netdev - Re: [PATCH net] bpf: rework prog_digest into prog

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Date:   Sat, 14 Jan 2017 00:41:09 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Andy Lutomirski <luto@...capital.net>
CC:     "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH net] bpf: rework prog_digest into prog_tag

On 01/14/2017 12:16 AM, Andy Lutomirski wrote:
> On Fri, Jan 13, 2017 at 2:38 PM, Daniel Borkmann <daniel@...earbox.net> wrote:
>> 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.

Thanks,
Daniel