certs: Add a secondary system keyring that can be added to dynamically

Add a secondary system keyring that can be added to by root whilst the
system is running - provided the key being added is vouched for by a key
built into the kernel or already added to the secondary keyring.

Rename .system_keyring to .builtin_trusted_keys to distinguish it more
obviously from the new keyring (called .secondary_trusted_keys).

The new keyring needs to be enabled with CONFIG_SECONDARY_TRUSTED_KEYRING.

If the secondary keyring is enabled, a link is created from that to
.builtin_trusted_keys so that the the latter will automatically be searched
too if the secondary keyring is searched.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
index c72330ae76df..614424029de7 100644
--- a/include/keys/system_keyring.h
+++ b/include/keys/system_keyring.h
@@ -24,6 +24,15 @@ extern int restrict_link_by_builtin_trusted(struct key *keyring,
 #define restrict_link_by_builtin_trusted restrict_link_reject
 #endif
 
+#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
+extern int restrict_link_by_builtin_and_secondary_trusted(
+	struct key *keyring,
+	const struct key_type *type,
+	const union key_payload *payload);
+#else
+#define restrict_link_by_builtin_and_secondary_trusted restrict_link_by_builtin_trusted
+#endif
+
 #ifdef CONFIG_IMA_MOK_KEYRING
 extern struct key *ima_mok_keyring;
 extern struct key *ima_blacklist_keyring;