Single sign-on (SSO) is a session and user authentication service that permits an end user to enter one set of login credentials (such as a name and password) and be able to access multiple applications.
In a basic web SSO service, an agent module on the application server retrieves the specific authentication credentials for an individual user from a dedicated SSO policy server, while authenticating the user against a user repository such as a lightweight directory access protocol (LDAP) directory. The service authenticates the end user for all the applications the user has been given rights to and eliminates future password prompts for individual applications during the same session.
How single sign-on works
Single sign-on is a federated identity management (FIM) arrangement and the use of such a system is sometimes called identity federation. OAuth, which is pronounced "oh-auth," is the framework that allows an end user's account information to be used by third-party services, such as Facebook, without exposing the user's password.
OAuth acts as an intermediary on behalf of the end user by providing the service with an access token that authorizes specific account information to be shared. When a user attempts to access an application from the service provider, the service provider will send a request to the identity provider for authentication. The service provider will then verify the authentication and log the user in.
Some SSO services use protocols such as Kerberos and the security assertion markup language (SAML). SAML is an XML standard that facilitates the exchange of user authentication and authorization data across secure domains. SAML-based SSO services involve communications between the user, an identity provider that maintains a user directory, and a service provider. In a Kerberos-based setup, once the user credentials are provided, a ticket-granting ticket (TGT) is issued. The TGT fetches service tickets for other applications the user wishes to access, without asking the user to re-enter credentials.
Security risks and SSO
Although single sign-on is a convenience to users, it present risks to enterprise security. An attacker who gains control over a user's SSO credentials will be granted access to every application the user has rights to, increasing the amount of potential damage. In order to avoid malicious access, it's essential that every aspect of SSO implementation be coupled with identity governance. Organizations can also use two factor authentication (2FA) or multifactor authentication (MFA) with SSO to improve security.
Google, LinkedIn, Twitter and Facebook all offer popular SSO services that allow an end user to log into a third-party application with their social media authentication credentials. Although social single sign-on is a convenience to users, it can present security risks because it creates a single point of failure that can be exploited by attackers. Many security professionals recommend that end users refrain from using social SSO services altogether, because once an attacker gains control over a user's SSO credentials, they will be able to access all other applications that use the same credentials.
Apple recently unveiled its own single sign-on service and is positioning it as a more private alternative to the SSO options provided by Google, Facebook, LinkedIn and Twitter. The new offering, which will be called Sign In with Apple, is expected to limit what data third-party services can access. Apple's single sign-on (SSO) will also enhance security by requiring users to use two-factor authentication on all Apple ID accounts to support integration with Face ID and Touch ID on iOS devices.
Enterprise single sign-on (eSSO) software products and services are password managers with client and server components that log the user on to target applications by replaying user credentials. These credentials are almost always username and password, and target applications do not need to be modified to work with the eSSO system.
Check out this buyer's guide for healthcare organizations considering an SSO technology purchase and explore the various options available, including federated SSO.