About F19 Firewall

Thomas Woerner twoerner at redhat.com
Fri Sep 20 13:59:37 UTC 2013

On 09/15/2013 08:52 PM, P J P wrote:
>       Hi,
> I upgraded to F19 recently. And I happened to look at the output of iptables(8) today.
>     $ iptables -nL
> It's baffling! It's crazy 4 pages long listing!!
> Why
>   are there so many chains? Most are empty. Those which have rules, jump
> from one chain to another and that jumps to yet another.
These chains are needed to

1) Separate zones.

NM connections, interfaces and source addresses or ranges can be bound 
to zones. The initial default zone is public and all connections will be 
bound to this zone. The user or administrator can bind connections to 
other zones by either doing this in the NM connection editor or within 
the ifcfg file.

2) Make sure that a newly added rule will have the desired effect.

If you are mixing deny and allow rules, you can not say which effect it 
will have. Either there are unwanted accepts or rejects or drops. A 
simple and straight forward solution is to have separate chains for deny 
and allow rules. The same applies also for logging rules.

> Multicast
>   DNS is allowed in the internal network(chain IN_internal_allow). I
> guess  IN_internal_allow  is meant for some closed group internal
> network, not sure.
>      ACCEPT     udp  --            udp dpt:5353 ctstate NEW
> Who uses it?
This has been added because of a FESCo decision to enable Multicast DNS 

> Then
>   I looked at the firewall configuration GUI tool. That's even more
> baffling. On the left hand side, it lists zones: home, internal, public,
>   work etc. without any explanation whatsoever what each one is suppose
> to do. It also has a default zone which is 'public'. I guess that must
> be the running firewall configuration. So even if I'm at work or at
> home, I'm using firewall configuration that is meant for public network,
>   am I? Besides, who is going to switch between these zones everyday from
>   home to work to home again?
You do not need to change it, but you can if you want to. If for example 
you are using wifi connections at home, work, .. you can bind these to 
the (for you) appropriate zone. For example work for your work wifi 
connection. It will be used only if you are connecting to your work wifi 
connection (it is bound to the SSID).

The default zone (initially public) is used for all connections and 
interfaces where the zone has not been set to another value.

You can customize the zones and services according to your needs.

> I think for individual users, which
> is majority of the users, this is a stupid firewall. It doesn't have to
> be so complicated that even if one tries to understand it, he/she can
> not. :(
> ---
> Regards
>     -Prasad
> http://feedmug.com

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