README.md

Reverse Engineering of DJI products

This repository contains tools for reverse engineering DJI products.

• tools/image.py is a tool to extract sig and image files
• tools/derive_key.py is a script that mimics the dji_derivekey binary
• tools/sign_uboot.py is a script that is capable of signing the secure U-boot parition
• tools/check_uboot.py is a script that checks the U-Boot signature and extracts it
• tools/fw_dec.py is a tool to analyse FC and ESC firmware and try different key schedules

Image structure

• Header
  • 4B Magic ("IM*H")
  • 4B Version (Currenly only 1 is seen)
  • 8B ??
  • 4B Header size
  • 4B RSA signature size
  • 4B Payload size
  • 12B Unknown
  • 4B Auth key identifier
  • 4B Encryption key identifier
  • 16B Scramble key
  • 32B Image name
  • 60B ??
  • 4B Block count
  • 32B SHA256 payload
• Per Block info
  • 4B Name
  • 4B Start offset
  • 4B Output size
  • 4B Attributes (Last bit 0 means ecrypted)
  • 16B ??
• RSA Signature of the Header (Size and Auth key described in header)
• Actual block data (Start offset 0)