Bluetooth: Fix link key persistent storage criteria

Link keys should only be stored if very specific criteria of the
authentication process are fulfilled. This patch essentially copies the
criteria that user space has so far been using to the kernel side so
that the management interface works properly.
Signed-off-by: Johan Hedberg <johan.hedberg@nokia.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>

include/net/bluetooth/hci_core.h

@@ -515,8 +515,8 @@ int hci_uuids_clear(struct hci_dev *hdev);
 
 int hci_link_keys_clear(struct hci_dev *hdev);
 struct link_key *hci_find_link_key(struct hci_dev *hdev, bdaddr_t *bdaddr);
-int hci_add_link_key(struct hci_dev *hdev, int new_key, bdaddr_t *bdaddr,
-						u8 *key, u8 type, u8 pin_len);
+int hci_add_link_key(struct hci_dev *hdev, struct hci_conn *conn, int new_key,
+			bdaddr_t *bdaddr, u8 *val, u8 type, u8 pin_len);
 int hci_remove_link_key(struct hci_dev *hdev, bdaddr_t *bdaddr);
 
 int hci_remote_oob_data_clear(struct hci_dev *hdev);

net/bluetooth/hci_core.c

@@ -1022,8 +1022,44 @@ struct link_key *hci_find_link_key(struct hci_dev *hdev, bdaddr_t *bdaddr)
 	return NULL;
 }
 
-int hci_add_link_key(struct hci_dev *hdev, int new_key, bdaddr_t *bdaddr,
-						u8 *val, u8 type, u8 pin_len)
+static int hci_persistent_key(struct hci_dev *hdev, struct hci_conn *conn,
+						u8 key_type, u8 old_key_type)
+{
+	/* Legacy key */
+	if (key_type < 0x03)
+		return 1;
+
+	/* Debug keys are insecure so don't store them persistently */
+	if (key_type == HCI_LK_DEBUG_COMBINATION)
+		return 0;
+
+	/* Changed combination key and there's no previous one */
+	if (key_type == HCI_LK_CHANGED_COMBINATION && old_key_type == 0xff)
+		return 0;
+
+	/* Security mode 3 case */
+	if (!conn)
+		return 1;
+
+	/* Neither local nor remote side had no-bonding as requirement */
+	if (conn->auth_type > 0x01 && conn->remote_auth > 0x01)
+		return 1;
+
+	/* Local side had dedicated bonding as requirement */
+	if (conn->auth_type == 0x02 || conn->auth_type == 0x03)
+		return 1;
+
+	/* Remote side had dedicated bonding as requirement */
+	if (conn->remote_auth == 0x02 || conn->remote_auth == 0x03)
+		return 1;
+
+	/* If none of the above criteria match, then don't store the key
+	 * persistently */
+	return 0;
+}
+
+int hci_add_link_key(struct hci_dev *hdev, struct hci_conn *conn, int new_key,
+				bdaddr_t *bdaddr, u8 *val, u8 type, u8 pin_len)
 {
 	struct link_key *key, *old_key;
 	u8 old_key_type;
@@ -1042,6 +1078,20 @@ int hci_add_link_key(struct hci_dev *hdev, int new_key, bdaddr_t *bdaddr,
 
 	BT_DBG("%s key for %s type %u", hdev->name, batostr(bdaddr), type);
 
+	/* Some buggy controller combinations generate a changed
+	 * combination key for legacy pairing even when there's no
+	 * previous key */
+	if (type == HCI_LK_CHANGED_COMBINATION &&
+					(!conn || conn->remote_auth == 0xff) &&
+					old_key_type == 0xff)
+		type = HCI_LK_COMBINATION;
+
+	if (new_key && !hci_persistent_key(hdev, conn, type, old_key_type)) {
+		list_del(&key->list);
+		kfree(key);
+		return 0;
+	}
+
 	bacpy(&key->bdaddr, bdaddr);
 	memcpy(key->val, val, 16);
 	key->type = type;

net/bluetooth/hci_event.c

@@ -2136,7 +2136,7 @@ static inline void hci_link_key_notify_evt(struct hci_dev *hdev, struct sk_buff
 	}
 
 	if (test_bit(HCI_LINK_KEYS, &hdev->flags))
-		hci_add_link_key(hdev, 1, &ev->bdaddr, ev->link_key,
+		hci_add_link_key(hdev, conn, 1, &ev->bdaddr, ev->link_key,
 							ev->key_type, pin_len);
 
 	hci_dev_unlock(hdev);

net/bluetooth/mgmt.c

@@ -945,7 +945,7 @@ static int load_keys(struct sock *sk, u16 index, unsigned char *data, u16 len)
 	for (i = 0; i < key_count; i++) {
 		struct mgmt_key_info *key = &cp->keys[i];
 
-		hci_add_link_key(hdev, 0, &key->bdaddr, key->val, key->type,
+		hci_add_link_key(hdev, NULL, 0, &key->bdaddr, key->val, key->type,
 								key->pin_len);
 	}