[Suit] How are firmware and firmware versions expressed in manifest?

[Hannes Tschofenig <[e-mail]>]

Hi all,

in his review of the recent manifest draft Saad (on CC) pointed out that it is not clear how the firmware version is identified in the manifest. This is a good question and I thought I bring up to the group. It turns out that there are different use cases that require identification of different pieces of software and here is a list of what I consider relevant:

* The manifest needs to point to a location where to obtain the firmware. This is accomplished with a URL. Section 7.3 describes an example (look for the uri parameters directive).

* There is the digest of the firmware, which is used for security purposes, and there is an example in Section 7.3 (look for the image digest parameters directive).

* Then, there is also the component id, which indicates where to store the software / image. We discussed this recently in the context of TEEP where the binaries of trusted applications are protected with the manifest and those binaries will typically end up on a file system. In the OP-TEE secure world OS those binaries are stored with the UUIDs in their file name. In a low end IoT device, like a Cortex M class processor, there is typically no file system and hence the firmware image ends up in a flash memory slot.

* There is also the case with a differential update where the manifest needs to indicate to what firmware images the differential update can be applied to. This is accomplished with the image match condition.

* Finally, there is also a version condition. This allows to express that a manifest is applicable to one or multiple versions of the firmware. As described in the information model draft, this situation occurs when you upload an application that relies on existing software to be present on the device. (Think of it as an API version.)

It is important to note that the manifest is not meant to be used to describe the software running on the device. This is the job of other tools, such as COSWID. The manifest instead provides instructions on how to update firmware and to accomplish secure boot.

Is this a topic that needs to be better described in the draft?

Ciao
Hannes
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