Subject: [Sipping] E2M security solution

From: Gonzalo Camarillo <[email-masked]>
Date: Mon, 23 Feb 2004 15:56:09 +0200

Hello,

The e2m security solution, described in the draft below,
http://www.ietf.org/internet-drafts/draft-ono-sipping-end2middle-security-01.txt

attempts to resolve some of the problems that the session-specific 
policies draft addresses:
http://www.ietf.org/internet-drafts/draft-hilt-sipping-session-spec-policy-00.txt

The need of a UA to obtain the policies that a particular proxy has is 
dealt with in both drafts. In addition, the e2m security draft talks 
about disclosing information to intermediaries. The policy draft 
addresses this issue and defines a means to disclose *only* the 
information needed by the proxy.

My comments on the e2m requirements draft apply also to this one. We 
should try to align both efforts (session policies and e2m security).

Thanks,

Gonzalo

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From: Kumiko Ono <[email-masked]>
Date: Tue, 24 Feb 2004 14:49:51 +0900

Hi,

I agree with you about the e2m security solution could partly solve the 
session-specific policies. 

In my understanding, the policy draft proposes new headers to disclose 
only the information to *all* proxies in the path. Some mechanism are 
needed in order to disclose the information to *specific* proxies. The 
e2m security can be applied as one of the mechanisms.

Regards,

Kumiko

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From: Kumiko Ono <[email-masked]>
Date: Wed, 25 Feb 2004 18:35:38 +0900

Hi Volker,

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?

Thanks,
Kumiko

---

From: Volker Hilt <[email-masked]>
Date: Wed, 25 Feb 2004 16:00:45 -0500

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