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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-15557) Crypto streams should not crash when mis-used
Date Fri, 22 Jun 2018 18:59:00 GMT
Todd Lipcon created HADOOP-15557:

             Summary: Crypto streams should not crash when mis-used
                 Key: HADOOP-15557
                 URL: https://issues.apache.org/jira/browse/HADOOP-15557
             Project: Hadoop Common
          Issue Type: Improvement
          Components: fs
    Affects Versions: 3.2.0
            Reporter: Todd Lipcon

In general, the non-positional read APIs for streams in Hadoop Common are meant to be used
by only a single thread at a time. It would not make much sense to have concurrent multi-threaded
access to seek+read because they modify the stream's file position. Multi-threaded access
on input streams can be done using positional read APIs. Multi-threaded access on output streams
probably never makes sense.

In the case of DFSInputStream, the positional read APIs are marked synchronized, so that even
when misused, no strange exceptions are thrown. The results are just somewhat undefined in
that it's hard for a thread to know which position was read from. However, when running on
an encrypted file system, the results are much worse: since CryptoInputStream's read methods
are not marked synchronized, the caller can get strange ByteBuffer exceptions or even a JVM
crash due to concurrent use and free of underlying OpenSSL Cipher buffers.

The crypto stream wrappers should be made more resilient to such misuse, for example by:
(a) making the read methods safer by making them synchronized (so they have the same behavior
as DFSInputStream)
(b) trying to detect concurrent access to these methods and throwing ConcurrentModificationException
so that the user is alerted to their probable misuse.

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