EVM Smart Contract Security | A Short Guide

As you may already know, the Ethereum network uses programmable software platforms or smart contracts built on blockchain technology for powering non-fungible tokens, decentralized applications, and decentralized autonomous organizations. And the high-level functionality of Ethereum smart contracts has laid a solid foundation for developers to create complex and productive blockchain-based applications. Unfortunately, however, while all these revolutionary concepts have developed a creative and vibrant ecosystem of interconnected, trustless smart contracts, they have also become the perfect target for attracting the curiosity of hackers and bad actors.

As a result, the need and demand for security practices such as EVM security audit, penetration testing, and preventive measures have reached their highest points.

This article will cover smart contract security methodologies, best practices, security tools, and helpful resources. So, without further ado, let’s begin.

General Understanding of Ethereum Smart Contracts

Before diving deep into the central part of our topic, let’s understand what Ethereum smart contracts are and how they work.

If in a few words, an Ethereum smart contract runs on the blockchain, and the EVM (Ethereum Virtual Machine) manages its execution and distributes it across multiple nodes around the globe. Additionally, Ethereum smart contracts are written and developed in a Solidity programming language, similar to programming languages like Javascript and C++.

Furthermore, the architecture and structure of Ethereum smart contracts slightly differ from that of other contracts. Depending on the goal and specifics of the project, a smart contract can be complex with multi-layered functionality or simple with limited functionality.

The Best Practices To Secure Ethereum Smart Contracts

Though the list of attack types and smart contract vulnerabilities is infinite, there are multiple recommendations and practices every Ethereum smart contract developer should keep in mind to write secure smart contracts. These methods and preventive measures help handle anything from simple blockchain security to external calls and commitment schemes when building dApps and deploying smart contracts on Ethereum or EVM-compatible blockchains.

So, let’s go on and review them one by one.

#1 Constant Smart Contract Audits

Developing smart contracts without a thorough security audit can be considered a crime in this digital age and day. However, even today, many developers are launching smart contracts without performing a proper security audit, which drastically increases the number of hacking attacks and safety issues.

Regular smart contract audits can save companies from troublesome situations like data leakage, security exploits, or financial loss. In addition, it helps to identify potential security vulnerabilities of the written smart contract code and spot the flaws that remained unnoticed during the development process.

Also, once the auditing is complete, the security experts provide a final audit report with details of discovered issues and vulnerabilities and appropriate solutions for fixing and remediating the current flaws.

#2 Testing The Smart Contract Code

Running various tests is the best way to detect mistakes and security vulnerabilities of the deployed smart contract code. Most developers use integrated and unit tests for a more comprehensive assessment. Unit testing, for example, helps to check the functions of smart contracts and verify whether the source code follows the predetermined agreements and conditions or not.

Other recommended options for testing Ethereum smart contracts are as follows:

• Kovan
• Rinkeby
• Truffle
• Robsten

#3 Reviewing Code With The Development Team

If you are working in a team, each developer needs to perform an independent contract code audit and report the results of the identified issues to other project members. It helps to enhance the security system and not miss the hidden vulnerabilities.

#4 Handling External Calls and Re-entrancy Attacks

Re-entrancy is one of the most widespread and crucial security issues developers need to consider when writing a smart contract code. When a re-entrancy attack occurs, the contract code functions in an attempt to drain transaction funds by making an external call to other untrusted contracts. The contract address and its function generally enable users to withdraw Ethers they have stored on their regular account and works as predetermined: msg. sender. call. value. However, if the malicious contract makes an external call, the attacker can easily access the code’s core information, such as token amount, transaction value, and wallet address. Moreover, the account funds will be sent to the hacker’s arbitrary address, while the original owner will lose their tokens.

It’s recommended to design the function of a deployed smart contract to prevent the possibility of such attacks, so it neither calls nor sends ETH to untrusted and unknown contracts ( such as calling transfer() of a provided token address).

#5 Designing Secure Access Control Mechanisms

Generally, access control mechanisms decide who can govern or alter particular components of the contract code, which is a vital part of designing the Ethereum smart contract’s architecture.

When a wrong person gets admin privileges or ownership of a smart contract, they can easily reprogram the contract code to execute malicious financial transactions. So, if you want to prevent malicious actors from accessing admin permissions, it’s a must to ensure that sensitive function accessibility is complex and requires several authorization levels.

#6 Reducing Software Complexity

The core rule of software and blockchain security is to keep the contract code simple, as more complexity can lead to more variables, which in its turn, can increase the possibility of flaws and mistakes.

However, it doesn’t necessarily mean you should avoid function-rich smart contracts. Instead, you need to start with a simple code structure and slowly expand functionality using familiar patterns and clean code.

#7 Implementing Fail-Safe Protection

What is the best practice while writing a code, if not preparing for possible failures and smart contract security issues beforehand? Because no matter how many times you check, test, and re-test, it’s impossible to cover every potential flaw and bug that can negatively affect the functionality of a smart contract. Hence, creating a fail-safe mechanism for your Ethereum smart contract project is a must to limit damage from cyber threats and attacks.

Smart Contract Security Tools and Resources For Developers

Smart contract security and privacy are serious for every blockchain-based platform and project. Therefore, before writing and deploying a code on the Ethereum network, it’s necessary to equip yourself with the best security tools and developer resources to eliminate the possibility of risks and problems.

Below we enlisted some analysis tools and resources that can help secure your code against bugs, exploits, and vulnerabilities.

Octopus

The first recommendation in our top list is Octopus. It is a well-known security analysis tool for reviewing and assessing the smart contract bytecode to fully understand all internal behaviors. This tool is compatible with contracts built on popular blockchain networks, including Bitcoin, Ethereum, and NEO.

Mythril

It is a smart contract security tool designed for testing and analyzing EVM bytecode. For identifying the contract code vulnerabilities, Mythril uses the combination of symbolic execution, SMT solving, and taint analysis.

Oyente

Oyente is also from the group of security analysis tools with the main focus on detecting common smart contract security vulnerabilities. In general, it comprises an Explorer, Validator, CGF builder, and CoreAnalysis tool. Each of these components executes a vital function: the Explorer, for example, is used to run the smart contract, and CoreAnalysis is used to search for potential issues in the resulting output.

Securify

Securify is an Ethereum smart contract scanner that can identify over 37 security vulnerabilities. Moreover, it also utilizes context-specific static analysis for more detailed and accurate security reports.

SWC Registry

The Smart Contract Weakness Classification or SWC Registry is a helpful resource that categorizes common contract weaknesses in one catalog. When browsing through it, you can learn about various vulnerabilities that have been used to exploit smart contract projects previously. Moreover, it also includes multiple test cases you can use for your project testing.

Solcurity

It is a handy opinionated security and code quality standard for Solidity smart contracts. Solcurity lists security questions and vulnerabilities you can consider when auditing or reviewing projects.

Smart Contract Attack Vectors

It is a famous repository for developers that includes a collection of known attacks, mitigation strategies, and security vulnerabilities for EVM-based projects. Through this repository, one can learn more about various known attack vectors and security issues such as honeypots, reentrancy, incorrect inheritance code, and signature malleability.

Blockchain Security Database

This open-source database by ConsenSys Diligence enlists security information for famous dApp projects and their smart contracts. Here you can find project audit samples and bug bounty payouts that reward individuals for finding contract security vulnerabilities.

Secureth

Another great resource worth mentioning is Secureth, focusing primarily on EVM systems and Blockchains. It is a commonly-driven educational resource designed for developers and beginner specialists who want to learn more about smart contract implementation and its importance.

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