[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>

3 files changed, 84 insertions, 5 deletions

diff --git a/include/linux/key-ui.h b/include/linux/key-ui.h
index 7a2e332..e8b8a7a 100644
--- a/include/linux/key-ui.h
+++ b/include/linux/key-ui.h
@@ -24,7 +24,8 @@ extern spinlock_t key_serial_lock;
 #define	KEY_WRITE	0x04	/* require permission to update / modify */
 #define	KEY_SEARCH	0x08	/* require permission to search (keyring) or find (key) */
 #define	KEY_LINK	0x10	/* require permission to link */
-#define	KEY_ALL		0x1f	/* all the above permissions */
+#define	KEY_SETATTR	0x20	/* require permission to change attributes */
+#define	KEY_ALL		0x3f	/* all the above permissions */
 
 /*
  * the keyring payload contains a list of the keys to which the keyring is
diff --git a/include/linux/key.h b/include/linux/key.h
index f1efa01..53513a3 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -40,28 +40,32 @@ struct key;
 #define KEY_POS_WRITE	0x04000000	/* possessor can update key payload / add link to keyring */
 #define KEY_POS_SEARCH	0x08000000	/* possessor can find a key in search / search a keyring */
 #define KEY_POS_LINK	0x10000000	/* possessor can create a link to a key/keyring */
-#define KEY_POS_ALL	0x1f000000
+#define KEY_POS_SETATTR	0x20000000	/* possessor can set key attributes */
+#define KEY_POS_ALL	0x3f000000
 
 #define KEY_USR_VIEW	0x00010000	/* user permissions... */
 #define KEY_USR_READ	0x00020000
 #define KEY_USR_WRITE	0x00040000
 #define KEY_USR_SEARCH	0x00080000
 #define KEY_USR_LINK	0x00100000
-#define KEY_USR_ALL	0x001f0000
+#define KEY_USR_SETATTR	0x00200000
+#define KEY_USR_ALL	0x003f0000
 
 #define KEY_GRP_VIEW	0x00000100	/* group permissions... */
 #define KEY_GRP_READ	0x00000200
 #define KEY_GRP_WRITE	0x00000400
 #define KEY_GRP_SEARCH	0x00000800
 #define KEY_GRP_LINK	0x00001000
-#define KEY_GRP_ALL	0x00001f00
+#define KEY_GRP_SETATTR	0x00002000
+#define KEY_GRP_ALL	0x00003f00
 
 #define KEY_OTH_VIEW	0x00000001	/* third party permissions... */
 #define KEY_OTH_READ	0x00000002
 #define KEY_OTH_WRITE	0x00000004
 #define KEY_OTH_SEARCH	0x00000008
 #define KEY_OTH_LINK	0x00000010
-#define KEY_OTH_ALL	0x0000001f
+#define KEY_OTH_SETATTR	0x00000020
+#define KEY_OTH_ALL	0x0000003f
 
 struct seq_file;
 struct user_struct;
@@ -119,6 +123,7 @@ struct key {
 	struct key_type		*type;		/* type of key */
 	struct rw_semaphore	sem;		/* change vs change sem */
 	struct key_user		*user;		/* owner of this key */
+	void			*security;	/* security data for this key */
 	time_t			expiry;		/* time at which key expires (or 0) */
 	uid_t			uid;
 	gid_t			gid;
diff --git a/include/linux/security.h b/include/linux/security.h
index 607ee20..f7e0ae0 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -30,6 +30,7 @@
 #include <linux/shm.h>
 #include <linux/msg.h>
 #include <linux/sched.h>
+#include <linux/key.h>
 
 struct ctl_table;
 
@@ -788,6 +789,27 @@ struct swap_info_struct;
  * @sk_free_security:
  *	Deallocate security structure.
  *
+ * Security hooks affecting all Key Management operations
+ *
+ * @key_alloc:
+ *	Permit allocation of a key and assign security data. Note that key does
+ *	not have a serial number assigned at this point.
+ *	@key points to the key.
+ *	Return 0 if permission is granted, -ve error otherwise.
+ * @key_free:
+ *	Notification of destruction; free security data.
+ *	@key points to the key.
+ *	No return value.
+ * @key_permission:
+ *	See whether a specific operational right is granted to a process on a
+ *      key.
+ *	@key_ref refers to the key (key pointer + possession attribute bit).
+ *	@context points to the process to provide the context against which to
+ *       evaluate the security data on the key.
+ *	@perm describes the combination of permissions required of this key.
+ *	Return 1 if permission granted, 0 if permission denied and -ve it the
+ *      normal permissions model should be effected.
+ *
  * Security hooks affecting all System V IPC operations.
  *
  * @ipc_permission:
@@ -1216,6 +1238,17 @@ struct security_operations {
 	int (*sk_alloc_security) (struct sock *sk, int family, gfp_t priority);
 	void (*sk_free_security) (struct sock *sk);
 #endif	/* CONFIG_SECURITY_NETWORK */
+
+	/* key management security hooks */
+#ifdef CONFIG_KEYS
+	int (*key_alloc)(struct key *key);
+	void (*key_free)(struct key *key);
+	int (*key_permission)(key_ref_t key_ref,
+			      struct task_struct *context,
+			      key_perm_t perm);
+
+#endif	/* CONFIG_KEYS */
+
 };
 
 /* global variables */
@@ -2764,5 +2797,45 @@ static inline void security_sk_free(struct sock *sk)
 }
 #endif	/* CONFIG_SECURITY_NETWORK */
 
+#ifdef CONFIG_KEYS
+#ifdef CONFIG_SECURITY
+static inline int security_key_alloc(struct key *key)
+{
+	return security_ops->key_alloc(key);
+}
+
+static inline void security_key_free(struct key *key)
+{
+	security_ops->key_free(key);
+}
+
+static inline int security_key_permission(key_ref_t key_ref,
+					  struct task_struct *context,
+					  key_perm_t perm)
+{
+	return security_ops->key_permission(key_ref, context, perm);
+}
+
+#else
+
+static inline int security_key_alloc(struct key *key)
+{
+	return 0;
+}
+
+static inline void security_key_free(struct key *key)
+{
+}
+
+static inline int security_key_permission(key_ref_t key_ref,
+					  struct task_struct *context,
+					  key_perm_t perm)
+{
+	return 0;
+}
+
+#endif
+#endif /* CONFIG_KEYS */
+
 #endif /* ! __LINUX_SECURITY_H */