Subject: RE: [Sipping] Re: E2M security solution

From: "Mary Barnes" <[email-masked]>
Date: Wed, 25 Feb 2004 17:38:14 -0600

Volker,

Yes, there is also a related m2e (and m2m) security problem that must be
solved for the History-Info header and is intended to apply to any
information inserted by intermediaries; right now basic requirements are
identified in:
http://www.ietf.org/internet-drafts/draft-barnes-sipping-sec-inserted-info-0
1.txt
(Note, the draft was not revved for IETF-59 as there's been little
discussion and I've not had a chance to make much progress).

And, yes, this does introduce the need for a mechanism for intermediaries to
add message bodies and to secure that information. I does seem that similar
security mechanisms could be used for both e2m and m2e. But, this is where
we need to dig through some more details. 

Also, with regards to policy, the document currently leaves whether or not
the intermediary is authorized to secure the information as something
implicitly associated with providing the service whereby it is adding the
information, but we need to decide if we want to explicitly define how
Session Policy might be used here, as well. 

Mary.

-----Original Message-----
From: Volker Hilt [mailto:[email-masked]] 
Sent: Wednesday, February 25, 2004 3:01 PM
To: Kumiko Ono
Cc: Gonzalo Camarillo; sipping; [email-masked]
Subject: Re: [Sipping] Re: E2M security solution

Kumiko,
> 
>> I have a question about security of the MIO. Let's consider for 
>> firewall control located with a proxy. The MIO header that you 
>> propose contains parts of SDP information. When UAs encrypt SDP for 
>> end-to-end in order to conceal IP addresses and port numbers, does 
>> the MIO also contain the same information to need to use e2e 
>> encryption?
 >
> the idea is that you place in these headers only the information that 
> the proxy needs. That is, the information that the UAC wants to 
> disclose to the proxy. Right now, if the UAC chooses to disclose some 
> information to a particular proxy, it has to disclose it to every 
> proxy in the path... this may not always be desirable. This is where 
> e2m security comes into the scene.
> 
Yes, I fully agree with Gonzalo. The two drafts should probably be 
aligned so that e2m security can be used in conjunction with session 
policies.

A related question might be "m2e" security: in some scenarios, a proxy 
may not want to disclose policies to other proxies. I would assume that 
the proxy could use the keys of the recipient (UAS/UAC) to encrypt these 
policies. However, it might not have these keys handy. Would it make 
sense to use the e2m infrastructure to also *encrypt* information 
inserted by a proxy?

This of course also raises the question whether a proxy may only insert 
headers, or if it can be enabled to add bodies to a SIP message (e.g. to 
a multipart/mime body). This would probably require the definition of a 
new mechanism for adding bodies.

Thanks,

Volker

-- 
Volker Hilt                      Bell Labs / Lucent Technologies
phone: +1 732 332 6432           101 Crawfords Corner Rd
email: [email-masked]     Holmdel, NJ 07733

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