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attack-surface.md

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Attack Surface Analysis for gofiber/fiber

Attack Surface: Route Parameter Injection (Fiber's Parsing)

  • Description: Exploiting how Fiber internally parses and handles route parameters (e.g., /users/:id), going beyond basic application-level input validation. This is about Fiber's parsing logic, not the developer's validation.
  • How Fiber Contributes: Fiber's ctx.Params() and related functions are responsible for extracting and making these parameters available. The underlying parsing logic, type handling, and any implicit conversions within Fiber are the key attack surface.
  • Example: If Fiber doesn't strictly enforce an expected integer :id at the routing level, an attacker might provide /users/abc or /users/1;DROP TABLE users. Even with application validation, Fiber's initial parsing could cause issues (panics, unexpected behavior). Injecting very long strings to test for buffer overflows or resource exhaustion within Fiber's parameter handling is another example.
  • Impact: Potential for application crashes (panics within Fiber), unexpected behavior in middleware that relies on ctx.Params(), bypassing of intended route constraints (if Fiber has them), and potentially influencing later application logic (though proper validation is still the application's responsibility).
  • Risk Severity: High.
  • Mitigation Strategies:
    • Developer: Utilize Fiber's built-in parameter constraints (if available and appropriate) to enforce data types and lengths at the routing level. This is Fiber's first line of defense. Example: :id<int> if supported.
    • Developer: Thoroughly review Fiber's source code and documentation related to parameter parsing to understand its limitations and edge cases.
    • Developer: Fuzz test routes with unexpected parameter values, specifically targeting Fiber's parsing logic. This is distinct from application-level input validation fuzzing.

Attack Surface: Middleware Bypass/Misconfiguration (Fiber's Pipeline)

  • Description: Incorrect ordering or conditional execution of Fiber middleware, allowing attackers to bypass security controls. This focuses on Fiber's middleware execution mechanism.
  • How Fiber Contributes: Fiber's middleware system (app.Use(), app.Group(), route-specific middleware application) defines the request processing pipeline. Incorrect configuration within Fiber's system is the vulnerability.
  • Example: Placing authorization middleware after authentication middleware (a configuration error within Fiber's setup). Another example: a bug in Fiber's middleware logic that allows a route to be accessed without going through the intended middleware chain.
  • Impact: Unauthorized access to protected resources, data breaches, privilege escalation – all stemming from bypassing Fiber's intended security flow.
  • Risk Severity: Critical.
  • Mitigation Strategies:
    • Developer: Carefully plan and document the middleware chain, paying close attention to the order of execution as defined by Fiber's API.
    • Developer: Thoroughly test all routes, including edge cases, to ensure that the intended middleware is executed in the correct order by Fiber.
    • Developer: Use Fiber's grouping features (app.Group()) to logically organize routes and apply middleware consistently, leveraging Fiber's mechanisms for structured application.
    • Developer: Audit Fiber's middleware execution logic (if possible) to identify potential bypass vulnerabilities within the framework itself.

Attack Surface: Request Body Parsing Vulnerabilities (Fiber's Parsers)

  • Description: Exploiting vulnerabilities in how Fiber itself parses request bodies (JSON, XML, form data, multipart). This is about Fiber's parsing implementations, not just the application's use of the parsed data.
  • How Fiber Contributes: Fiber's ctx.BodyParser(), ctx.FormValue(), and related functions are the direct attack surface. The underlying parsing libraries used by Fiber and Fiber's integration with them are crucial.
  • Example: Sending a deeply nested JSON payload to cause resource exhaustion within Fiber's JSON parser, sending an excessively large request body to cause a denial-of-service by overwhelming Fiber's parsing capabilities, or sending malformed XML to exploit vulnerabilities in Fiber's XML parsing implementation.
  • Impact: Denial of service (due to Fiber's resource exhaustion), application crashes (panics within Fiber's parsing logic), potential for remote code execution (if the underlying parsing library used by Fiber has vulnerabilities).
  • Risk Severity: High to Critical.
  • Mitigation Strategies:
    • Developer: Use Fiber's built-in body size limits (if available) to prevent excessively large requests at the Fiber level. This is a framework-provided defense.
    • Developer: Review Fiber's documentation and source code for the parsing libraries it uses. Investigate any known vulnerabilities in those libraries.
    • Developer: Fuzz test API endpoints with various malformed request bodies, specifically targeting Fiber's parsing functions. This is distinct from application-level input validation fuzzing.

Attack Surface: Unhandled Errors in Middleware (Fiber's Error Handling)

  • Description: Improper error handling within Fiber middleware functions, leading to information leakage due to Fiber's default or misconfigured error responses.
  • How Fiber Contributes: Fiber's middleware execution and error handling mechanisms (ctx.Next(err), and the behavior of Fiber's default or custom global error handlers) are the direct concern. If errors aren't caught by Fiber and handled gracefully by Fiber, internal details might be exposed.
  • Example: A middleware function panics, and Fiber's default error handler (or a poorly configured custom handler) returns a stack trace or other sensitive information. This is about Fiber's response to the error.
  • Impact: Information disclosure (stack traces, internal error messages, potentially revealing details about Fiber's internals or the application's structure).
  • Risk Severity: High
  • Mitigation Strategies:
    • Developer: Implement a global error handler in Fiber that catches all unhandled errors and returns a generic, non-sensitive error response. This is a Fiber-level configuration.
    • Developer: Ensure that Fiber's error handling mechanism is configured to not expose internal error messages or stack traces in production.
    • Developer: Thoroughly test error handling within middleware to ensure that Fiber behaves as expected and doesn't leak information.