Reverse Engineering a D-Link Backdoor

Here’s one true hack (Google cache link) for our dear Hackaday readers. On a Saturday night, as [Craig] didn’t have anything else to do, he decided to download the firmware of an old D-Link DIR-100 router (because who wouldn’t?). His goal was to see what interesting things he could find in it. He fired up binwalk to extract the SquashFS file system, then opened the router webserver on the multi-processor disassembler/debugger IDA. [Craig] discovered that the webserver is actually a modified version of thttpd, providing the administrative interface for the router. As you can see in the picture above, it seems Alphanetworks (a spin-off of D-Link) performed the modifications.

Luckily for [Craig], the guys at Alphanetworks were kind enough to prepend many of their custom function names with the string “alpha”. Looking at the disassembly of the http identification functions revealed that a backdoor is implemented on the firmware. If one malicious user has the string “xmlset_roodkcableoj28840ybtide” as his browser user agent, no authentication is required to gain access to the router. One of the comments on the reddit thread points out that reading that string backwords results in: “edit by (04882) joel backdoor”.

Double the RAM on D-Link router

d-link_double_ram

[Pelaca] upgraded the RAM on his D-Link DIR-320 router from 32MB to 64MB. This hack is simple enough: swap out the existing RAM chip for another one and change the bios to make use of the upgrade. The actual execution is not that simple because of the pitch of the TSOP II package; you’ll need to bring your mad soldering skills to pull this off.

This reminds us of when upgrading original Xbox RAM to 128MB was all the rage. It involved the same type of hack, adding four memory chips to unpopulated positions on the motherboard. The forums are thick with people complaining that their box not working after a failed upgrade attempt. Hopefully you’ll have better luck.

[Thanks Juan]

D-Link router captcha broken

d-link

We reported last week that D-Link was adding captchas to their routers to prevent automated login by malware. Unsurprisingly, it doesn’t work all time. The team from SourceSec grabbed the new firmware and began poking at it. They found that certain pages don’t require the authentication to be passed for access. One of these is WPS activation. WPS lets you do push button WPA configuration. Once activated, any nearby client can request the WPA key using a tool like WPSpy. Only user level credentials are needed to pull this off, so changing just the admin password won’t prevent it.

[photo: schoschie]

D-Link adds captcha to routers

D-Link is adding captcha support to its line of home routers. While default password lists have been abundant for many years, it was only recently that we started seeing the them implemented in malware. Last year, zlob variants started logging into routers and changing their DNS settings. It’s an interesting situation since the people who need the captcha feature are the ones who will never see it, since they won’t log in to change the default password.

[photo: fbz]

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