Re: [quicwg/base-drafts] Required state for retaining unacked RETIRE_CONNECTION_ID frames is unbound (#3509)

Kazuho Oku <> Fri, 27 March 2020 00:25 UTC

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Date: Thu, 26 Mar 2020 17:25:25 -0700
From: Kazuho Oku <>
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Subject: Re: [quicwg/base-drafts] Required state for retaining unacked RETIRE_CONNECTION_ID frames is unbound (#3509)
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> in this case isn't the client limited by active_connection_id_limit?

The attack here is that when a malicious client retires a CID to which the server has responded, that server would retire the CID that it has used on that path, and also provide a new CID to the client. But the client never ACKs the RCID frames that the server sends.

As an example, consider the case where a client uses sCID1 on a new path, the server responds on that path using cCID1, the client abandons that path and sends RCID (seq=sCID1). When receiving this RCID frame, the server would send RCID (seq=cCID1), and also send NCID(sCID2). The client intentionally does not ack the packet carrying these frames, but uses sCID2 on a new path, that carries NCID(cCID2), repeating this procedure.

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