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CLIENT-TO-CLIENT security

Posted: Tue Jan 14, 2020 11:20 am
by bruto
Fellow admins and users,
I'm willing to "sell" a secure phone solution based on OpenVPN. Clients talk one another by direct communication since Voip signalling and media is routed with a "client-to-client" setup. If I sniff tun0 on SERVER I can only see encrypted traffic (no SIP, no RTP).
So far so good.
Here's my question:
Could users be assured that - even modifying OpenVPN server-side source - traffic would be still impossible to decrypt?
This would be a real zero-trust scenario.
Thank you very much,
Bruto

Re: CLIENT-TO-CLIENT security

Posted: Tue Jan 14, 2020 1:35 pm
by Pippin
Hi,

Using --client-to-client, you would not see packets encrypted by OpenVPN on the tun interface.
You already found that here:
viewtopic.php?f=4&t=26615&p=79654

Take a look here:
https://community.openvpn.net/openvpn/w ... acketsFlow

Re: CLIENT-TO-CLIENT security

Posted: Tue Jan 14, 2020 3:55 pm
by bruto
Thank you sir.
But this time (sorry for the duplicate by the way) the question is more specific!
If I somehow modify server source code would this still be true?

Re: CLIENT-TO-CLIENT security

Posted: Tue Jan 14, 2020 4:01 pm
by TinCanTech
If you modify the source code then it is your own product.

Re: CLIENT-TO-CLIENT security

Posted: Tue Jan 14, 2020 7:24 pm
by bruto
Thank you TCT.
Of course but:
am I locked out if the client is genuine - not modified - OpenVPN software talking to its peer in a --client-to-client fashion?
Cheers,
B.

Re: CLIENT-TO-CLIENT security

Posted: Tue Jan 14, 2020 8:19 pm
by TinCanTech
bruto wrote:
Tue Jan 14, 2020 11:20 am
Could users be assured that - even modifying OpenVPN server-side source - traffic would be still impossible to decrypt?
Even without modifying OpenVPN source code, there are no such guarantees..

Re: CLIENT-TO-CLIENT security

Posted: Tue Jan 14, 2020 11:21 pm
by bruto
Ok thank you
Cheers
B.