Re: FW: New Version Notification for draft-bishop-httpbis-http2-additional-certs-05.txt

[Kazuho Oku <[e-mail]>]

Hi, Mike, Nick, Martin,

I have briefly asked this in the IETF meeting, but let me question if
it sounds logical to adjust the approach so that the client will be
required to proactively specify the certificate that is associated to
each HTTP request.

I ask this due to the following reason.

In HTTP/1, it was always clear from the server’s viewpoint which
certificate is associated to a HTTP request. This is because the
underlying connection allowed only one client certificate at maximum
to be used. CGI is designed after that model. A CGI gateway is
expected to designate _at most one_ certificate that has been
associated to the request by using a set of environment variables
(e.g., `SSL_CLIENT_S_DN` [1]). I would assume that it is the same for
other de-facto standards that have evolved from CGI (e.g., FastCGI,
Rack).

The secondary certificates draft changes the model. Under the model
proposed by the draft, the server is expected to choose from one of
the certificates that it has received with AUTOMATIC_USE flag set, or
to request the client to send a new certificate.

However, to me (as a HTTP server developer that acts as a CGI gateway)
it is unclear how a server can make such choice. Applications that are
run using the CGI protocol _might_ have sufficient information to make
such choice, but that is not the case for a CGI gateway.

That means that unless the draft (in the following revisions) specify
the guess logic that I should implement, I would be forced into
sending CERTIFICATE_NEEDED for every HTTP request I receive. Doing so
would introduce one extra roundtrip.

Considering that, I wonder if you could adjust the approach proposed
in the draft to require the client to proactively clarify the
certificate that is associated to each HTTP request.

For example, I believe that the draft could specify that:
* If the client does not specify a certificate that is associated to a
request, a server MAY request the client to specify the certificate.
* The client can specify the certificate that is associated to a
request proactively, instead of sending USE_CERTIFICATE frame in
response to a CERTIFICATE_NEEDED frame.

By changing the approach as such, the only case in which two
roundtrips are required for processing a request could become when the
client is required to send a new certificate. Also, AUTOMATIC_USE flag
becomes unnecessary.

One downside caused by such change is that the bandwidth slightly
increases due to the fact that the client would be required to specify
the certificate that is associated to every HTTP request. However that
is just sending Cert-ID per every HTTP request; I believe that the
increase of bandwidth is negligible.

To summarize, I am suggesting to push the responsibility of choosing
the certificate back to the client. Note that in the current draft the
client is still required to make such choice if the server sends a
CERTIFICATE_NEEDED frame; so I think requiring the client to _always_
make the choice does not increase the complexity on the client side.

[1] https://httpd.apache.org/docs/2.4/mod/mod_ssl.html

2017-10-31 8:14 GMT+08:00 Mike Bishop <[e-mail]>:
> In preparation for Singapore, we've updated the Additional Certs draft to track changes in TLS 1.3 and the Exported Authenticators TLS draft.  There's been substantial interest here, and we'll be discussing the draft during the WG meeting.
>
> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]]
> Sent: Monday, October 30, 2017 2:40 PM
> To: Martin Thomson <[e-mail]>; Mike Bishop <[e-mail]>; Nick Sullivan <[e-mail]>
> Subject: New Version Notification for draft-bishop-httpbis-http2-additional-certs-05.txt
>
>
> A new version of I-D, draft-bishop-httpbis-http2-additional-certs-05.txt
> has been successfully submitted by Mike Bishop and posted to the IETF repository.
>
> Name:           draft-bishop-httpbis-http2-additional-certs
> Revision:       05
> Title:          Secondary Certificate Authentication in HTTP/2
> Document date:  2017-10-30
> Group:          Individual Submission
> Pages:          21
> URL:            https://www.ietf.org/internet-drafts/draft-bishop-httpbis-http2-additional-certs-05.txt
> Status:         https://datatracker.ietf.org/doc/draft-bishop-httpbis-http2-additional-certs/
> Htmlized:       https://tools.ietf.org/html/draft-bishop-httpbis-http2-additional-certs-05
> Htmlized:       https://datatracker.ietf.org/doc/html/draft-bishop-httpbis-http2-additional-certs-05
> Diff:           https://www.ietf.org/rfcdiff?url2=draft-bishop-httpbis-http2-additional-certs-05
>
> Abstract:
>   TLS provides fundamental mutual authentication services for HTTP,
>   supporting up to one server certificate and up to one client
>   certificate associated to the session to prove client and server
>   identities as necessary.  This draft provides mechanisms for
>   providing additional such certificates at the HTTP layer when these
>   constraints are not sufficient.
>
>   Many HTTP servers host content from several origins.  HTTP/2
>   [RFC7540] permits clients to reuse an existing HTTP connection to a
>   server provided that the secondary origin is also in the certificate
>   provided during the TLS [I-D.ietf-tls-tls13] handshake.
>
>   In many cases, servers will wish to maintain separate certificates
>   for different origins but still desire the benefits of a shared HTTP
>   connection.  Similarly, servers may require clients to present
>   authentication, but have different requirements based on the content
>   the client is attempting to access.
>
>   This document describes how TLS exported authenticators
>   [I-D.ietf-tls-exported-authenticator] can be used to provide proof of
>   ownership of additional certificates to the HTTP layer to support
>   both scenarios.
>
>
>
>
> Please note that it may take a couple of minutes from the time of submission until the htmlized version and diff are available at tools.ietf.org.
>
> The IETF Secretariat
>
>



-- 
Kazuho Oku