JWT Authentication with Play Framework

In this blog, I will demonstrate how to implement JWT Authentication with Play Framework.

JSON Web Token (JWT) is a compact, self-contained means to securely transfer information between two parties. It can be sent via a Post request or inside the HTTP header. This information can be verified and trusted because it is digitally signed. JWTs can be signed using a secret or a public/private key pair using RSA. It consists of three parts separated by a dot(.): the Header, Payload, and Signature. The header tells the user the type of token and hashing algorithm, the payload contains the claims (and the claims in a JWT are encoded as a JSON object that is used as the payload or as the plaintext), and the signature is used to verify the sender of the JWT.

Here, we are using JSON Web Token for authentication with Play Framework. This is one of the most common ways of using JWT. Once the user is logged in, we need to include JWT with each request that allows the user to access the routes, services, and resources which authenticate the token in order to permit the request.

Let’s start with the implementation of JWT Authentication using Play Framework:

1. First, we need to include JWT library in our project. There are several libraries for JWT. You can use any of them depending on your requirement.

"com.jason-goodwin" %% "authentikat-jwt" % "0.4.5"

2. Next, you need to create a JWT utility class into which you need to add all these methods for creating, verifying, and decoding the JWT token, and provide the secret key and algorithm such as HMAC, SHA256.

val JwtSecretKey = "secretKey"
val JwtSecretAlgo = "HS256"

def createToken(payload: String): String = {
  val header = JwtHeader(JwtSecretAlgo)
  val claimsSet = JwtClaimsSet(payload)

  JsonWebToken(header, claimsSet, JwtSecretKey)
}

def isValidToken(jwtToken: String): Boolean =
  JsonWebToken.validate(jwtToken, JwtSecretKey)

def decodePayload(jwtToken: String): Option[String] =
  jwtToken match {
    case JsonWebToken(header, claimsSet, signature) => Option(claimsSet.asJsonString)
    case _                                          => None
  }

3. To implement JWT authentication, we need to create a reusable custom secured action by using ActionBuilder that authenticates each subsequent request and verifies the JWT in order to permit the request to access the corresponding service. ActionBuilder is the special case of functions that takes requests as input and thus can build actions and provides several factory methods that help in creating actions. To implement ActionBuilder, we need to implement the invokeBlock method. Here, I have created a custom JWTAuthentication using ActionBuilder.

case class User(email: String, userId: String) 
case class UserRequest[A](user: User, request: Request[A]) extends WrappedRequest(request)

object JWTAuthentication extends ActionBuilder[UserRequest] {
  def invokeBlock[A](request: Request[A], block: (UserRequest[A]) => Future[Result]): Future[Result] = {
    implicit val req = request

    val jwtToken = request.headers.get("jw_token").getOrElse("")

    if (JwtUtility.isValidToken(jwtToken)) {
      JwtUtility.decodePayload(jwtToken).fold(
        Future.successful(Unauthorized("Invalid credential"))
      ) { payload =>
        val userInfo = Json.parse(payload).validate[User].get

        // Replace this block with data source
        if (userInfo.email == "test@example.com" && userInfo.userId == "userId123") {
          Future.successful(Ok("Authorization successful"))
        } else {
          Future.successful(Unauthorized("Invalid credential"))
        }
      }
    }
    else {
      Future.successful(Unauthorized("Invalid credential"))
    }
  }
}

4. Now we can use “JWTAuthentication” the same way we use Action.

def index = JWTAuthentication { implicit request =>
  Ok(views.html.index("Hello world"))
}

5. You can test it through Postman (on which you can send the request and view responses), all we need to do is create a JWT and pass it to the Headers, corresponding to the field “jw_token.” You can create a JSON web token by the “createToken” method that I showed you in step 2 by passing payload as a parameter which can be anything. Here's an example:

val payload = """{"email":"test@example.com","userId":"userId123"}"""

JWT looks like this:

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJlbWFpbCI6InRlc3RAZXhhbXBsZS5jb20iLCJ1c2VySWQiOiJ1c2VySWQxMjMifQ.mjMQN8m_wH1NSE9GGexCW_GUh8uruNco18jgt7AWuO4

You can get the source code from here.

I hope this blog is helpful to you!

Thanks

References:

• https://jwt.io/introduction/