linux-kernel - Carrying over the ima log during kexec_file

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Message-ID: <CAEFn8q+rT2_0TFb0fKA6ixOvC3H5R5KpR0zFiTOXa_4U-9HeUw@mail.gmail.com>
Date:   Fri, 10 May 2019 17:16:16 -0700
From:   prakhar srivastava <prsriva02@...il.com>
To:     linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, kexec@...ts.infradead.org
Cc:     jmorris@...ei.org, Mimi Zohar <zohar@...ux.ibm.com>,
        dyoung@...hat.com, bhe@...hat.com, vgoyal@...hat.com
Subject: Carrying over the ima log during kexec_file_load

Hi,

I am currently looking at carrying over the ima log from the current
kernel to the next kernel during soft reboot(kexec_file_load) for arm64
and x86_64.
During soft reboot(kexec_file_load) TPM boot PCR’s(PCRs 0 through 7)
are not reset or extended and thus the boot aggregate does not change,
leaving the new kernel with a sense of secure boot.
During kexec_file_load the kernel file signature is validated through PE
file signature validation.
The boot cmdline args will also be measured with
“kexec cmdline buffer measure” change which is in progress.
https://lkml.org/lkml/2019/5/10/728

Looking at the powerpc implementation of kexec_file_load,  making
change to the kimage_arch as below seems most reasonable.

Struct kimage_arch {
                …
                ima_log_buffer
                ima_log_buffer_size
};

Add respective entries in dtb/fdt and read the same in the next kernel.
No changes to the purgatory should be needed since no kernel segments
are changed.

Is anyone already looking at this?
If not, I want to understand what’s the best approach for this is?

Thanks,
Prakhar Srivastava