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attack-surface.md

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Attack Surface Analysis for tiann/kernelsu

Attack Surface: Malicious Kernel Module Loading

  • Description: The ability to load arbitrary kernel modules is a fundamental feature of KernelSU, but it also presents the most significant risk. Malicious or vulnerable modules can compromise the entire system.
  • How KernelSU Contributes: KernelSU directly enables the loading of kernel modules, bypassing standard Android restrictions.
  • Example: An attacker distributes a seemingly benign module (e.g., a "battery optimizer") that contains hidden code to exfiltrate data or disable security features. A user installs this module via KernelSU.
  • Impact: Complete system compromise, data theft, denial of service, permanent device bricking.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Developer:
      • Implement strict module verification using code signing and cryptographic hashes. Maintain a whitelist of approved modules and/or a blacklist of known malicious ones.
      • Design modules with the principle of least privilege, minimizing their access to kernel resources.
      • Conduct thorough security audits and penetration testing of all modules.
      • Provide a secure and verifiable update mechanism for modules.
      • Explore (if feasible) sandboxing techniques for modules, although this is extremely challenging at the kernel level.
    • User:
      • Only install modules from trusted sources. Avoid modules from unknown developers or unofficial repositories.
      • Carefully review the permissions requested by a module before installing it.
      • Keep KernelSU and all modules updated to the latest versions.
      • Use a security solution that can detect malicious kernel modules (if available).

Attack Surface: KernelSU Manager Application Compromise

  • Description: The KernelSU manager application is the gatekeeper for root access and module management. If compromised, an attacker gains full control over KernelSU's functionality.
  • How KernelSU Contributes: The manager application is a necessary component of KernelSU, providing the user interface and controlling access to the kernel module.
  • Example: An attacker exploits a buffer overflow vulnerability in the KernelSU manager application to gain code execution, allowing them to load malicious modules or grant root access to arbitrary applications.
  • Impact: Complete system compromise, equivalent to malicious module loading.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Developer:
      • Adhere to secure coding practices (input validation, output encoding, memory safety, etc.) when developing the manager application.
      • Minimize the attack surface of the manager by exposing only essential functionality.
      • Implement robust input sanitization and validation to prevent injection attacks.
      • Regularly conduct security audits and penetration testing of the manager application.
      • Implement tamper detection and prevention mechanisms.
      • Provide a secure update mechanism for the manager application.
    • User:
      • Only install the KernelSU manager from the official source (e.g., the official GitHub repository).
      • Keep the manager application updated to the latest version.
      • Be cautious of any applications requesting unusual permissions that might interact with the KernelSU manager.

Attack Surface: Overly Permissive or Unintended Root Access Grants

  • Description: KernelSU allows granting root access to applications. If an application is granted root unnecessarily or with excessive privileges, a compromise of that application leads to a root compromise.
  • How KernelSU Contributes: KernelSU provides the mechanism for granting root access, and its configuration determines which applications receive it.
  • Example: A user grants root access to a seemingly harmless game, but the game contains a hidden vulnerability. An attacker exploits this vulnerability to gain root access via the game.
  • Impact: System compromise, data theft, privilege escalation.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developer:
      • Design applications to avoid requiring root access whenever possible.
      • If root access is absolutely necessary, request only the minimum required permissions.
      • Clearly document the reasons for requiring root access and the specific permissions needed.
    • User:
      • Exercise extreme caution when granting root access to applications. Only grant root to applications you absolutely trust and that have a clear and legitimate need for it.
      • Regularly review the list of applications with root access and revoke access for any that no longer need it.
      • Understand the risks associated with granting root access.

Attack Surface: Bypass of KernelSU's Access Control Mechanisms

  • Description: Vulnerabilities in KernelSU's internal logic for granting or denying root access could allow malicious applications to bypass these controls.
  • How KernelSU Contributes: KernelSU's core functionality is access control for root privileges; a flaw here directly undermines its purpose.
  • Example: An attacker discovers a race condition in KernelSU's permission checking logic, allowing their application to gain root access before the check is completed.
  • Impact: Unauthorized root access, system compromise.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developer:
      • Thoroughly review and test the access control logic in both the KernelSU manager and the kernel module.
      • Use formal verification techniques (if feasible) to prove the correctness of the access control mechanisms.
      • Implement multiple, independent layers of access control checks.
      • Regularly audit the code for potential bypass vulnerabilities.
    • User:
      • Keep KernelSU updated to the latest version to receive security patches.
      • There is limited direct user mitigation for this beyond keeping the software updated.

Attack Surface: Vulnerable Update Mechanism

  • Description: A compromised update mechanism for KernelSU or its modules could allow attackers to distribute malicious code.
  • How KernelSU Contributes: KernelSU relies on an update mechanism to deliver new features and security patches.
  • Example: An attacker compromises the KernelSU update server and replaces the legitimate KernelSU manager with a malicious version.
  • Impact: Widespread system compromise of devices using KernelSU.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developer:
      • Implement a secure update mechanism using code signing, cryptographic hashes, and HTTPS.
      • Protect the update server with strong security measures.
      • Regularly audit the update mechanism for vulnerabilities.
    • User:
      • Only install updates from the official KernelSU source.
      • Verify the integrity of downloaded updates (if possible) before installing them.