Android_boot_image_editor

A tool for reverse engineering Android ROM images.

Getting Started

install required packages

Mac: brew install lz4 xz dtc

Linux: sudo apt install git device-tree-compiler lz4 xz-utils zlib1g-dev openjdk-11-jdk gcc g++ python3

Windows: Make sure you have python3, JDK9+ and openssl properly installed. An easy way is to install Anaconda and Oracle JDK 11, then run the program under anaconda PowerShell.

Parsing and packing

Put your boot.img to current directory, then start gradle 'unpack' task:

cp <original_boot_image> boot.img
./gradlew unpack

Your get the flattened kernel and /root filesystem under ./build/unzip_boot:

build/unzip_boot/
├── boot.json     (boot image info)
├── boot.avb.json (AVB only)
├── kernel
├── second        (2nd bootloader, if exists)
├── dtb           (dtb, if exists)
├── dtbo          (dtbo, if exists)
└── root          (extracted initramfs)

Then you can edit the actual file contents, like rootfs or kernel. Now, pack the boot.img again

./gradlew pack

You get the repacked boot.img at $(CURDIR):

boot.img.signed

Well done you did it! The last step is to star this repo :smile

live demo

Supported ROM image types

Please note that the boot.img MUST follows AOSP verified boot flow, either Boot image signature in VBoot 1.0 or AVB HASH footer (a.k.a. AVB) in VBoot 2.0.

compatible devices

more examples

• recovery.img

If you are working with recovery.img, the steps are similar:

cp <your_recovery_image> recovery.img
./gradlew unpack
./gradlew pack

• vbmeta.img

cp <your_vbmeta_image> vbmeta.img
./gradlew unpack
./gradlew pack

• boot.img and vbmeta.img

cp <your_boot_image> boot.img
cp <your_vbmeta_image> vbmeta.img
./gradlew unpack
./gradlew pack

Your boot.img.signed and vbmeta.img.signd will be updated together.

boot.img layout

Read layout of Android boot.img and vendor_boot.img.

References