mitigations.md

Mitigation Strategies Analysis for grouper/flatuikit

Mitigation Strategy: Strict Schema Validation (Beyond FlatBuffers' Built-in Checks)

1. Deserialization: After receiving and deserializing the FlatBuffers data using flatuikit, obtain the root object.

2. Validation Function: Create a dedicated validation function (e.g., validateFlatUIConfig(config)). This function takes the deserialized FlatBuffers object as input.

3. Field-by-Field Checks: Inside the validation function, implement checks for each field in the FlatBuffers schema:

   • Type Checks: Verify that each field has the correct data type (e.g., integer, string, boolean, enum). Use the accessor methods provided by the FlatBuffers library to get the field values and check their types.
   • Range Checks: For numeric fields, check if the values fall within acceptable ranges. For example: if (config.width() < 0 || config.width() > MAX_WIDTH) { throw ValidationError("Invalid width"); }
   • String Length Checks: For string fields, limit the maximum length. For example: if (config.title() && config.title().length > MAX_TITLE_LENGTH) { throw ValidationError("Title too long"); }
   • Enum Validation: For enum fields, ensure the value is one of the allowed enum values. For example: if (config.alignment() != Alignment.Left && config.alignment() != Alignment.Center && config.alignment() != Alignment.Right) { throw ValidationError("Invalid alignment"); }
   • Required Field Checks: Verify that all required fields are present and not null (or have a default value if appropriate). For example: if (!config.title()) { throw ValidationError("Title is required"); }
   • Unexpected Field Checks: Iterate through the fields and check if any unexpected fields are present. This is more complex and might require reflection or schema introspection, but it's crucial for preventing schema confusion attacks.

4. Error Handling: If any validation check fails, throw a custom exception (e.g., ValidationError) or return an error code. Do not proceed with using the data if validation fails. Log the error appropriately.

5. Integration: Call the validation function immediately after deserializing the FlatBuffers data and before using the data for any UI rendering or other operations.

   Threats Mitigated: * Buffer Overflows (Severity: High): By limiting string lengths and validating numeric ranges, we prevent attackers from providing excessively large values that could cause buffer overflows in the application or in flatuikit itself. * Denial of Service (DoS) (Severity: Medium): Excessive string lengths or large numeric values could also lead to excessive memory allocation, potentially causing a DoS. Validation prevents this. * Schema Confusion Attacks (Severity: High): By checking for unexpected fields and validating data types strictly, we mitigate the risk of attackers exploiting inconsistencies between the expected schema and the actual data. * Logic Errors (Severity: Medium): Validating enums and required fields helps prevent logic errors in the application that could arise from unexpected or missing data.

   Impact: * Buffer Overflows: Risk reduced significantly (close to elimination if validation is comprehensive). * Denial of Service: Risk reduced significantly. * Schema Confusion Attacks: Risk reduced significantly. * Logic Errors: Risk reduced moderately.

   Currently Implemented: * Deserialization is implemented in src/data_loader.js. * Basic type checks are present in src/ui_renderer.js, but they are incomplete and inconsistent.

   Missing Implementation: * A dedicated, comprehensive validation function is missing. Validation is scattered and incomplete. * Range checks, string length checks, enum validation, and unexpected field checks are largely absent. * Consistent error handling for validation failures is missing. * Validation is not consistently performed before UI rendering.

Mitigation Strategy: Careful Handling of UI Element Attributes

1. Whitelist: Create a whitelist of allowed HTML attributes that can be set by flatuikit data. This list should be as short as possible and include only essential attributes. For example: const allowedAttributes = ['id', 'class', 'style', 'data-custom-attribute'];

2. Attribute Filtering: Before applying attributes from the FlatBuffers data to UI elements, filter them based on the whitelist.

   function applyAttributes(element, flatbufferAttributes) {
     for (const key in flatbufferAttributes) {
       if (allowedAttributes.includes(key)) {
         const value = flatbufferAttributes[key];
         // Sanitize the value (see next step)
         const sanitizedValue = sanitizeAttributeValue(key, value);
         element.setAttribute(key, sanitizedValue);
       }
     }
   }

3. Sanitization: Create a sanitizeAttributeValue(key, value) function. This function takes the attribute name and value as input and performs context-specific sanitization:

   • id and class: Allow only alphanumeric characters, hyphens, and underscores. Reject any other characters.
   • style: This is the most dangerous. Ideally, avoid allowing flatuikit to set inline styles directly. If you must, use a CSS parser/sanitizer library to parse the style string and remove any potentially dangerous properties or values (e.g., behavior, expression, URLs that don't match a whitelist). This is complex and error-prone; consider alternatives if possible.
   • data-* attributes: These are generally safer, but still sanitize them to prevent unexpected characters.
   • Event Handlers (e.g., onclick): Never allow flatuikit data to set event handler attributes directly. This is a direct XSS vector.

4. Contextual Encoding: If you are inserting data from FlatBuffers into HTML attributes (even after sanitization), use appropriate HTML entity encoding to prevent the data from being interpreted as HTML tags or JavaScript code. Most templating libraries provide functions for this (e.g., escapeHtml or similar).

5. Alternatives to Inline Styles: Instead of allowing arbitrary inline styles, consider:

   • Predefined CSS Classes: Define a set of CSS classes that represent the allowed styles, and have flatuikit data specify the class names to use.
   • CSS Variables: Use CSS variables (custom properties) to control styles, and have flatuikit data set the values of these variables.

   Threats Mitigated: * Cross-Site Scripting (XSS) (Severity: High): By whitelisting attributes, sanitizing values, and never allowing direct setting of event handlers, we prevent attackers from injecting malicious JavaScript code through HTML attributes. * CSS Injection (Severity: Medium): Sanitizing the style attribute (or avoiding it entirely) prevents attackers from injecting malicious CSS that could alter the appearance or behavior of the application.

   Impact: * XSS: Risk reduced significantly. * CSS Injection: Risk reduced significantly (or eliminated if inline styles are avoided).

   Currently Implemented: * No attribute whitelisting is implemented. * No attribute sanitization is implemented. * flatuikit data can currently set event handler attributes (this is a major vulnerability).

   Missing Implementation: * All aspects of this mitigation strategy are currently missing. This is a high-priority area for improvement.