gondor.apana.org.au> Link: https://lore.kernel.org/r/20250217185105.26751-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
49 lines
2.0 KiB
Plaintext
49 lines
2.0 KiB
Plaintext
# 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 selected 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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select 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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This option adds support for in-kernel verification of
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fs-verity builtin signatures.
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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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If unsure, say N.
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