When a user logs in to a vSphere component or when a vCenter Server solution user accesses another vCenter Server service, vCenter Single Sign-On performs authentication. Users must be authenticated with vCenter Single Sign-On and have the necessary privileges for interacting with vSphere objects.
vCenter Single Sign-On authenticates both solution users and other users.
Solution users represent a set of services in your vSphere environment. During installation, VMCA assigns a certificate to each solution user by default. The solution user uses that certificate to authenticate to vCenter Single Sign-On. vCenter Single Sign-On gives the solution user a SAML token, and the solution user can then interact with other services in the environment.
When other users log in to the environment, for example, from the vSphere Web Client, vCenter Single Sign-On prompts for a user name and password. If vCenter Single Sign-On finds a user with those credentials in the corresponding identity source, it assigns the user a SAML token. The user can now access other services in the environment without being prompted to authenticate again.
Which objects the user can view, and what a user can do, is usually determined by vCenter Server permission settings. vCenter Server administrators assign those permissions from the interface in the vSphere Web Client, not through vCenter Single Sign-On. See vSphere Permissions and User Management Tasks.
vCenter Single Sign-On and vCenter Server Users
Using the vSphere Web Client, users authenticate to vCenter Single Sign-On by entering their credentials on the vSphere Web Client login page. After connecting to vCenter Server, authenticated users can view all vCenter Server instances or other vSphere objects for which their role gives them privileges. No further authentication is required. See vSphere Permissions and User Management Tasks.
After installation, the firstname.lastname@example.org user has administrator access to both vCenter Single Sign-On and vCenter Server. That user can then add identity sources, set the default identity source, and manage users and groups in the vCenter Single Sign-On domain (vsphere.local).
All users that can authenticate to vCenter Single Sign-On can reset their password, even if the password has expired, as long as they know the password. See Change Your vCenter Single Sign-On Password. Only vCenter Single Sign-On administrators can reset the password for users who no longer have their password.
vCenter Single Sign-On Administrator Users
The vCenter Single Sign-On administrative interface is accessible from the vSphere Web Client.
To configure vCenter Single Sign-On and manage vCenter Single Sign-On users and groups, the user email@example.com or a user in the vCenter Single Sign-On Administrators group must log in to the vSphere Web Client. Upon authentication, that user can access the vCenter Single Sign-On administration interface from the vSphere Web Client and manage identity sources and default domains, specify password policies, and perform other administrative tasks. See Configuring vCenter Single Sign-On Identity Sources.
You cannot rename the firstname.lastname@example.org user. For improved security, consider creating additional named users in the vsphere.local domain and assigning them administrative privileges. You can then stop using email@example.com.
Authentication in Different Versions of vSphere
If a user connects to a vCenter Server system version 5.0.x or earlier, vCenter Server authenticates the user by validating the user against an Active Directory domain or against the list of local operating system users. In vCenter Server 5.1 and later, users authenticate through vCenter Single Sign-On.
You cannot use the vSphere Web Client to manage vCenter Server version 5.0 or earlier. Upgrade vCenter Server to version 5.1 or later.
ESXi is not integrated with vCenter Single Sign-On. You add the ESXi host to an Active Directory domain explicitly. See Configure a Host to Use Active Directory.
You can still create local ESXi users with the vSphere Client, vCLI, or PowerCLI. vCenter Server is not aware of users that are local to ESXi and ESXi is not aware of vCenter Server users.
Manage permissions for ESXi hosts through vCenter Server if possible.
How to Log In to vCenter Server Components
When a user logs in to a vCenter Server system from the vSphere Web Client, the login behavior depends on whether the user is in the default domain, that is, the domain that is set as the default identity source.
Users who are in the default domain can log in with their user name and password.
Users who are in a domain that has been added to vCenter Single Sign-On as an identity source but is not the default domain can log in to vCenter Server but must specify the domain in one of the following ways.
Including a domain name prefix, for example, MYDOMAIN\user1
Including the domain, for example, firstname.lastname@example.org
Users who are in a domain that is not a vCenter Single Sign-On identity source cannot log in to vCenter Server. If the domain that you add to vCenter Single Sign-On is part of a domain hierarchy, Active Directory determines whether users of other domains in the hierarchy are authenticated or not.
If your environment includes an Active Directory hierarchy, see VMware Knowledge Base article 2064250 for details on supported and unsupported setups.