RE: draft-tiesel-quic-unreliable-streams-01 - comments

[Roni Even <[e-mail]>]

> -----Original Message-----
> From: Philipp S. Tiesel [mailto:[e-mail]]
> Sent: יום ה 02 נובמבר 2017 22:50
> To: Roni Even
> Cc: QUIC WG
> Subject: Re: draft-tiesel-quic-unreliable-streams-01 - comments
> 
> Hi
> 
> > On 1. Nov 2017, at 14:03, Roni Even <[e-mail]> wrote:
> >
> > Hi,
> >
> > I think support for unreliable streams is important for unidirectional and bi-
> directional streams and even if it is V2 we still need to take support for it into
> account. One use case is RTP over QUIC.
> >
> > Small comments:
> >
> > In section 4.2 “ The loss of such a frame does not introduce state at the
> perceived receiver”. If new streams are opened with higher stream ID,  it
> implicitly opens this one frame stream that was lost in the receiver. I think it
> still requires the sender to send a reliable FIN to close this stream.
> 
> You’re right. I overlooked this. – The draft says:
>   Streams MUST be created in sequential order. Open streams can be used in
>   any order. Streams that are used out of order result in lower-numbered
>   streams in the same direction being counted as open.
> 
> I don’t know the rational behind this, but I think this is, besides the
> complications for unreliable streams, unfortunate:
>  - with unidirectional streams, this looks a little ambiguous.
>  - it prevents the application in encode its own flags within the stream ID.
> 
> Can anyone tell me the reason for this MUST?
> 
> I Put it on the ToDo-List for -02
> 
> > In the security section “ An active, on path attacker can drop selected
> frames “ . What does it mean selected frames, the whole payload is
> encrypted.
> 
> This is a little complicated:
>  - Assume having “stream-as-a-message” streams with two different kins of
> messages sized A,B
>  - Assume each message fits into one packet, but two messages will not fit
>  - Assume one doesn't want to split packets to fill packets to MTU due to
> latency constrains  => If an attacker know the inside protocol, the attacker
> can distinguish from the packet length wether it is an A or B kind message
> 
> To avoid this, one has to pad all packets… I should clarify this.
[Roni Even] I understand this case but what does selected frames mean, I assume that the attacker does not know what is in each stream in order to select a specific one, so why will he just drop one and not the other or why not both?
> 
> AVE!
>   Philipp S. Tiesel / phils…
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