Shinkai Protocol - Shinkai

Prepared by:

HALBORN

Last Updated 07/15/2025

Date of Engagement: August 14th, 2024 - August 23rd, 2024

Summary

100% of all REPORTED Findings have been addressed

All findings

Critical

High

Medium

Low

Informational

1. Introduction
2. Assessment summary
3. Test approach and methodology
4. Risk methodology
5. Scope
6. Assessment summary & findings overview
7. Findings & Tech Details

7.1 Hardcoded limiter based on current number of blocks per year
7.2 Missing visibility modifier for the available namespaces
7.3 Lack of storage gap in upgradeable contract
7.4 Use of ownableupgradeable library with single-step ownership transfer
7.5 Consider using named mappings
7.6 Use of unlicensed smart contracts
7.7 Redundant reward accrual
7.8 Unlocked pragma compilers

8. Automated Testing

1. Introduction

The Shinkai team engaged Halborn to conduct a security assessment on their smart contracts beginning on 2024-08-14 and ending on 2024-08-23. The security assessment was scoped to the smart contracts provided in the GitHub repositories:

https://github.com/dcSpark/shinkai-contracts

Commit hashes and further details can be found in the Scope section of this report.

2. Assessment Summary

Halborn was provided one week and two days for the engagement and assigned one full-time security engineer to check the security of the smart contract. The security engineer is a blockchain and smart-contract security expert with advanced penetration testing, smart-contract hacking, and deep knowledge of multiple blockchain protocols.

The purpose of this assessment is to:

Ensure that smart contract functions operate as intended.
Identify potential security issues with the smart contracts.

In summary, Halborn identified several security concerns that were acknowledged by the Shinkai team.

3. Test Approach and Methodology

Halborn performed a combination of manual review of the code and automated security testing to balance efficiency, timeliness, practicality, and accuracy in regard to the scope of the smart contract assessment. While manual testing is recommended to uncover flaws in logic, process, and implementation; automated testing techniques help enhance coverage of smart contracts and can quickly identify items that do not follow security best practices. The following phases and associated tools were used throughout the term of the assessment:

Research into the architecture, purpose, and use of the platform.
Smart contract manual code review and walkthrough to identify any logic issue.
Thorough assessment of safety and usage of critical Solidity variables and functions in scope that could led to arithmetic related vulnerabilities.
Manual testing by custom scripts.
Graphing out functionality and contract logic/connectivity/functions (solgraph).
Static Analysis of security for scoped contract, and imported functions. (Slither).
Local or public testnet deployment (Foundry, Remix IDE).

4. RISK METHODOLOGY

Every vulnerability and issue observed by Halborn is ranked based on two sets of Metrics and a Severity Coefficient. This system is inspired by the industry standard Common Vulnerability Scoring System.

The two Metric sets are: Exploitability and Impact. Exploitability captures the ease and technical means by which vulnerabilities can be exploited and Impact describes the consequences of a successful exploit.

The Severity Coefficients is designed to further refine the accuracy of the ranking with two factors: Reversibility and Scope. These capture the impact of the vulnerability on the environment as well as the number of users and smart contracts affected.

The final score is a value between 0-10 rounded up to 1 decimal place and 10 corresponding to the highest security risk. This provides an objective and accurate rating of the severity of security vulnerabilities in smart contracts.

The system is designed to assist in identifying and prioritizing vulnerabilities based on their level of risk to address the most critical issues in a timely manner.

4.1 EXPLOITABILITY

Attack Origin (AO):

Captures whether the attack requires compromising a specific account.

Attack Cost (AC):

Captures the cost of exploiting the vulnerability incurred by the attacker relative to sending a single transaction on the relevant blockchain. Includes but is not limited to financial and computational cost.

Attack Complexity (AX):

Describes the conditions beyond the attacker’s control that must exist in order to exploit the vulnerability. Includes but is not limited to macro situation, available third-party liquidity and regulatory challenges.

Metrics:

EXPLOITABILITY METRIC ( $m_e$ )	METRIC VALUE	NUMERICAL VALUE
Attack Origin (AO)	Arbitrary (AO:A) Specific (AO:S)	1 0.2
Attack Cost (AC)	Low (AC:L) Medium (AC:M) High (AC:H)	1 0.67 0.33
Attack Complexity (AX)	Low (AX:L) Medium (AX:M) High (AX:H)	1 0.67 0.33

Exploitability

E

is calculated using the following formula:

$E = \prod m_e$

4.2 IMPACT

Confidentiality (C):

Measures the impact to the confidentiality of the information resources managed by the contract due to a successfully exploited vulnerability. Confidentiality refers to limiting access to authorized users only.

Integrity (I):

Measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of data stored and/or processed on-chain. Integrity impact directly affecting Deposit or Yield records is excluded.

Availability (A):

Measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability. This metric refers to smart contract features and functionality, not state. Availability impact directly affecting Deposit or Yield is excluded.

Deposit (D):

Measures the impact to the deposits made to the contract by either users or owners.

Yield (Y):

Measures the impact to the yield generated by the contract for either users or owners.

Metrics:

IMPACT METRIC ( $m_I$ )	METRIC VALUE	NUMERICAL VALUE
Confidentiality (C)	None (C:N) Low (C:L) Medium (C:M) High (C:H) Critical (C:C)	0 0.25 0.5 0.75 1
Integrity (I)	None (I:N) Low (I:L) Medium (I:M) High (I:H) Critical (I:C)	0 0.25 0.5 0.75 1
Availability (A)	None (A:N) Low (A:L) Medium (A:M) High (A:H) Critical (A:C)	0 0.25 0.5 0.75 1
Deposit (D)	None (D:N) Low (D:L) Medium (D:M) High (D:H) Critical (D:C)	0 0.25 0.5 0.75 1
Yield (Y)	None (Y:N) Low (Y:L) Medium (Y:M) High (Y:H) Critical (Y:C)	0 0.25 0.5 0.75 1

Impact

I

is calculated using the following formula:

$I = max(m_I) + \frac{\sum{m_I} - max(m_I)}{4}$

4.3 SEVERITY COEFFICIENT

Reversibility (R):

Describes the share of the exploited vulnerability effects that can be reversed. For upgradeable contracts, assume the contract private key is available.

Scope (S):

Captures whether a vulnerability in one vulnerable contract impacts resources in other contracts.

Metrics:

SEVERITY COEFFICIENT ( $C$ )	COEFFICIENT VALUE	NUMERICAL VALUE
Reversibility ( $r$ )	None (R:N) Partial (R:P) Full (R:F)	1 0.5 0.25
Scope ( $s$ )	Changed (S:C) Unchanged (S:U)	1.25 1

Severity Coefficient

C

is obtained by the following product:

$C = rs$

The Vulnerability Severity Score

S

is obtained by:

$S = min(10, EIC * 10)$

The score is rounded up to 1 decimal places.

Severity	Score Value Range
Critical	9 - 10
High	7 - 8.9
Medium	4.5 - 6.9
Low	2 - 4.4
Informational	0 - 1.9

5. SCOPE

REPOSITORY

(a) Repository: shinkai-contracts

(b) Assessed Commit ID: 52a83ce

src/RegistryControlled.sol
src/ShinkaiNft.sol
src/ShinkaiToken.sol

↓ Expand ↓

Out-of-Scope: Third party dependencies and economic attacks.

Out-of-Scope: New features/implementations after the remediation commit IDs.

6. Assessment Summary & Findings Overview

Critical

High

Medium

Low

Informational

Security analysis	Risk level	Remediation Date
Hardcoded Limiter Based on Current Number Of Blocks Per Year	Low	Risk Accepted - 07/14/2025
Missing Visibility Modifier For The Available Namespaces	Informational	Acknowledged - 07/14/2025
Lack Of Storage Gap In Upgradeable Contract	Informational	Acknowledged - 07/14/2025
Use Of OwnableUpgradeable Library With Single-Step Ownership Transfer	Informational	Acknowledged - 07/14/2025
Consider Using Named Mappings	Informational	Acknowledged - 07/14/2025
Use Of Unlicensed Smart Contracts	Informational	Acknowledged - 07/14/2025
Redundant Reward Accrual	Informational	Acknowledged - 07/14/2025
Unlocked Pragma Compilers	Informational	Acknowledged - 07/14/2025

7. Findings & Tech Details

7.1 Hardcoded Limiter Based on Current Number Of Blocks Per Year

Low

Description

BVSS

AO:A/AC:L/AX:L/C:N/I:L/A:N/D:N/Y:N/R:N/S:U (2.5)

Recommendation

Remediation Comment

References

["https://github.com/dcSpark/shinkai-contracts/blob/52a83ce548eac47022b61f7aed23bfaa3e640c7d/src/ShinkaiRegistry.sol#L15"]

7.2 Missing Visibility Modifier For The Available Namespaces

Informational

Description

BVSS

AO:A/AC:L/AX:M/C:N/I:L/A:N/D:N/Y:N/R:N/S:U (1.7)

Recommendation

Remediation Comment

Recommendation

Remediation Comment

References

["https://github.com/dcSpark/shinkai-contracts/blob/52a83ce548eac47022b61f7aed23bfaa3e640c7d/src/ShinkaiRegistry.sol#L427"]

7.8 Unlocked Pragma Compilers

Informational

Description

BVSS

AO:A/AC:L/AX:L/C:N/I:N/A:N/D:N/Y:N/R:N/S:U (0.0)

Recommendation

Remediation Comment

8. Automated Testing

Halborn strongly recommends conducting a follow-up assessment of the project either within six months or immediately following any material changes to the codebase, whichever comes first. This approach is crucial for maintaining the project’s integrity and addressing potential vulnerabilities introduced by code modifications.

1. Introduction
2. Assessment summary
3. Test approach and methodology
4. Risk methodology
5. Scope
6. Assessment summary & findings overview
7. Findings & Tech Details

7.1 Hardcoded limiter based on current number of blocks per year
7.2 Missing visibility modifier for the available namespaces
7.3 Lack of storage gap in upgradeable contract
7.4 Use of ownableupgradeable library with single-step ownership transfer
7.5 Consider using named mappings
7.6 Use of unlicensed smart contracts
7.7 Redundant reward accrual
7.8 Unlocked pragma compilers