Hi All, I came across an issue with plugging in a custom PrincipalBuilder class using the config "principal.builder.class" along with a custom Authorizer class using the config "authorizer.class.name".
Consider the following scenario : For PlainText we don't supply any PrincipalBuilder. For SSL we want to supply a PrincipalBuilder using the property "principal.builder.class". a) Now consider we have a broker running on these 2 ports and supply that custom principalBuilder class using that config. b) The interbroker communication is using PlainText. I am using a single broker cluster for testing. c) Now we issue a produce request on the SSL port of the broker. d) The controller tries to build a channel for plaintext with this broker for the new topic instructions. e) PlainText tries to use the principal builder specified in the "principal.builder.class" config which was meant only for SSL port since the code path is same "ChannelBuilders.createPrincipalBuilder(configs)". f) In the custom principal Builder if we are trying to do some cert checks or down conversion of transportLayer to SSLTransportLayer so that we can use its functionality we get error/exception at runtime. The basic idea is the PlainText channel should not be using the PrincipalBuilder meant for other types of channels. Now there are few options/workarounds to avoid this : 1) Do instanceOf check in Authorizer.authorize() on TransportLayer instance passed in and do the correct handling. This is not intuitive and imposes a strict coding rule on the programmer. 2) TransportLayer should expose an API for telling the security protocol type. This is not too intuitive either. 3) Add extra configs for Authorizer and PrincipalBuilder for each channel type. This gives us a flexibility for the PrincipalBuilder and Authorizer handle requests on different types of ports in a different way. 4) PrincipalBuilder.buildPrincipal() should take in extra parameter for the type of protocol and we should document this in javadoc to use it to handle the type of request. This is little better than 1) and 2) but again imposes a strict coding rule on the programmer. Just wanted to know what the community thinks about this and get any suggestions/feedback . There's some discussion about this here : https://github.com/apache/kafka/pull/1403 Thanks, Mayuresh
