12/30/2023 0 Comments Freeswitch tls versions![]() ![]() Which in turn effectively makes using TLS SIP in production (where you need to support your customer’s issues with SIP traces) unrealistic. This is a major problem, and effectively makes the HEP feature useless when using TLS. I wasn’t the first person to experience this.įreeswitch has a bug (FS-9657) from October 2016 that means that incoming SIP packets are not delivered to SNGREP via HEP. You are seeing some packets in SNGREP, but they are only the responses that Freeswitch is sending to remoteĪll incoming packets are missing. If you’ve tried up until this point you will have found that A security limitation in Freeswitchīut there is a problem with this. But by only listening on the local loop back interface it should avoid you getting any packets captured twice. This is a bit of a kludge, as really I would prefer to disable its raw packet capture entirely, which is not currently possible. The -d lo part is to instruct sngrep to switch its raw packet capture to the local loopback interface. To start SNGREP and tell it to listen for decrypted packets from from Freeswitch, start it as so: sngrep -L udp:127.0.0.1:9060 -d lo Note: You will need to run this each time you want to start a capture, and when you’re done run: fs_cli -x 'sofia global capture off' Then restart Freeswitch and run: fs_cli -x 'sofia global capture on' In /etc/freeswitch/autoload_configs/ add a local SIP cature destination as follows: HEP and FreeswitchĮnabling HEP in Freeswitch is very simple. This way, the voice server and handset can use any form of encryption they both support, and the decrypted packets can be sent to a local capture agent. To a dedicated capture process after the packets have been decrypted. The basic idea behind HEP is to provide a way for the voice server itself to send the raw SIP packets This is where a protocol called HEP (Homer Encapsulation Protocol) comes to the rescue.Īs the name suggests, it originally came out of the Homer SIP capture project.īut since then has been integrated into many SIP tools, including Freeswitch and SNGREP. You’re using so that it can be intercepted seems to defeat the purpose. However I’ve never managed to get that to work, and besides, limiting the strength of the encryption Tools like SNGREP support this feature using the -keyfile flag. One approach to solve this problem is to restrict the type of encrypted connection that FreeswitchĬan establish (specifically forward secrecy) and then give the private key that your server is using to This renders SIP diagnosis using raw packet captures useless! HEP protocol to the rescue! However encrypted TLS connections are designed to stop exactly this sort of interception, and so these tools are not able to understand the raw packets they capture. These tools work by hooking themselves into the raw network packets that are flowing between your Freeswitch server and the remote user’s handset. Normally when you are diagnosing a SIP issue, one would use a SIP capture tool like SNGREP or Homer. However one aspect that has caused frustration is diagnosing SIP problems when using SIP over an encrypted connection (TLS). I have been using encrypted calls with Freeswitch for a number of years. One industry that hasn’t been so quick to adopt these new secure mentalities are wholesale VoIP providers.īut this is changing and providers like Simwood, Voxbone, DIDLogic and Twilio now offer encrypted voice calls using SIP over TLS with SRTP media. Encrypt all the things! This has been a popular sentiment in the open source community for the last few years.Īnd with the rise of Lets Encrypt this has never been easier and cheaper to do. ![]()
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