Noga Fallback Contracts - Tea-Fi

1. Introduction

TeaFi engaged Halborn to conduct a security assessment on their smart contracts beginning on October 10, 2025 and ending on October 20, 2025. The scope of this assessment was limited to the smart contracts provided to the Halborn team. Commit hashes and additional details are documented in the Scope section of this report.

TeaFi's Noga Fallback contract's are a modular smart contract system built on the Diamond Standard (EIP‑2535) for secure, gasless ERC‑20 token swaps and transfers. It features upgradeable facets for admin control, whitelisting, and execution, with strict role-based access and slippage protection. Using Permit2 and other permit standards, relayers can perform authorized actions on behalf of users. The system includes treasury-based fee collection, pausability, emergency withdrawals, and safeguards like whitelisted function selectors and reentrancy protection.

2. Assessment Summary

Halborn was provided 7 days for the engagement and assigned 1 full-time security engineer to review the security of the smart contracts in scope. The engineer is a blockchain and smart contract security expert with advanced penetration testing and smart contract hacking skills, and deep knowledge of multiple blockchain protocols.

The purpose of the assessment is to:

• Identify potential security issues within the smart contracts.

• Ensure that smart contract functionality operates as intended.

In summary, Halborn identified several areas for improvement to reduce both the likelihood and impact of potential risks, which were mostly addressed by the TeaFi team. The primary suggestions included:

• Modify LibPermit.makeTokenPermit() to check if the current allowance is already sufficient for the transfer amount.

• Extract and validate the amountOutMin from callData to ensure it matches.

• Implement pre-execution allowance validation before other operations and nonce consumption.

• Measure the actual amount received after transfer and use that for refunds.

• Remove the msg.value check inside _validateCall().

• Remove the unnecessary BaseFacet inheritance from DiamondCutFacet.

3. Test Approach and Methodology

Halborn performed a combination of manual code review and automated security testing to balance efficiency, timeliness, practicality, and accuracy in regard to the scope of this assessment. While manual testing is essential to uncover flaws in logic, process, and implementation, automated testing techniques enhance coverage of smart contracts and can quickly identify issues that do not follow security best practices.

The following phases and associated tools were used throughout the assessment:

• Research into the architecture, purpose, and use of the platform.

• Manual code review and walkthrough of the smart contracts to identify potential logic issues.

• Manual testing of all core functions, including createCampaign, claim to validate expected behavior and identify edge-case vulnerabilities.

• Local testing to simulate contract interactions and validate functional and security assumptions.

• Local deployment and testing with Foundry.