#!/bin/bash
#
# https://github.com/Nyr/wireguard-install
#
# Copyright (c) 2020 Nyr. Released under the MIT License.


# Detect Debian users running the script with "sh" instead of bash
if readlink /proc/$$/exe | grep -q "dash"; then
	echo 'This installer needs to be run with "bash", not "sh".'
	exit
fi

# Discard stdin. Needed when running from an one-liner which includes a newline
read -N 999999 -t 0.001

# Detect OpenVZ 6
if [[ $(uname -r | cut -d "." -f 1) -eq 2 ]]; then
	echo "The system is running an old kernel, which is incompatible with this installer."
	exit
fi

# Detect OS
# $os_version variables aren't always in use, but are kept here for convenience
if grep -qs "ubuntu" /etc/os-release; then
	os="ubuntu"
	os_version=$(grep 'VERSION_ID' /etc/os-release | cut -d '"' -f 2 | tr -d '.')
elif [[ -e /etc/debian_version ]]; then
	os="debian"
	os_version=$(grep -oE '[0-9]+' /etc/debian_version | head -1)
elif [[ -e /etc/almalinux-release || -e /etc/rocky-release || -e /etc/centos-release ]]; then
	os="centos"
	os_version=$(grep -shoE '[0-9]+' /etc/almalinux-release /etc/rocky-release /etc/centos-release | head -1)
elif [[ -e /etc/fedora-release ]]; then
	os="fedora"
	os_version=$(grep -oE '[0-9]+' /etc/fedora-release | head -1)
else
	echo "This installer seems to be running on an unsupported distribution.
Supported distros are Ubuntu, Debian, AlmaLinux, Rocky Linux, CentOS and Fedora."
	exit
fi

if [[ "$os" == "ubuntu" && "$os_version" -lt 1804 ]]; then
	echo "Ubuntu 18.04 or higher is required to use this installer.
This version of Ubuntu is too old and unsupported."
	exit
fi

if [[ "$os" == "debian" && "$os_version" -lt 10 ]]; then
	echo "Debian 10 or higher is required to use this installer.
This version of Debian is too old and unsupported."
	exit
fi

if [[ "$os" == "centos" && "$os_version" -lt 7 ]]; then
	echo "CentOS 7 or higher is required to use this installer.
This version of CentOS is too old and unsupported."
	exit
fi

# Detect environments where $PATH does not include the sbin directories
if ! grep -q sbin <<< "$PATH"; then
	echo '$PATH does not include sbin. Try using "su -" instead of "su".'
	exit
fi

systemd-detect-virt -cq
is_container="$?"

if [[ "$os" == "fedora" && "$os_version" -eq 31 && $(uname -r | cut -d "." -f 2) -lt 6 && ! "$is_container" -eq 0 ]]; then
	echo 'Fedora 31 is supported, but the kernel is outdated.
Upgrade the kernel using "dnf upgrade kernel" and restart.'
	exit
fi

if [[ "$EUID" -ne 0 ]]; then
	echo "This installer needs to be run with superuser privileges."
	exit
fi

if [[ "$is_container" -eq 0 ]]; then
	if [ "$(uname -m)" != "x86_64" ]; then
		echo "In containerized systems, this installer supports only the x86_64 architecture.
The system runs on $(uname -m) and is unsupported."
		exit
	fi
	# TUN device is required to use BoringTun if running inside a container
	if [[ ! -e /dev/net/tun ]] || ! ( exec 7<>/dev/net/tun ) 2>/dev/null; then
		echo "The system does not have the TUN device available.
TUN needs to be enabled before running this installer."
		exit
	fi
fi

new_client_dns () {
	echo "Select a DNS server for the client:"
	echo "   1) Current system resolvers"
	echo "   2) Google"
	echo "   3) 1.1.1.1"
	echo "   4) OpenDNS"
	echo "   5) Quad9"
	echo "   6) AdGuard"
	read -p "DNS server [1]: " dns
	until [[ -z "$dns" || "$dns" =~ ^[1-6]$ ]]; do
		echo "$dns: invalid selection."
		read -p "DNS server [1]: " dns
	done
		# DNS
	case "$dns" in
		1|"")
			# Locate the proper resolv.conf
			# Needed for systems running systemd-resolved
			if grep -q '^nameserver 127.0.0.53' "/etc/resolv.conf"; then
				resolv_conf="/run/systemd/resolve/resolv.conf"
			else
				resolv_conf="/etc/resolv.conf"
			fi
			# Extract nameservers and provide them in the required format
			dns=$(grep -v '^#\|^;' "$resolv_conf" | grep '^nameserver' | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}' | xargs | sed -e 's/ /, /g')
		;;
		2)
			dns="8.8.8.8, 8.8.4.4"
		;;
		3)
			dns="1.1.1.1, 1.0.0.1"
		;;
		4)
			dns="208.67.222.222, 208.67.220.220"
		;;
		5)
			dns="9.9.9.9, 149.112.112.112"
		;;
		6)
			dns="94.140.14.14, 94.140.15.15"
		;;
	esac
}

new_client_setup () {
	# Given a list of the assigned internal IPv4 addresses, obtain the lowest still
	# available octet. Important to start looking at 2, because 1 is our gateway.
	octet=2
	while grep AllowedIPs /etc/wireguard/wg0.conf | cut -d "." -f 4 | cut -d "/" -f 1 | grep -q "$octet"; do
		(( octet++ ))
	done
	# Don't break the WireGuard configuration in case the address space is full
	if [[ "$octet" -eq 255 ]]; then
		echo "253 clients are already configured. The WireGuard internal subnet is full!"
		exit
	fi
	key=$(wg genkey)
	psk=$(wg genpsk)
	# Configure client in the server
	cat << EOF >> /etc/wireguard/wg0.conf
# BEGIN_PEER $client
[Peer]
PublicKey = $(wg pubkey <<< $key)
PresharedKey = $psk
AllowedIPs = 10.7.0.$octet/32$(grep -q 'fddd:2c4:2c4:2c4::1' /etc/wireguard/wg0.conf && echo ", fddd:2c4:2c4:2c4::$octet/128")
# END_PEER $client
EOF
	# Create client configuration
	cat << EOF > ~/"$client".conf
[Interface]
Address = 10.7.0.$octet/24$(grep -q 'fddd:2c4:2c4:2c4::1' /etc/wireguard/wg0.conf && echo ", fddd:2c4:2c4:2c4::$octet/64")
DNS = $dns
PrivateKey = $key

[Peer]
PublicKey = $(grep PrivateKey /etc/wireguard/wg0.conf | cut -d " " -f 3 | wg pubkey)
PresharedKey = $psk
AllowedIPs = 0.0.0.0/0, ::/0
Endpoint = $(grep '^# ENDPOINT' /etc/wireguard/wg0.conf | cut -d " " -f 3):$(grep ListenPort /etc/wireguard/wg0.conf | cut -d " " -f 3)
PersistentKeepalive = 25
EOF
}

if [[ ! -e /etc/wireguard/wg0.conf ]]; then
	# Detect some Debian minimal setups where neither wget nor curl are installed
	if ! hash wget 2>/dev/null && ! hash curl 2>/dev/null; then
		echo "Wget is required to use this installer."
		read -n1 -r -p "Press any key to install Wget and continue..."
		apt-get update
		apt-get install -y wget
	fi
	clear
	echo 'Welcome to this WireGuard road warrior installer!'
	# If system has a single IPv4, it is selected automatically. Else, ask the user
	if [[ $(ip -4 addr | grep inet | grep -vEc '127(\.[0-9]{1,3}){3}') -eq 1 ]]; then
		ip=$(ip -4 addr | grep inet | grep -vE '127(\.[0-9]{1,3}){3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}')
	else
		number_of_ip=$(ip -4 addr | grep inet | grep -vEc '127(\.[0-9]{1,3}){3}')
		echo
		echo "Which IPv4 address should be used?"
		ip -4 addr | grep inet | grep -vE '127(\.[0-9]{1,3}){3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}' | nl -s ') '
		read -p "IPv4 address [1]: " ip_number
		until [[ -z "$ip_number" || "$ip_number" =~ ^[0-9]+$ && "$ip_number" -le "$number_of_ip" ]]; do
			echo "$ip_number: invalid selection."
			read -p "IPv4 address [1]: " ip_number
		done
		[[ -z "$ip_number" ]] && ip_number="1"
		ip=$(ip -4 addr | grep inet | grep -vE '127(\.[0-9]{1,3}){3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}' | sed -n "$ip_number"p)
	fi
	# If $ip is a private IP address, the server must be behind NAT
	if echo "$ip" | grep -qE '^(10\.|172\.1[6789]\.|172\.2[0-9]\.|172\.3[01]\.|192\.168)'; then
		echo
		echo "This server is behind NAT. What is the public IPv4 address or hostname?"
		# Get public IP and sanitize with grep
		get_public_ip=$(grep -m 1 -oE '^[0-9]{1,3}(\.[0-9]{1,3}){3}$' <<< "$(wget -T 10 -t 1 -4qO- "http://ip1.dynupdate.no-ip.com/" || curl -m 10 -4Ls "http://ip1.dynupdate.no-ip.com/")")
		read -p "Public IPv4 address / hostname [$get_public_ip]: " public_ip
		# If the checkip service is unavailable and user didn't provide input, ask again
		until [[ -n "$get_public_ip" || -n "$public_ip" ]]; do
			echo "Invalid input."
			read -p "Public IPv4 address / hostname: " public_ip
		done
		[[ -z "$public_ip" ]] && public_ip="$get_public_ip"
	fi
	# If system has a single IPv6, it is selected automatically
	if [[ $(ip -6 addr | grep -c 'inet6 [23]') -eq 1 ]]; then
		ip6=$(ip -6 addr | grep 'inet6 [23]' | cut -d '/' -f 1 | grep -oE '([0-9a-fA-F]{0,4}:){1,7}[0-9a-fA-F]{0,4}')
	fi
	# If system has multiple IPv6, ask the user to select one
	if [[ $(ip -6 addr | grep -c 'inet6 [23]') -gt 1 ]]; then
		number_of_ip6=$(ip -6 addr | grep -c 'inet6 [23]')
		echo
		echo "Which IPv6 address should be used?"
		ip -6 addr | grep 'inet6 [23]' | cut -d '/' -f 1 | grep -oE '([0-9a-fA-F]{0,4}:){1,7}[0-9a-fA-F]{0,4}' | nl -s ') '
		read -p "IPv6 address [1]: " ip6_number
		until [[ -z "$ip6_number" || "$ip6_number" =~ ^[0-9]+$ && "$ip6_number" -le "$number_of_ip6" ]]; do
			echo "$ip6_number: invalid selection."
			read -p "IPv6 address [1]: " ip6_number
		done
		[[ -z "$ip6_number" ]] && ip6_number="1"
		ip6=$(ip -6 addr | grep 'inet6 [23]' | cut -d '/' -f 1 | grep -oE '([0-9a-fA-F]{0,4}:){1,7}[0-9a-fA-F]{0,4}' | sed -n "$ip6_number"p)
	fi
	echo
	echo "What port should WireGuard listen to?"
	read -p "Port [51820]: " port
	until [[ -z "$port" || "$port" =~ ^[0-9]+$ && "$port" -le 65535 ]]; do
		echo "$port: invalid port."
		read -p "Port [51820]: " port
	done
	[[ -z "$port" ]] && port="51820"
	echo
	echo "Enter a name for the first client:"
	read -p "Name [client]: " unsanitized_client
	# Allow a limited set of characters to avoid conflicts
	client=$(sed 's/[^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-]/_/g' <<< "$unsanitized_client")
	[[ -z "$client" ]] && client="client"
	echo
	new_client_dns
	# Set up automatic updates for BoringTun if the user is fine with that
	if [[ "$is_container" -eq 0 ]]; then
		echo
		echo "BoringTun will be installed to set up WireGuard in the system."
		read -p "Should automatic updates be enabled for it? [Y/n]: " boringtun_updates
		until [[ "$boringtun_updates" =~ ^[yYnN]*$ ]]; do
			echo "$remove: invalid selection."
			read -p "Should automatic updates be enabled for it? [Y/n]: " boringtun_updates
		done
		[[ -z "$boringtun_updates" ]] && boringtun_updates="y"
		if [[ "$boringtun_updates" =~ ^[yY]$ ]]; then
			if [[ "$os" == "centos" || "$os" == "fedora" ]]; then
				cron="cronie"
			elif [[ "$os" == "debian" || "$os" == "ubuntu" ]]; then
				cron="cron"
			fi
		fi
	fi
	echo
	echo "WireGuard installation is ready to begin."
	# Install a firewall if firewalld or iptables are not already available
	if ! systemctl is-active --quiet firewalld.service && ! hash iptables 2>/dev/null; then
		if [[ "$os" == "centos" || "$os" == "fedora" ]]; then
			firewall="firewalld"
			# We don't want to silently enable firewalld, so we give a subtle warning
			# If the user continues, firewalld will be installed and enabled during setup
			echo "firewalld, which is required to manage routing tables, will also be installed."
		elif [[ "$os" == "debian" || "$os" == "ubuntu" ]]; then
			# iptables is way less invasive than firewalld so no warning is given
			firewall="iptables"
		fi
	fi
	read -n1 -r -p "Press any key to continue..."
	# Install WireGuard
	# If not running inside a container, set up the WireGuard kernel module
	if [[ ! "$is_container" -eq 0 ]]; then
		if [[ "$os" == "ubuntu" ]]; then
			# Ubuntu
			apt-get update
			apt-get install -y wireguard qrencode $firewall
		elif [[ "$os" == "debian" && "$os_version" -ge 11 ]]; then
			# Debian 11 or higher
			apt-get update
			apt-get install -y wireguard qrencode $firewall
		elif [[ "$os" == "debian" && "$os_version" -eq 10 ]]; then
			# Debian 10
			if ! grep -qs '^deb .* buster-backports main' /etc/apt/sources.list /etc/apt/sources.list.d/*.list; then
				echo "deb http://deb.debian.org/debian buster-backports main" >> /etc/apt/sources.list
			fi
			apt-get update
			# Try to install kernel headers for the running kernel and avoid a reboot. This
			# can fail, so it's important to run separately from the other apt-get command.
			apt-get install -y linux-headers-"$(uname -r)"
			# There are cleaner ways to find out the $architecture, but we require an
			# specific format for the package name and this approach provides what we need.
			architecture=$(dpkg --get-selections 'linux-image-*-*' | cut -f 1 | grep -oE '[^-]*$' -m 1)
			# linux-headers-$architecture points to the latest headers. We install it
			# because if the system has an outdated kernel, there is no guarantee that old
			# headers were still downloadable and to provide suitable headers for future
			# kernel updates.
			apt-get install -y linux-headers-"$architecture"
			apt-get install -y wireguard qrencode $firewall
		elif [[ "$os" == "centos" && "$os_version" -eq 8 ]]; then
			# CentOS 8
			dnf install -y epel-release elrepo-release
			dnf install -y kmod-wireguard wireguard-tools qrencode $firewall
			mkdir -p /etc/wireguard/
		elif [[ "$os" == "centos" && "$os_version" -eq 7 ]]; then
			# CentOS 7
			yum install -y epel-release https://www.elrepo.org/elrepo-release-7.el7.elrepo.noarch.rpm
			yum install -y yum-plugin-elrepo
			yum install -y kmod-wireguard wireguard-tools qrencode $firewall
			mkdir -p /etc/wireguard/
		elif [[ "$os" == "fedora" ]]; then
			# Fedora
			dnf install -y wireguard-tools qrencode $firewall
			mkdir -p /etc/wireguard/
		fi
	# Else, we are inside a container and BoringTun needs to be used
	else
		# Install required packages
		if [[ "$os" == "ubuntu" ]]; then
			# Ubuntu
			apt-get update
			apt-get install -y qrencode ca-certificates $cron $firewall
			apt-get install -y wireguard-tools --no-install-recommends
		elif [[ "$os" == "debian" && "$os_version" -ge 11 ]]; then
			# Debian 11 or higher
			apt-get update
			apt-get install -y qrencode ca-certificates $cron $firewall
			apt-get install -y wireguard-tools --no-install-recommends
		elif [[ "$os" == "debian" && "$os_version" -eq 10 ]]; then
			# Debian 10
			if ! grep -qs '^deb .* buster-backports main' /etc/apt/sources.list /etc/apt/sources.list.d/*.list; then
				echo "deb http://deb.debian.org/debian buster-backports main" >> /etc/apt/sources.list
			fi
			apt-get update
			apt-get install -y qrencode ca-certificates $cron $firewall
			apt-get install -y wireguard-tools --no-install-recommends
		elif [[ "$os" == "centos" && "$os_version" -eq 8 ]]; then
			# CentOS 8
			dnf install -y epel-release
			dnf install -y wireguard-tools qrencode ca-certificates tar $cron $firewall
			mkdir -p /etc/wireguard/
		elif [[ "$os" == "centos" && "$os_version" -eq 7 ]]; then
			# CentOS 7
			yum install -y epel-release
			yum install -y wireguard-tools qrencode ca-certificates tar $cron $firewall
			mkdir -p /etc/wireguard/
		elif [[ "$os" == "fedora" ]]; then
			# Fedora
			dnf install -y wireguard-tools qrencode ca-certificates tar $cron $firewall
			mkdir -p /etc/wireguard/
		fi
		# Grab the BoringTun binary using wget or curl and extract into the right place.
		# Don't use this service elsewhere without permission! Contact me before you do!
		{ wget -qO- https://wg.nyr.be/1/latest/download 2>/dev/null || curl -sL https://wg.nyr.be/1/latest/download ; } | tar xz -C /usr/local/sbin/ --wildcards 'boringtun-*/boringtun' --strip-components 1
		# Configure wg-quick to use BoringTun
		mkdir /etc/systemd/system/wg-quick@wg0.service.d/ 2>/dev/null
		echo "[Service]
Environment=WG_QUICK_USERSPACE_IMPLEMENTATION=boringtun
Environment=WG_SUDO=1" > /etc/systemd/system/wg-quick@wg0.service.d/boringtun.conf
		if [[ -n "$cron" ]] && [[ "$os" == "centos" || "$os" == "fedora" ]]; then
			systemctl enable --now crond.service
		fi
	fi
	# If firewalld was just installed, enable it
	if [[ "$firewall" == "firewalld" ]]; then
		systemctl enable --now firewalld.service
	fi
	# Generate wg0.conf
	cat << EOF > /etc/wireguard/wg0.conf
# Do not alter the commented lines
# They are used by wireguard-install
# ENDPOINT $([[ -n "$public_ip" ]] && echo "$public_ip" || echo "$ip")

[Interface]
Address = 10.7.0.1/24$([[ -n "$ip6" ]] && echo ", fddd:2c4:2c4:2c4::1/64")
PrivateKey = $(wg genkey)
ListenPort = $port

EOF
	chmod 600 /etc/wireguard/wg0.conf
	# Enable net.ipv4.ip_forward for the system
	echo 'net.ipv4.ip_forward=1' > /etc/sysctl.d/99-wireguard-forward.conf
	# Enable without waiting for a reboot or service restart
	echo 1 > /proc/sys/net/ipv4/ip_forward
	if [[ -n "$ip6" ]]; then
		# Enable net.ipv6.conf.all.forwarding for the system
		echo "net.ipv6.conf.all.forwarding=1" >> /etc/sysctl.d/99-wireguard-forward.conf
		# Enable without waiting for a reboot or service restart
		echo 1 > /proc/sys/net/ipv6/conf/all/forwarding
	fi
	if systemctl is-active --quiet firewalld.service; then
		# Using both permanent and not permanent rules to avoid a firewalld
		# reload.
		firewall-cmd --add-port="$port"/udp
		firewall-cmd --zone=trusted --add-source=10.7.0.0/24
		firewall-cmd --permanent --add-port="$port"/udp
		firewall-cmd --permanent --zone=trusted --add-source=10.7.0.0/24
		# Set NAT for the VPN subnet
		firewall-cmd --direct --add-rule ipv4 nat POSTROUTING 0 -s 10.7.0.0/24 ! -d 10.7.0.0/24 -j SNAT --to "$ip"
		firewall-cmd --permanent --direct --add-rule ipv4 nat POSTROUTING 0 -s 10.7.0.0/24 ! -d 10.7.0.0/24 -j SNAT --to "$ip"
		if [[ -n "$ip6" ]]; then
			firewall-cmd --zone=trusted --add-source=fddd:2c4:2c4:2c4::/64
			firewall-cmd --permanent --zone=trusted --add-source=fddd:2c4:2c4:2c4::/64
			firewall-cmd --direct --add-rule ipv6 nat POSTROUTING 0 -s fddd:2c4:2c4:2c4::/64 ! -d fddd:2c4:2c4:2c4::/64 -j SNAT --to "$ip6"
			firewall-cmd --permanent --direct --add-rule ipv6 nat POSTROUTING 0 -s fddd:2c4:2c4:2c4::/64 ! -d fddd:2c4:2c4:2c4::/64 -j SNAT --to "$ip6"
		fi
	else
		# Create a service to set up persistent iptables rules
		iptables_path=$(command -v iptables)
		ip6tables_path=$(command -v ip6tables)
		# nf_tables is not available as standard in OVZ kernels. So use iptables-legacy
		# if we are in OVZ, with a nf_tables backend and iptables-legacy is available.
		if [[ $(systemd-detect-virt) == "openvz" ]] && readlink -f "$(command -v iptables)" | grep -q "nft" && hash iptables-legacy 2>/dev/null; then
			iptables_path=$(command -v iptables-legacy)
			ip6tables_path=$(command -v ip6tables-legacy)
		fi
		echo "[Unit]
Before=network.target
[Service]
Type=oneshot
ExecStart=$iptables_path -t nat -A POSTROUTING -s 10.7.0.0/24 ! -d 10.7.0.0/24 -j SNAT --to $ip
ExecStart=$iptables_path -I INPUT -p udp --dport $port -j ACCEPT
ExecStart=$iptables_path -I FORWARD -s 10.7.0.0/24 -j ACCEPT
ExecStart=$iptables_path -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
ExecStop=$iptables_path -t nat -D POSTROUTING -s 10.7.0.0/24 ! -d 10.7.0.0/24 -j SNAT --to $ip
ExecStop=$iptables_path -D INPUT -p udp --dport $port -j ACCEPT
ExecStop=$iptables_path -D FORWARD -s 10.7.0.0/24 -j ACCEPT
ExecStop=$iptables_path -D FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT" > /etc/systemd/system/wg-iptables.service
		if [[ -n "$ip6" ]]; then
			echo "ExecStart=$ip6tables_path -t nat -A POSTROUTING -s fddd:2c4:2c4:2c4::/64 ! -d fddd:2c4:2c4:2c4::/64 -j SNAT --to $ip6
ExecStart=$ip6tables_path -I FORWARD -s fddd:2c4:2c4:2c4::/64 -j ACCEPT
ExecStart=$ip6tables_path -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
ExecStop=$ip6tables_path -t nat -D POSTROUTING -s fddd:2c4:2c4:2c4::/64 ! -d fddd:2c4:2c4:2c4::/64 -j SNAT --to $ip6
ExecStop=$ip6tables_path -D FORWARD -s fddd:2c4:2c4:2c4::/64 -j ACCEPT
ExecStop=$ip6tables_path -D FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT" >> /etc/systemd/system/wg-iptables.service
		fi
		echo "RemainAfterExit=yes
[Install]
WantedBy=multi-user.target" >> /etc/systemd/system/wg-iptables.service
		systemctl enable --now wg-iptables.service
	fi
	# Generates the custom client.conf
	new_client_setup
	# Enable and start the wg-quick service
	systemctl enable --now wg-quick@wg0.service
	# Set up automatic updates for BoringTun if the user wanted to
	if [[ "$boringtun_updates" =~ ^[yY]$ ]]; then
		# Deploy upgrade script
		cat << 'EOF' > /usr/local/sbin/boringtun-upgrade
#!/bin/bash
latest=$(wget -qO- https://wg.nyr.be/1/latest 2>/dev/null || curl -sL https://wg.nyr.be/1/latest 2>/dev/null)
# If server did not provide an appropriate response, exit
if ! head -1 <<< "$latest" | grep -qiE "^boringtun.+[0-9]+\.[0-9]+.*$"; then
	echo "Update server unavailable"
	exit
fi
current=$(boringtun -V)
if [[ "$current" != "$latest" ]]; then
	download="https://wg.nyr.be/1/latest/download"
	xdir=$(mktemp -d)
	# If download and extraction are successful, upgrade the boringtun binary
	if { wget -qO- "$download" 2>/dev/null || curl -sL "$download" ; } | tar xz -C "$xdir" --wildcards "boringtun-*/boringtun" --strip-components 1; then
		systemctl stop wg-quick@wg0.service
		rm -f /usr/local/sbin/boringtun
		mv "$xdir"/boringtun /usr/local/sbin/boringtun
		systemctl start wg-quick@wg0.service
		echo "Succesfully updated to $(boringtun -V)"
	else
		echo "boringtun update failed"
	fi
	rm -rf "$xdir"
else
	echo "$current is up to date"
fi
EOF
		chmod +x /usr/local/sbin/boringtun-upgrade
		# Add cron job to run the updater daily at a random time between 3:00 and 5:59
		{ crontab -l 2>/dev/null; echo "$(( $RANDOM % 60 )) $(( $RANDOM % 3 + 3 )) * * * /usr/local/sbin/boringtun-upgrade &>/dev/null" ; } | crontab -
	fi
	echo
	qrencode -t UTF8 < ~/"$client.conf"
	echo -e '\xE2\x86\x91 That is a QR code containing the client configuration.'
	echo
	# If the kernel module didn't load, system probably had an outdated kernel
	# We'll try to help, but will not will not force a kernel upgrade upon the user
	if [[ ! "$is_container" -eq 0 ]] && ! modprobe -nq wireguard; then
		echo "Warning!"
		echo "Installation was finished, but the WireGuard kernel module could not load."
		if [[ "$os" == "ubuntu" && "$os_version" -eq 1804 ]]; then
		echo 'Upgrade the kernel and headers with "apt-get install linux-generic" and restart.'
		elif [[ "$os" == "debian" && "$os_version" -eq 10 ]]; then
		echo "Upgrade the kernel with \"apt-get install linux-image-$architecture\" and restart."
		elif [[ "$os" == "centos" && "$os_version" -le 8 ]]; then
			echo "Reboot the system to load the most recent kernel."
		fi
	else
		echo "Finished!"
	fi
	echo
	echo "The client configuration is available in:" ~/"$client.conf"
	echo "New clients can be added by running this script again."
else
	clear
	echo "WireGuard is already installed."
	echo
	echo "Select an option:"
	echo "   1) Add a new client"
	echo "   2) Remove an existing client"
	echo "   3) Remove WireGuard"
	echo "   4) Exit"
	read -p "Option: " option
	until [[ "$option" =~ ^[1-4]$ ]]; do
		echo "$option: invalid selection."
		read -p "Option: " option
	done
	case "$option" in
		1)
			echo
			echo "Provide a name for the client:"
			read -p "Name: " unsanitized_client
			# Allow a limited set of characters to avoid conflicts
			client=$(sed 's/[^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-]/_/g' <<< "$unsanitized_client")
			while [[ -z "$client" ]] || grep -q "^# BEGIN_PEER $client$" /etc/wireguard/wg0.conf; do
				echo "$client: invalid name."
				read -p "Name: " unsanitized_client
				client=$(sed 's/[^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-]/_/g' <<< "$unsanitized_client")
			done
			echo
			new_client_dns
			new_client_setup
			# Append new client configuration to the WireGuard interface
			wg addconf wg0 <(sed -n "/^# BEGIN_PEER $client/,/^# END_PEER $client/p" /etc/wireguard/wg0.conf)
			echo
			qrencode -t UTF8 < ~/"$client.conf"
			echo -e '\xE2\x86\x91 That is a QR code containing your client configuration.'
			echo
			echo "$client added. Configuration available in:" ~/"$client.conf"
			exit
		;;
		2)
			# This option could be documented a bit better and maybe even be simplified
			# ...but what can I say, I want some sleep too
			number_of_clients=$(grep -c '^# BEGIN_PEER' /etc/wireguard/wg0.conf)
			if [[ "$number_of_clients" = 0 ]]; then
				echo
				echo "There are no existing clients!"
				exit
			fi
			echo
			echo "Select the client to remove:"
			grep '^# BEGIN_PEER' /etc/wireguard/wg0.conf | cut -d ' ' -f 3 | nl -s ') '
			read -p "Client: " client_number
			until [[ "$client_number" =~ ^[0-9]+$ && "$client_number" -le "$number_of_clients" ]]; do
				echo "$client_number: invalid selection."
				read -p "Client: " client_number
			done
			client=$(grep '^# BEGIN_PEER' /etc/wireguard/wg0.conf | cut -d ' ' -f 3 | sed -n "$client_number"p)
			echo
			read -p "Confirm $client removal? [y/N]: " remove
			until [[ "$remove" =~ ^[yYnN]*$ ]]; do
				echo "$remove: invalid selection."
				read -p "Confirm $client removal? [y/N]: " remove
			done
			if [[ "$remove" =~ ^[yY]$ ]]; then
				# The following is the right way to avoid disrupting other active connections:
				# Remove from the live interface
				wg set wg0 peer "$(sed -n "/^# BEGIN_PEER $client$/,\$p" /etc/wireguard/wg0.conf | grep -m 1 PublicKey | cut -d " " -f 3)" remove
				# Remove from the configuration file
				sed -i "/^# BEGIN_PEER $client/,/^# END_PEER $client/d" /etc/wireguard/wg0.conf
				echo
				echo "$client removed!"
			else
				echo
				echo "$client removal aborted!"
			fi
			exit
		;;
		3)
			echo
			read -p "Confirm WireGuard removal? [y/N]: " remove
			until [[ "$remove" =~ ^[yYnN]*$ ]]; do
				echo "$remove: invalid selection."
				read -p "Confirm WireGuard removal? [y/N]: " remove
			done
			if [[ "$remove" =~ ^[yY]$ ]]; then
				port=$(grep '^ListenPort' /etc/wireguard/wg0.conf | cut -d " " -f 3)
				if systemctl is-active --quiet firewalld.service; then
					ip=$(firewall-cmd --direct --get-rules ipv4 nat POSTROUTING | grep '\-s 10.7.0.0/24 '"'"'!'"'"' -d 10.7.0.0/24' | grep -oE '[^ ]+$')
					# Using both permanent and not permanent rules to avoid a firewalld reload.
					firewall-cmd --remove-port="$port"/udp
					firewall-cmd --zone=trusted --remove-source=10.7.0.0/24
					firewall-cmd --permanent --remove-port="$port"/udp
					firewall-cmd --permanent --zone=trusted --remove-source=10.7.0.0/24
					firewall-cmd --direct --remove-rule ipv4 nat POSTROUTING 0 -s 10.7.0.0/24 ! -d 10.7.0.0/24 -j SNAT --to "$ip"
					firewall-cmd --permanent --direct --remove-rule ipv4 nat POSTROUTING 0 -s 10.7.0.0/24 ! -d 10.7.0.0/24 -j SNAT --to "$ip"
					if grep -qs 'fddd:2c4:2c4:2c4::1/64' /etc/wireguard/wg0.conf; then
						ip6=$(firewall-cmd --direct --get-rules ipv6 nat POSTROUTING | grep '\-s fddd:2c4:2c4:2c4::/64 '"'"'!'"'"' -d fddd:2c4:2c4:2c4::/64' | grep -oE '[^ ]+$')
						firewall-cmd --zone=trusted --remove-source=fddd:2c4:2c4:2c4::/64
						firewall-cmd --permanent --zone=trusted --remove-source=fddd:2c4:2c4:2c4::/64
						firewall-cmd --direct --remove-rule ipv6 nat POSTROUTING 0 -s fddd:2c4:2c4:2c4::/64 ! -d fddd:2c4:2c4:2c4::/64 -j SNAT --to "$ip6"
						firewall-cmd --permanent --direct --remove-rule ipv6 nat POSTROUTING 0 -s fddd:2c4:2c4:2c4::/64 ! -d fddd:2c4:2c4:2c4::/64 -j SNAT --to "$ip6"
					fi
				else
					systemctl disable --now wg-iptables.service
					rm -f /etc/systemd/system/wg-iptables.service
				fi
				systemctl disable --now wg-quick@wg0.service
				rm -f /etc/systemd/system/wg-quick@wg0.service.d/boringtun.conf
				rm -f /etc/sysctl.d/99-wireguard-forward.conf
				# Different packages were installed if the system was containerized or not
				if [[ ! "$is_container" -eq 0 ]]; then
					if [[ "$os" == "ubuntu" ]]; then
						# Ubuntu
						rm -rf /etc/wireguard/
						apt-get remove --purge -y wireguard wireguard-tools
					elif [[ "$os" == "debian" && "$os_version" -ge 11 ]]; then
						# Debian 11 or higher
						rm -rf /etc/wireguard/
						apt-get remove --purge -y wireguard wireguard-tools
					elif [[ "$os" == "debian" && "$os_version" -eq 10 ]]; then
						# Debian 10
						rm -rf /etc/wireguard/
						apt-get remove --purge -y wireguard wireguard-dkms wireguard-tools
					elif [[ "$os" == "centos" && "$os_version" -eq 8 ]]; then
						# CentOS 8
						dnf remove -y kmod-wireguard wireguard-tools
						rm -rf /etc/wireguard/
					elif [[ "$os" == "centos" && "$os_version" -eq 7 ]]; then
						# CentOS 7
						yum remove -y kmod-wireguard wireguard-tools
						rm -rf /etc/wireguard/
					elif [[ "$os" == "fedora" ]]; then
						# Fedora
						dnf remove -y wireguard-tools
						rm -rf /etc/wireguard/
					fi
				else
					{ crontab -l 2>/dev/null | grep -v '/usr/local/sbin/boringtun-upgrade' ; } | crontab -
					if [[ "$os" == "ubuntu" ]]; then
						# Ubuntu
						rm -rf /etc/wireguard/
						apt-get remove --purge -y wireguard-tools
					elif [[ "$os" == "debian" && "$os_version" -ge 11 ]]; then
						# Debian 11 or higher
						rm -rf /etc/wireguard/
						apt-get remove --purge -y wireguard-tools
					elif [[ "$os" == "debian" && "$os_version" -eq 10 ]]; then
						# Debian 10
						rm -rf /etc/wireguard/
						apt-get remove --purge -y wireguard-tools
					elif [[ "$os" == "centos" && "$os_version" -eq 8 ]]; then
						# CentOS 8
						dnf remove -y wireguard-tools
						rm -rf /etc/wireguard/
					elif [[ "$os" == "centos" && "$os_version" -eq 7 ]]; then
						# CentOS 7
						yum remove -y wireguard-tools
						rm -rf /etc/wireguard/
					elif [[ "$os" == "fedora" ]]; then
						# Fedora
						dnf remove -y wireguard-tools
						rm -rf /etc/wireguard/
					fi
					rm -f /usr/local/sbin/boringtun /usr/local/sbin/boringtun-upgrade
				fi
				echo
				echo "WireGuard removed!"
			else
				echo
				echo "WireGuard removal aborted!"
			fi
			exit
		;;
		4)
			exit
		;;
	esac
fi