Hello I managed to set up JWT authentication in ktor It work kotlinlang #ktor

Hello. I managed to set up JWT authentication in ktor. It works. However I dont see how to get the claims containd in the token when processing a request. How can I get them?

Pedro Flores

08/22/2020, 8:57 AM

If I'm not mistaken, you can get them inside your call by accessing the Principal property

pascal_le_merrer

08/22/2020, 9:41 AM

That's what I did before replacing basic auth with JWT. I got it using

val principal: UserIdPrincipal? = call.authentication.principal<UserIdPrincipal>()

But with JWT, call.authentication.principal is null

I found the solution. I have to get the claim like this:

val principal: JWTPrincipal? = call.authentication.principal<JWTPrincipal>()
return principal!!.payload.getClaim("my_claim").asString()

Pedro Flores

08/22/2020, 10:25 AM

Glad that you've found it, on a test I wrote i'm able to get it directly from the ApplicationCall.principal, but I don't know how your validate lambda is implemented

pascal_le_merrer

08/24/2020, 7:54 AM

I’m interested in your validate lambda, @Pedro Flores. Could you post it please?

Mine looks like this:

fun validateCredential(jwtCredential: JWTCredential): Principal? {

    val sessionId = jwtCredential.payload.getClaim("sessionId").asString()

    if (isValidSessionId(cuid, sessionId)) {
        return JWTPrincipal(jwtCredential.payload)
    }

    return null
}

Pedro Flores

08/24/2020, 8:05 AM

Well it’s quite similar, the difference is that I have an extended Principal but still it should be working as the documentation intended :)

pascal_le_merrer

08/24/2020, 10:04 AM

That’s the point I missed. It’s much simpler with a class extending Principal. Thanks @Pedro Flores! 👍

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