openiddict-core/sandbox/OpenIddict.Sandbox.AspNetCore.Server/Controllers/AuthenticationController.cs

using System.Security.Claims;
using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Mvc;
using OpenIddict.Abstractions;
using OpenIddict.Client.AspNetCore;
using static OpenIddict.Abstractions.OpenIddictConstants;

namespace OpenIddict.Sandbox.AspNetCore.Server.Controllers;

public class AuthenticationController : Controller
{
    // Note: this controller uses the same callback action for all providers
    // but for users who prefer using a different action per provider,
    // the following action can be split into separate actions.
    [HttpGet("~/callback/login/{provider}"), HttpPost("~/callback/login/{provider}"), IgnoreAntiforgeryToken]
    public async Task<ActionResult> LogInCallback()
    {
        // Retrieve the authorization data validated by OpenIddict as part of the callback handling.
        var result = await HttpContext.AuthenticateAsync(OpenIddictClientAspNetCoreDefaults.AuthenticationScheme);

        // Multiple strategies exist to handle OAuth 2.0/OpenID Connect callbacks, each with their pros and cons:
        //
        //   * Directly using the tokens to perform the necessary action(s) on behalf of the user, which is suitable
        //     for applications that don't need a long-term access to the user's resources or don't want to store
        //     access/refresh tokens in a database or in an authentication cookie (which has security implications).
        //     It is also suitable for applications that don't need to authenticate users but only need to perform
        //     action(s) on their behalf by making API calls using the access token returned by the remote server.
        //
        //   * Storing the external claims/tokens in a database (and optionally keeping the essential claims in an
        //     authentication cookie so that cookie size limits are not hit). For the applications that use ASP.NET
        //     Core Identity, the UserManager.SetAuthenticationTokenAsync() API can be used to store external tokens.
        //
        //     Note: in this case, it's recommended to use column encryption to protect the tokens in the database.
        //
        //   * Storing the external claims/tokens in an authentication cookie, which doesn't require having
        //     a user database but may be affected by the cookie size limits enforced by most browser vendors
        //     (e.g Safari for macOS and Safari for iOS/iPadOS enforce a per-domain 4KB limit for all cookies).
        //
        //     Note: this is the approach used here, but the external claims are first filtered to only persist
        //     a few claims like the user identifier. The same approach is used to store the access/refresh tokens.

        // Important: if the remote server doesn't support OpenID Connect and doesn't expose a userinfo endpoint,
        // result.Principal.Identity will represent an unauthenticated identity and won't contain any claim.
        //
        // Such identities cannot be used as-is to build an authentication cookie in ASP.NET Core (as the
        // antiforgery stack requires at least a name claim to bind CSRF cookies to the user's identity) but
        // the access/refresh tokens can be retrieved using result.Properties.GetTokens() to make API calls.
        if (result.Principal is not ClaimsPrincipal { Identity.IsAuthenticated: true })
        {
            throw new InvalidOperationException("The external authorization data cannot be used for authentication.");
        }

        // Build an identity based on the external claims and that will be used to create the authentication cookie.
        var identity = new ClaimsIdentity(authenticationType: "ExternalLogin");

        // By default, OpenIddict will automatically try to map the email/name and name identifier claims from
        // their standard OpenID Connect or provider-specific equivalent, if available. If needed, additional
        // claims can be resolved from the external identity and copied to the final authentication cookie.
        identity.SetClaim(ClaimTypes.Email, result.Principal.GetClaim(ClaimTypes.Email))
                .SetClaim(ClaimTypes.Name, result.Principal.GetClaim(ClaimTypes.Name))
                .SetClaim(ClaimTypes.NameIdentifier, result.Principal.GetClaim(ClaimTypes.NameIdentifier));

        // Preserve the registration details to be able to resolve them later.
        identity.SetClaim(Claims.Private.RegistrationId, result.Principal.GetClaim(Claims.Private.RegistrationId))
                .SetClaim(Claims.Private.ProviderName, result.Principal.GetClaim(Claims.Private.ProviderName));

        // Build the authentication properties based on the properties that were added when the challenge was triggered.
        var properties = new AuthenticationProperties(result.Properties.Items)
        {
            RedirectUri = result.Properties.RedirectUri ?? "/"
        };

        // If needed, the tokens returned by the authorization server can be stored in the authentication cookie.
        // To make cookies less heavy, tokens that are not used are filtered out before creating the cookie.
        properties.StoreTokens(result.Properties.GetTokens().Where(token => token switch
        {
            // Preserve the access and refresh tokens returned in the token response, if available.
            {
                Name: OpenIddictClientAspNetCoreConstants.Tokens.BackchannelAccessToken or
                      OpenIddictClientAspNetCoreConstants.Tokens.RefreshToken
            } => true,

            // Ignore the other tokens.
            _ => false
        }));

        // Ask the default sign-in handler to return a new cookie and redirect the
        // user agent to the return URL stored in the authentication properties.
        //
        // For scenarios where the default sign-in handler configured in the ASP.NET Core
        // authentication options shouldn't be used, a specific scheme can be specified here.
        return SignIn(new ClaimsPrincipal(identity), properties);
    }
}