Security failed on central_uart and peripheral_uart example

[Arno]

Hi,

At first I've succesfully managed to get the central_uart and peripheral_uart example running on 2 custom boards with nRF5340. Both are connecting and pairing fine, I see that they are switching to security level 2 as expected.

But after a while, after doing nothing special I get security failed error's. I have tried these examples both in nrf 1.9.1 and nrf 2.3.0. Same result: at first it worked but after a while I got the security error's.

A lot of experiments, such as going back to the original examples without changing any code (other then some minimum changes (3 lines) in the board files to get it running) did not fix the problem. Trying to unbond by using the bt_unpair() function did not help.

The only situation I can reproduce that works is to put use the central_uart example from nrf2.3.0 in combination with the peripheral_uart example from nrf 1.9.1. as can be seen in the top picture.

Can somebody please give me some pointers on what is going on?

Any help greatly appreciated,

Arno

[Arno]

Hi,

Small update, after doing bt_unpair() on the peripheral_uart example from nrf 1.9.1. I got the same security failed error. So it has to do with pairing information that is lost. However the samples worked fine the first time, how can that be? How can I erase settings to go to a pristine situation that works out of the box? Is there some more simple example code for pairing other then the sample with nrf?

Kind regards,

Arno

[Hung Bui]

Hi Arno, 

You would need to call bt_unpair() on both sides of the connection, the central and the peripheral. 

The reason for that is that for security reason, a new pair can't be automatically created if one side of the connection lose bond information. 

Another option is to do a full erase of the chip on both side. Then they will start fresh. You can do a full erase by using nrfjprog.exe --eraseall. 

Or if you use Visual Studio Code, you click on double arrows button when flashing: 

[Arno]

Hi,

I have tried your suggestions (erase and unpair() ), but both fail. Please see the attached picture.

I was able to trace the -22 error on the central_uart example back to not having the .passkey_display nor 

.passkey_confirm callback functions. This seems to make sense because in connected() we are going to 

err = bt_conn_set_security(conn, BT_SECURITY_L2); So we need a display and a keyboard to show security code and confirm the verification code on the central as well? Please correct me if I'm missing something.

After this we also need something to push a button, so the button_changed() and num_comp_reply() functions

from the peripheral_uart example ported towards the central_uart. And now it works and we get the following result:

It is my impression that the flash erase all is helping a lot, however it is my impressing that unpair() does not remove the bonds from from settings flash. I have now unpair() standard in the code but now after a reset the bonding still is present. Only a full erase of the flash removes the bond.

Another suggestion I would like to give is to update the central_uart example because in my opinion it is far from complete. This problem has taken me a lot of time to figure out.

I have attached the sources, in the hope that somebody else benefits from this. For completeness I have

added the following to the prj.conf of both the central and peripheral (but probably it does not matter):

CONFIG_BT_SMP_SC_ONLY=y

CONFIG_BT_TINYCRYPT_ECC=y

Kind regards,

Arno

Code for the peripheral_uart:

/*
 * Copyright (c) 2018 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
 */

/** @file
 *  @brief Nordic UART Bridge Service (NUS) sample
 */
#include "uart_async_adapter.h"

#include <zephyr/types.h>
#include <zephyr/kernel.h>
#include <zephyr/drivers/uart.h>
#include <zephyr/usb/usb_device.h>

#include <zephyr/device.h>
#include <zephyr/devicetree.h>
#include <soc.h>

#include <zephyr/bluetooth/bluetooth.h>
#include <zephyr/bluetooth/uuid.h>
#include <zephyr/bluetooth/gatt.h>
#include <zephyr/bluetooth/hci.h>

#include <bluetooth/services/nus.h>

#include <dk_buttons_and_leds.h>

#include <zephyr/settings/settings.h>

#include <stdio.h>

#include <zephyr/logging/log.h>

#define LOG_MODULE_NAME peripheral_uart
LOG_MODULE_REGISTER(LOG_MODULE_NAME);

#define STACKSIZE CONFIG_BT_NUS_THREAD_STACK_SIZE
#define PRIORITY 7

#define DEVICE_NAME CONFIG_BT_DEVICE_NAME
#define DEVICE_NAME_LEN	(sizeof(DEVICE_NAME) - 1)

#define RUN_STATUS_LED DK_LED1
#define RUN_LED_BLINK_INTERVAL 1000

#define CON_STATUS_LED DK_LED2

#define KEY_PASSKEY_ACCEPT DK_BTN1_MSK
#define KEY_PASSKEY_REJECT DK_BTN2_MSK

#define UART_BUF_SIZE CONFIG_BT_NUS_UART_BUFFER_SIZE
#define UART_WAIT_FOR_BUF_DELAY K_MSEC(50)
#define UART_WAIT_FOR_RX CONFIG_BT_NUS_UART_RX_WAIT_TIME

static K_SEM_DEFINE(ble_init_ok, 0, 1);

static struct bt_conn *current_conn;
static struct bt_conn *auth_conn;

static const struct device *uart = DEVICE_DT_GET(DT_CHOSEN(nordic_nus_uart));
static struct k_work_delayable uart_work;

struct uart_data_t {
	void *fifo_reserved;
	uint8_t data[UART_BUF_SIZE];
	uint16_t len;
};

static K_FIFO_DEFINE(fifo_uart_tx_data);
static K_FIFO_DEFINE(fifo_uart_rx_data);

static const struct bt_data ad[] = {
	BT_DATA_BYTES(BT_DATA_FLAGS, (BT_LE_AD_GENERAL | BT_LE_AD_NO_BREDR)),
	BT_DATA(BT_DATA_NAME_COMPLETE, DEVICE_NAME, DEVICE_NAME_LEN),
};

static const struct bt_data sd[] = {
	BT_DATA_BYTES(BT_DATA_UUID128_ALL, BT_UUID_NUS_VAL),
};

#if CONFIG_BT_NUS_UART_ASYNC_ADAPTER
UART_ASYNC_ADAPTER_INST_DEFINE(async_adapter);
#else
static const struct device *const async_adapter;
#endif

static void uart_cb(const struct device *dev, struct uart_event *evt, void *user_data)
{
	ARG_UNUSED(dev);

	static size_t aborted_len;
	struct uart_data_t *buf;
	static uint8_t *aborted_buf;
	static bool disable_req;

	switch (evt->type) {
	case UART_TX_DONE:
		LOG_DBG("UART_TX_DONE");
		if ((evt->data.tx.len == 0) ||
		    (!evt->data.tx.buf)) {
			return;
		}

		if (aborted_buf) {
			buf = CONTAINER_OF(aborted_buf, struct uart_data_t,
					   data);
			aborted_buf = NULL;
			aborted_len = 0;
		} else {
			buf = CONTAINER_OF(evt->data.tx.buf, struct uart_data_t,
					   data);
		}

		k_free(buf);

		buf = k_fifo_get(&fifo_uart_tx_data, K_NO_WAIT);
		if (!buf) {
			return;
		}

		if (uart_tx(uart, buf->data, buf->len, SYS_FOREVER_MS)) {
			LOG_WRN("Failed to send data over UART");
		}

		break;

	case UART_RX_RDY:
		LOG_DBG("UART_RX_RDY");
		buf = CONTAINER_OF(evt->data.rx.buf, struct uart_data_t, data);
		buf->len += evt->data.rx.len;

		if (disable_req) {
			return;
		}

		if ((evt->data.rx.buf[buf->len - 1] == '\n') ||
		    (evt->data.rx.buf[buf->len - 1] == '\r')) {
			disable_req = true;
			uart_rx_disable(uart);
		}

		break;

	case UART_RX_DISABLED:
		LOG_DBG("UART_RX_DISABLED");
		disable_req = false;

		buf = k_malloc(sizeof(*buf));
		if (buf) {
			buf->len = 0;
		} else {
			LOG_WRN("Not able to allocate UART receive buffer");
			k_work_reschedule(&uart_work, UART_WAIT_FOR_BUF_DELAY);
			return;
		}

		uart_rx_enable(uart, buf->data, sizeof(buf->data),
			       UART_WAIT_FOR_RX);

		break;

	case UART_RX_BUF_REQUEST:
		LOG_DBG("UART_RX_BUF_REQUEST");
		buf = k_malloc(sizeof(*buf));
		if (buf) {
			buf->len = 0;
			uart_rx_buf_rsp(uart, buf->data, sizeof(buf->data));
		} else {
			LOG_WRN("Not able to allocate UART receive buffer");
		}

		break;

	case UART_RX_BUF_RELEASED:
		LOG_DBG("UART_RX_BUF_RELEASED");
		buf = CONTAINER_OF(evt->data.rx_buf.buf, struct uart_data_t,
				   data);

		if (buf->len > 0) {
			k_fifo_put(&fifo_uart_rx_data, buf);
		} else {
			k_free(buf);
		}

		break;

	case UART_TX_ABORTED:
		LOG_DBG("UART_TX_ABORTED");
		if (!aborted_buf) {
			aborted_buf = (uint8_t *)evt->data.tx.buf;
		}

		aborted_len += evt->data.tx.len;
		buf = CONTAINER_OF(aborted_buf, struct uart_data_t,
				   data);

		uart_tx(uart, &buf->data[aborted_len],
			buf->len - aborted_len, SYS_FOREVER_MS);

		break;

	default:
		break;
	}
}

static void uart_work_handler(struct k_work *item)
{
	struct uart_data_t *buf;

	buf = k_malloc(sizeof(*buf));
	if (buf) {
		buf->len = 0;
	} else {
		LOG_WRN("Not able to allocate UART receive buffer");
		k_work_reschedule(&uart_work, UART_WAIT_FOR_BUF_DELAY);
		return;
	}

	uart_rx_enable(uart, buf->data, sizeof(buf->data), UART_WAIT_FOR_RX);
}

static bool uart_test_async_api(const struct device *dev)
{
	const struct uart_driver_api *api =
			(const struct uart_driver_api *)dev->api;

	return (api->callback_set != NULL);
}

static int uart_init(void)
{
	int err;
	int pos;
	struct uart_data_t *rx;
	struct uart_data_t *tx;

	if (!device_is_ready(uart)) {
		return -ENODEV;
	}

	if (IS_ENABLED(CONFIG_USB_DEVICE_STACK)) {
		err = usb_enable(NULL);
		if (err && (err != -EALREADY)) {
			LOG_ERR("Failed to enable USB");
			return err;
		}
	}

	rx = k_malloc(sizeof(*rx));
	if (rx) {
		rx->len = 0;
	} else {
		return -ENOMEM;
	}

	k_work_init_delayable(&uart_work, uart_work_handler);


	if (IS_ENABLED(CONFIG_BT_NUS_UART_ASYNC_ADAPTER) && !uart_test_async_api(uart)) {
		/* Implement API adapter */
		uart_async_adapter_init(async_adapter, uart);
		uart = async_adapter;
	}

	err = uart_callback_set(uart, uart_cb, NULL);
	if (err) {
		k_free(rx);
		LOG_ERR("Cannot initialize UART callback");
		return err;
	}

	if (IS_ENABLED(CONFIG_UART_LINE_CTRL)) {
		LOG_INF("Wait for DTR");
		while (true) {
			uint32_t dtr = 0;

			uart_line_ctrl_get(uart, UART_LINE_CTRL_DTR, &dtr);
			if (dtr) {
				break;
			}
			/* Give CPU resources to low priority threads. */
			k_sleep(K_MSEC(100));
		}
		LOG_INF("DTR set");
		err = uart_line_ctrl_set(uart, UART_LINE_CTRL_DCD, 1);
		if (err) {
			LOG_WRN("Failed to set DCD, ret code %d", err);
		}
		err = uart_line_ctrl_set(uart, UART_LINE_CTRL_DSR, 1);
		if (err) {
			LOG_WRN("Failed to set DSR, ret code %d", err);
		}
	}

	tx = k_malloc(sizeof(*tx));

	if (tx) {
		pos = snprintf(tx->data, sizeof(tx->data),
			       "Starting Nordic UART service example\r\n");

		if ((pos < 0) || (pos >= sizeof(tx->data))) {
			k_free(rx);
			k_free(tx);
			LOG_ERR("snprintf returned %d", pos);
			return -ENOMEM;
		}

		tx->len = pos;
	} else {
		k_free(rx);
		return -ENOMEM;
	}

	err = uart_tx(uart, tx->data, tx->len, SYS_FOREVER_MS);
	if (err) {
		k_free(rx);
		k_free(tx);
		LOG_ERR("Cannot display welcome message (err: %d)", err);
		return err;
	}

	err = uart_rx_enable(uart, rx->data, sizeof(rx->data), 50);
	if (err) {
		LOG_ERR("Cannot enable uart reception (err: %d)", err);
		/* Free the rx buffer only because the tx buffer will be handled in the callback */
		k_free(rx);
	}

	return err;
}

static void connected(struct bt_conn *conn, uint8_t err)
{
	char addr[BT_ADDR_LE_STR_LEN];

	if (err) {
		LOG_ERR("Connection failed (err %u)", err);
		return;
	}

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));
	LOG_INF("Connected %s", addr);

	current_conn = bt_conn_ref(conn);

	dk_set_led_on(CON_STATUS_LED);
}

static void disconnected(struct bt_conn *conn, uint8_t reason)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_INF("Disconnected: %s (reason %u)", addr, reason);

	if (auth_conn) {
		bt_conn_unref(auth_conn);
		auth_conn = NULL;
	}

	if (current_conn) {
		bt_conn_unref(current_conn);
		current_conn = NULL;
		dk_set_led_off(CON_STATUS_LED);
	}
}

#ifdef CONFIG_BT_NUS_SECURITY_ENABLED
static void security_changed(struct bt_conn *conn, bt_security_t level,
			     enum bt_security_err err)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	if (!err) {
		LOG_INF("Security changed: %s level %u", addr, level);
	} else {
		LOG_WRN("Security failed: %s level %u err %d", addr,
			level, err);
	}
}
#endif

BT_CONN_CB_DEFINE(conn_callbacks) = {
	.connected    = connected,
	.disconnected = disconnected,
#ifdef CONFIG_BT_NUS_SECURITY_ENABLED
	.security_changed = security_changed,
#endif
};

#if defined(CONFIG_BT_NUS_SECURITY_ENABLED)
static void auth_passkey_display(struct bt_conn *conn, unsigned int passkey)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_INF("Passkey for %s: %06u", addr, passkey);
}

static void auth_passkey_confirm(struct bt_conn *conn, unsigned int passkey)
{
	char addr[BT_ADDR_LE_STR_LEN];

	auth_conn = bt_conn_ref(conn);

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_INF("Passkey for %s: %06u", addr, passkey);
	LOG_INF("Press Button 1 to confirm, Button 2 to reject.");
}


static void auth_cancel(struct bt_conn *conn)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_INF("Pairing cancelled: %s", addr);
}


static void pairing_complete(struct bt_conn *conn, bool bonded)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_INF("Pairing completed: %s, bonded: %d", addr, bonded);
}


static void pairing_failed(struct bt_conn *conn, enum bt_security_err reason)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_INF("Pairing failed conn: %s, reason %d", addr, reason);
}


static struct bt_conn_auth_cb conn_auth_callbacks = {
	.passkey_display = auth_passkey_display,
	.passkey_confirm = auth_passkey_confirm,
	.cancel = auth_cancel,
};

static struct bt_conn_auth_info_cb conn_auth_info_callbacks = {
	.pairing_complete = pairing_complete,
	.pairing_failed = pairing_failed
};
#else
static struct bt_conn_auth_cb conn_auth_callbacks;
static struct bt_conn_auth_info_cb conn_auth_info_callbacks;
#endif

static void bt_receive_cb(struct bt_conn *conn, const uint8_t *const data,
			  uint16_t len)
{
	int err;
	char addr[BT_ADDR_LE_STR_LEN] = {0};

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, ARRAY_SIZE(addr));

	LOG_INF("Received data from: %s", addr);

	for (uint16_t pos = 0; pos != len;) {
		struct uart_data_t *tx = k_malloc(sizeof(*tx));

		if (!tx) {
			LOG_WRN("Not able to allocate UART send data buffer");
			return;
		}

		/* Keep the last byte of TX buffer for potential LF char. */
		size_t tx_data_size = sizeof(tx->data) - 1;

		if ((len - pos) > tx_data_size) {
			tx->len = tx_data_size;
		} else {
			tx->len = (len - pos);
		}

		memcpy(tx->data, &data[pos], tx->len);

		pos += tx->len;

		/* Append the LF character when the CR character triggered
		 * transmission from the peer.
		 */
		if ((pos == len) && (data[len - 1] == '\r')) {
			tx->data[tx->len] = '\n';
			tx->len++;
		}

		err = uart_tx(uart, tx->data, tx->len, SYS_FOREVER_MS);
		if (err) {
			k_fifo_put(&fifo_uart_tx_data, tx);
		}
	}
}

static struct bt_nus_cb nus_cb = {
	.received = bt_receive_cb,
};

void error(void)
{
	dk_set_leds_state(DK_ALL_LEDS_MSK, DK_NO_LEDS_MSK);

	while (true) {
		/* Spin for ever */
		k_sleep(K_MSEC(1000));
	}
}

#ifdef CONFIG_BT_NUS_SECURITY_ENABLED
static void num_comp_reply(bool accept)
{
	if (accept) {
		bt_conn_auth_passkey_confirm(auth_conn);
		LOG_INF("Numeric Match, conn %p", (void *)auth_conn);
	} else {
		bt_conn_auth_cancel(auth_conn);
		LOG_INF("Numeric Reject, conn %p", (void *)auth_conn);
	}

	bt_conn_unref(auth_conn);
	auth_conn = NULL;
}

void button_changed(uint32_t button_state, uint32_t has_changed)
{
	uint32_t buttons = button_state & has_changed;

#ifdef NEVER
	if (auth_conn)
	{
		if (buttons & KEY_PASSKEY_ACCEPT)
		{
			printk("button_changed(): KEY_PASSKEY_ACCEPT\n");
			num_comp_reply(true);
		}

		if (buttons & KEY_PASSKEY_REJECT)
		{
			printk("button_changed(): KEY_PASSKEY_REJECT\n");
			num_comp_reply(false);
		}
	}
#endif
	if (auth_conn)
	{
		if (has_changed == 1)
		{
			// Mark event - white
			printk("button_changed(): KEY_PASSKEY_ACCEPT\n");
			num_comp_reply(true);
		}

		if (has_changed == 2)
		{
			// Pause resume -- green
			printk("button_changed(): KEY_PASSKEY_REJECT\n");
			num_comp_reply(false);
		}
	}

}
#endif /* CONFIG_BT_NUS_SECURITY_ENABLED */

static void configure_gpio(void)
{
	int err;

#ifdef CONFIG_BT_NUS_SECURITY_ENABLED
	err = dk_buttons_init(button_changed);
	if (err) {
		LOG_ERR("Cannot init buttons (err: %d)", err);
	}
#endif /* CONFIG_BT_NUS_SECURITY_ENABLED */

	err = dk_leds_init();
	if (err) {
		LOG_ERR("Cannot init LEDs (err: %d)", err);
	}
}

void clear_all_bonds()
{

	/** Clear pairing information.
	 *
	 * @param id    Local identity (mostly just BT_ID_DEFAULT).
	 * @param addr  Remote address, NULL or BT_ADDR_LE_ANY to clear all remote
	 *              devices.
	 *
	 * @return 0 on success or negative error value on failure.
	 */
	printk("clearing all bonds\n");
	int rc = bt_unpair(BT_ID_DEFAULT, BT_ADDR_LE_ANY);
	printk("done [%d]\n", rc);
}


void main(void)
{
	int blink_status = 0;
	int err = 0;

	configure_gpio();

	err = uart_init();
	if (err) {
		error();
	}

	if (IS_ENABLED(CONFIG_BT_NUS_SECURITY_ENABLED)) {
		err = bt_conn_auth_cb_register(&conn_auth_callbacks);
		if (err) {
			printk("Failed to register authorization callbacks.\n");
			return;
		}

		err = bt_conn_auth_info_cb_register(&conn_auth_info_callbacks);
		if (err) {
			printk("Failed to register authorization info callbacks.\n");
			return;
		}
	}

	err = bt_enable(NULL);
	if (err) {
		error();
	}

	clear_all_bonds();

	LOG_INF("Bluetooth initialized");

	k_sem_give(&ble_init_ok);

	if (IS_ENABLED(CONFIG_SETTINGS)) {
		settings_load();
	}

	err = bt_nus_init(&nus_cb);
	if (err) {
		LOG_ERR("Failed to initialize UART service (err: %d)", err);
		return;
	}

	err = bt_le_adv_start(BT_LE_ADV_CONN, ad, ARRAY_SIZE(ad), sd,
			      ARRAY_SIZE(sd));
	if (err) {
		LOG_ERR("Advertising failed to start (err %d)", err);
		return;
	}

	for (;;) {
		dk_set_led(RUN_STATUS_LED, (++blink_status) % 2);
		k_sleep(K_MSEC(RUN_LED_BLINK_INTERVAL));
	}
}

void ble_write_thread(void)
{
	/* Don't go any further until BLE is initialized */
	k_sem_take(&ble_init_ok, K_FOREVER);

	for (;;) {
		/* Wait indefinitely for data to be sent over bluetooth */
		struct uart_data_t *buf = k_fifo_get(&fifo_uart_rx_data,
						     K_FOREVER);

		if (bt_nus_send(NULL, buf->data, buf->len)) {
			LOG_WRN("Failed to send data over BLE connection");
		}

		k_free(buf);
	}
}

K_THREAD_DEFINE(ble_write_thread_id, STACKSIZE, ble_write_thread, NULL, NULL,
		NULL, PRIORITY, 0, 0);

Code for the central_uart:

/*
 * Copyright (c) 2018 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
 */

/** @file
 *  @brief Nordic UART Service Client sample
 */

#include <errno.h>
#include <zephyr/kernel.h>
#include <zephyr/device.h>
#include <zephyr/devicetree.h>
#include <zephyr/sys/byteorder.h>
#include <zephyr/sys/printk.h>

#include <zephyr/bluetooth/bluetooth.h>
#include <zephyr/bluetooth/hci.h>
#include <zephyr/bluetooth/conn.h>
#include <zephyr/bluetooth/uuid.h>
#include <zephyr/bluetooth/gatt.h>

#include <bluetooth/services/nus.h>
#include <bluetooth/services/nus_client.h>
#include <bluetooth/gatt_dm.h>
#include <bluetooth/scan.h>

#include <dk_buttons_and_leds.h>

#include <zephyr/settings/settings.h>

#include <zephyr/drivers/uart.h>

#include <zephyr/logging/log.h>

#define LOG_MODULE_NAME central_uart
LOG_MODULE_REGISTER(LOG_MODULE_NAME);

/* UART payload buffer element size. */
#define UART_BUF_SIZE 20

#define KEY_PASSKEY_ACCEPT DK_BTN1_MSK
#define KEY_PASSKEY_REJECT DK_BTN2_MSK

#define NUS_WRITE_TIMEOUT K_MSEC(150)
#define UART_WAIT_FOR_BUF_DELAY K_MSEC(50)
#define UART_RX_TIMEOUT 50

static const struct device *uart = DEVICE_DT_GET(DT_NODELABEL(uart0));
static struct k_work_delayable uart_work;

K_SEM_DEFINE(nus_write_sem, 0, 1);

struct uart_data_t
{
	void *fifo_reserved;
	uint8_t data[UART_BUF_SIZE];
	uint16_t len;
};

static K_FIFO_DEFINE(fifo_uart_tx_data);
static K_FIFO_DEFINE(fifo_uart_rx_data);

static struct bt_conn *default_conn;
static struct bt_conn *auth_conn;
static struct bt_nus_client nus_client;

static void ble_data_sent(struct bt_nus_client *nus, uint8_t err,
						  const uint8_t *const data, uint16_t len)
{
	ARG_UNUSED(nus);

	struct uart_data_t *buf;

	/* Retrieve buffer context. */
	buf = CONTAINER_OF(data, struct uart_data_t, data);
	k_free(buf);

	k_sem_give(&nus_write_sem);

	if (err)
	{
		LOG_WRN("ATT error code: 0x%02X", err);
	}
}

static uint8_t ble_data_received(struct bt_nus_client *nus,
								 const uint8_t *data, uint16_t len)
{
	ARG_UNUSED(nus);

	int err;

	for (uint16_t pos = 0; pos != len;)
	{
		struct uart_data_t *tx = k_malloc(sizeof(*tx));

		if (!tx)
		{
			LOG_WRN("Not able to allocate UART send data buffer");
			return BT_GATT_ITER_CONTINUE;
		}

		/* Keep the last byte of TX buffer for potential LF char. */
		size_t tx_data_size = sizeof(tx->data) - 1;

		if ((len - pos) > tx_data_size)
		{
			tx->len = tx_data_size;
		}
		else
		{
			tx->len = (len - pos);
		}

		memcpy(tx->data, &data[pos], tx->len);

		pos += tx->len;

		/* Append the LF character when the CR character triggered
		 * transmission from the peer.
		 */
		if ((pos == len) && (data[len - 1] == '\r'))
		{
			tx->data[tx->len] = '\n';
			tx->len++;
		}

		err = uart_tx(uart, tx->data, tx->len, SYS_FOREVER_MS);
		if (err)
		{
			k_fifo_put(&fifo_uart_tx_data, tx);
		}
	}

	return BT_GATT_ITER_CONTINUE;
}

static void uart_cb(const struct device *dev, struct uart_event *evt, void *user_data)
{
	ARG_UNUSED(dev);

	static size_t aborted_len;
	struct uart_data_t *buf;
	static uint8_t *aborted_buf;
	static bool disable_req;

	switch (evt->type)
	{
	case UART_TX_DONE:
		LOG_DBG("UART_TX_DONE");
		if ((evt->data.tx.len == 0) ||
			(!evt->data.tx.buf))
		{
			return;
		}

		if (aborted_buf)
		{
			buf = CONTAINER_OF(aborted_buf, struct uart_data_t,
							   data);
			aborted_buf = NULL;
			aborted_len = 0;
		}
		else
		{
			buf = CONTAINER_OF(evt->data.tx.buf,
							   struct uart_data_t,
							   data);
		}

		k_free(buf);

		buf = k_fifo_get(&fifo_uart_tx_data, K_NO_WAIT);
		if (!buf)
		{
			return;
		}

		if (uart_tx(uart, buf->data, buf->len, SYS_FOREVER_MS))
		{
			LOG_WRN("Failed to send data over UART");
		}

		break;

	case UART_RX_RDY:
		LOG_DBG("UART_RX_RDY");
		buf = CONTAINER_OF(evt->data.rx.buf, struct uart_data_t, data);
		buf->len += evt->data.rx.len;

		if (disable_req)
		{
			return;
		}

		if ((evt->data.rx.buf[buf->len - 1] == '\n') ||
			(evt->data.rx.buf[buf->len - 1] == '\r'))
		{
			disable_req = true;
			uart_rx_disable(uart);
		}

		break;

	case UART_RX_DISABLED:
		LOG_DBG("UART_RX_DISABLED");
		disable_req = false;

		buf = k_malloc(sizeof(*buf));
		if (buf)
		{
			buf->len = 0;
		}
		else
		{
			LOG_WRN("Not able to allocate UART receive buffer");
			k_work_reschedule(&uart_work, UART_WAIT_FOR_BUF_DELAY);
			return;
		}

		uart_rx_enable(uart, buf->data, sizeof(buf->data),
					   UART_RX_TIMEOUT);

		break;

	case UART_RX_BUF_REQUEST:
		LOG_DBG("UART_RX_BUF_REQUEST");
		buf = k_malloc(sizeof(*buf));
		if (buf)
		{
			buf->len = 0;
			uart_rx_buf_rsp(uart, buf->data, sizeof(buf->data));
		}
		else
		{
			LOG_WRN("Not able to allocate UART receive buffer");
		}

		break;

	case UART_RX_BUF_RELEASED:
		LOG_DBG("UART_RX_BUF_RELEASED");
		buf = CONTAINER_OF(evt->data.rx_buf.buf, struct uart_data_t,
						   data);

		if (buf->len > 0)
		{
			k_fifo_put(&fifo_uart_rx_data, buf);
		}
		else
		{
			k_free(buf);
		}

		break;

	case UART_TX_ABORTED:
		LOG_DBG("UART_TX_ABORTED");
		if (!aborted_buf)
		{
			aborted_buf = (uint8_t *)evt->data.tx.buf;
		}

		aborted_len += evt->data.tx.len;
		buf = CONTAINER_OF(aborted_buf, struct uart_data_t,
						   data);

		uart_tx(uart, &buf->data[aborted_len],
				buf->len - aborted_len, SYS_FOREVER_MS);

		break;

	default:
		break;
	}
}

static void uart_work_handler(struct k_work *item)
{
	struct uart_data_t *buf;

	buf = k_malloc(sizeof(*buf));
	if (buf)
	{
		buf->len = 0;
	}
	else
	{
		LOG_WRN("Not able to allocate UART receive buffer");
		k_work_reschedule(&uart_work, UART_WAIT_FOR_BUF_DELAY);
		return;
	}

	uart_rx_enable(uart, buf->data, sizeof(buf->data), UART_RX_TIMEOUT);
}

static int uart_init(void)
{
	int err;
	struct uart_data_t *rx;

	if (!device_is_ready(uart))
	{
		LOG_ERR("UART device not ready");
		return -ENODEV;
	}

	rx = k_malloc(sizeof(*rx));
	if (rx)
	{
		rx->len = 0;
	}
	else
	{
		return -ENOMEM;
	}

	k_work_init_delayable(&uart_work, uart_work_handler);

	err = uart_callback_set(uart, uart_cb, NULL);
	if (err)
	{
		return err;
	}

	return uart_rx_enable(uart, rx->data, sizeof(rx->data),
						  UART_RX_TIMEOUT);
}

static void discovery_complete(struct bt_gatt_dm *dm,
							   void *context)
{
	struct bt_nus_client *nus = context;
	LOG_INF("Service discovery completed");

	bt_gatt_dm_data_print(dm);

	bt_nus_handles_assign(dm, nus);
	bt_nus_subscribe_receive(nus);

	bt_gatt_dm_data_release(dm);
}

static void discovery_service_not_found(struct bt_conn *conn,
										void *context)
{
	LOG_INF("Service not found");
}

static void discovery_error(struct bt_conn *conn,
							int err,
							void *context)
{
	LOG_WRN("Error while discovering GATT database: (%d)", err);
}

struct bt_gatt_dm_cb discovery_cb = {
	.completed = discovery_complete,
	.service_not_found = discovery_service_not_found,
	.error_found = discovery_error,
};

static void gatt_discover(struct bt_conn *conn)
{
	int err;

	if (conn != default_conn)
	{
		return;
	}

	err = bt_gatt_dm_start(conn,
						   BT_UUID_NUS_SERVICE,
						   &discovery_cb,
						   &nus_client);
	if (err)
	{
		LOG_ERR("could not start the discovery procedure, error "
				"code: %d",
				err);
	}
}

static void exchange_func(struct bt_conn *conn, uint8_t err, struct bt_gatt_exchange_params *params)
{
	if (!err)
	{
		LOG_INF("MTU exchange done");
	}
	else
	{
		LOG_WRN("MTU exchange failed (err %" PRIu8 ")", err);
	}
}

static void connected(struct bt_conn *conn, uint8_t conn_err)
{
	char addr[BT_ADDR_LE_STR_LEN];
	int err;

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	if (conn_err)
	{
		LOG_INF("Failed to connect to %s (%d)", addr, conn_err);

		if (default_conn == conn)
		{
			bt_conn_unref(default_conn);
			default_conn = NULL;

			err = bt_scan_start(BT_SCAN_TYPE_SCAN_ACTIVE);
			if (err)
			{
				LOG_ERR("Scanning failed to start (err %d)",
						err);
			}
		}

		return;
	}

	LOG_INF("Connected: %s", addr);

	static struct bt_gatt_exchange_params exchange_params;

	exchange_params.func = exchange_func;
	err = bt_gatt_exchange_mtu(conn, &exchange_params);
	if (err)
	{
		LOG_WRN("MTU exchange failed (err %d)", err);
	}

	err = bt_conn_set_security(conn, BT_SECURITY_L2);
	if (err)
	{
		LOG_WRN("Failed to set security: %d", err);

		gatt_discover(conn);
	}

	err = bt_scan_stop();
	if ((!err) && (err != -EALREADY))
	{
		LOG_ERR("Stop LE scan failed (err %d)", err);
	}
}

static void disconnected(struct bt_conn *conn, uint8_t reason)
{
	char addr[BT_ADDR_LE_STR_LEN];
	int err;

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_INF("Disconnected: %s (reason %u)", addr, reason);

	if (default_conn != conn)
	{
		return;
	}

	bt_conn_unref(default_conn);
	default_conn = NULL;

	err = bt_scan_start(BT_SCAN_TYPE_SCAN_ACTIVE);
	if (err)
	{
		LOG_ERR("Scanning failed to start (err %d)",
				err);
	}
}

static void security_changed(struct bt_conn *conn, bt_security_t level,
							 enum bt_security_err err)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	if (!err)
	{
		LOG_INF("Security changed: %s level %u", addr, level);
	}
	else
	{
		LOG_WRN("Security failed: %s level %u err %d", addr,
				level, err);
	}

	gatt_discover(conn);
}

BT_CONN_CB_DEFINE(conn_callbacks) = {
	.connected = connected,
	.disconnected = disconnected,
	.security_changed = security_changed};

static void scan_filter_match(struct bt_scan_device_info *device_info,
							  struct bt_scan_filter_match *filter_match,
							  bool connectable)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(device_info->recv_info->addr, addr, sizeof(addr));

	LOG_INF("Filters matched. Address: %s connectable: %d",
			addr, connectable);
}

static void scan_connecting_error(struct bt_scan_device_info *device_info)
{
	LOG_WRN("Connecting failed");
}

static void scan_connecting(struct bt_scan_device_info *device_info,
							struct bt_conn *conn)
{
	default_conn = bt_conn_ref(conn);
}

static int nus_client_init(void)
{
	int err;
	struct bt_nus_client_init_param init = {
		.cb = {
			.received = ble_data_received,
			.sent = ble_data_sent,
		}};

	err = bt_nus_client_init(&nus_client, &init);
	if (err)
	{
		LOG_ERR("NUS Client initialization failed (err %d)", err);
		return err;
	}

	LOG_INF("NUS Client module initialized");
	return err;
}

BT_SCAN_CB_INIT(scan_cb, scan_filter_match, NULL,
				scan_connecting_error, scan_connecting);

static int scan_init(void)
{
	int err;
	struct bt_scan_init_param scan_init = {
		.connect_if_match = 1,
	};

	bt_scan_init(&scan_init);
	bt_scan_cb_register(&scan_cb);

	err = bt_scan_filter_add(BT_SCAN_FILTER_TYPE_UUID, BT_UUID_NUS_SERVICE);
	if (err)
	{
		LOG_ERR("Scanning filters cannot be set (err %d)", err);
		return err;
	}

	err = bt_scan_filter_enable(BT_SCAN_UUID_FILTER, false);
	if (err)
	{
		LOG_ERR("Filters cannot be turned on (err %d)", err);
		return err;
	}

	LOG_INF("Scan module initialized");
	return err;
}

static void auth_cancel(struct bt_conn *conn)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_INF("Pairing cancelled: %s", addr);
}

static void pairing_complete(struct bt_conn *conn, bool bonded)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_INF("Pairing completed: %s, bonded: %d", addr, bonded);
}

static void pairing_failed(struct bt_conn *conn, enum bt_security_err reason)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_WRN("Pairing failed conn: %s, reason %d", addr, reason);
}

static void auth_passkey_display(struct bt_conn *conn, unsigned int passkey)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_INF("Passkey for %s: %06u", addr, passkey);
}

static void auth_passkey_confirm(struct bt_conn *conn, unsigned int passkey)
{
	char addr[BT_ADDR_LE_STR_LEN];

	auth_conn = bt_conn_ref(conn);

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_INF("Passkey for %s: %06u", addr, passkey);
	LOG_INF("Press Button 1 to confirm, Button 2 to reject.");
}

static struct bt_conn_auth_cb conn_auth_callbacks = {
	.passkey_display = auth_passkey_display,
	.passkey_confirm = auth_passkey_confirm,
	.cancel = auth_cancel,
};

static struct bt_conn_auth_info_cb conn_auth_info_callbacks = {
	.pairing_complete = pairing_complete,
	.pairing_failed = pairing_failed};



//#ifdef CONFIG_BT_NUS_SECURITY_ENABLED
static void num_comp_reply(bool accept)
{
	if (accept) {
		bt_conn_auth_passkey_confirm(auth_conn);
		LOG_INF("Numeric Match, conn %p", (void *)auth_conn);
	} else {
		bt_conn_auth_cancel(auth_conn);
		LOG_INF("Numeric Reject, conn %p", (void *)auth_conn);
	}

	bt_conn_unref(auth_conn);
	auth_conn = NULL;
}

void button_changed(uint32_t button_state, uint32_t has_changed)
{
	uint32_t buttons = button_state & has_changed;

	//printk("button_changed(): button_state=0x%x, has_changed=0x%x\n", button_state, has_changed);
#ifdef NEVER
	if (auth_conn)
	{
		if (buttons & KEY_PASSKEY_ACCEPT)
		{
			printk("button_changed(): KEY_PASSKEY_ACCEPT\n");
			num_comp_reply(true);
		}

		if (buttons & KEY_PASSKEY_REJECT)
		{
			printk("button_changed(): KEY_PASSKEY_REJECT\n");
			num_comp_reply(false);
		}
	}
#endif
	if (auth_conn)
	{
		if (has_changed == 1)
		{
			// Mark event - white
			printk("button_changed(): KEY_PASSKEY_ACCEPT\n");
			num_comp_reply(true);
		}

		if (has_changed == 2)
		{
			// Pause resume -- green
			printk("button_changed(): KEY_PASSKEY_REJECT\n");
			num_comp_reply(false);
		}
	}

}
//#endif /* CONFIG_BT_NUS_SECURITY_ENABLED */

static void configure_gpio(void)
{
	int err;

//#ifdef CONFIG_BT_NUS_SECURITY_ENABLED
	err = dk_buttons_init(button_changed);
	if (err) {
		LOG_ERR("Cannot init buttons (err: %d)", err);
	}
//#endif /* CONFIG_BT_NUS_SECURITY_ENABLED */

	err = dk_leds_init();
	if (err) {
		LOG_ERR("Cannot init LEDs (err: %d)", err);
	}
}

void clear_all_bonds()
{

	/** Clear pairing information.
	 *
	 * @param id    Local identity (mostly just BT_ID_DEFAULT).
	 * @param addr  Remote address, NULL or BT_ADDR_LE_ANY to clear all remote
	 *              devices.
	 *
	 * @return 0 on success or negative error value on failure.
	 */
	printk("clearing all bonds\n");
	int rc = bt_unpair(BT_ID_DEFAULT, BT_ADDR_LE_ANY);
	printk("done [%d]\n", rc);
}

void main(void)
{
	int err;

	configure_gpio();

	err = bt_conn_auth_cb_register(&conn_auth_callbacks);
	if (err)
	{
		LOG_ERR("Failed to register authorization callbacks.");
		return;
	}

	err = bt_conn_auth_info_cb_register(&conn_auth_info_callbacks);
	if (err)
	{
		printk("Failed to register authorization info callbacks.\n");
		return;
	}

	err = bt_enable(NULL);
	if (err)
	{
		LOG_ERR("Bluetooth init failed (err %d)", err);
		return;
	}

	clear_all_bonds();
	LOG_INF("Bluetooth initialized");

	if (IS_ENABLED(CONFIG_SETTINGS))
	{
		settings_load();
	}

	int (*module_init[])(void) = {uart_init, scan_init, nus_client_init};
	for (size_t i = 0; i < ARRAY_SIZE(module_init); i++)
	{
		err = (*module_init[i])();
		if (err)
		{
			return;
		}
	}

	printk("Starting Bluetooth Central UART example\n");

	err = bt_scan_start(BT_SCAN_TYPE_SCAN_ACTIVE);
	if (err)
	{
		LOG_ERR("Scanning failed to start (err %d)", err);
		return;
	}

	LOG_INF("Scanning successfully started");

	for (;;)
	{
		/* Wait indefinitely for data to be sent over Bluetooth */
		struct uart_data_t *buf = k_fifo_get(&fifo_uart_rx_data,
											 K_FOREVER);

		err = bt_nus_client_send(&nus_client, buf->data, buf->len);
		if (err)
		{
			LOG_WRN("Failed to send data over BLE connection"
					"(err %d)",
					err);
		}

		err = k_sem_take(&nus_write_sem, NUS_WRITE_TIMEOUT);
		if (err)
		{
			LOG_WRN("NUS send timeout");
		}
	}
}

[Arno]

Hi,

I have 2 more additional questions.

1) Now I'm able to pair the 2 devices. Now I was expecting that after switch on the devices (reboot), that the pairing would be erased by 

bt_unpair(BT_ID_DEFAULT, BT_ADDR_LE_ANY);

However the devices stay paired as you can see in the picture. What I'm I forgetting?

2) We are asking for security level 2 with 

bt_conn_set_security(conn, BT_SECURITY_L2);

However in the picture is indicated "Security changed: EF:25:86:3D:7B:F2 (random) level 4", where is this level 4 coming from? Maybe from the options: CONFIG_BT_SMP_SC_ONLY=y or maybe does Bluetooth LE does not permit level 2 nor level 3?

Any help appreciated.

Kind regards,

Arno

[Hung Bui]

Hi Arno, 

Could you please double check if CONFIG_BT_NUS_AUTHEN is set to y ? 

If it's set then the NUS service will require the connection to be at security level 3 or 4. Security level 2 (Just Work) will not work. 

You can have a look here at this course to see the explanation on different security levels: https://academy.nordicsemi.com/topic/security-models/

If you have passkey and LE Secure Connection, you will get security level 4, even if you only ask for security level 2 (it will try to get the highest security level). 

However, if on one peer you don't define the callback for display or keyboard or confirm you will get only Just Work (level 2) . 

So in theory it should still work with L2 if you don't have these callback. I'm not so sure why it didn't work for you. 

You may want to try capture a sniffer trace. It will reveal how the communication is over the air and which side of the connection require higher security. 

[Arno]

Hi,

For your information, I'm following exactly the central_uart and periheral_uart examples. In both examples

CONFIG_BT_NUS_AUTHEN is not set the the prj.conf. So it remains a mystery why security level 4 comes out?

Kind regards,

Arno

[Hung Bui]

Hi Arno, 
Level 4 will automatically achieved if you have LESC and have MITM protection (passkey for example). 
What I'm not so sure about is why it's failed when you don't have display callback for passkey and you only request L2.