NAME
Authen::Libwrap - access to Wietse Venema's TCP Wrappers library
SYNOPSIS
use Authen::Libwrap qw( hosts_ctl STRING_UNKNOWN );
# we know the remote username (using identd)
$rc = hosts_ctl(
"programname",
"hostname.domain.com",
"10.1.1.1",
"username"
);
print "Access is ", $rc ? "granted" : "refused", "\n";
# we don't know the remote username
$rc = hosts_ctl(
"programname",
"hostname.domain.com",
"10.1.1.1"),
);
print "Access is ", $rc ? "granted" : "refused", "\n";
# use a socket instead
my $client = $listener->accept();
$rc = hosts_ctl( "programname" $socket );
print "Access is ", $rc ? "granted" : "refused", "\n";
DESCRIPTION
The Authen::Libwrap module allows you to access the hosts_ctl() function
from the popular TCP Wrappers security package. This allows validation
of network access from perl programs against the system-wide hosts.allow
file.
If any of the parameters to hosts_ctl() are not known (i.e. username due
to lack of an identd server), the constant STRING_UNKNOWN may be passed
to the function.
FUNCTIONS
Authen::Libwrap has only one function, though it can be invoked in
several ways. In each case, an true return code indicates that the
connection is allowed per the rules in hosts.allow and an undef value
indicates the opposite.
hosts_ctl($daemon, $hostname, $ip_addr, [ $user ] )
Takes three mandatory and one optional argument. $daemon is the service
for which access is being requested (like 'ftpd' or 'sendmail').
$hostname is the name of the host requesting access. $ip_addr is the IP
address of the host in dotted-quad notation. $user is the name of the
user requesting access. If unknown, $user can be omitted; STRING_UNKNOWN
will be passed in it's place.
hosts_ctl($daemon, $socket, [ $user ] )
If you have a socket (be it a glob, glob reference or an
IO::Socket::INET, you can pass that as the second argument. The hostname
and IP address will be determined using this socket. If the hostname or
IP address cannot be determined from the socket, STRING_UNKNOWN will be
passed in their place.
DEBUGGING
If you want to see the arguments that will be passed to the C function
hosts_ctl(), set $Authen::Libwrap::DEBUG to a true value.
EXPORTS
Nothing unless you ask for it.
hosts_ctl optionally
STRING_UNKNOWN optionally
EXPORT_TAGS
* functions
hosts_ctl
* constants
STRING_UNKNOWN
* all
everything the module has to offer.
CONSTANTS
STRING_UNKNOWN
BUGS
* twist in hosts.allow
Calls to hosts_ctl() which match a line in hosts.allow that uses the
"twist" option will terminate the running perl program. This is not
a bug in Authen::Libwrap per se -- libwrap uses exec(3) to replace
the running process with the specified program, so there's nothing
to return to.
Some operating systems ship with a default catch-all rule in
hosts.allow that uses the twist option. You may have to modify this
configuration to use Authen::Libwrap effectively.
* Test suite is not comprehensive
The test suite isn't very comprehensive because the path to
hosts.allow is set when libwrap is built and I can't tell what the
user's rules are. I can make sure the function calls don't die, but
I can't really tell if any call to hosts_ctl should give back a true
or false value.
TODO
In early 2003 I was contacted by another Perl developer who had
developed an XS interface to libwrap that covered more of the API than
mine did. Originally he offered it as a patch to my module, but at the
time I wasn't in a position to actively maintain anything on CPAN, so I
suggested that he upload it himself. I unfortunately lost the email
thread to a disk crash.
As of December 2003 I don't see any other modules professing to support
libwrap om CPAN. If that person is still out there, please get in
contact with me, otherwise I'll plan on implementing some of these TODOs
in the new year:
* provide support for hosts_access and request_* functions
* develop an OO interface
SEE ALSO
Authen::Tcpdmatch, a Pure Perl module that can parse hosts.allow and
hosts.deny if you don't need all the underlying features of libwrap.
hosts_access(3), hosts_access(5), hosts_options(5)
Wietse's tools and papers page:
<ftp://ftp.porcupine.org/pub/security/index.html>.
AUTHOR
James FitzGibbon, <jfitz@CPAN.org>