Mythril Tutorial: Smart Contract Security Analysis Guide

Introduction to Mythril Security Tool

In this comprehensive guide, we'll explore Mythril's installation process, core functionality, and practical techniques for identifying critical vulnerabilities in smart contracts. The tutorial covers essential modules like Ether Thief and Suicide, along with configuration parameters for transaction depth and execution timeout.

1. Installing the Mythril Security Analysis Tool

Execute the following command to install Mythril:

pip install mythril

Verify successful installation with version check (minimum v0.21.7 required):

myth version
Mythril version v0.21.15

Basic security analysis commands:

myth analyze
myth analyze -a

The default parameters perform a general analysis suitable for most use cases.

2. How Mythril Works: Symbolic Execution Explained

Mythril operates through specialized Ethereum Virtual Machine execution with these key steps:

1. Bytecode Acquisition: Obtains contract bytecode
2. State Initialization: Sets up contract account state
3. State Space Exploration: Examines potential states through transactions (default: 2)
4. Vulnerability Verification: Confirms reachability of undesirable states

👉 Master advanced symbolic execution techniques

Key components:

• Symbolic execution engine
• State space navigator
• Vulnerability detection modules

3. Practical Mythril Usage Guide

Analyzing TokenSale Contract

Consider this TokenSale contract scenario:

// tokensale.sol example
require(msg.value == numTokens * PRICE_PER_TOKEN);

Execute analysis with Ether Thief module:

myth analyze -m ether_thief tokensale.sol

4. Ether Thief Module: Detecting ETH Leakage

This module identifies unauthorized ETH withdrawals when:

• Non-zero ETH extraction is possible
• Withdrawing account ≠ contract creator
• Withdrawn amount > account's prior deposits

Sample detection output:

==== Unprotected Ether Withdrawal ====
SWC ID: 105 Severity: High
Contract: TokenSaleChallenge
Function: sell(uint256)
PC address: 696

👉 Learn about advanced vulnerability patterns

Attack sequence example:

1. Contract creation (creator)
2. Attacker transaction 1: buy() with crafted input
3. Attacker transaction 2: sell() exploit

5. Configuring Transaction Depth

Critical parameters:

• Default depth: 2 transactions
• Recommended for common vulnerabilities
• Increased depth reveals complex attack vectors

Adjust depth with -t parameter:

myth analyze killme.sol -t3

6. Execution Timeout Settings

Control analysis duration with:

myth analyze --execution-timeout 600

Important notes:

• Default: Runs until completion
• CTRL+C interrupts with partial results
• Essential for large contract analysis

FAQ Section

Q: How accurate is Mythril's vulnerability detection?

A: Highly accurate for common patterns, though complex contracts may require manual verification.

Q: What's the recommended transaction depth for beginners?

A: Start with default (2 transactions), increasing gradually as needed.

Q: Can Mythril analyze private variables?

A: Yes, private state isn't truly secret - Mythril can examine all contract storage.

Q: How does timeout affect analysis quality?

A: Longer timeouts yield more thorough results but require patience.

Q: Should I always use all analysis modules?

A: Focus on relevant modules (ether_thief, suicide) for targeted analysis.

Advanced Configuration Tips

Conclusion

This guide has covered Mythril's core functionality from installation to advanced analysis techniques. Remember:

1. Start with basic analysis (myth analyze)
2. Gradually incorporate modules (-m)
3. Adjust transaction depth as needed (-t)
4. Set reasonable timeouts for large contracts

For comprehensive smart contract security, combine Mythril with manual code review and testing frameworks.