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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 5070 (ref. 'IODEF') (Obsoleted by RFC 7970) ** Obsolete normative reference: RFC 5226 (Obsoleted by RFC 8126) == Outdated reference: A later version (-26) exists of draft-ietf-mile-rfc5070-bis-10 Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 INTERNET-DRAFT Adam W. Montville 3 Intended Status: Standards Track (CIS) 4 Expires: August 3, 2015 David Black 5 (EMC) 7 January 30, 2015 9 IODEF Enumeration Reference Format 10 draft-ietf-mile-enum-reference-format-14 12 Abstract 14 The Incident Object Description Exchange Format (IODEF) is an XML 15 data representation framework for sharing information about computer 16 security incidents. In IODEF, the Reference class provides 17 references to externally specified information such as a 18 vulnerability, Intrusion Detection System (IDS) alert, malware 19 sample, advisory, or attack technique. In practice, these references 20 are based on external enumeration specifications that define both the 21 enumeration format and the specific enumeration values, but the IODEF 22 Reference class (as specified in IODEF v1 in RFC 5070) does not 23 indicate how to include both of these important pieces of 24 information. 26 This document establishes a stand-alone data format to include both 27 the external specification and specific enumeration identification 28 value, and establishes an IANA registry to manage external 29 enumeration specifications. While this document does not update 30 IODEF v1, this enumeration reference format is used in IODEF v2 and 31 is applicable to other formats that support this class of enumeration 32 references. 34 Status of this Memo 36 This Internet-Draft is submitted to IETF in full conformance with the 37 provisions of BCP 78 and BCP 79. 39 Internet-Drafts are working documents of the Internet Engineering 40 Task Force (IETF), its areas, and its working groups. Note that 41 other groups may also distribute working documents as 42 Internet-Drafts. 44 Internet-Drafts are draft documents valid for a maximum of six months 45 and may be updated, replaced, or obsoleted by other documents at any 46 time. It is inappropriate to use Internet-Drafts as reference 47 material or to cite them other than as "work in progress." 49 The list of current Internet-Drafts can be accessed at 50 http://www.ietf.org/1id-abstracts.html 52 The list of Internet-Draft Shadow Directories can be accessed at 53 http://www.ietf.org/shadow.html 55 Copyright and License Notice 57 Copyright (c) 2015 IETF Trust and the persons identified as the 58 document authors. All rights reserved. 60 This document is subject to BCP 78 and the IETF Trust's Legal 61 Provisions Relating to IETF Documents 62 (http://trustee.ietf.org/license-info) in effect on the date of 63 publication of this document. Please review these documents 64 carefully, as they describe your rights and restrictions with respect 65 to this document. Code Components extracted from this document must 66 include Simplified BSD License text as described in Section 4.e of 67 the Trust Legal Provisions and are provided without warranty as 68 described in the Simplified BSD License. 70 Table of Contents 72 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 73 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 74 2. Referencing External Enumerations . . . . . . . . . . . . . . 3 75 3 Security Considerations . . . . . . . . . . . . . . . . . . . . 6 76 4 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 77 5 The ReferenceName Schema . . . . . . . . . . . . . . . . . . . . 8 78 6 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 9 79 7 References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 80 7.1 Normative References . . . . . . . . . . . . . . . . . . . 9 81 7.2 Informative References . . . . . . . . . . . . . . . . . . 10 82 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 84 1 Introduction 86 There is an identified need to specify a format to include relevant 87 enumeration values from other data representation formats in an IODEF 88 document. It is anticipated that this requirement will exist in other 89 standardization efforts within several IETF Working Groups, but the 90 scope of this document pertains solely to IODEF. This format is used 91 in IODEF v2 [I-D.draft-ietf-mile-rfc5070-bis] which replaces the 92 original IODEF v1 [IODEF] specification; this document does not 93 specify use of this format in IODEF v1 [IODEF]. 95 1.1 Terminology 97 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 98 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 99 document are to be interpreted as described in RFC 2119 [RFC2119]. 101 2. Referencing External Enumerations 103 The need is to place enumeration identifiers and their enumeration 104 format references in IODEF's Reference class. There are several ways 105 to accomplish this goal, but the most appropriate at this point is to 106 require a specific structure for the ReferenceName string of the 107 IODEF Reference class, and use an IANA registry to manage references 108 to specific enumeration reference formats. 110 Per IODEF [IODEF] the ReferenceName is of type ML_STRING. This 111 becomes problematic when specific references, especially enumeration 112 formats such as Common Vulnerability Enumeration [CVE], Common 113 Configuration Enumeration [CCE], Common Platform Enumeration [CPE] 114 and so on, are referenced - how is an implementer to know which type 115 of reference this is, and thus how to parse it? One solution, 116 presented here, is to require that ReferenceName follow a particular 117 format. 119 Inclusion of such enumeration values, especially those related to 120 security automation, is important to incident communication and 121 investigation. Typically, an enumeration identifier is simply an 122 identifier with a specific format as defined by an external party. 123 Further, that enumeration identifier is itself a reference to 124 specific information associated with the identifier. Thus, the 125 ReferenceName is an identifier that is formatted in a specific 126 manner, and which identifies some set of associated information. 128 For example, a vulnerability identifier following the CVE [CVE] 129 formatting specification may be: CVE-2014-0001. That identifier is 130 formatted in a specific manner and relates to information about a 131 specific vulnerability. Communicating the format for the identifier 132 is the subject of this document. 134 2.1 Reference Name Format 136 The ReferenceName class provides the XML representation for 137 identifying an enumeration and specifying a value from it. A given 138 enumeration is uniquely identified by the specIndex attribute. Each 139 specIndex value corresponds to an entry in the "Enumeration Reference 140 Type Identifiers" IANA registry (see Section 4). The child ID 141 element represents a particular value from the corresponding 142 enumeration identified by the specIndex attribute. The format of the 143 ID element is described in the IANA registry entry of the 144 enumeration. 146 +-------------------------+ 147 | ReferenceName | 148 +-------------------------+ 149 | INTEGER specIndex |<>----------[ ID ] 150 +-------------------------+ 152 Figure 1: The ReferenceName Class 154 The aggregate classes that constitute ReferenceName: 156 ID 157 One. The identifier assigned to represent the particular 158 enumeration object being referenced. 160 The ReferenceName class has one attribute. 162 specIndex 163 Required. INTEGER. Enumeration identifier. This value 164 corresponds to an entry in the "Enumeration Reference Type 165 Identifiers" IANA registry with an identical SpecIndex value. 167 An example of such a reference is as follows: 169 170 171 CXI-1234-XYZ 172 173 http://cxi.example.com 174 Foo 175 177 Information in the IANA table (see Section 4) would include: 179 Full Name: Concept X Identifier 180 SpecIndex: 1 181 Version: any 182 Specification URI: http://cxi.example.com/spec_url 184 2.2 Reference Method Applicability 186 While the scope of this document pertains to IODEF, any standard 187 needing to reference an enumeration identified by a specially 188 formatted string can use this method of providing structure after 189 the standard has been published. In effect, this method provides 190 a standardized interface for enumeration formats, thus allowing a 191 loose coupling between a given standard and the enumeration 192 identifiers it needs to reference now and in the future. 194 3 Security Considerations 196 Ensuring a proper mapping of enumeration reference ID elements to 197 the correct SpecIndex is important. Potential consequences of not 198 mapping correctly include inaccurate information references and 199 similar distribution of misinformation. 201 Use of enumeration reference IDs from trusted sources are 202 preferred to mitigate the risk of receiving and/or providing 203 misinformation. Trust decisions with respect to enumeration 204 reference providers are beyond the scope of this document. 205 However, receiving an IODEF [IODEF] document containing an unknown 206 ReferenceName (i.e. the SpecIndex does not exist in the IANA 207 table) may indicate a misled or malicious source. 209 This document is establishing a container for publicly available 210 enumeration values to be included in an IODEF [IODEF] document, 211 and it is important to note the distinction between the 212 enumeration value's format and the information conveyed by the 213 value itself. While the enumeration value may hold information 214 deemed to be private by relying parties, the enumeration format is 215 likely not subject to privacy concerns. 217 However, if the Reference class includes an enumeration value in 218 combination with other data in an IODEF [IODEF] document, the 219 resulting combination could expose information. An example might 220 include attack vectors or system descriptions used in a privacy- 221 related incident. As such, the reader is referred to the IODEF 222 [IODEF] Security Considerations section, which explicitly covers 223 protecting IODEF [IODEF] documents in transit and at rest, 224 ensuring proper recipient authentication, data confidence levels, 225 underlying transport security characteristics, and proper use of 226 IODEF's restriction attribute. 228 4 IANA Considerations 230 This document specifies an enumeration reference identifier 231 format. All fields, including abbreviation, are mandatory. 233 This document creates the following registry for IANA to manage: 235 Name of the Registry: "Security External Enumeration Registry" 237 Location of Registry: https://www.iana.org/assignments/sec-ext- 238 enum 240 Fields to record in the registry: 242 Full Name: The full name of the enumeration (i.e. the 243 referenced specification) as a string from the printable ASCII 244 character set [RFC0020] with individual embedded spaces 245 allowed. The ABNF [RFC5234] syntax for this field is: 247 1*VCHAR *(SP 1*VCHAR) 249 Abbreviation: An abbreviation may be an acronym - it consists 250 of upper-case characters (at least two, upper-case is used to 251 avoid mismatches due to case differences), as specified by this 252 ABNF [RFC5234] syntax: 254 ABBREVIATION = 2*UC-ALPHA ; At least two 255 UC-ALPHA = %x41-5A ; A-Z 257 Multiple registrations MAY use the same Abbreviation but 258 MUST have different Versions. 260 SpecIndex: This is an IANA-assigned positive integer that 261 identifies the registration. The first entry added to this 262 registry uses the value 1, and this value is incremented for 263 each subsequent entry added to the registry. 265 Version: The version of the enumeration (i.e. the referenced 266 specification) as a free-form string from the printable ASCII 267 character set [RFC0020] excepting white space, i.e., from VCHAR 268 as defined in [RFC5234]. Some of the characters allowed in the 269 version string are escaped when that string is used in XML 270 documents (e.g., '<' is represented as <); the registered 271 version string contains the unescaped ASCII character in all 272 such cases. 274 Specification URI/Reference: A list of one or more URIs 275 [RFC3986] from which the registered specification can be 276 obtained. The registered specification MUST be readily and 277 publicly available from that URI. The URI SHOULD be a stable 278 reference to a specific version of the specification. URIs 279 that designate the latest version of a specification (which 280 changes when a new version appears) SHOULD NOT be used. 282 Initial registry contents: 284 Full Name: Common Vulnerabilities and Exposures 286 Abbreviation: CVE 288 SpecIndex: 1 289 Version: 1.0 291 Specification URI/Reference: 292 https://nvd.nist.gov/download.cfm#CVE_FEED 294 Allocation Policy: Specification Required [RFC5226] (which implies 295 Expert Review [RFC5226]). 297 The Designated Expert is expected to consult with the MILE (Managed 298 Incident Lightweight Exchange) working group or its successor if any 299 such WG exists (e.g., via email to the working group's mailing list). 300 The Designated Expert is expected to review the request and validate 301 the appropriateness of the enumeration for the attribute. This 302 review includes review of the specification associated with the 303 request. 305 The Designated Expert is expected to ensure that the Full Name, 306 Abbreviation and Version are appropriate and that the information at 307 the Specification URI is sufficient to unambiguously parse 308 identifiers based on that specification. Additionally, the Designated 309 Expert should prefer short Abbreviations over long ones. 311 This document uses URNs to describe XML namespaces and XML schemas 312 conforming to a registry mechanism described in [RFC3688]. 314 Registration request for the IODEF enumeration reference format 315 namespace: 317 URI : urn:ietf:params:xml:ns:iodef-enum-1.0 319 Registrant Contact : See the "Authors' Addresses" section of this 320 document. 322 XML : None. 324 Registration request for the IODEF enumeration reference format XML 325 schema: 327 URI : urn:ietf:params:xml:schema:iodef-enum-1.0 329 Registrant Contact See the "Authors' Addresses" section of this 330 document. 332 XML : See Section 5, "The ReferenceName Schema", of this document. 334 5 The ReferenceName Schema 335 336 342 347 348 349 350 351 352 354 355 356 358 6 Acknowledgements 360 The authors would like to thank Eric Burger for the recommendation 361 to rely on XML, Roman D. Danyliw for his schema contribution and 362 insight, and Tim Bray, Panos Kampanakis, Barry Leiba, Ted Lemon, 363 Alexey Melnikov, Kathleen Moriarty, Takeshi Takahashi, Henry S. 364 Thompson, and David Waltermire for their contributions and 365 reviews. 367 7 References 369 7.1 Normative References 371 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 372 Requirement Levels", BCP 14, RFC 2119, March 1997. 374 [IODEF] Danyliw, R., Meijer, J., and Y. Demchenko, "The Incident 375 Object Description Exchange Format", RFC 5070, December 376 2007. 378 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 379 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 380 May 2008. 382 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 383 Resource Identifier (URI): Generic Syntax", STD 66, 384 RFC 3986, January 2005. 386 [RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for 387 Syntax Specifications: ABNF", STD 68, RFC 5234, January 388 2008. 390 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, 391 January 2004. 393 7.2 Informative References 395 [RFC0020] Cerf, V., "ASCII format for network interchange", RFC 20, 396 October 1969. 398 [I-D.draft-ietf-mile-rfc5070-bis] Danyliw, R., and Stoecker, P., "The 399 Incident Object Description Exchange Format v2", draft- 400 ietf-mile-rfc5070-bis-10 (work in progress), November 401 2014. 403 [CCE] http://cce.mitre.org 405 [CPE] http://cpe.mitre.org 407 [CVE] http://cve.mitre.org 409 Authors' Addresses 411 Adam W. Montville 413 EMail: adam.w.montville@gmail.com 415 David Black 416 EMC Corporation 418 EMail: david.black@emc.com