IMA: create machine owner and blacklist keyrings

This option creates IMA MOK and blacklist keyrings.  IMA MOK is an
intermediate keyring that sits between .system and .ima keyrings,
effectively forming a simple CA hierarchy.  To successfully import a key
into .ima_mok it must be signed by a key which CA is in .system keyring.
On turn any key that needs to go in .ima keyring must be signed by CA in
either .system or .ima_mok keyrings. IMA MOK is empty at kernel boot.

IMA blacklist keyring contains all revoked IMA keys.  It is consulted
before any other keyring.  If the search is successful the requested
operation is rejected and error is returned to the caller.
Signed-off-by: Petko Manolov <petkan@mip-labs.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

crypto/asymmetric_keys/x509_public_key.c

@@ -321,6 +321,8 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
 			goto error_free_cert;
 	} else if (!prep->trusted) {
 		ret = x509_validate_trust(cert, get_system_trusted_keyring());
+		if (ret)
+			ret = x509_validate_trust(cert, get_ima_mok_keyring());
 		if (!ret)
 			prep->trusted = 1;
 	}

include/keys/system_keyring.h

@@ -35,4 +35,28 @@ extern int system_verify_data(const void *data, unsigned long len,
 			      enum key_being_used_for usage);
 #endif
 
+#ifdef CONFIG_IMA_MOK_KEYRING
+extern struct key *ima_mok_keyring;
+extern struct key *ima_blacklist_keyring;
+
+static inline struct key *get_ima_mok_keyring(void)
+{
+	return ima_mok_keyring;
+}
+static inline struct key *get_ima_blacklist_keyring(void)
+{
+	return ima_blacklist_keyring;
+}
+#else
+static inline struct key *get_ima_mok_keyring(void)
+{
+	return NULL;
+}
+static inline struct key *get_ima_blacklist_keyring(void)
+{
+	return NULL;
+}
+#endif /* CONFIG_IMA_MOK_KEYRING */
+
+
 #endif /* _KEYS_SYSTEM_KEYRING_H */

security/integrity/digsig_asymmetric.c

@@ -17,6 +17,7 @@
 #include <linux/key-type.h>
 #include <crypto/public_key.h>
 #include <keys/asymmetric-type.h>
+#include <keys/system_keyring.h>
 
 #include "integrity.h"
 
@@ -32,9 +33,22 @@ static struct key *request_asymmetric_key(struct key *keyring, uint32_t keyid)
 
 	pr_debug("key search: \"%s\"\n", name);
 
+	key = get_ima_blacklist_keyring();
+	if (key) {
+		key_ref_t kref;
+
+		kref = keyring_search(make_key_ref(key, 1),
+				     &key_type_asymmetric, name);
+		if (!IS_ERR(kref)) {
+			pr_err("Key '%s' is in ima_blacklist_keyring\n", name);
+			return ERR_PTR(-EKEYREJECTED);
+		}
+	}
+
 	if (keyring) {
 		/* search in specific keyring */
 		key_ref_t kref;
+
 		kref = keyring_search(make_key_ref(keyring, 1),
 				      &key_type_asymmetric, name);
 		if (IS_ERR(kref))

security/integrity/ima/Kconfig

@@ -145,6 +145,24 @@ config IMA_TRUSTED_KEYRING
 
 	   This option is deprecated in favor of INTEGRITY_TRUSTED_KEYRING
 
+config IMA_MOK_KEYRING
+	bool "Create IMA machine owner keys (MOK) and blacklist keyrings"
+	depends on SYSTEM_TRUSTED_KEYRING
+	depends on IMA_TRUSTED_KEYRING
+	default n
+	help
+	   This option creates IMA MOK and blacklist keyrings.  IMA MOK is an
+	   intermediate keyring that sits between .system and .ima keyrings,
+	   effectively forming a simple CA hierarchy.  To successfully import a
+	   key into .ima_mok it must be signed by a key which CA is in .system
+	   keyring.  On turn any key that needs to go in .ima keyring must be
+	   signed by CA in either .system or .ima_mok keyrings. IMA MOK is empty
+	   at kernel boot.
+
+	   IMA blacklist keyring contains all revoked IMA keys.  It is consulted
+	   before any other keyring.  If the search is successful the requested
+	   operation is rejected and error is returned to the caller.
+
 config IMA_LOAD_X509
 	bool "Load X509 certificate onto the '.ima' trusted keyring"
 	depends on IMA_TRUSTED_KEYRING

security/integrity/ima/Makefile

@@ -8,3 +8,4 @@ obj-$(CONFIG_IMA) += ima.o
 ima-y := ima_fs.o ima_queue.o ima_init.o ima_main.o ima_crypto.o ima_api.o \
 	 ima_policy.o ima_template.o ima_template_lib.o
 ima-$(CONFIG_IMA_APPRAISE) += ima_appraise.o
+obj-$(CONFIG_IMA_MOK_KEYRING) += ima_mok.o

security/integrity/ima/ima_mok.c

+/*
+ * Copyright (C) 2015 Juniper Networks, Inc.
+ *
+ * Author:
+ * Petko Manolov <petko.manolov@konsulko.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, version 2 of the
+ * License.
+ *
+ */
+
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/cred.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <keys/asymmetric-type.h>
+
+
+struct key *ima_mok_keyring;
+struct key *ima_blacklist_keyring;
+
+/*
+ * Allocate the IMA MOK and blacklist keyrings
+ */
+__init int ima_mok_init(void)
+{
+	pr_notice("Allocating IMA MOK and blacklist keyrings.\n");
+
+	ima_mok_keyring = keyring_alloc(".ima_mok",
+			      KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
+			      (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+			      KEY_USR_VIEW | KEY_USR_READ |
+			      KEY_USR_WRITE | KEY_USR_SEARCH,
+			      KEY_ALLOC_NOT_IN_QUOTA, NULL);
+
+	ima_blacklist_keyring = keyring_alloc(".ima_blacklist",
+				KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
+				(KEY_POS_ALL & ~KEY_POS_SETATTR) |
+				KEY_USR_VIEW | KEY_USR_READ |
+				KEY_USR_WRITE | KEY_USR_SEARCH,
+				KEY_ALLOC_NOT_IN_QUOTA, NULL);
+
+	if (IS_ERR(ima_mok_keyring) || IS_ERR(ima_blacklist_keyring))
+		panic("Can't allocate IMA MOK or blacklist keyrings.");
+	set_bit(KEY_FLAG_TRUSTED_ONLY, &ima_mok_keyring->flags);
+	set_bit(KEY_FLAG_TRUSTED_ONLY, &ima_blacklist_keyring->flags);
+	return 0;
+}
+
+module_init(ima_mok_init);