RE: WuFTP server with Iptables.

["Mark Johnston" <mark.johnston () bluesq com>]

Hey there,

You might want to look at using the stateful mode of the firewall ... so it would look something like this ... you can 
add interfaces and destination IP's if you like.

iptables -A INPUT -p tcp --dport 21 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -p tcp --sport 21 -m state --state ESTABLISHED -j ACCEPT

You can then use the "RELATED" state to allow traffic for port 20 instead of creating new rules to specfically allow 
this.

Cheers
Mark

-----Original Message-----
From: Jari IT [mailto:jari_info () yahoo uk co]
Sent: 25 September 2004 05:55
To: security-basics () securityfocus com
Subject: WuFTP server with Iptables.



Hi all,

I am setting a FTP server with Iptable firewall.
Here is the rule, which I get from www.openna.com.


    # incoming request
    iptables -A INPUT  -i $EXTERNAL_INTERFACE -p tcp  \
             --source-port $UNPRIVPORTS \
             -d $IPADDR --destination-port 21 -j ACCEPT

    iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p tcp ! --syn \
             -s $IPADDR --source-port 21 \
             --destination-port $UNPRIVPORTS -j ACCEPT


    # PORT MODE data channel responses
    iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p tcp  \
             -s $IPADDR --source-port 20 \
             --destination-port $UNPRIVPORTS -j ACCEPT

    iptables -A INPUT  -i $EXTERNAL_INTERFACE -p tcp ! --syn \
             --source-port $UNPRIVPORTS \
             -d $IPADDR --destination-port 20 -j ACCEPT


    # PASSIVE MODE data channel responses
    iptables -A INPUT  -i $EXTERNAL_INTERFACE -p tcp  \
             --source-port $UNPRIVPORTS \
             -d $IPADDR --destination-port $UNPRIVPORTS -j ACCEPT

    iptables -A OUTPUT -o $EXTERNAL_INTERFACE -p tcp ! --syn \
             -s $IPADDR --source-port $UNPRIVPORTS \
             --destination-port $UNPRIVPORTS -j ACCEPT

However, I still cannot connect from my house (behind ADSL router/modem) to
that site.
Stop this firewall, the FTP server work well.

Please advice me about this.
Thanks in advance,
Jari





**********************************************************************
This e-mail and any files transmitted with it are confidential and 
intended solely for the use of the individual or entity to whom they 
are addressed. It may not be used or disclosed except for the 
purpose for which it has been sent. If you have received this 
e-mail in error please notify the system administrator 
postmaster () bluesq com quoting the senders address. If you are not the 
intended recipient you must not use, disclose, distribute, copy, 
print or rely on this e-mail and must delete the message and any 
documents. Please advise immediately if you or your employer 
do not consent to Internet e-mail for messages of this kind. 
Unless expressly stated, opinions in this message are those of 
the individual sender and not of Blue Square. Blue Square 
accepts no liability or responsibility for any onward transmission 
or use of e-mails and attachment having left the Blue Square domain.

 

This footnote also confirms that this e-mail message has been swept
 by MIMEsweeper for the presence of computer viruses. Whilst we 
have taken reasonable precautions to ensure that this e-mail and 
any attachments have been swept for viruses, we cannot accept 
liability for any damage sustained as a result of software viruses and 
would advise that you carry out your own virus checks before 
opening any attachment.

 

www.bluesq.com
**********************************************************************