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imagefv-extractor

Extract bootloader/charging pictures from imagefv blobs

How to use:

  1. Install python requirements
pip install -r requirements.txt
  1. Prepare your imagefv blob from the internet, or by pulling it from the device via adb
  2. Run extractor.py against the blob:
python ./extractor.py ./imagefv.elf

Usage:

usage: extractor.py [-h] [-o OUTPUT] [-v] input [input ...]

Extract bootloader/charging pictures from imagefv blobs

positional arguments:
  input                Input file to process

options:
  -h, --help           show this help message and exit
  -o, --output OUTPUT  Output directory (default: extracted_images)
  -v, --verbose        Enable verbose logging (default: False)

How it works:

  1. The script scans the input file for UEFI structures using the uefi-firmware package
  2. If it finds them, it dumps all files/sections to a temporary directory
  3. Then it identifies the dumped files for known types (defined in magic_map struct) and organizes them
  4. And also if found, any files containing GZip archives (most commonly logo.img) are extracted

Is it possible to repackage it, and create custom splashes?

During investigation, i have noticed the imagefv blob contains some CoT certificates, so it is absolutely possible that this partition is verified during the XBL phase, causing the device not to boot if it is altered.

DECIMAL       HEXADECIMAL     DESCRIPTION
--------------------------------------------------------------------------------
0             0x0             ELF, 32-bit LSB executable, ARM, version 1 (SYSV)
4096          0x1000          UEFI PI Firmware Volume, volume size: 6291456, header size: 0, revision: 0, EFI Firmware File System v2, GUID: 8C8CE578-8A3D-4F1C-3599-896185C32DD3
4216          0x1078          LZMA compressed data, properties: 0x5D, dictionary size: 16777216 bytes, uncompressed size: 7237640 bytes
6296088       0x601218        Certificate in DER format (x509 v3), header length: 4, sequence length: 596
6296688       0x601470        Certificate in DER format (x509 v3), header length: 4, sequence length: 685
6297377       0x601721        Certificate in DER format (x509 v3), header length: 4, sequence length: 720

I also couldn't find any open-source (re)packaging tools for it either, so one would need to be created. However i'm not risking a hard-brick.

Here are some references to it being loaded on xiaomi-amethyst during ABL phase:

GetAdjustLogoIndexpDisplayInfo->uDisplayWidth 1220: 2712, country_info = 1, uLogoIndex = 0, realLogoIndex = 128!
Display_Utils_RenderSplashScreen: load imagefv name is: logo.img
LoadCompressedImageFromLogoData: Setvariable Logo Image returned eStatus: Success, LogoMagic: LOGO!!!
LoadCompressedImageFromLogoData: LogoCompressedBlockNum:9 LogoCompressedBytesNum:35458 
Display_Utils_RenderSplashScreen: CompressedData size is: 35458 logo index = 128
DeCompressLogoData: DecompressBufferSize:9925976  ScratchSize:131072
DeCompressLogoData: logo decompress done, use time: 19ms
Display_Utils_RenderSplashScreen: OEM Logo Successfully Loaded

Requirements

  • Python 3.10 or newer
  • Installed uefi_firmware pip package