IPsec (Cisco/Juniper) VPN concentrator client#
VPNC is a VPN client compatible with Cisco's EasyVPN equipment. It supports IPSec (ESP) with Mode Configuration and Xauth. Supports only shared-secret IPSec authentication with Xauth, AES (256, 192, 128), 3DES, 1DES, MD5, SHA1, DH1/2/5 and IP tunneling. It runs entirely in userspace. Only "Universal TUN/TAP device driver support" is needed in kernel.
This repository has been forked to follow the work started originally by Maurice Massar. For more information about that, please, point to VPNC original web page.
As stated in
vpnc-devel mailing-list (vpnc-devel@2017-November), this repository hasn't been started to start working actively on this project, but to passively merge security patches, fixes and features additions explicitly requested by the community.
This means I won't even consider issues such as "Please, implement this", or "Look at that, maybe you can find ideas and fixes", but I will if requested via explicit PRs and/or issues pointing to a (or many) specific patch.
git clone https://github.com/streambinder/vpnc.git
sudo make install
Few libraries are required to let VPNC work properly:
libopenssl (optional, needed to provide hybrid support)
Configuration data gets read from:
- command-line options
- config file(s) specified on the command line
/etc/vpnc/default.conf, if no config file was given on the command line
/etc/vpnc.conf, if no config file was given on the command line
- output prompt, if a settings can't get loaded from any of those places above
Essential configuration informations (both with key name for specifying option via command line or config file) it currently needs are:
|Input option||File option|
A sample configuration file is:
IPSec gateway 127.0.0.1
IPSec ID sample-vpn
IPSec secret s4mpl3
Xauth username johndoe
Note that all strings start exactly one space after the keyword string, and run to the end of the line. This lets you put any kind of weird character (except CR, LF and NUL) in your strings, but it does mean you can't add comments after a string, or spaces before them.
It may be easier to use the
--print-config option to generate the config file, and then delete any lines (like a password) that you want to be prompted for.
If you don't know the Group ID and Secret string, ask your administrator. If (s)he declines and refers to the configuration files provided for the vpnclient program, tell him/her that the contents of that files are (though scrambled) not really protected. If you have a working configuration file (
.pcf file) for the Cisco client then you can use the
pcf2vpnc utility instead, which will extract most/all of the required information and convert it into a vpnc configuration file.
Using a modified script
Please note that VPNC itself does not setup routing. You need to do this yourself, or use
--script script.sh /
Script script.sh (the first one to pass it as input parameters, the other one as config file value). The default script is
/etc/vpnc/vpnc-script which sets a default route to the remote network, or if the Concentrator provided split-network settings, these are used to setup routes.
This option is passed to
system(), so you can use any shell-specials you like. This script gets called tree times:
$reason == pre-init: this is before VPNC opens the tun device, so you can do what is necessary to ensure that it is available. Note that none of the variables mentioned below is available.
$reason == connect: this is what used to be "Config Script". The connection is established, but vpnc will not begin forwarding packets until the script finishes.
$reason == disconnect: This is called just after vpnc received a signal. Note that VPNC will not forward packets anymore while the script is running or thereafter.
Information is passed from VPNC via environment variables:
reason: why this script was called, one of:
VPNGATEWAY: VPN gateway address (always present)
TUNDEV: tunnel device (always present)
INTERNAL_IP4_ADDRESS: address (always present)
INTERNAL_IP4_NETMASK: netmask (often unset)
INTERNAL_IP4_DNS: list of DNS servers
INTERNAL_IP4_NBNS: list of wins servers
CISCO_DEF_DOMAIN: default domain name
CISCO_BANNER: banner from server
CISCO_SPLIT_INC: number of networks in split-network-list
CISCO_SPLIT_INC_%d_ADDR: network address
CISCO_SPLIT_INC_%d_MASK: subnet mask (for example:
CISCO_SPLIT_INC_%d_MASKLEN: subnet mask length (for example:
CISCO_SPLIT_INC_%d_PROTOCOL: protocol (often just
CISCO_SPLIT_INC_%d_SPORT: source port (often just
CISCO_SPLIT_INC_%d_DPORT: destination port (often just
vpnc-script is not directly configurable from config files. However, a workaround is to use a
wrapper-script like this, to disable
/etc/resolv.conf rewriting and setup a custom split-routing:
# this effectively disables changes to /etc/resolv.conf
# This sets up split networking regardless
# of the concentrators specifications.
# You can add as many routes as you want,
# but you must set the counter $CISCO_SPLIT_INC
Store this example script, for example in
/etc/vpnc/custom-script, do a
chmod +x /etc/vpnc/custom-script and add
Script /etc/vpnc/custom-script to your configuration.
Additional steps to configure hybrid authentication
|Input option||File option|
Use Hybrid Auth
/etc/ssl. A link can also be used like in
As the trusted certificate is referenced by the hash of the subject name, the directory has to contain the certificate named like that hash value. As an example, the hash value can be calculated using the following command:
openssl x509 -in <ca_certfile.pem> -noout -hash
Use the client with Nortel Contivity
Matt Chapman (
firstname.lastname@example.org) got vpnc working with a Nortel Contivity VPN concentrator. According to him, the differences are:
The group name and password are pre-transformed:
key_id = SHA1(group_name)
shared_key = HMAC_SHA1(group_name, SHA1(group_password))
The XAUTH implementation follows
draft-ietf-ipsec-isakmp-xauth-02.txt (whereas CISCO uses a later version). Specifically:
- the encoding of the proposal is not defined in that spec, and Nortel does it differently;
XAUTH attributes have different numerical values (which overlap with
- success/failure are encoded as
Mode-Config message types 5/6 (or sometimes as an
ISAKMP notify?) rather than in an attribute;
- the concentrator always sends
XAUTH_TYPE and the client may have to return a different value (
xauth-02 is not clear on whether this is allowed, it is not clarified until
xauth-05). In my case I'm using an
ActivCard token for which I have to specify 5 (SecurID).
Mode-Config is done as a push, i.e. the server sends
SET, instead of a pull.
The concentrator wants to be the initiator in phase 2 quick mode, so we have to support being a responder.
Thus the changes are fairly intrusive - phase 1 is common but
Mode-Config/phase 2 diverge.
According to Zingo Andersen,
NORTELVPN_XAUTHTYPE_AS_REQUEST has to be set and this patch applied:
if (ap->af != isakmp_attr_16 || !(ap->u.attr_16 == 0 || ap->u.attr_16 == 5))
reject = ISAKMP_N_ATTRIBUTES_NOT_SUPPORTED;
xauth_type_requested = ap->u.attr_16;
if (ap->af != isakmp_attr_16 || ap->u.attr_16 != 0)
reject = ISAKMP_N_ATTRIBUTES_NOT_SUPPORTED;
Setting up VPNC on Windows Vista (64 bit)
cygwin: follow steps at cygwin.com
- Make sure you install the development options for
cygwin to give you access to
gcc, and all the other develpment libraries
- Make sure you install
cygwin as it is needed in the
- Modify the
bash.exe to run as administrator or you will have privilege issues later, this is done on the properties tab of the executable in
- Download the latest VPNC tarball
- Unzip and explode the tarball
tap-win32.h to change
#define TAP_COMPONENT_ID "tap0801" to
#define TAP_COMPONENT_ID "tap0901" (not sure if this is always necessary, but at least once it has been needed)
- Download OpenVPN. It has been tested with success on version
- Just install
TAP-Win32 Adapter V9
- Go to Control Panel, and then Network Connections and rename the TAP devic to
- Use a
default.conf built like this:
IPSec gateway YOURGATEWAY
IPSec ID YOURID
IPSec obfuscated secret YOURREALYLONGHEXVALUE (you can use your clear
text password here if you remove obfuscated)
Xauth username YOURUSERNAME
Xauth password YOURPASSWORD
Interface name my-tap
Interface mode tap
Local Port 0
Suddenly client stops without any specific reason
The DHCP leases are very short intervals and on each renew the DHCP client overwrites things like
/etc/resolv.conf and maybe the default route To solve the issue, fix your
dhcpclient: on Debian it can be done by installing and using
resolvconf to modify that file instead of modifying it directly.