Plugin Spotlight: D-Link DCC Protocol Security Bypass

Reconfiguring Access Points

Wireless threats come in many different forms, such as disclosure of cleartext credentials, breaking encryption schemes such as WEP and attacking wireless drivers on client systems. While you can extend the range of wireless signals, for the most part these attacks require that the attacker be in close physical proximity of the wireless network and/or client to execute. This is the primary reason why most organizations do not assign a high priority to defending against these attacks. There are far more attackers on the Internet than will be in close proximity to your wireless deployment.

However, something that worries me greatly are wireless attacks that break down these physical barriers. What if attackers could remotely attack a system and then use it to perform local wireless attacks? There have been some papers posted about using the local client system to enumerate wireless networks, but not much in the way of launching attacks. Malware that embeds itself in wireless routers has received limited exposure (except for the infamous "Chuck Norris" worm, that may have been due to the popularity of the "Chuck Norris Facts" web site).

In an effort to stay ahead of attackers, I recommend that organizations place a higher priority on protecting wireless clients and access points. There are several very concerning vulnerabilities in access points that are trivial to exploit. One example is the D-Link DCC Protocol Security Bypass.

Easy and Secure Never Mix

The DCC (D-Link Click 'n Connect) protocol runs on D-Link brand routers and claims to be:

"An interactive install wizard that allows you to install and connect your product to the Internet within minutes: No technical knowledge required" - D-Link Marketing Doc

D-Link Click 'n Connect is supposed to make it "easy" for the end user to configure "security" on their routers. It turns out that the protocol listens on UDP port 2003 of the router, and in some cases allows for reading and writing of the configuration without authentication. I’ve installed the latest version of D-link firmware on my DIR-755 router (1.34N) and have found no way to disable the "Click n' Connect" service. This means that several different D-link routers are vulnerable, and there is no way for the end user to patch this vulnerability or implement a workaround.

D-Link DCC Protocol Security Bypass Plugin

Tenable's Research team has written a plugin, ID 47606, that detects this condition as shown in the following example output:

Crossing Boundaries

What if you could get a client on the same network as the router to send UDP packets? This means the attack is now remote: a user browses to a web site, loads some code into the browser and reads configuration values or even changes the configuration of the router. The Nessus plugin will read the value of the SSID parameter, but could also be used to read the WPA or WEP key values stored in the router. Organizations should not limit wireless security to just using WPA, but consider all possible attack scenarios and audit and protect the network accordingly.

Resources

• Tenable Network Security Blog: Scanning Embedded Systems In The Enterprise With Nessus
• Tenable Network Security Blog: Nessus Plugin Spotlight: Linksys Router Detection
• Original Advisory - IS-2010-004 - D-Link DAP-1160 Unauthenticated Remote Configuration