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attack-surface.md

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Attack Surface Analysis for standardnotes/app

Attack Surface: Client-Side Encryption Key Compromise (App Code)

  • Description: An attacker gains access to the user's master encryption key due to flaws within the Standard Notes client application code.
  • How App Contributes: The client application is entirely responsible for generating, storing (temporarily), and using the encryption key. Any weakness in this process is a direct vulnerability in the app.
  • Example: A bug in the key derivation function (KDF) implementation, insecure storage of the key in memory (allowing for memory scraping), or a vulnerability that allows a malicious extension to access the key. A compromised build process injecting malicious code.
  • Impact: Complete loss of confidentiality for all user notes.
  • Risk Severity: Critical
  • Mitigation Strategies (Developers):
    • Use a strong, well-vetted KDF (e.g., Argon2id) with a high iteration count, ensuring correct implementation within the app code.
    • Implement robust input validation and sanitization within the client to prevent injection attacks that could compromise key handling.
    • Secure the build process to prevent supply chain attacks that could inject key-logging or key-exfiltration code.
    • Conduct regular security audits and penetration testing of the client application code, focusing on cryptographic operations.
    • Implement secure memory management to prevent key leakage, ensuring keys are zeroed out after use and protected from unauthorized access.
    • Implement robust extension sandboxing and permission controls within the client application to prevent extensions from accessing the key.
    • Provide a secure and transparent extension review process, focusing on code analysis for potential key compromise vulnerabilities.

Attack Surface: Malicious or Vulnerable Extensions (App Code Interaction)

  • Description: An attacker exploits a vulnerability in a Standard Notes extension, or publishes a malicious extension, to gain access to user data or the encryption key by interacting with vulnerabilities in the core application's extension handling.
  • How App Contributes: The Standard Notes client application defines the extension API and manages the interaction between extensions and the core application. Weaknesses in this interaction are direct vulnerabilities.
  • Example: The client application fails to properly sandbox an extension, allowing it to access the main application's memory space and steal the encryption key. The client's inter-process communication (IPC) mechanism between the app and extensions is insecure.
  • Impact: Potential loss of confidentiality, integrity, and availability of user data. Could lead to complete account compromise.
  • Risk Severity: High
  • Mitigation Strategies (Developers):
    • Implement a rigorous review process for all extensions, focusing on code analysis to identify potential security flaws that could interact with the main application.
    • Enforce strict sandboxing and permission controls for extensions within the client application code. This is the primary defense.
    • Provide clear documentation and guidelines for extension developers on secure coding practices, specifically addressing how to interact safely with the main application's API.
    • Regularly audit existing extensions for vulnerabilities, focusing on how they interact with the core application.
    • Implement a mechanism for quickly disabling or removing malicious extensions, controlled by the client application.
    • Use a Content Security Policy (CSP) within the client application to limit the resources extensions can access, further restricting their capabilities.
    • Secure the inter-process communication (IPC) between the client and extensions.

Attack Surface: Server-Side Vulnerabilities (Standard Notes Server Code)

  • Description: An attacker exploits a vulnerability in the Standard Notes server software code to gain access to encrypted user data, metadata, or the server infrastructure.
  • How App Contributes: This is entirely dependent on the code of the Standard Notes server application.
  • Example: A SQL injection vulnerability in the server code allows database access. A remote code execution vulnerability allows server takeover. Improper handling of authentication tokens.
  • Impact: Potential loss of confidentiality (of encrypted data and metadata), integrity, and availability. Could lead to a denial-of-service attack or compromise of the entire server infrastructure.
  • Risk Severity: High
  • Mitigation Strategies (Developers):
    • Follow secure coding practices within the server codebase to prevent common web application vulnerabilities (e.g., SQL injection, XSS, CSRF, command injection).
    • Regularly update all server-side dependencies to patch known vulnerabilities. This includes libraries used by the server application.
    • Conduct regular security audits and penetration testing of the server software code.
    • Implement robust logging and monitoring within the server application to detect and respond to security incidents.
    • Implement strong authentication and authorization mechanisms within the server code.