Re: [Ace] Token (In)Security

Hannes Tschofenig <Hannes.Tschofenig@arm.com> Fri, 14 December 2018 16:18 UTC

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From: Hannes Tschofenig <Hannes.Tschofenig@arm.com>
To: Stefanie Gerdes <gerdes@tzi.de>, Ludwig Seitz <ludwig.seitz@ri.se>, Jim Schaad <ietf@augustcellars.com>, "ace@ietf.org" <ace@ietf.org>
Thread-Topic: [Ace] Token (In)Security
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Date: Fri, 14 Dec 2018 16:18:16 +0000
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Subject: Re: [Ace] Token (In)Security
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Hi Steffi,

I anticipate that the use of tokens with IoT devices works similar to OAuth deployments today. As such, if you distribute self-contained tokens then you sign or mac them.
We have registered the necessary claims already, which includes the expiry. As such, I expect it to be used as well.

If we forgot to mention explicitly that we follow the best current practices in OAuth then we should add that reference. I will check the text...

Ciao
Hannes

-----Original Message-----
From: Ace <ace-bounces@ietf.org> On Behalf Of Stefanie Gerdes
Sent: Freitag, 14. Dezember 2018 16:15
To: Ludwig Seitz <ludwig.seitz@ri.se>; Jim Schaad <ietf@augustcellars.com>; ace@ietf.org
Subject: [Ace] Token (In)Security

Hi all,

as I understand the current proposal of the ACE framework, an attacker can send an access token to the RS that only contains a scope and is not signed or otherwise protected. Section 5.8.1.1 (titled verifying an access token) does not state that RS must check the authenticity of the token, therefore RS can accept it. Since the token does not contain an exp field, it is infinitely valid. The attacker thus gains infinite unconditional access. Is this really what we want from a security framework?

I would expect section 5.8.1.1 to provide information if and when RS must check that the token stems from an authorized AS to prevent this scenario.

Viele Grüße
Steffi

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