Re: [TLS] [OPSEC] Call For Adoption: draft-wang-opsec-tls-proxy-bp

Töma Gavrichenkov <ximaera@gmail.com> Thu, 30 July 2020 13:14 UTC

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From: =?UTF-8?Q?T=C3=B6ma_Gavrichenkov?= <ximaera@gmail.com>
Date: Thu, 30 Jul 2020 16:13:09 +0300
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To: "Salz, Rich" <rsalz@akamai.com>
Cc: Watson Ladd <watsonbladd@gmail.com>, "Eric Wang (ejwang)" <ejwang@cisco.com>, Jen Linkova <furry13@gmail.com>, OPSEC <opsec@ietf.org>, OpSec Chairs <opsec-chairs@ietf.org>, "tls@ietf.org" <tls@ietf.org>
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Subject: Re: [TLS] [OPSEC] Call For Adoption: draft-wang-opsec-tls-proxy-bp
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Peace,

On Thu, Jul 30, 2020 at 3:33 PM Salz, Rich <rsalz@akamai.com> wrote:
>> It is (in all but a couple of implementations I think)
> a *proxy* that the origin has contracted with.  Could
> you please elaborate on your point?
>
> It has a TLS cert that identifies itself as the origin.

It depends!

In the majority of cases (i.e. delivering preseeded static content),
no. It identifies as some-1337-garbage.static.example.com, which it
basically *is*.
The manner in which the content (hopefully uploaded by the origin via
an end-to-end encrypted connection) propagates to edge nodes is then
up to the implementation, and it is contained within the area of
responsibility of the CDN operator.

However, there's a minority of cases where a CDN is also used to
deliver *dynamically generated* content which could not be cached,
e.g. because it is only available to authenticated users.  In this
case, the CDN in fact impersonates the origin, processes all the
authentication data, and the only way to implement that is proxying
across different areas of responsibility.  How's that different from
what middleboxes are doing is not clear to me.

Proxy is a proxy.  There are various kind of proxies probably also
doing something which is deemed useful to their owners and users,
which doesn't relax the statement that such proxying is not endorsed
by the IETF.  The intent and purpose behind proxying are IMO in scope
of model-t and are, accordingly, out of scope here.

> How is it different from an origin that uses load-balancing to send you somewhere?  Is www.facebook.com a CDN or intermediary, or is it the origin?

Is www.facebook.com a Facebook-owned middlebox, or is it the endpoint
server?  (And this is *one* of the reasons I won't trust Facebook for
anything sensitive!)

Again, I think this is more of a topic for model-t.

The main difference though is that the data crosses the boundary
between the areas of responsibility in a way which is not transparent
to me.  It is a common approach to allow insecure connections over the
Internet from the edge nodes to the origin, and I have no way of
knowing if this is the case for the resource I'm currently using.
There are also more subtle differences but I think I've long crossed
the boundary of the off-topic area here myself!

--
Töma