All language subtitles for 003 How to decompile apks.en

One of the things that would be very helpful in terms of analyzing Android applications for vulnerabilities

is the ability to D compile the application back into its source code with Java and languages that are

similar to Java that compile into a bite code that is run against virtual machine.

It's possible for us to reverse the compilation process to turn the bike code back in to something that

resembles the original source code.

Now the matching won't always be perfect.

You will do some information typically from it.

However most of the important pieces are going to still be there.

And since those pieces will be there we'll be able to not only understand what the application is doing

but actually be able to see the source code and be able to pick out specific vulnerable aspects that

we want to be able to work with.

So in this video may demonstrate how we can reverse reverse engineer essentially or compile an application.

So there's a lot of different ways that people will typically use to do this.

There are tools like API key tool and JD that will allow us to actually D compile the application and

then reverse it back into Java code.

I actually use one called GTD at JD X. And again I'll put links to these inside of a resources section

but inside of here there is essentially in the bin there's a gooey that we can launch when we launch

this we're able to actually compile any AP K that we may have on our computer so it come into our directory

here and I'm going to go grab the diva application that we installed and run this through the compiler

and what you'll see here is that we'll get a set of source code and a set of resources that are used

inside of this application.

When you're first looking at an application there's a lot of different information that's valuable to

us.

The manifest file is one that's going to be extremely useful.

It's gonna tell you a lot of different things such as the permissions that are used by the application.

It will tell you what activities exist inside the application.

It will tell you about intense.

It will tell you about things like content providers and such if they exist.

It will tell you what versions we target.

It will give you a whole plethora of high level information that will allow you to better understand

the attack surface that you're working with.

So this is one file that would be very useful for us to be able to look at resources are going to be

a lot of like the graphical interfaces and such that you're gonna be working with a lot of this really

isn't particularly useful I don't think.

Most of the time this is just sort of like you know trivial information that comes from this process.

The meta info will tell you different information.

There's some cert details that are sometimes potentially helpful as well as the manifest file which

could tell you a bit of valuable information potentially gives you a bit of a layout of some of the

things that exists inside of like the rest folder and it will allow you to get a bit of an understanding

behind like the contents of of the manifest for instance and then we also have this lib folder in this

lib folder has any sort of shared objects libraries that are used inside of the application.

These are typically written in C or C++ and compiled these can't be d compiled what we can do with these

is we can analyze like strings that may exist inside of them we might be able to break it down into

something that might be able to tell us some information about the shared library or shared object but

a lot of time these are things that we won't be able to necessarily dig into too deeply.

You'll see in a few examples we actually can go through these and gain some form of relevant information

and then finally we have our actual source code files which are the actual source of the application

itself.

If you take a look at these you'll be able to see you make each of the different pieces that goes into

building the actual application itself.

So you could pull up any of the code that actually exists and you'll be able to see exactly what code

is being used.

You can do this sort of thing with all.

I would say basically any Android application you should be able to get source code and that's it's

like heavily encrypted or obscured in some way.

This will typically be possible so a few other things that are useful for this.

We can search this for specific keywords so for instance we find an error message or something like

that that we want to look up.

We can try looking it up.

We can try looking up common things like password.

So you want to check off like what you actually a search.

You could search classes you could search methods fields code for instance and you can see here we can

sort of like pick out pieces of information that might be of interest to us.

So here's an example here where we're inserting into sequel a user username and password it seems.

So this for instance would be some information that might be able to gather from D compiling the application.

So this gives you a bit of an idea of how we can actually D compile Android applications and from here

we sort of have all the tools that we're going to need to have to be able to analyzed different applications

to be able to look at common Android vulnerabilities.

So that's what we will take a look at next.