[RFC PATCH v14 15/19] fsverity: consume builtin signature via LSM hook

[Paul Moore]

On Tue, Mar 12, 2024 at 3:08 PM Fan Wu <wufan at linux.microsoft.com> wrote:
> We could also make security_inode_setsecurity() more generic instead of
> for xattr only, any suggestions?

For the sake of simplicity, since security_inode_setsecurity() doesn't
work, it probably makes more sense to create a new LSM hook rather
than make significant changes to security_inode_setsecurity().

I'm looking at the fsverity hook usage in this patch as well as the
device-mapper hook usage in 13/19 with security_bdev_setsecurity() and
I'm wondering if we could adopt a similar hook as we do with block
devices:

/* NOTE: these are just example values, more granularity would likely
be needed */
enum {
  LSM_INTGR_DIGEST,
  LSM_INTGR_SIG,
} lsm_intgr_type;

/**
 * security_inode_integrity() - Set the inode's integrity data
 * @inode: the inode
 * @integrity_type: type of integrity, e.g. hash digest, signature, etc.
 * @value: the integrity value
 * @value: size of the integrity value
 *
 * Register a verified integrity measurement of an inode with the LSM.
 *
 * Return: Returns 0 on success, negative values on failure.
 */
int security_inode_integrity(struct inode *inode,
                             enum lsm_intgr_type type,
                             const void *value, size_t size)

... if the above makes sense, I'd probably adjust
security_bdev_setsecurity() both to have a similar name, e.g.
/inode/bdev/, as well as to take a lsm_intgr_type enum instead of the
character string ... unless we really need a character string for some
reason, in which case use a character string in both places.

--
paul-moore.com