Rework the macro LEDGER_BLE_get_mac_address into a function

lib_blewbxx/include/ble_ledger.h

@@ -28,30 +28,7 @@ typedef enum {
     BLE_LEDGER_PROFILE_U2F  = 0x0004,
 } ble_ledger_profile_mask_e;
 
-#define BLE_ADDRESS_SET_MSB (0xC0)
-
 /* Exported defines   --------------------------------------------------------*/
-// Random static address is specified at
-// https://wiki.st.com/stm32mcu/wiki/Connectivity:STM32WB-WBA_BLE_Privacy#Random_static_address
-// In particular, the two most significant bits need to be set to 1.
-#define LEDGER_BLE_get_mac_address(address)                    \
-    {                                                          \
-        unsigned char se_serial[8] = {0};                      \
-        os_serial(se_serial, sizeof(se_serial));               \
-        unsigned int uid = cx_crc16(se_serial, 4);             \
-        address[0]       = uid;                                \
-        address[1]       = uid >> 8;                           \
-        uid              = cx_crc16(se_serial + 4, 4);         \
-        address[2]       = uid;                                \
-        address[3]       = uid >> 8;                           \
-        for (unsigned int i = 0; i < sizeof(se_serial); i++) { \
-            se_serial[i] = ~se_serial[i];                      \
-        }                                                      \
-        uid        = cx_crc16(se_serial, 8);                   \
-        address[4] = uid;                                      \
-        address[5] = (uid >> 8) | BLE_ADDRESS_SET_MSB;         \
-    }
-
 #define BLE_SLAVE_CONN_INTERVAL_MIN 12  // 15ms
 #define BLE_SLAVE_CONN_INTERVAL_MAX 24  // 30ms
 
@@ -73,6 +50,14 @@ void BLE_LEDGER_reset_pairings(void);
 void BLE_LEDGER_accept_pairing(uint8_t status);
 void BLE_LEDGER_name_changed(void);
 
+/**
+ * @brief Derives the BLE MAC address from the product serial number.
+ *
+ * @param address_buf Pointer to a buffer of at least 6 bytes.
+ * @param buf_len     Length of the provided buffer.
+ */
+void LEDGER_BLE_get_mac_address(uint8_t *address_buf, size_t buf_len);
+
 // Rx
 int BLE_LEDGER_rx_seph_evt(uint8_t *seph_buffer,
                            uint16_t seph_buffer_length,

lib_blewbxx/src/ble_addr.c

@@ -0,0 +1,65 @@
+/*****************************************************************************
+ *   (c) 2025 Ledger SAS.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *****************************************************************************/
+
+/* Includes ------------------------------------------------------------------*/
+#include <string.h>
+
+#include "os.h"
+#include "os_helpers.h"
+#include "lcx_crc.h"
+
+/* Private enumerations ------------------------------------------------------*/
+
+/* Private defines------------------------------------------------------------*/
+// Flag to set the two most significant bits to 11 = random static address
+#define BLE_ADDRESS_SET_MSB (0xC0)
+
+/* Private types, structures, unions -----------------------------------------*/
+
+/* Private macros-------------------------------------------------------------*/
+
+/* Private functions prototypes ----------------------------------------------*/
+
+/* Exported functions --------------------------------------------------------*/
+
+void LEDGER_BLE_get_mac_address(uint8_t *address_buf, size_t buf_len)
+{
+    // Ensure we have enough space for a 6-byte MAC address
+    if (address_buf == NULL || buf_len < 6) {
+        return;
+    }
+
+    uint8_t  se_serial[8] = {0};
+    uint16_t uid;
+
+    os_serial(se_serial, sizeof(se_serial));
+
+    uid            = cx_crc16(se_serial, 4);
+    address_buf[0] = (uint8_t) (uid & 0xff);
+    address_buf[1] = (uint8_t) (uid >> 8);
+    uid            = cx_crc16(se_serial + 4, 4);
+    address_buf[2] = (uint8_t) (uid & 0xff);
+    address_buf[3] = (uint8_t) (uid >> 8);
+
+    // Invert the serial number bits for the final derivation
+    for (size_t i = 0; i < sizeof(se_serial); i++) {
+        se_serial[i] = ~se_serial[i];
+    }
+    uid            = cx_crc16(se_serial, 8);
+    address_buf[4] = (uint8_t) (uid & 0xff);
+    // Set the two most significant bits for Random Static Address
+    address_buf[5] = (uint8_t) ((uid >> 8) | BLE_ADDRESS_SET_MSB);
+}