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Internet Engineering Task Force Dulaunoy
Internet-Draft CIRCL
Intended status: Informational Kaplan
Expires: October 13, 2013 CERT.at
Vixie
Farsight Security, Inc.
hs Stern
Cisco
April 2013
Passive DNS - Common Output Format
draft-ietf-dulaunoy-kaplan-pdns-cof-01
Abstract
This document describes the output format used between Passive DNS
query interface. The output format description includes also a
common meaning per Passive DNS system.
Status of this Memo
This Internet-Draft will expire on October 13, 2013.
Copyright Notice
Copyright (c) 2013 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 . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. Limitation . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Common Output Format . . . . . . . . . . . . . . . . . . . . . 3
3.1. Overview and Example . . . . . . . . . . . . . . . . . . . 3
3.2. Mandatory Fields . . . . . . . . . . . . . . . . . . . . . 3
3.2.1. rrname . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2.2. rrtype . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2.3. rdata . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2.4. time_first . . . . . . . . . . . . . . . . . . . . . . 4
3.2.5. time_last . . . . . . . . . . . . . . . . . . . . . . 4
3.3. Optional Fields . . . . . . . . . . . . . . . . . . . . . 4
3.3.1. count . . . . . . . . . . . . . . . . . . . . . . . . 4
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3.3.2. bailiwick . . . . . . . . . . . . . . . . . . . . . . 4
3.4. Additional Fields . . . . . . . . . . . . . . . . . . . . 4
3.4.1. sensor_id . . . . . . . . . . . . . . . . . . . . . . 4
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . . 5
Appendix A. Appendix . . . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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. Since then multiple Passive DNS implementations
evolved over time. Users of these Passive DNS servers query a server
(often via Whois [Ref: WHOIS] or HTTP and ReST), parse the results
and process them in other applications.
There are multiple implementation 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 three
Passive DNS Systems 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 format is following 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. [http://code.google.com/
p/passive-dns-query-tool/] currently implements multiple parsers due
to a lack of standardization. The document does not describe the
protocol (e.g. whois, HTTP REST or XMPP) nor the query format used
to query the Passive DNS. Neither does this document describe "pre-
recursor" Passive DNS Systems.
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 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 (c.f. http://www.isc.org/files/
passive_dns_hardening_handout.pdf) protects the Passive DNS Database
from cache poisoning attacks [ref: Dan Kaminsky]. Another
limitiation that clients querying the database need to be aware of is
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that each query simply gets an snapshot-answer of the time of
querying. Clients MUST NOT rely on consistent answers.
3. Common Output Format
The formatting of the answer follows the JSON [RFC4627] format. The
order of the fields is not significant for the same resource type.
That means, the same name tuple plus timing information identifies a
unique answer per server.
3.1. Overview and Example
The intent of this output format is to be easily parseable by
scripts. Every implementation MUST support the JSON output format.
A sample output using the JSON format:
... (list of )...
{ "count": 97167,
"time_first": "2010-06-25 17:07:02",
"rrtype": "A", "rrname": "google-public-dns-a.google.com.",
"rdata": "8.8.8.8",
"time_last": "2013-02-05 17:34:03" }
... (separated by newline)...
3.2. Mandatory Fields
Implementation MUST support all the mandatory fields.
The tuple (rrtype,rrname,rdata) will always be unique within one
answer per server.
3.2.1. rrname
This field returns the name of the queried resource.
3.2.2. 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. If the value cannot be interpreted the decimal value is
returned following the principle of transparency as described in RFC
3597 [RFC3597]. The resource record type can be any values as
described by IANA in the DNS parameters document in the section 'DNS
Label types' (http://www.iana.org/assignments/dns-parameters).
Currently known and supported textual descritptions 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 rtype values. In
addition, a client MUST be able to handle a decimal value (as
mentioned above) as answer.
3.2.3. rdata
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This field returns the data of the queried resource. In general,
this is to be interpreted as string. Depending on the rtype, 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 zone 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]. (binary stream if any?
base64?)
3.2.4. 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 ascii) since 1st of January 1970 (unix
timestamp). The time zone MUST be UTC.
3.2.5. 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 ascii) since 1st of January 1970 (unix
timestamp). The time zone MUST be UTC..
3.3. Optional Fields
Implementation SHOULD support one or more field.
3.3.1. count
Specifies how many answers were received with the set of answers
(i.e. same data). The number of requests is expressed as a decimal
value.
Specifies the number of times this particular event denoted by the
other type fields has been seen in the given time interval (between
time_last and time_first). Decimal number.
3.3.2. bailiwick
The bailiwick is the best estimate of the apex of the zone where this
data is authoritative. String.
3.4. Additional Fields
Implementations MAY support the following fields:
3.4.1. sensor_id
This field returns the sensor information where the record was seen.
The sensor_id is an opaque byte string as defined by RFC 5001 in
section 2.3 [RFC5001].
4. Acknowledgements
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Thanks to the Passive DNS developers who contributed to the document.
5. IANA Considerations
This memo includes no request to IANA.
6. Security Considerations
In some cases, Passive DNS output might contain confidential
information and its access might be restricted. When an user is
querying multiple Passive DNS and aggregating the data, the
sensitivity of the data must be considered.
7. References
7.1. Normative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3597] Gustafsson, A., "Handling of Unknown DNS Resource Record
(RR) Types", RFC 3597, September 2003.
[RFC4627] Crockford, D., "The application/json Media Type for
JavaScript Object Notation (JSON)", RFC 4627, July 2006.
[RFC5001] Austein, R., "DNS Name Server Identifier (NSID) Option",
RFC 5001, August 2007.
[min_ref] authSurName, authInitials, "Minimal Reference", 2006.
7.2. Informative References
[I-D.narten-iana-considerations-rfc2434bis]
Narten, T and H Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", Internet-Draft
draft-narten-iana-considerations-rfc2434bis-09, March
2008.
[RFC2629] Rose, M.T., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552, July
2003.
Appendix A. Appendix
This becomes an Appendix.
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Authors' Addresses
Alexandre Dulaunoy
CIRCL
41, avenue de la gare
Luxembourg, L-1611
LU
Phone: (+352) 247 88444
Email: alexandre.dulaunoy@circl.lu
URI: http://www.circl.lu/
Leon Aaron Kaplan
CERT.at
Karlsplatz 1/2/9
Vienna, A-1010
AT
Phone: +43 1 5056416 78
Email: kaplan@cert.at
URI: http://www.cert.at/
Paul Vixie
Farsight Security, Inc.
Email: paul@redbarn.org
URI: /
Henry Stern
Cisco
1741 Brunswick Street, Suite 500
Halifax, Nova Scotia B3J 3X8
Canada
Phone: +1 408 922 4555
Email: hestern@cisco.com
URI: http://www.cisco.com/security
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