It seemed worth copying this to the WG list; sorry for those getting an
extra copy.

-Ben

On Sun, Jul 21, 2019 at 10:26:56AM -0400, Martin Thomson wrote:
> On Sat, Jul 20, 2019, at 21:57, Benjamin Kaduk wrote:
> > > already supported by TLS libraries? Also, are we in effect deprecating 
> > > this TLS
> > > 1.3 feature because of the security issue of the mismatched record 
> > > boundaries?
> > 
> > I think in some peoples' minds that would be a good thing, though it's not
> > entirely clear that we are actually doing so.
> 
> This wouldn't deprecate post-HS auth.  It is intended to cover the cases 
> where post-HS auth does not work.  See 
> draft-ietf-httpbis-http2-secondary-certs.
> 
> > > "SHOULD use TLS", change to MUST. There's no way it can work otherwise 
> > > anyway.
> > 
> > What about QUIC?
> 
> I think that we can safely regard QUIC (at least those versions that use TLS) 
> as TLS.  An informative mention might help avoid any confusion regarding this 
> point.  We might also regard DTLS-SRTP as one such protocol.
> 
> > > * Is
> > > there a requirement for all protocol messages to be sent over a single TLS
> > > connection? If so, please mention it. Certainly this is true for the
> > > Authenticator message that must be sent over a single connection and 
> > > cannot be
> > > multiplexed by the high-level protocol. I think this protocol actually 
> > > assumes
> > > "nice" transport properties (no message reorder, reliability) that also 
> > > require
> > > a single, clean TLS connection.
> > 
> > It seems like we should be more clear about what we do (and do not)
> > require.  Though IIRC we can do separate authenticators in parallel and not
> > require them to be ordered with respect to each other.
> 
> See above regarding DTLS-SRTP.  Being too crisp might constrain usage 
> inappropriately.
> 
> > > * Why no authenticator request for servers?
> > > Don't we care about replay? OTOH if the client wants to detect replays, it
> > > would need to keep state on received authenticators, which would be very 
> > > messy.
> > 
> > IIUC the thinking is that there's no way to revoke an authenticator for a
> > connection, so replay (if  not detected by another layer anyway) would not
> > cause the authentication state to change.
> 
> Ben is correct.
> 
> > > *  7.1: this is
> > > changing TLS 1.3 by allowing this extension in Cert Request! I think it's 
> > > a
> > > really bad idea. Better to hack special support to existing libraries, 
> > > allowing
> > > this specific extension for this special case, than to change the base
> > > protocol. Otherwise, this document should UPDATE 8446.
> > 
> > Or, since extension codepoints are cheap, just use a newcodepoint.
> 
> We might want to discuss this one this week if we can.
> 

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