Linux strongSwan IPsec Clients (e.g., OpenWRT, Ubuntu Server, etc.)

Install strongSwan, then copy the included ipsec_user.conf, ipsec_user.secrets, user.crt (user certificate), and user.key (private key) files to your client device. These will require customization based on your exact use case. These files were originally generated with a point-to-point OpenWRT-based VPN in mind.

Ubuntu Server example

  1. sudo apt-get install strongswan libstrongswan-standard-plugins: install strongSwan
  2. /etc/ipsec.d/certs: copy <name>.crt from algo-master/configs/<server_ip>/ipsec/.pki/certs/<name>.crt
  3. /etc/ipsec.d/private: copy <name>.key from algo-master/configs/<server_ip>/ipsec/.pki/private/<name>.key
  4. /etc/ipsec.d/cacerts: copy cacert.pem from algo-master/configs/<server_ip>/ipsec/manual/cacert.pem
  5. /etc/ipsec.secrets: add your user.key to the list, e.g. <server_ip> : ECDSA <name>.key
  6. /etc/ipsec.conf: add the connection from ipsec_user.conf and ensure leftcert matches the <name>.crt filename
  7. sudo ipsec restart: pick up config changes
  8. sudo ipsec up <conn-name>: start the ipsec tunnel
  9. sudo ipsec down <conn-name>: shutdown the ipsec tunnel

One common use case is to let your server access your local LAN without going through the VPN. Set up a passthrough connection by adding the following to /etc/ipsec.conf:

conn lan-passthrough
leftsubnet= # Replace with your LAN subnet
rightsubnet= # Replace with your LAN subnet
authby=never # No authentication necessary
type=pass # passthrough
auto=route # no need to ipsec up lan-passthrough

To configure the connection to come up at boot time replace auto=add with auto=start.

Notes on SELinux

If you use a system with SELinux enabled you might need to set appropriate file contexts:

semanage fcontext -a -t ipsec_key_file_t "$(pwd)(/.*)?"
restorecon -R -v $(pwd)

See this comment.