Re: Client Certificates - re-opening discussion

On Fri, Sep 18, 2015 at 11:31 AM, Mike Bishop <Michael.Bishop@microsoft.com>
wrote:

> We have historically had cases where customers were either legally
> mandated to use client certificate authentication specifically, or more
> generally had an IT requirement to use two-factor authentication to access
> enterprise resources.  I’ll research the details of some of these, and see
> whether I can share some details to frame this conversation in Yokohama.
> Internally, we use it regularly – the certificate lives on a smartcard, the
> TPM, or was simply issued to the machine when it enrolled for device
> management.
>
>
>
> For us, at least, the “pain” is that we can’t support a legal requirement
> without falling back to HTTP/1.1 and generating even more round-trips.  Our
> HTTP/2 investments don’t apply as soon as we’re talking to the auth server.
>

Thanks, this sounds about right.  The usability of browser-based
client-auth was so awful, that unless "mandated" by some law, no real user
or website would use it :-)  If anyone on this thread hasn't tried client
auth, you should, and then imagine turning that on for any real website.

I hope the legal requirement doesn't require that client auth be done in
the HTTP protocol layer, just that the certificate based auth be done.  My
own opinion is that HTTP/1.1/TLS's client auth was a mistake, and my
evidence is the usability of both client-auth and basic-auth authentication
schemes at the protocol layer.  Neither is used in significant amounts.
The latter was definitely moved by millions of websites into the
application layer, and I see no reason why browsers shouldn't offer support
for client-auth like primitives which will help customers move
certificate-based client auth up a level too.

Given the flexibility of HTTP2s framing layer, it will be tricky to avoid
major security bugs in HTTP2 if we try to enable client-auth at the session
below the framing.

Mike





>
>
> *From:* Mike Belshe [mailto:mike@belshe.com]
> *Sent:* Friday, September 18, 2015 11:20 AM
> *To:* Mark Nottingham <mnot@mnot.net>
> *Cc:* Henry Story <henry.story@co-operating.systems>; HTTP Working Group <
> ietf-http-wg@w3.org>
> *Subject:* Re: Client Certificates - re-opening discussion
>
>
>
> In a strange twist of fate I find myself doing a lot of PKI work these
> days, and I've considered a fair bit about how client-certs might help with
> some of my application-level needs.
>
>
>
> However, just like HTTP's basic-auth, I wonder HTTP or TLS level
> client-certs will just never be used?  My concern, of course, is that we
> build something that has a user experience similar to HTTP's basic-auth.
> It's so bad that nobody can use it and authentication gets pulled into web
> pages (where ironically, it is less secure!).
>
>
>
> Mark - you said there is "pain".  Is there a set of use cases to be solved
> here?  Let me know if I missed them - I may be able to contribute.
>
>
>
> My suspicion is that we really need crypto features moved up a level from
> the protocol, as it will be very difficult to make satisfactory user
> interfaces from the protocol level alone.  Perhaps for machine-to-machine
> auth it would be okay.
>
>
>
> Mike
>
>
>
>
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>
>
>
>
> On Fri, Sep 18, 2015 at 10:05 AM, Mark Nottingham <mnot@mnot.net> wrote:
>
> Hi Henry,
>
> Thanks, but this is a much more narrowly-scoped discussion -- how to make
> client certs as they currently operate work in HTTP/2. At most, I think
> we'd be talking about incrementally improving client certs (e.g.,
> clarifying / optimising the scope of their applicability -- and that really
> just is an example, not a statement of intent).
>
> Cheers,
>
>
> > On 18 Sep 2015, at 11:53 am, Henry Story <
> henry.story@co-operating.systems> wrote:
> >
> >
> >> On 17 Sep 2015, at 23:10, Mark Nottingham <mnot@mnot.net> wrote:
> >>
>
> >> Hi,
> >>
> >> We've talked about client certificates in HTTP/2 (and elsewhere) for a
> while, but the discussion has stalled.
> >>
> >> I've heard from numerous places that this is causing Pain. So, I'd like
> to devote a chunk of our time in Yokohama to discussing this.
> >>
> >> If you have a proposal or thoughts that might become a proposal in this
> area, please brush it off and be prepared. Of course, we can discuss
> on-list in the meantime.
> >>
> >> Cheers,
> >>
> >> --
> >> Mark Nottingham   https://www.mnot.net/
> >
> >
>
> > Apart from the proposals as the proposal by Martin Thomson
> > and the follow up work  referenced earlier in this thread
> > by Mike Bishop [1], I'd like to mention more HTTP centric
> > prototypes which would rely perhaps not so much on certificates,
> > but on linked public keys, that build on existing HTTP
> > mechanisms such as WWW-Authenticate, which if they pass security
> > scrutiny would fit nicely it seems to me with HTTP/2.0 .
> >
> > • Andrei Sambra's first sketch authentication protocol
> >   https://github.com/solid/solid-spec#webid-rsa
> >
> > • Manu Sporny's more fully fleshed out HTTP Message signature
> >   https://tools.ietf.org/html/draft-cavage-http-signatures-04
> >
> > These and the more TLS centric protocols require the user
> > agent to be able to use public/private keys generated by
> > the agent, and signed  or published by that origin, to
> > authenticate or sign documents across origins.
> >
> > This is where one often runs into the Same Origin Policy (SOP)
> > stone wall. There was an important discussion on
> > public-webappsec@w3.org [1] and public-web-security@w3.org
> > entitled
> >
> >   "A Somewhat Critical View of SOP (Same Origin Policy)" [2]
> >
> > that I think has helped clarify the distinction between Same Origin
> > Policy, Linkability, Privacy and User Control, and which I hope
> > has helped show that this policy cannot be applied without
> > care nor can it apply everywhere.
> >
> > The arguments developed there should be helpful in opening discussion
> > here and elswhere too I think. In a couple of e-mails  in that
> > thread, I went into great detail showing how SOP, linkability and User
> > Control and privacy apply in very different ways to 4 technologies:
> > Cookies, FIDO, JS Crypto API and client certificates [3]. This shows
> > that the concepts don't overlap, two being technical and the two
> > legal/philosophical, each technology enabling some aspect of the
> > other, and not always the way one would expect.
> >
> > Having made those conceptual distinctions I think the path to
> > acceptance of solutions proposed by this group will be much eased.
> >
> > Looking forward to following and testing work developed here,
> >
> > All the best,
> >
> >       Henry
> >
> >
> > [1] • starting:
> https://lists.w3.org/Archives/Public/ietf-http-wg/2015AprJun/0558.html
> >    • most recent by Mike Bishop
> >
> https://lists.w3.org/Archives/Public/ietf-http-wg/2015JulSep/0310.html
> > [2] https://lists.w3.org/Archives/Public/public-webappsec/2015Sep/
> > [3]
> https://lists.w3.org/Archives/Public/public-webappsec/2015Sep/0101.html
> >  which is in part summarised with respect to FIDO in a much shorter
> >  email
> >
> https://lists.w3.org/Archives/Public/public-webappsec/2015Sep/0119.html
> >
>
> --
> Mark Nottingham   https://www.mnot.net/
>
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