Single Sign-On (SSO) is a protocol employed to authenticate and grant users access to multiple applications through a unified set of credentials. SSO proves highly convenient for users as it eliminates the need to remember multiple passwords and perform numerous login operations. Additionally, when implemented correctly, SSO solutions enhance security by mitigating risks associated with weak, repetitive, or misplaced passwords.
Enabling Single Sign-On (SSO) requires an identity provider (IdP) to furnish a central authentication server, allowing multiple applications to validate user identities. In the realm of SSO, Okta serves as an illustrative IdP. Okta is a cloud-based authentication solution that integrates with identity systems. The authentication server within Okta validates user identities and asserts their identity to the respective application by providing an encrypted access token.
The authentication server examines the user’s credentials against its central user directory (e.g., Active Directory), and upon validation, initiates a Single Sign-On (SSO) session. Subsequently, the user gains access to the application for a predefined duration without the need for reauthentication.
When a user tries to open a different application within the trusted group, there is no requirement to prompt for credentials once more. The application initiates authentication through the Identity Provider (IdP), utilising the existing Single Sign-On (SSO) session. The IdP issues an access token, enabling the application to authorise the user without displaying the login screen anew.
Single Sign-On (SSO) services typically do not retain the user’s ID, resulting in limited awareness of specific user identities. Normally, SSO services integrate with an identity management service, cross-referencing user credentials with the stored user data. Acting as an intermediary, Single Sign-On verifies that a user’s login credentials align with their identity without directly overseeing the user database.
Categories of SSO
When considering and implementing Single Sign-On (SSO), it is crucial to understand various protocols and standards. These are two most commons ones I’ve come across:
- Security Assertion Markup Language (SAML) SAML is an open standard designed for encoding text into machine language and facilitating the exchange of identifying information. Widely adopted as a fundamental SSO standard, many application providers use SAML to validate authentication requests. SAML 2.0 is particularly optimized for web applications and can transmit information through a web browser.
- Open Authorization (OAuth) OAuth is an open standard authentication protocol that secures the encryption and transmission of identity information between applications. This protocol enables users to access data from other applications without the need for manual identity verification. OAuth is particularly beneficial for native mobile applications.
Implementing Single Sign-On
The successful implementation of Single Sign-On (SSO) revolves around a central server trusted by all applications for accessing login credentials. If your organisation utilises multiple applications hosted on different servers with distinct user directories and authentication mechanisms, integrating all applications with the central SSO server is essential for SSO to function effectively.
1. Map Out Connected Applications:
Identify the applications to be included in your SSO structure by examining user login patterns. Create SSO “bundles” for sets of applications commonly accessed by specific user groups. Check if your SSO solution offers built-in integrations for these applications; if not, allocate development resources for integration.
2. Integrate with Identity Provider (IdP):
If your organization has its own identity provider, confirm that the SSO solution can integrate with it, and conduct thorough testing. Determine the protocol for connecting to the IdP, often using Security Assertion Markup Language (SAML). Alternatively, explore external IdPs supported by your SSO solution, such as social logins through platforms like Google or Facebook.
3. Verify Identity Directory Data:
Ensure that accurate and authoritative information about your users is available for SSO to function correctly. It is crucial for identities in the IdP to align with those used in applications connected through SSO. Validate user data, update email addresses and credentials, and take the opportunity to remove outdated users while revoking unnecessary privileges.
4. Evaluate User Privileges:
Carefully assess which users or roles should have access to specific applications before implementing SSO. Adhering to the least-privilege principle, grant users the minimal privileges necessary for their roles. Clearly define privileges based on a thorough understanding of the business functions served by each application.
5. Ensure High Availability and Security of SSO System:
Recognise that SSO is a mission-critical service and a potential single point of failure for applications. For on-premises SSO servers, establish redundancy and implement appropriate network and application layer security controls. In the case of a cloud service, review reliability and availability tiers, selecting the most suitable for your organisation. Ensure correct configuration of the provider’s security options to enhance system security.
