attack-surface.md

Attack Surface Analysis for gorilla/mux

Attack Surface: Overly Broad Route Matching

Description: Defining routes with excessively permissive patterns in mux (e.g., wildcards, overly broad regular expressions) can lead to unintended route matches, allowing access to handlers meant for different resources or paths.

• Mux Contribution: mux's flexible routing system, including path variables and regular expressions in route definitions, directly enables the creation of overly broad routes if developers are not sufficiently specific in their patterns.
• Example: A mux route defined as /api/{resource:.*} intended to handle API requests for various resources, might unintentionally match /api/admin/sensitive-endpoint, bypassing intended access controls for the admin endpoint if it was meant to be more specifically routed.
• Impact: Unintended access to sensitive functionalities or data, bypassing intended access control mechanisms, potentially leading to data breaches or unauthorized actions.
• Risk Severity: Critical
• Mitigation Strategies:
  • Principle of Least Privilege in Route Definitions: Define routes with the most specific path patterns possible. Avoid using broad wildcards (.*, {variable:.*}) or overly permissive regular expressions unless absolutely necessary and with extreme caution.
  • Prioritize Specific Routes: Ensure that more specific routes are defined and registered in mux before more general or wildcard routes to guarantee correct matching precedence.
  • Regular Route Audits: Conduct periodic reviews of mux route configurations to identify and rectify any overly broad patterns that could lead to unintended access.

Attack Surface: Lack of Input Validation on Path Parameters

Description: mux facilitates the extraction of path parameters from URLs based on route definitions. If application handlers fail to rigorously validate these path parameters, it can create pathways for severe injection vulnerabilities.

• Mux Contribution: mux's core functionality is to parse URLs and extract path parameters based on defined routes. This parameter extraction mechanism directly provides the input points that become vulnerable if not validated in subsequent handler logic. mux itself does not perform any input validation on these parameters.
• Example: A mux route /files/{filepath} where the filepath parameter is directly used within the handler to construct file paths for file retrieval without any validation. An attacker could manipulate filepath to include path traversal sequences like ../../../../etc/passwd, potentially reading sensitive system files.
• Impact: Path Traversal, Command Injection, SQL Injection (indirectly if parameters are used in database queries), arbitrary file read, and potential for full system compromise depending on the context of parameter usage in handlers.
• Risk Severity: Critical
• Mitigation Strategies:
  • Mandatory Input Validation: Implement strict input validation and sanitization for all path parameters extracted by mux within handler functions before using them in any application logic, especially when constructing file paths, system commands, or database queries.
  • Whitelist Validation: Where possible, validate path parameters against a strict whitelist of allowed values or patterns instead of relying solely on blacklist filtering.
  • Secure Parameter Handling Libraries: Utilize libraries specifically designed for input validation and sanitization to reduce the risk of common validation bypasses.

Attack Surface: Middleware Order Dependency Leading to Security Bypass

Description: mux's middleware chaining mechanism allows for request processing pipelines. However, an incorrect order of middleware, particularly placing security-critical middleware after request processing or error handling middleware, can lead to a complete bypass of security measures.

• Mux Contribution: mux's middleware functionality allows developers to define the order in which middleware functions are executed. This explicit ordering control, while powerful, becomes a potential attack surface if developers misconfigure the order, inadvertently placing security middleware in an ineffective position in the chain.
• Example: If authentication middleware is placed after a logging middleware that processes and logs request parameters, including sensitive data, an unauthenticated request might be logged with sensitive information before the authentication check occurs. Even worse, if authorization middleware is placed after middleware that handles requests and performs actions based on them, unauthorized actions could be executed before authorization is ever checked.
• Impact: Complete bypass of authentication and authorization controls, exposure of sensitive data due to logging before security checks, execution of unauthorized actions, and fundamental compromise of application security posture.
• Risk Severity: Critical
• Mitigation Strategies:
  • Security Middleware First: Always ensure that security-critical middleware (authentication, authorization, input validation, rate limiting) is placed at the very beginning of the mux middleware chain, before any middleware that processes requests, handles errors, or performs actions based on request data.
  • Middleware Chain Review and Documentation: Thoroughly document and regularly review the mux middleware chain to verify the correct order and ensure that security middleware is positioned effectively.
  • Testing Middleware Order: Implement integration tests that specifically verify the correct execution and enforcement of security middleware in the defined order within the mux middleware chain.