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Mitigation Strategies Analysis for existentialaudio/blackhole

Mitigation Strategy: Explicit User Consent and Control (BlackHole-Specific Aspects)

  • Description:

    1. BlackHole-Specific Disclosure: Within the user consent dialog, specifically mention "BlackHole" by name as the audio routing mechanism. Don't use generic terms like "virtual audio device." This ensures the user understands the specific technology being used.
    2. Channel Selection: If BlackHole offers multiple channels, allow the user to select which BlackHole channels the application is allowed to use. Don't assume access to all channels is acceptable. This provides finer-grained control.
    3. Visual Representation (If Possible): If feasible, provide a visual representation of the BlackHole routing configuration (e.g., a simple diagram showing the connections between applications and BlackHole channels). This aids user understanding.
    4. Revocation: Ensure the user can easily revoke access to specific BlackHole channels, not just a blanket disablement of all audio routing.

  • Threats Mitigated:

    • Unauthorized Audio Capture (Severity: High): Prevents the application from using BlackHole without the user's explicit knowledge and consent. Channel selection limits the scope of potential capture.
    • Unwanted Audio Injection (Severity: High): Channel selection limits the potential destinations for injected audio.
    • Privacy Violation (Severity: High): Ensures the user is fully informed about the use of BlackHole and has control over its configuration.

  • Impact:

    • Unauthorized Audio Capture: Risk reduced from High to Low (with informed user choices and channel restrictions).
    • Unwanted Audio Injection: Risk reduced from High to Low (with channel restrictions).
    • Privacy Violation: Risk significantly reduced.

  • Currently Implemented:

    • The consent dialog mentions BlackHole by name (src/audio/AudioSetup.cpp).

  • Missing Implementation:

    • Channel selection is not currently implemented. The application uses a default set of BlackHole channels. (Ticket #123)
    • No visual representation of the BlackHole routing is provided. (Ticket #124)
    • Revocation is all-or-nothing; it doesn't allow for per-channel control. (Ticket #140)

Mitigation Strategy: Restricted Audio Routing (BlackHole Configuration)

  • Description:

    1. Precise Channel Mapping: Use BlackHole's channel mapping features (if available) to strictly define which application outputs are routed to which BlackHole input channels, and which BlackHole output channels are connected to which application inputs. Avoid any "wildcard" or "catch-all" configurations.
    2. Minimal Channel Usage: Use the minimum number of BlackHole channels necessary for the application's functionality. Don't create or use unnecessary channels.
    3. Configuration Validation: After configuring BlackHole, implement checks within the application to verify that the routing configuration is as expected. This could involve:
      • Using system APIs (if available) to query the current BlackHole configuration.
      • Sending test audio signals through the configured routes and verifying that they are received at the expected destinations.
    4. Dynamic Reconfiguration (If Necessary): If the application needs to dynamically change the BlackHole routing configuration at runtime, implement robust error handling and validation to ensure that the new configuration is valid and secure before applying it.

  • Threats Mitigated:

    • Unauthorized Audio Capture (Severity: High): Prevents unintended applications from connecting to BlackHole and capturing audio.
    • Unwanted Audio Injection (Severity: High): Prevents audio from being injected into unintended destinations.
    • Configuration Errors (Severity: Medium): Validation helps detect and prevent misconfigurations that could lead to security vulnerabilities.

  • Impact:

    • Unauthorized Audio Capture: Risk reduced from High to Medium (further reduced with application-level validation).
    • Unwanted Audio Injection: Risk reduced from High to Medium (further reduced with application-level validation).
    • Configuration Errors: Risk reduced.

  • Currently Implemented:

    • The application uses a predefined set of BlackHole channels. (src/audio/AudioConfig.cpp)

  • Missing Implementation:

    • No precise channel mapping is used. The application assumes that any application listening on the designated BlackHole output channel is legitimate. (Ticket #126)
    • No configuration validation is performed after setting up BlackHole. (Ticket #141)
    • Dynamic reconfiguration is not supported, but if it were, it would need robust validation. (Ticket #142 - Placeholder)