On Fri, Oct 04, 2019 at 12:57:43AM +0300, Jarkko Sakkinen wrote: > On Fri, Oct 04, 2019 at 12:51:25AM +0300, Jarkko Sakkinen wrote: > > On Thu, Oct 03, 2019 at 02:53:47PM -0400, Mimi Zohar wrote: > > > [Cc'ing David Safford] > > > > > > On Thu, 2019-10-03 at 20:58 +0300, Jarkko Sakkinen wrote: > > > > On Thu, Oct 03, 2019 at 09:02:32AM -0400, Mimi Zohar wrote: > > > > > On Thu, 2019-10-03 at 14:41 +0300, Jarkko Sakkinen wrote: > > > > > > On Wed, Oct 02, 2019 at 10:00:19AM -0400, Mimi Zohar wrote: > > > > > > > On Thu, 2019-09-26 at 20:16 +0300, Jarkko Sakkinen wrote: > > > > > > > > Only the kernel random pool should be used for generating random numbers. > > > > > > > > TPM contributes to that pool among the other sources of entropy. In here it > > > > > > > > is not, agreed, absolutely critical because TPM is what is trusted anyway > > > > > > > > but in order to remove tpm_get_random() we need to first remove all the > > > > > > > > call sites. > > > > > > > > > > > > > > At what point during boot is the kernel random pool available? Does > > > > > > > this imply that you're planning on changing trusted keys as well? > > > > > > > > > > > > Well trusted keys *must* be changed to use it. It is not a choice > > > > > > because using a proprietary random number generator instead of defacto > > > > > > one in the kernel can be categorized as a *regression*. > > > > > > > > > > I really don't see how using the TPM random number for TPM trusted > > > > > keys would be considered a regression. That by definition is a > > > > > trusted key. If anything, changing what is currently being done would > > > > > be the regression. > > > > > > > > It is really not a TPM trusted key. It trusted key that gets sealed with > > > > the TPM. The key itself is used in clear by kernel. The random number > > > > generator exists in the kernel to for a reason. > > > > > > > > It is without doubt a regression. > > > > > > You're misusing the term "regression" here. A regression is something > > > that previously worked and has stopped working. In this case, trusted > > > keys has always been based on the TPM random number generator. Before > > > changing this, there needs to be some guarantees that the kernel > > > random number generator has a pool of random numbers early, on all > > > systems including embedded devices, not just servers. > > > > I'm not using the term regression incorrectly here. Wrong function > > was used to generate random numbers for the payload here. It is an > > obvious bug. > > At the time when trusted keys was introduced I'd say that it was a wrong > design decision and badly implemented code. But you are right in that as > far that code is considered it would unfair to speak of a regression. > > asym-tpm.c on the other hand this is fresh new code. There has been > *countless* of discussions over the years that random numbers should > come from multiple sources of entropy. There is no other categorization > than a bug for the tpm_get_random() there. Saying that regression is something that "stopped working" is very blunt and naive definition of regression, and is not true. Any misbehaviour can be categorized as a regression. /Jarkko
