Update Management Extensions for Software Updates for Internet of Things (SUIT) Manifests

3.1. suit-coswid

a CoSWID can enable Software Bill-of-Materials use-cases. A CoMID can enable monitoring of expected hardware. A CoRIM (which may contain both CoSWID and CoMID) can enable both of these use-cases, but can also act as the transport for expected values to an attestation Verifier. Tightly coupling update and attestation ensures that verification infrastructure always knows what software to expect on each device.¶

suit-coswid is a member of the suit-manifest. It contains a Concise Software Identifier (CoSWID) as defined in [I-D.ietf-sacm-coswid]. 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 typically requires no processing by the Recipient. However all Recipients MUST NOT fail if a suit-coswid is present.¶

suit-coswid is RECOMMENDED to implement and RECOMMENDED to include in manifests.¶

NOTE: CoRIM comprises a list of CoSWID and a list of CoMID, so it may be preferable to a CoSWID.¶

NOTE: CoMID may be a preferable alternative to Vendor ID/Class ID, however it consumes more bandwidth, so a UUID based on CoMID may be appropriate.¶

3.2. text-version-required

suit-text-version-required is used to represent a version-based dependency on suit-parameter-version as described in Section 4.4 and Section 5.5. 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 free text expression that is representative of the version constraints placed on the dependency. This text SHOULD be expressive enough that a device operator can be expected to understand the dependency. This is a free text field and there are no specific formatting rules.¶

By way of example only, 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"
}

4.1. suit-parameter-use-before

An expiry date for the use of the manifest encoded as the positive integer number of seconds since 1970-01-01. Implementations that use this parameter MUST use a 64-bit internal representation of the integer. Used with Section 5.1¶

4.2. suit-parameter-minimum-battery

This parameter sets the minimum battery level in mWh. This parameter is encoded as a positive integer. Used with suit-condition-minimum-battery (Section 5.3).¶

4.3. suit-parameter-update-priority

This parameter sets the priority of the update. This parameter is encoded as an integer. It is used along with suit-condition-update-authorized (Section 5.4) 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.¶

4.4. suit-parameter-version

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 suit-condition-version (Section 5.5) 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:¶

1. The first integer represents the major number. This indicates breaking changes to the component.¶
2. The second integer represents the minor number. This is typically reserved for new features or large, non-breaking changes.¶
3. The third integer is the patch version. This is typically reserved for bug fixes.¶
4. 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.¶

4.5. suit-parameter-wait-info

suit-directive-wait (Section 5.6) 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.¶

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.¶

4.6. suit-parameter-component-metadata

In some instances, a system may need to know the file metadata for a component. This metadata can include:¶

• creator¶
• creation time¶
• modification time¶
• default permissions (rwx)¶
• a map of user/permission pairs¶
• a map of role/permission pairs¶
• a map of group/permission pairs¶
• file type¶

Component metadata is applied at time of fetch, copy, or write; see [I-D.ietf-suit-manifest], sections 8.4.10.4, 8.4.10.5, 8.4.10.6. Therefore, the component metadata parameter must be set in advance of the component being fetched, copied into, or written.¶

SUIT_meta_actor_id = UUID_Tagged / bstr / str / int
UUID_Tagged = #6.37(bstr)

suit-meta-modification-time => #6.1(uint)
suit-meta-creation-time => #6.1(uint)

SUIT_meta_permissions = uint .bits SUIT_meta_permission_bits
SUIT_meta_permission_bits = &(
    r: 2, w: 1, x: 0,
    * $$SUIT_meta_permission_bits_extensions
)

SUIT_meta_permission_map = {
    + SUIT_meta_actor_id => SUIT_meta_permissions
}

5.1. suit-condition-use-before

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 (Section 4.1), which must have already been set as a parameter, encoded as seconds after 1970-01-01 00:00:00 UTC. Timestamp conditions MUST be evaluated in 64 bits, regardless of encoded CBOR size. suit-condition-use-before is OPTIONAL to implement.¶

5.2. suit-condition-image-not-match

Verify that the current component does not match the suit-parameter-image-digest (Section 8.4.8.6 of [I-D.ietf-suit-manifest]). If no digest is specified, the condition fails. suit-condition-image-not-match is OPTIONAL to implement.¶

5.3. suit-condition-minimum-battery

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 suit-parameter-minimum-battery (Section 4.2).¶

5.4. suit-condition-update-authorized

Request Authorization from the application and fail if not authorized. This can allow a user to decline an update. suit-parameter-update-priority (Section 4.3) 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.¶

5.5. suit-condition-version

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-parameter-version (Section 4.4)¶

5.6. suit-directive-wait

suit-directive-wait directs the manifest processor to pause until a specified event occurs. Some possible events include:¶

1. Authorization¶
2. External Power¶
3. Network availability¶
4. Other Device Firmware Version¶
5. Time¶
6. Time of Day¶
7. Day of Week¶

5.7. suit-directive-override-multiple

This directive enables setting parameters for multiple components at the same time. This allows a small reduction in encoding overhead:¶

• without override-multiple, the encoding for each component consists of:¶

  • set-component-index (2 bytes)¶
  • override-parameters (1 byte + parameter map)¶

• with override-multiple, the encoding for each component consists of:¶

  • the component index key (1 byte)¶
  • the parameter map¶

Override-multiple requires the command (1-2 bytes) and one additional map to hold the parameter sets (1 byte). For one component, there is no savings. For multiple components, there is an encoding savings of 2 bytes per component.¶

Proper structuring of code should ensure that override-multiple follows a code-path nearly identical to set-component-index + override-parameters.¶

This command is purely an encoding alias for set-component-index and override-parameters. The component index is set to the last component listed in the override-multiple argument when override-multiple completes.¶

The following CDDL defines the argument for suit-directive-override-multiple:¶

CDDL SUIT_Override_Mult_Arg = { uint => {+ $$SUIT_Parameters} } ¶

5.8. suit-directive-copy-params

suit-directive-copy-params enables a manifest author to specify one or more components to copy parameters from, and a list of parameters to copy from each specified source component.¶

The behaviour is exactly the same as override parameters, but with parameter values defined in existing components. Parameters are only copied between identical keys (no copying from URI to digest, for example).¶

For each entry in the map, the manifest processor sets the source component to be the component identified by the index contained in the map key. For each parameter identified in the copy list, the manifest processor copies the parameter from the source component to the current component.¶

The following CDDL defines the argument for suit-directive-copy-params:¶

CDDL SUIT_Directive_Copy_Params = { uint => [+ int] } ¶

6.1. SUIT Commands

6.2. SUIT Parameters