Re: Alternate Version + Salt in Alt-Svc
Mikkel Fahnøe Jørgensen <mikkelfj@gmail.com> Mon, 04 November 2019 21:47 UTC
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From: Mikkel Fahnøe Jørgensen <mikkelfj@gmail.com>
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Date: Mon, 04 Nov 2019 22:47:05 +0100
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Subject: Re: Alternate Version + Salt in Alt-Svc
To: Martin Thomson <mt@lowentropy.net>, quic@ietf.org
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Sorry, my response was on the wrong topic. It was in relation to version negotation. Kind Regards, Mikkel Fahnøe Jørgensen On 4 November 2019 at 22.43.42, Martin Thomson (mt@lowentropy.net) wrote: Some random observations reading through the document - Is the order relevant in the receiver version list? - It is tempting to just hash the received version list, but that requires agreeing on an algorithm, unless the algorithm is stated to be specific to that version, which is complicated. - VERSION_NEGOTIATION_ERROR vs drop - I’m not sure it is a good idea to close the connection. The initials are public so it is possible to inject false versions. There are probably many other similar attacks we don’t bother with, but still … - Checking that a transport parameter field is the same as the long header version seems redundant - why have those fields? Is it because the Initial header fields are not sufficiently protected via TLS magic (or similar)? - We generally use varint, but why have varints mixed with 32-bit version lists? I suggest making the list length 32-bit for easier processing. - Downgrade - I’m a bit worried about state management and server redeployments. A server could reject a valid packet because an Initial was routed to a new server. (Reading further, I see this is addressed). This is probably a pragmatic solution, but it has an assumption about eventual global coordination. I suspect something could be done here with tokens or CID routing, but it is not trivial. - Security Considerations - perhaps it is worth noting the transport parameters need additional protection beyond the Initial packet protection? This follows from TLS, but if TLS is not being used, this can version negotiation even if other parts of the protocol version is not sensitive to this in that particular version. - Greasing 0x?a?a?a?a - I’m not really sure about the point of this. Especially if we get salted versions in separate proposal. - It is not immediately obvious if version negotiation can go on and on, or if it settles after at most one roundtrip one way or the other. This might depend on the client QUIC version, but that is a fuzzy term in this context. - Improve discussion of Previously Attempted Version. While the requirements are readable, the purpose of doing this check is less obvious. Presumably this deals with downgrade attacks, but more explanation would be appreciated. Mikkel
- Alternate Version + Salt in Alt-Svc Ryan Hamilton
- Re: Alternate Version + Salt in Alt-Svc Tommy Pauly
- Re: Alternate Version + Salt in Alt-Svc Mikkel Fahnøe Jørgensen
- Re: Alternate Version + Salt in Alt-Svc Martin Thomson
- Re: Alternate Version + Salt in Alt-Svc Mikkel Fahnøe Jørgensen