Проект юного DevOps Глава 3: Настройка OpenVPN

В других версиях OpenVPN процесс и особенности настройки могут отличаться от описанных в данной статье.

#################################################
# Sample OpenVPN 2.0 config file for            #
# multi-client server.                          #
#                                               #
# This file is for the server side              #
# of a many-clients <-> one-server              #
# OpenVPN configuration.                        #
#                                               #
# OpenVPN also supports                         #
# single-machine <-> single-machine             #
# configurations (See the Examples page         #
# on the web site for more info).               #
#                                               #
# This config should work on Windows            #
# or Linux/BSD systems.  Remember on            #
# Windows to quote pathnames and use            #
# double backslashes, e.g.:                     #
# "C:\\Program Files\\OpenVPN\\config\\foo.key" #
#                                               #
# Comments are preceded with '#' or ';'         #
#################################################

# Which local IP address should OpenVPN
# listen on? (optional)
;local a.b.c.d

# Which TCP/UDP port should OpenVPN listen on?
# If you want to run multiple OpenVPN instances
# on the same machine, use a different port
# number for each one.  You will need to
# open up this port on your firewall.
port 1194

# TCP or UDP server?
;proto tcp
proto udp

# "dev tun" will create a routed IP tunnel,
# "dev tap" will create an ethernet tunnel.
# Use "dev tap0" if you are ethernet bridging
# and have precreated a tap0 virtual interface
# and bridged it with your ethernet interface.
# If you want to control access policies
# over the VPN, you must create firewall
# rules for the the TUN/TAP interface.
# On non-Windows systems, you can give
# an explicit unit number, such as tun0.
# On Windows, use "dev-node" for this.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
;dev tap
dev tun

# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel if you
# have more than one.  On XP SP2 or higher,
# you may need to selectively disable the
# Windows firewall for the TAP adapter.
# Non-Windows systems usually don't need this.
;dev-node MyTap

# SSL/TLS root certificate (ca), certificate
# (cert), and private key (key).  Each client
# and the server must have their own cert and
# key file.  The server and all clients will
# use the same ca file.
#
# See the "easy-rsa" directory for a series
# of scripts for generating RSA certificates
# and private keys.  Remember to use
# a unique Common Name for the server
# and each of the client certificates.
#
# Any X509 key management system can be used.
# OpenVPN can also use a PKCS #12 formatted key file
# (see "pkcs12" directive in man page).
ca ca.crt
cert server.crt
key server.key  # This file should be kept secret

# Diffie hellman parameters.
# Generate your own with:
#   openssl dhparam -out dh2048.pem 2048
;dh dh2048.pem
dh none

# Network topology
# Should be subnet (addressing via IP)
# unless Windows clients v2.0.9 and lower have to
# be supported (then net30, i.e. a /30 per client)
# Defaults to net30 (not recommended)
;topology subnet

# Configure server mode and supply a VPN subnet
# for OpenVPN to draw client addresses from.
# The server will take 10.8.0.1 for itself,
# the rest will be made available to clients.
# Each client will be able to reach the server
# on 10.8.0.1. Comment this line out if you are
# ethernet bridging. See the man page for more info.
server 10.8.0.0 255.255.255.0

# Maintain a record of client <-> virtual IP address
# associations in this file.  If OpenVPN goes down or
# is restarted, reconnecting clients can be assigned
# the same virtual IP address from the pool that was
# previously assigned.
ifconfig-pool-persist /var/log/openvpn/ipp.txt

# Configure server mode for ethernet bridging.
# You must first use your OS's bridging capability
# to bridge the TAP interface with the ethernet
# NIC interface.  Then you must manually set the
# IP/netmask on the bridge interface, here we
# assume 10.8.0.4/255.255.255.0.  Finally we
# must set aside an IP range in this subnet
# (start=10.8.0.50 end=10.8.0.100) to allocate
# to connecting clients.  Leave this line commented
# out unless you are ethernet bridging.
;server-bridge 10.8.0.4 255.255.255.0 10.8.0.50 10.8.0.100

# Configure server mode for ethernet bridging
# using a DHCP-proxy, where clients talk
# to the OpenVPN server-side DHCP server
# to receive their IP address allocation
# and DNS server addresses.  You must first use
# your OS's bridging capability to bridge the TAP
# interface with the ethernet NIC interface.
# Note: this mode only works on clients (such as
# Windows), where the client-side TAP adapter is
# bound to a DHCP client.
;server-bridge

# Push routes to the client to allow it
# to reach other private subnets behind
# the server.  Remember that these
# private subnets will also need
# to know to route the OpenVPN client
# address pool (10.8.0.0/255.255.255.0)
# back to the OpenVPN server.
;push "route 192.168.10.0 255.255.255.0"
;push "route 192.168.20.0 255.255.255.0"

# To assign specific IP addresses to specific
# clients or if a connecting client has a private
# subnet behind it that should also have VPN access,
# use the subdirectory "ccd" for client-specific
# configuration files (see man page for more info).

# EXAMPLE: Suppose the client
# having the certificate common name "Thelonious"
# also has a small subnet behind his connecting
# machine, such as 192.168.40.128/255.255.255.248.
# First, uncomment out these lines:
;client-config-dir ccd
;route 192.168.40.128 255.255.255.248
# Then create a file ccd/Thelonious with this line:
#   iroute 192.168.40.128 255.255.255.248
# This will allow Thelonious' private subnet to
# access the VPN.  This example will only work
# if you are routing, not bridging, i.e. you are
# using "dev tun" and "server" directives.

# EXAMPLE: Suppose you want to give
# Thelonious a fixed VPN IP address of 10.9.0.1.
# First uncomment out these lines:
;client-config-dir ccd
;route 10.9.0.0 255.255.255.252
# Then add this line to ccd/Thelonious:
#   ifconfig-push 10.9.0.1 10.9.0.2

# Suppose that you want to enable different
# firewall access policies for different groups
# of clients.  There are two methods:
# (1) Run multiple OpenVPN daemons, one for each
#     group, and firewall the TUN/TAP interface
#     for each group/daemon appropriately.
# (2) (Advanced) Create a script to dynamically
#     modify the firewall in response to access
#     from different clients.  See man
#     page for more info on learn-address script.
;learn-address ./script

# If enabled, this directive will configure
# all clients to redirect their default
# network gateway through the VPN, causing
# all IP traffic such as web browsing and
# and DNS lookups to go through the VPN
# (The OpenVPN server machine may need to NAT
# or bridge the TUN/TAP interface to the internet
# in order for this to work properly).
push "redirect-gateway def1 bypass-dhcp"

# Certain Windows-specific network settings
# can be pushed to clients, such as DNS
# or WINS server addresses.  CAVEAT:
# http://openvpn.net/faq.html#dhcpcaveats
# The addresses below refer to the public
# DNS servers provided by opendns.com.
push "dhcp-option DNS 208.67.222.222"
push "dhcp-option DNS 208.67.220.220"

# Uncomment this directive to allow different
# clients to be able to "see" each other.
# By default, clients will only see the server.
# To force clients to only see the server, you
# will also need to appropriately firewall the
# server's TUN/TAP interface.
;client-to-client

# Uncomment this directive if multiple clients
# might connect with the same certificate/key
# files or common names.  This is recommended
# only for testing purposes.  For production use,
# each client should have its own certificate/key
# pair.
#
# IF YOU HAVE NOT GENERATED INDIVIDUAL
# CERTIFICATE/KEY PAIRS FOR EACH CLIENT,
# EACH HAVING ITS OWN UNIQUE "COMMON NAME",
# UNCOMMENT THIS LINE OUT.
;duplicate-cn

# The keepalive directive causes ping-like
# messages to be sent back and forth over
# the link so that each side knows when
# the other side has gone down.
# Ping every 10 seconds, assume that remote
# peer is down if no ping received during
# a 120 second time period.
keepalive 10 120

# For extra security beyond that provided
# by SSL/TLS, create an "HMAC firewall"
# to help block DoS attacks and UDP port flooding.
#
# Generate with:
#   openvpn --genkey tls-auth ta.key
#
# The server and each client must have
# a copy of this key.
# The second parameter should be '0'
# on the server and '1' on the clients.
tls-crypt ta.key # This file is secret

# Select a cryptographic cipher.
# This config item must be copied to
# the client config file as well.
# Note that v2.4 client/server will automatically
# negotiate AES-256-GCM in TLS mode.
# See also the ncp-cipher option in the manpage
cipher AES-256-GCM
auth SHA256

# Enable compression on the VPN link and push the
# option to the client (v2.4+ only, for earlier
# versions see below)
;compress lz4-v2
;push "compress lz4-v2"

# For compression compatible with older clients use comp-lzo
# If you enable it here, you must also
# enable it in the client config file.
;comp-lzo

# The maximum number of concurrently connected
# clients we want to allow.
;max-clients 100

# It's a good idea to reduce the OpenVPN
# daemon's privileges after initialization.
#
# You can uncomment this out on
# non-Windows systems.
user nobody
group nobody

# The persist options will try to avoid
# accessing certain resources on restart
# that may no longer be accessible because
# of the privilege downgrade.
persist-key
persist-tun

# Output a short status file showing
# current connections, truncated
# and rewritten every minute.
status /var/log/openvpn/openvpn-status.log

# By default, log messages will go to the syslog (or
# on Windows, if running as a service, they will go to
# the "\Program Files\OpenVPN\log" directory).
# Use log or log-append to override this default.
# "log" will truncate the log file on OpenVPN startup,
# while "log-append" will append to it.  Use one
# or the other (but not both).
;log         /var/log/openvpn/openvpn.log
;log-append  /var/log/openvpn/openvpn.log

# Set the appropriate level of log
# file verbosity.
#
# 0 is silent, except for fatal errors
# 4 is reasonable for general usage
# 5 and 6 can help to debug connection problems
# 9 is extremely verbose
verb 3

# Silence repeating messages.  At most 20
# sequential messages of the same message
# category will be output to the log.
;mute 20

# Notify the client that when the server restarts so it
# can automatically reconnect.
explicit-exit-notify 1

Значение «eth0», которое применятся в нескольких опциях - это имя интерфейса vm, который смотрит в сеть - в вашем случае он может отличаться:

nikolay@vpn:~$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 0a:67:45:3e:3f:03 brd ff:ff:ff:ff:ff:ff
    altname enp0s3
    altname ens3
    inet 10.0.0.5/24 metric 100 brd 10.0.0.255 scope global dynamic eth0
       valid_lft 22804sec preferred_lft 22804sec

Опция «-p» может быть задана как «udp» или «tcp» - это зависит от настроек OpenVPN (по умолчанию используется «udp»).

Опция «--dport» тоже может быть отлична от значения по умолчанию 1194 - это тоже задается в настройках OpenVPN.

##############################################
# Sample client-side OpenVPN 2.0 config file #
# for connecting to multi-client server.     #
#                                            #
# This configuration can be used by multiple #
# clients, however each client should have   #
# its own cert and key files.                #
#                                            #
# On Windows, you might want to rename this  #
# file so it has a .ovpn extension           #
##############################################

# Specify that we are a client and that we
# will be pulling certain config file directives
# from the server.
client

# Use the same setting as you are using on
# the server.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
;dev tap
dev tun

# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel
# if you have more than one.  On XP SP2,
# you may need to disable the firewall
# for the TAP adapter.
;dev-node MyTap

# Are we connecting to a TCP or
# UDP server?  Use the same setting as
# on the server.
;proto tcp
proto udp

# The hostname/IP and port of the server.
# You can have multiple remote entries
# to load balance between the servers.
remote vpn.justnikobird.ru 1194
;remote my-server-2 1194

# Choose a random host from the remote
# list for load-balancing.  Otherwise
# try hosts in the order specified.
;remote-random

# Keep trying indefinitely to resolve the
# host name of the OpenVPN server.  Very useful
# on machines which are not permanently connected
# to the internet such as laptops.
resolv-retry infinite

# Most clients don't need to bind to
# a specific local port number.
nobind

# Downgrade privileges after initialization (non-Windows only)
user nobody
group nobody

# Try to preserve some state across restarts.
persist-key
persist-tun

# If you are connecting through an
# HTTP proxy to reach the actual OpenVPN
# server, put the proxy server/IP and
# port number here.  See the man page
# if your proxy server requires
# authentication.
;http-proxy-retry # retry on connection failures
;http-proxy [proxy server] [proxy port #]

# Wireless networks often produce a lot
# of duplicate packets.  Set this flag
# to silence duplicate packet warnings.
;mute-replay-warnings

# SSL/TLS parms.
# See the server config file for more
# description.  It's best to use
# a separate .crt/.key file pair
# for each client.  A single ca
# file can be used for all clients.
;ca ca.crt
;cert client.crt
;key client.key

# Verify server certificate by checking that the
# certificate has the correct key usage set.
# This is an important precaution to protect against
# a potential attack discussed here:
#  http://openvpn.net/howto.html#mitm
#
# To use this feature, you will need to generate
# your server certificates with the keyUsage set to
#   digitalSignature, keyEncipherment
# and the extendedKeyUsage to
#   serverAuth
# EasyRSA can do this for you.
remote-cert-tls server

# If a tls-auth key is used on the server
# then every client must also have the key.
;tls-crypt ta.key 1

# Select a cryptographic cipher.
# If the cipher option is used on the server
# then you must also specify it here.
# Note that v2.4 client/server will automatically
# negotiate AES-256-GCM in TLS mode.
# See also the data-ciphers option in the manpage
cipher AES-256-GCM
auth SHA256
key-direction 1

# Enable compression on the VPN link.
# Don't enable this unless it is also
# enabled in the server config file.
#comp-lzo

# Set log file verbosity.
verb 3

# Silence repeating messages
;mute 20

Версия на GitHub

#!/bin/bash

# активируем опцию, которая прерывает выполнение скрипта, если любая команда завершается с ненулевым статусом
set -e

# проверим, запущен ли скрипт от пользователя root
if [[ "${UID}" -ne 0 ]]; then
  echo "You need to run this script as root!"
  exit 1
fi

# проверим подключен ли репозиторий
if [[ ! $(grep -rhE ^deb /etc/apt/sources.list*) == *"deb https://repo.justnikobird.ru:1111/lab focal main"* ]]; then
  echo -e "Lab repo not connected!\nPlease run vm_start.sh script!\n"
  exit 1
fi

# функция, которая проверяет наличие пакета в системе и в случае его отсутствия выполняет установку
command_check() {
  if ! command -v "$1" &>/dev/null; then
    echo -e "\n====================\n$2 could not be found!\nInstalling...\n====================\n"
    apt-get install -y "$3"
    echo -e "\nDONE\n"
  fi
}

# функция, которая проверяет наличие правила в iptables и в случае отсутствия применяет его
iptables_add() {
  if ! iptables -C "$@" &>/dev/null; then
    iptables -A "$@"
  fi
}

# функция, которая проверяет наличие nat-правила в iptables и в случае отсутствия применяет его
iptables_nat_add() {
  if ! iptables -t nat -C "$@" &>/dev/null; then
    iptables -t nat -A "$@"
  fi
}

# функция, которая проверяет валидность пути в linux-системе
path_request() {
  while true; do
    read -r -e -p $'\n\n'"Please input valid path to ${1}: " path
    if [ -f "$path" ]; then
      echo "$path"
      break
    fi
  done
}

# выполним настройке OpenVPN
echo -e "\n====================\nOpenVPN server config\n===================="

while true; do
  read -r -n 1 -p "Continue or Skip? (c|s) " cs
  case $cs in
  [Cc]*)

    # установим все необходимые пакеты используя функцию command_check
    systemctl restart systemd-timesyncd.service
    apt-get update
    command_check openvpn "Openvpn" openvpn-lab
    command_check iptables "Iptables" iptables
    command_check netfilter-persistent "Netfilter-persistent" iptables-persistent
    command_check basename "Basename" coreutils

    # проверим наличие файла /etc/sysctl.conf в системе
    if [ ! -f /etc/sysctl.conf ]; then
      echo "File /etc/sysctl.conf not found!"
      exit 1
    fi

    # запросим путь до файла сертификата и перенесем его в рабочую директорию программы
    server_crt=$(path_request certificate)
    cp "$server_crt" /etc/openvpn/server/
    server_crt_file=$(basename "$server_crt")

    # запросим путь до файла ключа и перенесем его в рабочую директорию программы
    server_key=$(path_request key)
    cp "$server_key" /etc/openvpn/server/
    server_key_file=$(basename "$server_key")

    # запросим путь до файла ca-сертификата и перенесем его в рабочую директорию программы
    ca_crt=$(path_request "ca certificate")
    cp "$ca_crt" /etc/openvpn/server/
    cp "$ca_crt" /etc/openvpn/clients_config/keys/
    ca_crt_file=$(basename "$ca_crt")

    cd /etc/openvpn/server/

    # сгенерируем ключ для tls-crypt
    openvpn --genkey --secret ta.key
    cp /etc/openvpn/server/ta.key /etc/openvpn/clients_config/keys/
    echo -e "\n====================\nTls-crypt-key generated /etc/openvpn/server/ta.key\n====================\n"

    # внесем изменения в конфигурационный файл open-vpn
    sed -r -i 's/(^ca\s).*$/\1'"$ca_crt_file"'/' /etc/openvpn/server/server.conf
    sed -r -i 's/(^cert\s).*$/\1'"$server_crt_file"'/' /etc/openvpn/server/server.conf
    sed -r -i 's/(^key\s).*$/\1'"$server_key_file"'/' /etc/openvpn/server/server.conf

    # активируем функцию маршрутизации
    echo -e "\n====================\nIp forward configing\n====================\n"
    sed -i 's/#\?\(net.ipv4.ip_forward=1\s*\).*$/\1/' /etc/sysctl.conf
    sysctl -p
    echo -e "\nDONE\n"

    # cоздадим группу nobody для корректной работы vpn-сервиса
    if ! grep -q "nobody" /etc/group; then
      groupadd nobody
      echo -e "\n====================\nNobody group created\n====================\n"
    fi

    # выполним настройку openvpn
    echo -e "\n====================\nOpenVPN configuration\n====================\n"

    while true; do
      # выведем запрос для выбора транспорта для vpn (udp или tcp)
      read -r -n 3 -p $'\n'"OpenVPN protocol (tcp|udp) (default udp): " proto
      case $proto in
      tcp)
        # в случае выбора tcp внесем настройки в конфигурационные файлы openvpn
        sed -r -i 's/(^proto\sudp$)/\;\1/' /etc/openvpn/server/server.conf
        sed -r -i 's/^\;(proto\stcp$)/\1/' /etc/openvpn/server/server.conf
        sed -r -i 's/(^proto\sudp$)/\;\1/' /etc/openvpn/clients_config/confiles/base.conf
        sed -r -i 's/^\;(proto\stcp$)/\1/' /etc/openvpn/clients_config/confiles/base.conf
        sed -r -i 's/(^explicit-exit-notify\s1$)/\;\1/' /etc/openvpn/server/server.conf
        break
        ;;
      udp)
        # в случае выбора udp вносить изменения не нужно, так как udp настроен по умолчанию
        break
        ;;
      *) echo -e "\nPlease answer tcp or udp!\n" ;;
      esac
    done

    # запросим у оператора ввести порт, через который будет работать openvpn
    while true; do
      read -r -n 4 -p $'\n\n'"OpenVPN port number (default 1194): " port
      re='^[0-9]+$'
      if ! [[ $port =~ $re ]]; then
        echo "error: Not a number" >&2
        exit 1
      else
        if [ "$port" == 1194 ]; then
          break
        else
          # в случае если порт отличается от 1194, внесем изменения в конфигурационный файл
          sed -r -i 's/(^port\s).*$/\1'"$port"'/' /etc/openvpn/server/server.conf
          sed -r -i 's/(^port\s).*$/\1'"$port"'/' /etc/openvpn/clients_config/confiles/base.conf
          break
        fi
      fi
    done

    echo -e "\n"
    ip a
    echo -e "\n"

    # запросим hostname или ip openvpn сервера и занесем в конфигурационный файл
    read -r -p $'\n'"The hostname or IP of the server: " host
    sed -r -i 's/(^remote\s).*$/\1'"$host"' '"$port"'/' /etc/openvpn/clients_config/confiles/base.conf

    echo -e "\n====================\nIptables configuration\n====================\n"

    # запросим имя vpn-интерфейса для настройки iptables
    while true; do
      read -r -p $'\n'"VPN interface name: " eth
      if ! ip a | grep -q "$eth"; then
        echo -e "\nWrong interface name!\n"
      else
        break
      fi
    done

    # выполним настройку iptables
    # OpenVPN
    iptables_add INPUT -i "$eth" -m state --state NEW -p "$proto" --dport "$port" -j ACCEPT -m comment --comment openvpn
    # Allow TUN interfaces connections to OpenVPN server
    iptables_add INPUT -i tun+ -j ACCEPT -m comment --comment openvpn
    # Allow TUN interfaces connections to be forwarded through interfaces
    iptables_add FORWARD -i tun+ -j ACCEPT -m comment --comment openvpn
    iptables_add FORWARD -i tun+ -o "$eth" -m state --state RELATED,ESTABLISHED -j ACCEPT -m comment --comment openvpn
    iptables_add FORWARD -i "$eth" -o tun+ -m state --state RELATED,ESTABLISHED -j ACCEPT -m comment --comment openvpn
    # NAT the VPN client traffic to the interface
    iptables_nat_add POSTROUTING -s 10.8.0.0/24 -o "$eth" -j MASQUERADE -m comment --comment openvpn
    echo -e "\n====================\nSaving iptables config\n====================\n"
    service netfilter-persistent save
    echo -e "\nDONE\n"

    # перезагрузим сервис openvpn
    echo -e "\n====================\nRestarting Open-VPN service...\n====================\n"
    systemctl restart openvpn-server@server.service
    systemctl enable openvpn-server@server.service
    echo -e "\nDONE\n"
    break
    ;;
  [Ss]*)
    echo -e "\n"
    break
    ;;
  *) echo -e "\nPlease answer C or S!\n" ;;
  esac
done

# выполним настройку клиентского конфигурационного файла
echo -e "\n====================\nCreate OpenVPN client config-file\n===================="

while true; do
  read -r -n 1 -p "Continue or Skip? (c|s) " cs
  case $cs in
  [Cc]*)
    # запросим клиентский сертификат и перенесем в рабочую директорию программы
    client_crt=$(path_request "client certificate")
    cp "$client_crt" /etc/openvpn/clients_config/keys/
    client_crt_file=$(basename "$client_crt")

    # запросим клиентский ключ и перенесем в рабочую директорию программы
    client_key=$(path_request "client key")
    cp "$client_key" /etc/openvpn/clients_config/keys/
    client_key_file=$(basename "$client_key")

    # запустим скрипт для генерации клиентского конфигурационного файла
    read -r -p $'\n'"Client name: " client_name
    if /etc/openvpn/clients_config/make_config.sh "$client_crt_file" "$client_key_file" "$client_name"; then
      echo -e "\nDONE!\n\nCheck file /etc/openvpn/clients_config/${client_name}.ovpn"
    fi
    break
    ;;

  [Ss]*)
    echo -e "\n"
    break
    ;;
  *) echo -e "\nPlease answer C or S!\n" ;;
  esac
done

echo -e "\nOK\n"
exit 0