MH2p SD ModKit

Free ModKit that allows for modifying the MH2p unit used in some Volkswagen AG vehicles using only an SD card or flash drive.

License

• This file is part of MH2p_SD_ModKit, licensed under CC BY-NC-SA 4.0.
• https://creativecommons.org/licenses/by-nc-sa/4.0/
• See the LICENSE file in the project root for full license text.
• NOT FOR COMMERCIAL USE

Mod development

• each mod should be self-contained in its own folder /Mods/[modname]
• mod can include Update, Post, and Persist parts
  • Update: runs during update
    • if included, needs install.sh and uninstall.sh
  • Post: runs once after update, followed by persistant reboot (useful for 5F coding that does not work during an update)
    • if included, needs install.sh and uninstall.sh
  • Persist: runs at every startup
    • if included, needs install.sh
• mod output is logged to /Logs/[modname].log
• if uninstall.txt is present, uninstall.sh scripts are run
• otherwise, install.sh scripts are run
• users can choose to install or uninstall by adding or removing uninstall.txt
• MH2p ModKit exports a few useful variables:
  • MODKIT_VERSION: current release is 2
  • RELEASE_VERSION: release version string ex: MH2p_US_PO416_P2870
  • REGION: region ex: AS, CN, ER, US, ...
  • OEM: car brand ex: VW, AU, PO, LB, ...
  • TYPE: screen type ex: 416, 636, G33, G35, G36, ...
  • RELEASE_TYPE: E: engineering, K: customer update, P: production, S: security update
  • SOFTWARE_VERSION: software version number ex: 9830, 2870, ...
  • MOD: name of mod (same as mod's folder name) ex: [modname]
  • MOD_PATH: path to mod part's folder ex: /fs/sdb0/Mods/[modname]/Update
  • MEDIA_PATH: path to SD card (only available in Update) ex: /fs/sdb0

How it works

• the ModKit is a valid checksummed and signed update for MH2p
  • I discovered checksum and signing methods through reverse engineering MH2p binaries
• the update runs modkit.sh which runs modkit_install.sh which runs scripts under /Mods/ that are not checksummed or signed
• this allows easier development and installation of mods

Fail-Safe

• after running the ModKit, if update media is inserted with failsafe.sh at the root, the script will be run early in the startup process
  • this can be used to clean up a mistake and escape a boot loop without needing to use a PL2303TA cable to enter emergency SWUP