VW_Flash

This week, as most weeks, I split my time outside of the day job and my other hobbies and obligations between a few projects: https://github.com/bri3d/VW_Flash - Flashing tools for select control modules in VW MQB and now PQ35 platform cars. This week I'm working on old stuff: a simpler exploit chain for older Simos ECUs, as well as tweaks to expand support to older DSG control units used in PQ35 platform vehicles. https://github.com/fpv-wtf/msp-osd - I pushed a rearchitect of this on-screen-display overlay system for DJI FPV Goggles last week that seems to have sorted out a lot of issues - I switched from just passing through the OSD drawing messages from the Flight Controller to a system where the video transmitter maintains the OSD character buffer and sends a compressed representation of the screen state. This makes the system much mo

That's pretty cool! I wonder how properly they were really signed - there are _so many_ mistakes even in systems that at least don't use an example key off the Internet. The most common ones I know of are: * Out-of-bounds write issues allowing "signature was validated" flags to be overwritten in Flash memory, like https://github.com/jglim/UnsignedFlash * State machine mistakes, like https://github.com/bri3d/VW_Flash/blob/master/docs/docs.md - allowing Flash to be written again after it was already written, without an erase first. * File format parsing mistakes, like those in a number of VW AG head units: https://github.com/jilleb/mib2-toolbox/issues/122 * The use of RSA with E=3 and inadequate padding validation, like https://words.filippo.io/bleichenbacher-06-signature-forgery... . * Failure to understand the system boundaries, like in t

No, this EPS control module is remarkably primitive even by late 2000s standards and several generations behind today's state of the art. More modern control modules with a bit more resource available to them will use AES as the symmetric encryption (although there are also fixed-key XOR schemes and custom stuff used like this: https://github.com/bri3d/VW_Flash/blob/master/lib/decryptdsg... ). The keys and even IV are usually fixed across a "model line" of ECUs, so once a decrypted flash memory can be extracted, this isn't much of a protection measure, but it's a lot better than XOR. Then, in more modern control units, flash areas are also usually protected by both a checksum (usually some CRC permutation, although cute tweaks and random nonsense are common here too) and some form of digital signature.

The XOR encryption was just for the update container. Newer update files usually employ some stronger forms of compression/encryption. However, it's usually some strange in-house crypto, so eventually people figure it out. bri3d refers to using RSA signatures on the firmware once it's written to the flash. By ensuring the firmware is signed using the manufacturers private key it should (in theory) prevent messing with the firmware, even if all encryption/flashing steps have been reverse engineered. Some interesting reading: https://github.com/bri3d/VW_Flash/blob/master/docs/docs.md https://github.com/jglim/UnsignedFlash