I've been doing numerous searches and have learned a little every time but have not found the solution to my problem.
I have vsftpd setup, using SSL/TLS ive got it working as I needed, but am unable to apply the iptable rules below. Primarily PASV mode does not work. With
iptables -F everything works as expected. As soon as I apply the rules below it connects, but the client (CuteFTP) tries going into PASV mode it timesout.
my ip tables rules are as follows:
*filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT # ssh -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT # web -A INPUT -p tcp -m tcp --dport 80 -j ACCEPT # ssl #-A INPUT -p tcp -m tcp --dport 443 -j ACCEPT # subversion -A INPUT -p tcp -m tcp --dport 3690 -j ACCEPT # ftp + active ftp + pasv ftp -A INPUT -p tcp --dport 21 -m state --state ESTABLISHED,NEW -j ACCEPT -A INPUT -p tcp --dport 20 -m state --state ESTABLISHED -j ACCEPT -A INPUT -p tcp --dport 50000:60000 -m state --state RELATED,ESTABLISHED -j ACCEPT # mysql -A INPUT -p tcp -m tcp --dport 3306 -s 220.127.116.11 -j ACCEPT -A INPUT -p tcp -m tcp --dport 3306 -s 18.104.22.168 -j ACCEPT -A INPUT -p tcp -m tcp --dport 3306 -s 22.214.171.124 -j ACCEPT # ping -A INPUT -p icmp -j ACCEPT -A INPUT -i lo -j ACCEPT -A INPUT -j DROP -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT -A OUTPUT -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT COMMIT
I load them using (for testing purposes):
iptables-restore < /etc/iptables.test.rules
For reference I am running Ubuntu 10.04 LTS additionally here are some outputs I get with the following commands:
Module Size Used by xt_conntrack 2303 1 xt_helper 1155 0 nf_nat_ftp 1751 0 nf_nat 12653 1 nf_nat_ftp ipv6 220702 16 xt_state 1215 4 nf_conntrack_ftp 5108 1 nf_nat_ftp nf_conntrack_ipv4 9505 7 nf_nat nf_conntrack 43972 7 xt_conntrack,xt_helper,nf_nat_ftp,nf_nat,xt_state,nf_conntrack_ftp,nf_conntrack_ipv4 iptable_filter 2218 1 ip_tables 13794 1 iptable_filter nf_defrag_ipv4 1051 1 nf_conntrack_ipv4 dm_mirror 11338 0 dm_region_hash 6224 1 dm_mirror dm_log 7341 2 dm_mirror,dm_region_hash dm_snapshot 23956 0 dm_mod 50258 3 dm_mirror,dm_log,dm_snapshot
/lib/modules/126.96.36.199-rscloud/kernel/net/ipv4/netfilter/nf_nat_ftp.ko /lib/modules/188.8.131.52-rscloud/kernel/net/netfilter/ipvs/ip_vs_ftp.ko /lib/modules/184.108.40.206-rscloud/kernel/net/netfilter/nf_conntrack_ftp.ko /lib/security/pam_ftp.so /usr/share/man/man8/pam_ftp.8.gz
Additionally my vsftpd.conf passive ports are set as follows:
I've also tried loading the module with
modprobe ip_conntrack_ftp but that does not appear to work. Via the out put above it seems like the module isn't even on the system or is superseded by
nf_conntrack_ftp ... nf_ modules ...
So I think I found my answer: http://www.shorewall.net/FTP.html#Conntrack
Because the ftp helper modules must read and modify commands being sent over the command channel, they won't work when the command channel is encrypted through use of TLS/SSL.
Additionally another interesting fact which was causing some confusion was why I had
If you are running kernel 2.6.19 or earlier, then the module names are ip_nat_ftp and ip_conntrack_ftp
uname -r (gets the kernel version)
I've tested the above by disabling TLS/SSL and PASV works just fine with
RELATED,ESTABLISHED. However the main reason I want to use TLS/SSL is so that username/passwords would not be sent in the clear.