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# gmid
> dead simple, zero configuration Gemini server
gmid is a simple and minimal Gemini server. It can run without
configuration, so it's well suited for local development, but at the
same time has a configuration file flexible enough to meet the
requirements of most capsules.
It was initially written to serve static files, but can also
optionally execute CGI scripts. It was also written with security in
mind: on Linux, FreeBSD and OpenBSD is sandboxed via `seccomp(2)`,
`capsicum(4)`and `pledge(2)`+`unveil(2)` respectively.
gmid can be used from the command line to serve local directories
# serve the directory docs
gmid docs
or you can pass a configuration file and have access to all the
features
gmid -c /etc/gmid.conf
Please consult the [manpage](gmid.1) for more information.
## Features
- IRI support (RFC3987)
- dual stack: can serve over both IPv4 and IPv6
- CGI scripts
- (very) low memory footprint
- small codebase, easily hackable
- virtual hosts
- rules per-location
- directory listings
- mime types configurable
- index file configurable
- sandboxed by default on OpenBSD, Linux and FreeBSD
- chroot support
## Drawbacks
- not suited for very busy hosts. If you receive an high number of
connection per-second you'd probably want to run multiple gmid
instances behind relayd/haproxy or a different server.
## Building
gmid depends on a POSIX libc and libtls (provided either by LibreSSL
or libretls). At build time, flex and yacc (or GNU bison) are also
needed.
The build is as simple as
make
If the configure scripts fails to pick up something, please open an
issue or notify me via email.
To install execute:
make install
If you have trouble installing LibreSSL or libretls, as they aren't
available as package on various Linux distribution, you can use Docker
to build a `gmid` image with:
docker build -t gmid .
and then run it with something along the lines of
docker run --rm -it -p 1965:1965 \
-v /path/to/gmid.conf:...:ro \
-v /path/to/docs:/var/gemini \
gmid -c .../gmid.conf
ellipses for brevity.
### Local libretls
This is **NOT** recommended, please try to port LibreSSL/LibreTLS to
your distribution of choice or use docker instead.
However, it's possible to link `gmid` to locally-installed libtls
quite easily. (It's how I test gmid on Fedora, for instance)
Let's say you have compiled and installed libretls in `$LIBRETLS`,
then you can build `gmid` with
./configure CFLAGS="-I$LIBRETLS/include" \
LDFLAGS="$LIBRETLS/lib/libtls.a -lssl -lcrypto -lpthread"
make
### Testing
Execute
make regress
to start the suite. Keep in mind that the suite will create files
inside the `regress` directory and bind the 10965 port.
## Architecture/Security considerations
gmid is composed by two processes: a listener and an executor. The
listener process is the only one that needs internet access and is
sandboxed. When a CGI script needs to be executed, the executor
(outside of the sandbox) sets up a pipe and gives one end to the
listener, while the other is bound to the CGI script standard output.
This way, is still possible to execute CGI scripts without restriction
even in the presence of a sandbox.
On OpenBSD, the listener process runs with the `stdio recvfd rpath
inet` pledges and has `unveil(2)`ed only the directories that it
serves; the executor has `stdio sendfd proc exec` as pledges.
On FreeBSD, the executor process is sandboxed with `capsicum(4)`.
On Linux, a `seccomp(2)` filter is installed to allow only certain
syscalls, see [sandbox.c](sandbox.c) for more information on the BPF
program.
In any case, you are invited to run gmid inside some sort of
container/jail/chroot.
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