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https://issues.apache.org/jira/browse/ZOOKEEPER-2693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15876313#comment-15876313
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Rakesh R commented on ZOOKEEPER-2693:
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bq. There are some 4lw commands which ZooKeeper is using by itself
Good catch, [~arshad.mohammad].
bq. even though we are not doing much work in these commands but still the
connections will be created for every call.
IIUC, these are two problems -> {{case-1)}} restrict 4lw cmd execution as few
cmds taking too much time for execution. {{case-2)}} protection against overuse
because it creates many connections.
I think, {{case-1}} is matching with this jira reported issue and we could
provide {{whitelist}} config in both branches 3.4 and 3.5+ to solve this
problem.
In branch-3.4, we could give a simple fix by exposing {{whitelist}}
configuration and include {{srvr, isro}} cmds in default list. Since we have
plans to deprecate 4lws in branch-3.5, we could find alternative ways instead
of using {{srvr, isro}} cmd internally. Probably, we could raise separate jira
task and handle this case.
[~hanm], could you create a PR for branch-3.4, if no objection from anyone
about {{whitelist}} idea and that would help to unblock 3.4.10 releasing.
{{case-2}}, I like [~phunt]'s idea of introducing configuration to limit the
number of 4lw that would be allowed to run in parallel. For example, allows
only 1-n number of 4lw cmds to run in parallel. How about raising another jira
to implement this instead of clubbing with this issue?
> DOS attack on wchp/wchc four letter words (4lw)
> -----------------------------------------------
>
> Key: ZOOKEEPER-2693
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2693
> Project: ZooKeeper
> Issue Type: Bug
> Components: security, server
> Affects Versions: 3.4.0, 3.5.1, 3.5.2
> Reporter: Patrick Hunt
> Assignee: Michael Han
> Priority: Blocker
> Fix For: 3.4.10, 3.5.3
>
> Attachments: ZOOKEEPER-2693-01.patch
>
>
> The wchp/wchc four letter words can be exploited in a DOS attack on the ZK
> client port - typically 2181. The following POC attack was recently published
> on the web:
> https://webcache.googleusercontent.com/search?q=cache:_CNGIz10PRYJ:https://www.exploit-db.com/exploits/41277/+&cd=14&hl=en&ct=clnk&gl=us
> The most straightforward way to block this attack is to not allow access to
> the client port to non-trusted clients - i.e. firewall the ZooKeeper service
> and only allow access to trusted applications using it for coordination.
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