gmid/README.md

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# gmid
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> dead simple, zero configuration Gemini server
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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.
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gmid was initially written to serve static files, but can also
optionally execute CGI scripts. It was also written with security in
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mind: on Linux, FreeBSD and OpenBSD is sandboxed via `seccomp(2)`,
`capsicum(4)`and `pledge(2)`+`unveil(2)` respectively.
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## Features
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- IRI support (RFC3987)
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- dual stack: can serve over both IPv4 and IPv6
- CGI scripts
- (very) low memory footprint
- small codebase, easily hackable
- virtual hosts
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- sandboxed by default on OpenBSD, Linux and FreeBSD
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## Drawbacks
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- 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.
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## Building
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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.
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The build is as simple as
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make
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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.
To install execute:
make install
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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/cert.pem:...:ro \
-v /path/to/key.pem:...:ro \
-v /path/to/docs:/var/gemini \
gmid -f -d /var/gemini -K ... -C ...
ellipses used for brevity.
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### 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)
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Let's say you have compiled and installed libretls in `$LIBRETLS`,
then you can build `gmid` with
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./configure CFLAGS="-I$LIBRETLS/include" \
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LDFLAGS="$LIBRETLS/lib/libtls.a -lssl -lcrypto -lpthread"
make
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### Testing
The regression suite requires python3 at the moment. Execute
make regress
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to start the suite. Keep in mind that the suite will create files
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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
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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
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serves; the executor has `stdio sendfd proc exec` as pledges.
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On FreeBSD, the executor process is sandboxed with `capsicum(4)`.
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On Linux, a `seccomp(2)` filter is installed to allow only certain
syscalls, see [sandbox.c](sandbox.c) for more information on the BPF
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program.
In any case, you are invited to run gmid inside some sort of
container/jail.