Update user guide for OIDC authentication

Signed-off-by: Daniel Jiang <jiangd@vmware.com>

docs/user_guide.md

@@ -29,6 +29,7 @@ This guide walks you through the fundamentals of using Harbor. You'll learn how
   * [Working with Helm CLI](#working-with-helm-cli)
 * [Online Garbage Collection.](#online-garbage-collection)
 * [View build history.](#build-history)
+* [Using CLI after login via OIDC based SSO](#using-oidc-cli-secret)
 * [Manage robot account of a project.](#robot-account)
 * [Using API Explorer](#api-explorer)
 
@@ -48,7 +49,7 @@ Besides the above three roles, there are two system-wide roles:
 * **Anonymous**: When a user is not logged in, the user is considered as an "Anonymous" user. An anonymous user has no access to private projects and has read-only access to public projects.  
 
 ## User account
-Harbor supports two authentication modes:  
+Harbor supports different authentication modes:  
 
 * **Database(db_auth)**  
 
@@ -73,6 +74,30 @@ Harbor supports two authentication modes:
 	
 	Self-registration, deleting user, changing password and resetting password are not supported under LDAP/AD authentication mode because the users are managed by LDAP or AD.  
 
+* **OIDC Provider (oidc_auth)**
+
+    With this authentication mode, regular user will login to Harbor Portal via SSO flow.  
+    After the system administrator configure Harbor to authenticate via OIDC (more details refer to [this section](#managing-authentication)),
+    a button `LOGIN VIA OIDC PROVIDER` will appear on the login page.  
+    ![oidc_login](img/oidc_login.png)
+    
+    By clicking this button user will kick off the SSO flow and be redirected to the OIDC Provider for authentication.  After a successful
+    authentication at the remote site, user will be redirected to Harbor.  There will be an "onboard" step if it's the first time the user 
+    authenticate using his account, in which there will be a dialog popped up for him to set his user name in Harbor:
+    ![oidc_onboar](img/oidc_onboard_dlg.png)
+    
+    This user name will be the identifier for this user in Harbor, which will be used in the cases such as adding member to a project, assigning roles, etc.
+    This has to be a unique user name, if another user has used this user name to onboard, user will be prompted to choose another one.
+    
+    Regarding this user to use docker CLI, please refer to [Using CLI after login via OIDC based SSO](#using-oidc-cli-secret)
+   
+    **NOTE:**
+    1. After the onboard process, you still have to login to Harbor via SSO flow, the `Username` and `Password` fields are only for
+    local admin to login when Harbor is configured authentication via OIDC.
+    2. Similar to LDAP authentication mode, self-registration, updating profile, deleting user, changing password and 
+    resetting password are not supported.
+ 
+
 ## Managing projects
 A project in Harbor contains all repositories of an application. No images can be pushed to Harbor before the project is created. RBAC is applied to a project. There are two types of projects in Harbor:  
 
@@ -249,6 +274,21 @@ You can change authentication mode between **Database**(default) and **LDAP** be
 When using LDAP mode, user's self-registration is disabled. The parameters of LDAP server must be filled in. For more information, refer to [User account](#user-account).   
 ![browse project](img/ldap_auth.png)
 
+When using OIDC mode, user will login Harbor via OIDC based SSO.  A client has to be registered on the OIDC provider and Harbor's callback URI needs to be associated to that client as a redirectURI.
+![OIDC settings](img/oidc_auth_setting.png)
+
+The settings of this auth mode:
+* OIDC Provider Name: The name of the OIDC Provider.
+* OIDC Provider Endpoint: The URL of the endpoint of the OIDC provider(a.k.a the Authorization Server in OAuth's terminology), 
+which must service the "well-known" URI for its configuration, more details please refer to https://openid.net/specs/openid-connect-discovery-1_0.html#ProviderConfigurationRequest
+* OIDC Client ID: The ID of client configured on OIDC Provider.
+* OIDC Client Secret: The secret for this client.
+* OIDC Scope: The scope values to be used during the authentication.  It is the comma separated string, which must contain `openid`.  
+Normally it should also contain `profile` and `email`.  For getting the refresh token it should also contain `offline_access`.  Please check with the administrator of the OIDC Provider.
+* Verify Certificate: Whether to check the certificate when accessing the OIDC Provider. if you are running the OIDC Provider with self-signed
+certificate, make sure this value is set to false.
+
+
 ### Managing project creation
 Use the **Project Creation** drop-down menu to set which users can create projects. Select **Everyone** to allow all users to create projects. Select **Admin Only** to allow only users with the Administrator role to create projects.  
 ![browse project](img/new_proj_create.png)
@@ -612,6 +652,35 @@ In Harbor portal, enter your project, select the repository, click on the link o
 
 ![build_ history](img/build_history.png)
 
+## Using OIDC CLI secret
+
+Having authenticated via OIDC SSO and onboarded to Harbor, you can use Docker/Helm CLI to access Harbor to read/write the artifacts.
+As the CLI cannot handle redirection for SSO, we introduced `CLI secret`, which is only available when Harbor's authentication mode 
+is configured to OIDC based.  
+After logging into Harbor, click the drop down list to view user's profile:
+![user_profile](img/user_profile.png)
+
+You can copy your CLI secret via the dialog of profile:
+![profile_dlg](img/profile_dlg.png)
+
+After that you can authenticate using your user name in Harbor that you set during onboard process, and CLI secret as the password
+with Docker/Helm CLI, for example:
+```sh
+docker login -u testuser -p xxxxxx jt-test.local.goharbor.io
+
+``` 
+
+When you click the "..." icon in the profile dialog, a button for generating new CLI secret will appear, and you can generate a new 
+CLI secret by clicking this button.  Please be reminded one user can only have one CLI secret, so when a new secret is generated, the
+old one becomes invalid at once.
+
+**NOTE**:
+Under the hood the CLI secret is associated with the ID token, and Harbor will try to refresh the token, so the CLI secret will
+be valid after th ID token expires. However, if the OIDC Provider does not provide refresh token or the refresh fails for some 
+reason, the CLI secret will become invalid.  In that case you can logout and login Harbor via SSO flow again so Harbor can get a 
+new ID token and the CLI secret will work again.
+
+
 ## Robot Account
 Robot Accounts are accounts created by project admins that are intended for automated operations. They have the following limitations: