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SSO

Single Sign-On (SSO) is an authentication method that enables users to log in once and gain access to multiple connected applications or services without needing to re-enter their credentials. It simplifies user experience and centralizes authentication across systems.

SSO Key Concepts​

  • Identity Provider (IdP): The IdP is responsible for authenticating the user and issuing an authentication token, which allows access to connected applications. The IdP stores the user's credentials and is the authoritative source of authentication.
  • Service Provider (SP): An SP is any application or service that relies on the IdP for user authentication. After the IdP authenticates a user, the SP grants access based on the authentication token.
  • Centralized Authentication: SSO streamlines user authentication by consolidating it into a single service. After successfully authenticating with the IdP, the user gains automatic access to other associated applications (SPs) without re-entering credentials.
  • Token-Based Authentication: SSO systems frequently use tokens to manage user sessions across multiple services, such as JSON Web Tokens (JWT), SAML assertions, or OAuth tokens. These tokens are exchanged between the IdP and the SPs to confirm the user's identity.
  • Single Sign-Off: Some SSO systems support the Single Sign-Off (SSO) feature, which allows users to log out of all connected applications at the same time when they log out of one.

SSO Protocols​

  • Security Assertion Markup Language (SAML): SAML is an XML-based protocol for exchanging authentication and authorization data between an IdP and an SP. It is widely used in enterprise SSO implementations.
  • OAuth/OpenID Connect: OAuth is an authorization protocol that allows third-party applications limited access to a user's resources. OpenID Connect is a layer on top of OAuth 2.0 that adds authentication functionality, allowing it to function as an SSO solution.
  • Lightweight Directory Access Protocol (LDAP): LDAP is often used by identity providers to store and retrieve user credentials for authentication. It includes a directory service for user management and can be integrated with SSO systems.

Benefits of SSO​

  • Improved User Experience: SSO eliminates the need for users to remember and manage multiple passwords, increasing overall usability and lowering sign-in fatigue.
  • Enhanced Security: By centralizing authentication, SSO reduces the risk of phishing and password attacks. It also makes security measures like Multi-Factor Authentication (MFA) easier to implement at the IdP level for all services.
  • Reduced Administrative Overhead: IT administrators can manage user access more efficiently with a single point of authentication, eliminating the need to maintain separate credentials for multiple applications.

Limitations​

  • If the identity provider becomes unavailable or is compromised, users may lose access to all connected services. This makes high availability, redundancy, and robust security measures critical for the IdP.
  • Integrating SSO across multiple services requires careful configuration of trust relationships between IdPs and SPs. Improper token handling, misconfigured settings, or lack of encryption can introduce vulnerabilities.