Need

Implementation of robust data validation for date fields

Context

• Usage of Java 8 for developing applications with enhanced features and performance improvements
• Usage of javax.servlet for building 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 DateModificationServlet extends HttpServlet {

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String date = request.getParameter("date");
        // No server-side validation of the date parameter
        modifyDate(date);
    }

    private void modifyDate(String date) {
        // Code to modify date
    }
}
        
        

The above Java Servlet code is vulnerable due to the lack of server-side data validation. When the doPost method is called, it retrieves the "date" parameter from the HTTP request and directly passes it to the modifyDate method without any validation.

The modifyDate method is expected to modify the date based on the input string. However, as there is no validation of the input string, an attacker could potentially send a malicious request with an invalid or unexpected "date" parameter. This could lead to various security risks, such as data corruption, unexpected behavior, or even server crashes.

Even though there might be client-side restrictions on what can be passed as the "date" parameter, these can easily be bypassed. For example, an attacker can modify the HTTP request directly using tools like curl or Postman, or even modify the JavaScript code in their browser to remove the client-side restrictions.

Therefore, it is crucial to have server-side validation of all user inputs, including this "date" parameter. This validation should ensure that the input is in the expected format and range, and reject any requests that do not meet these criteria.

Steps

• Implement server-side validation for the 'date' parameter in the doPost() method.
• Validate the 'date' parameter against a specific format or range of acceptable values.
• Reject or handle invalid 'date' values appropriately.
• Consider using a date parsing library or built-in date validation functions to ensure the 'date' parameter is in the correct format.
• Implement proper access control and permission checks to ensure that only authorized users can modify the 'date' field.
• Consider implementing input sanitization or encoding to prevent any potential injection attacks.
• Regularly update and patch the server-side code to address any new vulnerabilities or security issues.

Compliant code

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

public class DateModificationServlet extends HttpServlet {

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String date = request.getParameter("date");
        // Server-side validation of the date parameter
        if(isValidDate(date)) {
            modifyDate(date);
        } else {
            // Handle invalid date
            response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Invalid date format");
        }
    }

    private boolean isValidDate(String date) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        sdf.setLenient(false);
        try {
            Date parsedDate = sdf.parse(date);
            return true;
        } catch (ParseException e) {
            return false;
        }
    }

    private void modifyDate(String date) {
        // Code to modify date
    }
}
        
        

The code above fixes the vulnerability by implementing server-side validation for the 'date' parameter in the doPost() method.

The isValidDate(String date) method is used to validate the 'date' parameter against a specific format ("yyyy-MM-dd"). This method uses the SimpleDateFormat class to parse the date string. If the parsing is successful, the date is valid and the method returns true. If a ParseException is thrown, the date is invalid and the method returns false.

In the doPost() method, the 'date' parameter is first validated using the isValidDate(String date) method. If the date is valid, the modifyDate(String date) method is called. If the date is invalid, an error response with the status code 400 (Bad Request) and an error message "Invalid date format" is sent to the client.

This code also needs to be supplemented with proper access control and permission checks to ensure that only authorized users can modify the 'date' field. This can be done using various authentication and authorization techniques depending on the specific requirements and context of the application.

Additionally, consider implementing input sanitization or encoding to prevent any potential injection attacks. Regularly update and patch the server-side code to address any new vulnerabilities or security issues.

References

• 196. Lack of data validation - Dates