[PATCH v3 10/10] integrity: restrict INTEGRITY_KEYRING_MACHINE to restrict_link_by_ca

[Eric Snowberg <eric.snowberg@oracle.com>]

Set the restriction check for INTEGRITY_KEYRING_MACHINE keys to
restrict_link_by_ca.  This will only allow CA keys into the machine
keyring.

Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
---
 security/integrity/Kconfig  | 10 ++++++++++
 security/integrity/digsig.c |  8 ++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/security/integrity/Kconfig b/security/integrity/Kconfig
index 14cc3c767270..3357883fa5a8 100644
--- a/security/integrity/Kconfig
+++ b/security/integrity/Kconfig
@@ -74,6 +74,16 @@ config INTEGRITY_MACHINE_KEYRING
 	 in the platform keyring, keys contained in the .machine keyring will
 	 be trusted within the kernel.
 
+config INTEGRITY_CA_MACHINE_KEYRING
+	bool "Only allow CA keys into the Machine Keyring"
+	depends on INTEGRITY_MACHINE_KEYRING
+	help
+	 If set, only Machine Owner Keys (MOK) that are Certificate
+	 Authority (CA) keys will be added to the .machine keyring. All
+	 other MOK keys will be added to the .platform keyring.  After
+	 booting, any other key signed by the CA key can be added to the
+	 secondary_trusted_keys keyring.
+
 config LOAD_UEFI_KEYS
        depends on INTEGRITY_PLATFORM_KEYRING
        depends on EFI
diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index 1fe8d1ed6e0b..b0ec615745e3 100644
--- a/security/integrity/digsig.c
+++ b/security/integrity/digsig.c
@@ -131,7 +131,8 @@ int __init integrity_init_keyring(const unsigned int id)
 		| KEY_USR_READ | KEY_USR_SEARCH;
 
 	if (id == INTEGRITY_KEYRING_PLATFORM ||
-	    id == INTEGRITY_KEYRING_MACHINE) {
+	    (id == INTEGRITY_KEYRING_MACHINE &&
+	    !IS_ENABLED(CONFIG_INTEGRITY_CA_MACHINE_KEYRING))) {
 		restriction = NULL;
 		goto out;
 	}
@@ -143,7 +144,10 @@ int __init integrity_init_keyring(const unsigned int id)
 	if (!restriction)
 		return -ENOMEM;
 
-	restriction->check = restrict_link_to_ima;
+	if (id == INTEGRITY_KEYRING_MACHINE)
+		restriction->check = restrict_link_by_ca;
+	else
+		restriction->check = restrict_link_to_ima;
 
 	/*
 	 * MOK keys can only be added through a read-only runtime services
-- 
2.27.0