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Workshop @ Hack.lu 2019: Reversing WebAssembly Module 101

2019/10/22 @ Hack.lu 2019

In this workshop, I will first introduce WebAssembly concepts and why it’s consider as a “game changer for the web”. Secondly, I will expose how to analyze a WebAssembly module using different techniques (static & dynamic) as well as some open-source tools that make you the life easier (Octopus, Wasabi, …). Finally, we will hands-on with simple examples/crackmes and finally go throws the analysis of cryptominers.

The following point will be discussed in this workshop.

  1. Introduction
  2. WebAssembly Basics
  3. WebAssembly Runtime VM
  4. Module dissection
  5. Reversing wasm module
  6. Dynamic analysis
  7. Cryptominers
  8. Conclusion

link / slides / repository

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Workshop @ BlackAlps 2018: Reversing and Vulnerability research of Ethereum Smart Contracts

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2018/11/08 @ BlackAlps 2018

Ethereum is the reference of smart contract platform due to the possibility to create decentralized applications (Dapps) by writing smart contracts. The Solidity source code of those smart contracts are not always available and can contains flaws (reentrancy, integer overflow/underflow, bad randomness, backdoor, ….). Some smart contract handle thousand of ETH and can’t be modified once pushed into the blockchain. More than 90% of them doesn’t provide the associated Solidity source code and that’s also why be able to reverse and analyze Ethereum smart contract (only with the EVM bytecode) make even more sense.

This workshop is intended to bring attendees the basic skills (theoretical and practical) to analyze Ethereum smart contracts. After the workshop, they will be able to reverse, debug and find basic vulnerabilities into real-life smart contracts without having the Solidity source code.

The following points will be covered in the workshop:

  1. Quick introduction of Ethereum
  2. Basic Ethereum testing lab
  3. Reverse engineering of Ethereum smart contracts
  4. Analysis and vulnerability research
  5. Going deeper & Questions

link / slides / video

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Talk @ Devcon 4 – 2018: Reversing Ethereum Smart Contracts to find out what’s behind EVM bytecode

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2018/11/01 @ Devcon iv.

Reverse engineering is a common technique used by security researcher to understand and analyze the behavior of closed-source binaries.

If you apply this to Ethereum smart contract (and more specifically on the EVM bytecode), thats allow you to analyze and verify the result of your Solidity source code compilation. 

From a developer point of view, it can save you a lot of time and money if you succeed to detect flaws and missing bytecode optimization.

Also, providing the Solidity source code it’s not mandatory during the smart contract creation, that’s why being able to directly reverse the EVM bytecode make even more sense if you want to understand the behavior of external smart contracts.

slides / video

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Talk @ ToorCon XX – 2018: Dissection of WebAssembly module

 

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2018/09/15 @ ToorCon XX – 2018

WebAssembly (WASM) is a new binary format currently developed and supported by all major browsers including Firefox, Chrome, WebKit /Safari and Microsoft Edge through the W3C. This new format have been designed to be “Efficient and fast“, “Debuggable“ and “Safe” that why it is often called as the “game changer for the web“. More than one year after the “official” release, it is not only used “for the web” by web browsers but also in some (huge) other projects like Blockchain Smart Contract platforms (EOS and Ethereum).

I will first introduce WebAssembly concepts and who currently used it in the wild. Secondly, I will show different WebAssembly VM available and explain the security measures implemented into it. Finally, I will show you, throw real life WASM modules, how to do static analysis, using techniques such as reversing, control flow and calls flow analysis, to understand deeper its behaviors. Along the talk, I will used multiple open source tools but mainly the one that I have developed and that is already available on Github (Octopus).

link / slides / video

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Talk @ Recon MTL 2018: Reverse Engineering Of Blockchain Smart Contracts

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RECON Montreal 2018

Many platforms using blockchain technology have emerged in 2017 and take the top 10 position of the cryptocurrencies’s MarketCap. One of the main reasons behind is the possibility to create decentralized applications (dapps) by writing Smart Contracts.

During this presentation, we will analyze the implementation of smart contract mechanism (Virtual Machine, assembly language, instructions sets, …) used by those platforms. We will analyze the assembly languages and instructions sets used by the Virtual Machine of the major blockchain platforms.

We will see how to disassemble and reconstruct the CFG (Control Flow Graph) of those smart contracts and the tools actually available to perform a deeper security analysis.

This talk aims at covering the following platforms:

link / slides / video (not yet)