Rob Sterenborg wrote:
Add this on top of the other INPUT rules :
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
Ok so I changed the rules to this:
Chain INPUT (policy DROP)
target prot opt source destination
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
ACCEPT all -- 127.0.0.0/8 0.0.0.0/0
ACCEPT udp -- 192.168.42.1 192.168.42.2 udp spt:53
ACCEPT tcp -- 0.0.0.0/0 192.168.42.2 tcp dpt:22
ACCEPT tcp -- 0.0.0.0/0 192.168.42.2 tcp dpt:80
LOG all -- 0.0.0.0/0 0.0.0.0/0 LOG level warning
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
But it won't accept new connections on port 80 or 22. The Established SSH conection is fine.
I can see new connections to port 80 or 22 in my logs, see:
IN=eth0 OUT= MAC=00:01:03:d2:db:0b:00:11:5b:50:ff:a4:08:00 SRC=192.168.42.34 DST=192.168.42.2 LEN=48 TOS=0x00 PREC=0x00
TTL=128 ID=18259 DF PROTO=TCP SPT=3704 DPT=80 WINDOW=65535 RES=0x00 SYN URGP=0
IN=eth0 OUT= MAC=00:01:03:d2:db:0b:00:11:5b:50:ff:a4:08:00 SRC=192.168.42.34 DST=192.168.42.2 LEN=48 TOS=0x00 PREC=0x00
TTL=128 ID=18526 DF PROTO=TCP SPT=3705 DPT=22 WINDOW=65535 RES=0x00 SYN URGP=0
Why they don't jump to accept? They match a rule.
So then I adjusted #1 above to this
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state NEW,RELATED,ESTABLISHED
Doesn't that now allow any new connection to any port on any protocol making my FW worthless?
Then I tried moving the RELATED,ESTABLISHED to the last rule like this:
imperium root # iptables -L INPUT -n
Chain INPUT (policy DROP)
target prot opt source destination
ACCEPT all -- 127.0.0.0/8 0.0.0.0/0
ACCEPT udp -- 192.168.42.1 192.168.42.2 udp spt:53
ACCEPT tcp -- 0.0.0.0/0 192.168.42.2 tcp dpt:22
ACCEPT tcp -- 0.0.0.0/0 192.168.42.2 tcp dpt:80
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
LOG all -- 0.0.0.0/0 0.0.0.0/0 LOG flags 0 level 4
But I still cannot get new connections in and my estabilshed SSH is still OK.
Should I not use policy DROP but add a last rule of DROP? Which is the "right" way?
I guess I learned so far that I need to accept new and established. But I cannot seem to get the rules to work.
I've been up and down the man page and samples but seem to be missing one more stupid little thing :(
Please help.
/djb
