linux-kernel - [PATCH v4 12/12] integrity: Only use mok keyring when uefi_check_trust_mok

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Message-Id: <20210819002109.534600-13-eric.snowberg@oracle.com>
Date:   Wed, 18 Aug 2021 20:21:09 -0400
From:   Eric Snowberg <eric.snowberg@...cle.com>
To:     keyrings@...r.kernel.org, linux-integrity@...r.kernel.org,
        zohar@...ux.ibm.com, dhowells@...hat.com, dwmw2@...radead.org,
        herbert@...dor.apana.org.au, davem@...emloft.net,
        jarkko@...nel.org, jmorris@...ei.org, serge@...lyn.com
Cc:     eric.snowberg@...cle.com, keescook@...omium.org,
        gregkh@...uxfoundation.org, torvalds@...ux-foundation.org,
        scott.branden@...adcom.com, weiyongjun1@...wei.com,
        nayna@...ux.ibm.com, ebiggers@...gle.com, ardb@...nel.org,
        nramas@...ux.microsoft.com, lszubowi@...hat.com,
        linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        James.Bottomley@...senPartnership.com, pjones@...hat.com,
        konrad.wilk@...cle.com
Subject: [PATCH v4 12/12] integrity: Only use mok keyring when uefi_check_trust_mok_keys is true

With the introduction of uefi_check_trust_mok_keys, it signifies the end-
user wants to trust the mok keyring as trusted keys.  If they have chosen 
to trust the mok keyring, load the qualifying keys into it during boot, 
then link it to the secondary keyring .  If the user has not chosen to 
trust the mok keyring, it will be empty and not linked to the secondary 
keyring.

Signed-off-by: Eric Snowberg <eric.snowberg@...cle.com>
---
v4: Initial version
---
 security/integrity/digsig.c                      |  2 +-
 security/integrity/integrity.h                   |  5 +++++
 .../integrity/platform_certs/keyring_handler.c   |  2 +-
 security/integrity/platform_certs/mok_keyring.c  | 16 ++++++++++++++++
 4 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index 0f14ffef9c43..fd255e5b6293 100644
--- a/security/integrity/digsig.c
+++ b/security/integrity/digsig.c
@@ -116,7 +116,7 @@ static int __init __integrity_init_keyring(const unsigned int id,
 	} else {
 		if (id == INTEGRITY_KEYRING_PLATFORM)
 			set_platform_trusted_keys(keyring[id]);
-		if (id == INTEGRITY_KEYRING_MOK)
+		if (id == INTEGRITY_KEYRING_MOK && trust_moklist())
 			set_mok_trusted_keys(keyring[id]);
 		if (id == INTEGRITY_KEYRING_IMA)
 			load_module_cert(keyring[id]);
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index be56ba49dc19..57683fdea2af 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -287,9 +287,14 @@ static inline void __init add_to_platform_keyring(const char *source,
 
 #ifdef CONFIG_INTEGRITY_MOK_KEYRING
 void __init add_to_mok_keyring(const char *source, const void *data, size_t len);
+bool __init trust_moklist(void);
 #else
 static inline void __init add_to_mok_keyring(const char *source,
 					     const void *data, size_t len)
 {
 }
+static inline bool __init trust_moklist(void)
+{
+	return false;
+}
 #endif
diff --git a/security/integrity/platform_certs/keyring_handler.c b/security/integrity/platform_certs/keyring_handler.c
index fc4ad85d9223..471bf103b444 100644
--- a/security/integrity/platform_certs/keyring_handler.c
+++ b/security/integrity/platform_certs/keyring_handler.c
@@ -82,7 +82,7 @@ __init efi_element_handler_t get_handler_for_db(const efi_guid_t *sig_type)
 __init efi_element_handler_t get_handler_for_mok(const efi_guid_t *sig_type)
 {
 	if (efi_guidcmp(*sig_type, efi_cert_x509_guid) == 0) {
-		if (IS_ENABLED(CONFIG_INTEGRITY_MOK_KEYRING))
+		if (IS_ENABLED(CONFIG_INTEGRITY_MOK_KEYRING) && trust_moklist())
 			return add_to_mok_keyring;
 		else
 			return add_to_platform_keyring;
diff --git a/security/integrity/platform_certs/mok_keyring.c b/security/integrity/platform_certs/mok_keyring.c
index bcfab894a9dc..3dbb6d17e17d 100644
--- a/security/integrity/platform_certs/mok_keyring.c
+++ b/security/integrity/platform_certs/mok_keyring.c
@@ -8,6 +8,8 @@
 #include <linux/efi.h>
 #include "../integrity.h"
 
+bool trust_mok;
+
 static __init int mok_keyring_init(void)
 {
 	int rc;
@@ -67,3 +69,17 @@ static __init bool uefi_check_trust_mok_keys(void)
 	 */
 	return (status == EFI_SUCCESS && (!(attr & EFI_VARIABLE_NON_VOLATILE)));
 }
+
+bool __init trust_moklist(void)
+{
+	static bool initialized;
+
+	if (!initialized) {
+		initialized = true;
+
+		if (uefi_check_trust_mok_keys())
+			trust_mok = true;
+	}
+
+	return trust_mok;
+}
-- 
2.18.4