[PATCH v9] Add getentropy, getrandom, <sys/random.h> [BZ #17252]

[Florian Weimer]

On 11/30/2016 02:33 PM, Florian Weimer wrote:
> This iteration of the patch implements both getrandom and getentropy at
> the same time.  getrandom is a cancellation point, has short reads, can
> return EINTR etc., but getentropy is the more uniform interface.  I
> added a retry loop in the getentropy implementation, to avoid exposing
> an implicit magic number in the kernel implementation (the maximum size
> of a single read; it differs between Solaris/OpenBSD/Linux).
>
> (You get to decide which function is Mulready and which one is Lang.)
>
> getentropy definitely needs interposition protection because it is
> frequently redefined.  We'll need to rebuild a distribution to see if
> the current approach is sufficient.  For consistency, I also added
> interposition protection for getrandom.
>
> In addition, I had to make a few fixes so that the ABI is stable across
> supported kernel headers, and had to tweak the stub implementations, too.

I received a request off-list to align the getentropy behavior more 
closely to the OpenBSD and Solaris behavior.  I think this makes sense 
(I had not realized before they were so closely aligned), so I've added 
the 256-byte check to the glibc version which is performed by the other 
implementation in the attached version of the patch.

Thanks,
Florian

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