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ASF GitHub Bot commented on ZOOKEEPER-2693: ------------------------------------------- Github user rakeshadr commented on a diff in the pull request: https://github.com/apache/zookeeper/pull/179#discussion_r101951840 --- Diff: src/java/main/org/apache/zookeeper/server/NettyServerCnxn.java --- @@ -267,10 +267,17 @@ private boolean checkFourLetterWord(final Channel channel, { // We take advantage of the limited size of the length to look // for cmds. They are all 4-bytes which fits inside of an int - String cmd = FourLetterCommands.getCmdMapView().get(len); - if (cmd == null) { + if (!FourLetterCommands.isKnown(len)) { return false; } + + // ZOOKEEPER-2693: don't execute 4lw if it's not enabled. + String cmd = FourLetterCommands.getCommandString(len); + if (!FourLetterCommands.isEnabled(cmd)) { + LOG.debug("Command {} is not executed because it is not white listed.", cmd); + return true; --- End diff -- Should we cleanup the this selection key from the selector? > 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 > > > 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. -- This message was sent by Atlassian JIRA (v6.3.15#6346)