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Data uniqueness not properly verified

Need​

Enforce proper data uniqueness verification

Context​

  • Usage of Java for building robust and scalable applications
  • Usage of javax.servlet for building Java web applications
  • Usage of java.io for input/output operations in Java programming

Description​

Non compliant code​

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

public class DataValidationServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        String inputData = request.getParameter("inputData");
        
        // Here the data is directly used without checking its uniqueness
        Database db = new Database();
        db.storeData(inputData);

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<html><body>Data stored successfully</body></html>");
    }
}

The above code represents a servlet in a Java backend application using javax.servlet. The servlet handles POST requests and retrieves the parameter inputData from the request.

The vulnerability lies in the doPost method where the input data is directly stored in the database without any validation for uniqueness. This means that if an attacker sends the same data multiple times, it will be stored multiple times in the database. This can lead to data redundancy, incorrect data retrieval, and other data integrity issues.

Additionally, if the data is supposed to be unique for each user (like a token or a one-time password), an attacker can reuse or regenerate this data, which should be valid for one use only.

This lack of data uniqueness validation can lead to various security issues such as replay attacks (where an attacker reuses a session ID to gain unauthorized access to the system) and data integrity attacks (where an attacker modifies data to cause incorrect operations).

Steps​

  • Implement proper data validation and uniqueness checks before storing the data.
  • Use a database query or other mechanism to check if the data already exists in the database.
  • If the data is found to be unique, store it in the database.
  • If the data is not unique, handle the error appropriately (e.g., display an error message to the user).
  • Consider using a unique constraint or index in the database to enforce data uniqueness at the database level.
  • Implement appropriate error handling and logging to detect and respond to any potential issues.

Compliant code​

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

public class DataValidationServlet extends HttpServlet {

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        String inputData = request.getParameter("inputData");
        
        Database db = new Database();
        
        // Check if the data is unique
        if(db.isDataUnique(inputData)) {
            // If the data is unique, store it in the database
            db.storeData(inputData);
            response.setContentType("text/html");
            PrintWriter out = response.getWriter();
            out.println("<html><body>Data stored successfully</body></html>");
        } else {
            // If the data is not unique, handle the error appropriately
            response.setContentType("text/html");
            PrintWriter out = response.getWriter();
            out.println("<html><body>Error: Data is not unique</body></html>");
        }
    }
}

The updated code now includes a check for data uniqueness before storing the data in the database. This is done by calling the isDataUnique method of the Database class, which should return true if the data is unique and false otherwise.

If the data is unique, it is stored in the database and a success message is returned to the user. If the data is not unique, an error message is returned to the user.

This approach helps to prevent the reuse or regeneration of information that should be valid for one use only, addressing the identified vulnerability.

In addition to this code-level fix, consider using a unique constraint or index in the database to enforce data uniqueness at the database level. This can provide an additional layer of protection against this type of vulnerability.

Finally, implement appropriate error handling and logging to detect and respond to any potential issues. This can help to identify any attempts to reuse or regenerate data, allowing for a quick response to any potential security incidents.

References​

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