FON Router allows anonymous web access
Description:
"La Fonera" routers distributed by FON allow web access to unauthenticated
users via DNS tunneling.
Explanation:
The router gives a client an DHCP answer but does not forward ip traffic until
the client authenticates via the captive portal. The given DNS server address
is the router itself so there is a DNS forwarder running on the router. Even an
unauthorized client is allowed to surf certain sites as of obvious reasons
(google, skype and the accesspoint's owner's site) but instead of filtering the
dns requests for these few domains, it resolves all domains. This is where an
DNS tunnel comes handy...
Environment:
Tested with router's standard config on 01/04/07. Runs smoothly with NSTX
(http://nstx.dereference.de/nstx/
Version 1.1-beta6) and an ssh-session for connection testing without any
authentication via the FON captive portal.
Impact:
Unauthorized ressource usage (internet bandwidth)
Solution:
New firmware from FON, workaround can be rate limiting DNS traffic on the real
router (if possible...)