There are many ways to extend `verdaccio`, currently we support `authentication plugins`, `middleware plugins` (since `v2.7.0`) and `storage plugins` since (`v3.x`).
This section will describe how it looks like a Verdaccio plugin in a ES5 way. Basically we have to return an object with a single method called `authenticate` that will recieve 3 arguments (`user, password, callback`). Once the authentication has been executed there is 2 options to give a response to `verdaccio`.
### API
```js
function authenticate (user, password, callback) {
...more stuff
}
```
##### OnError
Either something bad happened or auth was unsuccessful.
callback(null, false)
##### OnSuccess
The auth was successful.
`groups` is an array of strings where the user is part of.
callback(null, groups);
### Example
```javascript
function Auth(config, stuff) {
var self = Object.create(Auth.prototype);
self._users = {};
// config for this module
self._config = config;
// verdaccio logger
self._logger = stuff.logger;
// pass verdaccio logger to ldapauth
self._config.client_options.log = stuff.logger;
return self;
}
Auth.prototype.authenticate = function (user, password, callback) {
var LdapClient = new LdapAuth(self._config.client_options);
....
LdapClient.authenticate(user, password, function (err, ldapUser) {
...
var groups;
...
callback(null, groups);
});
};
module.exports = Auth;
```
And the setup
```yaml
auth:
htpasswd:
file: ./htpasswd
```
Where `htpasswd` is the sufix of the plugin name. eg: `verdaccio-htpasswd` and the rest of the body would be the plugin configuration params.
Middleware plugins have the capability to modify the API layer, either adding new endpoints or intercepting requests. A pretty good example of middleware plugin is the [sinopia-github-oauth](https://github.com/soundtrackyourbrand/sinopia-github-oauth) compatible with `verdaccio`.
function register_middlewares(expressApp, auth, storage) {
...more stuff
}
```
To register a middleware we need an object with a single method called `register_middlewares` that will recieve 3 arguments (`expressApp, auth, storage`). *Auth* is the authentification instance and *storage* is also the main Storage instance that will give you have access to all to the storage actions.
> The Storage API is still experimental and might change in the next minor versions. For further information about Storage API please follow the [types definitions in our official repository](https://github.com/verdaccio/flow-types).
### Storage Plugins Examples
The following list of plugins are implementing the Storage API and might be used them as example.