Difference between revisions of "OpenVPN"

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[[de:OpenVPN]]
 
[[de:OpenVPN]]
 
[[zh-CN:OpenVPN]]
 
[[zh-CN:OpenVPN]]
{{Expansion|(at least) add support for ipv6 and L2 ethernet bridging}}
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{{Expansion|(at least) add support for IPv6 and L2 Ethernet bridging}}
  
This article describes a basic installation and configuration of [http://openvpn.net OpenVPN], suitable for private and small business use. For more detailed information, please see the official [http://openvpn.net/index.php/manuals/427-openvpn-22.html OpenVPN 2.2 man page] and the [http://openvpn.net/index.php/open-source/documentation OpenVPN documentation].
+
This article describes a basic installation and configuration of [http://openvpn.net OpenVPN], suitable for private and small business use. For more detailed information, please see the [https://community.openvpn.net/openvpn/wiki/Openvpn23ManPage OpenVPN 2.3 man page] and the [http://openvpn.net/index.php/open-source/documentation OpenVPN documentation].
  
OpenVPN is a robust and highly flexible [[Wikipedia:VPN|VPN]] daemon. OpenVPN supports [[Wikipedia:SSL/TLS|SSL/TLS]] security, [[Wikipedia:Bridging_(networking)|ethernet bridging]], [[Wikipedia:Transmission_Control_Protocol|TCP]] or [[Wikipedia:User_Datagram_Protocol|UDP]] [[Wikipedia:Tunneling_protocol|tunnel transport]] through [[Wikipedia:Proxy_server|proxies]] or [[Wikipedia:Network address translation|NAT]], support for dynamic IP addresses and [[Wikipedia:Dynamic_Host_Configuration_Protocol|DHCP]], scalability to hundreds or thousands of users, and portability to most major OS platforms.
+
OpenVPN is a robust and highly flexible [[Wikipedia:VPN|VPN]] daemon. OpenVPN supports [[Wikipedia:SSL/TLS|SSL/TLS]] security, [[Wikipedia:Bridging_(networking)|Ethernet bridging]], [[Wikipedia:Transmission_Control_Protocol|TCP]] or [[Wikipedia:User_Datagram_Protocol|UDP]] [[Wikipedia:Tunneling_protocol|tunnel transport]] through [[Wikipedia:Proxy_server|proxies]] or [[Wikipedia:Network address translation|NAT]], support for dynamic IP addresses and [[Wikipedia:Dynamic_Host_Configuration_Protocol|DHCP]], scalability to hundreds or thousands of users, and portability to most major OS platforms.
  
 
OpenVPN is tightly bound to the [http://www.openssl.org OpenSSL] library, and derives much of its crypto capabilities from it.
 
OpenVPN is tightly bound to the [http://www.openssl.org OpenSSL] library, and derives much of its crypto capabilities from it.
  
OpenVPN supports conventional encryption using a [[Wikipedia:Pre-shared_key|pre-shared secret key]] (Static Key mode) or [[Wikipedia:Public_key|public key security]] ([[Wikipedia:SSL/TLS|SSL/TLS]] mode) using client & server certificates. OpenVPN also supports non-encrypted TCP/UDP tunnels.
+
OpenVPN supports conventional encryption using a [[Wikipedia:Pre-shared_key|pre-shared secret key]] (Static Key mode) or [[Wikipedia:Public_key|public key security]] ([[Wikipedia:SSL/TLS|SSL/TLS]] mode) using client & server certificates. OpenVPN also supports unencrypted TCP/UDP tunnels.
  
 
OpenVPN is designed to work with the [[Wikipedia:TUN/TAP|TUN/TAP]] virtual networking interface that exists on most platforms.
 
OpenVPN is designed to work with the [[Wikipedia:TUN/TAP|TUN/TAP]] virtual networking interface that exists on most platforms.
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OpenVPN was written by James Yonan and is published under the [[Wikipedia:GNU General Public License|GNU General Public License (GPL)]].
 
OpenVPN was written by James Yonan and is published under the [[Wikipedia:GNU General Public License|GNU General Public License (GPL)]].
  
==Install OpenVPN==
+
== Install OpenVPN ==
 +
 
 
[[pacman|Install]] {{Pkg|openvpn}} from the [[official repositories]].
 
[[pacman|Install]] {{Pkg|openvpn}} from the [[official repositories]].
  
{{Note|The software contained in this package supports both server and client mode, so install it on all machines that need to create vpn connections.}}
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{{Note|The software contained in this package supports both server and client mode, so install it on all machines that need to create VPN connections.}}
  
==Configure the system for TUN/TAP support==
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== Configure the system for TUN/TAP support ==
  
 
OpenVPN requires TUN/TAP support. Make sure to load at boot the {{ic|tun}} module.  
 
OpenVPN requires TUN/TAP support. Make sure to load at boot the {{ic|tun}} module.  
  
Read [[Kernel Modules]] for more information.
+
Read [[Kernel modules]] for more information.
  
The default kernel is already properly configured, but if you use another kernel make sure to enable the TUN/TAP module.  If {{ic|$ zgrep CONFIG_TUN /proc/config.gz}} returns {{ic|<nowiki>CONFIG_TUN=n</nowiki>}}, make the following change to the kernel config file and rebuild the kernel.
+
The default kernel is already properly configured, but if you use another kernel make sure to enable the TUN/TAP module.  If {{ic|$ zgrep CONFIG_TUN /proc/config.gz}} returns {{ic|1=CONFIG_TUN=n}}, make the following change to the kernel config file and rebuild the kernel.
  
 
{{hc|Kernel config file|
 
{{hc|Kernel config file|
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     [M] Universal TUN/TAP device driver support}}
 
     [M] Universal TUN/TAP device driver support}}
  
==Connect to a VPN provided by a third party==
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== Connect to a VPN provided by a third party ==
  
 
To connect to a VPN provided by a third party, most of the following can most likely be ignored.  Use the certificates and instructions given by your provider, for instance see: [[Airvpn]].
 
To connect to a VPN provided by a third party, most of the following can most likely be ignored.  Use the certificates and instructions given by your provider, for instance see: [[Airvpn]].
  
==Create a Public Key Infrastructure (PKI) from scratch==
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== Create a Public Key Infrastructure (PKI) from scratch ==
  
 
If you are setting up OpenVPN from scratch, you will need to create a [[Wikipedia:Public key infrastructure|Public Key Infrastructure (PKI)]].
 
If you are setting up OpenVPN from scratch, you will need to create a [[Wikipedia:Public key infrastructure|Public Key Infrastructure (PKI)]].
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The final step of the key creation process is to copy the files needed to the correct machines through a secure channel.
 
The final step of the key creation process is to copy the files needed to the correct machines through a secure channel.
  
{{Note|The rest of this article assumes that the keys and certificates are placed in /etc/openvpn.}}
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{{Note|The rest of this article assumes that the keys and certificates are placed in {{ic|/etc/openvpn}}.}}
  
 
The public ca.crt certificate is needed on all servers and clients. The private ca.key key is secret and only needed on the key generating machine.
 
The public ca.crt certificate is needed on all servers and clients. The private ca.key key is secret and only needed on the key generating machine.
  
A server needs server.crt, and dh2048.pem (public), and server.key and ta.key (private).
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A server needs server.crt, dh2048.pem (public), server.key, and ta.key (private).
 
   
 
   
A client needs client.crt (public), and client.key and ta.key (private).
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A client needs client.crt (public), client.key, and ta.key (private).
  
==A basic L3 IP routing configuration==
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== A basic L3 IP routing configuration ==
  
 
{{Note|Unless otherwise explicitly stated, the rest of this article assumes this basic configuration.}}
 
{{Note|Unless otherwise explicitly stated, the rest of this article assumes this basic configuration.}}
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OpenVPN is an extremely versatile piece of software and many configurations are possible, in fact machines can be both "servers" and "clients", blurring the distinction between server and client.
 
OpenVPN is an extremely versatile piece of software and many configurations are possible, in fact machines can be both "servers" and "clients", blurring the distinction between server and client.
  
What really distinguishes a server from a client (apart from the type of certificate used) is the configuration file itself. The openvpn daemon startup script reads all the .conf configuration files it finds in /etc/openvpn on startup and acts accordingly. In fact if it finds more than one configuration file, it will start one OpenVPN processes per configuration file.
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What really distinguishes a server from a client (apart from the type of certificate used) is the configuration file itself. The OpenVPN daemon start-up script reads all the .conf configuration files it finds in {{ic|/etc/openvpn}} on start-up and acts accordingly. If it finds more than one configuration file, it will start one OpenVPN process per configuration file.
  
This article explains how to setup a server called elmer, and a client that connects to it called bugs. More servers and clients can easily be added, by creating more key/certificate pairs and adding more server and client configuration files.
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This article explains how to set up a server named elmer and a client that connects to it named bugs. More servers and clients can easily be added by creating more key/certificate pairs and adding more server and client configuration files.
  
 
The OpenVPN package comes with a collection of example configuration files for different purposes. The sample server and client configuration files make an ideal starting point for a basic OpenVPN setup with the following features:
 
The OpenVPN package comes with a collection of example configuration files for different purposes. The sample server and client configuration files make an ideal starting point for a basic OpenVPN setup with the following features:
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For more advanced configurations, please see the official [http://openvpn.net/index.php/manuals/427-openvpn-22.html OpenVPN 2.2 man page] and the [http://openvpn.net/index.php/open-source/documentation OpenVPN documentation].
 
For more advanced configurations, please see the official [http://openvpn.net/index.php/manuals/427-openvpn-22.html OpenVPN 2.2 man page] and the [http://openvpn.net/index.php/open-source/documentation OpenVPN documentation].
  
===The server configuration file===
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=== The server configuration file ===
  
Copy the example server configuration file to /etc/openvpn/server.conf
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Copy the example server configuration file to {{ic|/etc/openvpn/server.conf}}:
  
{{bc|# cp /usr/share/openvpn/examples/server.conf /etc/openvpn/server.conf}}
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# cp /usr/share/openvpn/examples/server.conf /etc/openvpn/server.conf
  
 
Edit the following:
 
Edit the following:
  
* The ca, cert, key, and dh parameters to reflect the path and names of the keys and certificates. Specifying the paths will allow you to run the OpenVPN executable from any directory for testing purposes.
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* The {{ic|ca}}, {{ic|cert}}, {{ic|key}}, and {{ic|dh}} parameters to reflect the path and names of the keys and certificates. Specifying the paths will allow you to run the OpenVPN executable from any directory for testing purposes.
 
* Enable the SSL/TLS HMAC handshake protection. '''Note the use of the parameter 0 for a server'''.
 
* Enable the SSL/TLS HMAC handshake protection. '''Note the use of the parameter 0 for a server'''.
*It is recommended to run OpenVPN with reduced privileges once it has initialized, do this by uncommenting the user and group directives.
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* It is recommended to run OpenVPN with reduced privileges once it has initialized. Do this by uncommenting the {{ic|user}} and {{ic|group}} directives.
  
 
{{hc|/etc/openvpn/server.conf|
 
{{hc|/etc/openvpn/server.conf|
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{{Note|Note that if the server is behind a firewall or a NAT translating router, you will have to forward the OpenVPN UDP port (1194) to the server.}}
 
{{Note|Note that if the server is behind a firewall or a NAT translating router, you will have to forward the OpenVPN UDP port (1194) to the server.}}
  
===The client configuration file===
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=== The client configuration file ===
  
Copy the example client configuration file to /etc/openvpn/client.conf
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Copy the example client configuration file to {{ic|/etc/openvpn/client.conf}}:
  
{{bc|# cp /usr/share/openvpn/examples/client.conf /etc/openvpn/client.conf}}
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# cp /usr/share/openvpn/examples/client.conf /etc/openvpn/client.conf
  
 
Edit the following:
 
Edit the following:
  
* The remote directive to reflect either the server's [[Wikipedia:Fully qualified domain name|Fully Qualified Domain Name]] hostname (as known to the client) or its IP address.
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* The {{ic|remote}} directive to reflect either the server's [[Wikipedia:Fully qualified domain name|Fully Qualified Domain Name]], hostname (as known to the client), or its IP address.
* Uncomment the user and group directives to drop privileges.
+
* Uncomment the {{ic|user}} and {{ic|group}} directives to drop privileges.
* The ca, cert, and key parameters to reflect the path and names of the keys and certificates.
+
* The {{ic|ca}}, {{ic|cert}}, and {{ic|key}} parameters to reflect the path and names of the keys and certificates.
 
* Enable the SSL/TLS HMAC handshake protection. '''Note the use of the parameter 1 for a client'''.
 
* Enable the SSL/TLS HMAC handshake protection. '''Note the use of the parameter 1 for a client'''.
  
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}}
 
}}
  
===Testing the OpenVPN configuration===
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=== Testing the OpenVPN configuration ===
  
 
Run {{ic|# openvpn /etc/openvpn/server.conf}} on the server, and {{ic|# openvpn /etc/openvpn/client.conf}} on the client.  You should see something similar to this:
 
Run {{ic|# openvpn /etc/openvpn/server.conf}} on the server, and {{ic|# openvpn /etc/openvpn/client.conf}} on the client.  You should see something similar to this:
  
{{hc|# openvpn /etc/openvpn/server.conf|<nowiki>
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{{hc|# openvpn /etc/openvpn/server.conf|2=
 
Wed Dec 28 14:41:26 2011 OpenVPN 2.2.1 x86_64-unknown-linux-gnu [SSL] [LZO2] [EPOLL] [eurephia] built on Aug 13 2011
 
Wed Dec 28 14:41:26 2011 OpenVPN 2.2.1 x86_64-unknown-linux-gnu [SSL] [LZO2] [EPOLL] [eurephia] built on Aug 13 2011
 
Wed Dec 28 14:41:26 2011 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables
 
Wed Dec 28 14:41:26 2011 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables
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Wed Dec 28 14:41:57 2011 bugs/95.126.136.73:48904 PUSH: Received control message: 'PUSH_REQUEST'
 
Wed Dec 28 14:41:57 2011 bugs/95.126.136.73:48904 PUSH: Received control message: 'PUSH_REQUEST'
 
Wed Dec 28 14:41:57 2011 bugs/95.126.136.73:48904 SENT CONTROL [bugs]: 'PUSH_REPLY,route 10.8.0.1,topology net30,ping 10,ping-restart 120,ifconfig 10.8.0.6 10.8.0.5' (status=1)
 
Wed Dec 28 14:41:57 2011 bugs/95.126.136.73:48904 SENT CONTROL [bugs]: 'PUSH_REPLY,route 10.8.0.1,topology net30,ping 10,ping-restart 120,ifconfig 10.8.0.6 10.8.0.5' (status=1)
</nowiki>}}
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}}
  
{{hc|# openvpn /etc/openvpn/client.conf|<nowiki>
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{{hc|# openvpn /etc/openvpn/client.conf|2=
 
Wed Dec 28 14:41:50 2011 OpenVPN 2.2.1 i686-pc-linux-gnu [SSL] [LZO2] [EPOLL] [eurephia] built on Aug 13 2011
 
Wed Dec 28 14:41:50 2011 OpenVPN 2.2.1 i686-pc-linux-gnu [SSL] [LZO2] [EPOLL] [eurephia] built on Aug 13 2011
 
Wed Dec 28 14:41:50 2011 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables
 
Wed Dec 28 14:41:50 2011 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables
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Wed Dec 28 14:41:57 2011 UID set to nobody
 
Wed Dec 28 14:41:57 2011 UID set to nobody
 
Wed Dec 28 14:41:57 2011 Initialization Sequence Completed
 
Wed Dec 28 14:41:57 2011 Initialization Sequence Completed
</nowiki>}}
+
}}
  
On the server, find the IP assigned to the tunX device:
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On the server, find the IP address assigned to the tunX device:
  
{{hc|# ip addr show|<nowiki>
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{{hc|# ip addr show|2=
 
.
 
.
 
.
 
.
 
40: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 100
 
40: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 100
 
     link/none
 
     link/none
     inet 10.8.0.1 peer 10.8.0.2/32 scope global tun0</nowiki>}}
+
     inet 10.8.0.1 peer 10.8.0.2/32 scope global tun0
 +
}}
  
 
Here we see that the server end of the tunnel has been given the IP address 10.8.0.1.
 
Here we see that the server end of the tunnel has been given the IP address 10.8.0.1.
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Do the same on the client:
 
Do the same on the client:
  
{{hc|# ip addr show|<nowiki>
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{{hc|# ip addr show|2=
 
.
 
.
 
.
 
.
 
37: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 100
 
37: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 100
 
     link/none
 
     link/none
     inet 10.8.0.6 peer 10.8.0.5/32 scope global tun0</nowiki>}}
+
     inet 10.8.0.6 peer 10.8.0.5/32 scope global tun0
 +
}}
  
And the client side has been given the IP 10.8.0.6.
+
And the client side has been given the IP address 10.8.0.6.
  
 
Now try pinging the interfaces.
 
Now try pinging the interfaces.
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On the server:
 
On the server:
  
{{hc|# ping -c3 10.8.0.6|<nowiki>
+
{{hc|# ping -c3 10.8.0.6|2=
 
PING 10.8.0.6 (10.8.0.6) 56(84) bytes of data.
 
PING 10.8.0.6 (10.8.0.6) 56(84) bytes of data.
 
64 bytes from 10.8.0.6: icmp_req=1 ttl=64 time=238 ms
 
64 bytes from 10.8.0.6: icmp_req=1 ttl=64 time=238 ms
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3 packets transmitted, 3 received, 0% packet loss, time 2002ms
 
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
 
rtt min/avg/max/mdev = 205.862/227.266/238.788/15.160 ms
 
rtt min/avg/max/mdev = 205.862/227.266/238.788/15.160 ms
</nowiki>}}
+
}}
  
 
On the client:
 
On the client:
  
{{hc|# ping -c3 10.8.0.1|<nowiki>
+
{{hc|# ping -c3 10.8.0.1|2=
 
PING 10.8.0.1 (10.8.0.1) 56(84) bytes of data.
 
PING 10.8.0.1 (10.8.0.1) 56(84) bytes of data.
 
64 bytes from 10.8.0.1: icmp_req=1 ttl=64 time=158 ms
 
64 bytes from 10.8.0.1: icmp_req=1 ttl=64 time=158 ms
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3 packets transmitted, 3 received, 0% packet loss, time 2001ms
 
3 packets transmitted, 3 received, 0% packet loss, time 2001ms
 
rtt min/avg/max/mdev = 157.426/158.278/158.940/0.711 ms
 
rtt min/avg/max/mdev = 157.426/158.278/158.940/0.711 ms
</nowiki>}}
+
}}
  
 
You now have a working OpenVPN installation, and your client (bugs) will be able to use services on the server (elmer), and vice versa.
 
You now have a working OpenVPN installation, and your client (bugs) will be able to use services on the server (elmer), and vice versa.
  
{{Note|If using a firewall, make sure that ip packets on the TUN device are not blocked.}}
+
{{Note|If using a firewall, make sure that IP packets on the TUN device are not blocked.}}
  
===OpenVPN MTU, Fragment, and MSS configuration===
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=== Configure the MTU with Fragment and MSS ===
  
{{Note|If you do not configure MTU then you will notice that small packets like ping and DNS will work, however web browsing will not work.}}
+
{{Note|If you do not configure MTU, then you will notice that small packets like ping and DNS will work, however web browsing will not work.}}
  
Now it is time to configure the maximum segment size (MSS). In order to do this we need to discover what is the smallest MTU along the path between the client and server. In order to do this you can ping the server and disable fragmentation. Then specify the max packetsize.
+
Now it is time to configure the maximum segment size (MSS). In order to do this we need to discover what is the smallest MTU along the path between the client and server. In order to do this you can ping the server and disable fragmentation. Then specify the max packet size.
  
{{hc|# ping -c5 -M do -s 1500 elmer.acmecorp.org|<nowiki>
+
{{hc|# ping -c5 -M do -s 1500 elmer.acmecorp.org|2=
 
PING elmer.acmecorp.org (99.88.77.66) 1500(1528) bytes of data.
 
PING elmer.acmecorp.org (99.88.77.66) 1500(1528) bytes of data.
 
From 1.2.3.4 (99.88.77.66) icmp_seq=1 Frag needed and DF set (mtu = 576)
 
From 1.2.3.4 (99.88.77.66) icmp_seq=1 Frag needed and DF set (mtu = 576)
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--- core.myrelay.net ping statistics ---
 
--- core.myrelay.net ping statistics ---
 
0 packets transmitted, 0 received, +5 errors
 
0 packets transmitted, 0 received, +5 errors
</nowiki>}}
+
}}
  
 
We received an ICMP message telling us the MTU is 576 bytes. The means we need to fragment the UDP packets smaller then 576 bytes to allow for some UDP overhead.
 
We received an ICMP message telling us the MTU is 576 bytes. The means we need to fragment the UDP packets smaller then 576 bytes to allow for some UDP overhead.
  
{{hc|# ping -c5 -M do -s 548 elmer.acmecorp.org|<nowiki>
+
{{hc|# ping -c5 -M do -s 548 elmer.acmecorp.org|2=
 
PING elmer.acmecorp.org (99.88.77.66) 548(576) bytes of data.
 
PING elmer.acmecorp.org (99.88.77.66) 548(576) bytes of data.
 
556 bytes from 99.88.77.66: icmp_seq=1 ttl=48 time=206 ms
 
556 bytes from 99.88.77.66: icmp_seq=1 ttl=48 time=206 ms
Line 244: Line 247:
 
5 packets transmitted, 5 received, 0% packet loss, time 4001ms
 
5 packets transmitted, 5 received, 0% packet loss, time 4001ms
 
rtt min/avg/max/mdev = 206.027/210.603/224.158/6.832 ms
 
rtt min/avg/max/mdev = 206.027/210.603/224.158/6.832 ms
</nowiki>}}
+
}}
  
 
After some trial and error..., we discover that we need to fragment packets on 548 bytes. In order to do this we specify this fragment size in the configuration and instruct OpenVPN to fix the Maximum Segment Size (MSS).
 
After some trial and error..., we discover that we need to fragment packets on 548 bytes. In order to do this we specify this fragment size in the configuration and instruct OpenVPN to fix the Maximum Segment Size (MSS).
Line 269: Line 272:
  
  
{{Note|This will add about 3min's to OpenVPN start time. It is advisable to configure hard code the fragment size unless your client is a laptop that will be connecting over many different networks.}}
+
{{Note|This will add about 3 minutes to OpenVPN start time. It is advisable to configure the fragment size unless your client is a laptop that will be connecting over many different networks and the bottle neck is on the client side.}}
  
 
You can also allow OpenVPN to do this for you by having OpenVPN do the ping testing every time the client connects to the VPN.
 
You can also allow OpenVPN to do this for you by having OpenVPN do the ping testing every time the client connects to the VPN.
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}}
 
}}
  
==Starting OpenVPN==
+
== Starting OpenVPN ==
  
===Manual startup===
+
=== Manual startup ===
  
To troubleshoot a vpn connection, start the daemon manually with: {{ic|# openvpn /etc/openvpn/client.conf}}.
+
To troubleshoot a VPN connection, start the daemon manually with: {{ic|# openvpn /etc/openvpn/client.conf}}.
  
=== Systemd service configuration ===
+
=== systemd service configuration ===
  
To start openvpn automatically at system boot, [[Daemon|enable]] {{ic|openvpn@''<configuration>''.service}}.
+
To start OpenVPN automatically at system boot, [[Daemon|enable]] {{ic|openvpn@''<configuration>''.service}}.
  
 
For example, if the configuration file is {{ic|/etc/openvpn/client.conf}}, the service name is {{ic|openvpn@client.service}}.
 
For example, if the configuration file is {{ic|/etc/openvpn/client.conf}}, the service name is {{ic|openvpn@client.service}}.
  
==Advanced L3 IP routing==
+
== Advanced L3 IP routing==
  
===Prerequisites for routing a LAN===
+
=== Prerequisites for routing a LAN ===
  
====IPv4 forwarding====
+
==== IPv4 forwarding ====
  
 
For a host to be able to forward IPv4 packets between the LAN and VPN, it must be able to forward the packets between its NIC and its tun/tap device.
 
For a host to be able to forward IPv4 packets between the LAN and VPN, it must be able to forward the packets between its NIC and its tun/tap device.
  
Edit {{ic|etc/sysctl.conf}} to permanently enable ipv4 packet forwarding (takes effect at the next boot):
+
Edit or create {{ic|etc/sysctl.d/99-sysctl.conf}} to permanently enable IPv4 packet forwarding (takes effect at the next boot):
  
{{hc|/etc/sysctl.conf|<nowiki>
+
{{hc|/etc/sysctl.d/99-sysctl.conf|2=
 
# Enable packet forwarding
 
# Enable packet forwarding
 
net.ipv4.ip_forward=1
 
net.ipv4.ip_forward=1
</nowiki>}}
+
}}
  
To temporarily enable without rebooting: {{ic|# echo 1 > /proc/sys/net/ipv4/ip_forward}}
+
{{Tip|To temporarily enable without rebooting: {{ic|# echo 1 > /proc/sys/net/ipv4/ip_forward}}}}
  
====Promiscious LAN inteface====
+
==== Promiscuous LAN interface ====
  
The forwarding host's NIC (eth0 in the following examples) must also be able to accept packets for a different IP address than it is configured for, something known as [[Wikipedia:Promiscuous_mode|promiscious mode]]. To enable, add the following to {{ic|/etc/rc.local}} (takes effect at the next boot):
+
The forwarding host's NIC (enp1s0 in the following examples) must also be able to accept packets for a different IP address than it is configured for, something known as [[Wikipedia:Promiscuous_mode|promiscuous mode]]. To set the {{ic|enp1s0}} in promiscuous mode using systemd, use [[ Systemd/Services#Set_network_interface_in_promiscuous_mode | this service file ]] and enable it using:
  
{{hc|/etc/rc.local|ip link set dev eth0 promisc on}}
+
  # systemctl enable promiscuous@enp1s0
  
To temporarily enable without rebooting: {{ic|# ip link set dev eth0 promisc on}}
+
{{Tip|To temporarily enable without rebooting: {{ic|# ip link set dev enp1s0 promisc on}}.}}
  
To set the {{ic|eth0}} in promiscuous mode using systemd use [[ Systemd/Services#Set_network_interface_in_promiscuous_mode | this service file ]] and enable it using:
+
==== Routing tables ====
 
+
  # systemctl enable promiscuous@eth0.service
+
 
+
====Routing tables====
+
  
 
{{Accuracy|Investigate if a routing protocol like RIP, QUAGGA, BIRD, etc can be used}}
 
{{Accuracy|Investigate if a routing protocol like RIP, QUAGGA, BIRD, etc can be used}}
Line 342: Line 341:
 
* Use [[iptables]]' NAT feature on the LAN/VPN gateway to masquerade the incoming VPN IP packets.
 
* Use [[iptables]]' NAT feature on the LAN/VPN gateway to masquerade the incoming VPN IP packets.
  
===Connect the server LAN to a client===
+
=== Connect the server LAN to a client ===
  
 
The server is on a LAN using the 10.66.0.0/24 subnet.  To inform the client about the available subnet, add a push directive to the server configuration file:{{hc|/etc/openvpn/server.conf|push "route 10.66.0.0 255.255.255.0"}}
 
The server is on a LAN using the 10.66.0.0/24 subnet.  To inform the client about the available subnet, add a push directive to the server configuration file:{{hc|/etc/openvpn/server.conf|push "route 10.66.0.0 255.255.255.0"}}
  
{{Note|Remember to enable ipv4 forwarding and to make the LAN interface promiscuous on the server. Make sure the server LAN knows how to reach the VPN client.}}
+
{{Note|
 
+
* Remember to enable IPv4 forwarding and to make the LAN interface promiscuous on the server. Make sure the server LAN knows how to reach the VPN client.
{{Note|To route more LANs from the server to the client, add more push directives to the server configuration file, but keep in mind that the server side LANs will need to know how to route to the client.}}
+
* To route more LANs from the server to the client, add more push directives to the server configuration file, but keep in mind that the server side LANs will need to know how to route to the client.
 +
}}
  
===Connect the client LAN to a server===
+
=== Connect the client LAN to a server ===
  
 
Prerequisites:
 
Prerequisites:
Line 360: Line 360:
 
Create a client configuration directory on the server.  It will be searched for a file named the same as the client's common name, and the directives will be applied to the client when it connects.
 
Create a client configuration directory on the server.  It will be searched for a file named the same as the client's common name, and the directives will be applied to the client when it connects.
  
{{bc|# mkdir -p /etc/openvpn/ccd}}
+
# mkdir -p /etc/openvpn/ccd
  
 
Create a file in the client configuration directory called bugs, containing the {{ic|iroute 192.168.4.0 255.255.255.0}} directive.  It tells the server what subnet should be routed to the client:
 
Create a file in the client configuration directory called bugs, containing the {{ic|iroute 192.168.4.0 255.255.255.0}} directive.  It tells the server what subnet should be routed to the client:
Line 373: Line 373:
 
}}
 
}}
  
{{Note|Remember to enable ipv4 forwarding and to make the LAN interface promiscuous on the client. Make sure the client LAN knows how to reach the VPN server.}}
+
{{Note|
 
+
* Remember to enable IPv4 forwarding and to make the LAN interface promiscuous on the client. Make sure the client LAN knows how to reach the VPN server.
{{Note|To route more LANs from the client to the server, add more iroute and route directives to the appropriate configuration files, but keep in mind that the client side LANs will need to know how to route to the server.}}
+
* To route more LANs from the client to the server, add more iroute and route directives to the appropriate configuration files, but keep in mind that the client side LANs will need to know how to route to the server.
 +
}}
  
===Connect both the client and server LANs===
+
=== Connect both the client and server LANs ===
  
 
Combine the two previous sections:
 
Combine the two previous sections:
Line 388: Line 389:
 
route 192.168.4.0 255.255.255.0
 
route 192.168.4.0 255.255.255.0
 
}}
 
}}
 
  
 
{{hc|/etc/openvpn/ccd/bugs|iroute 192.168.4.0 255.255.255.0}}
 
{{hc|/etc/openvpn/ccd/bugs|iroute 192.168.4.0 255.255.255.0}}
  
 +
{{Note|Remember to enable IPv4 forwarding and to make the LAN interfaces promiscuous on both the client and the server. Make sure that all the LANs or the needed hosts can route to all the destinations.}}
  
{{Note|Remember to enable ipv4 forwarding and to make the LAN interfaces promiscuous on both the client and the server. Make sure that all the LANs or the needed hosts can route to all the destinations.}}
+
=== Connect clients and client LANs ===
 
+
===Connect clients and client LANs===
+
  
By default clients will not see each other, to allow ip packets to flow between clients and/or client LANs add a client-to-client directive to the server configuration file: {{hc|/etc/openvpn/server.conf|client-to-client}}
+
By default clients will not see each other. To allow IP packets to flow between clients and/or client LANs, add a client-to-client directive to the server configuration file: {{hc|/etc/openvpn/server.conf|client-to-client}}
  
In order for another client or client LAN to see a specific client LAN you will need to add a push directive for each client subnet to the server configuration file (this will make the server announce the available subnet(s) to other clients):
+
In order for another client or client LAN to see a specific client LAN, you will need to add a push directive for each client subnet to the server configuration file (this will make the server announce the available subnet(s) to other clients):
  
 
{{hc|/etc/openvpn/server.conf|
 
{{hc|/etc/openvpn/server.conf|
Line 411: Line 410:
 
{{Note|As always, make sure that the routing is properly configured.}}
 
{{Note|As always, make sure that the routing is properly configured.}}
  
==L2 Ethernet bridging==
+
== L2 Ethernet bridging ==
  
 
{{Expansion|Please add a well thought out section on L2 bridging.}}
 
{{Expansion|Please add a well thought out section on L2 bridging.}}
Line 417: Line 416:
 
For now see: [[OpenVPN Bridge]]
 
For now see: [[OpenVPN Bridge]]
  
==Contributions that do not yet fit into the main article==
+
== Contributions that do not yet fit into the main article ==
  
 
{{Accuracy|Not quite sure where this fits into the main article yet}}
 
{{Accuracy|Not quite sure where this fits into the main article yet}}
  
===Routing client traffic through the server===
+
=== Routing client traffic through the server ===
  
 
Append the following to your server's openvpn.conf configuration file:
 
Append the following to your server's openvpn.conf configuration file:
{{bc|
+
 
push "redirect-gateway def1"
+
push "redirect-gateway def1"
push "dhcp-option DNS 192.168.1.1"
+
push "dhcp-option DNS 192.168.1.1"
}}
+
 
 
Change "192.168.1.1" to your preferred DNS IP address.
 
Change "192.168.1.1" to your preferred DNS IP address.
  
If you have problems with non responsive DNS after connecting to server, install [[BIND]] as simple DNS forwarder and push openvpn ip address of server as DNS to clients.
+
If you have problems with non responsive DNS after connecting to server, install [[BIND]] as simple DNS forwarder and push the IP address of the OpenVPN server as DNS to clients.
 +
 
 +
==== Configure ufw for routing ====
  
====Configure ufw for routing====
 
 
Configure your ufw settings to enable routing traffic from clients through server.
 
Configure your ufw settings to enable routing traffic from clients through server.
  
You must change default forward policy, edit /etc/sysctl.conf to permanently enable ipv4 packet forwarding. Takes effect at the next boot.
+
You must change default forward policy, edit {{ic|/etc/sysctl.conf}} to permanently enable IPv4 packet forwarding. Takes effect at the next boot.
{{hc|/etc/sysctl.conf|<nowiki>
+
{{hc|/etc/sysctl.conf|2=
 
# Enable packet forwarding
 
# Enable packet forwarding
 
net.ipv4.ip_forward=1
 
net.ipv4.ip_forward=1
</nowiki>}}  
+
}}  
  
And then configure ufw in '''/etc/default/ufw'''
+
And then configure ufw in {{ic|/etc/default/ufw}}:
  
{{hc|/etc/default/ufw|<nowiki>
+
{{hc|/etc/default/ufw|2=
DEFAULT_FORWARD_POLICY=”ACCEPT”
+
DEFAULT_FORWARD_POLICY="ACCEPT"
</nowiki>}}
+
}}
  
Now change '''/etc/ufw/before.rules''', add following code after header and before *filter line, don't forget to change ip range to yours
+
Now change {{ic|/etc/ufw/before.rules}}, and add the following code after the header and before the "*filter" line. Don't forget to change the IP/subnet mask to match the one in {{ic|/etc/openvpn/server.conf}}.
  
{{hc|/etc/ufw/before.rules|<nowiki>
+
{{hc|/etc/ufw/before.rules|2=
# nat Table rules
+
# NAT (Network Address Translation) table rules
 
*nat
 
*nat
 
:POSTROUTING ACCEPT [0:0]
 
:POSTROUTING ACCEPT [0:0]
  
# Allow traffic from clients to eth0
+
# Allow traffic from clients to enp1s0
-A POSTROUTING -s 192.168.1.0/24 -o eth0 -j MASQUERADE
+
-A POSTROUTING -s 10.8.0.0/8 -o enp1s0 -j MASQUERADE
  
# don.t delete the .COMMIT. line or these nat table rules won.t be processed
+
# don't delete the "COMMIT" line or the NAT table rules above won't be processed
 
COMMIT
 
COMMIT
</nowiki>}}
+
}}
  
Open openvpn port 1194
+
Open OpenVPN port 1194:
  
{{bc|
+
ufw allow 1194
ufw allow 1194
+
}}
+
  
====usage of iptables====
+
==== Using iptables ====
  
 
Use an iptable for NAT forwarding:
 
Use an iptable for NAT forwarding:
{{bc|
 
echo 1 > /proc/sys/net/ipv4/ip_forward
 
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE
 
}}
 
  
If running ArchLinux in a OpenVZ VPS environment [http://thecodeninja.net/linux/openvpn-archlinux-openvz-vps/]:
+
echo 1 > /proc/sys/net/ipv4/ip_forward
{{bc|
+
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o enp1s0 -j MASQUERADE
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o venet0 -j SNAT --to (venet0 ip)
+
 
}}
+
If running Arch Linux in a OpenVZ VPS environment [http://thecodeninja.net/linux/openvpn-archlinux-openvz-vps/]:
 +
 
 +
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o venet0 -j SNAT --to (venet0 ip)
  
 
If all is well, make the changes permanent:
 
If all is well, make the changes permanent:
  
Edit /etc/conf.d/iptables and change IPTABLES_FORWARD=1
+
Edit {{ic|/etc/conf.d/iptables}} and change IPTABLES_FORWARD=1
 
+
{{bc|
+
/etc/rc.d/iptables save
+
}}
+
  
 +
# iptables-save > /etc/iptables/iptables.rules
  
===Configuring LDAP authorization===
+
=== Configuring LDAP authorization ===
 
   
 
   
 
{{Accuracy|what does the following do, and is the package still supported?}}
 
{{Accuracy|what does the following do, and is the package still supported?}}
You may also want to install {{AUR|openvpn-authldap-plugin}}, available in the [[Arch User Repository]].
+
You may also want to install {{AUR|openvpn-authldap-plugin}}, available in the [[AUR]].
  
===Deprecated older wiki content===
+
=== Deprecated older wiki content ===
  
 
{{Accuracy|See how this older content can be fitted into the new article}}
 
{{Accuracy|See how this older content can be fitted into the new article}}
  
 
====Using PAM and passwords to authenticate====
 
====Using PAM and passwords to authenticate====
 +
 
{{bc|
 
{{bc|
 
port 1194
 
port 1194
Line 525: Line 519:
 
client-cert-not-required
 
client-cert-not-required
 
username-as-common-name
 
username-as-common-name
plugin /usr/lib/openvpn/openvpn-auth-pam.so login
+
plugin /usr/lib/openvpn/plugins/openvpn-plugin-auth-pam.so login
 
}}
 
}}
  
====Using certs to authenticate====
+
==== Using certs to authenticate ====
 +
 
 
{{bc|
 
{{bc|
 
port 1194
 
port 1194
Line 554: Line 549:
 
}}
 
}}
  
====Routing traffic through the server====
+
==== Routing traffic through the server ====
  
 
Append the following to your server's openvpn.conf configuration file:
 
Append the following to your server's openvpn.conf configuration file:
{{bc|
+
 
push "dhcp-option DNS 192.168.1.1"
+
push "dhcp-option DNS 192.168.1.1"
push "redirect-gateway def1"
+
push "redirect-gateway def1"
}}
+
 
 
Change "192.168.1.1" to your external DNS IP address.
 
Change "192.168.1.1" to your external DNS IP address.
  
 
Use an iptable for NAT forwarding:
 
Use an iptable for NAT forwarding:
{{bc|
 
echo 1 > /proc/sys/net/ipv4/ip_forward
 
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE
 
}}
 
  
If running ArchLinux in a OpenVZ VPS environment [http://thecodeninja.net/linux/openvpn-archlinux-openvz-vps/]:
+
echo 1 > /proc/sys/net/ipv4/ip_forward
{{bc|
+
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o enp1s0 -j MASQUERADE
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o venet0 -j SNAT --to (venet0 ip)
+
 
}}
+
If running Arch Linux in a OpenVZ VPS environment [http://thecodeninja.net/linux/openvpn-archlinux-openvz-vps/]:
 +
 
 +
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o venet0 -j SNAT --to (venet0 ip)
  
 
If all is well, make the changes permanent:
 
If all is well, make the changes permanent:
  
Edit /etc/conf.d/iptables and change IPTABLES_FORWARD=1
+
Edit {{ic|/etc/conf.d/iptables}} and change IPTABLES_FORWARD=1
  
{{bc|
+
# iptables-save > /etc/iptables/iptables.rules
/etc/rc.d/iptables save
+
 
}}
+
==== Setting up the client ====
 +
 
 +
The client-side .conf file
 +
 
 +
===== With password authentication =====
  
====Setting up the Client====
 
The clientside .conf file
 
=====With password authentication=====
 
 
{{bc|
 
{{bc|
 
client
 
client
 
dev tap
 
dev tap
 
proto udp
 
proto udp
 +
mtu-test
 
remote <address> 1194
 
remote <address> 1194
 
resolv-retry infinite
 
resolv-retry infinite
Line 603: Line 598:
 
* second - password
 
* second - password
  
=====Certs authentication=====
+
===== Certificates authentication =====
 +
 
 
{{bc|
 
{{bc|
 
client
 
client
Line 625: Line 621:
  
 
Install the tunnel/tap module:
 
Install the tunnel/tap module:
{{bc|
 
# sudo modprobe tun
 
}}
 
  
To have the '''tun''' module loaded automatically at boot time add it to the Modules line in /etc/rc.conf
+
# modprobe tun
 +
 
 +
To have the '''tun''' module loaded automatically at boot, read [[Kernel_modules]].
  
=====DNS=====
+
===== DNS =====
The DNS servers used by the system are defined in '''/etc/resolv.conf'''.  Traditionally, this file is the responsibility of whichever program deals with connecting the system to the network (e.g. Wicd, NetworkManager, etc...)  However, OpenVPN will need to modify this file if you want to be able to resolve names on the remote side.  To achieve this in a sensible way, install '''openresolv''', which makes it possible for more than one program to modify resolv.conf without stepping on each-other's toes.  Before continuing, test openresolv by restarting your network connection and ensuring that resolv.conf states that it was generated by "resolvconf", and that your DNS resolution still works as before.  You should not need to configure openresolv; it should be automatically detected and used by your network system.
+
  
Next, save the following script at '''/usr/share/openvpn/update-resolv-conf''':
+
The DNS servers used by the system are defined in {{ic|/etc/resolv.conf}}.  Traditionally, this file is the responsibility of whichever program deals with connecting the system to the network (e.g. Wicd, NetworkManager, etc...)  However, OpenVPN will need to modify this file if you want to be able to resolve names on the remote side.  To achieve this in a sensible way, install {{pkg|openresolv}}, which makes it possible for more than one program to modify resolv.conf without stepping on each-other's toes.  Before continuing, test openresolv by restarting your network connection and ensuring that resolv.conf states that it was generated by "resolvconf", and that your DNS resolution still works as before.  You should not need to configure openresolv; it should be automatically detected and used by your network system.
 +
 
 +
Next, save the following script at {{ic|/usr/share/openvpn/update-resolv-conf}}:
 
{{bc|<nowiki>
 
{{bc|<nowiki>
 
#!/bin/bash
 
#!/bin/bash
Line 646: Line 642:
 
# and Chris Hanson
 
# and Chris Hanson
 
# Licensed under the GNU GPL.  See /usr/share/common-licenses/GPL.
 
# Licensed under the GNU GPL.  See /usr/share/common-licenses/GPL.
#
+
# 07/2013 colin@daedrum.net Fixed intet name
 
# 05/2006 chlauber@bnc.ch
 
# 05/2006 chlauber@bnc.ch
 
#
 
#
Line 654: Line 650:
 
# foreign_option_3='dhcp-option DOMAIN be.bnc.ch'
 
# foreign_option_3='dhcp-option DOMAIN be.bnc.ch'
  
 +
#[ -x $(which resolvconf) ] || exit 0
 
[ -x /usr/sbin/resolvconf ] || exit 0
 
[ -x /usr/sbin/resolvconf ] || exit 0
  
Line 670: Line 667:
 
         fi
 
         fi
 
         if [ "$part2" == "DOMAIN" ] ; then
 
         if [ "$part2" == "DOMAIN" ] ; then
             IF_DNS_SEARCH="$part3"
+
             IF_DNS_SEARCH="$IF_DNS_SEARCH $part3"
 
         fi
 
         fi
 
       fi
 
       fi
Line 683: Line 680:
 
"
 
"
 
   done
 
   done
 +
  #echo -n "$R" | resolvconf -p -a "${dev}"
 
   echo -n "$R" | /usr/sbin/resolvconf -a "${dev}.inet"
 
   echo -n "$R" | /usr/sbin/resolvconf -a "${dev}.inet"
 
   ;;
 
   ;;
 
down)
 
down)
   /usr/sbin/resolvconf -d "${dev}.inet"
+
   resolvconf -d "${dev}"
 
   ;;
 
   ;;
 
esac
 
esac
Line 694: Line 692:
 
   $ chmod +x /usr/share/openvpn/update-resolv-conf
 
   $ chmod +x /usr/share/openvpn/update-resolv-conf
 
Next, add the following lines to your OpenVPN client configuration file:
 
Next, add the following lines to your OpenVPN client configuration file:
{{bc|
+
 
script-security 2
+
script-security 2
up /usr/share/openvpn/update-resolv-conf
+
up /usr/share/openvpn/update-resolv-conf
down /usr/share/openvpn/update-resolv-conf
+
down /usr/share/openvpn/update-resolv-conf
}}
+
  
 
Now, when your launch your OpenVPN connection, you should find that your resolv.conf file is updated accordingly, and also returns to normal when your close the connection.
 
Now, when your launch your OpenVPN connection, you should find that your resolv.conf file is updated accordingly, and also returns to normal when your close the connection.
  
=====Webmin=====
+
===== Webmin =====
  
 
{{AUR|webmin-plugin-openvpn}} is available in the [[AUR]].
 
{{AUR|webmin-plugin-openvpn}} is available in the [[AUR]].
{{Note|You must add "openvpn" to the end of /etc/webmin/webmin.acl.}}
+
{{Note|You must add "openvpn" to the end of {{ic|/etc/webmin/webmin.acl}}.}}
 +
 
 +
==== Connecting to the server ====
  
====Connecting to the Server====
 
 
You need to start the service on the server
 
You need to start the service on the server
{{bc|
+
systemctl start openvpn
/etc/rc.d/openvpn start
+
 
}}
+
To make it permanent:
You can add it to rc.conf to make it permanet.
+
systemctl enable openvpn
  
 
On the client, in the home directory create a folder that will hold your OpenVPN client config files along with the '''.crt'''/'''.key''' files. Assuming your OpenVPN config folder is called '''.openvpn''' and your client config file is '''vpn1.conf''', to connect to the server issue the following command:
 
On the client, in the home directory create a folder that will hold your OpenVPN client config files along with the '''.crt'''/'''.key''' files. Assuming your OpenVPN config folder is called '''.openvpn''' and your client config file is '''vpn1.conf''', to connect to the server issue the following command:
{{bc|
+
# cd ~/.openvpn && openvpn vpn1.conf
cd ~/.openvpn && sudo openvpn vpn1.conf
+
}}
+

Revision as of 21:23, 11 October 2013

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: (at least) add support for IPv6 and L2 Ethernet bridging (Discuss in Talk:OpenVPN#)

This article describes a basic installation and configuration of OpenVPN, suitable for private and small business use. For more detailed information, please see the OpenVPN 2.3 man page and the OpenVPN documentation.

OpenVPN is a robust and highly flexible VPN daemon. OpenVPN supports SSL/TLS security, Ethernet bridging, TCP or UDP tunnel transport through proxies or NAT, support for dynamic IP addresses and DHCP, scalability to hundreds or thousands of users, and portability to most major OS platforms.

OpenVPN is tightly bound to the OpenSSL library, and derives much of its crypto capabilities from it.

OpenVPN supports conventional encryption using a pre-shared secret key (Static Key mode) or public key security (SSL/TLS mode) using client & server certificates. OpenVPN also supports unencrypted TCP/UDP tunnels.

OpenVPN is designed to work with the TUN/TAP virtual networking interface that exists on most platforms.

Overall, OpenVPN aims to offer many of the key features of IPSec but with a relatively lightweight footprint.

OpenVPN was written by James Yonan and is published under the GNU General Public License (GPL).

Install OpenVPN

Install openvpn from the official repositories.

Note: The software contained in this package supports both server and client mode, so install it on all machines that need to create VPN connections.

Configure the system for TUN/TAP support

OpenVPN requires TUN/TAP support. Make sure to load at boot the tun module.

Read Kernel modules for more information.

The default kernel is already properly configured, but if you use another kernel make sure to enable the TUN/TAP module. If $ zgrep CONFIG_TUN /proc/config.gz returns CONFIG_TUN=n, make the following change to the kernel config file and rebuild the kernel.

Kernel config file
 Device Drivers
  --> Network device support
    [M] Universal TUN/TAP device driver support

Connect to a VPN provided by a third party

To connect to a VPN provided by a third party, most of the following can most likely be ignored. Use the certificates and instructions given by your provider, for instance see: Airvpn.

Create a Public Key Infrastructure (PKI) from scratch

If you are setting up OpenVPN from scratch, you will need to create a Public Key Infrastructure (PKI).

Create the needed certificates and keys by following: Create a Public Key Infrastructure Using the easy-rsa Scripts.

The final step of the key creation process is to copy the files needed to the correct machines through a secure channel.

Note: The rest of this article assumes that the keys and certificates are placed in /etc/openvpn.

The public ca.crt certificate is needed on all servers and clients. The private ca.key key is secret and only needed on the key generating machine.

A server needs server.crt, dh2048.pem (public), server.key, and ta.key (private).

A client needs client.crt (public), client.key, and ta.key (private).

A basic L3 IP routing configuration

Note: Unless otherwise explicitly stated, the rest of this article assumes this basic configuration.

OpenVPN is an extremely versatile piece of software and many configurations are possible, in fact machines can be both "servers" and "clients", blurring the distinction between server and client.

What really distinguishes a server from a client (apart from the type of certificate used) is the configuration file itself. The OpenVPN daemon start-up script reads all the .conf configuration files it finds in /etc/openvpn on start-up and acts accordingly. If it finds more than one configuration file, it will start one OpenVPN process per configuration file.

This article explains how to set up a server named elmer and a client that connects to it named bugs. More servers and clients can easily be added by creating more key/certificate pairs and adding more server and client configuration files.

The OpenVPN package comes with a collection of example configuration files for different purposes. The sample server and client configuration files make an ideal starting point for a basic OpenVPN setup with the following features:

  • Uses Public Key Infrastructure (PKI) for authentication.
  • Creates a VPN using a virtual TUN network interface (OSI L3 IP routing).
  • Listens for client connections on UDP port 1194 (OpenVPN's official IANA port number).
  • Distributes virtual addresses to connecting clients from the 10.8.0.0/24 subnet.

For more advanced configurations, please see the official OpenVPN 2.2 man page and the OpenVPN documentation.

The server configuration file

Copy the example server configuration file to /etc/openvpn/server.conf:

# cp /usr/share/openvpn/examples/server.conf /etc/openvpn/server.conf

Edit the following:

  • The ca, cert, key, and dh parameters to reflect the path and names of the keys and certificates. Specifying the paths will allow you to run the OpenVPN executable from any directory for testing purposes.
  • Enable the SSL/TLS HMAC handshake protection. Note the use of the parameter 0 for a server.
  • It is recommended to run OpenVPN with reduced privileges once it has initialized. Do this by uncommenting the user and group directives.
/etc/openvpn/server.conf
ca /etc/openvpn/ca.crt
cert /etc/openvpn/elmer.crt
key /etc/openvpn/elmer.key

dh /etc/openvpn/dh2048.pem
.
.
tls-auth /etc/openvpn/ta.key 0
.
.
user nobody
group nobody
Note: Note that if the server is behind a firewall or a NAT translating router, you will have to forward the OpenVPN UDP port (1194) to the server.

The client configuration file

Copy the example client configuration file to /etc/openvpn/client.conf:

# cp /usr/share/openvpn/examples/client.conf /etc/openvpn/client.conf

Edit the following:

  • The remote directive to reflect either the server's Fully Qualified Domain Name, hostname (as known to the client), or its IP address.
  • Uncomment the user and group directives to drop privileges.
  • The ca, cert, and key parameters to reflect the path and names of the keys and certificates.
  • Enable the SSL/TLS HMAC handshake protection. Note the use of the parameter 1 for a client.
/etc/openvpn/client.conf
remote elmer.acmecorp.org 1194
.
.
user nobody
group nobody
.
.
ca /etc/openvpn/ca.crt
cert /etc/openvpn/bugs.crt
key /etc/openvpn/bugs.key
.
.
tls-auth /etc/openvpn/ta.key 1

Testing the OpenVPN configuration

Run # openvpn /etc/openvpn/server.conf on the server, and # openvpn /etc/openvpn/client.conf on the client. You should see something similar to this:

# openvpn /etc/openvpn/server.conf
Wed Dec 28 14:41:26 2011 OpenVPN 2.2.1 x86_64-unknown-linux-gnu [SSL] [LZO2] [EPOLL] [eurephia] built on Aug 13 2011
Wed Dec 28 14:41:26 2011 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables
Wed Dec 28 14:41:26 2011 Diffie-Hellman initialized with 2048 bit key
.
.
Wed Dec 28 14:41:54 2011 bugs/95.126.136.73:48904 MULTI: primary virtual IP for bugs/95.126.136.73:48904: 10.8.0.6
Wed Dec 28 14:41:57 2011 bugs/95.126.136.73:48904 PUSH: Received control message: 'PUSH_REQUEST'
Wed Dec 28 14:41:57 2011 bugs/95.126.136.73:48904 SENT CONTROL [bugs]: 'PUSH_REPLY,route 10.8.0.1,topology net30,ping 10,ping-restart 120,ifconfig 10.8.0.6 10.8.0.5' (status=1)
# openvpn /etc/openvpn/client.conf
Wed Dec 28 14:41:50 2011 OpenVPN 2.2.1 i686-pc-linux-gnu [SSL] [LZO2] [EPOLL] [eurephia] built on Aug 13 2011
Wed Dec 28 14:41:50 2011 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables
Wed Dec 28 14:41:50 2011 LZO compression initialized
.
.
Wed Dec 28 14:41:57 2011 GID set to nobody
Wed Dec 28 14:41:57 2011 UID set to nobody
Wed Dec 28 14:41:57 2011 Initialization Sequence Completed

On the server, find the IP address assigned to the tunX device:

# ip addr show
.
.
40: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 100
    link/none
    inet 10.8.0.1 peer 10.8.0.2/32 scope global tun0

Here we see that the server end of the tunnel has been given the IP address 10.8.0.1.

Do the same on the client:

# ip addr show
.
.
37: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 100
    link/none
    inet 10.8.0.6 peer 10.8.0.5/32 scope global tun0

And the client side has been given the IP address 10.8.0.6.

Now try pinging the interfaces.

On the server:

# ping -c3 10.8.0.6
PING 10.8.0.6 (10.8.0.6) 56(84) bytes of data.
64 bytes from 10.8.0.6: icmp_req=1 ttl=64 time=238 ms
64 bytes from 10.8.0.6: icmp_req=2 ttl=64 time=237 ms
64 bytes from 10.8.0.6: icmp_req=3 ttl=64 time=205 ms

--- 10.8.0.6 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 205.862/227.266/238.788/15.160 ms

On the client:

# ping -c3 10.8.0.1
PING 10.8.0.1 (10.8.0.1) 56(84) bytes of data.
64 bytes from 10.8.0.1: icmp_req=1 ttl=64 time=158 ms
64 bytes from 10.8.0.1: icmp_req=2 ttl=64 time=158 ms
64 bytes from 10.8.0.1: icmp_req=3 ttl=64 time=157 ms

--- 10.8.0.1 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2001ms
rtt min/avg/max/mdev = 157.426/158.278/158.940/0.711 ms

You now have a working OpenVPN installation, and your client (bugs) will be able to use services on the server (elmer), and vice versa.

Note: If using a firewall, make sure that IP packets on the TUN device are not blocked.

Configure the MTU with Fragment and MSS

Note: If you do not configure MTU, then you will notice that small packets like ping and DNS will work, however web browsing will not work.

Now it is time to configure the maximum segment size (MSS). In order to do this we need to discover what is the smallest MTU along the path between the client and server. In order to do this you can ping the server and disable fragmentation. Then specify the max packet size.

# ping -c5 -M do -s 1500 elmer.acmecorp.org
PING elmer.acmecorp.org (99.88.77.66) 1500(1528) bytes of data.
From 1.2.3.4 (99.88.77.66) icmp_seq=1 Frag needed and DF set (mtu = 576)
From 1.2.3.4 (99.88.77.66) icmp_seq=1 Frag needed and DF set (mtu = 576)
From 1.2.3.4 (99.88.77.66) icmp_seq=1 Frag needed and DF set (mtu = 576)
From 1.2.3.4 (99.88.77.66) icmp_seq=1 Frag needed and DF set (mtu = 576)
From 1.2.3.4 (99.88.77.66) icmp_seq=1 Frag needed and DF set (mtu = 576)

--- core.myrelay.net ping statistics ---
0 packets transmitted, 0 received, +5 errors

We received an ICMP message telling us the MTU is 576 bytes. The means we need to fragment the UDP packets smaller then 576 bytes to allow for some UDP overhead.

# ping -c5 -M do -s 548 elmer.acmecorp.org
PING elmer.acmecorp.org (99.88.77.66) 548(576) bytes of data.
556 bytes from 99.88.77.66: icmp_seq=1 ttl=48 time=206 ms
556 bytes from 99.88.77.66: icmp_seq=2 ttl=48 time=224 ms
556 bytes from 99.88.77.66: icmp_seq=3 ttl=48 time=206 ms
556 bytes from 99.88.77.66: icmp_seq=4 ttl=48 time=207 ms
556 bytes from 99.88.77.66: icmp_seq=5 ttl=48 time=208 ms

--- myrelay.net ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4001ms
rtt min/avg/max/mdev = 206.027/210.603/224.158/6.832 ms

After some trial and error..., we discover that we need to fragment packets on 548 bytes. In order to do this we specify this fragment size in the configuration and instruct OpenVPN to fix the Maximum Segment Size (MSS).

/etc/openvpn/client.conf
remote elmer.acmecorp.org 1194
.
.
fragment 548
mssfix
.
.
user nobody
group nobody
.
.
ca /etc/openvpn/ca.crt
cert /etc/openvpn/bugs.crt
key /etc/openvpn/bugs.key
.
.
tls-auth /etc/openvpn/ta.key 1


Note: This will add about 3 minutes to OpenVPN start time. It is advisable to configure the fragment size unless your client is a laptop that will be connecting over many different networks and the bottle neck is on the client side.

You can also allow OpenVPN to do this for you by having OpenVPN do the ping testing every time the client connects to the VPN.

/etc/openvpn/client.conf
remote elmer.acmecorp.org 1194
.
.
mtu-test
.
.
user nobody
group nobody
.
.
ca /etc/openvpn/ca.crt
cert /etc/openvpn/bugs.crt
key /etc/openvpn/bugs.key
.
.
tls-auth /etc/openvpn/ta.key 1

Starting OpenVPN

Manual startup

To troubleshoot a VPN connection, start the daemon manually with: # openvpn /etc/openvpn/client.conf.

systemd service configuration

To start OpenVPN automatically at system boot, enable openvpn@<configuration>.service.

For example, if the configuration file is /etc/openvpn/client.conf, the service name is openvpn@client.service.

Advanced L3 IP routing

Prerequisites for routing a LAN

IPv4 forwarding

For a host to be able to forward IPv4 packets between the LAN and VPN, it must be able to forward the packets between its NIC and its tun/tap device.

Edit or create etc/sysctl.d/99-sysctl.conf to permanently enable IPv4 packet forwarding (takes effect at the next boot):

/etc/sysctl.d/99-sysctl.conf
# Enable packet forwarding
net.ipv4.ip_forward=1
Tip: To temporarily enable without rebooting: # echo 1 > /proc/sys/net/ipv4/ip_forward

Promiscuous LAN interface

The forwarding host's NIC (enp1s0 in the following examples) must also be able to accept packets for a different IP address than it is configured for, something known as promiscuous mode. To set the enp1s0 in promiscuous mode using systemd, use this service file and enable it using:

 # systemctl enable promiscuous@enp1s0
Tip: To temporarily enable without rebooting: # ip link set dev enp1s0 promisc on.

Routing tables

Tango-inaccurate.pngThe factual accuracy of this article or section is disputed.Tango-inaccurate.png

Reason: Investigate if a routing protocol like RIP, QUAGGA, BIRD, etc can be used (Discuss in Talk:OpenVPN#)

By default, all IP packets on a LAN addressed to a different subnet get sent to the default gateway. If the LAN/VPN gateway is also the default gateway, there is no problem and the packets get properly forwarded. If not, the gateway has no way of knowing where to send the packets. There are a couple of solutions to this problem.

  • Add a static route to the default gateway routing the VPN subnet to the LAN/VPN gateway's IP address.
  • Add a static route on each host on the LAN that needs to send IP packets back to the VPN.
  • Use iptables' NAT feature on the LAN/VPN gateway to masquerade the incoming VPN IP packets.

Connect the server LAN to a client

The server is on a LAN using the 10.66.0.0/24 subnet. To inform the client about the available subnet, add a push directive to the server configuration file:
/etc/openvpn/server.conf
push "route 10.66.0.0 255.255.255.0"
Note:
  • Remember to enable IPv4 forwarding and to make the LAN interface promiscuous on the server. Make sure the server LAN knows how to reach the VPN client.
  • To route more LANs from the server to the client, add more push directives to the server configuration file, but keep in mind that the server side LANs will need to know how to route to the client.

Connect the client LAN to a server

Prerequisites:

  • Any subnets used on the client side, must be unique and not in use on the server or by any other client. In this example we will use 192.168.4.0/24 for the clients LAN.
  • Each client's certificate has a unique Common Name, in this case bugs.
  • The server may not use the duplicate-cn directive in its config file.

Create a client configuration directory on the server. It will be searched for a file named the same as the client's common name, and the directives will be applied to the client when it connects.

# mkdir -p /etc/openvpn/ccd

Create a file in the client configuration directory called bugs, containing the iroute 192.168.4.0 255.255.255.0 directive. It tells the server what subnet should be routed to the client:

/etc/openvpn/ccd/bugs
iroute 192.168.4.0 255.255.255.0

Add the client-config-dir and the route 192.168.4.0 255.255.255.0 directive to the server configuration file. It tells the server what subnet should be routed from the tun device to the server LAN:

/etc/openvpn/server.conf
client-config-dir ccd
route 192.168.4.0 255.255.255.0
Note:
  • Remember to enable IPv4 forwarding and to make the LAN interface promiscuous on the client. Make sure the client LAN knows how to reach the VPN server.
  • To route more LANs from the client to the server, add more iroute and route directives to the appropriate configuration files, but keep in mind that the client side LANs will need to know how to route to the server.

Connect both the client and server LANs

Combine the two previous sections:

/etc/openvpn/server.conf
push "route 10.66.0.0 255.255.255.0"
.
.
client-config-dir ccd
route 192.168.4.0 255.255.255.0
/etc/openvpn/ccd/bugs
iroute 192.168.4.0 255.255.255.0
Note: Remember to enable IPv4 forwarding and to make the LAN interfaces promiscuous on both the client and the server. Make sure that all the LANs or the needed hosts can route to all the destinations.

Connect clients and client LANs

By default clients will not see each other. To allow IP packets to flow between clients and/or client LANs, add a client-to-client directive to the server configuration file:
/etc/openvpn/server.conf
client-to-client

In order for another client or client LAN to see a specific client LAN, you will need to add a push directive for each client subnet to the server configuration file (this will make the server announce the available subnet(s) to other clients):

/etc/openvpn/server.conf
client-to-client
push "route 192.168.4.0 255.255.255.0"
push "route 192.168.5.0 255.255.255.0"
.
.
Note: As always, make sure that the routing is properly configured.

L2 Ethernet bridging

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: Please add a well thought out section on L2 bridging. (Discuss in Talk:OpenVPN#)

For now see: OpenVPN Bridge

Contributions that do not yet fit into the main article

Tango-inaccurate.pngThe factual accuracy of this article or section is disputed.Tango-inaccurate.png

Reason: Not quite sure where this fits into the main article yet (Discuss in Talk:OpenVPN#)

Routing client traffic through the server

Append the following to your server's openvpn.conf configuration file:

push "redirect-gateway def1"
push "dhcp-option DNS 192.168.1.1"

Change "192.168.1.1" to your preferred DNS IP address.

If you have problems with non responsive DNS after connecting to server, install BIND as simple DNS forwarder and push the IP address of the OpenVPN server as DNS to clients.

Configure ufw for routing

Configure your ufw settings to enable routing traffic from clients through server.

You must change default forward policy, edit /etc/sysctl.conf to permanently enable IPv4 packet forwarding. Takes effect at the next boot.

/etc/sysctl.conf
# Enable packet forwarding
net.ipv4.ip_forward=1

And then configure ufw in /etc/default/ufw:

/etc/default/ufw
DEFAULT_FORWARD_POLICY="ACCEPT"

Now change /etc/ufw/before.rules, and add the following code after the header and before the "*filter" line. Don't forget to change the IP/subnet mask to match the one in /etc/openvpn/server.conf.

/etc/ufw/before.rules
# NAT (Network Address Translation) table rules
*nat
:POSTROUTING ACCEPT [0:0]

# Allow traffic from clients to enp1s0
-A POSTROUTING -s 10.8.0.0/8 -o enp1s0 -j MASQUERADE

# don't delete the "COMMIT" line or the NAT table rules above won't be processed
COMMIT

Open OpenVPN port 1194:

ufw allow 1194

Using iptables

Use an iptable for NAT forwarding:

echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o enp1s0 -j MASQUERADE

If running Arch Linux in a OpenVZ VPS environment [1]:

iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o venet0 -j SNAT --to (venet0 ip)

If all is well, make the changes permanent:

Edit /etc/conf.d/iptables and change IPTABLES_FORWARD=1

# iptables-save > /etc/iptables/iptables.rules

Configuring LDAP authorization

Tango-inaccurate.pngThe factual accuracy of this article or section is disputed.Tango-inaccurate.png

Reason: what does the following do, and is the package still supported? (Discuss in Talk:OpenVPN#)

You may also want to install openvpn-authldap-pluginAUR, available in the AUR.

Deprecated older wiki content

Tango-inaccurate.pngThe factual accuracy of this article or section is disputed.Tango-inaccurate.png

Reason: See how this older content can be fitted into the new article (Discuss in Talk:OpenVPN#)

Using PAM and passwords to authenticate

port 1194
proto udp
mtu-test
dev tap
ca /etc/openvpn/easy-rsa/keys/ca.crt
cert /etc/openvpn/easy-rsa/keys/<MYSERVER>.crt
key /etc/openvpn/easy-rsa/keys/<MYSERVER>.key
dh /etc/openvpn/easy-rsa/keys/dh2048.pem
server 192.168.56.0 255.255.255.0
ifconfig-pool-persist ipp.txt
;learn-address ./script
client-to-client
;duplicate-cn
keepalive 10 120
;tls-auth ta.key 0
comp-lzo
;max-clients 100
;user nobody
;group nobody
persist-key
persist-tun
status /var/log/openvpn-status.log
verb 3
client-cert-not-required
username-as-common-name
plugin /usr/lib/openvpn/plugins/openvpn-plugin-auth-pam.so login

Using certs to authenticate

port 1194
proto tcp
dev tun0

ca /etc/openvpn/easy-rsa/keys/ca.crt
cert /etc/openvpn/easy-rsa/keys/<MYSERVER>.crt
key /etc/openvpn/easy-rsa/keys/<MYSERVER>.key
dh /etc/openvpn/easy-rsa/keys/dh2048.pem

server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt
keepalive 10 120
comp-lzo
user nobody
group nobody
persist-key
persist-tun
status /var/log/openvpn-status.log
verb 3

log-append /var/log/openvpn
status /tmp/vpn.status 10

Routing traffic through the server

Append the following to your server's openvpn.conf configuration file:

push "dhcp-option DNS 192.168.1.1"
push "redirect-gateway def1"

Change "192.168.1.1" to your external DNS IP address.

Use an iptable for NAT forwarding:

echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o enp1s0 -j MASQUERADE

If running Arch Linux in a OpenVZ VPS environment [2]:

iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o venet0 -j SNAT --to (venet0 ip)

If all is well, make the changes permanent:

Edit /etc/conf.d/iptables and change IPTABLES_FORWARD=1

# iptables-save > /etc/iptables/iptables.rules

Setting up the client

The client-side .conf file

With password authentication
client
dev tap
proto udp
mtu-test
remote <address> 1194
resolv-retry infinite
nobind
persist-tun
comp-lzo
verb 3
auth-user-pass passwd
ca ca.crt

passwd file (referenced by auth-user-pass) must contain two lines:

  • first line - username
  • second - password
Certificates authentication
client
remote <MYSERVER> 1194
dev tun0
proto tcp
resolv-retry infinite
nobind
persist-key
persist-tun
verb 2
ca ca.crt
cert client1.crt
key client1.key
comp-lzo

Copy three files from server to remote computer.

ca.crt
client1.crt
client1.key

Install the tunnel/tap module:

# modprobe tun

To have the tun module loaded automatically at boot, read Kernel_modules.

DNS

The DNS servers used by the system are defined in /etc/resolv.conf. Traditionally, this file is the responsibility of whichever program deals with connecting the system to the network (e.g. Wicd, NetworkManager, etc...) However, OpenVPN will need to modify this file if you want to be able to resolve names on the remote side. To achieve this in a sensible way, install openresolv, which makes it possible for more than one program to modify resolv.conf without stepping on each-other's toes. Before continuing, test openresolv by restarting your network connection and ensuring that resolv.conf states that it was generated by "resolvconf", and that your DNS resolution still works as before. You should not need to configure openresolv; it should be automatically detected and used by your network system.

Next, save the following script at /usr/share/openvpn/update-resolv-conf:

#!/bin/bash
#
# Parses DHCP options from openvpn to update resolv.conf
# To use set as 'up' and 'down' script in your openvpn *.conf:
# up /etc/openvpn/update-resolv-conf
# down /etc/openvpn/update-resolv-conf
#
# Used snippets of resolvconf script by Thomas Hood <jdthood@yahoo.co.uk>
# and Chris Hanson
# Licensed under the GNU GPL.  See /usr/share/common-licenses/GPL.
# 07/2013 colin@daedrum.net Fixed intet name
# 05/2006 chlauber@bnc.ch
#
# Example envs set from openvpn:
# foreign_option_1='dhcp-option DNS 193.43.27.132'
# foreign_option_2='dhcp-option DNS 193.43.27.133'
# foreign_option_3='dhcp-option DOMAIN be.bnc.ch'

#[ -x $(which resolvconf) ] || exit 0
[ -x /usr/sbin/resolvconf ] || exit 0

case $script_type in

up)
   for optionname in ${!foreign_option_*} ; do
      option="${!optionname}"
      echo $option
      part1=$(echo "$option" | cut -d " " -f 1)
      if [ "$part1" == "dhcp-option" ] ; then
         part2=$(echo "$option" | cut -d " " -f 2)
         part3=$(echo "$option" | cut -d " " -f 3)
         if [ "$part2" == "DNS" ] ; then
            IF_DNS_NAMESERVERS="$IF_DNS_NAMESERVERS $part3"
         fi
         if [ "$part2" == "DOMAIN" ] ; then
            IF_DNS_SEARCH="$IF_DNS_SEARCH $part3"
         fi
      fi
   done
   R=""
   if [ "$IF_DNS_SEARCH" ] ; then
           R="${R}search $IF_DNS_SEARCH
"
   fi
   for NS in $IF_DNS_NAMESERVERS ; do
           R="${R}nameserver $NS
"
   done
   #echo -n "$R" | resolvconf -p -a "${dev}"
   echo -n "$R" | /usr/sbin/resolvconf -a "${dev}.inet"
   ;;
down)
   resolvconf -d "${dev}"
   ;;
esac

Remember to make the file executable with:

 $ chmod +x /usr/share/openvpn/update-resolv-conf

Next, add the following lines to your OpenVPN client configuration file:

script-security 2
up /usr/share/openvpn/update-resolv-conf
down /usr/share/openvpn/update-resolv-conf

Now, when your launch your OpenVPN connection, you should find that your resolv.conf file is updated accordingly, and also returns to normal when your close the connection.

Webmin

webmin-plugin-openvpnAUR is available in the AUR.

Note: You must add "openvpn" to the end of /etc/webmin/webmin.acl.

Connecting to the server

You need to start the service on the server

systemctl start openvpn

To make it permanent:

systemctl enable openvpn

On the client, in the home directory create a folder that will hold your OpenVPN client config files along with the .crt/.key files. Assuming your OpenVPN config folder is called .openvpn and your client config file is vpn1.conf, to connect to the server issue the following command:

# cd ~/.openvpn && openvpn vpn1.conf