[PATCH v3 09/14] KEYS: Introduce link restriction to include builtin, secondary and mok keys

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

Introduce a new link restriction that includes the trusted builtin,
secondary and mok keys. The restriction is based on the key to be added
being vouched for by a key in any of these three keyrings.

Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
---
v3: Initial version
---
 certs/system_keyring.c        | 23 +++++++++++++++++++++++
 include/keys/system_keyring.h |  6 ++++++
 2 files changed, 29 insertions(+)

diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index 2baf5447b116..cb773e09ea67 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -74,6 +74,29 @@ int restrict_link_by_builtin_and_secondary_trusted(
 					  secondary_trusted_keys);
 }
 
+/**
+ * restrict_link_by_builtin_secondary_and_ca_trusted
+ *
+ * Restrict the addition of keys into a keyring based on the key-to-be-added
+ * being vouched for by a key in either the built-in, the secondary, or
+ * the mok keyrings.
+ */
+int restrict_link_by_builtin_secondary_and_ca_trusted(
+	struct key *dest_keyring,
+	const struct key_type *type,
+	const union key_payload *payload,
+	struct key *restrict_key)
+{
+	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_builtin_and_secondary_trusted(dest_keyring, type,
+							      payload, restrict_key);
+}
+
 /**
  * Allocate a struct key_restriction for the "builtin and secondary trust"
  * keyring. Only for use in system_trusted_keyring_init().
diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
index 4fe9cca58685..c9fcbfada567 100644
--- a/include/keys/system_keyring.h
+++ b/include/keys/system_keyring.h
@@ -34,9 +34,15 @@ extern int restrict_link_by_builtin_and_secondary_trusted(
 	const struct key_type *type,
 	const union key_payload *payload,
 	struct key *restriction_key);
+extern int restrict_link_by_builtin_secondary_and_ca_trusted(
+	struct key *dest_keyring,
+	const struct key_type *type,
+	const union key_payload *payload,
+	struct key *restrict_key);
 extern void __init set_mok_trusted_keys(struct key *keyring);
 #else
 #define restrict_link_by_builtin_and_secondary_trusted restrict_link_by_builtin_trusted
+#define restrict_link_by_builtin_secondary_and_ca_trusted restrict_link_by_builtin_trusted
 static inline void __init set_mok_trusted_keys(struct key *keyring)
 {
 }
-- 
2.18.4