Source code VPNC

IPsec (Cisco/Juniper) VPN concentrator client

About
Installation
FAQ

About

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.

Development status

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.

Installation

git clone https://github.com/streambinder/vpnc.git
cd vpnc
make
sudo make install

General configuration

Few libraries are required to let VPNC work properly:

libgcrypt (version: 1.1.90+)
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 information (both with key name for specifying option via command line or config file) it currently needs are:

Input option	File option
`--gateway`	`IPSec gateway`
`--id`	`IPSec ID`
`--secret`	`IPSec secret`
`--username`	`Xauth username`
`--password`	`Xauth password`

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 they decline and refer to the configuration files provided for the vpnclient program, tell them 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: pre-init, connect, disconnect
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: 255.255.255.0)
CISCO_SPLIT_INC_%d_MASKLEN: subnet mask length (for example: 24)
CISCO_SPLIT_INC_%d_PROTOCOL: protocol (often just 0)
CISCO_SPLIT_INC_%d_SPORT: source port (often just 0)
CISCO_SPLIT_INC_%d_DPORT: destination port (often just 0)

Currently 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:

#!/bin/sh

# this effectively disables changes to /etc/resolv.conf
INTERNAL_IP4_DNS=

# 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
# accordingly
CISCO_SPLIT_INC=1
CISCO_SPLIT_INC_0_ADDR=131.246.89.7
CISCO_SPLIT_INC_0_MASK=255.255.255.255
CISCO_SPLIT_INC_0_MASKLEN=32
CISCO_SPLIT_INC_0_PROTOCOL=0
CISCO_SPLIT_INC_0_SPORT=0
CISCO_SPLIT_INC_0_DPORT=0

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
`--hybrid`	`Use Hybrid Auth`
`--ca-file <ca.pem>`	`CA-File <ca.pem>`
`--ca-dir <ca/dir>`	`CA-Dir <ca/dir>`

Default CA-Dir is /etc/ssl. A link can also be used like in /etc/ssl/certs/.

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

FAQ

Use the client with Nortel Contivity

Matt Chapman (matthewc@cse.unsw.edu.au) 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;
- the XAUTH attributes have different numerical values (which overlap with Mode-Config);
- 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 0 in 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 XAUTH/Mode-Config/phase 2 diverge.

According to Zingo Andersen, NORTELVPN_XAUTHTYPE_AS_REQUEST has to be set and this patch applied:

#ifdef NORTELVPN_XAUTHTYPE_AS_REQUEST
    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;
#else
    if (ap->af != isakmp_attr_16 || ap->u.attr_16 != 0)
        reject = ISAKMP_N_ATTRIBUTES_NOT_SUPPORTED;
#endif

Setting up VPNC on Windows Vista (64 bit)

Install cygwin: follow steps at cygwin.com
Make sure you install the development options for cygwin to give you access to make, gcc, and all the other development libraries
Make sure you install libgcrypt for cygwin as it is needed in the make procedure
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 C:/cygwin/bin
Download the latest VPNC tarball
Unzip and explode the tarball
Modify 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)
make
Download OpenVPN. It has been tested with success on version 2.1_rc4
Just install TAP-Win32 Adapter V9
Go to Control Panel, and then Network Connections and rename the TAP device to my-tap
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.