Re: [PATCH net] bpf: rework prog_digest into prog_tag

On 01/14/2017 12:49 AM, Andy Lutomirski wrote:

On Fri, Jan 13, 2017 at 3:41 PM, Daniel Borkmann [off-list ref] wrote:

quoted

On 01/14/2017 12:16 AM, Andy Lutomirski wrote:

quoted

On Fri, Jan 13, 2017 at 2:38 PM, Daniel Borkmann [off-list ref]
wrote:

quoted

Commit 7bd509e311f4 ("bpf: add prog_digest and expose it via
fdinfo/netlink") was recently discussed, partially due to
admittedly suboptimal name of "prog_digest" in combination
with sha1 hash usage, thus inevitably and rightfully concerns
about its security in terms of collision resistance were
raised with regards to use-cases.

Seems reasonable.  My only question is whether you'd still want to
switch to SHA-256 just from a code cleanliness perspective.  With
SHA-256 you can use the easy streaming API I wrote, but with SHA-1
you're still stuck with the crappy API in lib/, and I'm not
volunteering to fix up the SHA-1 API.

We'd need to truncate that in kernel anyway to not get a too long
tag, so given that I'm actually fine with it as-is. I was planning
to submit the code for testing to bpf selftests for net-next once
it's merged back, too.

Unless you want to kill off that vmalloc()+vfree() pair...

That is really just in slow-path, and should that become a bottleneck
compared to the rest of the verification steps or allocs we do there,
then we can always clean it up in net-next.

Thanks,
Daniel