tcpwrappers in the kernel

matters · 05-18-2007, 09:05 AM

I heard that tcpwrappers are installed in the kernel. Is that true?

For some reason tcpwrappers dosent work with sshd.

Can someone point out to me how i can check if tcpwrappers are inside my current kernel?

Thanks!

anomie · 05-18-2007, 10:19 AM

Quote:

Originally Posted by matters

For some reason tcpwrappers dosent work with sshd.

Post the results of

Code:

$ ldd /usr/sbin/sshd | grep libwrap

If your sshd binary doesn't live in that path, use whereis -b sshd to determine where it is and modify the above command accordingly.

matters · 05-18-2007, 04:37 PM

Quote:

Originally Posted by anomie

Post the results of

Code:

$ ldd /usr/sbin/sshd | grep libwrap

If your sshd binary doesn't live in that path, use whereis -b sshd to determine where it is and modify the above command accordingly.

There is no output of ldd /usr/sbin/sshd | grep libwrap

however i do have /usr/sbin/tcpd - that should indicate that tcpwrappers are installed or am I wrong ?

anomie · 05-18-2007, 05:40 PM

If there's no output from that command (and you've specified the correct path to the sshd binary), then your sshd does not have tcp wrappers support compiled in.

You may be able to still take advantage of tcp wrappers by running sshd as an inetd service (presuming that has support compiled in - it should).

Since I don't run slackware, I'll leave the details of implementing that to someone who is familiar with that environment.

Petri Kaukasoina · 05-19-2007, 05:15 AM

Quote:

Originally Posted by matters

I heard that tcpwrappers are installed in the kernel. Is that true?

No, it's a userspace executable (tcpd) and a userspace library (libwrap.a).

Quote:

Originally Posted by matters

For some reason tcpwrappers dosent work with sshd.

Can someone point out to me how i can check if tcpwrappers are inside my current kernel?

libwrap.a is statically linked inside the sshd binary if you use the official Slackware openssh.

Code:

strings /usr/sbin/sshd | fgrep 'hosts.allow'

prints /etc/hosts.allow if that string is included in the sshd binary and it's there only if sshd has been linked against libwrap.a.