twins-upstream/CONFIGURATION.md

This page is also available at [gemini://twins.rocketnine.space/configuration.gmi](gemini://twins.rocketnine.space/configuration.gmi)

`twins` requires a configuration file to operate. It is loaded from
`~/.config/twins/config.yaml` by default. You may specify a different location
via the `--config` argument.

# Configuration options

## Listen

Address to listen for connections on in the format of `interface:port`.

### Listen on localhost

`localhost:1965`

### Listen on all interfaces

`:1965`

## Hosts

Hosts are defined by their hostname followed by one or more paths to serve.

Paths may be defined as fixed strings or regular expressions (starting with `^`).

Paths are matched in the order they are defined.

Fixed string paths will match with and without a trailing slash.

When accessing a directory the file `index.gemini` or `index.gmi` is served.

When a host is defined with the name `default`, other hosts and paths will use
those values as the default configuration. It is not currently possible to
enable an attribute by default and then disable it for individual paths.

### Certificates

A certificate and private key must be specified.

#### localhost certificate

Use `openssl` generate a certificate for localhost.

```bash
openssl req -x509 -out localhost.crt -keyout localhost.key \
  -newkey rsa:2048 -nodes -sha256 \
  -subj '/CN=localhost' -extensions EXT -config <( \
   printf "[dn]\nCN=localhost\n[req]\ndistinguished_name = dn\n[EXT]\nsubjectAltName=DNS:localhost\nkeyUsage=digitalSignature\nextendedKeyUsage=serverAuth")
```

#### Domain certificate

Use [certbot](https://certbot.eff.org) to get a certificate from [Let's Encrypt](https://letsencrypt.org) for a domain.

```bash
certbot certonly --config-dir /home/www/certs \
  --work-dir /home/www/certs \  
  --logs-dir /home/www/certs \
  --webroot \
  -w /home/www/gemini.rocks/public_html \
  -d gemini.rocks \
  -d www.gemini.rocks
```

Provide the path to the certificate file at `certs/live/$DOMAIN/fullchain.pem`
and the private key file at `certs/live/$DOMAIN/privkey.pem` to twins.

### DisableSize

The size of the response body is included in the media type header by default.
Set this option to `true` to disable this feature. See [PROPOSALS.md](https://gitlab.com/tslocum/twins/blob/master/PROPOSALS.md)
for more information.

### Path

#### Resources

One resource must be defined for each path.

##### Root

Serve static files from specified root directory.

##### Proxy

Forward requests to Gemini server at specified URL.

Use the pseudo-scheme `gemini-insecure://` to disable certificate verification.

##### Command

Serve output of system command.

When input is requested from the user, it is available as a pseudo-variable
`$USERINPUT` which does not require surrounding quotes. It may be used as an
argument to the command, otherwise user input is passed via standard input.

#### Attributes

Any number of attributes may be defined for a path.

##### Cache

Cache duration (in seconds). Set to `0` to disable caching entirely. This is an
out-of-spec feature. See [PROPOSALS.md](https://gitlab.com/tslocum/twins/blob/master/PROPOSALS.md)
for more information.

##### Log

Path to log file. Requests are logged in [Apache format](https://httpd.apache.org/docs/2.2/logs.html#combined),
excluding IP address and query.

##### SymLinks

When enabled, symbolic links may be accessed. This attribute is disabled by default.

##### HiddenFiles

When enabled, hidden files and directories may be accessed. This attribute is
disabled by default.

##### ListDirectory

When enabled, directories without an index file will serve a list their
contents.  This attribute is disabled by default.

##### Input

Request text input from user.

##### SensitiveInput

Request sensitive text input from the user. Text will not be shown as it is entered.

##### Type

Content type is normally detected automatically. This attribute forces a
specific content type for a path.

##### FastCGI

Forward requests to [FastCGI](https://en.wikipedia.org/wiki/FastCGI) server at
specified address or path.

A `Root` attribute must also be specified to use `FastCGI`.

## End-of-line indicator

The Gemini protocol requires `\r\n` (CRLF) as the end-of-line indicator. This
convention is carried over from protocol specifications **first written in the
1970s**. This requirement is antithetic to the spirit of Gemini (to improve
upon the Finger and Gopher protocols), increasing the complexity of client and
server implementations unnecessarily.

In anticipation of an improvement to the Gemini specification, administrators
may configure twins to send standard `\n` (LF) line endings by setting
`SaneEOL` to `true`.

References:
[1](https://lists.orbitalfox.eu/archives/gemini/2019/000131.html)
[2](https://lists.orbitalfox.eu/archives/gemini/2020/000756.html)
[3](https://lists.orbitalfox.eu/archives/gemini/2020/001339.html)
[4](https://lists.orbitalfox.eu/archives/gemini/2020/003065.html)

# Example config.yaml

```yaml
# Address to listen on
listen: :1965

# Hosts and paths to serve
hosts:
  default: # Default host configuration
    paths: # Default path attributes
      -
        log: /srv/log/gemini.log
        symlinks: true # Follow symbolic links
  gemini.rocks:
    cert: /srv/gemini.rocks/data/cert.crt
    key: /srv/gemini.rocks/data/cert.key
    paths:
      -
        path: ^/sites/.*\.php$
        root: /home/geminirocks/data
        fastcgi: unix:///var/run/php.sock
      -
        path: /sites
        root: /home/geminirocks/data
        cache: 604800 # Cache for 1 week
        listdirectory: true
      -
        path: ^/(help|info)$
        root: /home/geminirocks/data/help
      -
        path: ^/proxy-example$
        proxy: gemini://localhost:1966
      -
        path: ^/cmd-example$
        command: uname -a
        cache: 0 # Do not cache
      -
        path: /
        root: /home/geminirocks/data/home
  twins.rocketnine.space:
    cert: /srv/twins.rocketnine.space/data/cert.crt
    key: /srv/twins.rocketnine.space/data/cert.key
    paths:
      -
        path: /sites
        root: /home/twins/data/sites
      -
        path: /
        root: /home/twins/data/home
```