Re: [PATCH] Update the random(4) documentation towards a more accurate view on /dev/urandom

On Fri, Oct 21, 2016 at 06:50:58PM +0200, Stephan Mueller wrote:

quoted

It would certainly be a good idea to suggest the use of getrandom(2),
and the fact that the only difference between getrandom(2) and
/dev/urandom is that getrandom(2) will block until it can safely
generate random numbers.  Unfortunately, there are far too many
programs (including udev and systemd!) that try to use /dev/urandom at
boot time, and making a change to /dev/urandom would break users.  If
any of these use cases are security sensitive, they should really
change it so that users aren't vulnerable to security attacks.  (The
use of systemd on IOT devices especially terrifies me in this regard.)

Although I this is not related to the man page, please note that I have tried 
this approach during the development of my LRNG. systemd did not like that at 
all. The system did not come up, even though there was only 0.5 seconds it 
would need to wait until getrandom would unblock during my tests.

Although I'd argue this is a systemd bug, to be fair to systemd, when
I briefly tried this approach, the zero day kernel testing system, let
me know than an older version of Ubuntu (which wasn't using systemd),
and CeroWrt (which also doesn't use systemd) were also hanging.

I haven't checked to see if that was because Cerowrt was trying to do
something security sensitive such as creating ssh host keys.  I've
been too busy, and I was afriad the result would be too depressing....
Besides, I don't use Cerowrt thes days, since I'm using Google OnHub
now.  :-)

     	       	     	 	    	   - Ted
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