remote-code-execution-(rce)

Remote Code Execution (RCE)

Introduction

Remote Code Execution (RCE) is a technique where a piece of code executes outside its typical source file location. This allows attackers to execute malicious scripts without having access to the source file, making it a potent method for exploiting vulnerabilities.

Technical Explanation

Client-Server Environment

In RCE, the execution occurs between two servers: a client (target machine) and a server (remote host). The client executes code in a context that may differ from where it resides, enabling remote execution.

Server Execution Model (S3)

The server runs programs in multiple contexts:

  1. Current Execution Context - Source file directly
  2. Dynamic Environment - Changes source file path on each request
  3. Encapsulated Execution - Limited access to program files

Client-Side Script Execution

The client script executes code under a dynamically changed context, bypassing its original source file.

Example of RCE (HTML + JS)

<!DOCTYPE html>
<html>
<head>
    <title>RCE Example</title>
    <style>
        body {
            font-family: Arial, sans-serif;
            line-height: 1.6;
            background-color: #f0f2f5;
        }
    </style>
</head>
<body>
    <script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
    <script>
        function executeCode(targetDomain) {
            window.location.href = `https://${targetDomain}/remote-execution.php`;
            fetch(window.location)**kwargs;
        }

        // Example: Execute JS on server 80
        executeCode('/remoteExecution/1');
        // Execute JS on server 81
        executeCode('/remoteExecution/2');
    }
</body>
</html>

Defense or Mitigation Techniques

Patching and Anti-DDebugging Tools

Use known vulnerabilities in source files to patch them, preventing remote execution.

Secure Prxies and Proxy Addressing

Block external requests to a target domain with a proxy server, masking RCE attempts.

Source Code Inspection

Manually verify and modify source code for suspicious patterns like #exec script.js or #script=evil.

Conclusion

RCE can exploit vulnerabilities in environments where the client resides on a remote host. However, developers employ patches, secure proxies, and source code analysis to mitigate risks. Understanding the environment and tools used is crucial for effective defense against RCE threats.