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    SubjectRe: [PATCH v3] IMA: Measure kernel version in early boot
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    On Mon, 2021-01-25 at 16:50 -0800, Raphael Gianotti wrote:
    > The integrity of a kernel can be verified by the boot loader on cold
    > boot, and during kexec, by the current running kernel, before it is
    > loaded. However, it is still possible that the new kernel being
    > loaded is older than the current kernel, and/or has known
    > vulnerabilities. Therefore, it is imperative that an attestation
    > service be able to verify the version of the kernel being loaded on
    > the client, from cold boot and subsequent kexec system calls,
    > ensuring that only kernels with versions known to be good are loaded.
    >
    > Measure the kernel version using ima_measure_critical_data() early on
    > in the boot sequence, reducing the chances of known kernel
    > vulnerabilities being exploited. With IMA being part of the kernel,
    > this overall approach makes the measurement itself more trustworthy.
    >
    > To enable measuring the kernel version "ima_policy=critical_data"
    > needs to be added to the kernel command line arguments.
    > For example,
    > BOOT_IMAGE=/boot/vmlinuz-5.11.0-rc3+ root=UUID=fd643309-a5d2-4ed3-b10d-3c579a5fab2f ro nomodeset ima_policy=critical_data
    >
    > If runtime measurement of the kernel version is ever needed, the
    > following should be added to /etc/ima/ima-policy:
    >
    > measure func=CRITICAL_DATA label=kernel_info
    >
    > To extract the measured data after boot, the following command can be used:
    >
    > grep -m 1 "kernel_version" \
    > /sys/kernel/security/integrity/ima/ascii_runtime_measurements
    >
    > Sample output from the command above:
    >
    > 10 a8297d408e9d5155728b619761d0dd4cedf5ef5f ima-buf
    > sha256:5660e19945be0119bc19cbbf8d9c33a09935ab5d30dad48aa11f879c67d70988
    > kernel_version 352e31312e302d7263332d31363138372d676564623634666537383234342d6469727479
    >
    > The above corresponds to the following (decoded) version string:

    Instead of the above, the following is clearer.

    The above hex-ascii string corresponds to the kernel version
    (e.g. xxd -r -p):
    >
    > 5.11.0-rc3-16187-gedb64fe78244-dirty

    >
    > Signed-off-by: Raphael Gianotti <raphgi@linux.microsoft.com>

    Assuming the above or similar change,

    Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

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