Internet DRAFT - draft-ietf-mile-enum-reference-format
draft-ietf-mile-enum-reference-format
INTERNET-DRAFT Adam W. Montville
Intended Status: Standards Track (CIS)
Expires: August 3, 2015 David Black
(EMC)
January 30, 2015
IODEF Enumeration Reference Format
draft-ietf-mile-enum-reference-format-14
Abstract
The Incident Object Description Exchange Format (IODEF) is an XML
data representation framework for sharing information about computer
security incidents. In IODEF, the Reference class provides
references to externally specified information such as a
vulnerability, Intrusion Detection System (IDS) alert, malware
sample, advisory, or attack technique. In practice, these references
are based on external enumeration specifications that define both the
enumeration format and the specific enumeration values, but the IODEF
Reference class (as specified in IODEF v1 in RFC 5070) does not
indicate how to include both of these important pieces of
information.
This document establishes a stand-alone data format to include both
the external specification and specific enumeration identification
value, and establishes an IANA registry to manage external
enumeration specifications. While this document does not update
IODEF v1, this enumeration reference format is used in IODEF v2 and
is applicable to other formats that support this class of enumeration
references.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as
Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
Adam W. Montville Expires August 3, 2015 [Page 1]
INTERNET DRAFT IODEF Enumeration Reference Format January 30, 2015
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
Copyright and License Notice
Copyright (c) 2015 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
Provisions Relating to IETF Documents
(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
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 . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Referencing External Enumerations . . . . . . . . . . . . . . 3
3 Security Considerations . . . . . . . . . . . . . . . . . . . . 6
4 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
5 The ReferenceName Schema . . . . . . . . . . . . . . . . . . . . 8
6 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 9
7 References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1 Normative References . . . . . . . . . . . . . . . . . . . 9
7.2 Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
Adam W. Montville Expires August 3, 2015 [Page 2]
INTERNET DRAFT IODEF Enumeration Reference Format January 30, 2015
1 Introduction
There is an identified need to specify a format to include relevant
enumeration values from other data representation formats in an IODEF
document. It is anticipated that this requirement will exist in other
standardization efforts within several IETF Working Groups, but the
scope of this document pertains solely to IODEF. This format is used
in IODEF v2 [I-D.draft-ietf-mile-rfc5070-bis] which replaces the
original IODEF v1 [IODEF] specification; this document does not
specify use of this format in IODEF v1 [IODEF].
1.1 Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. Referencing External Enumerations
The need is to place enumeration identifiers and their enumeration
format references in IODEF's Reference class. There are several ways
to accomplish this goal, but the most appropriate at this point is to
require a specific structure for the ReferenceName string of the
IODEF Reference class, and use an IANA registry to manage references
to specific enumeration reference formats.
Per IODEF [IODEF] the ReferenceName is of type ML_STRING. This
becomes problematic when specific references, especially enumeration
formats such as Common Vulnerability Enumeration [CVE], Common
Configuration Enumeration [CCE], Common Platform Enumeration [CPE]
and so on, are referenced - how is an implementer to know which type
of reference this is, and thus how to parse it? One solution,
presented here, is to require that ReferenceName follow a particular
format.
Inclusion of such enumeration values, especially those related to
security automation, is important to incident communication and
investigation. Typically, an enumeration identifier is simply an
identifier with a specific format as defined by an external party.
Further, that enumeration identifier is itself a reference to
specific information associated with the identifier. Thus, the
ReferenceName is an identifier that is formatted in a specific
manner, and which identifies some set of associated information.
For example, a vulnerability identifier following the CVE [CVE]
formatting specification may be: CVE-2014-0001. That identifier is
formatted in a specific manner and relates to information about a
Adam W. Montville Expires August 3, 2015 [Page 3]
INTERNET DRAFT IODEF Enumeration Reference Format January 30, 2015
specific vulnerability. Communicating the format for the identifier
is the subject of this document.
2.1 Reference Name Format
The ReferenceName class provides the XML representation for
identifying an enumeration and specifying a value from it. A given
enumeration is uniquely identified by the specIndex attribute. Each
specIndex value corresponds to an entry in the "Enumeration Reference
Type Identifiers" IANA registry (see Section 4). The child ID
element represents a particular value from the corresponding
enumeration identified by the specIndex attribute. The format of the
ID element is described in the IANA registry entry of the
enumeration.
+-------------------------+
| ReferenceName |
+-------------------------+
| INTEGER specIndex |<>----------[ ID ]
+-------------------------+
Figure 1: The ReferenceName Class
The aggregate classes that constitute ReferenceName:
ID
One. The identifier assigned to represent the particular
enumeration object being referenced.
The ReferenceName class has one attribute.
specIndex
Required. INTEGER. Enumeration identifier. This value
corresponds to an entry in the "Enumeration Reference Type
Identifiers" IANA registry with an identical SpecIndex value.
An example of such a reference is as follows:
<iodef:Reference>
<enum:ReferenceName specIndex="1">
<enum:ID>CXI-1234-XYZ</enum:ID>
</enum:ReferenceName>
<iodef:URL>http://cxi.example.com</iodef:URL>
<iodef:Description>Foo</iodef:Description>
</iodef:Reference>
Information in the IANA table (see Section 4) would include:
Adam W. Montville Expires August 3, 2015 [Page 4]
INTERNET DRAFT IODEF Enumeration Reference Format January 30, 2015
Full Name: Concept X Identifier
SpecIndex: 1
Version: any
Specification URI: http://cxi.example.com/spec_url
2.2 Reference Method Applicability
While the scope of this document pertains to IODEF, any standard
needing to reference an enumeration identified by a specially
formatted string can use this method of providing structure after
the standard has been published. In effect, this method provides
a standardized interface for enumeration formats, thus allowing a
loose coupling between a given standard and the enumeration
identifiers it needs to reference now and in the future.
Adam W. Montville Expires August 3, 2015 [Page 5]
INTERNET DRAFT IODEF Enumeration Reference Format January 30, 2015
3 Security Considerations
Ensuring a proper mapping of enumeration reference ID elements to
the correct SpecIndex is important. Potential consequences of not
mapping correctly include inaccurate information references and
similar distribution of misinformation.
Use of enumeration reference IDs from trusted sources are
preferred to mitigate the risk of receiving and/or providing
misinformation. Trust decisions with respect to enumeration
reference providers are beyond the scope of this document.
However, receiving an IODEF [IODEF] document containing an unknown
ReferenceName (i.e. the SpecIndex does not exist in the IANA
table) may indicate a misled or malicious source.
This document is establishing a container for publicly available
enumeration values to be included in an IODEF [IODEF] document,
and it is important to note the distinction between the
enumeration value's format and the information conveyed by the
value itself. While the enumeration value may hold information
deemed to be private by relying parties, the enumeration format is
likely not subject to privacy concerns.
However, if the Reference class includes an enumeration value in
combination with other data in an IODEF [IODEF] document, the
resulting combination could expose information. An example might
include attack vectors or system descriptions used in a privacy-
related incident. As such, the reader is referred to the IODEF
[IODEF] Security Considerations section, which explicitly covers
protecting IODEF [IODEF] documents in transit and at rest,
ensuring proper recipient authentication, data confidence levels,
underlying transport security characteristics, and proper use of
IODEF's restriction attribute.
4 IANA Considerations
This document specifies an enumeration reference identifier
format. All fields, including abbreviation, are mandatory.
This document creates the following registry for IANA to manage:
Name of the Registry: "Security External Enumeration Registry"
Location of Registry: https://www.iana.org/assignments/sec-ext-
enum
Fields to record in the registry:
Adam W. Montville Expires August 3, 2015 [Page 6]
INTERNET DRAFT IODEF Enumeration Reference Format January 30, 2015
Full Name: The full name of the enumeration (i.e. the
referenced specification) as a string from the printable ASCII
character set [RFC0020] with individual embedded spaces
allowed. The ABNF [RFC5234] syntax for this field is:
1*VCHAR *(SP 1*VCHAR)
Abbreviation: An abbreviation may be an acronym - it consists
of upper-case characters (at least two, upper-case is used to
avoid mismatches due to case differences), as specified by this
ABNF [RFC5234] syntax:
ABBREVIATION = 2*UC-ALPHA ; At least two
UC-ALPHA = %x41-5A ; A-Z
Multiple registrations MAY use the same Abbreviation but
MUST have different Versions.
SpecIndex: This is an IANA-assigned positive integer that
identifies the registration. The first entry added to this
registry uses the value 1, and this value is incremented for
each subsequent entry added to the registry.
Version: The version of the enumeration (i.e. the referenced
specification) as a free-form string from the printable ASCII
character set [RFC0020] excepting white space, i.e., from VCHAR
as defined in [RFC5234]. Some of the characters allowed in the
version string are escaped when that string is used in XML
documents (e.g., '<' is represented as <); the registered
version string contains the unescaped ASCII character in all
such cases.
Specification URI/Reference: A list of one or more URIs
[RFC3986] from which the registered specification can be
obtained. The registered specification MUST be readily and
publicly available from that URI. The URI SHOULD be a stable
reference to a specific version of the specification. URIs
that designate the latest version of a specification (which
changes when a new version appears) SHOULD NOT be used.
Initial registry contents:
Full Name: Common Vulnerabilities and Exposures
Abbreviation: CVE
SpecIndex: 1
Adam W. Montville Expires August 3, 2015 [Page 7]
INTERNET DRAFT IODEF Enumeration Reference Format January 30, 2015
Version: 1.0
Specification URI/Reference:
https://nvd.nist.gov/download.cfm#CVE_FEED
Allocation Policy: Specification Required [RFC5226] (which implies
Expert Review [RFC5226]).
The Designated Expert is expected to consult with the MILE (Managed
Incident Lightweight Exchange) working group or its successor if any
such WG exists (e.g., via email to the working group's mailing list).
The Designated Expert is expected to review the request and validate
the appropriateness of the enumeration for the attribute. This
review includes review of the specification associated with the
request.
The Designated Expert is expected to ensure that the Full Name,
Abbreviation and Version are appropriate and that the information at
the Specification URI is sufficient to unambiguously parse
identifiers based on that specification. Additionally, the Designated
Expert should prefer short Abbreviations over long ones.
This document uses URNs to describe XML namespaces and XML schemas
conforming to a registry mechanism described in [RFC3688].
Registration request for the IODEF enumeration reference format
namespace:
URI : urn:ietf:params:xml:ns:iodef-enum-1.0
Registrant Contact : See the "Authors' Addresses" section of this
document.
XML : None.
Registration request for the IODEF enumeration reference format XML
schema:
URI : urn:ietf:params:xml:schema:iodef-enum-1.0
Registrant Contact See the "Authors' Addresses" section of this
document.
XML : See Section 5, "The ReferenceName Schema", of this document.
5 The ReferenceName Schema
Adam W. Montville Expires August 3, 2015 [Page 8]
INTERNET DRAFT IODEF Enumeration Reference Format January 30, 2015
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema attributeFormDefault="unqualified"
elementFormDefault="qualified"
targetNamespace="urn:ietf:params:xml:ns:iodef-enum-1.0"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:enum="urn:ietf:params:xml:ns:iodef-enum-1.0">
<!--
==========================================================
=== ReferenceName ===
==========================================================
-->
<xs:element name="ReferenceName">
<xs:complexType>
<xs:sequence>
<xs:element name="ID" type="xs:NCName"/>
</xs:sequence>
<xs:attribute name="specIndex"
type="xs:integer" use="required"/>
</xs:complexType>
</xs:element>
</xs:schema>
6 Acknowledgements
The authors would like to thank Eric Burger for the recommendation
to rely on XML, Roman D. Danyliw for his schema contribution and
insight, and Tim Bray, Panos Kampanakis, Barry Leiba, Ted Lemon,
Alexey Melnikov, Kathleen Moriarty, Takeshi Takahashi, Henry S.
Thompson, and David Waltermire for their contributions and
reviews.
7 References
7.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[IODEF] Danyliw, R., Meijer, J., and Y. Demchenko, "The Incident
Object Description Exchange Format", RFC 5070, December
2007.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Adam W. Montville Expires August 3, 2015 [Page 9]
INTERNET DRAFT IODEF Enumeration Reference Format January 30, 2015
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for
Syntax Specifications: ABNF", STD 68, RFC 5234, January
2008.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
7.2 Informative References
[RFC0020] Cerf, V., "ASCII format for network interchange", RFC 20,
October 1969.
[I-D.draft-ietf-mile-rfc5070-bis] Danyliw, R., and Stoecker, P., "The
Incident Object Description Exchange Format v2", draft-
ietf-mile-rfc5070-bis-10 (work in progress), November
2014.
[CCE] http://cce.mitre.org
[CPE] http://cpe.mitre.org
[CVE] http://cve.mitre.org
Authors' Addresses
Adam W. Montville
EMail: adam.w.montville@gmail.com
David Black
EMC Corporation
EMail: david.black@emc.com
Adam W. Montville Expires August 3, 2015 [Page 10]
