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Attack Tree Analysis for fizzed/font-mfizz

Objective: Achieve RCE or DoS via font-mfizz

Attack Tree Visualization

Attacker Goal: Achieve RCE or DoS via font-mfizz

├── 1. Achieve Remote Code Execution (RCE)
│   ├── 1.1 Exploit SVG Parsing Vulnerabilities [HIGH RISK]
│   │   ├── 1.1.1  XXE (XML External Entity) Injection in SVG [CRITICAL] [HIGH RISK]
│   │   │   ├── 1.1.1.1  Read Arbitrary Files (e.g., /etc/passwd)
│   │   │   ├── 1.1.1.2  Internal Port Scanning
│   │   │   ├── 1.1.1.3  SSRF (Server-Side Request Forgery) to internal services
│   │   │   └── 1.1.1.4  Trigger Out-of-Band Data Exfiltration (DNS, HTTP)
│   └── 1.3 Exploit Configuration File Vulnerabilities
│       ├── 1.3.1  Command Injection via Configuration [CRITICAL]
│       │   └── 1.3.1.1  If the configuration file allows for execution of arbitrary commands (e.g., through a poorly sanitized "post-processing" script), inject malicious commands.
└── 2. Achieve Denial of Service (DoS)
    ├── 2.1  Resource Exhaustion via SVG Parsing [HIGH RISK]
    │   ├── 2.1.1  Billion Laughs Attack (XML Entity Expansion) [CRITICAL]
    │   ├── 2.1.2  Quadratic Blowup Attack (Nested Entities)
    │   ├── 2.1.3  Deeply Nested XML Structures
    │   └── 2.1.4  Large Image Dimensions/Filesize [CRITICAL]

Attack Tree Path: 1. Achieve Remote Code Execution (RCE)

  • 1.1 Exploit SVG Parsing Vulnerabilities [HIGH RISK]

    • Description: This is the primary attack surface. SVG files are parsed as XML, and vulnerabilities in the XML parsing process can lead to RCE.

    • Mitigation Strategies:

      • Disable external entity resolution completely.
      • Use a secure and up-to-date XML parser.
      • Implement strict input validation and sanitization.
      • Limit resource consumption (entity expansion, image size, etc.).
      • Fuzz test the SVG parsing component.

    • 1.1.1 XXE (XML External Entity) Injection in SVG [CRITICAL] [HIGH RISK]

      • Description: The attacker crafts an SVG file that includes malicious external XML entities. If the parser resolves these entities, it can lead to:
        • 1.1.1.1 Read Arbitrary Files: The attacker can read files from the server's file system (e.g., /etc/passwd, configuration files).
        • 1.1.1.2 Internal Port Scanning: The attacker can probe internal ports on the server or other internal systems.
        • 1.1.1.3 SSRF (Server-Side Request Forgery): The attacker can make the server send requests to internal or external services, potentially exploiting vulnerabilities in those services.
        • 1.1.1.4 Trigger Out-of-Band Data Exfiltration: The attacker can exfiltrate data through DNS or HTTP requests.
      • Likelihood: Medium to High (if external entities are not disabled)
      • Impact: High to Very High
      • Effort: Low to Medium
      • Skill Level: Intermediate
      • Detection Difficulty: Medium
      • Mitigation: Completely disable external entity resolution in the XML parser. This is the most crucial mitigation.

  • 1.3 Exploit Configuration File Vulnerabilities

    • 1.3.1 Command Injection via Configuration [CRITICAL]
      • Description: If the application allows the configuration file to specify commands or scripts to be executed (e.g., for post-processing), and this input is not properly sanitized, the attacker can inject malicious commands.
      • 1.3.1.1: Inject malicious commands to be executed by the server.
      • Likelihood: Low (if configuration parsing is done securely)
      • Impact: Very High (Direct RCE)
      • Effort: Low
      • Skill Level: Intermediate
      • Detection Difficulty: Medium
      • Mitigation:
        • Strictly validate and sanitize all input from the configuration file.
        • Do not allow the configuration file to specify arbitrary commands or scripts.
        • If post-processing is necessary, use a tightly controlled and sandboxed environment.

Attack Tree Path: 2. Achieve Denial of Service (DoS)

  • 2.1 Resource Exhaustion via SVG Parsing [HIGH RISK]

    • Description: The attacker crafts SVG files designed to consume excessive server resources (CPU, memory, disk space), leading to a denial of service.

    • Mitigation Strategies:

      • Limit XML entity expansion depth and count.
      • Limit SVG image dimensions and file size.
      • Limit the number of glyphs and fonts that can be generated.

    • 2.1.1 Billion Laughs Attack (XML Entity Expansion) [CRITICAL]

      • Description: The attacker defines XML entities that recursively expand, leading to exponential growth in memory consumption.
      • Likelihood: Medium
      • Impact: Medium to High
      • Effort: Low
      • Skill Level: Novice
      • Detection Difficulty: Easy
      • Mitigation: Limit XML entity expansion depth and count.

    • 2.1.2 Quadratic Blowup Attack (Nested Entities)

      • Description: Similar to Billion Laughs, but uses a different pattern of nested entities to achieve resource exhaustion.
      • Likelihood: Medium
      • Impact: Medium to High
      • Effort: Low
      • Skill Level: Novice
      • Detection Difficulty: Easy
      • Mitigation: Limit XML entity expansion depth and count.

    • 2.1.3 Deeply Nested XML Structures

      • Description: Even without entity expansion, deeply nested XML structures can consume significant resources during parsing.
      • Likelihood: Medium
      • Impact: Medium
      • Effort: Low
      • Skill Level: Novice
      • Detection Difficulty: Easy
      • Mitigation: Limit the depth of nested XML structures.

    • 2.1.4 Large Image Dimensions/Filesize [CRITICAL]

      • Description: The attacker provides an SVG file with extremely large dimensions or a very large file size, causing the server to consume excessive memory or processing time.
      • Likelihood: Medium
      • Impact: Medium
      • Effort: Low
      • Skill Level: Novice
      • Detection Difficulty: Easy
      • Mitigation: Implement strict limits on SVG image dimensions and file size.