The Ssl Vpn Client Login - D-Link NetDefendOS User Manual

Chapter 9: VPN
Figure 9.6. The SSL VPN Client Login
The difference between the two approaches above is that when the SSL VPN client software is
started by browsing to the SSL VPN interface, the correct settings for the tunnel are downloaded
to the SSL VPN client software and stored as the client's configuration file.
As long as these settings have not changed between tunnel sessions, it is possible to start the
SSL VPN client software running by selecting it in the Start menu and connecting to the same SSL
VPN interface. In particular, the SSL VPN client checks the certificate used by the SSL VPN
interface by comparing a certificate fingerprint stored in the configuration file with a fingerprint
sent by the interface.
The reason for checking the certificate in this way is that it solves the "man in the middle"
problem where a malicious third party might try to intercept communications between the
firewall and the client.
Custom Server Connection
When the SSL VPN client software is started, it is possible to connect to an SSL VPN interface on a
NetDefend Firewall that has not been connected to before. This is done by enabling the option
Specify Custom Server and explicitly specifying the IP address, port and login credentials for the
server.
With the Specify Custom Server option enabled, the SSL VPN client ignores any configuration
file parameters previously downloaded by an SSL VPN connection established using the web
interface. In particular, it does not check the certificate used by the firewall.
The disadvantage of using the custom server option is that there is no certificate checking and
the "man in the middle" problem remains.
Client Transfer Statistics
When the SSL VPN client is running, an icon for it will appear in the system tray. Clicking this icon
will bring up the client's interface showing amounts of data transferred since tunnel setup.
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