Re: [patches] crypt_blowfish patch for eglibc

["Joseph S. Myers" <joseph@xxxxxxxxxxxxxxxx>]

On Fri, 29 Apr 2011, Paul DeBruicker wrote:

> *** ../eglibc-2.12.1/Versions.def	2010-01-26 06:27:38.000000000 -0500
> --- Versions.def	2011-04-28 11:26:15.614637002 -0400
> ***************
> *** 39,44 ****
> --- 39,46 ----
>   }
>   libcrypt {
>     GLIBC_2.0
> +   GLIBC_2.2.1
> +   GLIBC_2.2.2
>   }

You can't add symbol versions to existing libraries like that.  If you 
need a new symbol version for something in EGLIBC (or generally if you 
wish to export an EGLIBC-specific symbol), it needs to be in an option 
group that is disabled by default and the symbol version needs to be in 
the form EGLIBC_* with a name reflecting the option group involved.

Could you please explain (with appropriate references) what advantages 
this algorithm has over the SHA-256 and SHA-512 based algorithms added in 
glibc 2.7?  In the absence of clear cryptographic justification, adding 
the choice of more algorithms isn't generally a good idea, because of the 
risk of vulnerabilities in the new algorithms or in the way selection is 
made between the algorithms.  Is this about compatibility with existing 
passwords hashed using the blowfish scheme?  Controlling the set of 
supported algorithms with option groups does seem to make sense, if not 
already implemented.

-- 
Joseph S. Myers
joseph@xxxxxxxxxxxxxxxx