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Attack Tree Analysis for bpmn-io/bpmn-js

Objective: To manipulate the execution or interpretation of BPMN diagrams rendered by bpmn-js within a web application, leading to unauthorized actions, data leakage, or denial of service.

Attack Tree Visualization

Manipulate BPMN Diagram Execution/Interpretation (L:M, I:H, E:M, S:M, D:M)
    |
    ├── 1. Malicious BPMN XML Injection (L:M, I:H, E:M, S:M, D:M) ***
    │   ├── 1.1. Bypass Input Validation (L:M, I:H, E:L, S:L, D:L) ***
    │   │   └── 1.1.1. Find an entry point for user-provided XML (L:H, I:H, E:L, S:L, D:L) ***
    │   │       └── 1.1.1.1. Identify vulnerable form fields, API endpoints, or file upload features (L:H, I:H, E:L, S:L, D:L) ***
    │   └── 1.2. Leverage Server-Side Processing (L:M, I:H, E:M, S:M, D:M)
    │       └── 1.2.1. Inject malicious script tags or attributes that trigger server-side logic (L:M, I:H, E:M, S:H, D:M)
    │           └── 1.2.1.1. Identify vulnerable server-side libraries or functions that process BPMN XML (L:M, I:H, E:M, S:H, D:M)
    └── 2. Exploit Client-Side Rendering Logic
        └── 2.1. XSS via Diagram Elements/Attributes (L:H, I:H, E:M, S:M, D:M) ***
            └── 2.1.1. Inject malicious JavaScript into diagram element properties (e.g., `documentation`, `name`) that are rendered without proper sanitization. (L:H, I:H, E:M, S:M, D:M)
                └── 2.1.1.1. Identify vulnerable diagram elements and attributes. (L:H, I:H, E:M, S:M, D:M) ***

Attack Tree Path: 1. Malicious BPMN XML Injection (Critical Node)

  • Description: The attacker provides a crafted BPMN XML file or input that contains malicious code or data. This is the foundation for many attacks against systems that process BPMN.
  • Likelihood (Medium): Depends on the application's input validation and how it handles user-supplied XML. Many applications fail to properly validate XML.
  • Impact (High): Can lead to arbitrary code execution, data breaches, denial of service, and complete system compromise.
  • Effort (Medium): Requires understanding of BPMN XML structure and potential injection points. Tools and techniques are readily available.
  • Skill Level (Medium): Requires knowledge of XML, XSS, and potentially server-side scripting languages.
  • Detection Difficulty (Medium): Can be difficult to detect if the application doesn't have robust logging and intrusion detection systems.

Attack Tree Path: 1.1. Bypass Input Validation (Critical Node)

  • Description: The attacker circumvents any checks that are in place to prevent malicious XML from being processed.
  • Likelihood (Medium): Many applications have weak or incomplete input validation.
  • Impact (High): Allows the attacker to inject arbitrary XML, enabling further attacks.
  • Effort (Low): Often involves simple techniques like trying different encodings or bypassing client-side checks.
  • Skill Level (Low): Basic understanding of web application security.
  • Detection Difficulty (Low): Failed validation attempts can often be logged, but attackers may try to obfuscate their attempts.

Attack Tree Path: 1.1.1. Find an entry point for user-provided XML (Critical Node)

  • Description: The attacker identifies a location in the application where user input is accepted and used to construct or modify a BPMN XML document.
  • Likelihood (High): Many applications accept user input in various forms.
  • Impact (High): Provides the necessary pathway for the injection attack.
  • Effort (Low): Can be as simple as looking for forms, file upload features, or API endpoints.
  • Skill Level (Low): Basic web application reconnaissance skills.
  • Detection Difficulty (Low): Normal user activity; difficult to distinguish malicious intent at this stage without context.

Attack Tree Path: 1.1.1.1. Identify vulnerable form fields, API endpoints, or file upload features (Critical Node)

  • Description: The attacker specifically targets input fields, API calls, or file upload mechanisms that are not properly secured.
  • Likelihood (High): Vulnerabilities in these areas are common.
  • Impact (High): Directly leads to successful XML injection.
  • Effort (Low): Standard penetration testing techniques can identify these vulnerabilities.
  • Skill Level (Low): Basic web application security testing skills.
  • Detection Difficulty (Low): Can be detected through input validation failures and unusual request patterns.

Attack Tree Path: 1.2. Leverage Server-Side Processing

  • Description: The attacker exploits vulnerabilities in how the server processes the BPMN XML. This is particularly dangerous if the server executes code based on the XML content.
  • Likelihood (Medium): Depends on the server-side implementation. If the server uses the XML for logic or database queries, the risk is higher.
  • Impact (High): Can lead to remote code execution (RCE), data modification, or denial of service.
  • Effort (Medium): Requires understanding of the server-side technology and how it interacts with the BPMN XML.
  • Skill Level (Medium): Requires knowledge of server-side vulnerabilities and exploitation techniques.
  • Detection Difficulty (Medium): Can be difficult to detect without proper logging and intrusion detection.

Attack Tree Path: 1.2.1. Inject malicious script tags or attributes that trigger server-side logic

  • Description: The attacker inserts code into the BPMN XML that will be executed by the server.
  • Likelihood (Medium): Depends on the server-side processing logic.
  • Impact (High): Can lead to RCE or other severe consequences.
  • Effort (Medium): Requires understanding of the server-side scripting language and the BPMN XML structure.
  • Skill Level (High): Requires advanced knowledge of server-side vulnerabilities.
  • Detection Difficulty (Medium): Can be detected through input validation, code review, and monitoring of server logs.

Attack Tree Path: 1.2.1.1. Identify vulnerable server-side libraries or functions that process BPMN XML

  • Description: The attacker researches the server-side code to find weaknesses in how it handles the XML.
  • Likelihood (Medium): Depends on the complexity and security of the server-side code.
  • Impact (High): Enables the attacker to craft a targeted exploit.
  • Effort (Medium): Requires access to the server-side code or significant reverse engineering effort.
  • Skill Level (High): Requires advanced knowledge of server-side programming and security.
  • Detection Difficulty (Medium): Difficult to detect without code analysis or vulnerability scanning.

Attack Tree Path: 2. Exploit Client-Side Rendering Logic

Attack Tree Path: 2.1. XSS via Diagram Elements/Attributes (Critical Node)

  • Description: The attacker injects malicious JavaScript code into the BPMN XML, which is then executed by the victim's browser when the diagram is rendered.
  • Likelihood (High): If output encoding is not properly implemented, this is a very common vulnerability.
  • Impact (High): Can lead to session hijacking, data theft, defacement, and other client-side attacks.
  • Effort (Medium): Requires knowledge of XSS techniques and the specific attributes of BPMN elements that are rendered.
  • Skill Level (Medium): Requires understanding of JavaScript and DOM manipulation.
  • Detection Difficulty (Medium): Can be detected by web application firewalls (WAFs) and browser security extensions, but sophisticated XSS attacks can bypass these defenses.

Attack Tree Path: 2.1.1. Inject malicious JavaScript into diagram element properties (Critical Node)

  • Description: The attacker crafts a BPMN XML file where attributes like documentation or name contain JavaScript code.
  • Likelihood (High): If the application doesn't sanitize these attributes, this is a direct path to XSS.
  • Impact (High): Allows the attacker to execute arbitrary JavaScript in the victim's browser.
  • Effort (Medium): Requires understanding of HTML and JavaScript.
  • Skill Level (Medium): Standard XSS knowledge.
  • Detection Difficulty (Medium): Can be detected by input validation and output encoding, but attackers may use obfuscation techniques.

Attack Tree Path: 2.1.1.1. Identify vulnerable diagram elements and attributes (Critical Node)

  • Description: The attacker examines the bpmn-js library and the application's code to determine which elements and attributes are rendered without proper sanitization.
  • Likelihood (High): This is a necessary step for a successful XSS attack.
  • Impact (High): Directly enables the XSS attack.
  • Effort (Medium): Requires inspecting the rendered HTML and potentially the JavaScript code.
  • Skill Level (Medium): Requires understanding of HTML, JavaScript, and how bpmn-js renders diagrams.
  • Detection Difficulty (Medium): Requires careful code review and testing.