In the web application world, OAuth 2.0 and OpenID Connect (OIDC) are two important topics when considering security. Both are protocols primarily used for authorizing (OAuth) and authenticating (OIDC) users (human or system) to access web applications and APIs. In fact, OpenID Connect is built on top of the OAuth 2.0 specification and provides some authorization functionality. They work together to ensure the overall security of web applications, APIs, and native apps.
Understanding the differences between OAuth and OIDC is critical for developers and software architects creating modern web applications. For a deeper understanding, knowing how OAuth 2.0 works provides a good first step. It provides useful context for knowing the functionality OpenID Connect provides.
So, let's examine both OAuth 2.0 and OIDC in more detail. We cover the functionality of both protocols and how they interact with each other. Additionally, knowing the differences between the two is also important for web developers. Note that Duende IdentityServer provides an effective standards-compliant framework incorporating both OAuth 2.0 and OIDC for ASP.NET Core applications.
How OAuth 2.0 Works
OAuth 2.0 is a protocol standard defining an authorization framework for web and mobile applications and related resources, like APIs. In short, it authorizes one application to access resources and functionality from another. Importantly, it focuses on authorization without providing identification information about the user in question. As noted earlier, this user might be a human or another application.
Working with a centralized identity provider (IdP), it generates an access token used for connecting to application resources. This scenario highlights how OpenID Connect and OAuth 2.0 work together. OIDC supports logging in and providing identity information. At the same time, the access token generated by OAuth 2.0 identifies the resources that users can access.
The specification for OAuth 2.0 defines many important concepts. These include the authorization flow, options for extensibility, as well as details on access and refresh tokens. The full spec serves as an important resource for those initially learning both protocols as well as experienced developers.
A Closer Look at OpenID Connect
As noted earlier, OpenID Connect functions as an authentication protocol built on top of OAuth 2.0. OIDC confirms the identity of users logged in through an IdP or authorization server. The specification defines a RESTful HTTP API to obtain user information.
The protocol provides the means for applications to identify users by their name, email, or other identification data. It leverages an ID token for this purpose, differentiated from the access and refresh tokens used by OAuth 2.0. In fact, some applications use OIDC as a single platform for both authentication and authorization. This scenario requires OpenID Connect to issue both an ID token and an access token.
OIDC actually uses the OAuth authorization flow, which makes sense considering it's built on top of that protocol. However, using OpenID Connect especially matters when an application wants to know the information identifying a specific user. It effectively serves as a one-stop shop, providing applications with both authorization and authentication services.
Exploring the Differences between OAuth 2.0 and OpenID Connect
Understanding the differences between OAuth 2.0 and OIDC helps you grasp how they interact for securing web applications. Use this information as food for thought when architecting your next SPA or complex web app.
- Basic Functionality: OAuth 2.0 provides authorization services for users and services wanting access to a web app's resources. On the other hand, OpenID Connect focuses on identification and authentication, while also providing authorization if needed. In some cases, developers add OIDC to provide authentication to an existing application using only OAuth 2.0.
- User Identity: As noted earlier, OAuth 2.0 only supports authorization functionality and provides no identity information. This is the major reason many software developers use it in tandem with OpenID Connect. Remember, using OIDC by itself serves as another option for both authorization and authentication.
- Token Management: As an authorization protocol, OAuth 2.0 only handles access and refresh tokens. On the other hand, OIDC also generates ID tokens in addition to the other authorization-related tokens, if needed. Remember, access tokens provide apps with permission to protected resources and APIs. A refresh token generates a new access token without users having to log in again.
- Implementation Complexity: OAuth 2.0 remains easier to implement as it only provides authorization services. Since OIDC adds authentication and identity functionality to authentication, implementation becomes more complex. Ultimately, both protocols are relatively easy to add to your application, especially when using Duende IdentityServer.
- Application Scope: Again, OAuth 2.0 in general only grants access to web application resources, like databases, media, or APIs. OpenID Connect adds authentication functionality and user identity data to OAuth's resource access services.
- Integration Support: As a critical security standard, OAuth 2.0 enjoys wide support, with clients available in multiple programming languages. Since OIDC operates on top of OAuth, it also boasts a similar level of support. Both protocols together offer a flexible and scalable approach for securing web applications, no matter their size and complexity.
Simply put, many of these differences relate to a basic concept. OAuth 2.0 provides authorization for access to web application resources. However, OpenID Connect adds authentication and identity management services to the OAuth 2.0 protocol. Deciding on using one or both on your next project likely depends on the application scope. Determine whether you only need authorization services or identity and authentication functionality as well.
Duende IdentityServer is the Perfect Partner for OAuth 2.0 and OpenID Connect
If your shop develops applications for ASP.NET Core, providing support for OAuth 2.0 and OpenID Connect is critical. Duende IdentityServer serves as a perfect partner for both security protocols. Its standard-compliant approach provides an extensible framework for OAuth 2.0 and OIDC. Enjoy full control over your app's UX, business logic, and data, while providing a secure experience for your users.
Check out our robust documentation repository with technical insights on our entire product line, including IdentityServer and Backend for Frontend. "The Big Picture" page illustrates how IdentityServer works in tandem with OAuth 2.0 and OIDC to secure modern web applications. Our Quickstarts also provide useful tutorials with a hands-on approach for learning our products. Reach out to us for answers to your questions on implementation strategies.