In today’s interconnected digital world, authentication and authorization are essential for securing web applications and services. When users access a service, proper validation of their identity (authentication) and determining their level of access (authorization) is critical. OpenID Connect, OAuth 2.0, and SAML are three popular protocols used to manage these processes.
This blog post will break down these protocols, compare them, and explain why they’re important for modern identity management systems.
What is OpenID Connect?
OpenID Connect (OIDC) is an identity layer built on top of the OAuth 2.0 protocol. It provides a simple, secure way for applications to authenticate users, allowing them to log in with their existing accounts from identity providers (IDPs) such as Google, Facebook, or Microsoft.
OpenID Connect works by using OAuth 2.0 for authorization and adds authentication capabilities. It uses ID tokens, which are cryptographically signed pieces of data containing user identity details, to securely confirm the identity of the user.
Key Features of OpenID Connect:
- Built on top of OAuth 2.0, it leverages OAuth’s authorization capabilities for authentication.
- It supports Single Sign-On (SSO), allowing users to log in once and access multiple applications.
- OIDC provides a standard set of scopes and claims to retrieve user information like email, name, and profile.
What is OAuth 2.0?
OAuth 2.0 is an authorization framework that allows third-party applications to access a user’s resources without needing to share their credentials. This is done by granting access tokens, which are short-lived credentials that permit access to specific parts of the user’s data.
OAuth 2.0 is commonly used for granting permissions between applications in scenarios such as allowing a music streaming service to access your contacts or enabling a photo-sharing app to access your cloud storage.
Key Features of OAuth 2.0:
- It doesn’t authenticate users; it only authorizes access to resources.
- OAuth 2.0 supports various types of grants (authorization code, implicit, resource owner password credentials, and client credentials).
- It allows third-party apps to request access without knowing the user’s login credentials.
What is SAML?
Security Assertion Markup Language (SAML) is an XML-based framework used for exchanging authentication and authorization data between an identity provider (IDP) and a service provider (SP). It’s primarily used for Single Sign-On (SSO) in enterprise environments, allowing users to log in once to access multiple applications without re-authenticating.
Unlike OAuth 2.0 and OpenID Connect, which are more commonly used for web-based apps, SAML is often seen in older systems and corporate environments.
Key Features of SAML:
- It’s an XML-based standard used for exchanging authentication and authorization data.
- It’s widely used in enterprise settings for SSO across a range of applications.
- SAML assertions (i.e., XML documents) contain authentication information about the user, such as whether they have logged in and their role within the organization.
Key Differences Between OAuth 2.0, OpenID Connect, and SAML
| Feature | OAuth 2.0 | OpenID Connect | SAML |
|---|---|---|---|
| Protocol Type | Authorization Framework | Authentication Layer on top of OAuth 2.0 | Authentication & Authorization Framework |
| Used For | Granting access to resources | Authentication and SSO | Authentication and SSO |
| Token Format | Access Token | ID Token (JWT) and Access Token | SAML Assertion (XML) |
| Authentication | No | Yes (via OAuth) | Yes |
| Authorization | Yes | Yes (via OAuth) | Yes |
| Common Use Case | API Authorization | Web-based Single Sign-On (SSO) | Enterprise and Federated SSO |
| Format of Messages | JSON | JSON | XML |
| Standardization Body | IETF (Internet Engineering Task Force) | OpenID Foundation | OASIS (Organization for the Advancement of Structured Information Standards) |
| Mobile and Web Use | Common in mobile apps and APIs | Common in mobile apps and web applications | Common in enterprise applications |
What is Authentication and Authorization?
Authentication and Authorization are two critical concepts in identity management.
- Authentication is the process of verifying a user’s identity, confirming that they are who they claim to be. This is typically done by asking for credentials like usernames, passwords, or biometric data (fingerprints, facial recognition).
- Authorization, on the other hand, determines what an authenticated user is allowed to do or access. Once a user’s identity is authenticated, the system uses authorization to check whether the user has the necessary permissions to access a specific resource or perform a certain action.
To summarize:
- Authentication answers the question: “Who are you?”
- Authorization answers the question: “What can you do?”
Why OAuth 2.0 Cannot Do Authentication
OAuth 2.0 is an authorization protocol, not an authentication protocol. It is designed to allow third-party applications to access specific user resources (e.g., contacts, photos, etc.) but does not concern itself with confirming a user’s identity.
OAuth 2.0 provides access tokens that grant permissions for a third-party service to interact with a user’s resources. However, it does not return any information about the user’s identity, such as their name, email, or other personal details. To authenticate a user, you need an identity layer, such as OpenID Connect, which can confirm that a person is who they say they are.
Without an identity layer, OAuth 2.0 cannot ensure that the user accessing a service is actually the one they claim to be. This is why OAuth 2.0 is often paired with OpenID Connect to provide both authentication (user identity verification) and authorization (resource access permissions).
What is the Difference Between SAML and OpenID Connect?
While both SAML and OpenID Connect are used for Single Sign-On (SSO), they differ significantly in the following ways:
1. Technology Stack
- SAML is an XML-based standard, often used in older, enterprise environments. It works well for web applications but may be more cumbersome to implement in modern, mobile-first systems.
- OpenID Connect is built on top of OAuth 2.0 and uses JSON Web Tokens (JWT) for token-based authentication, making it lighter and more modern, especially for web and mobile applications.
2. Ease of Use and Flexibility
- SAML is generally more complex to implement due to its reliance on XML. It often requires heavy lifting in terms of integration and configuration.
- OpenID Connect is easier to implement, as it uses modern web technologies (JSON, JWT, REST) and is more suitable for cloud-based and mobile applications.
3. Target Audience
- SAML is more commonly used in enterprise environments with legacy systems requiring federated identity management.
- OpenID Connect is designed for the modern web and mobile applications, supporting OAuth 2.0 and more commonly used for services like Google, Facebook, and Microsoft account logins.
Conclusion
Understanding the differences between OpenID Connect, OAuth 2.0, and SAML is crucial for anyone working in identity and access management (IAM). Each protocol serves a different purpose, and understanding their roles can help you design secure, scalable, and efficient authentication and authorization systems for web and mobile applications.
- OAuth 2.0 is great for authorizing third-party applications to access user resources, but it lacks authentication capabilities.
- OpenID Connect is a modern solution for authentication and authorization, built on top of OAuth 2.0.
- SAML remains a robust solution in enterprise settings for federated SSO, but it can be more complex and less flexible than OpenID Connect.
Each protocol has its place, and knowing when and how to use them will ensure that your application is secure and provides the best user experience.
