= Vert.x Auth - Authentication and Authorisation

This Vert.x component provides interfaces for authentication and authorisation that can be used from
your Vert.x applications and can be backed by different providers.

Vert.x auth is also used by vertx-web to handle its authentication and authorisation.

To use this project, add the following dependency to the _dependencies_ section of your build descriptor:

* Maven (in your `pom.xml`):

[source,xml,subs="+attributes"]
----
<dependency>
  <groupId>io.vertx</groupId>
  <artifactId>vertx-auth-common</artifactId>
  <version>3.4.2</version>
</dependency>
----

* Gradle (in your `build.gradle` file):

[source,groovy,subs="+attributes"]
----
compile 'io.vertx:vertx-auth-common:3.4.2'
----

== Basic concepts

_Authentication_ means verifying the identity of a user.

_Authorisation_ means verifying a user has an authority.

What the authority means is determined by the particular implementation and we don't mandate any particular model,
e.g. a permissions/roles model, to keep things very flexible.

For some implementations an authority might represent a permission, for example the authority to access all printers,
or a specific printer. Other implementations must support roles too, and will often represent this by prefixing
the authority with something like `role:`, e.g. `role:admin`. Another implementation might have a completely
different model of representing authorities.

To find out what a particular auth provider expects, consult the documentation for that auth provider..

== Authentication

To authenticate a user you use `link:../../apidocs/io/vertx/ext/auth/AuthProvider.html#authenticate-io.vertx.core.json.JsonObject-io.vertx.core.Handler-[authenticate]`.

The first argument is a JSON object which contains authentication information. What this actually contains depends
on the specific implementation; for a simple username/password based authentication it might contain something like:

----
{
  "username": "tim"
  "password": "mypassword"
}
----

For an implementation based on JWT token or OAuth bearer tokens it might contain the token information.

Authentication occurs asynchronously and the result is passed to the user on the result handler that was provided in
the call. The async result contains an instance of `link:../../apidocs/io/vertx/ext/auth/User.html[User]` which represents the authenticated
user and contains operations which allow the user to be authorised.

Here's an example of authenticating a user using a simple username/password implementation:

[source,java]
----
JsonObject authInfo = new JsonObject().put("username", "tim").put("password", "mypassword");

authProvider.authenticate(authInfo, res -> {
  if (res.succeeded()) {

    User user = res.result();

    System.out.println("User " + user.principal() + " is now authenticated");

  } else {
    res.cause().printStackTrace();
  }
});
----

== Authorisation

Once you have an `link:../../apidocs/io/vertx/ext/auth/User.html[User]` instance you can call methods on it to authorise it.

to check if a user has a specific authority you use `link:../../apidocs/io/vertx/ext/auth/User.html#isAuthorised-java.lang.String-io.vertx.core.Handler-[isAuthorised]`.

The results of all the above are provided asynchronously in the handler.

Here's an example of authorising a user:

[source,java]
----
user.isAuthorised("printers:printer1234", res -> {
  if (res.succeeded()) {

    boolean hasAuthority = res.result();

    if (hasAuthority) {
      System.out.println("User has the authority");
    } else {
      System.out.println("User does not have the authority");
    }

  } else {
    res.cause().printStackTrace();
  }
});
----

And another example of authorising in a roles based model which uses `role:` as a prefix.

Please note, as discussed above how the authority string is interpreted is completely determined by the underlying
implementation and Vert.x makes no assumptions here.

=== Caching authorities

The user object will cache any authorities so subsequently calls to check if it has the same authorities will result
in the underlying provider being called.

In order to clear the internal cache you can use `link:../../apidocs/io/vertx/ext/auth/User.html#clearCache--[clearCache]`.

=== The User Principal

You can get the Principal corresponding to the authenticated user with `link:../../apidocs/io/vertx/ext/auth/User.html#principal--[principal]`.

What this returns depends on the underlying implementation.

== Creating your own auth implementation

If you wish to create your own auth provider you should implement the `link:../../apidocs/io/vertx/ext/auth/AuthProvider.html[AuthProvider]` interface.

We provide an abstract implementation of user called `link:../../apidocs/io/vertx/ext/auth/AbstractUser.html[AbstractUser]` which you can subclass
to make your user implementation. This contains the caching logic so you don't have to implement that yourself.

If you wish your user objects to be clusterable you should make sure they implement `link:../../apidocs/io/vertx/core/shareddata/impl/ClusterSerializable.html[ClusterSerializable]`.

== Pseudo Random Number Generator

Since Secure Random from java can block during the acquisition of entropy from the system, we provide a simple wrapper
around it that can be used without the danger of blocking the event loop.

By default this PRNG uses a mixed mode, blocking for seeding, non blocking for generating. The PRNG will also reseed
every 5 minutes with 64bits of new entropy. However this can all be configured using the system properties:

* io.vertx.ext.auth.prng.algorithm e.g.: SHA1PRNG
* io.vertx.ext.auth.prng.seed.interval e.g.: 1000 (every second)
* io.vertx.ext.auth.prng.seed.bits e.g.: 128

Most users should not need to configure these values unless if you notice that the performance of your application is
being affected by the PRNG algorithm.

=== Sharing Pseudo Random Number Generator

Since the Pseudo Random Number Generator objects are expensive in resources, they consume system entropy which is a
scarce resource it can be wise to share the PRNG's across all your handlers. In order to do this and to make this
available to all languages supported by Vert.x you should look into the `link:../../apidocs/io/vertx/ext/auth/VertxContextPRNG.html[VertxContextPRNG]`.

This interface relaxes the lifecycle management of PRNG's for the end user and ensures it can be reused across all
your application, for example:

[source,java]
----
String token = VertxContextPRNG.current(vertx).nextString(32);
// Generate a secure random integer
int randomInt = VertxContextPRNG.current(vertx).nextInt();
----
<a href="mailto:julien@julienviet.com">Julien Viet</a><a href="http://tfox.org">Tim Fox</a>