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From "Edoardo Comar (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (KAFKA-4206) Improve handling of invalid credentials to mitigate DOS issue (especially on SSL listeners)
Date Fri, 29 Sep 2017 10:43:00 GMT

     [ https://issues.apache.org/jira/browse/KAFKA-4206?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Edoardo Comar resolved KAFKA-4206.
    Resolution: Won't Do

> 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:,
>            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
> This has been tested to be very effective in reducing the cpu usage spikes caused by
non malicious clients using invalid SASL PLAIN credentials over SSL.

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