openvpn-auth-pam

SYNOPSIS

The openvpn-auth-pam module implements username/password
authentication via PAM, and essentially allows any authentication
method supported by PAM (such as LDAP, RADIUS, or Linux Shadow
passwords) to be used with OpenVPN.  While PAM supports
username/password authentication, this can be combined with X509
certificates to provide two indepedent levels of authentication.

This module uses a split privilege execution model which will
function even if you drop openvpn daemon privileges using the user,
group, or chroot directives.

BUILD

To build openvpn-auth-pam, you will need to have the pam-devel
package installed.

Build with the "make" command.  The module will be named
openvpn-auth-pam.so

USAGE

To use this plugin module, add to your OpenVPN config file:

  plugin openvpn-auth-pam.so service-type

The required service-type parameter corresponds to
the PAM service definition file usually found
in /etc/pam.d.

This plugin also supports the usage of a list of name/value
pairs to answer PAM module queries.

For example:

  plugin openvpn-auth-pam.so "login login USERNAME password PASSWORD pin OTP"

tells auth-pam to (a) use the "login" PAM module, (b) answer a
"login" query with the username given by the OpenVPN client,
(c) answer a "password" query with the password, and (d) answer a
"pin" query with the OTP given by the OpenVPN client.
This provides flexibility in dealing with different
types of query strings which different PAM modules might generate.
For example, suppose you were using a PAM module called
"test" which queried for "name" rather than "login":

  plugin openvpn-auth-pam.so "test name USERNAME password PASSWORD"

While "USERNAME" "COMMONNAME" "PASSWORD" and "OTP" are special strings which substitute
to client-supplied values, it is also possible to name literal values
to use as PAM module query responses.  For example, suppose that the
login module queried for a third parameter, "domain" which
is to be answered with the constant value "mydomain.com":

  plugin openvpn-auth-pam.so "login login USERNAME password PASSWORD domain mydomain.com"

The following OpenVPN directives can also influence
the operation of this plugin:

  client-cert-not-required
  username-as-common-name
  static-challenge

Use of --static challenege is required to pass a pin (represented by "OTP" in
parameter substituion) or a second password.

Run OpenVPN with --verb 7 or higher to get debugging output from
this plugin, including the list of queries presented by the
underlying PAM module.  This is a useful debugging tool to figure
out which queries a given PAM module is making, so that you can
craft the appropriate plugin directive to answer it.

CAVEATS

This module will only work on *nix systems which support PAM,
not Windows.
