| OAuth Working Group | D. Hardt |
| Internet-Draft | July 03, 2019 |
| Intended status: Standards Track | |
| Expires: January 4, 2020 |
Reciprocal OAuth
draft-ietf-oauth-reciprocal-02
There are times when a user has a pair of protected resources that would like to request access to each other. While OAuth flows typically enable the user to grant a client access to a protected resource, granting the inverse access requires an additional flow. Reciprocal OAuth enables a more seamless experience for the user to grant access to a pair of protected resources.
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In the usual three legged, authorization code grant, the OAuth flow enables a resource owner (user) to enable a client (party A) to be granted authorization to access a protected resource (party B). If party A also has a protected resource that the user would like to let party B access, then a second complete OAuth flow, but in the reverse direction, must be performed. In practice, this is a complicated user experience as the user is at Party A, but the OAuth flow needs to start from Party B. This requires the second flow to send the user back to party B, which then sends the user to Party A as the first step in the flow. At the end, the user is at Party B, even though the original flow started at Party A.
Reciprocal OAuth simplifies the user experience by eliminating the redirections in the second OAuth flow. After the intial OAuth flow, party A obtains consent from the user to grant party B access to a protected resource at party A, and then passes an authorization code to party B using the access token party A obtained from party B to provide party B the context of the user. Party B then exchanges the authorization code for an access token per the usual OAuth flow.
In this document, the key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” are to be interpreted as described in BCP 14, RFC 2119 [RFC2119].
Party A Party B
+---------------+ +---------------+
| |--(A)- Authorization Request ->| Resource |
| | | Owner B |
| |<-(B)-- Authorization Grant ---| |
| | +---------------+
| Client A |
| | +---------------+
| |--(C)-- Authorization Grant -->| |
| | | Authorization |
| |<-(D)---- Access Token B ------| Server B |
| | Reciprocol Request | |
+---------------+ +---------------+
|
Reciprocol Request
V
+---------------+ +---------------+
| Resource | | Authorization |
| Owner A |--(E)--- Reciprocol Grant ---->| Server B |
| | Access Token B | |
+---------------+ +---------------+
|
Reciprocol Grant
V
+---------------+ +---------------+
| |<-(F)--- Reciprocol Grant -----| |
| Authorization | | Client B |
| Server A |--(G)---- Access Token A ----->| |
+---------------+ +---------------+
Figure 1: Abstract Reciprocol Protocol Flow
The reciprocol authorization between party A and party B are abstractly represented in Figure 1 and includes the following steps:
When party B is providing an access token response per [RFC6749] 4.1.4, 4.2.1, 4.3.3 or 4.4.3, party B MAY include an additional query component in the redirection URI to indicate the scope requested in the reciprocal grant:
reciprocal OPTIONAL
The scope of party B's reciprocal access request per [RFC6749] 3.3.
If party B does not provide a reciprocal parameter in the access token response, the reciprocal scope will be a value previously preconfigured by party A and party B.
If an authorization code grant access token response per [RFC6749] 4.1.4, an example successful response (with extra line breaks for display purposes only):
HTTP/1.1 200 OK
Content-Type: application/json;charset=UTF-8
Cache-Control: no-store
Pragma: no-cache
{
"access_token":"2YotnFZFEjr1zCsicMWpAA",
"token_type":"example",
"expires_in":3600,
"refresh_token":"tGzv3JOkF0XG5Qx2TlKWIA",
"reciprocal":"example_scope",
"example_parameter":"example_value"
}
If an authorization code grant access token response per [RFC6749] 4.2.2, an example successful response (with extra line breaks for display purposes only):
HTTP/1.1 302 Found
Location: http://example.com/cb#
access_token=2YotnFZFEjr1zCsicMWpAA&
state=xyz&
token_type=example&
expires_in=3600&
reciprocal="example_scope"
When party B is providing an authorization response per [RFC6749] 4.1.2, party B MAY include an additional query component in the redirection URI to indicate the scope requested in the reciprocal grant.
reciprocal OPTIONAL. The scope of party B’s reciprocal access request per [RFC6749] 3.3.
If party B does not provide a reciprocal parameter in the authorization response, the reciprocal scope will be a value previously preconfigured by party A and party B.
The reciprocal authorization flow starts after the client (party A) has obtained an access token from the authorization server (party B) per [RFC6749] 4.1 Authorization Code Grant.
Party A obtains consent from the user to grant Party B access to protected resources at party A. The consent represents the scopes requested by party B from party A per Section 2.1.
Party A generates an authorization code representing the access granted to party B by the user. Party A then makes a request to party B’s token endpoint authenticating per [RFC6749] 2.3 and sending the following parameters using the “application/x-www-form-urlencoded” format per [RFC6749] Appendix B with a character encoding of UTF-8 in the HTTP request entity-body:
grant_type REQUIRED
Value MUST be set to "urn:ietf:params:oauth:grant-type:reciprocal".
code REQUIRED
the authorization code generated by party A.
client_id REQUIRED
party A'a client ID.
access_token REQUIRED the access token obtained from Party B. Used by Party B to identify which user authorization is being requested.
For example, the client makes the following HTTP request using TLS (with extra line breaks for display purposes only):
POST /token HTTP/1.1 Host: server.example.com Authorization: Basic ej4hsyfishwssjdusisdhkjsdksusdhjkjsdjk Content-Type: application/x-www-form-urlencoded grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3reciprocal &code=hasdyubasdjahsbdkjbasd &client_id=example.com &access_token=sadadojsadlkjasdkljxxlkjdas
Party B MUST verify the authentication provided by Party A per [RFC6749] 2.3
Party B MUST then verify the access token was granted to the client identified by the client_id.
Party B MUST respond with either an HTTP 200 (OK) response if the request is valid, or an HTTP 400 “Bad Request” if it is not.
Party B then plays the role of the client to make an access token request per [RFC6749] 4.1.3.
After the initial authorization, the user may add or remove scopes available to the client at the authorization server. For example, the user may grant additional scopes to the client using a voice interface, or revoke some scopes. The authorization server can update the client with the new authorization by sending a new authorization code per Section 2.2.2.
TBD.
TBD.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC6749] | Hardt, D., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, October 2012. |
| [RFC6750] | Jones, M. and D. Hardt, "The OAuth 2.0 Authorization Framework: Bearer Token Usage", RFC 6750, DOI 10.17487/RFC6750, October 2012. |