Messages in this thread | | | Subject | Re: [PATCH] ima: remove ACPI dependency | From | Eric Paris <> | Date | Tue, 27 Oct 2009 16:56:50 -0400 |
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On Tue, 2009-10-27 at 16:42 -0400, David Safford wrote: > On Tue, 2009-10-27 at 12:36 -0400, Eric Paris wrote: > > On Tue, 2009-10-27 at 11:59 -0400, David Safford wrote: > > > Basically, if running on a system with a TPM, IMA wants the TPM > > > boot measurement log, which the TPM driver can only get through > > > ACPI. If the platform does not have a TPM, then IMA does not > > > need ACPI. > > > > I'm afraid I'm not seeing the connection. Where does IMA gets the boot > > measurement log? I see that the TPM exports that log in securityfs as 2 > > files (ascii and binary) in tpm_bios.c but I don't see how IMA ever > > makes use of that log either internally to the kernel or through the > > securityfs files. > > > sorry - bad explanation. IMA reads PCR 0-7, and combines them into > a single "boot_aggregate" as the first entry in the IMA list. For full > attestation, a user level program needs access to both IMA's > boot aggregate, and to the detailed TPM event log upon which > the aggregate is based. So IMA does not itself access the logs, > but the boot aggregate is less useful without them.
So users of IMA in userspace may want TPM. Shouldn't the kernel really have this as a depends/select in the TPM code? This isn't IMA specific, it's TPM specific. Obviously I'm not a fan of the spurious ACPI requirement in the IMA code. How about a 'CONFIG_TPM_BIOS_LOG' or something which selects ACPI? We'll see what Rajiv thinks.
> As a separate issue, IMA requires the TPM driver to be compiled in > (not loaded as a module) so it is available at IMA initialization, and > the driver apparently requires ACPI in this case. I believe Rajiv > will comment more on this.
I know it's required to be built in. Didn't know that required ACPI, but if so, that's a good reason to push this to the TPM code and get it out of the IMA code....
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