< draft-ietf-tls-dtls-rrc-00.txt		draft-ietf-tls-dtls-rrc-01.txt >
	TLS H. Tschofenig, Ed.		TLS H. Tschofenig, Ed.
	Internet-Draft T. Fossati		Internet-Draft T. Fossati
	Updates: 6347 (if approved) Arm Limited		Updates: 6347 (if approved) Arm Limited
	Intended status: Standards Track 9 June 2021		Intended status: Standards Track 25 October 2021
	Expires: 11 December 2021		Expires: 28 April 2022
	Return Routability Check for DTLS 1.2 and DTLS 1.3		Return Routability Check for DTLS 1.2 and DTLS 1.3
	draft-ietf-tls-dtls-rrc-00		draft-ietf-tls-dtls-rrc-01
	Abstract		Abstract
	This document specifies a return routability check for use in context		This document specifies a return routability check for use in context
	of the Connection ID (CID) construct for the Datagram Transport Layer		of the Connection ID (CID) construct for the Datagram Transport Layer
	Security (DTLS) protocol versions 1.2 and 1.3.		Security (DTLS) protocol versions 1.2 and 1.3.
	Discussion Venues		Discussion Venues
	This note is to be removed before publishing as an RFC.		This note is to be removed before publishing as an RFC.
	skipping to change at page 1, line 44 ¶		skipping to change at page 1, line 44 ¶
	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 https://datatracker.ietf.org/drafts/current/.		Drafts is at https://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 11 December 2021.		This Internet-Draft will expire on 28 April 2022.
	Copyright Notice		Copyright Notice
	Copyright (c) 2021 IETF Trust and the persons identified as the		Copyright (c) 2021 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 (https://trustee.ietf.org/		Provisions Relating to IETF Documents (https://trustee.ietf.org/
	license-info) in effect on the date of publication of this document.		license-info) in effect on the date of publication of this document.
	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	skipping to change at page 2, line 28 ¶		skipping to change at page 2, line 28 ¶
	modifications of such material outside the IETF Standards Process.		modifications of such material outside the IETF Standards Process.
	Without obtaining an adequate license from the person(s) controlling		Without obtaining an adequate license from the person(s) controlling
	the copyright in such materials, this document may not be modified		the copyright in such materials, this document may not be modified
	outside the IETF Standards Process, and derivative works of it may		outside the IETF Standards Process, and derivative works of it may
	not be created outside the IETF Standards Process, except to format		not be created outside the IETF Standards Process, except to format
	it for publication as an RFC or to translate it into languages other		it for publication as an RFC or to translate it into languages other
	than English.		than English.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3		2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3
	3. The Return Routability Check Message . . . . . . . . . . . . 4		3. RRC Extension . . . . . . . . . . . . . . . . . . . . . . . . 3
	4. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 5		4. The Return Routability Check Message . . . . . . . . . . . . 4
	5. Security and Privacy Considerations . . . . . . . . . . . . . 7		5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7		6. Security and Privacy Considerations . . . . . . . . . . . . . 8
	7. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 7		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
	8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7		8. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 8
	9. Normative References . . . . . . . . . . . . . . . . . . . . 7		9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
	Appendix A. History . . . . . . . . . . . . . . . . . . . . . . 8		10. Normative References . . . . . . . . . . . . . . . . . . . . 8
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8		Appendix A. History . . . . . . . . . . . . . . . . . . . . . . 9
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
	1. Introduction		1. Introduction
	In "classical" DTLS, selecting a security context of an incoming DTLS		In "classical" DTLS, selecting a security context of an incoming DTLS
	record is accomplished with the help of the 5-tuple, i.e. source IP		record is accomplished with the help of the 5-tuple, i.e. source IP
	address, source port, transport protocol, destination IP address, and		address, source port, transport protocol, destination IP address, and
	destination port. Changes to this 5 tuple can happen for a variety		destination port. Changes to this 5 tuple can happen for a variety
	reasons over the lifetime of the DTLS session. In the IoT context,		reasons over the lifetime of the DTLS session. In the IoT context,
	NAT rebinding is common with sleepy devices. Other examples include		NAT rebinding is common with sleepy devices. Other examples include
	end host mobility and multi-homing. Without CID, if the source IP		end host mobility and multi-homing. Without CID, if the source IP
	skipping to change at page 4, line 10 ¶		skipping to change at page 3, line 44 ¶
	"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
	BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all		BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
	capitals, as shown here.		capitals, as shown here.
	This document assumes familiarity with the CID format and protocol		This document assumes familiarity with the CID format and protocol
	defined for DTLS 1.2 [I-D.ietf-tls-dtls-connection-id] and for DTLS		defined for DTLS 1.2 [I-D.ietf-tls-dtls-connection-id] and for DTLS
	1.3 [I-D.ietf-tls-dtls13]. The presentation language used in this		1.3 [I-D.ietf-tls-dtls13]. The presentation language used in this
	document is described in Section 4 of [RFC8446].		document is described in Section 4 of [RFC8446].
	3. The Return Routability Check Message		3. RRC Extension
			This specification uses the tls_flags extension defined in
			[I-D.ietf-tls-tlsflags] to allow a client and a server to negotiate
			support for this extension.
			The RRC flag is assigned the value (TBD1) and is used in the
			ClientHello (CH) and the ServerHello (SH).
			4. The Return Routability Check Message
	When a record with CID is received that has the source address of the		When a record with CID is received that has the source address of the
	enclosing UDP datagram different from the one previously associated		enclosing UDP datagram different from the one previously associated
	with that CID, the receiver MUST NOT update its view of the peer's IP		with that CID, the receiver MUST NOT update its view of the peer's IP
	address and port number with the source specified in the UDP datagram		address and port number with the source specified in the UDP datagram
	before cryptographically validating the enclosed record(s) but		before cryptographically validating the enclosed record(s) but
	instead perform a return routability check.		instead perform a return routability check.
	enum {		enum {
	invalid(0),		invalid(0),
	change_cipher_spec(20),		change_cipher_spec(20),
	alert(21),		alert(21),
	handshake(22),		handshake(22),
	application_data(23),		application_data(23),
	heartbeat(24), /* RFC 6520 */		heartbeat(24), /* RFC 6520 */
	return_routability_check(TBD), /* NEW */		return_routability_check(TBD), /* NEW */
	(255)		(255)
	} ContentType;		} ContentType;
	struct {		uint64 Cookie;
	opaque cookie<1..2^16-1>;
	} Cookie;		enum {
			path_challenge(0),
			path_response(1),
			reserved(2..255)
			} rrc_msg_type;
	struct {		struct {
	Cookie cookie;		rrc_msg_type msg_type;
			select (return_routability_check.msg_type) {
			case path_challenge: Cookie;
			case path_response: Cookie;
			};
	} return_routability_check;		} return_routability_check;
	The newly introduced return_routability_check message contains a		The newly introduced return_routability_check message contains a
	cookie. The semantic of the cookie is similar to the cookie used in		cookie. The cookie is a 8-byte field containing arbitrary data.
	the HelloRetryRequest message defined in [RFC8446].
	The return_routability_check message MUST be authenticated and		The return_routability_check message MUST be authenticated and
	encrypted using the currently active security context.		encrypted using the currently active security context.
	The receiver that observes the peer's address and or port update MUST		The receiver that observes the peer's address and or port update MUST
	stop sending any buffered application data (or limit the sending rate		stop sending any buffered application data (or limit the data sent to
	to a TBD threshold) and initiate the return routability check that		a TBD threshold) and initiate the return routability check that
	proceeds as follows:		proceeds as follows:
	1. A cookie is placed in the return_routability_check message;		1. A cookie is placed in a return_routability_check message of type
			path_challenge;
	2. The message is sent to the observed new address and a timeout T		2. The message is sent to the observed new address and a timeout T
	is started;		is started;
	3. The peer endpoint, after successfully verifying the received		3. The peer endpoint, after successfully verifying the received
	return_routability_check message echoes it back;		return_routability_check message echoes the cookie value in a
			return_routability_check message of type path_response;
	4. When the initiator receives and verifies the		4. When the initiator receives and verifies the
	return_routability_check message, it updates the peer address		return_routability_check message contains the sent cookie, it
	binding;		updates the peer address binding;
	5. If T expires, or the address confirmation fails, the peer address		5. If T expires, or the address confirmation fails, the peer address
	binding is not updated.		binding is not updated.
	After this point, any pending send operation is resumed to the bound		After this point, any pending send operation is resumed to the bound
	peer address.		peer address.
	4. Example		5. Example
	The example shown in Figure 1 illustrates a client and a server		The example TLS 1.3 handshake shown in Figure 1 shows a client and a
	exchanging application payloads protected by DTLS with an		server negotiating the support for CID and for the RRC extension.
	unilaterally used CIDs. At some point in the communication
	interaction the IP address used by the client changes and, thanks to		Client Server
	the CID usage, the security context to interpret the record is
	successfully located by the server. However, the server wants to		Key ^ ClientHello
	test the reachability of the client at his new IP address, to avoid		Exch | + key_share
	being abused (e.g., as an amplifier) by an attacker impersonating the		| + signature_algorithms
	client.		| + tls_flags (RRC)
			v + connection_id=empty
			-------->
			ServerHello ^ Key
			+ key_share | Exch
			+ connection_id=100 |
			+ tls_flags (RRC) v
			{EncryptedExtensions} ^ Server
			{CertificateRequest} v Params
			{Certificate} ^
			{CertificateVerify} | Auth
			<-------- {Finished} v
			^ {Certificate}
			Auth | {CertificateVerify}
			v {Finished} -------->
			[Application Data] <-------> [Application Data]
			+ Indicates noteworthy extensions sent in the
			previously noted message.
			* Indicates optional or situation-dependent
			messages/extensions that are not always sent.
			{} Indicates messages protected using keys
			derived from a [sender]_handshake_traffic_secret.
			[] Indicates messages protected using keys
			derived from [sender]_application_traffic_secret_N.
			Figure 1: Message Flow for Full TLS Handshake
			Once a connection has been established the client and the server
			exchange application payloads protected by DTLS with an unilaterally
			used CIDs. In our case, the client is requested to use CID 100 for
			records sent to the server.
			At some point in the communication interaction the IP address used by
			the client changes and, thanks to the CID usage, the security context
			to interpret the record is successfully located by the server.
			However, the server wants to test the reachability of the client at
			his new IP address.
	Client Server		Client Server
	------ ------		------ ------
	Application Data ========>		Application Data ========>
	<CID=100>		<CID=100>
	Src-IP=A		Src-IP=A
	Dst-IP=Z		Dst-IP=Z
	<======== Application Data		<======== Application Data
	Src-IP=Z		Src-IP=Z
	skipping to change at page 6, line 31 ¶		skipping to change at page 7, line 31 ¶
	Application Data ========>		Application Data ========>
	<CID=100>		<CID=100>
	Src-IP=B		Src-IP=B
	Dst-IP=Z		Dst-IP=Z
	<<< Unverified IP		<<< Unverified IP
	Address B >>		Address B >>
	<-------- Return Routability Check		<-------- Return Routability Check
	(cookie)		path_challenge(cookie)
	Src-IP=Z		Src-IP=Z
	Dst-IP=B		Dst-IP=B
	Return Routability Check -------->		Return Routability Check -------->
	(cookie)		path_response(cookie)
	Src-IP=B		Src-IP=B
	Dst-IP=Z		Dst-IP=Z
	<<< IP Address B		<<< IP Address B
	Verified >>		Verified >>
	<======== Application Data		<======== Application Data
	Src-IP=Z		Src-IP=Z
	Dst-IP=B		Dst-IP=B
	Figure 1: Return Routability Example		Figure 2: Return Routability Example
	5. Security and Privacy Considerations		6. Security and Privacy Considerations
	Note that the return routability checks do not protect against		Note that the return routability checks do not protect against
	flooding of third-parties if the attacker is on-path, as the attacker		flooding of third-parties if the attacker is on-path, as the attacker
	can redirect the return routability checks to the real peer (even if		can redirect the return routability checks to the real peer (even if
	those datagrams are cryptographically authenticated). On-path		those datagrams are cryptographically authenticated). On-path
	adversaries can, in general, pose a harm to connectivity.		adversaries can, in general, pose a harm to connectivity.
	6. IANA Considerations		7. IANA Considerations
	IANA is requested to allocate an entry to the existing TLS		IANA is requested to allocate an entry to the TLS "ContentType"
	"ContentType" registry, for the return_routability_check(TBD) defined		registry, for the return_routability_check(TBD) defined in this
	in this document.		document.
	7. Open Issues		IANA is requested to allocate an entry to the TLS Flags registry in
			the tls_flags type:
			* Value: [[IANA please assign a value from the 32-63 value range.]]
			* Flag Name: RRC
			* Message: CH,SH
			* Recommended: Y
			* Reference: [[This document]]
			8. Open Issues
	Issues against this document are tracked at https://github.com/tlswg/		Issues against this document are tracked at https://github.com/tlswg/
	dtls-rrc/issues		dtls-rrc/issues
	8. Acknowledgments		9. Acknowledgments
	We would like to thank Achim Kraus, Hanno Becker and Manuel Pegourie-		We would like to thank Achim Kraus, Hanno Becker, Hanno Boeck, Manuel
	Gonnard for their input to this document.		Pegourie-Gonnard, Mohit Sahni and Rich Salz for their input to this
			document.
	9. Normative References		10. Normative References
	[I-D.ietf-tls-dtls-connection-id]		[I-D.ietf-tls-dtls-connection-id]
	Rescorla, E., Tschofenig, H., Fossati, T., and A. Kraus,		Rescorla, E., Tschofenig, H., Fossati, T., and A. Kraus,
	"Connection Identifiers for DTLS 1.2", Work in Progress,		"Connection Identifiers for DTLS 1.2", Work in Progress,
	Internet-Draft, draft-ietf-tls-dtls-connection-id-12, 11		Internet-Draft, draft-ietf-tls-dtls-connection-id-13, 22
	May 2021, <https://tools.ietf.org/html/draft-ietf-tls-		June 2021, <https://datatracker.ietf.org/doc/html/draft-
	dtls-connection-id-12>.		ietf-tls-dtls-connection-id-13>.
	[I-D.ietf-tls-dtls13]		[I-D.ietf-tls-dtls13]
	Rescorla, E., Tschofenig, H., and N. Modadugu, "The		Rescorla, E., Tschofenig, H., and N. Modadugu, "The
	Datagram Transport Layer Security (DTLS) Protocol Version		Datagram Transport Layer Security (DTLS) Protocol Version
	1.3", Work in Progress, Internet-Draft, draft-ietf-tls-		1.3", Work in Progress, Internet-Draft, draft-ietf-tls-
	dtls13-43, 30 April 2021,		dtls13-43, 30 April 2021,
	<https://tools.ietf.org/html/draft-ietf-tls-dtls13-43>.		<https://datatracker.ietf.org/doc/html/draft-ietf-tls-
			dtls13-43>.
			[I-D.ietf-tls-tlsflags]
			Nir, Y., "A Flags Extension for TLS 1.3", Work in
			Progress, Internet-Draft, draft-ietf-tls-tlsflags-06, 13
			July 2021, <https://datatracker.ietf.org/doc/html/draft-
			ietf-tls-tlsflags-06>.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<https://www.rfc-editor.org/rfc/rfc2119>.		<https://www.rfc-editor.org/rfc/rfc2119>.
	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC		[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,		2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.		May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
	[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol		[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
	Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,		Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
	<https://www.rfc-editor.org/rfc/rfc8446>.		<https://www.rfc-editor.org/rfc/rfc8446>.
	Appendix A. History		Appendix A. History
	RFC EDITOR: PLEASE REMOVE THE THIS SECTION		RFC EDITOR: PLEASE REMOVE THE THIS SECTION
	draft-ietf-tls-dtls-rrc-00		draft-ietf-tls-dtls-rrc-01
	* Draft name changed after WG adoption		* Use the TLS flags extension for negotiating RRC
	draft-tschofenig-tls-dtls-rrc-01		* Enhanced IANA consideration section
			* Expanded example section
			* Revamp message layout:
			- Use 8-byte fixed size cookies
			- Explicitly separate path challenge from response
			draft-ietf-tls-dtls-rrc-00
			* Draft name changed after WG adoption
	* Removed text that overlapped with draft-ietf-tls-dtls-connection-		* Removed text that overlapped with draft-ietf-tls-dtls-connection-
	id		id
	draft-tschofenig-tls-dtls-rrc-00		draft-tschofenig-tls-dtls-rrc-00
	* Initial version		* Initial version
	Authors' Addresses		Authors' Addresses
	Hannes Tschofenig (editor)		Hannes Tschofenig (editor)
End of changes. 31 change blocks.
	57 lines changed or deleted		150 lines changed or added
This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/