mmaxjr / tcp-over-http

TCP over HTTP

TCP over HTTP

This is TCP over HTTP

Why?

My school filters the internet quite a bit, but they're weird about it.

• HTTPS is completely filtered. The network has a custom signing authority that allows them to view and filter any TLS data they see.
• Many other ports are completely banned, most notably port 22 (SSH).
• The school can detect if you're using a VPN, and will disable your WiFi for 5 minutes if you do. Tor does work with bridges, although it's quite slow and probably not very good for the network.
• The school will also block protocols, not just ports, so moving SSH to some other port won't work.
• Despite this, however, many protocols remain unblocked. Most notably, VNC, which would allow you to connect directly to a home desktop as long as you're fine with the school district being able to see your screen and monitor your keystrokes at all times.
• In addition, many other ports are completely unfiltered. Port 25 (can be used for email spam) is allowed, as is port 70 (Gopher), port 1965 (Gemini), and most importantly, port 80 (HTTP).

This means that if we can encode a VPN into one of these unblocked protocols, we can bypass all the filters with a fast internet connection. This repo obviously encodes TCP into HTTP.

How does it work?

We're not really trying to write a decent web server that follows all of the HTTP paradigms, we're trying to encode data. That's why this program sends two requests simultaneously and nothing else. One request sends data, the other receives.

The sending socket sends a POST request that looks like this:

POST / HTTP/1.1
Host: [CONFIG_HTTP_HOST]
Content-Length: 9223372036854775807

and the receiving socket sends a GET request that looks like this:

GET / HTTP/1.1
Host: [CONFIG_HTTP_HOST]

The server responds to that request with this response:

HTTP/1.1 200 OK
Content-Length: 9223372036854775807

Now, the client can send data through the POST request and the server can send data back through the GET request. We've created a TCP connection with the server that can send any data including SSH connections.

We can then use port forwarding to allow a program on the client to communicate with a program on the server.

My Dad (quite reasonably) got confused after hearing me explain this, so here's a diagram I made.

How do I configure this

Change config.h. I blame suckless for this.