Status of This Memo

This document is not an Internet Standards Track specification; it is published for informational purposes.¶

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are candidates for any level of Internet Standard; see Section 2 of RFC 7841.¶

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained athttps://www.rfc-editor.org/info/rfc9019.¶

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Table of Contents

1.Introduction

Firmware updates can help to fix security vulnerabilities, and performing updates is an important building block in securing IoT devices. Due to rising concerns about insecure IoT devices, the Internet Architecture Board (IAB) organized the Internet of Things Software Update (IoTSU) Workshop[RFC8240] to take a look at the bigger picture. The workshop revealed a number of challenges for developers and led to the formation of the IETF Software Updates for Internet of Things (SUIT) Working Group.¶

Developing secure IoT devices is not an easy task, and supporting a firmware update solution requires skillful engineers. Once devices are deployed, firmware updates play a critical part in their life-cycle management, particularly when devices have a long lifetime or are deployed in remote or inaccessible areas where manual intervention is cost prohibitive or otherwise difficult. Firmware updates for IoT devices are expected to work automatically, i.e., without user involvement. Conversely, non-IoT devices are expected to account for user preferences and consent when scheduling updates. Automatic updates that do not require human intervention are key to a scalable solution for fixing software vulnerabilities.¶

Firmware updates are done not only to fix bugs but also to add new functionality and to reconfigure the device to work in new environments or to behave differently in an already-deployed context.¶

The manifest specification has to allow the following:¶

• The firmware image is authenticated and integrity protected. Attempts to flash a maliciously modified firmware image or an image from an unknown, untrusted source must be prevented. This document uses asymmetric cryptography in examples because it is the preferred approach by many IoT deployments. The use of symmetric credentials is also supported and can be used by very constrained IoT devices.¶
• The firmware image can be confidentiality protected so that attempts by an adversary to recover the plaintext binary can be mitigated or at least made more difficult. Obtaining the firmware is often one of the first steps to mounting an attack since it gives the adversary valuable insights into the software libraries used, configuration settings, and generic functionality. Even though reverse engineering the binary can be a tedious process, modern reverse engineering frameworks have made this task a lot easier.¶

Authentication and integrity protection of firmware images must be used in a deployment, but the confidential protection of firmware is optional.¶

While the standardization work has been informed by and optimized for firmware update use cases of Class 1 devices (according to the device class definitions in RFC 7228[RFC7228]), there is nothing in the architecture that restricts its use to only these constrained IoT devices. Moreover, this architecture is not limited to managing firmware and software updates but can also be applied to managing the delivery of arbitrary data, such as configuration information and keys. Unlike higher-end devices, like laptops and desktop PCs, many IoT devices do not have user interfaces; therefore, support for unattended updates is essential for the design of a practical solution. Constrained IoT devices often use a software engineering model where a developer is responsible for creating and compiling all software running on the device into a single, monolithic firmware image. On higher-end devices, application software is, on the other hand, often downloaded separately and even obtained from developers different from the developers of the lower-level software. The details for how to obtain those application-layer software binaries then depend heavily on the platform, the programming language used, and the sandbox in which the software is executed.¶

While the IETF standardization work has been focused on the manifest format, a fully interoperable solution needs more than a standardized manifest. For example, protocols for transferring firmware images and manifests to the device need to be available, as well as the status tracker functionality. Devices also require a mechanism to discover the status tracker(s) and/or firmware servers, for example, using preconfigured hostnames or DNS-based Service Discovery (DNS-SD)[RFC6763]. These building blocks have been developed by various organizations under the umbrella of an IoT device management solution. The Lightweight Machine-to-Machine (LwM2M) protocol[LwM2M] is one IoT device management protocol.¶

However, there are several areas that (partially) fall outside the scope of the IETF and other standards organizations but need to be considered by firmware authors as well as device and network operators. Here are some of them, as highlighted during the IoTSU workshop:¶

• Installing firmware updates in a robust fashion so that the update does not break the device functionality of the environment in which this device operates. This requires proper testing and offering of recovery strategies when a firmware update is unsuccessful.¶
• Making firmware updates available in a timely fashion considering the complexity of the decision-making process for updating devices, potential recertification requirements, the length of a supply chain an update needs to go through before it reaches the end customer, and the need for user consent to install updates.¶
• Ensuring an energy-efficient design of a battery-powered IoT device; a firmware update, particularly radio communication and writing the firmware image to flash, is an energy-intensive task for a device.¶
• Creating incentives for device operators to use a firmware update mechanism and to require its integration from IoT device vendors.¶
• Ensuring that firmware updates addressing critical flaws can be obtained even after a product is discontinued or a vendor goes out of business.¶

This document starts with a terminology list followed by a description of the architecture. We then explain the bootloader and how it integrates with the firmware update mechanism. Subsequently, we offer a categorization of IoT devices in terms of their hardware capabilities relevant for firmware updates. Next, we talk about the manifest structure and how to use it to secure firmware updates. We conclude with a more detailed example of a message flow for distributing a firmware image to a device.¶

2.Conventions and Terminology

3.Architecture

More devices than ever before are connected to the Internet, which drives the need for firmware updates to be provided over the Internet rather than through traditional interfaces, such as USB or RS-232. Sending updates over the Internet requires the device to fetch the new firmware image as well as the manifest.¶

Hence, the following components are necessary on a device for a firmware update solution:¶

• The Internet protocol stack for firmware downloads. Firmware images are often multiple kilobytes, sometimes exceeding one hundred kilobytes, for low-end IoT devices and can even be several megabytes for IoT devices running full-fledged operating systems like Linux. The protocol mechanism for retrieving these images needs to offer features like congestion control, flow control, fragmentation and reassembly, and mechanisms to resume interrupted or corrupted transfers.¶
• The capability to write the received firmware image to persistent storage (most likely flash memory).¶
• A manifest parser with code to verify a digital signature or a message authentication code (MAC).¶
• The ability to unpack, decompress, and/or decrypt the received firmware image.¶
• A status tracker.¶

The features listed above are most likely provided by code in the application firmware image running on the device rather than by the bootloader itself. Note that cryptographic algorithms will likely run in a trusted execution environment on a separate MCU in a hardware security module or in a secure element rather than in the same context as the application code.¶

Figure 1 shows the architecture where a firmware image is created by an author and made available to a firmware server. For security reasons, the author will not have the permissions to upload firmware images to the firmware server and to initiate an update directly. Instead, authors will make firmware images available to the device operators. Note that there may be a longer supply chain involved to pass software updates from the author all the way to the authorizing party, which can then finally make a decision to deploy it with IoT devices.¶

As a first step in the firmware update process, the status tracker server needs to inform the status tracker client that a new firmware update is available. This can be accomplished via polling (client initiated), push notifications (server initiated), or more complex mechanisms (such as a hybrid approach):¶

• Client-initiated updates take the form of a status tracker client proactively checking (polling) for updates.¶
• With server-initiated updates, the server-side component of the status trackerlearns about a new firmware version and determines which devices qualify for afirmware update. Once the relevant devices have been selected, thestatus tracker informs these devices, and the firmware consumers obtain thoseimages and manifests. Server-initiated updates are important because they allow a quickresponse time. Note that in this mode, the client-side status tracker needs to be reachable by the server-sidecomponent. This may require devices to keep reachability information on theserver side up to date and the state at NATs and stateful packet filteringfirewalls alive.¶
• Using a hybrid approach, the server side of the status trackerpushes update availability notifications to the client side and requests thatthe firmware consumer pull the manifest and the firmware image from thefirmware server.¶

Once the device operator triggers an update via the status tracker, it will keeptrack of the update process on the device. This allows the device operator to know whatdevices have received an update and which of them are still pending an update.¶

Firmware images can be conveyed to devices in a variety of ways,including USB, Universal Asynchronous Receiver Transmitter (UART), WiFi, Bluetooth Low Energy (BLE), low-power WAN technologies, mesh networks and many more.At the application layer,a variety of protocols are also available: Message Queuing Telemetry Transport (MQTT), Constrained Application Protocol (CoAP), and HTTP are themost popular application-layer protocols used by IoT devices. This architecturedoes not make assumptions about how the firmware images are distributed to thedevices and therefore aims to support all these technologies.¶

In some cases, it may be desirable to distribute firmware images using a multicastor broadcast protocol. This architecture does not make recommendations for anysuch protocol. However, given that broadcast may be desirable for some networks,updates must cause the least disruption possible both in the metadataand firmware transmission. For an update to be broadcast friendly, it cannot rely on link-layer, network-layer, or transport-layer security. A solution hasto rely on security protection applied to the manifest and firmware imageinstead. In addition,the same manifest must be deliverable to many devices, both thoseto which it applies and those to which it does not, without achance that the wrong device will accept the update. Considerationsthat apply to network broadcasts apply equally to the use ofthird-party content distribution networks for payload distribution.¶

                                                      +----------+                                                      |          |                                                      |  Author  |                                                      |          |                                                      +----------+                       Firmware + Manifest                 |              +----------------------------------+         | Firmware +              |                                  |         | Manifest              |                               ---+-------  |              |                           ----   |       --|-              |                         //+----------+     | \\             -+--                      // |          |     |   \        ----/ |  ----                |/   | Firmware |<-+  |    \      //      |      \\              |    | Server   |  |  |     \     /        |        \             /    |          |  +  +      \    /         |         \           /     +----------+   \ /       |   / +--------+--------+ \         /                      |        |  /  |        v        |  \       /                       v        | |   | +------------+  |   |     |          +----------------+      | |   | |  Firmware  |  |   |     |          |     Device     |      | |   | |  Consumer  |  |   |     |          |     Management |      ||    | +------------+  |    |    |          |                |      ||    | +------------+  |    |    |          |    +--------+  |      ||    | |  Status    |<-+--------------------+->  |        |  |      ||    | |  Tracker   |  |    |    |          |    | Status |  |      ||    | |  Client    |  |    |    |          |    | Tracker|  |     | |   | +------------+  |   |     |          |    | Server |  |     | |   |    Device       |   |      |         |    +--------+  |     | |   +-----------------+   |       \        |                |    /  \                       /         \       +----------------+   /   \       Network       /           \                          /    \     Operator      /             \     Device Operator    /     \\               //               \\                    //        ----     ----                     ----           ----            -----                             -----------

Firmware images and manifests may be conveyed as a bundle or detached. Themanifest format must support both approaches.¶

For distribution as a bundle, the firmware image is embedded into the manifest.This is a useful approach for deployments where devices are not connectedto the Internet and cannot contact a dedicated firmware server for the firmwaredownload. It is also applicable when the firmware update happens via USB sticks or short-range radio technologies (such as Bluetooth Smart).¶

Alternatively, the manifest is distributed detached from the firmware image.Using this approach, the firmware consumer is presented with the manifest firstand then needs to obtain one or more firmware images as dictated in themanifest.¶

The pre-authorization step involves verifying whether the entitysigning the manifest is indeed authorized to perform an update.The firmware consumer must also determine whether it should fetch andprocess a firmware image, which is referenced in a manifest.¶

A dependency resolution phase is needed when more than onecomponent can be updated or when a differential update is used.The necessary dependencies must be available prior to installation.¶

The download step is the process of acquiring a local copy of thefirmware image. When the download is client initiated, this meansthat the firmware consumer chooses when a download occurs and initiatesthe download process. When a download is server initiated,this means that the status tracker tellsthe device when to download or that it initiates the transferdirectly to the firmware consumer. For example, a download from anHTTP/1.1-based firmware server is client initiated. Pushing a manifestand firmware image to the Package Resource of the LwM2MFirmware Update Object[LwM2M] is a server-initiated update.¶

If the firmware consumer has downloaded a new firmware image and is ready toinstall it, to initiate the installation, it may¶

• need to wait for a trigger from the status tracker,¶
• trigger the update automatically, or¶
• go through a more complex decision-making process to determine the appropriate timing for an update.¶

Sometimes the final decision mayrequire confirmation of the user of the device for safety reasons.¶

Installation is the act of processing the payload into a format thatthe IoT device can recognize, and the bootloader is responsible forthen booting from the newly installed firmware image.This process is different when a bootloader is not involved. For example,when an application is updated in a full-featured OS, theupdater may halt and restart the application in isolation. Devices must not fail when a disruption, such as a power failure or networkinterruption, occurs during the update process.¶

4.Invoking the Firmware

Section 3 describes the steps for getting the firmware image and the manifestfrom the author to the firmware consumer on the IoT device. Once the firmware consumerhas retrieved and successfully processed the manifest and the firmware image, it needsto invoke the new firmware image. This is managed in many different ways dependingon the type of device, but it typically involves halting the current version of thefirmware, handing over control to firmware with a higher privilege or trust level(the firmware verifier),verifying the new firmware's authenticity and integrity, and then invoking it.¶

In an execute-in-place microcontroller, this is often done by rebooting into abootloader (simultaneously halting the application and handing over control to the higherprivilege level) then executing a secure boot process (verifying and invokingthe new image).¶

In a rich OS, this may be done by halting one or more processes and then invokingnew applications. In some OSes, this implicitly involves the kernel verifyingthe code signatures on the new applications.¶

The invocation process is security sensitive. An attacker will typically try toretrieve a firmware image from the device for reverse engineering or will try to getthe firmware verifier to execute an attacker-modified firmware image. Therefore,firmware verifier will have to perform security checks on thefirmware image before it can be invoked. These security checks by thefirmware verifier happen in addition to the security checks that took placewhen the firmware image and the manifest were downloaded by the firmware consumer.¶

The overlap between the firmware consumer and the firmware verifierfunctionality comes in two forms, namely:¶

• A firmware verifier must verify the firmware image it boots aspart of the secure boot process. Doing so requires metadata to bestored alongside the firmware image so that the firmware verifier cancryptographically verify the firmware image before booting it toensure it has not been tampered with or replaced. This metadataused by the firmware verifier may well be the same manifest obtained with thefirmware image during the update process.¶
• An IoT device needs a recovery strategy in case the firmwareupdate/invocation process fails. The recoverystrategy may include storing two or more application firmware imageson the device or offering the ability to invoke a recovery image toperform the firmware update process again using firmware updates overserial, USB, or even wireless connectivity like Bluetooth Smart.In the latter case, the firmware consumer functionality is contained in therecovery image and requires the necessary functionality forexecuting the firmware update process, including manifest parsing.¶

While this document assumes that the firmware verifier itself isdistinct from the role of the firmware consumer and therefore does notmanage the firmware update process, this is not a requirement, and theseroles may be combined in practice.¶

Using a bootloader as the firmware verifier requires some specialconsiderations, particularly when the bootloaderimplements the robustness requirements identified by the IoTSU workshop[RFC8240].¶

5.Types of IoT Devices

Today, there are billions of MCUs used in devices produced by a largenumber of silicon manufacturers. While MCUs can vary significantlyin their characteristics, there are a number of similarities that allow us to categorize them into groups.¶

The firmware update architecture, and the manifest format in particular,needs to offer enough flexibility to cover these common deployment cases.¶

6.Manifests

In order for a firmware consumer to apply an update, it has to make several decisionsusing manifest-provided information and data available on the device itself. For moredetailed information and a longer list of information elements in the manifest, consult theinformation model specification[SUIT-INFO-MODEL], which offers justificationsfor each element, and the manifest specification[SUIT-MANIFEST] for details about how this information is included in the manifest.¶

(1):

A device presented with an old but valid manifest and firmwaremust not be tricked into installing such firmware since avulnerability in the old firmware image may allow an attacker togain control of the device.¶

Keeping the code size and complexity of a manifest parser small is importantfor constrained IoT devices. Since the manifest parsing code mayalso be used by the bootloader, it can be part of the trusted computing base.¶

A manifest may be used to protect not only firmware images but alsoconfiguration data such as network credentials or personalization datarelated to the firmware or software.Personalization data demonstrates the need for confidentiality to bemaintained between two or more stakeholders that deliver images tothe same device. Personalization data is used withTEEs, whichbenefit from a protocol for managing the life cycle of TAs running inside a TEE. TEEs may obtain TAsfrom different authors, and those TAs may require personalization data,such as payment information, to be securely conveyed to the TEE. TheTA's author does not want to expose the TA's code to any other stakeholderor third party.The user does not want to expose the payment information to any otherstakeholder or third party.¶

7.Securing Firmware Updates

Using firmware updates to fix vulnerabilities in devices is important, but securing thisupdate mechanism is equally important since security problems areexacerbated by the update mechanism. An update is essentially authorizedremote code execution, so any security problems in the update processexpose that remote code execution system. Failureto secure the firmware update process will help attackers take control of devices.¶

End-to-end security mechanisms are used to protect the firmwareimage and the manifest. The following assumptions are made to allowthe firmware consumer to verify the received firmware image andmanifest before updating the software:¶

• Authentication ensures that the device can cryptographically identifythe author(s) creating firmware images and manifests. Authenticatedidentities may be used as input to the authorization process. Not allentities creating and signing manifests have the samepermissions. A device needs to determine whether the requested actionis indeed covered by the permission of the party that signed the manifest.Informing the device about the permissions of the different partiesalso happens in an out-of-band fashion and is a duty of theTrust Provisioning Authority.¶
• Integrity protection ensures that no third party can modify the manifestor the firmware image. To accept an update, a device needs to verify the signature coveringthe manifest. There may be one or multiple manifests that need to bevalidated, potentially signed by different parties. The device needsto be in possession of the trust anchors to verify those signatures.Installing trust anchors to devices via the Trust Provisioning Authorityhappens in an out-of-band fashion prior to the firmware update process.¶
• Confidentiality protection of the firmware image must be done in such away that no one aside from the intended firmware consumer(s) and other authorized parties can decrypt it. The informationthat is encrypted individually for each device/recipient must be done in a way that is usable with Content Distribution Networks (CDNs), bulk storage, andbroadcast protocols. For confidentiality protection of firmware images, the author needsto be in possession of the certificate/public key or a pre-shared keyof a device. The use of confidentiality protection of firmware imagesis optional.¶

A manifest specification must support different cryptographic algorithmsand algorithm extensibility. Moreover, since signatureschemes based on RSA and Elliptic Curve Cryptography (ECC) may become vulnerable to quantum-accelerated key extraction in thefuture, unchangeable bootloader code in ROM is recommended to use post-quantumsecure signature schemes such as hash-based signatures[RFC8778]. Abootloader author must carefully consider the service lifetime of theirproduct and the time horizon for quantum-accelerated key extraction.At the time of writing, the worst-case estimate for the time horizon to keyextraction with quantum acceleration is approximately 2030, based oncurrent research[quantum-factorization].¶

When a device obtains a monolithic firmware image from a single authorwithout any additional approval steps, the authorization flow isrelatively simple. However, there are other cases where more complexpolicy decisions need to be made before updating a device.¶

In this architecture, the authorization policy is separated fromthe underlying communication architecture. This is accomplishedby separating the entities from their permissions. For example,an author may not have the authority to install a firmware imageon a device in critical infrastructure without the authorizationof a device operator. In this case, the device may be programmedto reject firmware updates unless they are signed both by the firmware author and by the device operator.¶

Alternatively, a device may trust precisely one entity thatdoes all permission management and coordination. This entityallows the device to offload complex permissionscalculations for the device.¶

8.Example

Figure 2 illustrates an example message flowfor distributing a firmware image to a device. The firmwareand manifest are stored on the same firmware server and distributed in a detached manner.¶

+--------+    +-----------------+    +-----------------------------+|        |    | Firmware Server |    |         IoT Device          || Author |    | Status Tracker  |    | +------------+ +----------+ |+--------+    | Server          |    | |  Firmware  | |Bootloader| |  |           +-----------------+    | |  Consumer  | |          | |  |                   |              | +------------+ +----------+ |  |                   |              |      |                |     |  |                   |              |  +-----------------------+  |  | Create Firmware   |              |  | Status Tracker Client |  |  |--------------+    |              |  +-----------------------+  |  |              |    |               `''''''''''''''''''''''''''''  |<-------------+    |                     |        |       |  |                   |                     |        |       |  | Upload Firmware   |                     |        |       |  |------------------>|                     |        |       |  |                   |                     |        |       |  | Create Manifest   |                     |        |       |  |---------------+   |                     |        |       |  |               |   |                     |        |       |  |<--------------+   |                     |        |       |  |                   |                     |        |       |  | Sign Manifest     |                     |        |       |  |-------------+     |                     |        |       |  |             |     |                     |        |       |  |<------------+     |                     |        |       |  |                   |                     |        |       |  | Upload Manifest   |                     |        |       |  |------------------>|  Notification of    |        |       |  |                   |  new firmware image |        |       |  |                   |----------------------------->|       |  |                   |                     |        |       |  |                   |                     |Initiate|       |  |                   |                     | Update |       |  |                   |                     |<-------|       |  |                   |                     |        |       |  |                   |   Query Manifest    |        |       |  |                   |<--------------------|        .       |  |                   |                     |        .       |  |                   |   Send Manifest     |        .       |  |                   |-------------------->|        .       |  |                   |                     | Validate       |  |                   |                     | Manifest       |  |                   |                     |--------+       |  |                   |                     |        |       |  |                   |                     |<-------+       |  |                   |                     |        .       |  |                   |  Request Firmware   |        .       |  |                   |<--------------------|        .       |  |                   |                     |        .       |  |                   | Send Firmware       |        .       |  |                   |-------------------->|        .       |  |                   |                     | Verify .       |  |                   |                     | Firmware       |  |                   |                     |--------+       |  |                   |                     |        |       |  |                   |                     |<-------+       |  |                   |                     |        .       |  |                   |                     | Store  .       |  |                   |                     | Firmware       |  |                   |                     |--------+       |  |                   |                     |        |       |  |                   |                     |<-------+       |  |                   |                     |        .       |  |                   |                     |        .       |  |                   |                     |        .       |  |                   |                     |        |       |  |                   |                     | Update |       |  |                   |                     |Complete|       |  |                   |                     |------->|       |  |                   |                              |       |  |                   |  Firmware Update Completed   |       |  |                   |<-----------------------------|       |  |                   |                              |       |  |                   |  Reboot                      |       |  |                   |----------------------------->|       |  |                   |                     |        |       |  |                   |                     |        |       |  |                   |                     |        |Reboot |  |                   |                     |        |------>|  |                   |                     |        |       |  |                   |                     |        .       |  |                   |                 +---+----------------+--+  |                   |                S|   |                |  |  |                   |                E|   | Verify         |  |  |                   |                C|   | Firmware       |  |  |                   |                U|   | +--------------|  |  |                   |                R|   | |              |  |  |                   |                E|   | +------------->|  |  |                   |                 |   |                |  |  |                   |                B|   | Activate new   |  |  |                   |                O|   | Firmware       |  |  |                   |                O|   | +--------------|  |  |                   |                T|   | |              |  |  |                   |                 |   | +------------->|  |  |                   |                P|   |                |  |  |                   |                R|   | Boot new       |  |  |                   |                O|   | Firmware       |  |  |                   |                C|   | +--------------|  |  |                   |                E|   | |              |  |  |                   |                S|   | +------------->|  |  |                   |                S|   |                |  |  |                   |                 +---+----------------+--+  |                   |                     |        .       |  |                   |                     |        |       |  |                   |                     .        |       |  |                   |  Device running new firmware |       |  |                   |<-----------------------------|       |  |                   |                     .        |       |  |                   |                              |       |

Figure 3 shows an exchange that starts with thestatus tracker querying the device for its current firmware version.Later, a new firmware version becomes available, and since thisdevice is running an older version, the status tracker server interactswith the device to initiate an update.¶

The manifest and the firmware are stored on different servers in thisexample. When the device processes the manifest, it learns where todownload the new firmware version. The firmware consumer downloadsthe firmware image with the newer version X.Y.Z after successful validationof the manifest. Subsequently, a reboot is initiated, and the secureboot process starts. Finally, the device reports the successful bootof the new firmware version.¶

 +---------+   +-----------------+    +-----------------------------+ | Status  |   | Firmware Server |    | +------------+ +----------+ | | Tracker |   | Status Tracker  |    | |  Firmware  | |Bootloader| | | Server  |   | Server          |    | |  Consumer  | |          | | +---------+   +-----------------+    | |  +Status   | +----------+ |      |                |              | |  Tracker   |        |     |      |                |              | |  Client    |        |     |      |                |              | +------------+        |     |      |                |              |      |  IoT Device    |     |      |                |               `''''''''''''''''''''''''''''      |                |                     |                |      |        Query Firmware Version        |                |      |------------------------------------->|                |      |        Firmware Version A.B.C        |                |      |<-------------------------------------|                |      |                |                     |                |      |         <<some time later>>          |                |      |                |                     |                |    _,...._         _,...._                  |                |  ,'       `.     ,'       `.                |                | |   New     |   |   New     |               |                | \ Manifest  /   \ Firmware  /               |                |  `.._   _,,'     `.._   _,,'                |                |      `''             `''                    |                |      |            Push manifest             |                |      |----------------+-------------------->|                |      |                |                     |                |      |                '                     |                '      |                |                     | Validate       |      |                |                     | Manifest       |      |                |                     |---------+      |      |                |                     |         |      |      |                |                     |<--------+      |      |                | Request firmware    |                |      |                | X.Y.Z               |                |      |                |<--------------------|                |      |                |                     |                |      |                | Firmware X.Y.Z      |                |      |                |-------------------->|                |      |                |                     |                |      |                |                     | Verify         |      |                |                     | Firmware       |      |                |                     |--------------+ |      |                |                     |              | |      |                |                     |<-------------+ |      |                |                     |                |      |                |                     | Store          |      |                |                     | Firmware       |      |                |                     |-------------+  |      |                |                     |             |  |      |                |                     |<------------+  |      |                |                     |                |      |                |                     |                |      |                |                     | Trigger Reboot |      |                |                     |--------------->|      |                |                     |                |      |                |                     |                |      |                |                     | __..-------..._'      |                |                    ,-'               `-.      |                |                   |      Secure Boot    |      |                |                   `-.                 _/      |                |                     |`--..._____,,.,-'      |                |                     |                |      | Device running firmware X.Y.Z        |                |      |<-------------------------------------|                |      |                |                     |                |      |                |                     |                |

9.IANA Considerations

This document has no IANA actions.¶

10.Security Considerations

This document describes the terminology, requirements, and an architecture forfirmware updates of IoT devices. The content of the document is therebyfocused on improving the security of IoT devices via firmware update mechanismsand informs the standardization of a manifest format.¶

An in-depth examination of the security considerations of thearchitecture is presented in[SUIT-INFO-MODEL].¶

Acknowledgements

We would like to thank the following individuals for their feedback:¶

• Geraint Luff¶

• Amyas Phillips¶

• Dan Ros¶

• Thomas Eichinger¶

• Michael Richardson¶

• Emmanuel Baccelli¶

• Ned Smith¶

• Jim Schaad¶

• Carsten Bormann¶

• Cullen Jennings¶

• Olaf Bergmann¶

• Suhas Nandakumar¶

• Phillip Hallam-Baker¶

• Marti Bolivar¶

• Andrzej Puzdrowski¶

• Markus Gueller¶

• Henk Birkholz¶

• Jintao Zhu¶

• Takeshi Takahashi¶

• Jacob Beningo¶

• Kathleen Moriarty¶

• Bob Briscoe¶

• Roman Danyliw¶

• Brian Carpenter¶

• Theresa Enghardt¶

• Rich Salz¶

• Mohit Sethi¶

• Éric Vyncke¶

• Alvaro Retana¶

• Barry Leiba¶

• Benjamin Kaduk¶

• Martin Duke¶

• Robert Wilton¶

We would also like to thank the WG chairs,Russ Housley,David Waltermire, andDave Thaler for their support and review.¶

Authors' Addresses