From: Jiri Bohac <jbohac@suse.cz>
Date: Mon, 19 Aug 2019 17:17:44 -0700
Subject: kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE
Patch-mainline: v5.4-rc1
Git-commit: 99d5cadfde2b1acb7650021df5abaa5ec447dd10
References: jsc#SLE-9870
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>
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
arch/arm64/Kconfig | 6 +--
arch/s390/Kconfig | 2 -
arch/s390/configs/debug_defconfig | 1
arch/s390/configs/defconfig | 1
arch/s390/kernel/kexec_elf.c | 4 +-
arch/s390/kernel/kexec_image.c | 4 +-
arch/s390/kernel/machine_kexec_file.c | 4 +-
arch/x86/Kconfig | 20 ++++++++---
arch/x86/kernel/ima_arch.c | 4 +-
crypto/asymmetric_keys/verify_pefile.c | 4 +-
include/linux/kexec.h | 4 +-
kernel/kexec_file.c | 60 ++++++++++++++++++++++++++++-----
security/integrity/ima/Kconfig | 2 -
security/integrity/ima/ima_main.c | 2 -
14 files changed, 87 insertions(+), 31 deletions(-)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -964,7 +964,7 @@ 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
@@ -979,13 +979,13 @@ 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
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -536,7 +536,7 @@ 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 && MODULE_SIG_FORMAT
help
--- a/arch/s390/configs/debug_defconfig
+++ b/arch/s390/configs/debug_defconfig
@@ -44,6 +44,7 @@ CONFIG_NR_CPUS=512
CONFIG_NUMA=y
CONFIG_HZ_100=y
CONFIG_KEXEC_FILE=y
+CONFIG_KEXEC_SIG=y
CONFIG_EXPOLINE=y
CONFIG_EXPOLINE_AUTO=y
CONFIG_CHSC_SCH=y
--- a/arch/s390/configs/defconfig
+++ b/arch/s390/configs/defconfig
@@ -44,6 +44,7 @@ CONFIG_NUMA=y
# CONFIG_NUMA_EMU is not set
CONFIG_HZ_100=y
CONFIG_KEXEC_FILE=y
+CONFIG_KEXEC_SIG=y
CONFIG_EXPOLINE=y
CONFIG_EXPOLINE_AUTO=y
CONFIG_CHSC_SCH=y
--- 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 *bu
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 */
};
--- 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 *
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 */
};
--- 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 kexe
NULL,
};
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
int s390_verify_sig(const char *kernel, unsigned long kernel_len)
{
const unsigned long marker_len = sizeof(MODULE_SIG_STRING) - 1;
@@ -68,7 +68,7 @@ int s390_verify_sig(const char *kernel,
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)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2025,20 +2025,30 @@ 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---
--- a/arch/x86/kernel/ima_arch.c
+++ b/arch/x86/kernel/ima_arch.c
@@ -74,9 +74,9 @@ 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",
--- a/crypto/asymmetric_keys/verify_pefile.c
+++ b/crypto/asymmetric_keys/verify_pefile.c
@@ -96,7 +96,7 @@ static int pefile_parse_binary(const voi
if (!ddir->certs.virtual_address || !ddir->certs.size) {
pr_debug("Unsigned PE binary\n");
- return -EKEYREJECTED;
+ return -ENODATA;
}
chkaddr(ctx->header_size, ddir->certs.virtual_address,
@@ -403,6 +403,8 @@ error_no_desc:
* (*) 0 if at least one signature chain intersects with the keys in the trust
* keyring, or:
*
+ * (*) -ENODATA if there is no signature present.
+ *
* (*) -ENOPKG if a suitable crypto module couldn't be found for a check on a
* chain.
*
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -125,7 +125,7 @@ typedef void *(kexec_load_t)(struct kima
unsigned long cmdline_len);
typedef int (kexec_cleanup_t)(void *loader_data);
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
typedef int (kexec_verify_sig_t)(const char *kernel_buf,
unsigned long kernel_len);
#endif
@@ -134,7 +134,7 @@ struct kexec_file_ops {
kexec_probe_t *probe;
kexec_load_t *load;
kexec_cleanup_t *cleanup;
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
kexec_verify_sig_t *verify_sig;
#endif
};
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -88,7 +88,7 @@ int __weak arch_kimage_file_post_load_cl
return kexec_image_post_load_cleanup_default(image);
}
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
static int kexec_image_verify_sig_default(struct kimage *image, void *buf,
unsigned long buf_len)
{
@@ -177,6 +177,51 @@ void kimage_file_post_load_cleanup(struc
image->image_loader_data = NULL;
}
+#ifdef CONFIG_KEXEC_SIG
+static int
+kimage_validate_signature(struct kimage *image)
+{
+ const char *reason;
+ int ret;
+
+ ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf,
+ image->kernel_buf_len);
+ switch (ret) {
+ case 0:
+ break;
+
+ /* Certain verification errors are non-fatal if we're not
+ * checking errors, provided we aren't mandating that there
+ * must be a valid signature.
+ */
+ case -ENODATA:
+ reason = "kexec of unsigned image";
+ goto decide;
+ case -ENOPKG:
+ reason = "kexec of image with unsupported crypto";
+ goto decide;
+ case -ENOKEY:
+ reason = "kexec of image with unavailable key";
+ decide:
+ if (IS_ENABLED(CONFIG_KEXEC_SIG_FORCE)) {
+ pr_notice("%s rejected\n", reason);
+ return ret;
+ }
+
+ return 0;
+
+ /* All other errors are fatal, including nomem, unparseable
+ * signatures and signature check failures - even if signatures
+ * aren't required.
+ */
+ default:
+ pr_notice("kernel signature verification failed (%d).\n", ret);
+ }
+
+ return ret;
+}
+#endif
+
/*
* In file mode list of segments is prepared by kernel. Copy relevant
* data from user space, do error checking, prepare segment list
@@ -186,7 +231,7 @@ kimage_file_prepare_segments(struct kima
const char __user *cmdline_ptr,
unsigned long cmdline_len, unsigned flags)
{
- int ret = 0;
+ int ret;
void *ldata;
loff_t size;
@@ -202,14 +247,11 @@ kimage_file_prepare_segments(struct kima
if (ret)
goto out;
-#ifdef CONFIG_KEXEC_VERIFY_SIG
- ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf,
- image->kernel_buf_len);
- if (ret) {
- pr_debug("kernel signature verification failed.\n");
+#ifdef CONFIG_KEXEC_SIG
+ ret = kimage_validate_signature(image);
+
+ if (ret)
goto out;
- }
- pr_debug("kernel signature verification successful.\n");
#endif
/* It is possible that there no initramfs is being loaded */
if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -160,7 +160,7 @@ config IMA_APPRAISE
config IMA_ARCH_POLICY
bool "Enable loading an IMA architecture specific policy"
- depends on (KEXEC_VERIFY_SIG && IMA) || IMA_APPRAISE \
+ depends on (KEXEC_SIG && IMA) || IMA_APPRAISE \
&& INTEGRITY_ASYMMETRIC_KEYS
default n
help
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -590,7 +590,7 @@ int ima_load_data(enum kernel_load_data_
switch (id) {
case LOADING_KEXEC_IMAGE:
- if (IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG)
+ if (IS_ENABLED(CONFIG_KEXEC_SIG)
&& arch_ima_get_secureboot()) {
pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
return -EACCES;