[PLUG] Tcp wrappers

[Jeff DeFouw]

On Mon, 27 Sep 1999, Josh Guffin wrote:

> Is it possible to restrict specific ports using tcpwrappers?  I think I
> found something about it in the manpage for tcpd but i'm not sure...

A TCP wrapper restricts access to a service defined in /etc/services which
maps to a protocol and port.  In /etc/hosts.allow and /etc/hosts.deny you
can allow and deny hosts from accessing specific services.

In hosts.deny a line:
telnet: ALL
would deny all hosts access to the telnet service

or you could put "ALL: ALL" in hosts.deny (the order is allow,deny by
default) and then give specific hosts access to specific tcp wrapped
services in hosts.allow:
telnet: .purdue.edu
ident: ALL
which would deny everyone except telnets from hosts matching *.purdue.edu
and ident requests from any host.

For more information look at the man pages for tcpd(8) and
hosts_access(5).

These only work for services handled through tcpd as seen in
/etc/inetd.conf.  Anything not handled by tcpd can be blocked by different
means with the Linux firewall utilities.

--
Jeff DeFouw <defouwj@purdue.edu>