Re: [quicwg/base-drafts] Spoofed retry token attack on IP authentication (#2394)

ekr <> Wed, 22 May 2019 13:50 UTC

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Subject: Re: [quicwg/base-drafts] Spoofed retry token attack on IP authentication (#2394)
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Discussion on London: I think this misunderstands the purpose of the retry token.

As a practical matter, we assume that servers under normal conditions respond to Initial with a full first flight. Otherwise, QUIC is a two-round trip protocol no better than TCP. So, there is a builtin 3x amplification attack on random victims.

The purpose of the retry token is when the *server* is under attack from spoofed packets, and wants to efficiently distinguish between true and false IPs so it can blacklist the attackers. A retry token collection attack is possible here too, but the anti-DoS system has to track IPs anyway, and so can just track any IP address which is associated with excessive traffic anyway.

Proposal: Close with no action.

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