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https://issues.apache.org/jira/browse/KAFKA-13360?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17426334#comment-17426334
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David Mao commented on KAFKA-13360:
-----------------------------------
Very thorough writeup, nice find!
> Wrong SSL messages when handshake fails
> ---------------------------------------
>
> Key: KAFKA-13360
> URL: https://issues.apache.org/jira/browse/KAFKA-13360
> Project: Kafka
> Issue Type: Bug
> Components: network
> Affects Versions: 2.8.0
> Environment: Two VMs, one running one Kafka broker and the other one
> running kafka-console-consumer.sh.
> The consumer is validating the server certificate.
> Both VMs are VirtualBox running in the same laptop.
> Using internal LAN.
> Latency is in the order of microseconds.
> More details in attached PDF.
> Reporter: Rodolfo Kohn
> Priority: Major
> Attachments: Kafka error.pdf,
> dump_192.168.56.101_192.168.56.102_32776_9093_2021_10_06_21_09_19.pcap,
> ssl_kafka_error_logs_match_ssl_logs.txt,
> ssl_kafka_error_logs_match_ssl_logs2.txt
>
>
> When a consumer tries to connect to a Kafka broker and there is an error in
> the SSL handshake, like the server sending a certificate that cannot be
> validated for not matching the common name with the server/domain name, Kafka
> sends out erroneous SSL messages before sending an SSL alert. This error
> occurs in client but also can be seen in server.
> Because of the nature of the problem it seems it will happen in more if not
> all handshake errors.
> I've debugged and analyzed the Kafka networking code in
> org.apache.kafka.common.network and wrote a detailed description of how the
> error occurs.
> Attaching the pcap file and a pdf with the detailed description of where the
> error is in the networking code (SslTransportLayer, Channel, Selector).
> I executed a very basic test between kafka-console-consumer and a simple
> installation of one Kafka broker with TLS.
> The test consisted on a Kafka broker with a certificate that didn’t match the
> domain name I used to identify the server. The CA was well set up to avoid
> related problems, like unknown CA error code. Thus, when the server sends the
> certificate to the client, the handshake fails with code error 46
> (certificate unknown). The goal was that my tool would detect the issue and
> send an event, describing a TLS handshake problem for both processes.
> However, I noticed the tool sent what I thought it was the wrong event, it
> sent a TLS exception event for an unexpected message instead of an event for
> TLS alert for certificate unknown.
> I noticed that during handshake, after the client receives Sever Hello,
> Certificate, Server Key Exchange, and Server Hello Done, it sends out the
> same Client Hello it sent at the beginning and then 3 more records with all
> zeroes, in two more messages. It sent a total of 16,709 Bytes including the
> 289 Bytes of Client Hello record.
>
> This looks also like a design error regarding how protocol failures are
> handled.
>
>
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