PTTH

An HTTP server that can run behind a firewall by connecting out to a relay.

Outside the tunnel
+--------+         +------------+        +-------------+
| Client | ------> | PTTH relay | <----- | PTTH server |
+--------+         +------------+        +-------------+

Inside the tunnel
+--------+         --------------        +-------------+
| Client | ----------------------------> |   Server    |
+--------+         --------------        +-------------+

The server can run behind a firewall, because it is actually a special HTTP client.

How to configure

The server must be configured first so that its tripcode can be registered with the relay.

Configuring a server:

• Copy ptth_server or ptth_server.exe onto the server
• Create ptth_server.toml in the server's working dir
• Add a human-readable name and a secret API key generated by diceware method
• Run the server and use Ctrl+C to close it. It will print a tripcode to the terminal. Copy that to the relay.

Configuring the relay:

• Copy ptth_relay onto the server (A Dockerfile is provided with no guarantees)
• Create ptth_relay.toml in the relay's working dir
• Add the tripcodes of all servers to the server_tripcodes table

Example server config: (Won't run because the key is too weak)

name = "my_server"
api_key = "secretpassword"
relay_url = "http://127.0.0.1:4000"

Example relay config:

[server_tripcodes]

my_server = "czpCob1t1T7IU9zIlYyoNRomyeN7pqKSg1R0EUPz6Pw="
some_other_server = "su2wWbTyf5xih4yiCTfAzqDlASatV+0dI+UVKFBIsEI="

How to run

The relay should run first so that the server(s) can connect to it without error.

1. Start the relay
2. Start a server
3. Use a client to access a server through the relay

From the source code directory:

• cargo run --bin ptth_relay
• cargo run --bin ptth_server
• firefox http://127.0.0.1:4000/servers/my_server/files/

If you only have pre-built binaries:

• ./ptth_relay
• ./ptth_server
• firefox http://127.0.0.1:4000/servers/my_server/files/

"ptth_file_server" is not needed for production. It's a standalone build of the file server module, for testing.

To run the relay behind Nginx, these directives improve time-to-first-byte when streaming:

client_max_body_size 0;
proxy_http_version 1.1;
proxy_request_buffering off;
proxy_buffering off;

Comparison with normal HTTP

Normal HTTP:

Client       Server

       H1
  O ---------> O
               | H2
  O <--------- O
          H3

1. The client connects to the server and sends a request
2. The server accepts the connection and processes the request
3. The server responds with a response

We'll call these steps "H1", "H2", and "H3" in the next section.

PTTH:

Client    Relay    Server

                P1
            O <----- O
    P2/H1   |
  O ------> O
            |   P3
            O -----> O
                     | P4/H2
            O <----- O
            |   P5
  O <------ O
      P6/H3

We'll call these steps "P1" through "P6".

1. The server makes a "listen" request to the relay, punching out through the server's firewall. The server and relay are now in a long-polling state with each other, waiting for a client to make a request.
2. A client makes a request to the relay. (P2 == H1)
3. The relay packages the request and sends it as a response to the server, completing the server's request in P1. The client and relay are now in a long-polling state, waiting for the server to respond.
4. The server processes the request. (P4 == H2)
5. The server packages its response in another request to the relay.
6. The relay unwraps the request and forwards it to the client. (P6 == H3)

Every step of the normal HTTP process is inverted for the server:

• It must stay connected to the relay even when nothing is happening
• A request arrives packaged in a response
• A response is sent out packaged as a request

There are twice as many steps, and the per-connection and per-request overhead is probably high. But once the connections are established, the only overhead is that of using a relay, which is similar to many other file transfer or remote desktop software.

Comparison with similar software

PTTH is very similar to PageKite. PTTH's relay is equivalent to PageKite's front-end server, and PTTH's server is equivalent to (I think) PageKite's backend.

WireGuard can also pierce firewalls, but it requires root permissions, and the client must be a WireGuard node. PTTH allows any normal HTTP client such as curl, Firefox, etc.

Module overview

+------------+       +-------------+       +------------------+
| ptth_relay |       | ptth_server |       | ptth_file_server |
+------------+       +-------------+       +------------------+
            |         |           |          |
             \       /             \        /
              V     V               V      V
           +------------+       +-------------+
           | http_serde |       | file_server |
           +------------+       +-------------+

The top-level binaries are ptth_relay, ptth_server, and ptth_file_server.

ptth_relay should run on a well-known public server, behind an HTTPS proxy such as Caddy, Nginx, or Apache.

ptth_file_server is a standalone HTTP file server, similar to Python2's -m SimpleHTTPServer command, or Python3's -m http.server.

ptth_server and ptth_file_server use the file_server module. ptth_server will connect out to a ptth_relay instance and serve files through the reverse HTTP tunnel.

The http_serde module is shared by ptth_relay and ptth_server so that they can communicate with each other easily.

Why are GitHub issues disabled?

Because they are not part of Git.

For now, either email me (if you know me personally) or make a pull request to add an item to todo.md.

License

PTTH is licensed under the GNU AGPLv3

Copyright 2020 "Trish"