On Sunday, April 26, 2015 06:41:58 PM Paul Wouters wrote:
> On Sun, 26 Apr 2015, Viktor Dukhovni wrote:
> > On Sun, Apr 26, 2015 at 04:59:12PM -0400, Paul Wouters wrote:
> >>> Great, it looks like the proposed standard for hardening SMTP/TLS
> >>> could be repurposed for either http(s) or arbitrary ports as per my
> >>> proposal no?
> >> 
> >> There is nothing left to harden. The presence of TLSA means, never go
> >> to the insecure port.
> > 
> > Yes, when the client is not already committed to using TLS, i.e. it is
> > opportunistic.
> 
> Unfortunately, the use of the standalone word "opportunistic" is
> confusing as it means different things.
> 
> >> I tried to get this meaing into the original TLSA spec, and there was
> >> resistence to it. It was sidetracked into the HASTLS record, which never
> >> saw the light. I'm not sure if the DANE OPS (SRV) draft clarifies this,
> >> but any sane client implementation of TLSA should really assume this.
> > 
> > We don't currently have a generic "opportunistic DANE TLS" document,
> > the SMTP draft directly specifies this behaviour for SMTP.  The
> > SRV draft mostly does the same, withouth explicitly calling this
> > out as being opportunistic.
> > 
> > I expect the OPS draft LC to start any day now.  If it should
> > generalize this observation, this is a good time to suggest suitable
> > language.
> 
> I'm behind on my dane and dnsop document reading :(
> 
> > When I started work on what is now the SMTP draft, it originally
> > was a generic opportunistic DANE TLS document.  It later split into
> > SMTP and OPS, with the former not covering non-SMTP use-cases, and
> > the latter not covering opportunistic security.
> 
> The opportune part is "hey, they are publishing a key to use for
> crypto". Once you're at that stage, doing TLS is not optional, but
> mandatory (IMHO, because people did not want to commit to this
> in the original DANE RFC)

Given https://tools.ietf.org/html/rfc7435 I don't see where there's ambiguity 
about what opportunistic is.

Scott K

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