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https://issues.apache.org/jira/browse/ZOOKEEPER-4790?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Andor Molnar reassigned ZOOKEEPER-4790:
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Assignee: Sönke Liebau
> TLS Quorum hostname verification breaks in some scenarios
> ---------------------------------------------------------
>
> Key: ZOOKEEPER-4790
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-4790
> Project: ZooKeeper
> Issue Type: Improvement
> Affects Versions: 3.9.1
> Reporter: Sönke Liebau
> Assignee: Sönke Liebau
> Priority: Minor
> Labels: pull-request-available
> Fix For: 3.10.0, 3.9.4
>
> Time Spent: 2h 10m
> Remaining Estimate: 0h
>
> Currently, enabling Quorum TLS will make the server validate SANs client
> certificates of connecting quorum peers against their reverse DNS address.
> We have seen this cause issues when running in Kubernetes, due to ip
> addresses resolving to multiple dns names, when ZooKeeper pods participate in
> multiple services.
> Since `InetAddress.getHostAddress()` returns a String, it basically becomes a
> game of chance which dns name is checked against the cert.
> This usually shakes itself loose after a few minutes, when the hostname that
> gets returned by the reverse lookup randomly changes and all of a sudden
> matches the certificate... but this is less than ideal.
> This has also caused issues in the Strimzi operator as well (see [this
> issue|https://github.com/strimzi/strimzi-kafka-operator/issues/3099]) - they
> solved this by pretty much adding anything they can find that might be
> relevant to the SAN, and a few wildcards on top of that.
> This is both, error prone and doesn't really add any relevant extra amount of
> security, since "This certificate matches the connecting peer" shouldn't
> automatically mean "this peer should be allowed to connect".
>
> There are two (probably more) ways to fix this:
> # Retrieve _all_ reverse entries and check against all of them
> # The ZK server could verify the SAN against the list of servers
> ({{{}servers.N{}}} in the config). A peer should be able to connect on the
> quorum port if and only if at least one SAN matches at least one of the
> listed servers.
> I'd argue that the second option is the better one, especially since the java
> api doesn't even seem to have the option of retrieving all dns entries, but
> also because it better matches the expressed intent of the ZK admin.
> Additionally, it would be nice to have a "disable client hostname
> verification" option that still leaves server hostname verification enabled.
> Strictly speaking this is a separate issue though, I'd be happy to spin that
> out into a ticket of its own..
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