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From "Rakesh R (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2693) DOS attack on wchp/wchc four letter words (4lw)
Date Tue, 21 Feb 2017 17:18:44 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15876313#comment-15876313

Rakesh R commented on ZOOKEEPER-2693:

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
 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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