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From "Jerry Chen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-11343) Overflow is not properly handled in caclulating final iv for AES CTR
Date Wed, 03 Dec 2014 04:42:13 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-11343?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14232575#comment-14232575
] 

Jerry Chen commented on HADOOP-11343:
-------------------------------------

Based on the above understanding, the upgrade would not be something be able  to be considered.
This is because once the issue happens in the encryption process, the decryption will fail
unless the descryption strictly follow the same calling patten of calculateIV at the same
sequnce of positions. But we know this is hard to achieve. 

So this fix would not be a pure improvement, but a crucial fix for unrecoverable data corrutption
caused by encryption.

> 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: trunk-win
>            Reporter: Jerry Chen
>
> 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.
> /**
>    * 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);
>   }



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