Forward connections on 0.0.0.0:80 to 127.0.0.1:9091

Question

I'm trying to set up a tor-relay.

In order to allow tor to present a static web page explaining what it is I want the server to listen on port 80 and 443.

In order to allow tor to use accounting/hibernation (throttle bandwidth after a data limit has been reached) I need the process to bind to >1024 port numbers (so that a non-privileged user can rebind the ports I guess).

Hence my tor configuration looks like such:

ORPort 443 NoListen
ORPort 127.0.0.1:9090 NoAdvertise
DirPort 80 NoListen
DirPort 127.0.0.1:9091 NoAdvertise
DirPortFrontPage /etc/tor/tor-exit-notice.html

After starting the server I can access the html-file localy:

$ wget 127.0.0.1:9091                                  
--2013-08-12 14:27:49--  http://127.0.0.1:9091/
Connecting to 127.0.0.1:9091... connected.
HTTP request sent, awaiting response... 200 OK
Length: 6762 (6.6K) [text/html]
Saving to: `index.html'

100%[=============================>] 6,762       --.-K/s   in 0.005s  

2013-08-12 14:28:15 (1.21 MB/s) - `index.html' saved [6762/6762]

And the ports seem opened properly:

$ sudo netstat -lnp | grep tor
tcp        0      0 127.0.0.1:9050          0.0.0.0:*               LISTEN      6328/tor        
tcp        0      0 127.0.0.1:9090          0.0.0.0:*               LISTEN      6328/tor        
tcp        0      0 127.0.0.1:9091          0.0.0.0:*               LISTEN      6328/tor

In order to get the last part working, where connections on 0.0.0.0:80 are redirected to 127.0.0.1:9091 I've tried using iptables.

$ sudo iptables -t nat -A PREROUTING -p tcp -i eth0 --dport 443 -j DNAT --to-destination 127.0.0.1:9090
$ sudo iptables -t nat -A PREROUTING -p tcp -i eth0 --dport 80 -j DNAT --to-destination 127.0.0.1:9091
$ sudo iptables -t nat -L -n
Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination         
DNAT       tcp  --  0.0.0.0/0            0.0.0.0/0            tcp dpt:443 to:127.0.0.1:9090
DNAT       tcp  --  0.0.0.0/0            0.0.0.0/0            tcp dpt:80 to:127.0.0.1:9091

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         

Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination         

But when I connect to the external ip on port 80 I get no response.

I've tried with ip_forward both on and off, neither works:

$ sudo sysctl net.ipv4.ip_forward=1
net.ipv4.ip_forward = 1
$ sudo sysctl net.ipv4.ip_forward=0
net.ipv4.ip_forward = 0

I've even tried MASQUERADE-ing, but it does'nt work, and I don't think it should be necessary:

$ sudo iptables -t nat -A POSTROUTING -j MASQUERADE

I've also tried PREROUTING per suggestion below, but it does not work:

$ sudo iptables -t nat -A PREROUTING -p tcp -i eth0 --dport 80 -j REDIRECT --to-port 127.0.0.1:9091
iptables v1.4.14: REDIRECT: Bad value for "--to-ports" option: "127.0.0.1:9091"
Try `iptables -h' or 'iptables --help' for more information.

What am I doing wrong?

The server is a raspberry pi, running wheezy with only the built in network interface connected directly to the internet with a public ip.

Answer 1

You could try enabling routing to localhost in the kernel:
sysctl -w net.ipv4.conf.eth0.route_localnet=1 when eth0 is the NIC of the machine.

See accepted answer on this post: https://unix.stackexchange.com/questions/111433/iptables-redirect-outside-requests-to-127-0-0-1

Answer 2

This should do the trick:

iptables -t nat -A PREROUTING -p tcp -i eth0 --dport 80 \
          -j REDIRECT --to-ports 127.0.0.1:9091
iptables -t nat -A PREROUTING -p tcp -i eth0 --dport 443 \
          -j REDIRECT --to-ports 127.0.0.1:9090