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Attack Tree Analysis for nikic/fastroute

Objective: To achieve Remote Code Execution (RCE) or Denial of Service (DoS) on the application server by exploiting vulnerabilities or misconfigurations within the nikic/fastroute routing mechanism.

Attack Tree Visualization

                                      +-------------------------------------------------+
                                      |  Attacker Achieves RCE or DoS via FastRoute  |
                                      +-------------------------------------------------+
                                                       |
          +------------------------------------------------------------------------------------------------+
          |                                                                                                |
+-------------------------+                                                                   
|  Exploit Route Handling  |                                                                  
+-------------------------+                                                                   
          |                                                                                                
+---------------------+                                    +---------------------+                         
|  Regex Vulnerabilities |                                    |  Variable Injection  |                         
|  [HIGH RISK]           |                                    |  [HIGH RISK] [CRITICAL] |                         
+---------------------+                                    +---------------------+                         
          |                                                                                                
+-------+-------+                                            +-------+-------+                                   
| ReDoS |  Catastrophic |                                            |  Uncontrolled |                                   
| [CRITICAL] |  Backtracking|                                            |  Route Vars  |                                   
|       |              |                                            |   [CRITICAL]   |                                   
+-------+-------+                                            +-------+-------+                                   
          |                                                                                                
+-------+-------+                                            +-------+-------+
| Craft |  Craft |                                            |  Craft |  Craft |
| Malicious|  Malicious|                                            |  Malicious|  Malicious|
| Regex |  Regex |                                            |  Route   |  Route   |
| Input |  Input |                                            |  Input   |  Input   |
| (User  |  (Admin/  |                                            |  (User)  |  (User)  |
|  Data) |  Dev)    |                                            |          |          |
+-------+-------+

Attack Tree Path: 1. Exploit Route Handling

Attack Tree Path: 1.a. Regex Vulnerabilities [HIGH RISK]

  • Description: This attack vector focuses on exploiting weaknesses in the regular expressions used by FastRoute to define and match routes. Poorly crafted regexes, especially those incorporating user input, can be vulnerable to attacks.

Attack Tree Path: 1.a.i. ReDoS (Regular Expression Denial of Service) [CRITICAL]

  • Description: A ReDoS attack occurs when an attacker provides a specially crafted input string that causes the regular expression engine to enter a state of excessive backtracking, consuming significant CPU resources and leading to a denial of service.
  • Likelihood: Medium to High
  • Impact: Medium to High (DoS)
  • Effort: Low to Medium
  • Skill Level: Intermediate
  • Detection Difficulty: Medium
  • Mitigation:
    • Strictly validate all user-supplied input used in regexes.
    • Audit all regular expressions for ReDoS vulnerabilities (nested quantifiers, overlapping alternations).
    • Implement timeouts for regex matching operations.
    • Monitor CPU usage and response times.

Attack Tree Path: 1.a.ii. Catastrophic Backtracking

  • Description: Similar to ReDoS, but can occur even without malicious user input if the developer-defined regular expression is inherently vulnerable due to its structure.
  • Likelihood: Low to Medium
  • Impact: Medium to High (DoS)
  • Effort: Medium
  • Skill Level: Intermediate to Advanced
  • Detection Difficulty: Medium to Hard
  • Mitigation:
    • Carefully review and audit all developer-defined regular expressions.
    • Use tools to test for catastrophic backtracking.
    • Implement timeouts.

Attack Tree Path: Entry Point

  • Craft Malicious Regex Input (User Data): The attacker provides malicious input through a user-facing form or API endpoint that is used, directly or indirectly, in a regular expression for route matching.
  • Craft Malicious Regex Input (Admin/Dev): In less common scenarios, if administrators or developers can define routes through an interface, a compromised admin account or a malicious developer could introduce a vulnerable regex.

Attack Tree Path: 1.b. Variable Injection [HIGH RISK] [CRITICAL]

  • Description: This attack vector involves injecting malicious data into route variables, potentially leading to arbitrary code execution or other security compromises. This occurs when user input is not properly validated and sanitized before being used within route parameters.

Attack Tree Path: 1.b.i. Uncontrolled Route Vars [CRITICAL]

  • Description: This is the core vulnerability. If the application does not properly validate and sanitize the data placed into route variables, an attacker can inject arbitrary values.
  • Likelihood: Low to Medium (depends heavily on application code)
  • Impact: High to Very High (potential RCE)
  • Effort: Medium to High
  • Skill Level: Advanced
  • Detection Difficulty: Medium to Hard
  • Mitigation:
    • Always validate and sanitize user input before using it in route parameters.
    • Use FastRoute's parameterized route syntax with type constraints (e.g., /user/{id:\d+}).
    • Avoid dynamic route generation based on user input.

Attack Tree Path: Entry Point

  • Craft Malicious Route Input (User): The attacker crafts a malicious request where the values provided for route parameters (e.g., in the URL) contain the injected code or data.