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Date: Thu, 11 Sep 2014 14:41:33 +0200
From: Florian Weimer <fweimer@...hat.com>
To: oss-security@...ts.openwall.com
Subject: Re: CVE Request: static IV used in Percona XtraBackup
On 11/26/2013 07:17 PM, Florian Weimer wrote:
> On 11/26/2013 11:52 AM, Marcus Meissner wrote:
>> Hi,
>>
>> This came to our desk:
>> https://bugzilla.novell.com/show_bug.cgi?id=852224
>> https://bugs.launchpad.net/percona-xtrabackup/+bug/1185343
>>
>> constant IV used in CTR Mode, allowing plaintext retrieval
>> attacks.
>
> Is suppose this is part of the fix.
>
> +void
> +xb_crypt_init_iv()
> +{
> + uint seed = time(NULL);
> + srandom(seed);
> +}
> +
> +void
> +xb_crypt_create_iv(void* ivbuf, size_t ivlen)
> +{
> + size_t i;
> + ulong rndval;
> +
> + for (i = 0; i < ivlen; i++) {
> + if (i % 4 == 0) {
> + rndval = (ulong) random();
> + }
> + ((uchar*)ivbuf)[i] = ((uchar*)&rndval)[i % 4];
> + }
> +}
>
> This still risks keystream reuse because time() is fairly coarse.
>
> What's worse, on 64-bit big-endian architectures, it results in a
> constant zero IV because RAND_MAX is not large enough to reach the upper
> 32 bits in the first four bytes of the rndval variable.
It appears that both issues have been addressed by the switch to
libgcrypt for the encryption.
--
Florian Weimer / Red Hat Product Security
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