Subject: Re: [PATCH v2] ima: defer arch_ima_get_secureboot() call to IMA init time

From: Chester Lin <[email-masked]>
Date: Thu, 15 Oct 2020 20:16:38 +0800

On Wed, Oct 14, 2020 at 07:38:50AM -0400, Mimi Zohar wrote:
> On Wed, 2020-10-14 at 17:35 +0800, Chester Lin wrote:
> > Hi Ard & Mimi,
> > 
> > On Tue, Oct 13, 2020 at 06:59:21PM +0200, Ard Biesheuvel wrote:
> > > On Tue, 13 Oct 2020 at 18:46, Mimi Zohar <[email-masked]> wrote:
> > > >
> > > > [Cc'ing [email-masked]]
> > > >
> > > > On Tue, 2020-10-13 at 10:18 +0200, Ard Biesheuvel wrote:
> > > > > Chester reports that it is necessary to introduce a new way to pass
> > > > > the EFI secure boot status between the EFI stub and the core kernel
> > > > > on ARM systems. The usual way of obtaining this information is by
> > > > > checking the SecureBoot and SetupMode EFI variables, but this can
> > > > > only be done after the EFI variable workqueue is created, which
> > > > > occurs in a subsys_initcall(), whereas arch_ima_get_secureboot()
> > > > > is called much earlier by the IMA framework.
> > > > >
> > > > > However, the IMA framework itself is started as a late_initcall,
> > > > > and the only reason the call to arch_ima_get_secureboot() occurs
> > > > > so early is because it happens in the context of a __setup()
> > > > > callback that parses the ima_appraise= command line parameter.
> > > > >
> > > > > So let's refactor this code a little bit, by using a core_param()
> > > > > callback to capture the command line argument, and deferring any
> > > > > reasoning based on its contents to the IMA init routine.
> > > > >
> > > > > Cc: Chester Lin <[email-masked]>
> > > > > Cc: Mimi Zohar <[email-masked]>
> > > > > Cc: Dmitry Kasatkin <[email-masked]>
> > > > > Cc: James Morris <[email-masked]>
> > > > > Cc: "Serge E. Hallyn" <[email-masked]>
> > > > > Link: https://lore.kernel.org/linux-arm-kernel/[email-masked]/
> > > > > Signed-off-by: Ard Biesheuvel <[email-masked]>
> > > > > ---
> > > > > v2: rebase onto series 'integrity: improve user feedback for invalid bootparams'
> > > >
> > > > Thanks, Ard.  Based on my initial, limited testing on Power, it looks
> > > > good, but I'm hesistant to include it in the integrity 5.10 pull
> > > > request without it having been in linux-next and some additional
> > > > testing.  It's now queued in the next-integrity-testing branch awaiting
> > > > some tags.
> > > >
> > 
> > Tested-by: Chester Lin <[email-masked]>
> > 
> > I have tested this patch on x86 VM.
> > 
> > * System configuration:
> >   - Platform: QEMU/KVM
> >   - Firmware: EDK2/OVMF + secure boot enabled.
> >   - OS: SLE15-SP2 + SUSE's kernel-vanilla (=linux v5.9) + the follow commits
> >     from linux-next and upstream:
> >     * [PATCH v2] ima: defer arch_ima_get_secureboot() call to IMA init time
> >       https://www.spinics.net/lists/linux-efi/msg20645.html
> >     * e4d7e2df3a09 "ima: limit secure boot feedback scope for appraise"
> >     * 7fe2bb7e7e5c "integrity: invalid kernel parameters feedback"
> >     * 4afb28ab03d5 "ima: add check for enforced appraise option"
> > 
> > * Logs with UEFI secure boot enabled:
> > 
> >   [    0.000000] Linux version 5.9.0-858-g865c50e1d279-1.g8764d18-vanilla (geeko@b
> >   uildhost) (gcc (SUSE Linux) 10.2.1 20200825 [revision c0746a1beb1ba073c7981eb09f
> >   55b3d993b32e5c], GNU ld (GNU Binutils; openSUSE Tumbleweed) 2.34.0.20200325-1) #
> >   1 SMP Wed Oct 14 04:00:11 UTC 2020 (8764d18)
> >   [    0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.9.0-858-g865c50e1d279-1.
> >   g8764d18-vanilla root=UUID=5304c03e-4d8a-4d67-873a-32a32e57cdeb console=ttyS0,11
> >   5200 resume=/dev/disk/by-path/pci-0000:04:00.0-part4 mitigations=auto ignore_log
> >   level crashkernel=192M,high crashkernel=72M,low ima_appraise=off
> >   [    0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point regi
> >   sters'
> >   [    0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
> >   [    0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
> >   ....
> >   ....
> >   [    1.720309] ima: Secure boot enabled: ignoring ima_appraise=off option
> >   [    1.720314] ima: No TPM chip found, activating TPM-bypass!
> >   [    1.722129] ima: Allocated hash algorithm: sha256
> 
> 
> Thank you for testing the options aren't being set in secure boot mode.
> My main concern, however, is that IMA doesn't go into TPM-bypass mode. 
> Does this system have a TPM?
> 
> Mimi
>

Last time I didn't emulate a TPM device in KVM so that's why the kernel couldn't
find a TPM chip. I have tested this patch again with a virtual TPM 1.2 by
running swtpm and here are some logs:

-----
[    0.000000] Linux version 5.9.0-858-g865c50e1d279-1.g8764d18-vanilla (geeko@b
uildhost) (gcc (SUSE Linux) 10.2.1 20200825 [revision c0746a1beb1ba073c7981eb09f
55b3d993b32e5c], GNU ld (GNU Binutils; openSUSE Tumbleweed) 2.34.0.20200325-1) #
1 SMP Wed Oct 14 04:00:11 UTC 2020 (8764d18)
[    0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.9.0-858-g865c50e1d279-1.
g8764d18-vanilla root=UUID=5304c03e-4d8a-4d67-873a-32a32e57cdeb console=ttyS0,11
5200 resume=/dev/disk/by-path/pci-0000:04:00.0-part4 mitigations=auto ignore_log
level crashkernel=192M,high crashkernel=72M,low ima_appraise=off
[    0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point regi
sters'
.....
.....
[    0.000000] efi: EFI v2.60 by EDK II
[    0.000000] efi: SMBIOS=0x7fe82000 ACPI=0x7feb0000 ACPI 2.0=0x7feb0014 MEMATTT
R=0x7ef89698 RNG=0x7ea12e18
[    0.000000] efi: seeding entropy pool
[    0.000000] random: fast init done
[    0.000000] SMBIOS 2.8 present.
[    0.000000] DMI: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
[    0.000000] Hypervisor detected: KVM
.....
.....
[    1.957625] Linux agpgart interface v0.103
[    1.961903] tpm_tis 00:04: 1.2 TPM (device-id 0x1, rev-id 1)
[    1.966306] tpm tpm0: starting up the TPM manually
[    1.981753] ahci 0000:00:1f.2: version 3.0
[    1.984503] PCI Interrupt Link [GSIA] enabled at IRQ 16
.....
.....
[    2.086645] ima: Secure boot enabled: ignoring ima_appraise=off option
[    2.086650] ima: Allocated hash algorithm: sha256
[    2.100662] evm: Initialising EVM extended attributes:
[    2.100689] audit: type=1807 audit(1602760724.564:2): action=measure func=KEX
EC_KERNEL_CHECK res=1
[    2.101849] evm: security.selinux
[    2.101849] evm: security.apparmor
[    2.101849] evm: security.ima
[    2.101850] evm: security.capability
[    2.101850] evm: HMAC attrs: 0x1
[    2.102083] PM:   Magic number: 8:588:327
[    2.106723] audit: type=1807 audit(1602760724.564:3): action=measure func=MODD
ULE_CHECK res=1
[    2.118761] RAS: Correctable Errors collector initialized.
.....
-----

In terms of TPM 2.0, swtpm seems to have issues while running the selftest so
I verified this patch on my laptop as well because it has a real TPM 2.0 chip:

-----
[    0.000000] microcode: microcode updated early to revision 0xd6, date = 2020-
04-27
[    0.000000] Linux version 5.9.0-858-g865c50e1d279-1.g8764d18-vanilla (geeko@b
uildhost) (gcc (SUSE Linux) 10.2.1 20200825 [revision c0746a1beb1ba073c7981eb09f
55b3d993b32e5c], GNU ld (GNU Binutils; openSUSE Tumbleweed) 2.34.0.20200325-1) #
1 SMP Wed Oct 1404:00:11 UTC 2020 (8764d18)
[    0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.9.0-858-g865c50e1d279-1.
g8764d18-vanilla root=UUID=2184bbb7-780e-48a2-98b8-3a8cd3366e5e splash=silent re
sume=/dev/disk/by-id/ata-INTEL_SSDSCKKF512G8_SATA_512GB_BTLA82850G3E512K-part3 i
gnore_loglevel crashkernel=222M,high crashkernel=72M,low ima_appraise=log
[    0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point regi
sters'
.....
.....
[    0.000000] efi: EFI v2.60 by American Megatrends
[    0.000000] efi: ACPI=0x7a34e000 ACPI 2.0=0x7a34e000 SMBIOS=0xf0000 SMBIOS 3.
0=0xf0020 TPMFinalLog=0x7ac8b000 ESRT=0x7b0e0018 MEMATTR=0x7762d018 RNG=0x7b133f
18 TPMEventLog=0x6ab96018
[    0.000000] efi: seeding entropy pool
[    0.000000] random: fast init done
[    0.000000] SMBIOS 3.1.0 present.
[    0.000000] DMI: Dell Inc. Latitude 7490/0KP0FT, BIOS 1.14.0 01/22/2020
.....
.....
[    7.182711] Non-volatile memory driver v1.3
[    7.182748] Linux agpgart interface v0.103
[    7.210826] tpm_tis MSFT0101:00: 2.0 TPM (device-id 0xFC, rev-id 1)
[    7.234324] ahci 0000:00:17.0: version 3.0
.....
.....
[    7.288573] integrity: Loading X.509 certificate: UEFI:MokListRT
[    7.289299] integrity: Loaded X.509 cert 'openSUSE Secure Boot CA: 6842600de22c4c477e95be23dfea9513e5971762'
[    7.289913] ima: Secure boot enabled: ignoring ima_appraise=log option
[    7.289921] ima: Allocated hash algorithm: sha256
[    7.314854] evm: Initialising EVM extended attributes:
[    7.314878] audit: type=1807 audit(1602778176.572:2): action=measure func=KEXEC_KERNEL_CHECK res=1
[    7.316656] evm: security.selinux
[    7.316659] evm: security.apparmor
[    7.318493] audit: type=1807 audit(1602778176.572:3): action=measure func=MODULE_CHECK res=1
[    7.320092] evm: security.ima
[    7.320093] evm: security.capability
[    7.322554] evm: HMAC attrs: 0x1