Are cookie-required handshakes at least REKEY_TIMEOUT long?

Are cookie-required handshakes at least REKEY_TIMEOUT long?

[Reid Rankin]

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Quick question: I've been looking at the code in
 wg_cookie_message_consume() and wg_receive_handshake_packet(), and as far
as I can tell there's no mechanism that re-initiates a handshake after
receiving a cookie reply to a first handshake other than the  REKEY_TIMEOUT
+ jitter timer.

Is this correct, and do, therefore, all handshakes involving cookies take
at least 5 seconds to complete?

Thanks,
Reid Rankin

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Re: Are cookie-required handshakes at least REKEY_TIMEOUT long?

[Jason A. Donenfeld]

Yes, to prevent certain types of DoS. Most packets only move around
the timer state machine, but don't actually result in a direct action.
Rather, a timer firing sometime later is what starts an action. In the
case of cookies, the cookie is used in the subsequent message. See
section 6.6 of https://www.wireguard.com/papers/wireguard.pdf
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