Identification of HTTP Method Tampering

HTTP method tampering is a security vulnerability that occurs when an attacker modifies the HTTP method used in a request to manipulate the behavior of the application. This type of attack can lead to unauthorized actions, access to sensitive data, or the execution of unintended functionality. As a penetration tester, identifying HTTP method tampering involves examining how the application handles different HTTP methods and checking for vulnerabilities that arise from improper handling or validation. Here's how you can identify HTTP method tampering:

Identification

  1. HTTP Method Usage Analysis: Review the application to identify all areas where HTTP methods are used. This includes not only standard HTTP methods like GET and POST but also less common methods like PUT, DELETE, PATCH, etc.
  2. HTTP Method Enforcement: Check if the application enforces proper usage of HTTP methods according to the intended functionality. For example, sensitive operations should only be allowed via specific methods (e.g., DELETE for deleting resources).
  3. Input Validation: Examine how the application validates and handles user input related to HTTP methods. Look for places where user-supplied data influences the HTTP method used in requests.
  4. HTTP Method Overrides: Check if the application supports the X-HTTP-Method-Override header or similar mechanisms that allow clients to override the HTTP method used in a request. Improper handling of method overrides can lead to security vulnerabilities.
  5. Unexpected Behavior: Test the application with different HTTP methods than those intended for specific functionalities. Observe how the application responds and look for unexpected behavior or actions that should not be allowed.
  6. Bypassing Access Controls: Try to bypass access controls or perform unauthorized actions by tampering with HTTP methods. For example, attempt to access privileged resources using HTTP methods that should be restricted.

Examples

  • Example 1: A penetration tester discovers that an application uses the GET method for sensitive operations, such as deleting user accounts. By changing the method to GET in a request, the tester is able to execute unintended actions, leading to unauthorized account deletions.
  • Example 2: During testing, the tester notices that the application uses client-supplied data to determine the HTTP method for processing requests without proper validation. This allows the tester to manipulate the method and perform actions that should be restricted.

Mitigation

  1. Strict Method Validation: Implement strict validation of HTTP methods used in requests, ensuring that each functionality is only accessible via the appropriate methods.
  2. Access Controls: Enforce proper access controls and permissions based on the HTTP method and the action being performed.
  3. Avoid Method Overrides: Disable or restrict mechanisms like X-HTTP-Method-Override that allow clients to override the HTTP method, especially for sensitive operations.
  4. Input Sanitization: Properly validate and sanitize user input related to HTTP methods to prevent injection attacks or method tampering.
  5. Security Headers: Utilize security headers like Allow and Strict-Transport-Security to communicate supported HTTP methods and enhance security.
  6. Regular Testing: Continuously test the application for HTTP method tampering vulnerabilities, especially after updates or changes to the application's functionality.

By identifying and addressing HTTP method tampering vulnerabilities, penetration testers can help organizations prevent unauthorized actions, protect sensitive data, and ensure the security of their web applications.