attack-surface.md

Attack Surface Analysis for tokio-rs/axum

Attack Surface: Path Parameter Injection

• Description: Exploiting path parameters in routes to manipulate application behavior, access unauthorized resources, or inject malicious payloads.
• Axum Contribution: Axum's routing system and Path extractor directly enable the use of path parameters. If these are not validated within Axum handlers, it creates a direct attack surface.
• Example: A route /users/{id} where id is used in a database query without validation. An attacker uses id=1; DELETE FROM users; -- to attempt SQL injection.
• Impact: Data breach, data manipulation, unauthorized access, denial of service.
• Risk Severity: High to Critical
• Mitigation Strategies:
  • Input Validation: Strictly validate all path parameters within handler functions using libraries like validator or manual checks. Ensure parameters conform to expected formats, types, and ranges before using them in application logic.
  • Parameterized Queries: Always use parameterized queries or ORM features when path parameters are used in database interactions to prevent SQL injection.
  • Principle of Least Privilege: Limit application access to only necessary resources, reducing the impact of potential path traversal vulnerabilities.

Attack Surface: Query Parameter Injection

• Description: Injecting malicious code or manipulating application logic through query parameters in the URL.
• Axum Contribution: Axum's automatic query parameter parsing and Query extractor make query parameters easily accessible. Lack of validation in Axum handlers directly leads to this attack surface.
• Example: An application uses a search query parameter in a database query without sanitization. An attacker injects SQL code in the search parameter.
• Impact: Data breach, data manipulation, unauthorized access, denial of service.
• Risk Severity: High to Critical
• Mitigation Strategies:
  • Input Validation: Validate and sanitize all query parameters within Axum handlers against expected formats and values. Use libraries like validator or manual checks.
  • Parameterized Queries: Utilize parameterized queries or ORM features to prevent SQL injection when query parameters are used in database interactions.
  • Content Security Policy (CSP): Implement CSP to reduce the impact of potential client-side injection vulnerabilities that might be triggered by query parameter manipulation.

Attack Surface: Request Body Deserialization Vulnerabilities

• Description: Exploiting vulnerabilities arising from deserializing request bodies (e.g., JSON, XML, forms) into application data structures. This includes deserialization of untrusted data leading to code execution or resource exhaustion.
• Axum Contribution: Axum's seamless integration with serde via extractors like Json and Form simplifies deserialization. However, insecure deserialization practices within Axum handlers directly expose the application.
• Example:
  • Deserialization of Untrusted Data: An Axum application deserializing JSON without schema validation is vulnerable if serde or application logic has flaws when processing unexpected JSON structures, potentially leading to Remote Code Execution if specific deserialization gadgets are present in dependencies.
  • Resource Exhaustion: Sending a very large or deeply nested JSON payload to an Axum endpoint, causing excessive resource consumption during deserialization and leading to Denial of Service.
• Impact: Remote code execution, denial of service, data corruption.
• Risk Severity: Medium to Critical (Critical in RCE scenarios)
• Mitigation Strategies:
  • Schema Validation: Implement strict schema validation for request bodies using libraries like serde_json_schema or schemars to ensure incoming data conforms to expected structures before deserialization within Axum handlers.
  • Request Body Size Limits: Enforce limits on the size of request bodies within Axum configuration or middleware to prevent resource exhaustion attacks.
  • Secure Deserialization Practices: Keep serde and related dependencies updated to patch known deserialization vulnerabilities. Be mindful of potential deserialization gadgets in project dependencies.

Attack Surface: Misconfigured HTTP Method Handling

• Description: Incorrectly configuring or handling HTTP methods (GET, POST, PUT, DELETE, etc.) for routes, leading to unintended access or actions, potentially allowing unauthorized modification of resources.
• Axum Contribution: Axum's method-aware routing directly relies on developers correctly configuring method handlers (e.g., .get(), .post()). Misconfigurations in Axum route definitions directly create this vulnerability.
• Example: A resource intended for read-only access via GET is inadvertently also accessible via POST due to a routing misconfiguration in Axum, allowing unauthorized data modification through POST requests.
• Impact: Unauthorized data modification, data corruption, privilege escalation.
• Risk Severity: Medium to High (Can be Critical if sensitive data modification is possible)
• Mitigation Strategies:
  • Explicit and Correct Route Definitions: Carefully define allowed HTTP methods for each route in Axum, ensuring they strictly align with the intended functionality and resource access control. Double-check route definitions for any unintended method handlers.
  • Testing: Thoroughly test route configurations, specifically method handling, to verify that only intended methods are allowed for each resource and that unauthorized methods are correctly rejected by Axum.
  • Principle of Least Privilege for Methods: Restrict HTTP methods to the absolute minimum required for each route and resource. Avoid allowing methods that are not explicitly needed.