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From hanm <...@git.apache.org>
Subject [GitHub] zookeeper pull request #179: ZOOKEEPER-2693: DOS attack on wchp/wchc four le...
Date Tue, 21 Feb 2017 19:52:17 GMT
Github user hanm commented on a diff in the pull request:

    https://github.com/apache/zookeeper/pull/179#discussion_r102301090
  
    --- 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 --
    
    @rakeshadr Turns out server socket not closed is a by design. Had a chat with @phunt offline
and the idea is we always prefer client to close socket first (which led to server socket
close) because a socket close at server might be premature and led to client not getting all
the data due to how TCP works. I'll leave these code as they are.


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