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Fuelet Wallet iOS App - Fuelet

Prepared by:

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HALBORN

Last Updated 01/15/2025

Date of Engagement: September 12th, 2024 - September 25th, 2024

Summary

100% of all REPORTED Findings have been addressed

All findings

3

Critical

0

High

0

Medium

1

Low

1

Informational

1

Table of Contents

1. Introduction

Fuelet engaged Halborn to conduct a security assessment of their Fuelet wallet iOS mobile application, which began on September 12th, 2024 and ended on September 25th, 2024. The security assessment was scoped to the Fuelet wallet iOS mobile application. The client team provided both the source code and the respective IPA file to allow the security engineers to conduct testing using tools for scanning, detecting, and validating possible vulnerabilities, and to report the findings at the end of the engagement.

2. Assessment Summary

The team at Halborn was provided a timeline for the engagement and assigned two full-time security engineers to verify the security of the assets in scope. The security engineers are penetration testing experts with advanced knowledge in web, mobile (Android and iOS), reconnaissance, blockchain and infrastructure penetration testing.

The goals of our security assessments are to improve the quality of the systems we review and to target sufficient remediation to help protect users.

The security assessment of the application revealed that the application lacks essential security controls such as jailbreak detection and anti-debugging mechanisms, making it vulnerable to manipulation, reverse engineering, and code tampering. The absence of an authentication check on application start further exposes the app to unauthorized access, allowing attackers to bypass security protocols easily.

To address these issues, it is imperative to implement robust mechanisms to detect and respond to compromised environments, such as jailbreaks and debugging attempts. Introducing mandatory authentication checks upon app startup will also enhance access control and protect user data from unauthorized access. These measures are crucial to mitigating security risks, protecting user information, and maintaining the overall trust and integrity of the application.

For public release, this report was redacted per Fuelet request to exclude certain critical issues. It should be noted that all removed critical issues were fully addressed and resolved by the Fuelet team prior to the report's publication

Scope

The security assessment was scoped to:

3. Test Approach and Methodology

Halborn performed a combination of manual and automated security testing to balance efficiency, timeliness, practicality, and accuracy regarding the scope of the pentest. While manual testing is recommended to uncover flaws in logic, process and implementation; automated testing techniques assist enhance coverage of the infrastructure and can quickly identify flaws in it.

The following phases and associated tools were used throughout the term of the assessment:

    • Storing private keys and assets securely

    • Send/Receive tokens and assets securely to another wallet

    • Any attack that impacts funds, such as draining or manipulating of funds

    • Application logic flaws

    • Areas where insufficient validation allows for hostile input

    • Application of cryptography to protect secrets

    • Brute-force attempts

    • Input handling

    • Source code review

    • Fuzzing of all input parameters

    • Technology stack-specific vulnerabilities and code assessment

    • Known vulnerabilities in 3rd party/OSS dependencies


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 (mem_e)METRIC VALUENUMERICAL 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 EE is calculated using the following formula:

E=∏meE = \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 (mIm_I)METRIC VALUENUMERICAL VALUE
Confidentiality (C)None (I:N)
Low (I:L)
Medium (I:M)
High (I:H)
Critical (I: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 II is calculated using the following formula:

I=max(mI)+∑mI−max(mI)4I = 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 (CC)COEFFICIENT VALUENUMERICAL VALUE
Reversibility (rr)None (R:N)
Partial (R:P)
Full (R:F)		1
0.5
0.25
Scope (ss)Changed (S:C)
Unchanged (S:U)		1.25
1
Severity Coefficient CC is obtained by the following product:

C=rsC = rs

The Vulnerability Severity Score SS is obtained by:

S=min(10,EIC∗10)S = min(10, EIC * 10)

The score is rounded up to 1 decimal places.
SeverityScore Value Range
Critical9 - 10
High7 - 8.9
Medium4.5 - 6.9
Low2 - 4.4
Informational0 - 1.9

5. SCOPE

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

6. Assessment Summary & Findings Overview

Critical

0

High

0

Medium

1

Low

1

Informational

1

Security analysisRisk levelRemediation Date
Missing Jailbreak DetectionMediumRisk Accepted - 12/06/2024
Lack of Anti-Debugging MechanismsLowRisk Accepted - 12/06/2024
Missing Authentication Check on Application StartInformationalAcknowledged - 12/06/2024

7. Findings & Tech Details

7.1 Missing Jailbreak Detection

//

Medium

Description

Jailbreaking is the process of removing iOS restrictions imposed by Apple, allowing users (and attackers) to gain root access to the device's file system and system functions. This enables the installation of unauthorized apps, access to restricted areas of the file system, and modifications to system security settings. Without proper jailbreak detection, the application is at risk of being run in a compromised environment, which significantly increases the likelihood of unauthorized access, tampering, data theft, and other malicious activities.

Proof of Concept
Jailbreak device with Fuelet application in execution
Score
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:N(4.7)
Recommendation

  • File System Checks: Validate the presence of files and directories commonly associated with jailbreaking, such as /Applications/Cydia.app, /bin/bash, /usr/sbin/sshd, and others.

  • Sandbox Integrity Checks: confirm whether the app can break out of its sandbox, which is usually not allowed on non-jailbroken devices.

  • Runtime Behavioral Checks: Detect suspicious runtime behavior, such as the presence of known jailbreak-related processes, dynamic libraries (e.g., MobileSubstrate), or elevated privileges.

  • Privileged API Detection: Check if the app can access restricted APIs or perform operations that are normally blocked on non-jailbroken devices.

  • Symbolic Link Checks: Detect symbolic links that are commonly used in jailbroken environments to modify the file system.

Remediation

RISK ACCEPTED: The Fuelet team accepted the risk derived from this issue.

7.2 Lack of Anti-Debugging Mechanisms

//

Low

Description

The absence of anti-debugging mechanisms in an application represents a significant security vulnerability. Anti-debugging techniques are employed to detect or prevent the use of debugging tools, such as Frida, GDB, LLDB, or other dynamic analysis tools, by attackers or reverse engineers. When these mechanisms are not implemented, it leaves the application vulnerable to manipulation, unauthorized code analysis, reverse engineering, and the extraction of sensitive data, such as encryption keys, credentials, or intellectual property.

Proof of Concept
Fuelet application with Objection attached.
Score
CVSS:3.1/AV:P/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:N(2.7)
Recommendation

  • Debugger Detection: Check for the presence of a debugger using system APIs or specific instructions that behave differently when run under a debugger.

  • Code Obfuscation: Rename functions and variables, adding bogus code paths, or using encryption for sensitive parts of the code.

  • Timing Checks: Validate the time taken by critical sections of code to execute. Debugging usually slows down code execution, and significant timing discrepancies can indicate debugging activity.

  • Environment Checks: Check for known debugging environments, such as checking for known emulator or debugger process names, unusual device states, or modified system libraries.

Remediation

RISK ACCEPTED: The Fuelet team accepted the risk derived from this issue.

7.3 Missing Authentication Check on Application Start

//

Informational

Description

When switching between applications, the Fuelet application did not lock the wallet to re-ask for the PIN or fingerprint when accessing it again after the application resumed from background.

Such a security measure would provide security in depth. In the case of a stolen phone with the application remaining opened in the background, the thief having access to the screen could view the list of applications opened, re-access the Fuelet wallet and attempt to steal the funds.

Proof of Concept

Put the application in the background, open another application and switch back to the Fuelet application. No prompt will appear asking for a fingerprint check or PIN verification.

Score
CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:N(0.0)
Recommendation

  • Implement a lockout mechanism when switching to another application.

  • Ask for a PIN or fingerprint check when accessing it again.

Remediation

ACKNOWLEDGED: The Fuelet team acknowledged the risks associated with this issue.

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.

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