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Date: Mon, 2 Jan 2012 05:11:38 +0400
From: Solar Designer <solar@...nwall.com>
To: dillon@...llo.backplane.com, Nolan Lum <nol888@...il.com>
Cc: oss-security@...ts.openwall.com
Subject: Re: weird crypt-sha* in DragonFly BSD
Matt - as far as I can see, nothing has been done on this yet.
DragonFly still uses by far the weakest password hashing of all *BSDs
(and even of all non-ancient Unix-like systems) by default. I suggest
that you revert to MD5-crypt ASAP - should be a trivial change for you
to make. Then change the default to bcrypt or something else
(reasonable) in the future (when you have time). Thanks!
On Tue, Nov 15, 2011 at 06:35:02AM +0400, Solar Designer wrote:
> Hi,
>
> Matthew - when I read that DragonFly moved to using SHA-256 for
> passwords by default, I thought this was referring to the SHA-256 based
> flavor of Ulrich Drepper's SHA-crypt. This would not be the best choice
> to make, in my opinion, but it would not be that bad. However, I just
> found this:
>
> http://gitweb.dragonflybsd.org/dragonfly.git/tree/HEAD:/lib/libcrypt
>
> Are these crypt-sha256.c and/or crypt-sha512.c files actually in use?
> I hope not... They do not include any password stretching, resulting in
> password hashes that are much quicker to crack than MD5-crypt's.
>
> There's also minor weirdness in the code - such as two local pointer
> variables being declared static seemingly for no reason, and only
> "final" but not "ctx" being zeroized in the end. But even this lack of
> proper cleanup is very minor compared to the lack of stretching.
>
> Oh, also the "$3$" prefix was apparently previously used for NTLM:
>
> http://en.wikipedia.org/wiki/Crypt_(Unix)#NT_Hash_Scheme
>
> "FreeBSD used the $3$ prefix for this."
>
> http://search.cpan.org/~zefram/Authen-Passphrase/lib/Authen/Passphrase/NTHash.pm
>
> "... crypt string must consist of "$3$$" (note the extra "$") followed
> by the hash in lowercase hexadecimal."
>
> BTW, I looked at DragonFly's code while analyzing a more subtle issue
> with Ulrich's SHA-crypt:
>
> http://www.openwall.com/lists/oss-security/2011/11/15/1
>
> I thought that maybe you reimplemented it in a better fashion avoiding
> that issue, but I found this... %-)
>
> Alexander
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