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Improper resource allocation

Need​

Efficient resource allocation and management

Context​

  • Usage of Dart for building cross-platform mobile, web, and desktop applications
  • Usage of Shelf for managing and organizing data in a Node.js application

Description​

Non compliant code​

import 'package:shelf/shelf.dart' as shelf;

shelf.Response handleRequest(shelf.Request request) {
  var size = int.parse(request.url.queryParameters['size']);

  // This allocation of resources based on user input can lead to improper resource allocation
  var data = List.filled(size, 0);

  return shelf.Response.ok('Resource allocated!');
}

The code above is an example of a function in a backend application that uses the Shelf framework in Dart. The function handleRequest is supposed to handle incoming requests.

The vulnerability lies in the line where we parse the size from the request's query parameters and then use it to allocate a list of integers of that size. This means that a user can send a request with a very large size and cause the server to allocate a huge amount of memory, potentially leading to a Denial of Service (DoS) if the server runs out of memory.

This is an example of improper resource allocation, as the resources allocated are controlled by an external source (user input) without any restrictions or checks. This can lead to inefficient use of resources and potential security risks.

Steps​

  • Validate the 'size' parameter to ensure it's within an acceptable range before using it to allocate resources. This can be done by setting a maximum limit for the 'size' parameter.
  • Implement error handling for the 'int.parse' function to handle cases where the 'size' parameter cannot be converted to an integer.
  • Consider using a more efficient data structure or algorithm if the resource allocation is still too high after validating the 'size' parameter.
  • If the resource allocation is still too high, consider implementing a throttling mechanism to limit the rate at which resources are allocated.

Compliant code​

import 'package:shelf/shelf.dart' as shelf;

const int MAX_SIZE = 10000; // Define a maximum limit for the size parameter

shelf.Response handleRequest(shelf.Request request) {
  var sizeParam = request.url.queryParameters['size'];

  // Validate the size parameter
  if (sizeParam == null || sizeParam.isEmpty) {
    return shelf.Response(400, body: 'Bad Request: Size parameter is required');
  }

  int size;
  try {
    size = int.parse(sizeParam);
  } catch (e) {
    return shelf.Response(400, body: 'Bad Request: Size parameter must be an integer');
  }

  // Check if the size is within the acceptable range
  if (size < 0 || size > MAX_SIZE) {
    return shelf.Response(400, body: 'Bad Request: Size parameter must be between 0 and $MAX_SIZE');
  }

  // This allocation of resources based on user input can lead to improper resource allocation
  var data = List.filled(size, 0);

  return shelf.Response.ok('Resource allocated!');
}

The updated code includes several improvements to address the improper resource allocation vulnerability:

  1. Size Parameter Validation: The code now checks if the 'size' parameter is provided and is not empty. If the 'size' parameter is missing or empty, the function returns a 400 Bad Request response.

  2. Integer Parsing with Error Handling: The 'size' parameter is parsed into an integer using the 'int.parse' function. If the parsing fails (e.g., because the 'size' parameter is not a valid integer), the function returns a 400 Bad Request response.

  3. Size Range Check: The code checks if the parsed 'size' is within an acceptable range (0 to MAX_SIZE). If the 'size' is not within this range, the function returns a 400 Bad Request response. This prevents the allocation of an excessive amount of resources based on user input.

  4. Resource Allocation: If all the checks pass, the function allocates a list of the specified size. This is the same as in the original code, but now it's guaranteed that the size is within an acceptable range.

By implementing these improvements, the code mitigates the risk of improper resource allocation, making it more robust and secure.

References​

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