[VoiceOps] question about stir/shaken - iat and DATE header

[Mary Lou Carey]

Interesting.....thanks for the explanation. Never know when someone else 
will run into the same thing and the fix being documented will help them 
resolve it!

MARY LOU CAREY
BackUP Telecom Consulting
Office: 615-791-9969
Cell: 615-796-1111

On 2021-07-02 11:55 AM, Matthew Yaklin wrote:
> Just to wrap this up and to thank those who responded…
> 
> IQNT's sonus (ribbon) do not support the DATE header. Ribbon plans to
> fix it soon. It is being stripped out.
> 
> Meta already loaded an efix for us. I think I typed out the issue
> wrong.
> 
> On verification the IAT has the time. The INVITE did not have the
> DATE. Meta's perimeta json schema choked due to that.
> 
> They will now use the SBC's date/time to do a comparison if the DATE
> is not there. Probably check to see if it is within a certain time
> frame. After all the DATE and iat may not match when the INVITE comes
> in when everything is there to process.
> 
> This should solve the problem and allow us to keep moving along with
> this.
> 
> Matt
> 
> From: VoiceOps <voiceops-bounces at voiceops.org> On Behalf Of John S.
> Robinson
> Sent: Thursday, July 1, 2021 3:31 PM
> To: voiceops at voiceops.org
> Subject: Re: [VoiceOps] question about stir/shaken - iat and DATE
> header
> 
> Date header has been part of  RFC-3261 SIP [1] for 19 years now, but
> was not used all that much.    IAT and Date are both part of the specs
> and more recent RFC's that define stir-shaken.   So the seldom-used
> but long time defined Date: header is now required.    Furthermore,
> IAT is part of the formal JSON in the Identity header and must be
> present, or the claims are not valid.
> 
> Normally, IAT would restate the Date with Unix Epoch date.   IAT is
> signed, but the Date header is not signed.
> 
> When a call is received and Verified, the the plain-text signed JSON
> is validated.   If verified IAT is stale, the call is rejected.
> True, someone could mess with Date header along the route or SIP From
> header or PAI.   And for that matter, someone could mess with the JSON
> attributes that are signed.   But then the verification would fail,
> and the call should not be delivered.   That's part of the beauty of
> the system.
> 
> Best regards,
> 
>> John
> 
> On 7/1/2021 12:29, Joseph Jackson wrote:
> 
>> I've heard that TNSi also counts on the date header being present.
>> 
>> So far we don't see a lot of people passing tokens with the date
>> header.
>> 
>> From: VoiceOps [mailto:voiceops-bounces at voiceops.org] On Behalf Of
>> Matthew Yaklin
>> Sent: Thursday, July 01, 2021 12:25 PM
>> To: voiceops at voiceops.org
>> Subject: [VoiceOps] question about stir/shaken - iat and DATE header
>> 
>> 
>> All,
>> 
>> Pretty simple question here. When you do a verify request are you
>> filling in the iat with your sbc's current date/time or using the
>> DATE information from the invite?
>> 
>> With Neustar the iat is currently optional. IQNT is basically
>> removing the DATE header in a test we are doing by sending them a
>> call and getting it back in a different region.
>> 
>> It really does not make sense to me to use the DATE header because
>> it could be messed with by anyone in the path. It is untrusted. The
>> iat is trusted so when you verify it makes more sense to use the
>> current date/time of your SBC because the limitation is 60 seconds
>> from AS to VS.
>> 
>> I imagine Neustar made it optional because their own system has some
>> intelligence when it comes to this expiration of the AS.
>> 
>> On top of that Metaswitch is not prepared for this situation. They
>> are basically counting on that DATE header to be there in their
>> recommended perimeta SBC config. They plan to fix it by using the
>> current date/time.
>> 
>> Just looking for how others are handling this. Just leaving it blank
>> for now?
>> 
>> Matt
>> 
>> _______________________________________________
>> 
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>> 
>> VoiceOps at voiceops.org
>> 
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> 
> 
> 
> Links:
> ------
> [1] https://datatracker.ietf.org/doc/html/rfc3261.html
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