Question

Setup Iptables for FTP Passive connections Ubuntu?

Posted September 15, 2013 21.5k views
Hi I have setup the iptables using the guide https://www.digitalocean.com/community/articles/how-to-set-up-a-firewall-using-ip-tables-on-ubuntu-12-04 and it works great. Now I need to also configure the iptables to allow FTP to use Passive Mode. I have read that you need to run command #modprobe ip_conntrack_ftp and modprobe ip_conntrack and these 2 are loaded. The current iptable looks like this. iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT iptables -A INPUT -p tcp --dport ssh -j ACCEPT iptables -A INPUT -p tcp --dport 80 -j ACCEPT iptables -A INPUT -p tcp --dport 21 -j ACCEPT iptables -A INPUT -p tcp --dport 25 -j ACCEPT iptables -A INPUT -p tcp --dport 443 -j ACCEPT iptables -A INPUT -p tcp --dport 2812 -j ACCEPT iptables -A INPUT -p tcp --dport 10000 -j ACCEPT iptables -A INPUT -j DROP Any idea how to allow Passive FTP sessions in Iptables? Many thanks Mike
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kreativbureau
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6 answers
kamaln7 September 15, 2013
Try adding these rules: 

iptables -A INPUT -p tcp --sport 1024: --dport 1024:  -m state --state ESTABLISHED -j ACCEPT

iptables -A OUTPUT -p tcp --sport 1024: --dport 1024:  -m state --state ESTABLISHED,RELATED -j ACCEPT


Also I recommend deleting the -A INPUT -j DROP rule and setting INPUT's default policy to DROP: 

iptables -D INPUT -j DROP

iptables -P INPUT DROP
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kreativbureau September 15, 2013
Thanks Kamal, I will try this. Do I need to reboot the machine also?
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kamaln7 September 16, 2013
You shouldn't have to reboot your droplet for the new rules to take effect.
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nightflash September 17, 2013
Use this line:

modprobe ip_conntrack_ftp
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bogdan747 December 17, 2013
Isn't the -D to Delete the Rule and -A to Add the rules?
Mike's file (list of rules) is used in Ubuntu by the script iptables-apply, iptables-save and iptables-reload to add the rulles.

So your last line "iptables -D INPUT -j DROP" will delete / remove the DROP rule from the Chain?
So by adding that rule anyone can to get into his systems?
that's is just silly to say the least....
bogdan
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kamaln7 December 17, 2013
@bogdan747: It will delete the rule and the second command will set INPUT's default policy to DROP. Basically moves the DROP-by-default config out of the way, but it's still there :]
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