attack-tree.md

Attack Tree Analysis for blueimp/jquery-file-upload

Objective: To achieve Remote Code Execution (RCE) on the server hosting the application using jquery-file-upload, or to exfiltrate sensitive data accessible to the application.

Attack Tree Visualization

                                      +-------------------------------------------------+
                                      |  Attacker Achieves RCE or Data Exfiltration     |
                                      |  via jquery-file-upload                          |
                                      +-------------------------------------------------+
                                                       |
          +----------------------------------------------------------------------------------------------------------------+
          |                                                                                                                |
+-------------------------+                                                                               +-------------------------------------+
|  1. Bypass File Type    |                                                                               |  3. Leverage Configuration Issues | [CRITICAL]
|     Restrictions        |  [HIGH-RISK]                                                                  |                                     |
+-------------------------+                                                                               +-------------------------------------+
          |                                                                                                                       |
+---------+---------+                                                                                     +---------+---------+---------+
| **1.1** |         |                                                                                     | **3.1** |         | 3.4     |
| **Client-**|         |                                                                                     | **Overly**|         | Insecure|
| **side** |         |                                                                                     | **Permis-**|         | Direct- |
| **Valida-**|         |                                                                                     | **sive** |         | ory     |
| **tion** |         |                                                                                     | **Upload**|         | Traver- |
| **Bypass**|         |                                                                                     | **Dir**  |         | sal     |
| [CRITICAL]|         |                                                                                     | [CRITICAL]|         | [CRITICAL]
+---------+---------+                                                                                     +---------+---------+---------+
          |                                                                                                        |         |
+---------+---------+                                                                                              +---------+
| **1.3** |         |                                                                                              |  3.6    |
| **MIME**|         |                                                                                              | **Missing**|
| **Type**|         |                                                                                              | **Content**|
| **Spoof-**|         |                                                                                              | **Type** |
| **ing** |         |                                                                                              | **Check**|
| [CRITICAL]|         |                                                                                              | [CRITICAL]|
+---------+---------+                                                                                              +---------+
          |
+---------+
|  **1.6** |
|  **File**|
|  **Name**|
|  **Manipu-**|
|  **lation**|
+---------+

          +-------------------------------------+          
          |  2. Exploit Server-Side Scripting  |          
          |     Vulnerabilities (Implicit)     |          
          +-------------------------------------+          
                       |
          +---------+---------+---------+
          | 2.1     | 2.2     | 2.3     |
          | Image   | PHP     | Node.js |
          | Tragic  | RCE     | RCE     |
          | Exploit | (e.g.,  | (e.g.,  |
          |         | CVEs)   | CVEs)   |
          +---------+---------+---------+

Attack Tree Path: 1. Bypass File Type Restrictions (High-Risk Path)

This is the most common initial attack vector.

• 1.1 Client-Side Validation Bypass [CRITICAL]:

  • Description: The attacker modifies the client-side JavaScript code (using browser developer tools or a proxy) to bypass any file type restrictions enforced by the jquery-file-upload library's client-side components. This is trivial to do.
  • Likelihood: Very High
  • Impact: Depends on server-side validation; can range from Low to Very High (if no server-side checks)
  • Effort: Very Low
  • Skill Level: Script Kiddie
  • Detection Difficulty: Very Hard (No server-side trace)
  • Mitigation: Never rely solely on client-side validation. Implement robust server-side checks.

• 1.3 MIME Type Spoofing [CRITICAL]:

  • Description: The attacker intercepts the HTTP request and changes the Content-Type header to a value that the server expects (e.g., image/jpeg), even though the file's actual content is malicious (e.g., a PHP script).
  • Likelihood: High (If server relies solely on Content-Type header)
  • Impact: Depends on server-side validation; can range from Low to Very High
  • Effort: Low (Use a proxy like Burp Suite)
  • Skill Level: Beginner
  • Detection Difficulty: Medium to Hard (Requires server-side content analysis)
  • Mitigation: Do not trust the Content-Type header. Validate the file content using server-side checks (e.g., magic number, file signature analysis).

• 1.6 File Name Manipulation:

  • Description: The attacker crafts a malicious filename to exploit vulnerabilities in how the server handles filenames. This could involve using special characters, long filenames, Unicode characters, or other techniques to cause unexpected behavior or bypass security checks.
  • Likelihood: Low to Medium (Depends on specific vulnerabilities)
  • Impact: Variable, could range from Low (DoS) to High (RCE, file overwrite)
  • Effort: Variable, depends on the specific vulnerability
  • Skill Level: Intermediate to Advanced
  • Detection Difficulty: Medium to Hard (Requires careful logging and analysis of filenames)
  • Mitigation: Sanitize filenames rigorously on the server-side. Remove or replace potentially dangerous characters. Consider generating unique filenames on the server.

Attack Tree Path: 3. Leverage Configuration Issues (Critical Nodes)

• 3.1 Overly Permissive Upload Directory [CRITICAL]:

  • Description: The directory where uploaded files are stored has incorrect permissions (e.g., 777 or world-writable), allowing any user on the system (including the web server user) to write and potentially execute files.
  • Likelihood: Medium (Unfortunately common misconfiguration)
  • Impact: Very High (RCE, data exfiltration)
  • Effort: Very Low (Just upload a file)
  • Skill Level: Script Kiddie
  • Detection Difficulty: Easy (If file permissions are checked regularly)
  • Mitigation: Set strict file permissions on the upload directory. Use the principle of least privilege. The web server user should only have the minimum necessary permissions (typically write access, but not execute).

• 3.4 Insecure Directory Traversal [CRITICAL]:

  • Description: The attacker uses ../ (or similar path traversal sequences) in the filename to attempt to upload files outside the intended upload directory. This could allow them to overwrite critical system files or place malicious files in locations where they can be executed.
  • Likelihood: Low to Medium (Depends on server-side code)
  • Impact: High to Very High (File overwrite, RCE, data exfiltration)
  • Effort: Low (Use ../ in filename)
  • Skill Level: Beginner
  • Detection Difficulty: Medium (Requires careful input validation and logging)
  • Mitigation: Sanitize filenames rigorously. Ensure that the server-side code properly handles relative paths and prevents access to directories outside the intended upload location. Use a well-tested library function for handling file paths, rather than manually constructing them.

• 3.6 Missing Content-Type Check (Server-Side) [CRITICAL]:

  • Description: The server-side code does not validate the actual content of the uploaded file. It might rely solely on the client-side checks (which are easily bypassed) or the Content-Type header (which is easily spoofed).
  • Likelihood: High (If developers rely on client-side checks or the Content-Type header)
  • Impact: High to Very High (Potential RCE)
  • Effort: Low
  • Skill Level: Beginner
  • Detection Difficulty: Medium to Hard
  • Mitigation: Implement robust server-side file type validation. Use multiple methods, such as checking the file extension (with awareness of double extensions), the magic number, and potentially using a library like finfo in PHP to determine the file type based on content. Do not trust the Content-Type header.

Attack Tree Path: 2. Exploit Server-Side Scripting Vulnerabilities (Implicit High-Risk Path)

This path becomes high-risk if the attacker successfully bypasses file type restrictions (branch 1).

• 2.1 ImageTragic Exploit (and similar): Exploiting vulnerabilities in image processing libraries (e.g., ImageMagick).
• 2.2 PHP RCE (e.g., CVEs): Exploiting known vulnerabilities in PHP.
• 2.3 Node.js RCE (e.g., CVEs): Exploiting known vulnerabilities in Node.js.

The likelihood, impact, effort, skill level, and detection difficulty for these depend on the specific vulnerability being exploited. The mitigation is to keep all server-side software (including libraries) up-to-date and to use secure coding practices.