NFC: Rudimentary iso14443_4a_listener_send_block() (no PCB handling) (OFW issue 4059)

lib/nfc/protocols/iso14443_4a/iso14443_4a_listener.c

@@ -70,7 +70,15 @@ static NfcCommand iso14443_4a_listener_run(NfcGenericEvent event, void* context)
                     instance->state = Iso14443_4aListenerStateActive;
                 }
             }
-        } else {
+        } else if(bit_buffer_get_size_bytes(rx_buffer) > 1) {
+            // TODO: This is a rudimentary PCB implementation!
+            // Just ignores its meaning and saves it for sending blocks to reader,
+            // there is no handling of S, R, I blocks and their different flags.
+            // We have iso14443_4_layer helper but it is entirely designed for poller,
+            // will need large rework for listener, for now this works.
+            instance->pcb_prev = bit_buffer_get_byte(rx_buffer, 0);
+            bit_buffer_copy_right(rx_buffer, rx_buffer, 1);
+
             instance->iso14443_4a_event.type = Iso14443_4aListenerEventTypeReceivedData;
             instance->iso14443_4a_event.data->buffer = rx_buffer;
 

lib/nfc/protocols/iso14443_4a/iso14443_4a_listener.h

@@ -25,6 +25,18 @@ typedef struct {
     Iso14443_4aListenerEventData* data;
 } Iso14443_4aListenerEvent;
 
+/**
+ * @brief Transmit Iso14443_4a blocks in listener mode.
+ *
+ * Must ONLY be used inside the callback function.
+ *
+ * @param[in, out] instance pointer to the instance to be used in the transaction.
+ * @param[in] tx_buffer pointer to the buffer containing the data to be transmitted.
+ * @return Iso14443_4aErrorNone on success, an error code on failure.
+ */
+Iso14443_4aError
+    iso14443_4a_listener_send_block(Iso14443_4aListener* instance, const BitBuffer* tx_buffer);
+
 #ifdef __cplusplus
 }
 #endif

lib/nfc/protocols/iso14443_4a/iso14443_4a_listener_i.c

@@ -30,3 +30,20 @@ Iso14443_4aError
         instance->iso14443_3a_listener, instance->tx_buffer);
     return iso14443_4a_process_error(error);
 }
+
+Iso14443_4aError
+    iso14443_4a_listener_send_block(Iso14443_4aListener* instance, const BitBuffer* tx_buffer) {
+    bit_buffer_reset(instance->tx_buffer);
+
+    // TODO: This is a rudimentary PCB implementation!
+    // Just sends back same PCB that was last received from reader,
+    // there is no handling of S, R, I blocks and their different flags.
+    // We have iso14443_4_layer helper but it is entirely designed for poller,
+    // will need large rework for listener, for now this works.
+    bit_buffer_append_byte(instance->tx_buffer, instance->pcb_prev);
+    bit_buffer_append(instance->tx_buffer, tx_buffer);
+
+    const Iso14443_3aError error = iso14443_3a_listener_send_standard_frame(
+        instance->iso14443_3a_listener, instance->tx_buffer);
+    return iso14443_4a_process_error(error);
+}

lib/nfc/protocols/iso14443_4a/iso14443_4a_listener_i.h

@@ -17,6 +17,7 @@ typedef enum {
 struct Iso14443_4aListener {
     Iso14443_3aListener* iso14443_3a_listener;
     Iso14443_4aData* data;
+    uint8_t pcb_prev;
     Iso14443_4aListenerState state;
 
     BitBuffer* tx_buffer;

targets/f7/api_symbols.csv

@@ -2163,6 +2163,7 @@ Function,+,iso14443_4a_get_fwt_fc_max,uint32_t,const Iso14443_4aData*
 Function,+,iso14443_4a_get_historical_bytes,const uint8_t*,"const Iso14443_4aData*, uint32_t*"
 Function,+,iso14443_4a_get_uid,const uint8_t*,"const Iso14443_4aData*, size_t*"
 Function,+,iso14443_4a_is_equal,_Bool,"const Iso14443_4aData*, const Iso14443_4aData*"
+Function,+,iso14443_4a_listener_send_block,Iso14443_4aError,"Iso14443_4aListener*, const BitBuffer*"
 Function,+,iso14443_4a_load,_Bool,"Iso14443_4aData*, FlipperFormat*, uint32_t"
 Function,+,iso14443_4a_poller_halt,Iso14443_4aError,Iso14443_4aPoller*
 Function,+,iso14443_4a_poller_read_ats,Iso14443_4aError,"Iso14443_4aPoller*, Iso14443_4aAtsData*"