kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE

This is a preparatory patch for kexec_file_load() lockdown.  A locked down
kernel needs to prevent unsigned kernel images from being loaded with
kexec_file_load().  Currently, the only way to force the signature
verification is compiling with KEXEC_VERIFY_SIG.  This prevents loading
usigned images even when the kernel is not locked down at runtime.

This patch splits KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE.
Analogous to the MODULE_SIG and MODULE_SIG_FORCE for modules, KEXEC_SIG
turns on the signature verification but allows unsigned images to be
loaded.  KEXEC_SIG_FORCE disallows images without a valid signature.

Signed-off-by: Jiri Bohac <jbohac@suse.cz>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
cc: kexec@lists.infradead.org
Signed-off-by: James Morris <jmorris@namei.org>

10 files changed, 30 insertions, 20 deletions

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 697ea0510729..f940500a941b 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -961,7 +961,7 @@ config KEXEC_FILE
 	  for kernel and initramfs as opposed to list of segments as
 	  accepted by previous system call.
 
-config KEXEC_VERIFY_SIG
+config KEXEC_SIG
 	bool "Verify kernel signature during kexec_file_load() syscall"
 	depends on KEXEC_FILE
 	help
@@ -976,13 +976,13 @@ config KEXEC_VERIFY_SIG
 config KEXEC_IMAGE_VERIFY_SIG
 	bool "Enable Image signature verification support"
 	default y
-	depends on KEXEC_VERIFY_SIG
+	depends on KEXEC_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 KEXEC_SIG
 	depends on !EFI || !SIGNED_PE_FILE_VERIFICATION
 
 config CRASH_DUMP
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 109243fdb6ec..c4a423f30d49 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -555,7 +555,7 @@ config ARCH_HAS_KEXEC_PURGATORY
 	def_bool y
 	depends on KEXEC_FILE
 
-config KEXEC_VERIFY_SIG
+config KEXEC_SIG
 	bool "Verify kernel signature during kexec_file_load() syscall"
 	depends on KEXEC_FILE && SYSTEM_DATA_VERIFICATION
 	help
diff --git a/arch/s390/configs/debug_defconfig b/arch/s390/configs/debug_defconfig
index b0920b35f87b..525e0a6addb9 100644
--- a/arch/s390/configs/debug_defconfig
+++ b/arch/s390/configs/debug_defconfig
@@ -64,7 +64,7 @@ CONFIG_NUMA=y
 CONFIG_PREEMPT=y
 CONFIG_HZ_100=y
 CONFIG_KEXEC_FILE=y
-CONFIG_KEXEC_VERIFY_SIG=y
+CONFIG_KEXEC_SIG=y
 CONFIG_EXPOLINE=y
 CONFIG_EXPOLINE_AUTO=y
 CONFIG_MEMORY_HOTPLUG=y
diff --git a/arch/s390/configs/defconfig b/arch/s390/configs/defconfig
index c59b922cb6c5..4c37279acdb4 100644
--- a/arch/s390/configs/defconfig
+++ b/arch/s390/configs/defconfig
@@ -39,7 +39,7 @@ CONFIG_NR_CPUS=256
 CONFIG_NUMA=y
 CONFIG_HZ_100=y
 CONFIG_KEXEC_FILE=y
-CONFIG_KEXEC_VERIFY_SIG=y
+CONFIG_KEXEC_SIG=y
 CONFIG_CRASH_DUMP=y
 CONFIG_HIBERNATION=y
 CONFIG_PM_DEBUG=y
diff --git a/arch/s390/configs/performance_defconfig b/arch/s390/configs/performance_defconfig
index 09aa5cb14873..158ad0f0d433 100644
--- a/arch/s390/configs/performance_defconfig
+++ b/arch/s390/configs/performance_defconfig
@@ -65,7 +65,7 @@ CONFIG_NR_CPUS=512
 CONFIG_NUMA=y
 CONFIG_HZ_100=y
 CONFIG_KEXEC_FILE=y
-CONFIG_KEXEC_VERIFY_SIG=y
+CONFIG_KEXEC_SIG=y
 CONFIG_EXPOLINE=y
 CONFIG_EXPOLINE_AUTO=y
 CONFIG_MEMORY_HOTPLUG=y
diff --git a/arch/s390/kernel/kexec_elf.c b/arch/s390/kernel/kexec_elf.c
index 6d0635ceddd0..9b4f37a4edf1 100644
--- a/arch/s390/kernel/kexec_elf.c
+++ b/arch/s390/kernel/kexec_elf.c
@@ -130,7 +130,7 @@ static int s390_elf_probe(const char *buf, unsigned long len)
 const struct kexec_file_ops s390_kexec_elf_ops = {
 	.probe = s390_elf_probe,
 	.load = s390_elf_load,
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC__SIG
 	.verify_sig = s390_verify_sig,
-#endif /* CONFIG_KEXEC_VERIFY_SIG */
+#endif /* CONFIG_KEXEC_SIG */
 };
diff --git a/arch/s390/kernel/kexec_image.c b/arch/s390/kernel/kexec_image.c
index 58318bf89fd9..af23eff5774d 100644
--- a/arch/s390/kernel/kexec_image.c
+++ b/arch/s390/kernel/kexec_image.c
@@ -59,7 +59,7 @@ static int s390_image_probe(const char *buf, unsigned long len)
 const struct kexec_file_ops s390_kexec_image_ops = {
 	.probe = s390_image_probe,
 	.load = s390_image_load,
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
 	.verify_sig = s390_verify_sig,
-#endif /* CONFIG_KEXEC_VERIFY_SIG */
+#endif /* CONFIG_KEXEC_SIG */
 };
diff --git a/arch/s390/kernel/machine_kexec_file.c b/arch/s390/kernel/machine_kexec_file.c
index fbdd3ea73667..c0f33ba49a9a 100644
--- a/arch/s390/kernel/machine_kexec_file.c
+++ b/arch/s390/kernel/machine_kexec_file.c
@@ -22,7 +22,7 @@ const struct kexec_file_ops * const kexec_file_loaders[] = {
 	NULL,
 };
 
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
 /*
  * Module signature information block.
  *
@@ -90,7 +90,7 @@ int s390_verify_sig(const char *kernel, unsigned long kernel_len)
 				      VERIFYING_MODULE_SIGNATURE,
 				      NULL, NULL);
 }
-#endif /* CONFIG_KEXEC_VERIFY_SIG */
+#endif /* CONFIG_KEXEC_SIG */
 
 static int kexec_file_update_purgatory(struct kimage *image,
 				       struct s390_load_data *data)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2bbbd4d1ba31..cd41998aa6e6 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2006,20 +2006,30 @@ config KEXEC_FILE
 config ARCH_HAS_KEXEC_PURGATORY
 	def_bool KEXEC_FILE
 
-config KEXEC_VERIFY_SIG
+config KEXEC_SIG
 	bool "Verify kernel signature during kexec_file_load() syscall"
 	depends on KEXEC_FILE
 	---help---
-	  This option makes kernel signature verification mandatory for
-	  the kexec_file_load() syscall.
 
-	  In addition to that option, you need to enable signature
+	  This option makes the kexec_file_load() syscall check for a valid
+	  signature of the kernel image.  The image can still be loaded without
+	  a valid signature unless you also enable KEXEC_SIG_FORCE, though if
+	  there's a signature that we can check, then it must be valid.
+
+	  In addition to this option, you need to enable signature
 	  verification for the corresponding kernel image type being
 	  loaded in order for this to work.
 
+config KEXEC_SIG_FORCE
+	bool "Require a valid signature in kexec_file_load() syscall"
+	depends on KEXEC_SIG
+	---help---
+	  This option makes kernel signature verification mandatory for
+	  the kexec_file_load() syscall.
+
 config KEXEC_BZIMAGE_VERIFY_SIG
 	bool "Enable bzImage signature verification support"
-	depends on KEXEC_VERIFY_SIG
+	depends on KEXEC_SIG
 	depends on SIGNED_PE_FILE_VERIFICATION
 	select SYSTEM_TRUSTED_KEYRING
 	---help---
diff --git a/arch/x86/kernel/ima_arch.c b/arch/x86/kernel/ima_arch.c
index 64b973f0e985..b98890894731 100644
--- a/arch/x86/kernel/ima_arch.c
+++ b/arch/x86/kernel/ima_arch.c
@@ -66,9 +66,9 @@ bool arch_ima_get_secureboot(void)
 
 /* secureboot arch rules */
 static const char * const sb_arch_rules[] = {
-#if !IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG)
+#if !IS_ENABLED(CONFIG_KEXEC_SIG)
 	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig",
-#endif /* CONFIG_KEXEC_VERIFY_SIG */
+#endif /* CONFIG_KEXEC_SIG */
 	"measure func=KEXEC_KERNEL_CHECK",
 #if !IS_ENABLED(CONFIG_MODULE_SIG)
 	"appraise func=MODULE_CHECK appraise_type=imasig",