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Lack of data validation - URL

Need​

Implementation of proper data validation for URL parameters

Context​

  • Usage of Java for building cross-platform applications
  • Usage of javax.servlet for Java Servlet development
  • Usage of java.io for input and output operations in Java programming

Description​

Non compliant code​

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

public class DocumentServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String date = request.getParameter("date");
        // Fetch documents based on the date
        List<Document> documents = DocumentService.getDocumentsByDate(date);

        // Display the documents
        request.setAttribute("documents", documents);
        RequestDispatcher view = request.getRequestDispatcher("result.jsp");
        view.forward(request, response);
    }
}

The above code represents a servlet in a Java-based web application that fetches documents based on a date passed as a parameter in the URL. The servlet uses the getParameter method to extract the date from the URL, then passes this date to the DocumentService.getDocumentsByDate method to fetch the corresponding documents. The fetched documents are then set as an attribute in the request and forwarded to a JSP page (result.jsp), where they are displayed.

The vulnerability lies in the fact that there is no validation performed on the date parameter. This allows any user to manipulate the URL and pass any date as a parameter, potentially gaining access to documents from any date. This is a serious security issue as it could lead to unauthorized access to sensitive documents.

Steps​

  • Implement input validation for the 'date' parameter to ensure it is in the expected format and range.
  • Use a whitelist approach to validate the 'date' parameter, allowing only specific characters or formats.
  • Sanitize the 'date' parameter to remove any potentially harmful characters or sequences.
  • Implement access control mechanisms to restrict access to sensitive information based on the user's authorization level.
  • Consider using a secure session management mechanism to authenticate and authorize users before accessing sensitive information.
  • Encrypt or obfuscate sensitive information in the URL to prevent unauthorized access or tampering.
  • Implement rate limiting or throttling mechanisms to prevent abuse or excessive requests for sensitive information.
  • Regularly update and patch the server and application to address any known vulnerabilities or security issues.

Compliant code​

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DocumentServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String date = request.getParameter("date");

        // Validate the date parameter
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        sdf.setLenient(false);
        try {
            Date validDate = sdf.parse(date);
        } catch (ParseException e) {
            throw new ServletException("Invalid date format");
        }

        // Fetch documents based on the date
        List<Document> documents = DocumentService.getDocumentsByDate(date);

        // Implement access control
        HttpSession session = request.getSession();
        User user = (User) session.getAttribute("user");
        if (user == null || !user.isAuthorized()) {
            throw new ServletException("Unauthorized access");
        }

        // Display the documents
        request.setAttribute("documents", documents);
        RequestDispatcher view = request.getRequestDispatcher("result.jsp");
        view.forward(request, response);
    }
}

The updated code includes several security enhancements to address the identified vulnerability:

  1. Input Validation: The 'date' parameter is validated using a SimpleDateFormat object to ensure it is in the expected "yyyy-MM-dd" format. If the date is not in this format, a ServletException is thrown.

  2. Access Control: Before fetching and displaying the documents, the code checks if the user is authenticated and authorized. This is done by retrieving the 'user' object from the session and checking its authorization status. If the user is not authenticated or not authorized, a ServletException is thrown.

These changes ensure that only valid dates are accepted and only authorized users can access the documents. This prevents unauthorized access and potential information leakage.

References​

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