UBUNTU: SAUCE: (noup) KEYS: Add a system blacklist keyring

BugLink: http://bugs.launchpad.net/bugs/1569924

This adds an additional keyring that is used to store certificates that
are blacklisted.  This keyring is searched first when loading signed modules
and if the module's certificate is found, it will refuse to load.  This is
useful in cases where third party certificates are used for module signing.
Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Andy Whitcroft <andy.whitcroft@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

certs/system_keyring.c

@@ -20,6 +20,9 @@
 
 struct key *system_trusted_keyring;
 EXPORT_SYMBOL_GPL(system_trusted_keyring);
+#ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
+struct key *system_blacklist_keyring;
+#endif
 
 extern __initconst const u8 system_certificate_list[];
 extern __initconst const unsigned long system_certificate_list_size;
@@ -41,6 +44,20 @@ static __init int system_trusted_keyring_init(void)
 		panic("Can't allocate system trusted keyring\n");
 
 	set_bit(KEY_FLAG_TRUSTED_ONLY, &system_trusted_keyring->flags);
+
+	#ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
+	system_blacklist_keyring = keyring_alloc(".system_blacklist_keyring",
+				    KUIDT_INIT(0), KGIDT_INIT(0),
+				    current_cred(),
+				    (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+				    KEY_USR_VIEW | KEY_USR_READ,
+				    KEY_ALLOC_NOT_IN_QUOTA, NULL);
+	if (IS_ERR(system_blacklist_keyring))
+		panic("Can't allocate system blacklist keyring\n");
+
+	set_bit(KEY_FLAG_TRUSTED_ONLY, &system_blacklist_keyring->flags);
+#endif
+
 	return 0;
 }
 
@@ -139,6 +156,16 @@ int system_verify_data(const void *data, unsigned long len,
 	if (ret < 0)
 		goto error;
 
+#ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
+	ret = pkcs7_validate_trust(pkcs7, system_blacklist_keyring, &trusted);
+	if (!ret) {
+		/* module is signed with a cert in the blacklist.  reject */
+		pr_err("Module key is in the blacklist\n");
+		ret = -EKEYREJECTED;
+		goto error;
+	}
+#endif
+
 	ret = pkcs7_validate_trust(pkcs7, system_trusted_keyring, &trusted);
 	if (ret < 0)
 		goto error;

include/keys/system_keyring.h

@@ -35,6 +35,10 @@ extern int system_verify_data(const void *data, unsigned long len,
 			      enum key_being_used_for usage);
 #endif
 
+#ifdef CONFIG_SYSTEM_BLACKLIST_KEYRING
+extern struct key *system_blacklist_keyring;
+#endif
+
 #ifdef CONFIG_IMA_MOK_KEYRING
 extern struct key *ima_mok_keyring;
 extern struct key *ima_blacklist_keyring;

init/Kconfig

@@ -1804,6 +1804,15 @@ config SYSTEM_DATA_VERIFICATION
 	  module verification, kexec image verification and firmware blob
 	  verification.
 
+config SYSTEM_BLACKLIST_KEYRING
+	bool "Provide system-wide ring of blacklisted keys"
+	depends on KEYS
+	help
+	  Provide a system keyring to which blacklisted keys can be added.
+	  Keys in the keyring are considered entirely untrusted.  Keys in this
+	  keyring are used by the module signature checking to reject loading
+	  of modules signed with a blacklisted key.
+
 config PROFILING
 	bool "Profiling support"
 	help