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Threat Model Analysis for home-assistant/core

Threat: Configuration Tampering via File System Access

  • Description: An attacker with access to the file system (e.g., through a vulnerability in the host OS, or physical access) modifies the configuration.yaml file or other core configuration files. They could add malicious automations, disable security features, or inject arbitrary code that is then executed by core components.
    • Impact:
      • Complete control over Home Assistant's behavior through core functionality.
      • Disabling of core security features (e.g., authentication).
      • Execution of arbitrary code with the privileges of the Home Assistant process as part of core operations.
      • Data exfiltration facilitated by core components.
    • Core Component Affected: homeassistant.config (Configuration loading and validation), and any core component configured through the modified files (e.g., homeassistant.core itself, homeassistant.components.automation, etc.).
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Developer: Implement robust input validation for all configuration files, even those considered "internal." Consider using a more secure configuration format (e.g., a database with access controls and integrity checks). Provide mechanisms for detecting configuration tampering (e.g., checksums, digital signatures, or a configuration validation service). Strive to minimize the attack surface exposed through configuration.
      • User: Run Home Assistant in a containerized environment (e.g., Docker) with strictly limited file system access, using a non-root user. Regularly back up configuration files and verify their integrity. Implement file integrity monitoring (e.g., AIDE, Tripwire) on the host system, specifically targeting the Home Assistant configuration directory. Restrict access to the host system to the absolute minimum.

Threat: Denial of Service via Event Bus Overload

  • Description: An attacker (potentially internal, through a core component malfunction or a carefully crafted, but technically valid, sequence of events) floods the Home Assistant event bus with a large number of events, overwhelming the core event handling system and causing it to become unresponsive. This is distinct from an external DoS targeting network services.
    • Impact:
      • Home Assistant core becomes unresponsive and unable to process events, control devices, or execute automations.
      • Loss of monitoring and control capabilities due to core failure.
      • Potential for data loss if events are not persisted due to core overload.
    • Core Component Affected: homeassistant.core.EventBus (Event bus implementation), and all other core components that rely on the event bus (which is essentially all of them).
    • Risk Severity: High
    • Mitigation Strategies:
      • Developer: Implement robust rate limiting and throttling mechanisms within the EventBus itself. Provide mechanisms for identifying and isolating sources of excessive events originating from within the core. Optimize event handling to minimize resource consumption in the core event loop. Consider using asynchronous task queues and worker pools to handle events more efficiently, preventing a single slow component from blocking the entire system. Implement circuit breakers to prevent cascading failures.
      • User: While users have limited control over core event bus behavior, they should monitor system resource usage and logs for signs of overload. If a specific, core-related pattern consistently causes issues, report it to the Home Assistant developers.

Threat: State Tampering via Direct State Machine Manipulation

  • Description: An attacker with deep access to the running Home Assistant process (e.g., through a severe vulnerability that allows arbitrary code execution within the core process, not just within an integration) directly modifies the StateMachine object, bypassing normal event handling and validation. This is a very low-level attack, requiring significant compromise.
    • Impact:
      • False device states are injected directly into the core, bypassing all validation and security checks.
      • Inappropriate triggering of automations due to manipulated state.
      • Fundamental disruption of Home Assistant's operation, potentially leading to instability or crashes.
      • Potential for data corruption within the core state representation.
    • Core Component Affected: homeassistant.core.StateMachine (State machine implementation).
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Developer: Implement extremely strict access controls to the StateMachine object. Validate all state changes, even those originating from within the core, using a robust internal validation mechanism. Consider using memory protection techniques (if feasible within the Python environment) to prevent unauthorized modification of the state machine's data structures. Explore using a more secure, externally managed state store (e.g., a database with strong access controls and auditing) instead of relying solely on in-memory representation. Regularly conduct security audits of the core code, focusing on memory safety and access control.
      • User: This threat is primarily mitigated by developer actions. Users should ensure they are running Home Assistant in a secure environment (containerized, minimal privileges) to reduce the likelihood of an attacker gaining the level of access required for this attack. Keeping the system and all components updated is crucial.

Threat: Elevation of Privilege via Core Component Vulnerability

  • Description: An attacker exploits a vulnerability within a core Home Assistant component (e.g., a flaw in the homeassistant.core logic, the HTTP server, or the WebSocket API implementation itself) to gain elevated privileges within the context of the Home Assistant process. This is distinct from exploiting an integration. The vulnerability would allow bypassing core security checks or executing arbitrary code as part of the core's operation.
    • Impact:
      • Complete control over the Home Assistant core functionality.
      • Access to all data managed by the core.
      • Potential for further exploitation and lateral movement if the Home Assistant process has elevated privileges on the host system.
    • Core Component Affected: Varies depending on the specific vulnerability, but by definition, it would be a core component (e.g., homeassistant.core, homeassistant.components.http, homeassistant.components.websocket_api, homeassistant.config).
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Developer: Adhere to strict secure coding practices throughout the entire core codebase. Conduct regular security audits and penetration testing of core components. Implement robust input validation and sanitization for all data handled by core components. Use memory-safe programming techniques where possible. Minimize the attack surface by reducing unnecessary features and functionality in core components. Respond promptly to security reports and release updates. Consider using a security linter and static analysis tools to identify potential vulnerabilities.
      • User: Keep Home Assistant core updated to the latest version. Run Home Assistant in a secure environment (containerized, minimal privileges) to limit the impact of any potential vulnerabilities.