threat-modeling.md

Threat Model Analysis for mingrammer/diagrams

Threat: Remote Code Execution (RCE) via Input Injection

• Description: An attacker crafts malicious input (e.g., through a web form field intended for a node label) that, when incorporated into the diagrams Python code, executes arbitrary commands on the server. The attacker might inject Python code snippets like __import__('os').system('rm -rf /') or similar, disguised within seemingly harmless text. This leverages the fact that diagrams generates and executes Python code. The vulnerability is in how the application uses diagrams to generate and run code.
• Impact: Complete system compromise. The attacker could gain full control of the server, steal data, install malware, disrupt services, or use the server for further attacks.
• Affected Component: The core diagrams code generation process, specifically where user-supplied data is interpolated into the Python code string that's later executed (e.g., within functions that create nodes, edges, or clusters). The vulnerability lies in how the application uses diagrams, not necessarily within diagrams itself.
• Risk Severity: Critical
• Mitigation Strategies:
  • Primary: Never directly embed user-provided data into the diagrams code string.
  • Data-Driven Approach: Create a validated data structure (e.g., a Python dictionary) representing the diagram, and then use a trusted function to convert this data structure into diagrams code. This separates data from code.
  • Strict Schema Validation: Define a strict schema for the data structure, specifying allowed data types, lengths, and patterns for each field (node names, labels, etc.). Reject any input that doesn't conform to the schema.
  • Whitelist Input Validation: For any data that must come from user input, use a whitelist of allowed characters and patterns. Reject anything outside the whitelist.
  • Sandboxing: Execute the diagrams code (the generated Python script) within a tightly controlled, isolated environment (e.g., a Docker container with minimal privileges and resource limits, or a chroot jail).
  • Least Privilege: Run the application (and the sandboxed environment) with the lowest possible privileges necessary.

Threat: Denial of Service (DoS) via Resource Exhaustion

• Description: An attacker submits input designed to create an extremely large or complex diagram. This could involve specifying a massive number of nodes, edges, or deeply nested clusters. The goal is to overwhelm the server's resources (CPU, memory) during the diagram generation process, causing the application to crash or become unresponsive. This directly exploits the processing requirements of diagrams and its underlying libraries.
• Impact: Application unavailability. Legitimate users cannot access the application or generate diagrams.
• Affected Component: The diagrams library itself, and potentially the underlying Graphviz library, when processing the generated code. The resource consumption happens during the execution of the diagrams code.
• Risk Severity: High
• Mitigation Strategies:
  • Input Limits: Enforce strict limits on the number of nodes, edges, clusters, and nesting levels allowed in a diagram. Reject input exceeding these limits.
  • Timeouts: Implement a timeout for the diagram generation process. If generation takes longer than a predefined threshold, terminate the process.
  • Resource Quotas: Run the diagrams code execution within an environment with resource quotas (e.g., a Docker container with CPU and memory limits).
  • Rate Limiting: Limit the number of diagram generation requests a user can make within a given time period.
  • Monitoring: Monitor resource usage (CPU, memory) during diagram generation. Alert administrators if usage exceeds predefined thresholds.