Petter Reinholdtsen

Jami as a Zoom client, a trick for password protected rooms...
8th May 2020

Half a year ago, I wrote about the Jami communication client, capable of peer-to-peer encrypted communication. It handle both messages, audio and video. It uses distributed hash tables instead of central infrastructure to connect its users to each other, which in my book is a plus. I mentioned briefly that it could also work as a SIP client, which came in handy when the higher educational sector in Norway started to promote Zoom as its video conferencing solution. I am reluctant to use the official Zoom client software, due to their copyright license clauses prohibiting users to reverse engineer (for example to check the security) and benchmark it, and thus prefer to connect to Zoom meetings with free software clients.

Jami worked OK as a SIP client to Zoom as long as there was no password set on the room. The Jami daemon leak memory like crazy (approximately 1 GiB a minute) when I am connected to the video conference, so I had to restart the client every 7-10 minutes, which is not a great. I tried to get other SIP Linux clients to work without success, so I decided I would have to live with this wart until someone managed to fix the leak in the dring code base. But another problem showed up once the rooms were password protected. I could not get my dial tone signaling through from Jami to Zoom, and dial tone signaling is used to enter the password when connecting to Zoom. I tried a lot of different permutations with my Jami and Asterisk setup to try to figure out why the signaling did not get through, only to finally discover that the fundamental problem seem to be that Zoom is simply not able to receive dial tone signaling when connecting via SIP. There seem to be nothing wrong with the Jami and Asterisk end, it is simply broken in the Zoom end. I got help from a very skilled VoIP engineer figuring out this last part. And being a very skilled engineer, he was also able to locate a solution for me. Or to be exact, a workaround that solve my initial problem of connecting to password protected Zoom rooms using Jami.

So, how do you do this, I am sure you are wondering by now. The trick is already documented from Zoom, and it is to modify the SIP address to include the room password. What is most surprising about this is that the automatically generated email from Zoom with instructions on how to connect via SIP do not mention this. The SIP address to use normally consist of the room ID (a number), an @ character and the IP address of the Zoom SIP gateway. But Zoom understand a lot more than just the room ID in front of the at sign. The format is "[Meeting ID].[Password].[Layout].[Host Key]", and you can hear see how you can both enter password, control the layout (full screen, active presence and gallery) and specify the host key to start the meeting. The full SIP address entered into Jami to provide the password will then look like this (all using made up numbers):

sip:657837644.522827@192.168.169.170

Now if only jami would reduce its memory usage, I could even recommend this setup to others. :)

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Tags: debian, english, sikkerhet, surveillance.

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