Re: Client-Cert Header draft

[Brian Campbell <[e-mail]>]

It's only anecdotal but in my experience HTTPS is overwhelmingly the lingua
franca used between reverse proxies/edge nodes/TLS terminators/whatever and
the origin servers. So HTTP is the scope of the proposal.

On Tue, May 19, 2020 at 8:11 AM Kazuho Oku <[e-mail]> wrote:

> +1 to what Mike said.
>
> As a side note, per my understanding, the PROXY Protocol [1] supported by
> some TLS terminators has the capability of forwarding client certificates.
> I think using that would be generally preferable to using HTTP header
> fields, because that entire protocol (and therefore existing deployment
> requirements of that protocol) is based on the assumption that it would be
> used only between a trusted TLS terminator and backend servers.
>
> [1] https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt
>
> 2020年4月18日(土) 4:23 Mike Bishop <[e-mail]>:
>
>> Despite the distaste for client certificates from some quarters, they are
>> still both used and useful.  I’m certainly interested in seeing this
>> progress.
>>
>>
>>
>> In today’s situation, the intermediary checks that the cert matches the
>> rules it has been given to authenticate clients, and only forwards the
>> requests from valid clients.  Arguably, the origin is offloading less trust
>> in this draft’s model – the intermediary is responsible for validating that
>> the client possesses the claimed certificate, but might leave the origin to
>> decide what scope of access the certificate actually grants.  That allows
>> finer-grained access control, but also allows greater ability to send
>> requests back to the origin.  It also opens the door for intermediaries
>> which don’t support this header to accidentally forward requests containing
>> it.  Requiring intermediaries to drop it doesn’t get you much, since only
>> those intermediaries aware of the spec will comply by dropping the header.
>> To help address these, I’d like to see this mix in something that the
>> intermediary holds and the client doesn’t, such as an exporter from its TLS
>> connection to the server.
>>
>>
>>
>> But all that is refinement – the core concept here is beneficial, and I’d
>> like to see more engagement here.
>>
>>
>>
>> *From:* Brian Campbell <[e-mail]>
>> *Sent:* Wednesday, April 15, 2020 5:01 PM
>> *To:* HTTP Working Group <[e-mail]>
>> *Subject:* Client-Cert Header draft
>>
>>
>>
>> Hello HTTP Working Group,
>>
>>
>>
>> I've somewhat inadvertently found myself working on this draft
>> https://datatracker.ietf.org/doc/draft-bdc-something-something-certificate/,
>> which aspires to define a "Client-Cert" HTTP header field that allows a TLS
>> terminating reverse proxy to convey information about the client
>> certificate of a mutually-authenticated TLS connection to an origin server
>> in a common and predictable manner.
>>
>>
>>
>> I presented the concept
>> <https://datatracker.ietf.org/meeting/107/materials/slides-107-secdispatch-client-cert-http-header-00>
>> at the recent virtual IETF 107 secdispatch meeting
>> <https://datatracker.ietf.org/meeting/107/materials/minutes-107-secdispatch-00>
>> and the outcome from that was basically that there seems to be some
>> interest in pursuing the work and the suggestion that the conversation be
>> taken to the HTTPbis WG (and also keep TLS WG involved - presumably if the
>> work progresses). And that's what brings me here. I also hope to get a
>> little bit of time at one of the upcoming virtual interims to
>> present/discuss the draft.
>>
>>
>>
>> Thanks,
>>
>> Brian
>>
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>
>
> --
> Kazuho Oku
>

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