Grant Negotiation and Authorization Protocol
Bespoke Engineering
ietf@justin.richer.org
https://bspk.io/
Okta
aaron@parecki.com
https://aaronparecki.com
acert.io
fabien.imbault@acert.io
https://acert.io/
Security
GNAP
Internet-Draft
GNAP defines a mechanism for delegating authorization to a
piece of software, and conveying that delegation to the software. This
delegation can include access to a set of APIs as well as information
passed directly to the software.
Introduction
This protocol allows a piece of software, the client instance, to request delegated
authorization to resource servers and to request direct information. This delegation is
facilitated by an authorization server usually on
behalf of a resource owner. The requesting party operating the software may interact
with the authorization server to authenticate, provide consent, and
authorize the request.
The process by which the delegation happens is known as a grant, and
GNAP allows for the negotiation of the grant process
over time by multiple parties acting in distinct roles.
This protocol solves many of the same use cases as OAuth 2.0 ,
OpenID Connect , and the family of protocols that have grown up
around that ecosystem. However, GNAP is not an extension of OAuth 2.0
and is not intended to be directly compatible with OAuth 2.0. GNAP seeks to
provide functionality and solve use cases that OAuth 2.0 cannot easily
or cleanly address. Even so, GNAP and OAuth 2.0 will exist in parallel
for many deployments, and considerations have been taken to facilitate
the mapping and transition from legacy systems to GNAP. Some examples
of these can be found in .
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 when, and only when, they
appear in all capitals, as shown here.
Roles
The parties in GNAP perform actions under different roles.
Roles are defined by the actions taken and the expectations leveraged
on the role by the overall protocol.
-
Authorization Server (AS)
-
Manages the requested delegations for the RO.
The AS issues tokens and directly delegated information to an instance of the client.
The AS is defined by its grant endpoint, a single URL that accepts a POST
request with a JSON payload. The AS could also have other endpoints,
including interaction endpoints and user code endpoints, and these are
introduced to the RC as needed during the delegation process.
-
Client
-
Requests tokens and directly delegated information from the AS, and uses tokens at the RS.
For some kinds of client software, there could be many instances
of a single piece of client software. This specification
differentiates between a specific instance (the client instance) and the
software running the instance (the client software).
A client instance is identified by its unique key, which can
be known to the AS prior to the first request or introduced
to the AS as part of the protocol. The AS determines
which policies apply to a given client instance, including what it can
request and on whose behalf.
-
Resource Server (RS, aka "API")
-
Accepts tokens from the client instance issued by the AS and serves delegated resources
on behalf of the RO. There could be multiple RSs protected
by the AS that the client instance will call.
-
Resource Owner (RO)
-
Authorizes the request from the client instance to the
RS, often interactively at the AS.
-
Requesting Party (RQ, aka "user")
-
Operates and interacts with the client instance.
The design of GNAP does not assume any one deployment architecture,
but instead attempts to define roles that can be fulfilled in a number
of different ways for different use cases. As long as a given role fulfills
all of its obligations and behaviors as defined by the protocol, GNAP does
not make additional requirements on its structure or setup.
Multiple roles can be fulfilled by the same party, and a given party
can switch roles in different instances of the protocol. For example,
the RO and RQ in many instances are the same person, where a user is
authorizing the client instance to act on their own behalf at the RS. In this case,
one party fulfills both of the RO and RQ roles, but the roles themselves
are still defined separately from each other to allow for other
use cases where they are fulfilled by different parties.
For another example,
in some complex scenarios, an RS receiving requests from one client instance can act as
a client instance for a downstream secondary RS in order to fulfill the
original request. In this case, one piece of software is both an
RS and a client instance from different perspectives, and it fulfills these
roles separately as far as the overall protocol is concerned.
A single role need not be deployed as a monolithic service. For example,
A client instance could have components that are installed on the RQ's device as
well as a back-end system that it communicates with. If both of these
components participate in the delegation protocol, they are both considered
part of the client instance. If there are several copies of the client software
that run separately but all share the same key material, such as a
deployed cluster, then this cluster is considered a single client instance.
For another example, an AS could likewise be built out of many constituent
components in a distributed architecture. The component that the client instance
calls directly could be different from the component that the the
RO interacts with to drive consent, since API calls and user interaction
have different security considerations in many environments. Furthermore,
the AS could need to collect identity claims about the RO from one system
that deals with user attributes while generating access tokens at
another system that deals with security rights. From the perspective of
GNAP, all of these are pieces of the AS and together fulfill the
role of the AS as defined by the protocol.
[[ See issue #29 ]]
Elements
In addition to the roles above, the protocol also involves several
elements that are acted upon by the roles throughout the process.
-
Access Token
-
A credential representing a set of access rights
delegated to the client instance. The access token is created by the AS, consumed
and verified by the RS, and issued to and carried by the client instance. The contents
and format of the access token are opaque to the client.
-
Grant
-
The process by which the client instance requests and is given delegated
access to the RS by the AS through the authority of the RO.
-
Cryptographic Key
-
A cryptographic element binding a request to a
holder of the key. Access tokens and client instances can be associated with
specific keys.
-
Resource
-
A protected API served by the RS and accessed by the client instance. Access to this
resource is delegated by the RO as part of the grant process.
-
Subject Information
-
Information about the RO that is returned directly to the client instance from the AS
without the client instance making a separate call to an RS. Access to this information
is delegated by the RO as part of the grant process.
Sequences
GNAP can be used in a variety of ways to allow the core
delegation process to take place. Many portions of this process are
conditionally present depending on the context of the deployments,
and not every step in this overview will happen in all circumstances.
Note that a connection between roles in this process does not necessarily
indicate that a specific protocol message is sent across the wire
between the components fulfilling the roles in question, or that a
particular step is required every time. For example, for a client instance interested
in only getting subject information directly, and not calling an RS,
all steps involving the RS below do not apply.
In some circumstances,
the information needed at a given stage is communicated out of band
or is preconfigured between the components or entities performing
the roles. For example, one entity can fulfil multiple roles, and so
explicit communication between the roles is not necessary within the
protocol flow.
| Resource |
|Instance| + | Server |
| | +---------------+ | (RS) |
| |--(2)->| Authorization | | |
| |<-(3)--| Server | | |
| | | (AS) | | |
| |--(4)->| | | |
| |<-(5)--| | | |
| |--------------(6)------------->| |
| | | |<~(7)~~| |
| |<-------------(8)------------->| |
| |--(9)->| | | |
| |<-(10)-| | | |
| |--------------(11)------------>| |
| | | |<~(12)~| |
| |-(13)->| | | |
| | | | | |
+--------+ +---------------+ +------------+
Legend
+ + + indicates a possible interaction with a human
----- indicates an interaction between protocol roles
~ ~ ~ indicates a potential equivalence or out-of-band communication between roles
]]>
- (A) The RQ interacts with the client instance to indicate a need for resources on
behalf of the RO. This could identify the RS the client instance needs to call,
the resources needed, or the RO that is needed to approve the
request. Note that the RO and RQ are often
the same entity in practice.
- (1) The client instance attempts to call the RS to determine
what access is needed.
The RS informs the client instance that access can be granted through the AS. Note that
for most situations, the client instance already knows which AS to talk to and which
kinds of access it needs.
- (2) The client instance requests access at the AS.
- (3) The AS processes the request and determines what is needed to fulfill
the request. The AS sends its response to the client instance.
- (B) If interaction is required, the
AS interacts with the RO to gather authorization.
The interactive component of the AS can function
using a variety of possible mechanisms including web page
redirects, applications, challenge/response protocols, or
other methods. The RO approves the request for the client instance
being operated by the RQ. Note that the RO and RQ are often
the same entity in practice.
- (4) The client instance continues the grant at the AS.
- (5) If the AS determines that access can be granted, it returns a
response to the client instance including an access token for
calling the RS and any directly returned information about the RO.
- (6) The client instance uses the access token to call the RS.
- (7) The RS determines if the token is sufficient for the request by
examining the token, potentially calling the AS. Note that
the RS could also examine the token directly, call an internal data store,
execute a policy engine request, or any number of alternative methods for
validating the token and its fitness for the request.
- (8) The client instance calls the RS using the access token
until the RS or client instance determine that the token is no longer valid.
- (9) When the token no longer works, the client instance fetches an
updated access token based on the
rights granted in (5).
- (10) The AS issues a new access token to the client instance.
- (11) The client instance uses the new access token to call the RS.
- (12) The RS determines if the new token is sufficient for the request by
examining the token, potentially calling the AS.
- (13) The client instance disposes of the token once the client instance
has completed its access of the RS and no longer needs the token.
The following sections and contain specific guidance on how to use
GNAP in different situations and deployments.
Redirect-based Interaction
In this example flow, the client instance is a web application that wants access to resources on behalf
of the current user, who acts as both the requesting party (RQ) and the resource
owner (RO). Since the client instance is capable of directing the user to an arbitrary URL and
receiving responses from the user's browser, interaction here is handled through
front-channel redirects using the user's browser. The client instance uses a persistent session
with the user to ensure the same user that is starting the interaction is the user
that returns from the interaction.
| | | |
| | | | | |
| |<-(3)-- Interaction Needed -------| | | |
| | | | | |
| |+ (4) + Redirect for Interaction + + + + + + + + + > | |
| | | | | |
| | | |<+ (5) +>| |
| | | | AuthN | |
| | | | | |
| | | |<+ (6) +>| |
| | | | AuthZ | |
| | | | | |
| |< (7) + Redirect for Continuation + + + + + + + + + +| |
| | | | +------+
| |--(8)--- Continue Request ------->| |
| | | |
| |<-(9)----- Grant Access ----------| |
| | | |
+--------+ +--------+
]]>
- The client instance establishes a verifiable session to the user, in the role of the RQ.
- The client instance requests access to the resource. The client instance indicates that
it can redirect to an arbitrary URL and
receive a callback from the browser. The client instance
stores verification information for its callback in the session created
in (1).
- The AS determines that interaction is needed and responds with
a URL to send the user to and
information needed to verify the callback in (7).
The AS also includes information the client instance will need to
continue the request in (8). The AS associates this
continuation information with an ongoing request that will be referenced in (4), (6), and (8).
- The client instance stores the verification and continuation information from (3) in the session from (1). The client instance
then redirects the user to the URL given by the AS in (3).
The user's browser loads the interaction redirect URL. The AS loads the pending
request based on the incoming URL generated in (3).
- The user authenticates at the AS, taking on the role of the RO.
- As the RO, the user authorizes the pending request from the client instance.
- When the AS is done interacting with the user, the AS
redirects the user back to the
client instance using the callback URL provided in (2). The callback URL is augmented with
an interaction reference that the AS associates with the ongoing
request created in (2) and referenced in (4). The callback URL is also
augmented with a hash of the security information provided
in (2) and (3). The client instance loads the verification information from (2) and (3) from
the session created in (1). The client instance calculates a hash
based on this information and continues only if the hash validates.
Note that the client instance needs to ensure that the parameters for the incoming
request match those that it is expecting from the session created
in (1). The client instance also needs to be prepared for the RQ never being returned
to the client instance and handle time outs appropriately.
- The client instance loads the continuation information from (3) and sends the
interaction reference from (7) in a request to
continue the request. The AS
validates the interaction reference ensuring that the reference
is associated with the request being continued.
- If the request has been authorized, the AS grants access to the information
in the form of access tokens and
direct subject information to the client instance.
An example set of protocol messages for this method can be found in .
User-code Interaction
In this example flow, the client instance is a device that is capable of presenting a short,
human-readable code to the user and directing the user to enter that code at
a known URL. The client instance is not capable of presenting an arbitrary URL to the user,
nor is it capable of accepting incoming HTTP requests from the user's browser.
The client instance polls the AS while it is waiting for the RO to authorize the request.
The user's interaction is assumed to occur on a secondary device. In this example
it is assumed that the user is both the RQ and RO, though the user is not assumed
to be interacting with the client instance through the same web browser used for interaction at
the AS.
| | | + |
| | | | | RQ |
| |<-(2)-- Interaction Needed -------| | |(User)|
| | | | | |
| |+ (3) + + Display User Code + + + + + + + + + + + + >| |
| | | | | |
| | | |<+ (4) + | |
| | | |Open URI | |
| | | | | |
| | | |<+ (5) +>| |
| | | | AuthN | |
| |--(9)--- Continue Request (A) --->| | | |
| | | |<+ (6) +>| |
| |<-(10)- Not Yet Granted (Wait) ---| | Code | |
| | | | | |
| | | |<+ (7) +>| |
| | | | AuthZ | |
| | | | | |
| | | |<+ (8) +>| |
| | | |Completed| |
| | | | | |
| |--(11)-- Continue Request (B) --->| | +------+
| | | |
| |<-(12)----- Grant Access ---------| |
| | | |
+--------+ +--------+
]]>
- The client instance requests access to the resource. The client instance indicates that
it can display a user code.
- The AS determines that interaction is needed and responds with
a user code to communicate to the user. This
could optionally include a URL to direct the user to, but this URL should
be static and so could be configured in the client instance's documentation.
The AS also includes information the client instance will need to
continue the request in (8) and (10). The AS associates this
continuation information with an ongoing request that will be referenced in (4), (6), (8), and (10).
- The client instance stores the continuation information from (2) for use in (8) and (10). The client instance
then communicates the code to the user given by the AS in (2).
- The user's directs their browser to the user code URL. This URL is stable and
can be communicated via the client software's documentation, the AS documentation, or
the client software itself. Since it is assumed that the RO will interact
with the AS through a secondary device, the client instance does not provide a mechanism to
launch the RO's browser at this URL.
- The RQ authenticates at the AS, taking on the role of the RO.
- The RO enters the code communicated in (3) to the AS. The AS validates this code
against a current request in process.
- As the RO, the user authorizes the pending request from the client instance.
- When the AS is done interacting with the user, the AS
indicates to the RO that the request has been completed.
- Meanwhile, the client instance loads the continuation information stored at (3) and
continues the request. The AS determines which
ongoing access request is referenced here and checks its state.
- If the access request has not yet been authorized by the RO in (6),
the AS responds to the client instance to continue the request
at a future time through additional polled continuation requests. This response can include
updated continuation information as well as information regarding how long the
client instance should wait before calling again. The client instance replaces its stored
continuation information from the previous response (2).
Note that the AS may need to determine that the RO has not approved
the request in a sufficient amount of time and return an appropriate
error to the client instance.
- The client instance continues to poll the AS with the new
continuation information in (9).
- If the request has been authorized, the AS grants access to the information
in the form of access tokens and
direct subject information to the client instance.
An example set of protocol messages for this method can be found in .
Asynchronous Authorization
In this example flow, the RQ and RO roles are fulfilled by different parties, and
the RO does not interact with the client instance. The AS reaches out asynchronously to the RO
during the request process to gather the RO's authorization for the client instance's request.
The client instance polls the AS while it is waiting for the RO to authorize the request.
| | | |
| | | | | |
| |<-(2)-- Not Yet Granted (Wait) ---| | | |
| | | |<+ (3) +>| |
| | | | AuthN | |
| |--(6)--- Continue Request (A) --->| | | |
| | | |<+ (4) +>| |
| |<-(7)-- Not Yet Granted (Wait) ---| | AuthZ | |
| | | | | |
| | | |<+ (5) +>| |
| | | |Completed| |
| | | | | |
| |--(8)--- Continue Request (B) --->| | +------+
| | | |
| |<-(9)------ Grant Access ---------| |
| | | |
+--------+ +--------+
]]>
- The client instance requests access to the resource. The client instance does not
send any interactions modes to the server, indicating that
it does not expect to interact with the RO. The client instance can also signal
which RO it requires authorization from, if known, by using the
user request section.
- The AS determines that interaction is needed, but the client instance cannot interact
with the RO. The AS responds with the information the client instance
will need to continue the request in (6) and (8), including
a signal that the client instance should wait before checking the status of the request again.
The AS associates this continuation information with an ongoing request that will be
referenced in (3), (4), (5), (6), and (8).
- The AS determines which RO to contact based on the request in (1), through a
combination of the user request, the
resources request, and other policy information. The AS
contacts the RO and authenticates them.
- The RO authorizes the pending request from the client instance.
- When the AS is done interacting with the RO, the AS
indicates to the RO that the request has been completed.
- Meanwhile, the client instance loads the continuation information stored at (3) and
continues the request. The AS determines which
ongoing access request is referenced here and checks its state.
- If the access request has not yet been authorized by the RO in (6),
the AS responds to the client instance to continue the request
at a future time through additional polling. This response can include
refreshed credentials as well as information regarding how long the
client instance should wait before calling again. The client instance replaces its stored
continuation information from the previous response (2).
Note that the AS may need to determine that the RO has not approved
the request in a sufficient amount of time and return an appropriate
error to the client instance.
- The client instance continues to poll the AS with the new
continuation information from (7).
- If the request has been authorized, the AS grants access to the information
in the form of access tokens and
direct subject information to the client instance.
An example set of protocol messages for this method can be found in .
Software-only Authorization
In this example flow, the AS policy allows the client instance to make a call on its own behalf,
without the need for a RO to be involved at runtime to approve the decision.
Since there is no explicit RO, the client instance does not interact with an RO.
| |
| | | |
| |<-(2)---- Grant Access -----------| |
| | | |
+--------+ +--------+
]]>
- The client instance requests access to the resource. The client instance does not
send any interactions modes to the server.
- The AS determines that the request is been authorized,
the AS grants access to the information
in the form of access tokens and
direct subject information to the client instance.
An example set of protocol messages for this method can be found in .
Refreshing an Expired Access Token
In this example flow, the client instance receives an access token to access a resource server through
some valid GNAP process. The client instance uses that token at the RS for some time, but eventually
the access token expires. The client instance then gets a new access token by rotating the
expired access token at the AS using the token's management URL.
| |
| | | |
| |<-(2)--- Grant Access --------------------| |
| | | |
| | +--------+ | |
| |--(3)--- Access Resource --->| RS | | |
| | | | | |
| |<-(4)--- Error Response -----| | | |
| | +--------+ | |
| | | |
| |--(5)--- Rotate Token ------------------->| |
| | | |
| |<-(6)--- Rotated Token -------------------| |
| | | |
+--------+ +--------+
]]>
- The client instance requests access to the resource.
- The AS grants access to the resource with an
access token usable at the RS. The access token
response includes a token management URI.
- The client instance presents the token to the RS. The RS
validates the token and returns an appropriate response for the
API.
- When the access token is expired, the RS responds to the client instance with
an error.
- The client instance calls the token management URI returned in (2) to
rotate the access token. The client instance
presents the access token as well as the appropriate key.
- The AS validates the rotation request including the signature
and keys presented in (5) and returns a
new access token. The response includes
a new access token and can also include updated token management
information, which the client instance will store in place of the values
returned in (2).
Requesting Access
To start a request, the client instance sends JSON document with an object as its root. Each
member of the request object represents a different aspect of the
client instance's request. Each field is described in detail in a section below.
-
resources (object / array of objects/strings)
-
Describes the rights that the client instance is requesting for one or more access tokens to be
used at RS's.
-
subject (object)
-
Describes the information about the RO that the client instance is requesting to be returned
directly in the response from the AS.
-
client (object / string)
-
Describes the client instance that is making this request, including
the key that the client instance will use to protect this request and any continuation
requests at the AS and any user-facing information about the client instance used in
interactions at the AS.
-
user (object / string)
-
Identifies the RQ to the AS in a manner that the AS can verify, either directly or
by interacting with the RQ to determine their status as the RO.
-
interact (object)
-
Describes the modes that the client instance has for allowing the RO to interact with the
AS and modes for the client instance to receive updates when interaction is complete.
-
capabilities (array of strings)
-
Identifies named extension capabilities that the client instance can use, signaling to the AS
which extensions it can use.
-
existing_grant (string)
-
Identifies a previously-existing grant that the client instance is extending with this request.
Additional members of this request object can be defined by extensions to this protocol
as described in
A non-normative example of a grant request is below:
The request MUST be sent as a JSON object in the body of the HTTP
POST request with Content-Type application/json,
unless otherwise specified by the signature mechanism.
Requesting Resources
If the client instance is requesting one or more access tokens for the
purpose of accessing an API, the client instance MUST include a resources
field. This field MUST be an array (for a single access token) or
an object (for multiple access tokens), as described in the following
sections.
Requesting a Single Access Token
When requesting an access token, the client instance MUST send a
resources field containing a JSON array. The elements of the JSON
array represent rights of access that the client instance is requesting in
the access token. The requested access is the union of all elements
within the array.
The client instance declares what access it wants to associate with the
resulting access token using objects that describe multiple
dimensions of access. Each object contains a type
property that determines the type of API that the client instance is calling.
-
type (string)
-
The type of resource request as a string. This field MAY
define which other fields are allowed in the request object.
This field is REQUIRED.
The value of this field is under the control of the AS.
This field MUST be compared using an exact byte match of the string
value against known types by the AS. The AS MUST ensure that there
is no collision between different authorization data types that it
supports. The AS MUST NOT do any collation or normalization of data
types during comparison. It is RECOMMENDED that designers of general-purpose
APIs use a URI for this field to avoid collisions between multiple
API types protected by a single AS.
While it is expected that many APIs will have its own properties, a set of
common properties are defined here. Specific API implementations
SHOULD NOT re-use these fields with different semantics or syntax. The
available values for these properties are determined by the API
being protected at the RS.
-
actions (array of strings)
-
The types of actions the client instance will take at the RS as an array of strings.
For example, a client instance asking for a combination of "read" and "write" access.
-
locations (array of strings)
-
The location of the RS as an array of
strings. These strings are typically URIs identifying the
location of the RS.
-
datatypes (array of strings)
-
The kinds of data available to the client instance at the RS's API as an
array of strings. For example, a client instance asking for access to
raw "image" data and "metadata" at a photograph API.
-
identifier (string)
-
A string identifier indicating a specific resource at the RS.
For example, a patient identifier for a medical API or
a bank account number for a financial API.
The following non-normative example is asking for three kinds of access (read, write, delete) to each of
two different locations and two different data types (metadata, images) for a single access token
using the fictitious photo-api type definition.
The access requested for a given object when using these fields
is the cross-product of all fields of the object. That is to
say, the object represents a request for all action values listed within the object
to be used at all locations values listed within the object for all datatype
values listed within the object. Assuming the request above was granted,
the RC could assume that it
would be able to do a read action against the images on the first server
as well as a delete action on the metadata of the second server, or any other
combination of these fields, using the same access token.
To request a different combination of access,
such as requesting one action against one location
and a different action against a different location, the
RC can include multiple separate objects in the resources array.
The following non-normative example uses the same fictitious photo-api
type definition to request a single access token with more specifically
targeted access rights by using two discrete objects within the request.
The access requested here is for read access to images on one server
while simultaneously requesting write and delete access for metadata on a different
server, but importantly without requesting write or delete access to images on the
first server.
It is anticipated that API designers will use a combination
of common fields defined in this specification as well as
fields specific to the API itself. The following non-normative
example shows the use of both common and API-specific fields as
part of two different fictitious API type values. The first
access request includes the actions, locations, and datatypes
fields specified here as well as the API-specific geolocation
field. The second access request includes the actions and
identifier fields specified here as well as the API-specific
currency field.
If this request is approved,
the resulting access token's access rights will be
the union of the requested types of access for each of the two APIs, just as above.
Requesting Resources By Reference
Instead of sending an object describing the requested resource,
a client instance MAY send a string known to
the AS or RS representing the access being requested. Each string
SHOULD correspond to a specific expanded object representation at
the AS.
This value is opaque to the client instance and MAY be any
valid JSON string, and therefore could include spaces, unicode
characters, and properly escaped string sequences. However, in some
situations the value is intended to be
seen and understood by the client software's developer. In such cases, the
API designer choosing any such human-readable strings SHOULD take steps
to ensure the string values are not easily confused by a developer,
such as by limiting the strings to easily disambiguated characters.
This functionality is similar in practice to OAuth 2's scope parameter , where a single string
represents the set of access rights requested by the client instance. As such, the reference
string could contain any valid OAuth 2 scope value as in . Note that the reference
string here is not bound to the same character restrictions as in OAuth 2's scope definition.
A single "resources" array MAY include both object-type and
string-type resource items. In this non-normative example,
the RC is requesting access to a photo-api and financial-transaction API type
as well as the reference values of read, dolphin-metadata, and some other thing.
The requested access is the union of all elements of the array, including both objects and
reference strings.
Requesting Multiple Access Tokens
When requesting multiple access tokens, the resources field is
a JSON object. The names of the JSON object fields are token
identifiers chosen by the client instance, and MAY be any valid string. The
values of the JSON object fields are JSON arrays representing a single
access token request, as specified in
requesting a single access token.
The following non-normative example shows a request for two
separate access tokens, token1 and token2.
Any approved access requests are returned in the
multiple access token response structure using
the token identifiers in the request.
Signaling Token Behavior
While the AS is ultimately in control of how tokens are returned and bound to the client instance,
sometimes the client instance has context about what it can support that can affect the AS's
response. This specification defines several flags that are passed as
resource reference strings.
Each flag applies only to the single resource request in which it appears.
Support of all flags is optional, such as any other resource reference value.
-
multi_token
-
The client instance wishes to support multiple simultaneous access tokens through the
token rotation process. When the client instance rotates an access token,
the AS does not invalidate the previous access token. The old access token
continues to remain valid until such time as it expires or is revoked
through other means.
-
split_token
-
The client instance is capable of receiving multiple access tokens
in response to any single token request, or
receiving a different number of tokens than specified in the
multiple token request. The labels of the
returned additional tokens are chosen by the AS. The client instance MUST be able
to tell from the token response where and how it can use each of the
access tokens.
[[ See issue #37 ]]
-
bind_token
-
The client instance wants the issued access token to be bound to the key the client instance used
to make the request. The resulting access token MUST be bound using the same
proof mechanism used by the client instance with a key value of true, indicating
the client instance's presented key is to be used for binding.
[[ See issue #38 ]]
The AS MUST respond with any applied flags in the token response
resources section.
In this non-normative example, the requested access token is to be bound to
the client instance's key and should be kept during rotation.
Additional flags can be registered in a registry TBD.
[[ See issue #39 ]]
Requesting User Information
If the client instance is requesting information about the RO from
the AS, it sends a subject field as a JSON object. This object MAY
contain the following fields (or additional fields defined in
a registry TBD).
-
sub_ids (array of strings)
-
An array of subject identifier subject types
requested for the RO, as defined by .
-
assertions (array of strings)
-
An array of requested assertion formats. Possible values include
id_token for an ID Token and saml2 for a SAML 2 assertion. Additional
assertion values are defined by a registry TBD.
[[ See issue #41 ]]
The AS can determine the RO's identity and permission for releasing
this information through interaction with the RO,
AS policies, or assertions presented by the client instance. If
this is determined positively, the AS MAY return the RO's information in its response
as requested.
Subject identifiers requested by the client instance serve only to identify
the RO in the context of the AS and can't be used as communication
channels by the client instance, as discussed in .
The AS SHOULD NOT re-use subject identifiers for multiple different ROs.
[[ See issue #42 ]]
Note: the "sub_ids" and "assertions" request fields are independent of
each other, and a returned assertion MAY omit a requested subject
identifier.
[[ See issue #43 ]]
Identifying the Client Instance
When sending a non-continuation request to the AS, the client instance MUST identify
itself by including the client field of the request and by signing the
request as described in . Note that for a
continuation request, the client instance is identified by its
association with the request being continued and so this field is
not sent under those circumstances.
When client instance information is sent
by value, the client field of the request consists of a JSON
object with the following fields.
-
key (object / string)
-
The public key of the client instance to be used in this request as
described in . This field is REQUIRED.
-
class_id (string)
-
An identifier string that the AS can use to identify the
client software comprising this client instance. The contents
and format of this field are up to the AS. This field
is OPTIONAL.
-
display (object)
-
An object containing additional information that the AS
MAY display to the RO during interaction, authorization,
and management. This field is OPTIONAL.
Additional fields are defined in a registry TBD.
The client instance MUST prove possession of any presented key by the proof mechanism
associated with the key in the request. Proof types
are defined in a registry TBD and an initial set of methods
is described in .
Note that the AS MAY know the client instance's public key ahead of time, and
the AS MAY apply different policies to the request depending on what
has been registered against that key.
If the same public key is sent by value on subsequent access requests, the AS SHOULD
treat these requests as coming from the same client instance for purposes
of identification, authentication, and policy application.
If the AS does not know the client instance's public key ahead of time, the AS
MAY accept or reject the request based on AS policy, attestations
within the client request, and other mechanisms.
[[ See issue #44 ]]
Identifying the Client Instance
If the client instance has an instance identifier that the AS can use to determine
appropriate key information, the client instance can send this value in the instance_id
field. The instance identifier MAY be assigned to a client instance at runtime
through the or MAY be obtained in another fashion,
such as a static registration process at the AS.
-
instance_id (string)
-
An identifier string that the AS can use to identify the
particular instance of this client software. The content and structure of
this identifier is opaque to the client instance.
If there are no additional fields to send, the client instance MAY send the instance
identifier as a direct reference value in lieu of the object.
When the AS receives a request with an instance identifier, the AS MUST
ensure that the key used to sign the request is
associated with the instance identifier.
If the instance_id field is sent, it MUST NOT be accompanied by other fields unless such
fields are explicitly marked safe for inclusion alongside the instance
identifier.
[[ See issue #45 ]]
If the AS does not recognize the instance identifier, the request MUST be rejected
with an error.
If the client instance is identified in this manner, the registered key for the client instance
MAY be a symmetric key known to the AS. The client instance MUST NOT send a
symmetric key by value in the request, as doing so would expose
the key directly instead of proving possession of it.
Identifying the Client Instance Key
The client instance key MUST be a public key in at least one
supported format and MUST be applicable to the
proofing mechanism used in the request. If the key is sent in multiple
formats, all the keys MUST be the same. The key presented in this
field MUST be the key used to sign the request.
-
proof (string)
-
The form of proof that the client instance will use when
presenting the key to the AS. The valid values of this field and
the processing requirements for each are detailed in
. This field is REQUIRED.
-
jwk (object)
-
Value of the public key as a JSON Web Key. 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.
-
cert (string)
-
PEM serialized value of the certificate used to
sign the request, with optional internal whitespace.
-
cert#S256 (string)
-
The certificate thumbprint calculated as
per OAuth-MTLS in base64 URL
encoding.
Additional key types are defined in a registry TBD.
This non-normative example shows a single key presented in multiple
formats using a single proofing mechanism.
Continuation requests
MUST use the same key (or its most recent rotation) and proof method as the initial request.
Providing Displayable Client Instance Information
If the client instance has additional information to display to the RO
during any interactions at the AS, it MAY send that information in the
"display" field. This field is a JSON object that declares information
to present to the RO during any interactive sequences.
-
name (string)
-
Display name of the client software
-
uri (string)
-
User-facing web page of the client software
-
logo_uri (string)
-
Display image to represent the client
software
[[ See issue #48 ]]
Additional display fields are defined by a registry TBD.
The AS SHOULD use these values during interaction with the RO.
The values are for informational purposes only and MUST NOT
be taken as authentic proof of the client instance's identity or source.
The AS MAY restrict display values to specific client instances, as identified
by their keys in .
Authenticating the Client Instance
If the presented key is known to the AS and is associated with a single instance
of the client software, the process of presenting a key and proving possession of that key
is sufficient to authenticate the client instance to the AS. The AS MAY associate policies
with the client instance identified by this key, such as limiting which resources
can be requested and which interaction methods can be used. For example, only
specific client instances with certain known keys might be trusted with access tokens without the
AS interacting directly with the RO as in .
The presentation of a key allows the AS to strongly associate multiple
successive requests from the same client instance with each other. This
is true when the AS knows the key ahead of time and can use the key to
authenticate the client instance, but also if the key is
ephemeral and created just for this series of requests. As such the
AS MAY allow for client instances to make requests with unknown keys. This pattern allows
for ephemeral client instances, such as single-page applications, and client software with many individual long-lived instances,
such as mobile applications, to generate key pairs per instance and use the keys within
the protocol without having to go through a separate registration step.
The AS MAY limit which capabilities are made available to client instances
with unknown keys. For example, the AS could have a policy saying that only
previously-registered client instances can request particular resources, or that all
client instances with unknown keys have to be interactively approved by an RO.
Identifying the User
If the client instance knows the identity of the RQ through one or more
identifiers or assertions, the client instance MAY send that information to the
AS in the "user" field. The client instance MAY pass this information by value
or by reference.
-
sub_ids (array of strings)
-
An array of subject identifiers for the
RQ, as defined by .
-
assertions (object)
-
An object containing assertions as values keyed on the assertion
type defined by a registry TBD. Possible keys include
id_token for an ID Token and saml2 for a SAML 2 assertion. Additional
assertion values are defined by a registry TBD.
[[ See issue #41 ]]
Subject identifiers are hints to the AS in determining the
RO and MUST NOT be taken as declarative statements that a particular
RO is present at the client instance and acting as the RQ. Assertions SHOULD be validated by the
AS.
[[ See issue #49 ]]
If the identified RQ does not match the RO present at the AS
during an interaction step, the AS SHOULD reject the request with an error.
[[ See issue #50 ]]
If the AS trusts the client instance to present verifiable assertions, the AS MAY
decide, based on its policy, to skip interaction with the RO, even
if the client instance provides one or more interaction modes in its request.
Identifying the User by Reference
User reference identifiers can be dynamically
issued by the AS to allow the client instance
to represent the same RQ to the AS over subsequent requests.
If the client instance has a reference for the RQ at this AS, the
client instance MAY pass that reference as a string. The format of this string
is opaque to the client instance.
User reference identifiers are not intended to be human-readable
user identifiers or structured assertions. For the client instance to send
either of these, use the full user request object instead.
[[ See issue #51 ]]
If the AS does not recognize the user reference, it MUST
return an error.
Interacting with the User
Many times, the AS will require interaction with the RO in order to
approve a requested delegation to the client instance for both resources and direct
claim information. Many times the RQ using the client instance is the same person as
the RO, and the client instance can directly drive interaction with the AS by redirecting
the RQ on the same device, or by launching an application. Other times, the
client instance can provide information to start the RO's interaction on a secondary
device, or the client instance will wait for the RO to approve the request asynchronously.
The client instance could also be signaled that interaction has completed by the AS making
callbacks. To facilitate all of these modes, the client instance declares the means that it
can interact using the interact field.
The interact field is a JSON object with keys that declare
different interaction modes. A client instance MUST NOT declare an
interaction mode it does not support.
The client instance MAY send multiple modes in the same request.
There is no preference order specified in this request. An AS MAY
respond to any, all, or none of the presented interaction modes in a request, depending on
its capabilities and what is allowed to fulfill the request. This specification
defines the following interaction modes:
-
redirect (boolean)
-
Indicates that the client instance can direct the RQ to an arbitrary URL
at the AS for interaction.
-
app (boolean)
-
Indicates that the client instance can launch an application on the RQ's
device for interaction.
-
callback (object)
-
Indicates that the client instance can receive a callback from the AS
after interaction with the RO has concluded.
-
user_code (boolean)
-
Indicates that the client instance can communicate a human-readable short
code to the RQ for use with a stable URL at the AS.
-
ui_locales (array of strings)
-
Indicates the RQ's preferred locales that the AS can use
during interaction, particularly before the RO has
authenticated.
The following sections detail requests for interaction
modes. Additional interaction modes are defined in
a registry TBD.
In this non-normative example, the client instance is indicating that it can redirect
the RQ to an arbitrary URL and can receive a callback through
a browser request.
In this non-normative example, the client instance is indicating that it can
display a user code and direct the RQ
to an arbitrary URL on a secondary
device, but it cannot accept a callback.
If the client instance does not provide a suitable interaction mechanism, the
AS cannot contact the RO asynchronously, and the AS determines
that interaction is required, then the AS SHOULD return an
error since the client instance will be unable to complete the
request without authorization.
The AS SHOULD apply suitable timeouts to any interaction mechanisms
provided, including user codes and redirection URLs. The client instance SHOULD
apply suitable timeouts to any callback URLs.
Redirect to an Arbitrary URL
If the client instance is capable of directing the RQ to a URL defined
by the AS at runtime, the client instance indicates this by sending the
"redirect" field with the boolean value "true". The means by which
the client instance will activate this URL is out of scope of this
specification, but common methods include an HTTP redirect,
launching a browser on the RQ's device, providing a scannable
image encoding, and printing out a URL to an interactive
console.
If this interaction mode is supported for this client instance and
request, the AS returns a redirect interaction response .
Open an Application-specific URL
If the client instance can open a URL associated with an application on
the RQ's device, the client instance indicates this by sending the "app"
field with boolean value "true". The means by which the client instance
determines the application to open with this URL are out of scope of
this specification.
If this interaction mode is supported for this client instance and
request, the AS returns an app interaction response with an app URL
payload .
[[ See issue #54 ]]
Receive a Callback After Interaction
If the client instance is capable of receiving a message from the AS indicating
that the RO has completed their interaction, the client instance
indicates this by sending the "callback" field. The value of this
field is an object containing the following members.
-
uri (string)
-
REQUIRED. Indicates the URI to send the RO to
after interaction. This URI MAY be unique per request and MUST
be hosted by or accessible by the client instance. This URI MUST NOT contain
any fragment component. This URI MUST be protected by HTTPS, be
hosted on a server local to the RO's browser ("localhost"), or
use an application-specific URI scheme. If the client instance needs any
state information to tie to the front channel interaction
response, it MUST use a unique callback URI to link to
that ongoing state. The allowable URIs and URI patterns MAY be restricted by the AS
based on the client instance's presented key information. The callback URI
SHOULD be presented to the RO during the interaction phase
before redirect.
[[ See issue #55 ]]
-
nonce (string)
-
REQUIRED. Unique value to be used in the
calculation of the "hash" query parameter sent to the callback URL,
must be sufficiently random to be unguessable by an attacker.
MUST be generated by the client instance as a unique value for this
request.
-
method (string)
-
REQUIRED. The callback method that the AS will use to contact the client instance.
Valid values include redirect
and push , with other values
defined by a registry TBD.
-
hash_method (string)
-
OPTIONAL. The hash calculation
mechanism to be used for the callback hash in . Can be one of sha3 or sha2. If
absent, the default value is sha3.
[[ See issue #56 ]]
If this interaction mode is supported for this client instance and
request, the AS returns a nonce for use in validating
the callback response.
Requests to the callback URI MUST be processed as described in
, and the AS MUST require
presentation of an interaction callback reference as described in
.
[[ See issue #58 ]]
[[ See issue #59 ]]
Receive an HTTP Callback Through the Browser
A callback method value of redirect indicates that the client instance
will expect a call from the RO's browser using the HTTP method
GET as described in .
Requests to the callback URI MUST be processed by the client instance as described in
.
Since the incoming request to the callback URL is from the RO's
browser, this method is usually used when the RO and RQ are the
same entity. As such, the client instance MUST ensure the RQ is present on the request to
prevent substitution attacks.
Receive an HTTP Direct Callback
A callback method value of push indicates that the client instance will
expect a call from the AS directly using the HTTP method POST
as described in .
Requests to the callback URI MUST be processed by the client instance as described in
.
Since the incoming request to the callback URL is from the AS and
not from the RO's browser, the client instance MUST NOT require the RQ to
be present on the incoming HTTP request.
[[ See issue #60 ]]
Display a Short User Code
If the client instance is capable of displaying or otherwise communicating
a short, human-entered code to the RO, the client instance indicates this
by sending the "user_code" field with the boolean value "true". This
code is to be entered at a static URL that does not change at
runtime, as described in .
If this interaction mode is supported for this client instance and
request, the AS returns a user code and interaction URL as specified
in .
Indicate Desired Interaction Locales
If the client instance knows the RQ's locale and language preferences, the
client instance can send this information to the AS using the ui_locales field
with an array of locale strings as defined by .
If possible, the AS SHOULD use one of the locales in the array, with
preference to the first item in the array supported by the AS. If none
of the given locales are supported, the AS MAY use a default locale.
Extending Interaction Modes
Additional interaction modes are defined in a registry TBD.
Declaring Client Capabilities
If the client software supports extension capabilities, the client instance MAY present them
to the AS in the "capabilities" field. This field is an array of
strings representing specific extensions and capabilities, as defined
by a registry TBD.
Referencing an Existing Grant Request
If the client instance has a reference handle from a previously granted
request, it MAY send that reference in the "existing_grant" field. This
field is a single string consisting of the value of the access_token
returned in a previous request's continuation response.
The AS MUST dereference the grant associated with the reference and
process this request in the context of the referenced one. The AS
MUST NOT alter the existing grant associated with the reference.
[[ See issue #62 ]]
Extending The Grant Request
The request object MAY be extended by registering new items in
a registry TBD. Extensions SHOULD be orthogonal to other parameters.
Extensions MUST document any aspects where the extension item affects or influences
the values or behavior of other request and response objects.
Grant Response
In response to a client instance's request, the AS responds with a JSON object
as the HTTP entity body. Each possible field is detailed in the sections below
-
continue (object)
-
Indicates that the client instance can continue the request by making one or
more continuation requests.
-
access_token (object)
-
A single access token that the client instance can use to call the RS on
behalf of the RO.
-
multiple_access_token (object)
-
Multiple named access tokens that the client instance can use to call the
RS on behalf of the RO.
-
interact (object)
-
Indicates that interaction through some set of defined mechanisms
needs to take place.
-
subject (object)
-
Claims about the RO as known and declared by the AS.
-
instance_id (string)
-
An identifier this client instance instance can use to identify itself when making
future requests.
-
user_handle (string)
-
An identifier this client instance instance can use to identify its current RQ when
making future requests.
-
error (object)
-
An error code indicating that something has gone wrong.
In this example, the AS is returning an interaction URL,
a callback nonce, and a continuation response.
In this example, the AS is returning a bearer access token
with a management URL and a subject identifier in the form of
an email address.
Request Continuation
If the AS determines that the request can be continued with
additional requests, it responds with the "continue" field. This field
contains a JSON object with the following properties.
-
uri (string)
-
REQUIRED. The URI at which the client instance can make
continuation requests. This URI MAY vary per
request, or MAY be stable at the AS if the AS includes
an access token. The client instance MUST use this
value exactly as given when making a continuation request.
-
wait (integer)
-
RECOMMENDED. The amount of time in integer
seconds the client instance SHOULD wait after receiving this continuation
handle and calling the URI.
-
access_token (object)
-
REQUIRED. A unique access token for continuing the request, in the format specified
in . This access token MUST be bound to the
client instance's key used in the request and MUST NOT be a bearer token. As a consequence,
the key field of this access token is always the boolean value true.
This access token MUST NOT be usable at resources outside of the AS.
The client instance MUST present the access token in all requests to the continuation URI as
described in .
[[ See issue #66 ]]
The client instance can use the values of this field to continue the
request as described in . Note that the
client instance MUST sign all continuation requests with its key as described
in and
MUST present the access token in its continuation request.
This field SHOULD be returned when interaction is expected, to
allow the client instance to follow up after interaction has been
concluded.
Access Tokens
If the AS has successfully granted one or more access tokens to the client instance,
the AS responds with either the access_token or the multiple_access_token
field. The AS MUST NOT respond with both
the access_token and multiple_access_token fields.
[[ See issue #68 ]]
Single Access Token
If the client instance has requested a single access token and the AS has
granted that access token, the AS responds with the "access_token"
field. The value of this field is an object with the following
properties.
-
value (string)
-
REQUIRED. The value of the access token as a
string. The value is opaque to the client instance. The value SHOULD be
limited to ASCII characters to facilitate transmission over HTTP
headers within other protocols without requiring additional encoding.
-
manage (string)
-
OPTIONAL. The management URI for this
access token. If provided, the client instance MAY manage its access
token as described in . This management
URI is a function of the AS and is separate from the RS
the client instance is requesting access to.
This URI MUST NOT include the
access token value and SHOULD be different for each access
token issued in a request.
-
resources (array of objects/strings)
-
RECOMMENDED. A description of the rights
associated with this access token, as defined in
. If included, this MUST reflect the rights
associated with the issued access token. These rights MAY vary
from what was requested by the client instance.
-
expires_in (integer)
-
OPTIONAL. The number of seconds in
which the access will expire. The client instance MUST NOT use the access
token past this time. An RS MUST NOT accept an access token
past this time. Note that the access token MAY be revoked by the
AS or RS at any point prior to its expiration.
-
key (object / string / boolean)
-
REQUIRED. The key that the token is bound to. If the boolean value true is used,
the token is bound to the key used by the client instance in its request
for access. If the boolean value false is used,
the token is a bearer token with no key bound to it.
Otherwise, the key MUST be an object or string in a format
described in , describing a public key to which the
client instance can use the associated private key. The client instance MUST be able to
dereference or process the key information in order to be able
to sign the request.
The following non-normative example shows a single bearer token with a management
URL that has access to three described resources.
The following non-normative example shows a single access token bound to the client instance's key, which
was presented using the detached JWS binding method.
If the client instance requested multiple access tokens, the AS MUST NOT respond with a
single access token structure unless the client instance sends the split_token flag as described in .
[[ See issue #69 ]]
Multiple Access Tokens
If the client instance has requested multiple access tokens and the AS has
granted at least one of them, the AS responds with the
"multiple_access_tokens" field. The value of this field is a JSON
object, and the property names correspond to the token identifiers
chosen by the client instance in the multiple access token request.
The values of the properties of this object are access
tokens as described in .
In this non-normative example, two bearer tokens are issued under the
names token1 and token2, and only the first token has a management
URL associated with it.
Each access token corresponds to the named resources arrays in
the client instance's request.
The multiple access token response MUST be used when multiple access tokens are
requested, even if only one access token is issued as a result of the request.
The AS MAY refuse to issue one or more of the
requested access tokens, for any reason. In such cases the refused token is omitted
from the response and all of the other issued access
tokens are included in the response the requested names appropriate names.
If the client instance requested a single access token, the AS MUST NOT respond with the multiple
access token structure unless the client instance sends the split_token flag as described in .
Each access token MAY have different proofing mechanisms. If
management is allowed, each access token SHOULD have different management URIs.
[[ See issue #70 ]]
Interaction Modes
If the client instance has indicated a capability to interact with the RO in its request,
and the AS has determined that interaction is both
supported and necessary, the AS responds to the client instance with any of the
following values in the interact field of the response. There is
no preference order for interaction modes in the response,
and it is up to the client instance to determine which ones to use. All supported
interaction methods are included in the same interact object.
-
redirect (string)
-
Redirect to an arbitrary URL.
-
app (string)
-
Launch of an application URL.
-
callback (string)
-
Callback to a client instance accessible URL after interaction is completed.
-
user_code (object)
-
Display a short user code.
Additional interaction mode responses can be defined in a registry TBD.
The AS MUST NOT respond with any interaction mode that the
client instance did not indicate in its request. The AS MUST NOT respond with
any interaction mode that the AS does not support. Since interaction
responses include secret or unique information, the AS SHOULD
respond to each interaction mode only once in an ongoing request,
particularly if the client instance modifies its request.
Redirection to an arbitrary URL
If the client instance indicates that it can redirect to an arbitrary URL and the AS supports this mode for the client instance's
request, the AS responds with the "redirect" field, which is
a string containing the URL to direct the RQ to. This URL MUST be
unique for the request and MUST NOT contain any security-sensitive
information.
The interaction URL returned represents a function of the AS but MAY be completely
distinct from the URL the client instance uses to request access, allowing an
AS to separate its user-interactive functionality from its back-end security
functionality.
[[ See issue #72 ]]
The client instance sends the RQ to the URL to interact with the AS. The
client instance MUST NOT alter the URL in any way. The means for the client instance
to send the RQ to this URL is out of scope of this specification,
but common methods include an HTTP redirect, launching the system
browser, displaying a scannable code, or printing out the URL in an
interactive console.
Launch of an application URL
If the client instance indicates that it can launch an application URL and
the AS supports this mode for the client instance's request, the AS
responds with the "app" field, which is a string containing the URL
to direct the RQ to. This URL MUST be unique for the request and
MUST NOT contain any security-sensitive information.
The client instance launches the URL as appropriate on its platform, and
the means for the client instance to launch this URL is out of scope of this
specification. The client instance MUST NOT alter the URL in any way. The
client instance MAY attempt to detect if an installed application will
service the URL being sent before attempting to launch the
application URL.
[[ See issue #71 ]]
Post-interaction Callback to a Client Instance Accessible URL
If the client instance indicates that it can receive a post-interaction callback on a URL and the AS supports this mode for the
client instance's request, the AS responds with a "callback" field containing a nonce
that the client instance will use in validating the callback as defined in
.
When the RO completes interaction at the AS, the AS MUST call the
client instance's callback URL using the method indicated in the
callback request as described in .
If the AS returns a "callback" nonce, the client instance MUST NOT
continue a grant request before it receives the associated
interaction reference on the callback URI.
Display of a Short User Code
If the client instance indicates that it can
display a short user-typeable code
and the AS supports this mode for the client instance's
request, the AS responds with a "user_code" field. This field is an
object that contains the following members.
-
code (string)
-
REQUIRED. A unique 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. It is RECOMMENDED that this code be no more than eight
characters in length.
-
url (string)
-
RECOMMENDED. The interaction URL that the client instance
will direct the RO to. This URL MUST be stable at the AS such
that client instance's can be statically configured with it.
The client instance MUST communicate the "code" to the RQ in some
fashion, such as displaying it on a screen or reading it out
audibly. The code is a one-time-use credential that the AS uses to identify
the pending request from the client instance. When the RO enters this code into the
AS, the AS MUST determine the pending request that it was associated
with. If the AS does not recognize the entered code, the AS MUST
display an error to the user. If the AS detects too many unrecognized codes
entered, it SHOULD display an error to the user.
The client instance SHOULD also communicate the URL if possible
to facilitate user interaction, but since the URL should be stable,
the client instance should be able to safely decide to not display this value.
As this interaction mode is designed to facilitate interaction
via a secondary device, it is not expected that the client instance redirect
the RQ to the URL given here at runtime. Consequently, the URL needs to
be stable enough that a client instance could be statically configured with it, perhaps
referring the RQ to the URL via documentation instead of through an
interactive means. If the client instance is capable of communicating an
arbitrary URL to the RQ, such as through a scannable code, the
client instance can use the "redirect" mode
for this purpose instead of or in addition to the user code mode.
The interaction URL returned represents a function of the AS but MAY be completely
distinct from the URL the client instance uses to request access, allowing an
AS to separate its user-interactive functionality from its back-end security
functionality.
[[ See issue #72 ]]
Extending Interaction Mode Responses
Extensions to this specification can define new interaction
mode responses in a registry TBD. Extensions MUST
document the corresponding interaction request.
Returning User Information
If information about the RO is requested and the AS
grants the client instance access to that data, the AS returns the approved
information in the "subject" response field. This field is an object
with the following OPTIONAL properties.
-
sub_ids (array of objects)
-
An array of subject identifiers for the
RO, as defined by
.
-
assertions (object)
-
An object containing assertions as values
keyed on the assertion type defined by a registry TBD.
[[ See issue #41 ]]
-
updated_at (string)
-
Timestamp as an ISO8610 date string, indicating
when the identified account was last updated. The client instance MAY use
this value to determine if it needs to request updated profile
information through an identity API. The definition of such an
identity API is out of scope for this specification.
The AS MUST return the subject field only in cases where the AS is sure that
the RO and the RQ are the same party. This can be accomplished through some forms of
interaction with the RO.
Subject identifiers returned by the AS SHOULD uniquely identify the RO at the
AS. Some forms of subject identifier are opaque to the client instance (such as the subject of an
issuer and subject pair), while others forms (such as email address and phone number) are
intended to allow the client instance to correlate the identifier with other account information
at the client instance. The client instance MUST NOT request or use any returned subject identifiers for communication
purposes (see ). That is, a subject identifier returned in the format of an email address or
a phone number only identifies the RO to the AS and does not indicate that the
AS has validated that the represented email address or phone number in the identifier
is suitable for communication with the current user. To get such information,
the client instance MUST use an identity protocol to request and receive additional identity
claims. The details of an identity protocol and associated schema
are outside the scope of this specification.
[[ See issue #75 ]]
Extensions to this specification MAY define additional response
properties in a registry TBD.
Returning Dynamically-bound Reference Handles
Many parts of the client instance's request can be passed as either a value
or a reference. The use of a reference in place of a value allows
for a client instance to optimize requests to the AS.
Some references, such as for the client instance's identity
or the requested resources, can be managed statically through an
admin console or developer portal provided by the AS or RS. The developer
of the client software can include these values in their code for a more
efficient and compact request.
If desired, the AS MAY also generate and return some of these references
dynamically to the client instance in its response to facilitate multiple
interactions with the same software. The client instance SHOULD use these
references in future requests in lieu of sending the associated data
value. These handles are intended to be used on future requests.
Dynamically generated handles are string values that MUST be
protected by the client instance as secrets. Handle values MUST be unguessable
and MUST NOT contain any sensitive information. Handle values are
opaque to the client instance.
All dynamically generated handles are returned as fields in the
root JSON object of the response. This specification defines the
following dynamic handle returns, additional handles can be defined in
a registry TBD.
-
instance_id (string)
-
A string value used to represent the information
in the client object that the client instance can use in a future request, as
described in .
-
user_handle (string)
-
A string value used to represent the current
user. The client instance can use in a future request, as described in
.
This non-normative example shows two handles along side an issued
access token.
[[ See issue #77 ]]
[[ See issue #78 ]]
Error Response
If the AS determines that the request cannot be issued for any
reason, it responds to the client instance with an error message.
-
error (string)
-
The error code.
The error code is one of the following, with additional values
available in a registry TBD:
-
user_denied
-
The RO denied the request.
-
too_fast
-
The client instance did not respect the timeout in the
wait response.
-
unknown_request
-
The request referenced an unknown ongoing access request.
[[ See issue #79 ]]
Extending the Response
Extensions to this specification MAY define additional fields for
the grant response in a registry TBD.
Interaction at the AS
If the client instance indicates that it is capable of driving interaction with the RO in its request, and
the AS determines that interaction is required and responds to one or
more of the client instance's interaction modes, the client instance SHOULD
initiate one of the returned
interaction modes in the response.
When the RO is interacting with the AS, the AS MAY perform whatever
actions it sees fit, including but not limited to:
- authenticate the current user (who may be the RQ) as the RO
- gather consent and authorization from the RO for access to
requested resources and direct information
- allow the RO to modify the parameters of the request (such as
disallowing some requested resources or specifying an account or
record)
- provide warnings to the RO about potential attacks or negative
effects of the requested information
Interaction at a Redirected URI
When the RO is directed to the AS through the "redirect"
mode, the AS can interact with the RO through their web
browser to authenticate the user as an RO and gather their consent.
Note that since the client instance does not add any parameters to the URL, the
AS MUST determine the grant request being referenced from the URL
value itself. If the URL cannot be associated with a currently active
request, the AS MUST display an error to the RO and MUST NOT attempt
to redirect the RO back to any client instance even if a callback is supplied.
The interaction URL MUST be reachable from the RO's browser, though
note that the RO MAY open the URL on a separate device from the client instance
itself. The interaction URL MUST be accessible from an HTTP GET
request, and MUST be protected by HTTPS or equivalent means.
With this method, it is common for the RO to be the same party as the RQ, since
the client instance has to communicate the redirection URI to the RQ.
Interaction at the User Code URI
When the RO is directed to the AS through the "user_code" mode, the
AS can interact with the RO through their web browser to collect the
user code, authenticate the user as an RO, and gather their consent.
Note that since the URL itself is static, the AS MUST determine the
grant request being referenced from the user code value itself. If the
user code cannot be associated with a currently active request, the AS
MUST display an error to the RO and MUST NOT attempt to redirect the
RO back to any client instance even if a callback is supplied.
The user code URL MUST be reachable from the RO's browser, though
note that the RO MAY open the URL on a separate device from the client instance
itself. The user code URL MUST be accessible from an HTTP GET request,
and MUST be protected by HTTPS or equivalent means.
While it is common for the RO to be the same party as the RQ, since
the client instance has to communicate the user code to someone, there are
cases where the RQ and RO are separate parties and the authorization
happens asynchronously.
Interaction through an Application URI
When the client instance successfully launches an application through the
"app" mode, the AS
interacts with the RO through that application to authenticate the
user as the RO and gather their consent. The details of this
interaction are out of scope for this specification.
Post-Interaction Completion
Upon completing an interaction with the RO, if a "callback" mode is
available with the current request, the AS MUST follow the appropriate
method at the end of interaction to allow the client instance to continue. If
this mode is not available, the AS SHOULD instruct the RO to
return to their client instance upon completion. Note that these steps
still take place in most error cases, such as when the RO has denied
access. This pattern allows the client instance to potentially recover from the error
state without restarting the request from scratch by modifying its
request or providing additional information directly to the AS.
The AS MUST create an interaction reference and associate that
reference with the current interaction and the underlying pending
request. This value MUST be sufficiently random so as not to be
guessable by an attacker. The interaction reference MUST be
one-time-use.
The AS MUST calculate a hash value based on the client instance and AS nonces and the
interaction reference, as described in
. The client instance will use this value to
validate the return call from the AS.
The AS then MUST send the hash and interaction reference based on
the interaction finalization mode as described in the following
sections.
Completing Interaction with a Browser Redirect to the Callback URI
When using the "callback" interaction mode with the redirect method,
the AS signals to the client instance that interaction is
complete and the request can be continued by directing the RO (in
their browser) back to the client instance's callback URL sent in the callback request.
The AS secures this callback by adding the hash and interaction
reference as query parameters to the client instance's callback URL.
-
hash
-
REQUIRED. The interaction hash value as
described in .
-
interact_ref
-
REQUIRED. The interaction reference
generated for this interaction.
The means of directing the RO to this URL are outside the scope
of this specification, but common options include redirecting the
RO from a web page and launching the system browser with the
target URL.
When receiving the request, the client instance MUST parse the query
parameters to calculate and validate the hash value as described in
. If the hash validates, the client instance
sends a continuation request to the AS as described in
using the interaction
reference value received here.
Completing Interaction with a Direct HTTP Request Callback
When using the
"callback" interaction mode with the push method,
the AS signals to the client instance that interaction is
complete and the request can be continued by sending an HTTP POST
request to the client instance's callback URL sent in the callback request.
The entity message body is a JSON object consisting of the
following two fields:
-
hash (string)
-
REQUIRED. The interaction hash value as
described in .
-
interact_ref (string)
-
REQUIRED. The interaction reference
generated for this interaction.
When receiving the request, the client instance MUST parse the JSON object
and validate the hash value as described in
. If the hash validates, the client instance sends
a continuation request to the AS as described in using the interaction
reference value received here.
Calculating the interaction hash
The "hash" parameter in the request to the client instance's callback URL ties
the front channel response to an ongoing request by using values
known only to the parties involved. This security mechanism allows the client instance to protect itself against
several kinds of session fixation and injection attacks. The AS MUST
always provide this hash, and the client instance MUST validate the hash when received.
To calculate the "hash" value, the party doing the calculation
first takes the "nonce" value sent by the client instance in the
interaction section of the initial request, the AS's nonce value
from the callback response, and the "interact_ref"
sent to the client instance's callback URL.
These three values are concatenated to each other in this order
using a single newline character as a separator between the fields.
There is no padding or whitespace before or after any of the lines,
and no trailing newline character.
The party then hashes this string with the appropriate algorithm
based on the "hash_method" parameter of the "callback".
If the "hash_method" value is not present in the client instance's
request, the algorithm defaults to "sha3".
[[ See issue #56 ]]
SHA3-512
The "sha3" hash method consists of hashing the input string
with the 512-bit SHA3 algorithm. The byte array is then encoded
using URL Safe Base64 with no padding. The resulting string is the
hash value.
SHA2-512
The "sha2" hash method consists of hashing the input string
with the 512-bit SHA2 algorithm. The byte array is then encoded
using URL Safe Base64 with no padding. The resulting string is the
hash value.
Continuing a Grant Request
While it is possible for the AS to return a with all the
client instance's requested information (including access tokens and
direct user information), it's more common that the AS and
the client instance will need to communicate several times over the lifetime of an access grant.
This is often part of facilitating interaction, but it could
also be used to allow the AS and client instance to continue negotiating the parameters of
the original grant request.
To enable this ongoing negotiation, the AS provides a continuation API to the client software.
The AS returns a continue field
in the response that contains information the client instance needs to
access this API, including a URI to access
as well as an access token to use during the continued requests.
The access token is initially bound to the same key and method the client instance used to make
the initial request. As a consequence,
when the client instance makes any calls to the continuation URL, the client instance MUST present
the access token as described in and present
proof of the client instance's key (or its most recent rotation)
by signing the request as described in .
[[ See issue #85 ]]
For example, here the client instance makes a POST request to a unique URI and signs
the request with detached JWS:
The AS MUST be able to tell from the client instance's request which specific ongoing request
is being accessed, using a combination of the continuation URL,
the provided access token, and the client instance identified by the key signature.
If the AS cannot determine a single active grant request to map the
continuation request to, the AS MUST return an error.
The ability to continue an already-started request allows the client instance to perform several
important functions, including presenting additional information from interaction,
modifying the initial request, and getting the current state of the request.
All requests to the continuation API are protected by this bound access token.
For example, here the client instance makes a POST request to a stable continuation endpoint
URL with the interaction reference,
includes the access token, and signs with detached JWS:
If a "wait" parameter was included in the continuation response, the
client instance MUST NOT call the continuation URI prior to waiting the number of
seconds indicated. If no "wait" period is indicated, the client instance SHOULD
wait at least 5 seconds. If the client instance does not respect the
given wait period, the AS MUST return an error.
[[ See issue #86 ]]
The response from the AS is a JSON object and MAY contain any of the
fields described in , as described in more detail in the
sections below.
If the AS determines that the client instance can
make a further continuation request, the AS MUST include a new
"continue" response.
The new continue response MUST include a bound access token as well, and
this token SHOULD be a new access token, invalidating the previous access token.
If the AS does not return a new continue response, the client instance
MUST NOT make an additional continuation request. If a client instance does so,
the AS MUST return an error.
[[ See issue #87 ]]
For continuation functions that require the client instance to send a message body, the body MUST be
a JSON object.
Continuing After a Completed Interaction
When the AS responds to the client instance's callback parameter as in , this
response includes an interaction reference. The client instance MUST include that value as the field
interact_ref in a POST request to the continuation URI.
Since the interaction reference is a one-time-use value as described in ,
if the client instance needs to make additional continuation calls after this request, the client instance
MUST NOT include the interaction reference. If the AS detects a client instance submitting the same
interaction reference multiple times, the AS MUST return an error and SHOULD invalidate
the ongoing request.
The MAY contain any newly-created access tokens or
newly-released subject claims. The response MAY contain
a new "continue" response as described above. The response
SHOULD NOT contain any interaction responses.
[[ See issue #89 ]]
For example, if the request is successful in causing the AS to issue access tokens and
release subject claims, the response could look like this:
With this example, the client instance can not make an additional continuation request because
a continue field is not included.
[[ See issue #88 ]]
Continuing During Pending Interaction
When the client instance does not include a callback parameter, the client instance will often need to
poll the AS until the RO has authorized the request. To do so, the client instance makes a POST
request to the continuation URI as in , but does not
include a message body.
The MAY contain any newly-created access tokens or
newly-released subject claims. The response MAY contain
a new "continue" response as described above. If a continue
field is included, it SHOULD include a wait field to facilitate a reasonable polling rate by
the client instance. The response SHOULD NOT contain interaction responses.
For example, if the request has not yet been authorized by the RO, the AS could respond
by telling the client instance to make another continuation request in the future. In this example,
a new, unique access token has been issued for the call, which the client instance will use in its
next continuation request.
[[ See issue #90 ]]
[[ See issue #91 ]]
If the request is successful in causing the AS to issue access tokens and
release subject claims, the response could look like this example:
Modifying an Existing Request
The client instance might need to modify an ongoing request, whether or not tokens have already been
issued or claims have already been released. In such cases, the client instance makes an HTTP PATCH
request to the continuation URI and includes any fields it needs to modify. Fields
that aren't included in the request are considered unchanged from the original request.
The client instance MAY include the resources and subject fields as described in
and . Inclusion of these fields override any values in the initial request,
which MAY trigger additional requirements and policies by the AS. For example, if the client instance is asking for
more access, the AS could require additional interaction with the RO to gather additional consent.
If the client instance is asking for more limited access, the AS could determine that sufficient authorization
has been granted to the client instance and return the more limited access rights immediately.
[[ See issue #92 ]]
The client instance MAY include the interact field as described in . Inclusion of
this field indicates that the client instance is capable of driving interaction with the RO, and this field
replaces any values from a previous request. The AS MAY respond to any of the interaction
responses as described in , just like it would to a new request.
The client instance MAY include the user field as described in to present new assertions
or information about the RQ.
[[ See issue #93 ]]
The client instance MUST NOT include the client section of the request.
[[ See issue #94 ]]
The client instance MAY include post-interaction responses such as described in .
[[ See issue #95 ]]
Modification requests MUST NOT alter previously-issued access tokens. Instead, any access
tokens issued from a continuation are considered new, separate access tokens. The AS
MAY revoke existing access tokens after a modification has occurred.
[[ See issue #96 ]]
If the modified request can be granted immediately by the AS,
the MAY contain any newly-created access tokens or
newly-released subject claims. The response MAY contain
a new "continue" response as described above. If interaction
can occur, the response SHOULD contain interaction responses as well.
For example, a client instance initially requests a set of resources using references:
Access is granted by the RO, and a token is issued by the AS.
In its final response, the AS includes a continue field, which includes
a separate access token for accessing the continuation API:
This continue field allows the client instance to make an eventual continuation call. In the future,
the client instance realizes that it no longer needs
"write" access and therefore modifies its ongoing request, here asking for just "read" access
instead of both "read" and "write" as before.
The AS replaces the previous resources from the first request, allowing the AS to
determine if any previously-granted consent already applies. In this case, the AS would
likely determine that reducing the breadth of the requested access means that new access
tokens can be issued to the client instance. The AS would likely revoke previously-issued access tokens
that had the greater access rights associated with them.
For another example, the client instance initially requests read-only access but later
needs to step up its access. The initial request could look like this example.
Access is granted by the RO, and a token is issued by the AS.
In its final response, the AS includes a continue field:
This allows the client instance to make an eventual continuation call. The client instance later realizes that it now
needs "write" access in addition to the "read" access. Since this is an expansion of what
it asked for previously, the client instance also includes a new interaction section in case the AS needs
to interact with the RO again to gather additional authorization. Note that the client instance's
nonce and callback are different from the initial request. Since the original callback was
already used in the initial exchange, and the callback is intended for one-time-use, a new one
needs to be included in order to use the callback again.
[[ See issue #97 ]]
From here, the AS can determine that the client instance is asking for more than it was previously granted,
but since the client instance has also provided a mechanism to interact with the RO, the AS can use that
to gather the additional consent. The protocol continues as it would with a new request.
Since the old access tokens are good for a subset of the rights requested here, the
AS might decide to not revoke them. However, any access tokens granted after this update
process are new access tokens and do not modify the rights of existing access tokens.
Getting the Current State of a Grant Request
If the client instance needs to get the current state of an ongoing grant request, it makes an
HTTP GET request to the continuation URI. This request MUST NOT alter the grant
request in any fashion, including causing the issuance of new access tokens or
modification of interaction parameters.
The AS MAY include existing access tokens and previously-released subject claims in
the response. The AS MUST NOT issue a new access token or release a new subject
claim in response to this request.
The response MAY include any fields described that are applicable to this
ongoing request, including the most recently issued access tokens, any released subject
claims, and any currently active interaction modes. The response MAY contain a
new "continue" response as described above.
[[ See issue #98 ]]
Canceling a Grant Request
If the client instance wishes to cancel an ongoing grant request, it makes an
HTTP DELETE request to the continuation URI.
If the request is successfully cancelled, the AS responds with an HTTP 202.
The AS MUST revoke all associated access tokens, if possible.
Token Management
If an access token response includes the "manage" parameter as
described in , the client instance MAY call
this URL to manage the access token with any of the actions defined in
the following sections. Other actions are undefined by this
specification.
The access token being managed acts as the access element for its own
management API. The client instance MUST present proof of an appropriate key
along with the access token.
If the token is sender-constrained (i.e., not a bearer token), it
MUST be sent with the appropriate binding for the access token.
If the token is a bearer token, the client instance MUST present proof of the
same key identified in the initial request as described in .
The AS MUST validate the proof and assure that it is associated with
either the token itself or the client instance the token was issued to, as
appropriate for the token's presentation type.
[[ See issue #99 ]]
Rotating the Access Token
The client instance makes an HTTP POST to the token management URI, sending
the access token in the appropriate header and signing the request
with the appropriate key.
The AS validates that the token presented is associated with the management
URL, that the AS issued the token to the given client instance, and that
the presented key is appropriate to the token.
If the access token has expired, the AS SHOULD honor the rotation request to
the token management URL since it is likely that the client instance is attempting to
refresh the expired token. To support this, the AS MAY apply different lifetimes for
the use of the token in management vs. its use at an RS. An AS MUST NOT
honor a rotation request for an access token that has been revoked, either by
the AS or by the client instance through the token management URI.
If the token is validated and the key is appropriate for the
request, the AS MUST invalidate the current access token associated
with this URL, if possible, and return a new access token response as
described in , unless the multi_token flag
is specified in the request. The value of the
access token MUST NOT be the same as the current value of the access
token used to access the management API. The response MAY include an
updated access token management URL as well, and if so, the client instance
MUST use this new URL to manage the new access token.
[[ See issue #101 ]]
[[ See issue #102 ]]
[[ See issue #103 ]]
Revoking the Access Token
If the client instance wishes to revoke the access token proactively, such as when
a user indicates to the client instance that they no longer wish for it to have
access or the client instance application detects that it is being uninstalled,
the client instance can use the token management URI to indicate to the AS that
the AS should invalidate the access token for all purposes.
The client instance makes an HTTP DELETE request to the token management
URI, presenting the access token and signing the request with
the appropriate key.
If the key presented is associated with the token (or the client instance, in
the case of a bearer token), the AS MUST invalidate the access token, if
possible, and return an HTTP 204 response code.
Though the AS MAY revoke an access token at any time for
any reason, the token management function is specifically for the client instance's use.
If the access token has already expired or has been revoked through other
means, the AS SHOULD honor the revocation request to
the token management URL as valid, since the end result is still the token
not being usable.
Using Access Tokens
The method the client instance uses to send an access token to the RS depends on the value of the
"key" and "proof" parameters in the access token response.
If the key value is the boolean false, the access token is a bearer token
sent using the HTTP Header method defined in .
The form parameter and query parameter methods of MUST NOT
be used.
If the "key" value is the boolean true, the access token MUST be sent
to the RS using the same key and proofing mechanism that the client instance used
in its initial request.
If the "key" value is an object, the value of the "proof" field within
the key indicates the particular proofing mechanism to use.
The access token is sent using the HTTP authorization scheme "GNAP" along with
a key proof as described in for the key bound to the
access token. For example, a "jwsd"-bound access token is sent as
follows:
[[ See issue #104 ]]
Binding Keys
Any keys presented by the client instance to the AS or RS MUST be validated as
part of the request in which they are presented. The type of binding
used is indicated by the proof parameter of the key section in the
initial request . Values defined by this
specification are as follows:
-
jwsd
-
A detached JWS signature header
-
jws
-
Attached JWS payload
-
mtls
-
Mutual TLS certificate verification
-
dpop
-
OAuth Demonstration of Proof-of-Possession key proof header
-
httpsig
-
HTTP Signing signature header
-
oauthpop
-
OAuth PoP key proof authentication header
Additional proofing methods are defined by a registry TBD.
All key binding methods used by this specification MUST cover all relevant portions
of the request, including anything that would change the nature of the request, to allow
for secure validation of the request by the AS. Relevant aspects include
the URI being called, the HTTP method being used, any relevant HTTP headers and
values, and the HTTP message body itself. The recipient of the signed message
MUST validate all components of the signed message to ensure that nothing
has been tampered with or substituted in a way that would change the nature of
the request.
When used for delegation in GNAP, these key binding mechanisms allow
the AS to ensure that the keys presented by the client instance in the initial request are in
control of the party calling any follow-up or continuation requests. To facilitate
this requirement, the continuation response includes
an access token bound to the client instance's key, and that key (or its most recent rotation)
MUST be proved in all continuation requests
. Token management requests are similarly bound
to either the access token's own key or, in the case of bearer tokens, the client instance's key.
The AS MUST validate all keys presented by the client instance or referenced in an
ongoing request for each call within that request.
[[ See issue #105 ]]
When used to bind to an access token, the access token MUST be covered by the signature method.
Detached JWS
This method is indicated by jwsd in the
proof field. A JWS signature object is created as follows:
The header of the JWS MUST contain the
kid field of the key bound to this client instance for this request. The JWS header
MUST contain an alg field appropriate for the key identified by kid
and MUST NOT be none. The b64 field MUST be set to false and the
crit field MUST contain at least b64 as specified in
To protect the request, the JWS header MUST contain the following
additional fields.
-
htm (string)
-
The HTTP Method used to make this request, as an uppercase ASCII string.
-
htu (string)
-
The HTTP URI used for this request, including all path and query components.
-
ts (integer)
-
A timestamp of the request in integer seconds
-
at_hash (string)
-
When to bind a request to an access token, the access token hash value. Its value is the
base64url encoding of the left-most half of the hash of the octets of the ASCII representation of the
access_token value, where the hash algorithm used is the hash algorithm used in the alg
header parameter of the JWS's JOSE Header. For instance, if the alg is RS256, hash the access_token
value with SHA-256, then take the left-most 128 bits and base64url encode them.
[[ See issue #106 ]]
The payload of the JWS object is the serialized body of the request, and
the object is signed according to detached JWS .
The client instance presents the signature in the Detached-JWS HTTP Header
field.
If the request being made does not have a message body, such as
an HTTP GET, OPTIONS, or DELETE method, the JWS signature is
calculated over an empty payload.
When the server (AS or RS) receives the Detached-JWS 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.
Attached JWS
This method is indicated by jws in the
proof field. A JWS signature object is created as follows:
The header of the JWS MUST contain the
kid field of the key bound to this client instance for this request. The JWS header
MUST contain an alg field appropriate for the key identified by kid
and MUST NOT be none.
To protect the request, the JWS header MUST contain the following
additional fields.
-
htm (string)
-
The HTTP Method used to make this request, as an uppercase ASCII string.
-
htu (string)
-
The HTTP URI used for this request, including all path and query components.
-
ts (integer)
-
A timestamp of the request in integer seconds
-
at_hash (string)
-
When to bind a request to an access token, the access token hash value. Its value is the
base64url encoding of the left-most half of the hash of the octets of the ASCII representation of the
access_token value, where the hash algorithm used is the hash algorithm used in the alg
header parameter of the JWS's JOSE Header. For instance, if the alg is RS256, hash the access_token
value with SHA-256, then take the left-most 128 bits and base64url encode them.
The payload of the JWS object is the JSON serialized body of the request, and
the object is signed according to JWS and serialized into compact form .
The client instance presents the JWS as the body of the request along with a
content type of application/jose. The AS
MUST extract the payload of the JWS and treat it as the request body
for further processing.
This example's JWS header decodes to:
And the JWS body decodes to:
If the request being made does not have a message body, such as
an HTTP GET, OPTIONS, or DELETE method, the JWS signature is
calculated over an empty payload and passed in the Detached-JWS
header as described in .
[[ See issue #109 ]]
Mutual TLS
This method is indicated by mtls in the
proof field. The client instance presents its TLS client
certificate during TLS negotiation with the server (either AS or RS).
The AS or RS takes the thumbprint of the TLS client certificate presented
during mutual TLS negotiation and compares that thumbprint to the
thumbprint presented by the client instance application as described in
section 3.
[[ See issue #110 ]]
Demonstration of Proof-of-Possession (DPoP)
This method is indicated by dpop in the
proof field. The client instance creates a Demonstration of Proof-of-Possession
signature header as described in
section 2. In addition to the required fields, the DPoP body MUST also
contain a digest of the request body:
-
digest (string)
-
Digest of the request body as the value of the Digest
header defined in .
HTTP Signing
This method is indicated by httpsig in
the proof field. The client instance creates an HTTP
Signature header as described in section 4. The client instance MUST
calculate and present the Digest header as defined in and include
this header in the signature.
When used to present an access token as in ,
the Authorization header MUST be included in the signature.
OAuth Proof of Possession (PoP)
This method is indicated by oauthpop in
the proof field. The client instance creates an HTTP
Authorization PoP header as described in section 4, with the
following additional requirements:
- The at (access token) field MUST be omitted
unless this method is being used in conjunction with
an access token as in .
[[ See issue #112 ]]
- The b (body hash) field MUST be calculated and supplied,
unless there is no entity body (such as a GET, OPTIONS, or
DELETE request).
- All components of the URL MUST be calculated and supplied
- The m (method) field MUST be supplied
[[ See issue #113 ]]
Discovery
By design, the protocol minimizes the need for any pre-flight
discovery. To begin a request, the client instance only needs to know the endpoint of
the AS and which keys it will use to sign the request. Everything else
can be negotiated dynamically in the course of the protocol.
However, the AS can have limits on its allowed functionality. If the
client instance wants to optimize its calls to the AS before making a request, it MAY
send an HTTP OPTIONS request to the grant request endpoint to retrieve the
server's discovery information. The AS MUST respond with a JSON document
containing the following information:
-
grant_request_endpoint (string)
-
REQUIRED. The full URL of the
AS's grant request endpoint. This MUST match the URL the client instance used to
make the discovery request.
-
capabilities (array of strings)
-
OPTIONAL. A list of the AS's
capabilities. The values of this result MAY be used by the client instance in the
capabilities section of
the request.
-
interaction_methods (array of strings)
-
OPTIONAL. A list of the AS's
interaction methods. The values of this list correspond to the
possible fields in the interaction section of the request.
-
key_proofs (array strings)
-
OPTIONAL. A list of the AS's supported key
proofing mechanisms. The values of this list correspond to possible
values of the proof field of the
key section of the request.
-
sub_ids (array of strings)
-
OPTIONAL. A list of the AS's supported
identifiers. The values of this list correspond to possible values
of the subject identifier section of the request.
-
assertions (array of strings)
-
OPTIONAL. A list of the AS's supported
assertion formats. The values of this list correspond to possible
values of the subject assertion section of the request.
The information returned from this method is for optimization
purposes only. The AS MAY deny any request, or any portion of a request,
even if it lists a capability as supported. For example, a given client instance
can be registered with the mtls key proofing
mechanism, but the AS also returns other proofing methods, then the AS
will deny a request from that client instance using a different proofing
mechanism.
Resource Servers
In some deployments, a resource server will need to be able to call
the AS for a number of functions.
[[ See issue #114 ]]
Introspecting a Token
When the RS receives an access token, it can call the introspection
endpoint at the AS to get token information.
[[ See issue #115 ]]
| RS | | AS |
|Instance| | |--(2)->| |
| | | |<-(3)--| |
| | | | +------+
| |<-(4)--| |
+--------+ +------+
]]>
- The client instance calls the RS with its access token.
- The RS introspects the access token value at the AS.
The RS signs the request with its own key (not the client instance's
key or the token's key).
- The AS validates the token value and the client instance's request
and returns the introspection response for the token.
- The RS fulfills the request from the client instance.
The RS signs the request with its own key and sends the access
token as the body of the request.
The AS responds with a data structure describing the token's
current state and any information the RS would need to validate the
token's presentation, such as its intended proofing mechanism and key
material.
Deriving a downstream token
Some architectures require an RS to act as a client instance and request a derived access
token for a secondary RS. This internal token is issued in the context
of the incoming access token.
| RS1 | | AS | | RS2 |
|Instance| | |--(2)->| | | |
| | | |<-(3)--| | | |
| | | | +------+ | |
| | | | | |
| | | |-----------(4)------->| |
| | | |<----------(5)--------| |
| |<-(6)--| | | |
+--------+ +-------+ +-------+
]]>
- The client instance calls RS1 with an access token.
- RS1 presents that token to the AS to get a derived token
for use at RS2. RS1 indicates that it has no ability
to interact with the RO.
RS1 signs its request with its own key, not the token's
key or the client instance's key.
- The AS returns a derived token to RS1 for use at RS2.
- RS1 calls RS2 with the token from (3).
- RS2 fulfills the call from RS1.
- RS1 fulfills the call from client instance.
If the RS needs to derive a token from one presented to it, it can
request one from the AS by making a token request as described in
and presenting the existing access token's
value in the "existing_access_token" field.
The RS MUST identify itself with its own key and sign the
request.
[[ See issue #116 ]]
The AS responds with a token as described in
.
Registering a Resource Handle
If the RS needs to, it can post a set of resources as described in
to the AS's resource
registration endpoint.
The RS MUST identify itself with its own key and sign the
request.
The AS responds with a handle appropriate to represent the
resources list that the RS presented.
The RS MAY make this handle available as part of a
response or as
documentation to developers.
[[ See issue #117 ]]
Requesting Resources With Insufficient Access
If the client instance calls an RS without an access token, or with an
invalid access token, the RS MAY respond to the client instance with an
authentication header indicating that GNAP needs to be used
to access the resource. The address of the GNAP
endpoint MUST be sent in the "as_uri" parameter. The RS MAY
additionally return a resource reference that the client instance MAY use in
its resource request. This
resource reference handle SHOULD be sufficient for at least the action
the client instance was attempting to take at the RS. The RS MAY use the dynamic resource handle request to register a new resource handle, or use a handle that
has been pre-configured to represent what the AS is protecting. The
content of this handle is opaque to the RS and the client instance.
The client instance then makes a call to the "as_uri" as described in
, with the value of "resource" as one of the members
of a "resources" array . The
client instance MAY request additional resources and other information, and MAY
request multiple access tokens.
[[ See issue #118 ]]
Acknowledgements
The editors would like to thank the feedback of the following individuals for their reviews,
implementations, and contributions:
Aaron Parecki,
Annabelle Backman,
Dick Hardt,
Dmitri Zagidulin,
Dmitry Barinov,
Fabien Imbault,
Francis Pouatcha,
George Fletcher,
Haardik Haardik,
Hamid Massaoud,
Jacky Yuan,
Joseph Heenan,
Justin Richer,
Kathleen Moriarty,
Mike Jones,
Mike Varley,
Nat Sakimura,
Takahiko Kawasaki,
Takahiro Tsuchiya.
The editors would also like to thank the GNAP working group design team of
Kathleen Moriarty, Fabien Imbault, Dick Hardt, Mike Jones, and Justin Richer, who incorporated
elements from the XAuth and XYZ proposals to create the first version of this document.
In addition, the editors would like to thank Aaron Parecki and Mike Jones for insights into how
to integrate identity and authentication systems into the core protocol, and Justin Richer and Dick Hardt for
the use cases, diagrams, and insights provided in the XYZ and XAuth proposals that have been
incorporated here. The editors would like to especially thank Mike Varley and the team at SecureKey
for feedback and development of early versions of the XYZ protocol that fed into this standards work.
IANA Considerations
[[ TBD: There are a lot of items in the document that are expandable
through the use of value registries. ]]
Security Considerations
[[ TBD: There are a lot of security considerations to add. ]]
All requests have to be over TLS or equivalent as per . Many handles act as
shared secrets, though they can be combined with a requirement to
provide proof of a key as well.
Privacy Considerations
[[ TBD: There are a lot of privacy considerations to add. ]]
Handles are passed between parties and therefore should not contain
any private data.
When user information is passed to the client instance, the AS needs to make
sure that it has the permission to do so.
Normative References
Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)
Key words for use in RFCs to Indicate Requirement Levels
In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.
Instance Digests in HTTP
HTTP/1.1 defines a Content-MD5 header that allows a server to include a digest of the response body. However, this is specifically defined to cover the body of the actual message, not the contents of the full file (which might be quite different, if the response is a Content-Range, or uses a delta encoding). Also, the Content-MD5 is limited to one specific digest algorithm; other algorithms, such as SHA-1 (Secure Hash Standard), may be more appropriate in some circumstances. Finally, HTTP/1.1 provides no explicit mechanism by which a client may request a digest. This document proposes HTTP extensions that solve these problems. [STANDARDS-TRACK]
Tags for Identifying Languages
This document describes the structure, content, construction, and semantics of language tags for use in cases where it is desirable to indicate the language used in an information object. It also describes how to register values for use in language tags and the creation of user-defined extensions for private interchange. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.
JSON Web Signature (JWS)
JSON Web Signature (JWS) represents content secured with digital signatures or Message Authentication Codes (MACs) using JSON-based data structures. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) specification and an IANA registry defined by that specification. Related encryption capabilities are described in the separate JSON Web Encryption (JWE) specification.
The OAuth 2.0 Authorization Framework
The OAuth 2.0 authorization framework enables a third-party application to obtain limited access to an HTTP service, either on behalf of a resource owner by orchestrating an approval interaction between the resource owner and the HTTP service, or by allowing the third-party application to obtain access on its own behalf. This specification replaces and obsoletes the OAuth 1.0 protocol described in RFC 5849. [STANDARDS-TRACK]
The OAuth 2.0 Authorization Framework: Bearer Token Usage
This specification describes how to use bearer tokens in HTTP requests to access OAuth 2.0 protected resources. Any party in possession of a bearer token (a "bearer") can use it to get access to the associated resources (without demonstrating possession of a cryptographic key). To prevent misuse, bearer tokens need to be protected from disclosure in storage and in transport. [STANDARDS-TRACK]
JSON Web Signature (JWS) Unencoded Payload Option
JSON Web Signature (JWS) represents the payload of a JWS as a base64url-encoded value and uses this value in the JWS Signature computation. While this enables arbitrary payloads to be integrity protected, some have described use cases in which the base64url encoding is unnecessary and/or an impediment to adoption, especially when the payload is large and/or detached. This specification defines a means of accommodating these use cases by defining an option to change the JWS Signing Input computation to not base64url- encode the payload. This option is intended to broaden the set of use cases for which the use of JWS is a good fit.
This specification updates RFC 7519 by stating that JSON Web Tokens (JWTs) MUST NOT use the unencoded payload option defined by this specification.
Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words
RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.
The JavaScript Object Notation (JSON) Data Interchange Format
JavaScript Object Notation (JSON) is a lightweight, text-based, language-independent data interchange format. It was derived from the ECMAScript Programming Language Standard. JSON defines a small set of formatting rules for the portable representation of structured data.
This document removes inconsistencies with other specifications of JSON, repairs specification errors, and offers experience-based interoperability guidance.
OAuth 2.0 Mutual-TLS Client Authentication and Certificate-Bound Access Tokens
This document describes OAuth client authentication and certificate-bound access and refresh tokens using mutual Transport Layer Security (TLS) authentication with X.509 certificates. OAuth clients are provided a mechanism for authentication to the authorization server using mutual TLS, based on either self-signed certificates or public key infrastructure (PKI). OAuth authorization servers are provided a mechanism for binding access tokens to a client's mutual-TLS certificate, and OAuth protected resources are provided a method for ensuring that such an access token presented to it was issued to the client presenting the token.
OAuth 2.0 Token Exchange
This specification defines a protocol for an HTTP- and JSON-based Security Token Service (STS) by defining how to request and obtain security tokens from OAuth 2.0 authorization servers, including security tokens employing impersonation and delegation.
Signing HTTP Messages
This document describes a mechanism for creating, encoding, and verifying digital signatures or message authentication codes over content within 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.
A Method for Signing HTTP Requests for OAuth
This document a method for offering data origin authentication and integrity protection of HTTP requests. To convey the relevant data items in the request a JSON-based encapsulation is used and the JSON Web Signature (JWS) technique is re-used. JWS offers integrity protection using symmetric as well as asymmetric cryptography.
OAuth 2.0 Demonstrating Proof-of-Possession at the Application Layer (DPoP)
This document describes a mechanism for sender-constraining OAuth 2.0 tokens via a proof-of-possession mechanism on the application level. This mechanism allows for the detection of replay attacks with access and refresh tokens.
Subject Identifiers for Security Event Tokens
Security events communicated within Security Event Tokens may support a variety of identifiers to identify the subject and/or other principals related to the event. This specification formalizes the notion of subject identifiers as named sets of well-defined claims describing the subject, a mechanism for representing subject identifiers within a JSON object such as a JSON Web Token (JWT) or Security Event Token (SET), and a registry for defining and allocating names for these claim sets.
OpenID Connect Core 1.0 incorporating errata set 1
Document History
-
-03
- Changed "resource client" terminology to separate "client instance" and "client software".
-
-02
- Moved all "editor's note" items to GitHub Issues.
- Added JSON types to fields.
- Changed "GNAP Protocol" to "GNAP".
- Editorial fixes.
-
-01
- "updated_at" subject info timestamp now in ISO 8601 string format.
- Editorial fixes.
- Added Aaron and Fabien as document authors.
-
-00
- Initial working group draft.
Component Data Models
While different implementations of this protocol will have different
realizations of all the components and artifacts enumerated here, the
nature of the protocol implies some common structures and elements for
certain components. This appendix seeks to enumerate those common
elements.
TBD: Client has keys, allowed requested resources, identifier(s),
allowed requested subjects, allowed
TBD: AS has "grant endpoint", interaction endpoints, store of trusted
client keys, policies
TBD: Token has RO, user, client, resource list, RS list,
Example Protocol Flows
The protocol defined in this specification provides a number of
features that can be combined to solve many different kinds of
authentication scenarios. This section seeks to show examples of how the
protocol would be applied for different situations.
Some longer fields, particularly cryptographic information, have been
truncated for display purposes in these examples.
Redirect-Based User Interaction
In this scenario, the user is the RO and has access to a web
browser, and the client instance can take front-channel callbacks on the same
device as the user. This combination is analogous to the OAuth 2
Authorization Code grant type.
The client instance initiates the request to the AS. Here the client instance
identifies itself using its public key.
The AS processes the request and determines that the RO needs to
interact. The AS returns the following response giving the client instance the
information it needs to connect. The AS has also indicated to the
client instance that it can use the given instance identifier to identify itself in
future requests.
The client instance saves the response and redirects the user to the
interaction_url by sending the following HTTP message to the user's
browser.
The user's browser fetches the AS's interaction URL. The user logs
in, is identified as the RO for the resource being requested, and
approves the request. Since the AS has a callback parameter, the AS
generates the interaction reference, calculates the hash, and
redirects the user back to the client instance with these additional values
added as query parameters.
The client instance receives this request from the user's browser. The
client instance ensures that this is the same user that was sent out by
validating session information and retrieves the stored pending
request. The client instance uses the values in this to validate the hash
parameter. The client instance then calls the continuation URL and presents the
handle and interaction reference in the request body. The client instance signs
the request as above.
The AS retrieves the pending request based on the handle and issues
a bearer access token and returns this to the client instance.
Secondary Device Interaction
In this scenario, the user does not have access to a web browser on
the device and must use a secondary device to interact with the AS.
The client instance can display a user code or a printable QR code.
The client instance is not able to accept callbacks from the AS and needs to poll
for updates while waiting for the user to authorize the request.
The client instance initiates the request to the AS.
The AS processes this and determines that the RO needs to interact.
The AS supports both redirect URIs and user codes for interaction, so
it includes both. Since there is no "callback" the AS does not include
a nonce, but does include a "wait" parameter on the continuation
section because it expects the client instance to poll for results.
The client instance saves the response and displays the user code visually
on its screen along with the static device URL. The client instance also
displays the short interaction URL as a QR code to be scanned.
If the user scans the code, they are taken to the interaction
endpoint and the AS looks up the current pending request based on the
incoming URL. If the user instead goes to the static page and enters
the code manually, the AS looks up the current pending request based
on the value of the user code. In both cases, the user logs in, is
identified as the RO for the resource being requested, and approves
the request. Once the request has been approved, the AS displays to
the user a message to return to their device.
Meanwhile, the client instance periodically polls the AS every 60 seconds at
the continuation URL. The client instance signs the request using the
same key and method that it did in the first request.
The AS retrieves the pending request based on the handle and
determines that it has not yet been authorized. The AS indicates to
the client instance that no access token has yet been issued but it can
continue to call after another 60 second timeout.
Note that the continuation URL and access token have been rotated since they were
used by the client instance to make this call. The client instance polls the
continuation URL after a 60 second timeout using this new information.
The AS retrieves the pending request based on the URL and access token,
determines that it has been approved, and issues an access
token for the client to use at the RS.
No User Involvement
In this scenario, the client instance is requesting access on its own
behalf, with no user to interact with.
The client instance creates a request to the AS, identifying itself with its
public key and using MTLS to make the request.
The AS processes this and determines that the client instance can ask for
the requested resources and issues an access token.
Asynchronous Authorization
In this scenario, the client instance is requesting on behalf of a specific
RO, but has no way to interact with the user. The AS can
asynchronously reach out to the RO for approval in this scenario.
The client instance starts the request at the AS by requesting a set of
resources. The client instance also identifies a particular user.
The AS processes this and determines that the RO needs to interact.
The AS determines that it can reach the identified user asynchronously
and that the identified user does have the ability to approve this
request. The AS indicates to the client instance that it can poll for
continuation.
The AS reaches out to the RO and prompts them for consent. In this
example, the AS has an application that it can push notifications in
to for the specified account.
Meanwhile, the client instance periodically polls the AS every 60 seconds at
the continuation URL.
The AS retrieves the pending request based on the handle and
determines that it has not yet been authorized. The AS indicates to
the client instance that no access token has yet been issued but it can
continue to call after another 60 second timeout.
Note that the continuation handle has been rotated since it was
used by the client instance to make this call. The client instance polls the
continuation URL after a 60 second timeout using the new handle.
The AS retrieves the pending request based on the handle and
determines that it has been approved and it issues an access
token.
Applying OAuth 2 Scopes and Client IDs
While GNAP is not designed to be directly compatible with
OAuth 2 , considerations have been made to enable the use of
OAuth 2 concepts and constructs more smoothly within GNAP.
In this scenario, the client developer has a client_id and set of
scope values from their OAuth 2 system and wants to apply them to the
new protocol. Traditionally, the OAuth 2 client developer would put
their client_id and scope values as parameters into a redirect request
to the authorization endpoint.
Now the developer wants to make an analogous request to the AS
using GNAP. To do so, the client instance makes an HTTP POST and
places the OAuth 2 values in the appropriate places.
The client_id can be used to identify the client instance's keys that it
uses for authentication, the scopes represent resources that the
client instance is requesting, and the redirect_uri and state value are
pre-combined into a callback URI that can be unique per request. The
client instance additionally creates a nonce to protect the callback, separate
from the state parameter that it has added to its return URL.
From here, the protocol continues as above.
JSON Structures and Polymorphism
GNAP makes use of polymorphism within the JSON structures used for
the protocol. Each portion of this protocol is defined in terms of the JSON data type
that its values can take, whether it's a string, object, array, boolean, or number. For some
fields, different data types offer different descriptive capabilities and are used in different
situations for the same field. Each data type provides a different syntax to express
the same underlying semantic protocol element, which allows for optimization and
simplification in many common cases.
Even though JSON is often used to describe strongly typed structures, JSON on its own is naturally polymorphic.
In JSON, the named members of an object have no type associated with them, and any
data type can be used as the value for any member. In practice, each member
has a semantic type that needs to make sense to the parties creating and
consuming the object. Within this protocol, each object member is defined in terms
of its semantic content, and this semantic content might have expressions in
different concrete data types for different specific purposes. Since each object
member has exactly one value in JSON, each data type for an object member field
is naturally mutually exclusive with other data types within a single JSON object.
For example, a resource request for a single access token is composed of an array
of resource request descriptions while a request for multiple access tokens is
composed of an object whose member values are all arrays. Both of these represent requests
for access, but the difference in syntax allows the client instance and AS to differentiate
between the two request types in the same request.
Another form of polymorphism in JSON comes from the fact that the values within JSON
arrays need not all be of the same JSON data type. However, within this protocol,
each element within the array needs to be of the same kind of semantic element for
the collection to make sense, even when the data types are different from each other.
For example, each aspect of a resource request can be described using an object with multiple
dimensional components, or the aspect can be requested using a string. In both cases, the resource
request is being described in a way that the AS needs to interpret, but with different
levels of specificity and complexity for the client instance to deal with. An API designer
can provide a set of common access scopes as simple strings but still allow
RC developers to specify custom access when needed for more complex APIs.
Extensions to this specification can use different data types for defined fields, but
each extension needs to not only declare what the data type means, but also provide
justification for the data type representing the same basic kind of thing it extends.
For example, an extension declaring an "array" representation for a field would need
to explain how the array represents something akin to the non-array element that it
is replacing.