[PATCH RFC v2 10/12] KEYS: link system_trusted_keys to mok_trusted_keys

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

Allow the .mok keyring to be linked to either the builtin_trusted_keys
or the secondary_trusted_keys. If CONFIG_SECONDARY_TRUSTED_KEYRING is
enabled, mok keys are linked to the secondary_trusted_keys.  Otherwise
they are linked to the builtin_trusted_keys.  After the link is created,
keys contained in the .mok keyring will automatically be searched when
searching either builtin_trusted_keys or secondary_trusted_keys.

Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
---
v2: Initial version
---
 certs/system_keyring.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index dcaf74102ab2..b27ae30eaadc 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -45,6 +45,15 @@ int restrict_link_by_builtin_trusted(struct key *dest_keyring,
 				     const union key_payload *payload,
 				     struct key *restriction_key)
 {
+	/* If the secondary trusted keyring is not enabled, we may link
+	 * through to the mok keyring and the search may follow that link.
+	 */
+	if (mok_trusted_keys && type == &key_type_keyring &&
+	    dest_keyring == builtin_trusted_keys &&
+	    payload == &mok_trusted_keys->payload)
+		/* Allow the mok keyring to be added to the builtin */
+		return 0;
+
 	return restrict_link_by_signature(dest_keyring, type, payload,
 					  builtin_trusted_keys);
 }
@@ -91,6 +100,15 @@ int restrict_link_by_builtin_and_secondary_trusted(
 		/* Allow the builtin keyring to be added to the secondary */
 		return 0;
 
+	/* If we have a secondary trusted keyring, it may contain a link
+	 * through to the mok keyring and the search may follow that link.
+	 */
+	if (mok_trusted_keys && type == &key_type_keyring &&
+	    dest_keyring == secondary_trusted_keys &&
+	    payload == &mok_trusted_keys->payload)
+		/* Allow the mok keyring to be added to the secondary */
+		return 0;
+
 	return restrict_link_by_signature(dest_keyring, type, payload,
 					  secondary_trusted_keys);
 }
@@ -321,5 +339,8 @@ void __init set_platform_trusted_keys(struct key *keyring)
 void __init set_mok_trusted_keys(struct key *keyring)
 {
 	mok_trusted_keys = keyring;
+
+	if (key_link(system_trusted_keys, mok_trusted_keys) < 0)
+		panic("Can't link (mok) trusted keyrings\n");
 }
 #endif
-- 
2.18.4