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T0maas
Asked: 2022-02-24 05:10:30 +0800 CST

How to disallow second OpenVPN client with the same key?

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I've setup my openvpn server, but I have this problem:

Clients connects in this order:

  1. client_A connects succesfully to server using it's own key.
  2. client_B connects to server using client_A's key and gets same ip as client_A.

When I try to ping client_A packets goes to client_B instead of client_A.

I don't have duplicate-cn in my server config.

How can I prevent this behavior? I want to kick client_B immediately and keep only client_A.

openvpn vpn-client

1 Answers

  1. I guess you can't.

    What is wrong in your scenario is client_B connects to server using client_A's key that should never happen.

    it's like if you'd says "what wrong ? I just published my login/password, and someone else used it ... !,"

    clients keys is like their email login/password. they don't publish it, they dont communicate it, they don't exchange it, or it may be a professional misconduct.

    you can just revoke the keys, and provide some news one with a private password, or make them sign a conduct agreement to not share their keys.

    if you can't, use 2fa instead.

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