MILE Working Group                                           S. Banghart
Internet-Draft                                                      NIST
Intended status: Standards Track                       September 5, 2019
Expires: March 8, 2020

            Definition of the ROLIE Vulnerability Extension


   This document extends the Resource-Oriented Lightweight Information
   Exchange (ROLIE) core to add the information type categories and
   related requirements needed to support Vulnerability use cases.
   Additional categories, properties, and requirements based on content
   type enables a higher level of interoperability between ROLIE
   implementations, and richer metadata for ROLIE consumers.  In
   particular, usage of the Common Vulnerability Enumeration (CVE) [cve]
   format is discussed.

Status of This Memo

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   This Internet-Draft will expire on March 8, 2020.

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   document authors.  All rights reserved.

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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
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  The "vulnerability" information type  . . . . . . . . . . . .   3
   4.  Common Vulnerability Enumeration (CVE) Format . . . . . . . .   4
     4.1.  Description . . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Requirements  . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Link relations for the 'vulnerability'
       information-type  . . . . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  information-type registrations  . . . . . . . . . . . . .   6
       6.1.1.  vulnerability information-type  . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   As our software becomes more complex and interconnected, the number
   of software vulnerabilities exploitable by actors with mal-intent has
   skyrocketed.  Huge amounts of resources have been poured into the
   preemptive discovery, description, and remediation of these
   vulnerabilities, but it is often a challenge to share and communicate
   the results of these efforts.  While bad-actors have vast
   collaboration networks that enable widespread knowledge of any
   vulnerability, the defensive community at large has no sharing
   consortium as prevalent.  If we are to keep up with the rising
   difficulty of defending our systems, we must increase our ability to
   quickly, efficiently, and automatically share information about

   The Resource-Oriented Lightweight Information Exchange (ROLIE)
   [RFC8322] provides a means to share computer security information
   with an eye towards automation and efficiency.  By utilizing ROLIE to
   share vulnerability data, we get one step closer to establishing
   automated communication between each party involved in fighting
   vulnerabilities.  A security researcher can send a newly discovered
   vulnerability to a vulnerability repository, where it is
   automatically retrieved and consumed by enterprise systems.  At this
   final stage, the enterprise can cross-reference against their
   enterprise wide software load to begin mitigating the issue.

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   This extension to ROLIE introduces new requirements and IANA
   registrations to allow ROLIE repositories to share vulnerability data
   in a standardized and compatible way.

   This extension does not attempt to solve the vulnerability data
   format issue, this work is being done across standards groups and
   industry consortiums.  Instead, this extension serves to address the
   problem of sharing these data formats to downstream consumers in a
   automated and efficient fashion.

2.  Terminology

   The key words "MUST," "MUST NOT," "REQUIRED," "SHALL," "SHALL NOT,"
   document are to be interpreted as described in [RFC2119].

   As an extension of [RFC8322], this document refers to many terms
   defined in that document.  In particular, the use of "Entry" and
   "Feed" are aligned with the definitions presented there.

   Several places in this document refer to the "information-type" of a
   Resource (Entry or Feed).  This refers to the "term" attribute of an
   "atom:category" element whose scheme is
   "urn:ietf:params:rolie:category:information-type".  For an Entry,
   this value can be inherited from it's containing Feed as per

3.  The "vulnerability" information type

   When an "atom:category" element has a "scheme" attribute equal to
   "urn:ietf:params:rolie:category:information-type", the "term"
   attribute defines the information type of the associated resource.  A
   new valid value for this attribute: "vulnerability", is described in
   this section, and registered in Section 6.1.1.  When this value is
   used, the resource in question is considered to have an information-
   type of "vulnerability" as per [RFC8322] Section 7.1.2.

   The "vulnerability" information-type represents any information
   describing or pertaining to a computer security vulnerability.  This
   document uses the definition of vulnerability provided by [RFC4949].
   Provided below is a non-exhaustive list of information that may be
   considered to be of a vulnerability information type.

   o  Fundamental identifying information, such as a global ID or
      number, that identifies a given vulnerability.

   o  Descriptive information, including but not limited to:

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      *  Severity scoring - using some standardized scoring algorithm or

      *  Execution details - how the vulnerability is exploited

      *  Impact - what the consequences are of this vulnerability

      *  History and provenance data - when was the vulnerability
         discovered, when was it reported and to whom,

      *  Plain text description of any of the above

   o  Metadata attached to a vulnerability, such as information about
      the entity that discovered or described the vulnerability.

   Note again that this list is not exhaustive, any information that in
   is the abstract realm of a vulnerability should be classified under
   this information-type.  The final decision as to the information type
   of an Entry is up to the provider and author of the Entry.

4.  Common Vulnerability Enumeration (CVE) Format

4.1.  Description

   The Common Vulnerability Enumeration (CVE) provides a globally unique
   identifier for vulnerabilities.  Each CVE provides a CVE-ID, by which
   a vulnerability can be referred to in any context, as well as
   descriptive information about that vulnerability.

   For more information and in-depth specifications, please see [cve].

   CVE provides a valuable set of information fields, but itself does
   not provide a standardized data format.  This extension provides
   standardization around two common serializations of the CVE standard,
   both used by the National Institute of Standards and Technology
   (NIST) National Vulnerability Database (NVD).  The NVD provides a
   repository of "CVE Entries" available in either serialization format.
   The first format is XML-based: the NIST NVD CVE Entry format
   [nvdcvexml], and the second is JSON based: NIST NVD JSON CVE Entry
   Format [nvdcvejson].  These two representations of a CVE are
   equivalent, and can be losslessly converted.

   This section defines usage guidance and additional requirements above
   and beyond those specified in [RFC8322] that apply when CVE data
   formats are in use.

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4.2.  Requirements

   For an Entry to be considered a "CVE Entry", it MUST fulfill the
   following conditions:

   o  The information-type of the Entry is "vulnerability".  For a
      typical Entry, this is derived from the information type of the
      Feed it is contained in.  For a standalone Entry, this is provided
      by an "atom:category" element.

   o  The document linked to by the "ref" attribute of the
      "atom:content" element is a CVE Entry as defined by either
      [nvdcvexml] or [nvdcvejson].  Other well-defined CVE
      serializations would be valid but would not be subject to the
      following requirements, reducing their interoperability.

   The XML and JSON NVD formats follow different requirements.

   A "XML CVE Entry" MUST conform to the following requirements:

   o  The value of the "type" attribute of the "atom:content" element
      MUST be "application/xml".

   o  There MUST be one "rolie:property" with the "name" attribute equal
      to "urn:ietf:params:rolie:property:content-id" and the "value"
      attribute exactly equal to the "<name>" element in the attached
      CVE Entry.  This allows for ROLIE consumers to more easily search
      for CVE Entries without needing to download the entry itself.

   A "JSON CVE Entry" MUST conform to the following requirements:

   o  The value of the "type" attribute of the "atom:content" element
      MUST be "application/json".

   o  There MUST be one "rolie:property" with the "name" attribute equal
      to "urn:ietf:params:rolie:property:content-id" and the "value"
      attribute exactly equal to the "cve:{cve_data_meta":{ID}}" element
      in the attached CVE Entry.  This allows for ROLIE consumers to
      more easily search for CVE Entries without needing to download the
      entry itself.

5.  Link relations for the 'vulnerability' information-type

   The atom:link element contains a "rel" attribute that describes the
   semantic meaning of the given link.

   If the category of an Entry is the vulnerability information type,
   then the following link relations MUST be respected, that is, not

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   removed, by the server.  Implementations can provide extra
   functionality by understanding the semantic meaning of these

   | Name     | Description                                            |
   | severity | Links to a document describing or scoring the severity |
   |          | of this vulnerability.                                 |

    Table 1: Link Relations for Resource-Oriented Lightweight Indicator

6.  IANA Considerations

6.1.  information-type registrations

   IANA has added the following entries to the "ROLIE Security Resource
   Information Type Sub-Registry" registry located at
   <> .

6.1.1.  vulnerability information-type

   The entry is as follows:

      name: vulnerability

      index: TBD

      reference: This document, Section 3

7.  Security Considerations

   All security considerations of the core ROLIE document apply to use
   of this extension.

   The use of this particular extension implies the use of ROLIE in
   sharing vulnerability information.  In automated use cases,
   downstream consumers may be dynamically acquiring and acting on
   vulnerabilities posted to a ROLIE repository.  In this case, a
   compromised server could serve up false vulnerability information to
   trigger dangerous activity in automated consumers.  Automatic
   remediation solutions that consume shared vulnerability information
   in high risk use cases should take care to verify data before taking
   action.  If some global ID, such as a CVE-ID, is included, this
   verification should be trivial.

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8.  Normative References

   [cve]      "Common Vulnerability Enumeration",

   [cvexml]   The MITRE Corporation, ,

              National Institute of Standards and Technology, "NVD CVE
              Entry JSON Schema",

              National Institute of Standards and Technology, "NVD CVE
              Entry XML Schema",

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC4287]  Nottingham, M., Ed. and R. Sayre, Ed., "The Atom
              Syndication Format", RFC 4287, DOI 10.17487/RFC4287,
              December 2005, <>.

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
              FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,

   [RFC5023]  Gregorio, J., Ed. and B. de hOra, Ed., "The Atom
              Publishing Protocol", RFC 5023, DOI 10.17487/RFC5023,
              October 2007, <>.

   [RFC8322]  Field, J., Banghart, S., and D. Waltermire, "Resource-
              Oriented Lightweight Information Exchange (ROLIE)",
              RFC 8322, DOI 10.17487/RFC8322, February 2018,

Author's Address

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   Stephen A. Banghart
   National Institute of Standards and Technology
   100 Bureau Drive
   Gaithersburg, Maryland

   Phone: (301)975-4288

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