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Re: [IPsec] [Cfrg] Beginning discussion on secure password-only authentication for IKEv2

Yaron Sheffer <yaronf@checkpoint.com> Fri, 05 March 2010 06:28 UTC

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From: Yaron Sheffer <yaronf@checkpoint.com>
To: Peter Gutmann <pgut001@cs.auckland.ac.nz>, "uri@ll.mit.edu" <uri@ll.mit.edu>
Date: Fri, 05 Mar 2010 08:27:36 +0200
Thread-Topic: [IPsec] [Cfrg] Beginning discussion on secure password-only authentication for IKEv2
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Subject: Re: [IPsec] [Cfrg] Beginning discussion on secure password-only authentication for IKEv2
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Hi Peter,

I completely agree with the rest of the argument. But I don't know of a realistic way to do it with TLS-PSK (people will *always* use short passwords, it's not like it's the exception to the rule). TLS-SRP is one possible solution. Or, as Yoav suggests, TLS-EAP with several alternatives, including EAP-PWD and EAP-EKE. In some interesting cases, EAP-AKA might also be appropriate.

Unfortunately the IAB thinks that TLS-EAP is Bad Bad Bad (http://tools.ietf.org/html/draft-iab-auth-mech-07#section-10.2.4). So it's back to PKI. Sigh.

Thanks,
	Yaron

> -----Original Message-----
> From: pgut001 [mailto:pgut001@wintermute02.cs.auckland.ac.nz] On Behalf
> Of Peter Gutmann
> Sent: Friday, March 05, 2010 2:07
> To: pgut001@cs.auckland.ac.nz; uri@ll.mit.edu; Yaron Sheffer
> Cc: cfrg@irtf.org; ipsec@ietf.org
> Subject: RE: [IPsec] [Cfrg] Beginning discussion on secure password-
> only authentication for IKEv2
> 
> Yaron Sheffer <yaronf@checkpoint.com> writes:
> 
> >Can someone please explain the joke to me? Nelson was asked about TLS-
> PSK
> >(RFC 4279) and he replied that it can easily be abused. TLS-PSK
> (similarly to
> >IKE- PSK) is vulnerable to dictionary attacks if used with a short
> secret
> >(a.k.a. "password"), at least in the presence of an active attacker.
> So I
> >think his response was entirely appropriate. What am I missing?
> 
> Thinking through the rest of the argument, which is:
> 
> - We currently have a (supposedly) multi-billion dollar global industry
> built
>   around the total failure of the existing browser authentication
> model.
> 
> - Mutual authentication, in which the server has to prove knowledge of
> the
>   user's credentials before the user can connect, would cause a serious
>   headache for phishers.
> 
> - The FF developers have chosen not to implement this because, in the
> special-
>   case situation where it's done really badly, it could theoretically
> be
>   abused (note the special-case qualification of "if used with a short
>   secret", for which the answer is "well don't do that, then").
> 
>   This is balanced against the currently-used model which pretty much
> doesn't
>   work at all right out of the box, no matter what you do with it.
> 
> - Phishers the world over breathe a sigh of relief, and business
> continues as
>   usual.
> 
> Peter.
> 
> Scanned by Check Point Total Security Gateway.

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