Arm Limited

Brendan.Moran@arm.com

Arm Limited

hannes.tschofenig@arm.com

Fraunhofer SIT

henk.birkholz@sit.fraunhofer.de

Inria

koen.zandberg@inria.fr

Security SUIT Internet-Draft This specification describes the format of a manifest. A manifest is a bundle of metadata about the firmware for an IoT device, where to find the firmware, the devices to which it applies, and cryptographic information protecting the manifest. Firmware updates and secure boot both tend to use sequences of common operations, so the manifest encodes those sequences of operations, rather than declaring the metadata. The manifest also serves as a building block for secure boot.

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 about the firmware for an IoT device, where to find the firmware, the devices to which it applies, and cryptographic information protecting the manifest. This specification defines the SUIT manifest format and it is intended to meet several goals: Meet the requirements defined in . Simple to parse on a constrained node Simple to process on a constrained node Compact encoding Comprehensible by an intermediate system Expressive enough to enable advanced use cases on advanced nodes Extensible The SUIT manifest can be used for a variety of purposes throughout its lifecycle, such as: the Firmware Author to reason about releasing a firmware. the Network Operator to reason about compatibility of a firmware. the Device Operator to reason about the impact of a firmware. the Device Operator to manage distribution of firmware to devices. the Plant Manager to reason about timing and acceptance of firmware updates. the device to reason about the authority & authenticity of a firmware prior to installation. the device to reason about the applicability of a firmware. the device to reason about the installation of a firmware. the device to reason about the authenticity & encoding of a firmware at boot. 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 and the threats, requirements, and user stories in . 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 secure boot are composed of a small group of operations: Copy some data from one place to another Transform some data Digest some data and compare to an expected value Compare some system parameters to an expected value Run some code In the SUIT manifest specification, 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 used language is tailored to software updates and secure boot. 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 secure boot use cases, there is nothing in the that restricts its use to only those use cases. Other use cases include the management of trusted applications in a Trusted Execution Environment (TEE), see .

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 when, and only when, they appear in all capitals, as shown here. The following terminology is used throughout this document: SUIT: Software Update for the Internet of Things, also the IETF working group for this standard. Payload: A piece of information to be delivered. Typically Firmware for the purposes of SUIT. Resource: A piece of information that is used to construct a payload. Manifest: A manifest is a bundle of metadata about the firmware for an IoT device, where to find the firmware, and the devices to which it applies. Envelope: A container with the manifest, an authentication wrapper with cryptographic information protecting the manifest, authorization information, and severed fields. Update: One or more manifests that describe one or more payloads. Update Authority: The owner of a cryptographic key used to sign updates, trusted by Recipients. Recipient: The system, typically an IoT device, that receives and processes a manifest. Manifest Processor: A component of the Recipient that consumes Manifests and executes the commands in the Manifest. Component: An updatable logical block of the Firmware, Software, configuration, or data of the Recipient. Component Set: A group of interdependent Components that must be updated simultaneously. Command: A Condition or a Directive. Condition: A test for a property of the Recipient or its Components. Directive: An action for the Recipient to perform. Trusted Execution: A process by which a system ensures that only trusted code is executed, for example secure boot. A/B images: Dividing a Recipient’s storage into two or more bootable images, at different offsets, such that the active image can write to the inactive image(s). Record: The result of a Command and any metadata about it. Report: A list of Records. Procedure: The process of invoking one or more sequences of commands. Update Procedure: A procedure that updates a Recipient by fetching dependencies, software images, and installing them. Boot Procedure: A procedure that boots a Recipient by verifying dependencies and images, loading images, and invoking one or more image. Software: Instructions and data that allow a Recipient to perform a useful function. Firmware: Instructions and data that allow a Recipient to perform a useful function. Typically, changed infrequently, stored in nonvolatile memory, and small enough to apply to Class 0-2 devices. Image: Information that a Recipient uses to perform its function, typically firmware/software, configuration, or resource data such as text or images. Also, a Payload, once installed is an Image. Slot: One of several possible storage locations for a given Component, typically used in A/B image systems Abort: The Manifest Processor immediately halts execution of the current Procedure. It creates a Record of an error condition.

This specification covers five aspects of firmware update: describes the device constraints, use cases, and design principles that informed the structure of the manifest. gives a general overview of the metadata structure to inform the following sections describes what actions a Manifest processor should take. describes the process of creating a Manifest. specifies the content of the Envelope and the Manifest. To implement an updatable device, see and . To implement a tool that generates updates, see and . The IANA consideration section, see , 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 , examples are given in and a design rational is offered in . Finally, gives a summarize of the mandatory-to-implement features of this specification.

Distributing firmware 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 . The security aspects are described in .

The various constraints of IoT devices and the range of use cases that need to be supported create a broad set of urequirements. 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 delivery 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.

There are several fundamental assumptions that inform the model of Update Procedure workflow: Compatibility must be checked before any other operation is performed. All dependency manifests should be present before any payload is fetched. In some applications, payloads must be fetched and validated prior to installation. There are several fundamental assumptions that inform the model of the Boot Procedure workflow: Compatibility must be checked before any other operation is performed. All dependencies and 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: Verify the signature of the manifest. Verify the applicability of the manifest. Resolve dependencies. Fetch payload(s). Install payload(s). When installation is complete, similar information can be used for validating and running images in a further three steps: Verify image(s). Load image(s). 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 MAC, to the manifest in order to prevent further verifications. When multiple manifests are used for an update, each manifest’s steps occur in a lockstep fashion; all manifests have dependency resolution performed before any manifest performs a payload fetch, etc.

This section provides a high level overview of the manifest structure. The full description of the manifest structure is in The manifest is structured from several key components: The Envelope (see ) contains Delegation Chains, the Authentication Block, the Manifest, any Severable Elements, and any Integrated Payloads or Dependencies. Delegation Chains (see ) allow a Recipient to work from one of its Trust Anchors to an authority of the Authentication Block. The Authentication Block (see ) contains a list of signatures or MACs of the manifest.. The Manifest (see ) contains all critical, non-severable metadata that the Recipient requires. It is further broken down into: Critical metadata, such as sequence number. Common metadata, including lists of dependencies and affected components. Command sequences, directing the Recipient how to install and use the payload(s). Integrity check values for severable fields. Severable fields (see ). Integrated dependencies (see ). Integrated payloads (see ). The diagram below illustrates the hierarchy of the Envelope.

+------------------------------+ | Severable Elements | | Manifest | | Human-Readable Text | +------------------------------+ | COSWID | | Structure Version | | Integrated Dependencies | | Sequence Number | | Integrated Payloads | | Reference to Full Manifest | +-------------------------+ +------ Common Structure | | +---- Commands | +-----------------------+ | | | Digests of Envelope Elements | | Common Structure | <--+ | +------------------------------+ +-----------------------+ | | Dependencies | +-> +-----------------------+ | Components IDs | | Commands | | Common Commands ---------------> +-----------------------+ +-----------------------+ | List of ( pairs of ( | | * command code | | * argument | | )) | +-----------------------+ ]]>

The SUIT Envelope is a container that encloses Delegation Chains, the Authentication Block, the Manifest, any Severable Elements, and any integrated payloads or dependencies. 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 for a description of the reasoning for this. See for more detail.

Delegation Chains allow a Recipient to validate intermediate Update Authorities against long-term a Trust Anchor. These are lists of CWTs, where the first in the list is signed by a Trust Anchor. See for more detail.

The Authentication Block contains one or more COSE authentication blocks. These blocks are one of: COSE_Sign_Tagged COSE_Sign1_Tagged COSE_Mac_Tagged COSE_Mac0_Tagged The payload element in each of these COSE elements is a SUIT_Digest . See for more detail.

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 for more detail.

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

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 three parts: a list of dependencies, 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 , for more detail.

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 ), update commands, and secure boot commands. Update Command Sequences are: Dependency Resolution, Payload Fetch, and Payload Installation. An Update Procedure is the complete set of each Update Command Sequence, each preceded by the Common Command Sequence. Boot Command Sequences are: System Validation, Image Loading, and Image Invocation. A Boot Procedure is the complete set of each Boot 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. See for more detail.

To enable , 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, CoSWID, or Text data. Integrated Dependencies and Integrated Payloads are integrity-checked using Command Sequences, so they do not have Integrity Check Values present in the Manifest. See for more detail.

Text is typically a Severable Element. 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 for more detail.

Severable Elements are elements of the Envelope that have Integrity Check Values in the Manifest. 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 and CoSWID 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 for more detail.

In some cases, it is beneficial to include a dependency or 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 requires encryption, it must be referenced as a dependency, so a trivial manifest may be used to enclose the encrypted manifest. The encrypted manifest may be contained in the dependent manifest’s envelope. When a manifest transports a small payload, such as an encrypted key, that payload may be placed in the manifest’s envelope. See , for more detail.

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

Prior to executing any command sequence, the interpreter or its host application MUST inspect the manifest version field and fail when it encounters an unsupported encoding version. Next, the interpreter 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 interpreter 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. 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 ID encountered. Payload not available. Dependency not available. Application crashed when executed. Watchdog timeout occurred. Dependency or Payload verification failed. Missing component from a set. These failure reasons MAY be combined with retry mechanisms prior to marking a manifest as invalid. Following these initial tests, the interpreter clears all parameter storage. This ensures that the interpreter begins without any leaked data.

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 interpreter MAY use an ACL (see ) to determine the extent of the rights conferred by that authenticity. Where a device supports only one level of access, it MAY choose to skip signature verification of dependencies, since they are referenced by digest. Where a device supports more than one trusted party, it MAY choose to defer the verification of signatures of dependencies until the list of affected components is known so that it can skip redundant signature verifications. For example, a dependency signed by the same author as the dependent does not require a signature verification. Similarly, if the signer of the dependent has full rights to the device, according to the ACL, then no signature verification is necessary on the dependency. Once a valid, authentic manifest has been selected, the interpreter MUST examine the component list and verify that its maximum number of components is not exceeded and that each listed component ID is supported. For each listed component, the interpreter MUST provide storage for the supported parameters. If the interpreter does not have sufficient temporary storage to process the parameters for all components, it MAY process components serially for each command sequence. See for more details. The interpreter SHOULD check that the common section contains at least one vendor ID check and at least one class ID check. If the manifest contains more than one component, each command sequence MUST begin with a Set Current Component command. If a dependency is specified, then the interpreter MUST perform the following checks: At the beginning of each section in the dependent: all previous sections of each dependency have been executed. At the end of each section in the dependent: The corresponding section in each dependency has been executed. If the interpreter does not support dependencies and a manifest specifies a dependency, then the interpreter MUST reject the manifest. If a Recipient supports groups of interdependent components (a Component Set), then it SHOULD require that all Components in the Component Set are specified by one manifest and its dependencies. This manifest is called the Root Manifest.

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 can receive many incompatible or inapplicable manifests, and The Recipient has a power budget that makes signature verification undesirable The guidelines in Creating Manifests 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, 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. When executing Common prior to authenticity validation, the Manifest Processor MUST evaluate the integrity of the manifest using the SUIT_Digest present in the authentication block. Alternatively, a Recipient MAY rely on network infrastructure to filter inapplicable manifests.

The interpreter has a small set of design goals: Executing an update MUST either result in an error, or a verifiably correct system state. Executing a secure boot MUST either result in an error, or a booted system. 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.

The heart of the manifest is the list of commands, which are processed by an interpreter. This interpreter 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 or dependency. A dependency is another SUIT_Envelope that describes additional components. Dependencies are identified by digest, but referenced in commands by Dependency Index, the index into the array of Dependencies. A component is a unit of code or data that can be targeted by an update. Components are identified by Component Identifiers, i.e. arrays of binary strings, but referenced in commands by Component Index, the 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 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. The following table describes the behavior of each command. “params” represents the parameters for the current component or dependency. Most commands operate on either a component or a dependency. Setting the Component Index clears the Dependency Index. Setting the Dependency Index clears the Component Index. 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 k,v in arg Set Dependency Index current := dependencies[arg] Set Parameters current.params[k] := v if not k in params for k,v in arg Process Dependency exec(current[common]); exec(current[current-segment]) Run run(current) Fetch store(current, fetch(current.params[uri])) Use Before assert(now() < arg) Check Component Offset assert(offsetof(current) == arg) Check Device Identifier assert(binary-match(current, current.params[device-id])) Check Image Not Match assert(not binary-match(digest(current), current.params[digest])) Check Minimum Battery assert(battery >= arg) Check Update Authorized assert(isAuthorized()) Check Version assert(version_check(current, arg)) Abort assert(0) Try Each break 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]) Wait For Event until event(arg), wait Run Sequence exec(arg) Run with Arguments run(current, arg)

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.

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 fork a process for each command until the Strict Order parameter is returned to True or the Command Sequence ends. Then, it joins all forked processes 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. Under each of these scenarios the parallel processing must halt: Set Parameters. Override Parameters. Set Strict Order = True. Set Dependency Index. Set Component Index. To perform more useful parallel operations, sequences of commands may be collected in a suit-directive-run-sequence. 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. The interpreter MUST track each Set Component Index directive, and cause an Abort if more than one Set Component Index directive targets the same Component Index. When Strict Order = False, each suit-directive-run-sequence MUST begin with a Set Component Index directive. Any further Set Component Index directives MUST cause an Abort. This allows the interpreter that forks suit-directive-run-sequence processes to check that the first element is correct, then fork a process to handle the remainder of the sequence.

As described in , each manifest must invoke each of its dependencies sections from the corresponding section of the dependent. Any changes made to parameters by the dependency persist in the dependent. When a Process Dependency command is encountered, the interpreter loads the dependency identified by the Current Dependency Index. The interpreter first executes the common-sequence section of the identified dependency, then it executes the section of the dependency that corresponds to the currently executing section of the dependent. The interpreter also performs the checks described in to ensure that the dependent is processing the dependency correctly.

When a system has multiple security domains they MAY require independent verification of authenticity or security policies. Security domains may be divided by separation technology such as Arm TrustZone, or Intel SGX. Security domains may also be divided into separate processors and memory spaces, with a communication interface between them. For example, an application processor may have an attached communications module that contains a processor. The communications module may require metadata signed by a specific Trust Authority for regulatory approval. This may be a different Trust Authority than the application processor. When there are two or more security domains, a manifest processor MAY be required in each. The first manifest processor is the normal manifest processor as described for the Recipient in Abstract Machine. The second manifest processor only executes sections when the first manifest processor requests it. An API interface is provided from the second manifest processor to the first. This allows the first manifest processor to request a limited set of operations from the second. These operations are limited to: setting parameters, inserting an Envelope, invoking a Manifest Command Sequence. The second manifest processor declares a prefix to the first, which tells the first manifest processor when it should delegate to the second. These rules are enforced by underlying separation of privilege infrastructure, such as TEEs, or physical separation. When the first manifest processor encounters a dependency prefix, that informs the first manifest processor that it should provide the second manifest processor with the corresponding dependency Envelope. This is done when the dependency is fetched. The second manifest processor immediately verifies any authentication information in the dependency Envelope. When a parameter is set for any component that matches the prefix, this parameter setting is passed to the second manifest processor via an API. As the first manifest processor works through the Procedure (set of command sequences) it is executing, each time it sees a Process Dependency command that is associated with the prefix declared by the second manifest processor, it uses the API to ask the second manifest processor to invoke that dependency section instead.

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 . 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. NOTE: On systems that support only a single component, Set Current Component has no effect and can be omitted. NOTE: A digest MUST always be set using Override Parameters, since this prevents a less-privileged dependent from replacing the digest.

The compatibility check ensures that Recipients only install compatible images. In this template all information is contained in the common block and the following sequence of operations are used: Set Component Index directive (see ) Set Parameters directive (see ) for Vendor ID and Class ID (see ) Check Vendor Identifier condition (see ) Check Class Identifier condication (see )

This template performs a secure boot operation. The following operations are placed into the common block: Set Component Index directive (see ) Override Parameters directive (see ) for Image Digest and Image Size (see ) Then, the run block contains the following operations: Set Component Index directive (see ) Check Image Match condition (see ) Run directive (see ) According to , the Run directive applies to the component referenced by the current Component Index. Hence, the Set Component Index directive has to be used to target a specific component.

This template triggers the download of firmware. The following operations are placed into the common block: Set Component Index directive (see ) Override Parameters directive (see ) for Image Digest and Image Size (see ) Then, the install block contains the following operations: Set Component Index directive (see ) Set Parameters directive (see ) for URI (see ) Fetch directive (see ) Check Image Match condition (see ) 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.

This template modifies the Firmware Download template and adds an additional sequence. The Firmware Download operations are moved from the Payload Install sequence to the Payload Fetch sequence. Then, the Install sequence contains the following operations: Set Component Index directive (see ) Set Parameters directive (see ) for Source Component (see ) Copy directive (see ) Check Image Match condition (see )

This template triggers the installation of a payload included in the manifest envelope. It is identical to except that it places an added restriction on the URI passed to the Set Parameters directive. An implementor MAY choose to place a payload in the envelope of a manifest. The payload envelope key MAY be a positive or negative integer. The payload envelope key MUST NOT be a value between 0 and 24 and it MUST NOT be used by any other envelope element in the manifest. The payload MUST be serialized in a bstr element. The URI for a payload enclosed in this way MUST be expressed as a fragment-only reference, as defined in , Section 4.4. The fragment identifier is the stringified envelope key of the payload. For example, an envelope that contains a payload a key 42 would use a URI “#42”, key -73 would use a URI “#-73”.

This directive loads an firmware image from external storage. The following operations are placed into the load block: Set Component Index directive (see ) Set Parameters directive (see ) for Component Index (see ) Copy directive (see ) As outlined in , 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.

The following operations are placed into the load block: Set Component Index directive (see ) Set Parameters directive (see ) for Source Component Index and Compression Info (see ) Copy directive (see ) This template is similar to but additionally performs decompression. Hence, the only difference is in setting the Compression Info parameter.

The following operations are placed into the dependency resolution block: Set Dependency Index directive (see ) Set Parameters directive (see ) for URI (see ) Fetch directive (see ) Check Image Match condition (see ) Process Dependency directive (see ) Then, the validate block contains the following operations: Set Dependency Index directive (see ) Check Image Match condition (see ) Process Dependency directive (see ) NOTE: Any changes made to parameters in a dependency persist in the dependent.

An implementor MAY choose to place a dependency’s envelope in the envelope of its dependent. The dependent envelope key for the dependency envelope MUST NOT be a value between 0 and 24 and it MUST NOT be used by any other envelope element in the dependent manifest. The URI for a dependency enclosed in this way MUST be expressed as a fragment-only reference, as defined in , Section 4.4. The fragment identifier is the stringified envelope key of the dependency. For example, an envelope that contains a dependency at key 42 would use a URI “#42”, key -73 would use a URI “#-73”.

To use an encrypted manifest, create a plaintext dependent, and add the encrypted manifest as a dependency. The dependent can include very little information. The following operations are placed into the dependency resolution block: Set Dependency Index directive (see ) Set Parameters directive (see ) for URI (see ) Encryption Info (see ) Fetch directive (see ) Check Image Match condition (see ) Process Dependency directive (see ) Then, the validate block contains the following operations: Set Dependency Index directive (see ) Check Image Match condition (see ) Process Dependency directive (see ) A plaintext manifest and its encrypted dependency may also form a composite manifest.

The following operations are placed in the common block: Set Component Index directive (see ) Try Each First Sequence: Override Parameters directive (see , ) for Offset A Check Offset Condition (see ) Override Parameters directive (see ) for Image Digest A and Image Size A (see ) Second Sequence: Override Parameters directive (see , ) for Offset B Check Offset Condition (see ) Override Parameters directive (see ) for Image Digest B and Image Size B (see ) The following operations are placed in the fetch block or install block Set Component Index directive (see ) Try Each First Sequence: Override Parameters directive (see , ) for Offset A Check Offset Condition (see ) Set Parameters directive (see ) for URI A (see ) Second Sequence: Override Parameters directive (see , ) for Offset B Check Offset Condition (see ) Set Parameters directive (see ) for URI B (see ) Fetch

The metadata for SUIT updates is composed of several primary constituent parts: the Envelope, Delegation Chains, Authentication Information, Manifest, and Severable Elements. For a diagram of the metadata structure, see .

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 uninitialised variables. Positive numbers in enumerations are reserved for IANA registration. Negative numbers are used to identify application-specific implementations. 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.

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.

The suit-delegation field MAY carry one or more CBOR Web Tokens (CWTs) , with cnf claims. They can be used to perform enhanced authorization decisions. The CWTs are arranged into a list of lists. Each list starts with CWT authorized by a Trust Anchor, and finishes with a key used to authenticate the Manifest (see ). This allows an Update Authority to delegate from a long term Trust Anchor, down through intermediaries, to a delegate without any out-of-band updates Trust Anchors. A Recipient MAY choose to cache intermediaries and/or delegates. If an Update Distributor knows that a targeted Recipient has cached some intermediaries or delegates, it MAY choose to strip any cached intermediaries or delegates from the Delegation Chains in order to reduce bandwidth and energy.

The suit-authentication-wrapper contains a list of one or more cryptographic authentication wrappers for the Manifest. These are implemented as COSE_Mac_Tagged or COSE_Sign_Tagged blocks. Each of these blocks contains a SUIT_Digest of the Manifest. This enables modular processing of the manifest. The COSE_Mac_Tagged and COSE_Sign_Tagged blocks are described in RFC 8152 . The suit-authentication-wrapper MUST come before any element in the SUIT_Envelope, except for the OPTIONAL suit-delegation, regardless of canonical encoding of CBOR. All validators MUST reject any SUIT_Envelope that begins with any element other than a suit-authentication-wrapper or suit-delegation. A SUIT_Envelope that has not had authentication information added MUST still contain the suit-authentication-wrapper element, but the content MUST be an empty list.

To use an encrypted manifest, it must be a dependency of a plaintext manifest. This allows fine-grained control of what information is accessible to intermediate systems for the purposes of management, while still preserving the confidentiality of the manifest contents. This also means that a Recipient can process an encrypted manifest in the same way as an encrypted payload, allowing code reuse. A template for using an encrypted manifest is covered in Encrypted Manifest Template.

The manifest contains: a version number (see ) a sequence number (see ) a reference URI (see ) a common structure with information that is shared between command sequences (see ) one or more lists of commands that the Recipient should perform (see ) a reference to the full manifest (see ) human-readable text describing the manifest found in the SUIT_Envelope (see ) a Concise Software Identifier found in the SUIT_Envelope (see ) The CoSWID, Text section, or any Command Sequence of the Update Procedure (Dependency Resolution, 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 field. Severable fields 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 for more detail.

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.

The suit-manifest-sequence-number is a monotonically increasing anti-rollback counter. It also helps Recipients to determine which in a set of manifests is the “root” manifest in a given update. Each manifest MUST have a sequence number higher than each of its dependencies. Each Recipient MUST reject any manifest that has a sequence number lower than its current sequence number. It MAY be convenient to use a UTC timestamp in seconds as the sequence number. suit-manifest-sequence-number is REQUIRED to implement.

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.

suit-text SHOULD be a severable element. suit-text is a map of pairs. It MAY contain two different types of pair: integer => text mappings SUIT_Component_Identifier => map mappings 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 or the suit-common of a dependency. 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: 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-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. 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 text version number suit-text-version-required A text expression of the required version number suit-text is OPTIONAL to implement.

suit-text-version-required is used to represent a version-based dependency on suit-parameter-version as described in and . To describe a version dependency, a Manifest Author should populate the suit-text map with a SUIT_Component_Identifier key for the dependency component, and place in the corresponding map a suit-text-version-required key with a text expression that is representative of the version constraints placed on the dependency. For example, to express a dependency on a component “[‘x’, ‘y’]”, where the version should be any v1.x later than v1.2.5, but not v2.0 or above, the author would add the following structure to the suit-text element. Note that this text is in cbor-diag notation. [h'78',h'79'] : { 7 : ">=1.2.5,<2" }

suit-coswid contains a Concise Software Identifier. This element SHOULD be made severable so that it can be discarded by the Recipient or an intermediary if it is not required by the Recipient. suit-coswid is OPTIONAL to implement.

suit-common encodes all the information that is shared between each of the command sequences, including: suit-dependencies, suit-components, and suit-common-sequence. suit-common is REQUIRED to implement. suit-dependencies is a list of blocks that specify manifests that must be present before the current manifest can be processed. suit-dependencies is OPTIONAL to implement. suit-components is a list of SUIT_Component_Identifier blocks that specify the component identifiers that will be affected by the content of the current manifest. suit-components is REQUIRED to implement; at least one manifest in a dependency tree MUST contain a suit-components block. 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 and for more information on conditional sequences). suit-common-sequence is RECOMMENDED to implement. It is REQUIRED if the optimizations described in will be used. Whenever a parameter or try-each is required by more than one Command Sequence, suit-common-sequence results in a smaller encoding.

SUIT_Dependency specifies a manifest that describes a dependency of the current manifest. The Manifest is identified, however the Recipient should expect an Envelope when it acquires the dependency. This is because the Manifest is the one invariant element of the Envelope, where other elements may change by countersigning, adding authentication blocks, or severing elements. The suit-dependency-digest specifies the dependency manifest uniquely by identifying a particular Manifest structure. This is identical to the digest that would be present as the payload of any suit-authentication-block in the dependency’s Envelope. The digest is calculated over the Manifest structure instead of the COSE Sig_structure or Mac_structure. This is necessary to ensure that removing a signature from a manifest does not break dependencies due to missing signature elements. This is also necessary to support the trusted intermediary use case, where an intermediary re-signs the Manifest, removing the original signature, potentially with a different algorithm, or trading COSE_Sign for COSE_Mac. The suit-dependency-prefix element contains a SUIT_Component_Identifier (see ). This specifies the scope at which the dependency operates. This allows the dependency to be forwarded on to a component that is capable of parsing its own manifests. It also allows one manifest to be deployed to multiple dependent Recipients without those Recipients needing consistent component hierarchy. This element is OPTIONAL. A dependency prefix can be used with a component identifier. This allows complex systems to understand where dependencies need to be applied. The dependency prefix can be used in one of two ways. The first simply prepends the prefix to all Component Identifiers in the dependency. A dependency prefix can also be used to indicate when a dependency manifest needs to be processed by a secondary manifest processor, as described in .

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. A dependency MAY declare a prefix to the components defined in the dependency manifest. Components are identified by Component Identifiers, i.e. arrays of binary strings, but referenced in commands 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.

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: Dependency Resolution: suit-dependency-resolution is a SUIT_Command_Sequence to execute in order to perform dependency resolution. Typical actions include configuring URIs of dependency manifests, fetching dependency manifests, and validating dependency manifests’ contents. suit-dependency-resolution is REQUIRED to implement and to use when suit-dependencies is present. 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. 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. 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 and manifest validation. suit-validate is REQUIRED to implement. If the manifest contains dependencies, one process-dependency invocation per dependency or one process-dependency invocation targeting all dependencies SHOULD be present in validate. 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. 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: either the “run” directive for the bootable manifest or the “process dependencies” directive for any dependents of the bootable manifest. suit-run is OPTIONAL to implement. Only one manifest in an update may contain the “run” directive. Goals 1,2,3 form the Update Procedure. Goals 4,5,6 form the Boot 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: Conditions that MUST be true–any failure is treated as a failure of the update/load/boot Directives that MUST be executed. Each condition is a command code identifier, followed by a SUIT_Reporting_Policy. Each directive is composed of: A command code identifier An argument block or a reporting policy Argument blocks are consumed only by flow-control directives: Set Component/Dependency Index Set/Override Parameters Try Each Run Sequence Reporting policies provide a hint to the manifest processor of whether or not 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 with a matching command to set the current dependency index. This index is a numeric index into the component ID tables defined at the beginning of the document. For the purpose of setting the index, the two component ID tables are considered to be concatenated together. To facilitate optional conditions, a special directive, , 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/boot, but a parameter is provided to override this behavior. See .

TODO: Records, bitfield 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. 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. SUIT does NOT REQUIRE a particular format of Records or Reports. SUIT only defines hints to the Reporting engine for which Records it should aggregate into the Report. An OPTIONAL Record format, SUIT_Record is defined in . It is encoded as a map, with the following elements. Element Description suit-record-success The boolean or integer success or failure code of the command. suit-record-component-id The current component when the record was generated. suit-record-dependency-id The current dependency digest when the record was generated. suit-record-command-sequence-id The label of the Command Sequence that was executing when the record was generated. suit-record-command-id The label of the command that was in progress when the record was generated. suit-record-params The set of parameters that was consumed by the current command. suit-record-actual The value against which a suit-condition compared a parameter. In Secure Boot operations, the Reporting engine MAY aggregate the Records produced in a Procedure into the evidence used for an attestation report.

Many conditions and directives require additional information. That information is contained within parameters that can be set in a consistent way. This allows reduction of manifest size and replacement of parameters from one manifest to the next. 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. Name CDDL Structure Reference Vendor ID suit-parameter-vendor-identifier Class ID suit-parameter-class-identifier Image Digest suit-parameter-image-digest Image Size suit-parameter-image-size Use Before suit-parameter-use-before Component Offset suit-parameter-component-offset Encryption Info suit-parameter-encryption-info Compression Info suit-parameter-compression-info Unpack Info suit-parameter-unpack-info URI suit-parameter-uri Source Component suit-parameter-source-component Run Args suit-parameter-run-args Device ID suit-parameter-device-identifier Minimum Battery suit-parameter-minimum-battery Update Priority suit-parameter-update-priority Version suit-parameter-version Wait Info suit-parameter-wait-info URI List suit-parameter-uri-list Fetch Arguments suit-parameter-fetch-arguments Strict Order suit-parameter-strict-order Soft Failure suit-parameter-soft-failure Custom suit-parameter-custom 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

Several conditions use identifiers to determine whether a manifest matches a given Recipient or not. These identifiers are defined to be RFC 4122 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. 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: Hardware model/revision OS WiFi module model/revision 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 . 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) The RECOMMENDED method to create a class ID is: Class ID = UUID5(Vendor ID, Class-Specific-Information) Class-specific information is composed of a variety of data, for example: Model number. Hardware revision. Bootloader version (for immutable bootloaders).

A RFC 4122 UUID representing the vendor 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

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

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

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

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

An expiry date for the use of the manifest encoded as a POSIX timestamp; a positive integer. Implementations that use this parameter MUST use a 64-bit internal representation of the integer.

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

Encryption Info defines the mechanism that Fetch or Copy should use to decrypt the data they transfer. SUIT_Parameter_Encryption_Info is encoded as a COSE_Encrypt_Tagged or a COSE_Encrypt0_Tagged, wrapped in a bstr.

Compression Info defines any information that is required for a Recipient to perform decompression operations. Typically, this includes the algorithm identifier. This document defines the use of ZLIB , Brotli , and ZSTD . Additional compression formats can be registered through the IANA-maintained registry.

SUIT_Unpack_Info defines the information required for a Recipient to interpret a packed format. This document defines the use of the following binary encodings: Intel HEX , Motorola S-record , Executable and Linkable Format (ELF) , and Common Object File Format (COFF) . Additional packing formats can be registered through the IANA-maintained registry.

A URI from which to fetch a resource.

This parameter sets the source component to be used with either or with . The current Component, as set by suit-directive-set-component-index defines the destination, and suit-parameter-source-component defines the source.

This parameter contains an encoded set of arguments for . The arguments MUST be provided as an implementation-defined bstr.

This parameter sets the minimum battery level in mWh. This parameter is encoded as a positive integer. Used with .

This parameter sets the priority of the update. This parameter is encoded as an integer. It is used along with suit-condition-update-authorized to ask an application for permission to initiate an update. This does not constitute a privilege inversion because an explicit request for authorization has been provided by the Update Authority in the form of the suit-condition-update-authorized command. Applications MAY define their own meanings for the update priority. For example, critical reliability & vulnerability fixes MAY be given negative numbers, while bug fixes MAY be given small positive numbers, and feature additions MAY be given larger positive numbers, which allows an application to make an informed decision about whether and when to allow an update to proceed.

Indicates allowable versions for the specified component. Allowable versions can be specified, either with a list or with range matching. This parameter is compared with version asserted by the current component when is invoked. The current component may assert the current version in many ways, including storage in a parameter storage database, in a metadata object, or in a known location within the component itself. The component version can be compared as: Greater. Greater or Equal. Equal. Lesser or Equal. Lesser. Versions are encoded as a CBOR list of integers. Comparisons are done on each integer in sequence. Comparison stops after all integers in the list defined by the manifest have been consumed OR after a non-equal match has occurred. For example, if the manifest defines a comparison, “Equal [1]”, then this will match all version sequences starting with 1. If a manifest defines both “Greater or Equal [1,0]” and “Lesser [1,10]”, then it will match versions 1.0.x up to, but not including 1.10. While the exact encoding of versions is application-defined, semantic versions map conveniently. For example, 1.2.3 = [1,2,3]. 1.2-rc3 = [1,2,-1,3]. 1.2-beta = [1,2,-2]. 1.2-alpha = [1,2,-3]. 1.2-alpha4 = [1,2,-3,4]. suit-condition-version is OPTIONAL to implement. Versions SHOULD be provided as follows: The first integer represents the major number. This indicates breaking changes to the component. The second integer represents the minor number. This is typically reserved for new features or large, non-breaking changes. The third integer is the patch version. This is typically reserved for bug fixes. The fourth integer is the build number. Where Alpha (-3), Beta (-2), and Release Candidate (-1) are used, they are inserted as a negative number between Minor and Patch numbers. This allows these releases to compare correctly with final releases. For example, Version 2.0, RC1 should be lower than Version 2.0.0 and higher than any Version 1.x. By encoding RC as -1, this works correctly: [2,0,-1,1] compares as lower than [2,0,0]. Similarly, beta (-2) is lower than RC and alpha (-3) is lower than RC.

suit-directive-wait directs the manifest processor to pause until a specified event occurs. The suit-parameter-wait-info encodes the parameters needed for the directive. The exact implementation of the pause is implementation-defined. For example, this could be done by blocking on a semaphore, registering an event handler and suspending the manifest processor, polling for a notification, or aborting the update entirely, then restarting when a notification is received. suit-parameter-wait-info is encoded as a map of wait events. When ALL wait events are satisfied, the Manifest Processor continues. The wait events currently defined are described in the following table. Name Encoding Description suit-wait-event-authorization int Same as suit-wait-event-power int Wait until power state suit-wait-event-network int Wait until network state suit-wait-event-other-device-version See below Wait for other device to match version suit-wait-event-time uint Wait until time (POSIX timestamp) suit-wait-event-time-of-day uint Wait until seconds since 00:00:00 suit-wait-event-day-of-week uint Wait until days since Sunday suit-wait-event-other-device-version reuses the encoding of suit-parameter-version-match. It is encoded as a sequence that contains an implementation-defined bstr identifier for the other device, and a list of one or more SUIT_Parameter_Version_Match.

Indicates a list of URIs from which to fetch a resource. The URI list is encoded as a list of tstr, in priority order. The Recipient should attempt to fetch the resource from each URI in turn, ruling out each, in order, if the resource is inaccessible or it is otherwise undesirable to fetch from that URI. suit-parameter-uri-list is consumed by .

An implementation-defined set of arguments to . Arguments are encoded in a bstr.

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 for behavioral description of Strict Order.

When executing a command sequence inside or 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.

This parameter is an extension point for any proprietary, application specific conditions and directives.

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 . Conditions include: Name CDDL Structure Reference Vendor Identifier suit-condition-vendor-identifier Class Identifier suit-condition-class-identifier Device Identifier suit-condition-device-identifier Image Match suit-condition-image-match Image Not Match suit-condition-image-not-match Use Before suit-condition-use-before Component Offset suit-condition-component-offset Minimum Battery suit-condition-minimum-battery Update Authorized suit-condition-update-authorized Version suit-condition-version Custom Condition SUIT_Condition_Custom The abstract description of these conditions is defined in . 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 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 use. See for more details.

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 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. The Recipient MAY treat them as scoped by component or as global identifiers. 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. Globally-scoped identifiers MUST match, regardless of current component index. Component-scoped identifiers match only when the current component index resolves to the component associated with the component-scoped identifier.

Verify that the current component matches the 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.

Verify that the current component does not match the . If no digest is specified, the condition fails. suit-condition-image-not-match is OPTIONAL to implement.

Verify that the current time is BEFORE the specified time. suit-condition-use-before is used to specify the last time at which an update should be installed. The recipient evaluates the current time against the suit-parameter-use-before parameter, which must have already been set as a parameter, encoded as a POSIX timestamp, that is seconds after 1970-01-01 00:00:00. Timestamp conditions MUST be evaluated in 64 bits, regardless of encoded CBOR size. suit-condition-use-before is OPTIONAL to implement.

Verify that the offset of the current component matches the offset set in . This condition allows a manifest to select between several images to match a target offset.

suit-condition-minimum-battery provides a mechanism to test a Recipient’s battery level before installing an update. This condition is primarily for use in primary-cell applications, where the battery is only ever discharged. For batteries that are charged, suit-directive-wait is more appropriate, since it defines a “wait” until the battery level is sufficient to install the update. suit-condition-minimum-battery is specified in mWh. suit-condition-minimum-battery is OPTIONAL to implement. suit-condition-minimum-battery consumes .

Request Authorization from the application and fail if not authorized. This can allow a user to decline an update. provides an integer priority level that the application can use to determine whether or not to authorize the update. Priorities are application defined. suit-condition-update-authorized is OPTIONAL to implement.

suit-condition-version allows comparing versions of firmware. Verifying image digests is preferred to version checks because digests are more precise. suit-condition-version examines a component’s version against the version info specified in

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 . SUIT_Condition_Custom is OPTIONAL to implement.

Directives are used to define the behavior of the recipient. Directives include: Name CDDL Structure Reference Set Component Index suit-directive-set-component-index Set Dependency Index suit-directive-set-dependency-index Abort suit-directive-abort Try Each suit-directive-try-each Process Dependency suit-directive-process-dependency Set Parameters suit-directive-set-parameters Override Parameters suit-directive-override-parameters Fetch suit-directive-fetch Copy suit-directive-copy Run suit-directive-run Wait For Event suit-directive-wait Run Sequence suit-directive-run-sequence Swap suit-directive-swap Fetch URI list suit-directive-fetch-uri-list The abstract description of these commands is defined in . When a Recipient executes a Directive, it MUST report a result code. If the Directive reports failure, then the current Command Sequence MUST terminate.

Set Component Index defines the component to which successive directives and conditions will apply. The supplied argument MUST be either a boolean or an unsigned integer index into suit-components. If the following directives apply to ALL components, then the boolean value “True” is used instead of an index. If the following directives apply to NO components, then the boolean value “False” is used. When suit-directive-set-dependency-index is used, suit-directive-set-component-index = False is implied. When suit-directive-set-component-index is used, suit-directive-set-dependency-index = False is implied.

Set Dependency Index defines the manifest to which successive directives and conditions will apply. The supplied argument MUST be either a boolean or an unsigned integer index into the dependencies. If the following directives apply to ALL dependencies, then the boolean value “True” is used instead of an index. If the following directives apply to NO dependencies, then the boolean value “False” is used. When suit-directive-set-component-index is used, suit-directive-set-dependency-index = False is implied. When suit-directive-set-dependency-index is used, suit-directive-set-component-index = False is implied. Typical operations that require suit-directive-set-dependency-index include setting a source URI or Encryption Information, invoking “Fetch,” or invoking “Process Dependency” for an individual dependency.

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

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

Execute the commands in the common section of the current dependency, followed by the commands in the equivalent section of the current dependency. For example, if the current section is “fetch payload,” this will execute “common” in the current dependency, then “fetch payload” in the current dependency. Once this is complete, the command following suit-directive-process-dependency will be processed. If the current dependency is False, this directive has no effect. If the current dependency is True, then this directive applies to all dependencies. If the current section is “common,” this directive MUST have no effect. When SUIT_Process_Dependency completes, it forwards the last status code that occurred in the dependency.

suit-directive-set-parameters allows the manifest to configure behavior of future directives by changing parameters that are read by those directives. When dependencies are used, suit-directive-set-parameters also allows a manifest to modify the behavior of its dependencies. Available parameters are defined in . If a parameter is already set, suit-directive-set-parameters will skip setting the parameter to its argument. This provides the core of the override mechanism, allowing dependent manifests to change the behavior of a manifest. suit-directive-set-parameters does not specify a reporting policy.

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

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 manifests and one or more payloads. suit-directive-fetch retrieves each component and each manifest listed in component-index and dependency-index, respectively. If component-index or dependency-index is True, instead of an integer, then all current manifest components/manifests are fetched. The current manifest’s dependent-components are not automatically fetched. In order to pre-fetch these, they MUST be specified in a component-index integer. 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. The behavior of suit-directive-fetch can be modified by setting one or more of SUIT_Parameter_Encryption_Info, SUIT_Parameter_Compression_Info, SUIT_Parameter_Unpack_Info. These three parameters each activate and configure a processing step that can be applied to the data that is transferred during suit-directive-fetch.

suit-directive-fetch-uri-list uses the same semantics as , however it iterates over the URI List to select a URI to fetch from.

suit-directive-copy instructs the manifest processor to obtain one or more payloads, as specified by the component index. suit-directive-copy retrieves each component listed in component-index, respectively. If component-index is True, instead of an integer, then all current manifest components are copied. The current manifest’s dependent-components are not automatically copied. In order to copy these, they MUST be specified in a component-index integer. The behavior of suit-directive-copy can be modified by setting one or more of SUIT_Parameter_Encryption_Info, SUIT_Parameter_Compression_Info, SUIT_Parameter_Unpack_Info. These three parameters each activate and configure a processing step that can be applied to the data that is transferred during suit-directive-copy. suit-directive-copy reads its source from .

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 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.

suit-directive-wait directs the manifest processor to pause until a specified event occurs. Some possible events include: Authorization External Power Network availability Other Device Firmware Version Time Time of Day Day of Week

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. defaults to False when suit-directive-run-sequence begins. Its value is discarded when suit-directive-run-sequence terminates.

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. 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.

When the CoSWID, 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 with an identical key, so that it matches the key of the corresponding Integrity Check Value. Each Integrity Check Value covers the corresponding Envelope Element as described in .

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.

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 ID prefixes to the listed identities or identity groups. Any identity may verify an image digest, but fetching into or fetching from a component ID requires approval from the ACL. A third model allows a Recipient to provide even more fine-grained controls: The ACL lists the component ID or component ID prefix that an identity may use, and also lists the commands that the identity may use in combination with that component ID.

RFC 8152 provides containers for signature, MAC, and encryption, but no basic digest container. The container needed for a digest requires a type identifier and a container for the raw digest data. Some forms of digest may require additional parameters. These can be added following the digest. The SUIT digest is a CBOR List containing two elements: a suit-digest-algorithm-id and a bstr containing the bytes of the digest.

IANA is requested to: allocate a CBOR tag for the SUIT Envelope and another for the SUIT Manifest. allocate a media type for suit: application/suit-envelope setup several registries as described below 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.

Label Name 1 Vendor Identifier 2 Class Identifier 3 Image Match 4 Use Before 5 Component Offset 12 Set Component Index 13 Set Dependency Index 14 Abort 15 Try Each 16 Reserved 17 Reserved 18 Process Dependency 19 Set Parameters 20 Override Parameters 21 Fetch 22 Copy 23 Run 24 Device Identifier 25 Image Not Match 26 Minimum Battery 27 Update Authorized 28 Version 29 Wait For Event 30 Fetch URI List 31 Swap 32 Run Sequence nint Custom Condition

Label Name 1 Vendor ID 2 Class ID 3 Image Digest 4 Use Before 5 Component Offset 12 Strict Order 13 Soft Failure 14 Image Size 18 Encryption Info 19 Compression Info 20 Unpack Info 21 URI 22 Source Component 23 Run Args 24 Device ID 26 Minimum Battery 27 Update Priority 28 Version 29 Wait Info 30 URI List 31 Component Index nint Custom

Label Name 1 Manifest Description 2 Update Description 3 Manifest JSON Source 4 Manifest YAML Source nint Custom

Label Name 1 Vendor Name 2 Model Name 3 Vendor Domain 4 Model Info 5 Component Description 6 Component Version 7 Component Version Required nint Custom

Label Name 1 SHA224 2 SHA256 3 SHA384 4 SHA512 5 SHA3-224 6 SHA3-256 7 SHA3-384 8 SHA3-512

Label Name 1 zlib 2 Brotli 3 zstd

Label Name 1 HEX 2 ELF 3 COFF 4 SREC

This document is about a manifest format describing and protecting firmware images and as such it is part of a larger solution for offering a standardized way of delivering firmware updates to IoT devices. A detailed security treatment can be found in the architecture and in the information model documents.

We would like to thank the following persons for their support in designing this mechanism: Milosch Meriac Geraint Luff Dan Ros John-Paul Stanford Hugo Vincent Carsten Bormann Øyvind Rønningstad Frank Audun Kvamtrø Krzysztof Chruściński Andrzej Puzdrowski Michael Richardson David Brown Emmanuel Baccelli

This specification defines a Uniform Resource Name namespace for UUIDs (Universally Unique IDentifier), also known as GUIDs (Globally Unique IDentifier). A UUID is 128 bits long, and can guarantee uniqueness across space and time. UUIDs were originally used in the Apollo Network Computing System and later in the Open Software Foundation\'s (OSF) Distributed Computing Environment (DCE), and then in Microsoft Windows platforms.This specification is derived from the DCE specification with the kind permission of the OSF (now known as The Open Group). Information from earlier versions of the DCE specification have been incorporated into this document. [STANDARDS-TRACK] Concise Binary Object Representation (CBOR) is a data format designed for small code size and small message size. There is a need for the ability to have basic security services defined for this data format. This document defines the CBOR Object Signing and Encryption (COSE) protocol. This specification describes how to create and process signatures, message authentication codes, and encryption using CBOR for serialization. This specification additionally describes how to represent cryptographic keys using CBOR. A Uniform Resource Identifier (URI) is a compact sequence of characters that identifies an abstract or physical resource. This specification defines the generic URI syntax and a process for resolving URI references that might be in relative form, along with guidelines and security considerations for the use of URIs on the Internet. The URI syntax defines a grammar that is a superset of all valid URIs, allowing an implementation to parse the common components of a URI reference without knowing the scheme-specific requirements of every possible identifier. This specification does not define a generative grammar for URIs; that task is performed by the individual specifications of each URI scheme. [STANDARDS-TRACK] In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Vulnerabilities with Internet of Things (IoT) devices have raised the need for a solid and secure firmware update mechanism that is also suitable for constrained devices. Incorporating such update mechanism to fix vulnerabilities, to update configuration settings as well as adding new functionality is recommended by security experts. This document lists requirements and describes an architecture for a firmware update mechanism suitable for IoT devices. The architecture is agnostic to the transport of the firmware images and associated meta-data. Vulnerabilities with Internet of Things (IoT) devices have raised the need for a solid and secure firmware update mechanism that is also suitable for constrained devices. Ensuring that devices function and remain secure over their service life requires such an update mechanism to fix vulnerabilities, to update configuration settings, as well as adding new functionality. One component of such a firmware update is a concise and machine- processable meta-data document, or manifest, that describes the firmware image(s) and offers appropriate protection. This document describes the information that must be present in the manifest. A Trusted Execution Environment (TEE) is an environment that enforces that any code within that environment cannot be tampered with, and that any data used by such code cannot be read or tampered with by any code outside that environment. This architecture document motivates the design and standardization of a protocol for managing the lifecycle of trusted applications running inside such a TEE. This specification defines a lossless compressed data format that compresses data using a combination of the LZ77 algorithm and Huffman coding, with efficiency comparable to the best currently available general-purpose compression methods. This specification defines a lossless compressed data format. This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. CBOR Web Token (CWT) is a compact means of representing claims to be transferred between two parties. The claims in a CWT are encoded in the Concise Binary Object Representation (CBOR), and CBOR Object Signing and Encryption (COSE) is used for added application-layer security protection. A claim is a piece of information asserted about a subject and is represented as a name/value pair consisting of a claim name and a claim value. CWT is derived from JSON Web Token (JWT) but uses CBOR rather than JSON. The Internet Protocol Suite is increasingly used on small devices with severe constraints on power, memory, and processing resources, creating constrained-node networks. This document provides a number of basic terms that have been useful in the standardization work for constrained-node networks. This specification describes how to declare in a CBOR Web Token (CWT) (which is defined by RFC 8392) that the presenter of the CWT possesses a particular proof-of-possession key. Being able to prove possession of a key is also sometimes described as being the holder-of-key. This specification provides equivalent functionality to "Proof-of-Possession Key Semantics for JSON Web Tokens (JWTs)" (RFC 7800) but using Concise Binary Object Representation (CBOR) and CWTs rather than JavaScript Object Notation (JSON) and JSON Web Tokens (JWTs). Zstandard, or "zstd" (pronounced "zee standard"), is a data compression mechanism. This document describes the mechanism and registers a media type and content encoding to be used when transporting zstd-compressed content via Multipurpose Internet Mail Extensions (MIME). It also registers a corresponding media type, content encoding, and structured syntax suffix. Despite use of the word "standard" as part of its name, readers are advised that this document is not an Internet Standards Track specification; it is being published for informational purposes only. This document replaces and obsoletes RFC 8478.

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

bstr .cbor SUIT_Delegation, ? suit-authentication-wrapper => bstr .cbor SUIT_Authentication, suit-manifest => bstr .cbor SUIT_Manifest, SUIT_Severable_Manifest_Members, * $$SUIT_Envelope_Extensions, (int => bstr) } SUIT_Delegation = [ + [ + bstr .cbor CWT ] ] CWT = SUIT_Authentication_Block SUIT_Authentication = [ + bstr .cbor SUIT_Authentication_Block ] SUIT_Authentication_Block /= COSE_Mac_Tagged SUIT_Authentication_Block /= COSE_Sign_Tagged SUIT_Authentication_Block /= COSE_Mac0_Tagged SUIT_Authentication_Block /= COSE_Sign1_Tagged SUIT_Severable_Manifest_Members = ( ? suit-dependency-resolution => bstr .cbor SUIT_Command_Sequence, ? suit-payload-fetch => bstr .cbor SUIT_Command_Sequence, ? suit-install => bstr .cbor SUIT_Command_Sequence, ? suit-text => bstr .cbor SUIT_Text_Map, ? suit-coswid => bstr .cbor concise-software-identity, * $$SUIT_severable-members-extensions, ) COSE_Mac_Tagged = any COSE_Sign_Tagged = any COSE_Mac0_Tagged = any COSE_Sign1_Tagged = any COSE_Encrypt_Tagged = any COSE_Encrypt0_Tagged = any SUIT_Digest = [ suit-digest-algorithm-id : suit-digest-algorithm-ids, suit-digest-bytes : bstr, * $$SUIT_Digest-extensions ] ; Named Information Hash Algorithm Identifiers suit-digest-algorithm-ids /= algorithm-id-sha224 suit-digest-algorithm-ids /= algorithm-id-sha256 suit-digest-algorithm-ids /= algorithm-id-sha384 suit-digest-algorithm-ids /= algorithm-id-sha512 suit-digest-algorithm-ids /= algorithm-id-sha3-224 suit-digest-algorithm-ids /= algorithm-id-sha3-256 suit-digest-algorithm-ids /= algorithm-id-sha3-384 suit-digest-algorithm-ids /= algorithm-id-sha3-512 algorithm-id-sha224 = 1 algorithm-id-sha256 = 2 algorithm-id-sha384 = 3 algorithm-id-sha512 = 4 algorithm-id-sha3-224 = 5 algorithm-id-sha3-256 = 6 algorithm-id-sha3-384 = 7 algorithm-id-sha3-512 = 8 SUIT_Manifest = { suit-manifest-version => 1, suit-manifest-sequence-number => uint, suit-common => bstr .cbor SUIT_Common, ? suit-reference-uri => tstr, SUIT_Severable_Members, SUIT_Severable_Members_Digests, SUIT_Unseverable_Members, * $$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, * $$unserverble-manifest-member-extensions, ) SUIT_Severable_Members_Digests = ( ? suit-dependency-resolution-digest => SUIT_Digest, ? suit-payload-fetch-digest => SUIT_Digest, ? suit-install-digest => SUIT_Digest, ? suit-text-digest => SUIT_Digest, ? suit-coswid-digest => SUIT_Digest, * $$severable-manifest-members-digests-extensions ) SUIT_Common = { ? suit-dependencies => SUIT_Dependencies, ? suit-components => SUIT_Components, ? suit-common-sequence => bstr .cbor SUIT_Common_Sequence, * $$SUIT_Common-extensions, } SUIT_Dependencies = [ + SUIT_Dependency ] SUIT_Components = [ + SUIT_Component_Identifier ] concise-software-identity = any SUIT_Dependency = { suit-dependency-digest => SUIT_Digest, ? suit-dependency-prefix => SUIT_Component_Identifier, * $$SUIT_Dependency-extensions, } SUIT_Component_Identifier = [* bstr] SUIT_Component_Reference = { suit-component-identifier => SUIT_Component_Identifier, suit-component-dependency-index => uint } SUIT_Common_Sequence = [ + ( SUIT_Condition // SUIT_Common_Commands ) ] SUIT_Common_Commands //= (suit-directive-set-component-index, uint/bool) SUIT_Common_Commands //= (suit-directive-set-dependency-index, uint/bool) 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-set-parameters, {+ SUIT_Parameters}) SUIT_Common_Commands //= (suit-directive-override-parameters, {+ SUIT_Parameters}) 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_Reporting_Policy) SUIT_Condition //= (suit-condition-class-identifier, SUIT_Reporting_Policy) SUIT_Condition //= (suit-condition-device-identifier, SUIT_Reporting_Policy) SUIT_Condition //= (suit-condition-image-match, SUIT_Reporting_Policy) SUIT_Condition //= (suit-condition-image-not-match, SUIT_Reporting_Policy) SUIT_Condition //= (suit-condition-use-before, SUIT_Reporting_Policy) SUIT_Condition //= (suit-condition-minimum-battery, SUIT_Reporting_Policy) SUIT_Condition //= (suit-condition-update-authorized, SUIT_Reporting_Policy) SUIT_Condition //= (suit-condition-version, SUIT_Reporting_Policy) SUIT_Condition //= (suit-condition-component-offset, SUIT_Reporting_Policy) SUIT_Directive //= (suit-directive-set-component-index, uint/bool) SUIT_Directive //= (suit-directive-set-dependency-index, uint/bool) 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_Reporting_Policy) SUIT_Directive //= (suit-directive-set-parameters, {+ SUIT_Parameters}) SUIT_Directive //= (suit-directive-override-parameters, {+ SUIT_Parameters}) SUIT_Directive //= (suit-directive-fetch, SUIT_Reporting_Policy) SUIT_Directive //= (suit-directive-copy, SUIT_Reporting_Policy) SUIT_Directive //= (suit-directive-swap, SUIT_Reporting_Policy) SUIT_Directive //= (suit-directive-run, SUIT_Reporting_Policy) SUIT_Directive //= (suit-directive-wait, SUIT_Reporting_Policy) SUIT_Directive //= (suit-directive-abort, SUIT_Reporting_Policy) SUIT_Directive //= (suit-directive-fetch-uri-list, SUIT_Reporting_Policy) SUIT_Directive_Try_Each_Argument = [ + bstr .cbor SUIT_Command_Sequence, nil / bstr .cbor SUIT_Command_Sequence ] SUIT_Reporting_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_Command_ID /= suit-command-custom SUIT_Command_ID /= suit-condition-vendor-identifier SUIT_Command_ID /= suit-condition-class-identifier SUIT_Command_ID /= suit-condition-image-match SUIT_Command_ID /= suit-condition-use-before SUIT_Command_ID /= suit-condition-component-offset SUIT_Command_ID /= suit-condition-device-identifier SUIT_Command_ID /= suit-condition-image-not-match SUIT_Command_ID /= suit-condition-minimum-battery SUIT_Command_ID /= suit-condition-update-authorized SUIT_Command_ID /= suit-condition-version SUIT_Command_ID /= suit-directive-set-component-index SUIT_Command_ID /= suit-directive-set-dependency-index SUIT_Command_ID /= suit-directive-abort SUIT_Command_ID /= suit-directive-try-each ;SUIT_Command_ID /= suit-directive-do-each ;SUIT_Command_ID /= suit-directive-map-filter SUIT_Command_ID /= suit-directive-process-dependency SUIT_Command_ID /= suit-directive-set-parameters SUIT_Command_ID /= suit-directive-override-parameters SUIT_Command_ID /= suit-directive-fetch SUIT_Command_ID /= suit-directive-copy SUIT_Command_ID /= suit-directive-run SUIT_Command_ID /= suit-directive-wait SUIT_Command_ID /= suit-directive-run-sequence SUIT_Command_ID /= suit-directive-swap SUIT_Command_ID /= suit-directive-fetch-uri-list suit-record = { suit-record-success => bool/int, ? suit-record-component-id => SUIT_Component_ID, ? suit-record-dependency-id => SUIT_Digest, ? suit-record-command-sequence-id => ( suit-common-sequence / suit-dependency-resolution / suit-payload-fetch / suit-install / suit-validate / suit-load / suit-run / * $$suit-command-sequence-list-extensions ), ? suit-record-interpeter-offset => uint, ? suit-record-command-id => SUIT_Command_ID, ? suit-record-params => SUIT_Parameters, ? suit-record-actual => SUIT_Parameters, * $$suit-record-extensions } SUIT_Wait_Event = { + SUIT_Wait_Events } SUIT_Wait_Events //= (suit-wait-event-authorization => int) SUIT_Wait_Events //= (suit-wait-event-power => int) SUIT_Wait_Events //= (suit-wait-event-network => int) SUIT_Wait_Events //= (suit-wait-event-other-device-version => SUIT_Wait_Event_Argument_Other_Device_Version) SUIT_Wait_Events //= (suit-wait-event-time => uint); Timestamp SUIT_Wait_Events //= (suit-wait-event-time-of-day => uint); Time of Day (seconds since 00:00:00) SUIT_Wait_Events //= (suit-wait-event-day-of-week => uint); Days since Sunday SUIT_Wait_Event_Argument_Other_Device_Version = [ other-device: bstr, other-device-version: [ + SUIT_Parameter_Version_Match ] ] SUIT_Parameters //= (suit-parameter-vendor-identifier => RFC4122_UUID) 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-use-before => uint) SUIT_Parameters //= (suit-parameter-component-offset => uint) SUIT_Parameters //= (suit-parameter-encryption-info => bstr .cbor SUIT_Encryption_Info) SUIT_Parameters //= (suit-parameter-compression-info => bstr .cbor SUIT_Compression_Info) SUIT_Parameters //= (suit-parameter-unpack-info => bstr .cbor SUIT_Unpack_Info) 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-minimum-battery => uint) SUIT_Parameters //= (suit-parameter-update-priority => uint) SUIT_Parameters //= (suit-parameter-version => SUIT_Parameter_Version_Match) SUIT_Parameters //= (suit-parameter-wait-info => bstr .cbor SUIT_Wait_Event) SUIT_Parameters //= (suit-parameter-custom => int/bool/tstr/bstr) SUIT_Parameters //= (suit-parameter-strict-order => bool) SUIT_Parameters //= (suit-parameter-soft-failure => bool) SUIT_Parameters //= (suit-parameter-uri-list => bstr .cbor SUIT_URI_List) RFC4122_UUID = bstr .size 16 SUIT_Parameter_Version_Match = [ suit-condition-version-comparison-type: SUIT_Condition_Version_Comparison_Types, suit-condition-version-comparison-value: SUIT_Condition_Version_Comparison_Value ] SUIT_Condition_Version_Comparison_Types /= suit-condition-version-comparison-greater SUIT_Condition_Version_Comparison_Types /= suit-condition-version-comparison-greater-equal SUIT_Condition_Version_Comparison_Types /= suit-condition-version-comparison-equal SUIT_Condition_Version_Comparison_Types /= suit-condition-version-comparison-lesser-equal SUIT_Condition_Version_Comparison_Types /= suit-condition-version-comparison-lesser suit-condition-version-comparison-greater = 1 suit-condition-version-comparison-greater-equal = 2 suit-condition-version-comparison-equal = 3 suit-condition-version-comparison-lesser-equal = 4 suit-condition-version-comparison-lesser = 5 SUIT_Condition_Version_Comparison_Value = [+int] SUIT_Encryption_Info = COSE_Encrypt_Tagged/COSE_Encrypt0_Tagged SUIT_Compression_Info = { suit-compression-algorithm => SUIT_Compression_Algorithms, * $$SUIT_Compression_Info-extensions, } SUIT_Compression_Algorithms /= SUIT_Compression_Algorithm_zlib SUIT_Compression_Algorithms /= SUIT_Compression_Algorithm_brotli SUIT_Compression_Algorithms /= SUIT_Compression_Algorithm_zstd SUIT_Compression_Algorithm_zlib = 1 SUIT_Compression_Algorithm_brotli = 2 SUIT_Compression_Algorithm_zstd = 3 SUIT_Unpack_Info = { suit-unpack-algorithm => SUIT_Unpack_Algorithms, * $$SUIT_Unpack_Info-extensions, } SUIT_Unpack_Algorithms /= SUIT_Unpack_Algorithm_Hex SUIT_Unpack_Algorithms /= SUIT_Unpack_Algorithm_Elf SUIT_Unpack_Algorithms /= SUIT_Unpack_Algorithm_Coff SUIT_Unpack_Algorithms /= SUIT_Unpack_Algorithm_Srec SUIT_Unpack_Algorithm_Hex = 1 SUIT_Unpack_Algorithm_Elf = 2 SUIT_Unpack_Algorithm_Coff = 3 SUIT_Unpack_Algorithm_Srec = 4 SUIT_URI_List = [+ tstr ] SUIT_Text_Map = { ? suit-text-components => [ + { 1 => SUIT_Component_Identifier SUIT_Text_Component_Keys } ], SUIT_Text_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-version-required => 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-delegation = 1 suit-authentication-wrapper = 2 suit-manifest = 3 suit-manifest-version = 1 suit-manifest-sequence-number = 2 suit-common = 3 suit-reference-uri = 4 suit-dependency-resolution = 7 suit-payload-fetch = 8 suit-install = 9 suit-validate = 10 suit-load = 11 suit-run = 12 suit-text = 13 suit-coswid = 14 suit-dependencies = 1 suit-components = 2 suit-dependency-components = 3 suit-common-sequence = 4 suit-dependency-digest = 1 suit-dependency-prefix = 2 suit-component-identifier = 1 suit-component-dependency-index = 2 suit-command-custom = nint suit-condition-vendor-identifier = 1 suit-condition-class-identifier = 2 suit-condition-image-match = 3 suit-condition-use-before = 4 suit-condition-component-offset = 5 suit-condition-device-identifier = 24 suit-condition-image-not-match = 25 suit-condition-minimum-battery = 26 suit-condition-update-authorized = 27 suit-condition-version = 28 suit-directive-set-component-index = 12 suit-directive-set-dependency-index = 13 suit-directive-abort = 14 suit-directive-try-each = 15 ;suit-directive-do-each = 16 ; TBD ;suit-directive-map-filter = 17 ; TBD suit-directive-process-dependency = 18 suit-directive-set-parameters = 19 suit-directive-override-parameters = 20 suit-directive-fetch = 21 suit-directive-copy = 22 suit-directive-run = 23 suit-directive-wait = 29 suit-directive-fetch-uri-list = 30 suit-directive-swap = 31 suit-directive-run-sequence = 32 suit-wait-event-authorization = 1 suit-wait-event-power = 2 suit-wait-event-network = 3 suit-wait-event-other-device-version = 4 suit-wait-event-time = 5 suit-wait-event-time-of-day = 6 suit-wait-event-day-of-week = 7 suit-parameter-vendor-identifier = 1 suit-parameter-class-identifier = 2 suit-parameter-image-digest = 3 suit-parameter-use-before = 4 suit-parameter-component-offset = 5 suit-parameter-strict-order = 12 suit-parameter-soft-failure = 13 suit-parameter-image-size = 14 suit-parameter-encryption-info = 18 suit-parameter-compression-info = 19 suit-parameter-unpack-info = 20 suit-parameter-uri = 21 suit-parameter-source-component = 22 suit-parameter-run-args = 23 suit-parameter-device-identifier = 24 suit-parameter-minimum-battery = 26 suit-parameter-update-priority = 27 suit-parameter-version = 28 suit-parameter-wait-info = 29 suit-parameter-uri-list = 30 suit-parameter-custom = nint suit-compression-algorithm = 1 suit-compression-parameters = 2 suit-unpack-algorithm = 1 suit-unpack-parameters = 2 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 suit-text-version-required = 7 ]]>

The following examples demonstrate a small subset of the functionality of the manifest. However, despite this, even a simple manifest processor can execute most of these manifests. The examples are signed using the following ECDSA secp256r1 key:

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

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. 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 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-offset 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

This example covers the following templates: Compatibility Check () Secure Boot () It also serves as the minimum example.

Total size of Envelope without COSE authentication object: 117 Envelope:

Total size of Envelope with COSE authentication object: 266 Envelope with COSE authentication object:

This example covers the following templates: Compatibility Check () Firmware Download () Simultaneous download and installation of payload. No secure boot is present in this example to demonstrate a download-only manifest.

Total size of Envelope without COSE authentication object: 152 Envelope:

Total size of Envelope with COSE authentication object: 301 Envelope with COSE authentication object:

This example covers the following templates: Compatibility Check () Secure Boot () Firmware Download () This example also demonstrates severable elements (), and text ().

Total size of the Envelope without COSE authentication object or Severable Elements: 191 Envelope:

Total size of the Envelope with COSE authentication object but without Severable Elements: 340 Envelope:

Total size of Envelope with COSE authentication object: 923 Envelope with COSE authentication object:

This example covers the following templates: Compatibility Check () Secure Boot () Firmware Download () A/B Image Template ()

Total size of Envelope without COSE authentication object: 288 Envelope:

Total size of Envelope with COSE authentication object: 437 Envelope with COSE authentication object:

This example covers the following templates: Compatibility Check () Secure Boot () Firmware Download () Install () Load & Decompress ()

Total size of Envelope without COSE authentication object: 245 Envelope:

Total size of Envelope with COSE authentication object: 394 Envelope with COSE authentication object:

This example covers the following templates: Compatibility Check () Secure Boot () Firmware Download () Furthermore, it shows using these templates with two images.

Total size of Envelope without COSE authentication object: 264 Envelope:

Total size of Envelope with COSE authentication object: 413 Envelope with COSE authentication object:

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 execution 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 execution 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.

The Envelope is used instead of a COSE structure for several reasons: This enables the use of Severable Elements This enables modular processing of manifests, particularly with large signatures. This enables multiple authentication schemes. 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

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.

This section summarizes the functionality a minimal 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. Name Reference Implementation Vendor Identifier REQUIRED Class Identifier REQUIRED Device Identifier OPTIONAL Image Match REQUIRED Image Not Match OPTIONAL Use Before OPTIONAL Component Offset OPTIONAL Minimum Battery OPTIONAL Update Authorized OPTIONAL Version OPTIONAL Custom Condition OPTIONAL The subsequent table shows the directives. Name Reference Implementation Set Component Index REQUIRED if more than one component Set Dependency Index REQUIRED if dependencies used Abort OPTIONAL Try Each OPTIONAL Process Dependency OPTIONAL Set Parameters OPTIONAL Override Parameters REQUIRED Fetch REQUIRED for Updater Copy OPTIONAL Run REQUIRED for Bootloader Wait For Event OPTIONAL Run Sequence OPTIONAL Swap OPTIONAL Fetch URI List OPTIONAL The subsequent table shows the parameters. Name Reference Implementation Vendor ID REQUIRED Class ID REQUIRED Image Digest REQUIRED Image Size REQUIRED Use Before RECOMMENDED Component Offset OPTIONAL Encryption Info RECOMMENDED Compression Info RECOMMENDED Unpack Info RECOMMENDED URI REQUIRED for Updater Source Component OPTIONAL Run Args OPTIONAL Device ID OPTIONAL Minimum Battery OPTIONAL Update Priority OPTIONAL Version Match OPTIONAL Wait Info OPTIONAL URI List OPTIONAL Strict Order OPTIONAL Soft Failure OPTIONAL Custom OPTIONAL