Tag: Kotlin

Since this topic became very extensive, I decided to split up the blog into 4 parts. To keep blog lengths manageable. Here is the split up

Part 1: Introduction
Part 2: Payara, Spring Boot and Quarkus
Part 3: Ktor and Atbash Runtime (this one)
Part 4: Discussion and conclusion

For an introduction around JWT Tokens, you can have a look at the first part of this blog. It also contains a description how the Keycloak service is created for the example programs described in this part.
Part 2 contains the description for Payara Micro, Spring Boot and Quarkus.

Ktor

Also within Ktor there is some excellent support for using JWT tokens although we need to code a little bit more if we want to have support for rotating public keys and easy checks on the roles within the tokens.

But first, Let us start again with the dependencies you need within your application.

        <!-- Ktor authentication -->
        <dependency>
            <groupId>io.ktor</groupId>
            <artifactId>ktor-server-auth-jvm</artifactId>
            <version>${ktor_version}</version>
        </dependency>
        <!-- Ktor support for JWT -->
        <dependency>
            <groupId>io.ktor</groupId>
            <artifactId>ktor-server-auth-jwt-jvm</artifactId>
            <version>${ktor_version}</version>
        </dependency>

We need a dependency to add the authentication support and another one for having the JWT token as the source for authentication and authorisation.

Just as with the Payara and Quarkus case, we need to define the location to retrieve the public key, expected issuer, and audience through the configuration of our application. In our example application, this is provided in the application.yml file.

jwt:
  issuer: "http://localhost:8888/auth/realms/atbash_project_ff"
  audience: "account"

We programmatically read these values in our own code, so the keys can be whatever you like, they are not predetermined as with the other runtimes. In the example, you see that we also don’t define the location of the public key endpoint as we can derive that from the issuer value in the case of KeyCloak. But you are free to specify a specific URL for this value of course.

Configuration of the modules in Ktor is commonly done by creating an extension function on Application object, as I have also done in this example. This is the general structure of this function

fun Application.configureSecurity() {

    authentication {
        jwt("jwt-auth") {
            realm = "Atbash project FF"
            // this@configureSecurity refers to Application.configureSecurity()
            val issuer = this@configureSecurity.environment.config.property("jwt.issuer").getString()
            val expectedAudience = this@configureSecurity.environment.config.property("jwt.audience").getString()
            val jwkUrl = URL("$issuer/protocol/openid-connect/certs")
            val jwkProvider = UrlJwkProvider(jwkUrl)

            verifier {
        // not shown for brevity              

            }

            validate { credential ->
                // If we need validation of the roles, use authorizeWithRoles
                // We cannot define the roles that we need to be able to check this here.
                JWTPrincipal(credential.payload)
            }

            challenge { defaultScheme, realm ->
                // Response when verification fails
                // Ideally should be a JSON payload that we sent back
                call.respond(HttpStatusCode.Unauthorized, "$realm: Token is not valid or has expired")
            }
        }
    }

}

The function jwt("jwt-auth") { indicates that we define an authentication protocol based on the JWT tokens and we name it jwt-auth. We can name it differently and can have even multiple protocols in the same application as long ask we correctly indicate which protocol name we want at the endpoint.

The JWT protocol in Ktor requires 3 parts, a verification part, a validation one, and lastly how the challenge is handled.

The verification part defines how the verification of the token is performed and will be discussed in more detail in a moment. We can do further validation on the token by looking at the roles that are in the token. If you have many different roles, this leads to many different named JWT protocols. Therefore I opted in this example to write another extension function on the Route object that handles this requirement more generically. And the challenge part is executed to formulate a response for the client in case the validation of the token failed.

The verifier method defines how the verification of the token is performed. We make use of the UrlJwkProvider which can read the keys in the JWKS format which contains keys in a JSON format. But it doesn’t try to reread the endpoint in case the key is not found. This also means we cannot apply rotating keys for signing the JWT tokens which is recommended in production. Therefore, we make use of a small helper which caches the keys but read the endpoint again when the key is not found. This functionality could be improved to avoid a DOS attack by calling your endpoint with some random key ids which would put Keycloak or the JWT Token provider under stress.

            val jwkProvider = UrlJwkProvider(jwkUrl)

            verifier {
                val publicKey = PublicKeyCache.getPublicKey(jwkProvider, it)

                JWT.require(Algorithm.RSA256(publicKey, null))
                    .withAudience(expectedAudience)
                    .withIssuer(issuer)
                    .build()

            }

The other improvement that you can find in the example is the validation part. Since you only have the credential as input for this validation, you can check if the token has a certain role, but you can’t make this check dynamic based on the endpoint. As mentioned, this would mean that for each role that you want to check, you should make a different JWT check.

The example contains an extension function on the Route object so that you can define the role that you expect. This is how you can use this new authorizeWithRoles function

        authorizeWithRoles("jwt-auth", listOf("administrator")) {
            get("/protected/admin") {
                call.respondText("Protected Resource; Administrator Only ")
            }
        }

So besides the name for the protocol we like to use, you can also define a set of roles that you expect to be in the token. The function itself is not that long but a little complex because we add a new interceptor in the pipeline used by Ktor to handle the request. If you want to look at the details, have a look at the example code.

If you just need a valid token, without any check on the roles, you can make use of the standard Ktor functionality

        authenticate("jwt-auth") {
            get("/protected/user") {
                val principal = call.authentication.principal<JWTPrincipal>()
                //val username = principal?.payload?.getClaim("username")?.asString()
                val username = principal?.payload?.getClaim("preferred_username")?.asString()
                call.respondText("Hello, $username!")
            }
        }

This last snippet also shows how you can get access to the claims within the token. You can access the principal associated with- the request by requesting call.authentication.principal<JWTPrincipal>() where you immediately make the cast to the JWTPrincipal class. This contains the entire token content easily accessible from within your Kotlin code as you can see in the example where I retrieve the preferred_username.

You can review all code presented here in the example https://github.com/rdebusscher/Project_FF/tree/main/jwt/ktor.

Atbash Runtime

Atbash Runtime is a small modular Jakarta EE Core profile runtime. So by default, it doesn’t has support for using JWT tokens. But since these tokens are the de facto standard, there is an Atbash Runtime module that supports them so that you can use it for your application.

As a dependency, you can add this JWT supporting module to your project

        <dependency>
            <!-- Adds JWT Support in the case we are using the Jakarta Runner, no addition of the MP JWT Auth API required -->
            <!-- Otherwise, when not using Jakarta Runner, the addition of JWT Auth API as provided is enough if you are using Atbash Runner Jar executable -->
            <groupId>be.atbash.runtime</groupId>
            <artifactId>jwt-auth-module</artifactId>
            <version>1.0.0-SNAPSHOT</version>
        </dependency>

Since we use the Jakarta Runner feature of the Atbash runtime, which allows you to execute your web application through a simple main method, we need to add the module itself. If you run your application as a war file, make sure you activate the JWT module within the configuration so that the module is active.

The JWT support within Atbash runtime is also based on the Microprofile JWT Auth specification, so you will see many similarities with the Payara and Quarkus examples we have discussed in part 2 of this blog.

Configuration requires the 3 values for public key location, expected issuer, and audience.

mp.jwt.verify.publickey.location=http://localhost:8888/auth/realms/atbash_project_ff/protocol/openid-connect/certs
mp.jwt.verify.issuer=http://localhost:8888/auth/realms/atbash_project_ff
mp.jwt.verify.audiences=account

You are also required to indicate the @LoginConfig (in case you are executing your application as a WAR file) so that the JWT Module is active for the application. But there is no need to define @DeclareRoles as Atbash Runtime takes the value of the individual @RolesAllowed as valid roles.

A difference with Payara, for example, is that you need to add @PermitAll to a method when you don’t want to check on any roles. Within Atbash Runtime there is the “principle of least privilege” implemented. If you don’t specify anything on a JAX_RS method no client can call it. This is to avoid that you forget to define some security requirements and expose the endpoint without any checks. The JavaDoc says “Specifies that all security roles are allowed to invoke the specified method(s)” and thus it is clearly what we need. Although, some runtimes, including Payara, interpret this differently and I’ll go deeper on this topic in part 4.

The example code is located at https://github.com/rdebusscher/Project_FF/tree/main/jwt/atbash.

Discussion

In the last part of the blog, I’ll have a discussion about similarities and differences. These differences are especially important when you don’t want to have a check on a role within the token.

Part 1: Introduction
Part 2: Payara, Spring Boot and Quarkus
Part 3: Ktor and Atbash Runtime (this one)
Part 4: Discussion and conclusion

Training and Support

Do you need a specific training session on Jakarta EE, Quarkus, Kotlin or MicroProfile? Have a look at the training support that I provide on the page https://www.atbash.be/training/ and contact me for more information.

Since this topic became very extensive, I decided to split up the blog into 4 parts. To keep blog lengths manageable. Here is the split up

Part 1: Introduction
Part 2: Payara, Spring Boot and Quarkus (this one)
Part 3: Ktor and Atbash Runtime
Part 4: Discussion and conclusion

For an introduction around JWT Tokens, you can have a look at the first part of this blog. It also contains a description how the Keycloak service is created for the example programs described in this part.

Payara

As an example of how you can work with JWT tokens with Jakarta EE and MicroProfile, we make use of Payara Micro.

The JWT Token support is provided by MicroProfile, so add the dependency to your project.

        <dependency>
            <groupId>org.eclipse.microprofile</groupId>
            <artifactId>microprofile</artifactId>
            <version>6.0</version>
            <type>pom</type>
            <scope>provided</scope>
        </dependency>

We are using MicroProfile 6, which requires Jakarta EE 10 runtime as this is the version that is supported by the Payara Micro community edition.

As configuration, we need to provide the endpoint where the MicroProfile JWT Auth implementation can retrieve the public key that is required to validate the content of the token against the provided signature. This can be done by specifying mp.jwt.verify.publickey.location configuration key. Two other configuration keys are required, one that verifies if the issuer of the token is as expected and the audience claim is the other one.

Other configuration aspects are the indication that a JWT token will be used as authentication and authorization for the endpoints through the @LoginConfig annotation. The @DeclareRoles annotation is a Jakarta EE annotation that indicates which roles are recognised and can be used. These annotations can be placed on any CDI bean.

@LoginConfig(authMethod = "MP-JWT")
@DeclareRoles({"administrator"})

On the JAX-RS method, we can add the @RolesAllowed annotation to indicate the role that must be present in the token before the client is allowed to call the endpoint.

    @GET
    @Path("/admin")
    @RolesAllowed("administrator")
    public String getAdminMessage() {

When there is no annotation placed on the method, only a valid JWT token is required to call the endpoint. Also, have a look at the part 4 of this blog for some important info and differences between runtimes.

Through the MicroProfile JWT Auth specification, we can also access one or all the claims that are present in the token. The following snippet shows how you can access a single claim or the entire token in a CDI bean or JAX-RS resource class.

    @Inject
    @Claim("preferred_username")
    private String name;

    @Inject
    private JsonWebToken jsonWebToken;
    // When you need access to every aspect of the JWT token.

The entire example can be found in the project https://github.com/rdebusscher/Project_FF/tree/main/jwt/payara.

Spring Boot

Also, Spring Boot has excellent support for using JWT tokens for the authentication and authorization of rest endpoints. Besides the Spring Boot Security starter, the Oauth2 Resource Server dependency is required within your application. So you don’t need to handle the JWT token yourself in a programmatic way as some resources on the internet claim.

In our example, we use Spring Boot 3 and JDK 17.

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-security</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-oauth2-resource-server</artifactId>
    </dependency>

In contrast to MicroProfile where you need to provide several configuration keys, Spring boot makes use of the OpenId Connect specification where it is defined that the endpoint .well-known/openid-configuration provides all info. This includes the location of the public key required for the validation of the token against the signature and the value of the issuer. The location can be specified through a Spring Configuration resource.

spring.security.oauth2.resourceserver.jwt.issuer-uri=http://localhost:8888/auth/realms/atbash_project_ff
spring.security.oauth2.resourceserver.jwt.audiences=account

The audience value is not required to be defined, Spring Boot works without it. But it is a recommended configuration aspect to make sure that tokens are correctly used, especially when you use tokens for multiple applications.

You can either define the requirements for the roles that should be present in the token using a Spring Bean that extends the WebSecurityConfigurerAdapter class and the HttpSecurity builder, but I prefer the method-based approach.
With this approach, you can define the required role using the @PreAuthorize annotation

    @GetMapping("/admin")
    @PreAuthorize("hasAuthority('administrator')")
    public String getAdminMessage() {

It makes it easier to find out which role is required before a client can call the endpoint and also easier to verify if you didn’t make any error in the security configuration of your application. This method-based approach requires a small activation and mapping between the roles within the token and the authority we check in the annotation.

@Configuration
@EnableMethodSecurity
public class MethodSecurityConfig {
}

The configuration for the JWT token roles is provided by a JwtAuthenticationConverter bean.

    @Bean
    public JwtAuthenticationConverter jwtAuthenticationConverter() {
        JwtGrantedAuthoritiesConverter grantedAuthoritiesConverter = new JwtGrantedAuthoritiesConverter();
        grantedAuthoritiesConverter.setAuthorityPrefix("");
        grantedAuthoritiesConverter.setAuthoritiesClaimName("groups");

        JwtAuthenticationConverter jwtAuthenticationConverter = new JwtAuthenticationConverter();
        jwtAuthenticationConverter.setJwtGrantedAuthoritiesConverter(grantedAuthoritiesConverter);
        return jwtAuthenticationConverter;
    }

Within the REST methods, we can have access to the JWT token claims, just as with the Jakarta EE and MicroProfile example. We need to add a JwtAuthenticationToken parameter to the method which allows access to claims through the getTokenAttributes() method.

    @GetMapping("/user")
    public String getUser(JwtAuthenticationToken authentication) {
        Object username = authentication.getTokenAttributes().get("preferred_username");

The entire example can be found in the project https://github.com/rdebusscher/Project_FF/tree/main/jwt/spring.

Quarkus

The Quarkus support is also based on MicroProfile, so you will see several similarities with the Payara case I described earlier. The Quarkus example is based on the recent Quarkus 3.x version. As a dependency, we need two artifacts related to the JWT support provided by the SmallRye project. Although it seems you do not need the build one at first sight, as it is about creating JWT tokens within your application, the example did not work without it.

        <dependency>
            <groupId>io.quarkus</groupId>
            <artifactId>quarkus-smallrye-jwt</artifactId>
        </dependency>
        <dependency>
            <groupId>io.quarkus</groupId>
            <artifactId>quarkus-smallrye-jwt-build</artifactId>
        </dependency>

Since the SmallRye JWT implementation is also using the SMicroProfile JWT auth specification, the configuration through key-value pairs is identical to the Payara one. We need to define the location of the publicKey, and the expected values for the issuer and audience. In the example, I have defined them in the application.properties file, a Quarkus-specific configuration source. But as long as they can be retrieved through any of the supported configuration sources, it is ok.

Since Quarkus is not a Jakarta-compliant runtime, it doesn’t require any indication that the application will make use of the JWT tokens for authentication and authorisation. The existence of the two dependencies we added earlier to the project is enough. In this case, it is similar to the Spring Boot case where we also did not do this.

On the JAX-RS resource methods, we can indicate if we need a certain role within the token, or that just the token itself is required and no specific role is required. If a role is required, we can make use of the same @RolesAllowed annotation we encountered in the Payara example or we need to add the @Authenticated annotation if we just need a valid token.

    @GET
    @Path("/admin")
    @RolesAllowed("administrator")
    public String getAdminMessage() {
        return "Protected Resource; Administrator Only ";
    }

    @GET
    @Path("/user")
    @Authenticated
    // No roles specified, so only valid JWT is required
    public String getUser() {
        return "Protected Resource; user : " + name;
    }

This @Authenticated annotation is defined in the Quarkus Security artifact, brought in transitively, and indicates that an authenticated user is required. Without this annotation, the endpoint would become publicly accessible, without the need for any token or authentication method.

More on that in a part 4 of this blog.

The retrieval of the claims is again identical to the Payara case. The example project can be found at https://github.com/rdebusscher/Project_FF/tree/main/jwt/quarkus.

Runtimes

The Ktor and Atbash Runtime versions of the example application are described in part 3.

Part 1: Introduction
Part 2: Payara, Spring Boot and Quarkus (this one)
Part 3: Ktor and Atbash Runtime
Part 4: Discussion and conclusion

Training and Support

Do you need a specific training session on Jakarta EE, Quarkus, Kotlin or MicroProfile? Have a look at the training support that I provide on the page https://www.atbash.be/training/ and contact me for more information.

Since this topic became very extensive, I decided to split up the blog into 4 parts. To keep blog lengths manageable. Here is the split up

Part 1: Introduction (this one)
Part 2: Payara, Spring Boot and Quarkus
Part 3: Ktor and Atbash Runtime
Part 4: Discussion and conclusion

But don’t worry, all these 4 parts will be released within the same week so that those people that are eager to process it in one go, do not need to wait a long time before the series is published.

Introduction

As the demand for secure and efficient authentication and authorization mechanisms grows, JSON Web Tokens (JWT) have emerged as a favored choice for developers. JWT tokens provide a modern approach to verifying user identity and defining access privileges within web applications. In this blog post, we will delve into the usage of JWT tokens across various frameworks, namely Spring Boot, Quarkus, Jakarta, and Kotlin Ktor. By comparing their implementation approaches, we aim to provide insights into how JWT tokens are utilized within each framework and help you make a transition from one to another easier.

Understanding the Basics of JWT Tokens

At the core of JWT tokens lies a simple yet powerful structure that encompasses all the necessary information for secure authentication and authorization. Let’s dive into the basics of JWT tokens and explore their three essential components: the header, the body, and the signature.

1. Header

The header of a JWT token contains metadata about the token itself and the algorithms used to secure it. It typically consists of two parts: the token type, which is always “JWT,” and the signing algorithm employed, such as HMAC, RSA, or ECDSA. This header is Base64Url encoded and forms the first part of the JWT token.

2. Body (Payload):

The body, also known as the payload, carries the actual data within the JWT token. It contains the claims, which are statements about the user and additional metadata. Claims can include information like the user’s ID, name, email, or any other relevant data. The payload is also Base64Url encoded and forms the second part of the JWT token.

3. Signature

The signature is the crucial component that ensures the integrity and authenticity of the JWT token. It is created by combining the encoded header, the encoded payload, and a secret key known only to the server. The signature is used to verify that the token has not been tampered with during transmission or storage. It acts as a digital signature and prevents unauthorized modifications to the token. The signature is appended as the third part of the JWT token.

Self-Contained and Secure

One of the significant advantages of JWT tokens is their self-contained nature. Since all the necessary information is embedded within the token itself, there is no need for additional database queries or session lookups during authentication and authorization processes. This inherent characteristic contributes to improved performance and scalability.

To verify the authenticity and integrity of a JWT token, the recipient needs access to the public key or shared secret used to generate the signature. By retrieving the public key or shared secret, the recipient can verify the token’s signature and ensure that no tampering or unauthorized modifications have occurred. This mechanism provides a robust security layer, assuring that the token’s contents can be trusted.

User Roles in JWT Tokens

JWT tokens can also include user roles as part of their payload. User roles define the permissions and privileges associated with a particular user. By including this information in the JWT token, applications can determine the user’s authorization level and grant or restrict access to specific resources or functionalities accordingly. This granular approach to authorization allows for fine-grained control over user permissions within the application.

In the upcoming sections, we will explore how different frameworks incorporate these fundamental JWT token concepts into their authentication and authorization workflows. Understanding the core principles behind JWT tokens sets the stage for a comprehensive comparison, enabling us to evaluate the strengths and nuances of each framework’s implementation.

Example application

The same example application is made with different runtimes. It contains a couple of endpoints, they all require a valid token before they should be executed. One of the endpoints requires that the token contains the role of administrator.

GET /protected/user -> Hello username
GET /protected/admin -> Protected Resource; Administrator Only

The tokens utilised in our example are sourced from Keycloak, a reliable and widely adopted Authorization provider. Keycloak offers various standard flows for obtaining these tokens, catering to diverse authentication scenarios.

One of the commonly employed flows is the authorization code flow, which involves user interaction through dedicated screens provided by the Authorization provider. Users are prompted to log in and provide their credentials, following which Keycloak generates the necessary tokens for authentication and authorization purposes.

Alternatively, Keycloak supports a username and password-based approach where users can submit their credentials to a designated endpoint. This method allows Keycloak to validate the provided information and issue the relevant tokens required for subsequent authentication and authorization processes.

For our example, a custom realm with a configuration that is suitable for all our runtimes is created by setup_jwt_example.py and can be found in the directory https://github.com/rdebusscher/Project_FF/tree/main/jwt/keycloak. The script prepares the realm and a OpenId Connect client so that in response to a valid user name and password combination, a JWT token with the roles of the user is returned. It creates also two users, one of them having the admin role.

The Python script test_jwt_example.py can be used to test out the solution in each of the runtimes. It calls both endpoints with the two users that are defined. And so, one of the calls will result in an error since the non-administrator user is not allowed to call the administrator endpoint.

Runtimes

The different runtimes are discussed in part 2 and part 3 of this series.

Part 1: Introduction (this one)
Part 2: Payara, Spring Boot and Quarkus
Part 3: Ktor and Atbash Runtime
Part 4: Discussion and conclusion

Training and Support

Do you need a specific training session on Jakarta EE, Quarkus, Kotlin or MicroProfile? Have a look at the training support that I provide on the page https://www.atbash.be/training/ and contact me for more information.