UPDATE: Read official announcement for role based auth in Ktor 2023 roadmap
Simplifying support for authorization and authentication. Providing end-to-end support for database authentication and session management, as well as role-based authorization

Ktor Role based Auth

ktor-role-based-auth is an easy to use and intuitive role-based access control library for Ktor Server

It works with the official ktor-server-auth library and adds role based authorization on top of it

Supported methods

• HTTP authentication (Basic/Digest/Bearer)
• Form-based authentication
• JWT
• Session
• OAuth
• LDAP
• Custom authentication

Installation

Step 1. Add the JitPack repository in build.gradle.kts

repositories {
    mavenCentral()
    maven { url = uri("https://jitpack.io") }
}

Step 2. Add the dependency

dependencies {
    implementation("com.github.omkar-tenkale:ktor-role-based-auth:0.2.0")
}

Usage

Initialize the plugin when configuring authentication

fun Application.configureSecurity(){
    authentication {
        jwt {
            // Configure jwt authentication
        }
        roleBased {
            extractRoles { principal ->
                //Extract roles from JWT payload
                (principal as JWTPrincipal).payload.claims?.get("roles")?.asList(String::class.java)?.toSet() ?: emptySet()
            }
        }
    }
}

fun Application.routing() {
    route("/") {
        
        //No authentication required to access this route
        get {
            call.respondText("Welcome!")
        }

        authenticate {

            //JWT authenticated route
            route("/profile") {
                get {
                    call.respondText("Joined: 2 years ago")
                }
            }

            //JWT authenticated + role authorized route
            route("/dashboard") {
                withAnyRole("ADMIN", "SUPER_ADMIN") {
                    get {
                        call.respondText("Total users: 2443")
                    }
                }
            }
            
            //JWT authenticated + role authorized route
            route("/system-stats") {
                withRole("SUPER_ADMIN") {
                    get {
                        call.respondText("CPU: 34%")
                    }
                }
            }
        }
    }
}

The plugin responds with 403 (Forbidden) by default if roles don't match Optionally, follow these steps to send a custom response

1. Set throwErrorOnUnauthorizedResponse to true

fun Application.configureSecurity(){
    authentication {
        jwt {
            // Configure jwt authentication
        }
        roleBased {
            extractRoles { principal ->
                //Extract roles from JWT payload
                (principal as JWTPrincipal).payload.claims?.get("roles")?.asList(String::class.java)?.toSet() ?: emptySet()
            }
            throwErrorOnUnauthorizedResponse = true
        }
    }
}

2. Catch the UnauthorizedAccessException exception globally with help of StatusPages plugin

fun Application.configureSecurity() {
    install(StatusPages) {
        exception<Throwable> { call, cause ->
            if (cause is UnauthorizedAccessException) {
                call.respondText(text = "You don't have enough permissions to access this route", status = HttpStatusCode.Forbidden)
            }
        }
    }
}

For complete example, Check out tests

Thanks

• Joris Portegies Zwart - Original implementation with pipelines and phases for older ktor versions