Bluetooth: host: Introduce a new bt_hci_le_rand() call

In order to get rid of the duplication of the code that we had until now
in the tree, consolidate the handling of multiple calls to
bt_hci_cmd_send_sync(BT_HCI_OP_LE_RAND, ...) in a single location,
namely in hci_core.

This allows all of the users of this HCI command to use a single
implementation of the iterated sending of the HCI command to fill a
buffer with random bytes.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>

drivers/entropy/entropy_bt_hci.c

@@ -20,31 +20,11 @@ static int entropy_bt_init(const struct device *dev)
 static int entropy_bt_get_entropy(const struct device *dev,
 				  uint8_t *buffer, uint16_t length)
 {
-	struct bt_hci_rp_le_rand *rp;
-	struct net_buf *rsp;
-	int req, ret;
-
 	if (!bt_is_ready()) {
 		return -EAGAIN;
 	}
 
-	while (length > 0) {
+	return bt_hci_le_rand(buffer, length);
-		/* Number of bytes to fill on this iteration */
-		req = MIN(length, sizeof(rp->rand));
-		/* Request the next 8 bytes over HCI */
-		ret = bt_hci_cmd_send_sync(BT_HCI_OP_LE_RAND, NULL, &rsp);
-		if (ret) {
-			return ret;
-		}
-		/* Copy random data into buffer */
-		rp = (void *)rsp->data;
-		memcpy(buffer, rp->rand, req);
-
-		net_buf_unref(rsp);
-		buffer += req;
-		length -= req;
-	}
-	return 0;
 }
 
 /* HCI commands cannot be run from an interrupt context */

include/bluetooth/hci.h

@@ -2873,6 +2873,22 @@ typedef bool bt_hci_vnd_evt_cb_t(struct net_buf_simple *buf);
   */
 int bt_hci_register_vnd_evt_cb(bt_hci_vnd_evt_cb_t cb);
 
+/** @brief Get Random bytes from the LE Controller.
+ *
+ * Send the HCI_LE_Rand to the LE Controller as many times as required to
+ * fill the provided @p buffer.
+ *
+ * @note This function is provided as a helper to gather an arbitrary number of
+ * random bytes from an LE Controller using the HCI_LE_Rand command.
+ *
+ * @param buffer Buffer to fill with random bytes.
+ * @param len Length of the buffer in bytes.
+ *
+ * @return 0 on success or negative error value on failure.
+ */
+int bt_hci_le_rand(void *buffer, size_t len);
+
+
 #ifdef __cplusplus
 }
 #endif

subsys/bluetooth/host/crypto.c

@@ -33,22 +33,11 @@ static int prng_reseed(struct tc_hmac_prng_struct *h)
 {
 	uint8_t seed[32];
 	int64_t extra;
-	size_t i;
 	int ret;
 
-	for (i = 0; i < (sizeof(seed) / 8); i++) {
+	ret = bt_hci_le_rand(seed, sizeof(seed));
-		struct bt_hci_rp_le_rand *rp;
+	if (ret) {
-		struct net_buf *rsp;
+		return ret;
-
-		ret = bt_hci_cmd_send_sync(BT_HCI_OP_LE_RAND, NULL, &rsp);
-		if (ret) {
-			return ret;
-		}
-
-		rp = (void *)rsp->data;
-		memcpy(&seed[i * 8], rp->rand, 8);
-
-		net_buf_unref(rsp);
 	}
 
 	extra = k_uptime_get();
@@ -65,26 +54,15 @@ static int prng_reseed(struct tc_hmac_prng_struct *h)
 
 int prng_init(void)
 {
-	struct bt_hci_rp_le_rand *rp;
+	uint8_t perso[8];
-	struct net_buf *rsp;
 	int ret;
 
-	/* Check first that HCI_LE_Rand is supported */
+	ret = bt_hci_le_rand(perso, sizeof(perso));
-	if (!BT_CMD_TEST(bt_dev.supported_commands, 27, 7)) {
-		return -ENOTSUP;
-	}
-
-	ret = bt_hci_cmd_send_sync(BT_HCI_OP_LE_RAND, NULL, &rsp);
 	if (ret) {
 		return ret;
 	}
 
-	rp = (void *)rsp->data;
+	ret = tc_hmac_prng_init(&prng, perso, sizeof(perso));
-
-	ret = tc_hmac_prng_init(&prng, rp->rand, sizeof(rp->rand));
-
-	net_buf_unref(rsp);
-
 	if (ret == TC_CRYPTO_FAIL) {
 		BT_ERR("Failed to initialize PRNG");
 		return -EIO;
@@ -118,39 +96,7 @@ int bt_rand(void *buf, size_t len)
 #else /* !CONFIG_BT_HOST_CRYPTO_PRNG */
 int bt_rand(void *buf, size_t len)
 {
-	int ret, size;
+	return bt_hci_le_rand(buf, len);
-	size_t i = 0;
-
-	/* Check first that HCI_LE_Rand is supported */
-	if (!BT_CMD_TEST(bt_dev.supported_commands, 27, 7)) {
-		return -ENOTSUP;
-	}
-
-	while (len) {
-		struct bt_hci_rp_le_rand *rp;
-		struct net_buf *rsp;
-
-		ret = bt_hci_cmd_send_sync(BT_HCI_OP_LE_RAND, NULL, &rsp);
-		if (ret) {
-			return ret;
-		}
-
-		rp = (void *)rsp->data;
-		if (rp->status) {
-			return -EIO;
-		}
-
-		size = MIN(len, sizeof(rp->rand));
-
-		(void)memcpy((uint8_t *)buf + i, rp->rand, size);
-
-		net_buf_unref(rsp);
-
-		i += size;
-		len -= size;
-	}
-
-	return 0;
 }
 #endif /* CONFIG_BT_HOST_CRYPTO_PRNG */
 

subsys/bluetooth/host/hci_core.c

@@ -331,6 +331,38 @@ int bt_hci_cmd_send_sync(uint16_t opcode, struct net_buf *buf,
 	return 0;
 }
 
+int bt_hci_le_rand(void *buffer, size_t len)
+{
+	struct bt_hci_rp_le_rand *rp;
+	struct net_buf *rsp;
+	size_t count;
+	int err;
+
+	/* Check first that HCI_LE_Rand is supported */
+	if (!BT_CMD_TEST(bt_dev.supported_commands, 27, 7)) {
+		return -ENOTSUP;
+	}
+
+	while (len > 0) {
+		/* Number of bytes to fill on this iteration */
+		count = MIN(len, sizeof(rp->rand));
+		/* Request the next 8 bytes over HCI */
+		err = bt_hci_cmd_send_sync(BT_HCI_OP_LE_RAND, NULL, &rsp);
+		if (err) {
+			return err;
+		}
+		/* Copy random data into buffer */
+		rp = (void *)rsp->data;
+		memcpy(buffer, rp->rand, count);
+
+		net_buf_unref(rsp);
+		buffer = (uint8_t *)buffer + count;
+		len -= count;
+	}
+
+	return 0;
+}
+
 static int hci_le_read_max_data_len(uint16_t *tx_octets, uint16_t *tx_time)
 {
 	struct bt_hci_rp_le_read_max_data_len *rp;