HTTP                                                     A. Backman, Ed.
Internet-Draft                                                    Amazon
Intended status: Standards Track                               J. Richer
Expires: 10 December 2021 14 February 2022                            Bespoke Engineering
                                                               M. Sporny
                                                          Digital Bazaar
                                                             8 June
                                                          13 August 2021

                         Signing

                        HTTP Messages
                draft-ietf-httpbis-message-signatures-05 Message Signatures
                draft-ietf-httpbis-message-signatures-06

Abstract

   This document describes a mechanism for creating, encoding, and
   verifying digital signatures or message authentication codes over
   content within
   components of an HTTP message.  This mechanism supports use cases
   where the full HTTP message may not be known to the signer, and where
   the message may be transformed (e.g., by intermediaries) before
   reaching the verifier.  This document also describes a means for
   requesting that a signature be applied to a subsequent HTTP message
   in an ongoing HTTP exchange.

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/).

   Working Group information can be found at https://httpwg.org/
   (https://httpwg.org/); source code and issues list for this draft can
   be found at https://github.com/httpwg/http-extensions/labels/
   signatures (https://github.com/httpwg/http-extensions/labels/
   signatures).

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 December 2021. 14 February 2022.

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   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3   4
     1.1.  Requirements Discussion . . . . . . . . . . . . . . . . .   4   5
     1.2.  HTTP Message Transformations  . . . . . . . . . . . . . .   5
     1.3.  Safe Transformations  . . . . . . . . . . . . . . . . . .   5   6
     1.4.  Conventions and Terminology . . . . . . . . . . . . . . .   6   7
     1.5.  Application of HTTP Message Signatures  . . . . . . . . .   8   9
   2.  HTTP Message Signature Covered Content Components . . . . . . . . . . .   8 . . . . . . . .  10
     2.1.  HTTP Headers Fields . . . . . . . . . . . . . . . . . . . . . .   9 .  11
       2.1.1.  Canonicalized Structured HTTP Headers Fields  . . . . . . . .  10  11
       2.1.2.  Canonicalization Examples . . . . . . . . . . . . . .  10  11
     2.2.  Dictionary Structured Field Members . . . . . . . . . . .  11  12
       2.2.1.  Canonicalization Examples . . . . . . . . . . . . . .  11  12
     2.3.  Specialty Content Fields  . Components  . . . . . . . . . . . . . . .  11
       2.3.1.  Request Target . . .  13
       2.3.1.  Signature Parameters  . . . . . . . . . . . . . . . .  12  14
       2.3.2.  Signature Parameters  Method  . . . . . . . . . . . . . . . .  13
     2.4.  Creating the Signature Input String . . . . . . . . .  15
       2.3.3.  Target URI  . .  14
   3.  HTTP Message Signatures . . . . . . . . . . . . . . . . . . .  16
     3.1.  Creating a Signature  . . . .
       2.3.4.  Authority . . . . . . . . . . . . . .  17
     3.2.  Verifying a Signature . . . . . . . .  16
       2.3.5.  Scheme  . . . . . . . . . .  18
       3.2.1.  Enforcing Application Requirements . . . . . . . . .  20
     3.3.  Signature Algorithm Methods . . . .  17
       2.3.6.  Request Target  . . . . . . . . . . .  21
       3.3.1.  RSASSA-PSS using SHA-512 . . . . . . . .  17
       2.3.7.  Path  . . . . . .  21
       3.3.2.  RSASSA-PKCS1-v1_5 using SHA-256 . . . . . . . . . . .  22
       3.3.3.  HMAC using SHA-256 . . . . . . .  19
       2.3.8.  Query . . . . . . . . . .  22
       3.3.4.  ECDSA using curve P-256 DSS and SHA-256 . . . . . . .  23
       3.3.5.  JSON Web Signature (JWS) algorithms . . . . . . .  19
       2.3.9.  Query Parameters  . .  23
   4.  Including a Message Signature in a Message . . . . . . . . .  23
     4.1.  The 'Signature-Input' HTTP Header . . . . . . .  20
       2.3.10. Status Code . . . . .  24
     4.2.  The 'Signature' HTTP Header . . . . . . . . . . . . . . .  24
     4.3.  Multiple Signatures .  21
       2.3.11. Request-Response Signature Binding  . . . . . . . . .  21
     2.4.  Creating the Signature Input String . . . . . . . . .  25
   5.  IANA Considerations . .  23

   3.  HTTP Message Signatures . . . . . . . . . . . . . . . . . . .  26
     5.1.  HTTP  25
     3.1.  Creating a Signature Algorithms Registry  . . . . . . . . . . .  26
       5.1.1.  Registration Template . . . . . . .  25
     3.2.  Verifying a Signature . . . . . . . . .  26
       5.1.2.  Initial Contents . . . . . . . . .  27
       3.2.1.  Enforcing Application Requirements  . . . . . . . . .  27
     5.2.  HTTP  29
     3.3.  Signature Metadata Parameters Registry . Algorithm Methods . . . . . .  28
       5.2.1.  Registration Template . . . . . . . . .  29
       3.3.1.  RSASSA-PSS using SHA-512  . . . . . . .  28
       5.2.2.  Initial Contents . . . . . . .  30
       3.3.2.  RSASSA-PKCS1-v1_5 using SHA-256 . . . . . . . . . . .  29
     5.3.  HTTP Signature Specialty Content Identifiers Registry  31
       3.3.3.  HMAC using SHA-256  . .  29
       5.3.1.  Registration Template . . . . . . . . . . . . . . .  31
       3.3.4.  ECDSA using curve P-256 DSS and SHA-256 .  29
       5.3.2.  Initial Contents . . . . . .  31
       3.3.5.  JSON Web Signature (JWS) algorithms . . . . . . . . .  32
   4.  Including a Message Signature in a Message  . . .  29
   6.  Security Considerations . . . . . .  32
     4.1.  The 'Signature-Input' HTTP Field  . . . . . . . . . . . .  33
     4.2.  The 'Signature' HTTP Field  .  30
   7.  References . . . . . . . . . . . . . .  33
     4.3.  Multiple Signatures . . . . . . . . . . .  30
     7.1.  Normative References . . . . . . . .  34
   5.  Requesting Signatures . . . . . . . . . .  30
     7.2.  Informative References . . . . . . . . . .  36
     5.1.  The Accept-Signature Field  . . . . . . .  31
   Appendix A.  Detecting HTTP Message Signatures . . . . . . . .  37
     5.2.  Processing an Accept-Signature  .  32
   Appendix B.  Examples . . . . . . . . . . . .  37
   6.  IANA Considerations . . . . . . . . . .  32
     B.1.  Example Keys . . . . . . . . . . .  38
     6.1.  HTTP Signature Algorithms Registry  . . . . . . . . . . .  32
       B.1.1.  Example Key RSA test  38
       6.1.1.  Registration Template . . . . . . . . . . . . . . . .  33
       B.1.2.  Example RSA PSS Key  39
       6.1.2.  Initial Contents  . . . . . . . . . . . . . . . . .  33
       B.1.3.  Example ECC P-256 Test Key .  39
     6.2.  HTTP Signature Metadata Parameters Registry . . . . . . .  41
       6.2.1.  Registration Template . . . . .  34
       B.1.4.  Example Shared Secret . . . . . . . . . . .  41
       6.2.2.  Initial Contents  . . . . .  35
     B.2.  Test Cases . . . . . . . . . . . . .  41
     6.3.  HTTP Signature Specialty Component Identifiers
           Registry  . . . . . . . . . .  35
       B.2.1.  Minimal Signature Header using rsa-pss-sha512 . . . .  36
       B.2.2.  Header Coverage using rsa-pss-sha512 . . . . . . . .  36
       B.2.3.  Full Coverage using rsa-pss-sha512 . .  41
       6.3.1.  Registration Template . . . . . . .  37
       B.2.4.  Signing a Response using ecdsa-p256-sha256 . . . . .  37
       B.2.5.  Signing a Request using hmac-sha256 . . . .  42
       6.3.2.  Initial Contents  . . . . .  38
   Acknowledgements . . . . . . . . . . . . .  42
   7.  Security Considerations . . . . . . . . . . .  38
   Document History . . . . . . . .  43
   8.  References  . . . . . . . . . . . . . . . .  39
   Authors' Addresses . . . . . . . . .  44
     8.1.  Normative References  . . . . . . . . . . . . . .  41

1.  Introduction . . . .  44
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  45
   Appendix A.  Detecting HTTP Message integrity and authenticity are important security properties
   that are critical to the secure operation of Signatures  . . . . . . . . .  46
   Appendix B.  Examples . . . . . . . . . . . . . . . . . . . . . .  46
     B.1.  Example Keys  . . . . . . . . . . . . . . . . . . . . . .  46
       B.1.1.  Example Key RSA test  . . . . . . . . . . . . . . . .  46
       B.1.2.  Example RSA PSS Key . . . . . . . . . . . . . . . . .  47
       B.1.3.  Example ECC P-256 Test Key  . . . . . . . . . . . . .  48
       B.1.4.  Example Shared Secret . . . . . . . . . . . . . . . .  49
     B.2.  Test Cases  . . . . . . . . . . . . . . . . . . . . . . .  49
       B.2.1.  Minimal Signature Using rsa-pss-sha512  . . . . . . .  50
       B.2.2.  Selective Covered Components using rsa-pss-sha512 . .  50
       B.2.3.  Full Coverage using rsa-pss-sha512  . . . . . . . . .  51
       B.2.4.  Signing a Response using ecdsa-p256-sha256  . . . . .  52
       B.2.5.  Signing a Request using hmac-sha256 . . . . . . . . .  53
     B.3.  TLS-Terminating Proxies . . . . . . . . . . . . . . . . .  53
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  55
   Document History  . . . . . . . . . . . . . . . . . . . . . . . .  56
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  59

1.  Introduction

   Message integrity and authenticity are important security properties
   that are critical to the secure operation of many HTTP applications.
   Application developers typically rely on the transport layer to
   provide these properties, by operating their application over [TLS].
   However, TLS only guarantees these properties over a single TLS
   connection, and the path between client and application may be
   composed of multiple independent TLS connections (for example, if the
   application is hosted behind a TLS-terminating gateway or if the
   client is behind a TLS Inspection appliance).  In such cases, TLS
   cannot guarantee end-to-end message integrity or authenticity between
   the client and application.  Additionally, some operating
   environments present obstacles that make it impractical to use TLS,
   or to use features necessary to provide message authenticity.
   Furthermore, some applications require the binding of an application-
   level key to the HTTP message, separate from any TLS certificates in
   use.  Consequently, while TLS can meet message integrity and
   authenticity needs for many HTTP-based applications, it is not a
   universal solution.

   This document defines a mechanism for providing end-to-end integrity
   and authenticity for components of an HTTP message.  The mechanism
   allows applications to create digital signatures or message
   authentication codes (MACs) over only the components of the message
   that are meaningful and appropriate for the application.  Strict
   canonicalization rules ensure that the verifier can verify the
   signature even if the message has been transformed in any of the many
   ways permitted by HTTP.

   The signing mechanism described in this document consists of three
   parts:

   *  A common nomenclature and canonicalization rule set for the
      different protocol elements and other components of HTTP messages.

   *  Algorithms for generating and verifying signatures over HTTP
      message components using this nomenclature and rule set.

   *  A mechanism for attaching a signature and related metadata to an
      HTTP message.

   This document also provides a mechanism for one party to signal to
   another party that a signature is desired in one or more subsequent
   messages.  This optional negotiation mechanism can be used along with
   opportunistic or application-driven message signatures by either
   party.

1.1.  Requirements Discussion

   HTTP permits and sometimes requires intermediaries to transform
   messages in a variety of ways.  This may result in a recipient
   receiving a message that is not bitwise equivalent to the message
   that was originally sent.  In such a case, the recipient will be
   unable to verify a signature over the raw bytes of the sender's HTTP
   message, as verifying digital signatures or MACs requires both signer
   and verifier to have the exact same signature input.  Since the exact
   raw bytes of the message cannot be relied upon as a reliable source
   of signature input, the signer and verifier must derive the signature
   input from their respective versions of the message, via a mechanism
   that is resilient to safe changes that do not alter the meaning of
   the message.

   For a variety of reasons, it is impractical to strictly define what
   constitutes a safe change versus an unsafe one.  Applications use
   HTTP in a wide variety of ways, and may disagree on whether a
   particular piece of information in a message (e.g., the body, or the
   "Date" header field) is relevant.  Thus a general purpose solution
   must provide signers with some degree of control over which message
   components are signed.

   HTTP applications may be running in environments that do not provide
   complete access to or control over HTTP messages (such as a web
   browser's JavaScript environment), or may be using libraries that
   abstract away the details of the protocol (such as the Java
   HTTPClient library (https://openjdk.java.net/groups/net/httpclient/
   intro.html)).  These applications need to be able to generate and
   verify signatures despite incomplete knowledge of the HTTP message.

1.2.  HTTP Message Transformations

   As mentioned earlier, HTTP explicitly permits and in some cases
   requires implementations to transform messages in a variety of ways.
   Implementations are required to tolerate many of these
   transformations.  What follows is a non-normative and non-exhaustive
   list of transformations that may occur under HTTP, provided as
   context:

   *  Re-ordering of header fields with different header field names
      ([MESSAGING], Section 3.2.2).

   *  Combination of header fields with the same field name
      ([MESSAGING], Section 3.2.2).

   *  Removal of header fields listed in the "Connection" header field
      ([MESSAGING], Section 6.1).

   *  Addition of header fields that indicate control options
      ([MESSAGING], Section 6.1).

   *  Addition or removal of a transfer coding ([MESSAGING],
      Section 5.7.2).

   *  Addition of header fields such as "Via" ([MESSAGING],
      Section 5.7.1) and "Forwarded" ([RFC7239], Section 4).

1.3.  Safe Transformations

   Based on the definition of HTTP and the requirements described above,
   we can identify certain types of transformations that should not
   prevent signature verification, even when performed on message
   components covered by the signature.  The following list describes
   those transformations:

   *  Combination of header fields with the same field name.

   *  Reordering of header fields with different names.

   *  Conversion between different versions of the HTTP protocol (e.g.,
      HTTP/1.x to HTTP/2, or vice-versa).

   *  Changes in casing (e.g., "Origin" to "origin") of any case-
      insensitive components such as header field names, request URI
      scheme, or host.

   *  Addition or removal of leading or trailing whitespace to a header
      field value.

   *  Addition or removal of "obs-folds".

   *  Changes to the "request-target" and "Host" header field that when
      applied together do not result in a change to the message's
      effective request URI, as defined in Section 5.5 of [MESSAGING].

   Additionally, all changes to components not covered by the signature
   are considered safe.

1.4.  Conventions and Terminology

   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.

   The terms "HTTP message", "HTTP request", "HTTP response", "absolute-
   form", "absolute-path", "effective request URI", "gateway", "header
   field", "intermediary", "request-target", "sender", and "recipient"
   are used as defined in [MESSAGING].

   The term "method" is to be interpreted as defined in Section 4 of
   [SEMANTICS].

   For brevity, the term "signature" on its own is used in this document
   to refer to both digital signatures and keyed MACs.  Similarly, the
   verb "sign" refers to the generation of either a digital signature or
   keyed MAC over a given input string.  The qualified term "digital
   signature" refers specifically to the output of an asymmetric
   cryptographic signing operation.

   In addition to those listed above, this document uses the following
   terms:

   HTTP Message Signature:
      A digital signature or keyed MAC that covers one or more portions
      of an HTTP message.  Note that a given HTTP Message can contain
      multiple HTTP Message Signatures.

   Signer:
      The entity that is generating or has generated an HTTP Message
      Signature.  Note that multiple entities can act as signers and
      apply separate HTTP Message Signatures to a given HTTP Message.

   Verifier:
      An entity that is verifying or has verified an HTTP Message
      Signature against an HTTP Message.  Note that an HTTP Message
      Signature may be verified multiple times, potentially by different
      entities.

   HTTP Message Component:
      A portion of an HTTP message that is capable of being covered by
      an HTTP Message Signature.

   HTTP Message Component Identifier:

      A value that uniquely identifies a specific HTTP Message Component
      in respect to a particular HTTP Message Signature and the HTTP
      Message it applies to.

   HTTP Message Component Value:
      The value associated with a given component identifier within the
      context of a particular HTTP Message.  Component values are
      derived from the HTTP Message and are usually subject to a
      canonicalization process.

   Covered Components:
      An ordered set of HTTP message component identifiers for fields
      (Section 2.1) and specialty components (Section 2.3) that
      indicates the set of message components covered by the signature,
      not including the "@signature-params" specialty identifier itself.
      The order of this set is preserved and communicated between the
      signer and verifier to facilitate reconstruction of the signature
      input.

   Signature Input:
      The sequence of bytes processed by the HTTP Message Signature
      algorithm to produce the HTTP Message Signature.  The signature
      input is generated by the signer and verifier using the covered
      components set and the HTTP Message.

   HTTP Message Signature Algorithm:
      A cryptographic algorithm that describes the signing and
      verification process for the signature.  When expressed
      explicitly, the value maps to a string defined in the HTTP
      Signature Algorithms Registry defined in this document.

   Key Material:
      The key material required to create or verify the signature.  The
      key material is often identified with an explicit key identifier,
      allowing the signer to indicate to the verifier which key was
      used.

   Creation Time:
      A timestamp representing the point in time that the signature was
      generated, as asserted by the signer.

   Expiration Time:
      A timestamp representing the point in time at which the signature
      expires, as asserted by the signer.  A signature's expiration time
      could be undefined, indicating that the signature does not expire
      from the perspective of the signer.

   The term "Unix time" is defined by [POSIX.1], Section 4.16
   (http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/
   V1_chap04.html#tag_04_16).

   This document contains non-normative examples of partial and complete
   HTTP messages.  Some examples use a single trailing backslash '' to
   indicate line wrapping for long values, as per [RFC8792].  The "\"
   character and leading spaces on wrapped lines are not part of the
   value.

1.5.  Application of HTTP Message Signatures

   HTTP Message Signatures are designed to be a general-purpose security
   mechanism applicable in a wide variety of circumstances and
   applications.  In order to properly and safely apply HTTP Message
   Signatures, an application or profile of this specification MUST
   specify all of the following items:

   *  The set of component identifiers (Section 2) that are expected and
      required.  For example, an authorization protocol could mandate
      that the "Authorization" header be covered to protect the
      authorization credentials and mandate the signature parameters
      contain a "created" parameter, while an API expecting HTTP message
      bodies could require the "Digest" header to be present and
      covered.

   *  A means of retrieving the key material used to verify the
      signature.  An application will usually use the "keyid" parameter
      of the signature parameters (Section 2.3.1) and define rules for
      resolving a key from there, though the appropriate key could be
      known from other means.

   *  A means of determining the signature algorithm used to verify the
      signature is appropriate for the key material.  For example, the
      process could use the "alg" parameter of the signature parameters
      (Section 2.3.1) to state the algorithm explicitly, derive the
      algorithm from the key material, or use some pre-configured
      algorithm agreed upon by the signer and verifier.

   *  A means of determining that a given key and algorithm presented in
      the request are appropriate for the request being made.  For
      example, a server expecting only ECDSA signatures should know to
      reject any RSA signatures, or a server expecting asymmetric
      cryptography should know to reject any symmetric cryptography.

   An application using signatures also has to ensure that the verifier
   will have access to all required information to re-create the
   signature input string.  For example, a server behind a reverse proxy
   would need to know the original request URI to make use of
   identifiers like "@target-uri".  Additionally, an application using
   signatures in responses would need to ensure that clients receiving
   signed responses have access to all the signed portions, including
   any portions of the request that were signed by the server.

   The details of this kind of profiling are the purview of the
   application and outside the scope of this specification.

2.  HTTP Message Components

   In order to allow signers and verifiers to establish which components
   are covered by a signature, this document defines component
   identifiers for components covered by an HTTP Message Signature, a
   set of rules for deriving and canonicalizing the values associated
   with these component identifiers from the HTTP Message, and the means
   for combining these canonicalized values into a signature input
   string.  The values for these items MUST be accessible to both the
   signer and the verifier of the message, which means these are usually
   derived from aspects of the HTTP message or signature itself.

   Some HTTP message components can undergo transformations that change
   the bitwise value without altering meaning of the component's value
   (for example, the merging together of header fields with the same
   name).  Message component values must therefore be canonicalized
   before it is signed, to ensure that a signature can be verified
   despite such intermediary transformations.  This document defines
   rules for each component identifier that transform the identifier's
   associated component value into such a canonical form.

   Component identifiers are serialized using the production grammar
   defined by RFC8941, Section 4 [RFC8941].  The component identifier
   itself is an "sf-string" value and MAY define parameters which are
   included using the "parameters" rule.

   component-identifier = sf-string parameters

   Note that this means the value of the component identifier itself is
   encased in double quotes, with parameters following as a semicolon-
   separated list, such as ""cache-control"", ""date"", or ""@signature-
   params"".

   The following sections define component identifier types, their
   parameters, their associated values, and the canonicalization rules
   for their values.  The method for combining component identifiers
   into the signature input is defined in Section 2.4.

2.1.  HTTP Fields

   The component identifier for an HTTP field is the lowercased form of
   its field name.  While HTTP field names are case-insensitive,
   implementations MUST use lowercased field names (e.g., "content-
   type", "date", "etag") when using them as component identifiers.

   Unless overridden by additional parameters and rules, the HTTP field
   value MUST be canonicalized with the following steps:

   1.  Create an ordered list of the field values of each instance of
       the field in the message, in the order that they occur (or will
       occur) in the message.

   2.  Strip leading and trailing whitespace from each item in the list.

   3.  Concatenate the list items together, with a comma "," and space "
       " between each item.

   The resulting string is the canonicalized component value.

2.1.1.  Canonicalized Structured HTTP applications.
   Application developers typically rely on Fields

   If value of the transport layer to
   provide these properties, by operating their application over [TLS].
   However, TLS only guarantees these properties over the HTTP field in question is a structured field
   ([RFC8941]), the component identifier MAY include the "sf" parameter.
   If this parameter is included, the HTTP field value MUST be
   canonicalized using the rules specified in Section 4 of RFC8941
   [RFC8941].  For example, this process will replace any optional
   internal whitespace with a single TLS
   connection, and space character.

   The resulting string is used as the path between client component value in Section 2.1.

2.1.2.  Canonicalization Examples

   This section contains non-normative examples of canonicalized values
   for header fields, given the following example HTTP message:

   Host: www.example.com
   Date: Tue, 07 Jun 2014 20:51:35 GMT
   X-OWS-Header:   Leading and application may be
   composed trailing whitespace.
   X-Obs-Fold-Header: Obsolete
       line folding.
   X-Empty-Header:
   Cache-Control: max-age=60
   Cache-Control:    must-revalidate
   X-Dictionary:  a=1,    b=2;x=1;y=2,   c=(a   b   c)
   The following table shows example canonicalized values for header
   fields, given that message:

        +=====================+==================================+
        | Header Field        | Canonicalized Value              |
        +=====================+==================================+
        | "cache-control"     | max-age=60, must-revalidate      |
        +---------------------+----------------------------------+
        | "date"              | Tue, 07 Jun 2014 20:51:35 GMT    |
        +---------------------+----------------------------------+
        | "host"              | www.example.com                  |
        +---------------------+----------------------------------+
        | "x-empty-header"    |                                  |
        +---------------------+----------------------------------+
        | "x-obs-fold-header" | Obsolete line folding.           |
        +---------------------+----------------------------------+
        | "x-ows-header"      | Leading and trailing whitespace. |
        +---------------------+----------------------------------+
        | "x-dictionary"      | a=1, b=2;x=1;y=2, c=(a b c)      |
        +---------------------+----------------------------------+
        | "x-dictionary";sf   | a=1, b=2;x=1;y=2, c=(a b c)      |
        +---------------------+----------------------------------+

             Table 1: Non-normative examples of multiple independent TLS connections (for example, if header field
                            canonicalization.

2.2.  Dictionary Structured Field Members

   An individual member in the
   application is hosted behind value of a TLS-terminating gateway or if Dictionary Structured Field is
   identified by using the
   client parameter "key" on the component identifier
   for the field.  The value of this parameter is behind a TLS Inspection appliance).  In such cases, TLS
   cannot guarantee end-to-end message integrity or authenticity between the client and application.  Additionally, some operating
   environments key being
   identified, without any parameters present obstacles on that make it impractical to use TLS,
   or to use features necessary to provide message authenticity.
   Furthermore, some applications require the binding of an application-
   level key to in the HTTP message, separate from any TLS certificates
   original dictionary.

   An individual member in
   use.  Consequently, while TLS can meet message integrity and
   authenticity needs for many HTTP-based applications, it the value of a Dictionary Structured Field is not
   canonicalized by applying the serialization algorithm described in
   Section 4.1.2 of RFC8941 [RFC8941] on a
   universal solution. Dictionary containing only
   that item.

2.2.1.  Canonicalization Examples

   This document defines a mechanism section contains non-normative examples of canonicalized values
   for providing end-to-end integrity
   and authenticity Dictionary Structured Field Members given the following example
   header field, whose value is known to be a Dictionary:

   X-Dictionary:  a=1, b=2;x=1;y=2, c=(a b c)
   The following table shows example canonicalized values for content within different
   component identifiers, given that field:

                +======================+=================+
                | Component Identifier | Component Value |
                +======================+=================+
                | "x-dictionary";key=a | 1               |
                +----------------------+-----------------+
                | "x-dictionary";key=b | 2;x=1;y=2       |
                +----------------------+-----------------+
                | "x-dictionary";key=c | (a, b, c)       |
                +----------------------+-----------------+

                    Table 2: Non-normative examples of
                   Dictionary member canonicalization.

2.3.  Specialty Components

   Message components not found in an HTTP message.  The mechanism
   allows applications to create digital signatures or message
   authentication codes (MACs) over only that content within field can be included in the message
   that is meaningful
   signature input by defining a component identifier and appropriate for the application.  Strict
   canonicalization rules ensure that method for its component value.

   To differentiate specialty component identifiers from HTTP fields,
   specialty component identifiers MUST start with the verifier can verify "at" "@"
   character.  This specification defines the following specialty
   component identifiers:

   @signature-params  The signature even if the message has been transformed in any metadata parameters for this
      signature.  (Section 2.3.1)

   @method  The method used for a request.  (Section 2.3.2)

   @target-uri  The full target URI for a request.  (Section 2.3.3)

   @authority  The authority of the many
   ways permitted by HTTP. target URI for a request.
      (Section 2.3.4)

   @scheme  The mechanism described in this document consists scheme of three parts:

   *  A common nomenclature and canonicalization rule set for the
      different protocol elements and other content within HTTP
      messages.

   *  Algorithms target URI for generating and verifying signatures over HTTP
      message content using this nomenclature and rule set.

   *  A mechanism a request.  (Section 2.3.5)

   @request-target  The request target.  (Section 2.3.6)

   @path  The absolute path portion of the target URI for attaching a signature and related metadata to an
      HTTP message.

1.1.  Requirements Discussion

   HTTP permits and sometimes requires intermediaries to transform
   messages in request.
      (Section 2.3.7)

   @query  The query portion of the target URI for a variety request.
      (Section 2.3.8)

   @query-params  The parsed query parameters of ways.  This may result in the target URI for a recipient
   receiving
      request.  (Section 2.3.9)

   @status  The status code for a response.  (Section 2.3.10).

   @request-response  A signature from a request message that is not bitwise equivalent to the message
   that was originally sent.  In such a case, the recipient will resulted
      in this response message.  (Section 2.3.11)

   Additional specialty component identifiers MAY be
   unable to verify a signature over the raw bytes of defined and
   registered in the sender's HTTP
   message, as verifying digital signatures or MACs requires both signer
   and verifier to Signatures Specialty Component Identifier
   Registry.  (Section 6.3)

2.3.1.  Signature Parameters

   HTTP Message Signatures have metadata properties that provide
   information regarding the exact same signed content.  Since the raw
   bytes of the message cannot be relied upon signature's generation and verification,
   such as signed content, the
   signer set of covered components, a timestamp, identifiers for
   verification key material, and verifier must derive other utilities.

   The signature parameters component identifier is "@signature-params".

   The signature parameters component value is the signed content from their
   respective versions serialization of the message, via a mechanism that is resilient
   to safe changes that do not alter
   signature parameters for this signature, including the meaning covered
   components set with all associated parameters.  These parameters
   include any of the message.

   For a variety following:

   *  "created": Creation time as an "sf-integer" UNIX timestamp value.
      Sub-second precision is not supported.  Inclusion of reasons, it this
      parameter is impractical to strictly define what
   constitutes a safe change versus RECOMMENDED.

   *  "expires": Expiration time as an unsafe one.  Applications use
   HTTP in a wide variety of ways, and may disagree on whether a
   particular piece of information in a message (e.g., the body, or the
   "Date" header field) "sf-integer" UNIX timestamp
      value.  Sub-second precision is relevant.  Thus a general purpose solution
   must provide signers with some degree of control over which not supported.

   *  "nonce": A random unique value generated for this signature.

   *  "alg": The HTTP message
   content is signed. signature algorithm from the HTTP applications may Message
      Signature Algorithm Registry, as an "sf-string" value.

   *  "keyid": The identifier for the key material as an "sf-string"
      value.

   Additional parameters can be running defined in environments that do not provide
   complete access to or control over the HTTP messages (such Signature Parameters
   Registry (Section 6.2.2).

   The signature parameters component value is serialized as a web
   browser's JavaScript environment), or may be
   parameterized inner list using libraries that
   abstract away the details rules in Section 4 of the protocol (such RFC8941
   [RFC8941] as follows:

   1.  Let the Java
   HTTPClient library (https://openjdk.java.net/groups/net/httpclient/
   intro.html)).  These applications need to output be able to generate and
   verify signatures despite incomplete knowledge of an empty string.

   2.  Determine an order for the HTTP message.

1.2.  HTTP Message Transformations

   As mentioned earlier, HTTP explicitly permits and in some cases
   requires implementations to transform messages in a variety of ways.
   Implementations are required to tolerate many component identifiers of these
   transformations.  What follows the covered
       components.  Once this order is a non-normative and non-exhaustive
   list of transformations that may occur under HTTP, provided as
   context:

   *  Re-ordering of header fields with different header field names
      ([MESSAGING], Section 3.2.2).

   *  Combination of header fields with chosen, it cannot be changed.
       This order MUST be the same field name
      ([MESSAGING], Section 3.2.2).

   *  Removal of header fields listed order as used in creating the "Connection" header field
      ([MESSAGING], Section 6.1).

   *  Addition of header fields that indicate control options
      ([MESSAGING], Section 6.1).

   *  Addition or removal of a transfer coding ([MESSAGING],
      Section 5.7.2).

   *  Addition
       signature input (Section 2.4).

   3.  Serialize the component identifiers of header fields such the covered components,
       including all parameters, as "Via" ([MESSAGING],
      Section 5.7.1) and "Forwarded" ([RFC7239], an ordered "inner-list" according to
       Section 4).

1.3.  Safe Transformations

   Based on the definition 4.1.1.1 of HTTP RFC8941 [RFC8941] and append this to the requirements described above,
   we can identify certain types
       output.

   4.  Determine an order for any signature parameters.  Once this order
       is chosen, it cannot be changed.

   5.  Append the parameters to the "inner-list" in the chosen order
       according to Section 4.1.1.2 of transformations RFC8941 [RFC8941], skipping
       parameters that should are not
   prevent signature verification, even when performed on content
   covered by the available or not used for this message
       signature.

   6.  The following list describes those
   transformations:

   *  Combination of header fields with output contains the same field name.

   *  Reordering of header fields with different names.

   *  Conversion between different versions signature parameters component value.

   Note that the "inner-list" serialization is used for the covered
   component value instead of the HTTP protocol (e.g.,
      HTTP/1.x to HTTP/2, or vice-versa).

   *  Changes "sf-list" serialization in casing (e.g., "Origin" order to "origin") of any case-
      insensitive content
   facilitate this value's inclusion in message fields such as header field names, request URI
      scheme, or host.

   *  Addition or removal of leading or trailing whitespace to the
   "Signature-Input" field's dictionary, as discussed in Section 4.1.

   This example shows a header
      field value.

   *  Addition or removal of "obs-folds".

   *  Changes to canonicalized value for the "request-target" and "Host" header field parameters of a
   given signature:

   NOTE: '\' line wrapping per RFC 8792

   ("@target-uri" "@authority" "date" "cache-control" "x-empty-header" \
     "x-example");keyid="test-key-rsa-pss";alg="rsa-pss-sha512";\
     created=1618884475;expires=1618884775

   Note that when
      applied together do not result an HTTP message could contain multiple signatures, but only
   the signature parameters used for the current signature are included
   in a change the entry.

2.3.2.  Method

   The "@method" component identifier refers to the message's
      effective HTTP method of a
   request URI, as defined in Section 5.5 message.  The component value of [MESSAGING].

   Additionally, all changes to content not covered is canonicalized by taking
   the signature are
   considered safe.

1.4.  Conventions and Terminology

   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 value of the method as described in
   BCP 14 [RFC2119] [RFC8174] when, a string.  Note that the method name is
   case-sensitive as per [SEMANTICS] Section 9.1, and conventionally
   standardized method names are uppercase US-ASCII.  If used, the
   "@method" component identifier MUST occur only when, they appear once in all
   capitals, as shown here.

   The terms "HTTP message", "HTTP request", "HTTP response", "absolute-
   form", "absolute-path", "effective the covered
   components.

   For example, the following request URI", "gateway", "header
   field", "intermediary", "request-target", "sender", and "recipient"
   are message:

   POST /path?param=value HTTP/1.1
   Host: www.example.com

   Would result in the following "@method" value:

   "@method": POST

   If used as defined in [MESSAGING]. a response message, the "@method" component identifier
   refers to the associated component value of the request that
   triggered the response message being signed.

2.3.3.  Target URI

   The term "method" is "@target-uri" component identifier refers to be interpreted the target URI of a
   request message.  The component value is the full absolute target URI
   of the request, potentially assembled from all available parts
   including the authority and request target as defined described in
   [SEMANTICS] Section 4 of
   [SEMANTICS]. 7.1.  If used, the "@target-uri" component
   identifier MUST occur only once in the covered components.

   For brevity, example, the term "signature" on its own is following message sent over HTTPS:

   POST /path?param=value HTTP/1.1
   Host: www.example.com

   Would result in the following "@target-uri" value:

   "@target-uri": https://www.example.com/path?param=value

   If used in this document
   to refer to both digital signatures and keyed MACs.  Similarly, a response message, the
   verb "sign" "@target-uri" component identifier
   refers to the generation associated component value of either a digital signature or
   keyed MAC over a given input string. the request that
   triggered the response message being signed.

2.3.4.  Authority

   The qualified term "digital
   signature" "@authority" component identifier refers specifically to the output authority
   component of the target URI of an asymmetric
   cryptographic signing operation.

   In addition to those listed above, this document uses the following
   terms:

   Signer:

      The entity that is generating or has generated an HTTP Message
      Signature.

   Verifier:
      An entity that is verifying or has verified an HTTP Message
      Signature against an HTTP Message.  Note that an request message, as defined
   in [SEMANTICS] Section 7.2.  In HTTP Message
      Signature may be verified multiple times, potentially by different
      entities.

   Covered Content:
      An ordered list of content identifiers for headers (Section 2.1)
      and specialty content (Section 2.3) that indicates 1.1, this is usually conveyed
   using the metadata "Host" header, while in HTTP 2 and message content that HTTP 3 it is covered by conveyed
   using the signature, not
      including ":authority" pseudo-header.  The value is the "@signature-params" specialty field itself.

   HTTP Signature Algorithm:
      A cryptographic algorithm that describes fully-
   qualified authority component of the signing and
      verification process for request, comprised of the signature.  When expressed
      explicitly, host
   and, optionally, port of the request target, as a string.  The
   component value maps MUST be normalized according to a string defined in the HTTP
      Signature Algorithms Registry defined rules in this document.

   Key Material:
      The key material required to create or verify
   [SEMANTICS] Section 4.2.3.  Namely, the signature.  The
      key material host name is often identified with an explicit key identifier,
      allowing the signer to indicate normalized to
   lowercase and the verifier which key was
      used.

   Creation Time:
      A timestamp representing default port is omitted.  If used, the point "@authority"
   component identifier MUST occur only once in time that the signature was
      generated, as asserted by covered components.

   For example, the signer.

   Expiration Time:
      A timestamp representing following request message:

   POST /path?param=value HTTP/1.1
   Host: www.example.com

   Would result in the point following "@authority" component value:

   "@authority": www.example.com

   If used in time at which a response message, the signature
      expires, as asserted by "@authority" component identifier
   refers to the signer.  A signature's expiration time
      could be undefined, indicating associated component value of the request that
   triggered the signature does not expire
      from response message being signed.

2.3.5.  Scheme

   The "@scheme" component identifier refers to the perspective scheme of the signer.

   The term "Unix time" is defined by [POSIX.1], Section 4.16
   (http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/
   V1_chap04.html#tag_04_16).

   This document contains non-normative examples target
   URL of partial and complete the HTTP messages.  Some examples use a single trailing backslash '' to
   indicate line wrapping for long values, as per [RFC8792]. request message.  The "\"
   character and leading spaces on wrapped lines are not part of component value is the
   value.

1.5.  Application of HTTP Message Signatures

   HTTP Message Signatures are designed to be scheme
   as a general-purpose security
   mechanism applicable string as defined in a wide variety of circumstances and
   applications.  In order [SEMANTICS] Section 4.2.  While the scheme
   itself is case-insensitive, it MUST be normalized to properly and safely apply HTTP Message
   Signatures, an application or profile of this specification lowercase for
   inclusion in the signature input string.  If used, the "@scheme"
   component identifier MUST
   specify all of occur only once in the following items:

   *  The set of content identifiers (Section 2) that are expected and
      required. covered components.

   For example, an authorization protocol could mandate
      that the "Authorization" header be covered to protect the
      authorization credentials and mandate the signature parameters
      contain a "created" parameter, while an API expecting HTTP following request message
      bodies could require requested over plain HTTP:

   POST /path?param=value HTTP/1.1
   Host: www.example.com

   Would result in the following "@scheme" value:

   "@scheme": http

   If used in a response message, the "Digest" header "@scheme" component identifier
   refers to be present and
      covered.

   *  A means the associated component value of retrieving the key material used request that
   triggered the response message being signed.

2.3.6.  Request Target

   The "@request-target" component identifier refers to verify the
      signature.  An application will usually use full request
   target of the "keyid" parameter HTTP request message, as defined in [SEMANTICS]
   Section 7.1.  The component value of the signature parameters (Section 2.3.2) and define rules for
      resolving a key from there, though request target can take
   different forms, depending on the appropriate key could be
      known from other means.

   *  A means type of determining request, as described
   below.  If used, the signature algorithm used "@request-target" component identifier MUST
   occur only once in the covered components.

   For HTTP 1.1, the component value is equivalent to verify the
      signature content request target
   portion of the request line.  However, this value is appropriate for more difficult
   to reliably construct in other versions of HTTP.  Therefore, it is
   NOT RECOMMENDED that this identifier be used when versions of HTTP
   other than 1.1 might be in use.

   The origin form value is combination of the key material. absolute path and query
   components of the request URL.  For example, the process could use following request
   message:

   POST /path?param=value HTTP/1.1
   Host: www.example.com

   Would result in the "alg" parameter following "@request-target" component value:

   "@request-target": /path?param=value

   The following request to an HTTP proxy with the absolute-form value,
   containing the fully qualified target URI:

   GET https://www.example.com/path?param=value HTTP/1.1

   Would result in the following "@request-target" component value:

   "@request-target": https://www.example.com/path?param=value

   The following CONNECT request with an authority-form value,
   containing the host and port of the
      signature parameters (Section 2.3.2) to state target:

   CONNECT www.example.com:80 HTTP/1.1
   Host: www.example.com

   Would result in the algorithm
      explicitly, derive following "@request-target" component value:

   "@request-target": www.example.com:80

   The following OPTIONS request message with the asterisk-form value,
   containing a single asterisk "*" character:

   OPTIONS * HTTP/1.1
   Host: www.example.com

   Would result in the algorithm from following "@request-target" component value:

   "@request-target": *
   If used in a response message, the key material, or use
      some pre-configured algorithm agreed upon by "@request-target" component
   identifier refers to the signer and
      verifier.

   *  A means associated component value of determining that a given key and algorithm presented in the request are appropriate for
   that triggered the request response message being made.  For
      example, a server expecting only ECDSA signatures should know to
      reject any RSA signatures, or a server expecting asymmetric
      cryptography should know to reject any symmetric cryptography. signed.

2.3.7.  Path

   The details of this kind of profiling are "@path" component identifier refers to the purview target path of the
   application and outside
   HTTP request message.  The component value is the scope absolute path of this specification.

2.  HTTP Message Signature Covered Content

   In order to allow signers
   the request target defined by [RFC3986], with no query component and verifiers
   no trailing "?" character.  The value is normalized according to establish which content the
   rules in [SEMANTICS] Section 4.2.3.  Namely, an empty path string is
   covered by
   normalized as a signature, this document defines content identifiers for
   data items covered single slash "/" character, and path components are
   represented by an HTTP Message Signature as well as the means
   for combining these canonicalized their values into a signature input
   string.

   Some content within HTTP messages can undergo transformations that
   change after decoding any percent-encoded
   octets.  If used, the bitwise value without altering meaning of "@path" component identifier MUST occur only
   once in the content (for covered components.

   For example, the merging together of header fields with the same name).
   Message content must therefore be canonicalized before it is signed,
   to ensure that a signature can be verified despite such intermediary
   transformations.  This document defines rules for each content following request message:

   POST /path?param=value HTTP/1.1
   Host: www.example.com

   Would result in the following "@path" value:

   "@path": /path

   If used in a response message, the "@path" identifier that transform refers to the identifier's
   associated content into
   such a canonical form.

   Content identifiers are defined using production grammar defined by
   RFC8941, Section 4 [RFC8941]. component value of the request that triggered the response
   message being signed.

2.3.8.  Query

   The content "@query" component identifier is an "sf-
   string" value. refers to the query component of
   the HTTP request message.  The content identifier type MAY define parameters
   which are included using component value is the "parameters" rule.

   content-identifier = sf-string parameters

   Note that this means entire
   normalized query string defined by [RFC3986], including the leading
   "?" character.  The value of is normalized according to the rules in
   [SEMANTICS] Section 4.2.3.  Namely, percent-encoded octets are
   decoded.  If used, the "@query" component identifier itself is encased MUST occur only
   once in
   double quotes, with parameters the covered components.

   For example, the following as a semicolon-separated
   list, such as ""cache-control"", ""date"", or ""@signature-params"". request message:

   POST /path?param=value&foo=bar&baz=batman HTTP/1.1
   Host: www.example.com

   Would result in the following "@query" value:

   "@query": ?param=value&foo=bar&baz=batman
   The following sections define content request message:

   POST /path?queryString HTTP/1.1
   Host: www.example.com

   Would result in the following "@query" value:

   "@query": ?queryString

   If used in a response message, the "@query" component identifier types, their
   parameters, their
   refers to the associated content, and their canonicalization
   rules.  The method for combining content identifiers into component value of the
   signature input request that
   triggered the response message being signed.

2.3.9.  Query Parameters

   If a request target URI uses HTML form parameters in the query string is
   as defined in [HTMLURL] Section 2.4.

2.1.  HTTP Headers 5, the "@query-params" component
   identifier allows addressing of individual query parameters.  The content
   query parameters MUST be parsed according to [HTMLURL] Section 5.1,
   resulting in a list of ("nameString", "valueString") tuples.  The
   REQUIRED "name" parameter of each input identifier for an HTTP header contains the
   "nameString" of a single query parameter.  Several different named
   query parameters MAY be included in the covered components.  Single
   named parameters MAY occur in any order in the covered components.

   The component value of a single named parameter is the lowercased form the
   "valueString" of
   its header field name.  While HTTP header field names are case-
   insensitive, implementations MUST use lowercased field names (e.g.,
   "content-type", "date", "etag") when using them as content
   identifiers.

   Unless overridden the named query parameter defined by additional parameters and rules, [HTMLURL]
   Section 5.1, which is the HTTP header
   field value MUST be canonicalized after percent-encoded octets are
   decoded.  Note that this value does not include any leading "?"
   characters, equals sign "=", or separating "&" characters.  Named
   query parameters with the following steps:

   1.  Create an ordered list of empty "valueString" are included with an
   empty string as the field component value.

   If a parameter name occurs multiple times in a request, all parameter
   values of each instance of
       the header field that name MUST be included in the message, separate signature input
   lines in the order that they in which the parameters occur (or
       will occur) in the message.

   2.  Strip leading target URI.

   For example for the following request:

   POST /path?param=value&foo=bar&baz=batman&qux= HTTP/1.1
   Host: www.example.com

   Indicating the "baz", "qux" and trailing whitespace from each item "param" named query parameters in
   would result in the list.

   3.  Concatenate following "@query-param" value:

   "@query-params";name="baz": batman
   "@query-params";name="qux":
   "@query-params";name="param": value
   If used in a response message, the list items together, with "@query-params" component
   identifier refers to the associated component value of the request
   that triggered the response message being signed.

2.3.10.  Status Code

   The "@status" component identifier refers to the three-digit numeric
   HTTP status code of a comma "," and space "
       " between each item. response message as defined in [SEMANTICS]
   Section 15.  The resulting string component value is the canonicalized value.

2.1.1.  Canonicalized Structured serialized three-digit
   integer of the HTTP Headers response code, with no descriptive text.  If value of
   used, the "@status" component identifier MUST occur only once in the
   covered components.

   For example, the HTTP header following response message:

   HTTP/1.1 200 OK
   Date: Fri, 26 Mar 2010 00:05:00 GMT

   Would result in the following "@status" value:

   "@status": 200

   The "@status" component identifier MUST NOT be used in a request
   message.

2.3.11.  Request-Response Signature Binding

   When a signed request message results in question is a structured field
   ([RFC8941]), signed response message,
   the content "@request-response" component identifier MAY include can be used to
   cryptographically link the "sf" parameter.
   If this parameter is included, request and the HTTP header value MUST be
   canonicalized using response to each other by
   including the rules specified identified request signature value in Section 4 the response's
   signature input without copying the value of RFC8941
   [RFC8941].  Note that this process will replace any optional
   whitespace with the request's signature
   to the response directly.  This component identifier has a single space.
   REQUIRED parameter:

   "key"  Identifies which signature from the response to sign.

   The resulting string component value is used as the field "sf-binary" representation of the
   signature value input in Section 2.1.

2.1.2.  Canonicalization Examples

   This section contains non-normative examples of canonicalized values
   for header fields, given the following example HTTP message:

   Server: www.example.com referenced request identified by the "key"
   parameter.

   For example, when serving this signed request:

   NOTE: '\' line wrapping per RFC 8792

   POST /foo?param=value&pet=dog HTTP/1.1
   Host: example.com
   Date: Tue, 07 Jun 2014 20:51:35 20 Apr 2021 02:07:55 GMT
   X-OWS-Header:   Leading and trailing whitespace.
   X-Obs-Fold-Header: Obsolete
       line folding.
   X-Empty-Header:
   Cache-Control: max-age=60
   Cache-Control:    must-revalidate

   The
   Content-Type: application/json
   Content-Length: 18
   Signature-Input: sig1=("@authority" "content-type")\
     ;created=1618884475;keyid="test-key-rsa-pss"
   Signature: sig1=:KuhJjsOKCiISnKHh2rln5ZNIrkRvue0DSu5rif3g7ckTbbX7C4\
     Jp3bcGmi8zZsFRURSQTcjbHdJtN8ZXlRptLOPGHkUa/3Qov79gBeqvHNUO4bhI27p\
     4WzD1bJDG9+6ml3gkrs7rOvMtROObPuc78A95fa4+skS/t2T7OjkfsHAm/enxf1fA\
     wkk15xj0n6kmriwZfgUlOqyff0XLwuH4XFvZ+ZTyxYNoo2+EfFg4NVfqtSJch2WDY\
     7n/qmhZOzMfyHlggWYFnDpyP27VrzQCQg8rM1Crp6MrwGLa94v6qP8pq0sQVq2DLt\
     4NJSoRRqXTvqlWIRnexmcKXjQFVz6YSA==:

   {"hello": "world"}

   This would result in the following table shows example canonicalized values for header
   fields, given that unsigned response message:

        +=====================+==================================+
        | Header Field        | Canonicalized Value              |
        +=====================+==================================+
        | "cache-control"     | max-age=60, must-revalidate      |
        +---------------------+----------------------------------+
        | "date"              |

   HTTP/1.1 200 OK
   Date: Tue, 07 Jun 2014 20:51:35 20 Apr 2021 02:07:56 GMT    |
        +---------------------+----------------------------------+
        | "server"            | www.example.com                  |
        +---------------------+----------------------------------+
        | "x-empty-header"    |                                  |
        +---------------------+----------------------------------+
        | "x-obs-fold-header" | Obsolete line folding.           |
        +---------------------+----------------------------------+
        | "x-ows-header"      | Leading
   Content-Type: application/json
   Content-Length: 62

   {"busy": true, "message": "Your call is very important to us"}

   The server signs the response with its own key and trailing whitespace. |
        +---------------------+----------------------------------+

             Table 1: Non-normative examples of header field
                            canonicalization.

2.2.  Dictionary Structured Field Members

   An individual member in includes the value
   signature of a Dictionary Structured Field is
   identified by using "sig1" from the parameter "key" on request in the content identifier for covered components of the header.
   response.  The value of signature input string for this parameter example is:

   NOTE: '\' line wrapping per RFC 8792

   "content-type": application/json
   "content-length": 62
   "@status": 200
   "@request-response";key="sig1": :KuhJjsOKCiISnKHh2rln5ZNIrkRvue0DSu\
     5rif3g7ckTbbX7C4Jp3bcGmi8zZsFRURSQTcjbHdJtN8ZXlRptLOPGHkUa/3Qov79\
     gBeqvHNUO4bhI27p4WzD1bJDG9+6ml3gkrs7rOvMtROObPuc78A95fa4+skS/t2T7\
     OjkfsHAm/enxf1fAwkk15xj0n6kmriwZfgUlOqyff0XLwuH4XFvZ+ZTyxYNoo2+Ef\
     Fg4NVfqtSJch2WDY7n/qmhZOzMfyHlggWYFnDpyP27VrzQCQg8rM1Crp6MrwGLa94\
     v6qP8pq0sQVq2DLt4NJSoRRqXTvqlWIRnexmcKXjQFVz6YSA==:
   "@signature-params": ("content-type" "content-length" "@status" \
     "@request-response";key="sig1");created=1618884475\
     ;keyid="test-key-ecc-p256"

   The signed response message is:

   NOTE: '\' line wrapping per RFC 8792

   HTTP/1.1 200 OK
   Date: Tue, 20 Apr 2021 02:07:56 GMT
   Content-Type: application/json
   Content-Length: 62
   Signature-Input: sig1=("content-type" "content-length" "@status" \
     "@request-response";key="sig1");created=1618884475\
     ;keyid="test-key-ecc-p256"
   Signature: sig1=:crVqK54rxvdx0j7qnt2RL1oQSf+o21S/6Uk2hyFpoIfOT0q+Hv\
     msYAXUXzo0Wn8NFWh/OjWQOXHAQdVnTk87Pw==:

   {"busy": true, "message": "Your call is a very important to us"}

   Since the key being
   identified, without any parameters present on that key request's signature value itself is not repeated in the
   original dictionary.

   An individual member in
   response, the requester MUST keep the original signature value around
   long enough to validate the signature of a Dictionary Structured Field is
   canonicalized by applying the serialization algorithm described response.

   The "@request-response" component identifier MUST NOT be used in
   Section 4.1.2 of RFC8941 [RFC8941] on a Dictionary containing only
   that member.

2.2.1.  Canonicalization Examples

   This section contains non-normative examples of canonicalized values
   for Dictionary Structured Field Members given
   request message.

2.4.  Creating the following example
   header field, whose value Signature Input String

   The signature input is assumed to be a Dictionary:

   X-Dictionary:  a=1, b=2;x=1;y=2, c=(a b c)

   The following table shows example US-ASCII string containing the canonicalized values for different
   content identifiers, given that field:

              +======================+=====================+
              | Content Identifier   | Canonicalized Value |
              +======================+=====================+
              | "x-dictionary";key=a | 1                   |
              +----------------------+---------------------+
              | "x-dictionary";key=b | 2;x=1;y=2           |
              +----------------------+---------------------+
              | "x-dictionary";key=c | (a, b, c)           |
              +----------------------+---------------------+

                    Table 2: Non-normative examples of
                   Dictionary member canonicalization.

2.3.  Specialty Content Fields

   Content not found
   HTTP message components covered by the signature.  To create the
   signature input string, the signer or verifier concatenates together
   entries for each identifier in an HTTP header can the signature's covered components
   (including their parameters) using the following algorithm:

   1.  Let the output be included an empty string.

   2.  For each message component item in the signature
   base string by defining a content identifier and covered components set (in
       order):

       1.  Append the canonicalization
   method component identifier for its content.

   To differentiate specialty content identifiers from HTTP headers,
   specialty content identifiers MUST start with the "at" "@" character.
   This specification defines covered component
           serialized according to the following specialty content
   identifiers:

   @request-target  The target request endpoint. "component-identifier" rule.

       2.  Append a single colon "":""

       3.  Append a single space "" ""

       4.  Append the covered component's canonicalized component value,
           as defined by the HTTP message component type.  (Section 2.3.1)

   @signature-params  The 2.1
           and Section 2.3)

       5.  Append a single newline ""\\n""

   3.  Append the signature metadata parameters for this
      signature. component (Section 2.3.2)

   Additional specialty content identifiers MAY be 2.3.1) as
       follows:

       1.  Append the component identifier for the signature parameters
           serialized according to the "component-identifier" rule, i.e.
           ""@signature-params""

       2.  Append a single colon "":""

       3.  Append a single space "" ""

       4.  Append the signature parameters' canonicalized component
           value as defined and
   registered in Section 2.3.1

   4.  Return the HTTP Signatures Specialty Content Identifier
   Registry.  (Section 5.3)

2.3.1.  Request Target

   The request target endpoint, consisting of output string.

   If covered components reference a component identifier that cannot be
   resolved to a component value in the request method and message, the
   path and query of implementation MUST
   produce an error.  Such situations are included but not limited to:

   *  The signer or verifier does not understand the effective request URI, component
      identifier.

   *  The component identifier identifies a field that is identified by not present in
      the
   "@request-target" identifier.

   Its message or whose value is canonicalized as follows:

   1.  Take the lowercased HTTP method of malformed.

   *  The component identifier is a Dictionary member identifier that
      references a field that is not present in the message.

   2.  Append message, is not a space " ".

   3.  Append
      Dictionary Structured Field, or whose value is malformed.

   *  The component identifier is a Dictionary member identifier that
      references a member that is not present in the path field value, or
      whose value is malformed.  E.g., the identifier is
      ""x-dictionary";key="c"" and query of the request target value of the message,
       formatted according to the rules defined for the :path pseudo- "x-dictionary"
      header in [HTTP2], Section 8.1.2.3.  The resulting string field is "a=1, b=2"

   In the
       canonicalized value.

2.3.1.1.  Canonicalization Examples

   The following table contains non-normative example example, the HTTP messages and
   their canonicalized "@request-target" values.

       +=========================+=================+
       |HTTP Message             | @request-target |
       +=========================+=================+
       |   POST /?param=value HTTP/1.1| post            |
       |   Host: www.example.com | /?param=value   |
       +-------------------------+-----------------+
       |   POST /a/b HTTP/1.1    | post /a/b       |
       |   Host: www.example.com |                 |
       +-------------------------+-----------------+
       |   GET http://www.example.com/a/ HTTP/1.1| get /a/         |
       +-------------------------+-----------------+
       | message being signed
   is the following request:

   GET http://www.example.com HTTP/1.1| get /           |
       +-------------------------+-----------------+
       |   CONNECT server.example.com:80 HTTP/1.1| connect /       |
       |   Host: server.example.com|                 |
       +-------------------------+-----------------+
       |   OPTIONS * /foo HTTP/1.1    | options *       |
       |
   Host: server.example.com|                 |
       +-------------------------+-----------------+

            Table 3: Non-normative examples of "@request-target"
                             canonicalization.

2.3.2.  Signature Parameters

   HTTP Message Signatures have metadata properties that provide
   information regarding the signature's generation and/or verification.

   The signature parameters specialty content is identified by the
   "@signature-params" identifier.

   Its canonicalized value is the serialization of the signature
   parameters for this signature, including the covered content list example.org
   Date: Tue, 20 Apr 2021 02:07:55 GMT
   X-Example: Example header
           with all associated parameters.

   *  "alg": some whitespace.
   X-Empty-Header:
   Cache-Control: max-age=60
   Cache-Control: must-revalidate
   The HTTP message signature algorithm from covered components consist of the "@method", "@path", and
   "@authority" specialty component identifiers followed by the "Cache-
   Control", "X-Empty-Header", "X-Example" HTTP Message
      Signature Algorithm Registry, as an "sf-string" value.

   *  "keyid": headers, in order.  The identifier for the key material as an "sf-string"
      value.

   *  "created": Creation time as an "sf-integer" UNIX
   signature parameters consist of a creation timestamp value.
      Sub-second precision is not supported.

   *  "expires": Expiration time as an "sf-integer" UNIX timestamp
      value.  Sub-second precision "1618884475"
   and the key identifier is not supported.

   *  "nonce": A random unique value generated "test-key-rsa-pss".  The signature input
   string for this signature.

   Additional message with these parameters can be defined in the is:

   NOTE: '\' line wrapping per RFC 8792

   "@method": GET
   "@path": /foo
   "@authority": example.org
   "cache-control": max-age=60, must-revalidate
   "x-empty-header":
   "x-example": Example header with some whitespace.
   "@signature-params": ("@method" "@path" "@authority" \
     "cache-control" "x-empty-header" "x-example");created=1618884475\
     ;keyid="test-key-rsa-pss"

              Figure 1: Non-normative example Signature Input

3.  HTTP Message Signatures

   An HTTP Message Signature Parameters
   Registry (Section 5.2.2).

   The is a signature parameters are serialized using over a string generated from
   a subset of the rules in Section 4 components of RFC8941 [RFC8941] as follows:

   1.  Let an HTTP message in addition to metadata
   about the output be signature itself.  When successfully verified against an empty string.

   2.  Determine
   HTTP message, an order for the content identifiers of HTTP Message Signature provides cryptographic proof
   that the covered
       content.  Once this order message is chosen, it cannot be changed.

   3.  Serialize semantically equivalent to the content identifiers of message for which
   the covered content,
       including all parameters, as an ordered "inner-list" according signature was generated, with respect to
       Section 4.1.1.1 the subset of RFC8941 [RFC8941] and append this message
   components that was signed.

3.1.  Creating a Signature

   In order to create a signature, a signer MUST follow the
       output.

   4.  Determine following
   algorithm:

   1.  The signer chooses an order for any HTTP signature parameters.  Once this order algorithm and key material
       for signing.  The signer MUST choose key material that is chosen, it cannot be changed.

   5.  Append
       appropriate for the parameters signature's algorithm, and that conforms to
       any requirements defined by the "inner-list" in algorithm, such as key size or
       format.  The mechanism by which the chosen order
       according to Section 4.1.1.2 signer chooses the algorithm
       and key material is out of RFC8941 [RFC8941], skipping
       parameters that are not available or not used scope for this signature.

   6. document.

   2.  The output contains signer sets the signature parameters value.

   Note that signature's creation time to the "inner-list" serialization is used for current
       time.

   3.  If applicable, the covered
   content value instead of signer sets the "sf-list" serialization in order signature's expiration time
       property to
   facilitate this value's additional inclusion in the "Signature-Input"
   header's dictionary, as discussed in Section 4.1.

   This example shows a canonicalized value for time at which the parameters of a
   given signature:

   ("@request-target" "host" "date" "cache-control" "x-empty-header" \
     "x-example");keyid="test-key-rsa-pss";alg="rsa-pss-sha512";\
     created=1618884475;expires=1618884775

   Note that signature is to expire.

   4.  The signer creates an HTTP ordered set of component identifiers
       representing the message could contain multiple signatures, but only components to be covered by the
       signature, and attaches signature metadata parameters used for the current signature are included
   in to this field.

2.4.  Creating the Signature Input String
       set.  The signature input is a US-ASCII string containing the content that serialized value of this is covered by the signature.  To create later used as the signature input string, value of
       the signer or verifier concatenates together entries for each
   identifier "Signature-Input" field as described in Section 4.1.

       *  Once an order of covered components is chosen, the signature's covered content and parameters using order MUST
          NOT change for the following algorithm:

   1.  Let life of the output signature.

       *  Each covered component identifier MUST be either an empty string.

   2.  For each covered content item HTTP field
          in the covered content list (in
       order):

       1.  Append the message Section 2.1 or a specialty component identifier for
          listed in Section 2.3 or its associated registry.

       *  Signers of a request SHOULD include some or all of the message
          control data in the covered content serialized
           according components, such as the "@method",
          "@authority", "@target-uri", or some combination thereof.

       *  Signers SHOULD include the "created" signature metadata
          parameter to indicate when the "content-identifier" rule.

       2.  Append a single colon "":""

       3.  Append a single space "" ""

       4.  Append signature was created.

       *  The "@signature-params" specialty component identifier is not
          explicitly listed in the list of covered content's canonicalized value, component
          identifiers, because it is required to always be present as defined
           by
          the covered content type.  (Section 2.1 last line in the signature input.  This ensures that a
          signature always covers its own metadata.

       *  Further guidance on what to include in this set and Section 2.3) in what
          order is out of scope for this document.

   5.  Append a single newline ""\\n""

   3.  Append  The signer creates the signature parameters input string based on these
       signature parameters.  (Section 2.3.2) as follows:

       1.  Append the identifier for 2.4)

   6.  The signer signs the signature parameters serialized
           according to input with the "content-identifier" rule, ""@signature-
           params""

       2.  Append a single colon "":""

       3.  Append a single space "" ""

       4.  Append chosen signing
       algorithm using the key material chosen by the signer.  Several
       signing algorithms are defined in in Section 3.3.

   7.  The byte array output of the signature parameters' canonicalized function is the HTTP
       message signature output value to be included in the "Signature"
       field as defined in Section 2.3.2

   4.  Return 4.2.

   For example, given the output string.

   If covered content references an identifier that cannot be resolved
   to a value HTTP message and signature parameters in the message,
   example in Section 2.4, the implementation MUST produce an error.
   Such situations are included but not limited to:

   *  The signer or verifier does not understand example signature input string when
   signed with the content identifier.

   *  The identifier identifies a header field that is not present "test-key-rsa-pss" key in Appendix B.1.2 gives the
   following message or whose signature output value, encoded in Base64:

   NOTE: '\' line wrapping per RFC 8792

   P0wLUszWQjoi54udOtydf9IWTfNhy+r53jGFj9XZuP4uKwxyJo1RSHi+oEF1FuX6O29\
   d+lbxwwBao1BAgadijW+7O/PyezlTnqAOVPWx9GlyntiCiHzC87qmSQjvu1CFyFuWSj\
   dGa3qLYYlNm7pVaJFalQiKWnUaqfT4LyttaXyoyZW84jS8gyarxAiWI97mPXU+OVM64\
   +HVBHmnEsS+lTeIsEQo36T3NFf2CujWARPQg53r58RmpZ+J9eKR2CD6IJQvacn5A4Ix\
   5BUAVGqlyp8JYm+S/CWJi31PNUjRRCusCVRj05NrxABNFv3r5S9IXf2fYJK+eyW4AiG\
   VMvMcOg==

              Figure 2: Non-normative example signature value is malformed.

   *  The identifier is

3.2.  Verifying a Dictionary member identifier that references Signature

   A verifier processes a
      header field that is not present signature and its associated signature input
   parameters in concert with each other.

   In order to verify a signature, a verifier MUST follow the message, following
   algorithm:

   1.  Parse the "Signature" and "Signature-Input" fields and extract
       the signatures to be verified.

       1.  If there is not a
      Dictionary Structured Field, or whose more than one signature value is malformed.

   *  The identifier is a Dictionary member identifier that references a
      member that present, determine
           which signature should be processed for this message.  If an
           applicable signature is not present in found, produce an error.

       2.  If the chosen "Signature" value does not have a corresponding
           "Signature-Input" value, produce an error.

   2.  Parse the values of the chosen "Signature-Input" field to get the
       parameters for the signature to be verified.

   3.  Parse the header field value, or whose value is malformed.  E.g., of the identifier is
      ""x-dictionary";key="c"" and corresponding "Signature" field to get the
       byte array value of the "x-dictionary"
      header field is "a=1, b=2"

   In signature to be verified.

   4.  Examine the following non-normative example, signature parameters to confirm that the HTTP signature
       meets the requirements described in this document, as well as any
       additional requirements defined by the application such as which
       message being signed components are required to be covered by the signature.
       (Section 3.2.1)

   5.  Determine the verification key material for this signature.  If
       the key material is known through external means such as static
       configuration or external protocol negotiation, the following request:

   GET /foo HTTP/1.1
   Host: example.org
   Date: Tue, 20 Apr 2021 02:07:55 GMT
   X-Example: Example header verifier will
       use that.  If the key is identified in the signature parameters,
       the verifier will dereference this to appropriate key material to
       use with some whitespace.
   X-Empty-Header:
   Cache-Control: max-age=60
   Cache-Control: must-revalidate the signature.  The covered content consists verifier has to determine the
       trustworthiness of the "@request-target" specialty
   content followed by key material for the "Host", "Date", "Cache-Control", "X-Empty-
   Header", "X-Example" HTTP headers, context in order.  The which the
       signature creation
   timestamp is "1618884475" and the presented.  If a key identifier is "test-key-rsa-
   pss".  The signature input string identified that the verifier
       does not know, does not trust for this message with these
   parameters is:

 "@request-target": get /foo
 "host": example.org
 "date": Tue, 20 Apr 2021 02:07:55 GMT
 "cache-control": max-age=60, must-revalidate
 "x-empty-header":
 "x-example": Example header with some whitespace.
 "@signature-params": ("@request-target" "host" "date" "cache-control" \
   "x-empty-header" "x-example");created=1618884475;\
   keyid="test-key-rsa-pss"

            Figure 1: Non-normative example Signature Input

3.  HTTP Message Signatures

   An HTTP Message Signature request, or does not match
       something preconfigured, the verification MUST fail.

   6.  Determine the algorithm to apply for verification:

       1.  If the algorithm is a known through external means such as
           static configuration or external protocol negotiation, the
           verifier will use this algorithm.

       2.  If the algorithm is explicitly stated in the signature over
           parameters using a string generated value from
   a subset of the content in an HTTP message and metadata about Message Signatures
           registry, the
   signature itself.  When successfully verified against verifier will use the referenced algorithm.

       3.  If the algorithm can be determined from the keying material,
           such as through an HTTP
   message, it provides cryptographic proof that with respect to algorithm field on the
   subset of content that was signed, key value itself,
           the message is semantically
   equivalent to verifier will use this algorithm.

       4.  If the message for which algorithm is specified in more that one location, such
           as through static configuration and the algorithm signature was generated.

3.1.  Creating a Signature

   In order to create a signature, a signer MUST follow
           parameter, or the following
   algorithm:

   1.  The signer chooses an HTTP signature algorithm signature parameter and from the
           key material
       for signing.  The signer itself, the resolved algorithms MUST choose key material that is
       appropriate for be the signature's algorithm,
           same.  If the algorithms are not the same, the verifier MUST
           vail the verification.

   7.  Use the received HTTP message and that conforms the signature's metadata to
       any requirements defined by
       recreate the algorithm, such as key size or
       format.  The mechanism by which signature input, using the signer chooses process described in
       Section 2.4.  The value of the algorithm
       and key material "@signature-params" input is out the
       value of scope the "SignatureInput" field for this document.

   2.  The signer sets the signature's creation time signature serialized
       according to the current
       time.

   3.  If applicable, the signer sets rules described in Section 2.3.1, not including
       the signature's expiration time
       property to label from the time at which "Signature-Input" field.

   8.  If the signature key material is to expire.

   4.  The signer creates an ordered list of content identifiers
       representing appropriate for the message content and signature metadata algorithm, apply the
       verification algorithm to be
       covered by the signature, recalculated signature
       input, signature parameters, key material, and assigns this list as the
       signature's Covered Content.

       *  Once an order algorithm.
       Several algorithms are defined in Section 3.3.

   9.  The results of covered content is chosen, the order MUST NOT
          change for verification algorithm function are the life final
       results of the signature.

       *  Each covered content identifier MUST either reference an HTTP
          header in signature verification.

   If any of the request message Section 2.1 or reference a
          specialty content field listed in Section 2.3 above steps fail or its
          associated registry.

       *  Signers SHOULD include "@request-target" in produce an error, the covered
          content list.

       *  Signers SHOULD include a date stamp signature
   validation fails.

3.2.1.  Enforcing Application Requirements

   The verification requirements specified in some form, such this document are intended
   as a baseline set of restrictions that are generally applicable to
   all use cases.  Applications using the "date" header.  Alternatively, the "created"
          signature metadata parameter can fulfil HTTP Message Signatures MAY impose
   requirements above and beyond those specified by this role. document, as
   appropriate for their use case.

   Some non-normative examples of additional requirements an application
   might define are:

   *  Further guidance on what to include in this list and in what
          order is out  Requiring a specific set of scope for this document.  However, note that
          the list order is significant and once established for header fields to be signed (e.g.,
      "Authorization", "Digest").

   *  Enforcing a given maximum signature it MUST be preserved for that signature. age.

   *  Note that  Prohibition of signature metadata parameters, such as runtime
      algorithm signaling with the "@signature-params" specialty identifier is not
          explicitly listed in "alg" parameter.

   *  Prohibiting the list use of covered content identifiers,
          because it is required certain algorithms, or mandating the use of
      a specific algorithm.

   *  Requiring keys to always be present as the last line
          in the signature input.  This ensures that of a signature always
          covers its own metadata.

   5.  The signer creates certain size (e.g., 2048 bits vs. 1024
      bits).

   *  Enforcing uniqueness of a "nonce" value.

   Application-specific requirements are expected and encouraged.  When
   an application defines additional requirements, it MUST enforce them
   during the signature input string.  (Section 2.4)

   6.  The signer signs the verification process, and signature input with verification
   MUST fail if the chosen signing
       algorithm using signature does not conform to the key material chosen by application's
   requirements.

   Applications MUST enforce the signer.  Several
       signing algorithms are requirements defined in in Section 3.3.

   7.  The byte array output this document.
   Regardless of the signature function is the use case, applications MUST NOT accept signatures that
   do not conform to these requirements.

3.3.  Signature Algorithm Methods

   HTTP
       message Message signatures MAY use any cryptographic digital signature output value to be included in
   or MAC method that is appropriate for the "Signature"
       header as defined in Section 4.2.

   For example, given key material, environment,
   and needs of the HTTP message signer and verifier.  All signatures are generated
   from and signature parameters in verified against the
   example in Section 2.4, byte values of the example signature input
   string when
   signed with the "test-key-rsa-pss" key in Appendix B.1.2 gives the
   following message signature output value, encoded defined in Base64:

   lPxkxqDEPhgrx1yPaKLO7eJ+oPjSwsQ5NjWNRfYP7Jw0FwnK1k8/GH7g5s2q0VTTKVm\
   xyfpUDp/HsDphh5Z7Fa/lvtujHyFe/0EP9z7bnVb7YBZrxV52LGvP8p4APhOYuG4yaH\
   z478GsJav9BQYK0B2IOHdLFJe8qwWPJs07J47gPewpNwCt0To/zZ2KPpylGX5UHVgJP\
   Uom64KjX43u2OwIvSoPEYk4nuBvLR9yxYAHURaTfLoEDUCtY1FsU1hOfG3jAlcT6ill\
   fnyS72PEdSSzw1KsxroMj9IYpFhva77YxmJRk4pCIW0F0Kj0ukl7J4y2aZJHMCYI3g8\
   yfqh/wQ==

              Figure 2: Non-normative example signature value

3.2.  Verifying a Signature

   A verifier processes a Section 2.4.

   Each signature and algorithm method takes as its associated input the signature
   input
   parameters in concert with each other.

   In order to verify a signature, string as a verifier MUST follow the following
   algorithm:

   1.  Parse set of byte values ("I"), the "Signature" and "Signature-Input" headers signing key material
   ("Ks"), and extract outputs the signatures to be verified.

       1.  If there is more than one signature value present, determine
           which signature should be processed for this request.  If an
           appropriate signature is not found, produce an error.

       2.  If the chosen "Signature" value does not have output as a corresponding
           "Signature-Input" value, produce an error.

   2.  Parse the values set of byte values
   ("S"):

   HTTP_SIGN (I, Ks)  ->  S

   Each verification algorithm method takes as its input the chosen "Signature-Input" header field to
       get the parameters for the
   recalculated signature to be verified.

   3.  Parse the value input string as a set of the corresponding "Signature" header field to
       get the byte array value of values ("I"),
   the signature to be verified.

   4.  Examine verification key material ("Kv"), and the presented signature parameters to confirm that the signature
       meets the requirements described in this document, as well
   be verified as any
       additional requirements defined by a set of byte values ("S") and outputs the application such
   verification result ("V") as which
       contents are required a boolean:

   HTTP_VERIFY (I, Kv, S) -> V

   This section contains several common algorithm methods.  The method
   to use can be covered by communicated through the signature.
       (Section 3.2.1)

   5.  Determine algorithm signature parameter
   defined in Section 2.3.1, by reference to the verification key material for material, or
   through mutual agreement between the signer and verifier.

3.3.1.  RSASSA-PSS using SHA-512

   To sign using this signature.  If algorithm, the key material is known through external means such as static
       configuration or external protocol negotiation, signer applies the verifier will
       use that.  If "RSASSA-PSS-SIGN
   (K, M)" function [RFC8017] with the signer's private signing key is identified in
   ("K") and the signature parameters,
       the verifier will dereference this to appropriate key material to
       use input string ("M") (Section 2.4).  The mask
   generation function is "MGF1" as specified in [RFC8017] with the signature. a hash
   function of SHA-512 [RFC6234].  The verifier has salt length ("sLen") is 64 bytes.
   The hash function ("Hash") SHA-512 [RFC6234] is applied to determine the
       trustworthiness of the key material for
   signature input string to create the context in digest content to which the
   digital signature is presented.  If a key applied.  The resulting signed content byte
   array ("S") is identified that the verifier
       does not know, does not trust for HTTP message signature output used in Section 3.1.

   To verify using this request, or does not match
       something preconfigured, algorithm, the verification MUST fail.

   6.  Determine verifier applies the algorithm to apply for verification:

       1.  If "RSASSA-PSS-
   VERIFY ((n, e), M, S)" function [RFC8017] using the algorithm is known through external means such as
           static configuration or external protocol negotiation, public key
   portion of the
           verifier will use this algorithm.

       2.  If verification key material ("(n, e)") and the algorithm signature
   input string ("M") re-created as described in Section 3.2.  The mask
   generation function is explicitly stated "MGF1" as specified in [RFC8017] with a hash
   function of SHA-512 [RFC6234].  The salt length ("sLen") is 64 bytes.
   The hash function ("Hash") SHA-512 [RFC6234] is applied to the
   signature
           parameters using a value from input string to create the HTTP Message Signatures
           registry, digest content to which the
   verification function is applied.  The verifier will use the referenced algorithm.

       3.  If extracts the algorithm can HTTP
   message signature to be determined from the keying material,
           such verified ("S") as through an algorithm field on described in Section 3.2.
   The results of the key value itself, verification function are compared to the verifier will use this algorithm.

       4.  If http
   message signature to determine if the algorithm signature presented is specified in more that one location, such
           as through static configuration and valid.

3.3.2.  RSASSA-PKCS1-v1_5 using SHA-256

   To sign using this algorithm, the algorithm signature
           parameter, or signer applies the algorithm signature parameter and from "RSASSA-
   PKCS1-V1_5-SIGN (K, M)" function [RFC8017] with the signer's private
   signing key material itself, ("K") and the resolved algorithms MUST be signature input string ("M") (Section 2.4).
   The hash SHA-256 [RFC6234] is applied to the
           same.  If signature input string
   to create the algorithms are not digest content to which the same, digital signature is
   applied.  The resulting signed content byte array ("S") is the HTTP
   message signature output used in Section 3.1.

   To verify using this algorithm, the verifier MUST
           vail applies the verification.

   7.  Use "RSASSA-
   PKCS1-V1_5-VERIFY ((n, e), M, S)" function [RFC8017] using the received HTTP message public
   key portion of the verification key material ("(n, e)") and the signature's metadata to
       recreate the
   signature input, using the process input string ("M") re-created as described in Section 2.4. 3.2.
   The value of the "@signature-params" input hash function SHA-256 [RFC6234] is applied to the
       value of the SignatureInput header field for this signature
       serialized according input
   string to create the rules described in Section 2.3.2, not
       including the signature's label from the "Signature-Input"
       header.

   8.  If the key material is appropriate for the algorithm, apply digest content to which the verification algorithm to
   function is applied.  The verifier extracts the signature, recalculated signature
       input, HTTP message
   signature parameters, key material, and algorithm.
       Several algorithms are defined to be verified ("S") as described in Section 3.3.

   9. 3.2.  The
   results of the verification algorithm function are compared to the final
       results of the signature verification.

   If any of the above steps fail, the http message
   signature validation fails.

3.2.1.  Enforcing Application Requirements

   The verification requirements specified in this document are intended
   as a baseline set of restrictions that are generally applicable to
   all use cases.  Applications using HTTP Message Signatures MAY impose
   requirements above and beyond those specified by this document, as
   appropriate for their use case.

   Some non-normative examples of additional requirements an application
   might define are:

   *  Requiring a specific set of header fields to be signed (e.g.,
      Authorization, Digest).

   *  Enforcing a maximum signature age.

   *  Prohibiting the use of certain algorithms, or mandating determine if the use of
      an algorithm.

   *  Requiring keys to be of a certain size (e.g., 2048 bits vs. 1024
      bits).

   *  Enforcing uniqueness of a nonce value.

   Application-specific requirements are expected and encouraged.  When
   an application defines additional requirements, it MUST enforce them
   during signature presented is valid.

3.3.3.  HMAC using SHA-256

   To sign and verify using this algorithm, the signature verification process, signer applies the
   "HMAC" function [RFC2104] with the shared signing key ("K") and the
   signature verification
   MUST fail if input string ("text") (Section 2.4).  The hash function
   SHA-256 [RFC6234] is applied to the signature does not conform input string to create
   the digest content to which the application's
   requirements.

   Applications MUST enforce HMAC is applied, giving the requirements defined signature
   result.

   For signing, the resulting value is the HTTP message signature output
   used in this document.
   Regardless of use case, applications MUST NOT accept signatures that
   do not conform to these requirements.

3.3.  Signature Algorithm Methods Section 3.1.

   For verification, the verifier extracts the HTTP Message signatures MAY use any cryptographic digital message signature
   or MAC method that to
   be verified ("S") as described in Section 3.2.  The output of the
   HMAC function is appropriate for compared to the key material, environment, value of the HTTP message signature,
   and needs the results of the signer comparison determine the validity of the
   signature presented.

3.3.4.  ECDSA using curve P-256 DSS and verifier.  All signatures are generated
   from SHA-256

   To sign using this algorithm, the signer applies the "ECDSA"
   algorithm [FIPS186-4] using curve P-256 with the signer's private
   signing key and verified against the byte values of signature input string (Section 2.4).  The hash
   SHA-256 [RFC6234] is applied to the signature input string defined to create
   the digest content to which the digital signature is applied.  The
   resulting signed content byte array is the HTTP message signature
   output used in Section 2.4.

   Each signature 3.1.

   To verify using this algorithm, the verifier applies the "ECDSA"
   algorithm method takes as its input [FIPS186-4] using the signature
   input string as a set public key portion of byte values ("I"), the signing
   verification key material
   ("Ks"), and outputs the signed content as a set of byte values ("S"):

   HTTP_SIGN (I, Ks)  ->  S

   Each verification algorithm method takes as its signature input string re-created
   as described in Section 3.2.  The hash function SHA-256 [RFC6234] is
   applied to the
   recalculated signature input string as a set of byte values ("I"), to create the digest content to
   which the verification key material ("Kv"), and function is applied.  The verifier extracts
   the presented HTTP message signature to be verified ("S") as a set described in
   Section 3.2.  The results of byte values ("S") and outputs the verification result ("V") as a boolean:

   HTTP_VERIFY (I, Kv, S) -> V

   This section contains several common algorithm methods.  The method function are compared
   to use can be communicated through the algorithm http message signature parameter
   defined in Section 2.3.2, by reference to determine if the key material, or
   through mutual agreement between signature presented
   is valid.

3.3.5.  JSON Web Signature (JWS) algorithms

   If the signer and verifier.

3.3.1.  RSASSA-PSS using SHA-512

   To sign using this algorithm, signing algorithm is a JOSE signing algorithm from the signer applies JSON
   Web Signature and Encryption Algorithms Registry established by
   [RFC7518], the "RSASSA-PSS-SIGN
   (K, M)" function [RFC8017] with JWS algorithm definition determines the signer's private signature and
   hashing algorithms to apply for both signing key
   ("K") and the signature input string ("M") (Section 2.4).  The mask
   generation function verification.  There
   is "MGF1" as specified in [RFC8017] with a hash
   function no use of SHA-512 [RFC6234].  The salt length ("sLen") the explicit "alg" signature parameter when using JOSE
   signing algorithms.

   For both signing and verification, the HTTP messages signature input
   string (Section 2.4) is 64 bytes. used as the entire "JWS Signing Input".  The hash function ("Hash") SHA-512 [RFC6234]
   JOSE Header defined in [RFC7517] is applied to not used, and the signature input
   string to create is not first encoded in Base64 before applying the digest content to which algorithm.
   The output of the
   digital JWS signature is applied.  The resulting signed content taken as a byte array ("S") is prior to the
   Base64url encoding used in JOSE.

   The JWS algorithm MUST NOT be "none" and MUST NOT be any algorithm
   with a JOSE Implementation Requirement of "Prohibited".

4.  Including a Message Signature in a Message

   Message signatures can be included within an HTTP message via the
   "Signature-Input" and "Signature" HTTP fields, both defined within
   this specification.  When attached to a message, an HTTP message
   signature output is identified by a label.  This label MUST be unique within
   a given HTTP message and MUST be used in Section 3.1.

   To verify using this algorithm, both the verifier applies "Signature-Input"
   and "Signature".  The label is chosen by the "RSASSA-PSS-
   VERIFY ((n, e), M, S)" function [RFC8017] using signer, except where a
   specific label is dictated by protocol negotiations.

   An HTTP message signature MUST use both fields containing the public key
   portion of same
   labels: the verification key material ("(n, e)") "Signature" HTTP field contains the signature value,
   while the "Signature-Input" HTTP field identifies the covered
   components and parameters that describe how the signature
   input string ("M") re-created as described in Section 3.2.  The mask
   generation function is "MGF1" as specified in [RFC8017] with a hash
   function of SHA-512 [RFC6234]. was
   generated.  Each field contains labeled values and MAY contain
   multiple labeled values, where the labels determine the correlation
   between the "Signature" and "Signature-Input" fields.

4.1.  The salt length ("sLen") is 64 bytes. 'Signature-Input' HTTP Field

   The hash function ("Hash") SHA-512 [RFC6234] "Signature-Input" HTTP field is applied to the
   signature input string to create a Dictionary Structured Field
   [RFC8941] containing the digest content to which metadata for one or more message signatures
   generated from components within the
   verification function is applied. HTTP message.  Each member
   describes a single message signature.  The verifier extracts member's name is an
   identifier that uniquely identifies the HTTP message signature to be verified ("S") as described in Section 3.2.
   The results within the
   context of the verification function are compared to HTTP message.  The member's value is the http
   message signature to determine if serialization
   of the covered components including all signature presented is valid.

3.3.2.  RSASSA-PKCS1-v1_5 using SHA-256

   To sign metadata
   parameters, using this algorithm, the signer applies serialization process defined in Section 2.3.1.

   NOTE: '\' line wrapping per RFC 8792

   Signature-Input: sig1=("@method" "@target-uri" "host" "date" \
     "cache-control" "x-empty-header" "x-example");created=1618884475\
     ;keyid="test-key-rsa-pss"

   To facilitate signature validation, the "RSASSA-
   PKCS1-V1_5-SIGN (K, M)" function [RFC8017] with "Signature-Input" field value
   MUST contain the signer's private
   signing key ("K") and same serialized value used in generating the
   signature input string ("M") (Section 2.4). string's "@signature-params" value.

   The hash SHA-256 [RFC6234] is applied to signer MAY include the signature input string "Signature-Input" field as a trailer to create the digest
   facilitate signing a message after its content has been processed by
   the signer.  However, since intermediaries are allowed to which drop
   trailers as per [SEMANTICS], it is RECOMMENDED that the digital "Signature-
   Input" HTTP field be included only as a header to avoid signatures
   being inadvertently stripped from a message.

   Multiple "Signature-Input" fields MAY be included in a single HTTP
   message.  The signature is
   applied. labels MUST be unique across all field
   values.

4.2.  The resulting signed content byte array ("S") 'Signature' HTTP Field

   The "Signature" HTTP field is a Dictionary Structured field [RFC8941]
   containing one or more message signatures generated from components
   within the HTTP
   message message.  Each member's name is a signature output used
   identifier that is present as a member name in Section 3.1.

   To verify using this algorithm, the verifier applies the "RSASSA-
   PKCS1-V1_5-VERIFY ((n, e), M, S)" function [RFC8017] using "Signature-Input"
   Structured field within the public
   key portion of HTTP message.  Each member's value is a
   Byte Sequence containing the verification key material ("(n, e)") and signature value for the message
   signature input string ("M") re-created as described identified by the member name.  Any member in Section 3.2. the
   "Signature" HTTP field that does not have a corresponding member in
   the HTTP message's "Signature-Input" HTTP field MUST be ignored.

   NOTE: '\' line wrapping per RFC 8792

   Signature: sig1=:P0wLUszWQjoi54udOtydf9IWTfNhy+r53jGFj9XZuP4uKwxyJo\
     1RSHi+oEF1FuX6O29d+lbxwwBao1BAgadijW+7O/PyezlTnqAOVPWx9GlyntiCiHz\
     C87qmSQjvu1CFyFuWSjdGa3qLYYlNm7pVaJFalQiKWnUaqfT4LyttaXyoyZW84jS8\
     gyarxAiWI97mPXU+OVM64+HVBHmnEsS+lTeIsEQo36T3NFf2CujWARPQg53r58Rmp\
     Z+J9eKR2CD6IJQvacn5A4Ix5BUAVGqlyp8JYm+S/CWJi31PNUjRRCusCVRj05NrxA\
     BNFv3r5S9IXf2fYJK+eyW4AiGVMvMcOg==:

   The hash function SHA-256 [RFC6234] is applied to signer MAY include the signature input
   string "Signature" field as a trailer to create the digest
   facilitate signing a message after its content to which has been processed by
   the verification
   function signer.  However, since intermediaries are allowed to drop
   trailers as per [SEMANTICS], it is applied.  The verifier extracts RECOMMENDED that the "Signature-
   Input" HTTP message
   signature to field be verified ("S") included only as described a header to avoid signatures
   being inadvertently stripped from a message.

   Multiple "Signature" fields MAY be included in Section 3.2. a single HTTP message.
   The
   results of the verification function are compared to the http message signature labels MUST be unique across all field values.

4.3.  Multiple Signatures

   Multiple distinct signatures MAY be included in a single message.
   Since "Signature-Input" and "Signature" are both defined as
   Dictionary Structured fields, they can be used to determine if include multiple
   signatures within the signature presented is valid.

3.3.3.  HMAC using SHA-256

   To sign and verify same HTTP message by using this algorithm, the distinct signature
   labels.  For example, a signer applies the
   "HMAC" function [RFC2104] with the shared may include multiple signatures
   signing key ("K") and the
   signature input string ("text") (Section 2.4).  The hash function
   SHA-256 [RFC6234] is applied same message components with different keys or algorithms
   to support verifiers with different capabilities, or a reverse proxy
   may include information about the signature input string to create client in fields when forwarding
   the digest content request to which the HMAC is applied, giving the signature
   result.

   For signing, the resulting value is the HTTP message a service host, including a signature output
   used in Section 3.1.

   For verification, the verifier extracts over the HTTP message
   client's original signature to
   be verified ("S") as described in Section 3.2. values.

   The output of the
   HMAC function following is compared a non-normative example of header fields a reverse
   proxy sets in addition to the value of examples in the HTTP message signature,
   and previous sections.

   NOTE: '\' line wrapping per RFC 8792

   Forwarded: for=192.0.2.123
   Signature-Input: sig1=("@method" "@path" "@authority" \
       "cache-control" "x-empty-header" "x-example")\
       ;created=1618884475;keyid="test-key-rsa-pss"
   Signature: sig1=:P0wLUszWQjoi54udOtydf9IWTfNhy+r53jGFj9XZuP4uKwxyJo\
       1RSHi+oEF1FuX6O29d+lbxwwBao1BAgadijW+7O/PyezlTnqAOVPWx9GlyntiCi\
       HzC87qmSQjvu1CFyFuWSjdGa3qLYYlNm7pVaJFalQiKWnUaqfT4LyttaXyoyZW8\
       4jS8gyarxAiWI97mPXU+OVM64+HVBHmnEsS+lTeIsEQo36T3NFf2CujWARPQg53\
       r58RmpZ+J9eKR2CD6IJQvacn5A4Ix5BUAVGqlyp8JYm+S/CWJi31PNUjRRCusCV\
       Rj05NrxABNFv3r5S9IXf2fYJK+eyW4AiGVMvMcOg==:

   The client's request includes a signature value under the results of label
   "sig1", which the comparison determine proxy signs in addition to the validity of "Forwarded" header
   defined in [RFC7239].  Note that since the client's signature presented.

3.3.4.  ECDSA using curve P-256 DSS and SHA-256

   To sign using this algorithm, the signer applies already
   covers the "ECDSA"
   algorithm [FIPS186-4] using curve P-256 with client's "Signature-Input" value for "sig1", this value is
   transitively covered by the signer's private
   signing key proxy's signature and the need not be added
   explicitly.  This results in a signature input string (Section 2.4).  The hash
   SHA-256 [RFC6234] is applied of:

   NOTE: '\' line wrapping per RFC 8792

   "signature";key="sig1": :P0wLUszWQjoi54udOtydf9IWTfNhy+r53jGFj9XZuP\
     4uKwxyJo1RSHi+oEF1FuX6O29d+lbxwwBao1BAgadijW+7O/PyezlTnqAOVPWx9Gl\
     yntiCiHzC87qmSQjvu1CFyFuWSjdGa3qLYYlNm7pVaJFalQiKWnUaqfT4LyttaXyo\
     yZW84jS8gyarxAiWI97mPXU+OVM64+HVBHmnEsS+lTeIsEQo36T3NFf2CujWARPQg\
     53r58RmpZ+J9eKR2CD6IJQvacn5A4Ix5BUAVGqlyp8JYm+S/CWJi31PNUjRRCusCV\
     Rj05NrxABNFv3r5S9IXf2fYJK+eyW4AiGVMvMcOg==:
   "forwarded": for=192.0.2.123
   "@signature-params": ("signature";key="sig1" "forwarded")\
     ;created=1618884480;keyid="test-key-rsa";alg="rsa-v1_5-sha256"

   And a signature output value of:

   NOTE: '\' line wrapping per RFC 8792

   cjGvZwbsq9JwexP9TIvdLiivxqLINwp/ybAc19KOSQuLvtmMt3EnZxNiE+797dXK2cj\
   PPUFqoZxO8WWx1SnKhAU9SiXBr99NTXRmA1qGBjqus/1Yxwr8keB8xzFt4inv3J3zP0\
   k6TlLkRJstkVnNjuhRIUA/ZQCo8jDYAl4zWJJjppy6Gd1XSg03iUa0sju1yj6rcKbMA\
   BBuzhUz4G0u1hZkIGbQprCnk/FOsqZHpwaWvY8P3hmcDHkNaavcokmq+3EBDCQTzgwL\
   qfDmV0vLCXtDda6CNO2Zyum/pMGboCnQn/VkQ+j8kSydKoFg6EbVuGbrQijth6I0dDX\
   2/HYcJg==

   These values are added to the HTTP request message by the proxy.  The
   original signature input string to create is included under the digest content to which identifier "sig1", and the digital
   reverse proxy's signature is applied. included under the label "proxy_sig".
   The
   resulting signed content byte array is proxy uses the HTTP message key "test-key-rsa" to create its signature
   output used in Section 3.1.

   To verify using this algorithm,
   the verifier applies "rsa-v1_5-sha256" signature algorithm, while the "ECDSA"
   algorithm [FIPS186-4] client's
   original signature was made using the public key portion id of the
   verification key material "test-key-rsa-pss"
   and the an RSA PSS signature input string re-created
   as described in Section 3.2. algorithm.

   NOTE: '\' line wrapping per RFC 8792

   Forwarded: for=192.0.2.123
   Signature-Input: sig1=("@method" "@path" "@authority" \
       "cache-control" "x-empty-header" "x-example")\
       ;created=1618884475;keyid="test-key-rsa-pss", \
     proxy_sig=("signature";key="sig1" "forwarded")\
       ;created=1618884480;keyid="test-key-rsa";alg="rsa-v1_5-sha256"
   Signature: sig1=:P0wLUszWQjoi54udOtydf9IWTfNhy+r53jGFj9XZuP4uKwxyJo\
       1RSHi+oEF1FuX6O29d+lbxwwBao1BAgadijW+7O/PyezlTnqAOVPWx9GlyntiCi\
       HzC87qmSQjvu1CFyFuWSjdGa3qLYYlNm7pVaJFalQiKWnUaqfT4LyttaXyoyZW8\
       4jS8gyarxAiWI97mPXU+OVM64+HVBHmnEsS+lTeIsEQo36T3NFf2CujWARPQg53\
       r58RmpZ+J9eKR2CD6IJQvacn5A4Ix5BUAVGqlyp8JYm+S/CWJi31PNUjRRCusCV\
       Rj05NrxABNFv3r5S9IXf2fYJK+eyW4AiGVMvMcOg==:, \
     proxy_sig=:cjGvZwbsq9JwexP9TIvdLiivxqLINwp/ybAc19KOSQuLvtmMt3EnZx\
       NiE+797dXK2cjPPUFqoZxO8WWx1SnKhAU9SiXBr99NTXRmA1qGBjqus/1Yxwr8k\
       eB8xzFt4inv3J3zP0k6TlLkRJstkVnNjuhRIUA/ZQCo8jDYAl4zWJJjppy6Gd1X\
       Sg03iUa0sju1yj6rcKbMABBuzhUz4G0u1hZkIGbQprCnk/FOsqZHpwaWvY8P3hm\
       cDHkNaavcokmq+3EBDCQTzgwLqfDmV0vLCXtDda6CNO2Zyum/pMGboCnQn/VkQ+\
       j8kSydKoFg6EbVuGbrQijth6I0dDX2/HYcJg==:

   The hash function SHA-256 [RFC6234] is
   applied to the proxy's signature input string to create the digest content to
   which the verification function is applied.  The verifier extracts and the HTTP message client's original signature to can be
   verified ("S") as described in
   Section 3.2.  The results of independently for the verification function are compared
   to same message, based on the http message signature to determine if needs of
   the application.  Since the proxy's signature presented
   is valid.

3.3.5.  JSON Web Signature (JWS) algorithms

   If covers the signing algorithm is a JOSE signing algorithm from client
   signature, the JSON
   Web Signature and Encryption Algorithms Registry established backend service fronted by
   [RFC7518], the JWS algorithm definition determines proxy can trust that
   the signature and
   hashing algorithms proxy has validated the incoming signature.

5.  Requesting Signatures

   While a signer is free to attach a signature to apply for both signing and verification.  There a request or response
   without prompting, it is no use of the explicit "alg" often desirable for a potential verifier to
   signal that it expects a signature parameter when from a potential signer using JOSE
   signing algorithms.

   For both signing and verification, the HTTP messages
   "Accept-Signature" field.

   The message to which the requested signature input
   string (Section 2.4) is used applied is known as
   the entire "JWS Signing Input".  The
   JOSE Header defined in [RFC7517] is not used, and "target message".  When the signature input
   string "Accept-Signature" field is not first encoded sent in Base64 before applying
   an HTTP Request message, the algorithm.
   The output of field indicates that the JWS signature is taken as a byte array prior client desires
   the server to sign the
   Base64url encoding used in JOSE.

   The JWS algorithm MUST NOT be "none" response using the identified parameters and MUST NOT
   the target message is the response to this request.  All responses
   from resources that support such signature negotiation SHOULD either
   be any algorithm uncacheable or contain a "Vary" header field that lists "Accept-
   Signature", in order to prevent a cache from returning a response
   with a JOSE Implementation Requirement of "Prohibited".

4.  Including signature intended for a Message Signature different request.

   When the "Accept-Signature" field is used in a Message

   Message signatures can be included within an HTTP message via Response
   message, the
   "Signature-Input" field indicates that the server desires the client to
   sign its next request to the server with the identified parameters,
   and "Signature" HTTP header fields, both defined
   within this specification.

   An HTTP the target message signature MUST use both headers: is the "Signature" HTTP
   header client's next request.  The client can
   choose to also continue signing future requests to the same server in
   the same way.

   The target message of an "Accept-Signature" field contains MUST include all
   labeled signatures indicated in the signature value, while "Accept-Header" signature, each
   covering the "Signature-
   Input" HTTP header field identifies same identified components of the covered content and
   parameters "Accept-Signature"
   field.

   The sender of an "Accept-Signature" field MUST include identifiers
   that describe how are appropriate for the signature was generated.  Each
   header MAY contain multiple labeled values, where type of the labels
   determine target message.  For
   example, if the correlation between target message is a response, the "Signature" and "Signature-
   Input" fields.

4.1. identifiers can not
   include the "@status" identifier.

5.1.  The 'Signature-Input' HTTP Header Accept-Signature Field

   The "Signature-Input" "Accept-Signature" HTTP header field is a Dictionary Structured
   Header
   field [RFC8941] containing the metadata for one or more requested
   message signatures to be generated from content within message components of the
   target HTTP message.  Each member describes a single message
   signature.  The member's name is an identifier that uniquely
   identifies the requested message signature within the context of the
   target HTTP message.  The member's value is the serialization of the
   desired covered content components of the target message, including all any
   allowed signature metadata parameters, using the serialization
   process defined in Section 2.3.2.

   Signature-Input: sig1=("@request-target" 2.3.1.

   NOTE: '\' line wrapping per RFC 8792

   Accept-Signature: sig1=("@method" "@target-uri" "host" "date" \
     "cache-control" "x-empty-header" "x-example");created=1618884475\ "x-example")\
     ;keyid="test-key-rsa-pss"

   To facilitate signature validation, the "Signature-Input" header
   value MUST contain the same serialized value used in generating the
   signature input string's "@signature-params" value.

4.2.  The 'Signature' HTTP Header

   The "Signature" HTTP header field is a Dictionary Structured Header
   [RFC8941] containing one or more message signatures generated from
   content within the HTTP message.  Each member's name is a signature
   identifier that is present as a member name in the "Signature-Input"
   Structured Header within the HTTP message.  Each member's value is a
   Byte Sequence containing the signature value for the message
   signature identified by the member name.  Any member in the
   "Signature" HTTP header field that does not have a corresponding
   member in the HTTP message's "Signature-Input" HTTP header field MUST
   be ignored.

   Signature: sig1=:lPxkxqDEPhgrx1yPaKLO7eJ+oPjSwsQ5NjWNRfYP7Jw0FwnK1k\
     8/GH7g5s2q0VTTKVmxyfpUDp/HsDphh5Z7Fa/lvtujHyFe/0EP9z7bnVb7YBZrxV5\
     2LGvP8p4APhOYuG4yaHz478GsJav9BQYK0B2IOHdLFJe8qwWPJs07J47gPewpNwCt\
     0To/zZ2KPpylGX5UHVgJPUom64KjX43u2OwIvSoPEYk4nuBvLR9yxYAHURaTfLoED\
     UCtY1FsU1hOfG3jAlcT6illfnyS72PEdSSzw1KsxroMj9IYpFhva77YxmJRk4pCIW\
     0F0Kj0ukl7J4y2aZJHMCYI3g8yfqh/wQ==:

4.3.  Multiple Signatures

   Since "Signature-Input" and "Signature" are both defined as
   Dictionary Structured Headers, they can be used to include multiple
   signatures within the same HTTP message.  For example, a signer may

   The requested signature MAY include multiple signatures signing the same content with different
   keys or algorithms to support verifiers with different capabilities,
   or parameters, such as a reverse proxy may desired
   algorithm or key identifier.  These parameters MUST NOT include information about the client in header
   fields when forwarding
   parameters that the request signer is expected to a service host, generate, including a
   signature over those fields and the client's original signature.
   "created" and "nonce" parameters.

5.2.  Processing an Accept-Signature

   The following is a non-normative example receiver of an "Accept-Signature" field fulfills that header fields a reverse
   proxy sets in addition to as
   follows:

   1.  Parse the examples in field value as a Dictionary
   2.  For each member of the previous sections. dictionary:

       1.  The
   original signature is included under the identifier "sig1", and name of the
   reverse proxy's signature member is included under "proxy_sig".  The proxy
   uses the key "rsa-test-key" to create its signature using label of the "rsa-
   v1_5-sha256" output signature value.  This results
           as specified in a signature input
   string of:

   "signature";key="sig1": \
     :lPxkxqDEPhgrx1yPaKLO7eJ+oPjSwsQ5NjWNRfYP7Jw0FwnK1k8/GH7g5s2q0VTT\
     KVmxyfpUDp/HsDphh5Z7Fa/lvtujHyFe/0EP9z7bnVb7YBZrxV52LGvP8p4APhOYu\
     G4yaHz478GsJav9BQYK0B2IOHdLFJe8qwWPJs07J47gPewpNwCt0To/zZ2KPpylGX\
     5UHVgJPUom64KjX43u2OwIvSoPEYk4nuBvLR9yxYAHURaTfLoEDUCtY1FsU1hOfG3\
     jAlcT6illfnyS72PEdSSzw1KsxroMj9IYpFhva77YxmJRk4pCIW0F0Kj0ukl7J4y2\
     aZJHMCYI3g8yfqh/wQ==:
   "x-forwarded-for": 192.0.2.123
   "@signature-params": ("signature";key="sig1" "x-forwarded-for")\
     ;created=1618884480;keyid="test-key-rsa";alg="rsa-v1_5-sha256"

   And a signature output Section 4.1

       2.  Parse the value of:

   XD1O/vEh772WVpY7jYvReXop2+b7xTIIPKH8/OCYzPn78Wd9jodCwAJPF5TYCn9L6n6\
   8j4EjGsqFOMkVLVdSQEZqMLjEbvMEdIe8m1a0CLd5kydeaAwoHoglqod6ijkwhhEtxt\
   aD8tDZmihQw2mZEH8u4aMSnRntqy7ExCNld0JLharsHV0iCbRO9jIP+d2ApD7gB+eZp\
   n3pIvvVJZlxTwPkahFpxKlQtNMPaSqa1lvejURx+ST8CEuz4sS+G/oLJiX3MZenuUoO\
   R8HeOHDnjN/VLzrEN4x44iF7WIL+iY2PtK87LUWRAsJAX9GqHL/upsGh1nxIdoVaoLV\
   V5w+fRw==

   These values are added of the member to obtain the HTTP request message by set of covered
           component identifiers

       3.  Process the proxy.  The
   different signature values are wrapped onto separate lines requested parameters, such as the signing
           algorithm and key material.  If any requested parameters
           cannot be fulfilled, or if the requested parameters conflict
           with those deemed appropriate to
   increase human-readability of the result.

   X-Forwarded-For: 192.0.2.123
   Signature-Input: sig1=("@request-target" "host" "date" \
       "cache-control" "x-empty-header" "x-example")\
       ;created=1618884475;keyid="test-key-rsa-pss", \
     proxy_sig=("signature";key="sig1" "x-forwarded-for")\
       ;created=1618884480;keyid="test-key-rsa";alg="rsa-v1_5-sha256"
   Signature: sig1=:lPxkxqDEPhgrx1yPaKLO7eJ+oPjSwsQ5NjWNRfYP7Jw0FwnK1k\
       8/GH7g5s2q0VTTKVmxyfpUDp/HsDphh5Z7Fa/lvtujHyFe/0EP9z7bnVb7YBZrx\
       V52LGvP8p4APhOYuG4yaHz478GsJav9BQYK0B2IOHdLFJe8qwWPJs07J47gPewp\
       NwCt0To/zZ2KPpylGX5UHVgJPUom64KjX43u2OwIvSoPEYk4nuBvLR9yxYAHURa\
       TfLoEDUCtY1FsU1hOfG3jAlcT6illfnyS72PEdSSzw1KsxroMj9IYpFhva77Yxm\
       JRk4pCIW0F0Kj0ukl7J4y2aZJHMCYI3g8yfqh/wQ==:, \
     proxy_sig=:XD1O/vEh772WVpY7jYvReXop2+b7xTIIPKH8/OCYzPn78Wd9jodCwA\
       JPF5TYCn9L6n68j4EjGsqFOMkVLVdSQEZqMLjEbvMEdIe8m1a0CLd5kydeaAwoH\
       oglqod6ijkwhhEtxtaD8tDZmihQw2mZEH8u4aMSnRntqy7ExCNld0JLharsHV0i\
       CbRO9jIP+d2ApD7gB+eZpn3pIvvVJZlxTwPkahFpxKlQtNMPaSqa1lvejURx+ST\
       8CEuz4sS+G/oLJiX3MZenuUoOR8HeOHDnjN/VLzrEN4x44iF7WIL+iY2PtK87LU\
       WRAsJAX9GqHL/upsGh1nxIdoVaoLVV5w+fRw==:

   The proxy's target message, the
           process fails and returns an error.

       4.  Select any additional parameters necessary for completing the
           signature

       5.  Create the "Signature-Input" and "Signature" header values
           and associate them with the label

   3.  Optionally create any additional "Signature-Input" and
       "Signature" values, with unique labels not found in the "Accept-
       Signature" field

   4.  Combine all labeled "Signature-Input" and "Signature" values and
       attach both headers to the client's original target message

   Note that by this process, a signature can be
   verified independently for applied to a target message
   MUST have the same message, depending on label, MUST have the needs same set of covered
   component, and MAY have additional parameters.  Also note that the application.

5.
   target message MAY include additional signatures not specified by the
   "Accept-Signature" field.

6.  IANA Considerations

5.1.

6.1.  HTTP Signature Algorithms Registry

   This document defines HTTP Signature Algorithms, for which IANA is
   asked to create and maintain a new registry titled "HTTP Signature
   Algorithms".  Initial values for this registry are given in
   Section 5.1.2. 6.1.2.  Future assignments and modifications to existing
   assignment are to be made through the Expert Review registration
   policy [RFC8126] and shall follow the template presented in
   Section 5.1.1. 6.1.1.

   Algorithms referenced by algorithm identifiers have to be fully
   defined with all parameters fixed.  Algorithm identifiers in this
   registry are to be interpreted as whole string values and not as a
   combination of parts.  That is to say, it is expected that
   implementors understand "rsa-pss-sha512" as referring to one specific
   algorithm with its hash, mask, and salt values set as defined here.
   Implementors do not parse out the "rsa", "pss", and "sha512" portions
   of the identifier to determine parameters of the signing algorithm
   from the string.

5.1.1.

6.1.1.  Registration Template

   Algorithm Name:
      An identifier for the HTTP Signature Algorithm.  The name MUST be
      an ASCII string consisting only of lower-case characters (""a"" -
      ""z""), digits (""0"" - ""9""), and hyphens (""-""), and SHOULD
      NOT exceed 20 characters in length.  The identifier MUST be unique
      within the context of the registry.

   Status:
      A brief text description of the status of the algorithm.  The
      description MUST begin with one of "Active" or "Deprecated", and
      MAY provide further context or explanation as to the reason for
      the status.

   Description:
      A brief description of the algorithm used to sign the signature
      input string.

   Specification document(s):
      Reference to the document(s) that specify the token endpoint
      authorization method, preferably including a URI that can be used
      to retrieve a copy of the document(s).  An indication of the
      relevant sections may also be included but is not required.

5.1.2.

6.1.2.  Initial Contents

5.1.2.1.

6.1.2.1.  rsa-pss-sha512

   Algorithm Name:
      "rsa-pss-sha512"

   Status:
      Active

   Definition:
      RSASSA-PSS using SHA-256

   Specification document(s):
      [[This document]], Section 3.3.1

5.1.2.2.

6.1.2.2.  rsa-v1_5-sha256

   Algorithm Name:
      "rsa-v1_5-sha256"

   Status:
      Active

   Description:
      RSASSA-PKCS1-v1_5 using SHA-256

   Specification document(s):
      [[This document]], Section 3.3.2

5.1.2.3.

6.1.2.3.  hmac-sha256

   Algorithm Name:
      "hmac-sha256"

   Status:
      Active

   Description:
      HMAC using SHA-256

   Specification document(s):
      [[This document]], Section 3.3.3

5.1.2.4.

6.1.2.4.  ecdsa-p256-sha256

   Algorithm Name:
      "ecdsa-p256-sha256"

   Status:
      Active

   Description:
      ECDSA using curve P-256 DSS and SHA-256

   Specification document(s):
      [[This document]], Section 3.3.4

5.2.

6.2.  HTTP Signature Metadata Parameters Registry

   This document defines the "Signature-Input" Structured Header, whose
   member signature parameters structure, the values
   of which may have parameters containing metadata about a message
   signature.  IANA is asked to create and maintain a new registry
   titled "HTTP Signature Metadata Parameters" to record and maintain
   the set of parameters defined for use with member values in the
   "Signature-Input" Structured Header.
   signature parameters structure.  Initial values for this registry are
   given in Section 5.2.2. 6.2.2.  Future assignments and modifications to
   existing assignments are to be made through the Expert Review
   registration policy [RFC8126] and shall follow the template presented
   in Section 5.2.1.

5.2.1. 6.2.1.

6.2.1.  Registration Template
5.2.2.

6.2.2.  Initial Contents

   The table below contains the initial contents of the HTTP Signature
   Metadata Parameters Registry.  Each row in the table represents a
   distinct entry in the registry.

           +=========+========+================================+
           | Name    | Status | Reference(s)                   |
           +=========+========+================================+
           | alg     | Active | Section 2.3.2 2.3.1 of this document |
           +---------+--------+--------------------------------+
           | created | Active | Section 2.3.2 2.3.1 of this document |
           +---------+--------+--------------------------------+
           | expires | Active | Section 2.3.2 2.3.1 of this document |
           +---------+--------+--------------------------------+
           | keyid   | Active | Section 2.3.2 2.3.1 of this document |
           +---------+--------+--------------------------------+
           | nonce   | Active | Section 2.3.2 2.3.1 of this document |
           +---------+--------+--------------------------------+

              Table 4: 3: Initial contents of the HTTP Signature
                       Metadata Parameters Registry.

5.3.

6.3.  HTTP Signature Specialty Content Component Identifiers Registry

   This document defines a method for canonicalizing HTTP message
   content,
   components, including content components that can be generated from the
   context of the HTTP message outside of the HTTP headers.  This content is fields.  These
   components are identified by a unique key. string, known as the component
   identifier.  IANA is asked to create and maintain a new registry
   typed "HTTP Signature Specialty Content Component Identifiers" to record and
   maintain the set of non-header content non-field component identifiers and the methods
   to produce their canonicalization method. associated component values.  Initial values for
   this registry are given in Section 5.3.2. 6.3.2.  Future assignments and
   modifications to existing assignments are to be made through the
   Expert Review registration policy [RFC8126] and shall follow the
   template presented in Section 5.3.1.

5.3.1. 6.3.1.

6.3.1.  Registration Template

5.3.2.

6.3.2.  Initial Contents

   The table below contains the initial contents of the HTTP Signature
   Specialty Content Component Identifiers Registry.

      +===================+========+================================+

   +===================+========+===================+==================+
   | Name              | Status | Target            | Reference        |
   +===================+========+===================+==================+
   | @signature-params | Active | Request,          | Section 2.3.1 of |
   |                   |        | Response          | this document    |
   +-------------------+--------+-------------------+------------------+
   | @method           | Active | Request,          | Section 2.3.2 of |
   |                   |        | Related-Response  | this document    |
   +-------------------+--------+-------------------+------------------+
   | @authority        | Active | Request,          | Section 2.3.4 of |
   |                   |        | Related-Response  | this document    |
   +-------------------+--------+-------------------+------------------+
   | @scheme           | Active | Request,          | Section 2.3.5 of |
   |                   |        | Related-Response  | this document    |
   +-------------------+--------+-------------------+------------------+
   | @target-uri       | Active | Request,          | Section 2.3.3 of |
   |                   |        | Related-Response  | this document    |
   +-------------------+--------+-------------------+------------------+
   | @request-target   | Active | Request,          | Section 2.3.6 of |
   |                   |        | Related-Response  | this document    |
   +-------------------+--------+-------------------+------------------+
   | @path             | Active | Request,          | Section 2.3.7 of |
   |                   |        | Related-Response  | this document    |
   +-------------------+--------+-------------------+------------------+
   | @query            | Active | Request,          | Section 2.3.8 of |
   |                   |        | Related-Response  | this document    |
   +-------------------+--------+-------------------+------------------+
   | @query-params     | Active | Request,          | Name Section 2.3.9 of | Status
   | Reference(s)                   |
      +===================+========+================================+        | @request-target Related-Response  | this document    |
   +-------------------+--------+-------------------+------------------+
   | @status           | Active | Response          | Section 2.3.1 2.3.10   |
   |                   |        |                   | of this document |
      +-------------------+--------+--------------------------------+
   +-------------------+--------+-------------------+------------------+
   | @signature-params @request-response | Active | Section 2.3.2 2.3.11    |                  |
   |                   |        | of this document  |
      +-------------------+--------+--------------------------------+                  |
   +-------------------+--------+-------------------+------------------+

    Table 5: 4: Initial contents of the HTTP Signature Specialty
                       Content Component
                           Identifiers Registry.

6.

7.  Security Considerations

   (( TODO: need to dive deeper on this section; not sure how much of
   what's referenced below is actually applicable, or if it covers
   everything we need to worry about. ))

   (( TODO: Should provide some recommendations on how to determine what
   content needs
   components need to be signed for a given use case. ))
   There are a number of security considerations to take into account
   when implementing or utilizing this specification.  A thorough
   security analysis of this protocol, including its strengths and
   weaknesses, can be found in [WP-HTTP-Sig-Audit].

7.

8.  References

7.1.

8.1.  Normative References

   [FIPS186-4]
              "Digital Signature Standard (DSS)", 2013,
              <https://csrc.nist.gov/publications/detail/fips/186/4/
              final>.

   [HTTP2]    Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
              DOI 10.17487/RFC7540, May 2015,
              <https://www.rfc-editor.org/rfc/rfc7540>.

   [HTMLURL]  "URL (Living Standard)", 2021,
              <https://url.spec.whatwg.org/>.

   [MESSAGING]
              Fielding, R., Ed. R. T., Nottingham, M., and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,
              <https://www.rfc-editor.org/rfc/rfc7230>.
              "HTTP/1.1", Work in Progress, Internet-Draft, draft-ietf-
              httpbis-messaging-17, 25 July 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
              messaging-17>.

   [POSIX.1]  "The Open Group Base Specifications Issue 7, 2018
              edition", 2018,
              <https://pubs.opengroup.org/onlinepubs/9699919799/>.

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104,
              DOI 10.17487/RFC2104, February 1997,
              <https://www.rfc-editor.org/rfc/rfc2104>.

   [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/rfc/rfc2119>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/rfc/rfc3986>.

   [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/rfc/rfc8174>.

   [RFC8792]  Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
              "Handling Long Lines in Content of Internet-Drafts and
              RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
              <https://www.rfc-editor.org/rfc/rfc8792>.

   [RFC8941]  Nottingham, M. and P-H. Kamp, "Structured Field Values for
              HTTP", RFC 8941, DOI 10.17487/RFC8941, February 2021,
              <https://www.rfc-editor.org/rfc/rfc8941>.

   [SEMANTICS]
              Fielding, R., Ed. R. T., Nottingham, M., 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/rfc/rfc7231>.

7.2. "HTTP
              Semantics", Work in Progress, Internet-Draft, draft-ietf-
              httpbis-semantics-17, 25 July 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
              semantics-17>.

8.2.  Informative References

   [I-D.ietf-httpbis-client-cert-field]
              Campbell, B. and M. Bishop, "Client-Cert HTTP Header
              Field: Conveying Client Certificate Information from TLS
              Terminating Reverse Proxies to Origin Server
              Applications", Work in Progress, Internet-Draft, draft-
              ietf-httpbis-client-cert-field-00, 8 June 2021,
              <https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
              client-cert-field-00>.

   [RFC6234]  Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
              (SHA and SHA-based HMAC and HKDF)", RFC 6234,
              DOI 10.17487/RFC6234, May 2011,
              <https://www.rfc-editor.org/rfc/rfc6234>.

   [RFC7239]  Petersson, A. and M. Nilsson, "Forwarded HTTP Extension",
              RFC 7239, DOI 10.17487/RFC7239, June 2014,
              <https://www.rfc-editor.org/rfc/rfc7239>.

   [RFC7517]  Jones, M., "JSON Web Key (JWK)", RFC 7517,
              DOI 10.17487/RFC7517, May 2015,
              <https://www.rfc-editor.org/rfc/rfc7517>.

   [RFC7518]  Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
              DOI 10.17487/RFC7518, May 2015,
              <https://www.rfc-editor.org/rfc/rfc7518>.

   [RFC8017]  Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch,
              "PKCS #1: RSA Cryptography Specifications Version 2.2",
              RFC 8017, DOI 10.17487/RFC8017, November 2016,
              <https://www.rfc-editor.org/rfc/rfc8017>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/rfc/rfc8126>.

   [TLS]      Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/rfc/rfc8446>.

   [WP-HTTP-Sig-Audit]
              "Security Considerations for HTTP Signatures", 2013,
              <https://web-payments.org/specs/source/http-signatures-
              audit/>.

Appendix A.  Detecting HTTP Message Signatures

   There have been many attempts to create signed HTTP messages in the
   past, including other non-standard definitions of the "Signature"
   header
   field used within this specification.  It is recommended that
   developers wishing to support both this specification and other
   historical drafts do so carefully and deliberately, as
   incompatibilities between this specification and various versions of
   other drafts could lead to unexpected problems.

   It is recommended that implementers first detect and validate the
   "Signature-Input" header field defined in this specification to detect that
   this standard is in use and not an alternative.  If the "Signature-
   Input" header field is present, all "Signature" headers fields can be parsed and
   interpreted in the context of this draft.

Appendix B.  Examples

B.1.  Example Keys

   This section provides cryptographic keys that are referenced in
   example signatures throughout this document.  These keys MUST NOT be
   used for any purpose other than testing.

   The key identifiers for each key are used throughout the examples in
   this specification.  It is assumed for these examples that the signer
   and verifier can unambiguously dereference all key identifiers used
   here, and that the keys and algorithms used are appropriate for the
   context in which the signature is presented.

B.1.1.  Example Key RSA test

   The following key is a 2048-bit RSA public and private key pair,
   referred to in this document as "test-key-rsa":

   -----BEGIN RSA PUBLIC KEY-----
   MIIBCgKCAQEAhAKYdtoeoy8zcAcR874L8cnZxKzAGwd7v36APp7Pv6Q2jdsPBRrw
   WEBnez6d0UDKDwGbc6nxfEXAy5mbhgajzrw3MOEt8uA5txSKobBpKDeBLOsdJKFq
   MGmXCQvEG7YemcxDTRPxAleIAgYYRjTSd/QBwVW9OwNFhekro3RtlinV0a75jfZg
   kne/YiktSvLG34lw2zqXBDTC5NHROUqGTlML4PlNZS5Ri2U4aCNx2rUPRcKIlE0P
   uKxI4T+HIaFpv8+rdV6eUgOrB2xeI1dSFFn/nnv5OoZJEIB+VmuKn3DCUcCZSFlQ
   PSXSfBDiUGhwOw76WuSSsf1D4b/vLoJ10wIDAQAB
   -----END RSA PUBLIC KEY-----

   -----BEGIN RSA PRIVATE KEY-----
   MIIEqAIBAAKCAQEAhAKYdtoeoy8zcAcR874L8cnZxKzAGwd7v36APp7Pv6Q2jdsP
   BRrwWEBnez6d0UDKDwGbc6nxfEXAy5mbhgajzrw3MOEt8uA5txSKobBpKDeBLOsd
   JKFqMGmXCQvEG7YemcxDTRPxAleIAgYYRjTSd/QBwVW9OwNFhekro3RtlinV0a75
   jfZgkne/YiktSvLG34lw2zqXBDTC5NHROUqGTlML4PlNZS5Ri2U4aCNx2rUPRcKI
   lE0PuKxI4T+HIaFpv8+rdV6eUgOrB2xeI1dSFFn/nnv5OoZJEIB+VmuKn3DCUcCZ
   SFlQPSXSfBDiUGhwOw76WuSSsf1D4b/vLoJ10wIDAQABAoIBAG/JZuSWdoVHbi56
   vjgCgkjg3lkO1KrO3nrdm6nrgA9P9qaPjxuKoWaKO1cBQlE1pSWp/cKncYgD5WxE
   CpAnRUXG2pG4zdkzCYzAh1i+c34L6oZoHsirK6oNcEnHveydfzJL5934egm6p8DW
   +m1RQ70yUt4uRc0YSor+q1LGJvGQHReF0WmJBZHrhz5e63Pq7lE0gIwuBqL8SMaA
   yRXtK+JGxZpImTq+NHvEWWCu09SCq0r838ceQI55SvzmTkwqtC+8AT2zFviMZkKR
   Qo6SPsrqItxZWRty2izawTF0Bf5S2VAx7O+6t3wBsQ1sLptoSgX3QblELY5asI0J
   YFz7LJECgYkAsqeUJmqXE3LP8tYoIjMIAKiTm9o6psPlc8CrLI9CH0UbuaA2JCOM
   cCNq8SyYbTqgnWlB9ZfcAm/cFpA8tYci9m5vYK8HNxQr+8FS3Qo8N9RJ8d0U5Csw
   DzMYfRghAfUGwmlWj5hp1pQzAuhwbOXFtxKHVsMPhz1IBtF9Y8jvgqgYHLbmyiu1
   mwJ5AL0pYF0G7x81prlARURwHo0Yf52kEw1dxpx+JXER7hQRWQki5/NsUEtv+8RT
   qn2m6qte5DXLyn83b1qRscSdnCCwKtKWUug5q2ZbwVOCJCtmRwmnP131lWRYfj67
   B/xJ1ZA6X3GEf4sNReNAtaucPEelgR2nsN0gKQKBiGoqHWbK1qYvBxX2X3kbPDkv
   9C+celgZd2PW7aGYLCHq7nPbmfDV0yHcWjOhXZ8jRMjmANVR/eLQ2EfsRLdW69bn
   f3ZD7JS1fwGnO3exGmHO3HZG+6AvberKYVYNHahNFEw5TsAcQWDLRpkGybBcxqZo
   81YCqlqidwfeO5YtlO7etx1xLyqa2NsCeG9A86UjG+aeNnXEIDk1PDK+EuiThIUa
   /2IxKzJKWl1BKr2d4xAfR0ZnEYuRrbeDQYgTImOlfW6/GuYIxKYgEKCFHFqJATAG
   IxHrq1PDOiSwXd2GmVVYyEmhZnbcp8CxaEMQoevxAta0ssMK3w6UsDtvUvYvF22m
   qQKBiD5GwESzsFPy3Ga0MvZpn3D6EJQLgsnrtUPZx+z2Ep2x0xc5orneB5fGyF1P
   WtP+fG5Q6Dpdz3LRfm+KwBCWFKQjg7uTxcjerhBWEYPmEMKYwTJF5PBG9/ddvHLQ
   EQeNC8fHGg4UXU8mhHnSBt3EA10qQJfRDs15M38eG2cYwB1PZpDHScDnDA0=
   -----END RSA PRIVATE KEY-----

B.1.2.  Example RSA PSS Key

   The following key is a 2048-bit RSA public and private key pair,
   referred to in this document as "test-key-rsa-pss":

   -----BEGIN PUBLIC KEY-----
   MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAr4tmm3r20Wd/PbqvP1s2
   +QEtvpuRaV8Yq40gjUR8y2Rjxa6dpG2GXHbPfvMs8ct+Lh1GH45x28Rw3Ry53mm+
   oAXjyQ86OnDkZ5N8lYbggD4O3w6M6pAvLkhk95AndTrifbIFPNU8PPMO7OyrFAHq
   gDsznjPFmTOtCEcN2Z1FpWgchwuYLPL+Wokqltd11nqqzi+bJ9cvSKADYdUAAN5W
   Utzdpiy6LbTgSxP7ociU4Tn0g5I6aDZJ7A8Lzo0KSyZYoA485mqcO0GVAdVw9lq4
   aOT9v6d+nb4bnNkQVklLQ3fVAvJm+xdDOp9LCNCN48V2pnDOkFV6+U9nV5oyc6XI
   2wIDAQAB
   -----END PUBLIC KEY-----

   -----BEGIN PRIVATE KEY-----
   MIIEvgIBADALBgkqhkiG9w0BAQoEggSqMIIEpgIBAAKCAQEAr4tmm3r20Wd/Pbqv
   P1s2+QEtvpuRaV8Yq40gjUR8y2Rjxa6dpG2GXHbPfvMs8ct+Lh1GH45x28Rw3Ry5
   3mm+oAXjyQ86OnDkZ5N8lYbggD4O3w6M6pAvLkhk95AndTrifbIFPNU8PPMO7Oyr
   FAHqgDsznjPFmTOtCEcN2Z1FpWgchwuYLPL+Wokqltd11nqqzi+bJ9cvSKADYdUA
   AN5WUtzdpiy6LbTgSxP7ociU4Tn0g5I6aDZJ7A8Lzo0KSyZYoA485mqcO0GVAdVw
   9lq4aOT9v6d+nb4bnNkQVklLQ3fVAvJm+xdDOp9LCNCN48V2pnDOkFV6+U9nV5oy
   c6XI2wIDAQABAoIBAQCUB8ip+kJiiZVKF8AqfB/aUP0jTAqOQewK1kKJ/iQCXBCq
   pbo360gvdt05H5VZ/RDVkEgO2k73VSsbulqezKs8RFs2tEmU+JgTI9MeQJPWcP6X
   aKy6LIYs0E2cWgp8GADgoBs8llBq0UhX0KffglIeek3n7Z6Gt4YFge2TAcW2WbN4
   XfK7lupFyo6HHyWRiYHMMARQXLJeOSdTn5aMBP0PO4bQyk5ORxTUSeOciPJUFktQ
   HkvGbym7KryEfwH8Tks0L7WhzyP60PL3xS9FNOJi9m+zztwYIXGDQuKM2GDsITeD
   2mI2oHoPMyAD0wdI7BwSVW18p1h+jgfc4dlexKYRAoGBAOVfuiEiOchGghV5vn5N
   RDNscAFnpHj1QgMr6/UG05RTgmcLfVsI1I4bSkbrIuVKviGGf7atlkROALOG/xRx
   DLadgBEeNyHL5lz6ihQaFJLVQ0u3U4SB67J0YtVO3R6lXcIjBDHuY8SjYJ7Ci6Z6
   vuDcoaEujnlrtUhaMxvSfcUJAoGBAMPsCHXte1uWNAqYad2WdLjPDlKtQJK1diCm
   rqmB2g8QE99hDOHItjDBEdpyFBKOIP+NpVtM2KLhRajjcL9Ph8jrID6XUqikQuVi
   4J9FV2m42jXMuioTT13idAILanYg8D3idvy/3isDVkON0X3UAVKrgMEne0hJpkPL
   FYqgetvDAoGBAKLQ6JZMbSe0pPIJkSamQhsehgL5Rs51iX4m1z7+sYFAJfhvN3Q/
   OGIHDRp6HjMUcxHpHw7U+S1TETxePwKLnLKj6hw8jnX2/nZRgWHzgVcY+sPsReRx
   NJVf+Cfh6yOtznfX00p+JWOXdSY8glSSHJwRAMog+hFGW1AYdt7w80XBAoGBAImR
   NUugqapgaEA8TrFxkJmngXYaAqpA0iYRA7kv3S4QavPBUGtFJHBNULzitydkNtVZ
   3w6hgce0h9YThTo/nKc+OZDZbgfN9s7cQ75x0PQCAO4fx2P91Q+mDzDUVTeG30mE
   t2m3S0dGe47JiJxifV9P3wNBNrZGSIF3mrORBVNDAoGBAI0QKn2Iv7Sgo4T/XjND
   dl2kZTXqGAk8dOhpUiw/HdM3OGWbhHj2NdCzBliOmPyQtAr770GITWvbAI+IRYyF
   S7Fnk6ZVVVHsxjtaHy1uJGFlaZzKR4AGNaUTOJMs6NadzCmGPAxNQQOCqoUjn4XR
   rOjr9w349JooGXhOxbu8nOxX
   -----END PRIVATE KEY-----

B.1.3.  Example ECC P-256 Test Key

   The following key is an elliptical curve key over the curve P-256,
   referred to in this document as "test-key-ecc-p256".

   -----BEGIN EC PRIVATE KEY-----
   MHcCAQEEIFKbhfNZfpDsW43+0+JjUr9K+bTeuxopu653+hBaXGA7oAoGCCqGSM49
   AwEHoUQDQgAEqIVYZVLCrPZHGHjP17CTW0/+D9Lfw0EkjqF7xB4FivAxzic30tMM
   4GF+hR6Dxh71Z50VGGdldkkDXZCnTNnoXQ==
   -----END EC PRIVATE KEY-----

   -----BEGIN PUBLIC KEY-----
   MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEqIVYZVLCrPZHGHjP17CTW0/+D9Lf
   w0EkjqF7xB4FivAxzic30tMM4GF+hR6Dxh71Z50VGGdldkkDXZCnTNnoXQ==
   -----END PUBLIC KEY-----

B.1.4.  Example Shared Secret

   The following shared secret is 64 randomly-generated bytes encoded in
   Base64, referred to in this document as "test-shared-secret".

   NOTE: '\' line wrapping per RFC 8792

   uzvJfB4u3N0Jy4T7NZ75MDVcr8zSTInedJtkgcu46YW4XByzNJjxBdtjUkdJPBt\
     bmHhIDi6pcl8jsasjlTMtDQ==

B.2.  Test Cases

   This section provides non-normative examples that may may be used as test
   cases to validate implementation correctness.  These examples are
   based on the following HTTP messages:

   For requests, this "test-request" message is used:

   POST /foo?param=value&pet=dog HTTP/1.1
   Host: example.com
   Date: Tue, 20 Apr 2021 02:07:55 GMT
   Content-Type: application/json
   Digest: SHA-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
   Content-Length: 18

   {"hello": "world"}

   For responses, this "test-response" message is used:

   HTTP/1.1 200 OK
   Date: Tue, 20 Apr 2021 02:07:56 GMT
   Content-Type: application/json
   Digest: SHA-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
   Content-Length: 18

   {"hello": "world"}

B.2.1.  Minimal Signature Using rsa-pss-sha512

   This example presents a minimal "Signature-Input" and "Signature"
   header for a signature using the "rsa-pss-sha512" algorithm over
   "test-request", covering none of the components of the HTTP message
   request but providing a timestamped signature proof of possession of
   the key.

   The corresponding signature input is:

   NOTE: '\' line wrapping per RFC 8792

   "@signature-params": ();created=1618884475\
     ;keyid="test-key-rsa-pss";alg="rsa-pss-sha512"

   This results in the following "Signature-Input" and "Signature"
   headers being added to the message:

   NOTE: '\' line wrapping per RFC 8792

   Signature-Input: sig1=();created=1618884475\
     ;keyid="test-key-rsa-pss";alg="rsa-pss-sha512"
   Signature: sig1=:HWP69ZNiom9Obu1KIdqPPcu/C1a5ZUMBbqS/xwJECV8bhIQVmE\
     AAAzz8LQPvtP1iFSxxluDO1KE9b8L+O64LEOvhwYdDctV5+E39Jy1eJiD7nYREBgx\
     TpdUfzTO+Trath0vZdTylFlxK4H3l3s/cuFhnOCxmFYgEa+cw+StBRgY1JtafSFwN\
     cZgLxVwialuH5VnqJS4JN8PHD91XLfkjMscTo4jmVMpFd3iLVe0hqVFl7MDt6TMkw\
     IyVFnEZ7B/VIQofdShO+C/7MuupCSLVjQz5xA+Zs6Hw+W9ESD/6BuGs6LF1TcKLxW\
     +5K+2zvDY/Cia34HNpRW5io7Iv9/b7iQ==:

   Note that since the covered components list is empty, this signature
   could be used as test
   cases applied by an attacker to validate implementation correctness.  These examples are
   based on the following an unrelated HTTP messages:

   For requests, this "test-request" message message.
   Therefore, use of an empty covered components set is used:

   POST /foo?param=value&pet=dog HTTP/1.1
   Host: discouraged.

B.2.2.  Selective Covered Components using rsa-pss-sha512

   This example covers additional components in "test-request" using the
   "rsa-pss-sha512" algorithm.

   The corresponding signature input is:

   NOTE: '\' line wrapping per RFC 8792

   "@authority": example.com
   Date: Tue, 20 Apr 2021 02:07:55 GMT
   Content-Type:
   "content-type": application/json
   Digest: SHA-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
   Content-Length: 18

   {"hello": "world"}

   For responses, this "test-response"
   "@signature-params": ("@authority" "content-type")\
     ;created=1618884475;keyid="test-key-rsa-pss"

   This results in the following "Signature-Input" and "Signature"
   headers being added to the message:

   NOTE: '\' line wrapping per RFC 8792

   Signature-Input: sig1=("@authority" "content-type")\
     ;created=1618884475;keyid="test-key-rsa-pss"
   Signature: sig1=:ik+OtGmM/kFqENDf9Plm8AmPtqtC7C9a+zYSaxr58b/E6h81gh\
     JS3PcH+m1asiMp8yvccnO/RfaexnqanVB3C72WRNZN7skPTJmUVmoIeqZncdP2mlf\
     xlLP6UbkrgYsk91NS6nwkKC6RRgLhBFqzP42oq8D2336OiQPDAo/04SxZt4Wx9nDG\
     uy2SfZJUhsJqZyEWRk4204x7YEB3VxDAAlVgGt8ewilWbIKKTOKp3ymUeQIwptqYw\
     v0l8mN404PPzRBTpB7+HpClyK4CNp+SVv46+6sHMfJU4taz10s/NoYRmYCGXyadzY\
     YDj0BYnFdERB6NblI/AOWFGl5Axhhmjg==:

B.2.3.  Full Coverage using rsa-pss-sha512

   This example covers all headers in "test-request" (including the
   message is used:

   HTTP/1.1 200 OK
   Date: body "Digest") plus various elements of the control data,
   using the "rsa-pss-sha512" algorithm.

   The corresponding signature input is:

   NOTE: '\' line wrapping per RFC 8792

   "date": Tue, 20 Apr 2021 02:07:56 GMT
   Content-Type:
   "@method": POST
   "@path": /foo
   "@query": ?param=value&pet=dog
   "@authority": example.com
   "content-type": application/json
   Digest:
   "digest": SHA-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
   Content-Length:
   "content-length": 18

   {"hello": "world"}

B.2.1.  Minimal Signature Header using rsa-pss-sha512
   "@signature-params": ("date" "@method" "@path" "@query" \
     "@authority" "content-type" "digest" "content-length")\
     ;created=1618884475;keyid="test-key-rsa-pss"

   This example presents a minimal results in the following "Signature-Input" and "Signature"
   headers being added to the message:

   NOTE: '\' line wrapping per RFC 8792

   Signature-Input: sig1=("date" "@method" "@path" "@query" \
     "@authority" "content-type" "digest" "content-length")\
     ;created=1618884475;keyid="test-key-rsa-pss"
   Signature: sig1=:JuJnJMFGD4HMysAGsfOY6N5ZTZUknsQUdClNG51VezDgPUOW03\
     QMe74vbIdndKwW1BBrHOHR3NzKGYZJ7X3ur23FMCdANe4VmKb3Rc1Q/5YxOO8p7Ko\
     yfVa4uUcMk5jB9KAn1M1MbgBnqwZkRWsbv8ocCqrnD85Kavr73lx51k1/gU8w673W\
     T/oBtxPtAn1eFjUyIKyA+XD7kYph82I+ahvm0pSgDPagu917SlqUjeaQaNnlZzO03\
     Iy1RZ5XpgbNeDLCqSLuZFVID80EohC2CQ1cL5svjslrlCNstd2JCLmhjL7xV3NYXe\
     rLim4bqUQGRgDwNJRnqobpS6C1NBns/Q==:

   Note in this example that the value of the "Date" header for a and the
   value of the "created" signature using parameter need not be the same.
   This is due to the fact that the "Date" header is added when creating
   the HTTP Message and the "created" parameter is populated when
   creating the signature over that message, and these two times could
   vary.  If the "rsa-pss-sha512" algorithm over
   "test-request", covering none of "Date" header is covered by the content signature, it is up to
   the verifier to determine whether its value has to match that of the HTTP message
   request but providing
   "created" parameter or not.

B.2.4.  Signing a timestamped signature proof of possession Response using ecdsa-p256-sha256

   This example covers portions of the key. "test-response" response message
   using the "ecdsa-p256-sha256" algorithm and the key "test-key-ecc-
   p256".

   The corresponding signature input is:

   NOTE: '\' line wrapping per RFC 8792

   "content-type": application/json
   "digest": SHA-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
   "content-length": 18
   "@signature-params": ();created=1618884475\
     ;keyid="test-key-rsa-pss";alg="rsa-pss-sha512" ("content-type" "digest" "content-length")\
     ;created=1618884475;keyid="test-key-ecc-p256"

   This results in the following "Signature-Input" and "Signature"
   headers being added to the message:

   NOTE: '\' line wrapping per RFC 8792

   Signature-Input: sig1=();created=1618884475\
     ;keyid="test-key-rsa-pss";alg="rsa-pss-sha512" sig1=("content-type" "digest" "content-length")\
     ;created=1618884475;keyid="test-key-ecc-p256"
   Signature: sig1=:VrfdC2KEFFLoGMYTbQz4PSlKat4hAxcr5XkVN7Mm/7OQQJG+uX\
     gOez7kA6n/yTCaR1VL+FmJd2IVFCsUfcc/jO9siZK3siadoK1Dfgp2ieh9eO781ty\
     SS70OwvAkdORuQLWDnaDMRDlQhg5sNP6JaQghFLqD4qgFrM9HMPxLrznhAQugJ0Fd\
     RZLtSpnjECW6qsu2PVRoCYfnwe4gu8TfqH5GDx2SkpCF9BQ8CijuIWlOg7QP73tKt\
     QNp65u14Si9VEVXHWGiLw4blyPLzWz/fqJbdLaq94Ep60Nq8WjYEAInYH6KyV7EAD\
     60LXdspwF50R3dkWXJP/x+gkAHSMsxbg==:

B.2.2.  Header Coverage sig1=:n8RKXkj0iseWDmC6PNSQ1GX2R9650v+lhbb6rTGoSrSSx18zmn\
     6fPOtBx48/WffYLO0n1RHHf9scvNGAgGq52Q==:

B.2.5.  Signing a Request using rsa-pss-sha512 hmac-sha256

   This example covers all portions of the specified headers in "test-request"
   except for the body digest header using the "rsa-pss-sha512"
   algorithm. "hmac-
   sha256" algorithm and the secret "test-shared-secret".

   The corresponding signature input is:

   "host":

   NOTE: '\' line wrapping per RFC 8792

   "@authority": example.com
   "date": Tue, 20 Apr 2021 02:07:55 GMT
   "content-type": application/json
   "@signature-params": ("host" ("@authority" "date" "content-type")\
     ;created=1618884475;keyid="test-key-rsa-pss"
     ;created=1618884475;keyid="test-shared-secret"

   This results in the following "Signature-Input" and "Signature"
   headers being added to the message:

   NOTE: '\' line wrapping per RFC 8792

   Signature-Input: sig1=("host" sig1=("@authority" "date" "content-type")\
     ;created=1618884475;keyid="test-key-rsa-pss"
     ;created=1618884475;keyid="test-shared-secret"
   Signature: sig1=:Zu48JBrHlXN+hVj3T5fPQUjMNEEhABM5vNmiWuUUl7BWNid5Rz\
     OH1tEjVi+jObYkYT8p09lZ2hrNuU3xm+JUBT8WNIlopJtt0EzxFnjGlHvkhu3KbJf\
     xNlvCJVlOEdR4AivDLMeK/ZgASpZ7py1UNHJqRyGCYkYpeedinXUertL/ySNp+VbK\
     2O/qCoui2jFgff2kXQd6rjL1Up83Fpr+/KoZ6HQkv3qwBdMBDyHQykfZHhLn4AO1I\
     G+vKhOLJQDfaLsJ/fYfzsgc1s46j3GpPPD/W2nEEtdhNwu7oXq81qVRsENChIu1XI\
     FKR9q7WpyHDKEWTtaNZDS8TFvIQRU22w==:

B.2.3.  Full Coverage using rsa-pss-sha512

   This example covers all headers sig1=:fN3AMNGbx0V/cIEKkZOvLOoC3InI+lM2+gTv22x3ia8=:

B.3.  TLS-Terminating Proxies

   In this example, there is a TLS-terminating reverse proxy sitting in "test-request" plus
   front of the resource.  The client does not sign the request
   target but
   instead uses mutual TLS to make its call.  The terminating proxy
   validates the TLS stream and message body digest using injects a "Client-Cert" header according
   to [I-D.ietf-httpbis-client-cert-field].  By signing this header
   field, a reverse proxy can not only attest to its own validation of
   the "rsa-pss-sha512" algorithm. initial request but also authenticate itself to the backend
   system independently of the client's actions.  The corresponding signature input is:

   "@request-target": post /foo?param=value&pet=dog
   "host": client makes the
   following request to the TLS terminating proxy using mutual TLS:

   POST /foo?Param=value&pet=Dog HTTP/1.1
   Host: example.com
   "date":
   Date: Tue, 20 Apr 2021 02:07:55 GMT
   Content-Type: application/json
   Content-Length: 18

   {"hello": "world"}

   The proxy processes the TLS connection and extracts the client's TLS
   certificate to a "Client-Cert" header field and passes it along to
   the internal service hosted at "service.internal.example".  This
   results in the following unsigned request:

   NOTE: '\' line wrapping per RFC 8792

   POST /foo?Param=value&pet=Dog HTTP/1.1
   Host: service.internal.example
   Date: Tue, 20 Apr 2021 02:07:55 GMT
   "content-type":
   Content-Type: application/json
   "digest": SHA-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
   "content-length":
   Content-Length: 18
   "@signature-params": ("@request-target" "host" "date" \
     "content-type" "digest" "content-length");created=1618884475\
     ;keyid="test-key-rsa-pss"

   This results in
   Client-Cert: :MIIBqDCCAU6gAwIBAgIBBzAKBggqhkjOPQQDAjA6MRswGQYDVQQKD\
     BJMZXQncyBBdXRoZW50aWNhdGUxGzAZBgNVBAMMEkxBIEludGVybWVkaWF0ZSBDQT\
     AeFw0yMDAxMTQyMjU1MzNaFw0yMTAxMjMyMjU1MzNaMA0xCzAJBgNVBAMMAkJDMFk\
     wEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE8YnXXfaUgmnMtOXU/IncWalRhebrXmck\
     C8vdgJ1p5Be5F/3YC8OthxM4+k1M6aEAEFcGzkJiNy6J84y7uzo9M6NyMHAwCQYDV\
     R0TBAIwADAfBgNVHSMEGDAWgBRm3WjLa38lbEYCuiCPct0ZaSED2DAOBgNVHQ8BAf\
     8EBAMCBsAwEwYDVR0lBAwwCgYIKwYBBQUHAwIwHQYDVR0RAQH/BBMwEYEPYmRjQGV\
     4YW1wbGUuY29tMAoGCCqGSM49BAMCA0gAMEUCIBHda/r1vaL6G3VliL4/Di6YK0Q6\
     bMjeSkC3dFCOOB8TAiEAx/kHSB4urmiZ0NX5r5XarmPk0wmuydBVoU4hBVZ1yhk=:

   {"hello": "world"}

   Without a signature, the following "Signature-Input" and "Signature"
   headers being added internal service would need to trust that
   the message:

   Signature-Input: sig1=("@request-target" "host" "date" \
     "content-type" "digest" "content-length");created=1618884475\
     ;keyid="test-key-rsa-pss"
   Signature: \
     sig1=:iD5NhkJoGSuuTpWMzS0BI47DfbWwsGmHHLTwOxT0n+0cQFSC+1c26B7IOfI\
     RTYofqD0sfYYrnSwCvWJfA1zthAEv9J1CxS/CZXe7CQvFpuKuFJxMpkAzVYdE/TA6\
     fELxNZy9RJEWZUPBU4+aJ26d8PC0XhPObXe6JkP6/C7XvG2QinsDde7rduMdhFN/H\
     j2MuX1Ipzvv4EgbHJdKwmWRNamfmKJZC4U5Tn0F58lzGF+WIpU73V67/6aSGvJGM5\
     7U9bRHrBB7ExuQhOX2J2dvJMYkE33pEJA70XBUp9ZvciTI+vjIUgUQ2oRww3huWML\
     mMMqEc95CliwIoL5aBdCnlQ==:

B.2.4.  Signing a Response using ecdsa-p256-sha256

   This example covers incoming connection has the right information.  By signing the
   "Client-Cert" header and other portions of the "test-response" response message
   using internal request, the "ecdsa-p256-sha256" algorithm
   internal service can be assured that the correct party, the trusted
   proxy, has processed the request and presented it to the key "test-key-ecc-
   p256". correct
   service.  The corresponding proxy's signature input is:

   "date": Tue, 20 Apr 2021 02:07:56 GMT
   "content-type": application/json
   "digest": SHA-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=
   "content-length": 18 consists of the following:

   NOTE: '\' line wrapping per RFC 8792

   "@path": /foo
   "@query": Param=value&pet=Dog
   "@method": POST
   "@authority": service.internal.example
   "client-cert": :MIIBqDCCAU6gAwIBAgIBBzAKBggqhkjOPQQDAjA6MRswGQYDVQQ\
     KDBJMZXQncyBBdXRoZW50aWNhdGUxGzAZBgNVBAMMEkxBIEludGVybWVkaWF0ZSBD\
     QTAeFw0yMDAxMTQyMjU1MzNaFw0yMTAxMjMyMjU1MzNaMA0xCzAJBgNVBAMMAkJDM\
     FkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE8YnXXfaUgmnMtOXU/IncWalRhebrXm\
     ckC8vdgJ1p5Be5F/3YC8OthxM4+k1M6aEAEFcGzkJiNy6J84y7uzo9M6NyMHAwCQY\
     DVR0TBAIwADAfBgNVHSMEGDAWgBRm3WjLa38lbEYCuiCPct0ZaSED2DAOBgNVHQ8B\
     Af8EBAMCBsAwEwYDVR0lBAwwCgYIKwYBBQUHAwIwHQYDVR0RAQH/BBMwEYEPYmRjQ\
     GV4YW1wbGUuY29tMAoGCCqGSM49BAMCA0gAMEUCIBHda/r1vaL6G3VliL4/Di6YK0\
     Q6bMjeSkC3dFCOOB8TAiEAx/kHSB4urmiZ0NX5r5XarmPk0wmuydBVoU4hBVZ1yhk=:
   "@signature-params": ("date" "content-type" "digest" ("@path" "@query" "@method" "@authority" \
     "content-length");created=1618884475;keyid="test-key-ecc-p256"
     "client-cert");created=1618884475;keyid="test-key-ecc-p256"

   This results in the following "Signature-Input" and "Signature"
   headers being added to the message:

   Signature-Input: sig1=("date" "content-type" "digest" \
     "content-length");created=1618884475;keyid="test-key-ecc-p256"
   Signature: \
     sig1=:3zmRDW6r50/RETqqhtx/N5sdd5eTh8xmHdsrYRK9wK4rCNEwLjCOBlcQxTL\
     2oJTCWGRkuqE2r9KyqZFY9jd+NQ==:

B.2.5.  Signing a Request using hmac-sha256

   This example covers portions of signature:

   NOTE: '\' line wrapping per RFC 8792

   5gudRjXaHrAYbEaQUOoY9TuvqWOdPcspkp7YyKCB0XhyAG9cB715hucPPanEK0OVyiN\
   LJqcoq2Yn1DPWQcnbog==

   Which results in the "test-request" using following signed request sent from the "hmac-
   sha256" algorithm and proxy to
   the secret "test-shared-secret".

   The corresponding signature input is:

   "host": example.com
   "date": internal service:

   NOTE: '\' line wrapping per RFC 8792

   POST /foo?Param=value&pet=Dog HTTP/1.1
   Host: service.internal.example
   Date: Tue, 20 Apr 2021 02:07:55 GMT
   "content-type":
   Content-Type: application/json
   "@signature-params": ("host" "date" "content-type")\
     ;created=1618884475;keyid="test-shared-secret"

   This results in
   Content-Length: 18
   Client-Cert: :MIIBqDCCAU6gAwIBAgIBBzAKBggqhkjOPQQDAjA6MRswGQYDVQQKD\
     BJMZXQncyBBdXRoZW50aWNhdGUxGzAZBgNVBAMMEkxBIEludGVybWVkaWF0ZSBDQT\
     AeFw0yMDAxMTQyMjU1MzNaFw0yMTAxMjMyMjU1MzNaMA0xCzAJBgNVBAMMAkJDMFk\
     wEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE8YnXXfaUgmnMtOXU/IncWalRhebrXmck\
     C8vdgJ1p5Be5F/3YC8OthxM4+k1M6aEAEFcGzkJiNy6J84y7uzo9M6NyMHAwCQYDV\
     R0TBAIwADAfBgNVHSMEGDAWgBRm3WjLa38lbEYCuiCPct0ZaSED2DAOBgNVHQ8BAf\
     8EBAMCBsAwEwYDVR0lBAwwCgYIKwYBBQUHAwIwHQYDVR0RAQH/BBMwEYEPYmRjQGV\
     4YW1wbGUuY29tMAoGCCqGSM49BAMCA0gAMEUCIBHda/r1vaL6G3VliL4/Di6YK0Q6\
     bMjeSkC3dFCOOB8TAiEAx/kHSB4urmiZ0NX5r5XarmPk0wmuydBVoU4hBVZ1yhk=:
   Signature-Input: ttrp=("@path" "@query" "@method" "@authority" \
     "client-cert");created=1618884475;keyid="test-key-ecc-p256"
   Signature: ttrp=:5gudRjXaHrAYbEaQUOoY9TuvqWOdPcspkp7YyKCB0XhyAG9cB7\
     15hucPPanEK0OVyiNLJqcoq2Yn1DPWQcnbog==:

   {"hello": "world"}

   The internal service can validate the following "Signature-Input" proxy's signature and "Signature"
   headers being added therefore
   be able to trust that the message:

   Signature-Input: sig1=("host" "date" "content-type")\
     ;created=1618884475;keyid="test-shared-secret"
   Signature: sig1=:x54VEvVOb0TMw8fUbsWdUHqqqOre+K7sB/LqHQvnfaQ=: client's certificate has been appropriately
   processed.

Acknowledgements

   This specification was initially based on the draft-cavage-http-
   signatures internet draft.  The editors would like to thank the
   authors of that draft, Mark Cavage and Manu Sporny, for their work on
   that draft and their continuing contributions.

   The editors would also like to thank the following individuals for
   feedback, insight, and implementation of this draft and its
   predecessors (in alphabetical order): Mark Adamcin, Mark Allen, Paul
   Annesley, Karl Boehlmark, Stephane Bortzmeyer, Sarven Capadisli, Liam
   Dennehy, ductm54, Stephen Farrell, Phillip Hallam-Baker, Eric Holmes,
   Andrey Kislyuk, Adam Knight, Dave Lehn, Dave Longley, Ilari
   Liusvaara, James H.  Manger, Kathleen Moriarty, Mark Nottingham, Yoav
   Nir, Adrian Palmer, Lucas Pardue, Roberto Polli, Julian Reschke,
   Michael Richardson, Wojciech Rygielski, Adam Scarr, Cory J.  Slep,
   Dirk Stein, Henry Story, Lukasz Szewc, Chris Webber, and Jeffrey
   Yasskin.

Document History

   _RFC EDITOR: please remove this section before publication_

   *  draft-ietf-httpbis-message-signatures

      -  -06

         o  Updated language for message components, including
            identifiers and values.

         o  Clarified that Signature-Input and Signature are fields
            which can be used as headers or trailers.

         o  Add "Accept-Signature" field and semantics for signature
            negotiation.

         o  Define new specialty content identifiers, re-defined
            request-target identifier.

         o  Added request-response binding.

      -  -05

         o  Remove list prefixes.

         o  Clarify signature algorithm parameters.

         o  Update and fix examples.

         o  Add examples for ECC and HMAC.

      -  -04

         o  Moved signature component definitions up to intro.

         o  Created formal function definitions for algorithms to
            fulfill.

         o  Updated all examples.

         o  Added nonce parameter field.

      -  -03

         o  Clarified signing and verification processes.

         o  Updated algorithm and key selection method.

         o  Clearly defined core algorithm set.

         o  Defined JOSE signature mapping process.

         o  Removed legacy signature methods.

         o  Define signature parameters separately from "signature"
            object model.

         o  Define serialization values for signature-input header based
            on signature input.

      -  -02

         o  Removed editorial comments on document sources.

         o  Removed in-document issues list in favor of tracked issues.

         o  Replaced unstructured "Signature" header with "Signature-
            Input" and "Signature" Dictionary Structured Header Fields.

         o  Defined content identifiers for individual Dictionary
            members, e.g., ""x-dictionary-field";key=member-name".

         o  Defined content identifiers for first N members of a List,
            e.g., ""x-list-field":prefix=4".

         o  Fixed up examples.

         o  Updated introduction now that it's adopted.

         o  Defined specialty content identifiers and a means to extend
            them.

         o  Required signature parameters to be included in signature.

         o  Added guidance on backwards compatibility, detection, and
            use of signature methods.

      -  -01
         o  Strengthened requirement for content identifiers for header
            fields to be lower-case (changed from SHOULD to MUST).

         o  Added real example values for Creation Time and Expiration
            Time.

         o  Minor editorial corrections and readability improvements.

      -  -00

         o  Initialized from draft-richanna-http-message-signatures-00,
            following adoption by the working group.

   *  draft-richanna-http-message-signatures

      -  -00

         o  Converted to xml2rfc v3 and reformatted to comply with RFC
            style guides.

         o  Removed Signature auth-scheme definition and related
            content.

         o  Removed conflicting normative requirements for use of
            algorithm parameter.  Now MUST NOT be relied upon.

         o  Removed Extensions appendix.

         o  Rewrote abstract and introduction to explain context and
            need, and challenges inherent in signing HTTP messages.

         o  Rewrote and heavily expanded algorithm definition, retaining
            normative requirements.

         o  Added definitions for key terms, referenced RFC 7230 for
            HTTP terms.

         o  Added examples for canonicalization and signature generation
            steps.

         o  Rewrote Signature header definition, retaining normative
            requirements.

         o  Added default values for algorithm and expires parameters.

         o  Rewrote HTTP Signature Algorithms registry definition.
            Added change control policy and registry template.  Removed
            suggested URI.

         o  Added IANA HTTP Signature Parameter registry.

         o  Added additional normative and informative references.

         o  Added Topics for Working Group Discussion section, to be
            removed prior to publication as an RFC.

Authors' Addresses

   Annabelle Backman (editor)
   Amazon
   P.O. Box 81226
   Seattle, WA 98108-1226
   United States of America

   Email: richanna@amazon.com
   URI:   https://www.amazon.com/

   Justin Richer
   Bespoke Engineering

   Email: ietf@justin.richer.org
   URI:   https://bspk.io/

   Manu Sporny
   Digital Bazaar
   203 Roanoke Street W.
   Blacksburg, VA 24060
   United States of America

   Email: msporny@digitalbazaar.com
   URI:   https://manu.sporny.org/