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

[Jiri Kuthan]

there are way too many ways how routing logic can be confused to bypass
admission control. poisoning user loc, having a DNS name or ENUM entry
to point to a gateway (scripting fails to see it as PSTN target and
may skip PSTN ACLs), etc. a good thing to do is to use onsend_route
and check if someone is trying to use a gateway whilst a call is not
being recognized as to a gateway.

-jiri

Klaus Darilion wrote:
> 
> Juha Heinanen schrieb:
>> Iñaki Baz Castillo writes:
>>
>>  > - alice sends this BYE:
>>  > 
>>  >   BYE sip:PSTN_NUMBER at PSTN_GATEWAY SIP/2.0
>>  >   Route: <sip:PROXY_IP>
>>  >   Route: <sip:alice at ALICE_PHONE_IP>
>>
>> in this particular case, you could call to_gw() and find out that
>> request is going to gw and, if so, drop the request it is has more than
>> one route header (the one for the proxy itself).
> 
> Not sure if this is enough - the attacker could omit the Route header 
> pointing to the proxy. Maybe the check should use $dd which is set if 
> another Route header is present.
> 
> regard
> klaus
> 
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