Re: Why does reading from /dev/urandom deplete entropy so much?

Matt Mackall
2007-12-04T22:35:20Z

On Tue, Dec 04, 2007 at 04:23:12PM -0600, Mike McGrath wrote:
> Matt Mackall wrote:
> >On Tue, Dec 04, 2007 at 03:18:27PM -0600, Mike McGrath wrote:
> >
> >>Matt Mackall wrote:
> >>
> >>>which would have been in v2.6.22-rc4 through the normal CVE process.
> >>>The only other bits in there are wall time and utsname, so systems
> >>>with no CMOS clock would behave repeatably. Can we find out what
> >>>kernels are affected?
> >>>
> >>>
> >>>
> >>We can but it will likely take a few weeks to get a good sampling. UUID
> >>is unique in the db so when someone checks in with the same UUID, the
> >>old one gets overwritten.
> >>
> >
> >We can probably assume that for whatever reason the two things with
> >duplicate UUID had the same seed. If not, we've got -much- bigger
> >problems.
> >
>
> Ok, I think I see whats going on here. I have some further investigation
> to do but it seems that the way our Live CD installer works is causing
> these issues. I'm going to try to grab some live CD's and hardware to
> confirm but at this point it seems thats whats going on.

Alright, keep me posted. We probably need a scheme to make the initial
seed more robust regardless of what you find out.

--
Mathematics is the supreme nostalgia of our time.