Introduction
We express our gratitude to the Aviator team for the collaborative engagement that enabled the execution of this Smart Contract Security Assessment.
SkyBridge by Aviator Technologies, LLC is a custom bridge and launchpad solution between the Ethereum Layer-1 and the Base Layer-2 networks that supports any arbitrary ERC-20 token.
| title | content |
|---|---|
| Platform | EVM, Optimism |
| Language | Solidity |
| Tags | Bridge, Liquidity Pool. |
| Timeline | 08/03/2024 - 05/04/2024 |
| Methodology | https://hackenio.cc/sc_methodology→ |
Review Scope | |
|---|---|
| Repository | https://github.com/AviatorAC/skybridge→ |
| Commit | 33a578d7766781cb1366355797b0c20759ffd856 |
Review Scope
- Repository
- https://github.com/AviatorAC/skybridge→
- Commit
- 33a578d7766781cb1366355797b0c20759ffd856
Audit Summary
10/10
100%
10/10
10/10
The system users should acknowledge all the risks summed up in the risks section of the report
Document Information
This report may contain confidential information about IT systems and the intellectual property of the Customer, as well as information about potential vulnerabilities and methods of their exploitation.
The report can be disclosed publicly after prior consent by another Party. Any subsequent publication of this report shall be without mandatory consent.
Document | |
|---|---|
| Name | Smart Contract Code Review and Security Analysis Report for Aviator |
| Audited By | Maksym Fedorenko, Roman Tiutiun |
| Approved By | Grzegorz Trawinski |
| Website | https://hacken.io→ |
| Changelog | 15/03/2024 - Preliminary Report, 05/04/2024 - Final Report |
Document
- Name
- Smart Contract Code Review and Security Analysis Report for Aviator
- Audited By
- Maksym Fedorenko, Roman Tiutiun
- Approved By
- Grzegorz Trawinski
- Website
- https://hacken.io→
- Changelog
- 15/03/2024 - Preliminary Report, 05/04/2024 - Final Report
System Overview
SkyBridge is a custom bridge and launchpad solution between the Ethereum Layer-1 and the Base Layer-2 networks that supports any arbitrary ERC-20 token. with the following contracts:
L1AviERC721Bridge.sol — is the bridging of ERC721 tokens between different domains (such as Ethereum Layer 1 and Layer 2 networks).
L1Bridge.sol — is responsible for transferring ETH and ERC20 tokens between L1 and L2. In the case that an ERC20 token is native to L1, it will be escrowed within this contract.
LiquidityPool.sol — is utilized to provide a central place to hold funds for fast bridging and the fees from Layer 1 to Layer 2 transfers.
L2AviERC721Bridge.sol — is a contract that works together with the L2 ERC721 bridge to make it possible to transfer ERC721 tokens from Ethereum to Optimism. This contract acts as an escrow for ERC721 tokens deposited into L2.
L2Bridge.sol — is responsible for transferring ETH and ERC20 tokens between L1 and L2. In the case that an ERC20 token is native to L2, it will be escrowed within this contract. If the ERC20 token is native to L1, it will be burnt.
AviPredeploys.sol — it contains constants representing predeployed contract addresses on Layer 1 (L1) and Layer 2 (L2) networks.
AviBridge.sol — is a base contract for the L1 and L2 standard ERC20 bridges. It handles the core bridging logic, including escrowing tokens that are native to the local chain and minting/burning tokens that are native to the remote chain.
AviERC721Bridge.sol — it serves as a base contract for both the Layer 1 (L1) and Layer 2 (L2) ERC721 bridges within the Avi ecosystem.
Privileged roles
Bridge Admin: Full control over the bridges. Able to change the fee structure, change the address of the liquidity pool, and other bridges, commit the fast withdrawals using the liquidity from the liquidity pool.
Executive Summary
Documentation quality
The total Documentation Quality score is 10 out of 10.
Functional requirements are provided.
Technical requirements are provided.
Code quality
The total Code Quality score is 10 out of 10.
Test coverage
Code coverage of the project is 100% (branch coverage).
The contracts and libraries are tested thoroughly.
Security score
Upon auditing, the code was found to contain 0 critical, 1 high, 1 medium, and 1 low severity issues, leading to a security score of 4 out of 10. Upon the retest, all issues were fixed resulting in the final score of 10 out of 10.
All identified issues are detailed in the “Findings” section of this report.
Summary
The comprehensive audit of the customer's smart contract yields an overall score of 10. This score reflects the combined evaluation of documentation, code quality, test coverage, and security aspects of the project.
Risks
The admin can withdraw all the liquidity form the liquidity pool.
The admin can increase the bridging fees up to 10% and flat fees up to 0.005 ETH.
The admin can prevent the bridging event transfer by updating the bridge configuration.
The admin can pause the system.
Findings
Code ― | Title | Status | Severity | |
|---|---|---|---|---|
| F-2024-1500 | Mismatch Between Documentation and Implementation | fixed | High | |
| F-2024-1511 | Unexpected Allowance Required to Bridge Tokens | fixed | Medium | |
| F-2024-1381 | Unrestricted Fees | fixed | Low | |
| F-2024-1505 | Non-Compliance with Naming Conventions for Contract and File Names | fixed | Observation | |
| F-2024-1490 | Redundant Getters For The Public State Variables | fixed | Observation | |
| F-2024-1486 | Precense of Redundant Code From The Upgradable Implementation | fixed | Observation | |
| F-2024-1378 | Missing Zero Address Validation | fixed | Observation | |
| F-2024-1367 | Floating Pragma | fixed | Observation |
Appendix 1. Severity Definitions
When auditing smart contracts, Hacken is using a risk-based approach that considers Likelihood, Impact, Exploitability and Complexity metrics to evaluate findings and score severities.
Reference on how risk scoring is done is available through the repository in our Github organization:
Severity | Description |
|---|---|
Critical | Critical vulnerabilities are usually straightforward to exploit and can lead to the loss of user funds or contract state manipulation. |
High | High vulnerabilities are usually harder to exploit, requiring specific conditions, or have a more limited scope, but can still lead to the loss of user funds or contract state manipulation. |
Medium | Medium vulnerabilities are usually limited to state manipulations and, in most cases, cannot lead to asset loss. Contradictions and requirements violations. Major deviations from best practices are also in this category. |
Low | Major deviations from best practices or major Gas inefficiency. These issues will not have a significant impact on code execution, do not affect security score but can affect code quality score. |
Severity
- Critical
Description
- Critical vulnerabilities are usually straightforward to exploit and can lead to the loss of user funds or contract state manipulation.
Severity
- High
Description
- High vulnerabilities are usually harder to exploit, requiring specific conditions, or have a more limited scope, but can still lead to the loss of user funds or contract state manipulation.
Severity
- Medium
Description
- Medium vulnerabilities are usually limited to state manipulations and, in most cases, cannot lead to asset loss. Contradictions and requirements violations. Major deviations from best practices are also in this category.
Severity
- Low
Description
- Major deviations from best practices or major Gas inefficiency. These issues will not have a significant impact on code execution, do not affect security score but can affect code quality score.
Appendix 2. Scope
The scope of the project includes the following smart contracts from the provided repository:
Primary Scope Details | |
|---|---|
| Repository | https://github.com/AviatorAC/skybridge→ |
| Commit | 33a578d7766781cb1366355797b0c20759ffd856 |
| Whitepaper | ./Aviator%20SkyBridge%20Technical%20Documenation%20v1.0.pdf |
| Requirements | ./Aviator%20SkyBridge%20Technical%20Documenation%20v1.0.pdf |
| Technical Requirements | ./Aviator%20SkyBridge%20Technical%20Documenation%20v1.0.pdf |
Primary Scope Details
- Repository
- https://github.com/AviatorAC/skybridge→
- Commit
- 33a578d7766781cb1366355797b0c20759ffd856
- Whitepaper
- ./Aviator%20SkyBridge%20Technical%20Documenation%20v1.0.pdf
- Requirements
- ./Aviator%20SkyBridge%20Technical%20Documenation%20v1.0.pdf
- Technical Requirements
- ./Aviator%20SkyBridge%20Technical%20Documenation%20v1.0.pdf
Secondary Scope Details | |
|---|---|
| Repository | https://github.com/AviatorAC/skybridge→ |
| Commit | 4e50feca34b10d1c0181699f2f4f114870bb29ba |
| Whitepaper | ./Aviator%20SkyBridge%20Technical%20Documenation%20v1.01.pdf |
| Requirements | ./Aviator%20SkyBridge%20Technical%20Documenation%20v1.01.pdf |
| Technical Requirements | ./Aviator%20SkyBridge%20Technical%20Documenation%20v1.01.pdf |
Secondary Scope Details
- Repository
- https://github.com/AviatorAC/skybridge→
- Commit
- 4e50feca34b10d1c0181699f2f4f114870bb29ba
- Whitepaper
- ./Aviator%20SkyBridge%20Technical%20Documenation%20v1.01.pdf
- Requirements
- ./Aviator%20SkyBridge%20Technical%20Documenation%20v1.01.pdf
- Technical Requirements
- ./Aviator%20SkyBridge%20Technical%20Documenation%20v1.01.pdf