I need to set up access to the HTTP(S) servers on devices like KVMs and PDUs on a private network (192.168.0.0/24). I must get through an isolated network (10.0.0.0/8) limited to ports 22 and 443. I have a dual-NIC Linux server inside the network that serves as a gateway to the private network. See diagram Here:
Network Diagram
I need to use a forward SSH tunnel to get to the Linux gateway, then use iptables NAT to route HTTP(s) traffic to the web frontends on the devices.
I've observed with both tcpdump and iptables trace that the inbound HTTP(s) request through the SSH tunnel shows up on interface lo , not eth1 as one might expect.
This has led me to come up with the following nat and filter rules:
*nat
-A PREROUTING -i lo -p tcp -m tcp --dport 8080 -j DNAT --to-destination 192.168.0.100:80
-A PREROUTING -i lo -p tcp -m tcp --dport 8081 -j DNAT --to-destination 192.168.0.101:443
-A POSTROUTING -d 10.0.0.0/8 -o lo -j SNAT --to-source <10.gateway_IP>
COMMIT
*filter
:INPUT ACCEPT [37234:5557621]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [26648:27864039]
-A FORWARD -d 192.168.0.0/24 -p tcp -m tcp --dport 80 -j ACCEPT
-A FORWARD -d 192.168.0.0/24 -p tcp -m tcp --dport 443 -j ACCEPT
COMMIT
So, when I set up the tunnel with:
ssh -L 8080:<gateway>:8080 <user>:#<gateway>
Then making sure on the gateway:
$ sysctl net.ipv4.ip_forward
net.ipv4.ip_forward = 1
and then execute http://localhost:8080,
The packets make it out of the tunnel onto the gateway, out of interface lo, but iptables doesn't seem to forward it to the destination in the PREROUTING rule. stderr from the tunnel returns "Connection refused."
What am I missing?
Related
I am using WireGuard (WG) as a VPN and only routing certain port based traffic over it. On the ingress side of the tunnel the traffic first hits eth0 then goes on to the WG TUN interface, wg0, so the following rule works for forwarding on ingress:
-A PREROUTING -d 192.#.#.# -i eth0 -p tcp -m tcp --dport 7054 -j DNAT --to-destination 10.#.#.#:7054
However I can not get traffic routed from TUN interface to eth0 on the egress side of the tunnel with the following rule, I think due to the "tunnel" being virtual and the traffic first must cross eth0 so PREROUTING is not valid??? I am not sure how to think about the TUN interface with regards to the routing sequence, i.e. is this still PREROUTEING or POSTROUTING or somewhere in the middle?
-A PREROUTING -d 10.#.#.# -i wg0 -p tcp -m tcp --dport 7054 -j DNAT --to-destination 192.#.#.#:7054
I tried the following to see if PREROUTING would then work for the wg0 interface but it did not. I also tried this with POSTROUTING, but not the solution.
iptables -t raw -A PREROUTING -i eth0 -j NOTRACK
I am running ubuntu 16.0.4 as a wifi hotspot and to share a vpn connection.
eth0 is on subnet 10.10.10.x
tun0 is on subnet 10.9.0.x
wlan0 is on subnet 10.10.11.x
I am able to share the vpn connection with the following rule...
iptables -t nat -A POSTROUTING -o tun0 -j MASQUERADE
... so any wired devices using the ubuntu box as its gateway can share the vpn.
I am also forwarding all traffic on the wireless interface through the vpn and allowing returning traffic with the following...
iptables -A FORWARD -i tun0 -o wlan0 -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -i wlan0 -o tun0 -j ACCEPT
So far, so good.
But, I want all traffic on port 32400 to be forwarded to eth0 instead, specifically IP 10.10.10.20 (and of course, allow return traffic).
With my current setup, my wireless connections on wlan0 can not see the subnet of eth0.
How can I achieve this? I am fine with either forwarding all traffic on port 32400... or forwarding everything for a single IP(e.g. 10.10.11.200 on wlan0) to 10.10.10.20(eth0).
I've tried both the port forwarding and the IP forwarding but cant't seem to get either working as I'm not sure of the method nor the correct syntax.
Thanks in advance for advice.
These rules should do the trick, assuming destination port is the same 32400 (but I'm not sure about the order refering to other your rules)
iptables -t nat -A PREROUTING -p tcp --dport 32400 -j DNAT --to-destination 10.10.10.20:32400
iptables -t nat -A POSTROUTING -p tcp -d 10.10.10.20 --dport 32400 -j SNAT --to-source 10.10.11.200
I have installed Seafile-server 3.0.4 64bit on a Ubuntu-server 14.04 with default ports settings (i.e. 8000, 8082, 10001, 12001) but fail to access the instance with the client.
Infrastructure
The Ubuntu-server is running as a KVM machine on a Gentoo host.
Iptables rules
After some time I add the following Iptables rules to the host machine (gentoo), that seems to match the Seafile's requirements:
#Iptables-Rules for Seafile
iptables -A INPUT -p tcp -m multiport --dports 8000,8082,10001,12001 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A output -p tcp -m multiport --sports 8000,8082,10001,12001 -m state --state ESTABLISHED -j ACCEPT
However I'm still unable to connect even with telnet to the seafile-server either from Internet or the host machine.
Update: issue might be related to fail2ban
As I'm using NAT to link my virtual machine to my host, I had to edit the rules as follow to get it to work:
#Iptables-Rules for Seafile
iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 10001 -j DNAT --to 192.168.8.8:10001
iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 12001 -j DNAT --to 192.168.8.8:12001
References
Linux Firewall Tutorial: IPTables Tables, Chains, Rules Fundamentals
I am trying to setup a cloud server as a gateway, which forwards all traffic to my second cloud server. The problem is that the destination server (2nd cloud) only sees the IP address of the first cloud server.
Is it possible to keep the source IP so it would show the IP address of the one connecting to the first cloud server. I have tried removing MASQUERADE, but the connection between cloud #1 -> cloud #2 did not work properly anymore.
-A FORWARD -p tcp -m tcp --dport 25565 -j ACCEPT
-A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
-A PREROUTING -p tcp -m tcp --dport 25565 -j DNAT --to-destination DESTINATIONIP:PORT
-A POSTROUTING -j MASQUERADE
It works with this setup, but does not show the source IP. Have you got any idea on how to not hide the IP that is connecting to the first cloud server?
Thanks
cloud 1 and 2 need to be in same network, a VPN is fine
on cloud1:
-A FORWARD -p tcp -m tcp --dport 25565 -j ACCEPT
-A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
-A PREROUTING -p tcp -m tcp --dport 25565 -j DNAT --to-destination DESTINATIONIP:PORT
-A POSTROUTING -j MASQUERADE
on cloud2, we mark the desired packet with 1, eth0 is the default gateway:
iptables -t mangle -A OUTPUT -o eth0 -p tcp --sport 25565 -j MARK --set-mark 1
you need to manipulate the routing table on cloud2:
edit /etc/iproute2/rt_tables, add the line
1 http
here the manipulation, tun0 is the vpn interface on cloud2:
ip route add default via ip_vpn_cloud1 dev tun0 table http
ip rule add from all fwmark 1 table http
be sure that net.ipv4.conf.all.rp_filter and net.ipv4.conf.default.rp_filter are set to 1 in /etc/sysctl.conf
With -A POSTROUTING -j MASQUERADE all outgoing forwarded packets will have the source IP of the corresponding outgoing interface.
You should be more specific on the packets you masquerade/SNAT.
I have a machine with 2 interfaces:
eth0 inet addr:1.1.1.1
eth1 inet addr:2.2.2.2
eth0 is a server, eth1 is the network on virtual machine.
I have ssh on server, so 1.1.1.1:22 is busy.
I need a rule for redirecting incoming connections on eth0 port 6000 to eth1, ip 2.2.2.100 on port 22 (virtual machine ip).
In this mode if I did, on an external machine,
ssh -p 6000 root#1.1.1.1
I would login on the virtual machine.
I tried this rule but it didn't work:
sudo iptables -P FORWARD ACCEPT
sudo iptables -t nat -A PREROUTING -p tcp -i eth0 --dport 6000 -j DNAT --to 2.2.2.100:22
Well there are like 1 million scripts/tutorials/things for this case, but if someone lands from google to here is something like this:
iptables -I FORWARD -d 2.2.2.2 -m comment --comment "Accept to forward ssh traffic" -m tcp -p tcp --dport 22 -j ACCEPT
iptables -I FORWARD -m comment --comment "Accept to forward ssh return traffic" -s 2.2.2.2 -m tcp -p tcp --sport 22 -j ACCEPT
iptables -t nat -I PREROUTING -m tcp -p tcp --dport 60000 -m comment --comment "redirect pkts to virtual machine" -j DNAT --to-destination 2.2.2.2:22
iptables -t nat -I POSTROUTING -m comment --comment "NAT the src ip" -d 2.2.2.2 -o eth1 -j MASQUERADE