Libwrap

libwrap is a free software program library that implements generic TCP Wrapper functionality for network service daemons to use (rather than, or in addition to, their own host access control schemes).

Originally part of the tcp_wrappers package, it per default was compiled as a static archive, and is still used as such some places, for instance in Slackware Linux 10.2. However most other FOSS Unix-like distributions, such as Debian, Red Hat and NetBSD, applied patches to the Makefile in order to compile it to a shared-object and generally include that as part of their base system. Some even decouple it (and testing utilities) from 'tcpd', which is then provided as an additional package.

One of the possible problems for end-user (sysadmins) to this situation is that the 'soname' is not standardized, although it generally is "libwrap.so.0.7.6" in Linux distributions, and "libwrap.so.2, 3 or 7" on BSD Unix systems.

See also

* TCP Wrapper
* Autoconf
* Unix security
* Access control list (ACL)

References

* [http://www.freebsddiary.org/ssh_refused.php Problem description of libwrap soname conflicts.]
* [http://packages.qa.debian.org/t/tcp-wrappers.html Overview of the Debian tcp-wrappers packages]
* [http://mia.ece.uic.edu/cgi-bin/lxr/http/source/configure.in?v=poptop-1.1.4 Example of libwrap Autoconf usage at: "dnl Check for libwrap (black magic check)" ]
* [http://netbsd.org/Documentation/software/3rdparty/ Third party software distributed with NetBSD]
* [ftp://ftp.netbsd.org/pub/NetBSD/NetBSD-current/src/doc/CHANGES.prev NetBSD current: List of changes (among which libwrap support)]

External links

*man|3|hosts_access|NetBSD|access control library
*OpenBSDs' [http://mirror.sg.depaul.edu/pub/OpenBSD/src/libexec/tcpd/tcpd/tcpd.c tcpd.c] as libwrap usage example code
* [http://www.phpbuilder.com/manual/en/ref.tcpwrap.php PHP interface: tcpwrap_check]
* [http://ples.sourceforge.net/index.cgi?PyTCPWrap Python interface: PyTCPWrap]
* [http://shugo.net/archive/ruby-tcpwrap Ruby interface: libwrap-ruby (originally ruby-tcpwrap)]
* [http://klomp.org/mod_hosts_access/ Apache module: mod_hosts_access]
* [http://web.tiscalinet.it/macchese/PAM/pam_tcpd.html PAM module: pam_tcpd]