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Domain Name System Operations                                A. Dulaunoy
Internet-Draft                                                     CIRCL
Intended status: Informational                                 A. Kaplan
Expires: May 16, 2016                                            CERT.at
                                                                P. Vixie
                                                                H. Stern
                                                 Farsight Security, Inc.
                                                       November 13, 2015


                   Passive DNS - Common Output Format
                draft-dulaunoy-dnsop-passive-dns-cof-01

Abstract

   This document describes a common output format of Passive DNS Servers
   which clients can query.  The output format description includes also
   in addition a common semantic for each Passive DNS system.  By having
   multiple Passive DNS Systems adhere to the same output format for
   queries, users of multiple Passive DNS servers will be able to
   combine result sets easily.

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 May 16, 2016.

Copyright 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



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Limitation  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Common Output Format  . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  ABNF grammar  . . . . . . . . . . . . . . . . . . . . . .   4
     3.3.  Mandatory Fields  . . . . . . . . . . . . . . . . . . . .   4
       3.3.1.  rrname  . . . . . . . . . . . . . . . . . . . . . . .   5
       3.3.2.  rrtype  . . . . . . . . . . . . . . . . . . . . . . .   5
       3.3.3.  rdata . . . . . . . . . . . . . . . . . . . . . . . .   5
       3.3.4.  time_first  . . . . . . . . . . . . . . . . . . . . .   5
       3.3.5.  time_last . . . . . . . . . . . . . . . . . . . . . .   6
     3.4.  Optional Fields . . . . . . . . . . . . . . . . . . . . .   6
       3.4.1.  count . . . . . . . . . . . . . . . . . . . . . . . .   6
       3.4.2.  bailiwick . . . . . . . . . . . . . . . . . . . . . .   6
     3.5.  Additional Fields . . . . . . . . . . . . . . . . . . . .   6
       3.5.1.  sensor_id . . . . . . . . . . . . . . . . . . . . . .   6
       3.5.2.  zone_time_first . . . . . . . . . . . . . . . . . . .   6
       3.5.3.  zone_time_last  . . . . . . . . . . . . . . . . . . .   7
       3.5.4.  origin  . . . . . . . . . . . . . . . . . . . . . . .   7
     3.6.  Additional Fields Registry  . . . . . . . . . . . . . . .   7
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     8.2.  References  . . . . . . . . . . . . . . . . . . . . . . .   9
     8.3.  Informative References  . . . . . . . . . . . . . . . . .  10
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   Passive DNS is a technique described by Florian Weimer in 2005 in
   Passive DNS replication, F Weimer - 17th Annual FIRST Conference on
   Computer Security [WEIMERPDNS].  Since then multiple Passive DNS
   implementations were created and evolved over time.  Users of these
   Passive DNS servers may query a server (often via WHOIS [RFC3912] or




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   HTTP REST [REST]), parse the results and process them in other
   applications.

   There are multiple implementations of Passive DNS software.  Users of
   passive DNS query each implementation and aggregate the results for
   their search.  This document describes the output format of four
   Passive DNS Systems ([DNSDB], [PDNSCERTAT], [PDNSCIRCL] and
   [PDNSCOF]) which are in use today and which already share a nearly
   identical output format.  As the format and the meaning of output
   fields from each Passive DNS need to be consistent, we propose in
   this document a solution to commonly name each field along with their
   corresponding interpretation.  The format follows a simple key-value
   structure in JSON [RFC4627] format.  The benefit of having a
   consistent Passive DNS output format is that multiple client
   implementations can query different servers without having to have a
   separate parser for each individual server. passivedns-client
   [PDNSCLIENT] currently implements multiple parsers due to a lack of
   standardization.  The document does not describe the protocol (e.g.
   WHOIS [RFC3912], HTTP REST [REST]) nor the query format used to query
   the Passive DNS.  Neither does this document describe "pre-recursor"
   Passive DNS Systems.  Both of these are separate topics and deserve
   their own RFC document.

1.1.  Requirements Language

   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.  Limitation

   As a Passive DNS servers can include protection mechanisms for their
   operation, results might be different due to those protection
   measures.  These mechanisms filter out DNS answers if they fail some
   criteria.  The bailiwick algorithm [BAILIWICK] protects the Passive
   DNS Database from cache poisoning attacks [CACHEPOISONING].  Another
   limitation that clients querying the database need to be aware of is
   that each query simply gets a snapshot-answer of the time of
   querying.  Clients MUST NOT rely on consistent answers.  Nor must
   they assume that answers must be identical across multiple Passive
   DNS Servers.

3.  Common Output Format








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3.1.  Overview

   The formatting of the answer follows the JSON [RFC4627] format.  In
   fact, it is a subset of the full JSON language.  Notable differences
   are the modified definition of whitespace ("ws").  The order of the
   fields is not significant for the same resource type.

   The intent of this output format is to be easily parsable by scripts.
   Each JSON object is expressed on a single line to be processed by the
   client line-by-line.  Every implementation MUST support the JSON
   output format.

   Examples of JSON (Appendix A) output are in the appendix.

3.2.  ABNF grammar

   Formal grammar as defined in ABNF [RFC2234]

   answer          = entries
   entries         = * ( entry CR)
   entry           = "{" keyvallist "}"
   keyvallist      = [ member *( value-separator member ) ]
   member          = qm field qm name-separator value
   name-separator  = ws %x3A ws            ; a ":" colon
   value           = value                 ; as defined in the JSON RFC
   value-separator = ws %x2C ws            ; , comma. As defined in JSON
   field           = "rrname" | "rrtype" | "rdata" | "time_first" |
                     "time_last" | "count" | "bailiwick" | "sensor_id" |
                     "zone_time_first" | "zone_time_last" | futureField
   futureField     = string
   CR              = %x0D
   qm              = %x22                  ; " a quotation mark
   ws              = *(
                       %x20 |              ; Space
                       %x09                ; Horizontal tab
                      )


   Note that value is defined in JSON [RFC4627] and has the exact same
   specification as there.  The same goes for the definition of string.

3.3.  Mandatory Fields

   Implementation MUST support all the mandatory fields.

   Uniqueness property: the tuple (rrname,rrtype,rdata) will always be
   unique within one answer per server.  While rrname and rrtype are
   always individual JSON primitive types (strings, numbers, booleans or



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   null), rdata MAY return multiple resource records or a single record.
   When multiple resource records are returned, rdata MUST be a JSON
   array.  In the case of a single resource record is returned, rdata
   MUST be a JSON string.

3.3.1.  rrname

   This field returns the name of the queried resource.

3.3.2.  rrtype

   This field returns the resource record type as seen by the passive
   DNS.  The key is rrtype and the value is in the interpreted record
   type represented as a JSON [RFC4627] string.  If the value cannot be
   interpreted the decimal value is returned following the principle of
   transparency as described in RFC 3597 [RFC3597].  Then the decimal
   value is represented as a JSON [RFC4627] number.  The resource record
   type can be any values as described by IANA in the DNS parameters
   document in the section 'Resource Record (RR) TYPEs'
   (http://www.iana.org/assignments/dns-parameters).  Currently known
   and supported textual descriptions of rrtypes are: A, AAAA, CNAME,
   PTR, SOA, TXT, DNAME, NS, SRV, RP, NAPTR, HINFO, A6.  A client MUST
   be able to understand these textual rrtype values represented as a
   JSON [RFC4627] string.  In addition, a client MUST be able to handle
   a decimal value (as mentioned above) as answer represented as a JSON
   [RFC4627] number.

3.3.3.  rdata

   This field returns the resource records of the queried resource.
   When multiple resource records are returned, rdata MUST be a JSON
   array.  In the case of a single resource record is returned, rdata
   MUST be a JSON string.  Each resource record is represented as a JSON
   [RFC4627] string.  Each resource record MUST be escaped as defined in
   section 2.6 of RFC4627 [RFC4627].  Depending on the rrtype, this can
   be an IPv4 or IPv6 address, a domain name (as in the case of CNAMEs),
   an SPF record, etc.  A client MUST be able to interpret any value
   which is legal as the right hand side in a DNS master file RFC 1035
   [RFC1035] and RFC 1034 [RFC1034].  If the rdata came from an unknown
   DNS resource records, the server must follow the transparency
   principle as described in RFC 3597 [RFC3597].

3.3.4.  time_first

   This field returns the first time that the record / unique tuple
   (rrname, rrtype, rdata) has been seen by the passive DNS.  The date
   is expressed in seconds (decimal) since 1st of January 1970 (Unix




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   timestamp).  The time zone MUST be UTC.  This field is represented as
   a JSON [RFC4627] number.

3.3.5.  time_last

   This field returns the last time that the unique tuple (rrname,
   rrtype, rdata) record has been seen by the passive DNS.  The date is
   expressed in seconds (decimal) since 1st of January 1970 (Unix
   timestamp).  The time zone MUST be UTC.  This field is represented as
   a JSON [RFC4627] number.

3.4.  Optional Fields

   Implementations SHOULD support one or more fields.

3.4.1.  count

   Specifies how many authoritative DNS answers were received at the
   Passive DNS Server's collectors with exactly the given set of values
   as answers (i.e. same data in the answer set - compare with the
   uniqueness property in "Mandatory Fields").  The number of requests
   is expressed as a decimal value.  This field is represented as a JSON
   [RFC4627] number.

3.4.2.  bailiwick

   The bailiwick is the best estimate of the apex of the zone where this
   data is authoritative.

3.5.  Additional Fields

   Implementations MAY support the following fields:

3.5.1.  sensor_id

   This field returns the sensor information where the record was seen.
   It is represented as a JSON [RFC4627] string.

3.5.2.  zone_time_first

   This field returns the first time that the unique tuple (rrname,
   rrtype, rdata) record has been seen via master file import.  The date
   is expressed in seconds (decimal) since 1st of January 1970 (Unix
   timestamp).  The time zone MUST be UTC.  This field is represented as
   a JSON [RFC4627] number.






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3.5.3.  zone_time_last

   This field returns the last time that the unique tuple (rrname,
   rrtype, rdata) record has been seen via master file import.  The date
   is expressed in seconds (decimal) since 1st of January 1970 (Unix
   timestamp).  The time zone MUST be UTC.  This field is represented as
   a JSON [RFC4627] number.

3.5.4.  origin

   Specifies the resource origin of the Passive DNS response.  This
   field is represented as a Uniform Resource Identifier [RFC3986]
   (URI).

3.6.  Additional Fields Registry

   In accordance with [RFC6648], designers of new passive DNS
   applications that would need additional fields can request and
   register new field name at https://github.com/adulau/pdns-qof/wiki/
   Additional-Fields.

4.  Acknowledgements

   Thanks to the Passive DNS developers who contributed to the document.

5.  IANA Considerations

   This memo includes no request to IANA.

6.  Privacy Considerations

   Passive DNS Servers capture DNS answers from multiple collecting
   points ("sensors") which are located on the Internet-facing side of
   DNS recursors ("post-recursor passive DNS").  In this process, they
   intentionally omit the source IP, source port, destination IP and
   destination port from the captured packets.  Since the data is
   captured "post-recursor", the timing information (who queries what)
   is lost, since the recursor will cache the results.  Furthermore,
   since multiple sensors feed into a passive DNS server, the resulting
   data gets mixed together, reducing the likelihood that Passive DNS
   Servers are able to find out much about the actual person querying
   the DNS records nor who actually sent the query.  In this sense,
   passive DNS Servers are similar to keeping an archive of all previous
   phone books - if public DNS records can be compared to phone numbers
   - as they often are.  Nevertheless, the authors strongly encourage
   Passive DNS implementors to take special care of privacy issues.
   bortzmeyer-dnsop-dns-privacy is an excellent starting point for this.
   Finally, the overall recommendations in RFC6973 [RFC6973] should be



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   taken into consideration when designing any application which uses
   Passive DNS data.

7.  Security Considerations

   In some cases, Passive DNS output might contain confidential
   information and its access might be restricted.  When a user is
   querying multiple Passive DNS and aggregating the data, the
   sensitivity of the data must be considered.

8.  References

8.1.  Normative References

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <http://www.rfc-editor.org/info/rfc1034>.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
              November 1987, <http://www.rfc-editor.org/info/rfc1035>.

   [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>.

   [RFC2234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 2234, DOI 10.17487/RFC2234,
              November 1997, <http://www.rfc-editor.org/info/rfc2234>.

   [RFC3597]  Gustafsson, A., "Handling of Unknown DNS Resource Record
              (RR) Types", RFC 3597, DOI 10.17487/RFC3597, September
              2003, <http://www.rfc-editor.org/info/rfc3597>.

   [RFC3912]  Daigle, L., "WHOIS Protocol Specification", RFC 3912, DOI
              10.17487/RFC3912, September 2004,
              <http://www.rfc-editor.org/info/rfc3912>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66, RFC
              3986, DOI 10.17487/RFC3986, January 2005,
              <http://www.rfc-editor.org/info/rfc3986>.

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, DOI
              10.17487/RFC4627, July 2006,
              <http://www.rfc-editor.org/info/rfc4627>.



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   [RFC5001]  Austein, R., "DNS Name Server Identifier (NSID) Option",
              RFC 5001, DOI 10.17487/RFC5001, August 2007,
              <http://www.rfc-editor.org/info/rfc5001>.

   [RFC6648]  Saint-Andre, P., Crocker, D., and M. Nottingham,
              "Deprecating the "X-" Prefix and Similar Constructs in
              Application Protocols", BCP 178, RFC 6648, DOI 10.17487/
              RFC6648, June 2012,
              <http://www.rfc-editor.org/info/rfc6648>.

   [RFC6973]  Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
              Morris, J., Hansen, M., and R. Smith, "Privacy
              Considerations for Internet Protocols", RFC 6973, DOI
              10.17487/RFC6973, July 2013,
              <http://www.rfc-editor.org/info/rfc6973>.

8.2.  References

   [BAILIWICK]
              "Passive DNS Hardening", 2010,
              <https://archive.farsightsecurity.com/Passive_DNS/
              passive_dns_hardening_handout.pdf>.

   [CACHEPOISONING]
              "Black ops 2008: It's the end of the cache as we know
              it.", 2008, <http://kurser.lobner.dk/dDist/DMK_BO2K8.pdf>.

   [DNSDB]    "DNSDB API", 2013, <https://api.dnsdb.info/>.

   [PDNSCERTAT]
              "pDNS presentation at 4th Centr R&D workshop Frankfurt Jun
              5th 2012", 2012,
              <http://www.centr.org/system/files/agenda/attachment/
              rd4-papst-passive_dns.pdf>.

   [PDNSCIRCL]
              "CIRCL Passive DNS", 2012, <https://www.circl.lu/services/
              passive-dns/>.

   [PDNSCLIENT]
              "Queries 5 major Passive DNS databases: BFK, CERTEE,
              DNSParse, ISC, and VirusTotal.", 2013,
              <https://github.com/chrislee35/passivedns-client>.

   [PDNSCOF]  "Passive DNS server interface using the common output
              format", 2013, <https://github.com/adulau/pdns-qof-
              server/>.




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   [REST]     "Representational State Transfer (REST)", 2000,
              <http://www.ics.uci.edu/~fielding/pubs/dissertation/
              rest_arch_style.htm>.

   [WEIMERPDNS]
              "Passive DNS Replication", 2005,
              <http://www.enyo.de/fw/software/dnslogger/
              first2005-paper.pdf>.

8.3.  Informative References

   [I-D.narten-iana-considerations-rfc2434bis]
              Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", draft-narten-iana-
              considerations-rfc2434bis-09 (work in progress), March
              2008.

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552, DOI
              10.17487/RFC3552, July 2003,
              <http://www.rfc-editor.org/info/rfc3552>.

Appendix A.  Examples

   The JSON output are represented on multiple lines for readability but
   each JSON object should on a single line.

   If you query a passive DNS for the rrname www.ietf.org, the passive
   dns common output format can be:


   {"count": 102, "time_first": 1298412391, "rrtype": "AAAA",
   "rrname": "www.ietf.org", "rdata": "2001:1890:1112:1::20",
   "time_last": 1302506851}
   {"count": 59, "time_first": 1384865833, "rrtype": "A",
   "rrname": "www.ietf.org", "rdata": "4.31.198.44",
   "time_last": 1389022219}


   If you query a passive DNS for the rrname ietf.org, the passive dns
   common output format can be:










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   {"count": 109877, "time_first": 1298398002, "rrtype": "NS",
   "rrname": "ietf.org", "rdata": "ns1.yyz1.afilias-nst.info",
   "time_last": 1389095375}
   {"count": 4, "time_first": 1298495035, "rrtype": "A",
   "rrname": "ietf.org", "rdata": "64.170.98.32",
   "time_last": 1298495035}
   {"count": 9, "time_first": 1317037550, "rrtype": "AAAA",
   "rrname": "ietf.org", "rdata": "2001:1890:123a::1:1e",
   "time_last": 1330209752}


   Please note that in the examples above, any backslashes "\" can be
   ignored and are an artefact of the tools which produced this
   document.

Authors' Addresses

   Alexandre Dulaunoy
   CIRCL
   41, avenue de la gare
   Luxembourg  L-1611
   Luxembourg

   Phone: (+352) 247 88444
   Email: alexandre.dulaunoy@circl.lu
   URI:   http://www.circl.lu/


   L. Aaron Kaplan
   CERT.at
   Karlsplatz 1/2/9
   Vienna  A-1010
   Austria

   Phone: +43 1 5056416 78
   Email: kaplan@cert.at
   URI:   http://www.cert.at/


   Paul Vixie
   Farsight Security, Inc.
   11400 La Honda Road
   Woodside, California  94062
   U.S.A.

   Email: paul@redbarn.org
   URI:   https://www.farsightsecurity.com/




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   Henry Stern
   Farsight Security, Inc.
   11400 La Honda Road
   Woodside, California  94062
   U.S.A.

   Phone: +1 650 542-7836
   Email: henry@stern.ca
   URI:   https://www.farsightsecurity.com/










































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