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 |
Encoded |
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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.
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.
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 Mesh Profile specification 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
-
enum bt_mesh_output_action_t
Available Provisioning output authentication actions.
Values:
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enumerator BT_MESH_NO_OUTPUT = 0
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enumerator BT_MESH_NO_OUTPUT = 0
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enum bt_mesh_input_action_t
Available Provisioning input authentication actions.
Values:
-
enumerator BT_MESH_NO_INPUT = 0
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enumerator BT_MESH_NO_INPUT = 0
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enum bt_mesh_prov_bearer_t
Available Provisioning bearers.
Values:
-
enum bt_mesh_prov_oob_info_t
Out of Band information location.
Values:
Functions
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
-
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.
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struct bt_mesh_dev_capabilities
- #include <main.h>
Device Capabilities.
Public Members
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uint8_t elem_count
Number of elements supported by the device
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uint16_t algorithms
Supported algorithms and other capabilities
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uint8_t pub_key_type
Supported public key types
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uint8_t static_oob
Supported static OOB Types
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bt_mesh_output_action_t output_actions
Supported Output OOB Actions
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bt_mesh_input_action_t input_actions
Supported Input OOB Actions
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uint8_t output_size
Maximum size of Output OOB supported
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uint8_t input_size
Maximum size in octets of Input OOB supported
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uint8_t elem_count
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struct bt_mesh_prov
- #include <main.h>
Provisioning properties & capabilities.
Public Members
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const uint8_t *uuid
The UUID that’s used when advertising as unprovisioned
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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.
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bt_mesh_prov_oob_info_t oob_info
Out of Band information field.
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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_KEYwhen initializing this parameter.Must be used together with bt_mesh_prov::private_key_be.
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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_KEYwhen initializing this parameter.Must be used together with bt_mesh_prov::public_key_be.
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const uint8_t *static_val
Static OOB value
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uint8_t static_val_len
Static OOB value length
-
uint8_t output_size
Maximum size of Output OOB supported
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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
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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.
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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
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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
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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
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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.
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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.
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void (*link_open)(bt_mesh_prov_bearer_t bearer)
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.
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void (*link_close)(bt_mesh_prov_bearer_t 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.
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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.
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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.
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void (*reset)(void)
Node has been reset.
This callback notifies the application that the local node has been reset and needs to be reprovisioned. 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.
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const uint8_t *uuid
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enum bt_mesh_output_action_t