[PATCH] Keys: Add LSM hooks for key management [try #3]

The attached patch adds LSM hooks for key management facilities. The notable
changes are:

 (1) The key struct now supports a security pointer for the use of security
     modules. This will permit key labelling and restrictions on which
     programs may access a key.

 (2) Security modules get a chance to note (or abort) the allocation of a key.

 (3) The key permission checking can now be enhanced by the security modules;
     the permissions check consults LSM if all other checks bear out.

 (4) The key permissions checking functions now return an error code rather
     than a boolean value.

 (5) An extra permission has been added to govern the modification of
     attributes (UID, GID, permissions).

Note that there isn't an LSM hook specifically for each keyctl() operation,
but rather the permissions hook allows control of individual operations based
on the permission request bits.

Key management access control through LSM is enabled by automatically if both
CONFIG_KEYS and CONFIG_SECURITY are enabled.

This should be applied on top of the patch ensubjected:

	[PATCH] Keys: Possessor permissions should be additive

Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Chris Wright <chrisw@osdl.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 40 insertions, 16 deletions

diff --git a/security/keys/key.c b/security/keys/key.c
index 2182be9..ccde17a 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -1,6 +1,6 @@
 /* key.c: basic authentication token and access key management
  *
- * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
+ * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  *
  * This program is free software; you can redistribute it and/or
@@ -13,6 +13,7 @@
 #include <linux/init.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
+#include <linux/security.h>
 #include <linux/workqueue.h>
 #include <linux/err.h>
 #include "internal.h"
@@ -253,6 +254,7 @@ struct key *key_alloc(struct key_type *type, const char *desc,
 	struct key_user *user = NULL;
 	struct key *key;
 	size_t desclen, quotalen;
+	int ret;
 
 	key = ERR_PTR(-EINVAL);
 	if (!desc || !*desc)
@@ -305,6 +307,7 @@ struct key *key_alloc(struct key_type *type, const char *desc,
 	key->flags = 0;
 	key->expiry = 0;
 	key->payload.data = NULL;
+	key->security = NULL;
 
 	if (!not_in_quota)
 		key->flags |= 1 << KEY_FLAG_IN_QUOTA;
@@ -315,16 +318,34 @@ struct key *key_alloc(struct key_type *type, const char *desc,
 	key->magic = KEY_DEBUG_MAGIC;
 #endif
 
+	/* let the security module know about the key */
+	ret = security_key_alloc(key);
+	if (ret < 0)
+		goto security_error;
+
 	/* publish the key by giving it a serial number */
 	atomic_inc(&user->nkeys);
 	key_alloc_serial(key);
 
- error:
+error:
 	return key;
 
- no_memory_3:
+security_error:
+	kfree(key->description);
+	kmem_cache_free(key_jar, key);
+	if (!not_in_quota) {
+		spin_lock(&user->lock);
+		user->qnkeys--;
+		user->qnbytes -= quotalen;
+		spin_unlock(&user->lock);
+	}
+	key_user_put(user);
+	key = ERR_PTR(ret);
+	goto error;
+
+no_memory_3:
 	kmem_cache_free(key_jar, key);
- no_memory_2:
+no_memory_2:
 	if (!not_in_quota) {
 		spin_lock(&user->lock);
 		user->qnkeys--;
@@ -332,11 +353,11 @@ struct key *key_alloc(struct key_type *type, const char *desc,
 		spin_unlock(&user->lock);
 	}
 	key_user_put(user);
- no_memory_1:
+no_memory_1:
 	key = ERR_PTR(-ENOMEM);
 	goto error;
 
- no_quota:
+no_quota:
 	spin_unlock(&user->lock);
 	key_user_put(user);
 	key = ERR_PTR(-EDQUOT);
@@ -556,6 +577,8 @@ static void key_cleanup(void *data)
 
 	key_check(key);
 
+	security_key_free(key);
+
 	/* deal with the user's key tracking and quota */
 	if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
 		spin_lock(&key->user->lock);
@@ -700,8 +723,8 @@ static inline key_ref_t __key_update(key_ref_t key_ref,
 	int ret;
 
 	/* need write permission on the key to update it */
-	ret = -EACCES;
-	if (!key_permission(key_ref, KEY_WRITE))
+	ret = key_permission(key_ref, KEY_WRITE);
+	if (ret < 0)
 		goto error;
 
 	ret = -EEXIST;
@@ -711,7 +734,6 @@ static inline key_ref_t __key_update(key_ref_t key_ref,
 	down_write(&key->sem);
 
 	ret = key->type->update(key, payload, plen);
-
 	if (ret == 0)
 		/* updating a negative key instantiates it */
 		clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
@@ -768,9 +790,11 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 
 	/* if we're going to allocate a new key, we're going to have
 	 * to modify the keyring */
-	key_ref = ERR_PTR(-EACCES);
-	if (!key_permission(keyring_ref, KEY_WRITE))
+	ret = key_permission(keyring_ref, KEY_WRITE);
+	if (ret < 0) {
+		key_ref = ERR_PTR(ret);
 		goto error_3;
+	}
 
 	/* search for an existing key of the same type and description in the
 	 * destination keyring
@@ -780,8 +804,8 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 		goto found_matching_key;
 
 	/* decide on the permissions we want */
-	perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK;
-	perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK;
+	perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR;
+	perm |= KEY_USR_VIEW | KEY_USR_SEARCH | KEY_USR_LINK | KEY_USR_SETATTR;
 
 	if (ktype->read)
 		perm |= KEY_POS_READ | KEY_USR_READ;
@@ -840,16 +864,16 @@ int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 	key_check(key);
 
 	/* the key must be writable */
-	ret = -EACCES;
-	if (!key_permission(key_ref, KEY_WRITE))
+	ret = key_permission(key_ref, KEY_WRITE);
+	if (ret < 0)
 		goto error;
 
 	/* attempt to update it if supported */
 	ret = -EOPNOTSUPP;
 	if (key->type->update) {
 		down_write(&key->sem);
-		ret = key->type->update(key, payload, plen);
 
+		ret = key->type->update(key, payload, plen);
 		if (ret == 0)
 			/* updating a negative key instantiates it */
 			clear_bit(KEY_FLAG_NEGATIVE, &key->flags);