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Mitigation Strategies Analysis for ocornut/imgui

Mitigation Strategy: Strict Input Validation After ImGui Processing

  • Description:

    1. Identify All Input Points: List every ImGui widget that accepts user input (e.g., InputText, InputInt, SliderFloat, Checkbox, Combo, etc.).
    2. Post-ImGui Validation: Immediately after retrieving the value from the ImGui widget (e.g., after calling ImGui::InputText), implement validation checks before the value is used anywhere else in the application. This is crucial because ImGui itself does minimal internal validation.
    3. Type Validation: Ensure the data type matches expectations. If you expect an integer, verify it's not a string or a floating-point number outside the integer range. Use C++ type checking and conversion functions (e.g., std::stoi, std::stof, with appropriate error handling) after retrieving the value from ImGui.
    4. Range Validation: For numerical inputs, define minimum and maximum acceptable values. Use if statements or similar constructs to check if the value (obtained from ImGui) falls within the allowed range.
    5. Length Validation: For text inputs (obtained from ImGui::InputText or similar), set a maximum length. Use std::string::length() or similar to check the string's length before using it.
    6. Format Validation: If the input (from an ImGui widget) must adhere to a specific format (e.g., email, date, URL), use regular expressions (std::regex) or specialized parsing libraries to validate the format.
    7. Whitelist (Preferred): Define a set of allowed characters or values. Reject any input (from ImGui) that doesn't match the whitelist.
    8. Error Handling: If validation fails, handle the error gracefully. This might involve:
      • Displaying an error message to the user (using ImGui itself, if appropriate, e.g., with ImGui::TextColored or a custom popup).
      • Resetting the ImGui widget to a default value (e.g., using the * pointer argument to ImGui::InputInt).
      • Preventing the application from using the invalid input.
      • Logging the error.
    9. Centralized Validation (Optional): Consider creating reusable validation functions that take the ImGui widget's output as input.

  • Threats Mitigated:

    • Cross-Site Scripting (XSS) (Severity: High): If ImGui input is directly rendered in a web context, unvalidated input could allow injection of malicious JavaScript. Impact: Eliminates the risk if input is properly sanitized for the target context after being retrieved from ImGui.
    • Buffer Overflow (Severity: High): Unbounded text input from ImGui::InputText could lead to buffer overflows. Impact: Prevents buffer overflows by enforcing length limits on data retrieved from ImGui.
    • Code Injection (Severity: Critical): If ImGui input is used to construct commands, unvalidated input could allow code injection. Impact: Reduces the risk by validating ImGui input against expected formats.
    • Logic Errors (Severity: Medium to High): Unexpected input values from ImGui can cause unintended behavior. Impact: Improves application stability by ensuring ImGui input conforms to constraints.
    • Denial of Service (DoS) (Severity: Medium): Extremely long input strings from ImGui could consume excessive resources. Impact: Reduces DoS risk by limiting ImGui input sizes.

  • Impact: Significantly reduces the risk of various vulnerabilities by ensuring that all data received from ImGui widgets is validated.

  • Currently Implemented: Partially. Validation exists for some numerical inputs and some text fields.

  • Missing Implementation:

    • Comprehensive validation is missing for many text input fields.
    • Format validation and whitelisting are not consistently implemented.
    • Centralized validation functions are not used.
    • Error handling for failed validation is inconsistent.

Mitigation Strategy: Rate Limiting and Input Throttling (ImGui Interaction Level)

  • Description:

    1. Identify High-Frequency Interactions: Determine which ImGui widgets can be interacted with rapidly (buttons, sliders, rapidly changing text fields using ImGuiInputTextFlags_EnterReturnsTrue or callbacks).
    2. Implement a Timer/Counter (Per Widget): For each identified widget, use a timer or counter within your ImGui code to track the time since the last interaction or the number of interactions within a time window. This can be done using ImGui::GetTime() or your own timer mechanism.
    3. Define Thresholds: Set reasonable thresholds for interaction frequency specific to each ImGui widget.
    4. Throttle Updates: If the interaction frequency exceeds the threshold, skip the processing of the ImGui widget's state change. Do not call the application logic that depends on the widget's value. You can achieve this by conditionally executing code based on the timer/counter.
    5. Consider User Feedback (Within ImGui): Optionally, provide visual feedback within ImGui (e.g., briefly disabling the widget using ImGui::BeginDisabled/ImGui::EndDisabled or displaying a message with ImGui::Text).
    6. Prioritize Critical Operations: If a user is rapidly clicking a critical button (like "Save"), ensure at least one operation completes.

  • Threats Mitigated:

    • Denial of Service (DoS) (Severity: Medium): Rapid interactions with ImGui widgets could trigger expensive operations. Impact: Reduces DoS risk by limiting the rate of ImGui interactions that trigger application logic.
    • Brute-Force Attacks (Severity: Low to Medium): If ImGui input is used for authentication, rate limiting can slow down attacks. Impact: Makes brute-force attacks more difficult.

  • Impact: Reduces DoS risk and makes brute-force attacks less effective. Improves responsiveness by preventing UI interactions from overwhelming the system.

  • Currently Implemented: Not implemented.

  • Missing Implementation: Rate limiting is not implemented for any ImGui widgets.

Mitigation Strategy: Secure imgui.ini Handling (or Disable It) - Direct ImGui API Control

  • Description:

    1. Assess Necessity: Determine if your application needs to persist ImGui's UI state.
    2. Disable if Possible: If persistence is not required, disable imgui.ini entirely using the ImGui API: 
      ImGuiIO& io = ImGui::GetIO();
io.IniFilename = nullptr; // Directly controls ImGui's behavior
    3. Secure Location (If Necessary): If imgui.ini is required, choose a secure, application-specific directory. Use platform-specific APIs to determine the appropriate location.
    4. Restrict Permissions: Set appropriate file system permissions.
    5. Validate Contents (If Used): If you must use imgui.ini, implement validation upon loading. This involves parsing the data that ImGui loads and checking it:
      • Parse the File: Use ImGui's built-in parsing functions (or a robust INI parser).
      • Check for Expected Keys: Verify that the file contains only expected keys.
      • Validate Values: Check values for reasonable ranges and formats.
      • Checksum/Signature (Optional): Calculate a checksum or signature.
    6. Limit Influence: Do not use imgui.ini to control critical application behavior. Use it only for UI layout as intended by ImGui.

  • Threats Mitigated:

    • Information Disclosure (Severity: Low to Medium): An attacker modifying imgui.ini might glean information. Impact: Reduces risk by securing the file or disabling it via the ImGui API.
    • Denial of Service (DoS) (Severity: Low): A malicious imgui.ini could cause ImGui to enter an unstable state. Impact: Reduces risk by validating the file's contents (loaded by ImGui).
    • Privilege Escalation (Severity: Low): Unlikely, but minimizes potential.

  • Impact: Reduces risks by securing or disabling the imgui.ini file using ImGui's own configuration options.

  • Currently Implemented: Partially. The application uses imgui.ini.

  • Missing Implementation:

    • The imgui.ini file contents are not validated.
    • File permissions are not explicitly set.
    • Checksum verification is not implemented.

Mitigation Strategy: Disable Debugging Features in Production - Direct ImGui API Calls

  • Description:

    1. Identify Debugging Features: Identify all ImGui debugging features:
      • ImGui::ShowDemoWindow()
      • ImGui::ShowMetricsWindow()
      • ImGui::ShowStyleEditor()
      • Any custom debugging windows using ImGui.
    2. Conditional Compilation: Use preprocessor directives to conditionally compile out these calls to the ImGui API: 
      #ifndef NDEBUG
    ImGui::ShowDemoWindow(); // Direct ImGui API call
#endif
    3. Build System Integration: Ensure your build system defines NDEBUG correctly.
    4. Testing: Test both debug and production builds.

  • Threats Mitigated:

    • Information Disclosure (Severity: Medium): Debugging features can reveal sensitive information. Impact: Eliminates risk by removing calls to ImGui debugging functions.
    • Denial of Service (DoS) (Severity: Low): Some debugging features might have overhead. Impact: Reduces risk by removing potentially vulnerable ImGui calls.
    • Reverse Engineering (Severity: Medium): Debugging features can aid reverse engineering. Impact: Makes reverse engineering harder.

  • Impact: Eliminates the risk of exposing sensitive information via ImGui's debugging features.

  • Currently Implemented: Partially. ImGui::ShowDemoWindow() is conditionally compiled out.

  • Missing Implementation:

    • Other debugging features might not be consistently disabled.

Mitigation Strategy: Secure Font Handling (ImGui Configuration)

  • Description:

    1. Prefer Embedded Fonts: Embed font data directly into your application. Use a tool like binary_to_compressed_c.cpp (from the ImGui repository) to convert font files to C++ code, then use ImGuiIO::Fonts->AddFontFromMemoryTTF or ImGuiIO::Fonts->AddFontFromMemoryCompressedTTF to load them. This is the most secure option as it avoids any external file loading by ImGui.
    2. Restrict Font Loading Paths (If Necessary): If you must load fonts from files, use ImGuiIO::Fonts->AddFontFromFileTTF with a carefully controlled path. Restrict this path to a trusted, application-specific location. Do not allow loading from arbitrary user-specified paths. This directly controls ImGui's font loading behavior.
    3. Validate Font Files (If Necessary): If you load fonts from external files, validate them before passing them to ImGuiIO::Fonts->AddFontFromFileTTF. This is complex and requires a font validation library.
    4. Avoid User-Provided Fonts: Do not allow users to upload or specify fonts.

  • Threats Mitigated:

    • Code Execution (Severity: Critical): Malicious font files can exploit vulnerabilities. Impact: Significantly reduces (or eliminates, with embedded fonts) risk by controlling how ImGui loads fonts.
    • Denial of Service (DoS) (Severity: Medium): A corrupted font file could cause issues. Impact: Reduces DoS risk by validating font files (if used) and restricting ImGui's loading paths.

  • Impact: Reduces code execution and DoS risks related to ImGui's font handling.

  • Currently Implemented: Partially. Fonts are loaded from the application's directory.

  • Missing Implementation:

    • Font file validation is not implemented.
    • Switching to embedded fonts (using ImGui's memory loading functions) is the best option.
    • The font loading path should be more restricted.