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From: Carsten Bormann <cabo@tzi.org>
In-Reply-To: <edc46af214244a119950582014c8dbfe@nordicsemi.no>
Date: Wed, 4 Jul 2018 22:38:21 +0200
Cc: suit <suit@ietf.org>, cbor@ietf.org
Message-Id: <F5F669C7-EBE8-41B7-B9C3-9A27F45F264B@tzi.org>
References: <edc46af214244a119950582014c8dbfe@nordicsemi.no>
To: Brendan Moran <Brendan.Moran@arm.com>,
 =?utf-8?Q?=C3=98yvind_R=C3=B8nningstad?= <Oyvind.Ronningstad@nordicsemi.no>
Archived-At: <https://mailarchive.ietf.org/arch/msg/suit/iBqWCq061T5Pve2Z3yaYn3BnccM>
Subject: Re: [Suit] draft-moran-suit-manifest-02
Precedence: list


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On Jul 4, 2018, at 10:26, R=C3=B8nningstad, =C3=98yvind =
<Oyvind.Ronningstad@nordicsemi.no> wrote:
>=20
> 	=E2=80=A2 CDDL nitpicking:
> 		=E2=80=A2 Some name inconsistencies: ProcessingStep vs =
Processor, TargetInfo vs Target.
> 		=E2=80=A2 There's probably a typo in the definition of =
Directive. Should it be an array of maps?
> 		=E2=80=A2 Target::storageIdentifier and =
Target::componentIdentifier don't use the custom types for =
StorageIdentifier and ComponentIdentifier.
> 		=E2=80=A2 I think digests should have a type, so the =
user can more easily restrict its format after choosing a digest =
algorithm.
> 		=E2=80=A2 Suggestion: Add nint to textKeys group.
> 		=E2=80=A2 AuthenticatedManifest should probably contain =
an authenticatedManifestVersion or similar.
> 		=E2=80=A2 "Processor" might be confusing (=E2=80=9Cdoes =
it mean CPU?=E2=80=9D).

It also helps to occasionally run instances of formal languages through =
some tool to check them=E2=80=A6

Apart from inconsistent use of names, most of the syntax errors stem =
from the arcane syntax that CDDL is using for its workaround for not =
having true enumerations (Section 2.2.2.2 of =
draft-ietf-cbor-cddl-03.txt); this requires commas (or nothing) instead =
of slashes, and an enclosing &, so with =C3=98yvind=E2=80=99s =
suggestion, textKeys becomes, e.g.:

  textKeys =3D &(
      uninitialised: 0
      manifestDescription: 1
      payloadDescription: 2
      vendorName: 3
      modelName: 4
      payloadVersion: 5
  ) / nint

And Processor starts off as:

  Processor       =3D [
      &(decrypt: 1, decompress: 2, undiff: 3, relocate: 4, unrelocate: =
5),


(Of course, the same thing can be expressed as:

  Processor       =3D [
      &(decrypt: 1, decompress: 2, undiff: 3, relocate: 4, unrelocate: =
5),
      decrypt: 1 // decompress: 2 // undiff: 3 // relocate: 4 // =
unrelocate: 5,

Not sure what the intent is here; in the first case, I=E2=80=99d =
probably also add a label, as in

  Processor       =3D [
      process: &(decrypt: 1, decompress: 2, undiff: 3, relocate: 4, =
unrelocate: 5),

I have attached a version that parses (I don=E2=80=99t think an =
attachment will make it to the lists) but does not address any other of =
=C3=98yvind=E2=80=99s suggestions.

The other problem that should probably be addressed is that most rules =
are unused =E2=80=94 there would need to be one cddl file for the =
manifest, and maybe one for the COSE envelope.  We simply don=E2=80=99t =
have a good way in CDDL yet to say =E2=80=9CManifest goes through an =
algorithm and turns up in COSE_Sign=E2=80=9D =E2=80=94 actually, in this =
case this could be solved in part as the manifest turns up in cleartezt.
I have included a dirty hack in the attached which I intend to fix.

I=E2=80=99m CCing the CBOR WG to give an example for CDDL being used in =
another WG.  If you want to discuss a CDDL feature, please strike SUIT =
from the list (and if you want to discuss a SUIT feature, maybe strike =
CBOR from the list).

Gr=C3=BC=C3=9Fe, Carsten


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  AuthenticatedManifest = [
      authenticatedManifest: COSE_Mac<Manifest> / COSE_Sign<Manifest>,
      text: bstr .cbor textMap
  ]
  COSE_Mac<what> = bstr .cbor what ; these are lies; FIXME
  COSE_Sign<what> = bstr .cbor what ; these are lies; FIXME

  textKeys = &(
      uninitialised: 0
      manifestDescription: 1
      payloadDescription: 2
      vendorName: 3
      modelName: 4
      payloadVersion: 5
  ) / nint

  textMap = { * textKeys => tstr }

  Manifest = [
      manifestVersion :    1,
      digestInfo :         DigestInfo,

      ; textReference is the digest of the associated
      ; text map in AuthenticatedManifest
      textReference :      bstr,
      nonce :              bstr,
      sequence :           SequenceNumber,
      preConditions :      [ * PreCondition ],
      postConditions :     [ * PostCondition ],
      directives :         [ * Directive ],
      resources :          [ * ResourceInfo ],
      processors :         [ * ProcessingStep ],
      targets :            [ * TargetInfo ],
      extensions :         { * int => bstr}
  ]

  ResourceInfo = [
      type:              &(payload:1, dependency:2, key:3, alias:4)
      indicator:         UriList,     ; where to find the resource
      size:              uint / nil,  ; size of the resource
                                      ; (nil when alias)
      digest:            bstr,        ; digest of the resource
      onode:             bstr          ; Node of the processing
                                      ; graph that the resource feeds
  ]

  ProcessingStep       = [
      process: &(decrypt: 1, decompress: 2, undiff: 3, relocate: 4, unrelocate: 5),
;      decrypt: 1 // decompress: 2 // undiff: 3 // relocate: 4 // unrelocate: 5,
      parameters: bstr ; TBD: more detail needed
      inode: bstr,     ; Node of the processing graph
                       ; that this processor consumes
      onode: bstr      ; Node of the processing graph
                       ; that this processor feeds
  ]
  TargetInfo = [
      componentIdentifier: [ * bstr],
      storageIdentifier:   tstr,        ; where to store the resource
      encoding:            bstr / nil,  ; the format of the resource
                                        ; (nil when alias)
      inode:               bstr         ; Node of the processing graph
                                        ; that this target consumes
  ]

  PreCondition    = IdCondition / TimeCondition /
                    ImageCondition / CustomCondition
  PostCondition   = ImageCondition / CustomCondition
  IdCondition     = [&(vendor: 1, class: 2, device: 3),
                     id:         Uuid]
  TimeCondition   = [&(installAfter: 4, bestBefore: 5),
                    time:       Timestamp]
  ImageCondition  = [&(currentContent: 6, notCurrentContent: 7),
                    digest:     bstr / nil, location: StorageIdentifier]
  CustomCondition = [nint, parameters: bstr]
  Directive       = [ int => bstr ]

  SequenceNumber      = uint
  Timestamp           = uint .size 8
  Uuid                = bstr .size 16
  StorageIdentifier   = bstr
  ComponentIdentifier = bstr                    ;;; XXX unused -- what is this for?
  UriList             = { + int => tstr }
  DigestInfo          = [
      digestAlgorithm  : uint,
      ? digestParameters : bstr
  ]

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