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
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