passive mode ftp high ports driving me nuts

[MargoAndTodd <margoandtodd@gmail.com>]

Hi All,

In my firewall, I deny all and then allow what
services though that I want.  Problem: on
passive mode ftp, where the second connection is
estabilshed using random high ports, other
services are using my (last three) ftp rules.

My passive mode rules:

/etc/sysconfig/iptables-config:
IPTABLES_MODULES="ip_conntrack_netbios_ns ip_nat_ftp ip_conntrack_ftp 
ip_conntrack_tftp"

unassgn=1024:65535
$tbls -A dsl-out  -o eth1  -p tcp  -s $eth1_addr --sport $unassgn 
--dport ftp         -m state --state NEW,ESTABLISHED           -j ACCEPT

$tbls -A dsl-in   -i eth1  -p tcp  ! --syn --sport ftp -d $eth1_addr 
--dport $unassgn -m state --state RELATED,ESTABLISHED       -j ACCEPT

$tbls -A dsl-for  -i eth1  -p tcp  ! --syn --sport ftp -d $internal_net 
  --dport $unassgn  -m state --state RELATED,ESTABLISHED  -j ACCEPT

# The "ftpdata" session is a "new" one when it sends the SYN.  However, 
the ftp_conntrack module marks it as related to its controlling
# ftp session, so that state=related matches.  This should deny any 
"ftpdata" session that doesn't have a controlling ftp session.

$tbls -A dsl-out  -o eth1  -p tcp  -s $eth1_addr --sport $unassgn -d 
$ANY_IP --dport $unassgn -m state --state RELATED,ESTABLISHED 
      -j ACCEPT

$tbls -A dsl-in   -i eth1  -p tcp  ! --syn  -s $ANY_IP --sport $unassgn 
-d $eth1_addr --dport $unassgn  -m state --state RELATED,ESTABLISHED 
   -j ACCEPT

$tbls -A dsl-for  -i eth1  -p tcp  ! --syn  -s $ANY_IP --sport $unassgn 
-d $internal_net --dport $unassgn   -m state --state RELATED,ESTABLISHED 
  -j ACCEPT


It is the "--sport $unassgn --dport $unassgn" that is killing me.
How do I restrict the last three to just passive mode ftp?

Also, what is the lowest port that the random passive mode ftp
port will choose?  20,000?  That may be all I need to do.

Many thanks,
-T