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Improper resource allocation

Need​

Efficient resource allocation and management

Context​

  • Usage of Java for building cross-platform applications
  • Usage of javax.servlet for building Java web applications with servlets
  • Usage of javax.servlet.http for handling HTTP requests and responses in Java web applications
  • Usage of java.io for input and output operations in Java

Description​

Non compliant code​

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;

public class ResourceAllocationServlet extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String input = request.getParameter("input");
        int size = Integer.parseInt(input);
        int[] array = new int[size];
        // Other operations
    }
}

The above code shows a servlet that accepts a POST request. The request contains a parameter named "input". The servlet reads this parameter and uses it to create an array of integers.

The vulnerability lies in the fact that the size of the array is determined by the user input. This means that an attacker can send a request with a very large value in the "input" parameter, causing the application to allocate a very large amount of memory for the array. If the value is large enough, this could lead to a Denial of Service (DoS) attack by exhausting the available memory of the system.

This is a classic example of an improper resource allocation vulnerability, where the allocation of system resources (in this case, memory) is controlled by an external source without any restriction or validation.

Steps​

  • Validate and sanitize user input to ensure it is within acceptable limits.
  • Implement proper input validation to prevent the allocation of unnecessary resources.
  • Use efficient algorithms and data structures to optimize resource allocation.
  • Implement rate limiting or other restrictions to prevent processing requests that consume an enormous amount of resources.
  • Regularly monitor and analyze resource usage to identify and address any potential resource allocation issues.

Compliant code​

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;

public class ResourceAllocationServlet extends HttpServlet {
    private static final int MAX_SIZE = 10000; // Define a maximum size limit

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String input = request.getParameter("input");
        int size = Integer.parseInt(input);

        // Validate the size
        if (size < 0 || size > MAX_SIZE) {
            throw new ServletException("Invalid size: " + size);
        }

        int[] array = new int[size];
        // Other operations
    }
}

The original code was vulnerable to improper resource allocation as it was directly using user input to allocate an array size. This could lead to a situation where an attacker could cause the system to allocate an enormous amount of resources by providing a very large number, leading to a Denial of Service (DoS) attack.

The fixed code introduces a maximum size limit for the array. The MAX_SIZE constant is used to define this limit. When a POST request is made, the size provided by the user is checked against this limit. If the size is less than 0 or greater than MAX_SIZE, a ServletException is thrown, preventing the allocation of unnecessary resources.

This fix ensures that the system only allocates a reasonable amount of resources, even if an attacker tries to force it to allocate more. It's a simple yet effective way to prevent improper resource allocation vulnerabilities.

Remember, it's also important to implement rate limiting or other restrictions to prevent processing requests that consume an enormous amount of resources and regularly monitor and analyze resource usage to identify and address any potential resource allocation issues.

References​

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