#!/bin/bash

#######
# Setup
#######
### Enable IPv4/6 forwarding:
# # In /etc/sysctl.d/30-ipforward.conf :
# net.ipv4.ip_forward=1
# net.ipv6.conf.default.forwarding=1
# net.ipv6.conf.all.forwarding=1

### Generate server keypair:
# servername=$(hostname)
# wg_iface="wg0"
# mkdir -p /etc/wireguard/keys
# touch "/etc/wireguard/keys/$servername.$wg_iface.key"
# chmod 600 "/etc/wireguard/keys/$servername.$wg_iface.key"
# wg genkey | tee "/etc/wireguard/keys/$servername.$wg_iface.key" | wg pubkey "/etc/wireguard/keys/$servername.$wg_iface.pub"

### Server config
# # In /etc/wireguard/<wgiface>.conf
# # Things to change: IPv4/6 addresses, network interface
# [Interface]
# PrivateKey = <read from /etc/wireguard/keys/<servername>.<wgiface>.key>
# Address = xxx.xxx.xxx.1/24, xxxx:xxxx:xxxx::1/128
# ListenPort = 51820
# PostUp = iptables -A FORWARD -i %i -j ACCEPT; iptables -t nat -A POSTROUTING -o <netiface> -j MASQUERADE; ip6tables -A FORWARD -i %i -j ACCEPT; ip6tables -t nat -A POSTROUTING -o <netiface> -j MASQUERADE
# PostDown = iptables -D FORWARD -i %i -j ACCEPT; iptables -t nat -D POSTROUTING -o <netiface> -j MASQUERADE; ip6tables -D FORWARD -i %i -j ACCEPT; ip6tables -t nat -D POSTROUTING -o <netiface> -j MASQUERADE
# SaveConfig = false

########
# Script
########

set -e

# Modify these per-server
wg_iface="wg0"
servername="<servername>"
config_file="/etc/wireguard/$wg_iface.conf"
server_pub_file="/etc/wireguard/keys/$servername.$wg_iface.pub"
server_domain="example.org"
server_port="51820"
ipv4_prefix="10.0.0."
ipv4_mask="32"
ipv6_prefix="xxxx:xxxx:xxxx::"
ipv6_mask="128"
dns_servers="192.168.1.1"

# Require root to change wg-related settings
if ! [ "$(id -u)" = "0" ]; then
    echo "ERROR: root is required to configure WireGuard clients"
    exit 1
fi

# Help and basic error checking
if [ $# -ne 2 ] || [ $# -gt 1 -a "$1" == "--help" ]; then
	echo "Usage:"
	echo "$(basename "$0") <client number> <device name>"
	exit 1
fi

# Pull server pubkey from file
server_pub=$(< "$server_pub_file")

# Params
client_number="$1"
name="$2"

# Generate and store keypair
priv=$(wg genkey)
pub=$(echo "$priv" | wg pubkey)

# Create IPv4/6 addresses based on client ID
client_ipv4="$ipv4_prefix$client_number/$ipv4_mask"
client_ipv6="$ipv6_prefix$client_number/$ipv6_mask"

# Can't add duplicate IPs
if grep -q "$client_ipv4" "$config_file" || grep -q "$client_ipv6" "$config_file"; then
	echo "ERROR: This client number has already been used in the config file"
	exit 1
fi

# Add peer to config file (blank line is on purpose)
cat >> $config_file <<-EOM

[Peer]
# $name
PublicKey = $pub
AllowedIPs = $client_ipv4, $client_ipv6 
EOM

# Make client config
client_config=$(cat <<-EOM
[Interface]
PrivateKey = $priv
Address = $client_ipv4, $client_ipv6
DNS = $dns_servers

[Peer]
PublicKey = $server_pub
AllowedIPs = 0.0.0.0/0, ::/0
Endpoint = $server_domain:$server_port
PersistentKeepalive = 25
EOM
)

# Output client configuration
echo "########## START CONFIG ##########"
echo "$client_config"
echo "########### END CONFIG ###########"
if command -v qrencode > /dev/null; then
	echo "$client_config" | qrencode -t ansiutf8
else
	echo "Install 'qrencode' to also generate a QR code of the above config"
fi

# Restart service
echo ""
read -p "Restart 'wg-quick@$wg_iface' ? [y]: " confirm
if [ $confirm == "y" ]; then
	systemctl restart "wg-quick@$wg_iface"
else
	echo "WARNING: 'wg-quick@$wg_iface' will need to be restarted before the new client can connect"
fi