On Thu, 2024-11-07 at 01:22 +0200, Jarkko Sakkinen wrote: > On Thu Nov 7, 2024 at 12:52 AM EET, James Bottomley wrote: > > > > I'm a bit confused here. It's TPM2_PCR_Extend we have the trouble with > > (as Mimi says in her email that you quoted) not TPM2_GetRandom. > > > > The random number generator reseed occurs in a kernel thread that fires > > about once a minute, so it doesn't show up in really any of the boot > > timings. Plus even with sessions added, what there now isn't a > > significant overhead even to the running kernel given it's asynchronous > > and called infrequently. > > Ah, right then we need the boot flag, and my earlier comments to the > parameter apply. I've never used IMA so I don't actually even know in > detail how it is using TPM. Huh? A simple explanation is that IMA-measurement maintains a measurement list, similar to the pre-boot event log. Each IMA-measurement record extends the TPM PCR (default PCR 10). Assuming IMA is enabled in the kernel, then just add "ima_policy=tcb" or "ima_policy=critical_data" on the boot command line. To view the measurement records, cat <securityfs>/integrity/ima/ascii_runtime_measurements. Normally the IMA policy specified on the boot command line is replaced with a finer grained custom policy. Mimi
