== The JWT auth provider

This component contains an out of the box a JWT implementation.

JSON Web Token is a simple way to send information in the clear (usually in a URL) whose contents can be verified to
be trusted. JWT are well suited for scenarios as:

* In a Single Sign-On scenario where you want a separate authentication server that can then send user information in
  a trusted way.
* Stateless API servers, very well suited for sinple page applications.
* etc...

Before deciding on using JWT, it's important to note that JWT does not encrypt the payload, it only signs it. You
should not send any secret information using JWT, rather you should send information that is not secret but needs to
be verified. For instance, sending a signed user id to indicate the user that should be logged in would work great!
Sending a user's password would be very, very bad.

Its main advantages are:

* It allows you to verify token authenticity.
* It has a json body to contain any variable amount of data you want.
* It's completely stateless.

To create an instance of the provider you use `link:yardoc/VertxAuthJwt/JWTAuth.html[JWTAuth]`. You specify the configuration
in a JSON object.

Here's an example of creating a JWT auth provider:

[source,java]
----
require 'vertx-auth-jwt/jwt_auth'

config = {
  'keyStore' => {
    'path' => "keystore.jceks",
    'type' => "jceks",
    'password' => "secret"
  }
}

provider = VertxAuthJwt::JWTAuth.create(vertx, config)

----

A typical flow of JWT usage is that in your application you have one end point that issues tokens, this end point
should be running in SSL mode, there after you verify the request user, say by its username and password you would
do:

[source,java]
----
require 'vertx-auth-jwt/jwt_auth'

config = {
  'keyStore' => {
    'path' => "keystore.jceks",
    'type' => "jceks",
    'password' => "secret"
  }
}

provider = VertxAuthJwt::JWTAuth.create(vertx, config)

# on the verify endpoint once you verify the identity of the user by its username/password
if ("paulo".==(username) && "super_secret".==(password))
  token = provider.generate_token({
    'sub' => "paulo"
  }, {
  })
  # now for any request to protected resources you should pass this string in the HTTP header Authorization as:
  # Authorization: Bearer <token>
end

----

TODO show example of authentication and authorisation with JWT and explain how the permission string passed
in authorisation maps to the claims in the JW token

=== The JWT keystore file

This auth provider requires a keystore in the classpath or in the filesystem with either a `link:unavailable[Mac]`
or a `link:unavailable[Signature]` in order to sign and verify the generated tokens.

The implementation will, by default, look for the following aliases, however not all are required to be present. As
a good practice `HS256` should be present:
----
`HS256`:: HMAC using SHA-256 hash algorithm
`HS384`:: HMAC using SHA-384 hash algorithm
`HS512`:: HMAC using SHA-512 hash algorithm
`RS256`:: RSASSA using SHA-256 hash algorithm
`RS384`:: RSASSA using SHA-384 hash algorithm
`RS512`:: RSASSA using SHA-512 hash algorithm
`ES256`:: ECDSA using P-256 curve and SHA-256 hash algorithm
`ES384`:: ECDSA using P-384 curve and SHA-384 hash algorithm
`ES512`:: ECDSA using P-521 curve and SHA-512 hash algorithm
----

When no keystore is provided the implementation falls back in unsecure mode and signatures will not be verified, this
is useful for the cases where the payload if signed and or encrypted by external means.

=== Generate a new Keystore file

The only required tool to generate a keystore file is `keytool`, you can now specify which algorithms you need by
running:

----
keytool -genseckey -keystore keystore.jceks -storetype jceks -storepass secret -keyalg HMacSHA256 -keysize 2048 -alias HS256 -keypass secret
keytool -genseckey -keystore keystore.jceks -storetype jceks -storepass secret -keyalg HMacSHA384 -keysize 2048 -alias HS384 -keypass secret
keytool -genseckey -keystore keystore.jceks -storetype jceks -storepass secret -keyalg HMacSHA512 -keysize 2048 -alias HS512 -keypass secret
keytool -genkey -keystore keystore.jceks -storetype jceks -storepass secret -keyalg RSA -keysize 2048 -alias RS256 -keypass secret -sigalg SHA256withRSA -dname "CN=,OU=,O=,L=,ST=,C=" -validity 360
keytool -genkey -keystore keystore.jceks -storetype jceks -storepass secret -keyalg RSA -keysize 2048 -alias RS384 -keypass secret -sigalg SHA384withRSA -dname "CN=,OU=,O=,L=,ST=,C=" -validity 360
keytool -genkey -keystore keystore.jceks -storetype jceks -storepass secret -keyalg RSA -keysize 2048 -alias RS512 -keypass secret -sigalg SHA512withRSA -dname "CN=,OU=,O=,L=,ST=,C=" -validity 360
keytool -genkeypair -keystore keystore.jceks -storetype jceks -storepass secret -keyalg EC -keysize 256 -alias ES256 -keypass secret -sigalg SHA256withECDSA -dname "CN=,OU=,O=,L=,ST=,C=" -validity 360
keytool -genkeypair -keystore keystore.jceks -storetype jceks -storepass secret -keyalg EC -keysize 256 -alias ES384 -keypass secret -sigalg SHA384withECDSA -dname "CN=,OU=,O=,L=,ST=,C=" -validity 360
keytool -genkeypair -keystore keystore.jceks -storetype jceks -storepass secret -keyalg EC -keysize 256 -alias ES512 -keypass secret -sigalg SHA512withECDSA -dname "CN=,OU=,O=,L=,ST=,C=" -validity 360
----