keys: Replace uid/gid/perm permissions checking with an ACL

Replace the uid/gid/perm permissions checking on a key with an ACL to allow
the SETATTR and SEARCH permissions to be split.  This will also allow a
greater range of subjects to represented.

============
WHY DO THIS?
============

The problem is that SETATTR and SEARCH cover a slew of actions, not all of
which should be grouped together.

For SETATTR, this includes actions that are about controlling access to a
key:

 (1) Changing a key's ownership.

 (2) Changing a key's security information.

 (3) Setting a keyring's restriction.

And actions that are about managing a key's lifetime:

 (4) Setting an expiry time.

 (5) Revoking a key.

and (proposed) managing a key as part of a cache:

 (6) Invalidating a key.

Managing a key's lifetime doesn't really have anything to do with
controlling access to that key.

Expiry time is awkward since it's more about the lifetime of the content
and so, in some ways goes better with WRITE permission.  It can, however,
be set unconditionally by a process with an appropriate authorisation token
for instantiating a key, and can also be set by the key type driver when a
key is instantiated, so lumping it with the access-controlling actions is
probably okay.

As for SEARCH permission, that currently covers:

 (1) Finding keys in a keyring tree during a search.

 (2) Permitting keyrings to be joined.

 (3) Invalidation.

But these don't really belong together either, since these actions really
need to be controlled separately.

Finally, there are number of special cases to do with granting the
administrator special rights to invalidate or clear keys that I would like
to handle with the ACL rather than key flags and special checks.


===============
WHAT IS CHANGED
===============

The SETATTR permission is split to create two new permissions:

 (1) SET_SECURITY - which allows the key's owner, group and ACL to be
     changed and a restriction to be placed on a keyring.

 (2) REVOKE - which allows a key to be revoked.

The SEARCH permission is split to create:

 (1) SEARCH - which allows a keyring to be search and a key to be found.

 (2) JOIN - which allows a keyring to be joined as a session keyring.

 (3) INVAL - which allows a key to be invalidated.

The WRITE permission is also split to create:

 (1) WRITE - which allows a key's content to be altered and links to be
     added, removed and replaced in a keyring.

 (2) CLEAR - which allows a keyring to be cleared completely.  This is
     split out to make it possible to give just this to an administrator.

 (3) REVOKE - see above.


Keys acquire ACLs which consist of a series of ACEs, and all that apply are
unioned together.  An ACE specifies a subject, such as:

 (*) Possessor - permitted to anyone who 'possesses' a key
 (*) Owner - permitted to the key owner
 (*) Group - permitted to the key group
 (*) Everyone - permitted to everyone

Note that 'Other' has been replaced with 'Everyone' on the assumption that
you wouldn't grant a permit to 'Other' that you wouldn't also grant to
everyone else.

Further subjects may be made available by later patches.

The ACE also specifies a permissions mask.  The set of permissions is now:

	VIEW		Can view the key metadata
	READ		Can read the key content
	WRITE		Can update/modify the key content
	SEARCH		Can find the key by searching/requesting
	LINK		Can make a link to the key
	SET_SECURITY	Can change owner, ACL, expiry
	INVAL		Can invalidate
	REVOKE		Can revoke
	JOIN		Can join this keyring
	CLEAR		Can clear this keyring


The KEYCTL_SETPERM function is then deprecated.

The KEYCTL_SET_TIMEOUT function then is permitted if SET_SECURITY is set,
or if the caller has a valid instantiation auth token.

The KEYCTL_INVALIDATE function then requires INVAL.

The KEYCTL_REVOKE function then requires REVOKE.

The KEYCTL_JOIN_SESSION_KEYRING function then requires JOIN to join an
existing keyring.

The JOIN permission is enabled by default for session keyrings and manually
created keyrings only.


======================
BACKWARD COMPATIBILITY
======================

To maintain backward compatibility, KEYCTL_SETPERM will translate the
permissions mask it is given into a new ACL for a key - unless
KEYCTL_SET_ACL has been called on that key, in which case an error will be
returned.

It will convert possessor, owner, group and other permissions into separate
ACEs, if each portion of the mask is non-zero.

SETATTR permission turns on all of INVAL, REVOKE and SET_SECURITY.  WRITE
permission turns on WRITE, REVOKE and, if a keyring, CLEAR.  JOIN is turned
on if a keyring is being altered.

The KEYCTL_DESCRIBE function translates the ACL back into a permissions
mask to return depending on possessor, owner, group and everyone ACEs.

It will make the following mappings:

 (1) INVAL, JOIN -> SEARCH

 (2) SET_SECURITY -> SETATTR

 (3) REVOKE -> WRITE if SETATTR isn't already set

 (4) CLEAR -> WRITE

Note that the value subsequently returned by KEYCTL_DESCRIBE may not match
the value set with KEYCTL_SETATTR.


=======
TESTING
=======

This passes the keyutils testsuite for all but a couple of tests:

 (1) tests/keyctl/dh_compute/badargs: The first wrong-key-type test now
     returns EOPNOTSUPP rather than ENOKEY as READ permission isn't removed
     if the type doesn't have ->read().  You still can't actually read the
     key.

 (2) tests/keyctl/permitting/valid: The view-other-permissions test doesn't
     work as Other has been replaced with Everyone in the ACL.

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

6 files changed, 39 insertions, 29 deletions

diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index e19c2eb72c51..3bd2cc28f4f5 100644
--- a/security/integrity/digsig.c
+++ b/security/integrity/digsig.c
@@ -51,7 +51,8 @@ int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
 
 	if (!keyring[id]) {
 		keyring[id] =
-			request_key(&key_type_keyring, keyring_name[id], NULL);
+			request_key(&key_type_keyring, keyring_name[id],
+				    NULL, NULL);
 		if (IS_ERR(keyring[id])) {
 			int err = PTR_ERR(keyring[id]);
 			pr_err("no %s keyring: %d\n", keyring_name[id], err);
@@ -73,14 +74,14 @@ int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
 	return -EOPNOTSUPP;
 }
 
-static int __integrity_init_keyring(const unsigned int id, key_perm_t perm,
+static int __integrity_init_keyring(const unsigned int id, struct key_acl *acl,
 				    struct key_restriction *restriction)
 {
 	const struct cred *cred = current_cred();
 	int err = 0;
 
 	keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
-				    KGIDT_INIT(0), cred, perm,
+				    KGIDT_INIT(0), cred, acl,
 				    KEY_ALLOC_NOT_IN_QUOTA, restriction, NULL);
 	if (IS_ERR(keyring[id])) {
 		err = PTR_ERR(keyring[id]);
@@ -98,10 +99,7 @@ static int __integrity_init_keyring(const unsigned int id, key_perm_t perm,
 int __init integrity_init_keyring(const unsigned int id)
 {
 	struct key_restriction *restriction;
-	key_perm_t perm;
-
-	perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW
-		| KEY_USR_READ | KEY_USR_SEARCH;
+	struct key_acl *acl = &internal_keyring_acl;
 
 	if (id == INTEGRITY_KEYRING_PLATFORM) {
 		restriction = NULL;
@@ -116,14 +114,14 @@ int __init integrity_init_keyring(const unsigned int id)
 		return -ENOMEM;
 
 	restriction->check = restrict_link_to_ima;
-	perm |= KEY_USR_WRITE;
+	acl = &internal_writable_keyring_acl;
 
 out:
-	return __integrity_init_keyring(id, perm, restriction);
+	return __integrity_init_keyring(id, acl, restriction);
 }
 
-int __init integrity_add_key(const unsigned int id, const void *data,
-			     off_t size, key_perm_t perm)
+static int __init integrity_add_key(const unsigned int id, const void *data,
+				    off_t size, struct key_acl *acl)
 {
 	key_ref_t key;
 	int rc = 0;
@@ -132,7 +130,7 @@ int __init integrity_add_key(const unsigned int id, const void *data,
 		return -EINVAL;
 
 	key = key_create_or_update(make_key_ref(keyring[id], 1), "asymmetric",
-				   NULL, data, size, perm,
+				   NULL, data, size, acl ?: &internal_key_acl,
 				   KEY_ALLOC_NOT_IN_QUOTA);
 	if (IS_ERR(key)) {
 		rc = PTR_ERR(key);
@@ -152,7 +150,6 @@ int __init integrity_load_x509(const unsigned int id, const char *path)
 	void *data;
 	loff_t size;
 	int rc;
-	key_perm_t perm;
 
 	rc = kernel_read_file_from_path(path, &data, &size, 0,
 					READING_X509_CERTIFICATE);
@@ -161,21 +158,19 @@ int __init integrity_load_x509(const unsigned int id, const char *path)
 		return rc;
 	}
 
-	perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ;
-
 	pr_info("Loading X.509 certificate: %s\n", path);
-	rc = integrity_add_key(id, (const void *)data, size, perm);
+	rc = integrity_add_key(id, data, size, NULL);
 
 	vfree(data);
 	return rc;
 }
 
 int __init integrity_load_cert(const unsigned int id, const char *source,
-			       const void *data, size_t len, key_perm_t perm)
+			       const void *data, size_t len, struct key_acl *acl)
 {
 	if (!data)
 		return -EINVAL;
 
 	pr_info("Loading X.509 certificate: %s\n", source);
-	return integrity_add_key(id, data, len, perm);
+	return integrity_add_key(id, data, len, acl);
 }
diff --git a/security/integrity/digsig_asymmetric.c b/security/integrity/digsig_asymmetric.c
index 358f614811e8..a8bd8b2f4fce 100644
--- a/security/integrity/digsig_asymmetric.c
+++ b/security/integrity/digsig_asymmetric.c
@@ -57,7 +57,7 @@ static struct key *request_asymmetric_key(struct key *keyring, uint32_t keyid)
 		else
 			key = key_ref_to_ptr(kref);
 	} else {
-		key = request_key(&key_type_asymmetric, name, NULL);
+		key = request_key(&key_type_asymmetric, name, NULL, NULL);
 	}
 
 	if (IS_ERR(key)) {
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index e11564eb645b..304cb0b21f7a 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -356,7 +356,7 @@ int evm_init_key(void)
 	struct encrypted_key_payload *ekp;
 	int rc;
 
-	evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
+	evm_key = request_key(&key_type_encrypted, EVMKEY, NULL, NULL);
 	if (IS_ERR(evm_key))
 		return -ENOENT;
 
diff --git a/security/integrity/ima/ima_mok.c b/security/integrity/ima/ima_mok.c
index 073ddc9bce5b..ce48303cfacc 100644
--- a/security/integrity/ima/ima_mok.c
+++ b/security/integrity/ima/ima_mok.c
@@ -21,6 +21,15 @@
 #include <keys/system_keyring.h>
 
 
+static struct key_acl integrity_blacklist_keyring_acl = {
+	.usage	= REFCOUNT_INIT(1),
+	.nr_ace	= 2,
+	.aces = {
+		KEY_POSSESSOR_ACE(KEY_ACE_SEARCH | KEY_ACE_WRITE),
+		KEY_OWNER_ACE(KEY_ACE_VIEW | KEY_ACE_READ | KEY_ACE_WRITE | KEY_ACE_SEARCH),
+	}
+};
+
 struct key *ima_blacklist_keyring;
 
 /*
@@ -40,9 +49,7 @@ __init int ima_mok_init(void)
 
 	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,
+			        &integrity_blacklist_keyring_acl,
 				KEY_ALLOC_NOT_IN_QUOTA,
 				restriction, NULL);
 
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 7de59f44cba3..1c50aff6f65a 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -17,6 +17,8 @@
 #include <linux/key.h>
 #include <linux/audit.h>
 
+struct key_acl;
+
 /* iint action cache flags */
 #define IMA_MEASURE		0x00000001
 #define IMA_MEASURED		0x00000002
@@ -154,7 +156,7 @@ int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
 int __init integrity_init_keyring(const unsigned int id);
 int __init integrity_load_x509(const unsigned int id, const char *path);
 int __init integrity_load_cert(const unsigned int id, const char *source,
-			       const void *data, size_t len, key_perm_t perm);
+			       const void *data, size_t len, struct key_acl *acl);
 #else
 
 static inline int integrity_digsig_verify(const unsigned int id,
@@ -172,7 +174,7 @@ static inline int integrity_init_keyring(const unsigned int id)
 static inline int __init integrity_load_cert(const unsigned int id,
 					     const char *source,
 					     const void *data, size_t len,
-					     key_perm_t perm)
+					     struct key_acl *acl)
 {
 	return 0;
 }
diff --git a/security/integrity/platform_certs/platform_keyring.c b/security/integrity/platform_certs/platform_keyring.c
index bcafd7387729..7646e35f2d91 100644
--- a/security/integrity/platform_certs/platform_keyring.c
+++ b/security/integrity/platform_certs/platform_keyring.c
@@ -14,6 +14,15 @@
 #include <linux/slab.h>
 #include "../integrity.h"
 
+static struct key_acl platform_key_acl = {
+	.usage	= REFCOUNT_INIT(1),
+	.nr_ace	= 2,
+	.aces = {
+		KEY_POSSESSOR_ACE(KEY_ACE_SEARCH | KEY_ACE_READ),
+		KEY_OWNER_ACE(KEY_ACE_VIEW),
+	}
+};
+
 /**
  * add_to_platform_keyring - Add to platform keyring without validation.
  * @source: Source of key
@@ -26,13 +35,10 @@
 void __init add_to_platform_keyring(const char *source, const void *data,
 				    size_t len)
 {
-	key_perm_t perm;
 	int rc;
 
-	perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW;
-
 	rc = integrity_load_cert(INTEGRITY_KEYRING_PLATFORM, source, data, len,
-				 perm);
+				 &platform_key_acl);
 	if (rc)
 		pr_info("Error adding keys to platform keyring %s\n", source);
 }