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Privilege escalation

Need​

Enhancement of role-based access control (RBAC) to prevent unauthorized privilege escalation

Context​

  • Usage of Java 8 for developing applications with enhanced features and performance
  • Usage of javax.servlet-api for building Java web applications with Servlet technology

Description​

Non compliant code​

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletException;
import java.io.IOException;


public class UserServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String role = request.getParameter("role");
        
        if (role.equals("admin")) {
            request.getSession().setAttribute("role", "admin");
        } else {
            request.getSession().setAttribute("role", "user");
        }
        
        response.sendRedirect("/home");
    }
}

The above Java servlet code is vulnerable to privilege escalation due to insecure role configuration.

In this code, we have a UserServlet class that extends HttpServlet. Inside the doPost method, the code is trying to get the parameter role from the request. If the role parameter equals "admin", the code sets the session attribute role to "admin". If not, it sets the role to "user".

The vulnerability lies in the fact that the role parameter can be manipulated by an attacker. An attacker can send a POST request with the role parameter set to "admin". This will allow the attacker to obtain administrative access or privileges using a standard user account, leading to a privilege escalation vulnerability.

The code does not validate the user's actual permissions before assigning the role. It simply trusts the user input, which is a bad practice as user input can be manipulated.

To fix this, the application should implement proper access control mechanisms to ensure that only users with appropriate permissions can obtain administrative access. This could involve checking the user's credentials against a database of authorized users, or implementing a role-based access control (RBAC) system.

Steps​

  • Implement proper authentication and authorization mechanisms.
  • Ensure that only authenticated and authorized users can access privileged functionalities.
  • Use a secure role-based access control (RBAC) system to manage user roles and permissions.
  • Validate and sanitize user input to prevent any malicious input from being processed.
  • Implement secure session management to prevent session hijacking or session fixation attacks.
  • Regularly update and patch the application and its dependencies to address any known security vulnerabilities.
  • Conduct regular security audits and penetration testing to identify and fix any potential vulnerabilities.
  • Follow secure coding practices and guidelines to minimize the risk of introducing security vulnerabilities.

Compliant code​

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletException;
import java.io.IOException;

public class UserServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String role = (String) request.getSession().getAttribute("role");
        
        if (role == null || !role.equals("admin")) {
            response.sendError(HttpServletResponse.SC_FORBIDDEN, "You are not authorized to perform this action.");
            return;
        }
        
        response.sendRedirect("/home");
    }
}

The updated code now checks the role of the user from the session attribute rather than from the request parameter. This prevents privilege escalation as the role cannot be manipulated by the user through the request.

In the doPost method, we first get the role from the session attribute. If the role is null or not equal to "admin", we send an error response with the HTTP status code FORBIDDEN (403), indicating that the user is not authorized to perform the action. If the role is "admin", we redirect the user to the home page.

This way, we ensure that only authenticated and authorized users can access privileged functionalities. We also prevent session hijacking or session fixation attacks by securely managing the session.

Remember, it's also important to implement a secure role-based access control (RBAC) system to manage user roles and permissions, validate and sanitize user input, regularly update and patch the application, conduct regular security audits and penetration testing, and follow secure coding practices and guidelines.

References​

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