On Wed, 2018-03-07 at 15:12 -0600, Jiandi An wrote: > > On 03/07/2018 01:41 PM, James Bottomley wrote: > > > > On Wed, 2018-03-07 at 14:21 -0500, Mimi Zohar wrote: > > > > > > On Wed, 2018-03-07 at 11:08 -0800, James Bottomley wrote: > > > > > > > > > > > > On Wed, 2018-03-07 at 13:55 -0500, Mimi Zohar wrote: > > > > > > > > > > > > > > > On Wed, 2018-03-07 at 11:51 -0700, Jason Gunthorpe wrote: > > > > > > > > > > > > > > > > > > > > > > > > On Tue, Mar 06, 2018 at 11:26:26PM -0600, Jiandi An wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > TPM_CRB driver is the TPM support for ARM64. If it > > > > > > > is built as module, TPM chip is registered after IMA > > > > > > > init. tpm_pcr_read() in IMA driver would fail and > > > > > > > display the following message even though eventually > > > > > > > there is TPM chip on the system: > > > > > > > > > > > > > > ima: No TPM chip found, activating TPM-bypass! (rc=-19) > > > > > > > > > > > > > > Fix IMA Kconfig to select TPM_CRB so TPM_CRB driver is > > > > > > > built in kernel and initializes before IMA driver. > > > > > > > > > > > > > > Signed-off-by: Jiandi An <anjiandi@xxxxxxxxxxxxxx> > > > > > > > security/integrity/ima/Kconfig | 1 + > > > > > > > 1 file changed, 1 insertion(+) > > > > > > > > > > > > > > diff --git a/security/integrity/ima/Kconfig > > > > > > > b/security/integrity/ima/Kconfig > > > > > > > index 35ef693..6a8f677 100644 > > > > > > > +++ b/security/integrity/ima/Kconfig > > > > > > > @@ -10,6 +10,7 @@ config IMA > > > > > > > select CRYPTO_HASH_INFO > > > > > > > select TCG_TPM if HAS_IOMEM && !UML > > > > > > > select TCG_TIS if TCG_TPM && X86 > > > > > > > > Well, this explains why IMA doesn't work on one of my X86 > > > > systems: it's got a non i2c infineon TPM. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > + select TCG_CRB if TCG_TPM && ACPI > > > > > > > select TCG_IBMVTPM if TCG_TPM && PPC_PSERIES > > > > > > > help > > > > > > > The Trusted Computing Group(TCG) runtime > > > > > > > Integrity > > > > > > > > > > > > This seems really weird, why are any specific TPM drivers > > > > > > linked to IMA config, we have lots of drivers.. > > > > > > > > > > > > I don't think I've ever seen this pattern in Kconfig > > > > > > before? > > > > > > > > > > As you've seen by the current discussions, the TPM driver > > > > > needs to be initialized prior to IMA. Otherwise IMA goes > > > > > into TPM-bypass mode. That implies that the TPM must be > > > > > builtin to the kernel, and not as a kernel module. > > > > > > > > Actually, that's not necessarily true: If we don't begin > > > > appraisal until after the initrd phase, then the initrd can > > > > load TPM modules before IMA starts. > > > > > > > > This would involve a bit of code rejigging to not require a TPM > > > > until IMA wants to write its first measurement, but it looks > > > > doable and would get us out of having to second guess TPM > > > > selections. > > > > > > The question is about measurement, not appraisal. Although the > > > initramfs might be measured, the initramfs can access files on > > > the real root filesystem. Those files need to be measured, > > > before they are used/accessed. > > > > Isn't it a question of threat model? Because the initrd is > > measured, you know it's the one you specified and you should know > > its security properties, so measurement doesn't really need to > > begin until the root pivots. At that point you pick up the boot > > aggregate so the log now is tied to the initrd measurement. > > Conversely, I can't really see a threat model where you could > > trick a correctly measured initrd into subverting IMA, especially > > because listening network daemons aren't usually active at this > > stage. > > > > I'm not saying there isn't a use case for wanting your TPM built > > in, I'm just saying I don't think it needs to be required for > > everyone who uses IMA. > > > > James > > > > ima_init() first calls tpm_pcr_read() which tries to use underlying > registered TPM chip driver and send read PCR TPM command to the TPM > chip. If IMA driver is enabled and ima_init() happens, we see this. > > In security/integrity/ima/ima_main.c, init_ima() is in late_initcall. > And it calls ima_init(). > > late_initcall(init_ima); /* Start IMA after the TPM is available */ > > So as long as init_ima() is called, need to at least enable the > TPM driver for the platform right? Well, that's not really relevant: I said "This would involve a bit of code rejigging to not require a TPM until IMA wants to write its first measurement, but it looks doable" James > I'm just following current IMA Kconfig where it's selecting different > underlying TPM chip drivers for various platforms respectively when > CONFIG_IMA is set to Y because IMA driver init calls tpm_pcr_read() > which needs to use TPM. >
