KEYS: Add a system blacklist keyring

Add the following:

 (1) A new system keyring that is used to store information about
     blacklisted certificates and signatures.

 (2) A new key type (called 'blacklist') that is used to store a
     blacklisted hash in its description as a hex string.  The key accepts
     no payload.

 (3) The ability to configure a list of blacklisted hashes into the kernel
     at build time.  This is done by setting
     CONFIG_SYSTEM_BLACKLIST_HASH_LIST to the filename of a list of hashes
     that are in the form:

	"<hash>", "<hash>", ..., "<hash>"

     where each <hash> is a hex string representation of the hash and must
     include all necessary leading zeros to pad the hash to the right size.

The above are enabled with CONFIG_SYSTEM_BLACKLIST_KEYRING.

Once the kernel is booted, the blacklist keyring can be listed:

	root@andromeda ~]# keyctl show %:.blacklist
	Keyring
	 723359729 ---lswrv      0     0  keyring: .blacklist
	 676257228 ---lswrv      0     0   \_ blacklist: 123412341234c55c1dcc601ab8e172917706aa32fb5eaf826813547fdf02dd46

The blacklist cannot currently be modified by userspace, but it will be
possible to load it, for example, from the UEFI blacklist database.

A later commit will make it possible to load blacklisted asymmetric keys in
here too.

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

1 files changed, 12 insertions, 0 deletions

diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
index fbd4647767e9..0d8762622ab9 100644
--- a/include/keys/system_keyring.h
+++ b/include/keys/system_keyring.h
@@ -33,6 +33,18 @@ extern int restrict_link_by_builtin_and_secondary_trusted(
 #define restrict_link_by_builtin_and_secondary_trusted restrict_link_by_builtin_trusted
 #endif
 
+#ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
+extern int mark_hash_blacklisted(const char *hash);
+extern int is_hash_blacklisted(const u8 *hash, size_t hash_len,
+			       const char *type);
+#else
+static inline int is_hash_blacklisted(const u8 *hash, size_t hash_len,
+				      const char *type)
+{
+	return 0;
+}
+#endif
+
 #ifdef CONFIG_IMA_BLACKLIST_KEYRING
 extern struct key *ima_blacklist_keyring;