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Anonymous connection

Need​

Restriction of anonymous connections and implementation of proper server configurations

Context​

  • Usage of Java 1.8 for running Java applications
  • Usage of javax.servlet-api for Java servlet development

Description​

Non compliant code​

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

public class AnonymousConnectionServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String username = req.getParameter("username");
        String password = req.getParameter("password");

        if("anonymous".equals(username) && "guest".equals(password)) {
            resp.getWriter().write("Access granted to protected resource");
        } else {
            resp.getWriter().write("Access denied");
        }
    }
}

The above servlet AnonymousConnectionServlet is vulnerable to anonymous connections. It is an example of a server-side Java application using the javax.servlet library.

In the doGet method, the servlet is checking for a username and password from the request parameters. If the username is "anonymous" and the password is "guest", the servlet grants access to a protected resource. This is the vulnerability, as anyone who knows these credentials can access the protected resource.

This vulnerability is due to the improper configuration of the server. In a real-world application, the username and password should not be hardcoded, and there should be a proper authentication and authorization mechanism in place to protect sensitive resources.

Steps​

  • Remove the use of hardcoded credentials in the code.
  • Implement proper authentication mechanisms to validate user credentials.
  • Use secure protocols (e.g., HTTPS) to protect the transmission of sensitive information.
  • Implement access control mechanisms to restrict unauthorized access to protected resources.
  • Regularly update and patch the server software to address any known vulnerabilities.
  • Implement logging and monitoring to detect and respond to any unauthorized access attempts.

Compliant code​

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

public class SecureConnectionServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Principal userPrincipal = req.getUserPrincipal();

        if(userPrincipal == null) {
            resp.getWriter().write("Access denied");
            return;
        }

        String username = userPrincipal.getName();

        if(username != null && !username.isEmpty()) {
            resp.getWriter().write("Access granted to protected resource");
        } else {
            resp.getWriter().write("Access denied");
        }
    }
}

The updated code removes the hardcoded credentials and instead uses the getUserPrincipal() method to get the authenticated user's principal. This method returns a java.security.Principal object representing the name of the authenticated user. If the user is not authenticated, this method returns null.

The getName() method of the Principal object is then used to get the username of the authenticated user. If the username is not null and not empty, access is granted to the protected resource. Otherwise, access is denied.

This code assumes that a proper authentication mechanism is in place to authenticate users and establish their principals. This could be a form-based authentication, a basic authentication, a digest authentication, or a client certificate authentication.

This code also assumes that a secure protocol (e.g., HTTPS) is used to protect the transmission of sensitive information, that access control mechanisms are in place to restrict unauthorized access to protected resources, that the server software is regularly updated and patched to address any known vulnerabilities, and that logging and monitoring are implemented to detect and respond to any unauthorized access attempts.

References​

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