+--------+ +---------------+
| |--(A)------- Authorization Grant --------->| |
| | | |
| |<-(B)----------- Access Token -------------| |
| | & Refresh Token | |
| | | |
| | +----------+ | |
| |--(C)---- Access Token ---->| | | |
| | | | | |
| |<-(D)- Protected Resource --| Resource | | Authorization |
| Client | | Server | | Server |
| |--(E)---- Access Token ---->| | | |
| | | | | |
| |<-(F)- Invalid Token Error -| | | |
| | +----------+ | |
| | | |
| |--(G)----------- Refresh Token ----------->| |
| | | |
| |<-(H)----------- Access Token -------------| |
+--------+ & Optional Refresh Token +---------------+
Figure 2: Refreshing an Expired Access Token
The flow illustrated in Figure 2 includes the following steps:
(A) The client requests an access token by authenticating with the
authorization server and presenting an authorization grant.
(B) The authorization server authenticates the client and validates
the authorization grant, and if valid, issues an access token
and a refresh token.
(C) The client makes a protected resource request to the resource
server by presenting the access token.
(D) The resource server validates the access token, and if valid,
serves the request.
(E) Steps (C) and (D) repeat until the access token expires. If the
client knows the access token expired, it skips to step (G);
otherwise, it makes another protected resource request.
(F) Since the access token is invalid, the resource server returns
an invalid token error.
使用refresh_token取得access_token
接著是使用Refresh Token換取Access Token的流程。這大概是所有中最簡單的一個模式之一了。
但因爲先決條件是取得可用的 Refresh Token ，所以無法單獨存在。在RCF6749相關的流程圖中，關注的是G、H的部分。
至於一開始有什麼方式取得Refresh Token就非常的多。在已經介紹的密碼模式和code模式都有可能返回refresh_token。