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Bionic in Android

In this tutorial, we will learn how to extract the user mapping in the Android libc: Bionic.

Context

Android, the mobile operating system, uses a custom libc: bionic. A few notable changes exist from the classic implementation of the libc found on most desktop Linux systems. One of them is that the user table is embedded within the binary.

Objective

Automatically extract the user mapping from the binary1.

Requirements

  • A working Quokka Installation
  • The bionic library (sha256sum: 5975c8366fce5e47ccdf80f5d01f3e4521fee3b1dcf719243f4e4236d9699443)
  • An export of the bionic library

Check requirements

import quokka
bionic = quokka.Program("libc.quokka", "libc.so")
assert bionic is not None

Final words

Once you are set, we can advance to the next steps.

  1. This exercise is based on an idea from Robin David in his IDA scripting training. ↩