IPsec VPN Server on Docker

Docker image to run an IPsec VPN server, with both IPsec/L2TP and Cisco IPsec.

Based on Debian 9 (Stretch) with Libreswan (IPsec VPN software) and xl2tpd (L2TP daemon).

Read this in other languages: English, 简体中文.

Install Docker

First, install and run Docker on your Linux server.

Download

Get the trusted build from the Docker Hub registry:

docker pull hwdsl2/ipsec-vpn-server

Alternatively, you may build from source code on GitHub.

How to use this image

Environment variables

This Docker image uses the following three variables, that can be declared in an env file (example):

VPN_IPSEC_PSK=your_ipsec_pre_shared_key
VPN_USER=your_vpn_username
VPN_PASSWORD=your_vpn_password

This will create a user account for VPN login, which can be used by your multiple devices* . The IPsec PSK (pre-shared key) is specified by the VPN_IPSEC_PSK environment variable. The VPN username is defined in VPN_USER, and VPN password is specified by VPN_PASSWORD.

Note: In your env file, DO NOT put "" or '' around values, or add space around =. DO NOT use these special characters within values: \ " '.

All the variables to this image are optional, which means you don't have to type in any environment variable, and you can have an IPsec VPN server out of the box! Read the sections below for details.

Start the IPsec VPN server

Important: First, load the IPsec NETKEY kernel module on the Docker host:

sudo modprobe af_key

Create a new Docker container from this image (replace ./vpn.env with your own env file):

docker run \
    --name ipsec-vpn-server \
    --env-file ./vpn.env \
    --restart=always \
    -p 500:500/udp \
    -p 4500:4500/udp \
    -v /lib/modules:/lib/modules:ro \
    -d --privileged \
    hwdsl2/ipsec-vpn-server

Retrieve VPN login details

If you did not specify an env file in the docker run command above, VPN_USER will default to vpnuser and both VPN_IPSEC_PSK and VPN_PASSWORD will be randomly generated. To retrieve them, view the container logs:

docker logs ipsec-vpn-server

Search for these lines in the output:

Connect to your new VPN with these details:

Server IP: your_vpn_server_ip
IPsec PSK: your_ipsec_pre_shared_key
Username: your_vpn_username
Password: your_vpn_password

(Optional) Backup the generated VPN login details (if any) to the current directory:

docker cp ipsec-vpn-server:/opt/src/vpn-gen.env ./

Check server status

To check the status of your IPsec VPN server, you can pass ipsec status to your container like this:

docker exec -it ipsec-vpn-server ipsec status

Or display current established VPN connections:

docker exec -it ipsec-vpn-server ipsec whack --trafficstatus

Next steps

Get your computer or device to use the VPN. Please refer to:

Configure IPsec/L2TP VPN Clients

Configure IPsec/XAuth ("Cisco IPsec") VPN Clients

If you get an error when trying to connect, see Troubleshooting.

Enjoy your very own VPN!

Important notes

Read this in other languages: English, 简体中文.

For Windows users, this one-time registry change is required if the VPN server and/or client is behind NAT (e.g. home router).

The same VPN account can be used by your multiple devices. However, due to an IPsec/L2TP limitation, if you wish to connect multiple devices simultaneously from behind the same NAT (e.g. home router), you must use only IPsec/XAuth mode.

For servers with an external firewall (e.g. EC2/GCE), open UDP ports 500 and 4500 for the VPN.

Before editing any VPN config files, you must first start a Bash session in the running container.

If you wish to add, edit or remove VPN user accounts, see Manage VPN Users. Important: After editing the VPN config files, you must also comment out the relevant sections in /opt/src/run.sh, to avoid losing your changes on container restart.

Clients are set to use Google Public DNS when the VPN connection is active. If another DNS provider is preferred, replace 8.8.8.8 and 8.8.4.4 in /opt/src/run.sh with the new servers. Then restart the Docker container.

Update Docker image

To update your Docker image and container, follow these steps:

docker pull hwdsl2/ipsec-vpn-server

If the Docker image is already up to date, you should see:

Status: Image is up to date for hwdsl2/ipsec-vpn-server:latest

Otherwise, it will download the latest version. To update your Docker container, first write down all your VPN login details (refer to "Retrieve VPN login details" above). Then remove the Docker container with docker rm -f ipsec-vpn-server. Finally, re-create it using instructions from the "How to use this image" section.

Advanced usage

Build from source code

Advanced users can download and compile the source code from GitHub:

git clone https://github.com/hwdsl2/docker-ipsec-vpn-server.git
cd docker-ipsec-vpn-server
docker build -t hwdsl2/ipsec-vpn-server .

Or use this if not modifying the source code:

docker build -t hwdsl2/ipsec-vpn-server github.com/hwdsl2/docker-ipsec-vpn-server.git

Bash shell inside container

To start a Bash session in the running container:

docker exec -it ipsec-vpn-server env TERM=xterm bash -l

(Optional) Install the nano editor:

apt-get update && apt-get -y install nano

Then run your commands inside the container. When finished, exit the container and restart if needed:

exit
docker restart ipsec-vpn-server

Enable Libreswan logs

To keep the Docker image small, Libreswan (IPsec) logs are not enabled by default. If you are an advanced user and wish to enable it for troubleshooting purposes, first start a Bash session in the running container:

docker exec -it ipsec-vpn-server env TERM=xterm bash -l

Then run the following commands:

apt-get update && apt-get -y install rsyslog
service rsyslog restart
service ipsec restart
sed -i '/modprobe/a service rsyslog restart' /opt/src/run.sh
exit

When finished, you may check Libreswan logs with:

docker exec -it ipsec-vpn-server grep pluto /var/log/auth.log

Technical details

There are two services running: Libreswan (pluto) for the IPsec VPN, and xl2tpd for L2TP support.

The default IPsec configuration supports:

IKEv1 with PSK and XAuth ("Cisco IPsec")
IPsec/L2TP with PSK

The ports that are exposed for this container to work are:

4500/udp and 500/udp for IPsec

License

This work is licensed under the Creative Commons Attribution-ShareAlike 3.0 Unported License
Attribution required: please include my name in any derivative and let me know how you have improved it!

wd101 / docker-ipsec-vpn-server