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Attack Tree Analysis for carrierwaveuploader/carrierwave

Objective: Gain unauthorized access to sensitive data, execute arbitrary code on the server, or disrupt the application's availability (DoS) specifically by exploiting CarrierWave's functionality.

Attack Tree Visualization

Compromise Application via CarrierWave | --------------------------------- | |

  1. Unauthorized Access 2. Arbitrary Code Execution | |
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1.1 2.1 Bypass File Upload Malicious Validation File (RCE) | |

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1.1.1 [HIGH RISK] 2.1.1 [HIGH RISK][CRITICAL] Improper MIME Type Double Extension (e.g., .php.jpg) Checking | ----- | 2.1.1.1 [HIGH RISK][CRITICAL] Bypass Content-Type Validation (e.g., using magic bytes) --------------------------------- | 2. Arbitrary Code Execution |

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2.2 Upload File with Exploitable Extension |

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2.2.1 [CRITICAL] ImageTragick Exploit (if used) |

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2.2.1.1 [CRITICAL]
Bypass Image
Processing Library
Validation

Attack Tree Path: High-Risk Path 1: Improper MIME Type Checking leading to RCE

  • Overall Description: This path represents the most likely route for an attacker to achieve Remote Code Execution (RCE) by exploiting weaknesses in how the application validates uploaded files. It leverages the common mistake of relying solely on the easily spoofed Content-Type HTTP header.

  • Steps:

    1. 1.1.1 Improper MIME Type Checking [HIGH RISK]:

      • Description: The application only checks the Content-Type header provided by the client (browser or attacker's tool) during file upload. This header can be easily manipulated. The application does not verify the actual file content.
      • Likelihood: Medium
      • Impact: High (potential for RCE)
      • Effort: Low
      • Skill Level: Intermediate
      • Detection Difficulty: Medium

    2. 2.1.1 Double Extension (e.g., .php.jpg) [HIGH RISK] [CRITICAL]:

      • Description: The attacker uploads a file with a double extension, such as malicious.php.jpg. This exploits misconfigured web servers (e.g., older Apache setups) that might execute the first extension (.php) if the last extension (.jpg) is not recognized or handled.
      • Likelihood: Low
      • Impact: Very High (RCE)
      • Effort: Low
      • Skill Level: Intermediate
      • Detection Difficulty: Medium

    3. 2.1.1.1 Bypass Content-Type Validation (e.g., using magic bytes) [HIGH RISK] [CRITICAL]:

      • Description: The attacker crafts a file that appears to be a valid image (e.g., a JPEG) by including the correct "magic bytes" (file signature) at the beginning of the file. However, after the initial bytes that make it look like an image, the file contains malicious PHP code. This bypasses simple content checks that only look at the beginning of the file.
      • Likelihood: Medium
      • Impact: Very High (RCE)
      • Effort: Medium
      • Skill Level: Intermediate
      • Detection Difficulty: Medium

Attack Tree Path: Critical Nodes (without High-Risk Path):

  1. 2.2.1 ImageTragick Exploit (if used) [CRITICAL]:
    • Description: If the application uses ImageMagick (or a wrapper like MiniMagick) for image processing, and an unpatched, vulnerable version is present, the attacker can upload a specially crafted image file designed to exploit known vulnerabilities (collectively known as "ImageTragick").
    • Likelihood: Low (due to widespread patching)
    • Impact: Very High (RCE)
    • Effort: Medium
    • Skill Level: Advanced
    • Detection Difficulty: Hard
  2. 2.2.1.1 Bypass Image Processing Library Validation [CRITICAL]:
    • Description: This represents a zero-day vulnerability scenario. The attacker discovers and exploits a previously unknown vulnerability in the image processing library (e.g., ImageMagick, MiniMagick, RMagick). They craft an image file that triggers this vulnerability, leading to RCE.
    • Likelihood: Low
    • Impact: Very High (RCE)
    • Effort: High
    • Skill Level: Expert
    • Detection Difficulty: Very Hard