On Fri, Nov 13, 2020 at 02:35:27PM +0000, luca.boccassi@xxxxxxxxx wrote: > From: Luca Boccassi <luca.boccassi@xxxxxxxxxxxxx> > > Factor out the 'fsverity enable' implementation in the library, to > give users a shortcut for reading signatures and enabling a file > with the default parameters. > > Signed-off-by: Luca Boccassi <luca.boccassi@xxxxxxxxxxxxx> > --- > Marked as RFC to get guidance on how to deal with helper functions > duplication, that right now are part of the "programs" utility objects > and not usable from the "library" objects. > There's dozens of different ways to handle this, all equally valid, so > it's down to the preference of the maintainer (eg: new common helpers, > include helpers at build time, further splits of sources, etc). > Please provide a preference and I'll follow up. > > common/common_defs.h | 9 ++ > include/libfsverity.h | 21 +++++ > lib/enable.c | 191 ++++++++++++++++++++++++++++++++++++++++++ > programs/cmd_enable.c | 66 ++------------- > programs/fsverity.h | 9 -- > 5 files changed, 227 insertions(+), 69 deletions(-) > create mode 100644 lib/enable.c > > diff --git a/common/common_defs.h b/common/common_defs.h > index 279385a..871db2c 100644 > --- a/common/common_defs.h > +++ b/common/common_defs.h > @@ -90,4 +90,13 @@ static inline int ilog2(unsigned long n) > # define le64_to_cpu(v) (__builtin_bswap64((__force u64)(v))) > #endif > > +/* The hash algorithm that 'fsverity' assumes when none is specified */ > +#define FS_VERITY_HASH_ALG_DEFAULT FS_VERITY_HASH_ALG_SHA256 > + > +/* > + * Largest digest size among all hash algorithms supported by fs-verity. > + * This can be increased if needed. > + */ > +#define FS_VERITY_MAX_DIGEST_SIZE 64 > + > #endif /* COMMON_COMMON_DEFS_H */ > diff --git a/include/libfsverity.h b/include/libfsverity.h > index 8f78a13..8d1f93b 100644 > --- a/include/libfsverity.h > +++ b/include/libfsverity.h > @@ -112,6 +112,27 @@ libfsverity_sign_digest(const struct libfsverity_digest *digest, > const struct libfsverity_signature_params *sig_params, > uint8_t **sig_ret, size_t *sig_size_ret); > > +/** > + * libfsverity_enable() - Enable fs-verity on a file > + * An fsverity_digest (also called a "file measurement") is the root of > + * a file's Merkle tree. Not to be confused with a traditional file > + * digest computed over the entire file. > + * @file: path to the file to enable > + * @signature: (optional) path to signature for @file > + * @params: struct libfsverity_merkle_tree_params specifying the fs-verity > + * version, the hash algorithm, the block size, and > + * optionally a salt. Reserved fields must be zero. > + * All fields bar the version are optional, and defaults will be used > + * if set to zero. > + * > + * Returns: > + * * 0 for success, -EINVAL for invalid input arguments, or a generic error > + * if the FS_IOC_ENABLE_VERITY ioctl fails. > + */ > +int > +libfsverity_enable(const char *file, const char *signature, > + struct libfsverity_merkle_tree_params *params); > + > /** > * libfsverity_find_hash_alg_by_name() - Find hash algorithm by name > * @name: Pointer to name of hash algorithm Hi Luca, can you consider https://lkml.kernel.org/linux-fscrypt/20201114001529.185751-1-ebiggers@xxxxxxxxxx/T/#u instead? It's somewhat useful to have a wrapper around FS_IOC_ENABLE_VERITY that takes 'struct libfsverity_merkle_tree_params', so that library users can deal with one common struct. (And I took advantage of that to simplify the code that parses the parameters.) But I think we should keep it as a thin wrapper, and not have file path parameters or set defaults in the libfsverity_merkle_tree_params. The library user is better suited to deal with those, like they already do for libfsverity_compute_digest(). - Eric
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