draft-ietf-httpbis-expect-ct-08.txt		draft-ietf-httpbis-expect-ct-latest.txt
	HTTP Working Group E. Stark		HTTP Working Group E. Stark
	Internet-Draft Google		Internet-Draft Google
	Intended status: Experimental December 9, 2018		Intended status: Experimental October 13, 2025
	Expires: June 12, 2019		Expires: April 16, 2026
	Expect-CT Extension for HTTP		Expect-CT Extension for HTTP
	draft-ietf-httpbis-expect-ct-08		draft-ietf-httpbis-expect-ct-latest
	Abstract		Abstract
	This document defines a new HTTP header field named Expect-CT, which		This document defines a new HTTP header field named Expect-CT, which
	allows web host operators to instruct user agents to expect valid		allows web host operators to instruct user agents to expect valid
	Signed Certificate Timestamps (SCTs) to be served on connections to		Signed Certificate Timestamps (SCTs) to be served on connections to
	these hosts. Expect-CT allows web host operators to discover		these hosts. Expect-CT allows web host operators to discover
	misconfigurations in their Certificate Transparency deployments.		misconfigurations in their Certificate Transparency deployments.
	Further, web host operaters can use Expect-CT to ensure that, if a UA		Further, web host operaters can use Expect-CT to ensure that, if a UA
	which supports Expect-CT accepts a misissued certificate, that		which supports Expect-CT accepts a misissued certificate, that
	certificate will be discoverable in Certificate Transparency logs.		certificate will be discoverable in Certificate Transparency logs.
	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/ [1].
	Working Group information can be found at http://httpwg.github.io/
	[2]; source code and issues list for this draft can be found at
	https://github.com/httpwg/http-extensions/labels/expect-ct [3].
	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 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 June 12, 2019.		This Internet-Draft will expire on April 16, 2026.
	Copyright Notice		Copyright Notice
	Copyright (c) 2018 IETF Trust and the persons identified as the		Copyright (c) 2025 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
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	skipping to change at page 2, line 35 ¶		skipping to change at page 2, line 23 ¶
	2. Server and Client Behavior . . . . . . . . . . . . . . . . . 5		2. Server and Client Behavior . . . . . . . . . . . . . . . . . 5
	2.1. Response Header Field Syntax . . . . . . . . . . . . . . 5		2.1. Response Header Field Syntax . . . . . . . . . . . . . . 5
	2.1.1. The report-uri Directive . . . . . . . . . . . . . . 6		2.1.1. The report-uri Directive . . . . . . . . . . . . . . 6
	2.1.2. The enforce Directive . . . . . . . . . . . . . . . . 7		2.1.2. The enforce Directive . . . . . . . . . . . . . . . . 7
	2.1.3. The max-age Directive . . . . . . . . . . . . . . . . 7		2.1.3. The max-age Directive . . . . . . . . . . . . . . . . 7
	2.1.4. Examples . . . . . . . . . . . . . . . . . . . . . . 7		2.1.4. Examples . . . . . . . . . . . . . . . . . . . . . . 7
	2.2. Host Processing Model . . . . . . . . . . . . . . . . . . 8		2.2. Host Processing Model . . . . . . . . . . . . . . . . . . 8
	2.2.1. HTTP-over-Secure-Transport Request Type . . . . . . . 8		2.2.1. HTTP-over-Secure-Transport Request Type . . . . . . . 8
	2.2.2. HTTP Request Type . . . . . . . . . . . . . . . . . . 8		2.2.2. HTTP Request Type . . . . . . . . . . . . . . . . . . 8
	2.3. User Agent Processing Model . . . . . . . . . . . . . . . 8		2.3. User Agent Processing Model . . . . . . . . . . . . . . . 8
	2.3.1. Missing or Malformed Expect-CT Header Fields . . . . 9		2.3.1. Missing or Malformed Expect-CT Header Fields . . . . 8
	2.3.2. Expect-CT Header Field Processing . . . . . . . . . . 9		2.3.2. Expect-CT Header Field Processing . . . . . . . . . . 9
	2.3.3. Reporting . . . . . . . . . . . . . . . . . . . . . . 11		2.3.3. Reporting . . . . . . . . . . . . . . . . . . . . . . 11
	2.4. Evaluating Expect-CT Connections for CT Compliance . . . 11		2.4. Evaluating Expect-CT Connections for CT Compliance . . . 11
	2.4.1. Skipping CT compliance checks . . . . . . . . . . . . 12		2.4.1. Skipping CT compliance checks . . . . . . . . . . . . 12
	3. Reporting Expect-CT Failure . . . . . . . . . . . . . . . . . 12		3. Reporting Expect-CT Failure . . . . . . . . . . . . . . . . . 12
	3.1. Generating a violation report . . . . . . . . . . . . . . 12		3.1. Generating a violation report . . . . . . . . . . . . . . 12
	3.2. Sending a violation report . . . . . . . . . . . . . . . 14		3.2. Sending a violation report . . . . . . . . . . . . . . . 14
	3.3. Receiving a violation report . . . . . . . . . . . . . . 15		3.3. Receiving a violation report . . . . . . . . . . . . . . 15
	4. Usability Considerations . . . . . . . . . . . . . . . . . . 16		4. Usability Considerations . . . . . . . . . . . . . . . . . . 15
	5. Authoring Considerations . . . . . . . . . . . . . . . . . . 16		5. Authoring Considerations . . . . . . . . . . . . . . . . . . 16
	6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 16		6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 16
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 17		7. Security Considerations . . . . . . . . . . . . . . . . . . . 17
	7.1. Hostile header attacks . . . . . . . . . . . . . . . . . 17		7.1. Hostile header attacks . . . . . . . . . . . . . . . . . 17
	7.2. Maximum max-age . . . . . . . . . . . . . . . . . . . . . 17		7.2. Maximum max-age . . . . . . . . . . . . . . . . . . . . . 17
	7.3. Amplification attacks . . . . . . . . . . . . . . . . . . 18		7.3. Amplification attacks . . . . . . . . . . . . . . . . . . 17
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
	8.1. Header Field Registry . . . . . . . . . . . . . . . . . . 18		8.1. Header Field Registry . . . . . . . . . . . . . . . . . . 18
	8.2. Media Types Registry . . . . . . . . . . . . . . . . . . 18		8.2. Media Types Registry . . . . . . . . . . . . . . . . . . 18
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 19		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
	9.1. Normative References . . . . . . . . . . . . . . . . . . 19		9.1. Normative References . . . . . . . . . . . . . . . . . . 19
	9.2. Informative References . . . . . . . . . . . . . . . . . 21		9.2. Informative References . . . . . . . . . . . . . . . . . 21
	9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 21		9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 21
	Appendix A. Changes . . . . . . . . . . . . . . . . . . . . . . 21		Appendix A. Changes . . . . . . . . . . . . . . . . . . . . . . 21
	A.1. Since -07 . . . . . . . . . . . . . . . . . . . . . . . . 21		A.1. Since -07 . . . . . . . . . . . . . . . . . . . . . . . . 21
	A.2. Since -06 . . . . . . . . . . . . . . . . . . . . . . . . 22		A.2. Since -06 . . . . . . . . . . . . . . . . . . . . . . . . 21
	A.3. Since -05 . . . . . . . . . . . . . . . . . . . . . . . . 22		A.3. Since -05 . . . . . . . . . . . . . . . . . . . . . . . . 22
	A.4. Since -04 . . . . . . . . . . . . . . . . . . . . . . . . 22		A.4. Since -04 . . . . . . . . . . . . . . . . . . . . . . . . 22
	A.5. Since -03 . . . . . . . . . . . . . . . . . . . . . . . . 22		A.5. Since -03 . . . . . . . . . . . . . . . . . . . . . . . . 22
	A.6. Since -02 . . . . . . . . . . . . . . . . . . . . . . . . 22		A.6. Since -02 . . . . . . . . . . . . . . . . . . . . . . . . 22
	A.7. Since -01 . . . . . . . . . . . . . . . . . . . . . . . . 22		A.7. Since -01 . . . . . . . . . . . . . . . . . . . . . . . . 22
	A.8. Since -00 . . . . . . . . . . . . . . . . . . . . . . . . 22		A.8. Since -00 . . . . . . . . . . . . . . . . . . . . . . . . 22
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 23		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 22
	1. Introduction		1. Introduction
	This document defines a new HTTP header field that enables UAs to		This document defines a new HTTP header field that enables UAs to
	identify web hosts that expect the presence of Signed Certificate		identify web hosts that expect the presence of Signed Certificate
	Timestamps (SCTs) [I-D.ietf-trans-rfc6962-bis] in subsequent		Timestamps (SCTs) [I-D.ietf-trans-rfc6962-bis] in subsequent
	Transport Layer Security (TLS) [RFC8446] connections.		Transport Layer Security (TLS) [RFC8446] connections.
	Web hosts that serve the Expect-CT HTTP header field are noted by the		Web hosts that serve the Expect-CT HTTP header field are noted by the
	UA as Known Expect-CT Hosts. The UA evaluates each connection to a		UA as Known Expect-CT Hosts. The UA evaluates each connection to a
	skipping to change at page 18, line 25 ¶		skipping to change at page 18, line 16 ¶
	the rate at which they emit reports, but an attacker may alter the		the rate at which they emit reports, but an attacker may alter the
	Expect-CT header's fields to induce UAs to submit different reports		Expect-CT header's fields to induce UAs to submit different reports
	to different URIs to still cause the same effect.		to different URIs to still cause the same effect.
	8. IANA Considerations		8. IANA Considerations
	8.1. Header Field Registry		8.1. Header Field Registry
	This document registers the "Expect-CT" header field in the		This document registers the "Expect-CT" header field in the
	"Permanent Message Header Field Names" registry located at		"Permanent Message Header Field Names" registry located at
	https://www.iana.org/assignments/message-headers [4].		https://www.iana.org/assignments/message-headers [1].
	Header field name: Expect-CT		Header field name: Expect-CT
	Applicable protocol: http		Applicable protocol: http
	Status: experimental		Status: experimental
	Author/Change controller: IETF		Author/Change controller: IETF
	Specification document(s): This document		Specification document(s): This document
	skipping to change at page 19, line 43 ¶		skipping to change at page 19, line 35 ¶
	Change controller: IETF		Change controller: IETF
	9. References		9. References
	9.1. Normative References		9.1. Normative References
	[I-D.ietf-trans-rfc6962-bis]		[I-D.ietf-trans-rfc6962-bis]
	Laurie, B., Langley, A., Kasper, E., Messeri, E., and R.		Laurie, B., Langley, A., Kasper, E., Messeri, E., and R.
	Stradling, "Certificate Transparency Version 2.0", draft-		Stradling, "Certificate Transparency Version 2.0", draft-
	ietf-trans-rfc6962-bis-30 (work in progress), November		ietf-trans-rfc6962-bis-42 (work in progress), August 2021.
	2018.
	[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>.
	[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:		[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
	Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,		Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
	<https://www.rfc-editor.org/info/rfc3339>.		<https://www.rfc-editor.org/info/rfc3339>.
	skipping to change at page 21, line 33 ¶		skipping to change at page 21, line 25 ¶
	[FETCH] WHATWG, "Fetch - Living Standard", n.d.,		[FETCH] WHATWG, "Fetch - Living Standard", n.d.,
	<https://fetch.spec.whatwg.org>.		<https://fetch.spec.whatwg.org>.
	[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/info/rfc8446>.		<https://www.rfc-editor.org/info/rfc8446>.
	9.3. URIs		9.3. URIs
	[1] https://lists.w3.org/Archives/Public/ietf-http-wg/		[1] https://www.iana.org/assignments/message-headers
	[2] http://httpwg.github.io/
	[3] https://github.com/httpwg/http-extensions/labels/expect-ct
	[4] https://www.iana.org/assignments/message-headers
	Appendix A. Changes		Appendix A. Changes
	A.1. Since -07		A.1. Since -07
	o Editorial changes		o Editorial changes
	o Specify that the end-entity certificate appears first in the		o Specify that the end-entity certificate appears first in the
	"validated-certificate-chain" field of an Expect-CT report.		"validated-certificate-chain" field of an Expect-CT report.
End of changes. 13 change blocks.
	30 lines changed or deleted		13 lines changed or added
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