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Versions: 00 01 02

Network Working Group                                     J. Richer, Ed.
Internet-Draft                                       Bespoke Engineering
Intended status: Standards Track                            July 3, 2019
Expires: January 4, 2020


                      Transactional Authorization
                  draft-richer-transactional-authz-01

Abstract

   This document defines a mechanism for delegating authorization to a
   piece of software, and conveying that delegation to the software.

Requirements Language

   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 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when, they
   appear in all capitals, as shown here.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 4, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Protocol  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Parties . . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Sequence  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Transaction request . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Client  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Resource  . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.3.  User  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.4.  Interact  . . . . . . . . . . . . . . . . . . . . . . . .   6
     2.5.  Keys  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Interaction response  . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Redirect interaction  . . . . . . . . . . . . . . . . . .   8
     3.2.  Callback response . . . . . . . . . . . . . . . . . . . .   9
     3.3.  Secondary device interaction  . . . . . . . . . . . . . .   9
   4.  Wait response . . . . . . . . . . . . . . . . . . . . . . . .  10
   5.  Interaction at the AS . . . . . . . . . . . . . . . . . . . .  11
   6.  Error response  . . . . . . . . . . . . . . . . . . . . . . .  11
   7.  Transaction continue request  . . . . . . . . . . . . . . . .  12
   8.  Token response  . . . . . . . . . . . . . . . . . . . . . . .  13
     8.1.  Presenting Tokens to the RS . . . . . . . . . . . . . . .  13
   9.  Handle references . . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  Presenting handles  . . . . . . . . . . . . . . . . . . .  14
     9.2.  Validating handles  . . . . . . . . . . . . . . . . . . .  14
     9.3.  Transaction handles . . . . . . . . . . . . . . . . . . .  14
     9.4.  Client handles  . . . . . . . . . . . . . . . . . . . . .  15
     9.5.  Resource handles  . . . . . . . . . . . . . . . . . . . .  15
       9.5.1.  Resource-first  . . . . . . . . . . . . . . . . . . .  16
     9.6.  User handles  . . . . . . . . . . . . . . . . . . . . . .  17
     9.7.  Key handles . . . . . . . . . . . . . . . . . . . . . . .  17
   10. Binding Keys  . . . . . . . . . . . . . . . . . . . . . . . .  18
     10.1.  Binding a key to a transaction . . . . . . . . . . . . .  18
     10.2.  Detached JWS . . . . . . . . . . . . . . . . . . . . . .  19
     10.3.  Validating MTLS  . . . . . . . . . . . . . . . . . . . .  19
     10.4.  Validating DID . . . . . . . . . . . . . . . . . . . . .  19
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  19
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
   13. Security Considerations . . . . . . . . . . . . . . . . . . .  19
   14. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  20
   15. Normative References  . . . . . . . . . . . . . . . . . . . .  20
   Appendix A.  Document History . . . . . . . . . . . . . . . . . .  21
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  21



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1.  Protocol

   This protocol allows a piece of software to request delegated
   authorization to an API, protected by an authorization server usually
   on behalf of a resource owner.

1.1.  Parties

   The Authorization Server (AS) manages the transactions.  It is
   defined by its transaction endpoint, a single URL that accepts a POST
   request with a JSON payload.  The AS MAY also have other endpoints,
   including interaction endpoints, but these are

   The Resource Client (RC) requests tokens from the AS and uses tokens
   at the RS.

   The Resource Server (RS) accepts tokens from the RC and validates
   them (potentially at the AS).

   The Resource Owner (RO) authorizes the request from the RC to the RS,
   often interactively at the AS.

1.2.  Sequence

   1.  The RC creates a transaction request and sends it to the AS

   2.  The AS processes the transaction request and determines if the RO
       needs to interact

   3.  If interaction is required, the AS interacts with the RO,
       possibly by directing the RC to send the RO there

   4.  The RC continues the transaction at the AS

   5.  The AS processess the transaction again, determining that a token
       can be issued

   6.  The AS issues a token to the RC

   7.  The RC uses the token with the RS

2.  Transaction request

   To start a transaction, the RC makes a transaction request to the
   transaction endpoint of the AS.  The RC creates a JSON [RFC8259]
   document with five primary sections, included as members of a root
   JSON object.




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   client  Information about the RC making the request, including
      display name, home page, logo, and other user-facing information.
      This section is RECOMMENDED.

   resources  Information about the RS's the resulting token will be
      applied to, including locations, extents of access, types of data
      being accessed, and other API information.  This section is
      REQUIRED.

   user  Information about the RO as known to or provided to the RC, in
      the form of assertions or references to external data.  This
      section is OPTIONAL.

   interact  Information about how the RC is able to interact with the
      RO, including callback URI's and state.  This section is REQUIRED
      if the RC is capable of driving interaction with the user.

   keys  Information about the keys known to the RC and able to be
      presented in future parts of the transaction.  This section is
      REQUIRED.  (Note: I can't think of a good reason for this to be
      optional.)

   Each section consists of either a JSON object or an array of JSON
   objects, as described in the subsections below.  Many sections MAY be
   represented by an appropriate handle instead as described in
   Section 9.  In such cases, the section is replaced entirely by the
   handle presentation, which is a single string instead of a JSON
   object.  The RC MAY present additional sections as defined by
   extensions of this specification.  The AS MUST ignore any sections
   that it does not understand.

2.1.  Client

   This section provides descriptive details of the RC software making
   the call.  This section is a JSON object, and all fields are
   OPTIONAL.  The RC MAY send additional fields, and the AS MUST ignore
   all fields that it does not understand.

   name  Display name of the RC software

   uri  User-facing web page of the RC software

   logo_uri  Display image to represent the RC software








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   client: {

     name: "Display Name",
     uri: "https://example.com/client"

   }

   The AS SHOULD use this information in presenting any authorization
   screens to the RO during interaction.

   The client information MAY instead be presented as a client handle
   reference Section 9.4.

2.2.  Resource

   This section identifies what the RC wants to do with the API hosted
   at the RS.  This section is a JSON array of objects, each object
   representing a single resource or resource set.  That AS MUST
   interpret the request as being for all of the resources listed.

   actions  The types of actions the RC will take at the RS

   locations  URIs the RC will call at the RS

   data  types of data available to the RC at the RS's API

   resources: [
     {
       actions: ["read", "write"],
       locations: ["https://exapmle.com/resource"]
       data: ["foo", "bar"]

     }
   ]

   This can also be presented as a set of resource handle references
   Section 9.5, or a combination of handles and resource structures.

2.3.  User

   This section provides a verifiable assertion about the RO interacting
   with the RC on behalf of the request.

   assertion  The value of the assertion as a string.

   type  The type of the assertion.  Possible values include
      "oidc_id_token"...




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   user: {

     assertion: "eyj0....",
     type: "oidc_id_token"

   }

   This can also be presented as a user handle reference Section 9.6.

2.4.  Interact

   This section provides details of how the RC can interact with the RO.
   All interact requests MUST have the "type" field.

   type  REQUIRED.  Type of interaction.  Can be "redirect" or "device".
      The "redirect" type indicates that the RO is capable of sending
      the user to an arbitrary URL to be returned from the AS.  The
      "device" type indicates that the RC is capable of communicating a
      short, human-readable code to the RO, which the RO can enter
      interactively to the AS.

   callback  OPTIONAL.  IF the RC is capable of receiving inbound
      messages from the RO's browser, this indicates the URI to send the
      RO to after interaction.  This URI SHOULD (MUST?) be unique per
      transaction and MUST be hosted or accessible by the RC.  This URI
      MUST NOT contain any fragment component.  This URI MUST be
      protected by HTTPS, be hosted on a server local to the user's
      browser ("localhost"), or use an application-specific URI scheme.
      The allowable URIs MAY be limited by the AS based on the RC's
      presented key information.

   state  REQUIRED if the "callback" parameter is used.  Unique value to
      be returned to the application as a query parameter on the
      callback URL, must be sufficiently random to be unguessable by an
      attacker.  MUST be generated by the RC for this transaction.

   Each interaction type has its own parameters and behaviors, detailed
   below.

   This section MUST NOT be represented by a handle reference.  (Note:
   this

2.5.  Keys

   This section lists the keys that the RC can present proof of
   ownership.  The RC MUST send at least one key.  The RC MAY send more
   than one key, but only one key of each type.




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   jwks  Value of the public key as a JWK Set JSON object [Note: should
      this be a single JWK instead?  And do we want to bother with url-
      based references?].  MUST contain an "alg" field which is used to
      validate the signature.  MUST contain the "kid" field to identify
      the key in the signed object.  This key type MUST be proved using
      either the detached JWS or HTTP-Signing mechanisms.

   cert  String serialized value of the certificate thumbprint as per
      OAuth-MTLS.  This key type MUST be proved using Mutual TLS.

   did  The DID URL identifying the key (or keys) used to sign this
      request.  This key type MUST be proved using [[ note -- how? ]]

   The RC MUST provide proof of possession of all presented
   keysSection 10.  All presented keys MUST be validated by the AS as
   per the Key Validation section.

   This section MAY also be presented as a key handle reference
   Section 9.7.  The keys referenced by a handle MUST be validated by
   the AS.

   The following non-normative example shows all three key methods:

   key: {

     jwks: { keys: [ alg: RS256, kty: ... ] },
     cert: "MII....",
     did: "did:v:foo...."

   }

3.  Interaction response

   When evaluating a transaction request, the AS MAY determine that it
   needs to have the RO present to interact with the AS before issuing a
   token.  This interaction can include the RO logging in to the AS,
   authorizing the transaction, providing proof claims, determining if
   the transaction decision should be remembered for the future, and
   other items.

   The AS responds to the RC based on the type of interaction supported
   by the RC in the transaction request.

   This response can indicate a set of keys are bound to the transaction
   as in Key Binding.  This response includes a transaction handle as in
   Transaction Handle.





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3.1.  Redirect interaction

   If the RC supports a "redirect" style interaction, the AS creates a
   unique interaction URL and returns it to the RC.  This URL MUST be
   associated with a single pending transaction.

   interaction_url  The interaction URL that the RC will direct the RO
      to.  This URL MUST be unique to this transaction request.  The URL
      SHOULD contain a random portion of sufficient entropy so as not to
      be guessable by the user.  The URL MUST NOT contain the
      transaction handle or any RC identifying information.  This URL
      MUST be protected by HTTPS.  This URL MUST NOT contain any
      fragment component.

   handle  The transaction handle to use in the continue request once
      the RO has been returned to the RC via the callback URL.  See the
      section on transaction handlesSection 9.3.

   {

     interaction_url: "https://server.example.com/interact/123asdfklj",
     handle: {
       value: "tghji76ytghj9876tghjko987yh",
       type: "bearer"
     }
   }

   When the RC receives this response, it MUST launch the system
   browser, redirect the RO through an HTTP 302 response, display the
   URL through a scannable barcode, or otherwise send the RO to the
   interaction URL.  The RC MUST NOT modify the interaction URL or
   append anything to it, including any query parameters, fragments, or
   special headers.

   The interaction URL MUST be reachable from the RO's browser, though
   note that the RO MAY open the interaction URL on a separate device
   from the RC itself.  The interaction URL MUST be accessible from an
   HTTP GET request, and MUST be protected by HTTPS or equivalent means.

   Upon receiving an incoming request at the interaction URL, the AS
   MUST determine the transaction associated with this unique URL.  If
   the transaction is not found, an error is returned to the end user
   through the browser and the AS MUST NOT attempt to redirect to a
   callback URL.  When interacting with the RO, the AS MAY perform any
   of the behaviors in the User Interaction section Section 5.






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3.2.  Callback response

   If the RC has supplied a callback URL in its interact request
   Section 2.4, the AS returns the user to the RC by redirecting the
   RO's browser to the RC's callback URL presented at the start of the
   transaction, with the addition of two query parameters.

   state  REQUIRED.  The (hashed?) value of the state parameter sent by
      the RC in the initial interaction request Section 2.4.

   interact_handle  REQUIRED.  A shared secret associated with this
      interaction.  This value MUST be sufficiently random so as not to
      be guessable by an attacker.  This value MUST be associated by the
      AS with the underlying transaction that is associated to with this
      interaction.

   Upon processing this request to the callback URL, the RC MUST match
   the state value to the value it sent in the original transaction
   request.  The RC then sends a transaction continuation request with
   the transaction handle returned in the interaction response and the
   (hash of?) the interaction handle returned as a query parameter to
   the callback URL.

   The RC sends (the hash of? example here is hashed) the interaction
   handle as the "interact_handle" field of the transaction continuation
   requestSection 7, using the transaction handle Section 7 returned in
   the most recent transaction response from the AS.

{
    "handle": "80UPRY5NM33OMUKMKSKU",
    "interact_handle": "CuD9MrpSXVKvvI6dN1awtNLx-HhZy46hJFDBicG4KoZaCmBofvqPxtm7CDMTsUFuvcmLwi_zUN70cCvalI6ENw"
}

3.3.  Secondary device interaction

   If the RC supports a "device" style interaction, the AS creates a
   unique interaction code and returns it to the RC.  The RC
   communicates this code to the RO and instructs the RO to enter the
   code at a URL hosted by the AS.

   user_code  REQUIRED.  A short code that the user can type into an
      authorization server.  This string MUST be case-insensitive, MUST
      consist of only easily typeable characters (such as letters or
      numbers).  The time in which this code will be accepted SHOULD be
      short lived, such as several minutes.






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   user_code_url  RECOMMENDED.  The interaction URL that the RC will
      direct the RO to.  This URL SHOULD be stable at the AS such that
      clients can be statically configured with it.

   wait  RECOMMENDED.  The amount of time to wait before polling again,
      in integer seconds.

   handle  REQUIRED.  The transaction handle to use in the continue
      request.  See the section on transaction handlesSection 9.3.

   {

     user_code: "ABCD1234"
     user_code_url: "https://server.example.com/device",
     wait: 30,
     handle: {
       value: "tghji76ytghj9876tghjko987yh",
       type: "bearer"
     }
   }

   When the RC receives this response, it MUST communicate the user code
   to the RO.  If possible the RC SHOULD communicate the interaction URL
   to the user as well.

   When the RO enters the unique user code at the user code URL, the AS
   MUST determine which active transaction is associated with the user
   code.  If a transaction is not found, the AS MUST return an error
   page to the user and MUST NOT attempt to redirect to a callback URL.
   The AS MAY use any mechanism to interact with the RO as listed in
   Section 5.

   Note that this method is strictly for allowing the user to enter a
   code at a static URL.  If the AS wishes to communicate a pre-composed
   URL to the RO containing both the user code and the URL at which to
   enter it, the AS MUST use the "interaction_url" Section 3.1 redirect
   mechanism instead as this allows the client to communicate an
   arbitrary interaction URL to the RO.

4.  Wait response

   If the AS needs the RC to wait before it can give a definitive
   response to a transaction continue requestSection 7, the AS replies
   to the transaction request with a wait response.  This tells the RC
   that it can poll the transaction after a set amount of time.

   This response includes a transaction handle as in Transaction Handle
   Section 9.3.



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   wait  REQUIRED.  The amount of time to wait before polling again, in
      integer seconds.

   handle  REQUIRED.  The transaction handle to use in the continue
      request.  This MUST be a newly-created handle and MUST replace any
      existing handle for this transaction.  See the section on
      transaction handles.

   {

     wait: 30,
     handle: {
       value: "tghji76ytghj9876tghjko987yh",
       type: "bearer"
     }

   }

5.  Interaction at the AS

   When the RO is interacting with the AS at the interaction endpoint,
   the AS MAY perform whatever actions it sees fit, including but not
   limited to:

   o  authenticate the RO

   o  gather identity claims about the RO

   o  gather consent and authorization from the RO

   o  allow the RO to modify the parameters of the requested transaction
      (such as disallowing some requested resources)

   When the AS has concluded interacting with the RO, the AS MUST
   determine if the RC has registered a callback URL and state parameter
   for this transaction.  If so, the AS MUST redirect the RO's browser
   to the callback URL as described in Section 3.  If the AS detects an
   error condition, such as an unknown transaction, an untrustworthy
   callback URL, an untrustworthy client, or suspicious RO behavior, the
   AS MUST return an error to the RO's browser and MUST NOT redirect to
   the callback URL.

6.  Error response

   If the AS determines that the token cannot be issued for any reason,
   it responds to the RC with an error message.  This message does not
   include a transaction handle, and the RC can no longer poll for this
   transaction.  The RC MAY create a new transaction and start again.



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   error  The error code.

   {

     error: user_denied

   }

   TODO: we should have a more robust error mechanism.  Current
   candidate list of errors:

   user_denied  The RO denied the transaction request.

   too_fast  The RC did not respect the timeout in the wait response.

   unknown_transaction  The transaction continuation request referenced
      an unknown transaction.

   unknown_handle  The request referenced an unknown handle.

7.  Transaction continue request

   Once a transaction has begun, the AS associates that transaction with
   a transaction handleSection 9.3 which is returned to the RC in one of
   the transaction responses Section 3.1, Section 3.3, Section 4.  This
   handle MUST be unique, MUST be associated with a single transaction,
   and MUST be one time use.

   The RC continues the transaction by making a request with the
   transaction handle in the body of the request.  The RC MAY add
   additional fields to the transaction continuation request, such as
   the interaction handle return in the callback response Section 3.

   handle  REQUIRED.  The (hash of?) transaction handle indicating which
      transaction to continue.

   interaction_handle  OPTIONAL.  If the RC has received an interaction
      handle from the callback response of the interaction URL, the RC
      MUST include the (hash of?) that handle in its transaction
      continue request.

   {

     handle: "tghji76ytghj9876tghjko987yh"

   }





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   The RC MUST prove all keys initially sent in the transaction
   requestSection 2.5 as described in Section 10.

8.  Token response

   access_token  The access token that the RC uses to call the RS.  The
      access token follows the handle structure described in Section 9.

   handle  The transaction handle to use in the continue
      requestSection 7 to get a new access token once the one issued is
      no longer usable.  See the section on transaction
      handlesSection 9.3.

   key: {

     access_token: {
       value: "08ur4kahfga09u23rnkjasdf",
       type: "bearer"
     },
     handle: {
       value: "tghji76ytghj9876tghjko987yh",
       type: "bearer"
     }

   }

8.1.  Presenting Tokens to the RS

   A bearer style access token MUST be presented using the Header method
   of OAuth 2 Bearer Tokens [RFC6750].  A sha3 style access token is
   hashed as described in Section 9 and presented using the Header
   method of OAuth 2 Bearer Tokens [RFC6750].

   An access token MAY be bound to any keys presented by the client
   during the transaction request.  A bound access token MUST be
   presented with proof of the key as described in Section 10.

9.  Handle references

   A handle in this protocol is a value presented from one party to
   another as proof that they are the appropriate party for part of the
   transaction.  Handles can be used to reference the transaction as a
   whole, or one of its constituent parts.  When a handle is used to
   represent a part of a transaction request, the handle presentation
   replaces the original value.  In practical terms, this often means
   that the values of a transaction request are either an object (when
   the full value is used) or a single string (when the handle is used).




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   value  The value of the handle as a string.

   method  The verification method, MUST be one of "bearer" or "sha3".

9.1.  Presenting handles

   Bearer handles are presented by giving the exact string value of the
   handle in the appropriate place.

   SHA3 handles are validated by taking the SHA3 hash of the handle
   value and encoding it in Base64URL with no padding, and presenting
   the encoded value.

9.2.  Validating handles

   Bearer handles are validated by doing an exact byte comparison of the
   string representation of the handle value.

   SHA3 handles are validated by taking the SHA3 hash of the handle
   value and encoding it in Base64URL with no padding, and comparing
   that using an exact byte comparison with the presented value.

9.3.  Transaction handles

   Transaction handles are issued by the AS to the RC to allow the RC to
   continue a transaction after every step.  A transaction handle MUST
   be discarded after it is used by both the AS and the RC.  A
   transaction MUST have only a single handle associated with it at any
   time.  If the AS determines that the RC can still continue the
   transaction after a handle has been used, a new transaction handle
   will be issued in its place.  If the AS does not issue a transaction
   handle in its response to the RC, the RC MUST NOT continue that
   transaction.

   Transaction handles always represent the current state of the
   transaction which they reference.

   Transactions can be continued by the RC if the AS needs to interact
   with the ROSection 5 and the RC is expecting a callbackSection 3 or
   if the AS is still waiting on some external conditionSection 4 while
   the RC is polling.  The transaction MAY also be continued after an
   access token is issued Section 8 as a means of refreshing an access
   token with the same rights associated with the transaction.








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9.4.  Client handles

   RC handles stand in for the client section of the initial transaction
   requestSection 2.1.  The AS MAY issue a client handle to a RC as part
   of a static registration process, analogous to a client ID in OAuth
   2, allowing the RC to be associated with an AS-side configuration
   that does not change at runtime.  Such static processes SHOULD be
   bound to a set of keys known only to the RC software.

   Client handles MAY be issued by the RS in response to a transaction
   request.  The AS MAY associate the client handle to the interact,
   resource, and key handles issued in the same response, requiring them
   to be used together.  When the RC receives this handle, it MAY
   present the handle in future transaction requests instead of sending
   its information again.

   {

     handle: {
       value: "tghji76ytghj9876tghjko987yh",
       method: "bearer"
     },
     client_handle: {
       value: "absc2948afgdkjnasdf9082ur3kjasdfasdf89",
       method: "bearer"
     }

   }

   The RC sends its handle in lieu of the client block of the
   transaction request:

   {

     client: "absc2948afgdkjnasdf9082ur3kjasdfasdf89"

   }

9.5.  Resource handles

   Resource handles stand in for the detailed resource request in the
   transaction requestSection 2.2.  Resource handles MAY be created by
   the authorization server as static stand-ins for specific resource
   requests, analogous to OAuth2 scopes.

   Resource handles MAY be issued by the RS in response to a transaction
   request.  When the RC receives this handle, it MAY present the handle




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   in future transaction requests instead of sending its information
   again.

   {

     handle: {
       value: "tghji76ytghj9876tghjko987yh",
       method: "bearer"
     },
     resource_handle: {
       value: "foo",
       method: "bearer"
     }

   }

   The RC sends its handle in lieu of the resource block of the future
   transaction request:

   {

     resources: ["foo"]

   }

   Handles and object values MAY be combined.

   {

     resources: [
       "foo",
       {
         actions: ["read", "write"],
         locations: ["https://exapmle.com/resource"]
         data: ["foo", "bar"]
       }
     ]

   }

9.5.1.  Resource-first

   [[ Strawman idea: ]]

   In order to facilitate dynamic API protection, an RS MAY pre-register
   a resource handle in response to an unauthorized request from the RC.
   In this scenario, the RS creates a transaction request with no client
   information but describing the resources being protected [[Note: this



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   is currently at odds with the required format above, perhaps this
   should be a special mode or flag?  We could still use the "keys"
   section here though.]] The AS returns a resource handle to the RS,
   which then communicates both the resource handle and the AS
   transaction endpoint to the RC.  The RC then begins its transaction
   as normal, using the resource handle as one of perhaps several
   resources it requests.

9.6.  User handles

   User handles MAY be issued by the AS in response to validating a
   specific RO during a transaction and stand in for the user section of
   a transaction requestSection 2.3.  This handle MAY refer to the RO
   that interacted with the AS, the user presented by claims in the
   transaction request, or a combination of these.  This handle can be
   used in future transactions to represent the current user, analogous
   to the persistent claims token of UMA 2.

   {

     handle: {
       value: "tghji76ytghj9876tghjko987yh",
       method: "bearer"
     },
     user_handle: {
       value: "absc2948afgdkjnasdf9082ur3kjasdfasdf89",
       method: "bearer"
     }

   }

   The RC sends its handle in lieu of the user block of the transaction
   request:

   {

     user: "absc2948afgdkjnasdf9082ur3kjasdfasdf89"

   }

9.7.  Key handles

   Key handles stand in for the keys section of the initial transaction
   requestSection 2.5.  The AS MAY issue a key handle to a RC as part of
   a static registration process, allowing the RC to be associated with
   an AS-side configuration that does not change at runtime.





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   Key handles MAY be issued by the AS in response to a transaction
   request.  The AS SHOULD bind this handle to the client, resource, and
   user handles issued in the same response.  When the RC receives this
   handle, it MAY present the handle in future transaction requests
   instead of sending its information again.

   {

     handle: {
       value: "tghji76ytghj9876tghjko987yh",
       method: "bearer"
     },
     key_handle: {
       value: "absc2948afgdkjnasdf9082ur3kjasdfasdf89",
       method: "bearer"
     }

   }

   The RC sends its handle in lieu of the client block of the
   transaction request:

   {

     key: "absc2948afgdkjnasdf9082ur3kjasdfasdf89"

   }

   When the AS receives a key handle, it MUST validate that the keys
   referenced by the handle are bound to the current transaction
   request.

10.  Binding Keys

   Any keys presented by the RC to the AS or RS MUST be validated as
   part of the transaction in which they are presented.  Any keys bound
   to the transaction are indicated by the bound_keys section of the
   transaction response.  Any keys referenced in this section MUST be
   used with all future transaction requests.

10.1.  Binding a key to a transaction

   All keys presented by the RC in the transaction requestSection 2 MUST
   be proved in all transaction continuation requestsSection 7 for that
   transaction.  The AS MUST validate all keys presented by the RC or
   referenced in the transaction.





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10.2.  Detached JWS

   To sign a request to the transaction endpoint, the RC takes the
   serialized body of the request and signs it using detached JWS
   [RFC7797].  The header of the JWS MUST contain the kid field of the
   key bound to this RC during this transaction.  The header MUST
   contain an alg field appropriate for the key identified by kid and
   MUST NOT be none.

   The RC presents the signature in the JWS-Signature HTTP Header field.
   [Note: this is a custom header field, do we need this?]

   JWS-Signature: eyj0....

   When the AS receives the JWS-Signature header, it MUST parse its
   contents as a detached JWS object.  The HTTP Body is used as the
   payload for purposes of validating the JWS, with no transformations.

10.3.  Validating MTLS

   The RC presents its client certificate during TLS negotiation with
   the server (either AS or RS).  The AS or RS takes the thumbprint of
   the client certificate presented during mutual TLS negotiation and
   compares that thumbprint to the thumbprint presented by the RC
   application.

10.4.  Validating DID

   [[ Note: validation of DID-based keys could potentially be either
   detached JWS or MTLS, depending on the type of key used, or some
   other validation mechanism. ]] The RC signs the request using [some
   HTTP signing mechanism] and its private key, and attaches the
   signature to the HTTP request using [a header method?].  [Note: is
   DID just a key-lookup mechanism here or should we use a different
   kind of crypto method as well?]

11.  Acknowledgements

12.  IANA Considerations

   This specification creates one registry and registers several values
   into existing registries.

13.  Security Considerations

   All requests have to be over TLS or equivalent.





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14.  Privacy Considerations

   Handles are passed between parties and therefore should be stateful
   and not contain any internal structure or information, which could
   leak private data.

15.  Normative References

   [BCP195]   Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <http://www.rfc-editor.org/info/bcp195>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
              RFC 6749, DOI 10.17487/RFC6749, October 2012,
              <https://www.rfc-editor.org/info/rfc6749>.

   [RFC6750]  Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
              Framework: Bearer Token Usage", RFC 6750,
              DOI 10.17487/RFC6750, October 2012,
              <https://www.rfc-editor.org/info/rfc6750>.

   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
              <https://www.rfc-editor.org/info/rfc7519>.

   [RFC7662]  Richer, J., Ed., "OAuth 2.0 Token Introspection",
              RFC 7662, DOI 10.17487/RFC7662, October 2015,
              <https://www.rfc-editor.org/info/rfc7662>.

   [RFC7797]  Jones, M., "JSON Web Signature (JWS) Unencoded Payload
              Option", RFC 7797, DOI 10.17487/RFC7797, February 2016,
              <https://www.rfc-editor.org/info/rfc7797>.

   [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/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.



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   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,
              <https://www.rfc-editor.org/info/rfc8259>.

Appendix A.  Document History

   - 01

   o  Made JSON multimodal for handle requests.

   o  Major updates to normative language and references throughout
      document.

   o  Allowed interaction to split between how the user gets to the AS
      and how the user gets back.

   - 00

   o  Initial submission.

Author's Address

   Justin Richer (editor)
   Bespoke Engineering

   Email: ietf@justin.richer.org
























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