I feel like I have started to grasp of the basics of iptables through experiment/logging and reading. I got my start at the CentOS iptables wiki. But one thing still puzzles me that I haven't been able to google up a clear answer on:
Why is the chain "RH-Firewall" used in some cases I've read (like the Samba HowTo , but not others?
For example, in the hardening CentOS wiki there is the following code (I've pared it down a bit):
- Code: Select all
:INPUT DROP [0:0]
:FORWARD DROP [0:0]
:OUTPUT ACCEPT [0:0]
:RH-Firewall-1-INPUT - [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp --icmp-type echo-reply -j ACCEPT
-A INPUT -i eth0 -s 10.0.0.0/8 -j LOG --log-prefix "IP DROP SPOOF A: "
-A INPUT -i eth0 -s 172.16.0.0/12 -j LOG --log-prefix "IP DROP SPOOF B: "
-A RH-Firewall-1-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
# Accept ssh traffic. Restrict this to known ips if possible.
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
#Log and drop everything else
-A RH-Firewall-1-INPUT -j LOG
-A RH-Firewall-1-INPUT -j DROP
Some specific parts that confuse me about this:
:RH-Firewall-1-INPUT - [0:0] ~ Seems to be defining a chain, but with no default (a "-")?
-A INPUT -j RH-Firewall-1-INPUT ~ Seems to forward INPUT packets to the RH-Firewall chain, but then rules are defined later for -A INPUT?
All of my experimentation and iptables rules have been absent of any RH-Firewall, using just INPUT, FORWARD, and OUTPUT chains. Is there a reason to use it? Where does it come from/Why does it crop up so often?
I'm running CentOS 6.2 and iptables v1.4.7. Thanks for any responses to these basic questions. Linux is fun!