On Fri, 2025-07-11 at 09:23 +0800, Ge Yang wrote:
在 2025/7/11 5:58, James Bottomley 写道:
[...]
I think someone has misread the spec. EV_NO_ACTION events produce no PCR extension. So the PCR value zero is conventional (and required by the TCG) since nothing gets logged. Therefore even if you're technically using PCR0 for something else EV_NO_ACTION events should still have the conventional PCR = 0 value to conform to the TCG spec. I assume it's too late to correct this in the implementation?
According to Table 14 in Section 10.4.1 of the TCG PC Client Specification, for EV_NO_ACTION events, the PCR (Platform Configuration Register) value can be 0 or other values, such as 6.
Link: https://trustedcomputinggroup.org/wp-content/uploads/TCG_PCClient_PFP_r1p05_...
You're selectively quoting one part of the spec out of context. Section 10.4.5 (which is the normative one about EV_NO_ACTION events) says:
1. All EV_NO_ACTION events SHALL set TCG_PCR_EVENT2.pcrIndex = 0, unless otherwise specified.
And the only update to this is in 10.4.5.4 where it says a vendor specific EV_NO_ACTION event may set pcrIndex to 6. Since the log header is not vendor specific, it must have pcr = 0.
Regards,
James