[CentOS] ftp and iptables

Agile Aspect agile.aspect at gmail.com
Thu Jan 22 22:28:02 UTC 2009


Hi - I have a ftp server running version 2.0.7 of vsftpd on
a CentSO 5.2 server using iptables behind a Linksys router.

The setup works for UNIX machines on either side of the Linksys
router.

For the Windows machines it only works if they're behind the Linksys
router - ftp does NOT work if they're outside the Linksys router.

I'd like to solve two problems:
  
    (1) make ftp work for Windows clients outside the Linksys
          router

and then ideally, if possible,

    (2) have ftp work for both active and passive connections
          and restrict those connections to use ports between
          40000 to 60000

The ports 20,21 and 40000 to 60000 on the Linksys router
are open, and vsftp is configured with  the following options

    pasv_min_port=40000
    pasv_max_port=60000
    pasv_address=xxx.xxx.xxx.xxx
    connect_from_port_20=NO

The ftp entry automatically generated the system in /etc/sysconfig/iptables
is
   
    -A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 21 
-j ACCEPT
   
and to IPTABLES_MODULES entry in /etc/sysconfig/iptabes-config I've
added

    ip_conntrack_ftp
   
Enclosed are my iptables and vsftp.conf files (which might not make it to
the list.)

Regarding item (2), I would guess I would have to add the following entries:

Active:
---------
 
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 20 
--sport 40000:60000 -j ACCEPT
-A OUTPUT -p tcp -m tcp --sport 20 --dport 40000:60000 -j ACCEPT

Passive:
----------
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 
40000:60000 --sport 40000:60000 -j ACCEPT
-A OUTPUT -p tcp -m tcp --sport 40000:60000 --dport 40000:60000 -j ACCEPT
 

Adding these entries doesn't noticeably impact the vsftpd, i.e., the
connections from the UNIX or Windows behaves identically - I just
doubt if they're correct.

Any help would be greatly appreciated!

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