Re: Stream0 Design Team Proposal

[Jana Iyengar <[e-mail]>]

Thank you for your implementation and your report -- this is terrific and
helpful!

On your note about CRYPTO_HS frames, I think your idea is clever. Just to
ensure that I am understanding it correctly, I believe you're proposing
defining:
0x10 - 0x17: STREAM frame
0x18 - 0x1F: CRYPTO_HS frame

We can the same frame format for CRYPTO_HS as STREAM except that CRYPTO_HS
will not have the stream ID field. This means an implementation handling
these frames can reuse the stream machinery with a small change to parse
the header bits as follows:

if (type & 0x10)  {  // STREAM or CRYPTO_HS frame
    if (type & 0x08) streamID = varint_consume(frame);
    if (type & 0x04) offset = varint_consume(frame);
    if (type & 0x02) length = varint_consume(frame);
    if (type & 0x01) fin = 1;
    read body if present
}

On Tue, May 22, 2018 at 9:57 PM, Kazuho Oku <[e-mail]> wrote:

> FWIW, I am happy to tell you that I have a working PoC code for the
> proposed approach.
>
> On the QUIC side, I saw 2% (124 lines) increase in code size (more on
> that below). On the TLS side, I also saw 2% (175 lines) increase.
> However please look at the code size change especially on the QUIC
> side with grain of salt, as it is just a PoC.
>
> As expected, the key and encryption-level management on the QUIC side
> became very clean. Following are some of the design decisions I made
> as well as the outcomes:
>
> * All the interaction between picotls and quicly are accompanied by
> "epoch". Handshake messages are attributed with their epochs so that
> they do not get protected by the wrong key, or so that octets received
> under an incorrect encryption context cannot be misused.
>
> * All the traffic keys are governed by quicly (managing some traffic
> keys in TLS while managing PNE key in QUIC seems messy).
>
> * The Initial key is setup by quicly, wheeras other traffic keys are
> installed by picotls by calling a callback named
> update_traffic_key_cb. The callback accepts and installs 6 keys in
> total: for three levels (i.e. 0-RTT, handshake, 1-RTT) in two
> directions (send-side and receive-side).
>
> * Three PN spaces have their own AEAD encryption key. Initial PN and
> Handshake PN spaces have one aead decryption key each. Application PN
> space has up to two decryption keys: either for 0-RTT and 1-RTT or for
> two 1-RTT keys during key update.
>
> It was a pain to have a dedicated frame encoding for CRYPTO_HS, even
> though we can reuse (and I reused) the retransmission and reassembly
> logic of QUIC streams for the handshake flows. About a half of the
> code size increase comes from that (the other half comes from the
> added abstraction for having two contexts for the handshake). I would
> prefer reusing the STREAM frame encoding for the handshake data. We
> could possibly use a different base offset (i.e. for CRYPTO_HS frames
> we could use 0b00011XXX, whereas the STREAM frames use 0b00010XXX), as
> well as omitting the Stream ID field.
>
> Overall, now that I have a PoC, I am more confident that the proposed
> approach is the correct path forward. It *simplifies* the QUIC stack
> at the same time giving us better security properties as well as
> fixing various issues in the current design (as discussed in the
> design doc).
>
>
> 2018-05-23 10:30 GMT+09:00 Ian Swett <ianswett=[e-mail]
> >:
> > Dear QUIC WG,
> >
> >
> > On behalf of the Stream 0 Design Team, I am pleased to report that we
> have
> > consensus on a proposed approach to share with the WG. The DT's proposal
> > will make QUIC and TLS work closer together and incorporates ideas from
> > DTLS, but it does not use the DTLS protocol itself.
> >
> >
> > The DT believes this solves the important open Stream 0 issues. The
> proposal
> > will be a bit more invasive in TLS, but we believe it is the right
> long-term
> > direction and several TLS stacks (BoringSSL, PicoTLS, NSS, and Mint) are
> > willing and able to do the work necessary.. A number of stacks are
> currently
> > working on implementations of this new approach, which we hope to have in
> > time for the Interim meeting.
> >
> >
> > A design document describing the overall approach can be found at:
> >
> > https://docs.google.com/document/d/1fRsJqPinJl8N3b-
> bflDRV6auojfJLkxddT93j6SwHY8/edit
> >
> >
> > A PR making the changes to the QUIC documents can be found at:
> >
> > https://github.com/quicwg/base-drafts/pull/1377
> >
> >
> > A few design details did not have clear consensus, but it was felt it
> would
> > be better to discuss those in the wider WG than delay the design team.  A
> > consistent choice was made in the PR and these issues are mentioned in
> > Appendix B of the design doc.
> >
> >
> > As always, comments and questions welcome. That said, this is a big PR
> and
> > we recognize that some editorial work is going to be needed before
> merging.
> > In the interest of letting people follow along, and to keep github from
> > falling over, we ask people to keep discussion on the mailing list and
> > refrain from making PR comments.
> >
> >
> > See you in Kista!
> >
> >
> > Ian and Eric
>
>
>
> --
> Kazuho Oku
>
>