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Re: firewall problems



On Sun, Sep 16, 2001, yaniv almog wrote about "firewall problems":
> Shalom,
> 
> I have recently installed Red-Hat 7.1 at work. My computer is connected th
> the network via eth0. The problem is that my maschine no longeraccept
> telnet, ftp, or e-mail. I tried to disable the firewall: by the gnome-lokkit

Disabling the firewall (or better yet, punching holes in it for these
services) is a good start but not enough. You also have to be listening
for those services!

Redhat, since version 7.1, don't listen to services by default (this is a
good security decision, to prevent cracking of clueless administrators'
machines). You have to enable them, either by manually editing files
in /etc/xinetd.d (e.g., /etc/xinetd.d/telnet), changing "disable = yes"
to "disable = no", and finally running /etc/init.d/xinetd restart,
or, by using the graphical linuxconf utility.
Do this for telnet and ftp (if you want them open). See hosts_access(5)
for instructions on how to limit which hosts can access them, or configure
a firewall for that.

To enable incoming smtp (if that is what you mean by "accept e-mail" -
note that this is not typically necessary on a personal machine!), you
need to start it (this time not with xinetd - running it one time is done
with  /etc/init.d/sendmail start but to enable it to run after every
boot, using linuxconf is the simplest choice), but that is not enough.
You also need to edit /etc/mail/sendmail.mc, comment out a line saying
	DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')
(the comments explain why), and restart sendmail with
	m4 /etc/mail/sendmail.mc > /etc/sendmail.cf
	/etc/init.d/sendmail restart

Good luck.

-- 
Nadav Har'El                        |      Tuesday, Sep 18 2001, 2 Tishri 5762
nyh@math.technion.ac.il             |-----------------------------------------
Phone: +972-53-245868, ICQ 13349191 |Does replacing myself with a shell-script
http://nadav.harel.org.il           |make me impressive or insignificant?

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