2022-07-12 09:40:41

by Coiby Xu

Subject: [PATCH] ima: force signature verification when CONFIG_KEXEC_SIG is configured

Currently, an unsigned kernel could be kexec'ed when IMA arch specific
policy is configured unless lockdown is enabled. Enforce kernel
signature verification check in the kexec_file_load syscall when IMA
arch specific policy is configured.

Fixes: 99d5cadfde2b ("kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE")
Reported-by: Mimi Zohar <[email protected]>
Suggested-by: Mimi Zohar <[email protected]>
Signed-off-by: Coiby Xu <[email protected]>
---
include/linux/kexec.h | 3 +++
kernel/kexec_file.c | 11 ++++++++++-
security/integrity/ima/ima_efi.c | 3 +++
3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index ce6536f1d269..4b8e8d5bcea9 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -134,6 +134,9 @@ typedef int (kexec_cleanup_t)(void *loader_data);
#ifdef CONFIG_KEXEC_SIG
typedef int (kexec_verify_sig_t)(const char *kernel_buf,
unsigned long kernel_len);
+void set_kexec_sig_enforced(void);
+#else
+static inline void set_kexec_sig_enforced(void) {}
#endif

struct kexec_file_ops {
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 145321a5e798..f9261c07b048 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -29,6 +29,15 @@
#include <linux/vmalloc.h>
#include "kexec_internal.h"

+#ifdef CONFIG_KEXEC_SIG
+static bool sig_enforce = IS_ENABLED(CONFIG_KEXEC_SIG_FORCE);
+
+void set_kexec_sig_enforced(void)
+{
+ sig_enforce = true;
+}
+#endif
+
static int kexec_calculate_store_digests(struct kimage *image);

/*
@@ -159,7 +168,7 @@ kimage_validate_signature(struct kimage *image)
image->kernel_buf_len);
if (ret) {

- if (IS_ENABLED(CONFIG_KEXEC_SIG_FORCE)) {
+ if (sig_enforce) {
pr_notice("Enforced kernel signature verification failed (%d).\n", ret);
return ret;
}
diff --git a/security/integrity/ima/ima_efi.c b/security/integrity/ima/ima_efi.c
index 71786d01946f..ae3fe4cb8d86 100644
--- a/security/integrity/ima/ima_efi.c
+++ b/security/integrity/ima/ima_efi.c
@@ -3,6 +3,7 @@
* Copyright (C) 2018 IBM Corporation
*/
#include <linux/efi.h>
+#include <linux/kexec.h>
#include <linux/module.h>
#include <linux/ima.h>
#include <asm/efi.h>
@@ -67,6 +68,8 @@ const char * const *arch_get_ima_policy(void)
if (IS_ENABLED(CONFIG_IMA_ARCH_POLICY) && arch_ima_get_secureboot()) {
if (IS_ENABLED(CONFIG_MODULE_SIG))
set_module_sig_enforced();
+ if (IS_ENABLED(CONFIG_KEXEC_SIG))
+ set_kexec_sig_enforced();
return sb_arch_rules;
}
return NULL;
--
2.35.3

2022-07-12 12:15:53

by Mimi Zohar

Subject: Re: [PATCH] ima: force signature verification when CONFIG_KEXEC_SIG is configured

On Tue, 2022-07-12 at 17:33 +0800, Coiby Xu wrote:
> Currently, an unsigned kernel could be kexec'ed when IMA arch specific
> policy is configured unless lockdown is enabled. Enforce kernel
> signature verification check in the kexec_file_load syscall when IMA
> arch specific policy is configured.
>
> Fixes: 99d5cadfde2b ("kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE")
> Reported-by: Mimi Zohar <[email protected]>
> Suggested-by: Mimi Zohar <[email protected]>
> Signed-off-by: Coiby Xu <[email protected]>

Thanks, Coiby. This patch is now queued in next-integrity/next-
integrity-testing.

Mimi

2022-07-13 07:49:40

by Coiby Xu

Subject: [PATCH v2] ima: force signature verification when CONFIG_KEXEC_SIG is configured

Currently, an unsigned kernel could be kexec'ed when IMA arch specific
policy is configured unless lockdown is enabled. Enforce kernel
signature verification check in the kexec_file_load syscall when IMA
arch specific policy is configured.

Fixes: 99d5cadfde2b ("kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE")
Reported-by: Mimi Zohar <[email protected]>
Suggested-by: Mimi Zohar <[email protected]>
Signed-off-by: Coiby Xu <[email protected]>
---
v2
- don't include linux/kexec.h since it's already been included in
linux/ima.h
- fix build errors when KEXEC_FILE/KEXEC_CORE is disable as caught by
kernel test robot <[email protected]>

---
include/linux/kexec.h | 6 ++++++
kernel/kexec_file.c | 11 ++++++++++-
security/integrity/ima/ima_efi.c | 2 ++
3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index ce6536f1d269..475683cd67f1 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -452,6 +452,12 @@ static inline int kexec_crash_loaded(void) { return 0; }
#define kexec_in_progress false
#endif /* CONFIG_KEXEC_CORE */

+#ifdef CONFIG_KEXEC_SIG
+void set_kexec_sig_enforced(void);
+#else
+static inline void set_kexec_sig_enforced(void) {}
+#endif
+
#endif /* !defined(__ASSEBMLY__) */

#endif /* LINUX_KEXEC_H */
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 145321a5e798..f9261c07b048 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -29,6 +29,15 @@
#include <linux/vmalloc.h>
#include "kexec_internal.h"

+#ifdef CONFIG_KEXEC_SIG
+static bool sig_enforce = IS_ENABLED(CONFIG_KEXEC_SIG_FORCE);
+
+void set_kexec_sig_enforced(void)
+{
+ sig_enforce = true;
+}
+#endif
+
static int kexec_calculate_store_digests(struct kimage *image);

/*
@@ -159,7 +168,7 @@ kimage_validate_signature(struct kimage *image)
image->kernel_buf_len);
if (ret) {

- if (IS_ENABLED(CONFIG_KEXEC_SIG_FORCE)) {
+ if (sig_enforce) {
pr_notice("Enforced kernel signature verification failed (%d).\n", ret);
return ret;
}
diff --git a/security/integrity/ima/ima_efi.c b/security/integrity/ima/ima_efi.c
index 71786d01946f..9db66fe310d4 100644
--- a/security/integrity/ima/ima_efi.c
+++ b/security/integrity/ima/ima_efi.c
@@ -67,6 +67,8 @@ const char * const *arch_get_ima_policy(void)
if (IS_ENABLED(CONFIG_IMA_ARCH_POLICY) && arch_ima_get_secureboot()) {
if (IS_ENABLED(CONFIG_MODULE_SIG))
set_module_sig_enforced();
+ if (IS_ENABLED(CONFIG_KEXEC_SIG))
+ set_kexec_sig_enforced();
return sb_arch_rules;
}
return NULL;
--
2.35.3

2022-07-13 15:25:01

by Mimi Zohar

Subject: Re: [PATCH v2] ima: force signature verification when CONFIG_KEXEC_SIG is configured

On Wed, 2022-07-13 at 15:21 +0800, Coiby Xu wrote:
> Currently, an unsigned kernel could be kexec'ed when IMA arch specific
> policy is configured unless lockdown is enabled. Enforce kernel
> signature verification check in the kexec_file_load syscall when IMA
> arch specific policy is configured.
>
> Fixes: 99d5cadfde2b ("kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE")
> Reported-by: Mimi Zohar <[email protected]>
> Suggested-by: Mimi Zohar <[email protected]>
> Signed-off-by: Coiby Xu <[email protected]>
> ---
> v2
> - don't include linux/kexec.h since it's already been included in
> linux/ima.h
> - fix build errors when KEXEC_FILE/KEXEC_CORE is disable as caught by
> kernel test robot <[email protected]>

Thanks, Coiby. This version of the patch is now queued in next-
integrity/next-
integrity-testing.

Mimi