Introduction to tcpwrappers

The tcpwrappers package provides daemon wrapper programs that report the name of the client requesting network services and the requested service.

Package information

Additional downloads

Installation of tcpwrappers

Install tcpwrappers with the following commands:

patch -Np1 -i ../tcp_wrappers-7.6-shared_lib_plus_plus-1.patch &&
sed -i -e "s,^extern char \*malloc();,/* & */," scaffold.c &&
make install

Command explanations

sed -i -e ... scaffold.c: This command removes an obsolete C declaration which causes the build to fail if using GCC-3.4.x.

Configuring tcpwrappers

Config files

/etc/hosts.allow, /etc/hosts.deny

File protections: the wrapper, all files used by the wrapper, and all directories in the path leading to those files, should be accessible but not writable for unprivileged users (mode 755 or mode 555). Do not install the wrapper set-uid.

Then perform the following edits on the /etc/inetd.conf configuration file:

finger stream tcp nowait nobody /usr/sbin/in.fingerd in.fingerd


finger stream tcp nowait nobody /usr/sbin/tcpd in.fingerd


The finger server is used as an example here.

Similar changes must be made if xinetd is used, with the emphasis being on calling /usr/sbin/tcpd instead of calling the service daemon directly, and passing the name of the service daemon to tcpd.


The tcpwrappers package contains tcpd, tcpdchk, tcpdmatch, try-from, safe_finger and the libwrap libraries.



tcpd is the main access control daemon for all Internet services, which inetd or xinetd will run instead of running the requested service daemon.


tcpdchk is a tool to examine a tcpd wrapper configuration and report problems with it.


tcpdmatch is used to predict how the tcp wrapper would handle a specific request for a service.


try-from can be called via a remote shell command to find out if the host name and address are properly recognized.


safe_finger is a wrapper for the finger utility, to provide automatic reverse name lookups.

Last updated on 2005-02-28 13:39:06 -0700