| Message ID | 20181115055254.2812-16-takahiro.akashi@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: kexec: add kexec_file_load() support | expand |
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@linaro.org> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Reviewed-by: James Morse <james.morse@arm.com> > --- > 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
On Fri, Nov 30, 2018 at 01:21:14PM +0000, Will Deacon wrote: > 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@linaro.org> > > Cc: Catalin Marinas <catalin.marinas@arm.com> > > Cc: Will Deacon <will.deacon@arm.com> > > Reviewed-by: James Morse <james.morse@arm.com> > > --- > > 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. This line comes from kexec-tools' code, but I don't mind removing it. (as lots of lines diverge now from kexec-tools.) -Takahiro Akashi > Will
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"); + return 0; } @@ -107,7 +113,18 @@ 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> Reviewed-by: James Morse <james.morse@arm.com> --- arch/arm64/Kconfig | 24 ++++++++++++++++++++++++ arch/arm64/kernel/kexec_image.c | 17 +++++++++++++++++ 2 files changed, 41 insertions(+)