How to enable OpenVPN's BF-CBC in Ubuntu 22.04?

hanshenrik

3/9/24, 8:05 AM

I recently upgraded from Ubuntu 20.04 (which ships OpenVPN 2.4.7) to Ubuntu 22.04 (which ships OpenVPN 2.5.5), and in OpenVPN 2.5.0 changelog i find

Removal of BF-CBC support in default configuration:

By default OpenVPN 2.5 will only accept AES-256-GCM and AES-128-GCM as data ciphers. OpenVPN 2.4 allows AES-256-GCM,AES-128-GCM and BF-CBC when no --cipher and --ncp-ciphers options are present. Accepting BF-CBC can be enabled by adding
data-ciphers AES-256-GCM:AES-128-GCM:BF-CBC
and when you need to support very old peers also
data-ciphers-fallback BF-CBC
To offer backwards compatibility with older configs an explicit
cipher BF-CBC
in the configuration will be automatically translated into adding BF-CBC to the data-ciphers option and setting data-ciphers-fallback to BF-CBC (as in the example commands above). We strongly recommend to switching away from BF-CBC to a more secure cipher.

and I can no longer connect to an OpenVPN server at work. Hence the question, how do I enable OpenVPN's BF-CBC in 22.04?

I did some googling, and allegedly in Fedora Linux, you enable it by adding providers legacy default to /etc/openvpn/client.conf , but that file does not exist in Ubuntu, instead there is an (empty) directory path /etc/openvpn/client

1707

1 + 3

openvpn

22.04

muru

3/9/24, 8:13 AM

How are you using OpenVPN? Is it via the Network Manager GUI? Or do you run `systemctl start openvpn-client@<something>`? Or some other way?

hanshenrik

3/9/24, 8:21 AM

@muru i run the cli ```sudo openvpn Hans.ovpn``` and the ovpn file looks like: https://termbin.com/jfdo2

muru

3/9/24, 8:26 AM

Try adding `data-ciphers AES-256-GCM:AES-128-GCM:BF-CBC` to the `Hans.ovpn` file.

Score:1

Ubuntu

Geo Angelopoulos

8/1/24, 8:18 PM

Adding the following line: providers legacy default in my conf.vpn file solves the issue for me.

+ 0

Elon Musk

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EN: How to enable OpenVPN's BF-CBC in Ubuntu 22.04?

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