Re: [quicwg/base-drafts] introduce a version alias mechanism (#2573)

Marten Seemann <> Mon, 01 April 2019 05:26 UTC

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From: Marten Seemann <>
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Subject: Re: [quicwg/base-drafts] introduce a version alias mechanism (#2573)
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> In addition to what @mikkelfj points out, a middlebox can inject a VN and force the client to retransmit the Initial packet in the version the middlebox prefers. Note that such an attack would not be noticed, because we are removing downgrade prevention from the VN design.

That's correct, *until* we define a QUIC version that has downgrade protection (assuming that this version contains the version alias mechanism proposed here). It seems to be the desire of many people I've spoken to quickly define a QUIC v2 that's identical to QUIC v1, with version negotiation being the only addition to the protocol. In that case, this attack would become infeasible as soon as v2 is deployed, because middleboxes have no way of distinguishing between a v1 and a v2 alias version.

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