Form Authentication in Ktor

问题

I'm new to Kotlin and Ktor trying to see the authentication part, so I got the below code.

Routes "/" and "/bye" are working fine, but route "login" given blank page!

package blog

import kotlinx.html.*
import kotlinx.html.stream.*    // for createHTML
import org.jetbrains.ktor.application.*
import org.jetbrains.ktor.auth.*
import org.jetbrains.ktor.features.*
import org.jetbrains.ktor.http.*
import org.jetbrains.ktor.response.*
import org.jetbrains.ktor.routing.*

import org.jetbrains.ktor.request.*   // for request.uri

import org.jetbrains.ktor.html.*
import org.jetbrains.ktor.pipeline.*

import org.jetbrains.ktor.host.*   // for embededServer
import org.jetbrains.ktor.netty.*  // for Netty

fun main(args: Array<String>) {
    embeddedServer(Netty, 8080, watchPaths = listOf("BlogAppKt"), module = Application::module).start()
}

fun Application.module() {
    install(DefaultHeaders)
    install(CallLogging)

    intercept(ApplicationCallPipeline.Call) { 
        if (call.request.uri == "/hi")
            call.respondText("Test String")
    }

    install(Routing) {
        get("/") {
            call.respondText("""Hello, world!<br><a href="/bye">Say bye?</a>""", ContentType.Text.Html)
        }
        get("/bye") {
            call.respondText("""Good bye! <br><a href="/login">Login?</a> """, ContentType.Text.Html)
        }
        route("/login") {
            authentication {
                formAuthentication { up: UserPasswordCredential ->
                    when {
                        up.password == "ppp" -> UserIdPrincipal(up.name)
                        else -> null
                    }
                }
            }

            handle {
                val principal = call.authentication.principal<UserIdPrincipal>()
                if (principal != null) {
                    call.respondText("Hello, ${principal.name}")
                } else {
                        val html = createHTML().html {
                        body {
                            form(action = "/login", encType = FormEncType.applicationXWwwFormUrlEncoded, method = FormMethod.post) {
                                p {
                                    +"user:"
                                    textInput(name = "user") {
                                        value = principal?.name ?: ""
                                    }
                                }

                                p {
                                    +"password:"
                                    passwordInput(name = "pass")
                                }

                                p {
                                    submitInput() { value = "Login" }
                                }
                            }
                        }
                    }
                    call.respondText(html, ContentType.Text.Html)
                }
            }
        }
    }
}

When I disabled the authentication part below, the route '/login' displayed the required form, which means the error is most likely in this part or in the way of calling it? I guess.

            authentication {
                formAuthentication { up: UserPasswordCredential ->
                    when {
                        up.password == "ppp" -> UserIdPrincipal(up.name)
                        else -> null
                    }
                }
            }

回答1:

You're not simply given a blank page, you get a HTTP status code of 401 (UNAUTHORIZED). That's because formAuthentication has four parameters, three of them with defaults. You only implemented the last one (validate, without default):

userParamName: String = "user",
passwordParamName: String = "password",
challenge: FormAuthChallenge = FormAuthChallenge.Unauthorized,
validate: (UserPasswordCredential) -> Principal?

Whenever you reach the /login route without the right credentials already in place, you get the default for challenge, which is FormAuthChallenge.Unauthorized, which is a 401 response.

Instead of using the default for challenge, you could use a FormAuthChallenge.Redirect. A short example that requires two routes:

get("/login") {
    val html = """
            <form action="/authenticate" enctype="..."
            REST OF YOUR LOGIN FORM
            </form>
            """
    call.respondText(html, ContentType.Text.Html)
}

route("/authenticate") {
    authentication {
        formAuthentication(challenge = FormAuthChallenge.Redirect({ _, _ -> "/login" })) {
            credential: UserPasswordCredential ->
            when {
                credential.password == "secret" -> UserIdPrincipal(credential.name)
                else -> null
            }
        }
    }

    handle {
        val principal = call.authentication.principal<UserIdPrincipal>()
        val html = "Hello, ${principal?.name}"
        call.respondText(html, ContentType.Text.Html)
    }
}

UPDATE

In case the above did not work well, define both the userid-parameter and password-parameter clearly as they appear in the form that do the POST, as below:

        authentication {
            formAuthentication("user", "pass",
                    challenge = FormAuthChallenge.Redirect({ _, _ -> "/login" })){
                credential: UserPasswordCredential ->
                when {
                credential.password == "secret" -> UserIdPrincipal(credential.name)
                else -> null
                }
            }
        }

来源：https://stackoverflow.com/questions/46500030/form-authentication-in-ktor