Re: [PATCH v6 0/3] Carry forward IMA measurement log on kexec on ARM64

Mimi Zohar
2020-09-23T20:04:40Z

[Cc'ing Nayna Jain, linuxppc-dev@lists.ozlabs.org]

Hi Lakshmi,

On Tue, 2020-09-08 at 16:08 -0700, Lakshmi Ramasubramanian wrote:
> On kexec file load Integrity Measurement Architecture(IMA) subsystem
> may verify the IMA signature of the kernel and initramfs, and measure
> it. The command line parameters passed to the kernel in the kexec call
> may also be measured by IMA. A remote attestation service can verify
> the measurement through the IMA log and the TPM PCR data. This can be
> achieved only if the IMA measurement log is carried over from
> the current kernel to the next kernel across the kexec call.
> However in the current implementation the IMA measurement logs are not
> carried over on ARM64 platforms. Therefore a remote attestation service
> cannot verify the authenticity of the running kernel on ARM64 platforms
> when the kernel is updated through the kexec system call.
>
> This patch series adds support for carrying forward the IMA measurement
> log on kexec on ARM64. powerpc already supports carrying forward
> the IMA measurement log on kexec.
>
> This series refactors the platform independent code defined for powerpc
> such that it can be reused for ARM64 as well. A chosen node namely
> "linux,ima-kexec-buffer" is added to the DTB for ARM64 to hold
> the address and the size of the memory reserved to carry
> the IMA measurement log.
>
> This patch series has been tested for ARM64 platform using QEMU.
> I would like help from the community for testing this change on powerpc.
> Thanks.

Getting access to and upgrading our group's Power system firmware took
time due to limited employee site access. Confirmed, with these
patches applied, ima-evm-utils still properly verifies carrying the IMA
measurement list across kexec.

I plan on reviewing this patch set shortly.

thanks,

Mimi

>
> This series is based on commit f4d51dffc6c0 ("Linux 5.9-rc4") in
> https://github.com/torvalds/linux "master" branch.
>
> Changelog:
>
> v6:
> - Remove any existing FDT_PROP_IMA_KEXEC_BUFFER property in the device
> tree and also its corresponding memory reservation in the currently
> running kernel.
> - Moved the function remove_ima_buffer() defined for powerpc to IMA
> and renamed the function to ima_remove_kexec_buffer(). Also, moved
> delete_fdt_mem_rsv() from powerpc to IMA.
>
> v5:
> - Merged get_addr_size_cells() and do_get_kexec_buffer() into a single
> function when moving the arch independent code from powerpc to IMA
> - Reverted the change to use FDT functions in powerpc code and added
> back the original code in get_addr_size_cells() and
> do_get_kexec_buffer() for powerpc.
> - Added fdt_add_mem_rsv() for ARM64 to reserve the memory for
> the IMA log buffer during kexec.
> - Fixed the warning reported by kernel test bot for ARM64
> arch_ima_add_kexec_buffer() - moved this function to a new file
> namely arch/arm64/kernel/ima_kexec.c
>
> v4:
> - Submitting the patch series on behalf of the original author
> Prakhar Srivastava <prsriva@linux.microsoft.com>
> - Moved FDT_PROP_IMA_KEXEC_BUFFER ("linux,ima-kexec-buffer") to
> libfdt.h so that it can be shared by multiple platforms.
>
> v3:
> Breakup patches further into separate patches.
> - Refactoring non architecture specific code out of powerpc
> - Update powerpc related code to use fdt functions
> - Update IMA buffer read related code to use of functions
> - Add support to store the memory information of the IMA
> measurement logs to be carried forward.
> - Update the property strings to align with documented nodes
> https://github.com/devicetree-org/dt-schema/pull/46
>
> v2:
> Break patches into separate patches.
> - Powerpc related Refactoring
> - Updating the docuemntation for chosen node
> - Updating arm64 to support IMA buffer pass
>
> v1:
> Refactoring carrying over IMA measuremnet logs over Kexec. This patch
> moves the non-architecture specific code out of powerpc and adds to
> security/ima.(Suggested by Thiago)
> Add Documentation regarding the ima-kexec-buffer node in the chosen
> node documentation
>
> v0:
> Add a layer of abstraction to use the memory reserved by device tree
> for ima buffer pass.
> Add support for ima buffer pass using reserved memory for arm64 kexec.
> Update the arch sepcific code path in kexec file load to store the
> ima buffer in the reserved memory. The same reserved memory is read
> on kexec or cold boot.
>
> Lakshmi Ramasubramanian (3):
> powerpc: Refactor kexec functions to move arch independent code to IMA
> arm64: Store IMA log information in kimage used for kexec
> arm64: Add IMA kexec buffer to DTB
>
> arch/arm64/Kconfig | 1 +
> arch/arm64/include/asm/ima.h | 18 ++++
> arch/arm64/include/asm/kexec.h | 3 +
> arch/arm64/kernel/Makefile | 1 +
> arch/arm64/kernel/ima_kexec.c | 34 ++++++++
> arch/arm64/kernel/machine_kexec_file.c | 18 ++++
> arch/powerpc/include/asm/ima.h | 11 +--
> arch/powerpc/include/asm/kexec.h | 1 -
> arch/powerpc/kexec/file_load.c | 33 +-------
> arch/powerpc/kexec/ima.c | 104 +-----------------------
> include/linux/ima.h | 2 +
> include/linux/kexec.h | 11 +++
> include/linux/libfdt.h | 3 +
> security/integrity/ima/Makefile | 3 +-
> security/integrity/ima/ima.h | 2 +
> security/integrity/ima/ima_fdt.c | 80 ++++++++++++++++++
> security/integrity/ima/ima_kexec.c | 58 +++++++++++++
> security/integrity/ima/ima_kexec_file.c | 51 ++++++++++++
> 18 files changed, 289 insertions(+), 145 deletions(-)
> create mode 100644 arch/arm64/include/asm/ima.h
> create mode 100644 arch/arm64/kernel/ima_kexec.c
> create mode 100644 security/integrity/ima/ima_fdt.c
> create mode 100644 security/integrity/ima/ima_kexec_file.c
>