2.2. Access Token Request

When the resource parameter is used on an access token request made to the token endpoint, for all grant types, it indicates the target service or protected resource where the client intends to use the requested access token.

The resource value(s) that is acceptable to an authorization server in fulfilling an access token request is at its sole discretion based on local policy or configuration. In the case of a refresh_token or authorization_code grant type request, such policy may limit the acceptable resources to those that were originally granted by the resource owner or a subset thereof. In the authorization_code case where the requested resources are a subset of the set of resources originally granted, the authorization server will issue an access token based on that subset of requested resources, whereas any refresh token that is returned is bound to the full original grant.

When requesting a token, the client can indicate the desired target service(s) where it intends to use that token by way of the resource parameter and can indicate the desired scope of the requested token using the scope parameter. The semantics of such a request are that the client is asking for a token with the requested scope that is usable at all the requested target services. Effectively, the requested access rights of the token are the cartesian product of all the scopes at all the target services. To the extent possible, when issuing access tokens, the authorization server should downscope the scope value associated with an access token to the value the respective resource is able to process and needs to know. (Here, "downscope" means give fewer permissions than originally authorized by the resource owner.) This further improves privacy as a list of scope values is an indication that the resource owner uses the multiple various services listed; downscoping a token to only that which is needed for a particular service can limit the extent to which such information is revealed across different services. As specified in Section 5.1 of [RFC6749], the authorization server must indicate the access token's effective scope to the client in the scope response parameter value when it differs from the scope requested by the client.

Following from the code flow authorization request shown in Figure 2, the below examples show an authorization_code grant type access token request (Figure 3) and response (Figure 4) where the client tells the authorization server that it wants the access token for use at https://cal.example.com/ (extra line breaks and indentation are for display purposes only).

POST /as/token.oauth2 HTTP/1.1
Host: authorization-server.example.com
Authorization: Basic czZCaGRSa3F0Mzpoc3FFelFsVW9IQUU5cHg0RlNyNHlJ
Content-Type: application/x-www-form-urlencoded

grant_type=authorization_code
&redirect_uri=https%3A%2F%2Fclient.example.org%2Fcb
&code=10esc29BWC2qZB0acc9v8zAv9ltc2pko105tQauZ
&resource=https%3A%2F%2Fcal.example.com%2F

Figure 3: Access Token Request

HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-cache, no-store

{
   "access_token":"eyJhbGciOiJFUzI1NiIsImtpZCI6Ijc3In0.eyJpc3MiOi
    JodHRwOi8vYXV0aG9yaXphdGlvbi1zZXJ2ZXIuZXhhbXBsZS5jb20iLCJzdWI
    iOiJfX2JfYyIsImV4cCI6MTU4ODQyMDgwMCwic2NvcGUiOiJjYWxlbmRhciIs
    ImF1ZCI6Imh0dHBzOi8vY2FsLmV4YW1wbGUuY29tLyJ9.nNWJ2dXSxaDRdMUK
    lzs-cYIj8MDoM6Gy7pf_sKrLGsAFf1C2bDhB60DQfW1DZL5npdko1_Mmk5sUf
    zkiQNVpYw",
   "token_type":"Bearer",
   "expires_in":3600,
   "refresh_token":"4LTC8lb0acc6Oy4esc1Nk9BWC0imAwH7kic16BDC2",
   "scope":"calendar"
}

Figure 4: Access Token Response

A subsequent access token request, using the refresh token, where the client tells the authorization server that it wants an access token for use at https://contacts.example.com/ is shown in Figure 5 below with the response shown in Figure 6 (extra line breaks and indentation are for display purposes only).

POST /as/token.oauth2 HTTP/1.1
Host: authorization-server.example.com
Authorization: Basic czZCaGRSa3F0Mzpoc3FFelFsVW9IQUU5cHg0RlNyNHlJ
Content-Type: application/x-www-form-urlencoded

grant_type=refresh_token
&refresh_token=4LTC8lb0acc6Oy4esc1Nk9BWC0imAwH7kic16BDC2
&resource=https%3A%2F%2Fcontacts.example.com%2F

Figure 5: Access Token Request

HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-cache, no-store

{
   "access_token":"eyJhbGciOiJFUzI1NiIsImtpZCI6Ijc3In0.eyJpc3MiOi
    JodHRwOi8vYXV0aG9yaXphdGlvbi1zZXJ2ZXIuZXhhbXBsZS5jb20iLCJzdWI
    iOiJfX2JfYyIsImV4cCI6MTU4ODQyMDgyNiwic2NvcGUiOiJjb250YWN0cyIs
    ImF1ZCI6Imh0dHBzOi8vY29udGFjdHMuZXhhbXBsZS5jb20vIn0.5f4yhqazc
    OSlJw4y94KPeWNEFQqj2cfeO8x4hr3YbHtIl3nQXnBMw5wREY5O1YbZED-GfH
    UowfmtNaA5EikYAw",
   "token_type":"Bearer",
   "expires_in":3600,
   "scope":"contacts"
}

Figure 6: Access Token Response

2.2. Access Token Request​

2.2. Access Token Request