A developer’s guide to smart contract security audits

Getting Started

We will first do a smart contract audit for bulk-uploading NFTs. Finding defects, vulnerabilities, and dangers in the code before deploying it to the Ethereum mainnet is a crucial step in the auditing of smart contracts.

A Decentralized app audit services does not provide a 100% assurance that the contract will be free of errors or vulnerabilities. But it does ensure that the smart contract is safe and has been thoroughly examined.

A Smart contract Audit’s general format

The following list of expected components for a smart contract audit report include information about found vulnerabilities, a disclaimer, and suggested remedies.

Disclaimer: This section is important for stating that the audit is not a legally binding document and provides no guarantee

Overview of the audit: A brief look at the contract and the best practices that have been observed in its creation

Attacks carried out on the contract: Outlines the attacks that have been carried out on the contract, ensuring its security

Critical-level vulnerabilities: Outline critical vulnerabilities found in the contract, such as a bug that allows attackers to steal currency

Medium-level vulnerabilities: Vulnerabilities that could damage the contract but with a limitation

Low-level vulnerabilities: Issues that don’t affect the contract

Inspecting the code line by line: Analysis of the lines of code with potential improvements

Disclaimer

On the Ethereum blockchain, smart contracts are implemented and put into action. Due to the possibility of new attack vectors being introduced by updates to the Ethereum platform, an audit cannot expressly guarantee that the smart contract will always be safe. This article is intended for discussion purposes only and is not intended to serve as a warranty on the usability or safety of the code contained in this smart contract.

Overview

The project only has one file, NftUpload.sol, which is made up of 114 lines of Solidity code. Based on the natspec documentation, pertinent functions and state variables have comments added to them.

This smart contract’s objective is to make it possible for NFT coins to be widely distributed over the Opensea network.

Summary of audit

The code is nicely written and understandable. The deploy and mint mechanisms are pretty straightforward and shouldn’t cause any significant problems.

My last piece of advice is to focus more on function visibility and consider adopting the ERC-721 extension for bulk minting.

Examining typical attack routes

George Santayana once said, “To know your future, you must know your history.” I bring up this quotation to emphasise that being aware of current assaults is one of the greatest strategies to prevent attacks on a smart contract. The SWC registry offers a number of categories that list all known assaults as of this writing. The SWC registry offers a title, list of code-related samples, and a SWC identification (ID).

A smart contract auditor must consider typical attack elements such access control problems, integer overflows and underflows, and reentrancy flaws (for DApps written in Solidity).

Decentralized finance’s use of smart contracts makes them particularly susceptible to front-running attempts. A bot preempts a transaction as it is being packed in a front-running attack. Before the attacked transaction is performed, the bot sets a higher gas cost to finish the transaction at a preferred rate. Due to the Blockchain dapp auditing company transaction-based architecture, such assaults are feasible. Sandwich attacks are the most common type of front-running attack.

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What is a sandwich attack?

A front-running strategy and frequent attack vector on decentralised exchanges using the automated market maker mechanism is the sandwich assault. When a predator discovers a pending transaction on the blockchain P2P network, Security Audit for dApp they try to surround it by making an order before it (front-running) and an order after it (following it) (back-running). The purpose of this approach is to influence an asset’s price by purchasing and selling.

Sandwich attacks are feasible because the mempool allows for full visibility of all blockchain transactions. As soon as the attack bot discovers a victim’s impending exchange of asset X for asset Y, the victim is front-run by purchasing asset Y.

The bot starts a transaction after the transaction is recognised, sets a higher gas charge, and effectively outperforms the user’s typical transaction via the gas competition mechanism. Following the victim’s typical trade, the bot promptly initiates a second sell deal.

As a developer working on smart contracts in the DeFi space, I can see how dealing with the blockchain’s transaction openness by encrypting data so that bots can’t process it could be a way to protect users from sandwich attacks.

There are now plans to implement encryption using zk-SNARKs, a zero-knowledge-proof method. Although this tactic is not yet developed enough, there is active community discussion about it.

Conclusion

Dapp verification services require smart contract audits in particular. While having a smart contract is not a sign of worth, it is quite significant. I urge developers to keep learning and expanding their understanding of the most recent developments in contract security and best practices.