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Threat Model Analysis for jgraph/drawio

Threat: Cross-Site Scripting (XSS) via Malicious Diagram Content

  • Description: An attacker crafts a draw.io diagram file (XML/SVG) containing malicious JavaScript code within <script> tags, on* event attributes, or javascript: URLs within shape attributes or text. When a victim opens the diagram, the injected script executes in the context of the victim's browser session. This is a direct threat because it exploits how draw.io handles and renders diagram data.
    • Impact: The attacker can steal cookies, session tokens, or other sensitive information, redirect the user to a phishing site, deface the application, or perform other actions on behalf of the victim.
    • Affected draw.io Component: mxEditor, mxGraph, diagram parsing and rendering logic (specifically, handling of XML/SVG content). The vulnerability lies in how draw.io processes and renders potentially untrusted diagram data.
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Strict Input Validation and Sanitization: Before rendering any diagram data, rigorously validate and sanitize the XML/SVG content. Use a whitelist approach, allowing only known-safe elements and attributes. Specifically, disallow <script> tags, on* event attributes, and javascript: URLs entirely. Use a robust XML/SVG parser with built-in security features.
      • Content Security Policy (CSP): Implement a strict CSP that prevents the execution of inline scripts (script-src 'self'), and restricts the loading of external resources. This is a crucial defense-in-depth measure. A well-configured CSP can prevent XSS even if input validation fails.
      • Output Encoding: While primarily relevant for user-generated text within diagrams, ensure that any text displayed within the diagram is properly encoded to prevent it from being interpreted as HTML.
      • Sandboxing (iframe): Render the draw.io editor and viewer within a sandboxed iframe with limited permissions (e.g., sandbox="allow-scripts allow-same-origin allow-forms" – carefully consider the necessary permissions). This limits the impact of a successful XSS attack.
      • Server-Side Validation: Always validate and sanitize diagram data on the server-side before storing or processing it. Client-side validation can be bypassed.

Threat: Denial of Service (DoS) via Resource Exhaustion (Large Diagram)

  • Description: An attacker uploads or creates a diagram file containing an extremely large number of elements (shapes, connectors, text), deeply nested structures, or excessively large embedded images. This overwhelms the draw.io library, causing excessive CPU and memory consumption, leading to a denial of service for other users. This is a direct threat because it targets the resource handling capabilities of draw.io.
    • Impact: The application becomes unresponsive or crashes, preventing legitimate users from accessing or using the draw.io functionality, and potentially affecting the entire application.
    • Affected draw.io Component: mxGraph, mxCodec, diagram parsing and rendering logic. The vulnerability lies in the library's handling of large or complex diagrams.
    • Risk Severity: High
    • Mitigation Strategies:
      • Input Size Limits: Enforce strict limits on the size of uploaded diagram files (e.g., maximum file size in bytes).
      • Element Count Limits: Limit the maximum number of elements (shapes, connectors, etc.) allowed in a diagram. This can be enforced both client-side (for immediate feedback) and server-side (for security).
      • Image Size and Dimension Limits: Restrict the size and dimensions of embedded images within diagrams. Reject images that exceed predefined limits.
      • Resource Quotas (Server-Side): If draw.io processing is done server-side (e.g., for image generation), implement resource quotas (CPU, memory) to prevent a single request from consuming excessive resources.
      • Rate Limiting: Limit the rate at which users can upload or process diagrams, preventing an attacker from flooding the system with malicious requests.
      • Progressive Loading/Rendering (if feasible): Explore techniques to load and render large diagrams incrementally, rather than all at once, to reduce the initial resource burden.

Threat: XML External Entity (XXE) Injection

  • Description: An attacker crafts a diagram file (XML format) that includes malicious external entity references. When the draw.io library (or a server-side component processing the XML) parses the file, it attempts to resolve these external entities, potentially leading to information disclosure, server-side request forgery (SSRF), or denial of service. This is a direct threat if draw.io's XML parsing is vulnerable.
    • Impact: The attacker can read local files on the server, access internal network resources, or cause a denial of service by triggering excessive resource consumption.
    • Affected draw.io Component: mxCodec, XML parsing logic (specifically, handling of external entities). This is most relevant if the application uses server-side processing of draw.io XML files.
    • Risk Severity: High
    • Mitigation Strategies:
      • Disable External Entities: Configure the XML parser used by draw.io (or the server-side component) to completely disable the resolution of external entities and DTDs. This is the most effective mitigation. For example, in Java, use XMLInputFactory.IS_SUPPORTING_EXTERNAL_ENTITIES = false and XMLInputFactory.SUPPORT_DTD = false.
      • Use a Secure XML Parser: Ensure that the XML parser used is configured securely and is up-to-date with the latest security patches.
      • Input Validation: While disabling external entities is the primary mitigation, as a defense-in-depth measure, validate the XML structure to ensure it conforms to the expected schema and doesn't contain suspicious elements or attributes.

Threat: Server-Side Request Forgery (SSRF) via Embedded URLs

  • Description: An attacker embeds malicious URLs within a diagram (e.g., in shape properties, hyperlinks, or custom attributes). If draw.io (or a server-side component) attempts to fetch resources from these URLs (e.g., for image previews or data retrieval), the attacker can trigger requests to internal network resources or external systems, potentially leading to information disclosure or other attacks. This is a direct threat if draw.io's handling of URLs is flawed.
    • Impact: The attacker can access internal services, scan internal networks, or potentially exploit vulnerabilities in other systems.
    • Affected draw.io Component: mxGraph, mxImageExport (if used server-side), any components that handle URL loading or processing. This is particularly relevant if the application uses server-side rendering or processing of diagrams.
    • Risk Severity: High
    • Mitigation Strategies:
      • URL Whitelisting: If the application needs to fetch resources from external URLs embedded in diagrams, implement a strict whitelist of allowed domains and protocols. Reject any URLs that don't match the whitelist.
      • Network Segmentation: Isolate the server-side components that process draw.io diagrams from sensitive internal networks.
      • Disable URL Loading (if possible): If fetching external resources is not required, disable this functionality entirely within draw.io's configuration.
      • Input Validation: Validate and sanitize all URLs embedded within diagrams, rejecting any URLs that contain suspicious characters or patterns.