Make 'fsverity digest' and 'fsverity sign' support writing the Merkle
tree and fs-verity descriptor to files, using new options
'--out-merkle-tree=FILE' and '--out-descriptor=FILE'.
Normally these new options aren't useful, but they can be needed in
cases where the fs-verity metadata needs to be consumed by something
other than one of the native Linux kernel implementations of fs-verity.
This is different from 'fsverity dump_metadata' in that
'fsverity dump_metadata' only works on a file with fs-verity enabled,
whereas these new options are for the userspace file digest computation.
Link: https://lore.kernel.org/r/20210603195812.50838-5-ebiggers@kernel.org
Reviewed-by: Victor Hsieh <victorhsieh@google.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Even though the kernel currently only supports PAGE_SIZE == Merkle tree
block size, PAGE_SIZE isn't a good default Merkle tree block size for
fsverity-utils, since it means that if someone doesn't explicitly
specify the block size, then the results of 'fsverity sign' and
'fsverity enable' will differ between different architectures.
So change the default Merkle tree block size to 4096, which is the most
common PAGE_SIZE. This will break anyone using the fsverity program
without the --block-size option on an architecture with a non-4K page
size. But I don't think anyone is actually doing that yet anyway.
Acked-by: Luca Boccassi <luca.boccassi@microsoft.com>
Link: https://lore.kernel.org/r/20201116205628.262173-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Add a 'fsverity digest' subcommand that prints the hex-encoded digest of
the specified file(s), ready to be signed offline. By default the
output is like 'fsverity measure', but if the --for-builtin-sig option
is given, the output is the hex-encoded "struct fsverity_signed_digest"
that the kernel expects to be signed for builtin signatures.
This subcommand is useful in case the integrated signing mechanism with
local cert/key cannot be used.
Signed-off-by: Luca Boccassi <luca.boccassi@microsoft.com>
Link: https://lore.kernel.org/r/20201026191839.3329948-1-luca.boccassi@gmail.com
[EB: commit message, comment, and whitespace tweaks]
Signed-off-by: Eric Biggers <ebiggers@google.com>
Eric Biggers