svn commit: r227520 - head/lib/libc/gen

[Andrey Chernov]

On Tue, Nov 15, 2011 at 05:49:24AM +0000, David Schultz wrote:
> Author: das
> Date: Tue Nov 15 05:49:24 2011
> New Revision: 227520
> URL: http://svn.freebsd.org/changeset/base/227520
> 
> Log:
>   Further reduce diffs with OpenBSD's arc4random.  The main functional
>   change here is to ensure that when a process forks after arc4random
>   is seeded, the parent and child don't observe the same random sequence.
>   OpenBSD's fix introduces some additional overhead in the form of a
>   getpid() call.  This could be improved upon, e.g., by setting a flag
>   in fork(), if it proves to be a problem.
>   
>   This was discussed with secteam (simon, csjp, rwatson) in 2008, shortly
>   prior to my going out of town and forgetting all about it.  The conclusion
>   was that the problem with forks is worrisome, but it doesn't appear to
>   have introduced an actual vulnerability for any known programs.
>   
>   The only significant remaining difference between our arc4random and
>   OpenBSD's is in how we seed the generator in arc4_stir().

Thanx for taking that!

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