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attack-surface.md

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Attack Surface Analysis for home-assistant/core

Attack Surface: Malicious/Vulnerable Integrations (Core Execution Framework)

  • Description: The core provides the execution environment and system access for integrations, making it directly responsible for managing the risks they introduce.
  • How Core Contributes: The core's architecture defines how integrations are loaded, executed, and interact with the system (event bus, state machine, services). It's the core's responsibility to provide isolation and security mechanisms.
  • Example: A malicious integration, loaded and executed by the core, uses the core-provided API to access sensitive data or control devices without proper authorization.
  • Impact: Complete system compromise, data exfiltration, unauthorized device control, denial of service.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • (Developers): Implement robust code review processes for official integrations. Provide clear security guidelines and best practices for community developers. Crucially, explore sandboxing or containerization of integrations to limit their access to the core and other integrations. Implement dependency vulnerability scanning. Improve the core's ability to restrict integration permissions.
    • (Users): Carefully vet integrations. Regularly update integrations. Consider running less-trusted integrations on a separate instance. (User mitigation is limited because the core's architecture is the fundamental issue).

Attack Surface: Integration Dependency Vulnerabilities (Core's Python Environment)

  • Description: The core's Python runtime environment and its handling of integration dependencies create a supply-chain risk.
  • How Core Contributes: The core establishes the Python environment in which integrations (and their dependencies) run. The core's update mechanism and dependency management practices directly impact this risk.
  • Example: An integration uses an outdated library with a known vulnerability. The core's environment allows this vulnerable library to be loaded and exploited.
  • Impact: System compromise, data theft, device manipulation (similar to direct integration vulnerabilities).
  • Risk Severity: High
  • Mitigation Strategies:
    • (Developers): Implement automated dependency vulnerability scanning and updates within the core build process. Enforce stricter dependency management policies for integrations, potentially including a curated list of approved libraries or a mechanism for verifying library integrity. Consider providing a way to isolate integration dependencies from each other and from the core.
    • (Users): Regularly update Home Assistant and all integrations. (User mitigation is limited; the core's handling of dependencies is the key).

Attack Surface: Event Bus Manipulation (Core Communication Mechanism)

  • Description: The core's central event bus, essential for internal communication, is vulnerable to injection and flooding attacks.
  • How Core Contributes: The event bus is a fundamental part of the core architecture. Its design and implementation are entirely within the core's control.
  • Example: An attacker injects events that the core processes, leading to unintended device actions or system instability.
  • Impact: Denial of service, unauthorized device control, system instability.
  • Risk Severity: High
  • Mitigation Strategies:
    • (Developers): Implement strict input validation for all events processed by the core. Implement rate limiting on event processing. Introduce access control mechanisms to restrict which components (including integrations) can publish specific event types. Explore event signing or authentication to verify the origin of events within the core.
    • (Users): Monitor event logs (limited effectiveness; the core needs to provide better protection).

Attack Surface: API and Web Interface Exploits (Core Interaction Points)

  • Description: The core's REST API and web interface are primary attack vectors, and their security is entirely the core's responsibility.
  • How Core Contributes: The core implements the API and web interface. Any vulnerabilities in their code, authentication, or authorization are direct core vulnerabilities.
  • Example: An authentication bypass in the core's API code allows an attacker to gain unauthorized access. A CSRF vulnerability in the core's web interface allows an attacker to perform actions on behalf of a logged-in user.
  • Impact: Complete system compromise, data exfiltration, unauthorized device control.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • (Developers): Adhere rigorously to secure coding practices (OWASP). Implement robust, multi-layered authentication and authorization. Conduct regular security audits and penetration testing specifically targeting the core's API and web interface code. Ensure proper handling of websockets and prevent common websocket vulnerabilities. Implement robust input validation and output encoding.
    • (Users): Use strong passwords, enable 2FA, keep Home Assistant updated. (User mitigation is secondary; the core's implementation is paramount).

Attack Surface: Insecure Configuration Handling (Core YAML Processing)

  • Description: While YAML itself isn't the vulnerability, the core's handling of YAML configuration and its potential for misconfiguration or secret exposure is a core-related risk.
  • How Core Contributes: The core parses and interprets the YAML configuration, and it's the core's responsibility to handle secrets securely and to validate configuration options.
  • Example: The core fails to properly sanitize user-provided input that is used to construct a YAML file, leading to YAML injection. The core doesn't adequately warn users about insecure configuration practices.
  • Impact: Credential theft, unauthorized access, system compromise, potential for code execution (in the case of YAML injection).
  • Risk Severity: High
  • Mitigation Strategies: 
    • **(Developers):** Implement robust YAML parsing with strict validation to prevent YAML injection. Provide clear and prominent warnings about insecure configuration practices *within the core's UI and documentation*. Enforce the use of `secrets.yaml` or other secure storage mechanisms. Improve the core's configuration validation to catch common errors.

    • **(Users):** Always use `secrets.yaml`. Carefully review configuration. (User actions are important, but the core needs to provide better safeguards).