#!/bin/bash
#
# https://github.com/Nyr/openvpn-install
#
# Copyright (c) 2013 Nyr. Released under the MIT License.


if grep -qs "14.04" /etc/os-release; then
        echo "Ubuntu 14.04 is too old and not supported"
        exit
fi

if grep -qs "jessie" /etc/os-release; then
        echo "Debian 8 is too old and not supported"
        exit
fi

if grep -qs "CentOS release 6" /etc/redhat-release; then
        echo "CentOS 6 is too old and not supported"
        exit
fi

if grep -qs "Ubuntu 16.04" /etc/os-release; then
        echo 'Ubuntu 16.04 is no longer supported in the current version of openvpn-install
Use an older version if Ubuntu 16.04 support is needed: https://git.io/vpn1604'
        exit
fi

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

if [[ "$EUID" -ne 0 ]]; then
        echo "Sorry, you need to run this as root"
        exit
fi

if [[ ! -e /dev/net/tun ]]; then
        echo "The TUN device is not available
You need to enable TUN before running this script"
        exit
fi

if ! iptables -t nat -nL &>/dev/null; then
        echo "Unable to initialize the iptables/netfilter NAT table, setup can't continue.
Make sure that your system has iptables/netfilter available.
If using OpenVZ, ask your provider to enable full netfilter support."
        exit
fi

if [[ -e /etc/debian_version ]]; then
        os="debian"
        group_name="nogroup"
elif [[ -e /etc/centos-release || -e /etc/redhat-release ]]; then
        os="centos"
        group_name="nobody"
else
        echo "Looks like you aren't running this installer on Debian, Ubuntu or CentOS"
        exit
fi

new_client () {
        # Generates the custom client.ovpn
        {
        cat /etc/openvpn/server/client-common.txt
        echo "<ca>"
        cat /etc/openvpn/server/easy-rsa/pki/ca.crt
        echo "</ca>"
        echo "<cert>"
        sed -ne '/BEGIN CERTIFICATE/,$ p' /etc/openvpn/server/easy-rsa/pki/issued/"$1".crt
        echo "</cert>"
        echo "<key>"
        cat /etc/openvpn/server/easy-rsa/pki/private/"$1".key
        echo "</key>"
        echo "<tls-crypt>"
        sed -ne '/BEGIN OpenVPN Static key/,$ p' /etc/openvpn/server/tc.key
        echo "</tls-crypt>"
        } > ~/"$1".ovpn
}

if [[ -e /etc/openvpn/server/server.conf ]]; then
        while :
        do
        clear
                echo "Looks like OpenVPN is already installed."
                echo
                echo "What do you want to do?"
                echo "   1) Add a new user"
                echo "   2) Revoke an existing user"
                echo "   3) Remove OpenVPN"
                echo "   4) Exit"
                read -p "Select an option: " option
                until [[ "$option" =~ ^[1-4]$ ]]; do
                        echo "$option: invalid selection."
                        read -p "Select an option: " option
                done
                case "$option" in
                        1)
                        echo
                        echo "Tell me a name for the client certificate."
                        read -p "Client name: " unsanitized_client
                        client=$(sed 's/[^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-]/_/g' <<< "$unsanitized_client")
                        while [[ -z "$client" || -e /etc/openvpn/server/easy-rsa/pki/issued/"$client".crt ]]; do
                                echo "$client: invalid client name."
                                read -p "Client name: " unsanitized_client
                                client=$(sed 's/[^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-]/_/g' <<< "$unsanitized_client")
                        done
                        cd /etc/openvpn/server/easy-rsa/
                        EASYRSA_CERT_EXPIRE=3650 ./easyrsa build-client-full "$client" nopass
                        # Generates the custom client.ovpn
                        new_client "$client"
                        echo
                        echo "Client $client added, configuration is available at:" ~/"$client.ovpn"
                        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=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -c "^V")
                        if [[ "$number_of_clients" = 0 ]]; then
                                echo
                                echo "You have no existing clients!"
                                exit
                        fi
                        echo
                        echo "Select the existing client certificate you want to revoke:"
                        tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | nl -s ') '
                        read -p "Select one client: " client_number
                        until [[ "$client_number" =~ ^[0-9]+$ && "$client_number" -le "$number_of_clients" ]]; do
                                echo "$client_number: invalid selection."
                                read -p "Select one client: " client_number
                        done
                        client=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | sed -n "$client_number"p)
                        echo
                        read -p "Do you really want to revoke access for client $client? [y/N]: " revoke
                        until [[ "$revoke" =~ ^[yYnN]*$ ]]; do
                                echo "$revoke: invalid selection."
                                read -p "Do you really want to revoke access for client $client? [y/N]: " revoke
                        done
                        if [[ "$revoke" =~ ^[yY]$ ]]; then
                                cd /etc/openvpn/server/easy-rsa/
                                ./easyrsa --batch revoke "$client"
                                EASYRSA_CRL_DAYS=3650 ./easyrsa gen-crl
                                rm -f pki/reqs/"$client".req
                                rm -f pki/private/"$client".key
                                rm -f pki/issued/"$client".crt
                                rm -f /etc/openvpn/server/crl.pem
                                cp /etc/openvpn/server/easy-rsa/pki/crl.pem /etc/openvpn/server/crl.pem
                                # CRL is read with each client connection, when OpenVPN is dropped to nobody
                                chown nobody:"$group_name" /etc/openvpn/server/crl.pem
                                echo
                                echo "Certificate for client $client revoked!"
                        else
                                echo
                                echo "Certificate revocation for client $client aborted!"
                        fi
                        exit
                        ;;
                        3)
                        echo
                        read -p "Do you really want to remove OpenVPN? [y/N]: " remove
                        until [[ "$remove" =~ ^[yYnN]*$ ]]; do
                                echo "$remove: invalid selection."
                                read -p "Do you really want to remove OpenVPN? [y/N]: " remove
                        done
                        if [[ "$remove" =~ ^[yY]$ ]]; then
                                port=$(grep '^port ' /etc/openvpn/server/server.conf | cut -d " " -f 2)
                                protocol=$(grep '^proto ' /etc/openvpn/server/server.conf | cut -d " " -f 2)
                                if pgrep firewalld; then
                                        ip=$(firewall-cmd --direct --get-rules ipv4 nat POSTROUTING | grep '\-s 10.8.0.0/24 '"'"'!'"'"' -d 10.8.0.0/24 -j SNAT --to ' | cut -d " " -f 10)
                                        # Using both permanent and not permanent rules to avoid a firewalld reload.
                                        firewall-cmd --remove-port="$port"/"$protocol"
                                        firewall-cmd --zone=trusted --remove-source=10.8.0.0/24
                                        firewall-cmd --permanent --remove-port="$port"/"$protocol"
                                        firewall-cmd --permanent --zone=trusted --remove-source=10.8.0.0/24
                                        firewall-cmd --direct --remove-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to "$ip"
                                        firewall-cmd --permanent --direct --remove-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to "$ip"
                                else
                                        systemctl disable --now openvpn-iptables.service
                                        rm -f /etc/systemd/system/openvpn-iptables.service
                                fi
                                if sestatus 2>/dev/null | grep "Current mode" | grep -q "enforcing" && [[ "$port" != 1194 ]]; then
                                        semanage port -d -t openvpn_port_t -p "$protocol" "$port"
                                fi
                                systemctl disable --now openvpn-server@server.service
                                rm -rf /etc/openvpn/server
                                rm -f /etc/systemd/system/openvpn-server@server.service.d/disable-limitnproc.conf
                                rm -f /etc/sysctl.d/30-openvpn-forward.conf
                                if [[ "$os" = "debian" ]]; then
                                        apt-get remove --purge -y openvpn
                                else
                                        yum remove openvpn -y
                                fi
                                echo
                                echo "OpenVPN removed!"
                        else
                                echo
                                echo "Removal aborted!"
                        fi
                        exit
                        ;;
                        4) exit;;
                esac
        done
else
        clear
        echo "Welcome to this OpenVPN "road warrior" installer!"
        echo
        echo "I need to ask you a few questions before starting setup."
        echo "You can use the default options and just press enter if you are ok with them."
        # If system has a single IPv4, it is selected automatically. Else, ask the user
        if [[ $(ip addr | grep inet | grep -v inet6 | grep -vEc '127\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}') -eq 1 ]]; then
                ip=$(ip addr | grep inet | grep -v inet6 | grep -vE '127\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}')
        else
                number_of_ips=$(ip addr | grep inet | grep -v inet6 | grep -vEc '127\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}')
                echo
                echo "What IPv4 address should the OpenVPN server bind to?"
                ip addr | grep inet | grep -v inet6 | grep -vE '127\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | nl -s ') '
                read -p "IPv4 address [1]: " ip_number
                until [[ -z "$ip_number" || "$ip_number" =~ ^[0-9]+$ && "$ip_number" -le "$number_of_ips" ]]; do
                        echo "$ip_number: invalid selection."
                        read -p "IPv4 address [1]: " ip_number
                done
                [[ -z "$ip_number" ]] && ip_number="1"
                ip=$(ip addr | grep inet | grep -v inet6 | grep -vE '127\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | sed -n "$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=$(wget -4qO- "http://whatismyip.akamai.com/" || curl -4Ls "http://whatismyip.akamai.com/")
                read -p "Public IPv4 address / hostname [$get_public_ip]: " public_ip
                [ -z "$public_ip" ] && public_ip="$get_public_ip"
        fi
        echo
        echo "Which protocol do you want for OpenVPN connections?"
        echo "   1) UDP (recommended)"
        echo "   2) TCP"
        read -p "Protocol [1]: " protocol
        until [[ -z "$protocol" || "$protocol" =~ ^[12]$ ]]; do
                echo "$protocol: invalid selection."
                read -p "Protocol [1]: " protocol
        done
        case "$protocol" in
                1|"")
                protocol=udp
                ;;
                2)
                protocol=tcp
                ;;
        esac
        echo
        echo "What port do you want OpenVPN listening to?"
        read -p "Port [1194]: " port
        until [[ -z "$port" || "$port" =~ ^[0-9]+$ && "$port" -le 65535 ]]; do
                echo "$port: invalid selection."
                read -p "Port [1194]: " port
        done
        [[ -z "$port" ]] && port="1194"
        echo
        echo "Which DNS do you want to use with the VPN?"
        echo "   1) Current system resolvers"
        echo "   2) 1.1.1.1"
        echo "   3) Google"
        echo "   4) OpenDNS"
        echo "   5) Verisign"
        read -p "DNS [1]: " dns
        until [[ -z "$dns" || "$dns" =~ ^[1-5]$ ]]; do
                echo "$dns: invalid selection."
                read -p "DNS [1]: " dns
        done
        echo
        echo "Finally, tell me a name for the client certificate."
        read -p "Client name [client]: " unsanitized_client
        # Allow a limited set of characters to avoid conflicts
        client=$(sed 's/[^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-]/_/g' <<< "$unsanitized_client")
        [[ -z "$client" ]] && client="client"
        echo
        echo "Okay, that was all I needed. We are ready to set up your OpenVPN server now."
        read -n1 -r -p "Press any key to continue..."
        # If running inside a container, disable LimitNPROC to prevent conflicts
        if systemd-detect-virt -cq; then
                mkdir /etc/systemd/system/openvpn-server@server.service.d/ 2>/dev/null
                echo "[Service]
LimitNPROC=infinity" > /etc/systemd/system/openvpn-server@server.service.d/disable-limitnproc.conf
        fi
        if [[ "$os" = "debian" ]]; then
                apt-get update
                apt-get install openvpn iptables openssl ca-certificates -y
        else
                # Else, the distro is CentOS
                yum install epel-release -y
                yum install openvpn iptables openssl ca-certificates -y
        fi
        # Get easy-rsa
        easy_rsa_url='https://github.com/OpenVPN/easy-rsa/releases/download/v3.0.5/EasyRSA-nix-3.0.5.tgz'
        wget -O ~/easyrsa.tgz "$easy_rsa_url" 2>/dev/null || curl -Lo ~/easyrsa.tgz "$easy_rsa_url"
        tar xzf ~/easyrsa.tgz -C ~/
        mv ~/EasyRSA-3.0.5/ /etc/openvpn/server/
        mv /etc/openvpn/server/EasyRSA-3.0.5/ /etc/openvpn/server/easy-rsa/
        chown -R root:root /etc/openvpn/server/easy-rsa/
        rm -f ~/easyrsa.tgz
        cd /etc/openvpn/server/easy-rsa/
        # Create the PKI, set up the CA and the server and client certificates
        ./easyrsa init-pki
        ./easyrsa --batch build-ca nopass
        EASYRSA_CERT_EXPIRE=3650 ./easyrsa build-server-full server nopass
        EASYRSA_CERT_EXPIRE=3650 ./easyrsa build-client-full "$client" nopass
        EASYRSA_CRL_DAYS=3650 ./easyrsa gen-crl
        # Move the stuff we need
        cp pki/ca.crt pki/private/ca.key pki/issued/server.crt pki/private/server.key pki/crl.pem /etc/openvpn/server
        # CRL is read with each client connection, when OpenVPN is dropped to nobody
        chown nobody:"$group_name" /etc/openvpn/server/crl.pem
        # Generate key for tls-crypt
        openvpn --genkey --secret /etc/openvpn/server/tc.key
        # Create the DH parameters file using the predefined ffdhe2048 group
        echo '-----BEGIN DH PARAMETERS-----
MIIBCAKCAQEA//////////+t+FRYortKmq/cViAnPTzx2LnFg84tNpWp4TZBFGQz
+8yTnc4kmz75fS/jY2MMddj2gbICrsRhetPfHtXV/WVhJDP1H18GbtCFY2VVPe0a
87VXE15/V8k1mE8McODmi3fipona8+/och3xWKE2rec1MKzKT0g6eXq8CrGCsyT7
YdEIqUuyyOP7uWrat2DX9GgdT0Kj3jlN9K5W7edjcrsZCwenyO4KbXCeAvzhzffi
7MA0BM0oNC9hkXL+nOmFg/+OTxIy7vKBg8P+OxtMb61zO7X8vC7CIAXFjvGDfRaD
ssbzSibBsu/6iGtCOGEoXJf//////////wIBAg==
-----END DH PARAMETERS-----' > /etc/openvpn/server/dh.pem
        # Generate server.conf
        echo "local $ip
port $port
proto $protocol
dev tun
ca /etc/openvpn/server/ca.crt
cert /etc/openvpn/server/server.crt
key /etc/openvpn/server/server.key
dh /etc/openvpn/server/dh.pem
auth SHA512
tls-crypt tc.key
topology subnet
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt" > /etc/openvpn/server/server.conf
        echo 'push "redirect-gateway def1 bypass-dhcp"' >> /etc/openvpn/server/server.conf
        # DNS
        case "$dns" in
                1|"")
                # Locate the proper resolv.conf
                # Needed for systems running systemd-resolved
                if grep -q "127.0.0.53" "/etc/resolv.conf"; then
                        resolv_conf="/run/systemd/resolve/resolv.conf"
                else
                        resolv_conf="/etc/resolv.conf"
                fi
                # Obtain the resolvers from resolv.conf and use them for OpenVPN
                grep -v '#' "$resolv_conf" | grep nameserver | grep -E -o '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | while read line; do
                        echo "push \"dhcp-option DNS $line\"" >> /etc/openvpn/server/server.conf
                done
                ;;
                2)
                echo 'push "dhcp-option DNS 1.1.1.1"' >> /etc/openvpn/server/server.conf
                echo 'push "dhcp-option DNS 1.0.0.1"' >> /etc/openvpn/server/server.conf
                ;;
                3)
                echo 'push "dhcp-option DNS 8.8.8.8"' >> /etc/openvpn/server/server.conf
                echo 'push "dhcp-option DNS 8.8.4.4"' >> /etc/openvpn/server/server.conf
                ;;
                4)
                echo 'push "dhcp-option DNS 208.67.222.222"' >> /etc/openvpn/server/server.conf
                echo 'push "dhcp-option DNS 208.67.220.220"' >> /etc/openvpn/server/server.conf
                ;;
                5)
                echo 'push "dhcp-option DNS 64.6.64.6"' >> /etc/openvpn/server/server.conf
                echo 'push "dhcp-option DNS 64.6.65.6"' >> /etc/openvpn/server/server.conf
                ;;
        esac
        echo "keepalive 10 120
cipher AES-256-CBC
user nobody
group $group_name
persist-key
persist-tun
status openvpn-status.log
verb 3
crl-verify /etc/openvpn/server/crl.pem" >> /etc/openvpn/server/server.conf
        if [[ "$protocol" = "udp" ]]; then
                echo "explicit-exit-notify" >> /etc/openvpn/server/server.conf
        fi
        # Enable net.ipv4.ip_forward for the system
        echo 'net.ipv4.ip_forward=1' > /etc/sysctl.d/30-openvpn-forward.conf
        # Enable without waiting for a reboot or service restart
        echo 1 > /proc/sys/net/ipv4/ip_forward
        if pgrep firewalld; then
                # Using both permanent and not permanent rules to avoid a firewalld
                # reload.
                # We don't use --add-service=openvpn because that would only work with
                # the default port and protocol.
                firewall-cmd --add-port="$port"/"$protocol"
                firewall-cmd --zone=trusted --add-source=10.8.0.0/24
                firewall-cmd --permanent --add-port="$port"/"$protocol"
                firewall-cmd --permanent --zone=trusted --add-source=10.8.0.0/24
                # Set NAT for the VPN subnet
                firewall-cmd --direct --add-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to "$ip"
                firewall-cmd --permanent --direct --add-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to "$ip"
        else
                # Create a service to set up persistent iptables rules
                echo "[Unit]
Before=network.target
[Service]
Type=oneshot
ExecStart=/sbin/iptables -t nat -A POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to $ip
ExecStart=/sbin/iptables -I INPUT -p $protocol --dport $port -j ACCEPT
ExecStart=/sbin/iptables -I FORWARD -s 10.8.0.0/24 -j ACCEPT
ExecStart=/sbin/iptables -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
ExecStop=/sbin/iptables -t nat -D POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to $ip
ExecStop=/sbin/iptables -D INPUT -p $protocol --dport $port -j ACCEPT
ExecStop=/sbin/iptables -D FORWARD -s 10.8.0.0/24 -j ACCEPT
ExecStop=/sbin/iptables -D FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
RemainAfterExit=yes
[Install]
WantedBy=multi-user.target" > /etc/systemd/system/openvpn-iptables.service
                systemctl enable --now openvpn-iptables.service
        fi
        # If SELinux is enabled and a custom port was selected, we need this
        if sestatus 2>/dev/null | grep "Current mode" | grep -q "enforcing" && [[ "$port" != 1194 ]]; then
                # Install semanage if not already present
                if ! hash semanage 2>/dev/null; then
                        if grep -qs "CentOS Linux release 7" "/etc/centos-release"; then
                                yum install policycoreutils-python -y
                        else
                                yum install policycoreutils-python-utils -y
                        fi
                fi
                semanage port -a -t openvpn_port_t -p "$protocol" "$port"
        fi
        # If the server is behind a NAT, use the correct IP address
        if [[ "$public_ip" != "" ]]; then
                ip="$public_ip"
        fi
        # client-common.txt is created so we have a template to add further users later
        echo "client
dev tun
proto $protocol
remote $ip $port
resolv-retry infinite
nobind
persist-key
persist-tun
remote-cert-tls server
auth SHA512
cipher AES-256-CBC
ignore-unknown-option block-outside-dns
block-outside-dns
verb 3" > /etc/openvpn/server/client-common.txt
        # Enable and start the OpenVPN service
        systemctl enable --now openvpn-server@server.service
        # Generates the custom client.ovpn
        new_client "$client"
        echo
        echo "Finished!"
        echo
        echo "Your client configuration is available at:" ~/"$client.ovpn"
        echo "If you want to add more clients, just run this script again!"
fi