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arm64: kexec_file: add kernel signature verification support

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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@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
[will: removed useless pr_debug()]
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
AKASHI Takahiro
2018-11-15 14:52:54 +09:00
committed by Will Deacon
parent 702ed5bb75
commit 732b7b93d8
2 changed files with 42 additions and 5 deletions
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23
arch/arm64/kernel/kexec_image.c
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@@ -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>
@@ -20,13 +22,13 @@
static int image_probe(const char *kernel_buf, unsigned long kernel_len)
{
const struct arm64_image_header *h;
const struct arm64_image_header *h =
(const struct arm64_image_header *)(kernel_buf);
h = (const struct arm64_image_header *)(kernel_buf);
if (!h || (kernel_len < sizeof(*h)))
return -EINVAL;
if (!h || (kernel_len < sizeof(*h)) ||
memcmp(&h->magic, ARM64_IMAGE_MAGIC,
sizeof(h->magic)))
if (memcmp(&h->magic, ARM64_IMAGE_MAGIC, sizeof(h->magic)))
return -EINVAL;
return 0;
@@ -107,7 +109,18 @@ static void *image_load(struct kimage *image,
return ERR_PTR(ret);
}
#ifdef CONFIG_KEXEC_IMAGE_VERIFY_SIG
static int image_verify_sig(const char *kernel, unsigned long kernel_len)
{
return verify_pefile_signature(kernel, kernel_len, NULL,
VERIFYING_KEXEC_PE_SIGNATURE);
}
#endif
const struct kexec_file_ops kexec_image_ops = {
.probe = image_probe,
.load = image_load,
#ifdef CONFIG_KEXEC_IMAGE_VERIFY_SIG
.verify_sig = image_verify_sig,
#endif
};