== The JWT auth provider

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

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-jwt</artifactId>
  <version>3.5.1</version>
</dependency>
----

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

[source,groovy,subs="+attributes"]
----
compile 'io.vertx:vertx-auth-jwt:3.5.1'
----

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 simple 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:../../apidocs/io/vertx/ext/auth/jwt/JWTAuth.html[JWTAuth]`. You specify the configuration
in a JSON object.

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

[source,java]
----
JWTAuthOptions config = new JWTAuthOptions()
  .setKeyStore(new KeyStoreOptions()
    .setPath("keystore.jceks")
    .setPassword("secret"));

AuthProvider provider = 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]
----
JWTAuthOptions config = new JWTAuthOptions()
  .setKeyStore(new KeyStoreOptions()
    .setPath("keystore.jceks")
    .setPassword("secret"));

JWTAuth provider = JWTAuth.create(vertx, config);

// on the verify endpoint once you verify the identity of the user by its username/password
if ("paulo".equals(username) && "super_secret".equals(password)) {
  String token = provider.generateToken(new JsonObject().put("sub", "paulo"), new JWTOptions());
  // now for any request to protected resources you should pass this string in the HTTP header Authorization as:
  // Authorization: Bearer <token>
}
----

=== The JWT keystore file

This auth provider requires a keystore in the classpath or in the filesystem with either a
`https://docs.oracle.com/javase/8/docs/api/javax/crypto/Mac.html[javax.crypto.Mac]`
or a `https://docs.oracle.com/javase/8/docs/api/java/security/Signature.html[java.security.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 384 -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 521 -alias ES512 -keypass secret -sigalg SHA512withECDSA -dname "CN=,OU=,O=,L=,ST=,C=" -validity 360
----

=== Read only tokens

If you need to consume JWT tokens issues by third parties you probably won't have the private key with you, in that
case all you need to have is a public key im PEM format.

[source,java]
----
JWTAuthOptions config = new JWTAuthOptions()
  .addPubSecKey(new PubSecKeyOptions()
    .setAlgorithm("RS256")
    .setPublicKey("BASE64-ENCODED-PUBLIC_KEY"));

AuthProvider provider = JWTAuth.create(vertx, config);
----

== AuthN/AuthZ with JWT

A common scenario when developing for example micro services is that you want you application to consume APIs. These
api's are not meant to be consumed by humans so we should remove all the interactive part of authenticating the
consumer out of the picture.

In this scenario one can use HTTP as the protocol to consume this API and the HTTP protocol already defines that there
is a header `Authorization` that should be used for passing authorization information. In most cases you will see that
tokens are sent as bearer tokens, i.e.: `Authorization: Bearer some+base64+string`.

=== Authenticating (AuthN)

For this provider a user is authenticated if the token passes the signature checks and that the token is not expired.
For this reason it is imperative that private keys are kept private and not copy pasted across project since it would
be a security hole.

[source,java]
----
jwtAuth.authenticate(new JsonObject().put("jwt", "BASE64-ENCODED-STRING"), res -> {
  if (res.succeeded()) {
    User theUser = res.result();
  } else {
    // Failed!
  }
});
----

In a nutshell the provider is checking for several things:

* token signature is valid against internal private key
* fields: `exp`, `iat`, `nbf`, `audience`, `issuer` are valid according to the config

If all these are valid then the token is considered good and a user object is returned.

While the fields `exp`, `iat` and `nbf` are simple timestamp checks only `exp` can be configured to be ignored:

[source,java]
----
jwtAuth.authenticate(new JsonObject()
  .put("jwt", "BASE64-ENCODED-STRING")
  .put("options", new JsonObject()
    .put("ignoreExpiration", true)), res -> {
  if (res.succeeded()) {
    User theUser = res.result();
  } else {
    // Failed!
  }
});
----

In order to verify the `aud` field one needs to pass the options like before:

[source,java]
----
jwtAuth.authenticate(new JsonObject()
  .put("jwt", "BASE64-ENCODED-STRING")
  .put("options", new JsonObject()
    .put("audience", new JsonArray().add("paulo@server.com"))), res -> {
  if (res.succeeded()) {
    User theUser = res.result();
  } else {
    // Failed!
  }
});
----

And the same for the issuer:

[source,java]
----
jwtAuth.authenticate(new JsonObject()
  .put("jwt", "BASE64-ENCODED-STRING")
  .put("options", new JsonObject()
    .put("issuer", "mycorp.com")), res -> {
  if (res.succeeded()) {
    User theUser = res.result();
  } else {
    // Failed!
  }
});
----

=== Authorizing (AuthZ)

Once a token is parsed and is valid we can use it to perform authorization tasks. The most simple is to verify if a
user has a specific authority. In this case one needs to to:

[source,java]
----
user.isAuthorised("create-report", res -> {
  if (res.succeeded() && res.result()) {
    // Yes the user can create reports
  }
});
----

By default the provider will lookup under the key `permissions` but like the other providers one can extend the
concept to authorities to roles by using the `:` as a splitter, so `role:authority` can be used to lookup the token.

Since JWT are quite free form and there is no standard on where to lookup for the claims the location can be
configured to use something else than `permissions`, for example one can even lookup under a path like this:

[source,java]
----
JsonObject config = new JsonObject()
  .put("public-key", "BASE64-ENCODED-PUBLIC_KEY")
  // since we're consuming keycloak JWTs we need to locate the permission claims in the token
  .put("permissionsClaimKey", "realm_access/roles");

AuthProvider provider = JWTAuth.create(vertx, config);
----

So in this example we configure the JWT to work with Keycloak token format. In this case the claims will be checked
under the path `realm_access/roles` rather than `permissions`.
<a href="mailto:julien@julienviet.com">Julien Viet</a><a href="http://tfox.org">Tim Fox</a><a href="mailto:pmlopes@gmail.com">Paulo Lopes</a>