On Mon, Nov 16, 2020 at 05:50:45PM +0000, Luca Boccassi wrote: > On Mon, 2020-11-16 at 09:41 -0800, Eric Biggers wrote: > > On Mon, Nov 16, 2020 at 11:52:57AM +0000, Luca Boccassi wrote: > > > On Fri, 2020-11-13 at 16:15 -0800, Eric Biggers wrote: > > > > From: Eric Biggers <ebiggers@xxxxxxxxxx> > > > > > > > > Add convenience functions that wrap FS_IOC_ENABLE_VERITY but take a > > > > 'struct libfsverity_merkle_tree_params' instead of > > > > 'struct fsverity_enable_arg'. This is useful because it allows > > > > libfsverity users to deal with one common struct. > > > > > > > > Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> > > > > --- > > > > include/libfsverity.h | 36 ++++++++++++++++++++++++++++++++++ > > > > lib/enable.c | 45 +++++++++++++++++++++++++++++++++++++++++++ > > > > programs/cmd_enable.c | 28 +++++++++++++++------------ > > > > 3 files changed, 97 insertions(+), 12 deletions(-) > > > > create mode 100644 lib/enable.c > > > > > > > > diff --git a/include/libfsverity.h b/include/libfsverity.h > > > > index 8f78a13..a8aecaf 100644 > > > > --- a/include/libfsverity.h > > > > +++ b/include/libfsverity.h > > > > @@ -112,6 +112,42 @@ 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 > > > > + * @fd: read-only file descriptor to the file > > > > + * @params: pointer to the Merkle tree parameters > > > > + * > > > > + * This is a simple wrapper around the FS_IOC_ENABLE_VERITY ioctl. > > > > + * > > > > + * Return: 0 on success, -EINVAL for invalid arguments, or a negative errno > > > > + * value from the FS_IOC_ENABLE_VERITY ioctl. See > > > > + * Documentation/filesystems/fsverity.rst in the kernel source tree for > > > > + * the possible error codes from FS_IOC_ENABLE_VERITY. > > > > + */ > > > > +int > > > > +libfsverity_enable(int fd, const struct libfsverity_merkle_tree_params *params); > > > > + > > > > +/** > > > > + * libfsverity_enable_with_sig() - Enable fs-verity on a file, with a signature > > > > + * @fd: read-only file descriptor to the file > > > > + * @params: pointer to the Merkle tree parameters > > > > + * @sig: pointer to the file's signature > > > > + * @sig_size: size of the file's signature in bytes > > > > + * > > > > + * Like libfsverity_enable(), but allows specifying a built-in signature (i.e. a > > > > + * singature created with libfsverity_sign_digest()) to associate with the file. > > > > + * This is only needed if the in-kernel signature verification support is being > > > > + * used; it is not needed if signatures are being verified in userspace. > > > > + * > > > > + * If @sig is NULL and @sig_size is 0, this is the same as libfsverity_enable(). > > > > + * > > > > + * Return: See libfsverity_enable(). > > > > + */ > > > > +int > > > > +libfsverity_enable_with_sig(int fd, > > > > + const struct libfsverity_merkle_tree_params *params, > > > > + const uint8_t *sig, size_t sig_size); > > > > + > > > > > > I don't have a strong preference either way, but any specific reason > > > for a separate function rather than treating sig == NULL and sig_size > > > == 0 as a signature-less enable? For clients deploying files, it would > > > appear easier to me to just use empty parameters to choose between > > > signed/not signed, without having to also change which API to call. But > > > maybe there's some use case I'm missing where it's better to be > > > explicit. > > > > libfsverity_enable_with_sig() works since that; it allows sig == NULL and > > sig_size == 0. > > > > The reason I don't want the regular libfsverity_enable() to take the signature > > parameters is that I'd like to encourage people to do userspace signature > > verification instead. I want to avoid implying that the in-kernel signature > > verification is something that everyone should use. Same reason I didn't want > > 'fsverity digest' to output fsverity_formatted_digest by default. > > Ok, I understand - makes sense to me, thanks. > > Maybe it's worth documenting in the the header description of the API > that empty/null values are accepted and will result in enabling without > signature check? > It's already there: * If @sig is NULL and @sig_size is 0, this is the same as libfsverity_enable().
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