threat-modeling.md

Threat Model Analysis for pallets/jinja

Threat: Server-Side Template Injection (SSTI)

• Description:
  • Attacker Action: An attacker injects malicious Jinja code into user-controlled input.
  • Method: By crafting payloads that exploit Jinja syntax, the attacker aims to execute arbitrary code on the server by manipulating template logic to break out of the intended template context.
• Impact:
  • Remote Code Execution (RCE): Full control over the server.
  • Data Breach: Access to sensitive data.
  • Privilege Escalation: Gaining higher privileges.
  • Denial of Service (DoS): Crashing the application or server.
• Affected Jinja Component:
  • Environment.from_string()
  • Environment.get_template() (in vulnerable scenarios)
  • Jinja Expression Parsing and Evaluation Engine
• Risk Severity: Critical
• Mitigation Strategies:
  • Parameterize Templates: Treat user input as data, not code, and pass it as context variables.
  • Principle of Least Privilege for Template Context: Limit the objects and functions exposed in the template context.
  • Sandboxed Jinja Environment (Defense-in-Depth): Consider using a sandboxed environment as a secondary defense.
  • Regular Security Audits and Penetration Testing: Specifically test for SSTI vulnerabilities.

Threat: Insecure Custom Filters and Global Functions

• Description:
  • Attacker Action: An attacker exploits vulnerabilities in custom Jinja filters or global functions.
  • Method: By providing malicious input to custom components that are not securely implemented, attackers can achieve code injection, information disclosure, or bypass security controls.
• Impact:
  • Code Injection (RCE): If custom filters/functions execute arbitrary code.
  • Information Disclosure: If custom filters/functions expose sensitive data.
  • Security Bypass: If custom filters/functions circumvent security measures.
• Affected Jinja Component:
  • Custom Filters (filters in Environment)
  • Global Functions (globals in Environment)
  • Python code implementing custom filters and functions
• Risk Severity: High (if RCE is possible)
• Mitigation Strategies:
  • Secure Coding Practices for Custom Components: Follow secure development guidelines.
  • Input Validation and Sanitization in Custom Components: Validate and sanitize all input.
  • Principle of Least Privilege for Custom Components: Grant minimal necessary permissions.
  • Code Review and Security Testing of Custom Components: Thoroughly review and test custom components.