The "id-" prefix for Digest Algorithms
draft-polli-id-digest-algorithms-00
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Expired".
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|---|---|---|---|
| Author | Roberto Polli | ||
| Last updated | 2020-09-08 | ||
| RFC stream | (None) | ||
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| Additional resources | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
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draft-polli-id-digest-algorithms-00
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
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 12, 2021.
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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.
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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].
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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, <http://www.ietf.org/
internet-drafts/draft-ietf-httpbis-digest-headers-03.txt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
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[RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF",
RFC 7405, DOI 10.17487/RFC7405, December 2014,
<https://www.rfc-editor.org/info/rfc7405>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[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,
<https://www.rfc-editor.org/info/rfc7231>.
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.
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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]