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https://issues.apache.org/jira/browse/KAFKA-4764?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15997107#comment-15997107
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Jun Rao commented on KAFKA-4764:
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[~rsivaram], thanks for creating the jira. It seems that it's a bit weird that
the SASL library doesn't provide a way to communicate an authentication error
back to the client. Do you know if ZK has the same issue (since our SASL
support is very similar to what's in ZK)?
Another approach that I was thinking is that if the client defects a disconnect
while it's in the authentication phase (i.e., after the connection is
established but before authentication completes), it can simply turn a
disconnect to an Authentication error and return it back to the caller instead
of treating this as a disconnect?
> Improve diagnostics for SASL authentication failures
> ----------------------------------------------------
>
> Key: KAFKA-4764
> URL: https://issues.apache.org/jira/browse/KAFKA-4764
> Project: Kafka
> Issue Type: Improvement
> Components: security
> Affects Versions: 0.10.2.0
> Reporter: Rajini Sivaram
> Assignee: Rajini Sivaram
> Fix For: 0.11.0.0
>
>
> At the moment, broker closes the client connection if SASL authentication
> fails. Clients see this as a connection failure and do not get any feedback
> for the reason why the connection was closed. Producers and consumers retry,
> attempting to create successful connections, treating authentication failures
> as transient failures. There are no log entries on the client-side which
> indicate that any of these connection failures were due to authentication
> failure.
> This JIRA will aim to improve diagnosis of authentication failures with the
> following changes:
> - Broker will send an authentication error code if SASL authentication fails,
> just before closing the connection. This will be treated as an invalid token
> by the client authenticator, and the error handling for invalid tokens will
> be updated to report authentication failure for this case. This is a bit of a
> hack, but would work with GSSAPI, PLAIN and SCRAM. SASL itself doesn't
> provide a mechanism-independent way of reporting authentication failures. An
> alternative would be to wrap SASL authentication in Kafka request/response to
> enables error codes to be sent as Kafka response, but that would be a much
> bigger change.
> - Log a warning in clients for authentication failures, distinguishing these
> from EOF exceptions due to connection failure
> - Blackout nodes to which connection failed due to authentication error, no
> more attempts will be made to connect to these nodes.
> - We should use the connection state to improve handling of producer/consumer
> requests, avoiding unnecessary blocking. This will not be addressed in this
> JIRA, KAFKA-3899 should be able to use the additional state from JIRA to fix
> this issue.
> This JIRA also does not change handling of SSL authentication failures.
> javax.net.debug provides sufficient diagnostics for this case, I don't
> believe there is sufficient information in `SslTransportLayer` to treat these
> in a consistent way with SASL authentication failures.
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