ocserv/README

=== About ===

This program is openconnect VPN server (ocserv), a server compatible with the
openconnect VPN client [0]. It is believed to be compatible with the protocol
used by CISCO's AnyConnect SSL VPN. 

[0]. http://www.infradead.org/openconnect/


=== Build instructions ===

To build from a distributed release use:

$ ./configure && make

To build from the git repository use:

$ autoreconf -fvi
$ ./configure && make


=== Installation instructions ===

Now you need to generate a certificate. E.g.
$ certtool --generate-privkey > ./test-key.pem
$ certtool --generate-self-signed --load-privkey test-key.pem --outfile test-cert.pem
(make sure you enable encryption or signing)

To run the server edit the src/sample.config and then run:
# src/ocserv -f -c src/sample.config


=== How the VPN works ===

The openconnect VPN server is an Internet-layer VPN server. That is, it provides 
the client with an IP address and a list of routes that this IP may access. 
Since this is not a Link-layer VPN a separate subnet must be allocated for the 
VPN addresses.

The subnet addresses are specified by the 'ipv4-network' and 'ipv4-netmask'
configuration options (and the corresponding ipv6 options). The routes that
are pushed to the client are specified by the 'route' option. For each client
two IPv4 addresses are assigned, its VPN address and its local image (remember
this is a point-to-point connection). The image isn't known to the client 
(the anyconnect protocol doesn't forward it). 

Note that ocserv doesn't do any packet forwarding or filtering between the
networks. It is expected that the server has any required routes or firewall
rules, set up. You may conditionally enable firewall rules, or even
enable routing rules through the client using the 'connect-script' and 
'disconnect-script' scripts based on the user who connected. Note that it 
is important for these scripts not to hang, and terminate without long delays.
You may find some examples in the scripts/ directory.


=== Authentication ===

The authentication in openconnect VPN server occurs in the initial TLS session.
That is an HTTPS session over which the client is provided with an XML authentication
page. The server is authenticated using its certificate and the client, either by
its certificate, or via a username and password pair which are forwarded to
PAM, or a combination of both. Because PAM supports various authentication types,
the username, password entered by the user could be a one-time-password or whatever
else. After the user is authenticated he is provided with a cookie that can
be used for future connections. The lifetime of the cookie is configurable using 
the 'cookie-validity' option, and is newed on every client connection.

After the user is authenticated, directly, or via the cookie, he may issue a CONNECT 
HTTP command which results to a direct connection with the VPN. Additionally
the user could connect using UDP and Datagram TLS. That connection is authenticated
using session resumption and a master key provided by the server, i.e., it is not really 
a DTLS 1.0 compliant connection.