[gentoo-user] Re: IPTables - Going Stateless

[Nick Khamis]

On 5/21/13, Neal Murphy <neal.p.murphy@××××××××.edu> wrote:
> You still aren't accepting *each* direction. Either accept each direction
> with
> explicit rules or rewrite the rules so they apply to both directions at
> once.
> The former is probably easier to understand months later, even though it is
>
> more verbose.
>
> Mea culpa. I missed the '--dport'; that should be changed to '--sport' in
> one
> of the rules. I adjusted the rule below.
>
> N
>
> On Tuesday, May 21, 2013 11:07:10 AM you wrote:
>> Hello Everyone,
>>
>> #echo -e "       - Accepting SSH Traffic"
>> $IPTABLES -A TCP -p tcp -m tcp -s 192.168.2.0/24 -d 192.168.2.5
>> --dport 22 -j ACCEPT
>> $IPTABLES -A TCP -p tcp -m tcp -s 0.0.0.0/0 -d 192.168.2.5 --dport 22 -j
>> DROP
>>
>> Everything works fine with the REJECT rules commented out, but when
>> included SSH access is blocked out. Not sure why, isn't the sequence
>> correct (i.e., the ACCPET entries before the DROP and REJECT)?
>
> SSH isn't a one-way protocol. I believe you need at least one more rule.
> This:
>     -A TCP -p tcp -m tcp -s 192.168.2.0/24 -d 192.168.2.5 \
>        --dport 22 -j ACCEPT
> only matches packets in one direction. You need to add:
>     -A TCP -p tcp -m tcp -s 192.168.2.5 -d 192.168.2.0/24 \
>        --sport 22 -j ACCEPT
> to accept packets in the other direction.
>
>


That was it!!! Thank you so much. For future searchers to similar problems:


#!/bin/bash
IPTABLES='/sbin/iptables'

#Set interface values
INTIF1='eth0'

#flush rules and delete chains
$IPTABLES -F
$IPTABLES -X

#echo -e "       - Accepting input lo traffic"
$IPTABLES -A INPUT -i lo -j ACCEPT

#echo -e "       - Accepting output lo traffic"
$IPTABLES -A OUTPUT -o lo -j ACCEPT

#echo -e "       - Defined Chains"
$IPTABLES -N TCP
$IPTABLES -N UDP

#echo -e "       - Accepting SSH Traffic"
$IPTABLES -A TCP -p tcp -m tcp -s 192.168.2.0/24 -d 192.168.2.5
--dport 22 -j ACCEPT
$IPTABLES -A TCP -p tcp -m tcp -s 192.168.2.5 --sport 22 -d
192.168.2.0/24 -j ACCEPT
$IPTABLES -A TCP -p tcp -m tcp -s 0.0.0.0/0 -d 192.168.2.5 --dport 22 -j DROP

#echo -e "       - Accepting input TCP and UDP traffic to open ports"
$IPTABLES -A INPUT -i $INTIF1 -p tcp -j TCP
$IPTABLES -A INPUT -i $INTIF1 -p udp -j UDP

#echo -e "       - Accepting output TCP and UDP traffic to open ports"
$IPTABLES -A OUTPUT -o $INTIF1 -p tcp -j TCP
$IPTABLES -A OUTPUT -o $INTIF1 -p udp -j UDP

#echo -e "       - Dropping input TCP and UDP traffic to closed ports"
$IPTABLES -A INPUT -i $INTIF1 -p tcp -j REJECT --reject-with tcp-rst
$IPTABLES -A INPUT -i $INTIF1 -p udp -j REJECT --reject-with
icmp-port-unreachable

#echo -e "       - Dropping output TCP and UDP traffic to closed ports"
$IPTABLES -A OUTPUT -o $INTIF1 -p tcp -j REJECT --reject-with tcp-rst
$IPTABLES -A OUTPUT -o $INTIF1 -p udp -j REJECT --reject-with
icmp-port-unreachable

#echo -e "       - Dropping input traffic to remaining protocols sent
to closed ports"
$IPTABLES -A INPUT -i $INTIF1 -j REJECT --reject-with icmp-proto-unreachable

#echo -e "       - Dropping output traffic to remaining protocols sent
to closed ports"
$IPTABLES -A OUTPUT -o $INTIF1 -j REJECT --reject-with icmp-proto-unreachable


Kind Regards,

Nick.