"TLS" <[email protected]> wrote on 19/11/2015 06:52:29 AM:
> From: [email protected] (Martin Rex) > To: Yoav Nir <[email protected]> > Cc: "[email protected]" <[email protected]> > Date: 19/11/2015 06:53 AM > Subject: Re: [TLS] Record header size? > Sent by: "TLS" <[email protected]> > > Yoav Nir wrote: > >> Peter Gutmann <[email protected]> wrote: > >> > >> Eric Rescorla <[email protected]> writes: > >>> > >>> The concern here is backward compatibility with inspection > middleboxes which > >>> expect the length field to be in a particular place. > >> > >> Given that the rest of TLS 1.3 is going to break compatibility with pretty > >> much everything everywhere, I can't see this as a big concern, may > >> as well fix it at the same time as everything else is being changed. > > > > A sanity check on TLS might involve validating 5-byte record headers > > with sane length and version fields. A firewall might be out there that > > verifies this. > > The issue is much more about breaking _applications_ on top of TLS > by changing the existing 5-byte record header. Padding the header > to 8 bytes (3 bytes into the original record body) would be OK, though. > > With several TLS implementations it is possible to completely seperate > network communication (of the application) from the processing of > TLS records (performed by the TLS protocol stack). For some TLS > implementations (e.g. Microsoft SChannel) this seems to be the only > possible mode of operation. We have the same kind of IO separation and I have observed a few times that some products either interleave/multiplex TLS records with other application data flow or route/buffer TLS traffic based on TLS record header checking. Padding the header to 8 bytes, as above, would probably be OK. -Mick
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