Understanding Key SSO Protocols and Their Use Cases
Tags: security, identity, webdev, oauth
Published: 2023-06-28 19:23:32

Single Sign-On (SSO) is a popular authentication method that allows users to access multiple applications with a single set of login credentials. This not only simplifies the login process but also improves security by reducing the need for users to remember multiple passwords. In this blog, we will discuss the key SSO protocols and their use cases.

## **What are SSO Protocols?**

SSO protocols are a set of rules and standards that define how authentication and authorization are performed between different applications. There are several SSO protocols available, but the most commonly used ones are:

- OpenID Connect (OIDC)
- Security Assertion Markup Language (SAML)
- OAuth 2.0


## **OpenID Connect (OIDC)**

OpenID Connect (OIDC) is an authentication protocol that builds upon the OAuth 2.0 framework to provide a secure and reliable method for authenticating users across different applications. It adds an identity layer to OAuth 2.0, allowing applications to obtain user identity information in a standardized and interoperable manner.

OIDC uses JSON Web Tokens (JWTs) as a means of exchanging information between the identity provider (IdP) and the service provider (SP). JWTs are digitally signed and encrypted tokens that contain claims about the user’s identity. These claims can include information such as the user’s unique identifier, name, email address, and other relevant attributes.

The primary objective of OIDC is to simplify the authentication process for users while maintaining security. It enables users to log in to multiple applications using a single set of credentials. This eliminates the need for users to remember and manage separate usernames and passwords for each application, enhancing convenience and user experience.

Let’s explore some common use cases where OIDC is frequently applied:

- **Social login:** OIDC enables users to log in to various applications using their existing social media accounts, such as Google, Facebook, or Twitter. Instead of creating a new account and remembering additional credentials, users can choose to authenticate themselves through their preferred social media platform. OIDC facilitates the authentication flow between the application and the social media provider, ensuring a streamlined login experience.


- **Enterprise Single Sign-On (SSO):** In enterprise environments, employees often need to access multiple internal applications, such as email, document management systems, or collaboration tools. OIDC can be employed to enable employees to use their corporate credentials, such as username and password, to access these applications without the need for separate logins. This centralized authentication mechanism simplifies the user experience and improves productivity by reducing the need to remember and manage multiple sets of credentials.

By leveraging OIDC for enterprise SSO, organizations can enhance security through centralized user management, authentication policies, and access controls. It also allows for better auditability and visibility into user activities across the various applications integrated with OIDC.

In both social login and enterprise SSO scenarios, OIDC ensures the secure exchange of authentication information between the IdP and the SP. The use of JWTs provides a standardized format for transmitting identity claims and allows applications to verify the authenticity and integrity of the received tokens.


## **Security Assertion Markup Language (SAML)**

Security Assertion Markup Language (SAML) is an XML-based standard that enables the secure exchange of authentication and authorization information between different applications. It provides a framework for identity federation, allowing users to access multiple applications or services using a single set of credentials.

SAML operates based on a trust relationship between two entities: the identity provider (IdP) and the service provider (SP). The IdP is responsible for authenticating the user and generating SAML assertions, which are XML-based security tokens containing information about the user’s identity and authentication status. The SP relies on these assertions to grant or deny access to its resources.

Here are some key aspects of SAML:

**1. Assertion: **The core component of SAML is the assertion, which is an XML document containing statements about the user’s identity and attributes. Assertions are digitally signed by the IdP to ensure integrity and authenticity. They can carry information such as the user’s unique identifier, name, email address, group membership, and other relevant attributes.

**2. Identity Provider (IdP):** The IdP is responsible for authenticating the user and generating SAML assertions. It acts as the trusted authority that verifies the user’s identity and issues assertions to the SPs. In an enterprise environment, the IdP is typically the centralized authentication system, such as an identity management solution or a directory service.

**3. Service Provider (SP):** The SP is the application or service that relies on SAML assertions to make access control decisions. It consumes the assertions provided by the IdP and grants or denies access to its resources based on the assertions' validity and the configured authorization rules. The SP trusts the IdP and relies on the integrity and accuracy of the assertions it receives.

Now, let’s explore the use cases where SAML is commonly employed:

**Enterprise Single Sign-On (SSO):** SAML enables employees to use their corporate credentials to access multiple internal applications without the need for separate logins. Once the user authenticates with the IdP, the IdP generates a SAML assertion containing the user’s identity information. This assertion is then sent to the SPs, allowing employees to access various applications seamlessly.

**Federated Single Sign-On (SSO):** SAML facilitates SSO across different organizations or domains. Users from one organization can access resources or services provided by another organization using their own set of credentials. The identity federation is established between the IdP of one organization and the SP of another, allowing users to authenticate with their own IdP and access resources in the SP’s domain.

By leveraging SAML, organizations can achieve centralized authentication, simplify user access management, and enhance security. SAML ensures that authentication and authorization information is exchanged securely and that users can access multiple applications or services without the need for separate sets of credentials.



## **OAuth 2.0**

OAuth 2.0 is an authorization framework that enables users to grant access to their protected resources to third-party applications without sharing their credentials. It provides a secure and standardized method for delegated authorization, allowing users to control which resources they want to share and for how long.

Here are the key components and concepts related to OAuth 2.0:

Actors:
**1. Resource Owner:** The user who owns the protected resources and grants access to them.

**2. Client:** The third-party application that wants to access the user’s resources with the user’s authorization.

**3. Authorization Server:** The server responsible for authenticating the user and obtaining their consent for access.

**4. Resource Server:** The server that hosts the protected resources that the client wants to access on behalf of the user.

**5. Authorization Grant:** The authorization grant is the credential obtained by the client to request access to the user’s resources. OAuth 2.0 defines multiple types of authorization grants, such as authorization code, implicit, client credentials, and resource owner password credentials.

**6. Access Token:** The access token is a credential that the client presents to the resource server to gain access to the user’s protected resources. It represents the authorization granted by the user and is typically issued by the authorization server.

**7. Scopes:** Scopes define the specific permissions or actions that the client is allowed to perform on behalf of the user. Each scope represents a different set of permissions, and the user can selectively grant or deny access to specific scopes during the authorization process.

Now, let’s explore the common use cases for OAuth 2.0:

**Social Login:** OAuth 2.0 is widely used by social media platforms like Google, Facebook, Twitter, and LinkedIn. Users can log in to various applications using their social media accounts as the authentication provider. The third-party application requests authorization to access the user’s basic profile information or perform actions on their behalf.

**API Access:** OAuth 2.0 allows third-party applications to access user data from different services or APIs (e.g., Google Drive, Dropbox, GitHub). The user authorizes the application to access specific scopes of their data, such as read-only access to files or the ability to write new files. The application receives an access token that it can use to make authorized API calls on behalf of the user.

OAuth 2.0 provides several benefits, including improved security, reduced reliance on shared credentials, and granular control over data access. It enables users to enjoy seamless integration with third-party applications while maintaining control over their sensitive information.

Comparison table: OpenID Connect (OIDC), Security Assertion Markup Language (SAML), and OAuth 2.0

Here’s a table comparing OpenID Connect (OIDC), Security Assertion Markup Language (SAML), and OAuth 2.0:


![Comparison Table](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/h391iggvcprus4wzs2gd.png)


OpenID Connect (OIDC) is primarily used for authentication, allowing users to authenticate across multiple applications using a single set of credentials. It relies on JSON Web Tokens (JWTs) for exchanging authentication information between the Identity Provider (IdP) and Service Provider (SP). OIDC is commonly used for social login and enterprise Single Sign-On (SSO).

Security Assertion Markup Language (SAML) is an XML-based standard used for authentication and authorization. It facilitates secure and centralized authentication within enterprise environments. SAML enables users to access multiple applications within an organization using their corporate credentials. It is also utilized for federated SSO, enabling users to access applications across different organizations using a single set of credentials.

OAuth 2.0, on the other hand, is an authorization protocol used to grant access to resources on behalf of a user. It focuses on resource access rather than authentication. OAuth 2.0 enables scenarios like social login, where users can use their social media accounts to log in to different applications. Additionally, it allows third-party applications to access user data from various services (e.g., Google Drive, Dropbox) without sharing user credentials.

While OIDC and SAML involve authentication and user identity, OAuth 2.0 centers around authorization and access to resources. Each protocol serves specific purposes and has different use cases, making them valuable tools for different aspects of secure authentication, authorization, and resource access in various scenarios.

## **Conclusion**
SSO protocols are an essential component of modern authentication systems. They provide a secure and reliable way to authenticate users across different applications. In this blog, we discussed the key SSO protocols and their use cases. By understanding these protocols, you can choose the right authentication method for your application and improve the user experience.