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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2693) DOS attack on wchp/wchc four letter words (4lw)
Date Tue, 07 Mar 2017 02:28:33 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15898621#comment-15898621
] 

ASF GitHub Bot commented on ZOOKEEPER-2693:
-------------------------------------------

Github user rakeshadr commented on a diff in the pull request:

    https://github.com/apache/zookeeper/pull/183#discussion_r104572803
  
    --- Diff: src/docs/src/documentation/content/xdocs/zookeeperAdmin.xml ---
    @@ -1042,6 +1042,40 @@ server.3=zoo3:2888:3888</programlisting>
                   </note>
                 </listitem>
               </varlistentry>
    +
    +          <varlistentry>
    +            <term>4lw.commands.whitelist</term>
    +
    +            <listitem>
    +              <para>(Java system property: <emphasis
    +                      role="bold">zookeeper.4lw.commands.whitelist</emphasis>)</para>
    +
    +              <para><emphasis role="bold">New in 3.4.10:</emphasis>
    +                This property contains a list of comma separated
    +                <ulink url="#sc_4lw">Four Letter Words</ulink> commands.
It is introduced
    +                to provide fine grained control over the set of commands ZooKeeper can
execute,
    +                so users can turn off certain commands if necessary.
    +                By default it contains all supported four letter word commands except
"wchp" and "wchc",
    +                if the property is not specified. If the property is specified, then
only commands listed
    +                in the whitelist are enabled.
    +              </para>
    +
    +              <para>Here's an example of the configuration that enables stat, ruok,
conf, and isro
    +                command while disabling the rest of Four Letter Words command:</para>
    +              <programlisting>
    +                4lw.commands.whitelist=stat, ruok, conf, isro
    +              </programlisting>
    +
    +              <para>Users can also use asterisk option so they don't have to include
every command one by one in the list.
    +                As an example, this will enable all four letter word commands:
    +              </para>
    +              <programlisting>
    +                4lw.commands.whitelist=*
    +              </programlisting>
    +
    +            </listitem>
    +          </varlistentry>
    +
             </variablelist>
    --- End diff --
    
    The below section is not included in br-3.4 patch, can we include this also?
    ```
    +        <varlistentry>
    +          <term>Publicly accessible deployment</term>
    +          <listitem>
    +            <para>
    +              A ZooKeeper ensemble is expected to operate in a trusted computing environment.
    +              It is thus recommended to deploy ZooKeeper behind a firewall.
    +            </para>
    +          </listitem>
    +        </varlistentry>
    ```


> 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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