BSides Algiers - Reversing Win32 applications - Yacine Hebbal

What is reverse engineering ?

Reverse engineering is the process of extracting the
knowledge or design blueprints from anything man-made.

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Reverse engineering can be practiced on: mechanical
devices, electronic components, or software programs, and we
will focus on reversing software programs

Reversing applications can be seen as "going backwards
through the development cycle”.

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Where do we need it?
It is used for
1-Evaluating the level of security that the application
provides
2-Analyzing and eventually defeat various copy protection
schemes (cracking)
3-Locating vulnerabilities in operating systems and other
software
4-Reversing Cryptographic Algorithms
5-Infecting application by viruses or to healing them from
the infection
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Is it legal ?

It depends on why you are reversing software, it is legal for
education purposes and illegal for stealing password and
private information

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Terminology

Patching : A technique of modification of a program.

Serial fishing : Finding the correct password for an
application.

Keygenning : Finding the algorithm that generate the
password of an application.

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So how to do it ?

Software reverse engineering requires a combination of
skills & tools
So to do it we need:
- Tools
- Knowledge
- A working mind , curiosity & the desire to learn

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So how to do it ?

Tools

1-disassemblers: are programs that let us get the
assembly code from any application such as

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IDA PRO DISASSEMBLER

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So how to do it ?

Tools

2- Debuggers: they are programs that let us execute
assembly code and see the results of any instruction
IDA & Olly are also debuggers

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So how to do it ?

Tools

3-Hex editors: they show the content of any file
(programs) in hexadecimal format, they allow us
to modify instructions or to get some information
(header information for ex)
Ex: hex workshop

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So how to do it ?

Tools
4- Other tools : We need also some other tools like :
- Peid
- ImpRec
- metasploit
- …

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1- Patching applications

Bypassing Authentication

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2 - Password fishing

Static passwords

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3 - Password fishing

Dynamic passwords

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4 - Keygenning

Create keygen

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Some defense methodes
To protect your application there is many defense methods
such as:

Packers

Protectors

Encryption algoritms

…

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Packers

they compress the application so the constant like text for
example will be changed, and they will be restored after the
execution of the application so we can’t see theme before the
execution
Ex : UPX , Morphine , Aspack , FSG …

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Protectors

they are small programs fused with the application that
can detect the debugger or the disassembler so they won’t let
us reverse the application
Sometimes we can find a packer and protector in the same
time
EX : YodaEncrypt , ARMprotect …

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Encryption

Also there are some other techniques like encrypting the
password by using hash functions like MD5, SHA-1 …

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Buffer overflow vulnerability

Overview ….

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Buffer overflow vulnerability

Exploitation

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Links:
http://www.kromcrack.com/

http://tuts4you.com/

http://www.newbiecontest.org
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Thank you

For you attention
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BSides Algiers - Reversing Win32 applications - Yacine Hebbal

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