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- [SCA] Sky Marvel | skyBridge-SmartContract | Jan2025
Audit name:
[SCA] Sky Marvel | skyBridge-SmartContract | Jan2025
Date:
Jan 27, 2025
Table of Content
Introduction
We express our gratitude to the Sky Marvel team for the collaborative engagement that enabled the execution of this Smart Contract Security Assessment.
The BridgeSKY contract is a cross-chain token bridge enabling users to deposit tokens on one blockchain and mint equivalent tokens on another.
Document | |
|---|---|
| Name | Smart Contract Code Review and Security Analysis Report for Sky Marvel |
| Audited By | Andy Cho |
| Approved By | Ataberk Yavuzer |
| Website | https://skymarvel.io/→ |
| Changelog | 17/01/2025 - Preliminary Report |
| 27/01/2025 - Final Report | |
| Platform | BSC, SKY Chain |
| Language | Solidity |
| Tags | Bridge, ERC20; Claims |
| Methodology | https://hackenio.cc/sc_methodology→ |
Document
- Name
- Smart Contract Code Review and Security Analysis Report for Sky Marvel
- Audited By
- Andy Cho
- Approved By
- Ataberk Yavuzer
- Website
- https://skymarvel.io/→
- Changelog
- 17/01/2025 - Preliminary Report
- 27/01/2025 - Final Report
- Platform
- BSC, SKY Chain
- Language
- Solidity
- Tags
- Bridge, ERC20; Claims
- Methodology
- https://hackenio.cc/sc_methodology→
Review Scope | |
|---|---|
| Repository | https://github.com/TheRavneet/skyBridge-SmartContract→ |
| Commit | 203d5a3 |
Review Scope
- Commit
- 203d5a3
Audit Summary
The system users should acknowledge all the risks summed up in the risks section of the report
Documentation quality
Functional requirements are partially missed.
Technical description is provided.
Code quality
The development environment is configured.
Test coverage
Code coverage of the project is 24.92% (branch coverage).
Deployment and basic user interactions are covered with tests.
Negative cases coverage is missed.
Interactions by several users are not tested thoroughly.
System Overview
The BridgeSKY is a cross-chain token bridge enabling users to deposit tokens on one blockchain and mint equivalent tokens on another.
BridgeSKY — Allows users to burn a token on one chain and mint an equivalent token on another chain through the bridge.
TOKEN — Simple erc20 token contract.
SkytokenPriceFeed — Price oracle contract to get the Sky coin price.
Privileged roles
The owner of the BridgeSKY contract can set a new fee, an SMC amount for the fee amount, a max length of the airdrop, a new receiver, a price feed address, a max token limit, whitelist tokens, and enable/disable currencies.
The owner of the TOKEN contract can mint tokens.
The admin of the SkytokenPriceFeed contract can add/remove an updater.
Potential Risks
Centralized Minting to a Single Address: The project concentrates minting tokens in a single address, raising the risk of fund mismanagement or theft, especially if key storage security is compromised.
Flexibility and Risk in Contract Upgrades: The project's contracts are upgradeable, allowing the administrator to update the contract logic at any time. While this provides flexibility in addressing issues and evolving the project, it also introduces risks if upgrade processes are not properly managed or secured, potentially allowing for unauthorized changes that could compromise the project's integrity and security.
Findings
Code ― | Title | Status | Severity | |
|---|---|---|---|---|
| F-2025-8274 | Duplicate Calculation in Each Iteration | accepted | Low | |
| F-2025-8284 | Inconsistent Type Declaration For _sourceChainType variable | accepted | Observation | |
| F-2025-8283 | Unused Modifier | accepted | Observation | |
| F-2025-8282 | Mismatch Between Documentation and Contract Logic | accepted | Observation | |
| F-2025-8276 | Inefficient Operation of Calculating The Amount to Be Airdropped | accepted | Observation | |
| F-2025-8180 | Unused State Variable | accepted | Observation | |
| F-2025-8179 | Missing _disableInitializers() in Upgradable Contract Constructor | accepted | Observation | |
| F-2025-8178 | Best Practice Violation: Non Upgradeable Ownable Inheritance | accepted | Observation |
Appendix 1. Definitions
Severities
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. |
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.
Potential Risks
The "Potential Risks" section identifies issues that are not direct security vulnerabilities but could still affect the project’s performance, reliability, or user trust. These risks arise from design choices, architectural decisions, or operational practices that, while not immediately exploitable, may lead to problems under certain conditions. Additionally, potential risks can impact the quality of the audit itself, as they may involve external factors or components beyond the scope of the audit, leading to incomplete assessments or oversight of key areas. This section aims to provide a broader perspective on factors that could affect the project's long-term security, functionality, and the comprehensiveness of the audit findings.
Appendix 2. Scope
The scope of the project includes the following smart contracts from the provided repository:
Scope Details | |
|---|---|
| Repository | https://github.com/TheRavneet/skyBridge-SmartContract→ |
| Commit | 203d5a34cb20074e1d6627f611c84877f43f94d4 |
| Whitepaper | N/A |
| Requirements | BridgeSKY Contract Documentation.pdf |
| Technical Requirements | NatSpec |
Scope Details
- Commit
- 203d5a34cb20074e1d6627f611c84877f43f94d4
- Whitepaper
- N/A
- Requirements
- BridgeSKY Contract Documentation.pdf
- Technical Requirements
- NatSpec
Assets in Scope
Appendix 3. Additional Valuables
Verification of System Invariants
During the audit of Sky Marvel, Hacken followed its methodology by performing fuzz-testing on the project's main functions. Foundry, a tool used for fuzz-testing, was employed to check how the protocol behaves under various inputs. Due to the complex and dynamic interactions within the protocol, unexpected edge cases might arise. Therefore, it was important to use fuzz-testing to ensure that several system invariants hold true in all situations.
Fuzz-testing allows the input of many random data points into the system, helping to identify issues that regular testing might miss. A specific Foundry fuzzing suite was prepared for this task, and throughout the assessment, 7 invariants were tested over 100,000 runs. This thorough testing ensured that the system works correctly even with unexpected or unusual inputs.
Invariant | Test Result | Run Count |
|---|---|---|
| Deposits should be performed correctly | Passed | 100k+ |
| Claims should be performed correctly | Passed | 100k+ |
| Prices should be updated correctly | Passed | 100k+ |
| Updating prices requires all validators to sign | Passed | 100k+ |
| Duplicate signatures are not allows to update prices | Passed | 100k+ |
| Should use a valid soure chain type to update prices | Passed | 100k+ |
| Airdrop should be performed correctly | Passed | 100k+ |
Invariant
- Deposits should be performed correctly
Test Result
- Passed
Run Count
- 100k+
Invariant
- Claims should be performed correctly
Test Result
- Passed
Run Count
- 100k+
Invariant
- Prices should be updated correctly
Test Result
- Passed
Run Count
- 100k+
Invariant
- Updating prices requires all validators to sign
Test Result
- Passed
Run Count
- 100k+
Invariant
- Duplicate signatures are not allows to update prices
Test Result
- Passed
Run Count
- 100k+
Invariant
- Should use a valid soure chain type to update prices
Test Result
- Passed
Run Count
- 100k+
Invariant
- Airdrop should be performed correctly
Test Result
- Passed
Run Count
- 100k+
Additional Recommendations
The smart contracts in the scope of this audit could benefit from the introduction of automatic emergency actions for critical activities, such as unauthorized operations like ownership changes or proxy upgrades, as well as unexpected fund manipulations, including large withdrawals or minting events. Adding such mechanisms would enable the protocol to react automatically to unusual activity, ensuring that the contract remains secure and functions as intended.
To improve functionality, these emergency actions could be designed to trigger under specific conditions, such as:
Detecting changes to ownership or critical permissions.
Monitoring large or unexpected transactions and minting events.
Pausing operations when irregularities are identified.
These enhancements would provide an added layer of security, making the contract more robust and better equipped to handle unexpected situations while maintaining smooth operations.