The following are my iptable rules on a ubuntu cloud server:
cat /etc/iptables.rules:
*filter
:INPUT DROP [598:41912]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [456:35354]
-A INPUT -i lo -j ACCEPT
-A INPUT -p tcp -m tcp --dport 80 -j ACCEPT
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -m state -i eth0 --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -s mycompany.dyndns.com -p tcp -m tcp --dport 22 -j ACCEPT
-A INPUT -s mycompany.dyndns.com -p tcp -m tcp --dport 3306 -j ACCEPT
-A INPUT -s mycompany.dyndns.com -p tcp -m tcp --dport 10000 -j ACCEPT
-A INPUT -j DROP
COMMIT
I did not open the ftp port 21 in the above iptable rules but I'm allowed to connect to the server via ftp. How?
nmap server-ip
Not shown: 987 closed ports
PORT STATE SERVICE
21/tcp open ftp
22/tcp open ssh
25/tcp open smtp
53/tcp open domain
80/tcp open http
111/tcp open rpcbind
135/tcp filtered msrpc
139/tcp filtered netbios-ssn
389/tcp open ldap
445/tcp filtered microsoft-ds
10000/tcp open java-or-OTGfileshare
2401/tcp open cvspserver
3306/tcp open mysql
Nmap done: 1 IP address (1 host up) scanned in 17.46 seconds
why these many ports are shown as open. I'm clear that these services are running on the server but how it could list or connect(ftp) these ports when it is not included in the iptable rules?.
need help...
The following script will be running at every 5 mins on cloud servers to update their iptables for the dyndns domain name:
#!/bin/bash
#
# A script to update iptable records for dynamic dns hosts.
# Written by: Dave Horner (http://dave.thehorners.com)
# Released into public domain.
#
# Run this script in your cron table to update ips.
#
# You might want to put all your dynamic hosts in a sep. chain.
# That way you can easily see what dynamic hosts are trusted.
#
# create the chain in iptables.
/sbin/iptables -N dynamichosts
# insert the chain into the input chain @ the head of the list.
/sbin/iptables -I INPUT 1 -j dynamichosts
# flush all the rules in the chain
/sbin/iptables -F dynamichosts
HOST=$1
HOSTFILE="/root/host-$HOST"
CHAIN="dynamichosts" # change this to whatever chain you want.
IPTABLES="/sbin/iptables"
# check to make sure we have enough args passed.
if [ "${#@}" -ne "1" ]; then
echo "$0 hostname"
echo "You must supply a hostname to update in iptables."
exit
fi
# lookup host name from dns tables
IP=`/usr/bin/dig +short $HOST | /usr/bin/tail -n 1`
if [ "${#IP}" = "0" ]; then
echo "Couldn't lookup hostname for $HOST, failed."
exit
fi
OLDIP=""
if [ -a $HOSTFILE ]; then
OLDIP=`cat $HOSTFILE`
# echo "CAT returned: $?"
fi
# save off new ip.
echo $IP>$HOSTFILE
echo "Updating $HOST in iptables."
if [ "${#OLDIP}" != "0" ]; then
echo "Removing old rule ($OLDIP)"
`$IPTABLES -D $CHAIN -s $OLDIP/32 -j ACCEPT`
fi
echo "Inserting new rule ($IP)"
`$IPTABLES -A $CHAIN -s $IP/32 -j ACCEPT`
This is the output of "ipables -L" on the cloud server.
dynamichosts all -- anywhere anywhere
dynamichosts all -- anywhere anywhere
dynamichosts all -- anywhere anywhere
dynamichosts all -- anywhere anywhere
dynamichosts all -- anywhere anywhere
ACCEPT all -- anywhere anywhere
ACCEPT tcp -- anywhere anywhere tcp dpt:www
ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED
ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED
ACCEPT tcp -- APKGS-AP-dynamic-145.136.165.59.airtelbroadband.in anywhere tcp dpt:ssh
ACCEPT tcp -- APKGS-AP-dynamic-145.136.165.59.airtelbroadband.in anywhere tcp dpt:10000
ACCEPT tcp -- APKGS-AP-dynamic-145.136.165.59.airtelbroadband.in anywhere tcp dpt:mysql
DROP all -- anywhere anywhere
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
Chain dynamichosts (937 references)
target prot opt source destination
ACCEPT all -- Telemedia-AP-dynamic-145.86.175.59.airtelbroadband.in anywhere
Here the airtelbroadband is mine(dyndns domainname). I think the previously posted script creates new chain and from this domain everything is allowed -is it so?. May be the allowed ports ssh, webmin, mysql and www are useless entries. But I want this domain should be allowed only to these ports and I may have nmap listing only allowed ports on the cloud server when I check from my dyndns domain systems. Any more help...?
