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Versions: 00 01 draft-ietf-sacm-coswid

SACM Working Group                                           H. Birkholz
Internet-Draft                                            Fraunhofer SIT
Intended status: Standards Track                     J. Fitzgerald-McKay
Expires: January 9, 2017                           Department of Defense
                                                              C. Schmidt
                                                   The MITRE Corporation
                                                           D. Waltermire
                                                                    NIST
                                                           July 08, 2016


                      Concise Software Identifiers
                     draft-birkholz-sacm-coswid-01

Abstract

   This document defines a concise representation of ISO 19770-2:2015
   Software Identifiers (SWID tags) that is interoperable with the XML
   schema definition of ISO 19770-2:2015.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 9, 2017.

Copyright Notice

   Copyright (c) 2016 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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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements notation . . . . . . . . . . . . . . . . . .   3
   2.  Concise SWID data definition  . . . . . . . . . . . . . . . .   4
   3.  Encoding hashes for Concise SWID tags . . . . . . . . . . . .   8
   4.  COSE signatures for Concise SWID tags . . . . . . . . . . . .   8
   5.  IANA considerations . . . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   8.  Change Log  . . . . . . . . . . . . . . . . . . . . . . . . .  11
   9.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  11
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     10.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   SWID tags have several use-applications including but not limited to:

   o  Software Inventory Management, a part of the Software Asset
      Management [SAM] process, which requires an accurate list of
      discernible deployed software instances.

   o  Vulnerability Assessment, which requires a semantic link between
      standardized vulnerability descriptions and [X.1520] IT-assets.

   o  Remote Attestation, which requires a link between golden (well-
      known) measurements and software instances [I-D-birkholz-tuda].

   SWID tags, as defined in ISO-19770-2:2015 [SWID], provide a
   standardized format for a record that identifies and describes a
   specific release of a software product.  Different software products,
   and even different releases of a particular software product, each
   have a different SWID tag record associated with them.  In addition
   to defining the format of these records, ISO-19770-2:2015 defines
   requirements concerning the SWID tag lifecycle.  Specifically, when a
   software product is installed on an endpoint, that product's SWID tag
   is also installed.  Likewise, when the product is uninstalled or
   replaced, the SWID tag is deleted or replaced, as appropriate.  As a
   result, ISO-19770-2:2015 describes a system wherein there is a
   correspondence between the set of installed software products on an




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   endpoint, and the presence on that endpoint of the SWID tags
   corresponding to those products.

   SWID tags are meant to be flexible and able to express a broad set of
   metadata about a software product.  Moreover, there are multiple
   types of SWID tags, each providing different types of information.
   For example, a "corpus tag" is used to describe an application's
   installation image on an installation media, while a "patch tag" is
   meant to describe a patch that modifies some other application.
   While there are very few required fields in SWID tags, there are many
   optional fields that support different uses of these different types
   of tags.  While a SWID tag that consisted only of required fields
   could be a few hundred bytes in size, a tag containing many of the
   optional fields could be many orders of magnitude larger.

   This document defines a more concise representation of SWID tags in
   the Concise Binary Object Representation (CBOR) [RFC7049].  This is
   described via the CBOR Data Definition Language (CDDL)
   [I-D.greevenbosch-appsawg-cbor-cddl].  The resulting Concise SWID
   data definition is interoperable with the XML schema definition of
   ISO-19770-2:2015 [SWID].  The vocabulary, i.e., the CDDL names of the
   types and members used in the Concise SWID data definition, is mapped
   to more concise labels represented as small integers.  The names used
   in the CDDL and the mapping to the CBOR representation using integer
   labels is based on the vocabulary of the XML attribute and element
   names defined in ISO-19770-2:2015.

   Real-world instances of SWID tags can be fairly large, and the
   communication of SWID tags in use-applications such as those
   described earlier can cause a large amount of data to be transported.
   This can be larger than acceptable for constrained devices and
   networks.  Concise SWID tags significantly reduce the amount of data
   transported as compared to a typical SWID tag.  This reduction is
   enable through the use of CBOR, which maps human-readable labels of
   that content to more concise integer labels (indices).  This allows
   SWID tags to be part of an enterprise security solution for a wider
   range of endpoints and environments.

1.1.  Requirements notation

   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, BCP 14 [RFC2119].







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2.  Concise SWID data definition

   The following is a CDDL representation of the ISO-19770-2:2015 [SWID]
   XML schema definition of SWID tags.  This representation includes all
   SWID tag fields and thus supports all SWID tag use cases.  The
   CamelCase notation used in the XML schema definition is changed to
   hyphen-separated notation (e.g.  ResourceCollection is named
   resource-collection in the Concise SWID data definition).  The human-
   readable names of members are mapped to integer indices via a block
   of rules at the bottom of the Concise SWID data definition.  The 48
   character strings of the SWID vocabulary that would have to be stored
   or transported in full if using the original vocabulary are replaced.

  concise-software-identity = {
    global-attr,
    * entity-entry,
    * evidence-entry,
    * link-entry,
    * software-meta-entry,
    * payload-entry,
    * any-element-entry,
  ;  ? content,
    ? corpus,
    ? patch,
    ? media,
    name,
    ? supplemental,
    tag-id,
    ? tag-version,
    ? version,
    ? version-scheme,
  }

  NMTOKEN = text            ; .regexp to add some validation?
  NMTOKENS = [ * NMTOKEN ]

  any-attr = text
  any-element = any

  date-time = time
  any-uri = uri

  global-attr = (
    * (text => any-attr),
    ? lang,
  )

  meta-type = (



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    global-attr,
    * (text => any-attr),
  )

  meta-element = [
    global-attr,
    * (text => any-attr),
  ]

  resource-collection = (
    global-attr,
    * (directory-entry // file-entry // process-entry // resource-entry)
  )

  file = {
    filesystem-item,
    ? size,
    ? version,
    * (text => any-attr),
  }

  filesystem-item = (
    meta-type,
    ? key,
    ? location,
    name,
    ? root,
  )

  directory = {
    filesystem-item,
    path-elements,
  }

  process = {
    global-attr,
    name,
    ? pid,
  }

  resource = {
    global-attr,
    type,
  }

  entity = {
    global-attr,
    meta-elements,



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    name,
    ? reg-id,
    role,
    ? thumbprint,
  }

  evidence = {
    global-attr,
    resource-collection,
    ? date,
    ? device-id,
  }

  link = {
    global-attr,
    ? artifact,
    href,
    ? media,
    ? ownership,
    rel,
    ? type,
    ? use,
  }

  software-meta = {
    global-attr,
    ? activation-status,
    ? channel-type,
    ? colloquial-version,
    ? description,
    ? edition,
    ? entitlement-data-required,
    ? entitlement-key,
    ? generator,
    ? persistent-id,
    ? product,
    ? product-family,
    ? revision,
    ? summary,
    ? unspsc-code,
    ? unspsc-version,
  }

  payload = {
    global-attr,
    resource-collection,
  }




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  tag-id = (0: text)
  name = (1: text)
  ; ambiguous, replaced
  ; content = (
  ;  2: [ * entity / evidence / link / software-meta /
  ;       payload / any-element ]
  ;)
  entity-entry = (2: entity)
  evidence-entry = (3: evidence)
  link-entry = (4: link)
  software-meta-entry = (5: software-meta)
  payload-entry = (6: payload)
  any-element-entry = (7: any-element)
  corpus = (8: bool)
  patch = (9: bool)
  media = (10: text)
  supplemental = (11: bool)
  tag-version = (12: integer)
  version = (13: text)
  version-scheme = (14: NMTOKEN)
  lang = (15: text)
  directory-entry = (16: directory)
  file-entry = (17: file)
  process-entry = (18: process)
  resource-entry = (19: resource)
  size = (20: integer)
  key = (21: bool)
  location = (22: text)
  root = (23: text)
  path-elements = (24: ([ * (directory / file) ]))
  pid = (25: integer)
  type = (26: text)
  meta-elements = (27: ([ * meta-element ]))
  reg-id = (28: any-uri)
  role = (29: NMTOKENS)
  thumbprint = (30: text)
  date = (31: date-time)
  device-id = (32: text)
  artifact = (33: text)
  href = (34: any-uri)
  ownership = (35: ("shared" / "private" / "abandon"))
  rel = (36: NMTOKEN)
  use = (37: ("optional" / "required" / "recommended"))
  activation-status = (38: text)
  channel-type = (39: text)
  colloquial-version = (40: text)
  description = (41: text)
  edition = (42: text)



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  entitlement-data-required = (43: bool)
  entitlement-key = (44: text)
  generator = (45: text)
  persistent-id = (46: text)
  product = (47: text)
  product-family = (48: text)
  revision = (49: text)
  summary = (50: text)
  unspsc-code = (51: text)
  unspsc-version = (52: text)


3.  Encoding hashes for Concise SWID tags

   Concise SWID support hashes that are registered at the Named
   Information Hash Algorithm Registry and the Hash Function Textual
   Names Registry.  A text string used as a value for hash-alg-id
   referes to the Hash Function Name in the Hash Function Textual Names
   table.  A number used as a value for hash-alg-id refers the ID in the
   Named Information Hash Algorithm table.

   If a hash value (e.g. a file hash) is to be the content of any-attr
   or any-element, it MUST be encoded as a coswid-hash array:

   coswid-hash = [
     hash-alg-id: int / tstr,
     hash-value: bstr,
   ]


   Example :

   file-hash = bstr .cbor coswid-hash


4.  COSE signatures for Concise SWID tags

   SWID tags, as defined in the ISO-19770-2:2015 XML schema, can include
   cryptographic signatures to protect the integrity of the SWID tag.
   In general, tags are signed by the tag creator (typically, although
   not exclusively, the vendor of the software product that the SWID tag
   identifies).  Cryptographic signatures can make any modification of
   the tag detectable, which is especially important if the integrity of
   the tag is important, such as when the tag is providing golden
   measurements for files.

   The ISO-19770-2:2015 XML schema uses XML DSIG to support
   cryptographic signatures.  Concise SWID tags require a different



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   signature scheme than this.  COSE (CBOR Encoded Message Syntax)
   provides the required mechanism [I-D.ietf-cose-msg].  Concise SWID
   can be wrapped in a COSE Single Signer Data Object (cose-sign1) that
   contains a single signature.  The following CDDL defines a more
   restrictive subset of header attributes allowed by COSE tailored to
   suit the requirements of Concise SWID.

signed-software-identity = #6.997(COSE-Sign1-coswid) ; see TBS7 in current COSE I-D

label = int / tstr  ; see COSE I-D 1.4.
values = any        ; see COSE I-D 1.4.

unprotected-signed-coswid-header = {
    1 => int / tstr,            ; algorithm identifier
    3 => "application/coswid",  ; request for CoAP IANA registry to become an int
    * label => values,
}

protected-signed-coswid-header = {
    4 => bstr,                  ; key identifier
    * label => values,
}

COSE-Sign1-coswid = [
    protected: bstr .cbor protected-signed-coswid-header,
    unprotected: unprotected-signed-coswid-header,
    payload: bstr .cbor concise-software-identity,
    signature: bstr,
]


5.  IANA considerations

   This document will include requests to IANA:

   o  Integer indices for SWID content attributes and information
      elements.

   o  Content-Type for CoAP to be used in COSE.

6.  Security Considerations

   SWID tags contain public information about software products and, as
   such, do not need to be protected against disclosure on an endpoint.
   Similarly, SWID tags are intended to be easily discoverable by
   applications and users on an endpoint in order to make it easy to
   identify and collect all of an endpoint's SWID tags.  As such, any
   security considerations regarding SWID tags focus on the application



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   of SWID tags to address security challenges, and the possible
   disclosure of the results of those applications.

   A signed SWID tag whose signature is intact can be relied upon to be
   unchanged since it was signed.  If the SWID tag was created by the
   software author, this generally means that it has undergone no change
   since the software application with which the tag is associated was
   installed.  By implication, this means that the signed tag reflects
   the software author's understanding of the details of that software
   product.  This can be useful assurance when the information in the
   tag needs to be trusted, such as when the tag is being used to convey
   golden measurements.  By contrast, the data contained in unsigned
   tags cannot be trusted to be unmodified.

   SWID tags are designed to be easily added and removed from an
   endpoint along with the installation or removal of software products.
   On endpoints where addition or removal of software products is
   tightly controlled, the addition or removal of SWID tags can be
   similarly controlled.  On more open systems, where many users can
   manage the software inventory, SWID tags may be easier to add or
   remove.  On such systems, it may be possible to add or remove SWID
   tags in a way that does not reflect the actual presence or absence of
   corresponding software products.  Similarly, not all software
   products automatically install SWID tags, so products may be present
   on an endpoint without providing a corresponding SWID tag.  As such,
   any collection of SWID tags cannot automatically be assumed to
   represent either a complete or fully accurate representation of the
   software inventory of the endpoint.  However, especially on devices
   that more strictly control the ability to add or remove applications,
   SWID tags are an easy way to provide an preliminary understanding of
   that endpoint's software inventory.

   Any report of an endpoint's SWID tag collection provides information
   about the software inventory of that endpoint.  If such a report is
   exposed to an attacker, this can tell them which software products
   and versions thereof are present on the endpoint.  By examining this
   list, the attacker might learn of the presence of applications that
   are vulnerable to certain types of attacks.  As noted earlier, SWID
   tags are designed to be easily discoverable by an endpoint, but this
   does not present a significant risk since an attacker would already
   need to have access to the endpoint to view that information.
   However, when the endpoint transmits its software inventory to
   another party, or that inventory is stored on a server for later
   analysis, this can potentially expose this information to attackers
   who do not yet have access to the endpoint.  As such, it is important
   to protect the confidentiality of SWID tag information that has been
   collected from an endpoint, not because those tags individually
   contain sensitive information, but because the collection of SWID



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   tags and their association with an endpoint reveals information about
   that endpoint's attack surface.

   Finally, both the ISO-19770-2:2015 XML schema definition and the
   Concise SWID data definition allow for the construction of "infinite"
   SWID tags or SWID tags that contain malicious content with the intend
   if creating non-deterministic states during validation or processing
   of SWID tags.  While software product vendors are unlikely to do
   this, SWID tags can be created by any party and the SWID tags
   collected from an endpoint could contain a mixture of vendor and non-
   vendor created tags.  For this reason, tools that consume SWID tags
   ought to treat the tag contents as potentially malicious and should
   employ input sanitizing on the tags they ingest.

7.  Acknowledgements

8.  Change Log

   Changes from version 00 to version 01:

   o  Ambiguity between evidence and payload eliminated by introducing
      explicit members (while still allowing for "empty" swid tags)

   o  Added a relatively restrictive COSE envelope using cose_sign1 to
      define signed coswids (single signer only, at the moment)

   o  Added a defintion how to encode hashes that can be stored in the
      any-member using existing IANA tables to reference hash-algorithms

   First version -00

9.  Contributors

10.  References

10.1.  Normative References

   [I-D.ietf-cose-msg]
              Schaad, J., "CBOR Object Signing and Encryption (COSE)",
              draft-ietf-cose-msg-14 (work in progress), June 2016.

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






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   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <http://www.rfc-editor.org/info/rfc7049>.

   [SAM]      "Information technology - Software asset management - Part
              5: Overview and vocabulary", ISO/IEC 19770-5:2013,
              November 2013.

   [SWID]     "Information technology - Software asset management - Part
              2: Software identification tag'", ISO/IEC 19770-2:2015,
              October 2015.

   [X.1520]   "Recommendation ITU-T X.1520 (2014), Common
              vulnerabilities and exposures", April 2011.

10.2.  Informative References

   [I-D-birkholz-tuda]
              Fuchs, A., Birkholz, H., McDonald, I., and C. Bormann,
              "Time-Based Uni-Directional Attestation", draft-birkholz-
              tuda-01 (work in progress), March 2016.

   [I-D.greevenbosch-appsawg-cbor-cddl]
              Vigano, C. and H. Birkholz, "CBOR data definition language
              (CDDL): a notational convention to express CBOR data
              structures", draft-greevenbosch-appsawg-cbor-cddl-08 (work
              in progress), March 2016.

Authors' Addresses

   Henk Birkholz
   Fraunhofer SIT
   Rheinstrasse 75
   Darmstadt  64295
   Germany

   Email: henk.birkholz@sit.fraunhofer.de


   Jessica Fitzgerald-McKay
   Department of Defense
   9800 Savage Road
   Ft. Meade, Maryland
   USA

   Email: jmfitz2@nsa.gov





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   Charles Schmidt
   The MITRE Corporation
   202 Burlington Road
   Bedford, Maryland  01730
   USA

   Email: cmschmidt@mitre.org


   David Waltermire
   National Institute of Standards and Technology
   100 Bureau Drive
   Gaithersburg, Maryland  20877
   USA

   Email: david.waltermire@nist.gov



































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