Aderyn is an open-source static analysis tool written in Rust that scans Solidity smart contracts for vulnerabilities and code quality issues. Developed by Cyfrin, Aderyn analyzes contract Abstract Syntax Trees to identify potential bugs without executing the code. Its speed, extensibility, and focus on smart contract security make it popular among auditors and developers preparing code for security reviews.

How Aderyn Works

Aderyn processes Solidity contracts through several stages:

Compilation: Aderyn uses the Solidity compiler to generate JSON AST files representing the contract's structure.

AST Analysis: Built-in detectors traverse the AST, looking for patterns that indicate vulnerabilities or bad practices.

Report Generation: Findings are compiled into reports categorized by severity (High, Medium, Low, Informational).

Running Aderyn is straightforward:

1aderyn ./src

This command analyzes all Solidity files in the source directory and produces a report highlighting potential issues.

Built-in Detectors

Aderyn ships with numerous detectors covering common vulnerability categories:

Reentrancy patterns: Identifies potential reentrancy vulnerabilities from state changes after external calls.

Access control issues: Flags functions lacking proper authorization checks.

Arithmetic concerns: Detects integer division precision loss, unchecked arithmetic in older Solidity versions, and other mathematical issues.

Gas optimization: Highlights patterns that waste gas, like using storage when memory would suffice.

Code quality: Reports on missing NatSpec documentation, unused variables, and style inconsistencies.

Writing Custom Detectors

One of Aderyn's strengths is its extensibility. Security researchers can write custom detectors in Rust to identify project-specific vulnerabilities or patterns unique to certain protocol types.

Custom detectors implement the IssueDetector trait:

1impl IssueDetector for CustomDetector {
2    fn detect(&mut self, context: &WorkspaceContext) -> Result<bool, Box<dyn Error>> {
3        // Traverse AST and identify issues
4        for node in context.binary_operations() {
5            if matches_vulnerability_pattern(node) {
6                capture!(self, context, node);
7            }
8        }
9        Ok(!self.found_instances.is_empty())
10    }
11    
12    fn severity(&self) -> IssueSeverity {
13        IssueSeverity::Medium
14    }
15    
16    fn title(&self) -> String {
17        String::from("Custom Vulnerability Title")
18    }
19}

This extensibility allows audit firms to build detector libraries for specific protocol types like AMMs, lending protocols, or bridges.

Aderyn vs Other Static Analyzers

Several static analysis tools exist for Solidity. Aderyn distinguishes itself in several ways:

Rust implementation: Aderyn's Rust foundation provides excellent performance. It analyzes large codebases quickly compared to Python-based alternatives.

Modern Solidity focus: Aderyn actively supports recent Solidity versions and patterns, including those used in Foundry projects.

Security-first design: Created by security professionals at Cyfrin, Aderyn prioritizes vulnerabilities relevant to audits rather than just style or optimization issues.

Slither: The most established Solidity static analyzer, written in Python. Slither has more detectors but runs slower on large projects.

Wake: Another static analyzer with fuzzing integration, offering different detection capabilities.

Both tools complement each other—many auditors run multiple static analyzers to maximize coverage.

Integration in Audit Workflows

Aderyn fits naturally into security review workflows:

Pre-audit screening: Run Aderyn on incoming audit projects to quickly identify obvious issues and gauge code quality.

Continuous integration: Add Aderyn to CI pipelines to catch issues before they reach production or audit.

Custom detector development: Build project-specific detectors for complex business logic that generic detectors miss.

Finding verification: Use Aderyn to verify that fixes for reported issues don't introduce new problems.

Limitations

Like all static analysis tools, Aderyn has limitations:

False positives: Some detected issues may be intentional design choices or safely handled elsewhere in the code.

False negatives: Not all vulnerabilities can be detected through static analysis. Logic errors, economic exploits, and complex interactions require manual review.

AST dependency: Aderyn analyzes compiled AST, so code that doesn't compile cannot be analyzed.

Rust knowledge for custom detectors: Writing custom detectors requires Rust proficiency, which may be a barrier for some teams.

Static analysis is one layer in a comprehensive security strategy that should also include fuzzing, formal verification, and expert manual review.