Re: [quicwg/base-drafts] Version validation fields can't move or change (#498)

[Mike Bishop <[e-mail]>]

It took me a couple times through the issue and the PR to figure out the actual attack here, and I don't think the current text actually captures it.  What finally clicked for me was that, although the version number is explicitly given in the packet, an on-path attacker who tried to force a version negotiation mismatch could also undetectably modify the contents of the version field in the packet header.  (Because the integrity protection / encryption on the packets at this point is trivially recalculated by an attacker.)  It's the contents of the handshake that can't be modified without detection, but we have to guard against getting just the right set of transport parameters in the future that looks like the version confirmation one would expect from the current version.

So what we're actually saying is that, if the version validation fields are in a different location in a different version of QUIC, they MUST be unmistakably different from a valid confirmation of having selected the current version or any future version that uses this handshake and transport settings format.

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/quicwg/base-drafts/pull/498#issuecomment-319196942