Internet DRAFT - draft-grayson-radext-rabble
draft-grayson-radext-rabble
RADEXT Working Group M. Grayson
Internet-Draft E. Lear
Intended status: Standards Track Cisco Systems
Expires: 11 January 2024 10 July 2023
RADIUS profile for Bonded Bluetooth Low Energy peripherals
draft-grayson-radext-rabble-01
Abstract
This document specifies an extension to the Remote Authentication
Dial-In User Service (RADIUS) protocol that enables a Bluetooth Low
Energy (BLE) peripheral device that has previously formed a bonded,
secure trusted relationship with a first "home" Bluetooth Low Energy
Central device to operate with a second "visited" Bluetooth Low
Energy Central device.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 11 January 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. BLE Roaming Overview . . . . . . . . . . . . . . . . . . . . 5
3. RADIUS Profile for BLE . . . . . . . . . . . . . . . . . . . 8
3.1. User-Name . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2. NAS-IP-Address, NAS-IPv6-Address . . . . . . . . . . . . 9
3.3. NAS-Port . . . . . . . . . . . . . . . . . . . . . . . . 9
3.4. Service-Type . . . . . . . . . . . . . . . . . . . . . . 9
3.5. State, Class, Proxy-State . . . . . . . . . . . . . . . . 9
3.6. Vendor-Specific . . . . . . . . . . . . . . . . . . . . . 9
3.7. Session-Timeout . . . . . . . . . . . . . . . . . . . . . 9
3.8. Idle-Timeout . . . . . . . . . . . . . . . . . . . . . . 9
3.9. Termination-Action . . . . . . . . . . . . . . . . . . . 9
3.10. Called-Station-Id . . . . . . . . . . . . . . . . . . . . 9
3.11. NAS-Identifier . . . . . . . . . . . . . . . . . . . . . 10
3.12. NAS-Port-Type . . . . . . . . . . . . . . . . . . . . . . 10
3.13. Hashed-Password . . . . . . . . . . . . . . . . . . . . . 10
3.13.1. Hashed-Password.Hmac-Sha256-128-Key . . . . . . . . 10
3.13.2. Hashed-Password.Hmac-Sha256-128-Password . . . . . . 11
3.13.3. Hashed-Password TLV-Type Usage . . . . . . . . . . . 11
3.14. GATT-Service-Profile . . . . . . . . . . . . . . . . . . 11
3.15. BLE-Keying-Material Attribute . . . . . . . . . . . . . . 12
3.15.1. BLE-Keying-Material.Peripheral-IA . . . . . . . . . 13
3.15.2. BLE-Keying-Material.Central-IA . . . . . . . . . . . 13
3.15.3. BLE-Keying-Material.IV . . . . . . . . . . . . . . . 13
3.15.4. BLE-Keying-Material.KEK-ID . . . . . . . . . . . . . 14
3.15.5. BLE-Keying-Material.KM-Type . . . . . . . . . . . . 14
3.15.6. BLE-Keying-Material.KM-Data . . . . . . . . . . . . 15
3.15.7. BLE-Keying-Material TLV-Type Usage . . . . . . . . . 16
3.16. Forwarding Bluetooth Messages . . . . . . . . . . . . . . 16
3.16.1. MQTT-Broker-URI . . . . . . . . . . . . . . . . . . 16
3.16.2. MQTT-Token . . . . . . . . . . . . . . . . . . . . . 17
3.17. RADIUS Accounting Attributes . . . . . . . . . . . . . . 18
3.17.1. Acct-Input-Octets and Acct-Output-Octets . . . . . . 18
3.17.2. Acct-Input-Packets . . . . . . . . . . . . . . . . . 18
3.17.3. Acct-Output-Packets . . . . . . . . . . . . . . . . 18
3.17.4. Acct-Terminate-Cause . . . . . . . . . . . . . . . . 19
4. BLE RADIUS Exchange . . . . . . . . . . . . . . . . . . . . . 19
5. Table of Attributes . . . . . . . . . . . . . . . . . . . . . 22
6. Security Considerations . . . . . . . . . . . . . . . . . . . 23
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.1. Normative References . . . . . . . . . . . . . . . . . . 25
8.2. Informative References . . . . . . . . . . . . . . . . . 25
Appendix A. MQTT Interworking . . . . . . . . . . . . . . . . . 26
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A.1. Establishing a Session to a MQTT-Broker-URI . . . . . . . 27
A.2. MQTT topics . . . . . . . . . . . . . . . . . . . . . . . 27
A.3. MQTT Exchange for Non-Connectable BLE Peripherals . . . . 28
A.4. Initial MQTT Exchange for Connectable BLE Peripherals . . 30
A.5. MQTT Exchange for Reading a GATT Attribute . . . . . . . 31
A.6. MQTT Exchange for Writing a GATT Attribute . . . . . . . 32
A.7. MQTT Exchange for BLE Peripheral initiated
Notifications . . . . . . . . . . . . . . . . . . . . . 33
A.8. MQTT Exchange for BLE Peripheral initiated Indications . 34
A.9. MQTT Exchange for dealing with NAS Mobility . . . . . . . 36
A.10. MQTT Exchange for ending a session for a connected BLE
Peripheral . . . . . . . . . . . . . . . . . . . . . . . 37
Appendix B. History of Changes . . . . . . . . . . . . . . . . . 38
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 39
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39
1. Introduction
This document specifies an extension to the Remote Authentication
Dial-In User Service (RADIUS) protocol [RFC2865] that enables a
Bluetooth Low Energy (BLE) peripheral device that has previously
formed a bonded, secure trusted relationship with a first "home"
Bluetooth Low Energy Central device to operate with a second
"visited" Bluetooth Low Energy Central device that is integrated with
a Network Access Server.
After being successfully authenticated, a signalling link is
established that enables Bluetooth messages advertised by the BLE
Peripheral to be forwarded from the Visited Bluetooth Low Energy
Central device to a Home MQTT Broker. For connectable BLE
Peripherals, the signalling link enables the Home MQTT Broker to send
BLE Requests or Commands to the Visited Bluetooth Low Energy Central
device that is then responsible for forwarding to the BLE peripheral.
The extensions allow administrative entities to collaborate to enable
RADIUS authentication of BLE devices onto their respective networks,
without requiring the peripheral to perform a re-pairing on the
visited network.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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1.2. Terminology
BLE Central Controller:
The BLE entity that implements the Bluetooth Link Layer and interacts
with the Bluetooth Radio Hardware.
BLE Central Host:
A BLE entity that interacts with the BLE Central Controller to enable
applications to communicate with peer BLE devices in a standard and
interoperable way.
BLE Peripheral Device:
A BLE device that is configured to repeatedly send advertising
messages.
BLE Security Database:
A database that stores the keying material associated with a bonded
Bluetooth Connection.
Bluetooth Low Energy (BLE):
A wireless technology designed for low power operation and specified
by the Bluetooth Special Interest Group.
Bonding:
A Bluetooth [BLUETOOTH] defined process that creates a relation
between a Bluetooth Central device and a Bluetooth Peripheral device
and which generates session keying material that is expected to be
stored by both Bluetooth devices, to be used for future
authentication.
Hash:
A Bluetooth [BLUETOOTH] specified 24-bit hash value which is
calculated using a hash function operating on IRK and prand as its
input parameters. The hash is encoded in the 24 least significant
bits of a Resolvable Private Address.
Home:
A network that has access to the keying material necessary to support
the pairing of a BLE peripheral and that is able to expose the keys
generated as part of the BLE bonding process.
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Identity Address (IA):
The 48-bit global (public) MAC address of a Bluetooth device.
Identity Resolving Key (IRK):
A Bluetooth [BLUETOOTH] specified key used in the Bluetooth privacy
feature. The Resolvable Private Address hash value is calculated
using a hash function of prand and the IRK.
Long-Term key (LTK):
A symmetric key which is generated during the Bluetooth bonding
procedure and used to generate the session key used to encrypt a
communication session between Bluetooth devices.
prand:
A 22-bit random number used by a BLE device to generate a Resolvable
Private Address. The prand is encoded in the 24 most significant
bits of a Resolvable Private Address.
Resolvable Private Address (RPA):
A Bluetooth [BLUETOOTH] specified private 48-bit address that can be
resolved to a permanent Bluetooth Identity Address through the use of
an Identity Resolving Key.
Visited:
A network that does not have access to the keying material necessary
to support the pairing of a BLE peripheral, but that is able to
support the RADIUS authentication of an already bonded BLE
Peripheral.
2. BLE Roaming Overview
This section provides an overview of the RADIUS BLE mechanism, which
is supported by the extensions described in this document. The
RADIUS profile is intended to be used between a Visited BLE Central
Host that is enhanced with Network Access Server (NAS) functionality
which enables it to exchange messages with a RADIUS server.
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+------------+ +-----------+
+------------+ | BLE | | BLE |
| BLE |---| Central#1 |---| Home |
| Peripheral | | Controller | | Central#1 |
+------------+ | | | Host |
+------------+ +-----------+
| |
| |
| +-------------------------+
| | BLE Security Database |
| | Peripheral: IA, IRK |
| | AP: IA, IRK |
| | Peripheral+AP: LTK |
| +-------------------------+
| |
| Bonded BLE |
| Peripheral +-------------+
| moves |RADIUS Server|
| +-------------+
\|/ |
- |
+------------+ +-----------+
+------------+ | BLE | | NAS/BLE |
| BLE |---| Central#2 |---| Visited |
| Peripheral | | Controller | | Central#2 |
+------------+ | | | Host |
+------------+ +-----------+
Figure 1: BLE RADIUS Authentication Overview
A BLE Peripheral is paired and bonded with the BLE Home Central Host.
The pairing requires the BLE Home Central Host to have access to the
keying material necessary to support the pairing of a BLE peripheral,
e.g., by using techniques described in
[I-D.shahzad-scim-device-model].
The bonding process generates new session specific keying material
that MUST be exposed by the BLE Home Central Host to a RADIUS server,
e.g., stored in a BLE Security Database which is accessible by the
RADIUS server. The keying material MUST include the peripheral's IA
and IRK, indicating that the BLE Peripheral has enabled the Bluetooth
privacy feature and is operating with a Resolvable Private Address
(RPA).
The BLE Peripheral then moves into the coverage of a second BLE
Central device which comprises a second BLE Central Controller and a
second BLE (Visited) Central Host which has been enhanced with
Network Access Server (NAS) functionality. The BLE Peripheral MUST
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be configured to send low duty cycle advertising events using the BLE
Peripheral's RPA that are detected by the NAS/BLE Visited Central
Host. The NAS/BLE Visited Central Host receives the Advertisement(s)
sent by the BLE Peripheral and MAY use the presence and/or contents
of specific Advertising Elements to decide whether to trigger a
RADIUS exchange with a RADIUS Server which has access to the keying
material exposed by the BLE Home Central Host.
The successful authentication of the BLE Peripheral onto the BLE
Visited Central Host MUST include the signalling of the keying
material exposed by the BLE Home Central Host to enable the re-
establishment of the secured communication session with the BLE
Peripheral. Bluetooth advertisements received from an authenticated
BLE Peripheral are forwarded between the BLE Visited Central Host and
a Home MQTT message broker.
If the BLE Peripheral is connectable, the Home MQTT Broker MAY send
BLE Requests or Commands to the Visited Bluetooth Low Energy Central
device that is then responsible for forwarding to the authenticated
BLE peripheral. The Home MQTT Broker MAY be configured to forward
the messages to/from a Bluetooth Application associated with the
authenticated BLE Peripheral, either directly, or via the first Home
Bluetooth Low Energy Central device.
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+-----------+
| BLE |
+--------|Application|
| +-----------+
| |
| |
| +-----------+
Optional direct | | BLE Home |
signalling between | | Central#1 |
broker and BLE | | Host |
application | +-----------+
| |
| |
| +-----------+
| | Home |
+--------| MQTT |
| Broker |
+-----------+
| -
| /|\
MQTT Publish | |
application | | MQTT Publish
to peripheral | | peripheral to
messages | | application
| | messages
\|/ |
- |
+------------+ +-----------+
+------------+ | BLE | | NAS/BLE |
| BLE |---| Central#2 |----| Visited |
| Peripheral | | Controller | | Central#2 |
+------------+ | | | Host |
+------------+ +-----------+
Figure 2: BLE Message Forwarding Overview
3. RADIUS Profile for BLE
3.1. User-Name
Contains a 6 character ASCII upper-case string corresponding to the
hexadecimal encoding of the 22-bit prand value derived from the
Bluetooth Resolvable Private Address, where the first string
character represents the most significant hexadecimal digit, i.e., a
prand value of 0x035fb2 is encoded as "035FB2".
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3.2. NAS-IP-Address, NAS-IPv6-Address
The NAS-IP-Address contains the IPv4 address of the BLE Central Host
acting as an Authenticator, and the NAS-IPv6-Address contains the
IPv6 address.
3.3. NAS-Port
For use with BLE the NAS-Port will contain the port number of the BLE
Central Host, if this is available.
3.4. Service-Type
For use with BLE, the Service-Type of Authenticate Only (8) is used.
3.5. State, Class, Proxy-State
These attributes are used for the same purposes as described in
[RFC2865].
3.6. Vendor-Specific
Vendor-specific attributes are used for the same purposes as
described in [RFC2865].
3.7. Session-Timeout
When sent in an Access-Accept without a Termination-Action attribute
or with a Termination-Action attribute set to Default, the Session-
Timeout attribute specifies the maximum number of seconds of service
provided prior to session termination.
3.8. Idle-Timeout
The Idle-Timeout attribute indicates the maximum time that the BLE
wireless device may remain idle.
3.9. Termination-Action
This attribute indicates what action should be taken when the service
is completed. The value Default (0) indicates that the session
should terminate.
3.10. Called-Station-Id
This attribute is used to store the public Identity Address (BD_ADDR)
of the Bluetooth Access Point in ASCII formatted as specified in
section 3.21 of [RFC3580].
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3.11. NAS-Identifier
This attribute contains a string identifying the BLE Central Host
originating the Access-Request.
3.12. NAS-Port-Type
TBA1: "Wireless - Bluetooth Low Energy"
3.13. Hashed-Password
Description
The Hashed-Password (TBA2) Attribute allows a RADIUS client to
include a key and hashed password.
Type
TBA2
Length
Variable
Data Type
TLV
Value
The TLV data type is specified in section 3.13 of [RFC8044] and
its value is determined by the TLV-Type field. Two TLV-Types are
defined for use with the Hashed-Password Attribute.
3.13.1. Hashed-Password.Hmac-Sha256-128-Key
TLV-Type
0 (Hashed-Password.Hmac-Sha256-128-Key)
TLV-Value:
A string data type, as defined in section 3.1 of [RFC8044],
encoding a sequence of octets representing a random 256-bit key.
The value SHOULD satisfy the requirements of [RFC4086]. A new key
value MUST be used whenever the value of Hashed-Password.Hmac-
Sha256-128-Password is changed. The key MUST NOT be changed when
a message is being retransmitted.
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TLV-Length:
34 octets
3.13.2. Hashed-Password.Hmac-Sha256-128-Password
TLV-Type
1 (Hashed-Password.Hmac-Sha256-128-Password)
TLV-Value:
A string data type encoding a sequence of octets representing the
first 128-bit (truncated) output of the HMAC-SHA-256-128 algorithm
[RFC4868] where the input data corresponds to the 24-bit hash
recovered from the Bluetooth Resolvable Private Address and the
key corresponds to the value of the TLV-Type Hashed-Password.Hmac-
Sha256-128-Key.
TLV-Length:
18 octets
3.13.3. Hashed-Password TLV-Type Usage
Two instances of the Hashed-Password Attribute MUST be included in an
Access-Request packet. One instance MUST correspond to the TLV-Type
0 (Hashed-Password.Hmac-Sha256-128-Key) and one instance MUST
correspond to the TLV-Type 1 (Hashed-Password.Hmac-
Sha256-128-Password).
3.14. GATT-Service-Profile
Description
The GATT-Service-Profile (TBA3) Attribute allows a RADIUS client to
include one or more GATT Service Profiles which are advertised by the
BLE Peripheral.
Zero or more GATT-Service-Profile Attributes MAY be included in an
Access-Request packet.
A summary of the GATT-Service-Profile Attribute format is shown
below. The fields are transmitted from left to right.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Value
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Value (cont) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Encoding GATT-Service-Profile Attribute
Type
TBA3
Length
6 octet
Data Type
Integer
Value
The field is 4 octets, containing a 32-bit unsigned integer that
represents a GATT Service Profile.
3.15. BLE-Keying-Material Attribute
Description
The BLE-Keying-Material (TBA3) Attribute allows the transfer of
Identity Address(es) and cryptographic keying material from a RADIUS
Server to the BLE Visited Central Host.
Type
TBA3
Length
Variable
Data Type
TLV
Value
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The TLV data type is specified in section 3.13 of [RFC8044] and
its value is determined by the TLV-Type field. Five TLV-Types are
defined for use with the BLE-Keying-Material Attribute.
3.15.1. BLE-Keying-Material.Peripheral-IA
TLV-Type
0 (BLE-Keying-Material.Peripheral-IA)
TLV-Value:
A string data type encoding a sequence of octets representing the
Peripheral's 6-octet Identity Address.
TLV-Length:
8 octets
3.15.2. BLE-Keying-Material.Central-IA
TLV-Type
1 (BLE-Keying-Material.Central-IA)
TLV-Value:
A string data type encoding a sequence of octets representing the
Central's 6-octet Identity Address.
TLV-Length:
8 octets
3.15.3. BLE-Keying-Material.IV
TLV-Type
2 (BLE-Keying-Material.IV)
TLV-Value:
A string data type encoding a sequence of octets representing an
8-octet initial value (IV). The value MUST be as specified in
section 2.2.3 of [RFC3394].
TLV-Length:
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10 octets
3.15.4. BLE-Keying-Material.KEK-ID
TLV-Type
3 (BLE-Keying-Material.KEK-ID)
TLV-Value:
A string data type encoding a sequence of octets representing the
identity of a Key Encryption Key (KEK). The combination of the
BLE-Keying-Material.KEK-ID value and the RADIUS client and server
IP addresses together uniquely identify a key shared between the
RADIUS client and server. As a result, the BLE-Keying-
Material.KEK-ID need not be globally unique. The BLE-Keying-
Material.KEK-ID MUST refer to an encryption key for use with the
AES Key Wrap with 128-bit KEK algorithm [RFC3394].
This key is used to protect the contents of the BLE-Keying-
Material.KM-Data TLV (see Section 3.15.6).
The BLE-Keying-Material.KEK-ID is a constant that is configured
through an out-of-band mechanism. The same value is configured on
both the RADIUS client and server. If no BLE-Keying-Material.KEK-
ID TLV-Type is signalled, then the field is set to 0. If only a
single KEK is configured for use between a given RADIUS client and
server, then 0 can be used as the default value.
TLV-Length:
18 octets
3.15.5. BLE-Keying-Material.KM-Type
TLV-Type:
4 (BLE-Keying-Material.KM-Type)
TLV-Value:
An integer data type identifying the type of keying material
included in the BLE-Keying-Material.KM-Data TLV.
This allows for multiple keys for different purposes to be present
in the same attribute. This document defines three values for the
The BLE-Keying-Material.KM-Type
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0 The BLE-Keying-Material.KM-Data TLV contains the
16-octet Peripheral IRK encrypted using the AES key wrapping
process with 128-bit KEK defined in [RFC3394]. The
Peripheral IRK is passed as input P1 and P2, with the
plaintext P1 corresponding to octet 0 through to octet 7 of
the IRK and plaintext P2 corresponding to octet 8 through to
octet 15 of the IRK.
1 The BLE-Keying-Material.KM-Data TLV contains the
encrypted 16-octet Peripheral IRK and the 16-octet LTK
generated during an LE Secure Connection bonding procedure
using the AES key wrapping process with 128-bit KEK defined
in [RFC3394]. The Peripheral IRK is passed as the plaintext
input P1 and P2, with P1 corresponding to octet 0 through to
octet 7 of the IRK and P2 corresponding to octet 8 through
to octet 15 of the IRK. The LTK is passed as the plaintext
input P3 and P4, with P3 corresponding to octet 0 through to
octet 7 of the LTK and P4 corresponding to octet 8 through
to octet 15 of the LTK.
2 The BLE-Keying-Material.KM-Data TLV contains the
encrypted 16-octet Peripheral IRK, the 16-octet LTK
generated during an LE Secure Connection bonding procedure
and the 16-octet Central IRK using the AES key wrapping
process with 128-bit KEK defined in [RFC3394]. The
Peripheral IRK is passed as the plaintext input P1 and P2,
with P1 corresponding to octet 0 through to octet 7 of the
IRK and P2 corresponding to octet 8 through to octet 15 of
the IRK. The LTK is passed as the plaintext input P3 and
P4, with P3 corresponding to octet 0 through to octet 7 of
the LTK and P4 corresponding to octet 8 through to octet 15
of the LTK. The Central IRK is passed as plaintext input P5
and P6, with P5 corresponding to octet 0 through to octet 7
of the Central IRK and P6 corresponding to octet 8 through
to octet 15 of the Central IRK.
TLV-Length:
6 octets
3.15.6. BLE-Keying-Material.KM-Data
TLV-Type:
5 (BLE-Keying-Material.KM-Data)
TLV-Value:
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A string data type encoding a sequence of octets representing the
actual encrypted keying material as identified using the BLE-
Keying-Material.KM-Type.
TLV-Length:
Variable
3.15.7. BLE-Keying-Material TLV-Type Usage
At least four instances of the BLE-Keying-Material Attribute MUST be
included in an Access-Accept packet, that include the following TLV-
Types:
* TLV-Type 0 (BLE-Keying-Material.Peripheral-IA)
* TLV-Type 2 (BLE-Keying-Material.IV)
* TLV-Type 4 (BLE-Keying-Material.KM-Type)
* TLV-Type 5 (BLE-Keying-Material.KM-Data)
If a KEK is configured, then in addition the Access-Accept packet
MUST include the BLE-Keying-Material Attribute with an instance of
TLV-Type 3 (BLE-Keying-Material.KEK-ID). When not present, the NAS
MUST use a default value of 0 for the KEK-ID.
If the BLE Peripheral is connectable and the RADIUS Server authorizes
connections, then in addition the Access-Accept message MUST include
the BLE-Keying-Material Attribute with an instance of TLV-Type 1
(BLE-Keying-Material.Central-IA).
3.16. Forwarding Bluetooth Messages
RADIUS attributes described in this section are used to exchange
information to allow non-IP Bluetooth messages to be transferred
between the BLE Visited Central Host and a Home MQTT Broker.
3.16.1. MQTT-Broker-URI
Description
The MQTT-Broker-URI (TBA5) Attribute allows a RADIUS server to
specify the URI of the MQTT Broker. A single MQTT-Broker-URI
Attributes MAY be included in an Access-Accept packet.
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If the RADIUS server operates with NAS/BLE Visited Hosts that are
deployed behind firewalls or NAT gateways, MQTT Messages SHOULD be
transported using WebSocket [RFC6455] as a network transport as
defined in MQTT [MQTT] and the the attribute SHOULD specify the URI
of a WebSocket server that supports the 'mqtt' Sec-WebSocket-
Protocol.
A summary of the MQTT-Broker-URI Attribute format is shown below.
The fields are transmitted from left to right.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Text...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Encoding MQTT-Broker-URI Attribute
Type
TBA5
Length
>=3 octet
Data Type
Text
Value
The text field encodes a URI where the MQTT service can be
accessed, e.g., "wss://broker.example.com:443".
3.16.2. MQTT-Token
Description
The MQTT-Token (TBA6) Attribute allows a RADIUS server to signal a
token for use by an MQTT client in an MQTT CONNECT packet [MQTT].
The token can be used by an MQTT Broker to associate an MQTT
Connection from an MQTT Client with a Network Access Server.
A MQTT-Token Attributes MAY be included in an Access-Accept packet.
A summary of the MQTT-Token Attribute format is shown below. The
fields are transmitted from left to right.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Text...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Encoding MQTT-Token Attribute
Type
TBA6
Length
>=3 octet
Data Type
Text
Value
The text field contains a token for use with an MQTT CONNECT
packet.
3.17. RADIUS Accounting Attributes
With a few exceptions, the RADIUS accounting attributes defined in
[RFC2866] have the same meaning within BLE sessions as they do in
dialup sessions and therefore no additional commentary is needed.
3.17.1. Acct-Input-Octets and Acct-Output-Octets
These attributes are not not used by BLE Authenticators.
3.17.2. Acct-Input-Packets
This attribute is used to indicate how many MQTT messages that
include the Peripheral Identity Address signalled in
the BLE-Keying-Material attribute have been sent by the BLE Central
Host.
3.17.3. Acct-Output-Packets
This attribute is used to indicate how many MQTT messages that
include the Peripheral Identity Address signalled in
the BLE-Keying-Material attribute have been received by the BLE
Central Host.
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3.17.4. Acct-Terminate-Cause
This attribute indicates how the session was terminated, as described
in [RFC2866]. When the idle-timeout attribute is used by the NAS/BLE
Visited Host to terminate a RADIUS Accounting session, it MUST set
the Acct-Terminate-Cause set to Lost Carrier (2).
4. BLE RADIUS Exchange
The BLE Peripheral uses techniques defined in Bluetooth Core
Specifications [BLUETOOTH] to establish a bonded, secure, trusted
relationship with a BLE Home Central device in the network. The
bonding procedure generates session specific keying material. The
BLE Peripheral sends low duty cycle advertising events.
The BLE Peripheral moves into coverage of a second BLE Central device
that is integrated with a NAS.
The BLE Peripheral sends Advertisements using its Resolvable Public
Address. The contents of the Advertisements are signalled to a BLE
Visited Central Host associated with the second BLE Central device.
The received Advertisements sent by the BLE Peripheral are used by
the BLE Visited Central Host to decide whether to trigger a RADIUS
exchange, e.g., using the presence and/or contents of specific
Advertising Elements.
The NAS associated with the BLE Visited Central Host is configured
with the identity of the RADIUS server. The NAS/BLE Visited Host MAY
be statically configured with the identity of a RADIUS Server.
Alternatively, the NAS/BLE Visited Host MAY use the contents of an
Advertisement Element received from the BLE Peripheral to derive an
FQDN of the RADIUS sever and use RFC 7585 [RFC7585] to dynamically
resolve the address of the RADIUS server. For example, the
peripheral can use the Bluetooth URI data type Advertisement Element
(0x24) to encode the Bluetooth defined 'empty scheme' name tag
together with a hostname that identifies the network which operates
the BLE Home Central Host associated with the peripheral.
Alternatively, a federation of operators of BLE Visited Centrals and
RADIUS Servers can define the use of the Bluetooth defined
Manufacturer Specific Advertisement Data Element (0xFF) together with
a Company Identifier that identifies the federation to signal a
federation defined sub-type that encodes information that enables the
BLE Visited Central Host to derive an FQDN of the RADIUS sever
associated with the advertising peripheral.
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The NAS/BLE Host generates a RADIUS Access-Request message using the
prand from the RPA as the User-Name attribute and the hash from the
RPA to generate the TLV-Type Hashed-Password.Hmac-
Sha256-128-Password. The NAS-Port-Type is set to "Wireless -
Bluetooth Low Energy".
On receiving the RADIUS Access-Request message, the RADIUS Server
uses the keying material exposed by the BLE Home Central Host and
attempts to resolve the User-Name and the TLV-Type Hashed-
Password.Hmac-Sha256-128-Password to a known BLE Identity Address
(IA). If the RADIUS Server cannot resolve the User-Name and TLV-Type
Hashed-Password.Hmac-Sha256-128-Password to a known BLE Identity
Address, the RADIUS server MUST reject the Access-Request.
If the RADIUS Server resolves the User-Name and TLV-Type Hashed-
Password.Hmac-Sha256-128-Password to a known BLE Identity Address,
and the BLE Identity Address is authorized to access via the BLE
Visited Host, the RADIUS server recovers the session specific keying
material exposed by the BLE Home Central Host.
If the BLE Peripheral is not connectable or connections are not
authorized, the RADIUS server signals the Peripheral Identity Address
in the TLV-type BLE-Keying-Material.Peripheral-IA, sets the value of
TLV-Type BLE-Keying-Material.KM-Type to 0 and encodes the Peripheral
Identity Resolving Key in the TLV-Type BLE-Keying-Material.KM-Data.
If the BLE Peripheral is connectable and connections are authorized
via the BLE Visited Host, the RADIUS server additionally includes the
Central Identity Address in the TLV-type BLE-Keying-Material.Central-
IA, sets the value of TLV-Type BLE-Keying-Material.KM-Type to 1 and
encodes the Peripheral Identity Resolving Key and the 16-octet Long
Term Key in the TLV-Type BLE-Keying-Material.KM-Data. Finally, if
the BLE Peripheral is connectable and connections are authorized via
the BLE Visited Host and the security database indicates that the BLE
Home Central Host operates using Bluetooth privacy, then the RADIUS
server sets the value of TLV-Type BLE-Keying-Material.KM-Type to 2
and encodes the Peripheral Identity Resolving Key, the 16-octet Long
Term Key and the 16-octet Central Identity Resolving Key in the TLV-
Type BLE-Keying-Material.KM-Data.
The RADIUS Server SHOULD include the MQTT-Broker-URI attribute and
MAY include the MQTT-Token attribute by which an MQTT client
associated with the BLE Visited Host can establish an MQTT connection
with a Home MQTT Broker for forwarding messages received to/from the
BLE peripheral.
On receiving the Access-Accept, the NAS/BLE Visited Host recovers the
keying material, including the BLE Peripheral's Identity Address and
then establishes an MQTT Connection with the Home MQTT Broker. The
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NAS/BLE Visited Host SHOULD include its NAS-Id in the User Name field
of the MQTT CONNECT message and MAY include an Operator Name, if for
example the NAS has been configured with the operator-name attribute
(#126) as specified in section 4.1 of RFC5580 [RFC5580].
If the advertisement that triggered the RADIUS exchange corresponds
to an ADV_IND then the NAS/BLE Visited Host can subsequently
establish a secure connection with the BLE Peripheral.
NAS/BLE
Visited Home Home
BLE Central#2 RADIUS MQTT
Peripheral Host Server Broker
| | | |
| | | |
|--BLE----------->| | |
| Advertisement | | |
| | | |
|<--------------->| | |
| Active Scan |--Access-Request------->| |
| | User-Name=prand | |
| | Hashed-Password.Hmac-Sha256-128-Password=hash
| | Hashed-Password.Hmac-Sha256-128-Key=key
| | NAS-Port-Type=BLE | |
| | GATT-Service-Profile | |
| | | |
| |<-Access-Accept---------| |
| | Idle-Timeout | |
| | BLE-Keying-Material | |
| | MQTT-Broker-URI | |
| | MQTT-Token | |
| | | |
| |--Accounting-Request--->| |
| | Acct-Status-Type=Start | |
| | Session-Id | |
| | | |
| |--MQTT CONNECT------------------------>|
| | User Name=[operator_name:]nas-id |
| | Password=MQTT Token | |
| | | |
| |--MQTT PUBLISH------------------------>|
| | Advertisement(s) | |
| | | |
+-----------------------------------------------------------+
| Further MQTT and associated BLE Exchanges |
+-----------------------------------------------------------+
| | | |
|--BLE ---------->|--+ Resolve to | |
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| Advertisement | | same Identity | |
| |<-+ Address | |
| +--| | |
| | | | |
| +->|Idle Timer Expiry | |
| | | |
| |--Accounting-Request--->| |
| | Acct-Status-Type=Stop | |
| | Session-Id | |
Figure 6: BLE RADIUS Exchange
5. Table of Attributes
The following table provides a guide to which of the attribute
defined may be found in which kinds of packets, and in what quantity.
+=========+========+========+===========+=========+====+===========+
| Request | Accept | Reject | Challenge | Acct- |# | Attribute |
| | | | | Request | | |
+=========+========+========+===========+=========+====+===========+
| 1+ | 0 | 0 | 0 | 0 |TBA2| Hashed- |
| | | | | | | Password |
+---------+--------+--------+-----------+---------+----+-----------+
| 0+ | 0 | 0 | 0 | 0 |TBA3| GATT- |
| | | | | | | Service- |
| | | | | | | Profile |
+---------+--------+--------+-----------+---------+----+-----------+
| 0 | 1+ | 0 | 0 | 0 |TBA4| BLE- |
| | | | | | | Keying- |
| | | | | | | Material |
+---------+--------+--------+-----------+---------+----+-----------+
| 0 | 0-1 | 0 | 0 | 0 |TBA5| MQTT- |
| | | | | | | Broker- |
| | | | | | | URI |
+---------+--------+--------+-----------+---------+----+-----------+
| 0 | 0-1 | 0 | 0 | 0 |TBA6| MQTT- |
| | | | | | | Token |
+---------+--------+--------+-----------+---------+----+-----------+
Table 1: Table of Attributes
The following table defines the meaning of the above table entries.
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+=======+===============================================+
| Entry | Meaning |
+=======+===============================================+
| 0 | This attribute MUST NOT be present in packet. |
+-------+-----------------------------------------------+
| 0+ | Zero or more instances of this attribute MAY |
| | be present in packet. |
+-------+-----------------------------------------------+
| 0-1 | Zero or one instance of this attribute MAY be |
| | present in packet. |
+-------+-----------------------------------------------+
| 1 | One instance of this attribute MUST be |
| | present in packet. |
+-------+-----------------------------------------------+
Table 2: Table of Attributes Entry Definition
6. Security Considerations
Use of this RADIUS profile for BLE can be between a NAS/BLE Visited
Host and a RADIUS Server inside a secure network, or between a NAS/
BLE Visited Host and RADIUS server operated in different
administrative domains which are connected over the Internet. All
implementations MUST follow
[I-D.draft-dekok-radext-deprecating-radius].
The RADIUS profile for BLE devices is designed to operate when BLE
devices operate their physical links with BLE Secure Connections
[BLUETOOTH]. This approach uses a secure exchange of data over the
Bluetooth connection, together with Elliptic Curve Diffie-Hellman
(ECDH) public key cryptography, to create the session specific
symmetric Long Term Key (LTK) which is then exchanged using the BLE-
Keying-Material attribute in the RADIUS Access-Accept message.
Bluetooth [BLUETOOTH] specifies how an IRK can be generated from an
Identity Root (IR) key. Removing the Bluetooth bond in a device will
typically trigger the generation of a new IRK key for the device.
The RADIUS profile for BLE devices is designed to operate when BLE
devices are configured to operate with Bluetooth Privacy Mode enabled
[BLUETOOTH]. The BLE device defines the policy of how often it
should generate a new Resolvable Private Address. This can be
configured to be between every second and every hour, with a default
value of every 15 minutes [BLUETOOTH]. This mode mitigates risks
associated with a malicious third-party scanning for and collecting
Bluetooth addresses over time and using such to build a picture of
the movements of BLE devices and, by inference, the human users of
those devices.
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The Home MQTT broker can observe the Bluetooth messages exchanged
with the BLE Peripheral. The Bluetooth GATT attributes SHOULD be
cryptographically protected at the application-layer. The Home MQTT
Broker MUST be configured with access control lists so that a NAS
cannot subscribe to a topic that is intended for another NAS.
The WebSocket connection MUST operate using a WebSocket Secure
connection. If the entropy of the MQTT-Token is known to be low, the
WebSocket Secure TLS connection SHOULD be secured with certificate-
based mutual TLS.
7. IANA Considerations
This document defines a new value of TBA1 for RADIUS Attribute Type
#61 (NAS-Port-Type) defined in https://www.iana.org/assignments/
radius-types/radius-types.xhtml#radius-types-13
+=======+===================================+==============+
| Value | Description | Reference |
+=======+===================================+==============+
| TBA1 | "Wireless - Bluetooth Low Energy" | Section 3.12 |
+-------+-----------------------------------+--------------+
Table 3: New NAS-Port-Type value defined in this document
This document defines new RADIUS attributes, (see section Section 3),
and assigns values of TBA2, TBA3, TBA4, TBA5 and TBA6 from the RADIUS
Attribute Type space https://www.iana.org/assignments/radius-types.
+======+======================+================+
| Tag | Attribute | Reference |
+======+======================+================+
| TBA2 | Hashed-Password | Section 3.13 |
+------+----------------------+----------------+
| TBA3 | GATT-Service-Profile | Section 3.14 |
+------+----------------------+----------------+
| TBA4 | BLE-Keying-Material | Section 3.15 |
+------+----------------------+----------------+
| TBA5 | MQTT-Broker-URI | Section 3.16.1 |
+------+----------------------+----------------+
| TBA6 | MQTT-Token | Section 3.16.2 |
+------+----------------------+----------------+
Table 4: New RADIUS attributes defined in
this document
8. References
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8.1. Normative References
[I-D.draft-dekok-radext-deprecating-radius]
DeKok, A., "Deprecating RADIUS/UDP and RADIUS/TCP", Work
in Progress, Internet-Draft, draft-dekok-radext-
deprecating-radius-01, 3 March 2023,
<https://datatracker.ietf.org/doc/html/draft-dekok-radext-
deprecating-radius-01>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)",
RFC 2865, DOI 10.17487/RFC2865, June 2000,
<https://www.rfc-editor.org/info/rfc2865>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005,
<https://www.rfc-editor.org/info/rfc4086>.
[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
384, and HMAC-SHA-512 with IPsec", RFC 4868,
DOI 10.17487/RFC4868, May 2007,
<https://www.rfc-editor.org/info/rfc4868>.
[RFC5580] Tschofenig, H., Ed., Adrangi, F., Jones, M., Lior, A., and
B. Aboba, "Carrying Location Objects in RADIUS and
Diameter", RFC 5580, DOI 10.17487/RFC5580, August 2009,
<https://www.rfc-editor.org/info/rfc5580>.
[RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol",
RFC 6455, DOI 10.17487/RFC6455, December 2011,
<https://www.rfc-editor.org/info/rfc6455>.
[RFC8044] DeKok, A., "Data Types in RADIUS", RFC 8044,
DOI 10.17487/RFC8044, January 2017,
<https://www.rfc-editor.org/info/rfc8044>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
8.2. Informative References
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[BLUETOOTH]
Bluetooth Core Specification Working Group, "BLUETOOTH
CORE SPECIFICATION v5.3", 13 July 2021,
<https://www.bluetooth.com/specifications/bluetooth-core-
specification/>.
[I-D.shahzad-scim-device-model]
Shahzad, M., Hassan, H., and E. Lear, "Device Schema
Extensions to the SCIM model", Work in Progress, Internet-
Draft, draft-shahzad-scim-device-model-05, 2 June 2023,
<https://datatracker.ietf.org/doc/html/draft-shahzad-scim-
device-model-05>.
[MQTT] OASIS, "MQTT Version 5.0", 7 March 2019,
<https://docs.oasis-open.org/mqtt/mqtt/v5.0/mqtt-
v5.0.html>.
[RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866,
DOI 10.17487/RFC2866, June 2000,
<https://www.rfc-editor.org/info/rfc2866>.
[RFC3394] Schaad, J. and R. Housley, "Advanced Encryption Standard
(AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394,
September 2002, <https://www.rfc-editor.org/info/rfc3394>.
[RFC3580] Congdon, P., Aboba, B., Smith, A., Zorn, G., and J. Roese,
"IEEE 802.1X Remote Authentication Dial In User Service
(RADIUS) Usage Guidelines", RFC 3580,
DOI 10.17487/RFC3580, September 2003,
<https://www.rfc-editor.org/info/rfc3580>.
[RFC7585] Winter, S. and M. McCauley, "Dynamic Peer Discovery for
RADIUS/TLS and RADIUS/DTLS Based on the Network Access
Identifier (NAI)", RFC 7585, DOI 10.17487/RFC7585, October
2015, <https://www.rfc-editor.org/info/rfc7585>.
Appendix A. MQTT Interworking
This section describes how a NAS/BLE Visited Host supporting the BLE
RADIUS profile can interwork with a Home MQTT Message Broker in order
to use MQTT topics to deliver Bluetooth messages to/from a BLE
Peripheral. It is intended to move this material to another document
- but is included here to describe, at a high level, the MQTT
interworking established by the RADIUS exchange.
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A.1. Establishing a Session to a MQTT-Broker-URI
If the NAS/BLE Visited Host is signalled a MQTT-Broker-URI in an
Access-Accept with which it does not have an established MQTT
connection, then it MUST establish an MQTT connection. It the NAS/
BLE Visited Host is behind a firewall or NAT gateway it MUST use
WebSocket transport for the MQTT connection. The user name in the
MQTT CONNECT message SHOULD include the NAS-ID and MAY include the
name of the operator of the NAS/BLE Visited Host.
NAS/BLE
Visited Home Home
BLE Central#2 RADIUS MQTT
Peripheral Host Server Broker
| | | |
| | | |
| |--Accounting-Request--->| |
| | Acct-Status-Type=Start | |
| | Session-Id | |
| | Chargeable-User-Id | |
| | | |
| |--HTTP GET---------------------------->|
| | Upgrade:websocket | |
| | Connection:upgrade | |
| | Sec-WebSocket-Protocol=mqtt |
| | | |
| |<-HTTP 101--------------|--------------|
| | Upgrade:websocket | |
| | Connection:upgrade | |
| | Sec-WebSocket-Protocol=mqtt |
| | | |
| |--MQTT CONNECT------------------------>|
| | User Name=[operator_name:]nas-id |
| | Password=MQTT Token | |
| | | |
| |<-MQTT CONNACK-------------------------|
| | | |
| | | |
Figure 7: Establishing an MQTT connection to a Home Broker using
WebSocket transport
A.2. MQTT topics
The following topic is used by the MQTT client of the BLE Visited
Host to signal active and passive scan advertisements received from
BLE Peripherals to the home MQTT Broker.
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* {peripheral_identity_address}/advertisement/gatt-ind
If the BLE Peripheral is connectable, the MQTT client of the BLE
Visited Host SHOULD subscribe to the following message topics to be
able to receive GATT requests from the Home MQTT Broker:
1. {peripheral_identity_address}/connect/gatt-req : when publishing
a message on the {peripheral_identity_address}/connect/gatt-req
topic, an MQTT client SHOULD include the following as a response
topic {peripheral_identity_address}/connect/gatt-res.
2. {peripheral_identity_address}/disconnect/gatt-req : when
publishing a message on the
{peripheral_identity_address}/disconnect/gatt-req topic, an MQTT
client SHOULD include the following as a response topic
{peripheral_identity_address}/disconnect/gatt-res.
3. {peripheral_identity_address}/read/gatt-req : when publishing a
message on the {peripheral_identity_address}/read/gatt-req topic,
an MQTT client SHOULD include the following as a response topic
{peripheral_identity_address}/read/gatt-res.
4. {peripheral_identity_address}/write/gatt-req : when publishing a
message on the {peripheral_identity_address}/write/gatt-req
topic, an MQTT client SHOULD include the following as a response
topic {peripheral_identity_address}/write/gatt-res.
5. {peripheral_identity_address}/service-discovery/gatt-req : when
publishing a message on the
{peripheral_identity_address}/service-discovery/gatt-req topic,
an MQTT client SHOULD include the following as a response topic
{peripheral_identity_address}/service-discovery/gatt-res.
6. {peripheral_identity_address}/notification/gatt-ind-res : when
sending indications, the MQTT client of the NAS/BLE Visited Host
SHOULD publish the message using the
topic:{peripheral_identity_address}/notification/gatt-ind-req
indication and SHOULD include the following as a response topic
{peripheral_identity_address}/notification/gatt-ind-res.
A.3. MQTT Exchange for Non-Connectable BLE Peripherals
If the BLE Peripheral indicates in its scan that it is not
connectable, the NAS/BLE Visited Host is responsible for publishing
the received advertisements received from the authenticated BLE
Peripheral.
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On idle-timeout the NAS/BLE Visited Host MUST send an Accounting-
Request message with Acct-Status-Type set to STOP and Acct-Terminate-
Cause set to Lost Carrier (2).
NAS/BLE
Visited Home
BLE Central#2 RADIUS MQTT
Peripheral Host Server Broker
| | | |
|--BLE ---------->| | |
| Advertisement | | |
+---------------------+ | |
| | Active Scan | | | |
| |<-BLE SCAN_REQ---| | | |
| | | | | |
| |--BLE SCAN_RSP-->| | | |
+---------------------+ | |
| |--MQTT PUBLISH------------------------>|
| | topic:{peripheral_identity_address}/ |
| | advertisement/gatt-ind | |
| | msg:Advertising Report | |
| | | |
|--BLE ---------->| | |
| Advertisement |--MQTT PUBLISH------------------------>|
| +--| topic:{peripheral_identity_address}/ |
| | | advertisement/gatt-ind | |
| | | msg:Advertising Report | |
| | | | |
| | | | |
| | | | |
| +->|Idle Timer Expiry | |
| | | |
| |--Accounting-Request--->| |
| | Acct-Status-Type=Stop | |
| | Session-Id | |
| | | |
| +-----------------------------------------------+
| | Last Session to MQTT Broker Stopped |
| +-----------------------------------------------+
| | |
| |--MQTT DISCONNECT--------------------->|
| | |
| |--Close WebSocket--------------------->|
| | |
Figure 8: MQTT Exchange for Non-Connectable BLE Peripherals
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A.4. Initial MQTT Exchange for Connectable BLE Peripherals
If the BLE Peripheral indicates in its scan that it is connectable,
the NAS/BLE Visited Host is responsible for publishing the received
advertisements received from the authenticated BLE Peripheral and to
subscribing to the GATT requests published for the BLE Peripheral's
Identity Address.
NAS/BLE
Visited Home
BLE Central#2 MQTT
Peripheral Host Broker
| | |
|--BLE----------->| |
| Advertisement |---MQTT PUBLISH------------------------>|
| | topic:{peripheral_identity_address}/ |
| | advertisement/gatt-ind |
| | msg:Advertising Report |
| | |
+--------------------------------------------------------------+
| GATT Subscription |
+--------------------------------------------------------------+
| | |
| |---MQTT SUBSCRIBE---------------------->|
| | topic:{peripheral_identity_address}/ |
| | +/gatt-req |
| | topic:{peripheral_identity_address}/ |
| | +/gatt-ind-res |
| | |
+--------------------------------------------------------------+
| GATT Connection and Service Discovery |
+--------------------------------------------------------------+
| | |
| |<--MQTT PUBLISH-------------------------|
| | topic:{peripheral_identity_address}/ |
|<-BLE PDU------->| connect/gatt-req |
| Exchange | response topic: |
| | {peripheral_identity_address}/ |
| | connect/gatt-res |
| | correlation data:{binary_data} |
| | msg: |
| | |
| |---MQTT PUBLISH------------------------>|
| | topic:{peripheral_identity_address}/ |
| | connect/gatt-res |
| | correlation data:{binary data} |
| | msg: connect-id or error |
| | |
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| |<--MQTT PUBLISH-------------------------|
| | topic:{peripheral_identity_address}/ |
|<-BLE PDU------->| service-discovery/gatt-req |
| Exchange | response topic: |
| | {peripheral_identity_address}/ |
| | service-discovery/gatt-res |
| | correlation data:{binary_data} |
| | msg: connect-id, optional UUID |
| | |
| |---MQTT PUBLISH------------------------>|
| | topic:{peripheral_identity_address}/ |
| | service-discovery/gatt-res |
| | correlation data:{binary data} |
| | msg: service UUID or error |
| | |
| |<--MQTT PUBLISH-------------------------|
| | topic:{peripheral_identity_address}/ |
|<-BLE PDU------->| disconnect/gatt-req |
| Exchange | response topic: |
| | {peripheral_identity_address}/ |
| | disconnect/gatt-res |
| | correlation data:{binary_data} |
| | msg: connect-id |
| | |
| |---MQTT PUBLISH------------------------>|
| | topic:{peripheral_identity_address}/ |
| | disconnect/gatt-res |
| | correlation data:{binary data} |
| | msg: ok or error |
| | |
Figure 9: MQTT Exchange for GATT Service Discovery
A.5. MQTT Exchange for Reading a GATT Attribute
If the BLE Peripheral is connectable, a Bluetooth Application can
read GATT attributes.
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BLE Central#2 MQTT
Peripheral Host Broker
| | |
+--------------------------------------------------------------+
| GATT Read Request |
+--------------------------------------------------------------+
| | |
| |<--MQTT PUBLISH-------------------------|
| | topic:{peripheral_identity_address}/ |
|<-BLE PDU------->| read/gatt-req |
| Exchange | response topic: |
| | {peripheral_identity_address}/ |
| | read/gatt-res |
| | correlation data:{binary_data} |
| | msg: Characteristic optional offset, |
| | optional maxlen |
| | |
| |---MQTT PUBLISH------------------------>|
| | topic:{peripheral_identity_address}/ |
| | read/gatt-res |
| | correlation data:{binary data} |
| | msg: Handle, opcode, offset, value or |
| | error |
Figure 10: MQTT Exchange for GATT Read Attribute
A.6. MQTT Exchange for Writing a GATT Attribute
If the BLE Peripheral is connectable, a Bluetooth Application can
write GATT attributes.
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Visited Home
BLE Central#2 MQTT
Peripheral Host Broker
| | |
+--------------------------------------------------------------+
| GATT Write Request |
+--------------------------------------------------------------+
| | |
| |<--MQTT PUBLISH-------------------------|
| | topic:{peripheral_identity_address}/ |
|<-BLE PDU------->| write/gatt-req |
| Exchange | response topic: |
| | {peripheral_identity_address}/ |
| | write/gatt-res |
| | correlation data:{binary_data} |
| | msg: characteristic, length, value |
| | |
| |---MQTT PUBLISH------------------------>|
| | topic:{peripheral_identity_address}/ |
| | write/gatt-res |
| | correlation data:{binary data} |
| | msg: success or error |
| | |
Figure 11: MQTT Exchange for GATT Write Attribute
A.7. MQTT Exchange for BLE Peripheral initiated Notifications
A Bluetooth Application can subscribe to receive Bluetooth
notifications sent by the BLE Peripheral.
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BLE Central#2 MQTT
Peripheral Host Broker
| | |
+--------------------------------------------------------------+
| GATT Set Notification Request |
+--------------------------------------------------------------+
| | |
| |<--MQTT PUBLISH-------------------------|
| | topic:{peripheral_identity_address}/ |
|<-BLE PDU------->| write/gatt-req |
| Exchange | response topic: |
| | {peripheral_identity_address}/ |
| | write/gatt-res |
| | correlation data:{binary_data} |
| | msg: characteristic, enable/disable |
| | |
| |---MQTT PUBLISH------------------------>|
| | topic:{peripheral_identity_address}/ |
| | write/gatt-res |
| | correlation data:{binary data} |
| | msg: success or error |
| | |
+--------------------------------------------------------------+
| GATT Notification |
+--------------------------------------------------------------+
| | |
|--BLE ---------->| |
| Notification |---MQTT PUBLISH------------------------>|
| | topic:{peripheral_identity_address}/ |
| | notification/gatt-ind |
| | msg:handle & value |
| | |
Figure 12: MQTT Exchange for BLE Peripheral Notifications
A.8. MQTT Exchange for BLE Peripheral initiated Indications
A Bluetooth Application can subscribe to receive Bluetooth
indications sent by the BLE Peripheral.
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BLE Central#2 MQTT
Peripheral Host Broker
| | |
+--------------------------------------------------------------+
| GATT Set Indication Request |
+--------------------------------------------------------------+
| | |
| |<--MQTT PUBLISH-------------------------|
| | topic:{peripheral_identity_address}/ |
|<-BLE PDU------->| write/gatt-req |
| Exchange | response topic: |
| | {peripheral_identity_address}/ |
| | write/gatt-res |
| | correlation data:{binary_data} |
| | msg: identifier & handle |
| | |
| |---MQTT PUBLISH------------------------>|
| | topic:{peripheral_identity_address}/ |
| | write/gatt-res |
| | correlation data:{binary data} |
| | msg: procedure complete |
| | |
+--------------------------------------------------------------+
| GATT Indication |
+--------------------------------------------------------------+
| | |
|--BLE----------->| |
| Indication |---MQTT PUBLISH------------------------>|
| | topic:{peripheral_identity_address}/ |
| | notification/gatt-ind-req |
| | response topic: |
| | {peripheral_identity_address}/ |
| | notification/gatt-ind-res |
| | correlation data:{binary_data} |
| | msg: Indication |
| | |
| |<--MQTT PUBLISH-------------------------|
|<-BLE------------| topic:{peripheral_identity_address}/ |
| Status | notification/gatt-ind-res |
| | correlation data:{binary data} |
| | msg: Indication confirmation |
| | |
Figure 13: MQTT Exchange for BLE Peripheral Indications
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A.9. MQTT Exchange for dealing with NAS Mobility
NAS/BLE NAS/BLE
Visited Visited Home
BLE Central#2 Central#3 MQTT
Peripheral Host Host Broker
| | | |
+--------------------------------------------------------------+
| Initial Authentication With Central#2 |
+--------------------------------------------------------------+
| | | |
| |--MQTT SUBSCRIBE --------------------------->|
| | topic:{periperal_identity_address}/ |
| | +/gatt-req |
| | | |
+--------------------------------------------------------------+
| NAS Mobility to Central#3 without MQTT unsubscription |
+--------------------------------------------------------------+
| | | |
| | |--MQTT SUBSCRIBE--------------> |
| | | topic: |
| | | {peripheral_identity_address}/ |
| | | +/gatt-req |
| | | |
+--------------------------------------------------------------+
| Example GATT Connection Request with NAS Mobility |
+--------------------------------------------------------------+
| | | |
| |<-MQTT PUBLISH-------------------------------|
| +--| topic:{peripheral_identity_address}/ |
| | | connect/gatt-req |
| | | response topic: |
| | | {peripheral_identity_address}/ |
| | | connect/gatt-res |
| | | correlation data:{binary_data} |
| | | msg: | |
| | | | |
| | | |<--MQTT PUBLISH-----------------|
| | | | topic: |
| | | | {peripheral_identity_address}/ |
| | | | connect/gatt-req |
|<-BLE----|-------------->| response topic: |
| PDU | | | {peripheral_identity_address}/ |
| Exchange | | connect/gatt-res |
| | | | correlation data:{binary_data} |
| | | | msg: |
| | | | |
| | | |---MQTT PUBLISH---------------->|
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| | | | topic: |
| | | | {peripheral_identity_address}/ |
|Central#2| | | connect/gatt-res |
| BLE| | | correlation data:{binary data} |
| Timeout| | | msg: connect-id |
| +->| | |
| |---MQTT PUBLISH----------------------------->|
| | topic:{peripheral_identity_address}/ |
| | connect/gatt-res |
| | correlation data:{binary data} |
| | msg: procedure timeout |
| | | |
+--------------------------------------------------------------+
| MQTT Broker drops timeout message for PUBLISH |
| with duplicated correlation data |
+--------------------------------------------------------------+
Figure 14: MQTT Exchange for Inter-NAS Mobility without MQTT
Unsubscription
A.10. MQTT Exchange for ending a session for a connected BLE Peripheral
On idle-timeout the NAS/BLE Visited Host MUST un-subscribe from any
subscribed to topics and send an Accounting-Request message with
Acct-Status-Type set to STOP and Acct-Terminate-Cause set to Lost
Carrier (2).
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NAS/BLE
Visited Home Home
BLE Central#2 RADIUS MQTT
Peripheral Host Server Broker
| | | |
|--BLE----------->| | |
| Advertisement |---MQTT PUBLISH------------------------>|
| +--| topic:{peripheral_identity_address}/ |
| | | advertisement/gatt-ind | |
| | | msg:Advertising Report | |
| | | | |
| | | | |
| +->|Idle Timer Expiry | |
| | | |
| |---Accounting-Request--->| |
| | Acct-Status-Type=Stop | |
| | | |
| |---MQTT UNSUBSCRIBE-------------------->|
| | topic:{peripheral_identity_address}/ |
| | +/gatt-req | |
| | topic:{peripheral_identity_address}/ |
| | +/gatt-ind-res | |
| | | |
| +------------------------------------------------+
| | Last Session to MQTT Broker Stopped |
| +------------------------------------------------+
| | | |
| |---MQTT DISCONNECT--------------------->|
| | | |
| |---Close WebSocket--------------------->|
| | | |
Figure 15: MQTT Exchange when disconnecting from a connected BLE
Peripheral
Appendix B. History of Changes
Note: This appendix will be deleted in the final version of the
document.
From version 00 -> 01:
* switched from User-Password to new Hashed-Password attribute using
SHA256
* switched to TLV-encoding of BLE-Keying-Material
* re-ordered MQTT topic definitions
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* removed redundant attribute sections
Acknowledgements
Thanks to Oleg Pekar and Eric Vyncke for their review comments.
Authors' Addresses
Mark Grayson
Cisco Systems
10 New Square Park
Feltham
TW14 8HA
United Kingdom
Email: mgrayson@cisco.com
Eliot Lear
Cisco Systems
Glatt-com
CH- CH-8301 Glattzentrum, Zurich
Switzerland
Email: elear@cisco.com
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