On Mon, 2018-10-08 at 13:19 -0700, Matthew Garrett wrote: > On Mon, Oct 8, 2018 at 4:25 AM Mimi Zohar <zohar@xxxxxxxxxxxxx> wrote: > > On Fri, 2018-10-05 at 12:25 -0700, Matthew Garrett wrote: > > > I agree that using FUSE in general is incompatible with IMA's goals, > > > but it's possible to configure systems where you can ensure that only > > > trustworthy code is involved. In that scenario this patch improves > > > performance without compromising security. > > > > If you trust a FUSE filesystem to not only behave properly, but also > > to return file hashes, what is the value of measuring/appraising the > > files? Define a custom policy that doesn't measure/appraise files on > > FUSE filesystems. > > We trust that the filesystem will return us accurate binaries and > hashes, but we don't the binaries themselves may not be trustworthy - > we want the same level of audit trail associated with their execution > that we'd have for something run off local disk. We could certainly > rearchitect our filesystems to generate audit events themselves, but > we'd be duplicating functionality that already exists in the kernel. I'm really not comfortable with the FUSE filesystem calculating the file hash being used by IMA. Adding FUSE i_version support would have been better, instead of returning the actual file hash. Based on a mount option and the i_version, the kernel could then decide whether or not to limit re-calculating the file hash. Mimi
