There is a special SASL response which uses the multi-line response to notify the client more information is required when authenticating. This overloads the possible meanings of the multi-line response, and is unnecessary as an additional single-line response would be adequate for all authentication methods which require more data.

There is no need to use the multi-line response as the completion of the "AUTH TYPE" command is easily indicated by "K authenticate". - dave

I think an additional positive single-line response should be added, an 'M' indicating more information is needed.

Given the above, no additional response code is needed. - dave

See also 5.2.2 are more status codes needed.

Issue done.