mitigations.md

Mitigation Strategies Analysis for gorilla/mux

Mitigation Strategy: Strict Route Definitions

• Description:

  1. Review Existing Routes: Examine all routes defined using gorilla/mux. Identify any routes that use broad matchers (e.g., {id}, {filename:.+}).
  2. Refine Matchers: Replace broad matchers with more specific ones provided by mux. For example:
     • If {id} is expected to be a numeric ID, use r.HandleFunc("/users/{id:[0-9]+}", ...)
     • If {filename} must adhere to a specific format, use a regular expression that enforces that format, leveraging mux's regex capabilities: r.HandleFunc("/files/{filename:[a-zA-Z0-9_-]+\.txt}", ...)
     • If a parameter has a limited set of valid values, consider using a custom matcher function in combination with mux.MatcherFunc.
  3. StrictSlash Consideration: Carefully evaluate the use of StrictSlash(true). Understand its implications for redirects and potential security considerations (e.g., caching, redirect loops). Only use it if the behavior is fully understood and desired.
  4. Test Thoroughly: After refining matchers, use a comprehensive suite of unit and integration tests to ensure that the routes behave as expected, including testing with invalid and malicious inputs. These tests should specifically target mux's routing logic.
  5. Document Route Specifications: Clearly document the expected format and constraints for each route parameter, as enforced by the mux configuration.

• List of Threats Mitigated:

  • Path Traversal (High Severity): By using more restrictive matchers within the route definition, we limit the input that mux will even consider for a given route, reducing the attack surface.
  • Parameter Pollution (Medium Severity): Similar to path traversal, stricter matchers limit the characters and values that mux accepts as part of the route.
  • Unexpected Routing (Medium Severity): Ensures that requests are routed to the correct handlers by design, as enforced by mux's matching rules.

• Impact:

  • Path Traversal: Risk significantly reduced (from High to Low) at the routing level.
  • Parameter Pollution: Risk reduced (from Medium to Low) at the routing level.
  • Unexpected Routing: Risk reduced (from Medium to Low) at the routing level.

• Currently Implemented: Partially implemented. Numeric IDs are enforced using [0-9]+ in /users/{id:[0-9]+}. Filename validation is present in the handler for /files/{filename}, but the route itself uses {filename:.+}.

• Missing Implementation: The /files/{filename} route needs to be updated to use a more restrictive matcher within mux (e.g., {filename:[a-zA-Z0-9_-]+\.txt}). Other routes using generic path parameters (if any) need review and refinement within their mux definitions.

Mitigation Strategy: Careful Middleware Ordering (within mux)

• Description:

  1. Identify mux Middleware: List all middleware used directly with mux (using router.Use(...) or subrouter-specific middleware).
  2. Analyze Dependencies: Determine the dependencies between middleware components as they relate to routing. For example, authentication middleware should run before authorization middleware, and both should be registered with mux.
  3. Establish Correct Order: Define the correct order of middleware execution within the mux context, ensuring that security-related middleware runs early in the chain.
  4. Apply Order (using router.Use): Apply the middleware in the defined order using router.Use(...) or by chaining middleware appropriately within the mux router or subrouters.
  5. Test Middleware Chain (with mux): Create integration tests that specifically test the behavior of the middleware chain as it interacts with mux's routing, including scenarios where middleware should block or modify requests before they reach a handler.

• List of Threats Mitigated:

  • Authentication Bypass (High Severity): Ensures that authentication checks (registered with mux) are performed before any sensitive operations are even considered by mux.
  • Authorization Bypass (High Severity): Ensures that authorization checks (registered with mux) are performed after authentication and before mux routes the request to a handler.
  • CORS Misconfiguration (Medium Severity): Ensures that CORS headers (if handled by mux middleware) are set correctly before any other processing by mux.
  • Rate Limiting Bypass (Medium Severity): Ensures that rate limiting (if handled by mux middleware) is applied before any resource-intensive operations are routed by mux.

• Impact:

  • Authentication/Authorization Bypass: Risk significantly reduced (from High to Low) at the routing level.
  • CORS Misconfiguration, Rate Limiting Bypass: Risk reduced (from Medium to Low) at the routing level.

• Currently Implemented: Middleware order is generally correct, with authentication and authorization before request processing, all registered with mux. CORS middleware is applied globally using router.Use.

• Missing Implementation: Review the global application of CORS middleware within mux. Consider applying it more selectively to specific routes or subrouters using mux's features. Add more comprehensive integration tests to verify the middleware chain's behavior within the context of mux routing under various conditions.

Mitigation Strategy: Route Ordering Awareness (within mux)

• Description:

  1. List All mux Routes: Create a list of all routes defined using mux, including those in subrouters.
  2. Analyze Specificity (within mux): Identify routes that could potentially conflict based on mux's matching rules. For example, /users/new and /users/{id}.
  3. Order by Specificity (in mux definition): Order routes from most specific to least specific within the mux router definition. More specific routes (e.g., /users/new) should be defined before less specific routes (e.g., /users/{id}) in the code where mux routes are registered.
  4. Test Route Matching (using mux): Create tests that specifically verify that requests are routed to the correct handlers by mux, especially for cases where routes might overlap. These tests should interact directly with the mux router.

• List of Threats Mitigated:

  • Unexpected Routing (Medium Severity): Prevents requests from being unintentionally routed to the wrong handler due to overlapping route definitions as interpreted by mux.

• Impact:

  • Unexpected Routing: Risk reduced (from Medium to Low) due to correct mux route ordering.

• Currently Implemented: Generally implemented correctly. Specific routes like /users/new are defined before more general routes like /users/{id} in the mux configuration.

• Missing Implementation: A comprehensive review of all routes and subrouters within the mux configuration should be performed to ensure that there are no unintended overlaps or conflicts. Add tests specifically for edge cases and potential conflicts, interacting directly with the mux router.

Mitigation Strategy: Regular Expression Review (for mux Routes)

• Description:

  1. Identify Regex Routes (in mux): Identify all routes defined using mux that use regular expressions.
  2. Review for Complexity (within mux context): Analyze each regular expression for complexity and potential for catastrophic backtracking, considering how mux uses these expressions.
  3. Simplify (If Possible, within mux): If possible, simplify the regular expression or use a different, non-regex matcher provided by mux.
  4. Test with Regex Tester (for mux compatibility): Use a regular expression testing tool, ensuring the expressions are compatible with Go's regexp package (which mux uses). Test with a variety of inputs, including malicious ones.
  5. Document Regex Intent (for mux usage): Clearly document the intended purpose and behavior of each regular expression as it relates to its use within mux.

• List of Threats Mitigated:

  • Regular Expression Denial of Service (ReDoS) (Medium Severity): Prevents attackers from crafting inputs that cause the regular expression engine (used by mux) to consume excessive CPU resources.
  • Unexpected Matching (Medium Severity): Ensures that the regular expression (within mux) matches only the intended inputs and does not have unintended side effects.

• Impact:

  • ReDoS: Risk reduced (from Medium to Low) at the routing level.
  • Unexpected Matching: Risk reduced (from Medium to Low) at the routing level.

• Currently Implemented: Limited. Some regular expressions are used in mux route definitions, but they haven't been thoroughly reviewed for ReDoS vulnerabilities.

• Missing Implementation: A comprehensive review of all regular expressions used in mux routes is needed. Each expression should be tested for ReDoS vulnerabilities and simplified if possible, within the context of how mux uses them.

Mitigation Strategy: Subrouter Best Practices (within mux)

• Description:

  1. Define Clear Boundaries (using mux subrouters): Establish clear boundaries and responsibilities for each subrouter created using mux.NewRouter().PathPrefix(...).Subrouter(). Avoid overlapping or ambiguous path prefixes.
  2. Consistent Middleware (applied to mux subrouters): Apply necessary middleware (authentication, authorization, etc.) consistently to subrouters using the subrouter's Use(...) method. Avoid situations where a subrouter bypasses security checks applied to the main router.
  3. Isolate Concerns (with mux subrouters): Use mux subrouters to logically group related routes and handlers, improving code organization and maintainability.
  4. Test Subrouter Interactions (with mux): Create integration tests that specifically test the interactions between subrouters and their parent routers within the mux framework, including middleware behavior.

• List of Threats Mitigated:

  • Unexpected Routing (Medium Severity): Prevents requests from being routed to the wrong handler due to misconfigured mux subrouters.
  • Middleware Bypass (High Severity): Ensures that security-related middleware is applied correctly to all mux subrouters.

• Impact:

  • Unexpected Routing: Risk reduced (from Medium to Low) due to correct mux subrouter configuration.
  • Middleware Bypass: Risk reduced (from High to Low) due to correct mux subrouter middleware application.

• Currently Implemented: Subrouters are used for API versioning (e.g., /v1/..., /v2/...) using mux. Middleware is applied to the main router.

• Missing Implementation: Explicitly apply security-related middleware to each mux subrouter, even if it's already applied to the main router. This provides an extra layer of defense and ensures consistency within the mux routing structure. Add integration tests to verify mux subrouter behavior.