On Tue, Mar 30, 2021 at 02:47:18PM -0700, Eric Biggers wrote:

On Sun, Mar 28, 2021 at 11:37:23PM +0300, Jarkko Sakkinen wrote:

quoted

Unfortunately, TPM trusted keys started this bad security practice, and
obviously it cannot be fixed without breaking uapi backwards compatibility.

The whole point of a randomness source is that it is random.  So userspace can't
be depending on any particular output, and the randomness source can be changed
without breaking backwards compatibility.

So IMO, trusted keys should simply be fixed to use get_random_bytes().

- Eric

It's a bummer but uapi is the god in the end. Since TPM does not do it
today, that behaviour must be supported forever. That's why a boot option
AND a warning would be the best compromise.

/Jarkko