a simple Python client for netExtender VPNs (SonicWALL/Dell)
Supports basic IPv4 connectivity with routing and DNS.
Install Python dependencies with:
pip install -r requirements.txt
You will also need pppd.
Very simply:
sudo ./nxBender --server my-sslvpn-host.com -u username -p password -d domainname
You can supply the server's SSL certificate fingerprint with --fingerprint if
you're using self-signed certificates or if you want pinning.
Options can also be placed into a configuration file - defaulting to
/etc/nxbender or ~/.nxbender - such as:
server = my-sslvpn-host.com
username = username
password = password
fingerprint = 9d:6a:fe:04:78:93:b0:a5:38:a0:04:ac:d2:10:cb:f7:9c:42:cf:74
At present the VPN routes are set up using pyroute2, which uses Linux's
netlink interface to manage routing. A cross-platform approach could use ip
and route binaries instead.
The output of pppd is parsed to determine the remote gateway address rather
than using the ip-up mechanism, to avoid headaches caused by differences in
implementation between distributions (somewhere Dell's client trips up). This
might prove fragile, but pppd is very stable nowadays.
The official client is a pain to use; it only works out of the box on some very specific Linux flavours, has little useful debugging output, and I had to disassemble the binaries to even get it working on Gentoo.
The CLI component also has a number of painful behaviours, including requiring
user input to acknowledge self-signed certificates - even when reconnecting
during a session - and with no way to store the fingerprint for some reason;
so acceptance can be automated with expect but is then vulnerable to MitM.
It frequently leaves entries in resolv.conf when the VPN is down, breaking
DNS for the entire system.
When I took a peek the protocol was trivial so I spent a couple of hours on a Sunday smashing out a replacement. Thus far it has proven quite reliable.
Not currently implemented are:
- IPv6
- DNS search suffixes
- auto reconnection
- configurable timeouts/link loss detection