| Message ID | 20180724065759.19186-16-takahiro.akashi@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | arm64: kexec: add kexec_file_load() support | expand |
Hi Akashi, On 24/07/18 07:57, 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 Reviewed-by: James Morse <james.morse@arm.com> > diff --git a/arch/arm64/kernel/kexec_image.c b/arch/arm64/kernel/kexec_image.c > index d64f5e9f9d22..578d358632d0 100644 > --- a/arch/arm64/kernel/kexec_image.c > +++ b/arch/arm64/kernel/kexec_image.c > @@ -102,7 +106,18 @@ 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 This is identical to x86's PE image verification helper. We can clean this up later by providing some kexec_image_verify_pe() in the core kexec_file code. Its not worth doing now. > 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 > }; Thanks, James
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index a9a3a5583c8b..1445eb2fc833 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -844,6 +844,30 @@ 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 d64f5e9f9d22..578d358632d0 100644 --- a/arch/arm64/kernel/kexec_image.c +++ b/arch/arm64/kernel/kexec_image.c @@ -13,6 +13,7 @@ #include <linux/kernel.h> #include <linux/kexec.h> #include <linux/string.h> +#include <linux/verification.h> #include <asm/boot.h> #include <asm/byteorder.h> #include <asm/cpufeature.h> @@ -28,6 +29,9 @@ static int image_probe(const char *kernel_buf, unsigned long kernel_len) memcmp(&h->magic, ARM64_MAGIC, sizeof(h->magic))) return -EINVAL; + pr_debug("PE format: %s\n", + memcmp(&h->mz_magic, "MZ", 2) ? "no" : "yes"); + return 0; } @@ -102,7 +106,18 @@ 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 };
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> --- arch/arm64/Kconfig | 24 ++++++++++++++++++++++++ arch/arm64/kernel/kexec_image.c | 15 +++++++++++++++ 2 files changed, 39 insertions(+) -- 2.18.0