Let's get started writing a drozer device enumeration module:

The next few recipes are all about writing some useful modules to extend your drozer framework; in each, I'll demonstrate some key module development skills that you'll find useful later in the book.

To start off with this explanation, I thought I'd discuss the code you just wrote for your new drozer module and how on earth it manages to extract information about your device.

Well, first of all, I'd like to talk about the structure of a drozer module. Every module you write will start with the following line:

import drozer.modules import Module
class Info(Module)

The first line is essentially an inclusion of some code from the modules library and it gives drozer modules access to all the magic methods and attributes they need to operate. The second line is called the header of a class declaration and marks the beginning of an object definition in Python. You may notice the (Module) part of the header; this is how the Info class manages to adopt the attributes of the Module class, and semantically this works a lot like inheritance in Java.

The next couple of lines are as follows:

name = ""
description = ""

license = ""

These are just variables drozer uses to associate some metadata to the module and to make documentation a bit more standardized and easy to perform—nothing technical to see here. Moving on:

def execute(self, arguments):

This particular piece of code is called a function header and marks the beginning of the definition of a Python function. What's special about this function is that it's the method that gets called to do all the hard work for the module, analogous to the Main method in a Java class. Let's talk about the arguments the execute method expects to be passed:

And then lastly we have the following piece of code:

build = self.new("android.os.Build")

Well, besides dereferencing the self object and using some magic method called new, we see a string value of android.os.Build being passed as an argument. This string is the name of a Java class in the Android Java API, and the new method uses something called Java Reflection to instantiate the Build class that holds all the information we want to print to the screen.

The rest of the code looks something like the following:

self.stdout.write("[*] BOARD : %s
" % (build.BOARD))

The preceding code simply prints out the device information.