how to only allow tcp on dport 443 on the OUTPUT chain?

[Bill Davidsen]

JD wrote:
> On 03/19/2011 02:19 PM, Bill Davidsen wrote:
>> erikmccaskey64 wrote:
>>> it's a normal desktop machines iptables firewall:
>>>
>>> If i want to block udp on dport 80 on the output chain, then is this
>>> enough? i want to only allow tcp on it!
>>> iptables -P OUTPUT DROP
>>> iptables -A OUTPUT -o $PUBIF --dport 80 -j ACCEPT
>>>
>>> or i need this rule?
>>> iptables -P OUTPUT DROP
>>> iptables -A OUTPUT -o $PUBIF -p tcp --dport 80 -j ACCEPT
>>>
>>> the second one is the good one?
>>>
>> You don't want to do that, if you block everything on OUTPUT things like DHCP,
>> ARP, ICMP, etc, fail. You would need pages of ACCEPT rules.
>>
>> iptables -A OUTPUT -p tcp ! --dport 80 -j REJECT
>>
>> Would at least block only tcp, although I bet you will find that you want to do
>> mail and such. You are rapidly entering deep waters, I fear, but it's your machine.
>>
> Blocking output on port 80 will render your web browsers largely useless,
> because web browsers send connection requests to web servers on port 80
> using the TCP protocol.
>
Reread that command again, it blocks all tcp EXCEPT port 80

-- 
Bill Davidsen <davidsen at tmr.com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot