mitigations.md

Mitigation Strategies Analysis for tapadoo/alerter

Mitigation Strategy: Input Sanitization for Alerter Content

1. Identify Alerter Data Sources: Pinpoint every location in your code where data is passed to Alerter's properties (e.g., title, text, customView). This includes data from user input, network requests, local storage, or any other source.
2. Implement Sanitization Before Alerter Usage: Immediately before setting any Alerter property with potentially untrusted data, use a robust HTML sanitization library (like SwiftSoup) to clean the input. This is the critical step.

   import SwiftSoup
   
   func sanitizeInput(input: String) -> String {
       do {
           let clean = try SwiftSoup.clean(input, Whitelist.basic) // Or a more restrictive whitelist
           return clean ?? input // Fallback (log!)
       } catch {
           print("Sanitization error: \(error)")
           return input // Fallback (log!)
       }
   }
   
   // ... When using Alerter ...
   let potentiallyUnsafeText = ... // Get data from somewhere
   alerter.text = sanitizeInput(input: potentiallyUnsafeText) // Sanitize *before* setting

3. Whitelist Approach: Configure the sanitization library to use a whitelist of allowed HTML tags and attributes. Start with a very restrictive whitelist (e.g., plain text only) and add elements only as strictly necessary.
4. Context-Specific Handling: If you intend to allow some limited HTML formatting (e.g., bolding), choose a whitelist that permits only those specific safe tags. If it's plain text, HTML-encode it.
5. Regular Expression Validation (For Specific Formats): If the input is expected to be in a specific format (e.g., a date, a phone number, an email address), use regular expressions in addition to sanitization to validate the format before displaying it.
6. Encoding: If you are displaying plain text, and not HTML, ensure the text is properly encoded.
7. Custom View Caution: If using Alerter's customView, apply the same sanitization principles to any data displayed within that custom view. This is often overlooked.

• Threats Mitigated:

  • Cross-Site Scripting (XSS) via Alerter: (Severity: High) - This is the primary threat this mitigation addresses. It prevents malicious code injection through Alerter content.
  • Information Disclosure (Partial): (Severity: Medium) - By controlling what's displayed, you reduce the risk of unintentionally showing sensitive data.

• Impact:

  • XSS: Risk reduction: Very High. This is the core defense against XSS in Alerter.
  • Information Disclosure: Risk reduction: Moderate.

• Currently Implemented:

  • Be very specific. Example: "Implemented for title and text properties using SwiftSoup with a basic whitelist. Not yet implemented for customView content in ProductDetailsViewController."
  • Or: "Not currently implemented."

• Missing Implementation:

  • Precisely list where sanitization is missing. Example: "Missing for customView content in all instances. Missing for text property when data comes from the NotificationService."

Mitigation Strategy: UI Redressing Prevention for Alerter

1. Padding Around Interactive Elements: Ensure that all buttons, text fields, or other interactive elements within the Alerter view have sufficient padding. This makes precise overlay attacks more difficult.
2. Avoid Alerter Transparency: Use a solid background color for the Alerter. Avoid transparency unless absolutely necessary, and if used, keep it to a minimum. This prevents underlying content from being visible and confusing the user.
3. Test Alerter Dismissal: Thoroughly test all ways the Alerter can be dismissed (tapping outside, dismiss buttons, programmatic dismissal). Ensure these methods work reliably and cannot be easily blocked by an attacker.
4. Short-Lived Alerter Instances: Design the application flow so that Alerter instances are displayed for a short duration. Either automatically dismiss them after a brief period or require explicit user interaction to dismiss. Avoid long-lived alerts.
5. Avoid Complex Layouts: Keep the layout of the alert simple. Complex layouts with many overlapping elements can increase the risk of UI redressing.

• Threats Mitigated:

  • UI Redressing (Clickjacking) targeting Alerter: (Severity: Medium) - Reduces the likelihood of successful clickjacking attacks specifically aimed at the Alerter component.

• Impact:

  • UI Redressing: Risk reduction: Moderate. Makes attacks harder, but doesn't eliminate the possibility.

• Currently Implemented:

  • Example: "Padding is implemented for buttons. Transparency is not used. Dismissal is tested. Some alerts are automatically dismissed, but others are not."
  • Or: "Not currently implemented."

• Missing Implementation:

  • Example: "Need to implement automatic dismissal for all informational alerts. Need to review padding for custom views within alerts."

Mitigation Strategy: Alerter Rate Limiting and Management

1. Identify Alerter Trigger Points: List all code locations that initiate the display of an Alerter.
2. Implement Rate Limiting Before Alerter Display: For each trigger point, implement rate limiting to control how frequently Alerter instances can be shown. This prevents an attacker from flooding the UI with alerts.
3. Queueing/Deduplication (Optional, but Recommended): If multiple alerts are triggered in quick succession, consider:
   • Queueing: Display them one at a time, in a controlled manner.
   • Deduplication: If the same alert is triggered repeatedly, show it only once.
4. Centralized Alert Service (Highly Recommended): Create a single service responsible for managing all Alerter displays. This makes it much easier to enforce rate limiting, queueing, and deduplication consistently across the application. All calls to show an Alerter should go through this service.

• Threats Mitigated:

  • Denial of Service (DoS) via Alerter Flooding: (Severity: Low) - Prevents attackers from overwhelming the application with Alerter instances.

• Impact:

  • DoS: Risk reduction: High. Directly addresses the threat of Alerter-based DoS.

• Currently Implemented:

  • Example: "Rate limiting implemented for alerts triggered by network errors using a centralized AlertService. Queueing and deduplication are not implemented."
  • Or: "Not currently implemented."

• Missing Implementation:

  • Example: "Need to implement rate limiting for alerts triggered by user actions in the ProfileViewController. Implement queueing and deduplication in the AlertService."

Mitigation Strategy: Avoid Sensitive Data in Alerter Content

1. Review All Alerter Content: Carefully examine every instance where Alerter is used and identify the data being displayed in its title, text, and customView.
2. Prohibit Sensitive Data: Ensure that no sensitive information (passwords, API keys, PII, etc.) is ever displayed directly within an Alerter. Use generic error messages or references to more detailed logs if necessary.
3. Use Placeholders: If you need to indicate that some data is missing or unavailable, use placeholders or generic messages instead of displaying partial or potentially sensitive information.

• Threats Mitigated:

  • Information Disclosure via Alerter: (Severity: High) - Prevents accidental exposure of sensitive data through the Alerter component.

• Impact:

  • Information Disclosure: Risk reduction: High. Directly addresses the threat.

• Currently Implemented:

  • Example: "Reviewed all Alerter usage. Confirmed no sensitive data is displayed."
  • Or: "Not currently implemented."

• Missing Implementation:

  • Example: "Need to review alerts in the PaymentViewController to ensure no partial credit card details are shown."

Mitigation Strategy: Proper Alerter Callback Handling

1. Review Alerter Callbacks: Examine all code that handles Alerter callbacks (button taps, dismissals, etc.). These are the actions triggered by user interaction with the Alerter.
2. Implement Error Handling Within Callbacks: Within each callback function, implement robust error handling using do-catch blocks. This prevents unexpected crashes or behavior if an error occurs during the callback's execution.
3. Avoid Blocking Operations in Callbacks: Ensure that Alerter callbacks do not perform long-running or blocking operations on the main thread. This can freeze the UI. Use background threads or asynchronous operations if necessary. This is crucial for responsiveness.

• Threats Mitigated:

  • Improper Alerter Callback Handling: (Severity: Medium) - Prevents unexpected application behavior or crashes due to errors in how Alerter callbacks are handled.

• Impact:

  • Improper Handling: Risk reduction: High. Ensures correct and predictable behavior.

• Currently Implemented:

  • Example: "Error handling implemented in most callbacks. Need to review for blocking operations."
  • Or: "Not currently implemented."

• Missing Implementation:

  • Example: "Need to add error handling to the callback for the 'Retry' button in the NetworkErrorAlert. Need to move a long-running network operation in the UpdateAlert callback to a background thread."