Awesome

Android_boot_image_editor

A tool for reverse engineering Android ROM images.

Requirements

Make sure you have JDK11+ and Python3.

• Linux / WSL: sudo apt install git device-tree-compiler lz4 xz-utils zlib1g-dev openjdk-17-jdk gcc g++ python3 python-is-python3 p7zip-full android-sdk-libsparse-utils erofs-utils

• Mac: brew install lz4 xz dtc

• Windows: Install openssl and device-tree compiler with chocolate choco install openssl dtc-msys2 zip vim

Getting Started

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

Please remember to clean the work directory first.

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

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

./gradlew clear

If your vbmeta.img contains hash of boot.img, you MUST update vbmeta image together.

rm *.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, then you can flash them to your device.

rm *.img
cp <your_vendor_boot_image> vendor_boot.img
cp <your_vbmeta_image> vbmeta.img
./gradlew unpack
./gradlew pack
./gradlew flash

Please note that to use 'gradle flash', your host machine must be connectted to your DUT with adb, and you already 'adb root'.

If you want to edit the device-tree blob in place:

cp <your_vendor_boot_image> vendor_boot.img
cp <your_vbmeta_image> vbmeta.img
./gradlew unpack
==> now you can edit build/unzip_boot/dtb.dts directly
./gradlew pack

During unpack stage, dtb will be dumped to file build/unzip_boot/dtb, dts will be decompiled to build/unzip_boot/dtb.dts. You can edit dtb.dts directly, and it will be compiled to dtb duing repack stage.

If you just want to replace the dtb with the one that is compiled outside this tool, please

cp <your_vendor_boot_image> vendor_boot.img
cp <your_vbmeta_image> vbmeta.img
./gradlew unpack
rm build/unzip_boot/dtb.dts
cp <your_dtb> build/unzip_boot/dtb
./gradlew pack

If you have a rooted device and want to pull /proc/device-tree

touch fake.dtb
./gradlew pull

This tool will copy dtc to the target device via adb, and dump the dtb and dts file. Eventually you should get something like this

+--------+------------------------------+
|  What  |            Where             |
+--------+------------------------------+
| source | /proc/device-tree            |
+--------+------------------------------+
| DTB    | panther.dtb                  |
+--------+------------------------------+
| DTS    | build/unzip_boot/panther.dts |
+--------+------------------------------+

If you have a dtb file and want to edit its content

cp <your_dtb_file> .
./gradlew unpack

This tool will decompile it and put the decompiled source to build/unzip_boot.

                        Unpack Summary of panther.dtb
+------+------------------------------+
| What |            Where             |
+------+------------------------------+
| DTB  | panther.dtb                  |
+------+------------------------------+
| DTS  | build/unzip_boot/panther.dts |
+------+------------------------------+

cp <your_system_image> system.img
./gradlew unpack

You get system.img.unsparse, that's a plain ext4 filesystem data.

The idea is to set flag=2 in main vbmeta.

rm *.img
cp <your_vbmeta_image> vbmeta.img
./gradlew unpack
vim -u NONE -N build/unzip_boot/vbmeta.avb.json  -c ":19s/0/2/g" -c ":wq"
./gradlew pack

Then flash vbmeta.img.signed to your device.

• unpack init_boot.img and copy out "build/unzip_boot/root".
• clear workspace by gradle clear, then unpack boot.img
• copy back the "build/unzip_boot/root"
• edit build/unzip_boot/boot.json

• change ramdisk.size to 1
• change ramdisk.file from "build/unzip_boot/ramdisk.img" to "build/unzip_boot/ramdisk.img.lz4"

• extract everything

Usage:

    gradle unpack

• extract only 1 specified partition Usage:

    gradle unpack -Dpart=<part_name>

Example:

    gradle unpack -Dpart=boot
    gradle unpack -Dpart=system

Note: "build/payload/" will be deleted before each "unpack" task

AOSP already has tools like apexer, deapexer, sign_apex.py, these should suffice the needs on .apex and .capex. Refer to Issue https://github.com/cfig/Android_boot_image_editor/issues/120

• For those who may be interested in apex generation flow, there is a graph here

cp <your_vendor_dlkm.img> vendor_dlkm.img
cp <your_vbmeta_image> vbmeta.img
./gradlew unpack
# replace your .ko
./gradlew pack

Then flash vbmeta.img.signed and vendor_dlkm.img.signed to the device.

boot.img layout

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

References and Acknowledgement

Android version list https://source.android.com/source/build-numbers.html<br/> Android build-numbers https://source.android.com/setup/start/build-numbers

cpio & fs_config<br> https://android.googlesource.com/platform/system/core<br/> https://www.kernel.org/doc/Documentation/early-userspace/buffer-format.txt<br/> AVB<br/> https://android.googlesource.com/platform/external/avb/<br/> boot_signer<br/> https://android.googlesource.com/platform/system/extras<br/> mkbootimg<br/> https://android.googlesource.com/platform/system/tools/mkbootimg/+/refs/heads/master/<br/> boot header definition<br/> https://android.googlesource.com/platform/system/tools/mkbootimg/+/refs/heads/master/include/bootimg/bootimg.h<br/> kernel info extractor<br/> https://android.googlesource.com/platform/build/+/refs/heads/master/tools/extract_kernel.py<br/> mkdtboimg<br/> https://android.googlesource.com/platform/system/libufdt/<br/> libsparse<br/> https://android.googlesource.com/platform/system/core/+/refs/heads/master/libsparse/<br/> Android Nexus/Pixle factory images<br/> https://developers.google.cn/android/images<br/>