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

[Mimi Zohar]

[Cc'ing Nayna Jain, linuxppc-dev@xxxxxxxxxxxxxxxx]

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@xxxxxxxxxxxxxxxxxxx>
>   - 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
>