[Kamailio-Users] Accounting: How to avoid a fraudulent BYE with lower CSeq?

Raúl Alexis Betancor Santana rabs at dimension-virtual.com
Mon Dec 22 17:47:02 CET 2008

El Lunes, 22 de Diciembre de 2008 14:33, Iñaki Baz Castillo escribió:
> Well, except in the case of BYE sent by the gateway (since the
> attacker could reply non-200 to the BYE and mantain the session open).
> But anyway, I imagine this exotica case:
> - alice (attacker) speaking with the PSTN gateway.
> - alice sends this BYE:
>   Route: <sip:PROXY_IP>
>   Route: <sip:alice at ALICE_PHONE_IP>
> The proxy could check the RURI to know that the destination in the
> gateway, so to account a BYE the gateway must reply 200 OK to the BYE.
> The first route is the proxy, so there is loose routing (as expected
> and required).
> But there is other Route pointing to alice again, so the BYE would be
> sent to alice who will reply 200 OK to this spoofed BYE.
> The proxy would trigger STOP action but the call session remains.

In all the thread I wonder why you allow users to speak with your GW's ... in 
our systems users only may speak with our proxies, and our gateway only speak 
with our proxies.
We know that this config overload the proxies, but powerfull machines are 
cheaper that aspirine truks ;-)

If you route all your traffic throught you proxies (SIP signaling, I mean) and 
you do your accounting based on your GW's information and not based on your 
proxies information, you will be safe.

Best regards
Raúl Alexis Betancor Santana

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