linux-kernel - Re: [RFC PATCH 4.10 0/6] Switch BPF's digest to SHA256

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Message-ID: <20161226082058.GA9013@gondor.apana.org.au>
Date:   Mon, 26 Dec 2016 16:20:58 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     daniel@...earbox.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        Jason@...c4.com, hannes@...essinduktion.org,
        alexei.starovoitov@...il.com, edumazet@...gle.com,
        ebiggers3@...il.com, tom@...bertland.com, davem@...emloft.net,
        luto@...nel.org
Subject: Re: [RFC PATCH 4.10 0/6] Switch BPF's digest to SHA256

Andy Lutomirski <luto@...nel.org> wrote:
> Since there are plenty of uses for the new-in-4.10 BPF digest feature
> that would be problematic if malicious users could produce collisions,
> the BPF digest should be collision-resistant.  SHA-1 is no longer
> considered collision-resistant, so switch it to SHA-256.
> 
> The actual switchover is trivial.  Most of this series consists of
> cleanups to the SHA256 code to make it usable as a standalone library
> (since BPF should not depend on crypto).
> 
> The cleaned up library is much more user-friendly than the SHA-1 code,
> so this also significantly tidies up the BPF digest code.
> 
> This is intended for 4.10.  If this series misses 4.10 and nothing
> takes its place, then we'll have an unpleasant ABI stability
> situation.

Can you please explain why BPF needs to be able to use SHA directly
rather than through the crypto API?

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt