Trestle Finance

Introduction

Trestle Protocol connects Celestia’s modular data-availability layer to Ethereum, introducing Wrapped TIA (wTIA) and a permissionless bridge for friction-less liquidity, trading, and application development between the two ecosystems.

Why Did They Need an Audit?

The launch version of Trestle custodies Celestia TIA on Ethereum, mints/burns wTIA, and levies swap-based taxes routed through an on-chain distributor. Failures in access control, slippage safeguards, or reward accounting could lead to unrecoverable asset loss, MEV-driven value extraction, or protocol insolvency. Trestle hired Three Sigma for an intensive review ahead of its public deployment.

Scope of the Engagement

• Files Audited: Trestle.sol , wTIA.sol
• Timeline: 7 Feb 2024 – 9 Feb 2024
• Team: 2 auditors · 3 calendar days
• Chain: Ethereum

Results and Findings

Key High-Severity Issue

Permissionless distribute() enables zero-slippage sandwiching

• Description: Anyone could call distribute() with amountOutMinimum = 0, forcing a swap at any price and extracting value via MEV.
• Resolution: The team disabled tax-based swaps and will gate future reward distributions behind a keeper role.

Notable Medium-Severity Issues

1 - Stuck tokens due to unsafe transfer()

• Description: reclaimToken() used raw transfer, which fails on non-standard ERC-20s and could permanently lock funds.
• Recommendation: Use SafeERC20.safeTransfer() for all token movements.
• Status: Acknowledged; fix planned for v1.1.

2 - Swaps lacked explicit deadline parameter

• Description: Using block.timestamp inside the same tx leaves validators a full block to reorder trades up to the minimum-out threshold.
• Recommendation: Require a user-supplied deadline in addition to amountOutMinimum.
• Status: Addressed by removing swap-tax path.

3 - Taxed sells vulnerable to MEV

• Description: Sells during tax mode set minimumAmountOut = 0, exposing users to toxic slippage.
• Recommendation: Either disable taxes (chosen) or enforce a non-zero slippage guard.

In conclusion

Three Sigma’s rapid review uncovered no critical bugs but highlighted one high-risk MEV path and a cluster of medium-severity logic flaws tied to tax-based swaps and reward accounting. By removing tax mechanics and tightening swap parameters, Trestle significantly reduced its attack surface. Remaining low-level items are slated for the next code push, and the team plans a public bug-bounty before enabling cross-chain mint/burn on main-net.