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.NET Assembly Decompilation

One Engine Two Tools

Presenting…Chris Eargle

Telerik EvangelistINETA DirectorC# MVP

Presenting…Chris Eargle

Blogsblogs.telerik.com/JustTeamkodefuguru.com

Contact@kodefuguruchris.eargle@telerik.com

AgendaPart 1 - Discussion

What is a Decompiler?LegalityPreventionCommon Scenarios

Part 2 - Products

JustDecompile – StandAlone

DemoJustCode – Visual Studio

DemoBonus

Part 3

Q&A

Removing some misconceptions

What is a Decompiler?

Performs the reverse operation of a compiler

Translates assemblies back into source code

Source code produced is a representation, not the original

Decompiler

Reflection allows you to observe and modify a program’s structure and behavior at runtime

Used to inspect types and members without knowing names at compile time

Allows for instantiation and method invocation without hard-coding names

It is not Reflection

Disassemblers translate machine code to assembly language

In .NET, translating byte code to common intermediate language (CIL) can be considered disassembly

This is one step in the decompilation process

ildasm.exe is an example of a .NET disassembler

It is not Disassembling

Warning: I am not a lawyer

Legality

Most software is covered by copyright laws

Copyright owners have exclusive rights to make copies

Decompilation can be necessary, and it is allowed in the US and Europe with some limitations

If there are any doubts, consult a lawyer in your jurisdiction

Copyright

United States"where disassembly is the only way to gain access to the ideas and functional elements embodied in a copyrighted computer program and where there is legitimate reason for seeking such access, disassembly is a fair use of the copyrighted work, as a matter of law."

-Sega v. Accolade

Covered under the 1991 Software Directive, Article 6• Must have a license to the program• Must be necessary for software interoperability• Must be confined to relevant elements for

interoperability• Information obtained may not be used for other

purposes or shared

Europe

Have a good reason

Check the laws for where you live

Be good

Bottom Line

How to keep your software safe

Prevention

If it was designed to run, the means by which it runs can be obtained

These techniques will only stop the casual reverse-engineer and the curious

Nothing’s 100%

Provide documentation essential for interoperability

Prevent bugs: test thoroughly

These steps will provide legal cover in some jurisdictions

Provide Good Documentation

Makes it difficult to decompile by making output unreadable

Use an obfuscator : bit.ly/obfuscators

Obfuscation

Why people “legitimately” use decompilers

Common Scenarios

This usage is to determine how to make an assembly work with another assembly or hardware

Optimizing for performance

Interoperability

A bug is creating issues, and there’s no fix available from the vendor

Fix or Workaround Bug

Everyone uses version control, right?

A developer left and the source can’t be found

Recover Lost Source Code

The vendor of a necessary system component has gone out of business

No updates coming and they are necessary

Out of Business

You have a project written in VB, and you need the code for a C# library (or vice-versa)

Language Translation

Performed as part of a build step, check-in, or during system migration

This is generally bad

Tools exist for this particular need

Code Standardization

Compilers change your code to IL constructs. In C#, optimization can affect the output

IL Weaving

Discover Effects on Code

Many people are simply curious about how a program works

Curiosity

May the source be with you

JustDecompile

100% guaranteed

Free for everyone

Free forever

Brand new decompilation engine

JustDecompile is Free

C#Visual BasicIL

Language Support

Create and maintain separate lists of assemblies

Useful when working on different projects

Assembly Lists

NavigationStandard

Navigation TreeInformation PanelCode PanelNavigation Buttons

Searching

Find UsagesGo to TypeGo to SymbolFull Text Search

Contains loaded assemblies

Add assemblies via Open button or drag and drop

Drill into assemblies to get references, resources, namespaces, types, and members

Navigation Tree

Below Navigation Tree

Contains information such as the platform architecture and assembly location

Information Panel

Contains decompiled code or resource

Code Panel

JustDecompile maintains navigation history

Easily return to a previous selection; no hunting through tons of assemblies

Navigation Buttons

Quickly find usages of types or members

Use ctrl+leftclick

Menu or ctrl+alt+u

Supports multiple modes of sorting

Find Usages

Quickly find types containing search term

ctrl+alt+t

Go to Type

Quickly find all symbols containing search term

ctrl+alt+s

This search includes types and members

Go to Symbol

Search for any text within an assemblyctrl+f

Full Text Search

Open local or from URL

Silverlight XAP Decompilation

Works with Windows Phone XAP files!

Toggle compiler generated information

Change code panel theme

Settings

Easy access from the main menu

justdecompile.uservoice.com

Feedback

Decompile and output a full assembly in one step

Was one of the highest requested features

Select an assembly and choose Create Project from tools or context menu

Fulfills Lost Source Code scenario

Create Project

DemoUsing JustDecompile

Decompilation within Visual Studio

JustCode

JustCode is a Visual Studio add-in for faster, smarter coding. It works with Visual Studio 2005, 2008, and 2010. It also works in Visual Studio 11 Beta

Supports: C#, VB.NET, JavaScript, CSS, HTML, Razor, XML, XAML

Works with cross-language solutions

What is JustCode?

Overview of JustCodeCode

AnalysisNavigationGenerationFormattingTemplatesCleaning

And More!

UnobtrusiveRuns out-of-processExtensibleUnit Test RunnerRefactorings

The same engine in JustDecompile is in JustCode

Completely integrated decompiling in Visual Studio

Simply navigated to a type contained in an assembly

Decompiler

JustCode enables you to handle the Code Standardization scenario without decompiling

Create solution options and share them. Code style options available for all languages supported by JustCode

Code cleaning should be used as well. This is extensible; you can add your own code cleaning steps

Code Standards

DemoDecompiling with JustCode

Visit telerik.com/justcode

Watch the videos “10 ways JustCode makes Visual Studio better”

Download a 60 day free trial of JustCode

Learn more about JustCode

One Engine Three Tools

Bonus

Optimize .NET application performance and memory

Includes tracing, sampling, and memory profilers in one easy-to-use package

Supports local and running .NET applications, Silverlight and Windows Service applications, and local IIS and ASP.NET web sites

What is JustTrace?

View source command available in performance profiles

Currently only shows code reconstructed from .pdb files

On the roadmap: including the JustDecompile engine

View Source

Visit telerik.com/justtrace

Find instructional videos at tv.telerik.com

Download a 60 day free trial of JustTrace

Learn more about JustTrace

• Download JustDecompile today : telerik.com/justdecompile

• Remember, it’s free for everyone, free forever!

• To make a feature suggestion: justdecompile.uservoice.com

Thank You

Q&A