host/ble_eatt: improve PDU rx management

Added check for link encryption. Removed unused flags for client/server
process. Before processing it is checked if PDU is an ATT one, and
channel is disconnected if not. If after processing PDU next one can't
be received link is discconnected.

nimble/host/src/ble_eatt.c

@@ -35,9 +35,7 @@ struct ble_eatt {
     uint16_t conn_handle;
     struct ble_l2cap_chan *chan;
     uint8_t client_op;
-    bool client_proceed;
 
-    bool server_proceed;
     /* Packet transmit queue */
     STAILQ_HEAD(, os_mbuf_pkthdr) eatt_tx_q;
 
@@ -209,6 +207,7 @@ static int
 ble_eatt_l2cap_event_fn(struct ble_l2cap_event *event, void *arg)
 {
     struct ble_eatt *eatt = arg;
+    struct ble_gap_conn_desc desc;
     uint8_t opcode;
     int rc;
 
@@ -254,23 +253,46 @@ ble_eatt_l2cap_event_fn(struct ble_l2cap_event *event, void *arg)
     case BLE_L2CAP_EVENT_COC_DATA_RECEIVED:
         assert(eatt->chan == event->receive.chan);
         opcode = event->receive.sdu_rx->om_data[0];
-        if (ble_att_is_request_op(opcode)) {
-            eatt->server_proceed = true;
-        } else if (ble_att_is_response_op(opcode)) {
-            eatt->client_proceed = false;
+        if (ble_att_is_response_op(opcode)) {
             ble_npl_eventq_put(ble_hs_evq_get(), &eatt->wakeup_ev);
-        } else {
-            assert(0);
+        } else if (!ble_att_is_request_op(opcode)) {
+            /* As per BLE 5.4 Standard, Vol. 3, Part F, section 5.3.2
+             * (ENHANCED ATT BEARER L2CAP INTEROPERABILITY REQUIREMENTS:
+             * Channel Requirements):
+             * All packets sent on this L2CAP channel shall be Attribute PDUs.
+             *
+             * Disconnect peer with invalid behavior.
+             */
+            ble_l2cap_disconnect(eatt->chan);
+            return BLE_HS_EREJECT;
+        }
+
+        assert (!ble_gap_conn_find(event->receive.conn_handle, &desc));
+        /* As per BLE 5.4 Standard, Vol. 3, Part F, section 5.3.2
+         * (ENHANCED ATT BEARER L2CAP INTEROPERABILITY REQUIREMENTS:
+         * Channel Requirements):
+         * The channel shall be encrypted.
+         *
+         * Disconnect peer with invalid behavior - ATT PDU received before
+         * encryption.
+         */
+        if (!desc.sec_state.encrypted) {
+            ble_l2cap_disconnect(eatt->chan);
+            return BLE_HS_EREJECT;
         }
+
         ble_eatt_att_rx_cb(event->receive.conn_handle, eatt->chan->scid, &event->receive.sdu_rx);
         if (event->receive.sdu_rx) {
             os_mbuf_free_chain(event->receive.sdu_rx);
             event->receive.sdu_rx = NULL;
         }
-        rc = ble_eatt_prepare_rx_sdu(event->receive.chan);
 
-        /* FIXME Figure out what to do here, probably disconnect EATT */
-        assert(rc == 0);
+        /* Receiving L2CAP data is no longer possible, terminate connection */
+        rc = ble_eatt_prepare_rx_sdu(event->receive.chan);
+        if (rc) {
+            ble_l2cap_disconnect(eatt->chan);
+            return BLE_HS_ENOMEM;
+        }
         break;
     default:
         break;