Re: [TrouSerS-tech] read error trying to use /dev/tpm0 with rngd

[Kent Y. <shp...@gm...>]

Hi Garey,

On Thu, May 31, 2012 at 3:37 PM, Garey Mills
<gm...@li...> wrote:
> Hello -
>
>     I am trying to use TPM for random number generation to supply
> /dev/random. I have owned the TPM, shut off tcsd, and I try to run
>
> /sbin/rngd -r /dev/tpm0 -o /dev/random -t 1
>
> I get 'read error' two times and rngd exits.
>
>     Am I doing something wrong?

  /dev/tpm0 is the interface that the tcsd opens in order to send
specially crafted requests to the TPM for specific TPM actions.
Generating random numbers is just one of those actions.  To achieve
what you're trying to do, you need an application that talks either
directly to /dev/tpm0 (such as those included in the ibm software tpm
utils, from [1]), or an application that uses the TSS [2],  to read
random numbers from the tpm and send them to stdout.  Then you'd point
rngd to one of those apps.

Kent

[1] https://sourceforge.net/projects/ibmswtpm/
[2] http://trousers.git.sourceforge.net/git/gitweb.cgi?p=trousers/testsuite;a=blob;f=tcg/tpm/Tspi_TPM_GetRandom01.c

> --
> Garey Mills
> Library Systems Office
> UC Berkeley
>
>
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