snimg - create an sn.img file for Lenovo device

Description

Some OEMs (like Lenovo) limit a user's ability to enable bootloader unlocking. Sometimes a small file called sn.img is required to enable bootloader unlocking. Lenovo does not always make this file available for all their devices.

To enable unlocking, the command is usually: fastboot flash unlock sn.img

The bootloader (LinuxLoader aka abl.elf) takes the sn.img file and passes it to VBVerifyImage( ) for authentication. It fibs to VBVerifyImage( ) and tells it that this is a 0x1000-byte boot image.

If successful, this authorises the command fastboot oem unlock-go to unlock the bootloader.

NOTE: not all Android bootloaders issued by these OEMs contain the "fastboot flash unlock" or "fastboot oem unlock-go" commands. So this sn.img file will be useless in that case.

See snimg.h for information on the format of the sn.img file.

How to use sn.img

usage:     snimg <serialno>

               serialno - serial number of device (mandatory), eg H0H0HEHE

How to build snimg

This program uses CMake and OpenSSL.

• Prereqs for Windows
• Prereqs for Linux
• Download source
• Compile the source

Prereqs for Windows

1. Visual Studio 2022 or later. Community Edition is ok.
2. in Visual Studio, install Visual Studio 2022 (v143) or later as the Platform Toolset
3. download and install latest CMake for Windows. It's easiest to use the *.msi installer.
4. download and install OpenSSL in c:\Program Files\OpenSSL. It's easiest to install the precompiled headers.

Prereqs for Linux

1. GCC 7.5.0 or later
2. OpenSSL 1.1.1. Usually pre-installed on Linux (type: openssl version). If not installed, visit: OpenSSL's github repo for instructions.
3. CMake 3.25.1 or later

    wget https://github.com/Kitware/CMake/releases/download/v3.25.1/cmake-3.25.1.tar.gz
    tar -zxvf cmake-3.25.1.tar.gz
    cd cmake-3.25.1
    ./bootstrap
    make
    sudo make install

Download source

    git clone https://github.com/Yahoo-Mike/snimg.git

Build the source

    cd snimg                                    # change to base directory
    cmake -S . -B build                         # configure the project
    cmake --build build                         # build the project