draft-ietf-dprive-edns0-padding-01.txt		draft-ietf-dprive-edns0-padding-02.txt
	Network Working Group A. Mayrhofer		Network Working Group A. Mayrhofer
	Internet-Draft nic.at GmbH		Internet-Draft nic.at GmbH
	Intended status: Standards Track November 24, 2015		Intended status: Standards Track January 25, 2016
	Expires: May 27, 2016		Expires: July 28, 2016
	The EDNS(0) Padding Option		The EDNS(0) Padding Option
	draft-ietf-dprive-edns0-padding-01		draft-ietf-dprive-edns0-padding-02
	Abstract		Abstract
	This document specifies the EDNS(0) 'Padding' option, which allows		This document specifies the EDNS(0) 'Padding' option, which allows
	DNS clients and servers to pad request and response messages by a		DNS clients and servers to pad request and response messages by a
	variable number of octets.		variable number of octets.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	skipping to change at page 1, line 32		skipping to change at page 1, line 32
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on May 27, 2016.		This Internet-Draft will expire on July 28, 2016.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2016 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	skipping to change at page 2, line 15		skipping to change at page 2, line 15
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
	3. The 'Padding' Option . . . . . . . . . . . . . . . . . . . . 3		3. The 'Padding' Option . . . . . . . . . . . . . . . . . . . . 3
	4. Usage Considerations . . . . . . . . . . . . . . . . . . . . 3		4. Usage Considerations . . . . . . . . . . . . . . . . . . . . 3
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 4		6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
	7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4		7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
	8. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 4		8. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
	8.1. draft-ietf-dprive-edns0-padding-01 . . . . . . . . . . . 4		8.1. draft-ietf-dprive-edns0-padding-02 . . . . . . . . . . . 4
	8.2. draft-ieft-dprive-edns0-padding-00 . . . . . . . . . . . 5		8.2. draft-ietf-dprive-edns0-padding-01 . . . . . . . . . . . 5
	8.3. draft-mayrhofer-edns0-padding-01 . . . . . . . . . . . . 5		8.3. draft-ieft-dprive-edns0-padding-00 . . . . . . . . . . . 5
	8.4. draft-mayrhofer-edns0-padding-00 . . . . . . . . . . . . 5		8.4. draft-mayrhofer-edns0-padding-01 . . . . . . . . . . . . 5
			8.5. draft-mayrhofer-edns0-padding-00 . . . . . . . . . . . . 5
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
	9.1. Normative References . . . . . . . . . . . . . . . . . . 5		9.1. Normative References . . . . . . . . . . . . . . . . . . 5
	9.2. Informative References . . . . . . . . . . . . . . . . . 5		9.2. Informative References . . . . . . . . . . . . . . . . . 5
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
	1. Introduction		1. Introduction
	The Domain Name System (DNS) [RFC1035] was specified to transport DNS		The Domain Name System (DNS) [RFC1035] was specified to transport DNS
	packets in clear text form. Since this can expose significant		messages in clear text form. Since this can expose significant
	amounts of information about the internet activities of an end user,		amounts of information about the internet activities of an end user,
	the IETF has undertaken work to provide confidentiality to DNS		the IETF has undertaken work to provide confidentiality to DNS
	transactions (see the DPRIVE WG). Encrypting the DNS transport is		transactions (see the DPRIVE WG). Encrypting the DNS transport is
	considered as one of the options to improve the situation.		considered as one of the options to improve the situation.
	However, even if both DNS query and response packets were encrypted,		However, even if both DNS query and response messages were encrypted,
	meta data of these packets could be used to correlate such packets		meta data of could still be used to correlate such messages with well
	with well known unencrypted packets, hence jeopardizing some of the		known unencrypted messages, hence jeopardizing some of the
	confidentiality gained by encryption. One such property is the		confidentiality gained by encryption. One such property is the
	message size.		message size.
	This document specifies the Extensions Mechanisms for DNS (EDNS(0))		This document specifies the Extensions Mechanisms for DNS (EDNS(0))
	"Padding" Option, which allows to artificially increase the size of a		"Padding" Option, which allows to artificially increase the size of a
	DNS message by a variable number of bytes, significantly hampering		DNS message by a variable number of bytes, significantly hampering
	size-based correlation of the encrypted packet.		size-based correlation of the encrypted message.
	2. Terminology		2. Terminology
	The terms "Requestor", "Responder" are to be interpreted as specified		The terms "Requestor", "Responder" are to be interpreted as specified
	in [RFC6891].		in [RFC6891].
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in		"OPTIONAL" in this document are to be interpreted as described in
	[RFC2119].		[RFC2119].
	3. The 'Padding' Option		3. The 'Padding' Option
	The EDNS(0) [RFC6891] specifies a mechanism to include new options in		The EDNS(0) [RFC6891] specifies a mechanism to include new options in
	DNS packets, contained in the RDATA of the OPT meta-RR. This		DNS packets, contained in the RDATA of the OPT meta-RR. This
	document specifies the 'Padding' option in order to allow clients and		document specifies the 'Padding' option in order to allow clients and
	servers pad DNS packets by a variable number of bytes. The 'Padding'		servers pad DNS packets by a variable number of bytes. The 'Padding'
	option MUST occur at most once per OPT meta-RR.		option MUST occur at most once per OPT meta-RR (and hence, at most
			once per message).
	The figure below specifies the structure of the option in the RDATA		The figure below specifies the structure of the option in the RDATA
	of the OPT RR:		of the OPT RR:
	0 8 16		0 8 16
	+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+		+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
	| OPTION-CODE |		| OPTION-CODE |
	+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+		+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
	| OPTION-LENGTH |		| OPTION-LENGTH |
	+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+		+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
	| (PADDING) ... (PADDING) ... /		| (PADDING) ... (PADDING) ... /
	+- - - - - - - - - - - - - - - -		+- - - - - - - - - - - - - - - -
	Figure 1		Figure 1
	The OPTION-CODE for the 'Padding' option is 12.		The OPTION-CODE for the 'Padding' option is 12.
	The OPTION-LENGTH for the 'Padding' option is the size (in octets) of		The OPTION-LENGTH for the 'Padding' option is the size (in octets) of
	the PADDING. The minimum number of padding octets is 0.		the PADDING. The minimum number of padding octets is 0.
	The PADDING octets SHOULD be set to 0x00. Application developers who		The PADDING octets SHOULD be set to 0x00. Other values MAY be used;
	are concerned about misguided lower layer compression MAY instead		for example, in cases where there is a concern that the padded
	fill the PADDING octets with the output of a cryptographic random		message could be subject to compression before encryption. PADDING
	number generator. Responders MUST NOT reject messages containing		octets of any value MUST be accepted in messages received.
	non-0x00 PADDING octets.
	4. Usage Considerations		4. Usage Considerations
	This document does not specify the actual amount of padding to be		This document does not specify the actual amount of padding to be
	used, since this depends on the situation in which the option is		used, since this depends on the situation in which the option is
	used. However, padded DNS messages MUST NOT exceed the number of		used. However, padded DNS messages MUST NOT exceed the number of
	octets specified in the Requestor's Payload Size field encoded in The		octets specified in the Requestor's Payload Size field encoded in The
	RR Class Field (see Section 6.2.3 and 6.2.4 of [RFC6891]).		RR Class Field (see Section 6.2.3 and 6.2.4 of [RFC6891]).
	Responders MUST pad DNS responses when the respective DNS query		Responders MUST pad DNS responses when the respective DNS query
	skipping to change at page 4, line 19		skipping to change at page 4, line 22
	IANA has assigned EDNS Option Code 12 for Padding.		IANA has assigned EDNS Option Code 12 for Padding.
	IANA is requested to update the respective registration record by		IANA is requested to update the respective registration record by
	changing the Reference field to [[THISRFC]] and the Status field to		changing the Reference field to [[THISRFC]] and the Status field to
	'Standard'.		'Standard'.
	6. Security Considerations		6. Security Considerations
	Padding DNS packets obviously increases their size, and will		Padding DNS packets obviously increases their size, and will
	therefore lead to increased traffic, can lead to increased number of		therefore lead to increased traffic.
	truncated packets when used over UDP-based transport.
	The use of the EDNS(0) Padding provides only a benefit when DNS		The use of the EDNS(0) Padding provides only a benefit when DNS
	packets are not transported in clear text. Implementations therefore		packets are not transported in clear text. Implementations therefore
	SHOULD avoid using this option if the DNS transport is not encrypted.		SHOULD avoid using this option if the DNS transport is not encrypted.
	Padding length might be affected by lower-level compression.		Padding length might be affected by lower-level compression.
	Therefore (as described in Section 3.3 of [RFC7525]), implementations		Therefore (as described in Section 3.3 of [RFC7525]), implementations
	and deployments SHOULD disable TLS-level compression.		and deployments SHOULD disable TLS-level compression.
	The payload of the 'Padding' option could (like many other fields in		The payload of the 'Padding' option could (like many other fields in
	the DNS protocol) be used as a covert channel.		the DNS protocol) be used as a covert channel.
	7. Acknowledgements		7. Acknowledgements
	This document was inspired by a discussion with Daniel Kahn Gillmor		This document was inspired by a discussion with Daniel Kahn Gillmor
	during IETF93, as an alternative to the proposed padding on the TLS		during IETF93, as an alternative to the proposed padding on the TLS
	layer. Allison Mankin and Christian Huitema suggested text for this		layer. Allison Mankin, Andreas Gustaffson, Christian Huitema and
	document.		Jinmei Tatuya suggested text for this document.
	8. Changes		8. Changes
	8.1. draft-ietf-dprive-edns0-padding-01		Note to RFC Editors: Please remove this whole section before
			publication
			8.1. draft-ietf-dprive-edns0-padding-02
			Clarified that changes section is to be removed before publication.
			Clarified that both Requestors and Responders are to ignore padding
			contents. changed text about non-zero padding contents based on WGLC
			comments. removed security considerations about truncation based on
			WGLC comment. added more acknowledgements. replaced "packets" with
			"messages" where appropriate.
			8.2. draft-ietf-dprive-edns0-padding-01
	Fixed 'octects' typo. Changed 'covert channel' text to align with		Fixed 'octects' typo. Changed 'covert channel' text to align with
	allowing non-0x00 padding. changed IANA considerations - assigned		allowing non-0x00 padding. changed IANA considerations - assigned
	option code is 12. Changed field definitions to allow for non-0x00		option code is 12. Changed field definitions to allow for non-0x00
	padding, removed FORMERR requirement. referenced rfc7525 in security		padding, removed FORMERR requirement. referenced rfc7525 in security
	considerations. added acknowledgements.		considerations. added acknowledgements.
	8.2. draft-ieft-dprive-edns0-padding-00		8.3. draft-ieft-dprive-edns0-padding-00
	Adopted by WG. Changed text about message size limit based on		Adopted by WG. Changed text about message size limit based on
	feedback.		feedback.
	8.3. draft-mayrhofer-edns0-padding-01		8.4. draft-mayrhofer-edns0-padding-01
	Changed minimum padding size to 0, rewrote Usage Considerations		Changed minimum padding size to 0, rewrote Usage Considerations
	section, extended Security considerations section		section, extended Security considerations section
	8.4. draft-mayrhofer-edns0-padding-00		8.5. draft-mayrhofer-edns0-padding-00
	Initial version		Initial version
	9. References		9. References
	9.1. Normative References		9.1. Normative References
	[RFC1035] Mockapetris, P., "Domain names - implementation and		[RFC1035] Mockapetris, P., "Domain names - implementation and
	specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,		specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
	November 1987, <http://www.rfc-editor.org/info/rfc1035>.		November 1987, <http://www.rfc-editor.org/info/rfc1035>.
End of changes. 17 change blocks.
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