Introduction to SSO Connection via the SAML 2.0 Protocol

What is Single Sign-On (SSO)?

Single Sign-On (SSO) allows a user to authenticate once to access multiple applications without needing to log in again for each service. This improves the user experience and enhances security by centralizing authentication.

What is the SAML 2.0 Protocol?

SAML (Security Assertion Markup Language) is a standard protocol for authentication and authorization. Version 2.0 is the most widely used today. SAML allows the exchange of authentication and authorization information between two parties:

  1. Identity Provider (IdP): The server that manages user authentication.
  2. Service Provider (SP): The application or service the user wants to access.

How does SAML 2.0 work?

SAML uses XML assertions to transmit user information from the IdP to the SP. Here are the main steps of authentication via SAML 2.0:

  1. Service Access: The user tries to access an application (the SP). If the user is not yet authenticated, the application redirects them to the IdP.

  2. Authentication via the IdP: The IdP authenticates the user, typically via login and password.

  3. SAML Assertion Creation: Once the user is authenticated, the IdP creates a SAML assertion, which is a message containing authentication information (such as the user’s identity) and additional attributes (role, permissions, etc.).

  4. Redirection to the SP: The IdP redirects the user to the SP, including the signed SAML assertion in a response.

  5. Validation of the Assertion by the SP: The SP verifies the assertion, ensures it comes from a trusted IdP, and grants access to the user if everything is valid.

  6. Application Access: If authentication is successful, the user gains access to the application without needing to log in again.

Key Components of SAML 2.0

  • SAML Assertion: An XML document sent by the IdP to the SP. It contains information about the user, such as their identifier and attributes.
  • Bindings: Methods for transporting SAML messages between the IdP and the SP, such as HTTP-POST or HTTP-Redirect.
  • SAML Metadata: XML files that describe the information of providers (IdP and SP), such as endpoints, public keys, etc.

SAML Request Flow (Classic SSO)

  1. SP Authentication Request to IdP: The SP generates a SAML authentication request and redirects it to the IdP via the user (HTTP Redirect).
  2. User Authentication: The IdP authenticates the user via a login form.
  3. SAML Response: The IdP generates a SAML response containing the assertion, then redirects the user to the SP with the response.
  4. SP Response Validation: The SP checks the signature of the response and the information it contains before validating access.

Security in SAML 2.0

SAML relies on cryptography to ensure secure communication:

  • XML Signature: SAML messages are often signed to ensure their integrity and authenticity.
  • Assertion Encryption: Sensitive information, such as the assertion, can be encrypted to prevent interception.

Advantages of SSO with SAML 2.0

  • Improved User Experience: One-time authentication to access multiple services.
  • Enhanced Security: Centralized authentication and reduced number of passwords to manage.
  • Interoperability: SAML 2.0 is a widely supported standard by many applications and service providers.

Disadvantages

  • Implementation Complexity: Setting up and integrating SAML can be complex, especially for smaller teams.
  • Dependence on the IdP: If the IdP is unavailable, users cannot access applications.

Conclusion

SAML 2.0 is a robust and secure protocol for SSO authentication, ideal for environments requiring centralized and secure access to multiple applications. Although it requires careful initial setup, its security and user experience benefits make it a popular choice for SSO authentication.

This is just a brief introduction and is not exhaustive. Should you have any questions or need further information about SSO, please feel free to contact our team.