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# gmid
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gmid is a fast Gemini server written with security in mind.  I
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initially wrote it to serve static files, but it has grown into a
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featureful server.
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## Features
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(random order)
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 - sandboxed by default on OpenBSD, Linux and FreeBSD
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 - reconfiguration: reload the running configuration without
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   interruption
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 - automatic redirect/error pages (see `block return`)
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 - IRI support (RFC3987)
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 - automatic certificate generation for config-less mode
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 - reverse proxying
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 - CGI and FastCGI support
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 - virtual hosts
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 - location rules
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 - event-based asynchronous I/O model
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 - low memory footprint
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 - small codebase, easily hackable
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## Internationalisation (IRIs, UNICODE, punycode, all that stuff)
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Even thought the current Gemini specification doesn't mention anything
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in this regard, I do think these are important things and so I tried
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to implement them in the most user-friendly way I could think of.
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For starters, gmid has full support for IRI (RFC3987 —
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Internationalized Resource Identifiers).  IRIs are a superset of URIs,
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so there aren't incompatibilities with URI-only clients.
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There is full support also for punycode.  In theory, the user doesn't
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even need to know that punycode is a thing.  The hostname in the
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configuration file can (and must be) in the decoded form (e.g. `naïve`
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and not `xn--nave-6pa`), gmid will do the rest.
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The only missing piece is UNICODE normalisation of the IRI path: gmid
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doesn't do that (yet).
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## Configuration
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gmid has a rich configuration file, heavily inspired by OpenBSD'
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httpd, with every detail carefully documented in the manpage.  Here's
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a minimal example of a config file:
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```conf
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server "example.com" {
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	cert "/path/to/cert.pem"
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	key  "/path/to/key.pem"
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	root "/var/gemini/example.com"
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}
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```
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and a slightly more complex one
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```conf
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ipv6 on     # enable ipv6
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# define a macro
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cert_root = "/path/to/keys"
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server "example.com" {
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	alias "foobar.com"
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	cert $cert_root "/example.com.crt"
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	key  $cert_root "/example.com.pem"
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	root "/var/gemini/example.com"
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	# lang for text/gemini files
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	lang "en"
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	# execute CGI scripts in /cgi/
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	cgi "/cgi/*"
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	# only for locations that matches /files/*
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	location "/files/*" {
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		# generate directory listings
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		auto index on
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	}
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	location "/repo/*" {
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		# change the index file name
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		index "README.gmi"
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		lang "it"
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	}
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}
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```
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## Building
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gmid depends on libevent2, OpenSSL/LibreSSL and libtls (provided
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either by LibreSSL or libretls).  At build time, yacc (or GNU bison)
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is also needed.
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The build is as simple as
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    ./configure
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    make
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or `make static` to build a statically-linked executable.
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If the configure scripts fails to pick up something, please open an
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issue or notify me via email.
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To install execute:
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    make install
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Please keep in mind that the master branch, from time to time, may be
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accidentally broken on some platforms.  gmid is developed primarily on
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OpenBSD/amd64 and commits on the master branch don't get always tested
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in other OSes.  Before tagging a release however, a comprehensive
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testing on various platform is done to ensure that everything is
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working as intended.
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### Testing
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Execute
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    make regress
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to start the suite.  Keep in mind that the regression tests needs to
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create files inside the `regress` directory and bind the 10965 port.
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## Contributing
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Any form of contribution is welcome, not only patches or bug reports.
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If you have a sample configuration for some specific use-case, a
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script or anything that could be useful to others, consider adding it
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to the `contrib` directory.
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## Architecture/Security considerations
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gmid is composed by four processes: the parent process, the logger,
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the listener and the executor.  The parent process is the only one
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that doesn't drop privileges, but all it does is to wait for a SIGHUP
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to reload the configuration and spawn a new generation of children
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process.  The logger process gathers the logs and prints 'em to
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stderr or syslog (for the time being.)  The listener process is the
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only one that needs internet access and is sandboxed by default.  The
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executor process exists only to fork and execute CGI scripts, and
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optionally to connect to FastCGI applications.
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On OpenBSD the processes are all `pledge(2)`d and `unveil(2)`ed.
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On FreeBSD, the listener and logger process are sandboxed with `capsicum(4)`.
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On Linux, a `seccomp(2)` filter is installed in the listener to allow
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only certain syscalls, see [sandbox.c](sandbox.c) for more information
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about the BPF program.  If available, landlock is used to limit the
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portion of the file system gmid can access (requires linux 5.13+.)
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In any case, it's advisable to run gmid inside some sort of
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container/jail/chroot.