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Overview

OpenID for ASP.NET Core enables ASP.NET Core applications to act as an OpenID Provider (OP) to support OpenID clients (also referred to as relying parties).

It provides a complete implementation of the OpenID Connect (OIDC) protocol, handling message creation, transport, validation, and security enforcement, while integrating cleanly with the ASP.NET Core authentication and authorization pipeline.

What Problem This Solves

OpenID Connect is widely used in enterprise environments to provide single sign-on (SSO), centralized identity management, and federation between organizations.

Implementing OpenID Connect correctly involves careful handling of:

  • Token signing and validation
  • Nonce, state, and replay protection
  • Time-based validation and clock skew
  • Interoperability differences between OpenID Connect clients

OpenID for ASP.NET Core abstracts those complexities, allowing ASP.NET Core applications to add standards-compliant OpenID Connect authentication without implementing the protocol directly.

Supported Scenarios

OpenID for ASP.NET Core supports all the common OpenID Connect scenarios, including:

  • Acting as an OpenID Provider (OP)
  • OpenID Connect Discovery
  • Authentication and Logout
  • Authorization Code, Implicit and Hybrid Flows
  • Proof Key for Code Exchange (PKCE)
  • JWT Access Tokens
  • Refresh Tokens

These features allow OpenID for ASP.NET Core to be used in both simple single-client deployments and more advanced multi-tenant or federated environments.

Platform and Hosting Support

OpenID for ASP.NET Core is designed specifically for ASP.NET Core applications and supports:

  • ASP.NET Core running on supported .NET runtimes
  • Hosting on IIS, Azure App Service, and containerized environments
  • Deployment on Windows and Linux

Security Responsibilities

OpenID for ASP.NET Core enforces all OpenID Connect protocol-level security requirements, including:

  • Signing and validation of ID tokens and other JWTs
  • Issuer, audience, and claim validation
  • Lifetime enforcement, nonce validation, and clock skew handling
  • Protection against replay and token substitution attacks
  • Validation of redirect URIs and protocol parameters

Application-level responsibilities such as authorization, role management, user provisioning, and session lifetime remain under the control of the host application.