KEYS: DigitalSignature link restriction

Add a new link restriction.  Restrict the addition of keys in a keyring
based on the key having digitalSignature usage set. Additionally, verify
the new certificate against the ones in the system keyrings.  Add two
additional functions to use the new restriction within either the builtin
or secondary keyrings.

[jarkko@kernel.org: Fix checkpatch.pl --strict issues]
Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
Reviewed-and-tested-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

1 files changed, 49 insertions, 0 deletions

diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index a7a49b17ceb1..b348e0898d34 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -51,6 +51,26 @@ int restrict_link_by_builtin_trusted(struct key *dest_keyring,
 					  builtin_trusted_keys);
 }
 
+/**
+ * restrict_link_by_digsig_builtin - Restrict digitalSignature key additions by the built-in keyring
+ * @dest_keyring: Keyring being linked to.
+ * @type: The type of key being added.
+ * @payload: The payload of the new key.
+ * @restriction_key: A ring of keys that can be used to vouch for the new cert.
+ *
+ * Restrict the addition of keys into a keyring based on the key-to-be-added
+ * being vouched for by a key in the built in system keyring. The new key
+ * must have the digitalSignature usage field set.
+ */
+int restrict_link_by_digsig_builtin(struct key *dest_keyring,
+				    const struct key_type *type,
+				    const union key_payload *payload,
+				    struct key *restriction_key)
+{
+	return restrict_link_by_digsig(dest_keyring, type, payload,
+				       builtin_trusted_keys);
+}
+
 #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
 /**
  * restrict_link_by_builtin_and_secondary_trusted - Restrict keyring
@@ -83,6 +103,35 @@ int restrict_link_by_builtin_and_secondary_trusted(
 					  secondary_trusted_keys);
 }
 
+/**
+ * restrict_link_by_digsig_builtin_and_secondary - Restrict by digitalSignature.
+ * @dest_keyring: Keyring being linked to.
+ * @type: The type of key being added.
+ * @payload: The payload of the new key.
+ * @restrict_key: A ring of keys that can be used to vouch for the new cert.
+ *
+ * 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 or the secondary system
+ * keyrings. The new key must have the digitalSignature usage field set.
+ */
+int restrict_link_by_digsig_builtin_and_secondary(struct key *dest_keyring,
+						  const struct key_type *type,
+						  const union key_payload *payload,
+						  struct key *restrict_key)
+{
+	/* If we have a secondary trusted keyring, then that contains a link
+	 * through to the builtin keyring and the search will follow that link.
+	 */
+	if (type == &key_type_keyring &&
+	    dest_keyring == secondary_trusted_keys &&
+	    payload == &builtin_trusted_keys->payload)
+		/* Allow the builtin keyring to be added to the secondary */
+		return 0;
+
+	return restrict_link_by_digsig(dest_keyring, type, payload,
+				       secondary_trusted_keys);
+}
+
 /*
  * Allocate a struct key_restriction for the "builtin and secondary trust"
  * keyring. Only for use in system_trusted_keyring_init().