Re: [abfab] AD review of draft-ietf-abfab-arch-09

[Stephen Farrell <[e-mail]>]

Hi Sam,

On 12/16/2013 04:48 PM, Sam Hartman wrote:
>>>>>> "Stephen" == Stephen Farrell <[e-mail]> writes:
> 
> 
>     Stephen> (1) Am I reading this right? 4.2.2 says: "The EAP MSK is
>     Stephen> transported between the IdP and the RP over the AAA
>     Stephen> infrastructure, for example through RADIUS headers.  This
>     Stephen> is a particularly important privacy consideration, as any
>     Stephen> AAA Proxy that has access to the EAP MSK is able to decrypt
>     Stephen> and eavesdrop on any traffic encrypted using that EAP MSK
>     Stephen> (i.e. all communications between the Client and IdP)." Does
>     Stephen> that mean that if a client authenticates with a password
>     Stephen> say, then that password could be read after the fact by any
>     Stephen> RP or AAA proxy involved in the transaction.  Wouldn't that
>     Stephen> be unacceptable, if e.g.  the equivalent of web-bugs or
>     Stephen> trackers could be inserted into a UI so as to get
>     Stephen> first-shot before a user has authenticated?  And that seems
>     Stephen> to contradict step 7 in 1.4 unless those messages also go
>     Stephen> via the RP, which is not shown in the diagram in 1.4.  What
>     Stephen> am I missing?
> 
> Fortunately, I think you're reading this slightly wrong.
> Learning the MSK is not sufficient to snoop on traffic  between the
> peer/client and IDP.
> Only on traffic between the peer/client AND RP.
> 
> The issue is that if the peer-client use the MSK to encrypt traffic say
> using the GSS per-message services or the GSS PRF, that an attacker who
> learns the MSK can decrypt that traffic.  They should not (and with EAP
> methods that are typically used are believed to be unable to) learn keys
> needed to observe the authentication conversation between peer/client
> and IDP.
> 
> honestly, I consider proxies being able to observe session traffic to be
> quite bad from a perpass standpoint, thus my interest in adding DH
> between client/peer and RP.

So when the text says "(i.e. all communications between the Client
and IdP)" I don't get what that means. Is it just a typo maybe?

S.


> 
>