#!/bin/bash

if [ "$EUID" -ne 0 ]; then
    echo "You need to run this script as root"
    exit 1
fi

if [ "$(systemd-detect-virt)" == "openvz" ]; then
    echo "OpenVZ is not supported"
    exit
fi

if [ "$(systemd-detect-virt)" == "lxc" ]; then
    echo "LXC is not supported (yet)."
    echo "WireGuard can technically run in an LXC container,"
    echo "but the kernel module has to be installed on the host,"
    echo "the container has to be run with some specific parameters"
    echo "and only the tools need to be installed in the container."
    exit
fi

# Check OS version
if [[ -e /etc/debian_version ]]; then
    source /etc/os-release
    OS=$ID # debian or ubuntu
elif [[ -e /etc/fedora-release ]]; then
    OS=fedora
elif [[ -e /etc/centos-release ]]; then
    OS=centos
elif [[ -e /etc/arch-release ]]; then
    OS=arch
else
    echo "Looks like you aren't running this installer on a Debian, Ubuntu, Fedora, CentOS or Arch Linux system"
    exit 1
fi

# Detect public IPv4 address and pre-fill for the user
SERVER_PUB_IPV4=$(ip addr | grep 'inet' | grep -v inet6 | grep -vE '127\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | grep -oE '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | head -1)
read -rp "IPv4 or IPv6 public address: " -e -i "$SERVER_PUB_IPV4" SERVER_PUB_IP

read -rp "Did you enter an IPv6 address? (y/n) " -e -i n SERVER_PUB_IPV6_USED

# Detect public interface and pre-fill for the user
SERVER_PUB_NIC="$(ip -4 route ls | grep default | grep -Po '(?<=dev )(\S+)' | head -1)"
read -rp "Public interface: " -e -i "$SERVER_PUB_NIC" SERVER_PUB_NIC

SERVER_WG_NIC="wg0"
read -rp "WireGuard interface name: " -e -i "$SERVER_WG_NIC" SERVER_WG_NIC

SERVER_WG_IPV4="10.66.66.1"
read -rp "Server's WireGuard IPv4 " -e -i "$SERVER_WG_IPV4" SERVER_WG_IPV4

SERVER_WG_IPV6="fd42:42:42::1"
read -rp "Server's WireGuard IPv6 " -e -i "$SERVER_WG_IPV6" SERVER_WG_IPV6

SERVER_PORT=1194
read -rp "Server's WireGuard port " -e -i "$SERVER_PORT" SERVER_PORT

CLIENT_WG_IPV4="10.66.66.2"
read -rp "Client's WireGuard IPv4 " -e -i "$CLIENT_WG_IPV4" CLIENT_WG_IPV4

CLIENT_WG_IPV6="fd42:42:42::2"
read -rp "Client's WireGuard IPv6 " -e -i "$CLIENT_WG_IPV6" CLIENT_WG_IPV6

# Adguard DNS by default
CLIENT_DNS_1="176.103.130.130"
read -rp "First DNS resolver to use for the client: " -e -i "$CLIENT_DNS_1" CLIENT_DNS_1

CLIENT_DNS_2="176.103.130.131"
read -rp "Second DNS resolver to use for the client: " -e -i "$CLIENT_DNS_2" CLIENT_DNS_2

if [[ $SERVER_PUB_IPV6_USED = 'y' ]]; then
    ENDPOINT="[$SERVER_PUB_IP]:$SERVER_PORT"
else
    ENDPOINT="$SERVER_PUB_IP:$SERVER_PORT"
fi

# Install WireGuard tools and module
if [[ "$OS" = 'ubuntu' ]]; then
    add-apt-repository ppa:wireguard/wireguard
    apt-get update
    apt-get install wireguard
elif [[ "$OS" = 'debian' ]]; then
    echo "deb http://deb.debian.org/debian/ unstable main" > /etc/apt/sources.list.d/unstable.list
    printf 'Package: *\nPin: release a=unstable\nPin-Priority: 90\n' > /etc/apt/preferences.d/limit-unstable
    apt update
    apt install wireguard
elif [[ "$OS" = 'fedora' ]]; then
    dnf copr enable jdoss/wireguard
    dnf install wireguard-dkms wireguard-tools
elif [[ "$OS" = 'centos' ]]; then
    curl -Lo /etc/yum.repos.d/wireguard.repo https://copr.fedorainfracloud.org/coprs/jdoss/wireguard/repo/epel-7/jdoss-wireguard-epel-7.repo
    yum install epel-release
    yum install wireguard-dkms wireguard-tools
elif [[ "$OS" = 'arch' ]]; then
    pacman -S wireguard-tools
fi

# Make sure the directory exists (this does not seem the be the case on fedora)
mkdir /etc/wireguard > /dev/null 2>&1

# Generate key pair for the server
SERVER_PRIV_KEY=$(wg genkey)
SERVER_PUB_KEY=$(echo "$SERVER_PRIV_KEY" | wg pubkey)

# Generate key pair for the server
CLIENT_PRIV_KEY=$(wg genkey)
CLIENT_PUB_KEY=$(echo "$CLIENT_PRIV_KEY" | wg pubkey)

# Add server interface
echo "[Interface]
Address = $SERVER_WG_IPV4/24,$SERVER_WG_IPV6/64
ListenPort = $SERVER_PORT
PrivateKey = $SERVER_PRIV_KEY
PostUp = iptables -t nat -A POSTROUTING -o $SERVER_PUB_NIC -j MASQUERADE; ip6tables -t nat -A POSTROUTING -o $SERVER_PUB_NIC -j MASQUERADE
PostDown = iptables -t nat -D POSTROUTING -o $SERVER_PUB_NIC -j MASQUERADE; ip6tables -t nat -D POSTROUTING -o $SERVER_PUB_NIC -j MASQUERADE" > "/etc/wireguard/$SERVER_WG_NIC.conf"

# Add the client as a peer to the server
echo "[Peer]
PublicKey = $CLIENT_PUB_KEY
AllowedIPs = $CLIENT_WG_IPV4/32,$CLIENT_WG_IPV6/128" >> "/etc/wireguard/$SERVER_WG_NIC.conf"

# Create client file with interface
echo "[Interface]
PrivateKey = $CLIENT_PRIV_KEY
Address = $CLIENT_WG_IPV4/24,$CLIENT_WG_IPV6/64
DNS = $CLIENT_DNS_1,$CLIENT_DNS_2" > "$HOME/$SERVER_WG_NIC-client.conf"

# Add the server as a peer to the client
echo "[Peer]
PublicKey = $SERVER_PUB_KEY
Endpoint = $ENDPOINT
AllowedIPs = 0.0.0.0/0,::/0" >> "$HOME/$SERVER_WG_NIC-client.conf"

# Ask for pre-shared symmetric key
read -r -p "Want to use pre-shared symmetric key? [y/N] " response
case "$response" in
    [yY][eE][sS]|[yY]) 
        CLIENT_SYMM_PRE_KEY=$( wg genpsk )
        echo "PresharedKey = $CLIENT_SYMM_PRE_KEY" >> "/etc/wireguard/$SERVER_WG_NIC.conf"
        echo "PresharedKey =$CLIENT_SYMM_PRE_KEY" >> "$HOME/$SERVER_WG_NIC-client.conf"
        ;;
esac

chmod 600 -R /etc/wireguard/

# Enable routing on the server
echo "net.ipv4.ip_forward = 1
net.ipv6.conf.all.forwarding = 1" > /etc/sysctl.d/wg.conf

sysctl --system

systemctl start "wg-quick@$SERVER_WG_NIC"
systemctl enable "wg-quick@$SERVER_WG_NIC"