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attack-surface.md

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Attack Surface Analysis for dotnet/aspnetcore

Attack Surface: Middleware Misconfiguration

  • Description: Incorrect ordering, omission, or overly permissive configuration of ASP.NET Core middleware components, leading to security bypass.
  • ASP.NET Core Contribution: The middleware pipeline is a core architectural feature of ASP.NET Core. Its flexibility, while powerful, is a direct source of this risk if mismanaged.
  • Example: Placing authentication middleware after authorization, allowing unauthenticated access. A CORS middleware allowing all origins (AllowAnyOrigin = true).
  • Impact: Bypass of security controls, unauthorized access, data breaches, denial of service.
  • Risk Severity: High to Critical.
  • Mitigation Strategies:
    • Correct Ordering: Prioritize security middleware (authentication, authorization, rate limiting) early in the pipeline.
    • Principle of Least Privilege: Configure middleware with the strictest necessary settings. Avoid wildcards.
    • Regular Review: Audit the middleware pipeline configuration frequently.
    • Secure Defaults: Use built-in middleware with secure defaults when possible.
    • Thorough Testing: Include negative test cases to verify security controls.
    • Robust Exception Handling: Prevent information leaks or DoS through proper exception handling in all middleware.

Attack Surface: Model Binding and Mass Assignment

  • Description: Attackers exploit ASP.NET Core's model binding to modify properties they shouldn't have access to.
  • ASP.NET Core Contribution: ASP.NET Core's model binding mechanism, while convenient, is the direct vector for this attack if not properly secured.
  • Example: An attacker adds IsAdmin=true to a form submission, leveraging model binding to gain admin privileges.
  • Impact: Privilege escalation, data corruption, unauthorized access.
  • Risk Severity: High to Critical.
  • Mitigation Strategies:
    • ViewModels/DTOs: Use dedicated ViewModels/DTOs, binding only to the necessary properties. Avoid binding directly to domain models.
    • [Bind] Attribute (Strictly): Use [Bind] to explicitly whitelist allowed properties for binding. Be extremely precise.
    • Server-Side Input Validation: Always validate input on the server, regardless of client-side checks.

Attack Surface: Unintended Endpoint Exposure

  • Description: Exposing internal APIs or administrative endpoints due to misconfiguration of ASP.NET Core's routing.
  • ASP.NET Core Contribution: ASP.NET Core's flexible routing system is the direct enabler of this vulnerability if not carefully managed.
  • Example: A controller action without an [Authorize] attribute, intended for internal use, becomes publicly accessible.
  • Impact: Unauthorized access to sensitive data or functionality.
  • Risk Severity: High to Critical.
  • Mitigation Strategies:
    • [Authorize] Attribute: Apply [Authorize] to all controllers/actions requiring authentication/authorization.
    • Route Constraints: Use constraints to restrict access based on HTTP verb, parameters, etc.
    • API Versioning: Clearly separate public and internal APIs using versioning.
    • Code Reviews: Regularly review code for unintentionally exposed endpoints.

Attack Surface: Insufficient Input Validation (within ASP.NET Core Context)

  • Description: Failing to properly validate input within the context of ASP.NET Core's features, such as model binding, routing, or SignalR hubs.
  • ASP.NET Core Contribution: While input validation is a general concept, ASP.NET Core provides specific mechanisms (Data Annotations, Fluent Validation, IValidatableObject) that, if misused or neglected, create this vulnerability. This also includes validation within SignalR hubs and gRPC services.
  • Example: Relying solely on client-side validation for data bound to a model, or failing to sanitize user input before broadcasting it via SignalR.
  • Impact: XSS (especially in SignalR), data corruption, potential for other injection attacks depending on how the data is used.
  • Risk Severity: High.
  • Mitigation Strategies:
    • Server-Side Validation (Always): Never trust client-side validation alone.
    • Data Annotations/Fluent Validation: Use these ASP.NET Core features effectively for model validation.
    • SignalR Input Sanitization: Sanitize all user input before broadcasting it in SignalR hubs.
    • gRPC Input Validation: Implement robust input validation within gRPC service methods.
    • Context-Aware Validation: Validate data in the context of how it will be used within the ASP.NET Core application (e.g., encoding for Razor views).

Attack Surface: Secrets Management Failures (within ASP.NET Core Configuration)

  • Description: Insecurely storing secrets, particularly within the context of ASP.NET Core's configuration system.
  • ASP.NET Core Contribution: ASP.NET Core's configuration system (e.g., appsettings.json, environment variables) is where secrets are typically managed. Misusing this system is the direct cause.
  • Example: Storing a database connection string in appsettings.json and committing it to source control.
  • Impact: Data breaches, unauthorized access.
  • Risk Severity: Critical.
  • Mitigation Strategies:
    • Environment Variables: Use environment variables for secrets.
    • Azure Key Vault (or similar): Use a dedicated secrets management service.
    • User Secrets (Development ONLY): Use User Secrets only for local development.
    • Never Commit Secrets: Absolutely never commit secrets to source control.
    • Configuration Builders: Load secrets dynamically at runtime.

Attack Surface: Authentication and Authorization Weaknesses (ASP.NET Core Identity & Features)

  • Description: Flaws in the implementation of authentication and authorization, specifically leveraging ASP.NET Core Identity or related features.
  • ASP.NET Core Contribution: ASP.NET Core Identity is a core framework component for managing users, roles, and claims. Misconfiguration or misuse of this framework is the direct source of the vulnerability.
  • Example: Weak password policies in ASP.NET Core Identity, improper session management, or failing to use [Authorize] correctly.
  • Impact: Account takeover, privilege escalation, data breaches.
  • Risk Severity: High to Critical.
  • Mitigation Strategies:
    • Strong Password Policies (Identity): Enforce strong password requirements within ASP.NET Core Identity.
    • Secure Session Management: Use secure cookies, short timeouts, and proper session invalidation.
    • [Authorize] Attribute (Consistent Use): Apply [Authorize] to all protected resources.
    • RBAC (Identity Roles): Use ASP.NET Core Identity's role-based access control effectively.
    • MFA: Implement multi-factor authentication.
    • Account Lockout: Prevent brute-force attacks with account lockout.
    • Token Validation (Strict): If using JWTs, rigorously validate all aspects (signature, expiration, audience, issuer).

Attack Surface: Outdated ASP.NET Core Framework/Packages

  • Description: Running an outdated version of the ASP.NET Core framework itself or its direct dependencies, containing known vulnerabilities.
  • ASP.NET Core Contribution: This is a direct vulnerability stemming from not keeping the core ASP.NET Core framework and its components up-to-date.
  • Example: Using an unpatched version of ASP.NET Core with a known remote code execution vulnerability.
  • Impact: Remote code execution, denial of service, data breaches.
  • Risk Severity: Critical.
  • Mitigation Strategies:
    • Regular Updates: Update ASP.NET Core and its direct dependencies to the latest stable versions.
    • Dependency Scanning: Use tools to identify outdated or vulnerable packages.
    • Automated Updates: Consider tools like Dependabot for automated updates.
    • Monitor Advisories: Stay informed about security advisories specifically for ASP.NET Core.