How to setup the Cisco VPN client on a Linux computer

Keonwook Kang and William Cash

Introduction

Cisco VPN is required to connect to many of Stanford's computer resources because of some past security lapses. Unlike the Windows and Mac OS clients, Cisco's Linux VPN requires use of the terminal and has very little documentation from the company. This guide will show you how to install and use the Linux client.

The outdated client has also become incompatible with newer Linux kernels and requires patches created by the Linux community. If you are using kernel 2.6.22, 2.6.24, or beyond, you will probably have to download a newer Cisco VPN client than Stanford provides as outlined in this guide.

Installing the VPN client

Note: most of the following steps require superuser access.

1. Download the v4.8 VPN client from http://vpn.stanford.edu.
2. Extract the downloaded file.

# mv vpnclient-linux-4.8.tar.gz /usr/local/src
# cd /usr/local/src
# tar -zxvf vpnclient-linux-4.8.tar.gz

3. Install the VPN client

# cd vpnclient
# ./vpn_install

4. Answer the following questions during the installation (the defaults should be fine)

# ./vpn_install 
Cisco Systems VPN Client Version 4.8.00 (0490) Linux Installer
Copyright (C) 1998-2005 Cisco Systems, Inc. All Rights Reserved.

By installing this product you agree that you have read the
license.txt file (The VPN Client license) and will comply with
its terms. 

Directory where binaries will be installed [/usr/local/bin]

Automatically start the VPN service at boot time [yes]yes

In order to build the VPN kernel module, you must have the
kernel headers for the version of the kernel you are running.

Directory containing linux kernel source code 
                      [/lib/modules/2.6.18-8.1.8.el5/build]

* Binaries will be installed in "/usr/local/bin".
* Modules will be installed in "/lib/modules/2.6.18-8.1.8.el5/CiscoVPN".
* The VPN service will be started AUTOMATICALLY at boot time.
* Kernel source from "/lib/modules/2.6.18-8.1.8.el5/build" 
  will be used to build the module.

Is the above correct [y]y

5. Note that you need to reinstall the VPN client whenever your kernel is upgraded. Before reinstalling it, first run:

# ./vpn_uninstall

to clean files and directories previously installed.

If you're receiving errors during installation

With the newer Linux kernels that are incompatible with the Cisco VPN you may receive an errors similiar to these:

* Binaries will be installed in "/usr/local/bin".
* Modules will be installed in "/lib/modules/2.6.24-19-generic/CiscoVPN".
* The VPN service will be started AUTOMATICALLY at boot time.
* Kernel source from "/lib/modules/2.6.24-19-generic/build"
 will be used to build the module.

Is the above correct [y]y

Making module
make -C /lib/modules/2.6.24-19-generic/build SUBDIRS=/usr/local/src/vpnclient modules
make[1]: Entering directory `/usr/src/linux-headers-2.6.24-19-generic'
  CC [M]  /usr/local/src/vpnclient/linuxcniapi.o
In file included from /usr/local/src/vpnclient/Cniapi.h:15,
                 from /usr/local/src/vpnclient/linuxcniapi.c:31:
/usr/local/src/vpnclient/GenDefs.h:113: error: conflicting types for ‘uintptr_t’
include/linux/types.h:40: error: previous declaration of ‘uintptr_t’ was here
make[2]: *** [/usr/local/src/vpnclient/linuxcniapi.o] Error 1
make[1]: *** [_module_/usr/local/src/vpnclient] Error 2
make[1]: Leaving directory `/usr/src/linux-headers-2.6.24-19-generic'
make: *** [default] Error 2
Failed to make module "cisco_ipsec.ko".

This is a fairly well known problem with numerous websites and forum postings on the topic. The website projects.tuxx-home.at has been releasing patches for the installation files of the Cisco VPN client for all the latest Linux kernels.

Instead of using the VPN client provided by Stanford, download the latest one from there (currently v4.8.01) and the patch file for the linux kernel you are running. If you aren't sure which you have run:

# uname -a
Linux cmoney 2.6.24-19-generic #1 SMP Fri Jul 11 23:41:49 UTC 2008 i686 GNU/Linux

Assuming you've already performed steps 1-2 of installation procedure for the new client, you will now place your patch file in the vpnclient directory and patch the installation:

# patch < vpnclient-linux-2.6.24-final.diff 
patching file GenDefs.h
patching file interceptor.c

Then follow steps 3 and 4 as before.