ZenRockLabs engaged Halborn to conduct a security assessment on their smart contracts beginning on 04-12-2024 and ending on 04-19-2024. The security assessment was scoped to the smart contracts provided in the https://github.com/zenrocklabs/zr-sign GitHub repository. Commit hashes and further details can be found in the Scope section of this report.

2. Assessment Summary

Halborn was provided 1 week for the engagement and assigned 1 full-time security engineer to review the security of the smart contracts in scope. The engineer is a blockchain and smart contract security expert with advanced penetration testing and smart contract hacking skills, and deep knowledge of multiple blockchain protocols.

The purpose of the assessment is to:

Identify potential security issues within the smart contracts.
Ensure that smart contract functionality operates as intended.

In summary, Halborn identified some improvements to reduce the likelihood and impact of risks, which were mostly addressed by the Zenrock Labs team.

The main identified issues were:

Response functions can be called during contract's paused state, allowing to continue contract operations.
Lack of match identification between response function caller and recovered address.
Lack of storage verification allows for duplicated public keys.

3. Test Approach and Methodology

Halborn performed a combination of manual and automated security testing to balance efficiency, timeliness, practicality, and accuracy in regard to the scope of this assessment. While manual testing is recommended to uncover flaws in logic, process, and implementation; automated testing techniques help enhance coverage of the contracts' solidity code 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 architecture and purpose.
Smart contract manual code review and walk-through.
Manual assessment of use and safety for the critical Solidity variables and functions in scope to identify any arithmetic-related vulnerability classes.
Manual testing with custom scripts (Foundry).
Static Analysis of security for scoped contract, and imported functions.

3.1 Out-of-scope

External libraries and financial-related attacks.
New features/implementations after/within the remediation commit IDs.

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: zr-sign

(b) Assessed Commit ID: 6c40093

contracts/proxy/ZrProxy.sol
contracts/zr/Sign.sol
contracts/zr/ZrSign.sol

Out-of-Scope: contracts/AccessControl.sol, contracts/Context.sol, contracts/ERC165.sol, contracts/Initializable.sol, contracts/Migrations.sol, contracts/Pausable.sol, contracts/proxy/ERC1967Proxy.sol, contracts/proxy/ERC1967Upgrade.sol, contracts/proxy/Proxy.sol

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
Lack of storage verification allows for duplicated public keys	Low	Solved - 05/01/2024
Missing threshold verification for fees	Low	Risk Accepted
Lack of input validation for destination chain id may allow for requests to invalid chains	Low	Risk Accepted
Response functions can be called during contract's paused state allowing to continue contract operations	Low	Solved - 05/01/2024
Lack of match identification between response functions caller and recovered address	Low	Risk Accepted
Missing traceId verification in signature resolve function	Low	Solved - 05/06/2024
Contract may emit multiple resolving events for the same data	Low	Solved - 05/01/2024
Insufficient public key validation	Low	Risk Accepted
Improper contract naming conventions in upgradeable OpenZeppelin inheritance	Informational	Solved - 05/01/2024
Missing namespace NatSpec tag for ERC-7201	Informational	Solved - 05/01/2024
PUSH0 is not supported by all chains	Informational	Solved - 05/01/2024
Transfer with hardcoded gas amount	Informational	Solved - 05/01/2024
Unused `SRC_WALLET_TYPE_ID` constant declaration	Informational	Acknowledged
Public functions not called within the contract can be made external	Informational	Acknowledged
Lack of verification for config functions input values	Informational	Acknowledged
Unnecessary payable modifier in `withdrawFees()`	Informational	Solved - 05/01/2024
Typo in function name	Informational	Solved - 05/01/2024
Misleading error name	Informational	Solved - 05/01/2024
Unnecessary storage access	Informational	Solved - 05/01/2024
Missing initialization function for AccessControl	Informational	Solved - 05/01/2024

7. Findings & Tech Details

7.1 Lack of storage verification allows for duplicated public keys

Low

Description

Proof of Concept

BVSS

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

Recommendation

References

Sign.sol#L437-L469

7.2 Missing threshold verification for fees

Low

Description

BVSS

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

Recommendation

References

ZrSign.sol#L90-L94

ZrSign.sol#L102-L106

7.3 Lack of input validation for destination chain id may allow for requests to invalid chains

Low

Description

BVSS

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

Recommendation

References

Sign.sol#L483-L511

7.4 Response functions can be called during contract's paused state allowing to continue contract operations

Low

Description

Proof of Concept

BVSS

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

Recommendation

References

Sign.sol#L145-L149

Sign.sol#L277-L279

7.5 Lack of match identification between response functions caller and recovered address

Low

Description

BVSS

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

Recommendation

References

Sign.sol#L553-L566

7.6 Missing traceId verification in signature resolve function

Low

Description

BVSS

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

Recommendation

References

Sign.sol#L525-L537

7.7 Contract may emit multiple resolving events for the same data

Low

BVSS

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

Recommendation

References

ZrProxy.sol#L6

References

Sign.sol#L289

Sign.sol#L384

7.15 Lack of verification for config functions input values

Informational

Description

BVSS

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

Recommendation

Recommendation

References

Sign.sol#L120-L123

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

3.1 Out-of-scope

4. Risk methodology
5. Scope
6. Assessment summary & findings overview
7. Findings & Tech Details

7.1 Lack of storage verification allows for duplicated public keys
7.2 Missing threshold verification for fees
7.3 Lack of input validation for destination chain id may allow for requests to invalid chains
7.4 Response functions can be called during contract's paused state allowing to continue contract operations
7.5 Lack of match identification between response functions caller and recovered address
7.6 Missing traceid verification in signature resolve function
7.7 Contract may emit multiple resolving events for the same data
7.8 Insufficient public key validation
7.9 Improper contract naming conventions in upgradeable openzeppelin inheritance
7.10 Missing namespace natspec tag for erc-7201
7.11 Push0 is not supported by all chains
7.12 Transfer with hardcoded gas amount
7.13 Unused `src_wallet_type_id` constant declaration
7.14 Public functions not called within the contract can be made external
7.15 Lack of verification for config functions input values
7.16 Unnecessary payable modifier in `withdrawfees()`
7.17 Typo in function name
7.18 Misleading error name
7.19 Unnecessary storage access
7.20 Missing initialization function for accesscontrol

Zr-sign

Zenrock Laboratories

Table of Contents

1. Introduction

2. Assessment Summary

3. Test Approach and Methodology

3.1 Out-of-scope

4. RISK METHODOLOGY

4.1 EXPLOITABILITY

Attack Origin (AO):

Attack Cost (AC):

Attack Complexity (AX):

Metrics:

4.2 IMPACT

Confidentiality (C):

Integrity (I):

Availability (A):

Deposit (D):

Yield (Y):

Metrics:

4.3 SEVERITY COEFFICIENT

Reversibility (R):

Scope (S):

Metrics:

5. SCOPE

6. Assessment Summary & Findings Overview

7. Findings & Tech Details

7.1 Lack of storage verification allows for duplicated public keys

Description

Proof of Concept

BVSS

Recommendation

References

7.2 Missing threshold verification for fees

Description

BVSS

Recommendation

References

7.3 Lack of input validation for destination chain id may allow for requests to invalid chains

Description

BVSS

Recommendation

References

7.4 Response functions can be called during contract's paused state allowing to continue contract operations

Description

Proof of Concept

BVSS

Recommendation

References

7.5 Lack of match identification between response functions caller and recovered address

Description

BVSS

Recommendation

References

7.6 Missing traceId verification in signature resolve function

Description

BVSS

Recommendation

References

7.7 Contract may emit multiple resolving events for the same data

Description

Proof of Concept

BVSS

Recommendation

References

7.8 Insufficient public key validation

Description

BVSS

Recommendation

References

7.9 Improper contract naming conventions in upgradeable OpenZeppelin inheritance

Description

BVSS

Recommendation

References

7.10 Missing namespace NatSpec tag for ERC-7201

Description

BVSS

Recommendation

7.11 PUSH0 is not supported by all chains