Captive portal with iptables and local dns server

Question

I'm trying to redirect all the browser's requests from my wifi interface wlan1 to a captive portal. I have a node web server running on my target on 10.4.30.34:4040.

It has to redirect the browser directly to the web server, on the good port, like I entered "10.4.30.34:4040" in the location bar.

For now, it only redirects to the first page of the web server but when I try to navigate through the widgets, nothing happen, like it redirects only the first request.

In addition, it does redirect only when the target is connected to internet. I supposed that it's because the dns server is missing when it's disconnected so I need to have my own DNS server running and redirect the dns requests.

Here's my iptables :

# Completed on Tue Mar  8 09:19:04 2016
# Generated by iptables-save v1.4.21 on Tue Mar  8 09:19:04 2016
*nat
:PREROUTING ACCEPT [9574:1494526]
:INPUT ACCEPT [4431:653511]
:OUTPUT ACCEPT [101:17500]
:POSTROUTING ACCEPT [47:8227]
-A PREROUTING -i br0 -p tcp -m mark --mark 0x63 -m tcp --dport 80 -j DNAT --to-destination 10.4.30.34:4040
-A PREROUTING -i br0 -p tcp -m mark --mark 0x63 -m tcp --dport 443 -j DNAT --to-destination 10.4.30.34:4040
-A POSTROUTING -o eth1 -j MASQUERADE
-A POSTROUTING -o wlan0 -j MASQUERADE
COMMIT
# Completed on Tue Mar  8 09:19:04 2016
# Generated by iptables-save v1.4.21 on Tue Mar  8 09:19:04 2016
*mangle
:PREROUTING ACCEPT [47457:9766851]
:INPUT ACCEPT [37596:7677987]
:FORWARD ACCEPT [5111:1392701]
:OUTPUT ACCEPT [16333:6011533]
:POSTROUTING ACCEPT [21605:7471587]
:internet - [0:0]
-A PREROUTING -i br0 -p tcp -m tcp --dport 80 -j internet
-A PREROUTING -i br0 -p tcp -m tcp --dport 443 -j internet
-A internet -j MARK --set-xmark 0x63/0xffffffff
COMMIT
# Completed on Tue Mar  8 09:19:04 2016
# Generated by iptables-save v1.4.21 on Tue Mar  8 09:19:04 2016
*filter
:INPUT DROP [0:0]
:FORWARD DROP [0:0]
:OUTPUT DROP [0:0]
-A INPUT -j ACCEPT
-A FORWARD -j ACCEPT
-A OUTPUT -j ACCEPT
COMMIT
# Completed on Tue Mar  8 09:19:04 2016

My /etc/resolv.conf :

nameserver 8.8.8.8
nameserver 8.8.4.4

I installed dnsmasq & bind, I followed this tutorial : http://openexhibits.org/wp-content/uploads/2012/05/CaptivePortalHowto.pdf

But it didn't work...

Thank you

Answer 1

Here's the solution :

1- Install a bind server as a local dns that will always return the same IP address

2- Redirect DNS requests to bind.

iptables -A PREROUTING -i br0 -p tcp -m mark --mark 0x63 -m tcp --dport 53 -j DNAT --to 10.4.30.34
iptables -A PREROUTING -i br0 -p udp -m mark --mark 0x63 -m udp --dport 53 -j DNAT --to 10.4.30.34
iptables -A PREROUTING -i br0 -p tcp -m tcp --dport 53 -j internet
iptables -A PREROUTING -i br0 -p udp -m udp --dport 53 -j internet
iptables -A internet -j MARK --set-xmark 0x63/0xffffffff

3- Install lighttpd that will redirect all internet requests on a specific URL

/etc/lighttpd.conf : 

server.modules          = ( "mod_redirect", "mod_rewrite" )
server.document-root    = "/www/pages/"
server.port             = 80

url.redirect = ( "^/(.*)$" => "http://10.4.30.34:4040" )