On Thu, Nov 15, 2018 at 02:52:54PM +0900, AKASHI Takahiro wrote:
> With this patch, kernel verification can be done without IMA security
> subsystem enabled. Turn on CONFIG_KEXEC_VERIFY_SIG instead.
>
> On x86, a signature is embedded into a PE file (Microsoft's format) header
> of binary. Since arm64's "Image" can also be seen as a PE file as far as
> CONFIG_EFI is enabled, we adopt this format for kernel signing.
>
> You can create a signed kernel image with:
> $ sbsign --key ${KEY} --cert ${CERT} Image
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> Reviewed-by: James Morse <james.morse@xxxxxxx>
> ---
> arch/arm64/Kconfig | 24 ++++++++++++++++++++++++
> arch/arm64/kernel/kexec_image.c | 17 +++++++++++++++++
> 2 files changed, 41 insertions(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 93dc4d36d6db..11f3e1a00588 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -867,6 +867,30 @@ config KEXEC_FILE
> for kernel and initramfs as opposed to list of segments as
> accepted by previous system call.
>
> +config KEXEC_VERIFY_SIG
> + bool "Verify kernel signature during kexec_file_load() syscall"
> + depends on KEXEC_FILE
> + help
> + Select this option to verify a signature with loaded kernel
> + image. If configured, any attempt of loading a image without
> + valid signature will fail.
> +
> + In addition to that option, you need to enable signature
> + verification for the corresponding kernel image type being
> + loaded in order for this to work.
> +
> +config KEXEC_IMAGE_VERIFY_SIG
> + bool "Enable Image signature verification support"
> + default y
> + depends on KEXEC_VERIFY_SIG
> + depends on EFI && SIGNED_PE_FILE_VERIFICATION
> + help
> + Enable Image signature verification support.
> +
> +comment "Support for PE file signature verification disabled"
> + depends on KEXEC_VERIFY_SIG
> + depends on !EFI || !SIGNED_PE_FILE_VERIFICATION
> +
> config CRASH_DUMP
> bool "Build kdump crash kernel"
> help
> diff --git a/arch/arm64/kernel/kexec_image.c b/arch/arm64/kernel/kexec_image.c
> index 9f0d8b5d62d3..d1c6c54c22e3 100644
> --- a/arch/arm64/kernel/kexec_image.c
> +++ b/arch/arm64/kernel/kexec_image.c
> @@ -12,7 +12,9 @@
> #include <linux/errno.h>
> #include <linux/kernel.h>
> #include <linux/kexec.h>
> +#include <linux/pe.h>
> #include <linux/string.h>
> +#include <linux/verification.h>
> #include <asm/byteorder.h>
> #include <asm/cpufeature.h>
> #include <asm/image.h>
> @@ -29,6 +31,10 @@ static int image_probe(const char *kernel_buf, unsigned long kernel_len)
> sizeof(h->magic)))
> return -EINVAL;
>
> + pr_debug("PE format: %s\n",
> + memcmp(&((struct mz_hdr *)h)->magic, "MZ", 2) ?
> + "no" : "yes");
>
Is this hunk really necessary? I'd prefer not to commit pr_debug()
invocations.
Will
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