English
In short, they describe two different usage scenarios of OAuth involving two respectively three parties.
3-legged OAuth describes the scenario for which OAuth was originally developed: a resource owner wants to give a client access to a server without sharing his credentials (i.e. username/password). A typical example is a user (resource owner) who wants to give a third-party application (client) access to his Twitter account (server).
On a conceptual level it works in the following way:
- Client has signed up to the server and got his client credentials (also known as “consumer key and secret”) ahead of time
- User wants to give the client access to his protected resources on the server
- Client retrieves the temporary credentials (also known as “request token”) from the server
- Client redirects the resource owner to the server
- Resource owner grants the client access to his protected resources on the server
- Server redirects the user back to the client
- Client uses the temporary credentials to retrieve the token credentials (also known as “access token”) from the server
- Client uses the token credentials to access the protected resources on the server
2-legged OAuth, on the other hand, describes a typical client-server scenario, without any user involvement. An example for such a scenario could be a local Twitter client application accessing your Twitter account.
On a conceptual level 2-legged OAuth simply consists of the first and last steps of 3-legged OAuth:
- Client has signed up to the server and got his client credentials (also known as “consumer key and secret”)
- Client uses his client credentials (and empty token credentials) to access the protected resources on the server
Chinese
3-legged oauth
resource owner, client, server.
resource owner 给client访问权限去访问resource owner在server上的resource，但是resource owner和client不共享credentials（用户名和密码）。
1. client在server上注册，获得client credentials（包括consumer key和consumer secret）
2. client从server获得temporay credentials（即request token）
3. client将user-agent定向到server
4. user授权client访问server上的resource
5. server将user-agent定向到client
6. client用temporary credentials(request token)从server换取token credentials（即 access token）
7. client使用access token访问server上的protected resource
2-legged oauth
没有user参与的 server/client形式
1. client在server上注册，获得client credentials（包括consumer key和consumer secret）
2. client使用client credential（和空的token credential）访问server上的protected resource
三条腿的OAuth（3-Legged
OAuth），这也是OAuth的标准版本。这里所谓的“三条腿”，指的是授权过程中涉及前面提到的三种角色，也就是：客户端，服务提供方，用户。不过有
些情况下，不需要用户的参与，此时就产生了一个变体，被称作两条腿的OAuth（2-Legged
OAuth），一般来说，访问私有数据的应用需要三条腿的OAuth，访问公共数据的应用需要两条腿的OAuth。
两条腿的OAuth和三条腿的OAuth相比，因为没有用户的参与，所以在流程中就不会涉及用户授权的环节，也就不需要使用Token，而主要是通
过Consumer Key和Consumer Secret来完成签名的，此时的Consumer Key和Consumer
Secret基本等价于账号和密码的作用。
Japanese
