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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 HTTPbis M. Bishop 3 Internet-Draft Akamai 4 Intended status: Standards Track 24 June 2020 5 Expires: 26 December 2020 7 GREASE for HTTP/2 8 draft-bishop-httpbis-grease-01 10 Abstract 12 Reserves several values in the HTTP/2 registries to exercise the 13 requirement that clients and servers ignore unknown values. 15 Status of This Memo 17 This Internet-Draft is submitted in full conformance with the 18 provisions of BCP 78 and BCP 79. 20 Internet-Drafts are working documents of the Internet Engineering 21 Task Force (IETF). Note that other groups may also distribute 22 working documents as Internet-Drafts. The list of current Internet- 23 Drafts is at https://datatracker.ietf.org/drafts/current/. 25 Internet-Drafts are draft documents valid for a maximum of six months 26 and may be updated, replaced, or obsoleted by other documents at any 27 time. It is inappropriate to use Internet-Drafts as reference 28 material or to cite them other than as "work in progress." 30 This Internet-Draft will expire on 26 December 2020. 32 Copyright Notice 34 Copyright (c) 2020 IETF Trust and the persons identified as the 35 document authors. All rights reserved. 37 This document is subject to BCP 78 and the IETF Trust's Legal 38 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 39 license-info) in effect on the date of publication of this document. 40 Please review these documents carefully, as they describe your rights 41 and restrictions with respect to this document. Code Components 42 extracted from this document must include Simplified BSD License text 43 as described in Section 4.e of the Trust Legal Provisions and are 44 provided without warranty as described in the Simplified BSD License. 46 Table of Contents 48 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 49 2. Using GREASE in HTTP/2 . . . . . . . . . . . . . . . . . . . 2 50 2.1. GREASE for Frame Types . . . . . . . . . . . . . . . . . 2 51 2.2. GREASE for SETTINGS . . . . . . . . . . . . . . . . . . . 3 52 3. Security Considerations . . . . . . . . . . . . . . . . . . . 3 53 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 54 4.1. Frame Types . . . . . . . . . . . . . . . . . . . . . . . 3 55 4.2. Settings . . . . . . . . . . . . . . . . . . . . . . . . 3 56 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 5.1. Normative References . . . . . . . . . . . . . . . . . . 3 58 5.2. Informative References . . . . . . . . . . . . . . . . . 4 59 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 4 60 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4 62 1. Introduction 64 [UseIt] observes that extension and negotiation mechanisms which 65 aren't exercised regularly can be found not to work when they are 66 later employed by an extension to the protocol. [GREASE] is one 67 mitigation which originated in TLS, registering multiple values in 68 various TLS registries which can be sent prospectively by clients. 70 The common requirement of the different spaces described by these 71 documents is the requirement that recipients ignore unrecognized 72 values. By reserving a scattered set of codepoints to have no 73 defined meaning, clients and servers can inject values from these 74 ranges into connections on a regular basis and exercise this 75 requirement. 77 HTTP/2 [HTTP2] frame types and settings employ a similar mechanism of 78 ignoring unknown values. This makes HTTP/2 a good candidate to 79 employ grease on connections. The need for such a technique was 80 demonstrated recently by an HTTP/2 implementation which closed the 81 connection upon receipt of an unknown setting. 83 2. Using GREASE in HTTP/2 85 2.1. GREASE for Frame Types 87 Frame types of the format "0xb + (0x1f * N)" are reserved for use as 88 grease. These frames have no semantic meaning, and SHOULD be send 89 instead of using padding on DATA or HEADERS frames where possible. 90 They MAY also be sent on connections where there is no application 91 data currently being transferred. Endpoints MUST NOT consider these 92 frames to have any meaning upon receipt. 94 The flags, the payload, and the length of the frames SHOULD be 95 selected randomly, subject to implementation-defined limits on the 96 length. 98 [HTTP2] is ambiguous about whether unknown frame types are permitted 99 on streams in the "idle", "reserved", "closed", or "half-closed 100 (local)" states. As a result, some implementations could 101 legitimately consider this to be an error. Therefore, these frames 102 SHOULD NOT be sent on streams in those states. 104 2.2. GREASE for SETTINGS 106 Settings identifiers of the format "0x?a?a" are reserved for use as 107 grease. Such settings have no defined meaning. Endpoints SHOULD 108 include at least one such setting in their initial SETTINGS frame, 109 and MAY send new SETTINGS frames during the connection containing 110 additional grease values. Endpoints MUST NOT consider such settings 111 to have any meaning upon receipt. 113 Because the setting has no defined meaning, the value of the setting 114 SHOULD be selected randomly. 116 3. Security Considerations 118 The ability to design, implement, and deploy new protocol mechanisms 119 can be critical to security. 121 4. IANA Considerations 123 4.1. Frame Types 125 This document reserves a range of entries in the "HTTP/2 Frame Type" 126 registry defined in [HTTP2]. Each code of the format "0xb + (0x1f * 127 N)" for values of N in the range (0..7) (that is, "0xb", "0x2a", 128 etc., through "0xe4") MUST NOT be assigned by IANA for any purpose. 130 4.2. Settings 132 This document reserves a range of entries in the "HTTP/2 Settings" 133 registry defined in [HTTP2]. Each code of the format "0x?a?a" where 134 each "?" is any octet (that is, "0x0a0a", "0x0a1a", etc. through 135 "0xfafa") MUST NOT be assigned by IANA for any purpose. 137 5. References 139 5.1. Normative References 141 [HTTP2] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext 142 Transfer Protocol Version 2 (HTTP/2)", RFC 7540, 143 DOI 10.17487/RFC7540, May 2015, 144 . 146 5.2. Informative References 148 [GREASE] Benjamin, D., "Applying GREASE to TLS Extensibility", Work 149 in Progress, Internet-Draft, draft-ietf-tls-grease-04, 22 150 August 2019, . 153 [UseIt] Thomson, M., "Long-term Viability of Protocol Extension 154 Mechanisms", Work in Progress, Internet-Draft, draft- 155 thomson-use-it-or-lose-it-04, 7 July 2019, 156 . 159 Appendix A. Acknowledgements 161 This draft arose from a discussion in the QUIC WG with Lucas Pardue, 162 Ryan Hamilton, and Martin Thomson. 164 Author's Address 166 Mike Bishop 167 Akamai 169 Email: mbishop@evequefou.be