Subject: Re: [Unbearable] Potential privacy bug if Include-Referer-Token-Binding-ID is improperly implemented client-side

From: =JeffH <[email-masked]>
Date: Thu, 24 Mar 2016 14:35:36 -0700

On 3/22/16, 6:15 PM, "Unbearable on behalf of Nick Harper"
<[email-masked] on behalf of [email-masked]> wrote:

 >On Tue, Mar 22, 2016 at 6:10 PM, =JeffH
 ><[email-masked]> wrote:
 >
 >thx for clarifications, Nick. further questions & thoughts..
 >
 >> Here's the problem: Suppose the connection to server A is over http.
 >> Now a network attacker B injects into some http page (from server C)
 >> code that will cause the client to make an http request to server A.
 >> The attacker B intercepts the request and responds with a redirect to
 >> server B (with the Include-Referer-Token-Binding-ID header).
 >
 >the redirect to B will be an HTTP 30x response not over TLS, regardless
 >of whether the Location: header field contains a https URI, yes?
 >
 >Correct.
 >
 >> The client dutifully follows that request and forwards the
 >> TokenBindingID it has for A to the attacker-controlled B.
 >
 >Should we not explicitly stipulate in -tokbind-https that the client MUST
 >NOT honor any Include-Referer-Token-Binding-ID header received over
 >insecure transport? This is how we addressed similar situations in the
 >HSTS and HPKP specs.
 >
 >The addition of
 >https://github.com/TokenBinding/Internet-Drafts/commit/2033a64397590a55811
 >cb78af8f5aa739cb8c981
 ><https://github.com/TokenBinding/Internet-Drafts/commit/2033a64397590a5581
 >1cb78af8f5aa739cb8c981> implicitly states that (since the Token-Binding
 >header is not sent over an insecure transport).

agreed, it does implicitly state that requirement, thx -- I had not
thorougly reviewed Dirk's updates in -03.

 >I don't have strong feelings for whether this needs to be more
 > explicit.

I would make it explicit.

 >> It would certainly be nice for the transport to be established error
 >> free, and to use HSTS and HPKP, but I don't think those need to be made
 >> as requirements for using Token Binding.
 >
 >I was not proposing stating any requirements wrt employing HSTS and HPKP
 >-- rather, I am thinking that we should have some deployment
 >considerations where HSTS and HPKP are dutifully mentioned and how their
 >use composes with TB to the benefit of the
 > web app provider and their users.

---

From: Dirk Balfanz <[email-masked]>
Date: Tue, 29 Mar 2016 05:06:10 +0000

On Thu, Mar 24, 2016 at 2:35 PM =JeffH <[email-masked]>
wrote:

>  ><
> https://github.com/TokenBinding/Internet-Drafts/commit/2033a64397590a5581

Open an issue on github?

Dirk.

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