According to the Dutch news site Tweakers, the Taiwan-based networking equipment manufacturer D-Link accidently published its private code signing keys inside its open source firmware packages.
One of the readers of the Dutch news site reported, “bartvbl,” reported the serious issues after he had bought a D-Link DCS-5020L security camera and downloaded the firmware from the official website of D-Link.
D-Link open sources its firmware under the GPL license allowing anyone to analyze it. bartvbl has discovered four different private keys used for code signing.
The reader also discovered other three private code signing keys that appear to be not valid and pass-phrases needed to sign the software.
The disconcerting discovery was confirmed by the security expert Yonathan Klijnsma from security firm Fox-IT.
“The code signing certificate is indeed a firmware package, firmware version 1.00b03, who’s source was released February 27 this year,” explained the expert.
Why the access to the code signing keys is so important?
Malware creators use to steal valid code signing certificates to sign the source code of their malware and evade detection of security firms.
At the time I was writing, it is still unclear whether the code signing private keys have been used by threat actors to sign their malicious code signing certificate, and released a new version of the firmware that doesn’t contain any code signing keys.
(Security Affairs – code signing keys, D-Link)