# Common Authentication and Authorization

This Vert.x component provides interfaces for authentication and authorization 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 authorization.

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

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

    <dependency>
      <groupId>io.vertx</groupId>
      <artifactId>vertx-auth-common</artifactId>
      <version>5.0.5</version>
    </dependency>

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

    compile 'io.vertx:vertx-auth-common:5.0.5'

## Basic concepts

Authentication means verifying the identity of a user.

Authorization means verifying a user is authorized to perform a specific task

To support many models and keep things very flexible, all authorization operations are performed on the type `Authorization`.

In some case, an authorization might represent a permission, for example the authorization to access all printers, or a specific printer. In others cases, an authorization might be a role (ie: `admin', 'manager', etc.) In order to provide a small set of implementation the following factories are available:

- `RoleBasedAuthorization` Role based authorization.

- `PermissionBasedAuthorization` Permission based authorization.

- `WildcardPermissionBasedAuthorization` Role based authorization matched as a wildcard.

- `AndAuthorization` Logical authorization.

- `OrAuthorization` Logical authorization.

- `NotAuthorization` Logical authorization.

This set of authorizations represent any kind of authorization such as:

- Role based authorization

- Permission based authorization

- Logical authorization (AND, OR, NOT)

- Time based authorization (ie: allow access the last 5 days of the month, from 8am till 10am, etc.)

- Context based authorization (ie: allow access if the ip address is 'xxx.xxx.xxx.xxx')

- Custom based authorization (ie: based on a script or hard-coded code specific to an application)

- etc…​

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

## Authentication

To authenticate a user you use `authenticate`.

The first argument is a Credentials 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 `User` which represents the authenticated user.

The authentication user object has no context or information on which authorizations the object is entitled. The reason why authorization and authentication are decoupled is because, authentication and authorization are two distinguished operations that are not required to be performed on the same provider. A simple example would be, a user authenticating with plain `OAuth2.0` can use a `JWT` authorization provider to match the token for a given authority, or any other scenario such as authenticating using `LDAP` and perform authorization using `MongoDB`.

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

    Credentials authInfo =
      new UsernamePasswordCredentials("tim", "mypassword");

    authProvider.authenticate(authInfo)
      .onSuccess(user -> {
        System.out.println("User " + user.principal() + " is now authenticated");
      })
      .onFailure(Throwable::printStackTrace);

## Authorization

Once you have an `User` instance you can call `authorizations` to get its authorizations. A newly created user will contain no authorizations. You can directly add authorization on the `User` itself or via an `AuthorizationProvider`.

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

Here’s an example adding authorizations via an `AuthorizationProvider`:

    authorizationProvider.getAuthorizations(user)
      .onSuccess(done -> {
        // cache is populated, perform query
        if (PermissionBasedAuthorization.create("printer1234").match(user)) {
          System.out.println("User has the authority");
        } else {
          System.out.println("User does not have the authority");
        }
      });

And another example of authorizing in a roles based model which uses the the interface `RoleBasedAuthorization`.

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.

### Listing authorizations

The user object holds a list of authorizations so subsequently calls should check if it has the same authorizations and it will result in avoiding one more IO operation to the underlying authorization provider to load the authorizations.

In order to clear the list of authorizations you can use `clear`.

### The User Principal and Attributes

You can get the Principal corresponding to the authenticated user with `principal`.

What this returns depends on the underlying implementation. The principal map is the source data that was used to create the user instance. The attributes are extra properties, that were not provided during the creation of the of the instance but are the result of the processing of the user data. The distinction is there to ensure that processing of the principal will not tamper or over write existing data.

In order to simplify the usage, two helper methods can be used to lookup and read values on both sources:

    if (user.containsKey("sub")) {
      // the check will first assert that the attributes contain
      // the given key and if not assert that the principal contains
      // the given key

      // just like the check before the get will follow the same
      // rules to retrieve the data, first "attributes" then "principal"
      String sub = user.get("sub");
    }

## Creating your own authentication or authorization provider implementation

If you wish to create your own auth provider you should implement the one or both of the interfaces:

- `AuthenticationProvider`

- `AuthorizationProvider`

The user factory can create a `User` object with the given `principal` JSON content. Optionally a second argument `attributes` can be provided to provide extra meta data for later usage. One example are the following attributes:

- `exp` - Expires at in seconds.

- `iat` - Issued at in seconds.

- `nbf` - Not before in seconds.

- `leeway` - clock drift leeway in seconds.

While the first 3 control how the `expired` method will compute the expiration of the user, the last can be used to allow clock drifting compensation while computing the expiration time.

## 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 `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:

    String token = VertxContextPRNG.current(vertx).nextString(32);
    // Generate a secure random integer
    int randomInt = VertxContextPRNG.current(vertx).nextInt();

## Working with Keys

When working with security you will face the need to load security keys. There are many formats and standards for security keys which makes it quite a complex task. In order to simplify the work on the developer side, this module contains 2 abstractions:

1. `KeyStoreOptions` that abstract the JVM keystore common format.

2. `PubSecKeyOptions` that abstract the PEM common format.

To load a local keystore modules shall ask for an options object like:

    KeyStoreOptions options = new KeyStoreOptions()
      .setPath("/path/to/keystore/file")
      .setType("pkcs8")
      .setPassword("keystore-password")
      .putPasswordProtection("key-alias", "alias-password");

The type is quite important as it varies with the JVM version used. Before 9, the default is `jks` which is JVM specific after it `pkcs12` which is a common standard.

Non JVM keystore keys can be imported to a `pkcs12` file, even without the need of the `keytool` command, for example this is how it can be done with `OpenSSL`:

    openssl pkcs12 -export -in mykeycertificate.pem -out mykeystore.pkcs12 -name myAlias -noiter -nomaciter

The command above will convert an existing pem file to a pkcs12 keystore and put the given key under the name `myAlias`. The extra arguments `-noiter -nomaciter` are required in order to make the file compatible with the JVM loader.

To load a `PEM` file you should be aware that there are a few limitations. The default JVM classes only support keys in `PKCS8` format, so if you have a different PEM file you need to convert it with `OpenSSL` like:

    openssl pkcs8 -topk8 -inform PEM -in private.pem -out private_key.pem -nocrypt

After this using such file is as trivial as:

    PubSecKeyOptions options = new PubSecKeyOptions()
      .setAlgorithm("RS256")
      .setBuffer(
        vertx.fileSystem()
          .readFileBlocking("/path/to/pem/file")
          .toString());

PEM files are common and easy to use but are not password protected, so private keys can easily be sniffed.

### JSON Web Keys

JWKs are a standard used by OpenID connect and JWT providers. They represent a key as a JSON object. Usually these JSON documents are provided by an identity provider server like Google, Microsoft, etc…​ but you can also generate your own keys using the online application https://mkjwk.org. For an offline experience there is also the tool: https://connect2id.com/products/nimbus-jose-jwt/generator.

## Chaining authentication providers

There are cases where it might be interesting to have support for chaining authentication providers, for example look up users on LDAP or properties files. This can be achieved with the `ChainAuth`.

    ChainAuth.any()
      .add(ldapAuthProvider)
      .add(propertiesAuthProvider);

It is also possible to perform a all match, a user must be matched on LDAP and Properties for example:

    ChainAuth.all()
      .add(ldapAuthProvider)
      .add(propertiesAuthProvider);