threat-modeling.md

Threat Model Analysis for stjohnjohnson/smartthings-mqtt-bridge

Threat: Credential Compromise (SmartThings API Keys/OAuth Tokens)

• Threat: Credential Compromise (SmartThings API Keys/OAuth Tokens)
• Description: An attacker compromises the server running smartthings-mqtt-bridge and extracts the stored SmartThings API keys or OAuth tokens. This can be done by exploiting vulnerabilities in the server or smartthings-mqtt-bridge itself, or through social engineering or physical access. With these credentials, the attacker can directly access the SmartThings API, bypassing MQTT and gaining full control over SmartThings devices.
• Impact:
  • Full, unauthorized control over all SmartThings devices connected to the compromised account via the SmartThings API.
  • Potential access to personal information associated with the SmartThings account.
  • Privacy breach and potential physical security risks through manipulation of smart home devices (e.g., unlocking doors, disabling security systems).
• Affected Component:
  • smartthings-mqtt-bridge configuration module (where credentials are loaded and potentially stored in memory).
  • Server's file system or environment where smartthings-mqtt-bridge configuration is stored.
• Risk Severity: High
• Mitigation Strategies:
  • Secure Credential Storage: Implement robust methods for storing SmartThings API keys and OAuth tokens, such as using environment variables with restricted access, encrypted configuration files, or dedicated secret management systems. Avoid storing credentials in plaintext in configuration files.
  • Principle of Least Privilege: Run smartthings-mqtt-bridge with minimal necessary privileges. Secure the server operating system and restrict access to configuration files.
  • Regular Security Audits: Periodically audit the security of the server and credential storage mechanisms.
  • Input Validation (Configuration): Ensure smartthings-mqtt-bridge properly handles and validates configuration inputs to prevent injection vulnerabilities that could lead to credential exposure.

Threat: Credential Compromise (MQTT Broker Credentials)

• Threat: Credential Compromise (MQTT Broker Credentials)
• Description: An attacker compromises the server running smartthings-mqtt-bridge and extracts the MQTT broker credentials (username, password, client certificates) used by the bridge to connect to the MQTT broker. This could be achieved through similar methods as described in Threat 1. Compromised MQTT credentials allow the attacker to connect to the MQTT broker and potentially control devices and monitor data.
• Impact:
  • Unauthorized access to all MQTT messages flowing through the broker, including sensitive smart home data published by smartthings-mqtt-bridge.
  • Ability to publish malicious MQTT messages via the compromised credentials, potentially controlling smart home devices connected via MQTT and managed by the bridge.
  • Potential for denial of service by disrupting MQTT broker services or flooding it with messages.
• Affected Component:
  • smartthings-mqtt-bridge configuration module (where MQTT credentials are loaded and potentially stored in memory).
  • Server's file system or environment where smartthings-mqtt-bridge configuration is stored.
• Risk Severity: High
• Mitigation Strategies:
  • Secure Credential Storage: Employ secure storage methods for MQTT broker credentials, similar to SmartThings API keys (environment variables, encrypted files, secret management).
  • Strong Credentials: Use strong, unique passwords for MQTT broker authentication. Consider using client certificates for mutual TLS authentication for enhanced security.
  • Principle of Least Privilege (MQTT Broker User): Grant the MQTT user used by smartthings-mqtt-bridge only the necessary permissions (publish/subscribe to specific topics) on the MQTT broker.
  • Regular Security Audits: Review MQTT broker access logs and security configurations periodically.

Threat: Insecure Storage of Credentials

• Threat: Insecure Storage of Credentials
• Description: smartthings-mqtt-bridge is configured or designed in a way that leads to storing SmartThings API keys or MQTT broker credentials in plaintext within configuration files or easily accessible environment variables. This makes credential theft trivial if an attacker gains even basic access to the server's file system or environment. This is a direct misconfiguration or vulnerability in how the bridge is set up or designed to handle secrets.
• Impact:
  • Credential compromise for SmartThings API and/or MQTT broker, leading to impacts described in Threat 1 and Threat 2. This is a direct enabler for those higher-level threats.
• Affected Component:
  • smartthings-mqtt-bridge configuration loading and handling module.
  • Default configuration practices or documentation of smartthings-mqtt-bridge that might encourage insecure storage.
• Risk Severity: Critical
• Mitigation Strategies:
  • Avoid Plaintext Storage: Ensure smartthings-mqtt-bridge documentation and configuration examples explicitly discourage plaintext credential storage.
  • Enforce Secure Configuration Practices: Provide clear guidance and examples on how to use secure credential storage methods (environment variables, encrypted files, secret management) in smartthings-mqtt-bridge documentation.
  • Configuration Validation: Ideally, smartthings-mqtt-bridge could include checks during startup to warn or prevent execution if it detects potentially insecure credential storage (e.g., plaintext in config files).

Threat: MQTT Broker Exposure (in context of bridge usage)

• Threat: MQTT Broker Exposure
• Description: While not a vulnerability in smartthings-mqtt-bridge code, if the MQTT broker used by smartthings-mqtt-bridge is misconfigured and directly exposed to the internet without proper security measures, it becomes a critical threat in the context of using the bridge. Attackers can bypass the bridge server and directly interact with the MQTT broker.
• Impact:
  • Unauthorized access to smart home data flowing through the MQTT broker, including data originating from smartthings-mqtt-bridge.
  • Unauthorized control of smart home devices via MQTT publishing, potentially affecting devices managed through smartthings-mqtt-bridge.
  • Denial of service of the MQTT broker, disrupting the functionality of smartthings-mqtt-bridge and connected smart home systems.
• Affected Component:
  • MQTT Broker configuration and network setup, which is a dependency for smartthings-mqtt-bridge to function securely.
  • Network security surrounding the MQTT broker deployment, which is a deployment consideration when using smartthings-mqtt-bridge.
• Risk Severity: Critical
• Mitigation Strategies:
  • Network Segmentation: Deploy the MQTT broker on a private network segment, not directly accessible from the internet. This is a crucial deployment practice when using smartthings-mqtt-bridge.
  • Firewall Rules: Implement strict firewall rules to block external access to the MQTT broker ports. This is a necessary security measure when setting up the infrastructure for smartthings-mqtt-bridge.
  • Authentication and Authorization (MQTT Broker): Mandatory requirement: Enable strong authentication and authorization on the MQTT broker. smartthings-mqtt-bridge documentation should strongly emphasize this.
  • Security Best Practices Documentation: smartthings-mqtt-bridge documentation should include clear and prominent warnings and instructions about securing the MQTT broker as a critical dependency.

Threat: Bridge Software Vulnerabilities

• Threat: Bridge Software Vulnerabilities
• Description: Vulnerabilities may exist in the smartthings-mqtt-bridge software code itself or its dependencies. Attackers could exploit these vulnerabilities to gain unauthorized access to the server running the bridge, execute arbitrary code, or cause denial of service of the bridge. This directly targets the smartthings-mqtt-bridge application.
• Impact:
  • Server compromise, potentially leading to credential theft (Threat 1 & 2) if vulnerabilities allow access to configuration or memory.
  • Denial of service of the bridge, disrupting smart home integration.
  • Potential for further exploitation of connected systems if the bridge is compromised and used as a pivot point.
• Affected Component:
  • smartthings-mqtt-bridge application code (modules, functions, libraries).
  • Dependencies of smartthings-mqtt-bridge (libraries, modules it relies on).
• Risk Severity: High (potential for critical depending on vulnerability type)
• Mitigation Strategies:
  • Regular Updates and Patching: Maintain smartthings-mqtt-bridge and its dependencies up-to-date with the latest security patches. This is a crucial ongoing maintenance task.
  • Vulnerability Scanning: Periodically scan the server and smartthings-mqtt-bridge application for known vulnerabilities using security scanning tools.
  • Code Reviews and Security Testing: If developing or modifying smartthings-mqtt-bridge code, conduct thorough security code reviews and penetration testing.
  • Minimize Dependencies: Keep dependencies to a minimum and only use trusted and well-maintained libraries to reduce the attack surface.

Threat: Lack of Updates and Patching (Bridge Specific)

• Threat: Lack of Updates and Patching
• Description: Failure to regularly update smartthings-mqtt-bridge software itself and its direct dependencies leaves known vulnerabilities unpatched within the bridge application. Attackers can exploit these vulnerabilities specifically targeting the bridge component.
• Impact:
  • Increased risk of Bridge Software Vulnerabilities (Threat 5) being exploited.
  • Potential for server compromise and subsequent credential theft or denial of service specifically due to unpatched bridge vulnerabilities.
• Affected Component:
  • smartthings-mqtt-bridge application itself.
  • Dependencies of smartthings-mqtt-bridge.
• Risk Severity: High
• Mitigation Strategies:
  • Establish Update Schedule: Implement a regular schedule for checking and applying updates to smartthings-mqtt-bridge and its dependencies.
  • Monitoring for Updates: Monitor the smartthings-mqtt-bridge project repository and security mailing lists for announcements of new releases and security patches.
  • Automated Update Checks (if feasible): Explore if there are mechanisms to automate checks for updates to smartthings-mqtt-bridge and its dependencies (depending on the installation method and environment).
  • Patch Management System (for server): Utilize a patch management system for the server operating system to ensure underlying system security is maintained, which indirectly supports the security of smartthings-mqtt-bridge.