[CentOS] Sendmail, localloop, and iptables -- should I be more paranoid?

[Les Mikesell]

On 11/22/2010 9:11 AM, Robert Moskowitz wrote:
> By default, sendmail only listens on the localloop:
>
> DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl
>
> But by default to allow sendmail to even work the iptables entry is:
>
> -A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 25 -j
> ACCEPT
>
> Without this, sendmail can't even connect to localloop.  But should I
> handedit this line to something like:
>
> -A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp -d 127.0.0.1
> --dport 25 -j ACCEPT
>
> And once you handedit iptables, you can't use the gnome firewall applet,
> I suspect...

Every security decision has its own tradeoffs, so first you need to 
consider what you are trying to protect against.  If you don't have a 
program listening on a port, it doesn't matter whether it is explicitly 
firewalled or not.  A program needs root access to listen on ports below 
1024 - and anyone with root access can change the iptables settings too...

-- 
  Les Mikesell
   lesmikesell at gmail.com