[CentOS] Low random entropy

Sun May 28 11:56:29 UTC 2017
Leon Fauster <leonfauster at googlemail.com>

> Am 28.05.2017 um 12:16 schrieb Robert Moskowitz <rgm at htt-consult.com>:
> On 05/28/2017 04:24 AM, Tony Mountifield wrote:
>> In article <792718e8-f403-1dea-367d-977b157af82c at htt-consult.com>,
>> Robert Moskowitz <rgm at htt-consult.com> wrote:
>>> On 05/26/2017 08:35 PM, Leon Fauster wrote:
>>> drops back to 30! for a few minutes.  Sigh.
>>>> http://issihosts.com/haveged/
>>>> EPEL: yum install haveged
>>> WOW!!!
>>> installed, enabled, and started.
>>> Entropy jumped from ~130 bits to ~2000 bits
>>> thanks
>>> Note to anyone running a web server, or creating certs.  You need
>>> entropy.  Without it your keys are weak and attackable.  Probably even
>>> known already.
>> Interesting. I just did a quick check of the various servers I support,
>> and have noticed that all the CentOS 5 and 6 systems report entropy in
>> the low hundreds of bits, but all the CentOS 4 systems and the one old
>> FC3 system all report over 3000 bits.
>> Since they were all pretty much stock installs, what difference between
>> the versions might explain what I observed?
> This is partly why so many certs found in the U of Mich study are weak and factorable.  So many systems have inadequate entropy for the generation of key pairs to use in TLS certs.  Worst are certs created in firstboot process where at times there is no entropy, but the firstboot still creates its certs.

/var/lib/random-seed and $HOME/.rnd are approaches to mitigate this scenario.