Provisioning

Provisioning is the process of adding devices to a mesh network. It requires two devices operating in the following roles:

  • The provisioner represents the network owner, and is responsible for adding new nodes to the mesh network.

  • The provisionee is the device that gets added to the network through the Provisioning process. Before the provisioning process starts, the provisionee is an unprovisioned device.

The Provisioning module in the Zephyr Bluetooth Mesh stack supports both the Advertising and GATT Provisioning bearers for the provisionee role, as well as the Advertising Provisioning bearer for the provisioner role.

The Provisioning process

All Bluetooth Mesh nodes must be provisioned before they can participate in a Bluetooth Mesh network. The Provisioning API provides all the functionality necessary for a device to become a provisioned mesh node. Provisioning is a five-step process, involving the following steps:

  • Beaconing

  • Invitation

  • Public key exchange

  • Authentication

  • Provisioning data transfer

Beaconing

To start the provisioning process, the unprovisioned device must first start broadcasting the Unprovisioned Beacon. This makes it visible to nearby provisioners, which can initiate the provisioning. To indicate that the device needs to be provisioned, call bt_mesh_prov_enable(). The device starts broadcasting the Unprovisioned Beacon with the device UUID and the OOB information field, as specified in the prov parameter passed to bt_mesh_init(). Additionally, a Uniform Resource Identifier (URI) may be specified, which can point the provisioner to the location of some Out Of Band information, such as the device’s public key or an authentication value database. The URI is advertised in a separate beacon, with a URI hash included in the unprovisioned beacon, to tie the two together.

Uniform Resource Identifier

The Uniform Resource Identifier shall follow the format specified in the Bluetooth Core Specification Supplement. The URI must start with a URI scheme, encoded as a single utf-8 data point, or the special none scheme, encoded as 0x01. The available schemes are listed on the Bluetooth website.

Examples of encoded URIs:

URI encoding examples

URI

Encoded

http://example.com

\x16//example.com

https://www.zephyrproject.org/

\x17//www.zephyrproject.org/

just a string

\x01just a string

Provisioning invitation

The provisioner initiates the Provisioning process by sending a Provisioning invitation. The invitations prompts the provisionee to call attention to itself using the Health Server Attention state, if available.

The Unprovisioned device automatically responds to the invite by presenting a list of its capabilities, including the supported Out of Band Authentication methods and algorithms.

Public key exchange

Before the provisioning process can begin, the provisioner and the unprovisioned device exchange public keys, either in-band or Out of Band (OOB).

In-band public key exchange is a part of the provisioning process and always supported by the unprovisioned device and provisioner.

If the application wants to support public key exchange via OOB, it needs to provide public and private keys to the mesh stack. The unprovisioned device will reflect this in its capabilities. The provisioner obtains the public key via any available OOB mechanism (e.g. the device may advertise a packet containing the public key or it can be encoded in a QR code printed on the device packaging). Note that even if the unprovisioned device has specified the public key for the Out of Band exchange, the provisioner may choose to exchange the public key in-band if it can’t retrieve the public key via OOB mechanism. In this case, a new key pair will be generated by the mesh stack for each Provisioning process.

To enable support of OOB public key on the unprovisioned device side, CONFIG_BT_MESH_PROV_OOB_PUBLIC_KEY needs to be enabled. The application must provide public and private keys before the Provisioning process is started by initializing pointers to bt_mesh_prov.public_key_be and bt_mesh_prov.private_key_be. The keys needs to be provided in big-endian bytes order.

To provide the device’s public key obtained via OOB, call bt_mesh_prov_remote_pub_key_set() on the provisioner side.

Authentication

After the initial exchange, the provisioner selects an Out of Band (OOB) Authentication method. This allows the user to confirm that the device the provisioner connected to is actually the device they intended, and not a malicious third party.

The Provisioning API supports the following authentication methods for the provisionee:

  • Static OOB: An authentication value is assigned to the device in production, which the provisioner can query in some application specific way.

  • Input OOB: The user inputs the authentication value. The available input actions are listed in bt_mesh_input_action_t.

  • Output OOB: Show the user the authentication value. The available output actions are listed in bt_mesh_output_action_t.

The application must provide callbacks for the supported authentication methods in bt_mesh_prov, as well as enabling the supported actions in bt_mesh_prov.output_actions and bt_mesh_prov.input_actions.

When an Output OOB action is selected, the authentication value should be presented to the user when the output callback is called, and remain until the bt_mesh_prov.input_complete or bt_mesh_prov.complete callback is called. If the action is blink, beep or vibrate, the sequence should be repeated after a delay of three seconds or more.

When an Input OOB action is selected, the user should be prompted when the application receives the bt_mesh_prov.input callback. The user response should be fed back to the Provisioning API through bt_mesh_input_string() or bt_mesh_input_number(). If no user response is recorded within 60 seconds, the Provisioning process is aborted.

If Provisionee wants to mandate OOB authentication, it is mandatory to use the BT_MESH_ECDH_P256_HMAC_SHA256_AES_CCM algorithm.

Data transfer

After the device has been successfully authenticated, the provisioner transfers the Provisioning data:

  • Unicast address

  • A network key

  • IV index

  • Network flags

    • Key refresh

    • IV update

Additionally, a device key is generated for the node. All this data is stored by the mesh stack, and the provisioning bt_mesh_prov.complete callback gets called.

Provisioning security

Depending on the choice of public key exchange mechanism and authentication method, the provisioning process can be secure or insecure.

On May 24th 2021, ANSSI disclosed a set of vulnerabilities in the Bluetooth Mesh provisioning protocol that showcased how the low entropy provided by the Blink, Vibrate, Push, Twist and Input/Output numeric OOB methods could be exploited in impersonation and MITM attacks. In response, the Bluetooth SIG has reclassified these OOB methods as insecure in the Bluetooth Mesh Profile Specification v1.0.1 erratum 16350, as AuthValue may be brute forced in real time. To ensure secure provisioning, applications should use a static OOB value and OOB public key transfer.

API reference

group bt_mesh_prov

Provisioning.

Enums

Available authentication algorithms.

Values:

enumerator BT_MESH_PROV_AUTH_CMAC_AES128_AES_CCM
enumerator BT_MESH_PROV_AUTH_HMAC_SHA256_AES_CCM

OOB Type field values.

Values:

enumerator BT_MESH_STATIC_OOB_AVAILABLE = BIT(0)

Static OOB information available.

enumerator BT_MESH_OOB_AUTH_REQUIRED = BIT(1)

OOB authentication required.

enum bt_mesh_output_action_t

Available Provisioning output authentication actions.

Values:

enumerator BT_MESH_NO_OUTPUT = 0

Blink.

enumerator BT_MESH_BEEP = BIT(1)

Beep.

enumerator BT_MESH_VIBRATE = BIT(2)

Vibrate.

enumerator BT_MESH_DISPLAY_NUMBER = BIT(3)

Output numeric.

enumerator BT_MESH_DISPLAY_STRING = BIT(4)

Output alphanumeric.

enum bt_mesh_input_action_t

Available Provisioning input authentication actions.

Values:

enumerator BT_MESH_NO_INPUT = 0
enumerator BT_MESH_PUSH = BIT(0)

Push.

enumerator BT_MESH_TWIST = BIT(1)

Twist.

enumerator BT_MESH_ENTER_NUMBER = BIT(2)

Input number.

enumerator BT_MESH_ENTER_STRING = BIT(3)

Input alphanumeric.

enum bt_mesh_prov_bearer_t

Available Provisioning bearers.

Values:

enumerator BT_MESH_PROV_ADV = BIT(0)

PB-ADV bearer.

enumerator BT_MESH_PROV_GATT = BIT(1)

PB-GATT bearer.

enumerator BT_MESH_PROV_REMOTE = BIT(2)

PB-Remote bearer.

enum bt_mesh_prov_oob_info_t

Out of Band information location.

Values:

enumerator BT_MESH_PROV_OOB_OTHER = BIT(0)

Other.

enumerator BT_MESH_PROV_OOB_URI = BIT(1)

Electronic / URI.

enumerator BT_MESH_PROV_OOB_2D_CODE = BIT(2)

2D machine-readable code

enumerator BT_MESH_PROV_OOB_BAR_CODE = BIT(3)

Bar Code.

enumerator BT_MESH_PROV_OOB_NFC = BIT(4)

Near Field Communication (NFC)

enumerator BT_MESH_PROV_OOB_NUMBER = BIT(5)

Number.

enumerator BT_MESH_PROV_OOB_STRING = BIT(6)

String.

enumerator BT_MESH_PROV_OOB_CERTIFICATE = BIT(7)

Support for certificate-based provisioning.

enumerator BT_MESH_PROV_OOB_RECORDS = BIT(8)

Support for provisioning records.

enumerator BT_MESH_PROV_OOB_ON_BOX = BIT(11)

On box.

enumerator BT_MESH_PROV_OOB_IN_BOX = BIT(12)

Inside box.

enumerator BT_MESH_PROV_OOB_ON_PAPER = BIT(13)

On piece of paper.

enumerator BT_MESH_PROV_OOB_IN_MANUAL = BIT(14)

Inside manual.

enumerator BT_MESH_PROV_OOB_ON_DEV = BIT(15)

On device.

Functions

int bt_mesh_input_string(const char *str)

Provide provisioning input OOB string.

This is intended to be called after the bt_mesh_prov input callback has been called with BT_MESH_ENTER_STRING as the action.

Parameters:

  • str – String.

Returns:

Zero on success or (negative) error code otherwise.

int bt_mesh_input_number(uint32_t num)

Provide provisioning input OOB number.

This is intended to be called after the bt_mesh_prov input callback has been called with BT_MESH_ENTER_NUMBER as the action.

Parameters:

  • num – Number.

Returns:

Zero on success or (negative) error code otherwise.

int bt_mesh_prov_remote_pub_key_set(const uint8_t public_key[64])

Provide Device public key.

Parameters:

  • public_key – Device public key in big-endian.

Returns:

Zero on success or (negative) error code otherwise.

int bt_mesh_auth_method_set_input(bt_mesh_input_action_t action, uint8_t size)

Use Input OOB authentication.

Provisioner only.

Instruct the unprovisioned device to use the specified Input OOB authentication action. When using BT_MESH_PUSH, BT_MESH_TWIST or BT_MESH_ENTER_NUMBER, the bt_mesh_prov::output_number callback is called with a random number that has to be entered on the unprovisioned device.

When using BT_MESH_ENTER_STRING, the bt_mesh_prov::output_string callback is called with a random string that has to be entered on the unprovisioned device.

Parameters:

  • action – Authentication action used by the unprovisioned device.

  • size – Authentication size.

Returns:

Zero on success or (negative) error code otherwise.

int bt_mesh_auth_method_set_output(bt_mesh_output_action_t action, uint8_t size)

Use Output OOB authentication.

Provisioner only.

Instruct the unprovisioned device to use the specified Output OOB authentication action. The bt_mesh_prov::input callback will be called.

When using BT_MESH_BLINK, BT_MESH_BEEP, BT_MESH_VIBRATE or BT_MESH_DISPLAY_NUMBER, and the application has to call bt_mesh_input_number with the random number indicated by the unprovisioned device.

When using BT_MESH_DISPLAY_STRING, the application has to call bt_mesh_input_string with the random string displayed by the unprovisioned device.

Parameters:

  • action – Authentication action used by the unprovisioned device.

  • size – Authentication size.

Returns:

Zero on success or (negative) error code otherwise.

int bt_mesh_auth_method_set_static(const uint8_t *static_val, uint8_t size)

Use static OOB authentication.

Provisioner only.

Instruct the unprovisioned device to use static OOB authentication, and use the given static authentication value when provisioning.

Parameters:

  • static_val – Static OOB value.

  • size – Static OOB value size.

Returns:

Zero on success or (negative) error code otherwise.

int bt_mesh_auth_method_set_none(void)

Don’t use OOB authentication.

Provisioner only.

Don’t use any authentication when provisioning new devices. This is the default behavior.

Warning

Not using any authentication exposes the mesh network to impersonation attacks, where attackers can pretend to be the unprovisioned device to gain access to the network. Authentication is strongly encouraged.

Returns:

Zero on success or (negative) error code otherwise.

int bt_mesh_prov_enable(bt_mesh_prov_bearer_t bearers)

Enable specific provisioning bearers.

Enable one or more provisioning bearers.

Parameters:

  • bearers – Bit-wise or of provisioning bearers.

Returns:

Zero on success or (negative) error code otherwise.

int bt_mesh_prov_disable(bt_mesh_prov_bearer_t bearers)

Disable specific provisioning bearers.

Disable one or more provisioning bearers.

Parameters:

  • bearers – Bit-wise or of provisioning bearers.

Returns:

Zero on success or (negative) error code otherwise.

int bt_mesh_provision(const uint8_t net_key[16], uint16_t net_idx, uint8_t flags, uint32_t iv_index, uint16_t addr, const uint8_t dev_key[16])

Provision the local Mesh Node.

This API should normally not be used directly by the application. The only exception is for testing purposes where manual provisioning is desired without an actual external provisioner.

Parameters:

  • net_key – Network Key

  • net_idx – Network Key Index

  • flags – Provisioning Flags

  • iv_index – IV Index

  • addr – Primary element address

  • dev_key – Device Key

Returns:

Zero on success or (negative) error code otherwise.

int bt_mesh_provision_adv(const uint8_t uuid[16], uint16_t net_idx, uint16_t addr, uint8_t attention_duration)

Provision a Mesh Node using PB-ADV.

Parameters:

  • uuid – UUID

  • net_idx – Network Key Index

  • addr – Address to assign to remote device. If addr is 0, the lowest available address will be chosen.

  • attention_duration – The attention duration to be send to remote device

Returns:

Zero on success or (negative) error code otherwise.

int bt_mesh_provision_gatt(const uint8_t uuid[16], uint16_t net_idx, uint16_t addr, uint8_t attention_duration)

Provision a Mesh Node using PB-GATT.

Parameters:

  • uuid – UUID

  • net_idx – Network Key Index

  • addr – Address to assign to remote device. If addr is 0, the lowest available address will be chosen.

  • attention_duration – The attention duration to be send to remote device

Returns:

Zero on success or (negative) error code otherwise.

int bt_mesh_provision_remote(struct bt_mesh_rpr_cli *cli, const struct bt_mesh_rpr_node *srv, const uint8_t uuid[16], uint16_t net_idx, uint16_t addr)

Provision a Mesh Node using PB-Remote.

Parameters:

  • cli – Remote Provisioning Client Model to provision with.

  • srv – Remote Provisioning Server that should be used to tunnel the provisioning.

  • uuid – UUID of the unprovisioned node

  • net_idx – Network Key Index to give to the unprovisioned node.

  • addr – Address to assign to remote device. If addr is 0, the lowest available address will be chosen.

Returns:

Zero on success or (negative) error code otherwise.

int bt_mesh_reprovision_remote(struct bt_mesh_rpr_cli *cli, struct bt_mesh_rpr_node *srv, uint16_t addr, bool comp_change)

Reprovision a Mesh Node using PB-Remote.

Reprovisioning can be used to change the device key, unicast address and composition data of another device. The reprovisioning procedure uses the same protocol as normal provisioning, with the same level of security.

There are three tiers of reprovisioning:

  1. Refreshing the device key

  2. Refreshing the device key and node address. Composition data may change, including the number of elements.

  3. Refreshing the device key and composition data, in case the composition data of the target node changed due to a firmware update or a similar procedure.

The target node indicates that its composition data changed by instantiating its composition data page 128. If the number of elements have changed, it may be necessary to move the unicast address of the target node as well, to avoid overlapping addresses.

Note

Changing the unicast addresses of the target node requires changes to all nodes that publish directly to any of the target node’s models.

Parameters:

  • cli – Remote Provisioning Client Model to provision on

  • srv – Remote Provisioning Server to reprovision

  • addr – Address to assign to remote device. If addr is 0, the lowest available address will be chosen.

  • comp_change – The target node has indicated that its composition data has changed. Note that the target node will reject the update if this isn’t true.

Returns:

Zero on success or (negative) error code otherwise.

bool bt_mesh_is_provisioned(void)

Check if the local node has been provisioned.

This API can be used to check if the local node has been provisioned or not. It can e.g. be helpful to determine if there was a stored network in flash, i.e. if the network was restored after calling settings_load().

Returns:

True if the node is provisioned. False otherwise.

struct bt_mesh_dev_capabilities
#include <main.h>

Device Capabilities.

Public Members

uint8_t elem_count

Number of elements supported by the device.

uint16_t algorithms

Supported algorithms and other capabilities.

uint8_t pub_key_type

Supported public key types.

uint8_t oob_type

Supported OOB Types.

bt_mesh_output_action_t output_actions

Supported Output OOB Actions.

bt_mesh_input_action_t input_actions

Supported Input OOB Actions.

uint8_t output_size

Maximum size of Output OOB supported.

uint8_t input_size

Maximum size in octets of Input OOB supported.

struct bt_mesh_prov
#include <main.h>

Provisioning properties & capabilities.

Public Members

const uint8_t *uuid

The UUID that’s used when advertising as unprovisioned.

const char *uri

Optional URI.

This will be advertised separately from the unprovisioned beacon, however the unprovisioned beacon will contain a hash of it so the two can be associated by the provisioner.

bt_mesh_prov_oob_info_t oob_info

Out of Band information field.

const uint8_t *public_key_be

Pointer to Public Key in big-endian for OOB public key type support.

Remember to enable CONFIG_BT_MESH_PROV_OOB_PUBLIC_KEY when initializing this parameter.

Must be used together with bt_mesh_prov::private_key_be.

const uint8_t *private_key_be

Pointer to Private Key in big-endian for OOB public key type support.

Remember to enable CONFIG_BT_MESH_PROV_OOB_PUBLIC_KEY when initializing this parameter.

Must be used together with bt_mesh_prov::public_key_be.

const uint8_t *static_val

Static OOB value.

uint8_t static_val_len

Static OOB value length.

uint8_t output_size

Maximum size of Output OOB supported.

uint16_t output_actions

Supported Output OOB Actions.

uint8_t input_size

Maximum size of Input OOB supported.

uint16_t input_actions

Supported Input OOB Actions.

void (*capabilities)(const struct bt_mesh_dev_capabilities *cap)

Provisioning Capabilities.

This callback notifies the application that the provisioning capabilities of the unprovisioned device has been received.

The application can consequently call bt_mesh_auth_method_set_<*> to select suitable provisioning oob authentication method.

When this callback returns, the provisioner will start authentication with the chosen method.

Param cap:

capabilities supported by device.

int (*output_number)(bt_mesh_output_action_t act, uint32_t num)

Output of a number is requested.

This callback notifies the application that it should output the given number using the given action.

Param act:

Action for outputting the number.

Param num:

Number to be outputted.

Return:

Zero on success or negative error code otherwise

int (*output_string)(const char *str)

Output of a string is requested.

This callback notifies the application that it should display the given string to the user.

Param str:

String to be displayed.

Return:

Zero on success or negative error code otherwise

int (*input)(bt_mesh_input_action_t act, uint8_t size)

Input is requested.

This callback notifies the application that it should request input from the user using the given action. The requested input will either be a string or a number, and the application needs to consequently call the bt_mesh_input_string() or bt_mesh_input_number() functions once the data has been acquired from the user.

Param act:

Action for inputting data.

Param num:

Maximum size of the inputted data.

Return:

Zero on success or negative error code otherwise

void (*input_complete)(void)

The other device finished their OOB input.

This callback notifies the application that it should stop displaying its output OOB value, as the other party finished their OOB input.

void (*unprovisioned_beacon)(uint8_t uuid[16], bt_mesh_prov_oob_info_t oob_info, uint32_t *uri_hash)

Unprovisioned beacon has been received.

This callback notifies the application that an unprovisioned beacon has been received.

Param uuid:

UUID

Param oob_info:

OOB Information

Param uri_hash:

Pointer to URI Hash value. NULL if no hash was present in the beacon.

void (*unprovisioned_beacon_gatt)(uint8_t uuid[16], bt_mesh_prov_oob_info_t oob_info)

PB-GATT Unprovisioned Advertising has been received.

This callback notifies the application that an PB-GATT unprovisioned Advertising has been received.

Param uuid:

UUID

Param oob_info:

OOB Information

Provisioning link has been opened.

This callback notifies the application that a provisioning link has been opened on the given provisioning bearer.

Param bearer:

Provisioning bearer.

Provisioning link has been closed.

This callback notifies the application that a provisioning link has been closed on the given provisioning bearer.

Param bearer:

Provisioning bearer.

void (*complete)(uint16_t net_idx, uint16_t addr)

Provisioning is complete.

This callback notifies the application that provisioning has been successfully completed, and that the local node has been assigned the specified NetKeyIndex and primary element address.

Param net_idx:

NetKeyIndex given during provisioning.

Param addr:

Primary element address.

void (*reprovisioned)(uint16_t addr)

Local node has been reprovisioned.

This callback notifies the application that reprovisioning has been successfully completed.

Param addr:

New primary element address.

void (*node_added)(uint16_t net_idx, uint8_t uuid[16], uint16_t addr, uint8_t num_elem)

A new node has been added to the provisioning database.

This callback notifies the application that provisioning has been successfully completed, and that a node has been assigned the specified NetKeyIndex and primary element address.

Param net_idx:

NetKeyIndex given during provisioning.

Param uuid:

UUID of the added node

Param addr:

Primary element address.

Param num_elem:

Number of elements that this node has.

void (*reset)(void)

Node has been reset.

This callback notifies the application that the local node has been reset and needs to be provisioned again. The node will not automatically advertise as unprovisioned, rather the bt_mesh_prov_enable() API needs to be called to enable unprovisioned advertising on one or more provisioning bearers.