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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group L. Pardue 3 Internet-Draft A. Ramine 4 Intended status: Standards Track Cloudflare 5 Expires: 17 September 2021 16 March 2021 7 Reserving the clear ALPN Protocol ID 8 draft-pardue-httpbis-dont-be-clear-00 10 Abstract 12 HTTP Alternative Services (Alt-Svc) are identified by a tuple of 13 Application-Protocol Layer Negotiation (ALPN) protocol identifier, a 14 host and a port. The wire format for Alt-Svc is defined in ABNF and 15 encodes this tuple or the keyword "clear", which has a special 16 meaning. This memo reserves the ALPN protocol identifier "clear" to 17 reduce the chances of accidental aliasing with the "clear" keyword. 19 Note to Readers 21 _RFC EDITOR: please remove this section before publication_ 23 Source code and issues list for this draft can be found at 24 https://github.com/LPardue/draft-pardue-httpbis-dont-be-clear 25 (https://github.com/LPardue/draft-pardue-httpbis-dont-be-clear). 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at https://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on 17 September 2021. 44 Copyright Notice 46 Copyright (c) 2021 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 51 license-info) in effect on the date of publication of this document. 52 Please review these documents carefully, as they describe your rights 53 and restrictions with respect to this document. Code Components 54 extracted from this document must include Simplified BSD License text 55 as described in Section 4.e of the Trust Legal Provisions and are 56 provided without warranty as described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 61 1.1. Conventions and Definitions . . . . . . . . . . . . . . . 2 62 2. Aliasing and Avoidance . . . . . . . . . . . . . . . . . . . 2 63 3. Security Considerations . . . . . . . . . . . . . . . . . . . 3 64 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 65 4.1. Registration of "clear" Identification String . . . . . . 3 66 5. Normative References . . . . . . . . . . . . . . . . . . . . 3 67 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 4 68 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4 70 1. Introduction 72 HTTP Alternative Services (Alt-Svc) [ALTSVC] are identified by a 73 tuple of Application-Protocol Layer Negotiation (ALPN) [ALPN] 74 protocol identifier, a host and a port. The wire format for Alt-Svc 75 is defined in ABNF and encodes this tuple or the keyword "clear", 76 which has a special meaning. This memo reserves the ALPN protocol 77 identifier "clear" to reduce the chances of accidental aliasing with 78 the "clear" keyword. 80 1.1. Conventions and Definitions 82 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 83 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 84 "OPTIONAL" in this document are to be interpreted as described in 85 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 86 capitals, as shown here. 88 2. Aliasing and Avoidance 90 [ALTSVC] Section 3 defines the Alt-Svc header field using ABNF. It 91 requires a custom parser, which introduces a possibility for custom 92 implementation errors. The Alt-Svc header field value can either be 93 the keyword "clear" - a special value that invalidates cached 94 alternative services, or a list of "alt-value", that includes an 95 encoded ALPN protocol identifier [ALPN]. There is a chance that 96 someone unwittingly defines the ALPN protocol identifier "clear" for 97 genuine purposes but is unaware of the use of protocol identifiers in 98 Alternative Services. This could trigger Alt-Svc parser errors that 99 might lead to confusion between the keyword with the protocol 100 identifier use. Since the "clear" keyword has special meaning, 101 confusion might lead to detrimental effects. 103 To prevent unintended aliasing, this document registers the "clear" 104 ALPN protocol identifier. It relates to no actual application-layer 105 protocol, effectively reserving the code point and preventing any 106 unintended aliasing. 108 3. Security Considerations 110 Broken Alt-Svc header field parsers might confuse a "clear" keyword 111 with a "clear" ALPN protocol identifier. This could invalidate 112 Alternative Service cache state but a conformant client should fall 113 back safely as described in Section 2.4 of [ALTSVC]. 115 4. IANA Considerations 117 4.1. Registration of "clear" Identification String 119 This document creates a new registration, "clear", in the 120 "Application-Layer Protocol Negotiation (ALPN) Protocol IDs" registry 121 established in [ALPN]. 123 The "clear" string is a reserved value that does not identify any 124 protocol: 126 Protocol: Reserved 128 Identification Sequence: 0x63 0x6C 0x65 0x61 0x72 ("clear") 130 Specification: This document 132 5. Normative References 134 [ALPN] Friedl, S., Popov, A., Langley, A., and E. Stephan, 135 "Transport Layer Security (TLS) Application-Layer Protocol 136 Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301, 137 July 2014, . 139 [ALTSVC] Nottingham, M., McManus, P., and J. Reschke, "HTTP 140 Alternative Services", RFC 7838, DOI 10.17487/RFC7838, 141 April 2016, . 143 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 144 Requirement Levels", BCP 14, RFC 2119, 145 DOI 10.17487/RFC2119, March 1997, 146 . 148 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 149 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 150 May 2017, . 152 Acknowledgments 154 Your name here. 156 Authors' Addresses 158 Lucas Pardue 159 Cloudflare 161 Email: lucaspardue.24.7@gmail.com 163 Anthony Ramine 164 Cloudflare 166 Email: nox@nox.paris