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Mitigation Strategies Analysis for wenchaod/fscalendar

Mitigation Strategy: Strict Input Validation and Sanitization (for FSCalendar Display)

Description:

  1. Identify FSCalendar Display Points: Pinpoint exactly where user-provided data is displayed within FSCalendar (e.g., event titles in calendar(_:titleFor:), subtitles in calendar(_:subtitleFor:), custom views).
  2. Sanitize Before Passing: Before returning any string or attributed string to FSCalendar's delegate methods for display, rigorously sanitize the data using a dedicated library (e.g., DOMPurify if within a web view, a native Swift sanitizer, or a backend sanitizer if data is pre-processed).
  3. Allowlist Approach: Use a strict allowlist, defining precisely which characters and (if any) HTML tags are permitted within each display context. Reject anything outside the allowlist.
  4. Context-Specific Sanitization: Sanitize data differently depending on where it will be displayed. A title might have stricter rules than a longer description.
  5. Output Encoding (if applicable): If you are manually constructing attributed strings or custom views, ensure proper output encoding (e.g., HTML entity encoding) to prevent misinterpretation.

Threats Mitigated:

  • Cross-Site Scripting (XSS) (within FSCalendar): (Severity: High) - Prevents attackers from injecting malicious JavaScript if FSCalendar is used within a web view or if it renders HTML content.
  • HTML Injection (within FSCalendar): (Severity: Medium) - Prevents attackers from injecting arbitrary HTML that could disrupt the calendar's appearance or display unwanted content.
  • Data Corruption (within FSCalendar): (Severity: Low) - Prevents malformed input from causing rendering errors within FSCalendar.

Impact:

  • XSS: Risk reduced from High to Very Low (with proper sanitization and CSP).
  • HTML Injection: Risk reduced from Medium to Very Low.
  • Data Corruption: Risk reduced from Low to Negligible.

Currently Implemented:

  • Example: "Partially implemented. Basic sanitization is done before setting event titles, but it's not comprehensive and doesn't use a dedicated library. Subtitles and custom views are not sanitized."

Missing Implementation:

  • Example: "Missing a robust sanitization library. The custom sanitization function needs to be replaced. Sanitization is missing for subtitles and any custom views used within FSCalendar."

Mitigation Strategy: Careful Delegate Implementation (FSCalendar-Specific Data Handling)

Description:

  1. Focus on FSCalendar Delegates: Review only the FSCalendarDelegate and FSCalendarDataSource methods your application implements.
  2. Minimize Data Exposure: Within these delegate methods, only access and process the data absolutely required by FSCalendar. Avoid accessing or manipulating unrelated data.
  3. Secure Data Handling: If delegate methods handle data that will be used outside of FSCalendar (e.g., sending it to a server, storing it locally):
    • Sanitize Before External Use: Sanitize the data again before sending it elsewhere, even if it was sanitized before being displayed in FSCalendar. This provides defense-in-depth.
    • Secure Communication: Use HTTPS for any network communication.
    • Secure Storage: Use appropriate secure storage mechanisms.
  4. Avoid Sensitive Operations in Delegates: Do not perform security-sensitive operations (e.g., authentication, authorization) directly within FSCalendar delegate methods. These should be handled separately.

Threats Mitigated:

  • Data Leakage (via FSCalendar Delegates): (Severity: High) - Prevents sensitive data from being exposed if delegate methods inadvertently log, transmit, or store data insecurely.
  • Injection Attacks (indirect): (Severity: Medium) - Reduces the risk of data passed from FSCalendar being used in injection attacks elsewhere in the application.

Impact:

  • Data Leakage: Risk reduced from High to Low (depending on the data and implementation).
  • Injection Attacks (indirect): Risk reduced from Medium to Low.

Currently Implemented:

  • Example: "Implemented. Delegate methods only access necessary data. Data passed to the backend is sanitized again before transmission."

Missing Implementation:

  • Example: "Needs review to ensure no unnecessary data is being accessed within the delegate methods."

Mitigation Strategy: Controlled Appearance Customization (FSCalendar-Specific)

Description:

  1. Limit Customization Options: Restrict the range of appearance customizations users can control through FSCalendar. Do not allow arbitrary CSS or styling. Provide a predefined set of safe options (e.g., colors, fonts from a fixed list).
  2. Validate Customization Data: If users can provide input for customizations (e.g., color codes), validate this input before passing it to FSCalendar's appearance methods.
  3. Image Handling (if applicable): If FSCalendar is used to display custom images (e.g., for events):
    • Source Control: Load images only from trusted sources (your server, a CDN).
    • Validation: Validate image types and sizes before passing them to FSCalendar.
    • Avoid User-Provided URLs: Do not allow users to directly provide URLs to images to be displayed in FSCalendar.

Threats Mitigated:

  • UI Distortion/Breakage (within FSCalendar): (Severity: Medium) - Prevents malicious or poorly designed customizations from disrupting FSCalendar's layout.
  • Denial of Service (DoS) via Image Loading (within FSCalendar): (Severity: Medium) - Prevents large or malicious images from causing FSCalendar to crash or become unresponsive.
  • Cross-Site Scripting (XSS) (indirect, via images): (Severity: Low) - Reduces the risk if images are loaded from untrusted sources.

Impact:

  • UI Distortion/Breakage: Risk reduced from Medium to Low.
  • DoS via Image Loading: Risk reduced from Medium to Low.
  • XSS (indirect): Risk reduced from Low to Very Low.

Currently Implemented:

  • Example: "Partially implemented. Users can choose from a predefined set of colors. Image customization is not used."

Missing Implementation:

  • Example: "If image customization is added, image validation and secure loading will be required."

Mitigation Strategy: Pagination/Lazy Loading (with FSCalendar)

Description:

  1. Implement Data Fetching Logic: Modify your FSCalendarDataSource implementation to fetch event data in batches, rather than all at once.
  2. Use Delegate Methods for Triggers: Utilize FSCalendar delegate methods like calendar(_:willDisplay:for:) or methods related to scrolling/paging to trigger the loading of additional data as the user navigates the calendar.
  3. Manage Visible Date Range: Keep track of the currently visible date range and only fetch events within that range (plus a small buffer, if desired).
  4. Handle Loading Indicators: Display appropriate loading indicators within FSCalendar (e.g., using custom views or appearance customizations) to inform the user when data is being fetched.
  5. Cache Data (Optional): Consider caching fetched event data to improve performance, but be mindful of data freshness and potential memory usage.

Threats Mitigated:

  • Denial of Service (DoS) (on FSCalendar): (Severity: Medium) - Prevents FSCalendar from becoming unresponsive due to a large number of events.
  • Performance Degradation (within FSCalendar): (Severity: Medium) - Improves the responsiveness of FSCalendar, especially with large datasets.

Impact:

  • DoS: Risk reduced from Medium to Low.
  • Performance Degradation: Risk reduced from Medium to Low.

Currently Implemented:

  • Example: "Not implemented."

Missing Implementation:

  • Example: "Requires modifying the FSCalendarDataSource implementation to fetch data in batches and using delegate methods to trigger loading."