Re: [Unbearable] Fwd: I-D Action: draft-ietf-tokbind-ttrp-01.txt

Vladimir Dzhuvinov <vladimir@connect2id.com> Fri, 04 August 2017 19:02 UTC

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From: Vladimir Dzhuvinov <vladimir@connect2id.com>
Organization: Connect2id Ltd.
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Date: Fri, 4 Aug 2017 22:02:15 +0300
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Subject: Re: [Unbearable] Fwd: I-D Action: draft-ietf-tokbind-ttrp-01.txt
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On 04/08/17 00:14, Brian Campbell wrote:
> I agree that standardizing the header names significantly increases the
> likelihood that implementations will properly scrub them.
>
> I'm told that this mod_token_binding module for Apache
> <https://github.com/zmartzone/mod_token_binding>, for example, was recently
> updated to do the header sanitation automatically in the course of
> processing rather than relying on configuration directives of other modules
> to overwrite the headers. So it can't be misconfigured, at least not with
> respect to this issue. Standardizing the header names allows and suggests
> for the sanitation to be an implementation thing rather than a
> configuration thing, which is a good thing.
If the proxy implementers get on board with this, as you mention, it
will be great. It helps that the implementations are relatively few.

I wonder, has there been anywhere work on standardizing a header pattern
that can only exist between a reverse proxy and a backend server?


> As John said, there were a number of suggestions in Prague and on-list
> around how to prevent/detect header injection in more of a fail closed way.
> Vladimir's specific idea didn't come up but there were conceptually similar
> ideas.
>
> I maintain that it would be very inappropriate for this draft to define a
> one-off mechanism for a backend server to detect client injection of the
> headers. The potential problem of client header injection is not at all
> unique to the functionality of the draft so the draft shouldn't define a
> unique solution.
+1
>  If there's the will and/or appetite to develop a common
> standardized mechanism detecting/preventing client header injection through
> reverse proxies, I'd be happy to help contribute to that effort.
>
>
> On Thu, Aug 3, 2017 at 9:31 AM, Bill Cox <waywardgeek@google.com> wrote:
>
>>
>> On Thu, Aug 3, 2017 at 6:32 AM, Vladimir Dzhuvinov <
>> vladimir@connect2id.com> wrote:
>>
>>> The downside of having set header names is that attacks on badly
>>> configured TLS proxies become much easier to carry out. This is my concern
>>> about the TTRP spec in this form.
>>>
>>> Thanks,
>>>
>>> Vladimir
>>>
>> I think most coders adding the standard header will the RFC, and will be
>> more likely to remember to scrub the header.
>>
>> One question about the spec: Why must the "sec-token-binding" header be
>> removed?  I did that originally in an implementation, and was asked to stop
>> "molesting the headers".
>>
>> Bill
>>
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