override def evaluateResponse()

in thriftserver/server/src/main/scala/org/apache/livy/thriftserver/auth/PlainSaslServer.scala [51:104]
50 lines of code
14 McCabe index (conditional complexity)

  override def evaluateResponse(response: Array[Byte]): Array[Byte] = {
    try {
      // parse the response
      // message = [authzid] UTF8NUL authcid UTF8NUL passwd'
      val tokenList: util.Deque[String] = new util.ArrayDeque[String]
      var messageToken = new StringBuilder
      for (b <- response) {
        if (b == 0) {
          tokenList.addLast(messageToken.toString)
          messageToken = new StringBuilder
        } else {
          messageToken.append(b.toChar)
        }
      }
      tokenList.addLast(messageToken.toString)
      // validate response
      if (tokenList.size < 2 || tokenList.size > 3) {
        throw new SaslException("Invalid message format")
      }
      val passwd: String = tokenList.removeLast()
      user = tokenList.removeLast()
      // optional authzid
      var authzId: String = null
      if (tokenList.isEmpty) {
        authzId = user
      } else {
        authzId = tokenList.removeLast()
      }
      if (user == null || user.isEmpty) {
        throw new SaslException("No user name provided")
      }
      if (passwd == null || passwd.isEmpty) {
        throw new SaslException("No password name provided")
      }
      val nameCallback = new NameCallback("User")
      nameCallback.setName(user)
      val pcCallback = new PasswordCallback("Password", false)
      pcCallback.setPassword(passwd.toCharArray)
      val acCallback = new AuthorizeCallback(user, authzId)
      val cbList = Array[Callback](nameCallback, pcCallback, acCallback)
      handler.handle(cbList)
      if (!acCallback.isAuthorized) {
        throw new SaslException("Authentication failed")
      }
    } catch {
      case eL: IllegalStateException =>
        throw new SaslException("Invalid message format", eL)
      case eI: IOException =>
        throw new SaslException("Error validating the login", eI)
      case eU: UnsupportedCallbackException =>
        throw new SaslException("Error validating the login", eU)
    }
    null
  }