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Lack of isolation methods

Need​

Implementation of robust isolation methods for running applications

Context​

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

Description​

Non compliant code​

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) {
        String command = request.getParameter("cmd");
        Process process = Runtime.getRuntime().exec(command);
        // Rest of the code
    }
}

The above servlet handles GET requests and takes a parameter from the request called 'cmd'. This parameter is directly used to execute a system command through the exec method of the Runtime class.

The main vulnerability here is that the application is not using any isolation methods when running these commands. This means that any command that is passed through the 'cmd' parameter will be run directly on the system which the application is running on.

This is a serious security vulnerability as it allows for arbitrary command execution. An attacker could potentially run any command they want on the system, leading to a wide variety of attacks such as data theft, data corruption, denial-of-service, or even full system takeover.

This vulnerability can be mitigated by using isolation methods such as running the commands in a sandbox environment or using secure coding techniques to ensure that only safe commands are run.

Steps​

  • Implement application sandboxing
  • Use containerization or virtualization techniques
  • Apply principle of least privilege
  • Implement strong input validation and sanitization
  • Use secure coding practices
  • Implement access controls and authentication mechanisms
  • Regularly update and patch the system and dependencies
  • Perform security testing and code reviews

Compliant code​

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.regex.Pattern;

public class MyServlet extends HttpServlet {
    private static final Pattern SAFE_COMMAND_PATTERN = Pattern.compile("[a-zA-Z0-9]*");

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        String command = request.getParameter("cmd");

        if (isSafeCommand(command)) {
            ProcessBuilder builder = new ProcessBuilder(command);
            builder.start();
        } else {
            throw new IllegalArgumentException("Unsafe command");
        }
        // Rest of the code
    }

    private boolean isSafeCommand(String command) {
        return SAFE_COMMAND_PATTERN.matcher(command).matches();
    }
}

The original code was vulnerable because it directly executed a command from an HTTP request parameter without any validation or sanitization. This could allow an attacker to execute arbitrary commands on the server.

The fixed code introduces a few changes to mitigate this vulnerability:

  1. Input Validation and Sanitization: The isSafeCommand method checks if the command only contains alphanumeric characters. This is a simple form of input validation and sanitization that prevents the execution of potentially harmful commands. Note that this is a very basic form of validation and may not cover all possible attack vectors. Depending on the specific requirements of your application, you might need a more sophisticated validation mechanism.

  2. Principle of Least Privilege: The code uses the ProcessBuilder class to execute the command. This class provides more control over the execution environment of the process and can be used to restrict the privileges of the process, for example by setting a security manager.

  3. Isolation: Although the code does not directly implement any isolation mechanisms, using ProcessBuilder can facilitate the implementation of such mechanisms. For example, you could configure the ProcessBuilder to execute the command in a separate, isolated environment.

Remember that this code is just a starting point. Depending on the specific requirements and threat model of your application, you might need to implement additional security measures, such as authentication, access controls, or more sophisticated input validation and sanitization mechanisms.

References​

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