< draft-ietf-httpbis-http2-encryption-03.txt		draft-ietf-httpbis-http2-encryption-04.txt >
	HTTP Working Group M. Nottingham		HTTP Working Group M. Nottingham
	Internet-Draft		Internet-Draft
	Intended status: Experimental M. Thomson		Intended status: Experimental M. Thomson
	Expires: June 19, 2016 Mozilla		Expires: September 18, 2016 Mozilla
	December 17, 2015		March 17, 2016
	Opportunistic Security for HTTP		Opportunistic Security for HTTP
	draft-ietf-httpbis-http2-encryption-03		draft-ietf-httpbis-http2-encryption-04
	Abstract		Abstract
	This document describes how "http" URIs can be accessed using		This document describes how "http" URIs can be accessed using
	Transport Layer Security (TLS) to mitigate pervasive monitoring		Transport Layer Security (TLS) to mitigate pervasive monitoring
	attacks.		attacks.
			Note to Readers
			Discussion of this draft takes place on the HTTP working group
			mailing list (ietf-http-wg@w3.org), which is archived at
			https://lists.w3.org/Archives/Public/ietf-http-wg/ .
			Working Group information can be found at http://httpwg.github.io/ ;
			source code and issues list for this draft can be found at
			https://github.com/httpwg/http-extensions/labels/opp-sec .
	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) 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.
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	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
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	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. Goals and Non-Goals . . . . . . . . . . . . . . . . . . . 3		1.1. Goals and Non-Goals . . . . . . . . . . . . . . . . . . . 3
	1.2. Notational Conventions . . . . . . . . . . . . . . . . . 3		1.2. Notational Conventions . . . . . . . . . . . . . . . . . 3
	2. Using HTTP URIs over TLS . . . . . . . . . . . . . . . . . . 3		2. Using HTTP URIs over TLS . . . . . . . . . . . . . . . . . . 3
	3. Server Authentication . . . . . . . . . . . . . . . . . . . . 4		3. Server Authentication . . . . . . . . . . . . . . . . . . . . 4
	4. Interaction with "https" URIs . . . . . . . . . . . . . . . . 4		4. Interaction with "https" URIs . . . . . . . . . . . . . . . . 5
	5. Requiring Use of TLS . . . . . . . . . . . . . . . . . . . . 5		5. Requiring Use of TLS . . . . . . . . . . . . . . . . . . . . 5
	5.1. The HTTP-TLS Header Field . . . . . . . . . . . . . . . . 5		5.1. Opportunistic Commitment . . . . . . . . . . . . . . . . 6
	5.2. Operational Considerations . . . . . . . . . . . . . . . 7		5.2. Client Handling of A Commitment . . . . . . . . . . . . . 6
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 7		5.3. Operational Considerations . . . . . . . . . . . . . . . 7
	6.1. Security Indicators . . . . . . . . . . . . . . . . . . . 7		6. The "http-opportunistic" well-known URI . . . . . . . . . . . 7
	6.2. Downgrade Attacks . . . . . . . . . . . . . . . . . . . . 7		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
	6.3. Privacy Considerations . . . . . . . . . . . . . . . . . 8		8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
	6.4. Confusion Regarding Request Scheme . . . . . . . . . . . 8		8.1. Security Indicators . . . . . . . . . . . . . . . . . . . 8
	7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8		8.2. Downgrade Attacks . . . . . . . . . . . . . . . . . . . . 8
	7.1. Normative References . . . . . . . . . . . . . . . . . . 8		8.3. Privacy Considerations . . . . . . . . . . . . . . . . . 9
	7.2. Informative References . . . . . . . . . . . . . . . . . 9		8.4. Confusion Regarding Request Scheme . . . . . . . . . . . 9
	Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9		9.1. Normative References . . . . . . . . . . . . . . . . . . 9
			9.2. Informative References . . . . . . . . . . . . . . . . . 10
			Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 11
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
	1. Introduction		1. Introduction
	This document describes a use of HTTP Alternative Services		This document describes a use of HTTP Alternative Services
	[I-D.ietf-httpbis-alt-svc] to decouple the URI scheme from the use		[I-D.ietf-httpbis-alt-svc] to decouple the URI scheme from the use
	and configuration of underlying encryption, allowing a "http" URI to		and configuration of underlying encryption, allowing a "http" URI
	be accessed using TLS [RFC5246] opportunistically.		[RFC7230] to be accessed using TLS [RFC5246] opportunistically.
	Serving "https" URIs require acquiring and configuring a valid		Serving "https" URIs require acquiring and configuring a valid
	certificate, which means that some deployments find supporting TLS		certificate, which means that some deployments find supporting TLS
	difficult. This document describes a usage model whereby sites can		difficult. This document describes a usage model whereby sites can
	serve "http" URIs over TLS without being required to support strong		serve "http" URIs over TLS without being required to support strong
	server authentication.		server authentication.
	Opportunistic Security [RFC7435] does not provide the same guarantees		Opportunistic Security [RFC7435] does not provide the same guarantees
	as using TLS with "https" URIs; it is vulnerable to active attacks,		as using TLS with "https" URIs; it is vulnerable to active attacks,
	and does not change the security context of the connection.		and does not change the security context of the connection.
	skipping to change at page 4, line 7 ¶		skipping to change at page 4, line 14 ¶
	A client can also explicitly probe for an alternative service		A client can also explicitly probe for an alternative service
	advertisement by sending a request that bears little or no sensitive		advertisement by sending a request that bears little or no sensitive
	information, such as one with the OPTIONS method. Likewise, clients		information, such as one with the OPTIONS method. Likewise, clients
	with existing alternative services information could make such a		with existing alternative services information could make such a
	request before they expire, in order minimize the delays that might		request before they expire, in order minimize the delays that might
	be incurred.		be incurred.
	3. Server Authentication		3. Server Authentication
	By their nature, "http" URIs do not require cryptographically strong		[I-D.ietf-httpbis-alt-svc] requires that an alternative service only
	server authentication; that is only implied by "https" URIs.		be used when there are "reasonable assurances" that it is under
	Furthermore, doing so (as per [RFC2818]) creates a number of		control of and valid for the whole origin.
	operational challenges. For these reasons, server authentication is
	not mandatory for "http" URIs when using the mechanism described in
	this specification.
	When connecting to an alternative service for an "http" URI, clients		As defined in that specification, one way of establishing this is
	are not required to perform the server authentication procedure		using a TLS-based protocol with the certificate checks defined in
	described in Section 3.1 of [RFC2818]. The server certificate, if		[RFC2818]. Clients MAY impose additional criteria for establishing
	one is proffered by the alternative service, is not necessarily		reasonable assurances.
	checked for validity, expiration, issuance by a trusted certificate
	authority or matched against the name in the URI. Therefore, the
	alternative service can provide any certificate, or even select TLS
	cipher suites that do not include authentication.
	A client MAY perform additional checks on the offered certificate if		For the purposes of this specification, an additional way of
	the server does not select an unauthenticated TLS cipher suite. This		establishing reasonable assurances is available when the alternative
	document doesn't define any such checks, though clients could be		is on the same host as the origin, using the "http-opportunistic"
	configured with a policy that defines what is acceptable.		well-known URI defined in Section 6.
	As stipulated by [I-D.ietf-httpbis-alt-svc], clients MUST NOT use		This allows deployment without the use of valid certificates, to
	alternative services with a host other than the origin's, unless the		encourage deployment of opportunistic security. When it is in use,
	alternative service itself is strongly authenticated (as the origin's		the alternative service can provide any certificate, or even select
	host); for example, using TLS with a certificate that validates as		TLS cipher suites that do not include authentication.
	per [RFC2818].
			When the client has a valid http-opportunistic response for an
			origin, it MAY consider there to be reasonable assurances when:
			o The origin and alternative service's hostnames are the same when
			compared in a case-insensitive fashion, and
			o The chosen alternative service returns the same response as above.
			For example, this request/response pair would constitute reasonable
			assurances for the origin "http://www.example.com" for any
			alternative service also on "www.example.com":
			GET /.well-known/http-opportunistic HTTP/1.1
			Host: www.example.com
			HTTP/1.1 200 OK
			Content-Type: application/json
			Connection: close
			{
			"origins": ["http://example.com", "http://www.example.com:81"]
			}
			Note that this mechanism is only defined to establish reasonable
			assurances for the purposes of this specification; it does not apply
			to other uses of alternative services unless they explicitly invoke
			it.
	4. Interaction with "https" URIs		4. Interaction with "https" URIs
	When using alternative services, requests for resources identified by		When using alternative services, requests for resources identified by
	both "http" and "https" URIs might use the same connection, because		both "http" and "https" URIs might use the same connection, because
	HTTP/2 permits requests for multiple origins on the same connection.		HTTP/2 permits requests for multiple origins on the same connection.
	Since "https" URIs rely on server authentication, a connection that		Since "https" URIs rely on server authentication, a connection that
	is initially created for "http" URIs without authenticating the		is initially created for "http" URIs without authenticating the
	server cannot be used for "https" URIs until the server certificate		server cannot be used for "https" URIs until the server certificate
	is successfully authenticated. Section 3.1 of [RFC2818] describes		is successfully authenticated. Section 3.1 of [RFC2818] describes
	the basic mechanism, though the authentication considerations in		the basic mechanism, though the authentication considerations in
	[I-D.ietf-httpbis-alt-svc] also apply.		[I-D.ietf-httpbis-alt-svc] also apply.
	Connections that are established without any means of server		Connections that are established without any means of server
	authentication (for instance, the purely anonymous TLS cipher		authentication (for instance, the purely anonymous TLS cipher
	suites), cannot be used for "https" URIs.		suites), cannot be used for "https" URIs.
	5. Requiring Use of TLS		5. Requiring Use of TLS
	Editors' Note: this is a very rough take on an approach that would		Even when the alternative service is strongly authenticated,
	provide a limited form of protection against downgrade attack. It's		opportunistically upgrading cleartext HTTP connections to use TLS is
	unclear at this point whether the additional effort (and modest		subject to active attacks. In particular:
	operational cost) is worthwhile.
	The mechanism described in this specification is trivial to mount an
	active attack against, for two reasons:
	o A client that doesn't perform authentication is an easy victim of		o Because the original HTTP connection is in cleartext, it is
	server impersonation, through man-in-the-middle attacks.		vulnerable to man-in-the-middle attacks, and
	o A client that is willing to use HTTP over cleartext to resolve the		o By default, if clients cannot reach the alternative service, they
	resource will do so if access to any TLS-enabled alternative		will fall back to using the original cleartext origin.
	services is blocked at the network layer.
	Given that the primary goal of this specification is to prevent		Given that the primary goal of this specification is to prevent
	passive attacks, these are not critical failings (especially		passive attacks, these are not critical failings (especially
	considering the alternative - HTTP over cleartext). However, a		considering the alternative - HTTP over cleartext). However, a
	modest form of protection against active attacks can be provided for		modest form of protection against active attacks can be provided for
	clients on subsequent connections.		clients on subsequent connections.
	When an alternative service is able to commit to providing service		When an origin is able to commit to providing service for a
	for a particular origin over TLS for a bounded period of time,		particular origin over TLS for a bounded period of time, clients can
	clients can choose to rely upon its availability, failing when it		choose to rely upon its availability, failing when it cannot be
	cannot be contacted. Effectively, this makes the choice to use a		contacted. Effectively, this makes the choice to use a secured
	secured protocol "sticky" in the client.		protocol "sticky".
	5.1. The HTTP-TLS Header Field		5.1. Opportunistic Commitment
	A alternative service can make this commitment by sending a "HTTP-		An origin can reduce the risk of attacks on opportunistically secured
	TLS" header field, described here using the '#' ABNF extension		connections by committing to provide an secured, authenticated
	defined in Section 7 of [RFC7230]:		alternative service. This is done by including the optional "commit"
			member in the http-opportunistic well-known resource (see Section 6).
			This feature is optional due to the requirement for server
			authentication and the potential risk entailed (see Section 5.3).
	HTTP-TLS = 1#parameter		The value of the "commit" member is a number ([RFC7159], Section 6)
			indicating the duration of the commitment interval in seconds.
	When it appears in a HTTP response from a strongly authenticated		{
	alternative service, this header field indicates that the		"origins": ["http://example.com", "http://www.example.com:81"],
	availability of the origin through TLS-protected alternative services		"commit": 86400
	is "sticky", and that the client MUST NOT fall back to cleartext		}
	protocols while this information is considered fresh.
	For example:		Including "commit" creates a commitment to provide a secured
			alternative service for the advertised period. Clients that receive
			this commitment can assume that a secured alternative service will be
			available for the indicated period. Clients might however choose to
			limit this time (see Section 5.3).
	GET /index.html HTTP/1.1		5.2. Client Handling of A Commitment
	Host: example.com
	HTTP/1.1 200 OK		The value of the "commit" member MUST be ignored unless the
	Content-Type: text/html		alternative service can be strongly authenticated. The same
	Cache-Control: max-age=600		authentication requirements that apply to "https://" resources SHOULD
	Age: 30		be applied to authenticating the alternative. Minimum authentication
	Date: Thu, 1 May 2014 16:20:09 GMT		requirements for HTTP over TLS are described in Section 2.1 of
	HTTP-TLS: ma=3600		[I-D.ietf-httpbis-alt-svc] and Section 3.1 of [RFC2818]. As noted in
			[I-D.ietf-httpbis-alt-svc], clients can impose other checks in
			addition to this minimum set. For instance, a client might choose to
			apply key pinning [RFC7469].
	This header field creates a commitment from the origin [RFC6454] of		A client that receives a commitment and that successfully
	the associated resource (in the example, "http://example.com"). For		authenticates the alternative service can assume that a secured
	the duration of the commitment, clients SHOULD strongly authenticate		alternative will remain available for the commitment interval. The
	the server for all subsequent requests made to that origin, though		commitment interval starts when the commitment is received and
	this creates some risks for clients (see Section 5.2).		authenticated and runs for a number of seconds equal to value of the
			"commit" member, less the current age of the http-opportunistic
			response (as defined in Section 4.2.3 of [RFC7234]). A client SHOULD
			avoid sending requests via cleartext protocols or to unauthenticated
			alternative services for the duration of the commitment interval,
			except to discover new potential alternatives.
	Authentication for HTTP over TLS is described in Section 3.1 of		A commitment only applies to the origin of the http-opportunistic
	[RFC2818], noting the additional requirements in Section 2.1 of		well-known resource that was retrieved; other origins listed in the
	[I-D.ietf-httpbis-alt-svc]. The header field MUST be ignored if		"origins" member MUST be independently discovered and authenticated.
	strong authentication fails; otherwise, an attacker could create a
	persistent denial of service by falsifying a commitment.
	The commitment to use authenticated TLS persists for a period		A commitment is not bound to a particular alternative service.
	determined by the value of the "ma" parameter. See Section 4.2.3 of		Clients are able to use alternative services that they become aware
	[RFC7234] for details of determining response age.		of. However, once a valid and authenticated commitment has been
			received, clients SHOULD NOT use an unauthenticated alternative
			service. Where there is an active commitment, clients SHOULD ignore
			advertisements for unsecured alternative services. A client MAY send
			requests to an unauthenticated origin in an attempt to discover
			potential alternative services, but these requests SHOULD be entirely
			generic and avoid including credentials.
	ma-parameter = delta-seconds		5.3. Operational Considerations
	The commitment made by the "HTTP-TLS" header field applies only to		Errors in configuration of commitments has the potential to render
	the origin of the resource that generates the "HTTP-TLS" header		even the unsecured origin inaccessible for the duration of a
	field.		commitment. Initial deployments are encouraged to use short duration
			commitments so that errors can be detected without causing the origin
			to become inaccessible to clients for extended periods.
	Requests for an origin that has a persisted, unexpired value for		To avoid situations where a commitment causes errors, clients MAY
	"HTTP-TLS" MUST fail if they cannot be made over an authenticated TLS		limit the time over which a commitment is respected for a given
	connection.		origin. A lower limit might be appropriate for initial commitments;
			the certainty that a site has set a correct value - and the
			corresponding limit on persistence - might increase as a commitment
			is renewed multiple times.
	Note that the commitment is not bound to a particular alternative		6. The "http-opportunistic" well-known URI
	service. Clients SHOULD use alternative services that they become
	aware of. However, clients MUST NOT use an unauthenticated
	alternative service for an origin with this commitment. Where there
	is an active commitment, clients MAY instead ignore advertisements
	for unsecured alternatives services.
	5.2. Operational Considerations		This specification defines the "http-opportunistic" well-known URI
			[RFC5785]. An origin is said to have a valid http-opportunistic
			resource when:
	To avoid situations where a persisted value of "HTTP-TLS" causes a		o The client has obtained a 200 (OK) response for the well-known URI
	client to be unable to contact a site, clients SHOULD limit the time		from the origin, or refreshed one in cache [RFC7234], and
	that a value is persisted for a given origin. A lower limit might be
	appropriate for initial observations of "HTTP-TLS"; the certainty
	that a site has set a correct value - and the corresponding limit on
	persistence - can increase as the value is seen more over time.
	Once a server has indicated that it will support authenticated TLS, a		o That response has the media type "application/json", and
	client MAY use key pinning [RFC7469] or any other mechanism that		o That response's payload, when parsed as JSON [RFC7159], contains
	would otherwise be restricted to use with "https" URIs, provided that		an object as the root.
	the mechanism can be restricted to a single HTTP origin.
	6. Security Considerations		o The "origins" member of the root object has a value of an array of
			strings, one of which is a case-insensitive character-for-
			character match for the origin in question, serialised into
			Unicode as per [RFC6454], Section 6.1, and
	6.1. Security Indicators		This specification defines one additional, optional member of the
			root object, "commit" in Section 5. Unrecognised members MUST be
			ignored.
			7. IANA Considerations
			This specification registers a Well-known URI [RFC5785]:
			o URI Suffix: http-opportunistic
			o Change Controller: IETF
			o Specification Document(s): [this specification]
			o Related Information:
			8. Security Considerations
			8.1. Security Indicators
	User Agents MUST NOT provide any special security indicia when an		User Agents MUST NOT provide any special security indicia when an
	"http" resource is acquired using TLS. In particular, indicators		"http" resource is acquired using TLS. In particular, indicators
	that might suggest the same level of security as "https" MUST NOT be		that might suggest the same level of security as "https" MUST NOT be
	used (e.g., using a "lock device").		used (e.g., a "lock device").
	6.2. Downgrade Attacks		8.2. Downgrade Attacks
	A downgrade attack against the negotiation for TLS is possible. With		A downgrade attack against the negotiation for TLS is possible. With
	the "HTTP-TLS" header field, this is limited to occasions where		commitment Section 5, this is limited to occasions where clients have
	clients have no prior information (see Section 6.3), or when		no prior information (see Section 8.3), or when persisted commitments
	persisted commitments have expired.		have expired.
	For example, because the "Alt-Svc" header field		For example, because the "Alt-Svc" header field
	[I-D.ietf-httpbis-alt-svc] likely appears in an unauthenticated and		[I-D.ietf-httpbis-alt-svc] likely appears in an unauthenticated and
	unencrypted channel, it is subject to downgrade by network attackers.		unencrypted channel, it is subject to downgrade by network attackers.
	In its simplest form, an attacker that wants the connection to remain		In its simplest form, an attacker that wants the connection to remain
	in the clear need only strip the "Alt-Svc" header field from		in the clear need only strip the "Alt-Svc" header field from
	responses.		responses.
	Downgrade attacks can be partially mitigated using the "HTTP-TLS"		Downgrade attacks can be partially mitigated using the "commit"
	header field, because when it is used, a client can avoid using		member of the http-opportunistic well-known resource, because when it
	cleartext to contact a supporting server. However, this only works		is used, a client can avoid using cleartext to contact a supporting
	when a previous connection has been established without an active		server. However, this only works when a previous connection has been
	attacker present; a continuously present active attacker can either		established without an active attacker present; a continuously
	prevent the client from ever using TLS, or offer its own certificate.		present active attacker can either prevent the client from ever using
			TLS, or offer its own certificate.
	6.3. Privacy Considerations		8.3. Privacy Considerations
	Cached alternative services can be used to track clients over time;		Cached alternative services can be used to track clients over time;
	e.g., using a user-specific hostname. Clearing the cache reduces the		e.g., using a user-specific hostname. Clearing the cache reduces the
	ability of servers to track clients; therefore clients MUST clear		ability of servers to track clients; therefore clients MUST clear
	cached alternative service information when clearing other origin-		cached alternative service information when clearing other origin-
	based state (i.e., cookies).		based state (i.e., cookies).
	6.4. Confusion Regarding Request Scheme		8.4. Confusion Regarding Request Scheme
	Many existing HTTP/1.1 implementations use the presence or absence of		Many existing HTTP/1.1 implementations use the presence or absence of
	TLS in the stack to determine whether requests are for "http" or		TLS in the stack to determine whether requests are for "http" or
	"https" resources. This is necessary in many cases because the most		"https" resources. This is necessary in many cases because the most
	common form of an HTTP/1.1 request does not carry an explicit		common form of an HTTP/1.1 request does not carry an explicit
	indication of the URI scheme.		indication of the URI scheme.
	HTTP/1.1 MUST NOT be used for opportunistically secured requests.		HTTP/1.1 MUST NOT be used for opportunistically secured requests.
	Some HTTP/1.1 implementations use ambient signals to determine if a		Some HTTP/1.1 implementations use ambient signals to determine if a
	request is for an "https" resource. For example, implementations		request is for an "https" resource. For example, implementations
	might look for TLS on the stack or a port number of 443. An		might look for TLS on the stack or a port number of 443. An
	implementation that supports opportunistically secured requests		implementation that supports opportunistically secured requests
	SHOULD suppress these signals if there is any potential for		SHOULD suppress these signals if there is any potential for
	confusion.		confusion.
	7. References		9. References
	7.1. Normative References		9.1. Normative References
	[I-D.ietf-httpbis-alt-svc]		[I-D.ietf-httpbis-alt-svc]
	mnot, m., McManus, P., and J. Reschke, "HTTP Alternative		mnot, m., McManus, P., and J. Reschke, "HTTP Alternative
	Services", draft-ietf-httpbis-alt-svc-09 (work in		Services", draft-ietf-httpbis-alt-svc-14 (work in
	progress), November 2015.		progress), March 2016.
	[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,
	<http://www.rfc-editor.org/info/rfc2119>.		<http://www.rfc-editor.org/info/rfc2119>.
	[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,		[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
	DOI 10.17487/RFC2818, May 2000,		DOI 10.17487/RFC2818, May 2000,
	<http://www.rfc-editor.org/info/rfc2818>.		<http://www.rfc-editor.org/info/rfc2818>.
	[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security		[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
	(TLS) Protocol Version 1.2", RFC 5246,		(TLS) Protocol Version 1.2", RFC 5246,
	DOI 10.17487/RFC5246, August 2008,		DOI 10.17487/RFC5246, August 2008,
	<http://www.rfc-editor.org/info/rfc5246>.		<http://www.rfc-editor.org/info/rfc5246>.
			[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
			Uniform Resource Identifiers (URIs)", RFC 5785,
			DOI 10.17487/RFC5785, April 2010,
			<http://www.rfc-editor.org/info/rfc5785>.
	[RFC6454] Barth, A., "The Web Origin Concept", RFC 6454,		[RFC6454] Barth, A., "The Web Origin Concept", RFC 6454,
	DOI 10.17487/RFC6454, December 2011,		DOI 10.17487/RFC6454, December 2011,
	<http://www.rfc-editor.org/info/rfc6454>.		<http://www.rfc-editor.org/info/rfc6454>.
			[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
			Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
			2014, <http://www.rfc-editor.org/info/rfc7159>.
	[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer		[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
	Protocol (HTTP/1.1): Message Syntax and Routing",		Protocol (HTTP/1.1): Message Syntax and Routing",
	RFC 7230, DOI 10.17487/RFC7230, June 2014,		RFC 7230, DOI 10.17487/RFC7230, June 2014,
	<http://www.rfc-editor.org/info/rfc7230>.		<http://www.rfc-editor.org/info/rfc7230>.
	[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,		[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
	Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",		Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
	RFC 7234, DOI 10.17487/RFC7234, June 2014,		RFC 7234, DOI 10.17487/RFC7234, June 2014,
	<http://www.rfc-editor.org/info/rfc7234>.		<http://www.rfc-editor.org/info/rfc7234>.
	[RFC7469] Evans, C., Palmer, C., and R. Sleevi, "Public Key Pinning
	Extension for HTTP", RFC 7469, DOI 10.17487/RFC7469, April
	2015, <http://www.rfc-editor.org/info/rfc7469>.
	[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext		[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
	Transfer Protocol Version 2 (HTTP/2)", RFC 7540,		Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
	DOI 10.17487/RFC7540, May 2015,		DOI 10.17487/RFC7540, May 2015,
	<http://www.rfc-editor.org/info/rfc7540>.		<http://www.rfc-editor.org/info/rfc7540>.
	7.2. Informative References		9.2. Informative References
	[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an		[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
	Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May		Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
	2014, <http://www.rfc-editor.org/info/rfc7258>.		2014, <http://www.rfc-editor.org/info/rfc7258>.
	[RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection		[RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection
	Most of the Time", RFC 7435, DOI 10.17487/RFC7435,		Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
	December 2014, <http://www.rfc-editor.org/info/rfc7435>.		December 2014, <http://www.rfc-editor.org/info/rfc7435>.
			[RFC7469] Evans, C., Palmer, C., and R. Sleevi, "Public Key Pinning
			Extension for HTTP", RFC 7469, DOI 10.17487/RFC7469, April
			2015, <http://www.rfc-editor.org/info/rfc7469>.
	Appendix A. Acknowledgements		Appendix A. Acknowledgements
	Thanks to Patrick McManus, Eliot Lear, Stephen Farrell, Guy Podjarny,		Thanks to Patrick McManus, Eliot Lear, Stephen Farrell, Guy Podjarny,
	Stephen Ludin, Erik Nygren, Paul Hoffman, Adam Langley, Eric Rescorla		Stephen Ludin, Erik Nygren, Paul Hoffman, Adam Langley, Eric Rescorla
	and Richard Barnes for their feedback and suggestions.		and Richard Barnes for their feedback and suggestions.
	Authors' Addresses		Authors' Addresses
	Mark Nottingham		Mark Nottingham
End of changes. 49 change blocks.
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