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Versions: (draft-moran-fud-manifest) 00 01 02

SUIT                                                            B. Moran
Internet-Draft                                             H. Tschofenig
Intended status: Standards Track                             Arm Limited
Expires: January 3, 2019                                   July 02, 2018


               A CBOR-based Manifest Serialisation Format
                      draft-moran-suit-manifest-02

Abstract

   This specification describes the serialization 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.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   This Internet-Draft will expire on January 3, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.



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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
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   Without obtaining an adequate license from the person(s) controlling
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   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Terminology . . . . . . . . . . . . . . . . .   3
     2.1.  Manifest Serialization Format . . . . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  Mailing List Information  . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     7.2.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   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 meta-data about the conveyed firmware image (in the form
   of a manifest) and the use of 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) is able to install firmware updates on IoT
   devices without adequate privileges.  This authorization process is
   ensured by the use of dedicated credentials and authorization
   permissions installed on the IoT device.

   This document is part of larger document set: the architecture
   document can be found in [I-D.ietf-suit-architecture] and the
   information model of the manifest is described in
   [I-D.ietf-suit-information-model].  This document focuses on the
   serialization format.




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2.  Conventions and Terminology

   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 RFC
   2119 [RFC2119].

2.1.  Manifest Serialization Format

   The following CDDL fragment defines the manifest.

   Wherever enumerations are used, they are started at 1.  This allows
   detection of several common software errors that are caused by
   uninitialised variables.

   The processing graph is a mechanism that maps from resources to
   installed firmware.  On one side of the graph are the resources.
   These are the raw content that a device acquires.  Resources can be
   remote (for example, on a server) or local (for example, an already
   installed firmware).  On the other side of the graph are targets.
   These are the locations that firmware is installed to.  In between
   these two sides are processors.  These are the steps that a device
   takes to translate raw content into firmware that is installed.  In
   the simplest case, this is a direct mapping; the resource is
   installed into the target directly.  In an example complex case, a
   device must use decryption, decompression, and differential patching
   to create the final resource.  Differential patching requires that
   the device refer to an already-installed firmware.  In this graph,
   there are two resources, three processors, and one target.  In some
   cases, one resource may be used by multiple processors, such as a
   compression table.  The nodes of the graph are the resources before
   or after transformation by a processor and the edges of the graph are
   the processors themselves.

   Resources, processors and targets are marked with node identifiers.
   Resources have an output node.  Targets have an input node.
   Processors have both.

  AuthenticatedManifest = [
      authenticatedManifest: COSE_Mac / COSE_Sign,
      text: bstr .cbor textMap
  ]
  COSE_Mac = any
  COSE_Sign = any

  textKeys = (
      uninitialised: 0 /
      manifestDescription: 1 /



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      payloadDescription: 2 /
      vendorName: 3 /
      modelName: 4 /
      payloadVersion: 5
  )

  textMap = { * textKeys / nint => 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
  ]

  Processor       = [
      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
  ]
  Target = [
      componentIdentifier: [ * bstr],
      storageIdentifier:   tstr,        ; where to store the resource



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      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
  UriList             = { + int => tstr }
  DigestInfo          = [
      digestAlgorithm  : uint,
      ? digestParameters : bstr
  ]

3.  IANA Considerations

   TBD: Several registries will be required for: * Standard Conditions *
   Standard Directives * Standard Processors * Standard text values

4.  Security Considerations

   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 more detailed discussion about security can be found in
   the architecture document [I-D.ietf-suit-architecture] and in the
   information model document [I-D.ietf-suit-information-model].

5.  Mailing List Information

   The discussion list for this document is located at the e-mail
   address suit@ietf.org [1].  Information on the group and information




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   on how to subscribe to the list is at
   https://www1.ietf.org/mailman/listinfo/suit

   Archives of the list can be found at: https://www.ietf.org/mail-
   archive/web/suit/current/index.html

6.  Acknowledgements

   We would like the following persons for their support in designing
   this mechanism

   -  Geraint Luff

   -  Amyas Phillips

   -  Dan Ros

   -  Carsten Bormann

   -  David Brown

   -  Markus Gueller

   -  Frank Audun Kvamtro

   -  Oyvind Ronningstad

7.  References

7.1.  Normative References

   [I-D.ietf-suit-architecture]
              Moran, B., Meriac, M., Tschofenig, H., and D. Brown, "A
              Firmware Update Architecture for Internet of Things
              Devices", draft-ietf-suit-architecture-01 (work in
              progress), July 2018.

   [I-D.ietf-suit-information-model]
              Moran, B., Tschofenig, H., Birkholz, H., and J. Jimenez,
              "Firmware Updates for Internet of Things Devices - An
              Information Model for Manifests", draft-ietf-suit-
              information-model-00 (work in progress), June 2018.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
              editor.org/info/rfc2119>.




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7.2.  URIs

   [1] mailto:suit@ietf.org

Authors' Addresses

   Brendan Moran
   Arm Limited

   EMail: Brendan.Moran@arm.com


   Hannes Tschofenig
   Arm Limited

   EMail: hannes.tschofenig@gmx.net



































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