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Date: Tue, 10 Feb 2015 16:49:19 -0600
From: Tyler Hicks <tyhicks@...onical.com>
To: oss-security@...ts.openwall.com
Subject: Re: eCryptfs key wrapping help to crack user password
On 2015-02-10 15:07:24, Sylvain Pelissier wrote:
> Hi,
>
> I have noticed that ecryptfs-utils is the default program used by the
> Ubuntu distributions for home folder encryption since version 10.04.
> In this case, a wrapping key is generated from the user password
> using the hash function SHA-512 applied 65536 times. By default, the
> wrapping key is hashed with the default fixed salt
> (0x0011223344556677) and stored in the a file.
> This was already noticed in bug :
> https://bugs.launchpad.net/ecryptfs/+bug/906550
> For Ubuntu installations time-memory trade-off (rainbow tables, etc.)
> can apply, as well as bulk dictionary attacks to crack user passwords
> of Ubuntu installations when the home folder encryption is activated.
> I am currently working to correct this weakness.
Thanks for reporting this issue, Sylvain.
I have confirmed the analysis above and upstream ecryptfs-utils is
working to correct the problem.
Tyler
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