OpenVPN

Let’s say you have an old dedicated server without AES-NI and you need 200 devices connected to it, but they only route traffic for a web server and a file server on your private network, and about 50% will be actively using the connection, and 50% will be idling, at any given time. As in the previous example this will of course vary somewhat as some users are working on other tasks and alternate this with retrieving files and data through the VPN tunnel. Let’s say you want to make sure each active users will have 10Mbps available, and let’s again assume they actually have that bandwidth on their Internet connection.

100 active users times 10Mbps is 1000Mbps or 1Gbps. Most systems nowadays have this by default, even servers that are several years old. 1000Mbps time 40MHz is about 40000MHz or 40GHz. Older servers with a dual octa-core setup with 2.5GHz will be able to get you to those requirements. With 200 connected devices in this example you would need about 2GB of memory, a fairly low amount.

PiVPN

curl -L https://install.pivpn.io | bash
vim /etc/pivpn/openvpn/setupVars.conf

PLAT=Raspbian
OSCN=buster
USING_UFW=0
pivpnforceipv6route=1
IPv4dev=wlan0
dhcpReserv=1
IPv4addr=10.19.83.103/24
IPv4gw=10.19.83.1
install_user=pi
install_home=/home/pi
VPN=openvpn
pivpnPROTO=udp
pivpnPORT=1194
pivpnDNS1=10.19.83.1
pivpnDNS2=10.19.83.100
pivpnSEARCHDOMAIN=dev.shahed.biz
pivpnHOST=vpn.shahed.biz
TWO_POINT_FOUR=0
pivpnENCRYPT=2048
USE_PREDEFINED_DH_PARAM=0
INPUT_CHAIN_EDITED=0
FORWARD_CHAIN_EDITED=0
INPUT_CHAIN_EDITEDv6=
FORWARD_CHAIN_EDITEDv6=
pivpnDEV=tun0
pivpnNET=10.20.30.0
subnetClass=24
pivpnenableipv6=0
ALLOWED_IPS=""
UNATTUPG=1
INSTALLED_PACKAGES=()
HELP_SHOWN=1

Server

vim /etc/openvpn/server.conf
: <<'END_COMMENT'
dev tun
proto udp
port 1194
ca /etc/openvpn/easy-rsa/pki/ca.crt
cert /etc/openvpn/easy-rsa/pki/issued/pi03_cd0b38fd-1194-4fc2-b8e8-284b04ad0d02.crt
key /etc/openvpn/easy-rsa/pki/private/pi03_cd0b38fd-1194-4fc2-b8e8-284b04ad0d02.key
dh /etc/openvpn/easy-rsa/pki/dh2048.pem
topology subnet
server 10.20.30.0 255.255.255.0
# Set your primary domain name server address for clients
push "dhcp-option DOMAIN dev.shahed.biz" 
push "dhcp-option DNS 10.19.83.1"
push "dhcp-option DNS 10.19.83.100"
# Prevent DNS leaks on Windows
push "block-outside-dns"
# Override the Client default gateway by using 0.0.0.0/1 and
# 128.0.0.0/1 rather than 0.0.0.0/0. This has the benefit of
# overriding but not wiping out the original default gateway.
push "redirect-gateway def1 bypass-dhcp"
client-to-client
client-config-dir /etc/openvpn/ccd
keepalive 15 120
remote-cert-tls client
tls-version-min 1.2
tls-auth /etc/openvpn/easy-rsa/pki/ta.key 0
cipher AES-256-CBC
auth SHA256
user openvpn
group openvpn
persist-key
persist-tun
crl-verify /etc/openvpn/crl.pem
status /var/log/openvpn-status.log 20
status-version 3
syslog
verb 3
#DuplicateCNs allow access control on a less-granular, per user basis.
#Remove # if you will manage access by user instead of device. 
#duplicate-cn
# Generated for use by PiVPN.io
END_COMMENT

openssl dhparam -out /etc/openvpn/easy-rsa/pki/dh1024.pem 1024
openssl dhparam -out /etc/openvpn/easy-rsa/pki/dh2048.pem 2048

sudo systemctl start  [email protected]
sudo systemctl status [email protected]

Client

pivpn add -n shahed_note : <<'EOC' How many days should the certificate last? 1080 Enter the password for the client: Enter the password again to verify: --more-skipped-- ======================================================== Done! shahed_note.ovpn successfully created! shahed_note.ovpn was copied to: /home/pi/ovpns for easy transfer. Please use this profile only on one device and create additional profiles for other devices. ======================================================== EOC
ls -lah /home/pi/ovpns/*.ovpn ls -lah /etc/openvpn/easy-rsa/pki/reqs/*.req ls -lah /etc/openvpn/easy-rsa/pki/issued/*.crt ls -lah /etc/openvpn/easy-rsa/pki/private/*.key		stat -c '%a %n' /home/pi/ovpns/*.ovpn chmod 644 /home/pi/ovpns/*.ovpn chmod 640 /home/pi/ovpns/*.ovpn stat -c '%a %n' /home/pi/ovpns/*.ovpn
ln -s /home/pi/ovpns/shahed_note.ovpn\ /var/shahed/www/vpn.shahed.biz/docs/comn/ovpns/shahed_note.ovpn https://vpn.shahed.biz/docs/comn/ovpns/

Debug

mkdir /etc/openvpn/ccd
systemctl restart openvpn
tail -f /var/log/openvpn.log
sysctl -w net.ipv4.ip_forward=1

nc -uv 10.20.13.1 1194
nc -uv 10.19.83.103 1194
nc -uv 10.19.83.203 1194
nc -uv vpn.shahed.biz 1194
nc -uv vpn0.dev.shahed.biz 1194

Connect

• OpenVPN » Connect » iPhone/iPad
• OpenVPN » Connect » Android
• OpenVPN » Connect » Windows
• OpenVPN » Connect » Mac OS
• OpenVPN » Client » Ubuntu
• OpenVPN » Client » Linux

NAT Route

vim /etc/sysctl.conf

# Uncomment the next line to enable packet forwarding for IPv4
net.ipv4.ip_forward=1

---

sudo sysctl -p
net.ipv4.ip_forward = 1

ip route | grep default
default via 10.19.83.1 dev wlan0 proto dhcp src 10.19.83.103 metric 303

---

sudo vim /etc/ufw/before.rules

# rules should be added to one of these chains:
#   ufw-before-input
#   ufw-before-output
#   ufw-before-forward
#

# Start OpenVPN Rules
# NAT table rules
*nat
:POSTROUTING ACCEPT [0:0]
# Allow traffic from OpenVPN client to wlan0
-A POSTROUTING -s 10.20.30.0/24 -o wlan0 -j MASQUERADE
COMMIT
# End OpenVPN Rules

# Don't delete these required lines, otherwise there will be errors
*filter

---

vim /etc/ufw/sysctl.conf

# Uncomment this to allow this host to route packets between interfaces
net/ipv4/ip_forward=1
net/ipv6/conf/default/forwarding=1
net/ipv6/conf/all/forwarding=1

---

sudo vim /etc/default/ufw

# Set the default forward policy to ACCEPT, DROP or REJECT.  Please note that
# if you change this you will most likely want to adjust your rules
DEFAULT_FORWARD_POLICY="ACCEPT"

---

sudo vim /lib/systemd/system/ufw.service

[Unit]
Description=Uncomplicated firewall
Documentation=man:ufw(8)
DefaultDependencies=no
Before=network.target
After=netfilter-persistent.service

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/lib/ufw/ufw-init start quiet
ExecStop=/lib/ufw/ufw-init stop

[Install]
WantedBy=multi-user.target

---

sudo ufw allow http
sudo ufw allow OpenSSH
sudo ufw allow 1194/udp

systemctl status ufw 
sudo ufw disable
sudo ufw enable

sudo systemctl start openvpn@server
sudo systemctl status openvpn@server

---

ip addr show tun0
:'
5: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 100
    link/none 
    inet 10.20.30.1/24 brd 10.20.30.255 scope global tun0
       valid_lft forever preferred_lft forever
    inet6 fe80::ab3a:dcac:98ba:b7a/64 scope link stable-privacy 
       valid_lft forever preferred_lft forever
'

---

ufw status verbose
: <<'EOC'
Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing), allow (routed)
New profiles: skip

To                         Action      From
--                         ------      ----
22/tcp                     ALLOW IN    Anywhere                  
1194                       ALLOW IN    Anywhere                  
80/tcp                     ALLOW IN    Anywhere                  
1194/udp                   ALLOW IN    Anywhere                  
22/tcp (OpenSSH)           ALLOW IN    Anywhere                  
22/tcp (v6)                ALLOW IN    Anywhere (v6)             
1194 (v6)                  ALLOW IN    Anywhere (v6)             
80/tcp (v6)                ALLOW IN    Anywhere (v6)             
1194/udp (v6)              ALLOW IN    Anywhere (v6)             
22/tcp (OpenSSH (v6))      ALLOW IN    Anywhere (v6)             

Anywhere on wlan0          ALLOW FWD   Anywhere on tun0          
10.19.83.0/24              ALLOW FWD   10.8.0.0/24               
Anywhere (v6) on wlan0     ALLOW FWD   Anywhere (v6) on tun0 
EOC

ufw status numbered
ufw status

Ubuntu Client

cat <<-'EXE'|sudo bash apt-get update;echo;apt list -a --upgradable;apt-get upgrade -y apt-get install -y apt-transport-https ca-certificates gnupg curl software-properties-common EXE curl -fsSL https://swupdate.openvpn.net/repos/repo-public.gpg\ | sudo gpg --dearmor -o /etc/apt/keyrings/openvpn.gpg cat << EOF | sudo tee /etc/apt/sources.list.d/openvpn.list >/dev/null deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/openvpn.gpg]\ http://build.openvpn.net/debian/openvpn/release/2.6 $(lsb_release -cs) main EOF cat <<-'EXE'|sudo bash apt-get update;echo;apt list -a --upgradable;apt-get upgrade -y apt-get install -y openvpn openvpn --version EXE
openvpn config-import\ --name vpn.chorke.org\ --config ~/ovpns/chorke_ceo.ovpn openvpn configs-list openvpn config-remove\ --config vpn.chorke.org openvpn config-remove\ --config ~/ovpns/chorke_ceo.ovpn openvpn config-remove --path\ /net/openvpn/v3/configuration/65c57d54xbd4fx40aex9819x47ba0803d7c5	openvpn session-start\ --config vpn.chorke.org openvpn session-start\ --config ~/ovpns/chorke_ceo.ovpn openvpn sessions-list openvpn session-manage\ --disconnect --config vpn.chorke.org openvpn session-manage --disconnect --config\ ~/ovpns/chorke_ceo.ovpn openvpn session-manage --disconnect --path\ /net/openvpn/v3/sessions/dab84ba8s3678s41d5saa61sf1515ffa690c
[Unit] Description=vpn.chorke.org After=network.target [Service] Type=simple Restart=always WorkingDirectory=/home/academia/ovpns ExecStart=/usr/sbin/openvpn --config vpn.chorke.org [Install] WantedBy=multi-user.target

Linux Service

cat << EOF | sudo tee /etc/systemd/system/academia-vpn-dev.service >>/dev/null [Unit] Description=Academia OpenVPN Dev Client After=network.target [Service] Restart=always Type=simple WorkingDirectory=/home/shahed/ovpns ExecStart=/usr/sbin/openvpn --config academia-vpn-dev.ovpn [Install] WantedBy=multi-user.target EOF	sudo systemctl daemon-reload sudo systemctl enable --now academia-vpn-dev systemctl status academia-vpn-dev sudo systemctl disable --now academia-vpn-dev systemctl status academia-vpn-dev sudo systemctl restart academia-vpn-dev systemctl status academia-vpn-dev sudo systemctl stop academia-vpn-dev systemctl status academia-vpn-dev

Knowledge

ufw status netstat -a netstat -lpn pivpn add pivpn list pivpn revoke pivpn -u # uninstall apt install ufw apt install nmap apt install telnet apt list --installed

netstat -uap|grep openvpn tail -f /var/log/openvpn.log nano /etc/openvpn/server.conf nmap -sT vpn0.dev.shahed.biz nmap -sU vpn0.dev.shahed.biz nc -uv 10.20.13.1 1194 nc -uv 10.19.83.103 1194 nc -uv 10.19.83.203 1194 nc -uv vpn.shahed.biz 1194 nc -uv vpn0.dev.shahed.biz 1194

telnet localhost 1194 telnet nas0.dev.shahed.biz 80 telnet nas0.dev.shahed.biz 1194 rm -f /etc/openvpn/pki/reqs/dev.shahed.biz.req apt purge openmediavault-openvpn rm -rf /opt/EasyRSA-v3.0.6/ rm -rf /etc/openvpn/ sysctl -w net.ipv4.ip_forward=1 sysctl -w net.ipv4.tcp_window_scaling=0 route add -net 10.20.30.0/24 gw 10.19.83.1 metric 1

References

OpenVPN Access Server System Requirements Config an OpenVPN Server on Ubuntu 22.04 Config an OpenVPN Server on Ubuntu 20.04 Config an OpenVPN Server on Ubuntu 18.04 Config an OpenVPN Server on Ubuntu 16.04 Config an OpenVPN Server on Ubuntu 14.04 OpenVPN Connect Client On Windows OpenVPN not Listening on Port 1194 OpenVPN Pi Setup not Listening OpenVPN How To	OpenVPN Ethernet Bridging Virtual TAP Interfaces Prevent SSH freezes over an OpenVPN Client ufw service not loaded after a reboot Should I use Tap or Tun for OpenVPN OpenVPN3 Linux Client Config OpenVPN Tap vs Tun Mode Calculate 10.19.83.0/24 Calculate 10.20.13.0/24 Calculate 10.20.30.0/24 Calculate 10.8.0.0/24	SSH Connection Hang Forever OpenVPN PiVPN
Systemd » Safe Remove Services Localtunnel