From: AKASHI Takahiro <takahiro.akashi@linaro.org>
To: catalin.marinas@arm.com, will.deacon@arm.com,
bauerman@linux.vnet.ibm.com, dhowells@redhat.com,
vgoyal@redhat.com, herbert@gondor.apana.org.au,
davem@davemloft.net, akpm@linux-foundation.org,
mpe@ellerman.id.au, dyoung@redhat.com, bhe@redhat.com,
arnd@arndb.de, ard.biesheuvel@linaro.org, julien.thierry@arm.com
Cc: kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
AKASHI Takahiro <takahiro.akashi@linaro.org>
Subject: [PATCH v7 11/11] arm64: kexec_file: enable KEXEC_VERIFY_SIG for Image
Date: Mon, 4 Dec 2017 11:58:01 +0900 [thread overview]
Message-ID: <20171204025801.12161-12-takahiro.akashi@linaro.org> (raw)
In-Reply-To: <20171204025801.12161-1-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>
---
arch/arm64/Kconfig | 10 ++++++++++
arch/arm64/include/asm/kexec.h | 16 ++++++++++++++++
arch/arm64/kernel/kexec_image.c | 15 +++++++++++++++
3 files changed, 41 insertions(+)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index c0b021736c10..289c7bede593 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -814,6 +814,16 @@ config KEXEC_FILE_IMAGE_FMT
---help---
Select this option to enable 'Image' kernel loading.
+config KEXEC_VERIFY_SIG
+ bool "Verify kernel signature during kexec_file_load() syscall"
+ depends on KEXEC_FILE
+ select SYSTEM_DATA_VERIFICATION
+ select SIGNED_PE_FILE_VERIFICATION if KEXEC_FILE_IMAGE_FMT
+ ---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.
+
config CRASH_DUMP
bool "Build kdump crash kernel"
help
diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index b6469bc64a89..2a63bf5f32ea 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -131,6 +131,7 @@ struct arm64_image_header {
};
static const u8 arm64_image_magic[4] = {'A', 'R', 'M', 0x64U};
+static const u8 arm64_image_pe_sig[2] = {'M', 'Z'};
/**
* arm64_header_check_magic - Helper to check the arm64 image header.
@@ -152,6 +153,21 @@ static inline int arm64_header_check_magic(const struct arm64_image_header *h)
&& h->magic[3] == arm64_image_magic[3]);
}
+/**
+ * arm64_header_check_pe_sig - Helper to check the arm64 image header.
+ *
+ * Returns non-zero if 'MZ' signature is found.
+ */
+
+static inline int arm64_header_check_pe_sig(const struct arm64_image_header *h)
+{
+ if (!h)
+ return 0;
+
+ return (h->pe_sig[0] == arm64_image_pe_sig[0]
+ && h->pe_sig[1] == arm64_image_pe_sig[1]);
+}
+
extern const struct kexec_file_ops kexec_image_ops;
struct kimage;
diff --git a/arch/arm64/kernel/kexec_image.c b/arch/arm64/kernel/kexec_image.c
index 1c106237901d..b840b6ed6ed9 100644
--- a/arch/arm64/kernel/kexec_image.c
+++ b/arch/arm64/kernel/kexec_image.c
@@ -15,6 +15,7 @@
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/kexec.h>
+#include <linux/verification.h>
#include <asm/byteorder.h>
#include <asm/memory.h>
@@ -27,6 +28,9 @@ static int image_probe(const char *kernel_buf, unsigned long kernel_len)
if ((kernel_len < sizeof(*h)) || !arm64_header_check_magic(h))
return -EINVAL;
+ pr_debug("PE format: %s\n",
+ (arm64_header_check_pe_sig(h) ? "yes" : "no"));
+
return 0;
}
@@ -84,7 +88,18 @@ static void *image_load(struct kimage *image, char *kernel,
return ERR_PTR(ret);
}
+#ifdef CONFIG_KEXEC_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_VERIFY_SIG
+ .verify_sig = image_verify_sig,
+#endif
};
--
2.14.1
next prev parent reply other threads:[~2017-12-04 2:56 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-04 2:57 [PATCH v7 00/11] arm64: kexec: add kexec_file_load() support AKASHI Takahiro
2017-12-04 2:57 ` [PATCH v7 01/11] resource: add walk_system_ram_res_rev() AKASHI Takahiro
2017-12-04 2:57 ` [PATCH v7 02/11] kexec_file: factor out arch_kexec_kernel_*() from x86, powerpc AKASHI Takahiro
2017-12-04 2:57 ` [PATCH v7 03/11] kexec_file: factor out crashdump elf header function from x86 AKASHI Takahiro
2018-02-07 18:37 ` James Morse
2018-02-09 12:23 ` AKASHI Takahiro
2017-12-04 2:57 ` [PATCH v7 04/11] asm-generic: add kexec_file_load system call to unistd.h AKASHI Takahiro
2017-12-04 2:57 ` [PATCH v7 05/11] arm64: kexec_file: create purgatory AKASHI Takahiro
2018-02-07 18:37 ` James Morse
2018-02-09 12:40 ` AKASHI Takahiro
2017-12-04 2:57 ` [PATCH v7 06/11] arm64: kexec_file: load initrd, device-tree and purgatory segments AKASHI Takahiro
2017-12-04 2:57 ` [PATCH v7 07/11] arm64: kexec_file: set up for crash dump adding elf core header AKASHI Takahiro
2017-12-04 2:57 ` [PATCH v7 08/11] arm64: kexec_file: enable KEXEC_FILE config AKASHI Takahiro
2017-12-04 2:57 ` [PATCH v7 09/11] arm64: kexec_file: add Image format support AKASHI Takahiro
2017-12-04 2:58 ` [PATCH v7 10/11] include: pe.h: remove message[] from mz header definition AKASHI Takahiro
2017-12-04 2:58 ` AKASHI Takahiro [this message]
2018-02-07 18:37 ` [PATCH v7 00/11] arm64: kexec: add kexec_file_load() support James Morse
2018-02-09 11:49 ` AKASHI Takahiro
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