< draft-schinazi-masque-01.txt		draft-schinazi-masque-02.txt >
	Network Working Group D. Schinazi		Network Working Group D. Schinazi
	Internet-Draft Google LLC		Internet-Draft Google LLC
	Intended status: Experimental July 08, 2019		Intended status: Experimental 8 January 2020
	Expires: January 9, 2020		Expires: 11 July 2020
	The MASQUE Protocol		The MASQUE Protocol
	draft-schinazi-masque-01		draft-schinazi-masque-02
	Abstract		Abstract
	This document describes MASQUE (Multiplexed Application Substrate		This document describes MASQUE (Multiplexed Application Substrate
	over QUIC Encryption). MASQUE is a mechanism that allows co-locating		over QUIC Encryption). MASQUE is a framework that allows
	and obfuscating networking applications behind an HTTPS web server.		concurrently running multiple networking applications inside an
	The currently prevalent use-case is to allow running a proxy or VPN		HTTP/3 connection. For example, MASQUE can allow a QUIC client to
	server that is indistinguishable from an HTTPS server to any		negotiate proxying capability with an HTTP/3 server, and subsequently
	unauthenticated observer. We do not expect major providers and CDNs		make use of this functionality while concurrently processing HTTP/3
	to deploy this behind their main TLS certificate, as they are not		requests and responses.
	willing to take the risk of getting blocked, as shown when domain
	fronting was blocked. An expected use would be for individuals to
	enable this behind their personal websites via easy to configure
	open-source software.
	This document is a straw-man proposal. It does not contain enough		This document is a straw-man proposal. It does not contain enough
	details to implement the protocol, and is currently intended to spark		details to implement the protocol, and is currently intended to spark
	discussions on the approach it is taking. Discussion of this work is		discussions on the approach it is taking. Discussion of this work is
	encouraged to happen on the MASQUE IETF mailing list masque@ietf.org		encouraged to happen on the MASQUE IETF mailing list masque@ietf.org
	[1] or on the GitHub repository which contains the draft:		(mailto:masque@ietf.org) or on the GitHub repository which contains
	https://github.com/DavidSchinazi/masque-drafts [2].		the draft: https://github.com/DavidSchinazi/masque-drafts
			(https://github.com/DavidSchinazi/masque-drafts).
	Status of This Memo		Status of This Memo
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	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
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	Copyright Notice		Copyright Notice
	Copyright (c) 2019 IETF Trust and the persons identified as the		Copyright (c) 2020 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
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	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Conventions and Definitions . . . . . . . . . . . . . . . 3		1.1. Conventions and Definitions . . . . . . . . . . . . . . . 3
	2. Usage Scenarios . . . . . . . . . . . . . . . . . . . . . . . 3		2. MASQUE Negotiation . . . . . . . . . . . . . . . . . . . . . 3
	2.1. Protection from Network Providers . . . . . . . . . . . . 3		3. MASQUE Applications . . . . . . . . . . . . . . . . . . . . . 3
	2.2. Protection from Web Servers . . . . . . . . . . . . . . . 4		3.1. HTTP Proxy . . . . . . . . . . . . . . . . . . . . . . . 3
	2.3. Making a Home Server Available . . . . . . . . . . . . . 4		3.2. DNS over HTTPS . . . . . . . . . . . . . . . . . . . . . 4
	2.4. Onion Routing . . . . . . . . . . . . . . . . . . . . . . 4		3.3. QUIC Proxying . . . . . . . . . . . . . . . . . . . . . . 4
	3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 4		3.4. UDP Proxying . . . . . . . . . . . . . . . . . . . . . . 4
	3.1. Invisibility of Usage . . . . . . . . . . . . . . . . . . 4		3.5. IP Proxying . . . . . . . . . . . . . . . . . . . . . . . 4
	3.2. Invisibility of the Server . . . . . . . . . . . . . . . 5		3.6. Service Registration . . . . . . . . . . . . . . . . . . 5
	3.3. Fallback to HTTP/2 over TLS over TCP . . . . . . . . . . 5		4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
	4. Overview of the Mechanism . . . . . . . . . . . . . . . . . . 5		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
	5. Mechanisms the Server Can Advertise to Authenticated Clients 6		6. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
	5.1. HTTP Proxy . . . . . . . . . . . . . . . . . . . . . . . 6		6.1. Normative References . . . . . . . . . . . . . . . . . . 5
	5.2. DNS over HTTPS . . . . . . . . . . . . . . . . . . . . . 6		6.2. Informative References . . . . . . . . . . . . . . . . . 6
	5.3. UDP Proxying . . . . . . . . . . . . . . . . . . . . . . 6		Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 6
	5.4. QUIC Proxying . . . . . . . . . . . . . . . . . . . . . . 6		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
	5.5. IP Proxying . . . . . . . . . . . . . . . . . . . . . . . 7
	5.6. Path MTU Discovery . . . . . . . . . . . . . . . . . . . 7
	5.7. Service Registration . . . . . . . . . . . . . . . . . . 7
	6. Operation over HTTP/2 . . . . . . . . . . . . . . . . . . . . 7
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
	7.1. Traffic Analysis . . . . . . . . . . . . . . . . . . . . 8
	7.2. Untrusted Servers . . . . . . . . . . . . . . . . . . . . 8
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
	9.1. Normative References . . . . . . . . . . . . . . . . . . 9
	9.2. Informative References . . . . . . . . . . . . . . . . . 10
	9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 11
	Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 11
	Design Justifications . . . . . . . . . . . . . . . . . . . . . . 11
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13
	1. Introduction		1. Introduction
	This document describes MASQUE (Multiplexed Application Substrate		This document describes MASQUE (Multiplexed Application Substrate
	over QUIC Encryption). MASQUE is a mechanism that allows co-locating		over QUIC Encryption). MASQUE is a framework that allows
	and obfuscating networking applications behind an HTTPS web server.		concurrently running multiple networking applications inside an
	The currently prevalent use-case is to allow running a proxy or VPN		HTTP/3 connection (see [HTTP3]). For example, MASQUE can allow a
	server that is indistinguishable from an HTTPS server to any		QUIC client to negotiate proxying capability with an HTTP/3 server,
	unauthenticated observer. We do not expect major providers and CDNs		and subsequently make use of this functionality while concurrently
	to deploy this behind their main TLS certificate, as they are not		processing HTTP/3 requests and responses.
	willing to take the risk of getting blocked, as shown when domain
	fronting was blocked. An expected use would be for individuals to		MASQUE Negotiation is performed using HTTP mechanisms, but MASQUE
	enable this behind their personal websites via easy to configure		applications can subsequently leverage QUIC [QUIC] features without
	open-source software.		using HTTP.
	This document is a straw-man proposal. It does not contain enough		This document is a straw-man proposal. It does not contain enough
	details to implement the protocol, and is currently intended to spark		details to implement the protocol, and is currently intended to spark
	discussions on the approach it is taking. Discussion of this work is		discussions on the approach it is taking. Discussion of this work is
	encouraged to happen on the MASQUE IETF mailing list masque@ietf.org		encouraged to happen on the MASQUE IETF mailing list masque@ietf.org
	[3] or on the GitHub repository which contains the draft:		(mailto:masque@ietf.org) or on the GitHub repository which contains
	https://github.com/DavidSchinazi/masque-drafts [4].		the draft: https://github.com/DavidSchinazi/masque-drafts
			(https://github.com/DavidSchinazi/masque-drafts).
	MASQUE leverages the efficient head-of-line blocking prevention
	features of the QUIC transport protocol [I-D.ietf-quic-transport]
	when MASQUE is used in an HTTP/3 [I-D.ietf-quic-http] server. MASQUE
	can also run in an HTTP/2 server [RFC7540] but at a performance cost.
	1.1. Conventions and Definitions		1.1. Conventions and Definitions
	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 BCP		"OPTIONAL" in this document are to be interpreted as described in BCP
	14 [RFC2119] [RFC8174] when, and only when, they appear in all		14 [RFC2119] [RFC8174] when, and only when, they appear in all
	capitals, as shown here.		capitals, as shown here.
	2. Usage Scenarios		2. MASQUE Negotiation
	There are currently multiple usage scenarios that can benefit from
	MASQUE.
	2.1. Protection from Network Providers
	Some users may wish to obfuscate the destination of their network
	traffic from their network provider. This prevents network providers
	from using data harvested from this network traffic in ways the user
	did not intend.
	2.2. Protection from Web Servers
	There are many clients who would rather not establish a direct
	connection to web servers, for example to avoid location tracking.
	The clients can do that by running their traffic through a MASQUE
	server. The web server will only see the IP address of the MASQUE
	server, not that of the client.
	2.3. Making a Home Server Available
	It is often difficult to connect to a home server. The IP address
	might change over time. Firewalls in the home router or in the
	network may block incoming connections. Using a MASQUE server as a
	rendez-vous point helps resolve these issues.
	2.4. Onion Routing
	Routing traffic through a MASQUE server only provides partial
	protection against tracking, because the MASQUE server knows the
	address of the client. Onion routing as it exists today mitigates
	this issue for TCP/TLS. A MASQUE server could allow onion routing
	over QUIC.
	In this scenario, the client establishes a connection to the MASQUE
	server, then through that to another MASQUE server, etc. This
	creates a tree of MASQUE servers rooted at the client. QUIC
	connections are mapped to a specific branch of the tree. The first
	MASQUE server knows the actual address of the client, but the other
	MASQUE servers only know the address of the previous server. To
	assure reasonable privacy, the path should include at least 3 MASQUE
	servers.
	3. Requirements
	This section describes the goals and requirements chosen for the
	MASQUE protocol.
	3.1. Invisibility of Usage
	An authenticated client using MASQUE features appears to observers as
	a regular HTTPS client. Observers only see that HTTP/3 or HTTP/2 is
	being used over an encrypted channel. No part of the exchanges
	between client and server may stick out. Note that traffic analysis
	is discussed in Section 7.1.
	3.2. Invisibility of the Server
	To anyone without private keys, the server is indistinguishable from
	a regular web server. It is impossible to send an unauthenticated
	probe that the server would reply to differently than if it were a
	normal web server.
	3.3. Fallback to HTTP/2 over TLS over TCP
	When QUIC is blocked, MASQUE can run over TCP and still satisfy
	previous requirements. Note that in this scenario performance may be
	negatively impacted.
	4. Overview of the Mechanism
	The server runs an HTTPS server on port 443, and has a valid TLS
	certificate for its domain. The client has a public/private key
	pair, and the server maintains a list of authorized MASQUE clients,
	and their public key. (Alternatively, clients can also be
	authenticated using a shared secret.) The client starts by
	establishing a regular HTTPS connection to the server (HTTP/3 over
	QUIC or HTTP/2 over TLS 1.3 [RFC8446] over TCP), and validates the
	server's TLS certificate as it normally would for HTTPS. If
	validation fails, the connection is aborted. At this point the
	client can send regular unauthenticated HTTP requests to the server.
	When it wishes to start MASQUE, the client uses HTTP Transport
	Authentication (draft-schinazi-httpbis-transport-auth) to prove its
	possession of its associated key. The client sends the Transport-
	Authentication header alongside an HTTP CONNECT request for "/.well-
	known/masque/initial" with the :protocol pseudo-header field set to
	"masque".
	When the server receives this CONNECT request, it authenticates the		In order to negotiate the use of the MASQUE protocol, the client
	client and if that fails responds with code "405 Method Not Allowed",		starts by sending a MASQUE request in the HTTP data of an HTTP POST
	making sure its response is the same as what it would return for any		request to "/.well-known/masque/initial". The client can use this to
	unexpected CONNECT request. If authentication succeeds, the server		request specific MASQUE applications and advertise support for MASQUE
	responds with code "101 Switching Protocols", and from then on this		extensions. The MASQUE server indicates support for MASQUE by
	HTTP stream is now dedicated to the MASQUE protocol. That protocol		sending an HTTP status code 200 response, and can use the data to
	provides a reliable bidirectional message exchange mechanism, which		inform the client of which MASQUE applications are now in use, and
	is used by the client and server to negotiate what protocol options		various configuration parameters.
	are supported and enabled by policy, and client VPN configuration
	such as IP addresses. When using QUIC, this protocol also allows
	endpoints to negotiate the use of QUIC extensions, such as support
	for the DATAGRAM extension [I-D.pauly-quic-datagram].
	Clients MUST NOT attempt to "resume" MASQUE state similarly to how		Both the MASQUE negotiation initial request and its response carry a
	TLS sessions can be resumed. Every new QUIC or TLS connection		list of type-length-value fields. The type field is a number
	requires fully authenticating the client and server. QUIC 0-RTT and		corresponding to a MASQUE application, and is encoded as a QUIC
	TLS early data MUST NOT be used with MASQUE as they are not forward		variable-length integer. The length field represents the length in
	secure.		bytes of the value field, encoded as a QUIC variable-length integer.
			The contents of the value field or defined by its corresponding
			MASQUE application. When parsing, endpoints MUST ignore unknown
			MASQUE applications.
	5. Mechanisms the Server Can Advertise to Authenticated Clients		3. MASQUE Applications
	Once a server has authenticated the client's MASQUE CONNECT request,		As soon as the server has accepted the client's MASQUE initial
	it advertises services that the client may use.		request, it can advertise support for MASQUE Applications, which will
			be multiplexed over this HTTP/3 connection.
	5.1. HTTP Proxy		3.1. HTTP Proxy
	The client can make proxied HTTP requests through the server to other		The client can make proxied HTTP requests through the server to other
	servers. In practice this will mean using the CONNECT method to		servers. In practice this will mean using the CONNECT method to
	establish a stream over which to run TLS to a different remote		establish a stream over which to run TLS to a different remote
	destination. The proxy applies back-pressure to streams in both		destination. The proxy applies back-pressure to streams in both
	directions.		directions.
	5.2. DNS over HTTPS		3.2. DNS over HTTPS
	The client can send DNS queries using DNS over HTTPS (DoH) [RFC8484]
	to the MASQUE server.
	5.3. UDP Proxying
	In order to support WebRTC or QUIC to further servers, clients need a		The client can send DNS queries using DNS over HTTPS [DOH] to the
	way to relay UDP onwards to a remote server. In practice for most		MASQUE server.
	widely deployed protocols other than DNS, this involves many
	datagrams over the same ports. Therefore this mechanism implements
	that efficiently: clients can use the MASQUE protocol stream to
	request an UDP association to an IP address and UDP port pair. In
	QUIC, the server would reply with a DATAGRAM_ID that the client can
	then use to have UDP datagrams sent to this remote server. Datagrams
	are then simply transferred between the DATAGRAMs with this ID and
	the outer server. There will also be a message on the MASQUE
	protocol stream to request shutdown of a UDP association to save
	resources when it is no longer needed. When running over TCP, the
	client opens a new stream with a CONNECT request to the "masque-udp-
	proxy" protocol and then sends datagrams encapsulated inside the
	stream with a two-byte length prefix in network byte order. The
	target IP and port are sent as part of the URL query. Resetting that
	stream instructs the server to release any associates resources.
	5.4. QUIC Proxying		3.3. QUIC Proxying
	By leveraging QUIC client connection IDs, a MASQUE server can act as		By leveraging QUIC client connection IDs, a MASQUE server can act as
	a QUIC proxy while only using one UDP port. The server informs the		a QUIC proxy while only using one UDP port. The server informs the
	client of a scheme for client connection IDs (for example, random of		client of a scheme for client connection IDs (for example, random of
	a minimum length or vended by the MASQUE server) and then the server		a minimum length or vended by the MASQUE server) and then the server
	can forward those packets to further web servers.		can forward those packets to further web servers.
	This mechanism can elide the connection IDs on the link between the		This mechanism can elide the connection IDs on the link between the
	client and MASQUE server by negotiating a mapping between		client and MASQUE server by negotiating a mapping between
	DATAGRAM_IDs and the tuple (client connection ID, server connection		DATAGRAM_IDs and the tuple (client connection ID, server connection
	ID, server IP address, server port).		ID, server IP address, server port).
	Compared to UDP proxying, this mode has the advantage of only		Compared to UDP proxying, this mode has the advantage of only
	requiring one UDP port to be open on the MASQUE server, and can lower		requiring one UDP port to be open on the MASQUE server, and can lower
	the overhead on the link between client and MASQUE server by		the overhead on the link between client and MASQUE server by
	compressing connection IDs.		compressing connection IDs.
	5.5. IP Proxying		3.4. UDP Proxying
			In order to support WebRTC or QUIC to further servers, clients need a
			way to relay UDP onwards to a remote server. In practice for most
			widely deployed protocols other than DNS, this involves many
			datagrams over the same ports. Therefore this mechanism implements
			that efficiently: clients can use the MASQUE protocol stream to
			request an UDP association to an IP address and UDP port pair. In
			QUIC, the server would reply with a DATAGRAM_ID that the client can
			then use to have UDP datagrams sent to this remote server. Datagrams
			are then simply transferred between the DATAGRAMs with this ID and
			the outer server. There will also be a message on the MASQUE
			protocol stream to request shutdown of a UDP association to save
			resources when it is no longer needed.
			3.5. IP Proxying
	For the rare cases where the previous mechanisms are not sufficient,		For the rare cases where the previous mechanisms are not sufficient,
	proxying can be performed at the IP layer. This would use a		proxying can be performed at the IP layer. This would use a
	different DATAGRAM_ID and IP datagrams would be encoded inside it		different DATAGRAM_ID and IP datagrams would be encoded inside it
	without framing. Over TCP, a dedicated stream with two byte length		without framing.
	prefix would be used. The server can inspect the IP datagram to look
	for the destination address in the IP header.
	5.6. Path MTU Discovery
	In the main deployment of this mechanism, QUIC will be used between
	client and server, and that will most likely be the smallest MTU link
	in the path due to QUIC header and authentication tag overhead. The
	client is responsible for not sending overly large UDP packets and
	notifying the server of the low MTU. Therefore PMTUD is currently
	seen as out of scope of this document.
	5.7. Service Registration		3.6. Service Registration
	MASQUE can be used to make a home server accessible on the wide area.		MASQUE can be used to make a home server accessible on the wide area.
	The home server authenticates to the MASQUE server and registers a		The home server authenticates to the MASQUE server and registers a
	domain name it wishes to serve. The MASQUE server can then forward		domain name it wishes to serve. The MASQUE server can then forward
	any traffic it receives for that domain name (by inspecting the TLS		any traffic it receives for that domain name (by inspecting the TLS
	Server Name Indication (SNI) extension) to the home server. This		Server Name Indication (SNI) extension) to the home server. This
	received traffic is not authenticated and it allows non-modified		received traffic is not authenticated and it allows non-modified
	clients to communicate with the home server without knowing it is not		clients to communicate with the home server without knowing it is not
	colocated with the MASQUE server.		colocated with the MASQUE server.
	To help obfuscate the home server, deployments can use Encrypted		To help obfuscate the home server, deployments can use Encrypted
	Server Name Indication (ESNI) [I-D.ietf-tls-esni]. That will require		Server Name Indication [ESNI]. That will require the MASQUE server
	the MASQUE server sending the cleartext SNI to the home server.		sending the cleartext SNI to the home server.
	6. Operation over HTTP/2
	MASQUE implementations using HTTP/3 MUST support the fallback to
	HTTP/2 to avoid incentivizing censors to block HTTP/3 or QUIC. When
	running over HTTP/2, MASQUE uses the Extended CONNECT method to
	negotiate the use of datagrams over an HTTP/2 stream
	[I-D.kinnear-httpbis-http2-transport].
	MASQUE implementations SHOULD discover that HTTP/3 is available (as
	opposed to only HTTP/2) using the same mechanism as regular HTTP
	traffic. This current standardized mechanism for this is HTTP
	Alternative Services [RFC7838], but future mechanisms such as
	[I-D.schwartz-httpbis-dns-alt-svc] can be used if they become
	widespread.
	7. Security Considerations		4. Security Considerations
	Here be dragons. TODO: slay the dragons.		Here be dragons. TODO: slay the dragons.
	7.1. Traffic Analysis		5. IANA Considerations
	While MASQUE ensures that proxied traffic appears similar to regular
	HTTP traffic, it doesn't inherently defeat traffic analysis.
	However, the fact that MASQUE leverages QUIC allows it to segment
	STREAM frames over multiple packets and add PADDING frames to change
	the observable characteristics of its encrypted traffic. The exact
	details of how to change traffic patterns to defeat traffic analysis
	is considered an open research question and is out of scope for this
	document.
	When multiple MASQUE servers are available, a client can leverage
	QUIC connection migration to seamlessly transition its end-to-end
	QUIC connections by treating separate MASQUE servers as different
	paths. This could afford an additional level of obfuscation in hopes
	of rendering traffic analysis less effective.
	7.2. Untrusted Servers
	As with any proxy or VPN technology, MASQUE hides some of the
	client's private information (such as who they are communicating
	with) from their network provider by transferring that information to
	the MASQUE server. It is paramount that clients only use MASQUE
	servers that they trust, as a malicious actor could easily setup a
	MASQUE server and advertise it as a privacy solution in hopes of
	attracting users to send it their traffic.
	8. IANA Considerations
	We will need to register:
	o the "/.well-known/masque/" URI (expert review)
	https://www.iana.org/assignments/well-known-uris/well-known-
	uris.xhtml [5]
	o The "masque" and "masque-udp-proxy" extended HTTP CONNECT
	protocols
	We will also need to define the MASQUE control protocol and that will
	be likely to define new registries of its own.
	9. References		This document will request IANA to register the "/.well-known/
			masque/" URI (expert review) https://www.iana.org/assignments/well-
			known-uris/well-known-uris.xhtml (https://www.iana.org/assignments/
			well-known-uris/well-known-uris.xhtml).
	9.1. Normative References		This document will request IANA to create a new MASQUE Applications
			registry which governs a 62-bit space of MASQUE application types.
	[I-D.ietf-quic-http]		6. References
	Bishop, M., "Hypertext Transfer Protocol Version 3
	(HTTP/3)", draft-ietf-quic-http-20 (work in progress),
	April 2019.
	[I-D.ietf-quic-transport]		6.1. Normative References
	Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
	and Secure Transport", draft-ietf-quic-transport-20 (work
	in progress), April 2019.
	[I-D.kinnear-httpbis-http2-transport]		[HTTP3] Bishop, M., "Hypertext Transfer Protocol Version 3
	Kinnear, E. and T. Pauly, "Using HTTP/2 as a Transport for		(HTTP/3)", Work in Progress, Internet-Draft, draft-ietf-
	Arbitrary Bytestreams", draft-kinnear-httpbis-		quic-http-24, 4 November 2019, <http://www.ietf.org/
	http2-transport-01 (work in progress), March 2019.		internet-drafts/draft-ietf-quic-http-24.txt>.
	[I-D.pauly-quic-datagram]		[QUIC] Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
	Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable		and Secure Transport", Work in Progress, Internet-Draft,
	Datagram Extension to QUIC", draft-pauly-quic-datagram-03		draft-ietf-quic-transport-24, 3 November 2019,
	(work in progress), July 2019.		<http://www.ietf.org/internet-drafts/draft-ietf-quic-
			transport-24.txt>.
	[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/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
	[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
	Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
	DOI 10.17487/RFC7540, May 2015,
	<https://www.rfc-editor.org/info/rfc7540>.
	[RFC7838] Nottingham, M., McManus, P., and J. Reschke, "HTTP
	Alternative Services", RFC 7838, DOI 10.17487/RFC7838,
	April 2016, <https://www.rfc-editor.org/info/rfc7838>.
	[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/info/rfc8174>.		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol		[DOH] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
	Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
	<https://www.rfc-editor.org/info/rfc8446>.
	[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
	(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,		(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
	<https://www.rfc-editor.org/info/rfc8484>.		<https://www.rfc-editor.org/info/rfc8484>.
	9.2. Informative References		6.2. Informative References
	[I-D.ietf-httpbis-http2-secondary-certs]
	Bishop, M., Sullivan, N., and M. Thomson, "Secondary
	Certificate Authentication in HTTP/2", draft-ietf-httpbis-
	http2-secondary-certs-04 (work in progress), April 2019.
	[I-D.ietf-tls-esni]
	Rescorla, E., Oku, K., Sullivan, N., and C. Wood,
	"Encrypted Server Name Indication for TLS 1.3", draft-
	ietf-tls-esni-03 (work in progress), March 2019.
	[I-D.pardue-httpbis-http-network-tunnelling]
	Pardue, L., "HTTP-initiated Network Tunnelling (HiNT)",
	draft-pardue-httpbis-http-network-tunnelling-01 (work in
	progress), October 2018.
	[I-D.schwartz-httpbis-dns-alt-svc]
	Schwartz, B. and M. Bishop, "Finding HTTP Alternative
	Services via the Domain Name Service", draft-schwartz-
	httpbis-dns-alt-svc-02 (work in progress), April 2018.
	[I-D.schwartz-httpbis-helium]
	Schwartz, B., "Hybrid Encapsulation Layer for IP and UDP
	Messages (HELIUM)", draft-schwartz-httpbis-helium-00 (work
	in progress), June 2018.
	[I-D.sullivan-tls-post-handshake-auth]
	Sullivan, N., Thomson, M., and M. Bishop, "Post-Handshake
	Authentication in TLS", draft-sullivan-tls-post-handshake-
	auth-00 (work in progress), August 2016.
	[RFC8441] McManus, P., "Bootstrapping WebSockets with HTTP/2",
	RFC 8441, DOI 10.17487/RFC8441, September 2018,
	<https://www.rfc-editor.org/info/rfc8441>.
	[RFC8471] Popov, A., Ed., Nystroem, M., Balfanz, D., and J. Hodges,
	"The Token Binding Protocol Version 1.0", RFC 8471,
	DOI 10.17487/RFC8471, October 2018,
	<https://www.rfc-editor.org/info/rfc8471>.
	9.3. URIs
	[1] mailto:masque@ietf.org
	[2] https://github.com/DavidSchinazi/masque-drafts
	[3] mailto:masque@ietf.org
	[4] https://github.com/DavidSchinazi/masque-drafts
	[5] https://www.iana.org/assignments/well-known-uris/well-known-		[ESNI] Rescorla, E., Oku, K., Sullivan, N., and C. Wood,
	uris.xhtml		"Encrypted Server Name Indication for TLS 1.3", Work in
			Progress, Internet-Draft, draft-ietf-tls-esni-05, 4
			November 2019, <http://www.ietf.org/internet-drafts/draft-
			ietf-tls-esni-05.txt>.
	Acknowledgments		Acknowledgments
	This proposal was inspired directly or indirectly by prior work from		This proposal was inspired directly or indirectly by prior work from
	many people. In particular, this work is related to		many people. The author would like to thank Nick Harper, Christian
	[I-D.schwartz-httpbis-helium] and		Huitema, Marcus Ihlar, Eric Kinnear, Mirja Kuehlewind, Brendan Moran,
	[I-D.pardue-httpbis-http-network-tunnelling]. The mechanism used to		Lucas Pardue, Tommy Pauly, Zaheduzzaman Sarker, Ben Schwartz, and
	run the MASQUE protocol over HTTP/2 streams was inspired by		Christopher A. Wood for their input.
	[RFC8441]. Brendan Moran is to thank for the idea of leveraging
	connection migration across MASQUE servers.
	The author would like to thank Christophe A., an inspiration and true
	leader of VPNs.
	Design Justifications
	Using an exported key as a nonce allows us to prevent replay attacks
	(since it depends on randomness from both endpoints of the TLS
	connection) without requiring the server to send an explicit nonce
	before it has authenticated the client. Adding an explicit nonce
	mechanism would expose the server as it would need to send these
	nonces to clients that have not been authenticated yet.
	The rationale for a separate MASQUE protocol stream is to allow
	server-initiated messages. If we were to use HTTP semantics, we
	would only be able to support the client-initiated request-response
	model. We could have used WebSocket for this purpose but that would
	have added wire overhead and dependencies without providing useful
	features.
	There are many other ways to authenticate HTTP, however the
	authentication used here needs to work in a single client-initiated
	message to meet the requirement of not exposing the server.
	The current proposal would also work with TLS 1.2, but in that case
	TLS false start and renegotiation must be disabled, and the extended
	master secret and renegotiation indication TLS extensions must be
	enabled.
	If the server or client want to hide that HTTP/2 is used, the client
	can set its ALPN to an older version of HTTP and then use the Upgrade
	header to upgrade to HTTP/2 inside the TLS encryption.
	The client authentication used here is similar to how Token Binding
	[RFC8471] operates, but it has very different goals. MASQUE does not
	use token binding directly because using token binding requires
	sending the token_binding TLS extension in the TLS ClientHello, and
	that would stick out compared to a regular TLS connection.
	TLS post-handshake authentication
	[I-D.sullivan-tls-post-handshake-auth] is not used by this proposal
	because that requires sending the "post_handshake_auth" extension in
	the TLS ClientHello, and that would stick out from a regular HTTPS
	connection.
	Client authentication could have benefited from Secondary Certificate
	Authentication in HTTP/2 [I-D.ietf-httpbis-http2-secondary-certs],
	however that has two downsides: it requires the server advertising
	that it supports it in its SETTINGS, and it cannot be sent unprompted
	by the client, so the server would have to request authentication.
	Both of these would make the server stick out from regular HTTP/2
	servers.
	MASQUE proposes a new client authentication method (as opposed to
	reusing something like HTTP basic authentication) because HTTP
	authentication methods are conceptually per-request (they need to be
	repeated on each request) whereas the new method is bound to the
	underlying connection (be it QUIC or TLS). In particular, this
	allows sending QUIC DATAGRAM frames without authenticating every
	frame individually. Additionally, HMAC and asymmetric keying are
	preferred to sending a password for client authentication since they
	have a tighter security bound. Going into the design rationale,
	HMACs (and signatures) need some data to sign, and to avoid replay
	attacks that should be a fresh nonce provided by the remote peer.
	Having the server provide an explicit nonce would leak the existence
	of the server so we use TLS keying material exporters as they provide
	us with a nonce that contains entropy from the server without
	requiring explicit communication.
	Author's Address		Author's Address
	David Schinazi		David Schinazi
	Google LLC		Google LLC
	1600 Amphitheatre Parkway		1600 Amphitheatre Parkway
	Mountain View, California 94043		Mountain View, California 94043,
	United States of America		United States of America
	Email: dschinazi.ietf@gmail.com		Email: dschinazi.ietf@gmail.com
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