Table of contents
A Bash script that takes Ubuntu Server 20.04 LTS or 18.04 LTS from clean install to production-ready IKEv2 VPN with strongSwan. Comments and pull requests welcome. It may still work on 17.10, 17.04 or 16.10 if you remove the version check, but these are not tested.
The VPN server identifies itself with a Let's Encrypt certificate, so there's no need for clients to install private certificates — they can simply authenticate with username and strong password (EAP-MSCHAPv2).
The only cipher set implemented is CNSA/RFC 6379 Suite B with confidentiality/encryption.
The box is firewalled with
iptablesand configured for unattended security upgrades, and the Let's Encrypt certificate is set up to auto-renew, so it could be safe to forget about it all until 18.04 reaches end-of-life in 2023. (Note that
iptablessetup includes basic rate-limiting, dropping new connections if there have been 60+ connection attempts in the last 5 minutes).
The VPN is tested working with:
- macOS 10.12 – 10.15, iOS 10 – 13 — Built-in clients. A
.mobileconfigprofile is generated for Mac and iOS, to set up secure ciphers and enable Connect on demand support.
- Windows 10 Pro — Built-in client. PowerShell commands are generated to configure the VPN and secure ciphers.
- Ubuntu (17.04 and presumably others) — Using strongSwan. A Bash script is generated to set this up.
- Android — Using the official strongSwan app.
Configuration files, scripts and instructions are sent by email. They are also dropped in the newly-created non-root user's home directory on the server (this point may be important, because VPS providers sometimes block traffic on port 25 by default and, even if successfully sent, conscientious email hosts will sometimes mark the email as spam).
- There's no IPv6 support — and, in fact, IPv6 networking is disabled — because supporting IPv6 prevents the use of
forceencaps, and honestly also because I haven't got to grips with the security implications (
ip6tablesrules and so on).
- The script won't work as-is on 16.04 LTS because the
certbotpackage is outdated, found under the name
letsencrypt, and doesn't renew certificates automatically.
- Don't use this unmodified on a server you use for anything else: it does as it sees fit with various wider settings that may conflict with what you're doing.
- Pick a domain name for the VPN server and ensure that it already resolves to the correct IP by creating the appropriate
Arecord in the DNS and making sure it has propagated. Let's Encrypt needs this in order to create your server certificate.
Don't want to use your own domain name here? You could try using the reverse DNS name provided by your server host, or an automatic IP/DNS alias service such as sslip.io, xip.io, nip.io, s.test.cab, or xip.lhjmmc.cn (earlier versions of this script used an sslip.io address by default). However, both of these options may fall foul of Let's Encrypt's per-domain rate limit of 50 certificates per week. Note that ephemeral AWS domain names like
ec2-34-267-212-76.compute-1.amazonaws.com are not accepted by Let's Encrypt.
Start with a clean Ubuntu 20.04 or 18.04 Server installation. The cheapest VPSs offered by Linode, OVH, vps.ag, Google, Hetzner and Vultr, and Scaleway's ARM64-2GB, have all been tested working. On Scaleway, unblock SMTP ports in the admin panel and hard reboot the server first, or your configuration email will not be delivered. On Vultr, port 25 may also be blocked, but you won't know, and the only way to fix it is to open a support ticket.
Optionally, set up key-based SSH authentication (alternatively, this may have been handled automatically by your server provider, or you may choose to stick with password-based authentication). This may require you to run some or all of the following commands, with appropriate substitutions, on the machine you're going to be logging in from:
ssh-keygen -t ed25519 -C "firstname.lastname@example.org" # if you need a new key, ed25519 is the latest and possibly most secure option ssh-keygen -t rsa -b 4096 -C "email@example.com" # alternatively, use RSA and go (4,096 bits) large ssh firstname.lastname@example.org # if your host forces a password change before anything else (e.g. Hetzner), do it now, then exit ssh-copy-id -i ~/.ssh/id_ed25519 email@example.com # copy your public key over to the VPN server ssh firstname.lastname@example.org # log back in to the server for the next step ...
On your new server installation, become
root, download the script, give it execute permissions, and run it:
wget https://raw.githubusercontent.com/jawj/IKEv2-setup/master/setup.sh chmod u+x setup.sh ./setup.sh
You'll be prompted to enter all the necessary details after the software updates and installations complete. If you are not using key-based SSH authentication, you must pick a really strong password for the login user when prompted, or your server will be compromised.
The part of your session where the script asks you questions should look something like this:
--- Configuration: VPN settings --- Network interface: eth0 External IP: 100.100.100.100 ** Note: hostname must resolve to this machine already, to enable Let's Encrypt certificate setup ** Hostname for VPN: VPN username: george VPN password (no quotes, please): Confirm VPN password: Public DNS servers include: 22.214.171.124,126.96.36.199 AdGuard https://adguard.com/en/adguard-dns/overview.html 188.8.131.52,184.108.40.206 AdGuard Family https://adguard.com/en/adguard-dns/overview.html 220.127.116.11,18.104.22.168 Cloudflare/APNIC https://22.214.171.124 126.96.36.199,188.8.131.52 DNS.WATCH https://dns.watch 184.108.40.206,220.127.116.11 Google https://developers.google.com/speed/public-dns/ 18.104.22.168,22.214.171.124 OpenDNS https://www.opendns.com 126.96.36.199,188.8.131.52 OpenDNS FamilyShield https://www.opendns.com 184.108.40.206,220.127.116.11 Quad9 https://quad9.net 18.104.22.168,22.214.171.124 Yandex https://dns.yandex.com 126.96.36.199,188.8.131.52 Yandex Safe https://dns.yandex.com 184.108.40.206,220.127.116.11 Yandex Family https://dns.yandex.com DNS servers for VPN users (default: 18.104.22.168,22.214.171.124): 126.96.36.199,188.8.131.52 --- Configuration: general server settings --- Timezone (default: Europe/London): Email address for sysadmin (e.g. email@example.com): firstname.lastname@example.org Desired SSH log-in port (default: 22): 2222 New SSH log-in user name: george Copy /root/.ssh/authorized_keys to new user and disable SSH password log-in [Y/n]? y New SSH user's password (e.g. for sudo): Confirm new SSH user's password:
Once you're up and running, use these commands for some insight into what's going on:
sudo ipsec statusall # status, who's connected, etc. sudo iptables -L -v # how much traffic has been forwarded, dropped, etc.? sudo tail -f /var/log/syslog # real-time logs of (dis)connections etc.
If things don't work out right away ...
On the client: make sure you created the connection using the newly emailed
.mobileconfigfile or PowerShell commands. Setting it up manually via the OS GUI will not work, since it will default to insecure ciphers which the server has not been configured to support. Also note that
.mobileconfigfiles generated with earlier iterations of this script may no longer be compatible, since the configured ciphers have changed from time to time.
On the server: check that network ingress for UDP on ports 500 and 4500 is enabled (on some cloud platforms you'll have to add appropriate firewall rules to your virtual network). Also check that packet forwarding is enabled (on some cloud platforms this is controlled by a configuration setting that's off by default).
Check the server logs on strongSwan startup and when you try to connect, and the client logs when you try to connect.
On the server: Log in via SSH, then
sudo tail -f /var/log/syslog. To see startup logs, log in to another session and
sudo ipsec restartthere, then switch back. To see what's logged during a connection attempt, try to connect from a client.
On the client: On a Mac, open Console.app in /Applications/Utilities. If connecting from an iPhone, plug the iPhone into the Mac. Pick the relevant device (in the bar down the left), filter the output (in the box at top right) to
nesession, and try to connect. (On Windows or Linux I don't know where you find the logs — if you know, feel free to write the explanation and send a pull request).
The setup script is now more or less idempotent — you should be able to run it repeatedly with no ill effects — so, when you've fixed any issues, simply run it again.
If you have a tricky question about strongSwan, it's probably better to raise it with the strongSwan team than file an issue here.
To add or change VPN users, it's:
sudo nano /etc/ipsec.secrets
Edit usernames and passwords as you see fit (but don't touch the first line, which specifies the server certificate). The line format for each user is:
someusername : EAP "somepassword"
To exit nano it's
Ctrl + O then
Ctrl + X, and to have strongSwan pick up the changes it's:
sudo ipsec secrets
If you're on a pre-18.04 version of Ubuntu, it's probably easiest to make a record of any changes to
ipsec.secrets, blow the whole thing away and reinstall, then reinstate
Note that you may also need to delete and recreate all your client connection settings using the updated PowerShell commands or .mobileconfig file, since there have been a few cipher changes over time.
Your traffic is not logged on the server, but if you're feeling especially paranoid there are various things you could do to reduce logging further. A simple and somewhat drastic option (once you've got everything working) is:
sudo rm /var/log/syslog && sudo ln -s /dev/null /var/log/syslog sudo rm /var/log/auth.log && sudo ln -s /dev/null /var/log/auth.log
- Fair security
- Built-in clients for latest iOS, Mac and Windows (+ trustworthy free install on Android)
- Connect on demand support on iOS and Mac
- Robust to connection switching and interruptions via MOBIKE
Why not Algo?
Feel free to use Algo instead. It has similar aims, and now configures WireGuard too. However, it has many more moving parts, and requires several local installation steps before you even start setting up your VPN. This script is intended to be much simpler.