Re: [PATCH 1/2] kexec, KEYS: make the code in bzImage64_verify_sig public

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Hi Dave,

On Thu, Sep 30, 2021 at 08:49:02PM +0800, Dave Young wrote:
Hi Coiby,
On 09/27/21 at 08:50am, Coiby Xu wrote:
From: Coiby Xu <coxu@xxxxxxxxxx>

The code in bzImage64_verify_sig could make use of system keyrings including
.buitin_trusted_keys, .secondary_trusted_keys and .platform keyring to verify
signed kernel image as PE file. Move it to a public function.

Signed-off-by: Coiby Xu <coiby.xu@xxxxxxxxx>
---
 arch/x86/kernel/kexec-bzimage64.c | 13 +------------
 include/linux/kexec.h             |  3 +++
 kernel/kexec_file.c               | 15 +++++++++++++++
 3 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index 170d0fd68b1f..4136dd3be5a9 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -17,7 +17,6 @@
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/efi.h>
-#include <linux/verification.h>

 #include <asm/bootparam.h>
 #include <asm/setup.h>
@@ -531,17 +530,7 @@ static int bzImage64_cleanup(void *loader_data)
 #ifdef CONFIG_KEXEC_BZIMAGE_VERIFY_SIG
 static int bzImage64_verify_sig(const char *kernel, unsigned long kernel_len)
 {
-	int ret;
-
-	ret = verify_pefile_signature(kernel, kernel_len,
-				      VERIFY_USE_SECONDARY_KEYRING,
-				      VERIFYING_KEXEC_PE_SIGNATURE);
-	if (ret == -ENOKEY && IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING)) {
-		ret = verify_pefile_signature(kernel, kernel_len,
-					      VERIFY_USE_PLATFORM_KEYRING,
-					      VERIFYING_KEXEC_PE_SIGNATURE);
-	}
-	return ret;
+	return arch_kexec_kernel_verify_pe_sig(kernel, kernel_len);
 }
 #endif

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 0c994ae37729..d45f32336dbe 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -19,6 +19,7 @@
 #include <asm/io.h>

 #include <uapi/linux/kexec.h>
+#include <linux/verification.h>

 #ifdef CONFIG_KEXEC_CORE
 #include <linux/list.h>
@@ -199,6 +200,8 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image);
 #ifdef CONFIG_KEXEC_SIG
 int arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
 				 unsigned long buf_len);
+int arch_kexec_kernel_verify_pe_sig(const char *kernel,
+				    unsigned long kernel_len);
 #endif
 int arch_kexec_locate_mem_hole(struct kexec_buf *kbuf);

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 33400ff051a8..85ed6984ad8f 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -106,6 +106,21 @@ int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
 {
 	return kexec_image_verify_sig_default(image, buf, buf_len);
 }
+
+int arch_kexec_kernel_verify_pe_sig(const char *kernel, unsigned long kernel_len)
+{
+	int ret;
+
+	ret = verify_pefile_signature(kernel, kernel_len,
+				      VERIFY_USE_SECONDARY_KEYRING,
+				      VERIFYING_KEXEC_PE_SIGNATURE);
+	if (ret == -ENOKEY && IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING)) {
+		ret = verify_pefile_signature(kernel, kernel_len,
+					      VERIFY_USE_PLATFORM_KEYRING,
+					      VERIFYING_KEXEC_PE_SIGNATURE);
+	}
+	return ret;
+}

Since the function is moved as generic code, the kconfig option
CONFIG_KEXEC_BZIMAGE_VERIFY_SIG can be removed.


Instead a CONFIG_KEXEC_PEFILE_VERIFY_SIG can be added so that it does
not need to be compiled for only platform which support UEFI pefile
signature verification.  And the related arch kexec_file kconfig can
just select it.


Thanks for the suggestion! I notice KEXEC_BZIMAGE_VERIFY_SIG depends on SIGNED_PE_FILE_VERIFICATION and selects SYSTEM_TRUSTED_KEYRING. So maybe SIGNED_PE_FILE_VERIFICATION could do the job of CONFIG_KEXEC_PEFILE_VERIFY_SIG. And arch/arm64/Kconfig also have KEXEC_IMAGE_VERIFY_SIG. So maybe it's better we don't keep
CONFIG_KEXEC_BZIMAGE_VERIFY_SIG.


Coiby, can you try above?

 #endif

 /*
--
2.33.0


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Thanks
Dave


--
Best regards,
Coiby

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