Re: [PATCH 0/2] backend/tpm: Resolve issue with TPM 2 DA lockout

[Marc-André Lureau]

Hi

On Fri, May 27, 2022 at 7:36 PM Stefan Berger <stefanb@linux.ibm.com> wrote:
>
> This series of patches resolves an issue with a TPM 2's dictionary attack
> lockout logic being triggered upon well-timed VM resets. Normally, the OS
> TPM driver sends a TPM2_Shutdown to the TPM 2 upon reboot and before a VM
> is reset. However, the OS driver cannot do this when the user resets a VM.
> In this case QEMU must send the command because otherwise several well-
> timed VM resets will trigger the TPM 2's dictionary attack (DA) logic and
> it will then refuse to do certain key-related operations until the DA
> logic has timed out.

How does real hardware deal with that situation? Shouldn't this
"shutdown"/reset logic be implemented on swtpm side instead, when
CMD_INIT is received? (when the VM is restarted)

>
> Regards,
>   Stefan
>
> Stefan Berger (2):
>   backends/tpm: Record the last command sent to the TPM
>   backends/tpm: Send TPM2_Shutdown upon VM reset
>
>  backends/tpm/tpm_emulator.c | 44 +++++++++++++++++++++++++++++++++++++
>  backends/tpm/tpm_int.h      |  3 +++
>  backends/tpm/tpm_util.c     |  9 ++++++++
>  backends/tpm/trace-events   |  1 +
>  include/sysemu/tpm_util.h   |  3 +++
>  5 files changed, 60 insertions(+)
>
> --
> 2.35.3
>