VPN

Troubleshooting

Introduction

This document describes a small (up to 253 node) server configuration wireguard network. Throughout a wireguard network IP is referred to as a.a.a.0/24, a typical node as a.a.a.x (x is replaced with another letter if it’s necessary to distinguish between nodes).

The servers public key is referred to as sssssssssssssssssssssssssssssssssssssssss= and the servers public ip as s.s.s.s and port sssss.

A client’s public key is referred to using another single letter string (e.g yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy=) and it’s public ip and port using the same letter (e.g y.y.y.y and yyyyy).

Server

Using wireguard in a server configuration, clients simply have the server in the Peer section. The server has all clients in the Peer section. All communications are inniated through the server.

Below is an example salt configuration (e.g. /srv/pillar/sites/my-vpn.sls) for a vpn server with 2 peers that also acts as a DNS server for the wireguard network (this is a very simplified example you may also want to add forwarders and allowed_ips etc.)

A node’s public key and IP Address needs to be added to the vpn section but the ip address only needs to be added to the dns section if it needs to be looked up, in this example only the server and the DNS/VPN server can be looked up.

Add the IP address to the dns, zones and vpn sections e.g for a network with 3 nodes:

- vpn server with an ip of a.a.a.1 (e.g. 10.10.10.1),
- a server with ip of a.a.a.11
- and a client with a.a.a.101

server_meta:
  dns:
    zones:
      - name: db.my.lan
        serial 1
        zone: my.lan
        primary_server: ns.my.lan
        email_address: root.my.lan
        entries:
          - { name: '',      type: A,    value: a.a.a.1 }
          - { name: '@',     type: NS,   value: ns.my.lan }
          - { name: '@',     type: A,    value: a.a.a.1 }
          - { name: server,  type: A,    value: a.a.a.11 }

  vpn:
    interface: wgx
    conf:
      Address: a.a.a.1
      PrivateKey: SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS=
      ListenPort: sssss
      DNS: a.a.a.1
    peers:
      server:
        PublicKey: yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy=
        AllowedIPs: a.a.a.11/32
      client:
        PublicKey: zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz=
        AllowedIPs: a.a.a.101/32

Once the configuration for the node is added the salt state needs to be applied to the vpn server…

Client (Linux)

Tip

Before installing Ubuntu Linux, decide on the hostname (e.g. cloud-a) This will make the Salt configuration much easier to do.

Tip

When installing Linux, do not use an existing username. Salt creates users with fixed UUID.

We’ve written a private script that installs salt configuration management and wireguard packages and creates a wireguard configuration for our vpn. Internally we use this salt-minion-setup script to allow linux nodes to request to be part of our configuration management and internal vpn. These then need to be accepted on the salt master and added to the piller configuration file (see above) for the vpn servers and the state applied to it:

The salt-minion-setup script creates the private and public keys on the client and displays the peer information to be added to the server on the screen this can then be cut and pasted into the sites/my-vpn.sls in the pillar file on the Salt master.
Apply the states.
Restart the interface (wg-quick down wg0 && wg-quick up wg0).

Tip

Don’t forget to setup the Wireguard - Configuration

Client (Windows)

Download and install Wireguard https://www.wireguard.com/install/

Log in as an administrator and Create a new connection (Add empty tunnel) This will create an ini file with a public and private key. Alternatively the configuration file could be created on a separate server and imported.

Using either method your configuration should contain the following directives

[Interface] PrivateKey = CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC= Address = a.a.a.<Free node number>/32 DNS = a.a.a.1

[Peer] PublicKey = sssssssssssssssssssssssssssssssssssssssssssssss= AllowedIPs = a.a.a.0/24 Endpoint = vpn-my.hatherleigh.info:sssss PersistentKeepalive = 25

Save and Activate

The Public key and IP address need to be added to your Salt pillar for your VPN server and the states applied.

Troubleshooting

Connection issues

To diagnose connection issues use (on both the client and the server):

sudo wg show

or if the interface is configured to start at boot time (assuming interface is called wg0) use:

sudo systemctl wg-quick@wg0 status

e.g a typical client will show:

interface: wgx
  public key: yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy=
  private key: (hidden)
  listening port: yyyyy

peer: sssssssssssssssssssssssssssssssssssssssssss=
  endpoint: s.s.s.s:sssss
  allowed ips: a.a.a.0/24
  latest handshake: 20 seconds ago
  transfer: 46.90 MiB received, 523.78 MiB sent
  persistent keepalive: every 25 seconds

A typical server will show:

interface: wgx
  public key: sssssssssssssssssssssssssssssssssssssssssss=
  private key: (hidden)
  listening port: sssss

peer: yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy=
  endpoint: y.y.y.y:yyyyy
  allowed ips: a.a.a.x/32
  latest handshake: 1 second ago
  transfer: 2.37 GiB received, 964.48 MiB sent

peer: zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz=
  endpoint: z.z.z.z:zzzzz
  allowed ips: a.a.a.z/32
  latest handshake: 3 seconds ago
  transfer: 28.27 MiB received, 20.33 MiB sent

peer: wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww=
  allowed ips: a.a.a.w/32

Lines to look out for in this output are:

- If there are no ``latest handshake`` or ``transfer lines`` (e.g peer
  wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww= above) this indicates the peer has
  not been seen since the service started.

- If the interface has been started recently a ``transfer`` line showing
  ``0B received`` indicates that the service is not connected.  This is
  usually due to a configuration issue.

- ``latest handshake`` should be less than a few minutes. if the transfer
  line shows a value for bytes received this indicates the configuration
  worked at some point so it may be a public network issue - the wireguard
  interface sends encrypted traffic over the public network imnterface.

Reset the interface

To reset a the wireguard interface (assuming it’s called wg0) use:

wg-quick wg0 down && wg-quick wg0 up

If the interface is started at boot time you can also use:

sudo systemctl restart wg-quick@wg0

Configuration issues

The PublicKey in the Peer section of the client configuration is the public key of the server, not the client:

[Peer]
PublicKey = sssssssssssssssssssssssssssssssssssssssssss=

DNS

If you only have a single wireguard network and have a DNS server configured to resolve the nodes on a wireguard network, you can configure nodes to use this with the DNS directive in the wireguard configuration file. e.g.

DNS = a.a.a.x

If your system is configured to start the VPN network at boot rebooting may resolve DNS issues or you can simply reset the interface as described above.

Tip

To check your name server information on ubuntu 20.04 and later use resolvectl status.

Unstable connection

Check to make sure you are not using the configuration in two (or more) places!

Wireguard identifies a node using the public key. The server is able to route to the node using the AllowedIPs = a.a.a.x/32 directive for the peer in the server configuration file. If two nodes have the same IP or public key they will constantly break each other.

Firewall Rules

A server protected by a firewall (recommended) needs a rule for it’s port to allow traffic.

A client with PersistentKeepalive directive only needs a firewall rules if the output chain is restricted (for iptables, check using sudo iptables -L).