Dʒɛmɪni

A gemini server written in Racket.

Features









Requirements




Note: OpenSSL is only required when you won't supply your own server certificate and key which can be passed in through the command-line.

Installation

There's two ways of installing dezhemini:



The first option creates a "launcher" which depends on your PATH containing whatever directory raco installs launchers in. This is typically something like ".local/share/racket/8.1/bin" in your home directory, where "8.1" is the version number of your racket installation.

raco pkg install git+https://git.sr.ht/~rwv/dezhemini

Now you can run:

dezhmnsrv -h

to find out what's what.

You can also just clone the repository from:

Link

and run the following command to install the required racket packages:

raco pkg install

From here you can run:

racket dezhmnsrv.rkt -h

for the same help message.

Examples in this document will assume you're using the latter method because they depend on other files in the repository.

Running

Start the server with the following command:

racket dezhmnsrv.rkt localhost:root

Point your gemini client to:

Link

Files will be served from the "root" directory in the current working directory. For all configuration options use the "-h" for more information.

CGI scripts

Simply make files in your document directory executable to create CGI scripts (don't forget the shebang!). The process will inherit all environment variables of the server with the following extra variables:











When a client certificate is supplied:




Here's an example:

Link

For more information about CGI see:

Link

Note: the CGI specification is written with HTTP in mind, therefore this implementation only supports a subset of the specification.

Server Name Indication

Different server names can be served from the same port on the same instance using TLS SNI. Here's an example:

racket dezhmnsrv.rkt business.com:business pleasure.com:pleasure

In the above example all requests for "business.com" will be served from the "business" directory and all requests for "pleasure.com" from "pleasure". The command-line switches for certificates, keys and roots all allow a server name prefix with a semicolon.

Note: it is not possible to start one instance which listens to a different port per domain. Just run a separate instance instead for such a setup.

Handlers

A list of handlers will be tried to respond to an incoming request. The first response is returned to the client.

The default handlers in order are:




Use the -A and -P switched to append or prepend handlers. These switches expect a racket loadable file which provides a procedure called "handler" and accepts an alist with the following shape:

((url . "gemini://example.com/path?query")
 (path-info . "/path")
 (query-string . "query")
 (document-root . "some_directory")
 (server-name . "example.com")
 (remote-addr . "1.2.3.4"))

When a client certificate is supplied it includes a "client-certificate" member like:

((digest . "SHA256:1A2B3C..")
 (common-name . "fred"))

The handler returns 3 values for a "success" response (status 20 <= status <= 29) or 2 values for other response or #f when the handler does not know how to handle the request, in which case the next handler is tried.




See also examples/handlers/hello.rkt for an example handler. Try it with:

racket dezhmnsrv.rkt -A examples/handlers/hello.rkt localhost:root

and point your gemini client to:

Link

Note you'll need to figure out where raco put the dezhemini files or run from a cloned git repository.

Wrappers

A wrapper will wrap the global handler to do pre or post processing. Multiple wrappers can be applied. Use cases include: templating, logging and setting environment variables for underlying handlers/scripts.

Use the -W switch to load a racket file which provide a "wrap" procedure. The procedure will take a handler procedure and return a new handler procedure. Here's a very basic example:

(define (wrap handler)
  (lambda (req)
    (displayln "do stuff before handling request")
    (handler req)))

Doing something after handling a request requires receiving the returned values and passing them on. That takes a bit more effort because the global handler can return 2 or 3 values depending on the type of response (status, meta and optionally body).

Here's an example of dealing with response values:

(define (wrap handler)
  (lambda (req)
    (displayln "do stuff before handling request")
    (call-with-values
     (lambda () (handler req))
     (lambda res
       (displayln "do stuff after handling request")
       (apply values res)))))

See also examples/censor.rkt for an example handler and try it with:

racket dezhmnsrv.rkt -W examples/wrappers/censor.rkt localhost:root

Logging

This application uses the standard Racket logger and posts messages to the "dezhmn" topic. Message on this topic of level "info" and higher will be written to standard output. To see more messages use the "-v" command-line flag.

For more information configuring logging see:

Link

Content Types

By default this implementation comes with common mappings from file extensions to content types. You can add your own by supplying a mime.types file at the command-line.

Development

This project is hosted on sourcehut:

Link

Code:

Link

Tickets:

Link

Mailing list:

Link

Before sending patches run the test suite:

raco test dezhmnsrv_test.rkt

Copying

This software is distributed under the GPLv3 license. For more information see:

Link

Source