Chao Sun created HDFS-14305:
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Summary: 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: Improvement
Components: security
Reporter: Chao Sun
Assignee: Chao Sun
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 formula:
{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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