linux-kernel - Re: TPMs and random numbers

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Message-ID: <CALCETrX0hN5hfW0rAsJ-uAKyV5eVSdhntT0TOVumLm2CDyLLBQ@mail.gmail.com>
Date:	Wed, 11 Sep 2013 12:08:24 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Jeff Garzik <jgarzik@...ox.com>
Cc:	"Theodore Ts'o" <tytso@....edu>,
	David Safford <safford@...ibm.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Leonidas Da Silva Barbosa <leosilva@...ux.vnet.ibm.com>,
	Ashley Lai <ashley@...leylai.com>,
	Rajiv Andrade <mail@...jiv.net>,
	Marcel Selhorst <tpmdd@...horst.net>,
	Sirrix AG <tpmdd@...rix.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kent Yoder <key@...ux.vnet.ibm.com>,
	David Safford <safford@...son.ibm.com>,
	Mimi Zohar <zohar@...ibm.com>,
	"Johnston, DJ" <dj.johnston@...el.com>
Subject: Re: TPMs and random numbers

On Wed, Sep 11, 2013 at 12:06 PM, Jeff Garzik <jgarzik@...ox.com> wrote:
> On Wed, Sep 11, 2013 at 2:45 PM, Theodore Ts'o <tytso@....edu> wrote:
>> We should definitely do this.  If the TPM driver could fetch some
>> randomness and then call add_device_randomness() to feed this into the
>> random driver's entropy pool when it initializes itself, that would be
>> ***really*** cool.
>
>
> rngd already does this.

And all those random numbers generated before rngd starts are quite
possibly crap.

I think that rngd makes sense as a tool to access strange sources of
entropy and to periodically reseed the pool, but I also think that the
kernel should really be pulling in easily available entropy on its own
at startup.

--Andy
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