@title Using the Phabricator OAuth Server
@group developer

How to use the Phabricator OAuth Server.

= Overview =

Phabricator includes an OAuth Server which supports the 
##Authorization Code Grant## flow as described in the OAuth 2.0 
specification:

http://tools.ietf.org/html/draft-ietf-oauth-v2-23

This functionality can allow clients to integrate with a given 
Phabricator instance in a secure way with granular data access. 
For example, Phabricator can be used as a central identity store for any 
clients that implement OAuth 2.0.

= Vocabulary =

- **Access token** - a token which allows a client to ask for data on 
behalf of a resource owner. A given client will only be able to access 
data included in the scope(s) the resource owner authorized that client for.
- **Authorization code** - a short-lived code which allows an authenticated 
client to ask for an access token on behalf of some resource owner.
- **Client** - this is the application or system asking for data from the 
OAuth Server on behalf of the resource owner.
- **Resource owner** - this is the user the client and OAuth Server are 
concerned with on a given request.
- **Scope** - this defines a specific piece of granular data a client can 
or can not access on behalf of a user. For example, if authorized for the 
"whoami" scope on behalf of a given resource owner, the client can get the 
results of Conduit.whoami for that resource owner when authenticated with 
a valid access token.

= Setup - Creating a Client =

# Visit https://phabricator.example.com/oauthserver/client/create/
# Fill out the form
# Profit

= Obtaining an Authorization Code =

POST or GET https://phabricator.example.com/oauthserver/auth/ with the 
following parameters:

- Required - **client_id** - the id of the newly registered client.
- Required - **response_type** - the desired type of authorization code 
response. Only code is supported at this time.
- Optional - **redirect_uri** - override the redirect_uri the client 
registered. This redirect_uri must have the same fully-qualified domain 
and have at least the same query parameters as the redirect_uri the client 
registered, as well as have no fragments.
- Optional - **scope** - specify what scope(s) the client needs access to
in a space-delimited list.
- Optional - **state** - an opaque value the client can send to the server 
for programmatic excellence. Some clients use this value to implement XSRF 
protection or for debugging purposes.

If done correctly and the resource owner has not yet authorized the client 
for the desired scope, then the resource owner will be presented with an 
interface to authorize the client for the desired scope. The OAuth Server 
will redirect to the pertinent redirect_uri with an authorization code or 
an error indicating the resource owner did not authorize the client, depending.

If done correctly and the resource owner has already authorized the client for 
the desired scope, then the OAuth Server will redirect to the pertinent 
redirect_uri with a valid authorization code. 

If there is an error, the OAuth Server will return a descriptive error 
message. This error will be presented to the resource owner on the 
Phabricator domain if there is reason to believe there is something fishy 
with the client. For example, if there is an issue with the redirect_uri. 
Otherwise, the OAuth Server will redirect to the pertinent redirect_uri 
and include the pertinent error information.

= Obtaining an Access Token =

POST or GET https://phabricator.example.com/oauthserver/token/ 
with the following parameters:

- Required - **client_id** - the id of the client
- Required - **client_secret** - the secret of the client. 
This is used to authenticate the client.
- Required - **code** - the authorization code obtained earlier.
- Required - **grant_type** - the desired type of access grant. 
Only token is supported at this time.
- Optional - **redirect_uri** - should be the exact same redirect_uri as 
the redirect_uri specified to obtain the authorization code. If no 
redirect_uri was specified to obtain the authorization code then this 
should not be specified.

If done correctly, the OAuth Server will redirect to the pertinent 
redirect_uri with an access token.

If there is an error, the OAuth Server will return a descriptive error 
message.

= Using an Access Token =

Simply include a query param with the key of "access_token" and the value 
as the earlier obtained access token. For example:

  https://phabricator.example.com/api/user.whoami?access_token=ykc7ly7vtibj334oga4fnfbuvnwz4ocp

If the token has expired or is otherwise invalid, the client will receive
an error indicating as such. In these cases, the client should re-initiate 
the entire ##Authorization Code Grant## flow.

NOTE: See "Scopes" section below for more information on what data is 
currently exposed through the OAuth Server.

= Scopes =

There are only two scopes supported at this time.

- **offline_access** - allows an access token to work indefinitely without 
expiring.
- **whoami** - allows the client to access the results of Conduit.whoami on 
behalf of the resource owner.
