What happens on the server if the client sends invalid input?

I can't find anywhere in the documentation where it says what happens if the client fails to login (enters the wrong password or otherwise gives malformed input).

Especially here, where it is the most important, and also expected. 

```js
// server
const { sessionKey } = opaque.server.finishLogin({
  finishLoginRequest,
  serverLoginState,
});
```