Re: [PATCH] KEYS: asym_tpm: Switch to get_random_bytes()

[Jarkko Sakkinen]

> > There are many good reasons for wanting the keys to be based on the
> > TPM generator.  As the source for the kernel random number generator
> > itself says, some systems lack good randomness at startup, and systems
> > should preserve and reload the pool across shutdown and startup.
> > There are use cases for trusted keys which need to generate keys 
> > before such scripts have run. Also, in some use cases, we need to show
> > that trusted keys are FIPS compliant, which is possible with TPM
> > generated keys.
> 
> If you are able to call tpm_get_random(), the driver has already
> registered TPN as hwrng. With this solution you fail to follow the
> principle of defense in depth. If the TPM random number generator
> is compromissed (has a bug) using the entropy pool will decrease
> the collateral damage.

I.e. you make everything depend on single point of failure instead
of multiple (e.g. rdrand, TPM, whatnot).

/Jarkko