VPNC
NAME
SYNOPSIS
DESCRIPTION
CONFIGURATION
OPTIONS
FILES
EXAMPLES
TODO
AUTHOR
SEE ALSO
NAME
vpnc − client for Cisco VPN3000 Concentrator, IOS and PIX
SYNOPSIS
vpnc [–version] [–print-config] [–help] [–long-help] [options] [config files]
DESCRIPTION
This manual page documents briefly the vpnc and vpnc−disconnect commands.
vpnc is a VPN client for the Cisco 3000 VPN Concentrator, creating a IPSec-like connection as a tunneling network device for the local system. It uses the TUN/TAP driver in Linux kernel 2.4 and above and device tun(4) on BSD. The created connection is presented as a tunneling network device to the local system.
OBLIGATORY WARNING: the most used configuration (XAUTH authentication with pre-shared keys and password authentication) is insecure by design, be aware of this fact when you use vpnc to exchange sensitive data like passwords!
The vpnc daemon by itself does not set any routes, but it calls vpnc−script to do this job. vpnc−script displays a connect banner. If the concentrator supplies a network list for split-tunneling these networks are added to the routing table. Otherwise the default-route will be modified to point to the tunnel. Further a host route to the concentrator is added in the later case. If the client host needs DHCP, care must be taken to add another host route to the DHCP-Server around the tunnel.
The vpnc−disconnect command is used to terminate the connection previously created by vpnc and restore the previous routing configuration.
CONFIGURATION
The daemon reads configuration data from the following places:
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command line options |
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config file(s) specified on the command line |
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/etc/vpnc/default.conf |
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/etc/vpnc.conf |
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prompting the user if not found above |
vpnc can parse options and configuration files in any order. However the first place to set an option wins. configuration filenames which do not contain a / will be searched at /etc/vpnc/
OPTIONS
The program options can be either given as arguments (but not all of them for security reasons) or be stored in a configuration file.
−−gateway
IP/name of your IPSec gateway
conf−variable: IPSec gateway
−−id
your group name
conf−variable: IPSec ID
(configfile only option)
your group password (cleartext)
conf−variable: IPSec secret
(configfile only option)
your group password (obfuscated)
conf−variable: IPSec obfuscated secret
−−username
your username
conf−variable: Xauth username
(configfile only option)
your password (cleartext)
conf−variable: Xauth password
(configfile only option)
your password (obfuscated)
conf−variable: Xauth obfuscated password
−−domain
(NT−) Domain name for authentication
conf−variable: Domain
−−xauth−inter
enable interactive extended authentication (for challenge response auth)
conf−variable: Xauth interactive
−−vendor
vendor of your IPSec gateway
Default: cisco
conf−variable: Vendor
−−natt−mode
Which NAT−Traversal Method to use:
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natt −− NAT−T as defined in RFC3947 |
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none −− disable use of any NAT−T method |
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force−natt −− always use NAT−T encapsulation even without presence of a NAT device (useful if the OS captures all ESP traffic) |
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cisco−udp −− Cisco proprietary UDP encapsulation, commonly over Port 10000 |
Note: cisco−tcp encapsulation is not yet supported
Default: natt
conf−variable: NAT Traversal Mode
−−script
command is executed using system() to configure the interface, routing and so on. Device name, IP, etc. are passed using enviroment variables, see README. This script is executed right after ISAKMP is done, but before tunneling is enabled. It is called when vpnc terminates, too
Default: /etc/vpnc/vpnc−script
conf−variable: Script
−−dh
name of the IKE DH Group
Default: dh2
conf−variable: IKE DH Group
−−pfs
Diffie−Hellman group to use for PFS
Default: server
conf−variable: Perfect Forward Secrecy
−−enable−1des
enables weak single DES encryption
conf−variable: Enable Single DES
−−enable−no−encryption
enables using no encryption for data traffic (key exchanged must be encrypted)
conf−variable: Enable no encryption
−−application−version
Application Version to report. Note: Default string is generated at runtime.
Default: Cisco Systems VPN Client 0.5.3:Linux
conf−variable: Application version
−−ifname
visible name of the TUN/TAP interface
conf−variable: Interface name
−−ifmode
mode of TUN/TAP interface:
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tun: virtual point to point interface (default) |
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tap: virtual ethernet interface |
Default: tun
conf−variable: Interface mode
−−debug <0/1/2/3/99>
Show verbose debug messages
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0: Do not print debug information. |
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1: Print minimal debug information. |
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2: Show statemachine and packet/payload type information. |
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3: Dump everything exluding authentication data. |
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99: Dump everything INCLUDING AUTHENTICATION data (e.g. PASSWORDS). |
conf−variable: Debug <0/1/2/3/99>
−−no−detach
Don’t detach from the console after login
conf−variable: No Detach
−−pid−file
store the pid of background process in
Default: /var/run/vpnc.pid
conf−variable: Pidfile
−−local−addr
local IP to use for ISAKMP / ESP / … (0.0.0.0 == automatically assign)
Default: 0.0.0.0
conf−variable: Local Addr
−−local−port <0−65535>
local ISAKMP port number to use (0 == use random port)
Default: 500
conf−variable: Local Port <0−65535>
−−udp−port <0−65535>
Local UDP port number to use (0 == use random port). This is only relevant if cisco−udp nat−traversal is used. This is the _local_ port, the remote udp port is discovered automatically. It is especially not the cisco−tcp port.
Default: 10000
conf−variable: Cisco UDP Encapsulation Port <0−65535>
−−dpd−idle <0,10−86400>
Send DPD packet after not receiving anything for
Default: 300
conf−variable: DPD idle timeout (our side) <0,10−86400>
−−non−inter
Don’t ask anything, exit on missing options
conf−variable: Noninteractive
−−auth−mode
Authentication mode:
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psk: pre−shared key (default) |
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cert: server + client certificate (not implemented yet) |
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hybrid: server certificate + xauth (if built with openssl support) |
Default: psk
conf−variable: IKE Authmode
−−ca−file
filename and path to the CA−PEM−File
conf−variable: CA−File
−−ca−dir
path of the trusted CA−Directory
Default: /etc/ssl/certs
conf−variable: CA−Dir
−−target−network
Target network in dotted decimal or CIDR notation
Default: 0.0.0.0/0.0.0.0
conf−variable: IPSEC target network
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−−print−config |
Prints your configuration; output can be used as vpnc.conf
FILES
/etc/vpnc.conf /etc/vpnc/default.conf
The default configuration file. You can specify the same config directives as with command line options and additionaly IPSec secret and Xauth password both supplying a cleartext password. Scrambled passwords from the Cisco configuration profiles can be used with IPSec obfuscated secret and Xauth obfuscated password.
See EXAMPLES for further details.
/etc/vpnc/*.conf
vpnc will read configuration files in this directory when the config filename (with or without .conf) is specified on the command line.
EXAMPLES
This is an example vpnc.conf with pre-shared keys:
IPSec gateway vpn.example.com
IPSec ID ExampleVpnPSK
IKE Authmode psk
IPSec secret PskS3cret!
Xauth username user@example.com
Xauth password USecr3t
And another one with hybrid authentication (requires that vpnc was built with openssl support):
IPSec gateway vpn.example.com
IPSec ID ExampleVpnHybrid
IKE Authmode hybrid
CA-Dir /etc/vpnc
or
CA-File /etc/vpnc/vpn-example-com.pem
IPSec secret HybS3cret?
Xauth username user@example.com
Xauth password 123456
The lines begin with a keyword (no leading spaces!). The values start exactly one space after the keywords, and run to the end of 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.
In case the the CA-Dir option is used, your certificate needs to be named something like 722d15bd.X, where X is a manually assigned number to make sure that files with colliding hashes have different names. The number can be derived from the certificate file itself:
openssl x509 -subject_hash -noout -in /etc/vpnc/vpn-example-com.pem
See also the −−print−config option to generate a config file, and the example file in the package documentation directory where more advanced usage is demonstrated.
Advanced features like manual setting of multiple target routes and disabling /etc/resolv.conf rewriting is documented in the README of the vpnc package.
TODO
Certificate support (Pre-Shared-Key + XAUTH is known to be insecure).
Further points can be found in the TODO file.
AUTHOR
This man-page has been written by Eduard Bloch
On Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common−licenses/GPL.
SEE ALSO
pcf2vpnc(1), cisco-decrypt(1), ip(8), ifconfig(8), route(1), http://www.unix−ag.uni−kl.de/~massar/vpnc/