On Fri, Dec 23, 2016 at 3:59 AM, Daniel Borkmann <dan...@iogearbox.net> wrote: > On 12/23/2016 11:59 AM, Hannes Frederic Sowa wrote: >> >> On Fri, 2016-12-23 at 11:04 +0100, Daniel Borkmann wrote: >>> >>> On 12/22/2016 05:59 PM, Hannes Frederic Sowa wrote: >>>> >>>> On Thu, 2016-12-22 at 08:07 -0800, Andy Lutomirski wrote: > > [...] > >>>> The hashing is not a proper sha1 neither, unfortunately. I think that >>>> is why it will have a custom implementation in iproute2? >>> >>> >>> Still trying to catch up on this admittedly bit confusing thread. I >>> did run automated tests over couple of days comparing the data I got >>> from fdinfo with the one from af_alg and found no mismatch on the test >>> cases varying from min to max possible program sizes. In the process >>> of testing, as you might have seen on netdev, I found couple of other >>> bugs in bpf code along the way and fixed them up as well. So my question, >>> do you or Andy or anyone participating in claiming this have any >>> concrete data or test cases that suggests something different? If yes, >>> I'm very curious to hear about it and willing fix it up, of course. >>> When I'm back from pto I'll prep and cook up my test suite to be >>> included into the selftests/bpf/, should have done this initially, >>> sorry about that. I'll also post something to expose the alg, that >>> sounds fine to me. >> >> >> Looking into your code closer, I noticed that you indeed seem to do the >> finalization of sha-1 by hand by aligning and padding the buffer >> accordingly and also patching in the necessary payload length. >> >> Apologies for my side for claiming that this is not correct sha1 >> output, I was only looking at sha_transform and its implementation and >> couldn't see the padding and finalization round with embedding the data >> length in there and hadn't thought of it being done manually. >> >> Anyway, is it difficult to get the sha finalization into some common >> code library? It is not very bpf specific and crypto code reviewers >> won't find it there at all. > > > Yes, sure, I'll rework it that way (early next year when I'm back if > that's fine with you).
Can we make it SHA-256 before 4.10 comes out, though? This really looks like it will be used in situations where collisions matter and it will be exposed to malicious programs, and SHA-1 should not be used for new designs for this purpose because it simply isn't long enough. Also, a SHA-1 digest isn't a pile of u32s, so u32 digest[...] is very misleading. That should be u8 or, at the very least, __be32. I realize that there isn't a sha-256 implementation in lib, but would it really be so bad to make the bpf digest only work (for now) when crypto is enabled? I would *love* to see the crypto core learn how to export simple primitives for direct use without needing the whole crypto core, and this doesn't seem particularly hard to do, but I don't think that's 4.10 material. --Andy
