[PATCH] IMA: Defined CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS to enable IMA hook to measure keys

[PATCH] IMA: Defined CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS to enable IMA hook to measure keys

[Lakshmi Ramasubramanian]

CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE is a tristate and not a bool.
If this config is set to "=m", ima_asymmetric_keys.c is built
as a kernel module when it is actually not.

Defined a new config CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS that is
defined when CONFIG_IMA and CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE
are defined.

Asymmetric key structure is defined only when
CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE is defined. Since the IMA hook
measures asymmetric keys, the IMA hook is defined in
ima_asymmetric_keys.c which is built only if
CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS is defined.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reported-by: kbuild test robot <lkp@intel.com> # ima_asymmetric_keys.c
is built as a kernel module when it is actually not.
Fixes: 88e70da170e8 ("IMA: Define an IMA hook to measure keys")
Fixes: cb1aa3823c92 ("KEYS: Call the IMA hook to measure keys")
---
 include/linux/ima.h             | 4 ++--
 security/integrity/ima/Kconfig  | 6 ++++++
 security/integrity/ima/Makefile | 2 +-
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 3b89136bc218..f4644c54f648 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -101,7 +101,7 @@ static inline void ima_add_kexec_buffer(struct kimage *image)
 {}
 #endif
 
-#if defined(CONFIG_IMA) && defined(CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE)
+#ifdef CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS
 extern void ima_post_key_create_or_update(struct key *keyring,
 					  struct key *key,
 					  const void *payload, size_t plen,
@@ -113,7 +113,7 @@ static inline void ima_post_key_create_or_update(struct key *keyring,
 						 size_t plen,
 						 unsigned long flags,
 						 bool create) {}
-#endif  /* CONFIG_IMA && CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE */
+#endif  /* CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS */
 
 #ifdef CONFIG_IMA_APPRAISE
 extern bool is_ima_appraise_enabled(void);
diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 838476d780e5..355754a6b6ca 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -310,3 +310,9 @@ config IMA_APPRAISE_SIGNED_INIT
 	default n
 	help
 	   This option requires user-space init to be signed.
+
+config IMA_MEASURE_ASYMMETRIC_KEYS
+	bool
+	depends on IMA
+	depends on ASYMMETRIC_PUBLIC_KEY_SUBTYPE=y
+	default y
diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
index 207a0a9eb72c..3e9d0ad68c7b 100644
--- a/security/integrity/ima/Makefile
+++ b/security/integrity/ima/Makefile
@@ -12,4 +12,4 @@ ima-$(CONFIG_IMA_APPRAISE) += ima_appraise.o
 ima-$(CONFIG_IMA_APPRAISE_MODSIG) += ima_modsig.o
 ima-$(CONFIG_HAVE_IMA_KEXEC) += ima_kexec.o
 obj-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
-obj-$(CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE) += ima_asymmetric_keys.o
+obj-$(CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS) += ima_asymmetric_keys.o
-- 
2.17.1

Re: [PATCH] IMA: Defined CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS to enable IMA hook to measure keys

[Mimi Zohar]

The subject line is too long.  How about "IMA: fix measuring
asymmetric keys Kconfig"?

On Tue, 2020-01-07 at 16:36 -0800, Lakshmi Ramasubramanian wrote:
> CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE is a tristate and not a bool.
> If this config is set to "=m", ima_asymmetric_keys.c is built
> as a kernel module when it is actually not.

Simplify the wording by removing the unnecessary "not a bool" and
"when it is actually not".

> 
> Defined a new config CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS that is
> defined when CONFIG_IMA and CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE
> are defined.

How about using James wording - "intermediate boolean config
variable"?

> Asymmetric key structure is defined only when
> CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE is defined. Since the IMA hook
> measures asymmetric keys, the IMA hook is defined in
> ima_asymmetric_keys.c which is built only if
> CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS is defined.
> 
> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>

Please include a "Suggested-by:" tag for James.

thanks,

Mimi