OpenVPN

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OpenVPN (Open Virtual Private Network) is software that enables the creation of secure point-to-point or site-to-site connections.

Installation

Kernel

KERNEL Enable CONFIG_TUN in the kernel
Device Drivers  --->
    [*] Network device support  --->
        [*] Network core driver support
        <*>   Universal TUN/TAP device driver support

USE flags

Cannot load package information. Is the atom net-vpn/openvpn correct?

Emerge

Install the OpenVPN package:

root #emerge -v net-vpn/openvpn

Configuration

Server side

If this is the first time setting up an openvpn server, we will need to create a PKI (Public Key Infrastructure) from scratch.

Note
In this example place all generated keys into /etc/openvpn/example/
Note
The example will just setup a single server. For multiple OpenVPN instances see the 'Gentoo specifics' section.

Write a server-side openvpn configuration.

FILE /etc/openvpn/openvpn.confSetup a example UDP OpenVPN server
# server binding port
port 12112

# openvpn protocol, could be tcp / udp / tcp6 / udp6
proto udp

# tun/tap device
dev tun0

# keys configuration, use generated keys
ca example/ca.crt
cert example/example.crt
key example/example.key
dh example/dh2048.pem

# optional tls-auth key to secure identifying
# tls-auth example/ta.key 0

# OpenVPN 'virtual' network infomation, network and mask
server 10.100.0.0 255.255.255.0

# persistent device and key settings
persist-key
persist-tun
ifconfig-pool-persist ipp.txt

# pushing route tables
push "route 192.168.1.0 255.255.255.0"
# push "dhcp-option DNS 192.168.1.1"

# connection
keepalive 10 120
comp-lzo

user nobody
group nobody

# logging
status openvpn-status.log
log /etc/openvpn/openvpn.log
verb 4

Start openvpn server, run

root #/etc/init.d/openvpn start

Client side

Copy the necessary key files to client, via a secure way (such as SSH), including

  • ca.crt
  • client1.csr (in this example)
  • client1.crt (in this example)
  • client1.key (in this example)
  • ta.key (if using tls-auth)

Write a client-side openvpn configuration file:

FILE /etc/openvpn/openvpn.confclient-side udp openvpn configuration
# specify client-side
client

# tun/tap device
dev tun0

# protocol, according to server
proto udp

# server address
remote address.to.server 12112

# connection
comp-lzo
resolv-retry 30
nobind

# persistent device and keys
persist-key
persist-tun

# keys settings
ca example/ca.crt
cert example/client1.crt
key example/client1.key

# optional tls-auth
# tls-auth exmaple/ta.key 1

# pull dns settings from the server
script-security 2

# These scripts are defaults within the service script. To specify custom scripts,
# use /etc/openvpn/${SVCNAME}-{up,down}.sh as suggested by the service script.
# If you use systemd, SVCNAME will not get set automatically.
# Add `setenv SVCNAME my_svc_name` to set it, where my_svc_name is determined by
# /etc/openvpn/client/my_svc_name.conf
# up /etc/openvpn/up.sh
# down /etc/openvpn/down.sh

# logging
log /etc/openvpn/openvpn.log
verb 4

To automatically provide username and password, or just username with the password still prompted, add the following option, where auth is the file name containing 1 line with a username, or 2 lines with a username and password.

FILE /etc/openvpn/openvpn.confclient-side openvpn configuration for automating username/password
auth-user-pass /etc/openvpn/auth

To start client, run

OpenRC

root #/etc/init.d/openvpn start

systemd

root #systemctl start openvpn

If all goes well, this would give you a working OpenVPN server and client connection.

Gentoo specifics

The init script allows multiple tunnels. Decide on a name for the tunnel - eg EXAMPLE

Using OpenRC

root #ln -s /etc/init.d/openvpn /etc/init.d/openvpn.EXAMPLE

Now create your config as /etc/openvpn/EXAMPLE.conf

root #/etc/init.d/openvpn.EXAMPLE start

Using systemd

Due to dependencies server and client operations are separated into two units.

Create your server config as /etc/openvpn/server/EXAMPLE.conf

root #systemctl start openvpn-server@EXAMPLE

Create your client config as /etc/openvpn/client/EXAMPLE.conf

root #systemctl start openvpn-client@EXAMPLE

You can then create more tunnels by replacing EXAMPLE with more names. Each one has its own configuration and can be stopped and started individually. The default is simply to use openvpn.conf and not symlink the service. You can of course use both methods.

Troubleshooting

See also

External resources