How to Find Smart Contract Vulnerabilities with Slither?

Smart contracts are the foundation blocks for blockchain and web3 applications, with the value advantages of decentralization and automation. You can execute smart contracts without involving any intermediaries, thereby ensuring faster transaction finality. However, smart contracts also feature vulnerabilities, which could affect user experiences. You can use detection tools like Slither for smart contracts vulnerabilities and optimize smart contract logic to avoid security issues.

It is important to note that you can modify smart contract code only before deploying on the mainnet. Once you have deployed the smart contracts on a blockchain, they will become immutable or completely immune to change. Imagine having a critical security error in a smart contract for your new DeFi application. Malicious actors could exploit the vulnerabilities in smart contracts leading to loss of millions of dollars.

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Why Do You Need Slither?

The necessity of Slither smart contract analysis framework in the existing technology landscape is one of the first things you must learn before using Slither. You must have witnessed many examples of blockchain and cryptocurrency platforms falling prey to security vulnerabilities. Every month, you could witness a major security flaw or incident with blockchain and web3 platforms. Fake NFT airdrops and impersonation of celebrities and top brands have emerged as some of the top security concerns. However, smart contract vulnerabilities are a major setback for the blockchain universe.

Smart contracts are software programs that can help you conduct transactions between two parties on blockchain networks. Developers need a comprehensive set of programming skills for creating smart contracts. On top of it, smart contract developers must also work on ensuring that the smart contracts are secure and deliver trustworthy results.

At this point of time, a smart contract vulnerability scanner could help you identify the security issues in smart contracts. Vulnerability analysis frameworks could support comprehensive smart contract audits, which are an integral part of the smart contract development lifecycle. Therefore, Slither has become one of the most promising additions among smart contract analysis tools.

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What is the Purpose of Smart Contract Audits?

Smart contract audits focus on assessment of code, with its technical specifications and relevant documentation. It would provide alerts to the project team about possible security issues, which you should address before deploying smart contracts.

For example, smart contract vulnerability detection with Slither would help in reducing the attack surface, mitigating risks, and improving the security posture. Audits help in detecting and resolving security issues prior to deployment. Developers can use audits to understand smart contract vulnerabilities along with their difficulty, vulnerabilities, and severity.

It is also important to note that smart contract audits are helpful in ensuring safeguards against the cost associated with smart contract bugs. On the other hand, you should also notice that hiring a professional for smart contract audits could pile up the costs of your smart contract development budget.

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What is the Value of Smart Contract Auditing Tools?

Smart contract auditing can be an expensive process with an in-house team of professionals. On the other hand, a smart contract analysis tool like Slither could serve promising advantages for helping you recognize bugs. It is important to note that you might come across smart contract bugs more frequently and face hefty consequences. Some of the most popular security vulnerabilities for smart contracts include,

• Invalid input sanitation.
• Non-compliance to standards.
• State machine traps result in locked contracts.
• Lack of access controls.
• Incorrect inheritance.
• Business logic errors.
• External interactions with other smart contracts.
• Arithmetic errors such as underflow and overflow.

You would need tools like Slither for smart contracts vulnerabilities in the smart contract development lifecycle for secure development. Smallest smart contract bugs could lead to major exploits with formidable losses. Smart contract auditing tools can recognize these vulnerabilities and help you stay safe from unwanted costs.

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How Will Smart Contract Security Auditing Tools Help You?

The primary objective of smart contract security auditing tools focuses on safeguarding you from the troubles of additional costs. You can find a better explanation for using Slither smart contract testing framework by identifying important requirements in smart contract audits. Smart contract audits involve external security assessment of the code of smart contracts, generally requested by the developer team. However, most of the smart contract developer teams rely on manual code review with smart contract auditors.

Interestingly, you can find a better alternative to manual code reviews with automated smart contract auditing tools. The working of smart contract auditing tools involves automation of different auditing tasks through encoding in rules, featuring distinct levels of precision, coverage, and correctness. You can capitalize on the benefits of smart contract vulnerability detection using Slither for high-level design review. Here are some of the notable aspects in which you define the value of smart contract testing frameworks like Slither for your new smart contract projects.

Smart contract auditing tools are faster, more scalable, and cheaper in comparison to manual analysis. On top of it, smart contract testing frameworks also offer a more deterministic approach in comparison to manual code review.

The next crucial advantage of a smart contract vulnerability scanner like Slither is the flexibility for detection of common pitfalls in smart contract security. Smart contract security testing frameworks also ensure that smart contract code complies with best practices at the EVM and Solidity levels.

Smart contract analysis tools could also support manual programming to support business logic constraints or application-level limitations.

The advantages of smart contract security auditing tools serve as promising benefits for the smart contract development lifecycle. However, a smart contract analysis tool cannot serve as a replacement for smart contract auditors or security experts. On the contrary, the tools serve as a supplement for smart contract developers and help them achieve desired results.

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What is Slither?

Slither is one of the popular tools which have gained considerable momentum in the blockchain and web3 ecosystem in recent times. It is a static analysis framework for Solidity smart contract code. Slither can take one or multiple contracts as inputs and create an outline of security vulnerabilities. On top of it, the results of Slither for smart contracts vulnerabilities also include recommendations on best practices for resolving the vulnerabilities.

Slither follows a static analysis approach in which it could evaluate the properties of a program without execution. It involves the combination of inferences from analysis of data flow and control flow. Some of the other notable examples of static analysis tools include Solhint and ESLint, which work for Solidity and JavaScript, respectively.

Slither is capable of addressing data flow and control flow analysis tasks for smart contracts with respect to relevant sets of detectors for encoding general security issues and best practices. The effectiveness of smart contract vulnerability detection using Slither is evident in the accessibility of more than 70 in-built detectors for multiple smart contract security pitfalls.

For example, it can help in detecting structural issues, uninitialized variables, access control, and inheritance. Interestingly, developers could also add custom detector functions for identifying specific security pitfalls or patterns. On top of it, Slither also features a collection of printers that helps in inspection of the variable dependencies and inheritance tree of the smart contract.

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How Can You Use Slither for Detecting Smart Contract Vulnerabilities?

Slither offers a low-cost, open-source static analysis framework for Solidity smart contracts. You can run Slither directly on your contracts to determine the presence of common security issues and vulnerabilities. On top of it, Slither also serves as a valuable asset for enforcing smart contract development best practices.

Interestingly, Slither is more than a smart contract vulnerability scanner with the facility of printers to review the structure of a smart contract. You can explore other details about the fundamentals of Slither in an introductory course to the static analysis framework. Let us take a look at some of the essential practices for using Slither for smart contract vulnerability analysis.

Installation of Slither

The most obvious requirement for using Slither is the installation process. First of all, you need to install the Solidity compiler, solc, by using the following command.

sudo apt install software-properties-common

sudo add-apt-repository ppa:ethereum/ethereum

sudo apt install solc

It is also important to ensure installation of ‘solc-select’ for faster installation of the Solidity compiler. On top of it, ‘solc-select’ also helps in easier transition among different versions of Solidity compiler. You can install the ‘solc-select’ by using the following command.

pip3 install solc-select

Once you have installed ‘solc’ and ‘solc-select’ without any errors, you can move toward the procedure for installing Slither. You can install the Slither smart contract analysis framework by using GitHub, Docker, or Pip. Here is an outline of the commands for installing Slither through three popular tools.

• Installing Slither by Using Pip

pip3 install slither-analyzer  

• Installing Slither with Docker

docker pull trailofbits/eth-security-toolbox

• Installing Slither with GitHub

git clone <https://github.com/crytic/slither.git> && cd slither

python3 setup.py install

You can check whether Slither has been installed on your machine by using the terminal. If Slither has been successfully installed, the ‘slither –version” command will return the latest version of the tool.

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Best Practices for Checking Smart Contracts with Slither

Once you have provided the definition for a smart contract you want to verify, you should choose the easiest approach. You can execute the following command for checking a smart contract,

slither [target]

The ‘target’ in this case could include multiple specifications such as the following,

• Local copy of contract file, such as slither SecureContract.sol
• Mainnet contract address, such as slither 0xe54860d9d40be15cC1D5Afc1A6F013A923a27813
• Project directory, such as slither /path/to/the/project/SecureProject

The applications of Slither for smart contracts vulnerabilities also point towards the support for different networks. You can find support for almost 15 different networks, such as Ethereum, Ropsten, Goerli, Rinkeby, Kovan, Avax, BSC, Arbi, and Poly.

• Checking a Smart Contract with Errors

How could you identify whether a smart contract has a specific vulnerability? Let us assume the example of a smart contract with vulnerabilities to re-entrancy attacks. First of all, you can scan the local copy of a smart contract by running slither with the concerned contract’s name. Subsequently, you can receive the desired results within a few minutes.

You can find colored highlights in the results by Slither for your concerned smart contract. The colored highlights in the output reflect the most important findings from the audit. In addition, the smart contract analysis tool also offers a detailed explanation of the smart contract vulnerabilities. For example, you can find the following details in the Slither output results for a smart contract audit.

• Working of the vulnerability.
• Functions that are being used.
• Relevant references.

• Filtering Output Results of Slither

After receiving the results from Slither smart contract testing, you should filter the outputs. Here are some of the noticeable examples for filtering the results from output by Slither.

• You can filter dependencies by using “-exclude-dependencies.”
• You can filter optimization by using “-exclude-optimization.”
• Developers can also use “-exclude-informational” for filtering the informational aspects of the smart contract.
• You can also rely on “-exclude-low” command for filtering low findings.
• Developers could also exclude the medium and high-impact findings according to their desired preferences.

• Applications of Detectors and Printers

Detectors are ideal tools for smart contract vulnerability detection using Slither, and you can find 83 vulnerability detectors with Slither. You can use detectors in Slither by using the following command,

run slither –detect [detector_name]

Printers are also powerful tools for obtaining important contract information and could help in conducting manual analysis. Here is an example of running printers in Slither,

slither SecureContract.sol –print contract-summary

Bottom Line

The guide to smart contract vulnerability testing with Slither offers a clear explanation of the reasons to choose smart contract auditing tools. You found out how a smart contract vulnerability scanner could support the work of smart contract developers, security experts, and auditors. One of the major highlights in the working of Slither is the flexibility for installation and simple steps for using the smart contract testing framework.

As a static analysis tool, Slither has been criticized for flagging false positives. On the contrary, fluency in the best practices for using Slither and awareness regarding value of smart contract audits can help you use the tool to your advantage. Learn more about creating and deploying smart contracts with your desired functionalities now. 

*Disclaimer: The article should not be taken as, and is not intended to provide any investment advice. Claims made in this article do not constitute investment advice and should not be taken as such. 101 Blockchains shall not be responsible for any loss sustained by any person who relies on this article. Do your own research!