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Date: Tue, 26 Nov 2013 19:17:40 +0100
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 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.
--
Florian Weimer / Red Hat Product Security Team
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