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For testing, I need to drop all input connections to postgres db running on port 5432 on localhost. I set an iptables rule :
iptables -A INPUT -s 127.0.0.1 -p tcp --dport 5432 -j DROP
But I am able to do read/write operations to the db. I used dbvisualizer as well as the product to test. What am I missing?
Thanks in advance.
The target DROP will just drop the packet, no further processing or forwarding.
try this:
iptables -t nat -A PREROUTING -p tcp -j REDIRECT --to-ports 5432
I am not sure if this is the right method but rule
iptables -A OUTPUT -p tcp --dport 5432 -j REJECT
worked as expected.
Did your server listen on localhost or ethernet nic network ip address?
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I inherited a complex iptables script acting as our gateway/router. It handles everything well, including NAT and harpin nat. It also does port forwarding. However, the port forwarding can't be specified by source IP. So if the port 25 is forwarded, every IP can connect to that port.
The FORWARD chain policy is ACCEPT. I tried to change it to DROP and built some rules. It seems that there are too much on specifying rules for every allow scenario.
What I am looking for is to specify things like this:
iptables -A FORWARD -p tcp -i $WAN_IFACE --dport 25 -s (!(1.1.1.1 and
1.1.1.2)) -j DROP
But iptables does not support and and or.
Is there any way to implement this?
You can create a new chain for all packets going to Port 25 and then do more specific filtering there:
iptables -N port25
iptables -A FORWARD -p tcp -i $WAN_IFACE --dport 25 -j port25
iptables -A port25 -s 1.1.1.1 -j ACCEPT
iptables -A port25 -s 1.1.1.2 -j ACCEPT
iptables -A port25 -j DROP
The creation of user-defined chains is the way to implement and and or rules.
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I am trying to apply these firewall rules over SSH. When I run the script with ./script.sh, the terminal will hang and I am forced to quit using ~ . Enter. The rules are applied, but my SSH connection is dropped and my terminal hangs. However, when I do bash -x ./script.sh, it runs the script while outputting debug information and doesn't interrupt my session.
My firewall rules are simple. Allow incoming/outgoing SSH and allow outgoing DNS and HTTP/S for updates.
This behavior was witnessed on Red Hat, Debian, and Ubuntu machines.
I consider you are running the scripts on a ssh session established on default port 22
then please replace the ssh rules
iptables -A INPUT -p tcp -m tcp --dport 22 -m limit --limit 5/minute --limit-burst 15 -m state --state NEW -j ACCEPT
iptables -A OUTPUT -p tcp -m tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT
for a less restrictive set i.e.
iptables -A INPUT -p tcp --dport 22 -j ACCEPT
iptables -A OUTPUT -p tcp --sport 22 -j ACCEPT
once you get it working you can add to these now simpler rules the more restrictive parameters one at the time.
please consider if your input rule includes
--state NEW
only new ssh connections will be accepted; already established will not.
Move this rule to the top and test again:
iptables -A INPUT -m state --state ESTABLISHED -j ACCEPT
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I want redirect all outgoing traffic with port 8080 to local port 8080
for example i create server with this command nc -l -p 8080 and i want when use this command nc 1.2.3.4 8080 , nc redirect and connect to 127.0.0.1:8080
i try with this command:
iptables -t nat -A POSTROUTING -p tcp --dport 80 -o eth0 -j SNAT --to-source IP
but not worked!
how to do it?
Local originated traffic isn't passing through nat/POSTROUTING chain. You should add rule like this:
iptables -t nat -A OUTPUT -p tcp --dport 8080 -j DNAT --to-destination 127.0.0.1:8080
Additional info:
http://upload.wikimedia.org/wikipedia/commons/3/37/Netfilter-packet-flow.svg
http://www.linuxtopia.org/Linux_Firewall_iptables/index.html Chapter 4.
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I have a VDS running CentOS with two interfaces: eth0 and ham0. eth0 is my WAN interface and has external IP accessible from the Internet, and ham0 is an interface to a small VPN network (Logmein Hamachi).
There are three machines in the VPN network, one of them is a linux box at my home which runs Apache on port 80. This machine is behind ISP's NAT and cannot be seen from outside.
I want to create a rule on my VDS to forward connections to port 8081 coming from the Internet (eth0 interface) to this linux box inside my VPN network. Something like this:
[Internet] ---> [VDS server with public IP] ---> [Apache server inside VPN]
I used the following rules:
iptables -t nat -A PREROUTING -p tcp -d *external_ip* --dport 8081 -j DNAT --to *internal_ip*:80
iptables -A FORWARD -p tcp -d *internal_ip* --dport 80 -j ACCEPT
iptables -t nat -A POSTROUTING -p tcp --dst *internal_ip* -j LOG --log-level warning --log-prefix "[REQUEST_FORWARDED]"
But it does not work. I can see a "REQUEST_FORWARDED" message in /var/log/messages, but when I go to the http://my_eternal_ip:8081/ in my browser, it tries to connect to the host for a very long time, and then shows a message that server did not respond.
What can cause this problem?
I guess you need to make sure "/proc/sys/net/ipv4/ip_forward" has been enabled, if not
echo 1 > /proc/sys/net/ipv4/ip_forward
Above command can help you allow IP forwarding.
Hope this helpful to you.
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I have multiple IP addresses on the same server and I would like to redirect all outgoing traffic on port 80 to a different IP on the same server just no to use always main IP.
Currently I'm using this:
/sbin/iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to-source IP;
and it works well, but it redirects everything and when I make backups over SSH backup it's failing.
System: CentOS 5.8 64-bit
This worked:
iptables -t nat -A POSTROUTING -p tcp --dport 80 -o eth0 -j SNAT --to-source IP