RE: Client-Cert Header draft

[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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