Re: [quicwg/base-drafts] How to reject a connection attempt (#3690)

Kazuho Oku <notifications@github.com> Sun, 24 May 2020 11:01 UTC

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Date: Sun, 24 May 2020 04:01:41 -0700
From: Kazuho Oku <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] How to reject a connection attempt (#3690)
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I tend to think that adding an error code that affects client behavior is not a good idea, when that error code is intended to indicate a handshake failure. The signal carried by an Initial packet or a Handshake packet is not authenticated, and we should be wary of using that to convey something that affects more than just that connection.

> * INVALID_TOKEN: try again immediately
> * SERVER_BUSY: try again after a few minutes
> * CONNECTION_REFUSED: don't try again for a day / week or so

In case of this example, CONNECTION_REFUSED would become an attractive tool for MITM attackers, because it can be used for preventing the client for reconnecting for as long as a day or a week.

If we need these signal, I think that they have to be carried at the application-level after the QUIC handshake concludes. In case of HTTP, we already have 503 + Retry-After header field.

To summarize, I think my position is:
* We should not add error codes that affect the client behavior after that connection gets closed.
* We might want to get rid of SERVER_BUSY, or at least state that a client cannot really tell if the server was really busy, as the signal is not authenticated.

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