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Internet Engineering Task Force (IETF)                     N. BorensteinRequest for Comments: 7071                                      MimecastCategory: Standards Track                                   M. KucherawyISSN: 2070-1721                                            November 2013A Media Type for Reputation InterchangeAbstract   This document defines the format of reputation response data   ("reputons"), the media type for packaging it, and definition of a   registry for the names of reputation applications and response sets.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc7071.Copyright Notice   Copyright (c) 2013 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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.Borenstein & Kucherawy       Standards Track                    [Page 1]

RFC 7071                  Reputation Media Type            November 2013Table of Contents1. Introduction ....................................................22. Terminology and Definitions .....................................32.1. Reputon ....................................................32.2. Key Words ..................................................32.3. Other Definitions ..........................................33. Description .....................................................33.1. Reputon Attributes .........................................44. Ratings .........................................................55. Caching .........................................................56. Reputons ........................................................66.1. Syntax .....................................................66.2. Formal Definition ..........................................66.2.1. Imported JSON Terms .................................66.2.2. Reputon Structure ...................................76.3. Examples ...................................................97. IANA Considerations ............................................117.1. application/reputon+json Media Type Registration ..........117.2. Reputation Applications Registry ..........................138. Security Considerations ........................................159. References .....................................................159.1. Normative References ......................................159.2. Informative References ....................................15Appendix A. Acknowledgments .......................................161.  Introduction   This document defines a data object for use when answering a   reputation query.  It also defines a media type to carry the response   set data when using a transport method that follows the media type   framework, such as the query method based on the HyperText Transfer   Protocol (HTTP) defined in [RFC7072].  Any future query methods that   might be developed are expected to use the same data object.   Also included is the specification for an IANA registry to contain   definitions and symbolic names for known reputation applications and   corresponding response sets.Borenstein & Kucherawy       Standards Track                    [Page 2]

RFC 7071                  Reputation Media Type            November 20132.  Terminology and Definitions   This section defines terms used in the rest of the document.2.1.  Reputon   A "reputon" is a single independent object containing reputation   information.  A particular query about a subject of interest will   receive one or more reputons in response, depending on the nature of   the data collected and reported by the server.2.2.  Key Words   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 [KEYWORDS].2.3.  Other Definitions   Other terms of importance in this document are defined in [RFC7070],   the base document in this document series.3.  Description   The meta-format selected for the representation of a reputon is   JavaScript Object Notation (JSON), defined in [JSON].  Accordingly, a   new media type, "application/reputon+json", is defined for the JSON   representation of reputational data, typically in response to a   client making a request for such data about some subject.  This media   type takes no parameters.   The body of the media type consists of a JSON document that contains   the reputation information requested.  A detailed description of the   expected structure of the reply is provided below.   The media type comprises a single member indicating the name of the   application context (seeSection 5.1 of [RFC7070]) in which the   reputational data are being returned.  The application name refers to   a registration as described inSection 7.2, which defines the valid   assertions and any extensions that might also be valid (i.e., the   response set) for that application.Borenstein & Kucherawy       Standards Track                    [Page 3]

RFC 7071                  Reputation Media Type            November 20133.1.  Reputon Attributes   The key pieces of data found in a reputon for all reputation   applications are defined as follows:   rater:  The identity of the entity aggregating, computing, and      providing the reputation information, typically expressed as a DNS      domain name.   assertion:  A key word indicating the specific assertion or claim      being rated.   rated:  The identity of the entity being rated.  The nature of this      field is application specific; it could be domain names, email      addresses, driver's license numbers, or anything that uniquely      identifies the entity being rated.  Documents that define specific      reputation applications are required to define syntax and      semantics for this field.   rating:  The overall rating score for that entity, expressed as a      floating-point number between 0.0 and 1.0 inclusive.  SeeSection 4 for discussion.   The following are OPTIONAL for all applications, to be used in   contexts where they are appropriate:   confidence:  the level of certainty the reputation provider has that      the value presented is appropriate, expressed as a floating-point      number between 0.0 and 1.0 inclusive.   normal-rating:  An indication of what the reputation provider would      normally expect as a rating for the subject.  This allows the      client to note that the current rating is or is not in line with      expectations.   sample-size:  The number of data points used to compute the rating,      possibly an approximation.  Expressed as an unsigned 64-bit      integer.  Consumers can assume that the count refers to distinct      data points rather than a count of aggregations (for example,      individual votes rather than aggregated vote counts) unless it is      specified out-of-band that some other interpretation is more      appropriate.  The units are deliberately not normatively      specified, since not all reputation service providers will collect      data the same way.   generated:  A timestamp indicating when this value was generated.      Expressed as the number of seconds since January 1, 1970 00:00      UTC.Borenstein & Kucherawy       Standards Track                    [Page 4]

RFC 7071                  Reputation Media Type            November 2013   expires:  A timestamp indicating a time beyond which the score      reported is likely not to be valid.  Expressed as the number of      seconds since January 1, 1970 00:00 UTC.  SeeSection 5 for      discussion.   A particular application that registers itself with IANA (perSection 7.2, below) can define additional application-specific   attribute/value pairs beyond these standard ones.   An application service provider might operate with an enhanced form   of common services, which might in turn prompt development and   reporting of specialized reputation information.  The details of the   enhancements and specialized information are beyond the scope of this   document, except that the underlying JSON syntax is extensible for   encoding such provider-specific information.4.  Ratings   The score presented as the value in the rating attribute appears as a   floating-point value between 0.0 and 1.0 inclusive.  The intent is   that the definition of an assertion within an application will   declare what the anchor values 0.0 and 1.0 specifically mean.   Generally speaking, 1.0 implies full agreement with the assertion,   while 0.0 indicates no support for the assertion.   The definition will also specify the type of scale in use when   generating scores, to which all reputation service providers for that   application space must adhere.  Further discussion can be found in   [RFC7070].5.  Caching   A reputon can contain an "expires" field indicating a timestamp after   which the client SHOULD NOT use the rating it contains and SHOULD   issue a new query.   This specification does not mandate any caching of ratings on the   part of the client, but there are obvious operational benefits to   doing so.  In the context of reputation, a cached (and hence, stale)   rating can cause desirable traffic to be identified as undesirable,   or vice versa.   Reputation data is typically most volatile when the subject of the   reputation is young.  Accordingly, if a service chooses to include   expiration timestamps as part a reply, these values SHOULD be lower   for subjects about which little data has been collected.Borenstein & Kucherawy       Standards Track                    [Page 5]

RFC 7071                  Reputation Media Type            November 20136.  Reputons6.1.  Syntax   A reputon expressed in JSON is a set of key-value pairs, where the   keys are the names of particular attributes that comprise a reputon   (as listed above, or as provided with specific applications), and   values are the content associated with those keys.  The set of keys   that make up a reputon within a given application are known as that   application's "response set".   A reputon object typically contains a reply corresponding to the   assertion for which a client made a specific request.  For example, a   client asking for assertion "sends-spam" about domain "example.com"   would expect a reply consisting of a reputon making a "sends-spam"   assertion about "example.com" and nothing more.  If a client makes a   request about a subject but does not specify an assertion of   interest, the server can return reputons about any assertion for   which it has data; in effect, the client has asked for any available   information about the subject.  A client that receives an irrelevant   reputon simply ignores it.   An empty reputon is an acknowledgment by the server that the request   has been received, and serves as a positive indication that the   server does not have the information requested.  This is semantically   equivalent to returning a reputon with a "sample-size" of zero.6.2.  Formal Definition   [JSON] defines the structure of JSON objects and arrays using a set   of primitive elements.  Those elements will be used to describe the   JSON structure of a reputation object.6.2.1.  Imported JSON Terms   OBJECT:  a JSON object, defined in Section 2.2 of [JSON]   MEMBER:  a member of a JSON object, defined in Section 2.2 of [JSON]   MEMBER-NAME:  the name of a MEMBER, defined as a "string" in      Section 2.2 of [JSON]   MEMBER-VALUE:  the value of a MEMBER, defined as a "value" in      Section 2.2 of [JSON]   ARRAY:  an array, defined in Section 2.3 of [JSON]Borenstein & Kucherawy       Standards Track                    [Page 6]

RFC 7071                  Reputation Media Type            November 2013   ARRAY-VALUE:  an element of an ARRAY, defined in Section 2.3 of      [JSON]   NUMBER:  a "number" as defined in Section 2.4 of [JSON]   INTEGER:  an "integer" as defined in Section 2.4 of [JSON]   STRING:  a "string" as defined in Section 2.5 of [JSON]6.2.2.  Reputon Structure   Using the above terms for the JSON structures, the syntax of a   reputation object is defined as follows:   reputation-object:  an OBJECT containing a MEMBER reputation-context      and a MEMBER reputon-list   reputation-context:  a MEMBER with MEMBER-NAME "application" and      MEMBER-VALUE a STRING (seeSection 3)   reputon-list:  a MEMBER with MEMBER-NAME "reputons" and MEMBER-VALUE      a reputon-array   reputon-array:  an ARRAY, where each ARRAY-VALUE is a reputon   reputon:  an OBJECT, where each MEMBER is a reputon-element   reputon-element:  one of the following, defined below: rater-value,      assertion-value, rated-value, rating-value, conf-value, normal-      value, sample-value, gen-value, expire-value, ext-value; note the      following:      *  The order of reputon-element members is not significant.      *  A specific reputon-element MUST NOT appear more than once.      *  rater-value, assertion-value, rated-value, and rating-value are         REQUIRED.   rater-value:  a MEMBER with MEMBER-NAME "rater" and MEMBER-VALUE a      STRING (see "rater" inSection 3.1)   assertion-value:  a MEMBER with MEMBER-NAME "assertion" and MEMBER-      VALUE a STRING (see "assertion" inSection 3.1)   rated-value:  a MEMBER with MEMBER-NAME "rated" and MEMBER-VALUE a      STRING (see "rated" inSection 3.1)Borenstein & Kucherawy       Standards Track                    [Page 7]

RFC 7071                  Reputation Media Type            November 2013   rating-value:  a MEMBER with MEMBER-NAME "rating" and MEMBER-VALUE a      NUMBER between 0.0 and 1.0 inclusive (see "rating" inSection 3.1); the number SHOULD NOT not have more than three      decimal places of precision   conf-value:  a MEMBER with MEMBER-NAME "confidence" and MEMBER-VALUE      a NUMBER between 0.0 and 1.0 inclusive (see "confidence" inSection 3.1); the number SHOULD NOT not have more than three      decimal places of precision   normal-value:  a MEMBER with MEMBER-NAME "normal-rating" and MEMBER-      VALUE a NUMBER between 0.0 and 1.0 inclusive (see "normal" inSection 3.1); the number SHOULD NOT not have more than three      decimal places of precision   sample-value:  a MEMBER with MEMBER-NAME "sample-size" and MEMBER-      VALUE a non-negative INTEGER (see "sample-size" in "normal" inSection 3.1)   gen-value:  a MEMBER with MEMBER-NAME "generated" and MEMBER-VALUE a      non-negative INTEGER (see "generated" inSection 3.1)   expire-value:  a MEMBER with MEMBER-NAME "expires" and MEMBER-VALUE a      non-negative INTEGER (see "expires" inSection 3.1)   ext-value:  a MEMBER, for extension purposes; MEMBER-NAME and MEMBER-      VALUE will be defined in separate application registrationsBorenstein & Kucherawy       Standards Track                    [Page 8]

RFC 7071                  Reputation Media Type            November 20136.3.  Examples   The following simple example:     Content-Type: application/reputon+json     {       "application": "baseball",       "reputons": [         {           "rater": "RatingsRUs.example.com",           "assertion": "is-good",           "rated": "Alex Rodriguez",           "rating": 0.99,           "sample-size": 50000         }       ]     }   ...indicates to the client that "RatingsRUs.example.com" consolidated   50000 data points (perhaps from everyone in Yankee Stadium) and   concluded that Alex Rodriguez is very, very good (0.99) at something.   It doesn't tell us what he's good at, and while it might be playing   baseball, it could just as well be paying his taxes on time.   A more sophisticated usage would define a baseball application with a   response set of specific assertions, so that this example:     Content-Type: application/reputon+json     {       "application": "baseball",       "reputons:" [         {           "rater": "baseball-reference.example.com",           "assertion": "hits-for-power",           "rated": "Alex Rodriguez",           "rating": 0.99,           "sample-size": 50000         }       ]     }   ...would indicate that 50000 fans polled by the entity baseball-   reference.example.com rate Alex Rodriguez very highly in hitting for   power, whereas this example:Borenstein & Kucherawy       Standards Track                    [Page 9]

RFC 7071                  Reputation Media Type            November 2013     Content-Type: application/reputon+json     {       "application": "baseball",       "reputons": [         {           "rater": "baseball-reference.example.com",           "assertion": "strong-hitter",           "rated": "Alex Rodriguez",           "rating": 0.4,           "confidence": 0.2,           "sample-size": 50000         }       ]     }   ...would indicate that a similar poll indicated a somewhat weak   consensus that Alex Rodriguez tends to fail in critical batting   situations during baseball games.   The following is an example reputon generated using this schema,   including the media type definition line that identifies a specific   reputation application context.  Here, reputation agent   "rep.example.net" is asserting within the context of the "email-id"   application (see [RFC7073]) that "example.com" appears to be   associated with spam 1.2% of the time, based on just short of 17   million messages analyzed or reported to date.  The "email-id"   application has declared the extension key "email-id-identity" to   indicate how the subject identifier was used in the observed data,   establishing some more-specific semantics for the "rating" value.  In   this case, the extension is used to show the identity "example.com",   the subject of the query, is extracted from the analyzed messages   using the DomainKeys Identified Mail [DKIM] "d=" parameter for   messages where signatures validate.  The reputation agent is 95%   confident of this result.  A second reputon is also present   indicating similar information for the same domain as it is used in   the context of Sender Policy Framework [SPF] evaluations.  (See   [RFC7073] for details about the registered email identifiers   application.)Borenstein & Kucherawy       Standards Track                   [Page 10]

RFC 7071                  Reputation Media Type            November 2013     Content-Type: application/reputon+json     {       "application": "email-id",       "reputons": [         {           "rater": "rep.example.net",           "assertion": "spam",           "identity": "dkim",           "rated": "example.com",           "confidence": 0.95,           "rating": 0.012,           "sample-size": 16938213,           "updated": 1317795852         },         {           "rater": "rep.example.net",           "assertion": "spam",           "identity": "spf",           "rated": "example.com",           "confidence": 0.98,           "rating": 0.023,           "sample-size": 16938213,           "updated": 1317795852         }       ]     }7.  IANA Considerations   This document presents two actions for IANA -- namely, the creation   of the new media type "application/reputon+json" and the creation of   a registry for reputation application types.  Another document in   this series creates an initial registry entry for the latter.7.1.  application/reputon+json Media Type Registration   This section provides the media type registration application from   [MIME-REG] for processing by IANA.   To:  media-types@iana.org   Subject:  Registration of media type application/reputon+json   Type name:  application   Subtype name:  reputon+jsonBorenstein & Kucherawy       Standards Track                   [Page 11]

RFC 7071                  Reputation Media Type            November 2013   Required parameters:  none   Optional parameters:  none   Encoding considerations:  "7bit" encoding is sufficient and is used      to maintain readability when viewed by non-MIME mail readers.   Security considerations:  SeeSection 8 of [RFC7071].   Interoperability considerations:  Implementers may encounter "app"      values, attribute/value pairs, or response set items that they do      not support, which are to be ignored.   Published specification:  [RFC7071]   Applications that use this media type:  Any application that wishes      to query a service that provides reputation data using the form      defined in [RFC7072].  The example application is one that      provides reputation data about DNS domain names and other      identifiers found in email messages.   Fragment identifier considerations:  N/A   Additional information:  The value of the "app" parameter is      registered with IANA.      Deprecated alias names for this type:  N/A      Magic number(s):  N/A      File extension(s):  N/A      Macintosh file type code(s):  N/A   Person and email address to contact for further information:      Murray S. Kucherawy <superuser@gmail.com>   Intended usage:  COMMON   Restrictions on usage:  N/A   Author:      Nathaniel Borenstein      Murray S. Kucherawy   Change controller:  IESGBorenstein & Kucherawy       Standards Track                   [Page 12]

RFC 7071                  Reputation Media Type            November 2013   Provisional registration?:  no7.2.  Reputation Applications Registry   IANA has created the "Reputation Applications" registry.  This   registry contains names of applications used with the   application/reputon+json media type (and other media types that carry   reputons), as defined by this document.   New registrations or updates are published in accordance with either   the "IETF Review" or "Specification Required" guidelines as described   in [IANA-CONSIDERATIONS].   New registrations and updates are to contain the following   information:   1.  Symbolic name of the application being registered or updated.       Valid names conform to the ABNF construction "token" as defined       in Multipurpose Internet Mail Extensions (MIME) Part One [MIME]   2.  Short description of the application (i.e., the class of entity       about which it reports reputation data)   3.  The document in which the application is defined   4.  New or updated status, which is to be one of:       current:  The application is in current use       deprecated:  The application is in current use but its use is             discouraged       historic:  The application is no longer in current use   A specification for an application space needs to be specific and   clear enough to allow interoperability, and include at least the   following details:   o  The application's symbolic name, as it appears in the registration      (see above)   o  A description of the subject of a query within this reputation,      and a legal syntax for the sameBorenstein & Kucherawy       Standards Track                   [Page 13]

RFC 7071                  Reputation Media Type            November 2013   o  An optional table of query parameters that are specific to this      application; each table entry must include:      Name: Name of the query parameter      Status:  (as above)      Description:  A short description of the purpose of this parameter      Syntax:  A reference to a description of valid syntax for the            parameter's value      Required:  "yes" if the parameter is mandatory; "no" otherwise   o  A list of one or more assertions registered within this      application; each table entry is to include:      Name: Name of the assertion      Description:  A short description of the assertion, with specific            meanings for values of 0.0 and 1.0      Scale:  A short description of the scale used in computing the            value (seeSection 4 of this document)   o  An optional list of one or more response set extension keys for      use within this application; each table entry is to include:      Name: Name of the extension key      Description:  A short description of the key's intended meaning      Syntax:  A description of valid values that can appear associated            with the key   The names of attributes registered should be prefixed by the name of   the application itself (e.g., the "foo" application registering a   "bar" attribute should call it "foo-bar") to avoid namespace   collisions.   For registrations qualifying under "Specification Required" rules,   the Designated Expert [IANA-CONSIDERATIONS] should confirm the   document meets the minima described above and otherwise looks   generally acceptable, and then approve the registration.Borenstein & Kucherawy       Standards Track                   [Page 14]

RFC 7071                  Reputation Media Type            November 20138.  Security Considerations   This document is primarily an IANA action registering a media type.   It does not describe a new protocol that might introduce security   considerations.   Discussion of the security and operational impacts of using   reputation services in general can be found throughout   [CONSIDERATIONS].9.  References9.1.  Normative References   [JSON]     Crockford, D., "The application/json Media Type for              JavaScript Object Notation (JSON)",RFC 4627, July 2006.   [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC7070]  Borenstein, N., Kucherawy, M., and A. Sullivan, "An              Architecture for Reputation Reporting",RFC 7070, November              2013.   [RFC7072]  Borenstein, N. and M. Kucherawy, "A Reputation Query              Protocol",RFC 7072, November 2013.9.2.  Informative References   [CONSIDERATIONS]              Kucherawy, M., "Operational Considerations Regarding              Reputation Services", Work in Progress, May 2013.   [DKIM]     Crocker, D., Ed., Hansen, T., Ed., and M. Kucherawy, Ed.,              "DomainKeys Identified Mail (DKIM) Signatures", STD 76,RFC 6376, September 2011.   [IANA-CONSIDERATIONS]              Narten, T. and H. Alvestrand, "Guidelines for Writing an              IANA Considerations Section in RFCs",BCP 26,RFC 5226,              May 2008.   [MIME-REG] Freed, N., Klensin, J., and T. Hansen, "Media Type              Specifications and Registration Procedures",BCP 13,RFC6838, January 2013.Borenstein & Kucherawy       Standards Track                   [Page 15]

RFC 7071                  Reputation Media Type            November 2013   [MIME]     Freed, N. and N. Borenstein, "Multipurpose Internet Mail              Extensions (MIME) Part One: Format of Internet Message              Bodies",RFC 2045, November 1996.   [RFC7073]  Borenstein, N. and M. Kucherawy, "A Reputation Response              Set for Email Identifiers",RFC 7073, November 2013.   [SPF]      Wong, M. and W. Schlitt, "Sender Policy Framework (SPF)              for Authorizing Use of Domains in E-Mail, Version 1",RFC4408, April 2006.Borenstein & Kucherawy       Standards Track                   [Page 16]

RFC 7071                  Reputation Media Type            November 2013Appendix A.  Acknowledgments   The authors wish to acknowledge the contributions of the following to   this specification: Frank Ellermann, Tony Hansen, Jeff Hodges, Simon   Hunt, John Levine, David F. Skoll, and Mykyta Yevstifeyev.Authors' Addresses   Nathaniel Borenstein   Mimecast   203 Crescent St., Suite 303   Waltham, MA 02453   USA   Phone: +1 781 996 5340   EMail: nsb@guppylake.com   Murray S. Kucherawy   270 Upland Drive   San Francisco, CA 94127   USA   EMail: superuser@gmail.comBorenstein & Kucherawy       Standards Track                   [Page 17]