mitigations.md

Mitigation Strategies Analysis for gui-cs/terminal.gui

Mitigation Strategy: Input Whitelisting and Length Limits (Direct terminal.gui Interaction)

• Description:

  1. Identify terminal.gui Input Fields: Identify all instances of terminal.gui input controls like TextField, TextView, Dialog's input fields, and any custom controls built upon terminal.gui that accept user input.
  2. Define Allowed Input (Per Field): For each identified input field, determine the precise set of allowed characters and patterns. Be as restrictive as possible. Consider data type (numeric, alphanumeric, specific symbols), expected format, and any business logic constraints.
  3. Implement Whitelist Validation (Using terminal.gui Events): Attach event handlers to the relevant terminal.gui events:
     • KeyPress: Use this to intercept each key press before it's processed by the control. Check if the pressed key is allowed based on your whitelist. If not, set keyEvent.Handled = true; to prevent the key from being added to the input.
     • TextChanged: Use this to validate the entire input after it has changed. This is useful for more complex validation rules that depend on the entire input string (e.g., checking for a valid email format). If the input is invalid, you can either:
       • Revert the text to the previous valid state.
       • Display an error message and disable any associated actions (e.g., a "Submit" button).
       • Clear the input field.
     • Consider using both KeyPress (for immediate feedback) and TextChanged (for comprehensive validation).
  4. Set MaxLength Property: Utilize the MaxLength property (or an equivalent if you've created custom controls) of each terminal.gui input field. Set this to a reasonable maximum length based on the expected input and to prevent excessively long inputs.
  5. Provide User Feedback (Within terminal.gui): If input is rejected (either by KeyPress or TextChanged), provide immediate and clear feedback to the user within the terminal.gui interface. This could involve:
     • Displaying an error message in a Label near the input field.
     • Changing the background color of the input field to indicate an error.
     • Using a MessageBox to display a more detailed error message.
     • Disabling the "Submit" button (or equivalent) until the input is valid.
  6. Example (C#, KeyPress and TextChanged):

     myTextField.KeyPress += (keyEvent) => {
         if (!IsValidChar(keyEvent.KeyEvent.Key)) {
             keyEvent.Handled = true;
             DisplayValidationError("Only alphanumeric characters allowed."); // Show error
         }
     };
     
     myTextField.TextChanged += () => {
         if (!IsValidInput(myTextField.Text)) {
             // Revert to previous valid text, or clear the field
             myTextField.Text = previousValidText;
             DisplayValidationError("Invalid input format."); // Show error
         } else {
             previousValidText = myTextField.Text; // Store valid text
             ClearValidationError(); // Clear any previous error
         }
     };
     
     myTextField.MaxLength = 50;
     
     // ... (Implement IsValidChar, IsValidInput, DisplayValidationError, ClearValidationError)

• Threats Mitigated:

  • Command Injection: (Severity: Critical) - Limits characters, reducing the attack surface if input is (incorrectly) used in commands.
  • Denial of Service (DoS): (Severity: High) - MaxLength prevents excessively large inputs.
  • Buffer Overflow: (Severity: High) - MaxLength provides a defense-in-depth layer.
  • XSS (Theoretical): (Severity: Medium) - Limits injection of control characters.

• Impact:

  • Command Injection: Reduces risk, but doesn't eliminate it without proper command parameterization.
  • DoS/Buffer Overflow: Substantial protection due to MaxLength.
  • XSS: Reduces likelihood.

• Currently Implemented:

  • [Example: "Implemented for username and password fields in LoginDialog using KeyPress and MaxLength."]
  • [Example: "TextChanged validation is used for email format in the RegistrationDialog."]

• Missing Implementation:

  • [Example: "Missing for the 'search query' field (TextField) in MainView."]
  • [Example: "No whitelisting on the TextView used for multi-line input in NoteEditor."]

Mitigation Strategy: Secure UI Practices for Sensitive Data (Direct terminal.gui Handling)

• Description:

  1. Identify Sensitive Data Display: Locate all terminal.gui controls that display or handle sensitive data (passwords, API keys, tokens, personal information). This includes TextField, TextView, Label, ListView (if displaying sensitive columns), and any custom controls.
  2. Use terminal.gui Password Handling (If Available, Or Create Custom):
     • If terminal.gui provides a dedicated "password field" control (check the documentation and latest version), use it. This control should automatically mask input.
     • If no built-in password field exists, create a custom terminal.gui control that inherits from TextField (or a suitable base class) and overrides the drawing and input handling methods to:
       • Replace displayed characters with asterisks (*) or another masking character.
       • Store the actual password securely (e.g., in a SecureString in C#).
       • Prevent the password from being copied to the clipboard.
  3. Minimize Display (Control-Specific Logic): Avoid displaying sensitive data directly in Label, TextView, or other controls intended for general text display. If display is necessary:
     • Label: Consider a "Show/Hide" button (using a Button and toggling the Text property of the Label).
     • TextView: Avoid displaying sensitive data in TextView altogether. If unavoidable, implement a custom drawing routine that only reveals the data when explicitly requested by the user (e.g., via a mouse click or key press) and hides it again immediately after.
     • Partial Display: If appropriate, display only a portion of the sensitive data (e.g., "Last 4 digits: XXXX").
  4. Clear Data After Use (Control Lifecycle): Ensure sensitive data is cleared from terminal.gui controls when it's no longer needed. This is critical and involves:
     • Dispose Method: If you create custom controls, override the Dispose method to explicitly clear any internal buffers or variables holding sensitive data.
     • VisibleChanged Event: Use the VisibleChanged event of controls to clear their contents when they become hidden (e.g., when switching views).
     • Explicit Clearing: Before hiding, closing, or disposing of a control that has held sensitive data, explicitly set its Text property (or equivalent) to an empty string or a safe default value. For custom controls, clear any internal data structures.
  5. Review Redraws (Custom Drawing): If you implement custom drawing for controls that handle sensitive data (e.g., to implement masking), be extremely careful to ensure that the sensitive data is never briefly visible during redraw operations. Use double buffering or other techniques to prevent flickering or temporary exposure.

• Threats Mitigated:

  • Information Disclosure: (Severity: High) - Prevents shoulder surfing, screen recording, and unauthorized access to sensitive data displayed in the UI.

• Impact:

  • Information Disclosure: Significantly reduces the risk of exposure.

• Currently Implemented:

  • [Example: "Password fields in LoginDialog use a custom control (PasswordField) that masks input and clears the buffer on Dispose."]
  • [Example: "API keys are never displayed directly; a 'Copy to Clipboard' button is provided instead."]

• Missing Implementation:

  • [Example: "Session tokens are displayed in a Label in the debug view; this needs to be removed or hidden behind a toggle."]
  • [Example: "The TextView used for displaying configuration files might contain sensitive data; we need to implement a mechanism to redact or hide this information."]

Mitigation Strategy: Sanitize Untrusted Input for Display (Within terminal.gui Context)

• Description:

  1. Identify Untrusted Input Display: Identify all terminal.gui controls that display data from untrusted sources. This is most likely to involve TextView, Label, ListView (if displaying data from external sources), and potentially custom controls. Untrusted sources include:
     • User-provided input (even after validation, it might contain control characters).
     • Data loaded from external files (especially if the files could be modified by other users or processes).
     • Data received from network requests (e.g., from a web service).
  2. Implement Sanitization (Before Setting Text): Before setting the Text property (or equivalent) of a terminal.gui control with untrusted data, always sanitize the input. This sanitization is specifically for the terminal.gui context:
     • Remove Control Characters: Remove or replace characters that could be interpreted as control characters or escape sequences by the terminal. This is crucial to prevent unexpected behavior or potential (though unlikely) injection attacks. Use a robust method; a simple char.IsControl check might not be sufficient.
     • Context-Aware Encoding: If you need to display characters that have special meaning in the terminal (e.g., you're building a terminal emulator), use appropriate encoding to ensure they are displayed literally and not interpreted. This is a complex task and should ideally be handled by a dedicated library, if available. Do not attempt to write your own encoding/decoding routines unless you have a deep understanding of terminal emulators and escape sequences.
     • Example (C#, Simplified Sanitization - Before setting myTextView.Text):

       string sanitizedText = SanitizeForTerminalDisplay(untrustedText);
       myTextView.Text = sanitizedText;
       
       // ...
       
       string SanitizeForTerminalDisplay(string input) {
           // 1. Remove/Replace Control Characters (More Robust Example)
           StringBuilder sb = new StringBuilder();
           foreach (char c in input) {
               if (char.IsControl(c)) {
                   // Replace with a space or a specific replacement character
                   sb.Append(' ');
               } else {
                   sb.Append(c);
               }
           }
           string result = sb.ToString();
       
           // 2. Basic Escape Sequence Removal (VERY SIMPLIFIED - Use a library if possible)
           result = result.Replace("\x1b", ""); // Remove ESC character
       
           return result;
       }

  3. Prefer "Plain Text" Controls: When possible, use terminal.gui controls that are designed for displaying plain text and are less likely to interpret special characters. If terminal.gui offers a control specifically for plain text, use it.

• Threats Mitigated:

  • Cross-Site Scripting (XSS) - (Theoretical): (Severity: Medium) - Prevents injection of malicious control sequences.
  • Unexpected UI Behavior: (Severity: Low) - Prevents formatting issues and unexpected behavior.

• Impact:

  • XSS: Reduces the (low) risk.
  • Unexpected UI Behavior: Improves UI stability.

• Currently Implemented:

  • [Example: "No sanitization is currently performed on data loaded from external configuration files before displaying in a TextView."]
  • [Example: "User comments are sanitized (using a basic control character removal) before display in the ActivityLog view (ListView)."]

• Missing Implementation:

  • [Example: "Need to implement sanitization for data received from the remote API before displaying it in the ServerStatus view (TextView)."]
  • [Example: "The HelpText view (TextView) loads content from Markdown files; this content needs to be sanitized before display."]