From: AKASHI Takahiro takahiro.akashi@linaro.org
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 --- arch/arm64/Kconfig | 24 ++++++++++++++++++++++++ arch/arm64/kernel/kexec_image.c | 23 ++++++++++++++++++----- 2 files changed, 42 insertions(+), 5 deletions(-)
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..1ad1d5f8f024 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> @@ -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 };