draft-ietf-tls-ticketrequests-00.txt		draft-ietf-tls-ticketrequests-01.txt
	Network Working Group T. Pauly		Network Working Group T. Pauly
	Internet-Draft Apple Inc.		Internet-Draft Apple Inc.
	Intended status: Informational D. Schinazi		Intended status: Informational D. Schinazi
	Expires: July 22, 2019 Google LLC		Expires: December 8, 2019 Google LLC
	C. Wood		C. Wood
	Apple Inc.		Apple Inc.
	January 18, 2019		June 06, 2019
	TLS Ticket Requests		TLS Ticket Requests
	draft-ietf-tls-ticketrequests-00		draft-ietf-tls-ticketrequests-01
	Abstract		Abstract
	TLS session tickets enable stateless connection resumption for		TLS session tickets enable stateless connection resumption for
	clients without server-side per-client state. Servers vend session		clients without server-side, per-client state. Servers vend an
	tickets to clients, at their discretion, upon connection		arbitrary number of session tickets to clients, at their discretion,
	establishment. Clients store and use tickets when resuming future		upon connection establishment. Clients store and use tickets when
	connections. Moreover, clients should use tickets at most once for		resuming future connections. This document describes a mechanism by
	session resumption, especially if such keying material protects early		which clients may specify the desired number of tickets needed for
	application data. Single-use tickets bound the number of parallel		future connections. This extension aims to provide a means for
	connections a client may initiate by the number of tickets received		servers to determine the number of tickets to generate in order to
	from a given server. To address this limitation, this document		reduce ticket waste, while simultaneously priming clients for future
	describes a mechanism by which clients may specify the desired number		connection attempts.
	of tickets needed for future connections.
	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
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	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 July 22, 2019.		This Internet-Draft will expire on December 8, 2019.
	Copyright Notice		Copyright Notice
	Copyright (c) 2019 IETF Trust and the persons identified as the		Copyright (c) 2019 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
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2		1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
	2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3		2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3
	3. Ticket Requests . . . . . . . . . . . . . . . . . . . . . . . 3		3. Ticket Requests . . . . . . . . . . . . . . . . . . . . . . . 4
	4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4		4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 4		5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
	6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 4		6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
	7. Normative References . . . . . . . . . . . . . . . . . . . . 5		7. Normative References . . . . . . . . . . . . . . . . . . . . 5
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
	1. Introduction		1. Introduction
	As per [RFC5077], and as described in [RFC8446], TLS servers send		As per [RFC5077], and as described in [RFC8446], TLS servers send
	clients session tickets at their own discretion in NewSessionTicket		clients an arbitrary number of session tickets at their own
	messages. Clients are in complete control of how many tickets they		discretion in NewSessionTicket messages. There are two limitations
	may use when establishing future and subsequent connections. For		with this design. First, servers choose some (often hard-coded)
	example, clients may open multiple TLS connections to the same server		number of tickets vended per connection. Second, clients do not have
	for HTTP, or may race TLS connections across different network		a way of expressing their desired number of tickets, which may impact
	interfaces. The latter is especially useful in transport systems		future connection establishment. For example, clients may open
	that implement Happy Eyeballs [RFC8305]. Since connection		multiple TLS connections to the same server for HTTP, or may race TLS
	concurrency and resumption is controlled by clients, a standard		connections across different network interfaces. The latter is
	mechanism to request more than one ticket is desirable.		especially useful in transport systems that implement Happy Eyeballs
			[RFC8305]. Since clients control connection concurrency and
			resumption, a standard mechanism for requesting more than one ticket
			is desirable.
	This document specifies a new TLS extension - ticket_request - that		This document specifies a new TLS extension - "ticket_request" - that
	may be used by clients to express their desired number of session		may be used by clients to express their desired number of session
	tickets. Servers may use this extension as a hint of the number of		tickets. Servers may use this extension as a hint of the number of
	NewSessionTicket messages to vend. This extension is only applicable		NewSessionTicket messages to vend. This extension is only applicable
	to TLS 1.3 [RFC8446] and future versions of TLS.		to TLS 1.3 [RFC8446], DTLS 1.3 [I-D.ietf-tls-dtls13], and future
			versions thereof.
	1.1. Requirements Language		1.1. Requirements Language
	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] [RFC8174] when, and only when, they appear in all capitals,		[RFC2119] [RFC8174] when, and only when, they appear in all capitals,
	as shown here.		as shown here.
	2. Use Cases		2. Use Cases
	skipping to change at page 4, line 27 ¶		skipping to change at page 4, line 37 ¶
	tickets they are willing to vend to clients. Thus, the number of		tickets they are willing to vend to clients. Thus, the number of
	NewSessionTicket messages sent should be the minimum of the server's		NewSessionTicket messages sent should be the minimum of the server's
	self-imposed limit and TicketRequestContents.count. Servers MUST NOT		self-imposed limit and TicketRequestContents.count. Servers MUST NOT
	send more than 255 tickets to clients.		send more than 255 tickets to clients.
	Servers that support ticket requests MUST NOT echo "ticket_request"		Servers that support ticket requests MUST NOT echo "ticket_request"
	in the EncryptedExtensions.		in the EncryptedExtensions.
	4. IANA Considerations		4. IANA Considerations
	IANA is requested to Create an entry, ticket_requests(TBD), in the		IANA is requested to Create an entry, ticket_request(TBD), in the
	existing registry for ExtensionType (defined in [RFC8446]), with "TLS		existing registry for ExtensionType (defined in [RFC8446]), with "TLS
	1.3" column values being set to "CH", and "Recommended" column being		1.3" column values being set to "CH", and "Recommended" column being
	set to "Yes".		set to "Yes".
	5. Security Considerations		5. Security Considerations
	Ticket re-use is a security and privacy concern. Moreover, ticket		Ticket re-use is a security and privacy concern. Moreover, clients
	pooling as a means of avoiding or amortizing handshake costs must be		must take care when pooling tickets as a means of avoiding or
	used carefully. If servers do not rotate session ticket encryption		amortizing handshake costs. If servers do not rotate session ticket
	keys frequently, clients may be encouraged to obtain and use tickets		encryption keys frequently, clients may be encouraged to obtain and
	beyond common lifetime windows of, e.g., 24 hours. Despite ticket		use tickets beyond common lifetime windows of, e.g., 24 hours.
	lifetime hints provided by servers, clients SHOULD dispose of pooled		Despite ticket lifetime hints provided by servers, clients SHOULD
	tickets after some reasonable amount of time that mimics the ticket		dispose of pooled tickets after some reasonable amount of time that
	rotation period.		mimics the ticket rotation period.
	6. Acknowledgments		6. Acknowledgments
	The authors would like to thank David Benjamin, Eric Rescorla, Nick		The authors would like to thank David Benjamin, Eric Rescorla, Nick
	Sullivan, and Martin Thomson for discussions on earlier versions of		Sullivan, Martin Thomson, and other members of the TLS Working Group
	this draft.		for discussions on earlier versions of this draft.
	7. Normative References		7. Normative References
	[I-D.ietf-taps-impl]		[I-D.ietf-taps-impl]
	Brunstrom, A., Pauly, T., Enghardt, T., Grinnemo, K.,		Brunstrom, A., Pauly, T., Enghardt, T., Grinnemo, K.,
	Jones, T., Tiesel, P., Perkins, C., and M. Welzl,		Jones, T., Tiesel, P., Perkins, C., and M. Welzl,
	"Implementing Interfaces to Transport Services", draft-		"Implementing Interfaces to Transport Services", draft-
	ietf-taps-impl-02 (work in progress), October 2018.		ietf-taps-impl-03 (work in progress), March 2019.
			[I-D.ietf-tls-dtls13]
			Rescorla, E., Tschofenig, H., and N. Modadugu, "The
			Datagram Transport Layer Security (DTLS) Protocol Version
			1.3", draft-ietf-tls-dtls13-31 (work in progress), March
			2019.
	[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, <https://www.rfc-		DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
	editor.org/info/rfc2119>.		editor.org/info/rfc2119>.
	[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,		[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
	"Transport Layer Security (TLS) Session Resumption without		"Transport Layer Security (TLS) Session Resumption without
	Server-Side State", RFC 5077, DOI 10.17487/RFC5077,		Server-Side State", RFC 5077, DOI 10.17487/RFC5077,
	January 2008, <https://www.rfc-editor.org/info/rfc5077>.		January 2008, <https://www.rfc-editor.org/info/rfc5077>.
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