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From "Andrew Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-11343) Overflow is not properly handled in caclulating final iv for AES CTR
Date Fri, 05 Dec 2014 23:38:13 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-11343?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14236311#comment-14236311
] 

Andrew Wang commented on HADOOP-11343:
--------------------------------------

Nice patch, thanks Yi for running with Jerry's patch. I spent some time staring at the bitshifts
and it looks right, this is some nice tight code.

Couple comments on the unit test, +1 pending though:

* typo: Calcualted -> Calculated
* We could use Longs.toByteArray from Guava rather than a new method
* Could we add a randomized test that's in the danger zone for overflow? This could be as
simple as testing with a really big counter and random IV, then with a really big bottom 8
of the IV and a random counter.

> Overflow is not properly handled in caclulating final iv for AES CTR
> --------------------------------------------------------------------
>
>                 Key: HADOOP-11343
>                 URL: https://issues.apache.org/jira/browse/HADOOP-11343
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: security
>    Affects Versions: 2.6.0
>            Reporter: Jerry Chen
>            Assignee: Jerry Chen
>            Priority: Blocker
>         Attachments: HADOOP-11343.001.patch, HADOOP-11343.002.patch, HADOOP-11343.patch
>
>
> In the AesCtrCryptoCodec calculateIV, as the init IV is a random generated 16 bytes,

> final byte[] iv = new byte[cc.getCipherSuite().getAlgorithmBlockSize()];
>       cc.generateSecureRandom(iv);
> Then the following calculation of iv and counter on 8 bytes (64bit) space would easily
cause overflow and this overflow gets lost.  The result would be the 128 bit data block was
encrypted with a wrong counter and cannot be decrypted by standard aes-ctr.
> {code}
> /**
>    * The IV is produced by adding the initial IV to the counter. IV length 
>    * should be the same as {@link #AES_BLOCK_SIZE}
>    */
>   @Override
>   public void calculateIV(byte[] initIV, long counter, byte[] IV) {
>     Preconditions.checkArgument(initIV.length == AES_BLOCK_SIZE);
>     Preconditions.checkArgument(IV.length == AES_BLOCK_SIZE);
>     
>     System.arraycopy(initIV, 0, IV, 0, CTR_OFFSET);
>     long l = 0;
>     for (int i = 0; i < 8; i++) {
>       l = ((l << 8) | (initIV[CTR_OFFSET + i] & 0xff));
>     }
>     l += counter;
>     IV[CTR_OFFSET + 0] = (byte) (l >>> 56);
>     IV[CTR_OFFSET + 1] = (byte) (l >>> 48);
>     IV[CTR_OFFSET + 2] = (byte) (l >>> 40);
>     IV[CTR_OFFSET + 3] = (byte) (l >>> 32);
>     IV[CTR_OFFSET + 4] = (byte) (l >>> 24);
>     IV[CTR_OFFSET + 5] = (byte) (l >>> 16);
>     IV[CTR_OFFSET + 6] = (byte) (l >>> 8);
>     IV[CTR_OFFSET + 7] = (byte) (l);
>   }
> {code}



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