Conditional HTTP Requests Using Digests
draft-thomson-http-if-digest-00

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HTTPBIS                                                       M. Thomson
Internet-Draft                                                   Mozilla
Intended status: Informational                              9 March 2020
Expires: 10 September 2020

                Conditional HTTP Requests Using Digests
                    draft-thomson-http-if-digest-00

Abstract

   Header fields are defined for making HTTP requests that are
   conditional on the content of the selected representation of a
   resource.

Note to Readers

   Discussion of this document 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/).

   Source for this draft and an issue tracker can be found at
   https://github.com/martinthomson/if-digest
   (https://github.com/martinthomson/if-digest).

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
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   This Internet-Draft will expire on 10 September 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Thomson                 Expires 10 September 2020               [Page 1]
Internet-Draft             Digest Conditionals                March 2020

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   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
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   2
   3.  If-Digest Header Field  . . . . . . . . . . . . . . . . . . .   3
   4.  If-None-Digest Header field . . . . . . . . . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Conditional HTTP requests [HTTP] allow a client to specify
   preconditions on processing of a request.  Conditional requests can
   be used to avoid making requests that could be unnecessary based on
   information available to the server, but not the client.

   This document defines new If-Digest and If-None-Digest preconditions
   that are based on the digest of selected representations, as
   described in [DIGEST].  These preconditions create a concise and
   strong binding to the content of a representation as they use a
   cryptographic hash function.

2.  Conventions and Definitions

   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.

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3.  If-Digest Header Field

   Conditional requests can be used to prevent actions that involve
   representations that are not expected by a client.  For instance, a
   PATCH [PATCH] request might include the conditional If-Match header
   field to ensure that the requested changes are only applied if the
   selected representation is what the client expects, preventing
   mutation of a resource that might be in an state that is incompatible
   with the desire change.

   The If-Digest conditional header field allows a client to indicate
   the digest of representations that the request can be applied to.
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