% Introduction to Reverse Engineering
% Stefan Friese
% 02 November, 2023

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# Topics

* Effective Reverse Engineering
* Reversing with Ghidra

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## How Do You Reverse

Reverse Engineering demands a lot of knowledge in multiple fields.  

**Some topics are**

* Assembly Language
* ANSI C
* Other Languages
* Syscalls
* Cryptography

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How do you reverse engineer without knowing little about these topics?

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## Reversing is Work

Work is a product of power by time.  
`P` is your power to solve an issue.

`W = P x t`

The smarter you tackle work, the less time you need to solve an issue.

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## Knowledge is a Map

You conventiently drive around the city using the underground.
That's how you get to know the main spots of the city.

<img src="./images/london_underground.jpg" alt="London Underground" width="50%" height="auto">

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## Knowledge is a Map

Invest some time and explore deeper on foot.
That's how you get to know the back alleys.

<img src="./images/london_by_foot.jpg" alt="London by Foot" width="50%" height="auto">

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# Ghidra -- an Overview

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![Main View of Ghidra](./images/Ghidra-Overview.png)

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## Watch Out for Low Hanging Fruits

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* Data Segment
* Names of Functions
* Conditions & Comparisons
* Strings: Usernames, Passwords
* URLs, IP & Port Numbers

**Do not try to understand the whole code at once, it will only drive you mad.**

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### Data Segments

![A look into the read only data segment](./images/data-segments.png)

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### Name of Functions

![Functions contained in the binary a.k.a. Symbol Tree](./images/symbol-tree.png)

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### Conditions & Comparisions 

<img src="./images/decompiled-code.png" alt="Input is Compared to a Hard Coded String" width="50%" height="auto">

Input is compared to a hard coded string

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### Function Graph

<img src="./images/function-graph.png" alt="Take a Look at the Flow Graph of Functions" width="50%" height="auto">

Take a look at the flow graph of functions

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### Strings

<img src="./images/defined-strings-menu.png" alt="Open the Defined Strings Menu" width="50%" height="auto">

Strings can not only be located in data but also in other code segments, sometimes obfuscated

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### Strings

![An old friend](./images/defined-strings.png)

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### Do It Yourselves!

* [Download Ghidra](https://ghidra-sre.org/)
* [Download binaries at crackmes.one](https://crackmes.one)
* [Find more binaries on hackthebox](https://hackthebox.eu)
* [Or Find even more on tryhackme](https://tryhackme.com)
* Download firmware of your favorite IoT appliances