Re: [PATCH RESEND v4 0/1] add sysfs exports for TPM 2 PCR registers

On Mon, 2020-09-07 at 16:23 +0300, Jarkko Sakkinen wrote:

On Mon, Sep 07, 2020 at 07:38:24AM +0200, Greg KH wrote:

quoted

Please just use a binary blob format.  Binary sysfs files are
exactly what this is for, you are just passing the data through the
kernel from the hardware to userspace.

You can have 24 binary files if that makes it easier, but the
existing format really is an abuse of sysfs.

There is no existing format for TPM 2.0 ... that's part of the problem
since we certainly didn't want to carry over the TPM 1.2 format.

I've got to say I think binary attributes are actively evil.  I can see
they're a necessity when there's no good way to represent the data they
contain, like the bios measurement log or firmware code or a raw
interface like we do for the SMP frame code in libsas.  But when
there's a well understood and easy to produce user friendly non-binary
representation, I think dumping binary is inimical to being a good API.

quoted

Or use securityfs, that's fine too, but as you say, you have to
write more code for that.

thanks,

greg k-h

I suggested this in previous round: to have a single 'pcrs' binary
file with <TPM Alg ID, blob> pairs contained.

There's no current use case today that wants all values.  Every current
use case wants either a single PCR or a selection mostly from a single
bank, so forcing every current user to dig out the values they want 
from a binary blob rather than being able to gather them simply also
seems to be an API that makes users' lives harder than they need to be.

James