Edoardo Comar created KAFKA-4206:
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Summary: Improve handling of invalid credentials to mitigate DOS
issue (especially on SSL listeners)
Key: KAFKA-4206
URL: https://issues.apache.org/jira/browse/KAFKA-4206
Project: Kafka
Issue Type: Improvement
Components: network, security
Affects Versions: 0.10.0.1, 0.10.0.0
Reporter: Edoardo Comar
Assignee: Edoardo Comar
The current handling of invalid credentials (ie wrong user/password) is to let
the `SaslException` thrown from an implementation of
`javax.security.sasl.SaslServer.evaluateResponse()`
bubble up the call stack until it gets caught in
`org.apache.kafka.common.network.Selector.pollSelectionKeys()`
where the `KafkaChannel` gets closed - which will cause the client that made
the request to be disconnected.
This will happen however after the server has used considerable resources,
especially for the SSL handshake which appears to be computationally expensive
in Java.
We have observed that if just a few clients keep repeating requests with the
wrong credentials, it is quite easy to get all the network processing threads
in the Kafka server busy doing SSL handshakes.
This makes a Kafka cluster to easily suffer from a Denial Of Service - also non
intentional - attack.
It can be non intentional, i.e. also caused by friendly clients, for example
because a Kafka Java client Producer supplied with the wrong credentials will
not throw an exception on publishing, so it may keep attempting to connect
without the caller realising.
An easy fix which we have implemented and will supply a PR for is to *delay*
considerably closing the `KafkaChannel` in the `Selector`, but obviously
without blocking the processing thread.
This has be tested to be very effective in reducing the cpu usage spikes caused
by non malicious ssl clients using invalid credentials.
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