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attack-surface.md

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Attack Surface Analysis for getstream/stream-chat-flutter

Attack Surface: Improper Token Handling/Storage

  • Description: User authentication and authorization in Stream Chat rely on tokens. Mishandling these tokens on the client-side exposes the application to significant risks.
  • How stream-chat-flutter Contributes: The library provides methods for connecting users with tokens (connectUser). It's the developer's responsibility to securely manage these tokens. The library itself doesn't enforce secure storage.
  • Example: A developer stores the user token in plain text in SharedPreferences (Android) or UserDefaults (iOS) without encryption. An attacker with root access to the device, or using a compromised backup, can retrieve the token.
  • Impact: Complete account takeover. The attacker can impersonate the user, read/send messages, and access any data the user has permission to access.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Developers: Use secure storage mechanisms provided by the OS (Keychain on iOS, Keystore on Android). Utilize the flutter_secure_storage package for a convenient cross-platform solution. Never hardcode tokens. Avoid logging tokens. Use environment-specific tokens.
    • Users: (Limited direct mitigation). Be cautious about installing untrusted applications on the same device.

Attack Surface: Client-Side Permission Bypass

  • Description: Attempting to bypass client-side UI restrictions or logic that appears to enforce permissions, even though the Stream Chat API (server-side) is the ultimate authority.
  • How stream-chat-flutter Contributes: The library provides information about user roles and permissions (e.g., through the User object). Developers might use this information to show/hide UI elements. The vulnerability arises if developers rely on these client-side checks for security.
  • Example: An application hides an "Admin Settings" button for non-admin users based on the user.role property. An attacker modifies the application's memory to change their user.role to "admin" and gains access to the button. (The server should still prevent unauthorized actions, but the attacker might gain access to sensitive information displayed in the UI).
  • Impact: Potential unauthorized access to UI features and potentially sensitive data displayed within those features. May lead to further attacks if the client-side logic is flawed.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developers: Treat client-side permission checks as purely cosmetic. Always rely on the Stream Chat API (server-side) for authorization. Any action that requires specific permissions must be validated by the server. Don't expose sensitive data in the UI based solely on client-side checks.
    • Users: (No direct mitigation).

Attack Surface: Cross-Site Scripting (XSS) in Message Content

  • Description: Injecting malicious JavaScript into message content, which is then executed in the context of other users' browsers or applications.
  • How stream-chat-flutter Contributes: The library handles the display of message content. If custom rendering is used (e.g., to support Markdown or custom HTML), and the developer doesn't properly sanitize the input, XSS is possible. The default rendering should be safe, but custom implementations are a risk.
  • Example: An attacker sends a message containing <script>alert('XSS')</script>. If the application renders this directly without sanitization, the JavaScript will execute when another user views the message.
  • Impact: The attacker can steal cookies, session tokens, or other sensitive data. They can redirect the user to a malicious website, deface the application, or perform other actions in the context of the victim's session.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developers: Always sanitize user-generated content before displaying it. Use a robust HTML sanitizer like the html_sanitizer package or configure flutter_html very carefully to prevent XSS. Avoid custom rendering logic unless absolutely necessary, and if used, ensure thorough sanitization. Consider using a Content Security Policy (CSP).
    • Users: (Limited direct mitigation).

Attack Surface: Improper handling of custom events

  • Description: Vulnerabilities related to the use of custom events.
    • How stream-chat-flutter Contributes: The library allows sending and receiving custom events.
    • Example: An attacker sends custom event with malicious payload that is not validated on client side.
    • Impact: Attackers can inject false data, trigger unauthorized actions, or potentially cause denial of service.
    • Risk Severity: High
    • Mitigation Strategies:
      • Developers: Always validate custom event data on the client side, before processing it.
      • Users: (No direct mitigation).