[openssl-dev] Input on renegotiation behaviour

[Benjamin Kaduk]

On 09/28/2016 03:27 AM, Matt Caswell wrote:
> The current behaviour is not *wrong* either for TLS or DTLS, but the
> discrepancy is quite weird and confusing. Should we:
>
> 1) Change TLS to behave like it used to, and like DTLS still does
>
> 2) Change DTLS to be consistent with the TLS behaviour
>
> 3) Keep it as it is and retain the current inconsistency
>
> And if we change things, should we just change it in the current dev
> branch - or backport it as a bug fix?
>
> Thoughts?
>

I don't think any change should be backported --it's potentially
disruptive, and if the behavior (change) has gone unnoticed for so long,
it hardly seems urgent to normalize between DTLS and TLS.

It seems like the abbreviated handshake would save some computational
resources; on the flip side, it would not have the opportunity for a
fresh DH exchange to stir the key material.  If anything, that would
almost suggest a

(4) change DTLS to default to abbreviated handshakes and change TLS to
default to normal handshakes

since the DTLS server could be sending a HelloRequest because it had to
dump state, but the TLS/TCP connection is persistent and the potential
need for key update greater there.

That said, I do prefer consistency between DTLS and TLS, so would lean
towards option (2), myself, for the resource savings.

-Ben
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