Example solution for SO question 55408452

ConcreteVerticle.kt

import io.vertx.core.Handler
import io.vertx.core.http.HttpMethod
import io.vertx.ext.web.Router
import io.vertx.ext.web.RoutingContext
import io.vertx.ext.web.handler.*
import io.vertx.ext.web.sstore.LocalSessionStore
import io.vertx.core.Vertx
import io.vertx.kotlin.core.deployVerticleAwait
import io.vertx.kotlin.core.http.listenAwait
import io.vertx.kotlin.core.json.json
import io.vertx.kotlin.core.json.obj
import io.vertx.kotlin.coroutines.CoroutineVerticle
import io.vertx.kotlin.ext.auth.isAuthorizedAwait
import kotlinx.coroutines.launch

class ConcreteVerticle : CoroutineVerticle() {
    override suspend fun start() {
        val adminAuth = MockAuthProvider()
        val router = Router.router(vertx)
        router.route()
            .handler(BodyHandler.create().setBodyLimit(1024 * 1024))
            .handler(CookieHandler.create())
            .handler(SessionHandler.create(LocalSessionStore.create(vertx)))
            .handler(UserSessionHandler.create(adminAuth))
            .handler(CorsHandler.create("https://localhost:3000")
                .allowCredentials(true)
                .allowedHeader("Content-Type")
                .allowedMethod(HttpMethod.GET)
                .allowedMethod(HttpMethod.POST)
                .allowedMethod(HttpMethod.OPTIONS))
        router
            .get("/admin/login")
            .handler { rc ->
                adminAuth.authenticate(json { obj("username" to "francesco") }) { res ->
                    launch {
                        var retJson = json { obj() }

                        if (res.succeeded()) {
                            var user = res.result()
                            rc.session()?.regenerateId()
                            rc.setUser(user)

                            retJson = retJson.put("succeed", true)

                            if (user.isAuthorizedAwait("createadmin"))
                                retJson = retJson.put("createadmin", true)
                        } else {
                            retJson = retJson
                                .put("succeed", false)
                                .put("message", res.cause().message)
                        }

                        rc.response()
                            .putHeader("content-type", "application/json")
                            .end(retJson.encode())
                    }
                }}
        router
            .get("/admin/stuff")
            .handler { rc ->

                if (rc.user() == null)
                    rc.response().setStatusCode(403).end()
                else {
                    val user = rc.user()
                    val session = rc.session()
                    println(session)
                    val principal = user.principal()
                    rc.response().setStatusCode(200).end(principal.toBuffer())
                }
            }
        vertx.createHttpServer().requestHandler(router).listenAwait(3000)
    }
}

suspend fun main() {
    val vertx = Vertx.vertx()
    vertx.deployVerticleAwait(ConcreteVerticle())
}

MockAuthProvider.kt

import io.vertx.core.AsyncResult
import io.vertx.core.Future
import io.vertx.core.Handler
import io.vertx.core.json.JsonObject
import io.vertx.ext.auth.AbstractUser
import io.vertx.ext.auth.AuthProvider
import io.vertx.ext.auth.User
import io.vertx.kotlin.core.json.json
import io.vertx.kotlin.core.json.obj

class MockAuthProvider : AuthProvider {
    override fun authenticate(authInfo: JsonObject?, resultHandler: Handler<AsyncResult<User>>?) {
       resultHandler!!.handle(Future.succeededFuture(
           object: AbstractUser() {
               override fun doIsPermitted(permission: String?, resultHandler: Handler<AsyncResult<Boolean>>?) {
                   resultHandler!!.handle(Future.succeededFuture(true))
               }

               override fun setAuthProvider(authProvider: AuthProvider?) {}

               override fun principal(): JsonObject {
                   return json { obj( "username" to authInfo!!.getString("username")) }
               }

           }
       ))
    }

}