OpenVPN

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echo " echo "
dev tap0 dev tap0
- port 51236+ port 54321
proto tcp-server proto tcp-server
mode server mode server
Line 472: Line 472:
-----BEGIN DH PARAMETERS----- -----BEGIN DH PARAMETERS-----
... ...
- -----END DH PARAMETERS-----+ -----END DH PARAMETERS-----
- -----END DH PARAMETERS-----+
" > /tmp/openvpnsrv/dh1024.pem " > /tmp/openvpnsrv/dh1024.pem
echo " echo "
Line 487: Line 486:
Do not forget the rc_firewall Do not forget the rc_firewall
- iptables -I INPUT 1 -p tcp --dport 51236 -j logaccept+ iptables -I INPUT 1 -p tcp --dport 54321 -j logaccept
===Additional Server Protection with usernames and passwords=== ===Additional Server Protection with usernames and passwords===

Revision as of 10:32, 27 December 2008

OpenVPN is a full-featured SSL VPN solution which can accomodate a wide range of configurations, including road warrior access, home/office/campus telecommuting, WiFi security, secure branch office linking, and enterprise-scale remote access solutions with load balancing, failover, and fine-grained access-controls.

There are two methods how to get OpenVPN on your router:

  • use firmware with OpenVPN client included (starting from 23b2 from 2005-11-21 there is separate firmware). (easy method)
  • install openvpn package to jffs partition

Before you begin, you'll need to obtain the OpenVPN client (with the GUI) (Windows, Mac) for your client computer (if you don't already have it).



Contents

WARNING

Description
Description

WRT54G V1 (possibly others) will not boot (red light) using the scripts in the sections below. Documented case.

Your rc_startup is way longer then max size for one nvram variable, which is 1024 bytes. Consider writing keys and other information to the filesystem outside of NVRAM; e.g. if you have jffs enabled store your scripts and certs there and launch the scripts from NVRAM.


Notes: - The scripts on section 3.3 "Server Mode with Certificates" were run in a WRT150N v1.1 without any problems. After seeing the warning I was hesitant to run any of the scripts but risked it anyways. The case above may be specific to the WRT54G V1. --Wrtman 10:02, 18 May 2008 (CEST).
- Also no problems with dd-wrt.v24_mega_generic.bin on wrt54gs v1.0 with full server mode with certificates.--mutrax 21:42, 18 May 2008 (CEST)
- Tested on Asus WL-500G Premium v1 without any issues.
- Tested & running on a WRT54GL V1.1 V2.4 SP1 VPN w/ no issues
- Tested & running on a WRT54GS V2.1 V2.4 SP1 VPN w/ no issues
[Please, add your own experience with different routers here.]

There are a few changes between the v23 and v24 SP1 since there is somewhat of a gui for the vpn builds. I noticed that the gui frequently truncated the private key when saving the settings which caused openvpn to die. Syslogd is essential for debugging purposes! Additionally the key file extentions in the openvpn directory are different than the names used in most of the scripts in the wiki and the filenames in the config need to include the path. SSH into the router and check out the filenames in the openvpn directory. Even though in v24 SP1 you don't have to use the scripts to copy the keys into files, you still need: brctl addif br0 tap0 ifconfig tap0 0.0.0.0 promisc up and the firewall directives for openvpn to work. I have never seen any output on the status/vpn page, but in bridged mode clients will show up on the LAN/clients list.

Download OpenVPN

Before you begin, you'll need to obtain and install the OpenVPN client (with the GUI) (Windows, Mac) for your client computer.

Please note that it consists of one binary for both client and server connections, so don't look for individually labeled client or server packages.

Enable OpenVPN in the Router

In this section, it is assumed that you already have the VPN flavor of DD-WRT installed in your router.

Client Mode

  1. Using the Web Interface, go to the "Administration" tab and the "Services" sub-tab.
  2. Enable the "Open VPN Client" If new options do not appear, Apply Settings.
  3. Fill in parameters (see below)
  4. Apply Settings


Regular Parameters

192.168.1.1
IP address of the OpenVPN server you want to work with
80
port which OpenVPN server listens on
Use LZO Compression
where to use or not compression on vpn traffic; must be the same value as on server
Tunnel protocol
what transport to use to transfer VPN traffic; default is udp, but if routers/nat devices causes problems, choose tcp; must be the same as on server
Public Server Cert
Certificate of OpenVPN CA (not the server's public cert) in pem form; only part between (and including) -----BEGIN CERTIFICATE----- and -----END CERTIFICATE----- is necessary; as it is stored in nvram, everything else from that file should be removed to conserve space
Public Client Cert
Client certificate issued by CA for this particular router; also only part between 'BEGIN' and 'END' is required
Private Client Key
Key associated with certificate above; should be kept secret because anybody who knows this key can successfully authenticate as this client

Custom Parameters

If you want to set custom parameters (e.g. encryption settings, verbosity, ...) for OpenVPN, you'll have to re-create the /tmp/openvpn/openvpn.conf file and restart OpenVPN.

For more detailed information on Startup Commands, please read the Startup Scripts wiki entry.

To do this, use the Web Interface, go to the "Administration" tab and the "Commands" sub-tab.

In the box, enter the configuration how you'd want it, and echo it into /tmp/openvpn/openvpn.conf.

Example (add this in the edit box at the top):

echo "dev tap
link-mtu 1492
remote <remote-ip>
resolv-retry infinite

ifconfig <local ip> <local netmask>
client
ca /tmp/openvpn/ca.crt
cert /tmp/openvpn/client.crt
key /tmp/openvpn/client.key
comp-lzo
persist-tun
persist-key
verb 3
cipher AES-256-CBC" > /tmp/openvpn/openvpn.conf

killall openvpn
openvpn --config /tmp/openvpn/openvpn.conf

Next, click the Save Startup, et voila, it should now start openvpn using your custom configuration.

Note: In "v23 SP2 (09/13/06) vpn" I've found that the openvpn startup script can run after the above during startup, so I work around that by doing the echo to "/tmp/openvpn/myopenvpn.conf" and replacing the killall/openvpn commands with:

( sleep 20 ; killall openvpn ; openvpn --config /tmp/openvpn/myopenvpn.conf --route-up /tmp/openvpn/route-up.sh --down /tmp/openvpn/route-down.sh --daemon ) &

You may need to tune the amount of sleep time. Use "ps" to verify that the "openvpn" process you want to be running is running.

--Ripper42 19:42, 30 Sep 2006 (CEST)


Note: In "v23 SP2" the /tmp/ directory exist a few seconds after booting. So the script cannot run immediately during bootup. Also I added a cronjob to check the openvpn connection every 5 minutes. Here is my startup Script thats work for me:

#!/bin/sh
sleep 20
echo "tls-client
dev tun
...
cert /tmp/openvpn/client.crt
key /tmp/openvpn/client.key" > /tmp/openvpn/myopenvpn.conf 
sleep 20
killall openvpn
/usr/sbin/openvpn --config /tmp/openvpn/myopenvpn.conf --route-up /tmp/openvpn/route-up.sh --down /tmp/openvpn/route-down.sh --daemon

# install cronjob, which restart tunnel if not running, but dont install cronjob, if it is already active
if test -s /tmp/cron.d/openvpn_check_status; then echo "" ;else echo '*/5 * * * * root if [ `ps | grep -c "openvp[n]"openvp[n].*myopen"` -ne 1 ] ; then logger OpenVpn restart;. /tmp/.rc_startup  ; fi' >> /tmp/cron.d/openvpn_check_status
# restart cron daemon
stopservice cron && startservice cron
fi                     

--notdefine 16:52, 26.02.2006 after 100 edits

After looking at some posts and WiKi, I have simplified the process of using openVPN as a client.

First, I enabled the openVPN client via the web interface and entered the 3 certificates/keys that are requested. Once I saved that, I disabled openVPN. This got the 3 certs/keys into nvram. I then ran the following 3 nvram commands in the command window at the same time:

nvram set openvpn_tls='
-----BEGIN OpenVPN Static key V1-----
...
-----END OpenVPN Static key V1-----
'
nvram set openvpn_cfg='
remote remote_server_ip_address
dev tun0
tun-mtu 1500
fragment 1300
mssfix
tls-client
ca /tmp/myvpn/ca.crt
cert /tmp/myvpn/client.crt
key /tmp/myvpn/client.key
ns-cert-type server
tls-auth /tmp/myvpn/tls.key
ping-restart 60
ping-timer-rem
persist-tun
persist-key
resolv-retry 86400
ping 10
comp-lzo
'
nvram commit

I then set the startup script to:

/usr/sbin/openvpn --mktun --dev tun0
ifconfig tun0 192.168.tunnel.2 netmask 255.255.255.252 promisc up
route add -net 192.168.rlan.0 netmask 255.255.255.0 gw 192.168.tunnel.1
sleep 20
mkdir /tmp/myvpn
nvram get openvpn_ca >/tmp/myvpn/ca.crt
nvram get openvpn_client >/tmp/myvpn/client.crt
nvram get openvpn_key >/tmp/myvpn/client.key
nvram get openvpn_tls >/tmp/myvpn/tls.key
nvram get openvpn_cfg >/tmp/myvpn/remote.ovpn
/usr/sbin/openvpn --daemon --config /tmp/myvpn/remote.ovpn

and firewall to:

iptables -I INPUT 2 -p udp --dport 1194 -j ACCEPT
iptables -I FORWARD -i br0 -o tun0 -j ACCEPT
iptables -I FORWARD -i tun0 -o br0 -j ACCEPT

Explanations:
openvpn_tls is set to your TLS key.
remote_server_ip_address = IP address of remote openVPN running in server mode.
192.168.tunnel.2 = 192.168.x.x address of the local openVPN tunnel. Must be different subnet from remote and local LANs.
192.168.tunnel.1 = 192.168.x.x address of the remote end ofl openVPN tunnel. Must be different subnet from remote and local LANs.
192.168.rlan.0 = IP address range of remote LAN
sleep 20 = wait period to ensure /tmp has been created.

This disables the firewall and NAT on the VPN, uses TLS authentication, etc. Hope this helps some. It is easy to change nvram and was much easier for me to review than trying to put it all in startup scripts.

This is working on a Buffalo WHR-G54S running 2.3 SP2.

--Pete 14:29, 5 May 2007 (CEST)

Disabling NAT

To have OpenVPN pass traffic normally without address translation, you'll want to turn off masquerading on the tunnel interface as well as set a more permissive default for the firewall. Unfortunately, dd-wrt currently does not have an easy button to do this. Instead, use the startup script to replace the default route-up script with your own version.

To do this, use the Web Interface, go to the "Administration" tab and the "Commands" sub-tab, and add the following line to your Startup Script:

( while [ ! -f /tmp/openvpn/route-up.sh ]; do sleep 1; done; \
 echo "iptables -t filter -I INPUT -i tun0 -j ACCEPT; iptables -t filter -I FORWARD -i tun0 -j ACCEPT" > /tmp/openvpn/route-up.sh ) &


Alternatively you may specifiy the following in the Firewall Script what is much more efficient:

iptables -I FORWARD -i br0 -o tun0 -j ACCEPT
iptables -I FORWARD -i tun0 -o br0 -j ACCEPT
iptables -I INPUT -i tun0 -j ACCEPT


IMPORTANT NOTE: I have tried the above workarounds to no avail. The first approach burns precious CPU cycles. The second one has no effect whatsoever. The reason being that in iptables, NAT table manipulations are applied after the routing chains are processed and there is no way of bypassing that with the above rules. The problem is that the openVPN daemon is passed with immutable route up & down scripts on startup. My solution is based on the custom parameters already discussed above. Simply copy and paste the following script into the Command window and save it as the startup script:

( sleep 20 ; killall openvpn ; iptables -t nat -F POSTROUTING ; openvpn --config /tmp/openvpn/openvpn.conf --daemon ) &

Then restart the box and voila! --Narseh 17:48, 16 December 2008 (CET)

Server mode with Static Key

Note: with DD-WRT v23 SP1 Final (05/16/06) vpn this allows only 1 client connection!! [1]. See below for multiple connections.

Server Configuration

1. Create a static.key file on your computer

Unix:

   openvpn --genkey --secret static.key

Windows: (downloaded at http://www.openvpn.se)

   Click on "Start > Programs ->OpenVPN -> Generate a static OpenVPN key"
  • Note: this will create a c:\Program Files\OpenVPN\config\key.txt file, you will want to rename it to static.key


2. Paste the command below into your router at "Administration > Commands > Commands text box" and replace the text "...INSERT YOUR STATIC KEY HERE..." with the static.key you just made. Click "Save Startup":

   openvpn --mktun --dev tap0
   brctl addif br0 tap0
   ifconfig tap0 0.0.0.0 promisc up
   echo "
   -----BEGIN OpenVPN Static key V1-----
   ...INSERT YOUR STATIC KEY HERE...
   -----END OpenVPN Static key V1-----
   " > /tmp/static.key
   ln -s /usr/sbin/openvpn /tmp/myvpn
   /tmp/myvpn --dev tap0 --secret /tmp/static.key --comp-lzo --port 1194 --proto udp --verb 3 --daemon


3. Paste the command below into your router at "Administration > Commands > Commands text box" and click "Save firewall":

   iptables -I INPUT 1 -p udp --dport 1194 -j ACCEPT


4. Reboot your router. Login with ssh and check that "myvpn" is running (ps | grep vpn)


You can also paste the "ps | grep vpn" command into the Administration > Commands box to see if it is running.

Client Configuration

1. Create an openvpn config file on your client computer using one of the following templates. For Windows clients, save it as a .ovpn file in the C:\Program Files\OpenVPN\config folder.

   # Use the following for simple connections:
   remote XXXX.dyndns.org
   port 1194
   dev tap
   secret static.key
   proto udp
   comp-lzo
   # Use the following to have your client computer send all traffic through your router
   # (remote gateway)
   remote XXXX.dyndns.org
   port 1194
   dev tap
   secret static.key
   proto udp
   comp-lzo
   route-gateway 192.168.1.1
   redirect-gateway
   # Use the following if you have an office proxy:
   remote XXXX.dyndns.org
   http-proxy-retry
   http-proxy my.office.proxy.server 8080
   port 1194
   dev tap
   secret static.key
   proto udp
   comp-lzo
   route-gateway 192.168.1.1
   redirect-gateway
  • Reference: fgimenez's post


2. Try to connect

Windows: right click the open vpn icon in your system tray and click connect.


That should do it. This has been tested on DD-WRT v23 SP1 Final vpn.

If everything is working correctly you should receive an IP address from your router (if you have a running dhcp server) when you connect and that IP address will be in your internal LAN so now you just connect to your home PC the same way you would do it from inside your LAN.

Server Mode with Certificates (Recommended)

This section describes how to configure an OpenVPN server that uses SSL certificates for client authentication. The method offers better security than using a static key and allows multiple clients to connect at the same time.


Public Key Infrastructure (PKI)

Follow these instructions to create the required certificates and keys. You begin by creating a key and certificate pair for the certificate authority (CA) you are establishing. Then for the server and each client, you create a private key and certificate pair and sign the certificates using the CA's key. Afterwards, you should have the following files:

ca.crt
ca.key
dh{n}.pem
server.crt
server.key

and a private key and certificate pair for each client. For example, if you have two clients, you should have:

client1.crt
client1.key
client2.crt
client2.key

Note that the CA private key, ca.key, is used only to sign the certificates. It should be kept securely and not be copied to the server or clients.


Server Configuration

  • Warning: This Script EXCEEDS NVRAM - will semi-brick you router - JTAG required to recover. See first section.
  • NOTE: This is only true for some (few) routers. To my knowledge it's been reported only for WRT54Gv1 & v2. Better to ask first if you are in doubt.


1. Install DD-WRT with VPN, v23 SP2 or later, on your router.

2. Create a rc_startup script (temporarily prepare in a simple text editor, e.g. notepad or PSPad)

cd /tmp
openvpn --mktun --dev tap0
brctl addif br0 tap0
ifconfig tap0 0.0.0.0 promisc up

echo '
# Tunnel options
mode server       # Set OpenVPN major mode
proto udp         # Setup the protocol (server)
port 1194         # TCP/UDP port number
dev tap0          # TUN/TAP virtual network device
keepalive 15 60   # Simplify the expression of --ping 
daemon            # Become a daemon after all initialization
verb 3            # Set output verbosity to n 
comp-lzo          # Use fast LZO compression 

# OpenVPN server mode options
client-to-client  # tells OpenVPN to internally route client-to-client traffic 
duplicate-cn      # Allow multiple clients with the same common name

# TLS Mode Options
tls-server        # Enable TLS and assume server role during TLS handshake 
ca ca.crt         # Certificate authority (CA) file
dh dh1024.pem     # File containing Diffie Hellman parameters 
cert server.crt   # Local peers signed certificate
key server.key    # Local peers private key 
' > openvpn.conf

echo '
-----BEGIN CERTIFICATE-----
...INSERT YOUR ca.crt HERE...
-----END CERTIFICATE-----
' > ca.crt
echo '
-----BEGIN RSA PRIVATE KEY-----
...INSERT YOUR server.key HERE...
-----END RSA PRIVATE KEY-----
' > server.key
chmod 600 server.key
echo '
-----BEGIN CERTIFICATE-----
...INSERT YOUR server.crt HERE...
-----END CERTIFICATE-----
' > server.crt
echo '
-----BEGIN DH PARAMETERS-----
...INSERT YOUR dh1024.pem HERE...
-----END DH PARAMETERS-----
' > dh1024.pem

sleep 5
openvpn --config openvpn.conf --daemon

Replace "...INSERT YOUR [FILE] HERE..." with the appropriate contents of the files you created earlier. Open these files in a simple text editor and paste contents between the BEGIN and END statements into this script.

Notes:

  • This script bridges the VPN with the LAN, so no routing is required so that clients can communicate with systems and devices on the LAN.
  • The server is configured to use UDP packets since TCP over TCP can lead to poor performance. If you need to use TCP instead of UDP, specify tcp-server as the protocol. TCP is also required if you want your clients to be able to connect through a HTTP Proxy.
  • Script was updated to change the " to '. The use of " in the script can break the rc_startup causing unpredictable behavior.
  • Removed 2 ' in the words peers as they were causing the script not to execute completely with echo using '.
  • You might need to change the last line of the script to (strongly recommended):
ln -s /usr/sbin/openvpn /tmp/myvpn
/tmp/myvpn --config openvpn.conf 

The reason is that with the original command, openvpn might start but mysteriously not stay open.

3. Add the following line to your rc_firewall script (create a new file in simple text editor that will temporarily hold your rc_firewall script):

/usr/sbin/iptables -I INPUT -p udp --dport 1194 -j ACCEPT

This command allows connections to the OpenVPN server.

4. Use the web interface method to store the rc_startup and rc_firewall scripts on the router.

5. Enable NTP and uncheck Use Local Time in the router setup. Then reboot your router.

Note: As of V24-RC4 Use Local Time does not exist. Instead set Time Zone to "UTC" and Summer Time(DST) to "none".

6. Login via ssh or telnet and execute the command

ps | grep openvpn

to verify that the OpenVPN process is running.

7. A little evolution of the so great rc_startup script.

Tested with WRT54GL V1.1 under DD-WRT v24-sp1 (07/27/08) vpn

[ -d /tmp/openvpnsrv ] || mkdir /tmp/openvpnsrv
openvpn --mktun --dev tap0
brctl addif br0 tap0
ifconfig tap0 0.0.0.0 promisc up
echo "
dev tap0
port 54321
proto tcp-server
mode server
client-to-client
keepalive 15 60
comp-lzo
tls-server
tls-auth /tmp/openvpnsrv/ta.key 0
ca /tmp/openvpnsrv/ca.crt
cert /tmp/openvpnsrv/server.crt
key /tmp/openvpnsrv/server.key
dh /tmp/openvpnsrv/dh1024.pem
verb 3
" > /tmp/myvpnsrv.conf
echo "
-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----
" > /tmp/openvpnsrv/ca.crt
echo "
-----BEGIN RSA PRIVATE KEY-----
...
-----END RSA PRIVATE KEY-----
" > /tmp/openvpnsrv/server.key
echo "
-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----
" > /tmp/openvpnsrv/server.crt
echo "
-----BEGIN DH PARAMETERS-----
...
 -----END DH PARAMETERS-----
" > /tmp/openvpnsrv/dh1024.pem
echo "
-----BEGIN OpenVPN Static key V1-----
...
-----END OpenVPN Static key V1-----
" > /tmp/openvpnsrv/ta.key
ln -s /usr/sbin/openvpn /tmp/myvpn
sleep 5
chmod 400 /tmp/openvpnsrv/*
/tmp/myvpn --config /tmp/myvpnsrv.conf --daemon

Do not forget the rc_firewall

iptables -I INPUT 1 -p tcp --dport 54321 -j logaccept

Additional Server Protection with usernames and passwords

I wanted to make the access to my network easy but secure. Certificates are nice, but I still like username and password even more. You can use the following simple script to check for usernames/passwords.

Add this to the config on the server and set the right path for the script:

auth-user-pass-verify /path/to/your/script/verify.sh via-file

This line tells openvpn server to check for passed username and password by calling the script verify.sh and passing the username and password in a tmp file


Every client have to have this in its config file:

auth-user-pass

This just tells openvpn client to ask the user for username and password or s/he will not be able to log in. You can also use "--auth-user-pass" (instead of the line in the config file) on the command line.


This is a simple shell script called "verify.sh" which contains usernames and passwords in clear text. I wanted to encrypt passwords with "passwd", but command "passwd" is not available in dd-wrt (and I have no idea how dd-wrt encrypts root password for /etc/passwd). If someone knows how to encrypt passwords in dd-wrt, plese add it here.

#!/bin/sh
 
 ## format: username:password username:password ...
 ## you can even have same usernames with different passwords
 USERS='user1:pass1 user2:pass2 user3:pass3'
 
 ## you could put username:password in
 ## a separate file and read it like this
 #USERS=`cat file_with_users`
 
 vpn_verify() {
     if [[ ! $1 ]] || [[ ! $2 ]]; then
         #echo "No username or password: $*"
         exit 1
     fi
  
     ## it can also be done with grep or sed
     for i in $USERS; do
         if [[ "$i" == "$1:$2" ]]; then

             ## you can add here logging of users
             ## if you have enough space for log file
             #echo `date` $1:$2 >> your_log_file

             exit 0
         fi
     done
 }
   
 if [[ ! $1 ]] || [[ ! -e $1 ]]; then
     #echo "No file"
     exit 1
 fi
   
 ## $1 is file name which contains
 ## passed username and password
 vpn_verify `cat $1`
  
 #echo "No user with this password found"
 exit 1

You can delete all lines which begin with #. "echo" commands are here just for you to know what happens at that and they can be used for debugging.

This verification with the script does not work if openvpn is running in "daemon" mode. I have no idea what is the reason for that, probably some wrong interpretation of the output ("exit 0" means user/pass OK, everything else means user/pass NOT OK). Thats why I am running openvpn server as a background process and all output is going to /dev/null:

 openvpn --config openvpn.conf >/dev/null 2>&1 &

--Comma 23:53, 11 August 2008 (CEST)

I was getting the error

  
   openvpn_execve: external program may not be called due to setting of --script-security level
   

I had to add the following lines to my config file work in v24-SP2

  
   tmp-dir /tmp/openvpn
   script-security 3
   

Additionally, the ">/dev/null 2>&1 &" hack wouldn't work but running from the command line did. I resorted to using the /tmp/myvpn symlink as well as --daemon in the command line. All works now with out an interactive shell. --JoeM 23:28, 22 October 2008 (CEST)

Client Configuration

1) Copy the CA certificate and a private key and certificate pair to the client.

2) Create an OpenVPN configuration file on your client computer:

client
dev tap
proto udp
remote router-address 1194
resolv-retry infinite
nobind
persist-key
persist-tun
ca ca.crt
cert client1.crt
key client1.key
ns-cert-type server
comp-lzo
verb 3

Replace router-address in the fourth line with your router's IP address or host name and, obviously, use the appropriate file names in the script for the client's certificate and key. On Windows, save this script using notepad as a file with extension .ovpn and copy it into \Program Files\OpenVPN\config (along with the files ca.crt, clientX.crt and clientX.key created earlier.)

Notes:

  • If you need to use TCP instead of UDP, set the protocol to tcp-client. Clients must use the same protocol that the server does.
  • Mac OS X users need to add the line
up "./vpn-up.sh"

to the configuration file and create a script file vpn-up.sh in the same directory as the configuration file with the following contents:

#!/bin/bash 
sleep 2
ipconfig set $1 DHCP

This script configures the TAP interface to request an IP address using DHCP. Make sure to make the script executable with 'chmod 755 vpn-up.sh'

3) Use the configuration file you just created with whatever OpenVPN client software you're using to establish a connection to your router.

If everything works, you will be connected to your internal LAN. If your router is running a DHCP server, the TAP interface will be assigned an IP address on your internal LAN. At this point, you just connect to your home PC the same way you would do it from inside your LAN.

Installing into jffs partition (Deprecated)

old method only recommended for non-vpn firmware

This no longer works with the latest firmware version, please download the new VPN inclusive version. !!However, with at least some new firmware versions (I'm using V23SP1 6/5/06 VOIP), the hurdle can be overcome with some extra effort ... details are provided below in the Troubleshooting section... 19:22, 30 Jun 2006 (CEST)!!

Prerequisites

You should already have:
-a Linksys WRT54G/GS product
-DD-WRT installed as the firmware
-SCP or some other way to copy files to and from your desktop setup
-some knowledge of using ipkg to install packages
-jffs already configured if you don't want to install to ram
If you are running Windows on your desktop: -TextPad or Win32Pad
(or other *nix friendly text editor. DO NOT USE NOTEPAD)

Install the OpenVPN ipkg package

-Find the openvpn package in the THIS LINK DOES NOT WORK ANY MORE OpenWRT Package Tracker.
You will need the URI of package to install it.
-telnet or ssh shell into the router -run the command ipkg -d <dest_name> install <URI of package>
<dest_name> should be root to install to /jffs <dest_name> should be ram to install to /tmp *Remember, /tmp is deleted on router reboot* Ex: ipkg -d root install http://nthill.free.fr/openwrt/ipkg/experimental/20050420/openvpn-static_2.0-1_mipsel.ipk

EDIT: Can't find the right package? Yeah, neither can anyone else. Don't bother. The best strategy is to download and flash the distro with the built-in VPN and copy the binary off of that then re-flash with another distro and copy the binary to the jffs partition. The packages on the openWRT tracker don't seem to work for v23 on WRT54Gv3 ("Bus Error"). The version originally linked above and the version in the VPN firmware are statically compiled. I had to do it this way because the nvram startup script only ran the first command in the variable and I needed the VPN to survive a WRT reboot. Not enough room for jffs on all but the mini distro... so no shell scripts for me! YMMV. Note to the powers that be: How about posting this stuff with the mini firmware so we don't have to do it this way?????

Create the openvpn config file

-Using your method of choice, copy the file /<dest_name>/etc/openvpn/office.conf
to your desktop machine -Using a *nix friendly text editor, edit office.conf (the config file in my setup).
See http://openvpn.net for more informations and examples.

19:16, 30 Jun 2006 (CEST) pagedude

- NOTE : openvpn is highly configurable. Distinct from the original writer of this portion of the wiki, I setup my configuration files much more along the lines of the earlier section in this Wiki on configuring the OpenVPN server with certificates in bridging mode. Certificates provide a more robust dynamic configuration scheme, but take a little bit more time up-front to generate (but the http://www.openvpn.net site has an excellent, easy-to-follow guide on how to generate them). Bridging mode is very convenient in that the remote VPN client effectively appears to be part of the remote(server) LAN, plus much less routing configuration (i.e. use of ifconfig, route etc.) is required on either the OpenVPN server or the OpenVPN client.

19:16, 30 Jun 2006 (CEST) pagedude

?? BUT HOW WOULD YOU SET THIS UP (with Certificates and Bridging) IF YOU HAVE MULTIPLE CLIENTS?

##############################################################################
# this is a sample configuration file for openvpn
# it should be changed to contain your values and
# placed in /jffs/etc/openvpn
#
remote servername.domain.com
rport 5000
dev tap
ifconfig 10.0.1.2 255.255.255.252
secret /jffs/etc/openvpn/key.txt
ping 10
ping-restart 60
ping-timer-rem
persist-tun
persist-key
resolv-retry 86400
verb 1
mute 10
route-up "route add -net 192.168.1.0 netmask 255.255.255.0 gw 10.0.1.1"
#
##############################################################################

This is the OpenVPN config file of the other side (a Linux server or another WRT54G/GS)

##############################################################################
#
dev tap
secret /etc/openvpn/key.txt
persist-key
persist-tun
ifconfig 10.0.1.1 255.255.255.252
ping-restart 60
ping 10
verb 5
mute 10
lport 5000
route-up "route add -net 192.168.2.0/24 gw 10.0.1.2"
#
###############################################################################

Usage & Troubleshooting

Launching the Client

-cd to the install folder (/<dest_name>/usr/sbin)
-run ./openvpn --config ./../../etc/openvpn/office.conf --log openvpn.log

See openvpn.log for debugging

Load on Router Startup

-Using a *nix friendly text editor, create openvpn.startup as:

#!/bin/sh
killall -q openvpn
/jffs/usr/sbin/openvpn --config /jffs/etc/openvpn/office.conf

-Follow the instructions in Startup Scripts#Shell Script Method to make your script load on startup.

Additional notes for improved JFFS installation and security with public hotspots

19:10, 30 Jun 2006 (CEST) pagedude

i) The instructions above confine the OpenVPN server configuration entirely into a rc_startup script. This is elegant when OpenVPN is installed in RAM, since there's no convenient place to put a configuration file for OpenVPN (RAM contents are not persistent). However, if the user instead installs OpenVPN into persistent storage, i.e. the jffs partition, then instead of configuring OpenVPN on the command line, a config file can be used. There are several advantages to doing this; not only is RAM usage minimized (key files don't need to be copied to rc_startup, command line options get transferred to the config file, etc.), but the config file allows the description of more complicated openvpn server configurations.

ii) One interesting capability of the OpenVPN tunnel is to optionally allow the client to pass all traffic through the VPN tunnel when connected. For example, when you are using an unsecure WiFi hotspot, you might want to ensure that eavesdroppers are not able to monitor your WiFi traffic. One way to do this is to route all your WiFi traffic through the encrypted VPN tunnel, using the "redirect-gateway" option on the server or the client. When configured on the server, all clients will reroute all their traffic through the VPN. The "redirect-gateway" option requires pushing two pieces of information from the server to the client, the remote gateway and DNS IP addresses.

Here are my example rc_startup, server, and client config files. Note that I installed OpenVPN in /jffs/tmp and copied the PKI files, ca.crt, server.crt, server.key, dh1024.pem, and the server config file, server.conf, there.

rc_startup: cd /jffs/tmp ./openvpn --mktun --dev tap0 brctl addif br0 tap0 ifconfig tap0 0.0.0.0 promisc up sleep 5

I had to install this library, since my ddwrt distro didnt have it
See Troubleshooting section at the bottom of this wiki for JFFS installations

export LD_PRELOAD=/jffs/sbin/libuClibc-0.9.28.so

./openvpn --config server.conf --daemon </pre>

Note: With V23 SP2, I did not need the LD_PRELOAD statement. I did have to create a link:

ln -s /usr/sbin/openvpn /jffs/tmp/myvpn

and change the last part of the code above to:

sleep 5
./myvpn --config server.conf --daemon

server.conf:

mode server
tls-server
port 1194
proto tcp-server
dev tap0

ca ca.crt
cert server.crt
key server.key
dh dh1024.pem

#These IP addresses need to be changed to be *your* ddwrt LAN addresses ...
push "route-gateway 192.168.3.1"
push "dhcp-option DNS 192.168.3.1"

client-to-client

keepalive 15 60

comp-lzo
persist-key
persist-tun
status openvpn-status.log
verb 3

client.conf:

tls-client
dev tap
proto tcp-client
port 1194
resolv-retry infinite
nobind
persist-key
persist-tun
remote XXXX.dyndns.org 1194

ca ca.crt
cert client.crt
key client.key
ns-cert-type server

comp-lzo
verb 3

#Pull info from server, viz. server-side LAN IP's for gateway and DNS
pull
# Uncomment the following to send all traffic through VPN
redirect-gateway

19:10, 30 Jun 2006 (CEST)

76472429234521330421186

Troubleshooting

Correct time

OpenVPN requires client and server to have more or less synchronized time. Therefore make sure that router has correct time. To check it use command date and if you get info about year 1970, you should enable NTP client. Also, ntp server has to be outside of your VPN as time should be corrected before VPN is established. If you have syslog enabled (to local server, or the server outside your VPN), errors like TLS Error: Unroutable control packet received from server_ip:1194 may indicate this problem. (This error message may appear if your certificates are not valid or have expired, too.) If you get an error message saying that your certificate is not yet valid, set the dd-wrt clock to UTC time (in the first configuration page).

To set the time manually connect via telnet or ssh and issue the following command at the prompt:
date MMDDHHMMYYYY

openvpn does not start, gives error message " ... can't resolve symbol 'fopen64' "

19:13, 30 Jun 2006 (CEST) pagedude

I have V23SP1 5/6/06 VOIP, extracted the openvpn executable from V23SP1 5/6/06 VPN and copied it to my jffs partition as outlined above, and set everything up as outlined above, except that I setup my own configuration files, of course. Then I got the above error message. The reason for this error message is that the openvpn executable requires an updated version of the libuClibc library. For my build, this should be libuClibc-0.9.28.so. Fortunately the package for this library can be located on the dd-wrt downloads page. Look for the "packages" folder at http://www.dd-wrt.com/dd-wrtv2/downloads.php, and retrieve the package named uclibc_0.9.28-6_mipsel.ipk. Install this package on the jffs partition - refer to the ipkg documentation for details. After installation, note down the exact path for libuClibc-0.9.28.so .. e.g. I installed mine at /jffs/sbin/liuClibc-0.9.8.so. Now you need to ensure that when openvpn is launched as a daemon, the executing environment has the variable LD_PRELOAD set to point to the path to this library. In simpler language, what you need to do is insert the following line:

export LD_PRELOAD=<replace_this_whole_angle_bracketed_region_with_your_full_path_to_library>

at the start of the script that launches the openvpn server. openvpn will then use this library, instead of the older one that exists in the non-vpn OpenVPN distributions.

19:13, 30 Jun 2006 (CEST) pagedude

Connecting to DD-WRT OpenVPN Server via Mac Client

Currently, there are two OpenVPN clients for OS X

Viscosity has a more user friendly gui but is a commercial product. It can also import settings created for the Tunnelblick application.

PROBLEM: When I used the sample client.conf file above, nothing happened when I clicked connect on Tunnelblick.

Tunnelblick is a GUI OpenVPN application for the Mac. The last official release is 2.0.1, but I am going to explain how to connect using version 3.0rc3. This version has everything in one app and requires no extra components to be installed.

NOTE: I used certificates to connect my MacBook Pro to the OpenVPN server. You can find documentation on how to do this further up in this page. Remember to place your certificate files in the same directory as the client.conf file. Tunnelblick looks for the files in ~/Library/openvpn.

Download Tunnelblick and drag it to the Applications folder. It will say that you don't have a client.conf file and will make one for you. You can examine the sample client.conf file that Tunnelblick makes and find that it does a few things differently than the example provided above. Set up your client.conf file using the sample I have provided below, and Tunnelblick should connect properly now.

The file I have provided is the same as the sample, except with a few things disabled and a few things added to make it do what we want. The reason I disabled a few things using the # line is that I didn't want to delete anything, so I just disabled them.

You might notice that the command

up "./vpn-up.sh"

This is a fix that I found here.

You will need to make a script called vpn-up.sh and place it in the same directory as the client.conf file. Make the files contents:

#!/bin/bash
sleep 2
ipconfig set tap0 DHCP

client.conf:

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

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

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

# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel
# if you have more than one.  On XP SP2,
# you may need to disable the firewall
# for the TAP adapter.
#dev-node MyTap
 
# Are we connecting to a TCP or
# UDP server?  Use the same setting as
# on the server.
proto tcp

# The hostname/IP and port of the server.
# You can have multiple remote entries
# to load balance between the servers.
remote xxxxxxxxx.dyndns.org 1194 

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

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

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

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

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

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

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

# SSL/TLS parms.
# See the server config file for more
# description.  It's best to use
# a separate .crt/.key file pair
# for each client.  A single ca
# file can be used for all clients.
ca ca.crt
cert client1.crt
key client1.key

up "./vpn-up.sh"

# Verify server certificate by checking
# that the certicate has the nsCertType
# field set to "server".  This is an
# important precaution to protect against
# a potential attack discussed here:
# http://openvpn.net/howto.html#mitm

# To use this feature, you will need to generate
# your server certificates with the nsCertType
# field set to "server".  The build-key-server
# script in the easy-rsa folder will do this.
ns-cert-type server

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

# Select a cryptographic cipher.
# If the cipher option is used on the server
# then you must also specify it here.
#cipher x

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

# Set log file verbosity.
verb 3

# Silence repeating messages
;mute 20

Can't Load DH Parameters

If you get the following:

Tue Jan 23 03:03:05 2007 OpenVPN 2.0.7 mipsel-unknown-linux [SSL] [LZO] [EPOLL] built on Jan 15 2007
Tue Jan 23 03:03:05 2007 Cannot load DH parameters from dh1024.pem: error:0906D064:lib(9):func(109):reason(100)
Tue Jan 23 03:03:05 2007 Exiting

you should check your certificates. Did you paste them correctly?

Note: you must include new lines.

Connection reset by peer (WSAECONNRESET) (code=10054)

If you received error when trying to connect to your VPN server verify the following:

  • Make sure the protocol is the same on the server and client, ie UDP/TCP
  • Verify the port number is the same on the client and server; Default port is UDP 1194
  • Check to see if the port is open on the server by using nMap or another utility