Internet-Draft CBOR-based SUIT Manifest April 2022
Moran, et al. Expires 30 October 2022 [Page]
Workgroup:
SUIT
Internet-Draft:
draft-ietf-suit-manifest-17
Published:
Intended Status:
Standards Track
Expires:
Authors:
B. Moran
Arm Limited
H. Tschofenig
Arm Limited
H. Birkholz
Fraunhofer SIT
K. Zandberg
Inria

A Concise Binary Object Representation (CBOR)-based Serialization Format for the Software Updates for Internet of Things (SUIT) Manifest

Abstract

This specification describes the format of a manifest. A manifest is a bundle of metadata about code/data obtained by a recipient (chiefly the firmware for an IoT device), where to find the that code/data, the devices to which it applies, and cryptographic information protecting the manifest. Software updates and Trusted Invocation both tend to use sequences of common operations, so the manifest encodes those sequences of operations, rather than declaring the metadata.

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 working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

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 30 October 2022.

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Table of Contents

1. Introduction

A firmware update mechanism is an essential security feature for IoT devices to deal with vulnerabilities. While the transport of firmware images to the devices themselves is important there are already various techniques available. Equally important is the inclusion of metadata about the conveyed firmware image (in the form of a manifest) and the use of a security wrapper to provide end-to-end security protection to detect modifications and (optionally) to make reverse engineering more difficult. End-to-end security allows the author, who builds the firmware image, to be sure that no other party (including potential adversaries) can install firmware updates on IoT devices without adequate privileges. For confidentiality protected firmware images it is additionally required to encrypt the firmware image. Starting security protection at the author is a risk mitigation technique so firmware images and manifests can be stored on untrusted repositories; it also reduces the scope of a compromise of any repository or intermediate system to be no worse than a denial of service.

A manifest is a bundle of metadata describing one or more code or data payloads and how to:

This specification defines the SUIT manifest format and it is intended to meet several goals:

The SUIT manifest can be used for a variety of purposes throughout its lifecycle, such as:

Each of these uses happens at a different stage of the manifest lifecycle, so each has different requirements.

It is assumed that the reader is familiar with the high-level firmware update architecture [RFC9019] and the threats, requirements, and user stories in [RFC9124].

The design of this specification is based on an observation that the vast majority of operations that a device can perform during an update or Trusted Invocation are composed of a small group of operations:

In this document, these operations are called commands. Commands are classed as either conditions or directives. Conditions have no side-effects, while directives do have side-effects. Conceptually, a sequence of commands is like a script but the language is tailored to software updates and Trusted Invocation.

The available commands support simple steps, such as copying a firmware image from one place to another, checking that a firmware image is correct, verifying that the specified firmware is the correct firmware for the device, or unpacking a firmware. By using these steps in different orders and changing the parameters they use, a broad range of use cases can be supported. The SUIT manifest uses this observation to optimize metadata for consumption by constrained devices.

While the SUIT manifest is informed by and optimized for firmware update and Trusted Invocation use cases, there is nothing in the SUIT Information Model ([RFC9124]) that restricts its use to only those use cases. Other use cases include the management of trusted applications (TAs) in a Trusted Execution Environment (TEE), as discussed in [I-D.ietf-teep-architecture].

2. Conventions and Terminology

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.

Additionally, the following terminology is used throughout this document:

3. How to use this Document

This specification covers five aspects of firmware update:

To implement an updatable device, see Section 6 and Section 8. To implement a tool that generates updates, see Section 7 and Section 8.

The IANA consideration section, see Section 11, provides instructions to IANA to create several registries. This section also provides the CBOR labels for the structures defined in this document.

The complete CDDL description is provided in Appendix A, examples are given in Appendix B and a design rational is offered in Appendix C. Finally, Appendix D gives a summarize of the mandatory-to-implement features of this specification.

This specification covers the core features of SUIT. Additional specifications describe functionality of advanced use cases, such as:

4. Background

Distributing software updates to diverse devices with diverse trust anchors in a coordinated system presents unique challenges. Devices have a broad set of constraints, requiring different metadata to make appropriate decisions. There may be many actors in production IoT systems, each of whom has some authority. Distributing firmware in such a multi-party environment presents additional challenges. Each party requires a different subset of data. Some data may not be accessible to all parties. Multiple signatures may be required from parties with different authorities. This topic is covered in more depth in [RFC9019]. The security aspects are described in [RFC9124].

4.1. IoT Firmware Update Constraints

The various constraints of IoT devices and the range of use cases that need to be supported create a broad set of requirements. For example, devices with:

  • limited processing power and storage may require a simple representation of metadata.
  • bandwidth constraints may require firmware compression or partial update support.
  • bootloader complexity constraints may require simple selection between two bootable images.
  • small internal storage may require external storage support.
  • multiple microcontrollers may require coordinated update of all applications.
  • large storage and complex functionality may require parallel update of many software components.
  • extra information may need to be conveyed in the manifest in the earlier stages of the device lifecycle before those data items are stripped when the manifest is delivered to a constrained device.

Supporting the requirements introduced by the constraints on IoT devices requires the flexibility to represent a diverse set of possible metadata, but also requires that the encoding is kept simple.

4.2. SUIT Workflow Model

There are several fundamental assumptions that inform the model of Update Procedure workflow:

  • Compatibility must be checked before any other operation is performed.
  • In some applications, payloads must be fetched and validated prior to installation.

There are several fundamental assumptions that inform the model of the Invocation Procedure workflow:

  • Compatibility must be checked before any other operation is performed.
  • All payloads must be validated prior to loading.
  • All loaded images must be validated prior to execution.

Based on these assumptions, the manifest is structured to work with a pull parser, where each section of the manifest is used in sequence. The expected workflow for a Recipient installing an update can be broken down into five steps:

  1. Verify the signature of the manifest.
  2. Verify the applicability of the manifest.
  3. Fetch payload(s).
  4. Install payload(s).

When installation is complete, similar information can be used for validating and running images in a further three steps:

  1. Verify image(s).
  2. Load image(s).
  3. Run image(s).

If verification and running is implemented in a bootloader, then the bootloader MUST also verify the signature of the manifest and the applicability of the manifest in order to implement secure boot workflows. The bootloader may add its own authentication, e.g. a Message Authentication Code (MAC), to the manifest in order to prevent further verifications.

5. Metadata Structure Overview

This section provides a high level overview of the manifest structure. The full description of the manifest structure is in Section 8.4

The manifest is structured from several key components:

  1. The Envelope (see Section 5.1) contains the Authentication Block, the Manifest, any Severable Elements, and any Integrated Payloads.
  2. The Authentication Block (see Section 5.2) contains a list of signatures or MACs of the manifest..

  3. The Manifest (see Section 5.3) contains all critical, non-severable metadata that the Recipient requires. It is further broken down into:

    1. Critical metadata, such as sequence number.
    2. Common metadata, such as affected components.
    3. Command sequences, directing the Recipient how to install and use the payload(s).
    4. Integrity check values for severable elements.
  4. Severable elements (see Section 5.4).
  5. Integrated payloads (see Section 5.5).

The diagram below illustrates the hierarchy of the Envelope.

+-------------------------+
| Envelope                |
+-------------------------+
| Authentication Block    |
| Manifest           --------------> +------------------------------+
| Severable Elements      |          | Manifest                     |
| Human-Readable Text     |          +------------------------------+
| Integrated Payloads     |          | Structure Version            |
+-------------------------+          | Sequence Number              |
                                     | Reference to Full Manifest   |
                               +------ Common Structure             |
                               | +---- Command Sequences            |
+-------------------------+    | |   | Digests of Envelope Elements |
| Common Structure        | <--+ |   +------------------------------+
+-------------------------+      |
| Components IDs          |      +-> +-----------------------+
| Common Command Sequence ---------> | Command Sequence      |
+-------------------------+          +-----------------------+
                                     | List of ( pairs of (  |
                                     |   * command code      |
                                     |   * argument /        |
                                     |      reporting policy |
                                     | ))                    |
                                     +-----------------------+

5.1. Envelope

The SUIT Envelope is a container that encloses the Authentication Block, the Manifest, any Severable Elements, and any integrated payloads. The Envelope is used instead of conventional cryptographic envelopes, such as COSE_Envelope because it allows modular processing, severing of elements, and integrated payloads in a way that would add substantial complexity with existing solutions. See Appendix C.1 for a description of the reasoning for this.

See Section 8.2 for more detail.

5.2. Authentication Block

The Authentication Block contains a bstr-wrapped SUIT Digest Container, see Section 10, and one or more [RFC8152] CBOR Object Signing and Encryption (COSE) authentication blocks. These blocks are one of:

  • COSE_Sign_Tagged
  • COSE_Sign1_Tagged
  • COSE_Mac_Tagged
  • COSE_Mac0_Tagged

Each of these objects is used in detached payload mode. The payload is the bstr-wrapped SUIT_Digest.

See Section 8.3 for more detail.

5.3. Manifest

The Manifest contains most metadata about one or more images. The Manifest is divided into Critical Metadata, Common Metadata, Command Sequences, and Integrity Check Values.

See Section 8.4 for more detail.

5.3.1. Critical Metadata

Some metadata needs to be accessed before the manifest is processed. This metadata can be used to determine which manifest is newest and whether the structure version is supported. It also MAY provide a URI for obtaining a canonical copy of the manifest and Envelope.

See Section 8.4.1, Section 8.4.2, and Section 8.4.3 for more detail.

5.3.2. Common

Some metadata is used repeatedly and in more than one command sequence. In order to reduce the size of the manifest, this metadata is collected into the Common section. Common is composed of two parts: a list of components referenced by the manifest, and a command sequence to execute prior to each other command sequence. The common command sequence is typically used to set commonly used values and perform compatibility checks. The common command sequence MUST NOT have any side-effects outside of setting parameter values.

See Section 8.4.5 for more detail.

5.3.3. Command Sequences

Command sequences provide the instructions that a Recipient requires in order to install or use an image. These sequences tell a device to set parameter values, test system parameters, copy data from one place to another, transform data, digest data, and run code.

Command sequences are broken up into three groups: Common Command Sequence (see Section 5.3.2), update commands, and secure boot commands.

Update Command Sequences are: Payload Fetch, and Payload Installation. An Update Procedure is the complete set of each Update Command Sequence, each preceded by the Common Command Sequence.

Invocation Command Sequences are: System Validation, Image Loading, and Image Invocation. An Invocation Procedure is the complete set of each Invocation Command Sequence, each preceded by the Common Command Sequence.

Command Sequences are grouped into these sets to ensure that there is common coordination between dependencies and dependents on when to execute each command (dependencies are not defined in this specification).

See Section 8.4.6 for more detail.

5.3.4. Integrity Check Values

To enable Section 5.4, there needs to be a mechanism to verify integrity of any metadata outside the manifest. Integrity Check Values are used to verify the integrity of metadata that is not contained in the manifest. This MAY include Severable Command Sequences, or Text data. Integrated Payloads are integrity-checked using Command Sequences, so they do not have Integrity Check Values present in the Manifest.

See Section 8.4.11 for more detail.

5.3.5. Human-Readable Text

Text is typically a Severable Element (Section 5.4). It contains all the text that describes the update. Because text is explicitly for human consumption, it is all grouped together so that it can be Severed easily. The text section has space both for describing the manifest as a whole and for describing each individual component.

See Section 8.4.4 for more detail.

5.4. Severable Elements

Severable Elements are elements of the Envelope (Section 5.1) that have Integrity Check Values (Section 5.3.4) in the Manifest (Section 5.3).

Because of this organisation, these elements can be discarded or "Severed" from the Envelope without changing the signature of the Manifest. This allows savings based on the size of the Envelope in several scenarios, for example:

  • A management system severs the Text sections before sending an Envelope to a constrained Recipient, which saves Recipient bandwidth.
  • A Recipient severs the Installation section after installing the Update, which saves storage space.

See Section 8.5 for more detail.

5.5. Integrated Payloads

In some cases, it is beneficial to include a payload in the Envelope of a manifest. For example:

  • When an update is delivered via a comparatively unconstrained medium, such as a removable mass storage device, it may be beneficial to bundle updates into single files.
  • When a manifest transports a small payload, such as an encrypted key, that payload may be placed in the manifest's envelope.

See Section 7.5 for more detail.

6. Manifest Processor Behavior

This section describes the behavior of the manifest processor and focuses primarily on interpreting commands in the manifest. However, there are several other important behaviors of the manifest processor: encoding version detection, rollback protection, and authenticity verification are chief among these.

6.1. Manifest Processor Setup

Prior to executing any command sequence, the manifest processor or its host application MUST inspect the manifest version field and fail when it encounters an unsupported encoding version. Next, the manifest processor or its host application MUST extract the manifest sequence number and perform a rollback check using this sequence number. The exact logic of rollback protection may vary by application, but it has the following properties:

  • Whenever the manifest processor can choose between several manifests, it MUST select the latest valid, authentic manifest.
  • If the latest valid, authentic manifest fails, it MAY select the next latest valid, authentic manifest, according to application-specific policy.

Here, valid means that a manifest has a supported encoding version and it has not been excluded for other reasons. Reasons for excluding typically involve first executing the manifest and may include:

  • Test failed (e.g. Vendor ID/Class ID).
  • Unsupported command encountered.
  • Unsupported parameter encountered.
  • Unsupported Component Identifier encountered.
  • Payload not available.
  • Application crashed when executed.
  • Watchdog timeout occurred.
  • Payload verification failed.
  • Missing required component from a Component Set.
  • Required parameter not supplied.

These failure reasons MAY be combined with retry mechanisms prior to marking a manifest as invalid.

Selecting an older manifest in the event of failure of the latest valid manifest is a robustness mechanism that is necessary for supporting the requirements in [RFC9019], section 3.5. It may not be appropriate for all applications. In particular Trusted Execution Environments MAY require a failure to invoke a new installation, rather than a rollback approach. See [RFC9124], Section 4.2.1 for more discussion on the security considerations that apply to rollback.

Following these initial tests, the manifest processor clears all parameter storage. This ensures that the manifest processor begins without any leaked data.

6.2. Required Checks

The RECOMMENDED process is to verify the signature of the manifest prior to parsing/executing any section of the manifest. This guards the parser against arbitrary input by unauthenticated third parties, but it costs extra energy when a Recipient receives an incompatible manifest.

When validating authenticity of manifests, the manifest processor MAY use an ACL (see Section 9) to determine the extent of the rights conferred by that authenticity.

Once a valid, authentic manifest has been selected, the manifest processor MUST examine the component list and verify that its maximum number of components is not exceeded and that each listed component is supported.

For each listed component, the manifest processor MUST provide storage for the supported parameters. If the manifest processor does not have sufficient temporary storage to process the parameters for all components, it MAY process components serially for each command sequence. See Section 6.6 for more details.

The manifest processor SHOULD check that the common sequence contains at least Check Vendor Identifier command and at least one Check Class Identifier command.

Because the common sequence contains Check Vendor Identifier and Check Class Identifier command(s), no custom commands are permitted in the common sequence. This ensures that any custom commands are only executed by devices that understand them.

If the manifest contains more than one component, each command sequence MUST begin with a Set Component Index.

If a Recipient supports groups of interdependent components (a Component Set), then it SHOULD verify that all Components in the Component Set are specified by one update, that is the manifest:

  1. has sufficient permissions imparted by its signatures
  2. specifies a digest and a payload for every Component in the Component Set.

6.2.1. Minimizing Signature Verifications

Signature verification can be energy and time expensive on a constrained device. MAC verification is typically unaffected by these concerns. A Recipient MAY choose to parse and execute only the SUIT_Common section of the manifest prior to signature verification, if all of the below apply:

  • The Authentication Block contains a COSE_Sign_Tagged or COSE_Sign1_Tagged
  • The Recipient receives manifests over an unauthenticated channel, exposing it to more inauthentic or incompatible manifests, and
  • The Recipient has a power budget that makes signature verification undesirable

When executing Common prior to authenticity validation, the Manifest Processor MUST first evaluate the integrity of the manifest using the SUIT_Digest present in the authentication block.

The guidelines in Creating Manifests (Section 7) require that the common section contains the applicability checks, so this section is sufficient for applicability verification. The parser MUST restrict acceptable commands to conditions and the following directives: Override Parameters, Set Parameters, Try Each, and Run Sequence ONLY. The manifest parser MUST NOT execute any command with side-effects outside the parser (for example, Run, Copy, Swap, or Fetch commands) prior to authentication and any such command MUST Abort. The Common Sequence MUST be executed again, in its entirety, after authenticity validation.

A Recipient MAY rely on network infrastructure to filter inapplicable manifests.

6.3. Interpreter Fundamental Properties

The interpreter has a small set of design goals:

  1. Executing an update MUST either result in an error, or a verifiably correct system state.
  2. Executing a Trusted Invocation MUST either result in an error, or an invoked image.
  3. Executing the same manifest on multiple Recipients MUST result in the same system state.

NOTE: when using A/B images, the manifest functions as two (or more) logical manifests, each of which applies to a system in a particular starting state. With that provision, design goal 3 holds.

6.4. Abstract Machine Description

The heart of the manifest is the list of commands, which are processed by a Manifest Processor--a form of interpreter. This Manifest Processor can be modeled as a simple abstract machine. This machine consists of several data storage locations that are modified by commands.

There are two types of commands, namely those that modify state (directives) and those that perform tests (conditions). Parameters are used as the inputs to commands. Some directives offer control flow operations. Directives target a specific component. A component is a unit of code or data that can be targeted by an update. Components are identified by Component Identifiers, but referenced in commands by Component Index; Component Identifiers are arrays of binary strings and a Component Index is an index into the array of Component Identifiers.

Conditions MUST NOT have any side-effects other than informing the interpreter of success or failure. The Interpreter does not Abort if the Soft Failure flag (Section 8.4.8.14) is set when a Condition reports failure.

Directives MAY have side-effects in the parameter table, the interpreter state, or the current component. The Interpreter MUST Abort if a Directive reports failure regardless of the Soft Failure flag.

To simplify the logic describing the command semantics, the object "current" is used. It represents the component identified by the Component Index:

current := components\[component-index\]

As a result, Set Component Index is described as current := components[arg].

The following table describes the behavior of each command. "params" represents the parameters for the current component. Most commands operate on a component.

Table 1
Command Name Semantic of the Operation
Check Vendor Identifier assert(binary-match(current, current.params[vendor-id]))
Check Class Identifier assert(binary-match(current, current.params[class-id]))
Verify Image assert(binary-match(digest(current), current.params[digest]))
Set Component Index current := components[arg]
Override Parameters current.params[k] := v for-each k,v in arg
Set Parameters current.params[k] := v if not k in params for-each k,v in arg
Run run(current)
Fetch store(current, fetch(current.params[uri]))
Use Before assert(now() < arg)
Check Component Slot assert(current.slot-index == arg)
Check Device Identifier assert(binary-match(current, current.params[device-id]))
Abort assert(0)
Try Each try-each-done if exec(seq) is not error for-each seq in arg
Copy store(current, current.params[src-component])
Swap swap(current, current.params[src-component])
Run Sequence exec(arg)
Run with Arguments run(current, arg)

6.5. Special Cases of Component Index

Component Index can take on one of three types:

  1. Integer
  2. Array of integers
  3. True

Integers MUST always be supported by Set Component Index. Arrays of integers MUST be supported by Set Component Index if the Recipient supports 3 or more components. True MUST be supported by Set Component Index if the Recipient supports 2 or more components. Each of these operates on the list of components declared in the manifest.

Integer indices are the default case as described in the previous section. An array of integers represents a list of the components (Set Component Index) to which each subsequent command applies. The value True replaces the list of component indices with the full list of components, as defined in the manifest.

When a command is executed, it either 1. operates on the component identified by the component index if that index is an integer, or 2. it operates on each component identified by an array of indicies, or 3. it operates on every component if the index is the boolean True. This is described by the following pseudocode:

if component-index is true:
    current-list = components
else if component-index is array:
    current-list = [ components[idx] for idx in component-index ]
else:
    current-list = [ components[component-index] ]
for current in current-list:
    cmd(current)

Try Each and Run Sequence are affected in the same way as other commands: they are invoked once for each possible Component. This means that the sequences that are arguments to Try Each and Run Sequence are NOT invoked with Component Index = True, nor are they invoked with array indices. They are only invoked with integer indices. The interpreter loops over the whole sequence, setting the Component Index to each index in turn.

6.6. Serialized Processing Interpreter

In highly constrained devices, where storage for parameters is limited, the manifest processor MAY handle one component at a time, traversing the manifest tree once for each listed component. In this mode, the interpreter ignores any commands executed while the component index is not the current component. This reduces the overall volatile storage required to process the update so that the only limit on number of components is the size of the manifest. However, this approach requires additional processing power.

In order to operate in this mode, the manifest processor loops on each section for every supported component, simply ignoring commands when the current component is not selected.

When a serialized Manifest Processor encounters a component index of True, it does not ignore any commands. It applies them to the current component on each iteration.

6.7. Parallel Processing Interpreter

Advanced Recipients MAY make use of the Strict Order parameter and enable parallel processing of some Command Sequences, or it may reorder some Command Sequences. To perform parallel processing, once the Strict Order parameter is set to False, the Recipient may issue each or every command concurrently until the Strict Order parameter is returned to True or the Command Sequence ends. Then, it waits for all issued commands to complete before continuing processing of commands. To perform out-of-order processing, a similar approach is used, except the Recipient consumes all commands after the Strict Order parameter is set to False, then it sorts these commands into its preferred order, invokes them all, then continues processing.

When the manifest processor encounters any of these scenarios the parallel processing MUST halt until all issued commands have completed:

  • Set Parameters.
  • Override Parameters.
  • Set Strict Order = True.
  • Set Component Index.

To perform more useful parallel operations, a manifest author may collect sequences of commands in a Run Sequence command. Then, each of these sequences MAY be run in parallel. Each sequence defaults to Strict Order = True. To isolate each sequence from each other sequence, each sequence MUST begin with a Set Component Index directive with the following exception: when the index is either True or an array of indices, the Set Component Index is implied. Any further Set Component Index directives MUST cause an Abort. This allows the interpreter that issues Run Sequence commands to check that the first element is correct, then issue the sequence to a parallel execution context to handle the remainder of the sequence.

7. Creating Manifests

Manifests are created using tools for constructing COSE structures, calculating cryptographic values and compiling desired system state into a sequence of operations required to achieve that state. The process of constructing COSE structures and the calculation of cryptographic values is covered in [RFC8152].

Compiling desired system state into a sequence of operations can be accomplished in many ways. Several templates are provided below to cover common use-cases. These templates can be combined to produce more complex behavior.

The author MUST ensure that all parameters consumed by a command are set prior to invoking that command. Where Component Index = True, this means that the parameters consumed by each command MUST have been set for each Component.

This section details a set of templates for creating manifests. These templates explain which parameters, commands, and orders of commands are necessary to achieve a stated goal.

NOTE: On systems that support only a single component, Set Component Index has no effect and can be omitted.

NOTE: A digest MUST always be set using Override Parameters.

7.1. Compatibility Check Template

The goal of the compatibility check template ensure that Recipients only install compatible images.

In this template all information is contained in the common sequence and the following sequence of commands is used:

7.2. Trusted Invocation Template

The goal of the Trusted Invocation template is to ensure that only authorized code is invoked; such as in Secure Boot or when a Trusted Application is loaded into a TEE.

The following commands are placed into the common sequence:

The system validation sequence contains the following commands:

Then, the run sequence contains the following commands:

7.3. Component Download Template

The goal of the Component Download template is to acquire and store an image.

The following commands are placed into the common sequence:

Then, the install sequence contains the following commands:

The Fetch directive needs the URI parameter to be set to determine where the image is retrieved from. Additionally, the destination of where the component shall be stored has to be configured. The URI is configured via the Set Parameters directive while the destination is configured via the Set Component Index directive.

7.4. Install Template

The goal of the Install template is to use an image already stored in an identified component to copy into a second component.

This template is typically used with the Component Download template, however a modification to that template is required: the Component Download operations are moved from the Payload Install sequence to the Payload Fetch sequence.

Then, the install sequence contains the following commands:

7.5. Integrated Payload Template

The goal of the Integrated Payload template is to install a payload that is included in the manifest envelope. It is identical to the Component Download template (Section 7.3).

An implementer MAY choose to place a payload in the envelope of a manifest. The payload envelope key MUST be a string. The payload MUST be serialized in a bstr element.

The URI for a payload enclosed in this way MAY be expressed as a fragment-only reference, as defined in [RFC3986], Section 4.4.

A distributor MAY choose to pre-fetch a payload and add it to the manifest envelope, using the URI as the key.

7.6. Load from Nonvolatile Storage Template

The goal of the Load from Nonvolatile Storage template is to load an image from a non-volatile component into a volatile component, for example loading a firmware image from external Flash into RAM.

The following commands are placed into the load sequence:

As outlined in Section 6.4, the Copy directive needs a source and a destination to be configured. The source is configured via Component Index (with the Set Parameters directive) and the destination is configured via the Set Component Index directive.

7.7. A/B Image Template

The goal of the A/B Image Template is to acquire, validate, and invoke one of two images, based on a test.

The following commands are placed in the common block:

The following commands are placed in the fetch block or install block

If Trusted Invocation (Section 7.2) is used, only the run sequence is added to this template, since the common sequence is populated by this template:

NOTE: Any test can be used to select between images, Check Slot Condition is used in this template because it is a typical test for execute-in-place devices.

8. Metadata Structure

The metadata for SUIT updates is composed of several primary constituent parts: the Envelope, Authentication Information, Manifest, and Severable Elements.

For a diagram of the metadata structure, see Section 5.

8.1. Encoding Considerations

The map indices in the envelope encoding are reset to 1 for each map within the structure. This is to keep the indices as small as possible. The goal is to keep the index objects to single bytes (CBOR positive integers 1-23).

Wherever enumerations are used, they are started at 1. This allows detection of several common software errors that are caused by uninitialized variables. Positive numbers in enumerations are reserved for IANA registration. Negative numbers are used to identify application-specific values, as described in Section 11.

All elements of the envelope must be wrapped in a bstr to minimize the complexity of the code that evaluates the cryptographic integrity of the element and to ensure correct serialization for integrity and authenticity checks.

8.2. Envelope

The Envelope contains each of the other primary constituent parts of the SUIT metadata. It allows for modular processing of the manifest by ordering components in the expected order of processing.

The Envelope is encoded as a CBOR Map. Each element of the Envelope is enclosed in a bstr, which allows computation of a message digest against known bounds.

8.3. Authenticated Manifests

The suit-authentication-wrapper contains a SUIT Digest Container (see Section 10) and one or more SUIT Authentication Blocks. The SUIT_Digest carries the result of computing the indicated hash algorithm over the suit-manifest element. A signing application MUST verify the suit-manifest element against the SUIT_Digest prior to signing. A SUIT Authentication Block is implemented as COSE_Mac_Tagged, COSE_Mac0_Tagged, COSE_Sign_Tagged or COSE_Sign1_Tagged structures with detached payloads, as described in RFC 8152 [RFC8152].

For COSE_Sign and COSE_Sign1 a special signature structure (called Sig_structure) has to be created onto which the selected digital signature algorithm is applied to, see Section 4.4 of [RFC8152] for details. This specification requires Sig_structure to be populated as follows: * The external_aad field MUST be set to a zero-length binary string (i.e. there is no external additional authenticated data). * The payload field contains the SUIT_Digest wrapped in a bstr, as per the requirements in Section 4.4 of RFC 8152. All other fields in the Sig_structure are populated as described in Section 4.4 of [RFC8152].

Likewise, Section 6.3 of [RFC8152] describes the details for computing a MAC and the fields of the MAC_structure need to be populated. The rules for external_aad and the payload fields described in the paragraph above also apply to this structure.

The suit-authentication-wrapper MUST come before the suit-manifest element, regardless of canonical encoding of CBOR.

A SUIT_Envelope that has not had authentication information added MUST still contain the suit-authentication-wrapper element, but the content MUST be a list containing only the SUIT_Digest.

8.4. Manifest

The manifest contains:

The Text section, or any Command Sequence of the Update Procedure (Image Fetch, Image Installation) can be either a CBOR structure or a SUIT_Digest. In each of these cases, the SUIT_Digest provides for a severable element. Severable elements are RECOMMENDED to implement. In particular, the human-readable text SHOULD be severable, since most useful text elements occupy more space than a SUIT_Digest, but are not needed by the Recipient. Because SUIT_Digest is a CBOR Array and each severable element is a CBOR bstr, it is straight-forward for a Recipient to determine whether an element has been severed. The key used for a severable element is the same in the SUIT_Manifest and in the SUIT_Envelope so that a Recipient can easily identify the correct data in the envelope. See Section 8.4.11 for more detail.

8.4.1. suit-manifest-version

The suit-manifest-version indicates the version of serialization used to encode the manifest. Version 1 is the version described in this document. suit-manifest-version is REQUIRED to implement.

8.4.2. suit-manifest-sequence-number

The suit-manifest-sequence-number is a monotonically increasing anti-rollback counter. Each Recipient MUST reject any manifest that has a sequence number lower than its current sequence number. For convenience, an implementer MAY use a UTC timestamp in seconds as the sequence number. suit-manifest-sequence-number is REQUIRED to implement.

8.4.3. suit-reference-uri

suit-reference-uri is a text string that encodes a URI where a full version of this manifest can be found. This is convenient for allowing management systems to show the severed elements of a manifest when this URI is reported by a Recipient after installation.

8.4.4. suit-text

suit-text SHOULD be a severable element. suit-text is a map containing two different types of pair:

  • integer => text
  • SUIT_Component_Identifier => map

Each SUIT_Component_Identifier => map entry contains a map of integer => text values. All SUIT_Component_Identifiers present in suit-text MUST also be present in suit-common (Section 8.4.5).

suit-text contains all the human-readable information that describes any and all parts of the manifest, its payload(s) and its resource(s). The text section is typically severable, allowing manifests to be distributed without the text, since end-nodes do not require text. The meaning of each field is described below.

Each section MAY be present. If present, each section MUST be as described. Negative integer IDs are reserved for application-specific text values.

The following table describes the text fields available in suit-text:

Table 2
CDDL Structure Description
suit-text-manifest-description Free text description of the manifest
suit-text-update-description Free text description of the update
suit-text-manifest-json-source The JSON-formatted document that was used to create the manifest
suit-text-manifest-yaml-source The YAML ([YAML])-formatted document that was used to create the manifest

The following table describes the text fields available in each map identified by a SUIT_Component_Identifier.

Table 3
CDDL Structure Description
suit-text-vendor-name Free text vendor name
suit-text-model-name Free text model name
suit-text-vendor-domain The domain used to create the vendor-id condition
suit-text-model-info The information used to create the class-id condition
suit-text-component-description Free text description of each component in the manifest
suit-text-component-version A free text representation of the component version

suit-text is OPTIONAL to implement.

8.4.5. suit-common

suit-common encodes all the information that is shared between each of the command sequences, including: suit-components, and suit-common-sequence. suit-common is REQUIRED to implement.

suit-components is a list of SUIT_Component_Identifier (Section 8.4.5.1) blocks that specify the component identifiers that will be affected by the content of the current manifest. suit-components is REQUIRED to implement.

suit-common-sequence is a SUIT_Command_Sequence to execute prior to executing any other command sequence. Typical actions in suit-common-sequence include setting expected Recipient identity and image digests when they are conditional (see Section 8.4.10.2 and Section 7.7 for more information on conditional sequences). suit-common-sequence is RECOMMENDED to implement. It is REQUIRED if the optimizations described in Section 6.2.1 will be used. Whenever a parameter or Try Each command is required by more than one Command Sequence, placing that parameter or command in suit-common-sequence results in a smaller encoding.

8.4.5.1. SUIT_Component_Identifier

A component is a unit of code or data that can be targeted by an update. To facilitate composite devices, components are identified by a list of CBOR byte strings, which allows construction of hierarchical component structures. Components are identified by Component Identifiers, but referenced in commands by Component Index; Component Identifiers are arrays of binary strings and a Component Index is an index into the array of Component Identifiers.

A Component Identifier can be trivial, such as the simple array [h'00']. It can also represent a filesystem path by encoding each segment of the path as an element in the list. For example, the path "/usr/bin/env" would encode to ['usr','bin','env'].

This hierarchical construction allows a component identifier to identify any part of a complex, multi-component system.

8.4.6. SUIT_Command_Sequence

A SUIT_Command_Sequence defines a series of actions that the Recipient MUST take to accomplish a particular goal. These goals are defined in the manifest and include:

  1. Payload Fetch: suit-payload-fetch is a SUIT_Command_Sequence to execute in order to obtain a payload. Some manifests may include these actions in the suit-install section instead if they operate in a streaming installation mode. This is particularly relevant for constrained devices without any temporary storage for staging the update. suit-payload-fetch is OPTIONAL to implement.
  2. Payload Installation: suit-install is a SUIT_Command_Sequence to execute in order to install a payload. Typical actions include verifying a payload stored in temporary storage, copying a staged payload from temporary storage, and unpacking a payload. suit-install is OPTIONAL to implement.
  3. Image Validation: suit-validate is a SUIT_Command_Sequence to execute in order to validate that the result of applying the update is correct. Typical actions involve image validation. suit-validate is REQUIRED to implement.
  4. Image Loading: suit-load is a SUIT_Command_Sequence to execute in order to prepare a payload for execution. Typical actions include copying an image from permanent storage into RAM, optionally including actions such as decryption or decompression. suit-load is OPTIONAL to implement.
  5. Run or Boot: suit-run is a SUIT_Command_Sequence to execute in order to run an image. suit-run typically contains a single instruction: the "run" directive. suit-run is OPTIONAL to implement.

Goals 1,2 form the Update Procedure. Goals 4,5,6 form the Invocation Procedure.

Each Command Sequence follows exactly the same structure to ensure that the parser is as simple as possible.

Lists of commands are constructed from two kinds of element:

  1. Conditions that MUST be true and any failure is treated as a failure of the update/load/invocation
  2. Directives that MUST be executed.

Each condition is composed of:

  1. A command code identifier
  2. A SUIT_Reporting_Policy (Section 8.4.7)

Each directive is composed of:

  1. A command code identifier
  2. An argument block or a SUIT_Reporting_Policy (Section 8.4.7)

Argument blocks are consumed only by flow-control directives:

  • Set Component Index
  • Set/Override Parameters
  • Try Each
  • Run Sequence

Reporting policies provide a hint to the manifest processor of whether to add the success or failure of a command to any report that it generates.

Many conditions and directives apply to a given component, and these generally grouped together. Therefore, a special command to set the current component index is provided. This index is a numeric index into the Component Identifier table defined at the beginning of the manifest.

To facilitate optional conditions, a special directive, suit-directive-try-each (Section 8.4.10.2), is provided. It runs several new lists of conditions/directives, one after another, that are contained as an argument to the directive. By default, it assumes that a failure of a condition should not indicate a failure of the update/invocation, but a parameter is provided to override this behavior. See suit-parameter-soft-failure (Section 8.4.8.14).

8.4.7. Reporting Policy

To facilitate construction of Reports that describe the success or failure of a given Procedure, each command is given a Reporting Policy. This is an integer bitfield that follows the command and indicates what the Recipient should do with the Record of executing the command. The options are summarized in the table below.

Table 4
Policy Description
suit-send-record-on-success Record when the command succeeds
suit-send-record-on-failure Record when the command fails
suit-send-sysinfo-success Add system information when the command succeeds
suit-send-sysinfo-failure Add system information when the command fails

Any or all of these policies may be enabled at once.

At the completion of each command, a Manifest Processor MAY forward information about the command to a Reporting Engine, which is responsible for reporting boot or update status to a third party. The Reporting Engine is entirely implementation-defined, the reporting policy simply facilitates the Reporting Engine's interface to the SUIT Manifest Processor.

The information elements provided to the Reporting Engine are:

  • The reporting policy
  • The result of the command
  • The values of parameters consumed by the command
  • The system information consumed by the command

Together, these elements are called a Record. A group of Records is a Report.

If the component index is set to True or an array when a command is executed with a non-zero reporting policy, then the Reporting Engine MUST receive one Record for each Component, in the order expressed in the Components list or the component index array.

This specification does not define a particular format of Records or Reports. This specification only defines hints to the Reporting Engine for which Records it should aggregate into the Report. The Reporting Engine MAY choose to ignore these hints and apply its own policy instead.

When used in a Invocation Procedure, the report MAY form the basis of an attestation report. When used in an Update Process, the report MAY form the basis for one or more log entries.

8.4.8. SUIT_Parameters

Many conditions and directives require additional information. That information is contained within parameters that can be set in a consistent way. This allows reuse of parameters between commands, thus reducing manifest size.

Most parameters are scoped to a specific component. This means that setting a parameter for one component has no effect on the parameters of any other component. The only exceptions to this are two Manifest Processor parameters: Strict Order and Soft Failure.

The defined manifest parameters are described below.

Table 5
Name CDDL Structure Reference
Vendor ID suit-parameter-vendor-identifier Section 8.4.8.3
Class ID suit-parameter-class-identifier Section 8.4.8.4
Device ID suit-parameter-device-identifier Section 8.4.8.5
Image Digest suit-parameter-image-digest Section 8.4.8.6
Image Size suit-parameter-image-size Section 8.4.8.7
Component Slot suit-parameter-component-slot Section 8.4.8.8
URI suit-parameter-uri Section 8.4.8.9
Source Component suit-parameter-source-component Section 8.4.8.10
Run Args suit-parameter-run-args Section 8.4.8.11
Fetch Arguments suit-parameter-fetch-arguments Section 8.4.8.12
Strict Order suit-parameter-strict-order Section 8.4.8.13
Soft Failure suit-parameter-soft-failure Section 8.4.8.14
Custom suit-parameter-custom Section 8.4.8.15

CBOR-encoded object parameters are still wrapped in a bstr. This is because it allows a parser that is aggregating parameters to reference the object with a single pointer and traverse it without understanding the contents. This is important for modularization and division of responsibility within a pull parser. The same consideration does not apply to Directives because those elements are invoked with their arguments immediately.

8.4.8.1. CBOR PEN UUID Namespace Identifier

The CBOR PEN UUID Namespace Identifier is constructed as follows:

It uses the OID Namespace as a starting point, then uses the CBOR absolute OID encoding for the IANA PEN OID (1.3.6.1.4.1):

D8 6F                # tag(111)
   45                # bytes(5)
# Absolute OID encoding of IANA Private Enterprise Number:
#    1.3. 6. 1. 4. 1
      2B 06 01 04 01 # X.690 Clause 8.19

Computing a type 5 UUID from these produces:

NAMESPACE_CBOR_PEN = UUID5(NAMESPACE_OID, h'D86F452B06010401')
NAMESPACE_CBOR_PEN = 47fbdabb-f2e4-55f0-bb39-3620c2f6df4e
8.4.8.2. Constructing UUIDs

Several conditions use identifiers to determine whether a manifest matches a given Recipient or not. These identifiers are defined to be RFC 4122 [RFC4122] UUIDs. These UUIDs are not human-readable and are therefore used for machine-based processing only.

A Recipient MAY match any number of UUIDs for vendor or class identifier. This may be relevant to physical or software modules. For example, a Recipient that has an OS and one or more applications might list one Vendor ID for the OS and one or more additional Vendor IDs for the applications. This Recipient might also have a Class ID that must be matched for the OS and one or more Class IDs for the applications.

Identifiers are used for compatibility checks. They MUST NOT be used as assertions of identity. They are evaluated by identifier conditions (Section 8.4.9.1).

A more complete example: Imagine a device has the following physical components: 1. A host MCU 2. A WiFi module

This same device has three software modules: 1. An operating system 2. A WiFi module interface driver 3. An application

Suppose that the WiFi module's firmware has a proprietary update mechanism and doesn't support manifest processing. This device can report four class IDs:

  1. Hardware model/revision
  2. OS
  3. WiFi module model/revision
  4. Application

This allows the OS, WiFi module, and application to be updated independently. To combat possible incompatibilities, the OS class ID can be changed each time the OS has a change to its API.

This approach allows a vendor to target, for example, all devices with a particular WiFi module with an update, which is a very powerful mechanism, particularly when used for security updates.

UUIDs MUST be created according to RFC 4122 [RFC4122]. UUIDs SHOULD use versions 3, 4, or 5, as described in RFC4122. Versions 1 and 2 do not provide a tangible benefit over version 4 for this application.

The RECOMMENDED method to create a vendor ID is:

Vendor ID = UUID5(DNS_PREFIX, vendor domain name)

If the Vendor ID is a UUID, the RECOMMENDED method to create a Class ID is:

Class ID = UUID5(Vendor ID, Class-Specific-Information)

If the Vendor ID is a CBOR PEN (see Section 8.4.8.3), the RECOMMENDED method to create a Class ID is:

Class ID = UUID5(
    UUID5(NAMESPACE_CBOR_PEN, CBOR_PEN),
    Class-Specific-Information)

Class-specific-information is composed of a variety of data, for example:

  • Model number.
  • Hardware revision.
  • Bootloader version (for immutable bootloaders).
8.4.8.3. suit-parameter-vendor-identifier

suit-parameter-vendor-identifier may be presented in one of two ways:

  • A Private Enterprise Number
  • A byte string containing a UUID ([RFC4122])

Private Enterprise Numbers are encoded as a relative OID, according to the definition in [I-D.ietf-cbor-tags-oid]. All PENs are relative to the IANA PEN: 1.3.6.1.4.1.

8.4.8.4. suit-parameter-class-identifier

A RFC 4122 UUID representing the class of the device or component. The UUID is encoded as a 16 byte bstr, containing the raw bytes of the UUID. It MUST be constructed as described in Section 8.4.8.2

8.4.8.5. suit-parameter-device-identifier

A RFC 4122 UUID representing the specific device or component. The UUID is encoded as a 16 byte bstr, containing the raw bytes of the UUID. It MUST be constructed as described in Section 8.4.8.2

8.4.8.6. suit-parameter-image-digest

A fingerprint computed over the component itself, encoded in the SUIT_Digest Section 10 structure. The SUIT_Digest is wrapped in a bstr, as required in Section 8.4.8.

8.4.8.7. suit-parameter-image-size

The size of the firmware image in bytes. This size is encoded as a positive integer.

8.4.8.8. suit-parameter-component-slot

This parameter sets the slot index of a component. Some components support multiple possible Slots (offsets into a storage area). This parameter describes the intended Slot to use, identified by its index into the component's storage area. This slot MUST be encoded as a positive integer.

8.4.8.9. suit-parameter-uri

A URI Reference ([RFC3986]) from which to fetch a resource, encoded as a text string. CBOR Tag 32 is not used because the meaning of the text string is unambiguous in this context.

8.4.8.10. suit-parameter-source-component

This parameter sets the source component to be used with either suit-directive-copy (Section 8.4.10.5) or with suit-directive-swap (Section 8.4.10.8). The current Component, as set by suit-directive-set-component-index defines the destination, and suit-parameter-source-component defines the source.

8.4.8.11. suit-parameter-run-args

This parameter contains an encoded set of arguments for suit-directive-run (Section 8.4.10.6). The arguments MUST be provided as an implementation-defined bstr.

8.4.8.12. suit-parameter-fetch-arguments

An implementation-defined set of arguments to suit-directive-fetch (Section 8.4.10.4). Arguments are encoded in a bstr.

8.4.8.13. suit-parameter-strict-order

The Strict Order Parameter allows a manifest to govern when directives can be executed out-of-order. This allows for systems that have a sensitivity to order of updates to choose the order in which they are executed. It also allows for more advanced systems to parallelize their handling of updates. Strict Order defaults to True. It MAY be set to False when the order of operations does not matter. When arriving at the end of a command sequence, ALL commands MUST have completed, regardless of the state of SUIT_Parameter_Strict_Order. If SUIT_Parameter_Strict_Order is returned to True, ALL preceding commands MUST complete before the next command is executed.

See Section 6.7 for behavioral description of Strict Order.

8.4.8.14. suit-parameter-soft-failure

When executing a command sequence inside suit-directive-try-each (Section 8.4.10.2) or suit-directive-run-sequence (Section 8.4.10.7) and a condition failure occurs, the manifest processor aborts the sequence. For suit-directive-try-each, if Soft Failure is True, the next sequence in Try Each is invoked, otherwise suit-directive-try-each fails with the condition failure code. In suit-directive-run-sequence, if Soft Failure is True the suit-directive-run-sequence simply halts with no side-effects and the Manifest Processor continues with the following command, otherwise, the suit-directive-run-sequence fails with the condition failure code.

suit-parameter-soft-failure is scoped to the enclosing SUIT_Command_Sequence. Its value is discarded when SUIT_Command_Sequence terminates. It MUST NOT be set outside of suit-directive-try-each or suit-directive-run-sequence.

When suit-directive-try-each is invoked, Soft Failure defaults to True. An Update Author may choose to set Soft Failure to False if they require a failed condition in a sequence to force an Abort.

When suit-directive-run-sequence is invoked, Soft Failure defaults to False. An Update Author may choose to make failures soft within a suit-directive-run-sequence.

8.4.8.15. suit-parameter-custom

This parameter is an extension point for any proprietary, application specific conditions and directives. It MUST NOT be used in the common sequence. This effectively scopes each custom command to a particular Vendor Identifier/Class Identifier pair.

8.4.9. SUIT_Condition

Conditions are used to define mandatory properties of a system in order for an update to be applied. They can be pre-conditions or post-conditions of any directive or series of directives, depending on where they are placed in the list. All Conditions specify a Reporting Policy as described Section 8.4.7. Conditions include:

Table 6
Name CDDL Structure Reference
Vendor Identifier suit-condition-vendor-identifier Section 8.4.9.1
Class Identifier suit-condition-class-identifier Section 8.4.9.1
Device Identifier suit-condition-device-identifier Section 8.4.9.1
Image Match suit-condition-image-match Section 8.4.9.2
Component Slot suit-condition-component-slot Section 8.4.9.3
Abort suit-condition-abort Section 8.4.9.4
Custom Condition suit-condition-custom Section 8.4.9.5

The abstract description of these conditions is defined in Section 6.4.

Conditions compare parameters against properties of the system. These properties may be asserted in many different ways, including: calculation on-demand, volatile definition in memory, static definition within the manifest processor, storage in known location within an image, storage within a key storage system, storage in One-Time-Programmable memory, inclusion in mask ROM, or inclusion as a register in hardware. Some of these assertion methods are global in scope, such as a hardware register, some are scoped to an individual component, such as storage at a known location in an image, and some assertion methods can be either global or component-scope, based on implementation.

Each condition MUST report a result code on completion. If a condition reports failure, then the current sequence of commands MUST terminate. A subsequent command or command sequence MAY continue executing if suit-parameter-soft-failure (Section 8.4.8.14) is set. If a condition requires additional information, this MUST be specified in one or more parameters before the condition is executed. If a Recipient attempts to process a condition that expects additional information and that information has not been set, it MUST report a failure. If a Recipient encounters an unknown condition, it MUST report a failure.

Condition labels in the positive number range are reserved for IANA registration while those in the negative range are custom conditions reserved for proprietary definition by the author of a manifest processor. See Section 11 for more details.

8.4.9.1. suit-condition-vendor-identifier, suit-condition-class-identifier, and suit-condition-device-identifier

There are three identifier-based conditions: suit-condition-vendor-identifier, suit-condition-class-identifier, and suit-condition-device-identifier. Each of these conditions match a RFC 4122 [RFC4122] UUID that MUST have already been set as a parameter. The installing Recipient MUST match the specified UUID in order to consider the manifest valid. These identifiers are scoped by component in the manifest. Each component MAY match more than one identifier. Care is needed to ensure that manifests correctly identify their targets using these conditions. Using only a generic class ID for a device-specific firmware could result in matching devices that are not compatible.

The Recipient uses the ID parameter that has already been set using the Set Parameters directive. If no ID has been set, this condition fails. suit-condition-class-identifier and suit-condition-vendor-identifier are REQUIRED to implement. suit-condition-device-identifier is OPTIONAL to implement.

Each identifier condition compares the corresponding identifier parameter to a parameter asserted to the Manifest Processor by the Recipient. Identifiers MUST be known to the Manifest Processor in order to evaluate compatibility.

8.4.9.2. suit-condition-image-match

Verify that the current component matches the suit-parameter-image-digest (Section 8.4.8.6) for the current component. The digest is verified against the digest specified in the Component's parameters list. If no digest is specified, the condition fails. suit-condition-image-match is REQUIRED to implement.

8.4.9.3. suit-condition-component-slot

Verify that the slot index of the current component matches the slot index set in suit-parameter-component-slot (Section 8.4.8.8). This condition allows a manifest to select between several images to match a target slot.

8.4.9.4. suit-condition-abort

Unconditionally fail. This operation is typically used in conjunction with suit-directive-try-each (Section 8.4.10.2).

8.4.9.5. suit-condition-custom

suit-condition-custom describes any proprietary, application specific condition. This is encoded as a negative integer, chosen by the firmware developer. If additional information must be provided to the condition, it should be encoded in a custom parameter (a nint) as described in Section 8.4.8. SUIT_Condition_Custom is OPTIONAL to implement.

8.4.10. SUIT_Directive

Directives are used to define the behavior of the recipient. Directives include:

Table 7
Name CDDL Structure Reference
Set Component Index suit-directive-set-component-index Section 8.4.10.1
Try Each suit-directive-try-each Section 8.4.10.2
Override Parameters suit-directive-override-parameters Section 8.4.10.3
Fetch suit-directive-fetch Section 8.4.10.4
Copy suit-directive-copy Section 8.4.10.5
Run suit-directive-run Section 8.4.10.6
Run Sequence suit-directive-run-sequence Section 8.4.10.7
Swap suit-directive-swap Section 8.4.10.8

The abstract description of these commands is defined in Section 6.4.

When a Recipient executes a Directive, it MUST report a result code. If the Directive reports failure, then the current Command Sequence MUST be terminated.

8.4.10.1. suit-directive-set-component-index

Set Component Index defines the component to which successive directives and conditions will apply. The supplied argument MUST be one of three types:

  1. An unsigned integer (REQUIRED to implement in parser)
  2. A boolean (REQUIRED to implement in parser ONLY IF 2 or more components supported)
  3. An array of unsigned integers (REQUIRED to implement in parser ONLY IF 3 or more components supported)

If the following commands apply to ONE component, an unsigned integer index into the component list is used. If the following commands apply to ALL components, then the boolean value "True" is used instead of an index. If the following commands apply to more than one, but not all components, then an array of unsigned integer indices into the component list is used. See Section 6.5 for more details.

If component index is set to True when a command is invoked, then the command applies to all components, in the order they appear in suit-common-components. When the Manifest Processor invokes a command while the component index is set to True, it must execute the command once for each possible component index, ensuring that the command receives the parameters corresponding to that component index.

8.4.10.2. suit-directive-try-each

This command runs several SUIT_Command_Sequence instances, one after another, in a strict order. Use this command to implement a "try/catch-try/catch" sequence. Manifest processors MAY implement this command.

suit-parameter-soft-failure (Section 8.4.8.14) is initialized to True at the beginning of each sequence. If one sequence aborts due to a condition failure, the next is started. If no sequence completes without condition failure, then suit-directive-try-each returns an error. If a particular application calls for all sequences to fail and still continue, then an empty sequence (nil) can be added to the Try Each Argument.

The argument to suit-directive-try-each is a list of SUIT_Command_Sequence. suit-directive-try-each does not specify a reporting policy.

8.4.10.3. suit-directive-override-parameters

suit-directive-override-parameters replaces any listed parameters that are already set with the values that are provided in its argument. This allows a manifest to prevent replacement of critical parameters.

Available parameters are defined in Section 8.4.8.

suit-directive-override-parameters does not specify a reporting policy.

8.4.10.4. suit-directive-fetch

suit-directive-fetch instructs the manifest processor to obtain one or more manifests or payloads, as specified by the manifest index and component index, respectively.

suit-directive-fetch can target one or more payloads. suit-directive-fetch retrieves each component listed in component-index. If component-index is True, instead of an integer, then all current manifest components are fetched. If component-index is an array, then all listed components are fetched.

suit-directive-fetch typically takes no arguments unless one is needed to modify fetch behavior. If an argument is needed, it must be wrapped in a bstr and set in suit-parameter-fetch-arguments.

suit-directive-fetch reads the URI parameter to find the source of the fetch it performs.

8.4.10.5. suit-directive-copy

suit-directive-copy instructs the manifest processor to obtain one or more payloads, as specified by the component index. As described in Section 6.5 component index may be a single integer, a list of integers, or True. suit-directive-copy retrieves each component specified by the current component-index, respectively.

suit-directive-copy reads its source from suit-parameter-source-component (Section 8.4.8.10).

If either the source component parameter or the source component itself is absent, this command fails.

8.4.10.6. suit-directive-run

suit-directive-run directs the manifest processor to transfer execution to the current Component Index. When this is invoked, the manifest processor MAY be unloaded and execution continues in the Component Index. Arguments are provided to suit-directive-run through suit-parameter-run-arguments (Section 8.4.8.11) and are forwarded to the executable code located in Component Index in an application-specific way. For example, this could form the Linux Kernel Command Line if booting a Linux device.

If the executable code at Component Index is constructed in such a way that it does not unload the manifest processor, then the manifest processor may resume execution after the executable completes. This allows the manifest processor to invoke suitable helpers and to verify them with image conditions.

8.4.10.7. suit-directive-run-sequence

To enable conditional commands, and to allow several strictly ordered sequences to be executed out-of-order, suit-directive-run-sequence allows the manifest processor to execute its argument as a SUIT_Command_Sequence. The argument must be wrapped in a bstr.

When a sequence is executed, any failure of a condition causes immediate termination of the sequence.

When suit-directive-run-sequence completes, it forwards the last status code that occurred in the sequence. If the Soft Failure parameter is true, then suit-directive-run-sequence only fails when a directive in the argument sequence fails.

suit-parameter-soft-failure (Section 8.4.8.14) defaults to False when suit-directive-run-sequence begins. Its value is discarded when suit-directive-run-sequence terminates.

8.4.10.8. suit-directive-swap

suit-directive-swap instructs the manifest processor to move the source to the destination and the destination to the source simultaneously. Swap has nearly identical semantics to suit-directive-copy except that suit-directive-swap replaces the source with the current contents of the destination in an application-defined way. As with suit-directive-copy, if the source component is missing, this command fails.

If SUIT_Parameter_Compression_Info or SUIT_Parameter_Encryption_Info are present, they MUST be handled in a symmetric way, so that the source is decompressed into the destination and the destination is compressed into the source. The source is decrypted into the destination and the destination is encrypted into the source. suit-directive-swap is OPTIONAL to implement.

8.4.11. Integrity Check Values

When the Text section or any Command Sequence of the Update Procedure is made severable, it is moved to the Envelope and replaced with a SUIT_Digest. The SUIT_Digest is computed over the entire bstr enclosing the Manifest element that has been moved to the Envelope. Each element that is made severable from the Manifest is placed in the Envelope. The keys for the envelope elements have the same values as the keys for the manifest elements.

Each Integrity Check Value covers the corresponding Envelope Element as described in Section 8.5.

8.5. Severable Elements

Because the manifest can be used by different actors at different times, some parts of the manifest can be removed or "Severed" without affecting later stages of the lifecycle. Severing of information is achieved by separating that information from the signed container so that removing it does not affect the signature. This means that ensuring integrity of severable parts of the manifest is a requirement for the signed portion of the manifest. Severing some parts makes it possible to discard parts of the manifest that are no longer necessary. This is important because it allows the storage used by the manifest to be greatly reduced. For example, no text size limits are needed if text is removed from the manifest prior to delivery to a constrained device.

Elements are made severable by removing them from the manifest, encoding them in a bstr, and placing a SUIT_Digest of the bstr in the manifest so that they can still be authenticated. The SUIT_Digest typically consumes 4 bytes more than the size of the raw digest, therefore elements smaller than (Digest Bits)/8 + 4 SHOULD NOT be severable. Elements larger than (Digest Bits)/8 + 4 MAY be severable, while elements that are much larger than (Digest Bits)/8 + 4 SHOULD be severable.

Because of this, all command sequences in the manifest are encoded in a bstr so that there is a single code path needed for all command sequences.

9. Access Control Lists

To manage permissions in the manifest, there are three models that can be used.

First, the simplest model requires that all manifests are authenticated by a single trusted key. This mode has the advantage that only a root manifest needs to be authenticated, since all of its dependencies have digests included in the root manifest.

This simplest model can be extended by adding key delegation without much increase in complexity.

A second model requires an ACL to be presented to the Recipient, authenticated by a trusted party or stored on the Recipient. This ACL grants access rights for specific component IDs or Component Identifier prefixes to the listed identities or identity groups. Any identity can verify an image digest, but fetching into or fetching from a Component Identifier requires approval from the ACL.

A third model allows a Recipient to provide even more fine-grained controls: The ACL lists the Component Identifier or Component Identifier prefix that an identity can use, and also lists the commands and parameters that the identity can use in combination with that Component Identifier.

10. SUIT Digest Container

The SUIT digest is a CBOR List containing two elements: an algorithm identifier and a bstr containing the bytes of the digest. Some forms of digest may require additional parameters. These can be added following the digest.

The values of the algorithm identifier are defined by [I-D.ietf-cose-hash-algs]. The following algorithms MUST be implemented by all Manifest Processors:

The following algorithms MAY be implemented in a Manifest Processor:

11. IANA Considerations

IANA is requested to:

IANA is requested to setup a registry for SUIT manifests. Several registries defined in the subsections below need to be created.

For each registry, values 0-23 are Standards Action, 24-255 are IETF Review, 256-65535 are Expert Review, and 65536 or greater are First Come First Served.

Negative values -23 to 0 are Experimental Use, -24 and lower are Private Use.

11.1. SUIT Commands

Table 8
Label Name Reference
1 Vendor Identifier Section 8.4.9.1
2 Class Identifier Section 8.4.9.1
3 Image Match Section 8.4.9.2
4 Reserved  
5 Component Slot Section 8.4.9.3
12 Set Component Index Section 8.4.10.1
13 Reserved  
14 Abort  
15 Try Each Section 8.4.10.2
16 Reserved  
17 Reserved  
18 Reserved  
19 Reserved  
20 Override Parameters Section 8.4.10.3
21 Fetch Section 8.4.10.4
22 Copy Section 8.4.10.5
23 Run Section 8.4.10.6
24 Device Identifier Section 8.4.9.1
25 Reserved  
26 Reserved  
27 Reserved  
28 Reserved  
29 Reserved  
30 Reserved  
31 Swap Section 8.4.10.8
32 Run Sequence Section 8.4.10.7
33 Reserved  
nint Custom Condition Section 8.4.9.5

11.2. SUIT Parameters

Table 9
Label Name Reference
1 Vendor ID Section 8.4.8.3
2 Class ID Section 8.4.8.4
3 Image Digest Section 8.4.8.6
4 Reserved  
5 Component Slot Section 8.4.8.8
12 Strict Order Section 8.4.8.13
13 Soft Failure Section 8.4.8.14
14 Image Size Section 8.4.8.7
18 Reserved  
19 Reserved  
20 Reserved  
21 URI Section 8.4.8.9
22 Source Component Section 8.4.8.10
23 Run Args Section 8.4.8.11
24 Device ID Section 8.4.8.5
26 Reserved  
27 Reserved  
28 Reserved  
29 Reserved  
30 Reserved  
nint Custom Section 8.4.8.15

11.3. SUIT Text Values

Table 10
Label Name Reference
1 Manifest Description Section 8.4.4
2 Update Description Section 8.4.4
3 Manifest JSON Source Section 8.4.4
4 Manifest YAML Source Section 8.4.4
nint Custom Section 8.4.4

11.4. SUIT Component Text Values

Table 11
Label Name Reference
1 Vendor Name Section 8.4.4
2 Model Name Section 8.4.4
3 Vendor Domain Section 8.4.4
4 Model Info Section 8.4.4
5 Component Description Section 8.4.4
6 Component Version Section 8.4.4
7 Component Version Required Section 8.4.4
nint Custom Section 8.4.4

12. Security Considerations

This document is about a manifest format protecting and describing how to retrieve, install, and invoke firmware images and as such it is part of a larger solution for delivering firmware updates to IoT devices. A detailed security treatment can be found in the architecture [RFC9019] and in the information model [RFC9124] documents.

13. Acknowledgements

We would like to thank the following persons for their support in designing this mechanism:

14. References

14.1. Normative References

[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC3986]
Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, , <https://www.rfc-editor.org/info/rfc3986>.
[RFC4122]
Leach, P., Mealling, M., and R. Salz, "A Universally Unique IDentifier (UUID) URN Namespace", RFC 4122, DOI 10.17487/RFC4122, , <https://www.rfc-editor.org/info/rfc4122>.
[RFC8152]
Schaad, J., "CBOR Object Signing and Encryption (COSE)", RFC 8152, DOI 10.17487/RFC8152, , <https://www.rfc-editor.org/info/rfc8152>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/info/rfc8174>.
[RFC9019]
Moran, B., Tschofenig, H., Brown, D., and M. Meriac, "A Firmware Update Architecture for Internet of Things", RFC 9019, DOI 10.17487/RFC9019, , <https://www.rfc-editor.org/info/rfc9019>.
[RFC9124]
Moran, B., Tschofenig, H., and H. Birkholz, "A Manifest Information Model for Firmware Updates in Internet of Things (IoT) Devices", RFC 9124, DOI 10.17487/RFC9124, , <https://www.rfc-editor.org/info/rfc9124>.

14.2. Informative References

[I-D.ietf-cbor-tags-oid]
Bormann, C., "Concise Binary Object Representation (CBOR) Tags for Object Identifiers", Work in Progress, Internet-Draft, draft-ietf-cbor-tags-oid-08, , <https://www.ietf.org/archive/id/draft-ietf-cbor-tags-oid-08.txt>.
[I-D.ietf-cose-hash-algs]
Schaad, J., "CBOR Object Signing and Encryption (COSE): Hash Algorithms", Work in Progress, Internet-Draft, draft-ietf-cose-hash-algs-09, , <https://www.ietf.org/archive/id/draft-ietf-cose-hash-algs-09.txt>.
[I-D.ietf-suit-firmware-encryption]
Tschofenig, H., Housley, R., and B. Moran, "Firmware Encryption with SUIT Manifests", Work in Progress, Internet-Draft, draft-ietf-suit-firmware-encryption-04, , <https://www.ietf.org/archive/id/draft-ietf-suit-firmware-encryption-04.txt>.
[I-D.ietf-suit-report]
Moran, B. and H. Birkholz, "Secure Reporting of Update Status", Work in Progress, Internet-Draft, draft-ietf-suit-report-01, , <https://www.ietf.org/archive/id/draft-ietf-suit-report-01.txt>.
[I-D.ietf-suit-trust-domains]
Moran, B., "SUIT Manifest Extensions for Multiple Trust Domains", Work in Progress, Internet-Draft, draft-ietf-suit-trust-domains-00, , <https://www.ietf.org/archive/id/draft-ietf-suit-trust-domains-00.txt>.
[I-D.ietf-suit-update-management]
Moran, B., "Update Management Extensions for Software Updates for Internet of Things (SUIT) Manifests", Work in Progress, Internet-Draft, draft-ietf-suit-update-management-00, , <https://www.ietf.org/archive/id/draft-ietf-suit-update-management-00.txt>.
[I-D.ietf-teep-architecture]
Pei, M., Tschofenig, H., Thaler, D., and D. Wheeler, "Trusted Execution Environment Provisioning (TEEP) Architecture", Work in Progress, Internet-Draft, draft-ietf-teep-architecture-17, , <https://www.ietf.org/archive/id/draft-ietf-teep-architecture-17.txt>.
[RFC7228]
Bormann, C., Ersue, M., and A. Keranen, "Terminology for Constrained-Node Networks", RFC 7228, DOI 10.17487/RFC7228, , <https://www.rfc-editor.org/info/rfc7228>.
[YAML]
"YAML Ain't Markup Language", , <https://yaml.org/>.

Appendix A. A. Full CDDL

In order to create a valid SUIT Manifest document the structure of the corresponding CBOR message MUST adhere to the following CDDL data definition.

To be valid, the following CDDL MUST have the COSE CDDL appended to it. The COSE CDDL can be obtained by following the directions in [RFC8152], Section 1.3.

SUIT_Envelope_Tagged = #6.107(SUIT_Envelope)
SUIT_Envelope = {
  suit-authentication-wrapper => bstr .cbor SUIT_Authentication,
  suit-manifest  => bstr .cbor SUIT_Manifest,
  SUIT_Severable_Manifest_Members,
  * SUIT_Integrated_Payload,
  * $$SUIT_Envelope_Extensions,
  * (int => bstr)
}

SUIT_Authentication = [
    bstr .cbor SUIT_Digest,
    * bstr .cbor SUIT_Authentication_Block
]

SUIT_Digest = [
  suit-digest-algorithm-id : suit-cose-hash-algs,
  suit-digest-bytes : bstr,
  * $$SUIT_Digest-extensions
]

SUIT_Authentication_Block /= COSE_Mac_Tagged
SUIT_Authentication_Block /= COSE_Sign_Tagged
SUIT_Authentication_Block /= COSE_Mac0_Tagged
SUIT_Authentication_Block /= COSE_Sign1_Tagged

SUIT_Severable_Manifest_Members = (
  ? suit-payload-fetch => bstr .cbor SUIT_Command_Sequence,
  ? suit-install => bstr .cbor SUIT_Command_Sequence,
  ? suit-text => bstr .cbor SUIT_Text_Map,
  * $$SUIT_severable-members-extensions,
)

SUIT_Integrated_Payload = (suit-integrated-payload-key => bstr)
suit-integrated-payload-key = tstr

SUIT_Manifest_Tagged = #6.1070(SUIT_Manifest)

SUIT_Manifest = {
    suit-manifest-version         => 1,
    suit-manifest-sequence-number => uint,
    suit-common                   => bstr .cbor SUIT_Common,
    ? suit-reference-uri          => tstr,
    SUIT_Severable_Members_Choice,
    SUIT_Unseverable_Members,
    * $$SUIT_Manifest_Extensions,
}

SUIT_Unseverable_Members = (
  ? suit-validate => bstr .cbor SUIT_Command_Sequence,
  ? suit-load => bstr .cbor SUIT_Command_Sequence,
  ? suit-run => bstr .cbor SUIT_Command_Sequence,
  * $$unseverable-manifest-member-extensions,
)

SUIT_Severable_Members_Choice = (
  ? suit-payload-fetch =>
    bstr .cbor SUIT_Command_Sequence / SUIT_Digest,
  ? suit-install => bstr .cbor SUIT_Command_Sequence / SUIT_Digest,
  ? suit-text => bstr .cbor SUIT_Command_Sequence / SUIT_Digest,
  * $$severable-manifest-members-choice-extensions
)

SUIT_Common = {
    ? suit-components             => SUIT_Components,
    ? suit-common-sequence        => bstr .cbor SUIT_Common_Sequence,
    * $$SUIT_Common-extensions,
}

SUIT_Components           = [ + SUIT_Component_Identifier ]

SUIT_Dependency = {
    suit-dependency-digest => SUIT_Digest,
    ? suit-dependency-prefix => SUIT_Component_Identifier,
    * $$SUIT_Dependency-extensions,
}

;REQUIRED to implement:
suit-cose-hash-algs /= cose-alg-sha-256

;OPTIONAL to implement:
suit-cose-hash-algs /= cose-alg-shake128
suit-cose-hash-algs /= cose-alg-sha-384
suit-cose-hash-algs /= cose-alg-sha-512
suit-cose-hash-algs /= cose-alg-shake256

SUIT_Component_Identifier =  [* bstr]

SUIT_Common_Sequence = [
    + ( SUIT_Condition // SUIT_Common_Commands )
]

SUIT_Common_Commands //= (suit-directive-set-component-index,  IndexArg)
SUIT_Common_Commands //= (suit-directive-run-sequence,
    bstr .cbor SUIT_Command_Sequence)
SUIT_Common_Commands //= (suit-directive-try-each,
    SUIT_Directive_Try_Each_Argument)
SUIT_Common_Commands //= (suit-directive-override-parameters,
    {+ SUIT_Parameters})

IndexArg /= uint
IndexArg /= bool
IndexArg /= [+uint]

SUIT_Command_Sequence = [ + (
    SUIT_Condition // SUIT_Directive // SUIT_Command_Custom
) ]

SUIT_Command_Custom = (suit-command-custom, bstr/tstr/int/nil)
SUIT_Condition //= (suit-condition-vendor-identifier, SUIT_Rep_Policy)
SUIT_Condition //= (suit-condition-class-identifier,  SUIT_Rep_Policy)
SUIT_Condition //= (suit-condition-device-identifier, SUIT_Rep_Policy)
SUIT_Condition //= (suit-condition-image-match,       SUIT_Rep_Policy)
SUIT_Condition //= (suit-condition-component-slot,    SUIT_Rep_Policy)
SUIT_Condition //= (suit-condition-abort,             SUIT_Rep_Policy)

SUIT_Directive //= (suit-directive-set-component-index,  IndexArg)
SUIT_Directive //= (suit-directive-run-sequence,
    bstr .cbor SUIT_Command_Sequence)
SUIT_Directive //= (suit-directive-try-each,
    SUIT_Directive_Try_Each_Argument)
SUIT_Directive //= (suit-directive-process-dependency, SUIT_Rep_Policy)
SUIT_Directive //= (suit-directive-override-parameters,
    {+ SUIT_Parameters})
SUIT_Directive //= (suit-directive-fetch,             SUIT_Rep_Policy)
SUIT_Directive //= (suit-directive-copy,              SUIT_Rep_Policy)
SUIT_Directive //= (suit-directive-swap,              SUIT_Rep_Policy)
SUIT_Directive //= (suit-directive-run,               SUIT_Rep_Policy)

SUIT_Directive_Try_Each_Argument = [
    2* bstr .cbor SUIT_Command_Sequence,
    ?nil
]

SUIT_Rep_Policy = uint .bits suit-reporting-bits

suit-reporting-bits = &(
    suit-send-record-success : 0,
    suit-send-record-failure : 1,
    suit-send-sysinfo-success : 2,
    suit-send-sysinfo-failure : 3
)

SUIT_Parameters //= (suit-parameter-vendor-identifier =>
    (RFC4122_UUID / cbor-pen))
cbor-pen = #6.112(bstr)

SUIT_Parameters //= (suit-parameter-class-identifier => RFC4122_UUID)
SUIT_Parameters //= (suit-parameter-image-digest
    => bstr .cbor SUIT_Digest)
SUIT_Parameters //= (suit-parameter-image-size => uint)
SUIT_Parameters //= (suit-parameter-component-slot => uint)

SUIT_Parameters //= (suit-parameter-uri => tstr)
SUIT_Parameters //= (suit-parameter-source-component => uint)
SUIT_Parameters //= (suit-parameter-run-args => bstr)

SUIT_Parameters //= (suit-parameter-device-identifier => RFC4122_UUID)

SUIT_Parameters //= (suit-parameter-custom => int/bool/tstr/bstr)

SUIT_Parameters //= (suit-parameter-strict-order => bool)
SUIT_Parameters //= (suit-parameter-soft-failure => bool)

RFC4122_UUID = bstr .size 16

SUIT_Text_Map = {
    SUIT_Text_Keys,
    * SUIT_Component_Identifier => {
        SUIT_Text_Component_Keys
    }
}

SUIT_Text_Component_Keys = (
    ? suit-text-vendor-name           => tstr,
    ? suit-text-model-name            => tstr,
    ? suit-text-vendor-domain         => tstr,
    ? suit-text-model-info            => tstr,
    ? suit-text-component-description => tstr,
    ? suit-text-component-version     => tstr,
    * $$suit-text-component-key-extensions
)

SUIT_Text_Keys = (
    ? suit-text-manifest-description => tstr,
    ? suit-text-update-description   => tstr,
    ? suit-text-manifest-json-source => tstr,
    ? suit-text-manifest-yaml-source => tstr,
    * $$suit-text-key-extensions
)

suit-authentication-wrapper = 2
suit-manifest = 3

;REQUIRED to implement:
cose-alg-sha-256 = -16

;OPTIONAL to implement:
cose-alg-shake128 = -18
cose-alg-sha-384 = -43
cose-alg-sha-512 = -44
cose-alg-shake256 = -45

suit-manifest-version = 1
suit-manifest-sequence-number = 2
suit-common = 3
suit-reference-uri = 4
suit-payload-fetch = 8
suit-install = 9
suit-validate = 10
suit-load = 11
suit-run = 12
suit-text = 13

suit-components = 2
suit-common-sequence = 4

suit-command-custom = nint

suit-condition-vendor-identifier = 1
suit-condition-class-identifier  = 2
suit-condition-image-match       = 3
suit-condition-component-slot    = 5

suit-condition-abort                    = 14
suit-condition-device-identifier        = 24

suit-directive-set-component-index      = 12
suit-directive-try-each                 = 15
suit-directive-override-parameters      = 20
suit-directive-fetch                    = 21
suit-directive-copy                     = 22
suit-directive-run                      = 23

suit-directive-swap                     = 31
suit-directive-run-sequence             = 32

suit-parameter-vendor-identifier = 1
suit-parameter-class-identifier  = 2
suit-parameter-image-digest      = 3
suit-parameter-component-slot    = 5

suit-parameter-strict-order      = 12
suit-parameter-soft-failure      = 13
suit-parameter-image-size        = 14

suit-parameter-uri               = 21
suit-parameter-source-component  = 22
suit-parameter-run-args          = 23

suit-parameter-device-identifier = 24

suit-parameter-custom = nint

suit-text-manifest-description  = 1
suit-text-update-description    = 2
suit-text-manifest-json-source  = 3
suit-text-manifest-yaml-source  = 4

suit-text-vendor-name           = 1
suit-text-model-name            = 2
suit-text-vendor-domain         = 3
suit-text-model-info            = 4
suit-text-component-description = 5
suit-text-component-version     = 6

Appendix B. B. Examples

The following examples demonstrate a small subset of the functionality of the manifest. Even a simple manifest processor can execute most of these manifests.

The examples are signed using the following ECDSA secp256r1 key:

-----BEGIN PRIVATE KEY-----
MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgApZYjZCUGLM50VBC
CjYStX+09jGmnyJPrpDLTz/hiXOhRANCAASEloEarguqq9JhVxie7NomvqqL8Rtv
P+bitWWchdvArTsfKktsCYExwKNtrNHXi9OB3N+wnAUtszmR23M4tKiW
-----END PRIVATE KEY-----

The corresponding public key can be used to verify these examples:

-----BEGIN PUBLIC KEY-----
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEhJaBGq4LqqvSYVcYnuzaJr6qi/Eb
bz/m4rVlnIXbwK07HypLbAmBMcCjbazR14vTgdzfsJwFLbM5kdtzOLSolg==
-----END PUBLIC KEY-----

Each example uses SHA256 as the digest function.

Note that reporting policies are declared for each non-flow-control command in these examples. The reporting policies used in the examples are described in the following tables.

Table 12
Policy Label
suit-send-record-on-success Rec-Pass
suit-send-record-on-failure Rec-Fail
suit-send-sysinfo-success Sys-Pass
suit-send-sysinfo-failure Sys-Fail
Table 13
Command Sys-Fail Sys-Pass Rec-Fail Rec-Pass
suit-condition-vendor-identifier 1 1 1 1
suit-condition-class-identifier 1 1 1 1
suit-condition-image-match 1 1 1 1
suit-condition-component-slot 0 1 0 1
suit-directive-fetch 0 0 1 0
suit-directive-copy 0 0 1 0
suit-directive-run 0 0 1 0

B.1. Example 0: Secure Boot

This example covers the following templates:

It also serves as the minimum example.

107({
        / authentication-wrapper / 2:<<[
            digest: <<[
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'a6c4590ac53043a98e8c4106e1e31b305516d7cf0a655eddfac6d45c810e036a'
            ]>>,
            signature: <<18([
                    / protected / <<{
                        / alg / 1:-7 / "ES256" /,
                    }>>,
                    / unprotected / {
                    },
                    / payload / F6 / nil /,
                    / signature / h'd11a2dd9610fb62a707335f58407922570
9f96e8117e7eeed98a2f207d05c8ecfba1755208f6abea977b8a6efe3bc2ca3215e119
3be201467d052b42db6b7287'
                ])>>
            ]
        ]>>,
        / manifest / 3:<<{
            / manifest-version / 1:1,
            / manifest-sequence-number / 2:0,
            / common / 3:<<{
                / components / 2:[
                    [h'00']
                ],
                / common-sequence / 4:<<[
                    / directive-override-parameters / 20,{
                        / vendor-id /
1:h'fa6b4a53d5ad5fdfbe9de663e4d41ffe' / fa6b4a53-d5ad-5fdf-
be9d-e663e4d41ffe /,
                        / class-id /
2:h'1492af1425695e48bf429b2d51f2ab45' /
1492af14-2569-5e48-bf42-9b2d51f2ab45 /,
                        / image-digest / 3:<<[
                            / algorithm-id / -16 / "sha256" /,
                            / digest-bytes /
h'00112233445566778899aabbccddeeff0123456789abcdeffedcba9876543210'
                        ]>>,
                        / image-size / 14:34768,
                    } ,
                    / condition-vendor-identifier / 1,15 ,
                    / condition-class-identifier / 2,15
                ]>>,
            }>>,
            / validate / 10:<<[
                / condition-image-match / 3,15
            ]>>,
            / run / 12:<<[
                / directive-run / 23,2
            ]>>,
        }>>,
    })

Total size of Envelope without COSE authentication object: 161

Envelope:

d86ba2025827815824822f5820a6c4590ac53043a98e8c4106e1e31b3055
16d7cf0a655eddfac6d45c810e036a035871a50101020003585fa2028181
41000458568614a40150fa6b4a53d5ad5fdfbe9de663e4d41ffe02501492
af1425695e48bf429b2d51f2ab45035824822f5820001122334455667788
99aabbccddeeff0123456789abcdeffedcba98765432100e1987d0010f02
0f0a4382030f0c43821702

Total size of Envelope with COSE authentication object: 237

Envelope with COSE authentication object:

d86ba2025873825824822f5820a6c4590ac53043a98e8c4106e1e31b3055
16d7cf0a655eddfac6d45c810e036a584ad28443a10126a0f65840d11a2d
d9610fb62a707335f584079225709f96e8117e7eeed98a2f207d05c8ecfb
a1755208f6abea977b8a6efe3bc2ca3215e1193be201467d052b42db6b72
87035871a50101020003585fa202818141000458568614a40150fa6b4a53
d5ad5fdfbe9de663e4d41ffe02501492af1425695e48bf429b2d51f2ab45
035824822f582000112233445566778899aabbccddeeff0123456789abcd
effedcba98765432100e1987d0010f020f0a4382030f0c43821702

B.2. Example 1: Simultaneous Download and Installation of Payload

This example covers the following templates:

Simultaneous download and installation of payload. No secure boot is present in this example to demonstrate a download-only manifest.

107({
        / authentication-wrapper / 2:<<[
            digest: <<[
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'60c61d6eb7a1aaeddc49ce8157a55cff0821537eeee77a4ded44155b03045132'
            ]>>,
            signature: <<18([
                    / protected / <<{
                        / alg / 1:-7 / "ES256" /,
                    }>>,
                    / unprotected / {
                    },
                    / payload / F6 / nil /,
                    / signature / h'5249dacaf0ffc8326931b09586eb7e3769
e71a0e6a40ad8153db4980db9b05bd1742ddb46085fa11e62b65a79895c12ac7abe266
8ccc5afdd74466aed7bca389'
                ])>>
            ]
        ]>>,
        / manifest / 3:<<{
            / manifest-version / 1:1,
            / manifest-sequence-number / 2:1,
            / common / 3:<<{
                / components / 2:[
                    [h'00']
                ],
                / common-sequence / 4:<<[
                    / directive-override-parameters / 20,{
                        / vendor-id /
1:h'fa6b4a53d5ad5fdfbe9de663e4d41ffe' / fa6b4a53-d5ad-5fdf-
be9d-e663e4d41ffe /,
                        / class-id /
2:h'1492af1425695e48bf429b2d51f2ab45' /
1492af14-2569-5e48-bf42-9b2d51f2ab45 /,
                        / image-digest / 3:<<[
                            / algorithm-id / -16 / "sha256" /,
                            / digest-bytes /
h'00112233445566778899aabbccddeeff0123456789abcdeffedcba9876543210'
                        ]>>,
                        / image-size / 14:34768,
                    } ,
                    / condition-vendor-identifier / 1,15 ,
                    / condition-class-identifier / 2,15
                ]>>,
            }>>,
            / install / 9:<<[
                / directive-set-parameters / 19,{
                    / uri / 21:'http://example.com/file.bin',
                } ,
                / directive-fetch / 21,2 ,
                / condition-image-match / 3,15
            ]>>,
            / validate / 10:<<[
                / condition-image-match / 3,15
            ]>>,
        }>>,
    })

Total size of Envelope without COSE authentication object: 196

Envelope:

d86ba2025827815824822f582060c61d6eb7a1aaeddc49ce8157a55cff08
21537eeee77a4ded44155b03045132035894a50101020103585fa2028181
41000458568614a40150fa6b4a53d5ad5fdfbe9de663e4d41ffe02501492
af1425695e48bf429b2d51f2ab45035824822f5820001122334455667788
99aabbccddeeff0123456789abcdeffedcba98765432100e1987d0010f02
0f0958258613a115781b687474703a2f2f6578616d706c652e636f6d2f66
696c652e62696e1502030f0a4382030f

Total size of Envelope with COSE authentication object: 272

Envelope with COSE authentication object:
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B.3. Example 2: Simultaneous Download, Installation, Secure Boot, Severed Fields

This example covers the following templates:

This example also demonstrates severable elements (Section 5.4), and text (Section 8.4.4).

107({
        / authentication-wrapper / 2:<<[
            digest: <<[
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'e45dcdb2074b951f1c88b866469939c2a83ed433a31fc7dfcb3f63955bd943ec'
            ]>>,
            signature: <<18([
                    / protected / <<{
                        / alg / 1:-7 / "ES256" /,
                    }>>,
                    / unprotected / {
                    },
                    / payload / F6 / nil /,
                    / signature / h'b4fd3a6a18fe1062573488cf24ac96ef9f
30ac746696e50be96533b356b8156e4332587fe6f4e8743ae525d72005fddd4c1213d5
5a8061b2ce67b83640f4777c'
                ])>>
            ]
        ]>>,
        / manifest / 3:<<{
            / manifest-version / 1:1,
            / manifest-sequence-number / 2:2,
            / common / 3:<<{
                / components / 2:[
                    [h'00']
                ],
                / common-sequence / 4:<<[
                    / directive-override-parameters / 20,{
                        / vendor-id /
1:h'fa6b4a53d5ad5fdfbe9de663e4d41ffe' / fa6b4a53-d5ad-5fdf-
be9d-e663e4d41ffe /,
                        / class-id /
2:h'1492af1425695e48bf429b2d51f2ab45' /
1492af14-2569-5e48-bf42-9b2d51f2ab45 /,
                        / image-digest / 3:<<[
                            / algorithm-id / -16 / "sha256" /,
                            / digest-bytes /
h'00112233445566778899aabbccddeeff0123456789abcdeffedcba9876543210'
                        ]>>,
                        / image-size / 14:34768,
                    } ,
                    / condition-vendor-identifier / 1,15 ,
                    / condition-class-identifier / 2,15
                ]>>,
            }>>,
            / install / 9:[
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'3ee96dc79641970ae46b929ccf0b72ba9536dd846020dbdc9f949d84ea0e18d2'
            ],
            / validate / 10:<<[
                / condition-image-match / 3,15
            ]>>,
            / run / 12:<<[
                / directive-run / 23,2
            ]>>,
            / text / 13:[
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'2bfc4d0cc6680be7dd9f5ca30aa2bb5d1998145de33d54101b80e2ca49faf918'
            ],
        }>>,
        / install / 9:<<[
            / directive-set-parameters / 19,{
                / uri /
21:'http://example.com/very/long/path/to/file/file.bin',
            } ,
            / directive-fetch / 21,2 ,
            / condition-image-match / 3,15
        ]>>,
        / text / 13:<<{
            [h'00']:{
                    / vendor-domain / 3:'arm.com',
                    / component-description / 5:'This component is a
demonstration. The digest is a sample pattern, not a real one.',
                }
        }>>,
    })

Total size of the Envelope without COSE authentication object or Severable Elements: 235

Envelope:

d86ba2025827815824822f5820e45dcdb2074b951f1c88b866469939c2a8
3ed433a31fc7dfcb3f63955bd943ec0358bba70101020203585fa2028181
41000458568614a40150fa6b4a53d5ad5fdfbe9de663e4d41ffe02501492
af1425695e48bf429b2d51f2ab45035824822f5820001122334455667788
99aabbccddeeff0123456789abcdeffedcba98765432100e1987d0010f02
0f09822f58203ee96dc79641970ae46b929ccf0b72ba9536dd846020dbdc
9f949d84ea0e18d20a4382030f0c438217020d822f58202bfc4d0cc6680b
e7dd9f5ca30aa2bb5d1998145de33d54101b80e2ca49faf918

Total size of the Envelope with COSE authentication object but without Severable Elements: 311

Envelope:
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Total size of Envelope with COSE authentication object and Severable Elements: 894

Envelope with COSE authentication object:
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B.4. Example 3: A/B images

This example covers the following templates:

107({
        / authentication-wrapper / 2:<<[
            digest: <<[
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'7c9b3cb72c262608a42f944d59d659ff2b801c78af44def51b8ff51e9f45721b'
            ]>>,
            signature: <<18([
                    / protected / <<{
                        / alg / 1:-7 / "ES256" /,
                    }>>,
                    / unprotected / {
                    },
                    / payload / F6 / nil /,
                    / signature / h'e33d618df0ad21e609529ab1a876afb231
faff1d6a3189b5360324c2794250b87cf00cf83be50ea17dc721ca85393cd8e839a066
d5dec0ad87a903ab31ea9afa'
                ])>>
            ]
        ]>>,
        / manifest / 3:<<{
            / manifest-version / 1:1,
            / manifest-sequence-number / 2:3,
            / common / 3:<<{
                / components / 2:[
                    [h'00']
                ],
                / common-sequence / 4:<<[
                    / directive-override-parameters / 20,{
                        / vendor-id /
1:h'fa6b4a53d5ad5fdfbe9de663e4d41ffe' / fa6b4a53-d5ad-5fdf-
be9d-e663e4d41ffe /,
                        / class-id /
2:h'1492af1425695e48bf429b2d51f2ab45' /
1492af14-2569-5e48-bf42-9b2d51f2ab45 /,
                    } ,
                    / directive-try-each / 15,[
                        <<[
                            / directive-override-parameters / 20,{
                                / offset / 5:33792,
                            } ,
                            / condition-component-offset / 5,5 ,
                            / directive-override-parameters / 20,{
                                / image-digest / 3:<<[
                                    / algorithm-id / -16 / "sha256" /,
                                    / digest-bytes /
h'00112233445566778899aabbccddeeff0123456789abcdeffedcba9876543210'
                                ]>>,
                                / image-size / 14:34768,
                            }
                        ]>> ,
                        <<[
                            / directive-override-parameters / 20,{
                                / offset / 5:541696,
                            } ,
                            / condition-component-offset / 5,5 ,
                            / directive-override-parameters / 20,{
                                / image-digest / 3:<<[
                                    / algorithm-id / -16 / "sha256" /,
                                    / digest-bytes /
h'0123456789abcdeffedcba987654321000112233445566778899aabbccddeeff'
                                ]>>,
                                / image-size / 14:76834,
                            }
                        ]>>
                    ] ,
                    / condition-vendor-identifier / 1,15 ,
                    / condition-class-identifier / 2,15
                ]>>,
            }>>,
            / install / 9:<<[
                / directive-try-each / 15,[
                    <<[
                        / directive-set-parameters / 19,{
                            / offset / 5:33792,
                        } ,
                        / condition-component-offset / 5,5 ,
                        / directive-set-parameters / 19,{
                            / uri / 21:'http://example.com/file1.bin',
                        }
                    ]>> ,
                    <<[
                        / directive-set-parameters / 19,{
                            / offset / 5:541696,
                        } ,
                        / condition-component-offset / 5,5 ,
                        / directive-set-parameters / 19,{
                            / uri / 21:'http://example.com/file2.bin',
                        }
                    ]>>
                ] ,
                / directive-fetch / 21,2 ,
                / condition-image-match / 3,15
            ]>>,
            / validate / 10:<<[
                / condition-image-match / 3,15
            ]>>,
        }>>,
    })

Total size of Envelope without COSE authentication object: 332

Envelope:

d86ba2025827815824822f58207c9b3cb72c262608a42f944d59d659ff2b
801c78af44def51b8ff51e9f45721b0359011ba5010102030358aaa20281
8141000458a18814a20150fa6b4a53d5ad5fdfbe9de663e4d41ffe025014
92af1425695e48bf429b2d51f2ab450f8258368614a105198400050514a2
035824822f582000112233445566778899aabbccddeeff0123456789abcd
effedcba98765432100e1987d0583a8614a1051a00084400050514a20358
24822f58200123456789abcdeffedcba9876543210001122334455667788
99aabbccddeeff0e1a00012c22010f020f095861860f82582a8613a10519
8400050513a115781c687474703a2f2f6578616d706c652e636f6d2f6669
6c65312e62696e582c8613a1051a00084400050513a115781c687474703a
2f2f6578616d706c652e636f6d2f66696c65322e62696e1502030f0a4382
030f

Total size of Envelope with COSE authentication object: 408

Envelope with COSE authentication object:

d86ba2025873825824822f58207c9b3cb72c262608a42f944d59d659ff2b
801c78af44def51b8ff51e9f45721b584ad28443a10126a0f65840e33d61
8df0ad21e609529ab1a876afb231faff1d6a3189b5360324c2794250b87c
f00cf83be50ea17dc721ca85393cd8e839a066d5dec0ad87a903ab31ea9a
fa0359011ba5010102030358aaa202818141000458a18814a20150fa6b4a
53d5ad5fdfbe9de663e4d41ffe02501492af1425695e48bf429b2d51f2ab
450f8258368614a105198400050514a2035824822f582000112233445566
778899aabbccddeeff0123456789abcdeffedcba98765432100e1987d058
3a8614a1051a00084400050514a2035824822f58200123456789abcdeffe
dcba987654321000112233445566778899aabbccddeeff0e1a00012c2201
0f020f095861860f82582a8613a105198400050513a115781c687474703a
2f2f6578616d706c652e636f6d2f66696c65312e62696e582c8613a1051a
00084400050513a115781c687474703a2f2f6578616d706c652e636f6d2f
66696c65322e62696e1502030f0a4382030f

B.5. Example 4: Load from External Storage

This example covers the following templates:

107({
        / authentication-wrapper / 2:<<[
            digest: <<[
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'15736702a00f510805dcf89d6913a2cfb417ed414faa760f974d6755c68ba70a'
            ]>>,
            signature: <<18([
                    / protected / <<{
                        / alg / 1:-7 / "ES256" /,
                    }>>,
                    / unprotected / {
                    },
                    / payload / F6 / nil /,
                    / signature / h'3ada2532326d512132c388677798c24ffd
cc979bfae2a26b19c8c8bbf511fd7dd85f1501662c1a9e1976b759c4019bab44ba5434
efb45d3868aedbca593671f3'
                ])>>
            ]
        ]>>,
        / manifest / 3:<<{
            / manifest-version / 1:1,
            / manifest-sequence-number / 2:4,
            / common / 3:<<{
                / components / 2:[
                    [h'00'] ,
                    [h'02'] ,
                    [h'01']
                ],
                / common-sequence / 4:<<[
                    / directive-set-component-index / 12,0 ,
                    / directive-override-parameters / 20,{
                        / vendor-id /
1:h'fa6b4a53d5ad5fdfbe9de663e4d41ffe' / fa6b4a53-d5ad-5fdf-
be9d-e663e4d41ffe /,
                        / class-id /
2:h'1492af1425695e48bf429b2d51f2ab45' /
1492af14-2569-5e48-bf42-9b2d51f2ab45 /,
                        / image-digest / 3:<<[
                            / algorithm-id / -16 / "sha256" /,
                            / digest-bytes /
h'00112233445566778899aabbccddeeff0123456789abcdeffedcba9876543210'
                        ]>>,
                        / image-size / 14:34768,
                    } ,
                    / condition-vendor-identifier / 1,15 ,
                    / condition-class-identifier / 2,15
                ]>>,
            }>>,
            / payload-fetch / 8:<<[
                / directive-set-component-index / 12,1 ,
                / directive-set-parameters / 19,{
                    / uri / 21:'http://example.com/file.bin',
                } ,
                / directive-fetch / 21,2 ,
                / condition-image-match / 3,15
            ]>>,
            / install / 9:<<[
                / directive-set-component-index / 12,0 ,
                / directive-set-parameters / 19,{
                    / source-component / 22:1 / [h'02'] /,
                } ,
                / directive-copy / 22,2 ,
                / condition-image-match / 3,15
            ]>>,
            / validate / 10:<<[
                / directive-set-component-index / 12,0 ,
                / condition-image-match / 3,15
            ]>>,
            / load / 11:<<[
                / directive-set-component-index / 12,2 ,
                / directive-set-parameters / 19,{
                    / image-digest / 3:<<[
                        / algorithm-id / -16 / "sha256" /,
                        / digest-bytes /
h'0123456789abcdeffedcba987654321000112233445566778899aabbccddeeff'
                    ]>>,
                    / image-size / 14:76834,
                    / source-component / 22:0 / [h'00'] /,
                    / compression-info / 19:<<{
                        / compression-algorithm / 1:1 / "gzip" /,
                    }>>,
                } ,
                / directive-copy / 22,2 ,
                / condition-image-match / 3,15
            ]>>,
            / run / 12:<<[
                / directive-set-component-index / 12,2 ,
                / directive-run / 23,2
            ]>>,
        }>>,
    })

Total size of Envelope without COSE authentication object: 292

Envelope:
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Total size of Envelope with COSE authentication object: 368

Envelope with COSE authentication object:
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B.6. Example 5: Two Images

This example covers the following templates:

Furthermore, it shows using these templates with two images.

107({
        / authentication-wrapper / 2:<<[
            digest: <<[
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'd1e73f16e4126007bc4d804cd33b0209fbab34728e60ee8c00f3387126748dd2'
            ]>>,
            signature: <<18([
                    / protected / <<{
                        / alg / 1:-7 / "ES256" /,
                    }>>,
                    / unprotected / {
                    },
                    / payload / F6 / nil /,
                    / signature / h'b7ae0a46a28f02e25cda6d9a255bbaf863
30141831fae5a78012d648bc6cee55102e0f1890bdeacc3adaa4fae0560f83a45eecae
65cabce642f56d84ab97ef8d'
                ])>>
            ]
        ]>>,
        / manifest / 3:<<{
            / manifest-version / 1:1,
            / manifest-sequence-number / 2:5,
            / common / 3:<<{
                / components / 2:[
                    [h'00'] ,
                    [h'01']
                ],
                / common-sequence / 4:<<[
                    / directive-set-component-index / 12,0 ,
                    / directive-override-parameters / 20,{
                        / vendor-id /
1:h'fa6b4a53d5ad5fdfbe9de663e4d41ffe' / fa6b4a53-d5ad-5fdf-
be9d-e663e4d41ffe /,
                        / class-id /
2:h'1492af1425695e48bf429b2d51f2ab45' /
1492af14-2569-5e48-bf42-9b2d51f2ab45 /,
                        / image-digest / 3:<<[
                            / algorithm-id / -16 / "sha256" /,
                            / digest-bytes /
h'00112233445566778899aabbccddeeff0123456789abcdeffedcba9876543210'
                        ]>>,
                        / image-size / 14:34768,
                    } ,
                    / condition-vendor-identifier / 1,15 ,
                    / condition-class-identifier / 2,15 ,
                    / directive-set-component-index / 12,1 ,
                    / directive-override-parameters / 20,{
                        / image-digest / 3:<<[
                            / algorithm-id / -16 / "sha256" /,
                            / digest-bytes /
h'0123456789abcdeffedcba987654321000112233445566778899aabbccddeeff'
                        ]>>,
                        / image-size / 14:76834,
                    }
                ]>>,
            }>>,
            / install / 9:<<[
                / directive-set-component-index / 12,0 ,
                / directive-set-parameters / 19,{
                    / uri / 21:'http://example.com/file1.bin',
                } ,
                / directive-fetch / 21,2 ,
                / condition-image-match / 3,15 ,
                / directive-set-component-index / 12,1 ,
                / directive-set-parameters / 19,{
                    / uri / 21:'http://example.com/file2.bin',
                } ,
                / directive-fetch / 21,2 ,
                / condition-image-match / 3,15
            ]>>,
            / validate / 10:<<[
                / directive-set-component-index / 12,0 ,
                / condition-image-match / 3,15 ,
                / directive-set-component-index / 12,1 ,
                / condition-image-match / 3,15
            ]>>,
            / run / 12:<<[
                / directive-set-component-index / 12,0 ,
                / directive-run / 23,2
            ]>>,
        }>>,
    })

Total size of Envelope without COSE authentication object: 306

Envelope:

d86ba2025827815824822f5820d1e73f16e4126007bc4d804cd33b0209fb
ab34728e60ee8c00f3387126748dd203590101a601010205035895a20282
8141008141010458898c0c0014a40150fa6b4a53d5ad5fdfbe9de663e4d4
1ffe02501492af1425695e48bf429b2d51f2ab45035824822f5820001122
33445566778899aabbccddeeff0123456789abcdeffedcba98765432100e
1987d0010f020f0c0114a2035824822f58200123456789abcdeffedcba98
7654321000112233445566778899aabbccddeeff0e1a00012c2209584f90
0c0013a115781c687474703a2f2f6578616d706c652e636f6d2f66696c65
312e62696e1502030f0c0113a115781c687474703a2f2f6578616d706c65
2e636f6d2f66696c65322e62696e1502030f0a49880c00030f0c01030f0c
45840c001702

Total size of Envelope with COSE authentication object: 382

Envelope with COSE authentication object:

d86ba2025873825824822f5820d1e73f16e4126007bc4d804cd33b0209fb
ab34728e60ee8c00f3387126748dd2584ad28443a10126a0f65840b7ae0a
46a28f02e25cda6d9a255bbaf86330141831fae5a78012d648bc6cee5510
2e0f1890bdeacc3adaa4fae0560f83a45eecae65cabce642f56d84ab97ef
8d03590101a601010205035895a202828141008141010458898c0c0014a4
0150fa6b4a53d5ad5fdfbe9de663e4d41ffe02501492af1425695e48bf42
9b2d51f2ab45035824822f582000112233445566778899aabbccddeeff01
23456789abcdeffedcba98765432100e1987d0010f020f0c0114a2035824
822f58200123456789abcdeffedcba987654321000112233445566778899
aabbccddeeff0e1a00012c2209584f900c0013a115781c687474703a2f2f
6578616d706c652e636f6d2f66696c65312e62696e1502030f0c0113a115
781c687474703a2f2f6578616d706c652e636f6d2f66696c65322e62696e
1502030f0a49880c00030f0c01030f0c45840c001702

Appendix C. C. Design Rational

In order to provide flexible behavior to constrained devices, while still allowing more powerful devices to use their full capabilities, the SUIT manifest encodes the required behavior of a Recipient device. Behavior is encoded as a specialized byte code, contained in a CBOR list. This promotes a flat encoding, which simplifies the parser. The information encoded by this byte code closely matches the operations that a device will perform, which promotes ease of processing. The core operations used by most update and trusted invocation operations are represented in the byte code. The byte code can be extended by registering new operations.

The specialized byte code approach gives benefits equivalent to those provided by a scripting language or conventional byte code, with two substantial differences. First, the language is extremely high level, consisting of only the operations that a device may perform during update and trusted invocation of a firmware image. Second, the language specifies linear behavior, without reverse branches. Conditional processing is supported, and parallel and out-of-order processing may be performed by sufficiently capable devices.

By structuring the data in this way, the manifest processor becomes a very simple engine that uses a pull parser to interpret the manifest. This pull parser invokes a series of command handlers that evaluate a Condition or execute a Directive. Most data is structured in a highly regular pattern, which simplifies the parser.

The results of this allow a Recipient to implement a very small parser for constrained applications. If needed, such a parser also allows the Recipient to perform complex updates with reduced overhead. Conditional execution of commands allows a simple device to perform important decisions at validation-time.

Dependency handling is vastly simplified as well. Dependencies function like subroutines of the language. When a manifest has a dependency, it can invoke that dependency's commands and modify their behavior by setting parameters. Because some parameters come with security implications, the dependencies also have a mechanism to reject modifications to parameters on a fine-grained level.

Developing a robust permissions system works in this model too. The Recipient can use a simple ACL that is a table of Identities and Component Identifier permissions to ensure that operations on components fail unless they are permitted by the ACL. This table can be further refined with individual parameters and commands.

Capability reporting is similarly simplified. A Recipient can report the Commands, Parameters, Algorithms, and Component Identifiers that it supports. This is sufficiently precise for a manifest author to create a manifest that the Recipient can accept.

The simplicity of design in the Recipient due to all of these benefits allows even a highly constrained platform to use advanced update capabilities.

C.1. C.1 Design Rationale: Envelope

The Envelope is used instead of a COSE structure for several reasons:

  1. This enables the use of Severable Elements (Section 8.5)
  2. This enables modular processing of manifests, particularly with large signatures.
  3. This enables multiple authentication schemes.
  4. This allows integrity verification by a dependent to be unaffected by adding or removing authentication structures.

Modular processing is important because it allows a Manifest Processor to iterate forward over an Envelope, processing Delegation Chains and Authentication Blocks, retaining only intermediate values, without any need to seek forward and backwards in a stream until it gets to the Manifest itself. This allows the use of large, Post-Quantum signatures without requiring retention of the signature itself, or seeking forward and back.

Four authentication objects are supported by the Envelope:

  • COSE_Sign_Tagged
  • COSE_Sign1_Tagged
  • COSE_Mac_Tagged
  • COSE_Mac0_Tagged

The SUIT Envelope allows an Update Authority or intermediary to mix and match any number of different authentication blocks it wants without any concern for modifying the integrity of another authentication block. This also allows the addition or removal of an authentication blocks without changing the integrity check of the Manifest, which is important for dependency handling. See Section 6.2

C.2. C.2 Byte String Wrappers

Byte string wrappers are used in several places in the suit manifest. The primary reason for wrappers it to limit the parser extent when invoked at different times, with a possible loss of context.

The elements of the suit envelope are wrapped both to set the extents used by the parser and to simplify integrity checks by clearly defining the length of each element.

The common block is re-parsed in order to find components identifiers from their indices, to find dependency prefixes and digests from their identifiers, and to find the common sequence. The common sequence is wrapped so that it matches other sequences, simplifying the code path.

A severed SUIT command sequence will appear in the envelope, so it must be wrapped as with all envelope elements. For consistency, command sequences are also wrapped in the manifest. This also allows the parser to discern the difference between a command sequence and a SUIT_Digest.

Parameters that are structured types (arrays and maps) are also wrapped in a bstr. This is so that parser extents can be set correctly using only a reference to the beginning of the parameter. This enables a parser to store a simple list of references to parameters that can be retrieved when needed.

Appendix D. D. Implementation Conformance Matrix

This section summarizes the functionality a minimal manifest processor implementation needs to offer to claim conformance to this specification, in the absence of an application profile standard specifying otherwise.

The subsequent table shows the conditions.

Table 14
Name Reference Implementation
Vendor Identifier Section 8.4.8.2 REQUIRED
Class Identifier Section 8.4.8.2 REQUIRED
Device Identifier Section 8.4.8.2 OPTIONAL
Image Match Section 8.4.9.2 REQUIRED
Component Slot Section 8.4.9.3 OPTIONAL
Abort Section 8.4.9.4 OPTIONAL
Custom Condition Section 8.4.9.5 OPTIONAL

The subsequent table shows the directives.

Table 15
Name Reference Implementation
Set Component Index Section 8.4.10.1 REQUIRED if more than one component
Try Each Section 8.4.10.2 OPTIONAL
Override Parameters Section 8.4.10.3 REQUIRED
Fetch Section 8.4.10.4 REQUIRED for Updater
Copy Section 8.4.10.5 OPTIONAL
Run Section 8.4.10.6 REQUIRED for Bootloader
Run Sequence Section 8.4.10.7 OPTIONAL
Swap Section 8.4.10.8 OPTIONAL

The subsequent table shows the parameters.

Table 16
Name Reference Implementation
Vendor ID Section 8.4.8.3 REQUIRED
Class ID Section 8.4.8.4 REQUIRED
Image Digest Section 8.4.8.6 REQUIRED
Image Size Section 8.4.8.7 REQUIRED
Component Slot Section 8.4.8.8 OPTIONAL
URI Section 8.4.8.9 REQUIRED for Updater
Source Component Section 8.4.8.10 OPTIONAL
Run Args Section 8.4.8.11 OPTIONAL
Device ID Section 8.4.8.5 OPTIONAL
Strict Order Section 8.4.8.13 OPTIONAL
Soft Failure Section 8.4.8.14 OPTIONAL
Custom Section 8.4.8.15 OPTIONAL

Authors' Addresses

Brendan Moran
Arm Limited
Hannes Tschofenig
Arm Limited
Henk Birkholz
Fraunhofer SIT
Koen Zandberg
Inria

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