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Bitlayer

Audit name:

[SCA] Bitlayer | Bridge + GetBTC | Apr2024

Date:

Apr 18, 2024

Table of Content

→Introduction
→Audit Summary
→Document Information
→System Overview
→Executive Summary
→Risks
→Findings
→Appendix 1. Severity Definitions
→Appendix 2. Scope
→Disclaimer

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Introduction

We express our gratitude to the Bitlayer team for the collaborative engagement that enabled the execution of this Smart Contract Security Assessment.

Bitlayer represents a revolutionary integration, melding elite decentralized exchange (DEX) mechanisms into an innovative, high-efficiency system. This pioneering approach is designed to streamline token exchanges and cross-chain transactions, ensuring seamless operability and liquidity management within the crypto ecosystem.

titlecontent
PlatformEVM
LanguageSolidity
TagsBridge
Timeline02/04/2024 - 04/04/2024
Methodologyhttps://hackenio.cc/sc_methodology→

    Review Scope

    Repositoryhttps://github.com/bitlayer-org/bitlayer-bridge→
    Commit41c7c06
    Repositoryhttps://github.com/bitlayer-org/getBTC→
    Commit345036b

    Audit Summary

    Total9/10
    Security Score

    10/10

    Test Coverage

    86.36%

    Code Quality Score

    9/10

    Documentation Quality Score

    7/10

    12Total Findings
    7Resolved
    4Accepted
    1Mitigated

    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

    NameSmart Contract Code Review and Security Analysis Report for Bitlayer
    Audited ByKaan Caglan
    Approved ByPrzemyslaw Swiatowiec
    Websitehttps://www.bitlayer.org/→
    Changelog04/04/2024 - Preliminary Report
    08/04/2024 - Final Report

    • Document

      Name
      Smart Contract Code Review and Security Analysis Report for Bitlayer
      Audited By
      Kaan Caglan
      Approved By
      Przemyslaw Swiatowiec
      Website
      https://www.bitlayer.org/→
      Changelog
      04/04/2024 - Preliminary Report
      08/04/2024 - Final Report

    System Overview

    Bitlayer bridge comprises three main contracts:

    TokenExchange: Facilitates the exchange of tokens with rigorous permission and signature verification mechanisms. It supports operations like swapping tokens under specific conditions, withdrawing tokens, and modifying contract administrative roles.

    BitlayerProxy: Serves as a proxy following the ERC1967 standard, allowing for future upgrades and changes to the contract logic without affecting the deployed version.

    BitlayerBridge: Enables the locking and unlocking of native cryptocurrency transactions across different blockchain networks, with roles and permissions managed through AccessControl. It supports liquidity management, fee adjustments, and pausable functionality for emergency stops.

    Contracts

    TokenExchange

    • Functionalities:

      • Facilitates token swaps with ERC20 tokens using EIP712 signatures for permissioned operations.

      • Allows the withdrawal of ERC20 tokens and native cryptocurrency (referred to as "BTC" in comments) by the owner.

      • Supports owner and operator role management for executing sensitive contract operations.

      • Manages vaults that designate supported token addresses for swapping.

    • Attributes:

      • owner: Address of the contract owner.

      • operator: Address of the contract operator.

      • vaults: A mapping of addresses to boolean values, indicating whether a token address is supported for swaps.

    • Privileged Roles:

      • owner: Can transfer ownership, set the operator, manage vaults, and withdraw tokens.

      • operator: Can execute the permitAndSwap function.

    BitlayerProxy

    • Functionalities: Serves as a minimalistic instance of the ERC1967Proxy, primarily for deployment purposes without additional specific functionalities.

    BitlayerBridge

    • Functionalities:

      • Manages cross-chain transactions with functionality to lock and unlock native cryptocurrency.

      • Handles liquidity contributions and withdrawals, enabling users to support the bridge's operations with their assets.

      • Allows role-based management for pausing and unpausing contract operations, setting fee addresses, and adjusting fees.

    • Attributes:

      • feeAddress: Address where transaction fees are collected.

      • lockFeeAmount: The amount charged as a fee for locking transactions.

      • liquidityOf: Mapping of addresses to their contributed liquidity amounts.

      • totalLocked: Total amount of cryptocurrency locked through the bridge.

      • totalUnlocked: Total amount of cryptocurrency unlocked.

    • Privileged Roles:

      • AdminRole: Can upgrade the contract, manage roles, pause/unpause the bridge, and adjust fees and the fee address.

      • PauseRole: Can pause contract operations.

      • UnlockRole: Can unlock transactions, allowing the withdrawal of locked funds.

      • LiquidityRole: Can manage liquidity withdrawals on behalf of others.

    Executive Summary

    Documentation quality

    The total Documentation Quality score is 7 out of 10.

    • Functional requirements are partially missed.

    • Technical description is not provided.

    • Technical flow is not provided.

    Code quality

    The total Code Quality score is 9 out of 10.

    • Missing best practices

    • The development environment is configured.

    Test coverage

    Code coverage of the project is 86.36% (branch coverage),

    • Not all branches are covered with tests.

    Security score

    Upon auditing, the code was found to contain 0 critical, 0 high, 1 medium, and 3 low severity issues. After remediation part of the audit process 1 medium issue was mitigated, 2 low issues were fixed and 1 low issue was accepted, leading to a security 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 9. This score reflects the combined evaluation of documentation, code quality, test coverage, and security aspects of the project.

    Scoring Methodologyarrow right

    Risks

    Authorized used can call unlock function anytime to get balances in the contract..

    Solidity version 0.8.20 might not work on all chains due to PUSH0 opcode.

    There is no upper limit set for lockFeeAmount, allowing the admin to assign any valid integer value to it.

    Findings

    Code
    ―
    Title
    Status
    Severity
    F-2024-1925Missing return value check on permit function
    mitigated

    Medium
    F-2024-1957Missing two-step ownership transfer process
    accepted

    Low
    F-2024-1956Missing lock limitations
    fixed

    Low
    F-2024-1915Missing checks for the zero address
    fixed

    Low
    F-2024-1984Unnecessary payable usage
    fixed

    Observation
    F-2024-1930Possible Gas optimization by using unchecked subtractions
    fixed

    Observation
    F-2024-1929Unneeded initializations of uint256 and bool variable to 0/false
    fixed

    Observation
    F-2024-1927Avoid using state variables directly in emit for Gas efficiency
    fixed

    Observation
    F-2024-1926Missing array length cache in for loop
    fixed

    Observation
    F-2024-1924Typos in the code
    accepted

    Observation
    1-10 of 12 findings

    Identify vulnerabilities in your smart contracts.

    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:

    Scope Details

    Repositoryhttps://github.com/bitlayer-org/bitlayer-bridge→
    Commit41c7c064117218eef147f4ae7e7052708846273d
    Remediation1f2b25eb3d7f8afef937bdd57be188fbe063abb3
    Repositoryhttps://github.com/bitlayer-org/getBTC→
    Commit345036b3d5ce868347e5c46ab8a6fe2a071d78df
    Remediation752b04b9b2856cc5f187c2190a07b0a26cf0cead
    WhitepaperNot provided
    RequirementsNot provided
    Technical RequirementsNot provided

    Contracts in Scope

    contracts
    TokenExchange.sol - contracts › TokenExchange.sol
    BitlayerProxy.sol - contracts › BitlayerProxy.sol
    BitlayerBridge.sol - contracts › BitlayerBridge.sol

    Disclaimer

    Bitlayer audit by Hacken