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

4.1. IoT Firmware Update Constraints

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

• limited processing power and storage may require a simple representation of metadata.¶

• bandwidth constraints may require firmware compression or partial update support.¶

• bootloader complexity constraints may require simple selection between two bootable images.¶

• small internal storage may require external storage support.¶

• multiple microcontrollers may require coordinated update of all applications.¶

• large storage and complex functionality may require parallel update of many software components.¶

• extra information may need to be conveyed in the manifest in the earlier stages of the device lifecycle before those data items are stripped when the manifest is delivered to a constrained device.¶

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

4.2. SUIT Workflow Model

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

• Compatibility must be checked before any other operation is performed.¶

• In some applications, payloads must be fetched and validated prior to installation.¶

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

• Compatibility must be checked before any other operation is performed.¶

• All payloads must be validated prior to loading.¶

• All loaded images must be validated prior to execution.¶

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

1. Verify the signature of the manifest.¶

2. Verify the applicability of the manifest.¶

3. Fetch payload(s).¶

4. Install payload(s).¶

5. Verify image(s).¶

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

1. Verify image(s).¶

2. Load image(s).¶

3. Invoke image(s).¶

If verification and invocation 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. Because signature verifications can be costly in constrained applications, the bootloader may add its own authentication, e.g. a Message Authentication Code (MAC), to the manifest in order to prevent further signature verifications and save energy, provided that the bootloader can protect its authentication key.¶

5.1. Envelope

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

See Section 8.2 for more detail.¶

5.2. Authentication Block

The Authentication Block contains a bstr-wrapped SUIT Digest Container, see Section 10, and one or more [RFC9052] CBOR Object Signing and Encryption (COSE) authentication blocks. These blocks are one of:¶

• COSE_Sign_Tagged¶

• COSE_Sign1_Tagged¶

• COSE_Mac_Tagged¶

• COSE_Mac0_Tagged¶

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

See Section 8.3 for more detail.¶

5.3. Manifest

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

See Section 8.4 for more detail.¶

5.4. Severable Elements

Severable Elements are elements of the Envelope (Section 5.1) that have Integrity Check Values (Section 5.3.4) in the Manifest (Section 5.3). This is a form of elision of hashed data. The elements in the envelope are verified by Integrity Check Values and therefore cannot be replaced with other elements even if they are authenticated elements.¶

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

• A management system severs the Text sections before sending an Envelope to a constrained Recipient, which saves Recipient bandwidth.¶

• A Recipient severs the Installation section after installing the Update, which saves storage space.¶

See Section 8.5 for more detail.¶

5.5. Integrated Payloads

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

• When an update is delivered via a comparatively unconstrained medium, such as a removable mass storage device, it may be beneficial to bundle updates into single files.¶

• When a manifest transports a small payload, such as an encrypted key, that payload may be placed in the manifest's envelope.¶

See Section 7.5 for more detail.¶

6.1. Manifest Processor Setup

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

• Whenever the manifest processor can choose between several manifests, it MUST select the latest valid, authentic manifest.¶

• If the latest valid, authentic manifest fails, it MAY select the next latest valid, authentic manifest, according to application-specific policy.¶

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

• Test failed (e.g. Vendor ID/Class ID).¶

• Unsupported command encountered.¶

• Unsupported parameter encountered.¶

• Unsupported Component Identifier encountered.¶

• Payload not available.¶

• Application crashed when executed.¶

• Watchdog timeout occurred.¶

• Payload verification failed.¶

• Missing required component from a Component Set.¶

• Required parameter not supplied.¶

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

Selecting an older manifest in the event of failure of the latest valid manifest is one possible strategy to provide robustness of the firmware update process. It may not be appropriate for all applications. In particular Trusted Execution Environments MAY require a failure to invoke a new installation, rather than a rollback approach. See [RFC9124], Section 4.2.1 for more discussion on the security considerations that apply to rollback.¶

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

6.2. Required Checks

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

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

Once a valid, authentic manifest has been selected, the manifest processor MUST examine the component list and check that the number of components listed in the manifest is not larger than the number in the target system.¶

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

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

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

If the manifest contains more than one component, each command sequence MUST begin with a Set Component Index Section 8.4.10.1.¶

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

1. the manifest Author has sufficient permissions for the requested operations (see Section 9) and¶

2. the manifest specifies a digest and a payload for every Component in the Component Set.¶

6.3. Interpreter Fundamental Properties

The interpreter has a small set of design goals:¶

1. Executing an update MUST either result in an error, or a correct system state that can be checked against known digests.¶

2. Executing a Trusted Invocation MUST either result in an error, or an invoked image.¶

3. Executing the same manifest on multiple Recipients MUST result in the same system state.¶

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

AND

6.4. Abstract Machine Description

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

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

Conditions MUST NOT have any side-effects other than informing the interpreter of success or failure. The Interpreter does not Abort if the Soft Failure flag (Section 8.4.8.15) is set when a Condition reports failure.¶

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

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

current := components[component-index]

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

The following table describes the semantics of each operation. The pseudo-code semantics are inspired by the Python programming language.¶

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

6.5. Special Cases of Component Index

Component Index can take on one of three types:¶

1. Integer¶

2. Array of integers¶

3. True¶

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

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

When a command is executed, it¶

1. operates on the component identified by the component index if that index is an integer, or¶

2. it operates on each component identified by an array of indicies, or¶

3. it operates on every component if the index is the boolean True.¶

This is described by the following pseudocode:¶

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

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

6.6. Serialized Processing Interpreter

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

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

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

6.7. Parallel Processing Interpreter

To enable parallel or out-of-order processing of Command Sequences, Recipients MAY make use of the Strict Order parameter. The Strict Order parameter indicates to the Manifest Processor that Commands MUST be executed strictly in order. When the Strict Order parameter is False, this indicates to the Manifest Processor that Commands MAY be executed in parallel and/or out of order.¶

To perform parallel processing, once the Strict Order parameter is set to False, the Recipient MAY add each command to an issue queue for parallel processing or an issue pool for out-of-order processing. The Manifest Processor then executes these pending commands in whatever order or parallelism it deems appropriate. Once there are no more commands to add to the issue queue/pool, the Manifest Processor drains the issue queue/pool by issuing all pending commands and waits for every issued command to complete. The Manifest Processor MAY issue commands before it has completed adding all remaining commands to the issue queue/pool.¶

While adding commands to the issue queue or pool, if the Manifest Processor encounters any of the following commands, it MUST treat the command as a barrier, draining the issue queue/pool and waiting for all issued commands to complete.¶

• Override Parameters.¶

• Set Strict Order = True.¶

• Set Component Index.¶

Extensions MAY alter this list. Once all issued commands have completed, the Manifest Processor issues the barrier command, after which it may resume parallel processing if Strict Order is still False.¶

A Component MUST NOT be both a target of an operation and a source of data (for example, in Copy or Swap) in a Command Sequence where Strict Order is False. This would cause a race condition if the Component is written to, then later read from. The Manifest Processor MUST issue an Abort if it detects this exception.¶

To perform more useful parallel operations, a manifest author may collect sequences of commands in a Run Sequence command. Then, each of these sequences MAY be run in parallel. There are several invocation options for Run Sequence:¶

• Component Index is a positive integer, Strict Order is False: Strict Order is set to True before the sequence argument is run. The sequence argument MUST begin with set-component-index.¶

• Component Index is true or an array of positive integers, Strict Order is False: The sequence argument is run once for each component (or each component in the array); the Manifest Processor presets the component index and Strict Order = True before each iteration of the sequence argument.¶

• Component Index is a positive integer, Strict Order is True: No special considerations¶

• Component Index is True or an array of positive integers, Strict Order is True: The sequence argument is run once for each component (or each component in the array); the Manifest Processor presets the component index before each iteration of the sequence argument.¶

These rules isolate each sequence from each other sequence, ensuring that they operate as expected. When Strict Order = False, any further Set Component Index directives in the Run Sequence command sequence argument MUST cause an Abort. This allows the interpreter that issues Run Sequence commands to check that the first element is correct, then issue the sequence to a parallel execution context to handle the remainder of the sequence.¶

7.1. Compatibility Check Template

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

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

• Set Component Index directive (see Section 8.4.10.1)¶

• Override Parameters directive (see Section 8.4.10.3) for Vendor ID and Class ID (see Section 8.4.8)¶

• Check Vendor Identifier condition (see Section 8.4.8.2)¶

• Check Class Identifier condition (see Section 8.4.8.2)¶

7.2. Trusted Invocation Template

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

The following commands are placed into the shared sequence:¶

• Set Component Index directive (see Section 8.4.10.1)¶

• Override Parameters directive (see Section 8.4.10.3) for Image Digest and Image Size (see Section 8.4.8)¶

The system validation sequence contains the following commands:¶

• Set Component Index directive (see Section 8.4.10.1)¶

• Check Image Match condition (see Section 8.4.9.2)¶

Then, the run sequence contains the following commands:¶

• Set Component Index directive (see Section 8.4.10.1)¶

• Invoke directive (see Section 8.4.10.7)¶

7.3. Component Download Template

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

The following commands are placed into the shared sequence:¶

• Set Component Index directive (see Section 8.4.10.1)¶

• Override Parameters directive (see Section 8.4.10.3) for Image Digest and Image Size (see Section 8.4.8)¶

Then, the install sequence contains the following commands:¶

• Set Component Index directive (see Section 8.4.10.1)¶

• Override Parameters directive (see Section 8.4.10.3) for URI (see Section 8.4.8.10)¶

• Fetch directive (see Section 8.4.10.4)¶

• Check Image Match condition (see Section 8.4.9.2)¶

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

7.4. Install Template

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

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

Then, the install sequence contains the following commands:¶

• Set Component Index directive (see Section 8.4.10.1)¶

• Override Parameters directive (see Section 8.4.10.3) for Source Component (see Section 8.4.8.11)¶

• Copy directive (see Section 8.4.10.5)¶

• Check Image Match condition (see Section 8.4.9.2)¶

7.5. Integrated Payload Template

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

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

The URI for a payload enclosed in this way MAY be expressed as a fragment-only reference, as defined in [RFC3986], Section 4.4, for example: "#device-model-v1.2.3.bin".¶

An intermediary, such as a Network Operator, MAY choose to pre-fetch a payload and add it to the manifest envelope, using the URI as the key.¶

7.6. Load from Nonvolatile Storage Template

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

The following commands are placed into the load sequence:¶

• Set Component Index directive (see Section 8.4.10.1)¶

• Override Parameters directive (see Section 8.4.10.3) for Source Component (see Section 8.4.8)¶

• Copy directive (see Section 8.4.10.5)¶

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

7.7. A/B Image Template

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

The following commands are placed in the common block:¶

• Set Component Index directive (see Section 8.4.10.1)¶

• Try Each¶

  • First Sequence:¶

    • Override Parameters directive (see Section 8.4.10.3, Section 8.4.8) for Slot A¶

    • Check Slot Condition (see Section 8.4.9.4)¶

    • Override Parameters directive (see Section 8.4.10.3) for Image Digest A and Image Size A (see Section 8.4.8)¶

  • Second Sequence:¶

    • Override Parameters directive (see Section 8.4.10.3, Section 8.4.8) for Slot B¶

    • Check Slot Condition (see Section 8.4.9.4)¶

    • Override Parameters directive (see Section 8.4.10.3) for Image Digest B and Image Size B (see Section 8.4.8)¶

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

• Set Component Index directive (see Section 8.4.10.1)¶

• Try Each¶

  • First Sequence:¶

    • Override Parameters directive (see Section 8.4.10.3, Section 8.4.8) for Slot A¶

    • Check Slot Condition (see Section 8.4.9.4)¶

    • Set Parameters directive (see Section 8.4.10.3) for URI A (see Section 8.4.8)¶

  • Second Sequence:¶

    • Override Parameters directive (see Section 8.4.10.3, Section 8.4.8) for Slot B¶

    • Check Slot Condition (see Section 8.4.9.4)¶

    • Set Parameters directive (see Section 8.4.10.3) for URI B (see Section 8.4.8)¶

• Fetch¶

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

• Set Component Index directive (see Section 8.4.10.1)¶

• Try Each¶

  • First Sequence:¶

    • Override Parameters directive (see Section 8.4.10.3, Section 8.4.8) for Slot A¶

    • Check Slot Condition (see Section 8.4.9.4)¶

  • Second Sequence:¶

    • Override Parameters directive (see Section 8.4.10.3, Section 8.4.8) for Slot B¶

    • Check Slot Condition (see Section 8.4.9.4)¶

• Invoke¶

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

8.1. Encoding Considerations

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

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

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

All CBOR maps in the Manifest and manifest envelope MUST be encoded with the canonical CBOR ordering as defined in [RFC8949].¶

8.2. Envelope

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

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

8.3. Authenticated Manifests

SUIT_Authentication contains a list of elements, which consist of a SUIT_Digest calculated over the manifest, and zero or more SUIT_Authentication_Block's calculated over the SUIT_Digest.¶

SUIT_Authentication = [
    bstr .cbor SUIT_Digest,
    * 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

The SUIT_Digest is computed over the bstr-wrapped SUIT_Manifest that is present in the SUIT_Envelope at the suit-manifest key. The SUIT_Digest MUST always be present. The Manifest Processor requires a SUIT_Authentication_Block to be present. The manifest MUST be protected from tampering between the time of creation and the time of signing/MACing.¶

The SUIT_Authentication_Block is computed using detached payloads, as described in RFC 9052 [RFC9052]. The detached payload in each case is the bstr-wrapped SUIT_Digest at the beginning of the list. Signers (or MAC calculators) MUST verify the SUIT_Digest prior to performing the cryptographic computation to avoid "Time-of-check to time-of-use" type of attack. When multiple SUIT_Authentication_Blocks are present, then each SUIT_Authentication_Block MUST be computed over the same SUIT_Digest but using a different algorithm or signing/MAC authority. This feature also allows to transition to new algorithms, such as post-quantum cryptography (PQC) algorithms.¶

The SUIT_Authentication structure MUST come before the suit-manifest element, regardless of canonical encoding of CBOR. The algorithms used in SUIT_Authentication are defined by the profiles declared in [I-D.ietf-suit-mti].¶

8.4. Manifest

The manifest contains:¶

• a version number (see Section 8.4.1)¶

• a sequence number (see Section 8.4.2)¶

• a reference URI (see Section 8.4.3)¶

• a common structure with information that is shared between command sequences (see Section 8.4.5)¶

• one or more lists of commands that the Recipient should perform (see Section 8.4.6)¶

• a reference to the full manifest (see Section 8.4.3)¶

• human-readable text describing the manifest found in the SUIT_Envelope (see Section 8.4.4)¶

The Text section, or any Command Sequence of the Update Procedure (Image Fetch, Image Installation and, System Validation) can be either a CBOR structure or a SUIT_Digest. In each of these cases, the SUIT_Digest provides for a severable element. Severable elements are RECOMMENDED to implement. In particular, the human-readable text SHOULD be severable, since most useful text elements occupy more space than a SUIT_Digest, but are not needed by the Recipient. Because SUIT_Digest is a CBOR Array and each severable element is a CBOR bstr, it is straight-forward for a Recipient to determine whether an element has been severed. The key used for a severable element is the same in the SUIT_Manifest and in the SUIT_Envelope so that a Recipient can easily identify the correct data in the envelope. See Section 8.4.12 for more detail.¶

tag38-ltag = text .regexp "[a-zA-Z]{1,8}(-[a-zA-Z0-9]{1,8})*"

SUIT_Text_Map = {
    + tag38-ltag => SUIT_Text_LMap
}
SUIT_Text_LMap = {
    SUIT_Text_Keys,
    * SUIT_Component_Identifier => {
        SUIT_Text_Component_Keys
    }
}

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

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

Vendor ID = UUID5(DNS_PREFIX, vendor domain name)

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

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

// content & component must be same length
// returns 0 for match
int check_content(content, component, length) {
    int residual = 0;
    for (i = 0; i < length; i++) {
        residual |= content[i] ^ component[i];
    }
    return residual;
}

8.5. Severable Elements

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

At time of manifest creation, the Author MAY chose to make a manifest element severable by removing it from the manifest, encoding it in a bstr, and placing a SUIT_Digest of the bstr in the manifest so that it can still be authenticated. Making an element severable changes the digest of the manifest, so the signature MUST be computed after manifest elements are made severable. Only Manifest Elements with corresponding elements in the SUIT_Envelope can be made severable (see Section 11.1 for SUIT_Envelope elements). 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.¶

11.1. SUIT Envelope Elements

IANA is requested to create a new registry for SUIT envelope elements.¶

11.2. SUIT Manifest Elements

IANA is requested to create a new registry for SUIT manifest elements.¶

11.3. SUIT Common Elements

IANA is requested to create a new registry for SUIT common elements.¶

11.4. SUIT Commands

IANA is requested to create a new registry for SUIT commands.¶

11.5. SUIT Parameters

IANA is requested to create a new registry for SUIT parameters.¶

11.6. SUIT Text Values

IANA is requested to create a new registry for SUIT text values.¶

11.7. SUIT Component Text Values

IANA is requested to create a new registry for SUIT component text values.¶

11.8. Expert Review Instructions

The IANA registries established in this document allow values to be added based on expert review. This section gives some general guidelines for what the experts should be looking for, but they are being designated as experts for a reason, so they should be given substantial latitude.¶

Expert reviewers should take into consideration the following points:¶

• Point squatting should be discouraged. Reviewers are encouraged to get sufficient information for registration requests to ensure that the usage is not going to duplicate one that is already registered, and that the point is likely to be used in deployments. The zones tagged as private use are intended for testing purposes and closed environments; code points in other ranges should not be assigned for testing.¶

• Specifications are required for the standards track range of point assignment. Specifications should exist for all other ranges, but early assignment before a specification is available is considered to be permissible. When specifications are not provided, the description provided needs to have sufficient information to identify what the point is being used for.¶

• Experts should take into account the expected usage of fields when approving point assignment. The fact that there is a range for standards track documents does not mean that a standards track document cannot have points assigned outside of that range. The length of the encoded value should be weighed against how many code points of that length are left, the size of device it will be used on, and the number of code points left that encode to that size.¶

11.9. Media Type Registration

This section registers the 'application/suit-envelope+cose' media type in the "Media Types" registry. This media type are used to indicate that the content is a SUIT envelope.¶

      Type name: application

      Subtype name: suit-envelope+cose

      Required parameters: N/A

      Optional parameters: N/A

      Encoding considerations: binary

      Security considerations: See the Security Considerations section
      of [[This RFC]].

      Interoperability considerations: N/A

      Published specification: [[This RFC]]

      Applications that use this media type: Primarily used for
        Firmware and software updates although the content may
        also contain configuration data and other information
        related to software and firmware.

      Fragment identifier considerations: N/A

      Additional information:

      *  Deprecated alias names for this type: N/A

      *  Magic number(s): N/A

      *  File extension(s): cbor, suit

      *  Macintosh file type code(s): N/A

      Person & email address to contact for further information:
      [email protected]

      Intended usage: COMMON

      Restrictions on usage: N/A

      Author: Brendan Moran, <[email protected]>

      Change Controller: IESG

      Provisional registration?  No

B.1. Example 0: Secure Boot

This example covers the following templates:¶

• Compatibility Check (Section 7.1)¶

• Secure Boot (Section 7.2)¶

It also serves as the minimum example.¶

107({
        / authentication-wrapper / 2:<< [
            / digest: / << [
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'6658ea560262696dd1f13b782239a064da7c6c5cbaf52fded428a6fc83c7e5af'
            ] >>,
            / signature: / << 18([
                    / protected / << {
                        / alg / 1:-7 / "ES256" /,
                    } >>,
                    / unprotected / {
                    },
                    / payload / F6 / nil /,
                    / signature / h'56acf3c133338f558bbbac1e73a62bffac
2a0067d0f7a2e860e20b9119a61d964af04fb56c2c7618d3d74558c14f5daf7cafa877
1b34ec42160f5c94250a57eb'
                ]) >>
            ]
        ] >>,
        / manifest / 3:<< {
            / manifest-version / 1:1,
            / manifest-sequence-number / 2:0,
            / common / 3:<< {
                / components / 2:[
                    [h'00']
                ],
                / shared-sequence / 4:<< [
                    / directive-override-parameters / 20,{
                        / vendor-id /
1:h'fa6b4a53d5ad5fdfbe9de663e4d41ffe' / fa6b4a53-d5ad-5fdf-
be9d-e663e4d41ffe /,
                        / class-id /
2:h'1492af1425695e48bf429b2d51f2ab45' /
1492af14-2569-5e48-bf42-9b2d51f2ab45 /,
                        / image-digest / 3:<< [
                            / algorithm-id / -16 / "sha256" /,
                            / digest-bytes /
h'00112233445566778899aabbccddeeff0123456789abcdeffedcba9876543210'
                        ] >>,
                        / image-size / 14:34768,
                    } ,
                    / condition-vendor-identifier / 1,15 ,
                    / condition-class-identifier / 2,15
                ] >>,
            } >>,
            / validate / 7:<< [
                / condition-image-match / 3,15
            ] >>,
            / run / 9:<< [
                / directive-run / 23,2
            ] >>,
        } >>,
    })

Total size of Envelope without COSE authentication object: 161¶

Envelope:¶

d86ba2025827815824822f58206658ea560262696dd1f13b782239a064da
7c6c5cbaf52fded428a6fc83c7e5af035871a50101020003585fa2028181
41000458568614a40150fa6b4a53d5ad5fdfbe9de663e4d41ffe02501492
af1425695e48bf429b2d51f2ab45035824822f5820001122334455667788
99aabbccddeeff0123456789abcdeffedcba98765432100e1987d0010f02
0f074382030f0943821702

Total size of Envelope with COSE authentication object: 237¶

Envelope with COSE authentication object:¶

d86ba2025873825824822f58206658ea560262696dd1f13b782239a064da
7c6c5cbaf52fded428a6fc83c7e5af584ad28443a10126a0f6584056acf3
c133338f558bbbac1e73a62bffac2a0067d0f7a2e860e20b9119a61d964a
f04fb56c2c7618d3d74558c14f5daf7cafa8771b34ec42160f5c94250a57
eb035871a50101020003585fa202818141000458568614a40150fa6b4a53
d5ad5fdfbe9de663e4d41ffe02501492af1425695e48bf429b2d51f2ab45
035824822f582000112233445566778899aabbccddeeff0123456789abcd
effedcba98765432100e1987d0010f020f074382030f0943821702

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

This example covers the following templates:¶

• Compatibility Check (Section 7.1)¶

• Firmware Download (Section 7.3)¶

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

107({
        / authentication-wrapper / 2:<< [
            / digest: / << [
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'ef14b7091e8adae8aa3bb6fca1d64fb37e19dcf8b35714cfdddc5968c80ff50e'
            ] >>,
            / signature: / << 18([
                    / protected / << {
                        / alg / 1:-7 / "ES256" /,
                    } >>,
                    / unprotected / {
                    },
                    / payload / F6 / nil /,
                    / signature / h'9c44e07766a26fd33d41ded913363c0ec7
465c06c30be70df32a73a4dea1bbb353d880d9d1813f7b6f0c6987dc4b289838468477
9c17ca9062085487254cf203'
                ]) >>
            ]
        ] >>,
        / manifest / 3:<< {
            / manifest-version / 1:1,
            / manifest-sequence-number / 2:1,
            / common / 3:<< {
                / components / 2:[
                    [h'00']
                ],
                / shared-sequence / 4:<< [
                    / directive-override-parameters / 20,{
                        / vendor-id /
1:h'fa6b4a53d5ad5fdfbe9de663e4d41ffe' / fa6b4a53-d5ad-5fdf-
be9d-e663e4d41ffe /,
                        / class-id /
2:h'1492af1425695e48bf429b2d51f2ab45' /
1492af14-2569-5e48-bf42-9b2d51f2ab45 /,
                        / image-digest / 3:<< [
                            / algorithm-id / -16 / "sha256" /,
                            / digest-bytes /
h'00112233445566778899aabbccddeeff0123456789abcdeffedcba9876543210'
                        ] >>,
                        / image-size / 14:34768,
                    } ,
                    / condition-vendor-identifier / 1,15 ,
                    / condition-class-identifier / 2,15
                ] >>,
            } >>,
            / validate / 7:<< [
                / condition-image-match / 3,15
            ] >>,
            / install / 17:<< [
                / directive-override-parameters / 20,{
                    / uri / 21:'http://example.com/file.bin',
                } ,
                / directive-fetch / 21,2 ,
                / condition-image-match / 3,15
            ] >>,
        } >>,
    })

Total size of Envelope without COSE authentication object: 196¶

Envelope:¶

d86ba2025827815824822f5820ef14b7091e8adae8aa3bb6fca1d64fb37e
19dcf8b35714cfdddc5968c80ff50e035894a50101020103585fa2028181
41000458568614a40150fa6b4a53d5ad5fdfbe9de663e4d41ffe02501492
af1425695e48bf429b2d51f2ab45035824822f5820001122334455667788
99aabbccddeeff0123456789abcdeffedcba98765432100e1987d0010f02
0f074382030f1158258614a115781b687474703a2f2f6578616d706c652e
636f6d2f66696c652e62696e1502030f

Total size of Envelope with COSE authentication object: 272¶

Envelope with COSE authentication object:¶

d86ba2025873825824822f5820ef14b7091e8adae8aa3bb6fca1d64fb37e
19dcf8b35714cfdddc5968c80ff50e584ad28443a10126a0f658409c44e0
7766a26fd33d41ded913363c0ec7465c06c30be70df32a73a4dea1bbb353
d880d9d1813f7b6f0c6987dc4b2898384684779c17ca9062085487254cf2
03035894a50101020103585fa202818141000458568614a40150fa6b4a53
d5ad5fdfbe9de663e4d41ffe02501492af1425695e48bf429b2d51f2ab45
035824822f582000112233445566778899aabbccddeeff0123456789abcd
effedcba98765432100e1987d0010f020f074382030f1158258614a11578
1b687474703a2f2f6578616d706c652e636f6d2f66696c652e62696e1502
030f

B.3. Example 2: Simultaneous Download, Installation, Secure Boot, Severed Fields

This example covers the following templates:¶

• Compatibility Check (Section 7.1)¶

• Secure Boot (Section 7.2)¶

• Firmware Download (Section 7.3)¶

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

107({
        / authentication-wrapper / 2:<< [
            / digest: / << [
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'56c894f743ca34ff0ae76271f964dcb8c139edb4a8dc64b01444504620be28a8'
            ] >>,
            / signature: / << 18([
                    / protected / << {
                        / alg / 1:-7 / "ES256" /,
                    } >>,
                    / unprotected / {
                    },
                    / payload / F6 / nil /,
                    / signature / h'd6fc4cd4119a261c9e7f782226a235aa06
960781a537064131238203e9fcde17f9a04e09f6ace03ef861971ef3d4b519558cdd96
6a6303e7e82783d6b2a99cf2'
                ]) >>
            ]
        ] >>,
        / manifest / 3:<< {
            / manifest-version / 1:1,
            / manifest-sequence-number / 2:2,
            / common / 3:<< {
                / components / 2:[
                    [h'00']
                ],
                / shared-sequence / 4:<< [
                    / directive-override-parameters / 20,{
                        / vendor-id /
1:h'fa6b4a53d5ad5fdfbe9de663e4d41ffe' / fa6b4a53-d5ad-5fdf-
be9d-e663e4d41ffe /,
                        / class-id /
2:h'1492af1425695e48bf429b2d51f2ab45' /
1492af14-2569-5e48-bf42-9b2d51f2ab45 /,
                        / image-digest / 3:<< [
                            / algorithm-id / -16 / "sha256" /,
                            / digest-bytes /
h'00112233445566778899aabbccddeeff0123456789abcdeffedcba9876543210'
                        ] >>,
                        / image-size / 14:34768,
                    } ,
                    / condition-vendor-identifier / 1,15 ,
                    / condition-class-identifier / 2,15
                ] >>,
            } >>,
            / reference-uri / 4:'https://git.io/JJYoj',
            / validate / 7:<< [
                / condition-image-match / 3,15
            ] >>,
            / run / 9:<< [
                / directive-run / 23,2
            ] >>,
            / install / 17:[
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'cfa90c5c58595e7f5119a72f803fd0370b3e6abbec6315cd38f63135281bc498'
            ],
            / text / 23:[
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'302196d452bce5e8bfeaf71e395645ede6d365e63507a081379721eeecf00007'
            ],
        } >>,
    })

Total size of the Envelope without COSE authentication object or Severable Elements: 257¶

Envelope:¶

d86ba2025827815824822f582056c894f743ca34ff0ae76271f964dcb8c1
39edb4a8dc64b01444504620be28a80358d1a80101020203585fa2028181
41000458568614a40150fa6b4a53d5ad5fdfbe9de663e4d41ffe02501492
af1425695e48bf429b2d51f2ab45035824822f5820001122334455667788
99aabbccddeeff0123456789abcdeffedcba98765432100e1987d0010f02
0f047468747470733a2f2f6769742e696f2f4a4a596f6a074382030f0943
82170211822f5820cfa90c5c58595e7f5119a72f803fd0370b3e6abbec63
15cd38f63135281bc49817822f5820302196d452bce5e8bfeaf71e395645
ede6d365e63507a081379721eeecf00007

Total size of the Envelope with COSE authentication object but without Severable Elements: 333¶

Envelope:¶
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Total size of Envelope with COSE authentication object and Severable Elements: 923¶

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

This example covers the following templates:¶

• Compatibility Check (Section 7.1)¶

• Secure Boot (Section 7.2)¶

• Firmware Download (Section 7.3)¶

• A/B Image Template (Section 7.7)¶

107({
        / authentication-wrapper / 2:<< [
            / digest: / << [
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'b3e6a52776bf3ed218feba031c609c98260e1a52fc1f019683edb6d1c5c4a379'
            ] >>,
            / signature: / << 18([
                    / protected / << {
                        / alg / 1:-7 / "ES256" /,
                    } >>,
                    / unprotected / {
                    },
                    / payload / F6 / nil /,
                    / signature / h'a72d9dabc04af139a0a5b3ef775234b9ed
1c2390e03ffa1454458b2394cca16aced37039bbf84ea898a54a242d0d04883f22135a
9b98efe042015041f0142d4e'
                ]) >>
            ]
        ] >>,
        / manifest / 3:<< {
            / manifest-version / 1:1,
            / manifest-sequence-number / 2:3,
            / common / 3:<< {
                / components / 2:[
                    [h'00']
                ],
                / shared-sequence / 4:<< [
                    / directive-override-parameters / 20,{
                        / vendor-id /
1:h'fa6b4a53d5ad5fdfbe9de663e4d41ffe' / fa6b4a53-d5ad-5fdf-
be9d-e663e4d41ffe /,
                        / class-id /
2:h'1492af1425695e48bf429b2d51f2ab45' /
1492af14-2569-5e48-bf42-9b2d51f2ab45 /,
                    } ,
                    / directive-try-each / 15,[
                        << [
                            / directive-override-parameters / 20,{
                                / slot / 5:0,
                            } ,
                            / condition-component-slot / 5,5 ,
                            / directive-override-parameters / 20,{
                                / image-digest / 3:<< [
                                    / algorithm-id / -16 / "sha256" /,
                                    / digest-bytes /
h'00112233445566778899aabbccddeeff0123456789abcdeffedcba9876543210'
                                ] >>,
                                / image-size / 14:34768,
                            }
                        ] >> ,
                        << [
                            / directive-override-parameters / 20,{
                                / slot / 5:1,
                            } ,
                            / condition-component-slot / 5,5 ,
                            / directive-override-parameters / 20,{
                                / image-digest / 3:<< [
                                    / algorithm-id / -16 / "sha256" /,
                                    / digest-bytes /
h'0123456789abcdeffedcba987654321000112233445566778899aabbccddeeff'
                                ] >>,
                                / image-size / 14:76834,
                            }
                        ] >>
                    ] ,
                    / condition-vendor-identifier / 1,15 ,
                    / condition-class-identifier / 2,15
                ] >>,
            } >>,
            / validate / 7:<< [
                / condition-image-match / 3,15
            ] >>,
            / install / 17:<< [
                / directive-try-each / 15,[
                    << [
                        / directive-override-parameters / 20,{
                            / slot / 5:0,
                        } ,
                        / condition-component-slot / 5,5 ,
                        / directive-override-parameters / 20,{
                            / uri / 21:'http://example.com/file1.bin',
                        }
                    ] >> ,
                    << [
                        / directive-override-parameters / 20,{
                            / slot / 5:1,
                        } ,
                        / condition-component-slot / 5,5 ,
                        / directive-override-parameters / 20,{
                            / uri / 21:'http://example.com/file2.bin',
                        }
                    ] >>
                ] ,
                / directive-fetch / 21,2 ,
                / condition-image-match / 3,15
            ] >>,
        } >>,
    })

Total size of Envelope without COSE authentication object: 320¶

Envelope:¶
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Total size of Envelope with COSE authentication object: 396¶

Envelope with COSE authentication object:¶

d86ba2025873825824822f5820b3e6a52776bf3ed218feba031c609c9826
0e1a52fc1f019683edb6d1c5c4a379584ad28443a10126a0f65840a72d9d
abc04af139a0a5b3ef775234b9ed1c2390e03ffa1454458b2394cca16ace
d37039bbf84ea898a54a242d0d04883f22135a9b98efe042015041f0142d
4e0359010fa5010102030358a4a2028181410004589b8814a20150fa6b4a
53d5ad5fdfbe9de663e4d41ffe02501492af1425695e48bf429b2d51f2ab
450f8258348614a10500050514a2035824822f5820001122334455667788
99aabbccddeeff0123456789abcdeffedcba98765432100e1987d0583686
14a10501050514a2035824822f58200123456789abcdeffedcba98765432
1000112233445566778899aabbccddeeff0e1a00012c22010f020f074382
030f11585b860f8258288614a10500050514a115781c687474703a2f2f65
78616d706c652e636f6d2f66696c65312e62696e58288614a10501050514
a115781c687474703a2f2f6578616d706c652e636f6d2f66696c65322e62
696e1502030f

B.5. Example 4: Load from External Storage

This example covers the following templates:¶

• Compatibility Check (Section 7.1)¶

• Secure Boot (Section 7.2)¶

• Firmware Download (Section 7.3)¶

• Install (Section 7.4)¶

• Load (Section 7.6)¶

107({
        / authentication-wrapper / 2:<< [
            / digest: / << [
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'838eb848698c9d9dd29b5930102ea1f29743857d975f52ed4d19589b821e82cf'
            ] >>,
            / signature: / << 18([
                    / protected / << {
                        / alg / 1:-7 / "ES256" /,
                    } >>,
                    / unprotected / {
                    },
                    / payload / F6 / nil /,
                    / signature / h'42e4185517635842a5715c63772436588c
c366d6a4c2beff3f3e0736806062c4208a756da9cfb0cc1325168eb3c743834b5f5a5d
c00b33acd2a9073c6eb09e5c'
                ]) >>
            ]
        ] >>,
        / manifest / 3:<< {
            / manifest-version / 1:1,
            / manifest-sequence-number / 2:4,
            / common / 3:<< {
                / components / 2:[
                    [h'00'] ,
                    [h'02'] ,
                    [h'01']
                ],
                / shared-sequence / 4:<< [
                    / directive-set-component-index / 12,0 ,
                    / directive-override-parameters / 20,{
                        / vendor-id /
1:h'fa6b4a53d5ad5fdfbe9de663e4d41ffe' / fa6b4a53-d5ad-5fdf-
be9d-e663e4d41ffe /,
                        / class-id /
2:h'1492af1425695e48bf429b2d51f2ab45' /
1492af14-2569-5e48-bf42-9b2d51f2ab45 /,
                        / image-digest / 3:<< [
                            / algorithm-id / -16 / "sha256" /,
                            / digest-bytes /
h'00112233445566778899aabbccddeeff0123456789abcdeffedcba9876543210'
                        ] >>,
                        / image-size / 14:34768,
                    } ,
                    / condition-vendor-identifier / 1,15 ,
                    / condition-class-identifier / 2,15
                ] >>,
            } >>,
            / validate / 7:<< [
                / directive-set-component-index / 12,0 ,
                / condition-image-match / 3,15
            ] >>,
            / load / 8:<< [
                / directive-set-component-index / 12,2 ,
                / directive-override-parameters / 20,{
                    / image-digest / 3:<< [
                        / algorithm-id / -16 / "sha256" /,
                        / digest-bytes /
h'0123456789abcdeffedcba987654321000112233445566778899aabbccddeeff'
                    ] >>,
                    / image-size / 14:76834,
                    / source-component / 22:0 / [h'00'] /,
                } ,
                / directive-copy / 22,2 ,
                / condition-image-match / 3,15
            ] >>,
            / run / 9:<< [
                / directive-set-component-index / 12,2 ,
                / directive-run / 23,2
            ] >>,
            / payload-fetch / 16:<< [
                / directive-set-component-index / 12,1 ,
                / directive-override-parameters / 20,{
                    / image-digest / 3:<< [
                        / algorithm-id / -16 / "sha256" /,
                        / digest-bytes /
h'00112233445566778899aabbccddeeff0123456789abcdeffedcba9876543210'
                    ] >>,
                    / uri / 21:'http://example.com/file.bin',
                } ,
                / directive-fetch / 21,2 ,
                / condition-image-match / 3,15
            ] >>,
            / install / 17:<< [
                / directive-set-component-index / 12,0 ,
                / directive-override-parameters / 20,{
                    / source-component / 22:1 / [h'02'] /,
                } ,
                / directive-copy / 22,2 ,
                / condition-image-match / 3,15
            ] >>,
        } >>,
    })

Total size of Envelope without COSE authentication object: 327¶

Envelope:¶

d86ba2025827815824822f5820838eb848698c9d9dd29b5930102ea1f297
43857d975f52ed4d19589b821e82cf03590116a801010204035867a20283
814100814102814101045858880c0014a40150fa6b4a53d5ad5fdfbe9de6
63e4d41ffe02501492af1425695e48bf429b2d51f2ab45035824822f5820
00112233445566778899aabbccddeeff0123456789abcdeffedcba987654
32100e1987d0010f020f0745840c00030f085838880c0214a3035824822f
58200123456789abcdeffedcba987654321000112233445566778899aabb
ccddeeff0e1a00012c2216001602030f0945840c02170210584e880c0114
a2035824822f582000112233445566778899aabbccddeeff0123456789ab
cdeffedcba987654321015781b687474703a2f2f6578616d706c652e636f
6d2f66696c652e62696e1502030f114b880c0014a116011602030f

Total size of Envelope with COSE authentication object: 403¶

Envelope with COSE authentication object:¶

d86ba2025873825824822f5820838eb848698c9d9dd29b5930102ea1f297
43857d975f52ed4d19589b821e82cf584ad28443a10126a0f6584042e418
5517635842a5715c63772436588cc366d6a4c2beff3f3e0736806062c420
8a756da9cfb0cc1325168eb3c743834b5f5a5dc00b33acd2a9073c6eb09e
5c03590116a801010204035867a20283814100814102814101045858880c
0014a40150fa6b4a53d5ad5fdfbe9de663e4d41ffe02501492af1425695e
48bf429b2d51f2ab45035824822f582000112233445566778899aabbccdd
eeff0123456789abcdeffedcba98765432100e1987d0010f020f0745840c
00030f085838880c0214a3035824822f58200123456789abcdeffedcba98
7654321000112233445566778899aabbccddeeff0e1a00012c2216001602
030f0945840c02170210584e880c0114a2035824822f5820001122334455
66778899aabbccddeeff0123456789abcdeffedcba987654321015781b68
7474703a2f2f6578616d706c652e636f6d2f66696c652e62696e1502030f
114b880c0014a116011602030f

B.6. Example 5: Two Images

This example covers the following templates:¶

• Compatibility Check (Section 7.1)¶

• Secure Boot (Section 7.2)¶

• Firmware Download (Section 7.3)¶

Furthermore, it shows using these templates with two images.¶

107({
        / authentication-wrapper / 2:<< [
            / digest: / << [
                / algorithm-id / -16 / "sha256" /,
                / digest-bytes /
h'264dc89eb4a39ae7a8ed05e4d6232153bce4fb9a111a31310b90627d1edfc3bb'
            ] >>,
            / signature: / << 18([
                    / protected / << {
                        / alg / 1:-7 / "ES256" /,
                    } >>,
                    / unprotected / {
                    },
                    / payload / F6 / nil /,
                    / signature / h'9350fcb80d59f9be2a923bc144c5f64022
b57d18ccddd9c0477a5be608b04200689373d42fc42fc154dce2d54255d64be9f5bd55
efddb5de22354ec0894e979a'
                ]) >>
            ]
        ] >>,
        / manifest / 3:<< {
            / manifest-version / 1:1,
            / manifest-sequence-number / 2:5,
            / common / 3:<< {
                / components / 2:[
                    [h'00'] ,
                    [h'01']
                ],
                / shared-sequence / 4:<< [
                    / directive-set-component-index / 12,0 ,
                    / directive-override-parameters / 20,{
                        / vendor-id /
1:h'fa6b4a53d5ad5fdfbe9de663e4d41ffe' / fa6b4a53-d5ad-5fdf-
be9d-e663e4d41ffe /,
                        / class-id /
2:h'1492af1425695e48bf429b2d51f2ab45' /
1492af14-2569-5e48-bf42-9b2d51f2ab45 /,
                        / image-digest / 3:<< [
                            / algorithm-id / -16 / "sha256" /,
                            / digest-bytes /
h'00112233445566778899aabbccddeeff0123456789abcdeffedcba9876543210'
                        ] >>,
                        / image-size / 14:34768,
                    } ,
                    / condition-vendor-identifier / 1,15 ,
                    / condition-class-identifier / 2,15 ,
                    / directive-set-component-index / 12,1 ,
                    / directive-override-parameters / 20,{
                        / image-digest / 3:<< [
                            / algorithm-id / -16 / "sha256" /,
                            / digest-bytes /
h'0123456789abcdeffedcba987654321000112233445566778899aabbccddeeff'
                        ] >>,
                        / image-size / 14:76834,
                    }
                ] >>,
            } >>,
            / validate / 7:<< [
                / directive-set-component-index / 12,0 ,
                / condition-image-match / 3,15 ,
                / directive-set-component-index / 12,1 ,
                / condition-image-match / 3,15
            ] >>,
            / run / 9:<< [
                / directive-set-component-index / 12,0 ,
                / directive-run / 23,2
            ] >>,
            / install / 17:<< [
                / directive-set-component-index / 12,0 ,
                / directive-override-parameters / 20,{
                    / uri / 21:'http://example.com/file1.bin',
                } ,
                / directive-fetch / 21,2 ,
                / condition-image-match / 3,15 ,
                / directive-set-component-index / 12,1 ,
                / directive-override-parameters / 20,{
                    / uri / 21:'http://example.com/file2.bin',
                } ,
                / directive-fetch / 21,2 ,
                / condition-image-match / 3,15
            ] >>,
        } >>,
    })

Total size of Envelope without COSE authentication object: 306¶

Envelope:¶
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Total size of Envelope with COSE authentication object: 382¶

Envelope with COSE authentication object:¶

d86ba2025873825824822f5820264dc89eb4a39ae7a8ed05e4d6232153bc
e4fb9a111a31310b90627d1edfc3bb584ad28443a10126a0f658409350fc
b80d59f9be2a923bc144c5f64022b57d18ccddd9c0477a5be608b0420068
9373d42fc42fc154dce2d54255d64be9f5bd55efddb5de22354ec0894e97
9a03590101a601010205035895a202828141008141010458898c0c0014a4
0150fa6b4a53d5ad5fdfbe9de663e4d41ffe02501492af1425695e48bf42
9b2d51f2ab45035824822f582000112233445566778899aabbccddeeff01
23456789abcdeffedcba98765432100e1987d0010f020f0c0114a2035824
822f58200123456789abcdeffedcba987654321000112233445566778899
aabbccddeeff0e1a00012c220749880c00030f0c01030f0945840c001702
11584f900c0014a115781c687474703a2f2f6578616d706c652e636f6d2f
66696c65312e62696e1502030f0c0114a115781c687474703a2f2f657861
6d706c652e636f6d2f66696c65322e62696e1502030f

C.1. C.1 Design Rationale: Envelope

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

1. This enables the use of Severable Elements (Section 8.5)¶

2. This enables modular processing of manifests, particularly with large signatures.¶

3. This enables multiple authentication schemes.¶

4. This allows integrity verification by a dependent to be unaffected by adding or removing authentication structures.¶

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

Four authentication objects are supported by the Envelope:¶

• COSE_Sign_Tagged¶

• COSE_Sign1_Tagged¶

• COSE_Mac_Tagged¶

• COSE_Mac0_Tagged¶

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

C.2. C.2 Byte String Wrappers

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

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

The common block is re-parsed in order to find components identifiers from their indices, to find dependency prefixes and digests from their identifiers, and to find the shared sequence. The shared 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.¶