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howtos:network_services:openvpn [2013/05/19 19:09 (UTC)] chrisabelahowtos:network_services:openvpn [2023/02/04 18:36 (UTC)] (current) – [13. Firewalls] chrisabela
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 +
 ====== OpenVPN - How to Set Up a Slackware Server and a Slackware Client ====== ====== OpenVPN - How to Set Up a Slackware Server and a Slackware Client ======
  
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 OpenVPN is an open source software application that implements virtual private network (VPN) techniques for creating secure point-to-point or site-to-site connections in routed or bridged configurations and remote access facilities. It uses a custom security protocol that utilizes SSL/TLS for key exchange. It is capable of traversing network address translators (NATs) and firewalls. It was written by James Yonan and is published under the GNU General Public License (GPL). OpenVPN is an open source software application that implements virtual private network (VPN) techniques for creating secure point-to-point or site-to-site connections in routed or bridged configurations and remote access facilities. It uses a custom security protocol that utilizes SSL/TLS for key exchange. It is capable of traversing network address translators (NATs) and firewalls. It was written by James Yonan and is published under the GNU General Public License (GPL).
  
-OpenVPN allows peers to authenticate each other using a pre-shared secret key, certificates, or username/password. When used in a multiclient-server configuration , it allows the server to release an authentication certificate for every client, using signature and Certificate authority. It uses the OpenSSL encryption library extensively, as well as the SSLv3/TLSv1 protocol, and contains many security and control features.+OpenVPN allows peers to authenticate each other using a pre-shared secret key, certificates, or username/password. When used in a multiclient-server configuration, it allows the server to release an authentication certificate for every client, using signature and Certificate authority. It uses the OpenSSL encryption library extensively, as well as the SSLv3/TLSv1 protocol, and contains many security and control features.
  
 ===== 2. Scope and Objective ===== ===== 2. Scope and Objective =====
  
-The objective of this how-to is to serve as a tutorial for the readers to set up a basic but functional Slackware VPN Server and Client over the Internet.+The objective of this article is to serve as a tutorial for the readers to set up a basic but functional Slackware VPN Server and Client over the Internet.
  
-The emphasis of this tutorial is to provide you with a reliable method that you can easily follow to setup OpenVPN on Slackware Servers and Clients. Nevertheless the process is still not free from pitfalls and require some attention and determination to set up.+The emphasis is to provide a reliable method that can be easily followed to set-up OpenVPN on Slackware Servers and Clients. Nevertheless the process is still not free from pitfalls and require some attention and determination.
  
-This document comprises of a selection of other similar tutorials found on the Internet. In  particular the methods described here were extracted from References (2) and (3). However these were cutomised to satisfy the objective. +This article comprises of a selection of other similar tutorials found on the Internet particularly (2) and (3) and the documents contained in the downloaded source files. However these are reformatted to satisfy the objective. 
  
 ===== 3. Installation ===== ===== 3. Installation =====
  
-Openvpn is already installed on Slackware if a default installation was followed. If this was not the case, then it is available from the "n" directory of the Slackware DVD. Refer to other Slackware specific documents on how to go about this installation.+OpenVPN is already installed on Slackware if a default installation was followed. If this was not the case, then the package is available from the "n" directory of the Slackware repository. Refer to other Slackware specific documents on how to go about this installation.
  
-If you want to confirm that Openvpn is indeed installed, you can check it by listing the /var/log/packages/ directory:+If you want to confirm that OpenVPN is indeed installed, you can check it by listing the ''/var/lib/pkgtools/packages/'' directory:
  
 <code> <code>
-# ls /var/log/packages/openvpn* +# ls /var/lib/pkgtools/packages/openvpn*
-/var/log/packages/openvpn-2.2.2-i486-1+
 </code> </code>
  
 ===== 4. Requirements ===== ===== 4. Requirements =====
  
-Server and a Client computers would be needed. They would have to be connected to the Internet on two different Routers and different Network Routes.  For the purpose of this tutorial, specific details are defined in order to enhance the readability. Of course, you will probably have different addresses, so you will need to amend accordingly.+Server and a Client computers would be needed. They would have to be connected to the Internet on two different Routers and different Network Routes.  For the purpose of this tutorial, specific details are defined in order to enhance the readability. Of course, you will probably have different addresses, so you will need to amend accordingly.
  
 ==== 4.1. Server DNS ==== ==== 4.1. Server DNS ====
  
-A URL is normally used to address the Server. This is not mandatory and instead you may use only the Internet IP. However I recommend using a URL for the Server, especially if it is connected to a dynamic IP, which is typical for domestic Internet connections. The author is using noip2(4) as it is free upon subscription. Noip2 is available from http://slackbuilds.org.+A URL is normally used to address the Server. This is not mandatory and instead you may use only the Internet IP. However it is recommended to use a URL to access the Server from the Internet, especially if it is connected to a dynamic IP, which is typical for domestic Internet connections. The author is using duckdns.org (4) as it is free upon subscription.
  
 ==== 4.2. Server details ==== ==== 4.2. Server details ====
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 <code> <code>
 hostname: server1 hostname: server1
-IP: 192.168.200.199/255.255.255.0 +IP: 192.168.200.195/255.255.255.0 
-URL:  servervpn.no-ip.org+URL:  servervpn.duckdns.org
 Network Interface: eth0 Network Interface: eth0
 </code> </code>
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 <code> <code>
 hostname: client1 hostname: client1
-IP: 192.168.1.234/255.255.255.0+IP: 192.168.1.101/255.255.255.0
 Network Interface: wlan0 Network Interface: wlan0
 </code> </code>
  
-==== 4.Administrator Rights ====+==== 4.Administrator Rights ====
  
-You will need to have administrator rights to set up the Openvpn. This applies to both the Server and the Client. In this tutorial, it will be assumed that all actions will be performed by the root user.+You will need to have administrator rights to set up OpenVPN. This applies to both the Server and the Client. For simplicity, in this tutorial, it will be assumed that all actions will be performed by the root user. Naturally, advanced users might be more discerning.
  
-==== 4.Possible Constraints and Possible Solutions for a WiFi equipped Client ====+==== 4.Possible Constraints and Possible Solutions for a WiFi equipped Client ====
  
 The availability of two Routers might be challenging. Consider that interactive sessions on both the Server and Client will be needed before the VPN is set up. If the Client is equipped with a WiFi interface there might be some easy solutions that may be considered: The availability of two Routers might be challenging. Consider that interactive sessions on both the Server and Client will be needed before the VPN is set up. If the Client is equipped with a WiFi interface there might be some easy solutions that may be considered:
  
-  - Use a 3G smart phone's "Portable Wi-Fi Hot Spot" facility to connect the Client as the VPN Client.  As 3G bandwidth is expensive you may want to minimise traffic. For example, you might want to switch off services that are not absolutely essential during the course of this exercise, such as ntpd, dropbox and tor. +  - Use the data smart phone's "Portable Wi-Fi Hot Spot" facility to connect the Client as the VPN Client. 
-  - Connect the Client to another WiFi available in the vicinity of the Server. Some lucky people live in areas were benevolent neighbours provide them with openly accessible Internet WiFi. It is recommended to request permission before taking up this solution. In case that no such open service exists, you may find it appropriate to request a temporary password from a friendly neighbour for the private encrypted WiFi service+  - Nowadays, many public premises, such as libraries, gardens and Local Councils provide free WiFi service. Other places such as fast food outlets, pubs, cafés, etc. also provide free WiFi from their location to their esteemed customers.
-  - Nowadays, many governmental premises, such as libraries and Local Councils provide free WiFi service. Other places such as fast food outlets, pubs, cafés, etc. also provide free WiFi from their location to their valuable customers. You may access the Server via an available service such as SSH from a WiFi equipped Client. If this option is chosen for this solution, be aware that the Client may have to pass through some firewalls. Besides the VPN connection might be a breach of the terms of conditions that should be accepted before using the WiFi service.+
  
 ===== 5. Creating a Public Key Infrastructure (PKI) using the easy-rsa Scripts ===== ===== 5. Creating a Public Key Infrastructure (PKI) using the easy-rsa Scripts =====
  
-The PKI may be created on any computer with an Openvpn installation, but it is probably more sensible to be done on the Server. In any case, in this tutorial it will be assumed that this is the case. +The PKI may be created on any computer, but it is probably more sensible to be done on both the Server and the Client as both would need it. An easy way to build the PKI is to use the ''easy-rsa'' scriptsThese may be downloaded like this:
- +
-The easy-rsa scripts referred to in this chapter reside in the /usr/doc/ directory. +
- +
-It is not recommended to use this directory to create the PKI. This directory may be overwritten by an Openvpn package upgrade, and some files that will be created, should kept secret as otherwise the security of the created VPN would be compromised. +
- +
-Copy the whole easy-rsa directory to root's home directory.+
  
 <code> <code>
-cp -r /usr/doc/openvpn-2.2.2/easy-rsa /root  +cd 
-# cd /root/easy-rsa/2.0/+# git clone http://github.com/OpenVPN/easy-rsa
 </code> </code>
  
-Find the vars file. As a minimum it is recommended to edit the following:+and then archive it for future purposes:
  
 <code> <code>
-KEY_COUNTRY +# tar czvf easy-rsa.tgz easy-rsa
-KEY_PROVINCE +
-KEY_ORG +
-KEY_EMAIL+
 </code> </code>
  
-The purpose of this recommendation is to assure consistency in the default values of some following steps that need to be followedYou should not be really worried about the exact meaning or the correctness of the chosen entries as the actual values will have no bearing on the success or failure of this exercise.+==== 5.1 Create the keys and certificates for the Server ====
  
-The following is my complete vars file. You may note some additional entries that were entered. Most of these are meant to enhance the range of default values that will be immediately available, thus increasing the chances of a successful creation of the PKI.+Follow these steps on the Server to create the needed keys and certificates:
  
 <code> <code>
-# easy-rsa parameter settings  +cd easy-rsa/easyrsa3
- +
-# NOTE: If you installed from an RPM,  +
-# don't edit this file in place in  +
-/usr/share/openvpn/easy-rsa --  +
-# instead, you should copy the whole  +
-# easy-rsa directory to another location  +
-# (such as /etc/openvpn) so that your  +
-# edits will not be wiped out by a future  +
-# OpenVPN package upgrade.  +
- +
-# This variable should point to  +
-# the top level of the easy-rsa  +
-# tree.  +
-export EASY_RSA="`pwd`"  +
- +
-#  +
-# This variable should point to  +
-# the requested executables  +
-#  +
-export OPENSSL="openssl"  +
-export PKCS11TOOL="pkcs11-tool"  +
-export GREP="grep"  +
- +
- +
-# This variable should point to  +
-# the openssl.cnf file included  +
-# with easy-rsa.  +
-export KEY_CONFIG=`$EASY_RSA/whichopensslcnf $EASY_RSA`  +
- +
-# Edit this variable to point to  +
-# your soon-to-be-created key  +
-# directory.  +
-#  +
-# WARNING: clean-all will do  +
-# a rm -rf on this directory  +
-# so make sure you define  +
-# it correctly!  +
-export KEY_DIR="$EASY_RSA/keys"  +
- +
-# Issue rm -rf warning  +
-echo NOTE: If you run ./clean-all, I will be doing a rm -rf on $KEY_DIR  +
- +
-# PKCS11 fixes  +
-export PKCS11_MODULE_PATH="dummy"  +
-export PKCS11_PIN="dummy"  +
- +
-# Increase this to 2048 if you  +
-# are paranoid.  This will slow  +
-# down TLS negotiation performance  +
-# as well as the one-time DH parms  +
-# generation process.  +
-export KEY_SIZE=2048  +
- +
-# In how many days should the root CA key expire?  +
-export CA_EXPIRE=3650  +
- +
-# In how many days should certificates expire?  +
-export KEY_EXPIRE=3650  +
- +
-# These are the default values for fields  +
-# which will be placed in the certificate.  +
-# Don't leave any of these fields blank.  +
-export KEY_COUNTRY="MT"  +
-export KEY_PROVINCE="Malta"  +
-export KEY_CITY="Valletta"  +
-export KEY_ORG="ABCDEF Co. Ltd."  +
-#export KEY_EMAIL="me@myhost.mydomain"  +
-export KEY_EMAIL=support@abcdef.com  +
-export KEY_CN=server1  +
-export KEY_NAME=server1  +
-export KEY_OU=""  +
-export PKCS11_MODULE_PATH=changeme  +
-export PKCS11_PIN=1234 +
 </code> </code>
  
-Source the vars file:+Create the PKI and the CA:
  
 <code> <code>
-source ./vars +# ./easyrsa init-pki 
-NOTE: If you run ./clean-all, I will be doing a rm -rf on /root/easy-rsa/2.0/keys+./easyrsa build-ca
 </code> </code>
  
-Proceed like this:+Enter a PEM pass phrase, reverify it and then enter a name for the server. In this article I am using the hostnames for clarity (in this case: server1), but you may choose any name. 
 + 
 +Then generate the request:
  
 <code> <code>
-# ./clean-all +# ./easyrsa gen-req server1
-# ./build-ca +
-Generating a 2048 bit RSA private key  +
-.....................+++  +
-.......................................................................+++  +
-writing new private key to 'ca.key'  +
------  +
-You are about to be asked to enter information that will be incorporated  +
-into your certificate request.  +
-What you are about to enter is what is called a Distinguished Name or a DN.  +
-There are quite a few fields but you can leave some blank  +
-For some fields there will be a default value,  +
-If you enter '.', the field will be left blank.  +
------  +
-Country Name (2 letter code) [MT]:  +
-State or Province Name (full name) [Malta]:  +
-Locality Name (eg, city) [Valletta]:  +
-Organization Name (eg, company) [ABCDEF Co. Ltd.]:  +
-Organizational Unit Name (eg, section) []:  +
-Common Name (eg, your name or your server's hostname) [server1]:  +
-Name [server1]:  +
-Email Address [support@abcdef.com]: +
 </code> </code>
  
-**Hint: The less information you enter, the less likely it will cause you problems later on.**+You will be prompted for the PEM pass phrase, to reverify it and to confirm that the name of the entity is indeed server1Now you may proceed to sign this request:
  
 <code> <code>
-# ./build-key-server server1+# ./easyrsa sign-req server server1
 </code> </code>
  
-**Do not enter a challenge password or company name when prompted.**+Confirm the request by entering "yes", then enter the original ca PEM passphrase. 
 + 
 +Now create two additional key files:
  
 <code> <code>
-Generating a 2048 bit RSA private key  +# cd /etc/openvpn/certs/ 
-........................+++  +# openssl dhparam -out dh2048.pem 2048 
-................................................+++  +# cd /etc/openvpn/keys/ 
-writing new private key to 'server1.key'  +# /usr/sbin/openvpn --genkey secret ta.key  
------  +</code>
-You are about to be asked to enter information that will be incorporated  +
-into your certificate request.  +
-What you are about to enter is what is called a Distinguished Name or a DN.  +
-There are quite a few fields but you can leave some blank  +
-For some fields there will be a default value,  +
-If you enter '.', the field will be left blank.  +
------  +
-Country Name (2 letter code) [MT]:  +
-State or Province Name (full name) [Malta]:  +
-Locality Name (eg, city) [Valletta]:  +
-Organization Name (eg, company) [ABCDEF Co. Ltd.]:  +
-Organizational Unit Name (eg, section) []:  +
-Common Name (eg, your name or your server's hostname) [server1]:  +
-Name [server1]:  +
-Email Address [support@abcdef.com]: +
  
-Please enter the following 'extra' attributes  +==== 5.Create the keys and certificates for the Client ====
-to be sent with your certificate request  +
-A challenge password []:  +
-An optional company name []:  +
-Using configuration from /root/easy-rsa/2.0/openssl-1.0.0.cnf  +
-Check that the request matches the signature  +
-Signature ok  +
-The Subject's Distinguished Name is as follows  +
-countryName           :PRINTABLE:'MT'  +
-stateOrProvinceName   :PRINTABLE:'Malta'  +
-localityName          :PRINTABLE:'Valletta'  +
-organizationName      :PRINTABLE:'ABCDEF Co. Ltd.'  +
-commonName            :PRINTABLE:'server1'  +
-name                  :PRINTABLE:'server1'  +
-emailAddress          :IA5STRING:'support@abcdef.com'  +
-Certificate is to be certified until Jan 18 19:37:43 2023 GMT (3650 days)  +
-Sign the certificate? [y/n]:+
  
 +Follow these steps on the Client to create the needed keys and certificates:
  
-1 out of 1 certificate requests certifiedcommit? [y/n]y  +You will need the ''easy-rsa'' scriptsso you can copy the ''easy-rsa'' tarball from the Server to the Client and extract it:
-Write out database with 1 new entries  +
-Data Base Updated  +
-</code>+
  
 <code> <code>
-./build-dh +cd 
-This is going to take a long time  +# tar xvf easy-rsa.tgz
-..................+...........................................................................................................  +
-.................................................................+
 </code> </code>
 +
 +Now create the PKI and generate the request:
  
 <code> <code>
-# ./build-key client1+# cd easy-rsa/easyrsa3 
 +# ./easyrsa init-pki 
 +# ./easyrsa gen-req client1
 </code> </code>
  
-** Do not enter challenge password or company name when prompted.**+You will be prompted for PEM pass phrase, to re-verify it and to confirm that the name of the entity is indeed client1. In this article I am using the hostnames for clarity (in this case: client1), but you may choose any name.
  
-<code> +Copy ''pki/reqs/client1.req'' back to the Server.
-Generating a 2048 bit RSA private key  +
-...............................................................................................+++  +
-..+++  +
-writing new private key to 'client1.key +
------  +
-You are about to be asked to enter information that will be incorporated  +
-into your certificate request.  +
-What you are about to enter is what is called a Distinguished Name or a DN.  +
-There are quite a few fields but you can leave some blank  +
-For some fields there will be a default value,  +
-If you enter '.', the field will be left blank.  +
------  +
-Country Name (2 letter code) [MT]:  +
-State or Province Name (full name) [Malta]:  +
-Locality Name (eg, city) [Valletta]:  +
-Organization Name (eg, company) [ABCDEF Co. Ltd.]:  +
-Organizational Unit Name (eg, section) []:  +
-Common Name (eg, your name or your server's hostname) [client1]:  +
-Name [server1]:  +
-Email Address [support@abcdef.com]: +
  
-Please enter the following 'extra' attributes  +=== 5.2.1 Sign the Client'request on the Server ===
-to be sent with your certificate request  +
-A challenge password []:  +
-An optional company name []:  +
-Using configuration from /root/easy-rsa/2.0/openssl-1.0.0.cnf  +
-Check that the request matches the signature  +
-Signature ok  +
-The Subject'Distinguished Name is as follows  +
-countryName           :PRINTABLE:'MT'  +
-stateOrProvinceName   :PRINTABLE:'Malta'  +
-localityName          :PRINTABLE:'Valletta'  +
-organizationName      :PRINTABLE:'ABCDEF Co. Ltd.'  +
-commonName            :PRINTABLE:'client1'  +
-name                  :PRINTABLE:'server1'  +
-emailAddress          :IA5STRING:'support@abcdef.com'  +
-Certificate is to be certified until Jan 18 19:42:33 2023 GMT (3650 days)  +
-Sign the certificate? [y/n]:+
  
- +For the purpose of this articleit is assumed that the Client's request file (''client1.req'') has been transferred to the ''$HOME/openvpn/'' directory of the Server. Now you can proceed to import and sign the client1 request:
-1 out of 1 certificate requests certifiedcommit? [y/n]y  +
-Write out database with 1 new entries  +
-Data Base Updated  +
-</code>+
  
 <code> <code>
-openvpn --genkey --secret /root/easy-rsa/2.0/keys/ta.key+cd $HOME/easy-rsa/easyrsa3 
 +./easyrsa import-req $HOME/openvpn/client1.req client1 
 +# ./easyrsa sign-req client client1
 </code> </code>
 +
 +When prompted enter "yes" and the server1 CA PEM pass phrase. 
 +
 +Copy the generated ''$HOME/easy-rsa/easyrsa3/pki/issued/client1.crt''
 +back to the client.
  
 ===== 6. Setting up the Server ===== ===== 6. Setting up the Server =====
  
-Copy the following files generated by the easy-rsa scripts to their respective directories in the /etc/openvpn/ directory:+Copy the following files generated by the easy-rsa scripts to their respective directories in the ''/etc/openvpn/'' directory:
  
 <code> <code>
-# cp /root/easy-rsa/2.0/keys/{ca.crt,server1.crt,dh2048.pem} \+# cp $HOME/easy-rsa/easyrsa3/pki/ca.crt \
 > /etc/openvpn/certs/ > /etc/openvpn/certs/
-# cp /root/easy-rsa/2.0/keys/{server1.key,ta.key\+# cp $HOME/easy-rsa/easyrsa3/pki/issued/server1.crt \ 
 +> /etc/openvpn/certs/ 
 +# cp $HOME/easy-rsa/easyrsa3/pki/private/server1.key \
 > /etc/openvpn/keys/ > /etc/openvpn/keys/
 </code> </code>
  
-Restrict the permission of /etc/openvpn/keys/+Copy the provided ''server.conf'' from the OpenVPN package to the configuration directory:
  
 <code> <code>
-chmod 700 /etc/openvpn/keys+cp /etc/openvpn/sample-config-files/server.conf /etc/openvpn/
 </code> </code>
  
-On the Server machine copy the sample server.conf onto the openvpn's configuration directory. +Edit the following lines of ''/etc/openvpn/server.conf''
- +
-<code> +
-# cp /usr/doc/openvpn-2.2.2/sample-config-files/server.conf \ +
-> /etc/openvpn/ +
-</code> +
- +
-Edit the following lines of /etc/openvpn/server.conf+
  
 From these lines: From these lines:
Line 353: Line 184:
 cert server.crt cert server.crt
 key server.key  # This file should be kept secret key server.key  # This file should be kept secret
- 
  
 dh dh1024.pem dh dh1024.pem
-;tls-auth ta.key 0 # This file is secret 
  
-;user nobody  +;topology subnet 
-;group nobody+ 
 +tls-auth ta.key 0 # This file is secret 
 + 
 +cipher AES-256-CBC 
 + 
 +;log-append  openvpn.log 
 </code> </code>
  
-To+To:
  
 <code> <code>
Line 370: Line 205:
  
 dh /etc/openvpn/certs/dh2048.pem dh /etc/openvpn/certs/dh2048.pem
 +
 +topology subnet
  
 tls-auth /etc/openvpn/keys/ta.key 0 # This file is secret tls-auth /etc/openvpn/keys/ta.key 0 # This file is secret
  
-user nobody  +data-ciphers-fallback AES-256-CBC 
-group nobody+ 
 +log-append  /var/log/openvpn.log
 </code> </code>
  
-**Note** that comments in server.conf may be either start with # or ; In order to help you with entering parameters, the former are used to comment out text while the latter are for commented out configuration lines.+<note>Note that comments in server.conf may start with either start with # or ; In order to help you with entering parameters, the former are used to comment out text while the latter are for commented out configuration lines.</note>
  
-Copy the rc.openvpn-server listed hereunder and place under /etc/rc.d/+Create a file containing your PEM pass phrase in a secure location; e.g. ''/root/password.ovpn'' which contains only this pass phrase. Then restrict its permission:
  
 <code> <code>
-#!/bin/sh  +chmod 600 /root/password.ovpn 
-#  +</code>
-# /etc/rc.d/rc.openvpn-server  +
-#  +
-# Start/stop/restart the openvpn server.  +
-#  +
-# To make OpenVPN start automatically at boot, make this  +
-# file executable:  chmod 755 /etc/rc.d/rc.openvpn-server  +
-+
  
-ovpn_start() {  +On the Server, edit ''/etc/openvpn/server.conf'' with the following lines:
-  if [ -x /usr/sbin/openvpn -a -r /etc/openvpn/server.conf ]; then  +
-    echo "Starting OpenVPN /usr/sbin/openvpn server.conf"  +
-    /usr/sbin/openvpn /etc/openvpn/server.conf &  +
-  fi  +
-+
  
-ovpn_stop() {  +<code> 
-  killall openvpn  +askpass /root/password.ovpn 
-+auth-nocache 
 +</code>
  
-ovpn_restart() {  +Create a directory to store the OpenVPN service PID and restrict its permissions:
-  ovpn_stop  +
-  sleep 2  +
-  ovpn_start  +
-+
  
-case "$1" in  +<code> 
-'start' +mkdir /run/openvpn/ 
-  ovpn_start  +chmod 700 /run/openvpn/
-  ;;  +
-'stop')  +
-  ovpn_stop  +
-  ;;  +
-'restart')  +
-  ovpn_restart  +
-  ;;  +
-*)  +
-  echo "Usage: $0 {start|stop|restart}"  +
-esac+
 </code> </code>
  
-Then give it executable permissions:+Give the OpenVPN ''rc'' script executable permissions, so that the OpenVPN service is started everytime you boot up:
  
 <code> <code>
-# chmod 755 /etc/rc.d/rc.openvpn-server+# chmod +x /etc/rc.d/rc.openvpn
 </code> </code>
  
 ===== 7. Port Forwarding ===== ===== 7. Port Forwarding =====
  
-You will need to forward traffic from the port you have chosen for Openvpn to be routed to the Server. To accomplish this you will need to provide your Server with a fixed IP and you will need to configure your router. You may use netconfig, wicd or network-manager to set the fixed IP on Slackware. Then you also need to consult the documentation provided with your router to set up the selected IP address reserved for the Server, and the port forwarding. For our default Openvpn set up, the UDP Port would be 1194. +You will need to forward traffic from the port you have chosen for OpenVPN to be routed to the Server. To accomplish this you will need to provide your Server with a fixed IP and you will need to configure your router. You may use netconfig to set the fixed IP on Slackware. Then you also need to consult the documentation provided with your router to set up the selected IP address reserved for the Server, and the port forwarding. For this default OpenVPN set up, the UDP Port would be 1194. 
  
-In case if you have misplaced such documentation, you may search on the Internet on how this may be achieved. A good place to start is http://portforward.com/. Astute readers are warned that typical port scanning tools like nmap might not be able to detect your open ports at this stage.+In case if you have misplaced such documentation, you may search on the Internet on how this may be achieved. A good place to start is https://portforward.com/.
  
 ===== 8. Setting up the Client ===== ===== 8. Setting up the Client =====
  
-On the client machine perform the following instructions to set it up.+On the Client machine perform the following instructions to set it up. 
 + 
 +Copy the provided ''client.conf'' from the OpenVPN package to the configuration directory:
  
 <code> <code>
-# cp /usr/doc/openvpn-2.2.2/sample-config-files/client.conf +# cp /etc/openvpn/sample-config-files/client.conf /etc/openvpn/
-/etc/openvpn/+
 </code> </code>
  
Line 457: Line 271:
 key client.key  key client.key 
  
-;tls-auth ta.key 1+tls-auth ta.key 1 
 + 
 +cipher AES-256-CBC
 </code> </code>
  
Line 463: Line 279:
  
 <code> <code>
-remote servervpn.no-ip.org 1194+remote servervpn.duckdns.org 1194
  
 user nobody  user nobody 
Line 473: Line 289:
  
 tls-auth /etc/openvpn/keys/ta.key 1 tls-auth /etc/openvpn/keys/ta.key 1
-</code> 
  
-**Note** that comments in client.conf may be either # or ; The former are used to comment out text while the latter are for commented out configuration lines. This should help you a lot in the configuration process.+data-ciphers-fallback AES-256-CBC
  
-You will need the following files that were generated by the easy-rsa scripts:+auth-nocache
  
-<code> +log-append  /var/log/openvpn.log
-ca.crt +
-client1.crt +
-client1.key +
-ta.key+
 </code> </code>
  
-Place these files as indicated in client.conf. So ca.crt and client1.crt go under /etc/openvpn/certs/ while client1.key and ta.key go under /etc/openvpn/keys/+<note>Note that comments in client.conf may start with either # or ; The former are used to comment out text while the latter are for commented out configuration linesThis should help you a lot in the configuration process.</note>
  
-Copy the following rc.openvpn-client listed hereunder and place under /etc/rc.d/+You will need this file that was generated by the Client's ''easy-rsa'' scripts:
  
 <code> <code>
-#!/bin/sh  +cp $HOME/easy-rsa/easyrsa3/pki/private/client1.key \ 
-#  +/etc/openvpn/keys/ 
-/etc/rc.d/rc.openvpn-client  +</code>
- +
-# Start/stop/restart the openvpn client.  +
-+
  
-ovpn_start() {  +and the following from the Server's ''easy-rsa'' scripts:
-  if [ -x /usr/sbin/openvpn -a -r /etc/openvpn/client.conf ]; then  +
-    echo "Starting OpenVPN /usr/sbin/openvpn client.conf"  +
-    /usr/sbin/openvpn /etc/openvpn/client.conf &  +
-  fi  +
-+
  
-ovpn_stop() {  +<code> 
-  killall openvpn  +$HOME/easy-rsa/easyrsa3/pki/ca.crt 
-}  +$HOME/easy-rsa/easyrsa3/pki/issued/client1.crt
- +
-ovpn_restart() {  +
-  ovpn_stop  +
-  sleep 2  +
-  ovpn_start  +
-}  +
-  +
-case "$1" in  +
-'start')  +
-  ovpn_start  +
-  ;;  +
-'stop')  +
-  ovpn_stop  +
-  ;;  +
-'restart')  +
-  ovpn_restart  +
-  ;;  +
-*)  +
-  echo "Usage: $0 {start|stop|restart}"  +
-esac+
 </code> </code>
  
-Then give it executable permissions:+and this file from the Server as well:
  
 <code> <code>
-# chmod +x /etc/rc.d/rc.openvpn-client+/etc/openvpn/keys/ta.key
 </code> </code>
 +
 +Place these files as indicated in ''client.conf''. So ''ca.crt'' and ''client1.crt'' go under ''/etc/openvpn/certs/'' while ''client1.key'' and ''ta.key'' go under ''/etc/openvpn/keys/''
  
 ===== 9. Testing the VPN ===== ===== 9. Testing the VPN =====
Line 541: Line 326:
  
 <code> <code>
-# /etc/rc.d/rc.openvpn-server start+# /etc/rc.d/rc.openvpn restart
 </code> </code>
 +
 +Enter the Server PEM pass phrase when prompted.
  
 On the Client: On the Client:
  
 <code> <code>
-# /etc/rc.d/rc.openvpn-client start+# /usr/sbin/openvpn --config /etc/openvpn/client.conf
 </code> </code>
  
-On both you should see a new network interface called tun0On the Server, I obtained the following: +Enter the Client PEM pass phrase when promptedTo stop OpenVPN on the Client just hit CTRL+C
- +
-<code> +
-# ifconfig tun0  +
-tun0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST>  mtu 1500  +
-        inet 10.8.0.1  netmask 255.255.255.255  destination 10.8.0.2  +
-        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 100  (UNSPEC)  +
-        RX packets 0  bytes 0 (0.0 B)  +
-        RX errors 0  dropped 0  overruns 0  frame 0  +
-        TX packets 0  bytes 0 (0.0 B)  +
-        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0  +
-</code>+
  
-Similarly on the Client:+On both you should see a new network interface called tun0. To verify, run this ip command:
  
 <code> <code>
-ifconfig tun0  +/usr/sbin/ip addr show tun0
-tun0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST>  mtu 1500  +
-        inet 10.8.0.6  netmask 255.255.255.255  destination 10.8.0.5  +
-        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 100  (UNSPEC)  +
-        RX packets 0  bytes 0 (0.0 B)  +
-        RX errors 0  dropped 0  overruns 0  frame 0  +
-        TX packets 0  bytes 0 (0.0 B)  +
-        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0+
 </code> </code>
  
Line 592: Line 361:
 </code> </code>
  
-To start the openvpn service automatically on boot-up from the Serverinclude these lines in /etc/rc.d/rc.local+If you fail to set-up a VPN connectionyou may want to look in ''/var/log/openvpn.log''
  
 <code> <code>
-# Start the OpenVPN Server +tal -/var/log/openvpn.log
-if [ -/etc/rc.d/rc.openvpn-server ]; then  +
-  /etc/rc.d/rc.openvpn-server start  +
-fi+
 </code> </code>
  
-===== 10. IP Routing =====+===== 10. Logrotate (6) ===== 
 + 
 +This is logrotate configuration for OpenVPN. It prevents you from ending up with huge OpenVPN log files. ''copytruncate'' option here is very important - OpenVPN does not want to close the logfile it's writing to, so this file is automatically truncated after copying its contents. Edit this file as ''/etc/logrotate.d/openvpn'' 
 + 
 +<code> 
 +/var/log/openvpn.log { 
 +    daily 
 +    rotate 12 
 +    compress 
 +    copytruncate 
 +    delaycompress 
 +    missingok 
 +    notifempty 
 +
 +</code> 
 + 
 +===== 11. Storing the PEM pass phrase in a secure file and automatic start of service after booting ===== 
 + 
 +As hinted in Chapter 6, to start the OpenVPN service on boot, an entry in ''/etc/rc.d/rc.local'' is not needed as the provided ''/etc/rc.d/rc.openvpn'' is started by ''/etc/rc.d/rc.inet2'' at boot up. 
 + 
 +As ''/etc/rc.d/rc.openvpn'' starts OpenVPN with ''--daemon'' option, it would not start if you still need to enter the password. In Chapter 6, we showed how this can be resolved for the Server. Naturally, if this is your intention, you may repeat the process for the Client: 
 + 
 +On the Client, edit ''/etc/openvpn/client.conf'' with the following lines: 
 + 
 +<code> 
 +askpass /root/password.ovpn 
 +auth-nocache 
 +</code> 
 + 
 +Create a directory to store the OpenVPN service PID and restrict its permissions: 
 + 
 +<code> 
 +mkdir /run/openvpn/ 
 +chmod 700 /run/openvpn/ 
 +</code> 
 + 
 +An alternate method (albeit less secure) is to remove the passphrase from ''server1.key'' and/or ''client1.key'' files altogether.  Ensure to restrict the permissions of the ensuing key. For the Server: 
 + 
 +<code> 
 +# cd /etc/openvpn/keys 
 +# openssl rsa -in server1.key -out tmp.key 
 +</code> 
 + 
 +Enter the pass phrase. 
 + 
 +<code> 
 +# mv tmp.key server1.key 
 +# chmod 600 server1.key 
 +</code> 
 + 
 +If you had them remove these lines from ''/etc/openvpn/server.conf'' 
 + 
 +<code> 
 +askpass /root/password.ovpn 
 +auth-nocache 
 +</code> 
 + 
 +Similarly, this can be repeated for the Client: 
 + 
 +<code> 
 +# cd /etc/openvpn/keys 
 +# openssl rsa -in client1.key -out tmp.key 
 +</code> 
 + 
 +Enter the pass phrase. 
 + 
 +<code> 
 +# mv tmp.key client1.key 
 +# chmod 600 client1.key 
 +</code> 
 + 
 +Then, if you had it, remove this line from ''/etc/openvpn/client.conf'' 
 + 
 +<code> 
 +askpass /root/password.ovpn 
 +</code> 
 + 
 +If you intend to use the ''rc'' script on the Client, proceed like this: 
 + 
 +<code> 
 +mkdir /run/openvpn/ 
 +chmod 700 /run/openvpn/ 
 +chmod +x /etc/rc.d/rc.openvpn 
 +</code> 
 + 
 +===== 12. IP Routing =====
  
 Up to now we have created a tunnel device on both the Server and the Client called tun0 which is visible only to these two machines. However more work is needed to route the Client's connection via tun0 and then to the WAN that is connected to the Server. Up to now we have created a tunnel device on both the Server and the Client called tun0 which is visible only to these two machines. However more work is needed to route the Client's connection via tun0 and then to the WAN that is connected to the Server.
  
-==== 10.1 Server Configuration ====+==== 12.1 IP Forwarding ====
  
-Enable IP forwarding:+On the Server, enable IP forwarding:
  
 <code> <code>
Line 622: Line 473:
 </code> </code>
  
-Create a file with the same name of the client (in this case client1) and enter the following line in /etc/openvpn/ccd/client1+Create a file with the same name of the client (in this case ''client1'') and enter the following line in ''/etc/openvpn/ccd/client1''
  
 <code> <code>
Line 630: Line 481:
 Replace 192.168.1.0 255.255.255.0 by the Network Route of your Client. Replace 192.168.1.0 255.255.255.0 by the Network Route of your Client.
  
-Similarly edit /etc/openvpn/server.conf with the following lines:+Similarly edit ''/etc/openvpn/server.conf'' with the following lines:
  
 <code> <code>
 push "route 192.168.200.0 255.255.255.0" push "route 192.168.200.0 255.255.255.0"
  
-client-config-dir ccd +client-config-dir /etc/openvpn/ccd 
 route 192.168.1.0 255.255.255.0  route 192.168.1.0 255.255.255.0 
  
Line 645: Line 496:
  
 Naturally replace 192.168.200.0 255.255.255.0 with the Server's Network Route, and  192.168.1.0 255.255.255.0 with the Client's Network Route. Naturally replace 192.168.200.0 255.255.255.0 with the Server's Network Route, and  192.168.1.0 255.255.255.0 with the Client's Network Route.
 +208.67.222.222 and 208.67.220.220 are the OpenDNS IPv4 DNS service addresses.
  
-208.67.222.222 and 208.67.220.220 are the OpenDNS IP addresses. Up to now the DNS push configuration has not been successful. You can either use the original Client DNS servers or else you may edit /etc/resolv.conf manually. However it is still worth trying to use the DNS servers listed by the Client, I find that they are generally still be available from the Server's Network, so you would not need to do anything.+<note warning>Up to now the DNS push configuration has not been successful.</note>
  
-Next you will have to configure some iptables NAT forwarding on the Server (only). You can do this by first flushing the iptables:+You can either use the original Client DNS servers or else you may rewrite /etc/resolv.conf manually:
  
 <code> <code>
-# iptables -F+OpenDNS Servers 
 +nameserver 208.67.222.222 
 +nameserver 208.67.220.220 
 +</code> 
 + 
 +According to your routing table however, it is still worth trying to use the DNS servers listed by the Client, I find that they are generally still available, so you would not need to do anything. However do be aware of possible DNS leaks if you are concerned about your privacy. 
 + 
 +Some users have reported that their Client's Network Manager, (or any other similar application) re-wrote the original /etc/resolv.conf back after their manual editing. This could not be reproduced by the author of this article (yet), but you may consider installing and configuring openresolv(5) if this actually happens to you. A SlackBuild for openresolv may be found on http://slackbuilds.org. Openresolv is currently out of the scope of this article. 
 + 
 +Next you will have to configure NAT forwarding on the Server (only). 
 + 
 +You can do this by means of iptables or the newer nftables (not both). 
 + 
 +==== 12.2 NAT forwarding with iptables ==== 
 + 
 +Start by flushing the ''iptables'' 
 + 
 +<code> 
 +# /usr/sbin/iptables -F
 </code> </code>
  
Line 657: Line 527:
  
 <code> <code>
-# iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE+/usr/sbin/iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE
 </code> </code>
  
-On Slackware, such a line may be included in /etc/rc.d/rc.firewall and /etc/rc.d/rc.inet2 will run it each time you reboot the Server if the former has executable permissions. You do not have to include anything in /etc/rc.d/rc.local.+On Slackware, such a line may be included in ''/etc/rc.d/rc.firewall'' and ''/etc/rc.d/rc.inet2'' will run it each time you reboot the Server if the former has executable permissions. You do not have to include anything in ''/etc/rc.d/rc.local''.
  
 The exact lines which you need to include depend on whether you already entered your own iptables filter chains and rules, but I will assume that that this is not the case. The exact lines which you need to include depend on whether you already entered your own iptables filter chains and rules, but I will assume that that this is not the case.
  
-As already explained, as a minimum you only need to enter the following lines in /etc/rc.d/rc.firewall+As already explained, as a minimum you only need to enter the following lines in ''/etc/rc.d/rc.firewall''
  
 <code> <code>
Line 671: Line 541:
 </code> </code>
  
-If on the other hand you would like a better firewall and you are at least moderately confident with iptables, I propose the following script to be included in your /etc/rc.d/rc.firewall. The comments in the script should help you understand the impact they will have on the Server.+Give the firewall ''rc'' script executable permission:
  
 <code> <code>
-#!/bin/sh  +chmod +x /etc/rc.d/rc.firewall 
-# Start/stop/restart the firewall  +</code>
-# A VPN server iptable filter rules  +
-  +
-IPT=/usr/sbin/iptables # This will provide some portability +
  
-firewall_start() { +and start it:
  
-  # flush the iptables  +<code> 
-  $IPT -F  +# /etc/rc.d/rc.firewall start
- +
-  policies  +
-  $IPT -P OUTPUT ACCEPT  +
-  $IPT -P INPUT DROP  +
-  $IPT -P FORWARD DROP  +
-  $IPT -N SERVICES # services is a custom chain  +
- +
-  # allowed inputs  +
-  #$IPT -A INPUT -i lo -j ACCEPT # Uncomment if the Server is a desktop  +
-  $IPT -A INPUT -j SERVICES # Append the services chain to the input  +
- +
-  # allowed forwards  +
-  $IPT -A FORWARD -i eth0 -o tun0 -m state --state ESTABLISHED,RELATED -j ACCEPT  +
-  $IPT -A FORWARD -s 10.8.0.0/24 -o eth0 -j ACCEPT  +
- +
-  # masquerade the openvpn network  +
-  $IPT -t nat -A POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -o eth0 -j MASQUERADE  +
- +
-  # allow responses  +
-  $IPT -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT  +
- +
-  # allow services  +
- +
-  # allow vpn on the default udp port 1194  +
-  $IPT -A SERVICES -p udp --dport 1194 -j ACCEPT  +
- +
-  # allow sshd on the default tcp port 22  +
-  $IPT -A SERVICES -p tcp --dport 22 -j ACCEPT  +
- +
-}  +
- +
-firewall_stop() {  +
- +
-  # polcies (permissive)  +
-  $IPT -P INPUT ACCEPT  +
- +
-  # flush the iptables  +
-  $IPT -F  +
- +
-  # delete the services custom chain  +
-  $IPT -X SERVICES  +
-}  +
- +
-case "$1" in  +
-'start')  +
-  firewall_start  +
-  ;;  +
-'stop')  +
-  firewall_stop  +
-  ;;  +
-'restart')  +
-  firewall_stop  +
-  firewall_start  +
-  ;;  +
-*)  +
-  echo "Usage $0 start|stop|restart"  +
-esac+
 </code> </code>
  
-Give the firewall rc script executable permission:+Restart the OpenVPN service on the Server:
  
 <code> <code>
-chmod +x /etc/rc.d/rc.firewall+# /etc/rc.d/rc.openvpn restart
 </code> </code>
  
-and start it:+and reconnect from the Client:
  
 <code> <code>
-# /etc/rc.d/rc.firewall+/usr/sbin/openvpn /etc/openvpn/client.conf
 </code> </code>
  
-Now you will you need to do is to restart the OpenVPN service on the Server and restart the Client connection.+==== 12.3 NAT forwarding with nftables ====
  
-===== 11. Firewalls =====+If you prefer ''nftables'', these are the commands you can use:
  
-In the previous chapter we referred to a firewall you may include to protect your Openvpn Server However this chapter refers to firewalls on the Client LAN that may block the VPN connection by blocking traffic on UDP port 1194.+<code> 
 +/usr/sbin/nft flush ruleset 
 +/usr/sbin/nft add table nat 
 +/usr/sbin/nft 'add chain nat postrouting { type nat hook postrouting priority 100 ; }' 
 +/usr/sbin/nft add rule nat postrouting ip saddr 10.8.0.0/24 oif eth0 masquerade 
 +</code>
  
-In order to penetrate through the Client firewall your may want to try changing the port to 443 - normally reserved for https. Using TCP instead of UDP will also help. To make these change you will need to amend /etc/openvpn/server.conf of the Server, from+===== 13. Firewalls ===== 
 + 
 +You may find that on some networks, UDP port 1194 is blocked, and so the Client will be unable to connect. In order to penetrate through the firewall you may want to try changing the port to 443 - normally reserved for https. Using TCP instead of UDP will also help. To make these change you will need to amend /etc/openvpn/server.conf of the Server, from
  
 <code> <code>
Line 775: Line 592:
 </code> </code>
  
-and /etc/openvpn/client.conf of the Client, from+Also, comment out ''explicit-exit-notify 1'' in ''/etc/openvpn/server.conf'' 
 + 
 +You also have to modify your Router's port forwarding to TCP port 443. 
 + 
 +Edit ''/etc/openvpn/client.conf'' of the Client, from
  
 <code> <code>
Line 791: Line 612:
 </code> </code>
  
-The Server's firewall script would also need to be modified. Change these lines: +===== 14Sources =====
- +
-<code> +
-# allow vpn on the default udp port 1194  +
-$IPT -A SERVICES -p udp --dport 1194 -j ACCEPT  +
-</code> +
- +
-to: +
- +
-<code> +
-# allow vpn on the custom tcp port 443  +
-$IPT -A SERVICES -p tcp --dport 443 -j ACCEPT  +
-</code> +
- +
-You also have to modify your Router's port forwarding to TCP port 443. +
- +
-===== 12References =====+
    
 (1) http://en.wikipedia.org/wiki/OpenVPN (1) http://en.wikipedia.org/wiki/OpenVPN
Line 815: Line 620:
 (3) http://slackwiki.com/OpenVPN_smcr_2012 (3) http://slackwiki.com/OpenVPN_smcr_2012
  
-(4) http://www.no-ip.com+(4) http://www.duckdns.org
  
 +(5) http://roy.marples.name/projects/openresolv/index
 +
 +(6) https://gist.github.com/adaRn/337838d87cd8f544407d6446cf7daa80
 +
 +  * Written for Slackware 15.0 in April 2022
   * Originally written by [[wiki:user:chrisabela | Chris Abela]]   * Originally written by [[wiki:user:chrisabela | Chris Abela]]
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 {{tag>howtos network openvpn}} {{tag>howtos network openvpn}}
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 howtos:network_services:openvpn ()