Need

Enhanced data authenticity validation and verification

Context

• Usage of Java for building cross-platform applications and enterprise-level software
• Usage of javax.servlet for building Java web applications with Servlet technology
• 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 VulnerableServlet extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String name = request.getParameter("name");
        String value = request.getParameter("value");

        // No validation is performed on the data received
        updateData(name, value);
    }

    private void updateData(String name, String value) {
        // Assume this method updates a database or some data structure
    }
}
        
        

The above servlet accepts HTTP POST requests and updates some data based on the parameters received.

The doPost method retrieves two parameters from the request: name and value. These parameters are assumed to represent the name of a field to update and the new value for that field respectively.

The problem lies in the fact that there is no validation performed on these parameters before they are used to update data. This means that an attacker could potentially send a request with arbitrary name and value parameters, leading to unauthorized data modification.

For example, if the updateData method updates a database, an attacker could potentially modify any field in any record. This could lead to serious data integrity issues.

Furthermore, the application does not check if the name exists, which could potentially lead to errors if non-existing field names are provided.

This is a classic example of an Insufficient Data Authenticity Validation vulnerability.

Steps

• Implement server-side validation to ensure the authenticity and integrity of the data received.
• Verify the user's permission to modify the specific fields before updating the data.
• Use proper input validation techniques to prevent the use of invalid or non-existing names.
• Consider implementing a whitelist or blacklist approach to validate the data received.
• Sanitize the input data to prevent any potential injection attacks.
• Implement proper error handling and logging to detect and respond to any unauthorized or invalid data modifications.

Compliant code

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

public class SecureServlet extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String name = request.getParameter("name");
        String value = request.getParameter("value");

        // Validate the input data
        if (!isValidData(name, value)) {
            // Log the invalid data attempt
            logInvalidDataAttempt(request);
            return;
        }

        // Check user's permission
        if (!hasPermission(request)) {
            // Log the unauthorized attempt
            logUnauthorizedAttempt(request);
            return;
        }

        // Update the data
        updateData(name, value);
    }

    private boolean isValidData(String name, String value) {
        // Implement your validation logic here
        // For example, check if the name exists in the database
        // and if the value is in a valid format
        return true;
    }

    private boolean hasPermission(HttpServletRequest request) {
        // Implement your permission checking logic here
        // For example, check if the user is logged in and has the right role
        return true;
    }

    private void updateData(String name, String value) {
        // Assume this method updates a database or some data structure
    }

    private void logInvalidDataAttempt(HttpServletRequest request) {
        // Implement your logging logic here
    }

    private void logUnauthorizedAttempt(HttpServletRequest request) {
        // Implement your logging logic here
    }
}
        
        

The updated code now includes server-side validation to ensure the authenticity and integrity of the data received.

The isValidData method is used to validate the input data. This method should contain the logic to check if the name exists in the database and if the value is in a valid format. If the data is invalid, the method returns false and the logInvalidDataAttempt method is called to log the invalid data attempt.

The hasPermission method is used to check the user's permission to modify the specific fields. This method should contain the logic to check if the user is logged in and has the right role. If the user does not have permission, the method returns false and the logUnauthorizedAttempt method is called to log the unauthorized attempt.

The updateData method is then called to update the data if the data is valid and the user has permission.

This approach ensures that only valid data is used and only authorized users can modify the data, thereby fixing the vulnerability.

References

• 204. Insufficient data authenticity validation