Merge branch 'keys-trust' into keys-next

Here's a set of patches that changes how certificates/keys are determined
to be trusted.  That's currently a two-step process:

 (1) Up until recently, when an X.509 certificate was parsed - no matter
     the source - it was judged against the keys in .system_keyring,
     assuming those keys to be trusted if they have KEY_FLAG_TRUSTED set
     upon them.

     This has just been changed such that any key in the .ima_mok keyring,
     if configured, may also be used to judge the trustworthiness of a new
     certificate, whether or not the .ima_mok keyring is meant to be
     consulted for whatever process is being undertaken.

     If a certificate is determined to be trustworthy, KEY_FLAG_TRUSTED
     will be set upon a key it is loaded into (if it is loaded into one),
     no matter what the key is going to be loaded for.

 (2) If an X.509 certificate is loaded into a key, then that key - if
     KEY_FLAG_TRUSTED gets set upon it - can be linked into any keyring
     with KEY_FLAG_TRUSTED_ONLY set upon it.  This was meant to be the
     system keyring only, but has been extended to various IMA keyrings.
     A user can at will link any key marked KEY_FLAG_TRUSTED into any
     keyring marked KEY_FLAG_TRUSTED_ONLY if the relevant permissions masks
     permit it.

These patches change that:

 (1) Trust becomes a matter of consulting the ring of trusted keys supplied
     when the trust is evaluated only.

 (2) Every keyring can be supplied with its own manager function to
     restrict what may be added to that keyring.  This is called whenever a
     key is to be linked into the keyring to guard against a key being
     created in one keyring and then linked across.

     This function is supplied with the keyring and the key type and
     payload[*] of the key being linked in for use in its evaluation.  It
     is permitted to use other data also, such as the contents of other
     keyrings such as the system keyrings.

     [*] The type and payload are supplied instead of a key because as an
         optimisation this function may be called whilst creating a key and
         so may reject the proposed key between preparse and allocation.

 (3) A default manager function is provided that permits keys to be
     restricted to only asymmetric keys that are vouched for by the
     contents of the system keyring.

     A second manager function is provided that just rejects with EPERM.

 (4) A key allocation flag, KEY_ALLOC_BYPASS_RESTRICTION, is made available
     so that the kernel can initialise keyrings with keys that form the
     root of the trust relationship.

 (5) KEY_FLAG_TRUSTED and KEY_FLAG_TRUSTED_ONLY are removed, along with
     key_preparsed_payload::trusted.

This change also makes it possible in future for userspace to create a private
set of trusted keys and then to have it sealed by setting a manager function
where the private set is wholly independent of the kernel's trust
relationships.

Further changes in the set involve extracting certain IMA special keyrings
and making them generally global:

 (*) .system_keyring is renamed to .builtin_trusted_keys and remains read
     only.  It carries only keys built in to the kernel.  It may be where
     UEFI keys should be loaded - though that could better be the new
     secondary keyring (see below) or a separate UEFI keyring.

 (*) An optional secondary system keyring (called .secondary_trusted_keys)
     is added to replace the IMA MOK keyring.

     (*) Keys can be added to the secondary keyring by root if the keys can
         be vouched for by either ring of system keys.

 (*) Module signing and kexec only use .builtin_trusted_keys and do not use
     the new secondary keyring.

 (*) Config option SYSTEM_TRUSTED_KEYS now depends on ASYMMETRIC_KEY_TYPE as
     that's the only type currently permitted on the system keyrings.

 (*) A new config option, IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY,
     is provided to allow keys to be added to IMA keyrings, subject to the
     restriction that such keys are validly signed by a key already in the
     system keyrings.

     If this option is enabled, but secondary keyrings aren't, additions to
     the IMA keyrings will be restricted to signatures verifiable by keys in
     the builtin system keyring only.

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

4 files changed, 42 insertions, 34 deletions

diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index 8ef15118cc78..4304372b323f 100644
--- a/security/integrity/digsig.c
+++ b/security/integrity/digsig.c
@@ -18,6 +18,8 @@
 #include <linux/cred.h>
 #include <linux/key-type.h>
 #include <linux/digsig.h>
+#include <crypto/public_key.h>
+#include <keys/system_keyring.h>
 
 #include "integrity.h"
 
@@ -40,6 +42,12 @@ static bool init_keyring __initdata = true;
 static bool init_keyring __initdata;
 #endif
 
+#ifdef CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY
+#define restrict_link_to_ima restrict_link_by_builtin_and_secondary_trusted
+#else
+#define restrict_link_to_ima restrict_link_by_builtin_trusted
+#endif
+
 int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
 			    const char *digest, int digestlen)
 {
@@ -83,10 +91,9 @@ int __init integrity_init_keyring(const unsigned int id)
 				    ((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(keyring[id]))
-		set_bit(KEY_FLAG_TRUSTED_ONLY, &keyring[id]->flags);
-	else {
+				    KEY_ALLOC_NOT_IN_QUOTA,
+				    restrict_link_to_ima, NULL);
+	if (IS_ERR(keyring[id])) {
 		err = PTR_ERR(keyring[id]);
 		pr_info("Can't allocate %s keyring (%d)\n",
 			keyring_name[id], err);
diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index e54a8a8dae94..5487827fa86c 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -155,23 +155,33 @@ 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"
+config IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY
+	bool "Permit keys validly signed by a built-in or secondary CA cert (EXPERIMENTAL)"
+	depends on SYSTEM_TRUSTED_KEYRING
+	depends on SECONDARY_TRUSTED_KEYRING
+	depends on INTEGRITY_ASYMMETRIC_KEYS
+	select INTEGRITY_TRUSTED_KEYRING
+	default n
+	help
+	  Keys may be added to the IMA or IMA blacklist keyrings, if the
+	  key is validly signed by a CA cert in the system built-in or
+	  secondary trusted keyrings.
+
+	  Intermediate keys between those the kernel has compiled in and the
+	  IMA keys to be added may be added to the system secondary keyring,
+	  provided they are validly signed by a key already resident in the
+	  built-in or secondary trusted keyrings.
+
+config IMA_BLACKLIST_KEYRING
+	bool "Create IMA machine owner blacklist keyrings (EXPERIMENTAL)"
 	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.
+	   This option creates an IMA blacklist keyring, which contains all
+	   revoked IMA keys.  It is consulted before any other keyring.  If
+	   the search is successful the requested operation is rejected and
+	   an error is returned to the caller.
 
 config IMA_LOAD_X509
 	bool "Load X509 certificate onto the '.ima' trusted keyring"
diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
index a8539f9e060f..9aeaedad1e2b 100644
--- a/security/integrity/ima/Makefile
+++ b/security/integrity/ima/Makefile
@@ -8,4 +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-$(CONFIG_IMA_MOK_KEYRING) += ima_mok.o
+obj-$(CONFIG_IMA_BLACKLIST_KEYRING) += ima_mok.o
diff --git a/security/integrity/ima/ima_mok.c b/security/integrity/ima/ima_mok.c
index 676885e4320e..74a279957464 100644
--- a/security/integrity/ima/ima_mok.c
+++ b/security/integrity/ima/ima_mok.c
@@ -17,38 +17,29 @@
 #include <linux/cred.h>
 #include <linux/err.h>
 #include <linux/init.h>
-#include <keys/asymmetric-type.h>
+#include <keys/system_keyring.h>
 
 
-struct key *ima_mok_keyring;
 struct key *ima_blacklist_keyring;
 
 /*
- * Allocate the IMA MOK and blacklist keyrings
+ * Allocate the IMA blacklist keyring
  */
 __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);
+	pr_notice("Allocating IMA blacklist keyring.\n");
 
 	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);
+				KEY_ALLOC_NOT_IN_QUOTA,
+				restrict_link_by_builtin_trusted, 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);
+	if (IS_ERR(ima_blacklist_keyring))
+		panic("Can't allocate IMA blacklist keyring.");
 
-	set_bit(KEY_FLAG_TRUSTED_ONLY, &ima_blacklist_keyring->flags);
 	set_bit(KEY_FLAG_KEEP, &ima_blacklist_keyring->flags);
 	return 0;
 }