Network Working Group R. Polli Internet-Draft Digital Transformation Department, Italian Government Intended status: Standards Track September 8, 2020 Expires: March 12, 2021 The "id-" prefix for Digest Algorithms draft-polli-id-digest-algorithms-00 Abstract This document defines the "id-" prefix for digest-algorithms used in the Digest HTTP field. This prefix explicits that the value of the digest-algorithm is independent from Content-Encoding. Note to Readers _RFC EDITOR: please remove this section before publication_ 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/ (https://lists.w3.org/Archives/Public/ietf-http-wg/). The source code and issues list for this draft can be found at https://github.com/ioggstream/draft-polli-Retry-Scope (https://github.com/ioggstream/draft-polli-Retry-Scope). Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on March 12, 2021. Polli Expires March 12, 2021 [Page 1] Internet-Draft The "id-" prefix for Digest Algorithms September 2020 Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3 2. The "id-" prefix for digest-algorithms . . . . . . . . . . . 3 3. Security Considerations . . . . . . . . . . . . . . . . . . . 4 3.1. Disclosure of encrypted content . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 4.1. TBD how to reserve "id-" prefix? . . . . . . . . . . . . 4 5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5.1. The id-crc32c digest-algorithm . . . . . . . . . . . . . 4 6. Normative References . . . . . . . . . . . . . . . . . . . . 4 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 5 FAQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Code Samples . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction The [DIGEST] defines a way to convey a checksum of a representation- data as specified in [SEMANTICS]. As the representation data depends on the value of "Content- Encoding", it is useful to convey the checksum value of a representation without any content-coding applied. This proposal introduces the "id-" prefix to specify that the provided digest-algorithm value is computed on the representation- data without any content-coding applied. Polli Expires March 12, 2021 [Page 2] Internet-Draft The "id-" prefix for Digest Algorithms September 2020 1.1. Notational Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. These words may also appear in this document in lower case as plain English words, absent their normative meanings. This document uses the Augmented BNF defined in [RFC5234] and updated by [RFC7405]. The definitions "representation", "selected representation", "representation data", "representation metadata", and "payload body" in this document are to be interpreted as described in [SEMANTICS]. The definitions "digest-algorithm" and "representation-data-digest" in this document are to be interpreted as described in [DIGEST]. 2. The "id-" prefix for digest-algorithms A digest-algorithm to be registered within the HTTP Digest Algorithm Values (https://www.iana.org/assignments/http-dig-alg/http-dig- alg.xhtml) MUST NOT start with the string "id-". The following two examples show two digest-algorithm names that cannot be registered id-crc32c id-adler32 For every digest-algorithm registered in the HTTP Digest Algorithm Values (https://www.iana.org/assignments/http-dig-alg/http-dig- alg.xhtml) the associate "id-" digest-algorithm has the following properties: * the checksum is computed on the representation-data of the resource when no content coding is applied; * the checksum is computed according to the original digest- algorithm Description field, and uses the same encoding of the original digest-algorithm. This definition is compatible, and thus extends, the definition of the "id-sha-256" and "id-sha-512" digest-algorithms contained in Section X of [DIGEST]. Polli Expires March 12, 2021 [Page 3] Internet-Draft The "id-" prefix for Digest Algorithms September 2020 3. Security Considerations 3.1. Disclosure of encrypted content Like the "id-sha-256" digest-algoritm defined in [DIGEST] if the content-coding provides encryption features, sending the checksum of unencoded representation can disclose information. 4. IANA Considerations 4.1. TBD how to reserve "id-" prefix? 5. Examples 5.1. The id-crc32c digest-algorithm The following request conveys a brotli encoded json object {"hello": "world"} The "Digest" computed using the "crc32c" digest-algorithm present in HTTP Digest Algorithm Values (https://www.iana.org/assignments/http- dig-alg/http-dig-alg.xhtml) is content-coding aware, while its associated "id-" digest-algorithm is not "id-crc32c" POST /data HTTP/1.1 Content-Type: application/json Content-Encoding: br Digest: id-crc32c=43794720, crc32c=DB329237 CwGAZG9nAw== 6. Normative References [DIGEST] Polli, R. and L. Pardue, "Digest Headers", Work in Progress, Internet-Draft, draft-ietf-httpbis-digest- headers-03, September 7, 2020, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008, . Polli Expires March 12, 2021 [Page 4] Internet-Draft The "id-" prefix for Digest Algorithms September 2020 [RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF", RFC 7405, DOI 10.17487/RFC7405, December 2014, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [SEMANTICS] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231, DOI 10.17487/RFC7231, June 2014, . Appendix A. Acknowledgements This specification was born from a thread created by James Manger and the subsequent discussion here https://github.com/httpwg/http- extensions/issues/885. FAQ Q: Question 1 Answer 1 Code Samples _RFC Editor: Please remove this section before publication._ How can I generate and validate the "Digest" values shown in the examples throughout this document? The following python3 code can be used to generate digests for json objects using crc32c algorithm. Note that these are formatted as base64. This function could be adapted to other algorithms and should take into account their specific formatting rules. Polli Expires March 12, 2021 [Page 5] Internet-Draft The "id-" prefix for Digest Algorithms September 2020 import base64, json, brotli, crc32c identity = lambda x: x def digest(item, content_coding=identity, algorithm=crc32c.crc32c): json_bytes = json.dumps(item).encode() content_encoded = content_coding(json_bytes) checksum = algorithm(content_encoded) # encode result has uppercase hex return hex(checksum)[2:].upper() item = {"hello": "world"} print("crc32c digest value for a br-coded representation: ", digest(item, content_coding=brotli.compress) ) print("id-crc32c digest value for a br-coded representation: ", digest(item, content_coding=identity) ) Change Log RFC EDITOR PLEASE DELETE THIS SECTION. Author's Address Roberto Polli Digital Transformation Department, Italian Government Email: robipolli@gmail.com Polli Expires March 12, 2021 [Page 6]