Re: [quicwg/base-drafts] Add initial threat model to security considerations (#2925)

[MikkelFJ <[e-mail]>]

mikkelfj commented on this pull request.



> +Computing the server's first flight for a full handshake is potentially
+expensive, requiring both a signature and a key exchange computation.  In order
+to prevent computational DoS attacks, QUIC incorporates a cheap token exchange
+mechanism which allows servers to validate a client's IP address prior to doing
+any expensive computations at the cost of a single round trip.  After a
+successful handshake, servers can issue new tokens to a client which will allow
+new connection establishment without incurring this cost.
+
+#### On-Path Handshake Termination
+
+An on-path attacker can force the QUIC handshake to fail by replacing either the
+client or server Initial messages with invalid messages.  An off-path attacker
+can also mount this attack by racing the Initials.  Once valid Initial messages
+have been exchanged, the remaining handshake messages are protected with the
+handshake keys and an on-path attacker cannot force handshake failure, though
+they can produce a handshake timeout by dropping packets.

@erickinnear added https://github.com/quicwg/base-drafts/issues/3512

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