MikroTik (RouterOS) script for setup OpenVPN server and generate certificates

ovpn-server-with-certs.md

OpenVPN Server and certificate management on MikroTik

Contents

• Setup OpenVPN server and generate certificates
• Add a new user
• Setup OpenVPN client
• Decrypt private key to avoid password asking (optional)
• Delete a user and revoke his certificate
• Revert OpenVPN server configuration on MikroTik

Setup OpenVPN server and generate certificates

# Setup OpenVPN Server and generate certs
#
# Change variables below if needed then copy the whole script
# and paste into MikroTik terminal window.
#

:global CN [/system identity get name]
:global PORT 1194

## generate a CA certificate
/certificate
add name=ca-template common-name="$CN" days-valid=3650 \
  key-usage=crl-sign,key-cert-sign
sign ca-template ca-crl-host=127.0.0.1 name="$CN"
:delay 10

## generate a server certificate
/certificate
add name=server-template common-name="server@$CN" days-valid=3650 \
  key-usage=digital-signature,key-encipherment,tls-server
sign server-template ca="$CN" name="server@$CN"
:delay 10

## create a client template
/certificate
add name=client-template common-name="client" days-valid=3650 \
  key-usage=tls-client

## create IP pool
/ip pool
add name=VPN-POOL ranges=192.168.252.128-192.168.252.224

## add VPN profile
/ppp profile
add dns-server=192.168.252.1 local-address=192.168.252.1 name=VPN-PROFILE \
  remote-address=VPN-POOL use-encryption=yes

## setup OpenVPN server
/interface ovpn-server server
set auth=sha1 certificate="server@$CN" cipher=aes128,aes192,aes256 \
  default-profile=VPN-PROFILE mode=ip netmask=24 port="$PORT" \
  enabled=yes require-client-certificate=yes

## add a firewall rule
/ip firewall filter
add chain=input action=accept dst-port="$PORT" protocol=tcp \
  comment="Allow OpenVPN"
add chain=input action=accept dst-port=53 protocol=udp \
  src-address=192.168.252.0/24 \
  comment="Accept DNS requests from VPN clients"
move [find comment="Allow OpenVPN"] 0
move [find comment="Accept DNS requests from VPN clients"] 1

## Setup completed. Do not forget to create a user.

NOTE: To allow clients to surf the Internet, make sure that there are permissive rules, such as:

/ip firewall filter
add chain=forward action=accept src-address=192.168.252.0/24 \
  out-interface-list=WAN place-before=0
add chain=forward action=accept in-interface-list=WAN \
  dst-address=192.168.252.0/24 place-before=1
/ip firewall nat
add chain=srcnat src-address=192.168.252.0/24 out-interface-list=WAN \
  action=masquerade

Add a new user

# Add a new user and generate/export certs
#
# Change variables below if needed then copy the whole script
# and paste into MikroTik terminal window.
#

:global CN [/system identity get name]
:global USERNAME "user"
:global PASSWORD "password"

## add a user
/ppp secret
add name=$USERNAME password=$PASSWORD profile=VPN-PROFILE service=ovpn

## generate a client certificate
/certificate
add name=client-template-to-issue copy-from=client-template \
  common-name="$USERNAME@$CN"
sign client-template-to-issue ca="$CN" name="$USERNAME@$CN"
:delay 10

## export the CA, client certificate, and private key
/certificate
export-certificate "$CN" export-passphrase=""
export-certificate "$USERNAME@$CN" export-passphrase="$PASSWORD"

## Done. You will find the created certificates in Files.

Setup OpenVPN client

1. Copy the exported certificates from the MikroTik

   sftp admin@MikroTik_IP:cert_export_\*

   Also, you can download the certificates from the web interface or Winbox. Open Winbox/WebFig → Files for this.

2. Create user.auth file

   The file auth.auth holds your username/password combination. On the first line must be the username and on the second line your password.

   user
   password
   

3. Create OpenVPN config that named like USERNAME.ovpn:

   client
   dev tun
   proto tcp-client
   remote MikroTik_IP 1194
   nobind
   persist-key
   persist-tun
   cipher AES-128-CBC
   auth SHA1
   pull
   verb 2
   mute 3
   
   # Create a file 'user.auth' with a username and a password
   #
   # cat << EOF > user.auth
   # user
   # password
   # EOF
   auth-user-pass user.auth
   
   # Copy the certificates from MikroTik and change
   # the filenames below if needed
   ca cert_export_MikroTik.crt
   cert cert_export_user@MikroTik.crt
   key cert_export_user@MikroTik.key
   
   # Uncomment the following line if Internet access is needed
   #redirect-gateway def1
   
   # Add routes to networks behind MikroTik
   #route 192.168.88.0 255.255.255.0

4. Try to connect

   sudo openvpn USERNAME.ovpn
   

Decrypt private key to avoid password asking (optional)

openssl rsa -passin pass:password -in cert_export_user@MikroTik.key -out cert_export_user@MikroTik.key

Delete a user and revoke his certificate

# Delete a user and revoke his certificate
#
# Change variables below and paste the script
# into MikroTik terminal window.
#

:global CN [/system identity get name]
:global USERNAME "user"

## delete a user
/ppp secret
remove [find name=$USERNAME profile=VPN-PROFILE]

## revoke a client certificate
/certificate
issued-revoke [find name="$USERNAME@$CN"]

## Done.

Revert OpenVPN server configuration on MikroTik

## Revert OpenVPN configuration

/interface ovpn-server server
set enabled=no default-profile=default port=1194

/ip pool
remove [find name=VPN-POOL]

/ppp secret
remove [find profile=VPN-PROFILE]

/ppp profile
remove [find name=VPN-PROFILE]

/ip firewall filter
remove [find comment="Allow OpenVPN"]
remove [find comment="Accept DNS requests from VPN clients"]

/certificate
## delete the certificates manually

Thanks a lot for the script. I got VPN connection between Android 13 and Mikrotik working, but there was no access to LAN and no firewall filter rules helped.
I have 192.168.200.0 addresses assigned to VPN clients and 192.168.100.0 LAN (so route 192.168.100.0 255.255.255.0 was added to client open vpn profile just like in the script above).
However adding firewal nat masquerade helped.
/ip firewall nat add action=masquerade
chain=srcnat
src-address=192.168.200.0/24
comment="Allow OpenVPN clients to access LAN"