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How to allow outgoing trafic only for http and ssh?
i've tried:
iptables -A OUTPUT -p tcp --dport ssh -j ACCEPT
iptables -A OUTPUT -p tcp --dport http -j ACCEPT
but as soon as i add
iptables -A OUTPUT -j DROP
nothing works, it blocks everything.
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT tcp -- anywhere anywhere tcp dpt:ssh
ACCEPT tcp -- anywhere anywhere tcp dpt:22151
ACCEPT tcp -- anywhere anywhere tcp dpt:http
ACCEPT tcp -- anywhere anywhere tcp dpt:sso-service
ACCEPT all -- anywhere anywhere
DROP all -- anywhere anywhere
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
ACCEPT all -- anywhere anywhere
Try with --sport instead of --dport.
First of all, the output of your iptables configuration does not matches the rules you have typed. Did you restarted iptable service? Second, you will need to allow udp on port 53 to get DNS working as well:
iptables -A OUTPUT -p udp --dport 53 -j ACCEPT
Related
I need help regarding iptables. I have the following iptables rules when i use the command iptables -L
Chain INPUT (policy DROP)
target prot opt source destination
ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED
ACCEPT icmp -- anywhere anywhere
ACCEPT all -- anywhere anywhere
ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:ssh
Chain FORWARD (policy DROP)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
Chain MYSSH (0 references)
target prot opt source destination
Now I want to add a rule to the INPUT chain of my filter table that will send all ssh traffic to the MYSSH chain. I have to make sure this new rule follows (not precedes) the RELATED,ESTABLISHED rule, so it doesn't apply to existing connections!
I tried:
iptables -I INPUT 1 -p tcp -m MYSSH --dport 22 -j ACCEPT
but this is not working. Can you please tell me how to do that?
This is kind of a question for Superuser, but okay. I have my admin hat on today. :P
The main thing is that you can use your chain as a target like ACCEPT, REJECT or DROP, so you want to pass it as -j option, i.e.
iptables -A INPUT -p tcp --dport 22 -j MYSSH
would append a rule to pipe all TCP traffic to port 22 through the MYSSH chain to the INPUT chain.
The other question is where to insert this rule. Generally, when I do this kind of stuff manually (these days I usually use shorewall because its easier to maintain), I just work with iptables -A commands and run them in the right order. In your case, it looks as though you want to insert it as the second or third rule, before the catchall
ACCEPT all -- anywhere anywhere
rule (although that might have some additionall conditions that iptables -L will not show without -v; I can't know that). Then we're looking at
iptables -I INPUT 2 -p tcp --dport 22 -j MYSSH
or
iptables -I INPUT 3 -p tcp --dport 22 -j MYSSH
depending on where you want it.
Note, by the way, that if this catch-all rule doesn't have additional conditions that I'm not seeing, the rule below it will never be reached.
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I added packet forwarding rule in my iptable
sudo iptables -t nat -A PREROUTING -p tcp --dport 1111 -j DNAT --to-destination 10.0.3.126:80
and I can see that the packet coming to port 1111 is correctly forwarded to 10.0.3.126:80. However if I list up the rules, I cannot see the rule that I added.
sudo iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT tcp -- anywhere anywhere tcp dpt:domain
ACCEPT udp -- anywhere anywhere udp dpt:domain
ACCEPT tcp -- anywhere anywhere tcp dpt:bootps
ACCEPT udp -- anywhere anywhere udp dpt:bootps
Chain FORWARD (policy ACCEPT)
target prot opt source destination
ACCEPT all -- anywhere anywhere
ACCEPT all -- anywhere anywhere
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
How can I view the rule I added?
Thank you in advance.
Use iptables -L -n -t nat command Because PREROUTING chain is a part of NAT rules
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with the following rules, php can't make a redirect to another file. it's freezes at the point when it gets toheader("Content-type: video/x-flv");
header("Location:" . $VIDEO);
or could be get_headers(); on my php script.
my iptables:
iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT tcp -- anywhere anywhere tcp dpt:22151
ACCEPT tcp -- anywhere anywhere tcp dpt:http
ACCEPT all -- anywhere anywhere
ACCEPT tcp -- anywhere anywhere tcp dpt:webcache
ACCEPT tcp -- anywhere anywhere tcp spt:webcache
ACCEPT tcp -- anywhere anywhere tcp spt:http
DROP all -- anywhere anywhere
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
what i've tried
iptables -A INPUT -p ICMP --icmp-type 8 -j ACCEPT
as soon as i remove the DROP all -- anywhere anywhere everything works fine.
When you use get_headers(), your script makes an outgoing HTTP connection. You need to allow the reply traffic back in, by allowing established sessions.
sudo iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
See here for more info
I'm struggling to understand why I can't open port 61616 by adding IPTABLES rule. Here is the listing of all rules, obtained via IPTABLES -L command.
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT tcp -- anywhere anywhere tcp dpt:61616
ACCEPT udp -- anywhere anywhere udp dpt:cslistener
ACCEPT tcp -- anywhere anywhere tcp dpt:cslistener
ACCEPT tcp -- anywhere anywhere tcp dpt:webcache
ACCEPT tcp -- anywhere anywhere tcp dpt:smtp
RH-Firewall-1-INPUT all -- anywhere anywhere
Chain FORWARD (policy ACCEPT)
target prot opt source destination
RH-Firewall-1-INPUT all -- anywhere anywhere
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
Chain RH-Firewall-1-INPUT (2 references)
target prot opt source destination
ACCEPT tcp -- anywhere anywhere tcp dpt:61616
ACCEPT tcp -- anywhere anywhere tcp dpt:http
ACCEPT all -- anywhere anywhere
ACCEPT icmp -- anywhere anywhere icmp any
ACCEPT esp -- anywhere anywhere
ACCEPT ah -- anywhere anywhere
ACCEPT udp -- anywhere 224.0.0.251 udp dpt:mdns
ACCEPT udp -- anywhere anywhere udp dpt:ipp
ACCEPT tcp -- anywhere anywhere tcp dpt:ipp
ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED
ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:ssh
REJECT all -- anywhere anywhere reject-with icmp-host-prohibited
As much as I'm ignorant about IPTABLES, what confuses me is that http port is visible from the outside, yet port 61616 still isn't. For me, the rules look the same. Anyways, all help's appreciated.
Best
Maybe you try to open port for host in the network behind the CentOS host (CentOS host is firewall for network)?
If so, you must add rule for chain FORWARD of table filter, and you should
add rule for DNAT to some IP in network x.x.x.x
iptables -A FORWARD -p tcp --dport 61616 -j ACCEPT
iptables -A PREROUTING -t nat -p tcp --dport 61616 -j DNAT --to-destinanion x.x.x.x
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I'm writing a bash script to add simple firewalling for Xen.
Here's the actual firewall configuration :
Chain INPUT (policy ACCEPT)
target prot opt source destination
RH-Firewall-1-INPUT all -- anywhere anywhere
Chain FORWARD (policy ACCEPT)
target prot opt source destination
RH-Firewall-1-INPUT all -- anywhere anywhere
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
Chain RH-Firewall-1-INPUT (2 references)
target prot opt source destination
ACCEPT all -- anywhere anywhere
ACCEPT icmp -- anywhere anywhere icmp any
ACCEPT esp -- anywhere anywhere
ACCEPT ah -- anywhere anywhere
ACCEPT udp -- anywhere 224.0.0.251 udp dpt:mdns
ACCEPT udp -- anywhere anywhere udp dpt:ipp
ACCEPT tcp -- anywhere anywhere tcp dpt:ipp
ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED
ACCEPT udp -- anywhere anywhere state NEW udp dpt:ha-cluster
ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:ssh
ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:http
ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:https
REJECT all -- anywhere anywhere reject-with icmp-host-prohibited
I'd like to add a new chain for each of my virtual machines (each of them has a virtual interface called vif1.0, vif2.0, etc). Output interface (bridge) is xenbr0.
Here's what I do (for example to block ping 'in'to domU1, vif1.0) :
iptables -N domUFirewall
iptables -I FORWARD -j domUFirewall
iptables -I INPUT -j domUFirewall
iptables -A domUFirewall -i vif1.0 -p icmp -j DROP
But .. it doesn't work, i'm still able to ping in/out the domU.
Must be something really 'dumb' but I can't find out what's wrong.
Any clues ?
Thx
Since you're using XEN with bridged networking, packets are being intercepted at a level before ordinary iptables commands can influence them. Thus, you'll probably need to use the ebtables command to influence packet routing in the way that you want to.
ebtables/iptables interaction on a Linux-based bridge
ebtables(8) - Linux man page
Xen Wiki * XenNetworking
Original answer left below that will work for other configurations, but not for XEN with bridged networking.
I am going to pretend for the sake of example that the IP address of vif1.0 is 192.168.1.100.
I would redo the logic to not check the input device, but to instead check by IP Address. At the input chain, the packet is coming from (say) device eth0, not from vif1.0. Thus, this rule:
iptables -I INPUT -i vif1.0 -j domUFirewall
that I previously proposed will never match any packets. However, if you do the following, it should do what you want:
iptables -I INPUT -d 192.168.1.100 -j domUFirewall
where in this case the chain domUFirewall is set up by:
iptables -N domUFirewall
iptables -F domUFirewall
iptables -A domUFirewall -p icmp -j DROP
If a given chain is for a single device, then you want to make this check before jumping into the chain, on a rule with the "-j chainName" action. Then, in the chain itself, you never have to check for the device or IP Address.
Second, I would always flush (empty) the chain in your script, just in case you're re-running the script. Note that when you rerun the script, you may get complaints on the -N line. That's OK.
There are other ways you could do this, but to give a different example, I would need to know specifically how your VM is set up -- bridged networking? NAT? Etc. But the example I gave here should work in any of these modes.
Here are some useful links for the future:
Quick HOWTO, Ch14: Linux Firewalls Using iptables
Sandbox a VMware Virtual Machine With iptables