.\" Copyright (c) 2021 Omar Polo <op@omarpolo.com>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
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.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.Dd $Mdocdate: January 30 2021$
.Dt GMID 1
.Os
.Sh NAME
.Nm gmid
.Nd simple and secure Gemini server
.Sh SYNOPSIS
.Nm
.Bk -words
.Op Fl fnv
.Op Fl c Ar config
.Ek
.Nm
.Bk -words
.Op Fl 6hv
.Op Fl d Pa certs-dir
.Op Fl H Ar hostname
.Op Fl p Ar port
.Op Fl x Pa cgi
.Op Pa dir
.Ek
.Sh DESCRIPTION
.Nm
is a simple and minimal gemini server that can serve static files and
execute CGI scripts.
It can run without a configuration file with a limited set of features
available.
.Pp
.Nm
rereads the configuration file when it receives
.Dv SIGHUP .
.Pp
The options are as follows:
.Bl -tag -width 14m
.It Fl c Pa config
Specify the configuration file.
.It Fl f
Stays and logs on the foreground.
.It Fl n
Check that the configuration is valid, but don't start the server.
.El
.Pp
If no configuration file is given,
.Nm
will look for the following options
.Bl -tag -width 14m
.It Fl 6
Enable IPv6.
.It Fl d Pa certs-path
Directory where certificates for the config-less mode are stored.
By default is
.Pa $XDG_DATA_HOME/gmid ,
i.e.
.Pa ~/.local/share/gmid .
.It Fl H Ar hostname
The hostname, by default
.Ar localhost .
Certificates for the given
.Ar hostname
are searched inside the
.Pa certs-dir
directory given with the
.Fl d
option.
They have the form
.Pa hostname.cert.pem
and
.Pa hostname.key.pem .
If a certificate or key don't exists for a given hostname they
will be automatically generated.
.It Fl h
Print the usage and exit.
.It Fl p Ar port
The port to listen on, by default 1965.
.It Fl v
Verbose mode.
Multiple
.Fl v
options increase the verbosity.
.It Fl x Pa path
Enable execution of CGI scripts.
See the description of the
.Ic cgi
option in the section
.Sq Servers
below to learn how
.Pa path
is processed.
Cannot be provided more than once.
.It Pa dir
The root directory to serve.
By default the current working directory is assumed.
.El
.Sh CONFIGURATION FILE
The configuration file is divided into two sections:
.Bl -tag -width xxxx
.It Sy Global Options
Global settings for
.Nm .
.It Sy Servers
Virtual hosts definition.
.El
.Pp
Within the sections, empty lines are ignored and comments can be put
anywhere in the file using a hash mark
.Pq Sq # ,
and extend to the end of the current line.
A boolean is either the symbol
.Sq on
or
.Sq off .
A string is a sequence of characters wrapped in double quotes,
.Dq like this .
.Ss Global Options
.Bl -tag -width 12m
.It Ic chroot Pa path
.Xr chroot 2
the process to the given
.Pa path .
The daemon has to be run with root privileges and thus the option
.Ic user
needs to be provided, so privileges can be dropped.
Note that
.Nm
will enter the chroot after loading the TLS keys, but before opening
the virtual host root directories.
It's recommended to keep the TLS keys outside the chroot.
Future version of
.Nm
may enforce this.
.It Ic ipv6 Ar bool
Enable or disable IPv6 support.
By default is off.
.It Ic mime Ar mime-type Ar file-extension
Add a mapping for the given
.Ar file-extension
to the given
.Ar mime-type .
Both argument are strings.
.It Ic port Ar portno
The port to listen on.
By default is 1965.
.It Ic prefork Ar number
Run the specified number of server processes.
This increases the performance and prevents delays when connecting to
a server.
.Nm
runs 3 server processes by default, when not in config-less mode.
The maximum number allowed is 16.
.It Ic protocols Ar string
Specify the TLS protocols to enable.
Refer to
.Xr tls_config_parse_protocols 3
for the valid protocol string values.
By default, both TLSv1.3 and TLSv1.2 are enabled.
Use
.Dq tlsv1.3
to enable only TLSv1.3.
.It Ic user Ar string
Run the daemon as the given user.
.El
.Ss Servers
Every virtual host is defined by a
.Ic server
block:
.Bl -tag -width Ds
.It Ic server Ar hostname Brq ...
Match the server name using shell globbing rules.
This can be an explicit name,
.Ar www.example.com ,
or a name including a wildcards,
.Ar *.example.com .
.El
.Pp
Followed by a block of options that is enclosed in curly brackets:
.Bl -tag -width Ds
.It Ic auto Ic index Ar bool
If no index file is found, automatically generate a directory listing.
It's disabled by default.
.It Ic block Op Ic return Ar code Op Ar meta
Send a reply and close the connection;
.Ar code
is 40
and
.Ar meta
is
.Dq temporary failure
by default.
If
.Ar code
is in the 3x range, then
.Ar meta
must be provided.
Inside
.Ar meta ,
the following special sequences are replaced:
.Bl -tag -compact
.It \&%\&%
is replaced with a single
.Sq \&% .
.It \&%p
is replaced with the request path.
.It \&%q
is replaced with the query string of the request.
.It \&%P
is replaced with the server port.
.It \&%N
is replaced with the server name.
.El
.It Ic cert Pa file
Path to the certificate to use for this server.
The
.Pa file
should contain a PEM encoded certificate.
This option is mandatory.
.It Ic cgi Pa path
Execute CGI scripts that matches
.Pa path
using shell globbing rules.
.It Ic default type Ar string
Set the default media type that is used if the media type for a
specified extension is not found.
If not specified, the
.Ic default type
is set to
.Dq application/octet-stream .
.It Ic entrypoint Pa path
Handle all the requests for the current virtual host using the
CGI script at
.Pa path .
.It Ic index Ar string
Set the directory index file.
If not specified, it defaults to
.Pa index.gmi .
.It Ic key Pa file
Specify the private key to use for this server.
The
.Pa file
should contain a PEM encoded private key.
This option is mandatory.
.It Ic lang Ar string
Specify the language tag for the text/gemini content served.
If not specified, no
.Dq lang
parameter will be added in the response.
.It Ic location Pa path Brq ...
Specify server configuration rules for a specific location.
The
.Pa path
argument will be matched against the request path with shell globbing
rules.
In case of multiple location statements in the same context, the first
matching location will be put into effect and the later ones ignored.
Therefore is advisable to match for more specific paths first and for
generic ones later on.
A
.Ic location
section may include most of the server configuration rules
except
.Ic cert , Ic key , Ic root , Ic location ,
.Ic entrypoint No and Ic cgi .
.It Ic root Pa directory
Specify the root directory for this server.
This option is mandatory.
It's relative to the chroot, if enabled.
.It Ic require Ic client Ic ca Pa path
Allow requests only from clients that provide a certificate signed by
the CA certificate in
.Pa path .
It needs to be a PEM-encoded certificate and it's not relative to the
chroot.
.It Ic strip Ar number
Strip
.Ar number
components from the beginning of the path.
It's only considered for the
.Ar meta
parameter in the scope of a
.Ic block return .
.El
.Sh CGI
When a request for an executable file matches the
.Ic cgi
rule, that file will be execute and its output fed to the client.
.Pp
The CGI scripts are executed in the directory they reside and inherit
the environment from
.Nm
with these additional variables set:
.Bl -tag -width 24m
.It Ev GATEWAY_INTERFACE
.Dq CGI/1.1
.It Ev GEMINI_DOCUMENT_ROOT
The root directory of the virtual host.
.It Ev GEMINI_SCRIPT_FILENAME
Full path to the CGI script being executed.
.It Ev GEMINI_URL
The full IRI of the request.
.It Ev GEMINI_URL_PATH
The path of the request.
.It Ev PATH_INFO
The portion of the requested path that is derived from the the IRI
path hierarchy following the part that identifies the script itself.
Can be unset.
.It Ev PATH_TRANSLATED
Present if and only if
.Ev PATH_INFO
is set.
It represent the translation of the
.Ev PATH_INFO .
.Nm
builds this by appending the
.Ev PATH_INFO
to the virtual host directory root.
.It Ev QUERY_STRING
The decoded query string.
.It Ev REMOTE_ADDR , Ev REMOTE_HOST
Textual representation of the client IP.
.It Ev REQUEST_METHOD
This is present only for RFC3875 (CGI) compliance.
It's always set to the empty string.
.It Ev SCRIPT_NAME
The part of the
.Ev GEMINI_URL_PATH
that identifies the current CGI script.
.It Ev SERVER_NAME
The name of the server
.It Ev SERVER_PORT
The port the server is listening on.
.It Ev SERVER_PROTOCOL
.Dq GEMINI
.It Ev SERVER_SOFTWARE
The name and version of the server, i.e.
.Dq gmid/1.5
.It Ev AUTH_TYPE
The string "Certificate" if the client used a certificate, otherwise
unset.
.It Ev REMOTE_USER
The subject of the client certificate if provided, otherwise unset.
.It Ev TLS_CLIENT_ISSUER
The is the issuer of the client certificate if provided, otherwise
unset.
.It Ev TLS_CLIENT_HASH
The hash of the client certificate if provided, otherwise unset.
The format is
.Dq ALGO:HASH .
.It Ev TLS_VERSION
The TLS version negotiated with the peer.
.It Ev TLS_CIPHER
The cipher suite negotiated with the peer.
.It Ev TLS_CIPHER_STRENGTH
The strength in bits for the symmetric cipher that is being used with
the peer.
.It Ev TLS_CLIENT_NOT_AFTER
The time corresponding to the end of the validity period of the peer
certificate in the ISO 8601 format
.Pq e.g. Dq 2021-02-07T20:17:41Z .
.It Ev TLS_CLIENT_NOT_BEFORE
The time corresponding to the start of the validity period of the peer
certificate in the ISO 8601 format.
.El
.Pp
.Sh MIME
To auto-detect the MIME type of the response
.Nm
looks at the file extension and consults its internal table.
By default the following mappings are loaded, but they can be
overridden or extended using the
.Ic mime
configuration option.
If no MIME is found, the value of
.Ic default type
matching the file
.Ic location
will be used, which is
.Dq application/octet-stream
by default.
.Pp
.Bl -tag -offset indent -width 14m -compact
.It diff
text/x-patch
.It gemini, gmi
text/gemini
.It gif
image/gif
.It jpeg
image/jpeg
.It jpg
image/jpeg
.It markdown, md
text/markdown
.It patch
text/x-patch
.It pdf
application/pdf
.It png
image/png
.It svg
image/svg+xml
.It txt
text/plain
.It xml
text/xml
.El
.Sh EXAMPLES
Serve the current directory
.Bd -literal -offset indent
$ gmid .
.Ed
.Pp
To serve the directory
.Pa docs
and enable CGI scripts inside
.Pa docs/cgi ,
you can
.Bd -literal -offset indent
$ mkdir docs/cgi
$ cat <<EOF > docs/cgi/hello
#!/bin/sh
printf "20 text/plain\\r\\n"
echo "hello world"
EOF
$ chmod +x docs/cgi/hello
$ gmid -x '/cgi/*' docs
.Ed
.Pp
The following is an example of a possible configuration for a site
that enables only TLSv1.3, adds a mime type for the file extension
"rtf" and defines two virtual host:
.Bd -literal -offset indent
ipv6 on		# enable ipv6

protocols "tlsv1.3"

mime "application/rtf" "rtf"

server "example.com" {
	cert "/path/to/cert.pem"
	key  "/path/to/key.pem"
	root "/var/gemini/example.com"
}

server "it.example.com" {
	cert "/path/to/cert.pem"
	key  "/path/to/key.pem"
	root "/var/gemini/it.example.com"
	cgi  "/cgi-bin/*"
	lang "it"
}
.Ed
.Pp
Yet another example, showing how to enable a
.Ic chroot
and use
.Ic location
rule
.Bd -literal -offset indent
chroot "/var/gemini"
user "_gmid"

server "example.com" {
	cert "/path/to/cert.pem"
	key  "/path/to/key.pem"
	root "/example.com" # in the /var/gemini chroot

	location "/static/*" {
		auto index on
		index "index.gemini"
	}
}
.Ed
.Sh ACKNOWLEDGEMENTS
.Nm
uses the
.Dq Flexible and Economical
UTF-8 decoder written by
.An Bjoern Hoehrmann .
.Sh AUTHORS
.An -nosplit
The
.Nm
program was written by
.An Omar Polo Aq Mt op@omarpolo.com .
.Sh CAVEATS
.Bl -bullet
.It
The root directories of all virtual hosts are opened during the daemon
startup; this means that if a root directory gets deleted and then
re-created,
.Nm
won't be able to serve files inside that directory until a restart.
This restriction applies only to the root directories and not their content.
.It
a %2F sequence is indistinguishable from a literal slash: this is not
RFC3986-compliant.
.It
a %00 sequence is treated as invalid character and thus rejected.
.El