Re: [quicwg/base-drafts] Stateless Reset needs "on-path" proof (#1230)

[Kazuho Oku <[e-mail]>]

> OK, thanks for clearing that up. I think that you have an attack, though it might not be that interesting.
> 
> Connection IDs are scoped to a state store, whereas your proposed key is global. That means that an attacker that can learn the key for a given connection ID in any state store can use it to attack all other state stores. For high entropy connection IDs, that takes some doing, but it isn't generically safe, especially now we allow as little as 32 bits.

Thank you for considering the approach and pointing out the issue. I had not considered of the attack vector.

And considering of the attack vector, I realize that there is a less complex approach.

Assuming that the ID of the POP (i.e. the "state-store") is included in the DCID, a server can determine if it should have known the state a connection that the DCID designates, and send a connection reset or a path rejection based on that.

With that said, I am personally fine with _requiring co-extant state_. As expressed in https://github.com/quicwg/base-drafts/issues/1230#issuecomment-379963211, my intent behind the proposal has been under the premise that some might want to reject path creation when packets arrive at a POP that does not have access tho the state store.

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