Jetforce

An experimental TCP server for the new, under development Gemini Protocol. Learn more about Gemini here.

Features

• A built-in static file server with support for gemini directories and CGI scripts.
• A full framework for writing python applications that loosely mimics WSGI.
• A lean, modern python codebase with type hints and black formatting.
• A solid foundation built on top of the twisted asynchronous networking engine.

Installation

Requires Python 3.7 or newer.

The latest stable release can be installed from PyPI:

$ pip install jetforce

Or, install from source:

$ git clone https://github.com/michael-lazar/jetforce
$ cd jetforce
$ python setup.py install

Usage

Use the --help flag to view command-line options:

$ jetforce --help
usage: jetforce [-h] [-V] [--host HOST] [--port PORT] [--hostname HOSTNAME]
                [--tls-certfile FILE] [--tls-keyfile FILE] [--tls-cafile FILE]
                [--tls-capath DIR] [--dir DIR] [--cgi-dir DIR]
                [--index-file FILE]

An Experimental Gemini Protocol Server

optional arguments:
  -h, --help           show this help message and exit
  -V, --version        show program's version number and exit

server configuration:
  --host HOST          Server address to bind to (default: 127.0.0.1)
  --port PORT          Server port to bind to (default: 1965)
  --hostname HOSTNAME  Server hostname (default: localhost)
  --tls-certfile FILE  Server TLS certificate file (default: None)
  --tls-keyfile FILE   Server TLS private key file (default: None)
  --tls-cafile FILE    A CA file to use for validating clients (default: None)
  --tls-capath DIR     A directory containing CA files for validating clients
                       (default: None)

fileserver configuration:
  --dir DIR            Root directory on the filesystem to serve (default:
                       /var/gemini)
  --cgi-dir DIR        CGI script directory, relative to the server's root
                       directory (default: cgi-bin)
  --index-file FILE    If a directory contains a file with this name, that
                       file will be served instead of auto-generating an index
                       page (default: index.gmi)

Setting the hostname

The server's hostname should be set to the DNS name that you expect to receive traffic from. For example, if your jetforce server is running on "gemini://cats.com", you should set the hostname to "cats.com". Any URLs that do not match this hostname will be refused by the server, including URLs that use a direct IP address such as "gemini://174.138.124.169".

Setting the host

The server's host should be set to the local socket that you want to bind to:

• --host "127.0.0.1" - Accept local connections only
• --host "0.0.0.0" - Accept remote connections over IPv4
• --host "::" - Accept remote connections over IPv6
• --host "" - Accept remote connections over any interface (IPv4 + IPv6)

TLS Certificates

The gemini specification requires that all connections be sent over TLS.

If you do not provide a TLS certificate file using the --tls-certfile flag, jetforce will automatically generate a temporary cert for you to use. This is great for making development easier, but before you expose your server to the public internet you should setup something more permanent. You can generate your own self-signed server certificate, or obtain one from a Certificate Authority like Let's Encrypt.

Here's an example openssl command that you can use to generate a self-signed certificate:

$ openssl req -newkey rsa:2048 -nodes -keyout {hostname}.key \
    -nodes -x509 -out {hostname}.crt -subj "/CN={hostname}"

Jetforce also supports TLS client certificates (both self-signed and CA authorised). Requests that are made with client certificates will include additional CGI/environment variables with information about the TLS connection.

You can specify a CA for client validation with the --tls-cafile or --tls-capath flags. Connections validated by the CA will have the TLS_CLIENT_AUTHORISED environment variable set to True. Instructions on how to generate CA's are outside of the scope of this readme, but you can find many helpful tutorials online.

Static Files

Jetforce will serve static files in the /var/gemini/ directory by default. Files ending with *.gmi will be interpreted as the text/gemini type. If a directory is requested, jetforce will look for a file named index.gmi in that directory to return. Otherwise, a directory file listing will be automatically generated.

CGI Scripts

Jetforce supports a simplified version of CGI scripting. It doesn't exactly follow the RFC 3875 specification for CGI, but it gets the job done for the purposes of Gemini.

Any executable file placed in the server's cgi-bin/ directory will be considered a CGI script. When a CGI script is requested by a gemini client, the jetforce server will execute the script and pass along information about the request using environment variables:

Variable Name	Description	Example
GATEWAY_INTERFACE	CGI version (for compatability).	GCI/1.1
SERVER_PROTOCOL	The server protocol.	GEMINI
SERVER_SOFTWARE	The server version string.	jetforce/0.0.7
GEMINI_URL	Raw URL string from the request.	gemini://mozz.us/cgi-bin/example.cgi/hello?world
SCRIPT_NAME	The part of the URL's path that corresponds to the CGI script location.	/cgi-bin/example.cgi
PATH_INFO	The remainder of the URL's path after the CGI script location.	/hello
QUERY_STRING	The query string portion of the request URL.	world
HOSTNAME	Server hostname.	mozz.us
SERVER_NAME	Server hostname (alias for HOSTNAME).	mozz.us
REMOTE_ADDR	Client IP address.	10.10.0.2
REMOTE_HOST	Client IP address (alias for REMOTE_ADDR).	10.10.0.2
SERVER_PORT	Server port number.	1965
TLS_CIPHER	TLS cipher that was negotiated.	TLS_AES_256_GCM_SHA384
TLS_VERSION	TLS version that was negotiated.	TLSv1.3

Additional CGI variables will also be included when the connection uses a TLS client certificate:

Variable Name	Description	Example
AUTH_TYPE	Authentication type (for compatability).	CERTIFICATE
REMOTE_USER	The subject CommonName attribute, if provided.	michael123
TLS_CLIENT_HASH	A base64-encoded certificate fingerprint.	hjQftIC/4zPDQ1MNdav5nRQ39pM482xoTIgxtjyZOpY=
TLS_CLIENT_NOT_BEFORE	Certificate activation date.	2020-04-05T04:18:22Z
TLS_CLIENT_NOT_AFTER	Certificate expiration date.	2021-04-05T04:18:22Z
TLS_CLIENT_SERIAL_NUMBER	Certificate serial number.	73629018972631
TLS_CLIENT_AUTHORISED	Was the certificate verified by the server's CA?	0 (not authorised) / 1 (authorised)

The CGI script must then write the gemini response to the stdout stream. This includes the status code and meta string on the first line, and the optional response body on subsequent lines. The bytes generated by the CGI script will be forwarded verbatim to the gemini client, without any additional modification by the server.

Deployment

Jetforce is intended to be run behind a process manager that handles daemonizing the script, redirecting output to system logs, etc. I prefer to use systemd for this because it's installed on my operating system and easy to set up.

Here's how I configure my server over at gemini://mozz.us:

# /etc/systemd/system/jetforce.service
[Unit]
Description=Jetforce Server

[Service]
Type=simple
Restart=always
RestartSec=5
Environment="PYTHONUNBUFFERED=1"
ExecStart=/usr/local/bin/jetforce \
    --host 0.0.0.0 \
    --port 1965 \
    --hostname mozz.us \
    --dir /var/gemini \
    --tls-certfile /etc/letsencrypt/live/mozz.us/fullchain.pem \
    --tls-keyfile /etc/letsencrypt/live/mozz.us/privkey.pem \
    --tls-cafile /etc/pki/tls/jetforce_client/ca.cer

[Install]
WantedBy=default.target

• --host 0.0.0.0 allows the server to accept external connections from any IP address over IPv4.
• PYTHONUNBUFFERED=1 disables buffering stderr and is sometimes necessary for logging to work.
• --tls-certfile and --tls-keyfile point to my WWW server's Let's Encrypt certificate chain.
• --tls-cafile points to a self-signed CA that I created in order to test accepting client TLS connections.

With this service installed, I can start and stop the server using

systemctl start jetforce
systemctl stop jetforce

And I can view the server logs using

journalctl -u jetforce -f

WARNING

You are exposing a server to the internet. You (yes you!) are responsible for securing your server and setting up appropriate access permissions. This likely means not running jetforce as the root user. Security best practices are outside of the scope of this document and largely depend on your individual threat model.

License

This project is licensed under the Floodgap Free Software License.

The Floodgap Free Software License (FFSL) has one overriding mandate: that software using it, or derivative works based on software that uses it, must be free. By free we mean simply "free as in beer" -- you may put your work into open or closed source packages as you see fit, whether or not you choose to release your changes or updates publicly, but you must not ask any fee for it.