.\" Copyright (c) 2022, 2023, 2024 Omar Polo <op@omarpolo.com>
.\"
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.\" 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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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.Dd June 28, 2024
.Dt GMID.CONF 5
.Os
.Sh NAME
.Nm gmid.conf
.Nd gmid Gemini server configuration file
.Sh DESCRIPTION
.Nm
is the configuration file format for the
.Xr gmid 8
Gemini server.
.Pp
The configuration file is divided into the following sections:
.Bl -tag -width Ds
.It Sy Macros
User-defined variables may be defined and used later, simplifying the
configuration file.
.It Sy Global Options
Global settings for
.Xr gmid 8 .
.It Sy Types
Media types and extensions.
.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 .
Multiple strings one next to the other are joined into a single
string:
.Bd -literal -offset indent
# equivalent to "temporary-failure"
block return 40 "temporary" "-" "failure"
.Ed
.Pp
Furthermore, quoting is necessary only when a string needs to contain
special characters
.Pq like spaces or punctuation ,
something that looks like a number or a reserved keyword.
The last example could have been written also as:
.Bd -literal -offset indent
block return 40 temporary "-" failure
.Ed
.Pp
Strict ordering of the sections is not enforced, so that is possible
to mix macros, options and
.Ic server
blocks.
However, defining all the
.Ic server
blocks after the macros and the global options is recommended.
.Pp
Newlines are often optional, except around top-level instructions, and
semicolons
.Dq \&;
can also be optionally used to separate options.
.Pp
Additional configuration files can be included with the
.Ic include
keyword, for example:
.Bd -literal -offset indent
include "/etc/gmid.conf.local"
.Ed
.Ss Macros
Macros can be defined that will later be expanded in context.
Macro names must start with a letter, digit or underscore and may
contain any of those characters.
Macros names may not be reserved words.
Macros are not expanded inside quotes.
.Pp
Two kinds of macros are supported: variable-like and proper macros.
When a macro is invoked with a
.Dq $
before its name its expanded as a string, whereas when it's invoked
with a
.Dq @
its expanded in-place.
.Pp
For example:
.Bd -literal -offset indent
ext_ip = "10.0.0.1"
dir = "/var/gemini"
certdir = "/etc/keys"
common = "lang it; auto index on"

server "foo" {
	listen on $ext_ip
	root $dir "/foo"         # "/var/gemini/foo"
	cert $certdir "/foo.pem" # "/etc/keys/foo.pem"
	key  $certdir "/foo.key" # "/etc/keys/foo.key"
	@common
}
.Ed
.Ss Global Options
.Bl -tag -width 12m
.It Ic chroot Ar path
.Xr chroot 2
the process to the given
.Ar path .
The daemon has to be run with root privileges and thus the option
.Ic user
needs to be provided too, so privileges can be dropped afterwards.
All the paths in the configuration file are relative to the chroot
directory, except for the
.Ic cert ,
.Ic key
and
.Ic ocsp
paths.
Defaults to the
.Ic user
home directory, if provided.
.It Ic log Ar options
Specify logging options.
Multiple options may be provided within curly braces.
The available options are as follows:
.Bl -tag -width Ds
.It Ic access Ar file
Log the requests to
.Ar file .
The path is relative to the
.Ic chroot .
.It Ic style Ar style
Set the logging style, defaults to
.Ic legacy .
The
.Ar style
can be one of:
.Bl -tag -width Ds
.It Ic common
Attempt to be compatible with the default Apache httpd log format.
Each line is formatted as follows: the matching host name,
the remote IP address, one dash
.Sq - ,
Common Name of the client certificate
.Pq if provided, '-' otherwise ,
the timestamp of the request, the request URI wrapped in double quotes,
the response code and the size of the response.
.It Ic combined
Attempt to be compatible with the default nginx log format.
Each line is formatted as follows: the remote IP address, one dash
.Sq - ,
Common Name of the client certificate
.Pq if provided, '-' otherwise ,
the timestamp wrapped in square brackets, the request URI wrapped in
double quotes, the response code, the size of the response, a dash
wrapped in double quotes and "".
The strangness of these two last fields is because Gemini doesn't have
the notion of the
.Dq Referer
header nor the
.Dq User-agent .
.\" .It Ic condensed
.\" The native
.\" .Xr gmid 8
.\" format since 2.0.
.\" Each line is formatted as follows: RFC 3339 date time,
.\" remote IP address, Common Name of the client certificate
.\" .Pq if provided, '-' otherwise ,
.\" the matching host name, the request URI, the size of the request,
.\" the size of the response, the response code and meta.
.It Ic legacy
Each line is formatted as follows: the remote IP address and port, the
.Sq GET
keyword, the request URI, the response code and meta.
.El
.It Ic syslog Op Ic off
Log to syslog.
It is enabled by default, use the
.Ic off
argument to disable.
.It Ic syslog facility Ar facility
Log to
.Xr syslog 3
using specified
.Ar facility .
Available facilities are as follows: daemon, ftp, local0 through local7 and
user.
These are case insensitive and can be prefixed with
.Sq LOG_ .
Not all level may be available on all operating systems.
The default facility is
.Ev LOG_DAEMON .
.El
.It Ic prefork Ar number
Run the specified number of server processes.
This increases the performance and prevents delays when connecting to
a server.
.Xr gmid 8
runs 3 server processes by default.
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.
Mandatory if the
.Ic chroot
option is used.
.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.
It can be an explicit name,
.Ar www.example.com ,
or a name including wildcards,
.Ar *.example.com .
.El
.Pp
Followed by a block of options that is enclosed in curly brackets:
.Bl -tag -width Ds
.It Ic alias Ar name
Specify an additional alias
.Ar name
for this server.
.It Ic auto Ic index Ar bool
If no index file is found, automatically generate a directory listing.
Disabled by default.
.It Ic block Op Ic return Ar code Op Ar meta
Send a reply and close the connection;
by default
.Ar code
is 40
and
.Ar meta
is
.Dq temporary failure .
If
.Ar code
is in the 3x range, then
.Ar meta
is mandatory.
Inside
.Ar meta ,
the following special sequences are supported:
.Bl -tag -width Ds -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 Ar file
Path to the certificate to use for this server.
.Ar file
should contain a PEM encoded certificate.
This option is mandatory.
.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 fastcgi Ar option
Enable FastCGI instead of serving files.
Multiple options may be specified within curly braces.
Valid options are:
.Bl -tag -width Ds
.It Ic param Ar name Cm = Ar value
Set the param
.Ar name
to
.Ar value .
.It Ic socket Oo Ic tcp Oc Ar socket Oo Cm port Ar port Oc
The
.Ar socket
can either be a UNIX-domain socket or a TCP socket.
If the FastCGI application is listening on a UNIX domain socket,
.Ar socket
is a local path name within the
.Xr chroot 2
root directory of
.Xr gmid 8 .
Otherwise, the
.Ic tcp
keyword must be provided and
.Ar socket
is interpreted as a hostname or an IP address.
.Ar port
can be either a port number or the name of a service enclosed in
double quotes.
If not specified defaults to 9000.
.It Ic strip Ar number
Strip
.Ar number
leading path components from the request URL before splitting it in
.Ev SCRIPT_NAME
and
.Ev PATH_INFO .
.El
.Pp
The FastCGI handler will be given the following variables by default:
.Bl -tag -width 24m
.\" .It Ev GEMINI_DOCUMENT_ROOT
.\" The root directory of the virtual host.
.It Ev GEMINI_URL_PATH
Full path of the request.
.It Ev GEMINI_SEARCH_STRING
The decoded
.Ev QUERY_STRING
if defined in the request and if it doesn't contain any unencoded
.Sq =
characters, otherwise unset.
.It Ev GATEWAY_INTERFACE
.Dq CGI/1.1
.It Ev AUTH_TYPE
The string "Certificate" if the client used a certificate, otherwise
unset.
.It Ev PATH_INFO
The portion of the requested path that is derived from the the IRI
path hierarchy following
.Ev SCRIPT_NAME .
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 gmid
builds this by appending the
.Ev PATH_INFO
to the virtual host directory root.
.It Ev QUERY_STRING
The URL-encoded search or parameter 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
.Dq GET .
.It Ev SCRIPT_NAME
The virtual URI path to the script.
Since it's impossible to determine in all cases the correct
.Ev SCRIPT_NAME
programmatically
.Nm gmid
assumes it's the empty string.
It is recommended to manually specify this parameter when serving a
sub-tree of a virtual host via FastCGI.
.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/2.0.5
.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
.It Ic fastcgi off
Disable FastCGI handling in the current location.
.It Ic index Ar string
Set the directory index file.
If not specified, it defaults to
.Pa index.gmi .
.It Ic key Ar file
Specify the private key to use for this server.
.Ar 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 listen on Ar address Oo Ic port Ar number Oc Op Ic proxy-v1
Set the listen
.Ar address
and
.Ar port
which defaults to
.Sq 1965 .
This statement can be specified multiple times.
If
.Ar address
is
.Sq *
then
.Xr gmid 8
will listen on all IPv4 and IPv6 addresses.
.Ar 0.0.0.0
can be used to listen on all IPv4 addresses and
.Ar ::
on all IPv6 addresses.
If
.Ic proxy-v1
is specified, then connections speaking the proxy protocol v1 are
expected on this listener.
If multiple
.Ic listen
directive share the same
.Ar address
and
.Ar port ,
then all of them must have or lack
.Ic proxy-v1 .
.It Ic location Ar path Brq ...
Specify server configuration rules for a specific location.
.Ar 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 alias , Ic cert , Ic key , Ic listen , Ic location
and
.Ic proxy .
.It Ic log Ar bool
Enable or disable the logging for the current server or location block.
.It Ic ocsp Ar file
Specify an OCSP response to be stapled during TLS handshakes
with this server.
The
.Ar file
should contain a DER-format OCSP response retrieved from an
OCSP server for the
.Ic cert
in use.
If the OCSP response in
.Ar file
is empty, OCSP stapling will not be used.
The default is to not use OCSP stapling.
.It Ic proxy Oo Cm proto Ar name Oc Oo Cm for-host Ar host Oo Cm port Ar port Oc Oc Brq ...
Set up a reverse proxy.
The optional matching rules
.Cm proto
and
.Cm for-host
can be used to enable proxying only for protocols matching
.Ar name
.Po Dq gemini
by default
.Pc
and/or whose request IRI matches
.Ar host
and
.Ar port
.Pq 1965 by default .
Matching happens using shell globbing rules.
.Pp
In case of multiple matching proxy blocks in the same context, the
first matching proxy will be put into effect and the later ones
ignored.
.Pp
Valid options are:
.Bl -tag -width Ds
.It Ic cert Ar file
Specify the client certificate to use when making requests.
.It Ic key Ar file
Specify the client certificate key to use when making requests.
.It Ic protocols Ar string
Specify the TLS protocols allowed when making remote requests.
Refer to the
.Xr tls_config_parse_protocols 3
function for the valid protocol string values.
By default, both TLSv1.2 and TLSv1.3 are enabled.
.It Ic relay-to Ar host Op Cm port Ar port
Relay the request to the given
.Ar host
at the given
.Ar port ,
1965 by default.
This is the only mandatory option in a
.Ic proxy
block.
.It Ic require Ic client Ic ca Ar file
Allow the proxying only from clients that provide a certificate
signed by the CA certificate in
.Ar file .
.It Ic sni Ar hostname
Use the given
.Ar hostname
instead of the one extracted from the
.Ic relay-to
rule for the TLS handshake with the proxied gemini server.
.It Ic use-tls Ar bool
Specify whether to use TLS when connecting to the proxied host.
Enabled by default.
.It Ic verifyname Ar bool
Enable or disable the TLS server name verification.
Enabled by default.
.El
.It Ic root Ar directory
Specify the root directory for this server
.Pq alas the current Dq document root .
It's relative to the chroot if enabled.
.It Ic require Ic client Ic ca Ar path
Allow requests only from clients that provide a certificate signed by
the CA certificate in
.Ar 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 before doing a lookup in the
root directory.
It's also considered for the
.Ar meta
parameter in the scope of a
.Ic block return .
.El
.Ss Types
The
.Ic types
section must include one or more lines of the following syntax, enclosed
in curly brances:
.Bl -tag -width Ds
.It Ar type Ns / Ns Ar subtype Ar name Op Ar name ...
Set the media
.Ar type
and
.Ar subtype
to the specified extension
.Ar name .
One or more names can be specified per line.
Earch line may end with an optional semicolon.
.It Ic include Ar file
Include types definition from an external file, for example
.Pa /usr/share/misc/mime.types .
.El
.Pp
By default
.Nm gmid
uses the following mapping if no
.Ic types
block is defined:
.Pp
.Bl -tag -offset indent -width 15m -compact
.It application/pdf
pdf
.It image/gif
gif
.It image/jpeg
jpg jpeg
.It image/png
png
.It image/svg+xml
svg
.It text/gemini
gemini gmi
.It text/markdown
markdown md
.It text/x-patch
diff patch
.It text/xml
xml
.El
.Pp
As an exception,
.Nm gmid
uses the MIME type
.Ar text/gemini
for file extensions
.Ar gemini
or
.Ar gmi
if no mapping was found.
.Sh EXAMPLES
The following is an example of a possible configuration for a site
that enables only TLSv1.3, adds the MIME types mapping from
.Pa /usr/share/misc/mime.types
and defines two virtual host:
.Bd -literal -offset indent
protocols "tlsv1.3"

types {
	include "/usr/share/misc/mime.types"
}

server "example.com" {
	listen on * port 1965
	cert "/etc/ssl/example.com.pem"
	key  "/etc/ssl/private/example.com.key"
	root "/var/gemini/example.com"
}

server "example.it" {
	listen on * port 1965
	cert "/etc/ssl/example.it.pem"
	key  "/etc/ssl/private/example.it.key"
	root "/var/gemini/example.it"

	# set the language for text/gemini files
	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" {
	listen on * port 1965

	# absolute paths:
	cert "/etc/ssl/example.com.pem"
	key  "/etc/ssl/private/example.com.key"

	# relative to the chroot:
	root "/example.com"

	location "/static/*" {
		# load the following rules only for
		# requests that matches "/static/*"

		auto index on
		index "index.gemini"
	}
}
.Ed
.Pp
This shows how to set up a reverse proxy: all request for
.Sq example.com
will be forwarded to 10.0.0.6 transparently.
Proxying establish a new TLS connection, so any client-certificates used
to connect to
.Xr gmid 8
cannot be provided to the proxied server as well.
.Bd -literal -offset indent
server "example.com" {
	listen on * port 1965
	cert "/etc/ssl/example.com.pem"
	key "/etc/ssl/private/example.com.key"
	proxy {
		relay-to 10.0.0.6 port 1965
	}
}
.Ed
.Sh SEE ALSO
.Xr gmid 8 ,
.Xr slowcgi 8
.Sh AUTHORS
.An -nosplit
The
.Nm gmid
program was written by
.An Omar Polo Aq Mt op@omarpolo.com .