[SR-Users] TLS and SIP

[Fabian Borot]

Hi

I am using Kamailio 4.0.1 in front of an asterisk servers farm to handle TLS with our clients and providers. The idea is to have kamailio "talking" SIP/UDP/5060 and TLS/TCP/5061 with the customers and providers and regular SIP/UDP/5060 with our internal asterisk servers. 

So far at least for the customers it looks like it can work. But I have a problem, when the call is established and the called person hangs up, the BYE from the called person to the calling person is ignored. Only when the calling person hangs up first the call is terminated properly.

This is what I have been able to see:

1- Customer starts the TLS handshake/connection.
2- Kamailio authenticate it, then routes the call to the asterisk server using regular SIP/UDP/5060 but I see that it is inserting 2 Record Routes in the INVITE:

Record-Route: <sip:192.168.1.58;r2=on;lr=on>

Record-Route: <sip:192.168.1.58:5061;transport=tls;r2=on;lr=on>

3- The Contact on that INVITE to the asterisk also comes like this:

Contact: <sip:94167032 at 172.31.196.21:53325;transport=tls>

4- The ACK sent to the asterisk once it accepts the call (200 OK) also has those 2 Record-Routes:

Record-Route: <sip:192.168.1.58;r2=on;lr=on>

Record-Route: <sip:192.168.1.58:5061;transport=tls;r2=on;lr=on>

5- The call is established, once the called person decides to hang up the BYE looks like this:

BYE sip:94167032 at 172.31.196.21:53325;transport=tls SIP/2.0
Via: SIP/2.0/UDP 192.168.1.59:5060;branch=z9hG4bK40fa1c23;rport
Route: <sip:192.168.1.58;r2=on;lr=on>,<sip:192.168.1.58:5061;transport=tls;r2=on;lr=on>
Max-Forwards: 70
From: <sip:3030500 at 1.2.3.4>;tag=as37953869
To: "kamailio" <sip:kamailio at 1.2.3.4>;tag=788cd7c892df40f3b1967112395e2ca4
Call-ID: f9fe65daf1074219be26cb0c224339f1
CSeq: 102 BYE
User-Agent: Asterisk PBX 11.3.0
X-Asterisk-HangupCause: Normal Clearing
X-Asterisk-HangupCauseCode: 16
Content-Length: 0

My kamailio TLS config is shown below:

enable_tls=yes

loadmodule "tls.so"

# ----- tls params -----
modparam("tls", "config", "/usr/local/kamailio-4.1//etc/kamailio/tls.cfg")
modparam("tls", "private_key", "./privkey.pem")
modparam("tls", "certificate", "./kamailio1_cert.pem")
modparam("tls", "ca_list", "./calist.pem")
modparam("tls", "verify_certificate", 1)
modparam("tls", "require_certificate", 1)

The TLS client that I am using is called Blink.At this point I don't know whether kamailio is sending the BYE using TLS to the customer and waiting for the 200 OK from the customer or whether kamailio does not like something in the BYE and that is why is ignoring it.

I see some encrypted packets from kamailio to the client but I don't know what is inside. 
Any help would be very appreciated.
thank you

fabian