Bluetooth: Double check sec req for pre 2.1 device

In case of pre v2.1 devices authentication request will return
success immediately if the link key already exists without any
authentication process.

That means, it's not possible to re-authenticate the link if you
already have combination key and for instance want to re-authenticate
to get the high security (use 16 digit pin).

Therefore, it's necessary to check security requirements on auth
complete event to prevent not enough secure connection.
Signed-off-by: Waldemar Rymarkiewicz <waldemar.rymarkiewicz@tieto.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>

include/net/bluetooth/hci_core.h

@@ -422,6 +422,7 @@ void hci_conn_check_pending(struct hci_dev *hdev);
 
 struct hci_conn *hci_connect(struct hci_dev *hdev, int type, bdaddr_t *dst, __u8 sec_level, __u8 auth_type);
 int hci_conn_check_link_mode(struct hci_conn *conn);
+int hci_conn_check_secure(struct hci_conn *conn, __u8 sec_level);
 int hci_conn_security(struct hci_conn *conn, __u8 sec_level, __u8 auth_type);
 int hci_conn_change_link_key(struct hci_conn *conn);
 int hci_conn_switch_role(struct hci_conn *conn, __u8 role);

net/bluetooth/hci_conn.c

@@ -623,6 +623,23 @@ int hci_conn_security(struct hci_conn *conn, __u8 sec_level, __u8 auth_type)
 }
 EXPORT_SYMBOL(hci_conn_security);
 
+/* Check secure link requirement */
+int hci_conn_check_secure(struct hci_conn *conn, __u8 sec_level)
+{
+	BT_DBG("conn %p", conn);
+
+	if (sec_level != BT_SECURITY_HIGH)
+		return 1; /* Accept if non-secure is required */
+
+	if (conn->key_type == HCI_LK_AUTH_COMBINATION ||
+			(conn->key_type == HCI_LK_COMBINATION &&
+			conn->pin_length == 16))
+		return 1;
+
+	return 0; /* Reject not secure link */
+}
+EXPORT_SYMBOL(hci_conn_check_secure);
+
 /* Change link key */
 int hci_conn_change_link_key(struct hci_conn *conn)
 {

net/bluetooth/rfcomm/core.c

@@ -2096,7 +2096,7 @@ static void rfcomm_security_cfm(struct hci_conn *conn, u8 status, u8 encrypt)
 		if (!test_and_clear_bit(RFCOMM_AUTH_PENDING, &d->flags))
 			continue;
 
-		if (!status)
+		if (!status && hci_conn_check_secure(conn, d->sec_level))
 			set_bit(RFCOMM_AUTH_ACCEPT, &d->flags);
 		else
 			set_bit(RFCOMM_AUTH_REJECT, &d->flags);