net.inet{,6}.fw.enable in /etc/rc

[Julian Elischer]

On 9/23/14, 2:01 AM, Andrey V. Elsukov wrote:
> On 21.09.2014 09:58, Hiroki Sato wrote:
>> Hi,
>>
>>   I would like your comments about the attached patch to /etc/rc.
>>
>>   The problem I want to fix by this patch is as follows.
>>   net.inet{,6}.fw.enable are set to 1 by default at boot time if IPFW
>>   kernel module is loaded or statically compiled into a kernel.  And by
>>   default IPFW has only a "deny ip from any to any" rule if it is
>>   compiled without IPFIREWALL_DEFAULT_TO_ACCEPT option.  In this case,
>>   the default-deny rule can prevent rc.d scripts before rc.d/ipfw from
>>   working as described in the patch.
>>
>>   To fix this, the patch turns IPFW off before running rc.d scripts at
>>   boot time, and enables it again in rc.d/ipfw script.
> Hi,
>
> I think this should be configurable, the change can be an unexpected for
> someone.
it does open a window where there is networking but no firewalling.
given that a reboot is remotely detectable. (ping stops responding etc.)
there is a possibility that a targeted attack could include
"use exploit ABC to cause a crash of the target and then strike with
exploit XYZ after target system reboots while the firewall is disabled".

I have not evaluated the danger of this window.