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From "Erik Krogen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-14305) Serial number in BlockTokenSecretManager could overlap between different namenodes
Date Mon, 25 Feb 2019 16:11:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-14305?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16777046#comment-16777046

Erik Krogen commented on HDFS-14305:

The idea seems sound to me. The helper method for the unit test has indentation issues (method
parameters are typically indented by 4 spaces, not to match the indentation of the first parameter)
and I think the test could use a comment describing what it is testing.

I think 10 bits for the mask seems a little high to me; I agree with Chao that I can't think
of a situation where you would need more than 32 or 64, and fewer bits for the per-NN key
space mean a higher chance of collision on a NameNode restart.

> Serial number in BlockTokenSecretManager could overlap between different namenodes
> ----------------------------------------------------------------------------------
>                 Key: HDFS-14305
>                 URL: https://issues.apache.org/jira/browse/HDFS-14305
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: security
>            Reporter: Chao Sun
>            Assignee: Chao Sun
>            Priority: Major
>         Attachments: HDFS-14305.001.patch, HDFS-14305.002.patch, HDFS-14305.003.patch
> Currently, a {{BlockTokenSecretManager}} starts with a random integer as the initial
serial number, and then use this formula to rotate it:
> {code:java}
>     this.intRange = Integer.MAX_VALUE / numNNs;
>     this.nnRangeStart = intRange * nnIndex;
>     this.serialNo = (this.serialNo % intRange) + (nnRangeStart);
>  {code}
> while {{numNNs}} is the total number of NameNodes in the cluster, and {{nnIndex}} is
the index of the current NameNode specified in the configuration {{dfs.ha.namenodes.<nameservice>}}.
> However, with this approach, different NameNode could have overlapping ranges for serial
number. For simplicity, let's assume {{Integer.MAX_VALUE}} is 100, and we have 2 NameNodes
{{nn1}} and {{nn2}} in configuration. Then the ranges for these two are:
> {code}
> nn1 -> [-49, 49]
> nn2 -> [1, 99]
> {code}
> This is because the initial serial number could be any negative integer.
> Moreover, when the keys are updated, the serial number will again be updated with the
> {code}
> this.serialNo = (this.serialNo % intRange) + (nnRangeStart);
> {code}
> which means the new serial number could be updated to a range that belongs to a different
NameNode, thus increasing the chance of collision again.
> When the collision happens, DataNodes could overwrite an existing key which will cause
clients to fail because of {{InvalidToken}} error.

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