> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of
> Hannes Tschofenig
>
> SIP Identity works nice in certain environments. The fields that are
> covered by the digital signature calculation in SIP Identity have not
> been chosen arbitrarily. When an SBC changes some of the protected
> fields then there are obviously problems.

Actually, I think some of the fields chosen for signing did NOT need to be 
signed, and added nothing tangible; or if they did, the result of it making it 
unusable in many environments was not worth the specific security issue(s) they 
prevented. (specifically I am talking about the Contact, CSeq, and Call-Id)

There are plenty of valuable SIP Requests which SBCs don't change 
bodies/From/To of that could use 4474 as is today, if it did not sign those 3 
fields.  For example a MESSAGE request (which does not even have a Contact, but 
would fail the Call-Id changing).  Or a SUBSCRIBE.  Or an INFO. :)


> Imagine a mechanism that wouldn't compute a signature at all then SBCs
> could do whatever they want.
> Good for SBCs; not so good for security.

Depends on how you define secure, at what layer, and most importantly for whom, 
but we don't need to get into that on this list. :)

-hadriel
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