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attack-surface.md

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Attack Surface Analysis for greenrobot/eventbus

Attack Surface: Information Disclosure via Event Data

  • Description: Sensitive data included in events is unintentionally exposed to unauthorized subscribers or logging mechanisms due to the broadcast nature of EventBus.
  • EventBus Contribution: EventBus broadcasts events to all registered subscribers, increasing the risk of sensitive data reaching unintended components if subscriptions are not carefully managed.
  • Example: An event carrying user credentials is posted. A debugging subscriber, unintentionally active in production or accessible to an attacker, logs the event data, leading to credential exposure.
  • Impact: Confidentiality breach, unauthorized access to user accounts or sensitive resources.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Minimize Sensitive Data in Events: Avoid including highly sensitive information directly in event payloads. Use identifiers and retrieve sensitive data within authorized subscribers.
    • Secure Subscriber Design: Ensure subscribers handling sensitive data are strictly controlled and follow the principle of least privilege.
    • Data Sanitization/Obfuscation: If sensitive data must be in events, sanitize or obfuscate it before posting, especially for events that might be logged.
    • Disable Debugging Subscribers in Production: Ensure debugging or logging subscribers that could expose sensitive data are disabled or properly secured in production environments.

Attack Surface: Event Injection/Manipulation (If Event Source is Compromised)

  • Description: If a component responsible for posting events is compromised, an attacker can inject malicious events into EventBus, manipulating application behavior through subscribers.
  • EventBus Contribution: EventBus acts as a central communication channel, amplifying the impact of a compromised event source as malicious events are widely propagated to subscribers.
  • Example: A component receiving external API data is compromised. The attacker injects crafted data that, when posted as an event, triggers malicious actions in subscribers, such as unauthorized data modification or privilege escalation.
  • Impact: Data manipulation, unauthorized actions, privilege escalation, application compromise.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Secure Event Sources: Harden and secure components responsible for posting events. Implement strong input validation and sanitization at the event source.
    • Authentication and Authorization for Event Posting: Implement mechanisms to control which components are allowed to post specific event types, limiting the impact of a compromised component.
    • Input Validation and Sanitization in Subscribers: Subscribers should still validate and sanitize event data they receive as a defense-in-depth measure, even if the event source is considered trusted.

Attack Surface: Denial of Service (DoS) through Event Flooding

  • Description: An attacker floods EventBus with a large volume of events, overwhelming application resources due to resource-intensive event processing in subscribers.
  • EventBus Contribution: EventBus's asynchronous and broadcast nature can amplify DoS impact, as multiple subscribers might concurrently process the flood of events, exacerbating resource exhaustion.
  • Example: An attacker repeatedly triggers an event that initiates expensive operations (e.g., database queries, external API calls) in multiple subscribers, leading to server overload and service unavailability.
  • Impact: Service unavailability, performance degradation, resource exhaustion, impacting application availability and responsiveness.
  • Risk Severity: High
  • Mitigation Strategies:
    • Rate Limiting/Throttling: Implement rate limiting on event posting, especially for events originating from external or less trusted sources.
    • Resource Management in Subscribers: Design subscribers to be resource-efficient and avoid performing overly expensive operations in response to events. Implement timeouts and resource limits.
    • Event Prioritization/Queueing: Implement event prioritization or queueing to manage high event volumes and prevent resource exhaustion.
    • Monitoring and Alerting: Monitor event processing metrics and system resource usage to detect and respond to potential event flooding attacks.

Attack Surface: Unintended Event Handling leading to Critical Side Effects

  • Description: Posting an event, while seemingly innocuous, triggers critical unintended actions in unrelated parts of the application due to complex event flows facilitated by EventBus.
  • EventBus Contribution: EventBus's decoupling makes it easier to create complex event flows where unintended subscribers might react to events, leading to critical and unforeseen side effects.
  • Example: An event intended for UI updates inadvertently triggers a critical security function in a poorly designed subscriber, such as disabling security features or granting administrative privileges under specific conditions.
  • Impact: Privilege escalation, security bypass, critical data corruption, significant disruption of application functionality.
  • Risk Severity: High
  • Mitigation Strategies:
    • Principle of Least Privilege for Subscribers: Design subscribers to only react to events strictly relevant to their function, minimizing the scope of potential unintended actions.
    • Well-Defined Event Contracts and Scopes: Clearly define the purpose, intended recipients, and scope of each event type to prevent unintended subscriptions and actions.
    • Rigorous Testing and Code Reviews: Implement extensive integration and system tests, focusing on event interactions and potential side effects. Conduct thorough code reviews to identify and mitigate unintended logic flows.
    • Modular and Well-Separated Design: Design application components to be modular and well-separated, reducing the likelihood of unintended interactions through the event bus.