c# - Implementing OpenIdConnectOptions Events when using Authentication.AzureAD.UI Library

Question

I have been using a library I created from samples allowing me to authenticate a .NET core web app with Azure Active Directory and to take advantage of the various OpenIdConnectOptions events (e.g. OnTokenValidated) to add certain claims to the principal as well as add that data to an identity-like database so that APIs can make policy-based determinations of the caller based on their token.

But I would just rather use the Microsoft.AspNetCore.Authentication.AzureAD.UI NuGet package than my customized variation, I am just not sure how to reach in and access the event on the OpenIdConnectOptions.

I don't know if it's not something that can be done, or I just haven't got enough of a handle on dependency injection to figure out how to do that.

Or should I consider adding claims, etc. in a different part of the process?

public static AuthenticationBuilder AddAzureAD(
    this AuthenticationBuilder builder,
    string scheme,
    string openIdConnectScheme,
    string cookieScheme,
    string displayName,
    Action<AzureADOptions> configureOptions) {

    AddAdditionalMvcApplicationParts(builder.Services);
    builder.AddPolicyScheme(scheme, displayName, o => {
        o.ForwardDefault = cookieScheme;
        o.ForwardChallenge = openIdConnectScheme;
    });

    builder.Services.Configure(
        TryAddOpenIDCookieSchemeMappings(scheme, openIdConnectScheme, cookieScheme));

    builder.Services.TryAddSingleton<IConfigureOptions<AzureADOptions>, AzureADOptionsConfiguration>();

    // They put in their custom OpenIdConnect configuration, but I can't see how to get at the events.
    builder.Services.TryAddSingleton<IConfigureOptions<OpenIdConnectOptions>, OpenIdConnectOptionsConfiguration>();

    builder.Services.TryAddSingleton<IConfigureOptions<CookieAuthenticationOptions>, CookieOptionsConfiguration>();

    builder.Services.Configure(scheme, configureOptions);

    builder.AddOpenIdConnect(openIdConnectScheme, null, o => { });
    builder.AddCookie(cookieScheme, null, o => { });

    return builder;
}

Answer 1

I might be a little late to the party here, but I've come across the same issue and found that the AzureAD authentication middleware is very sparsely documented. Adding the solution here for others struggling with the same question.

As you can see at the bottom of the code snippet in the question, the AzureAD provider actually relies on OpenIdConnect and Cookie auth providers under the hoods, and does not implement any authentication logic itself.

To accomplish this, two additional authentication schemes are added, using the names defined as AzureADDefaults.OpenIdScheme and AzureADDefaults.CookieScheme, respectively.

(Although the names can also be customized when using the AddAzureAD(this Microsoft.AspNetCore.Authentication.AuthenticationBuilder builder, string scheme, string openIdConnectScheme, string cookieScheme, string displayName, Action<Microsoft.AspNetCore.Authentication.AzureAD.UI.AzureADOptions> configureOptions) overload).

That, in turn, allows to configure the effective OpenIdConnectOptions and CookieAuthenticationOptions by using the scheme names from above, including access to OpenIdConnectEvents.

See this complete example:

        services.AddAuthentication(AzureADDefaults.AuthenticationScheme)
            .AddAzureAD(options => Configuration.Bind("AzureAd", options));

        services.Configure<OpenIdConnectOptions>(AzureADDefaults.OpenIdScheme, options =>
        {
            options.Events = new OpenIdConnectEvents
            {
                OnRedirectToIdentityProvider = async ctxt =>
                {
                    // Invoked before redirecting to the identity provider to authenticate. This can be used to set ProtocolMessage.State
                    // that will be persisted through the authentication process. The ProtocolMessage can also be used to add or customize
                    // parameters sent to the identity provider.
                    await Task.Yield();
                },
                OnMessageReceived = async ctxt =>
                {
                    // Invoked when a protocol message is first received.
                    await Task.Yield();
                },
                OnTicketReceived = async ctxt =>
                {
                    // Invoked after the remote ticket has been received.
                    // Can be used to modify the Principal before it is passed to the Cookie scheme for sign-in.
                    // This example removes all 'groups' claims from the Principal (assuming the AAD app has been configured
                    // with "groupMembershipClaims": "SecurityGroup"). Group memberships can be checked here and turned into
                    // roles, to be persisted in the cookie.
                    if (ctxt.Principal.Identity is ClaimsIdentity identity)
                    {
                        ctxt.Principal.FindAll(x => x.Type == "groups")
                            .ToList()
                            .ForEach(identity.RemoveClaim);
                    }                        
                    await Task.Yield();
                },
            };
        });

        services.Configure<CookieAuthenticationOptions>(AzureADDefaults.CookieScheme, options =>
        {
            options.Events = new CookieAuthenticationEvents
            {
                // ...
            };
        });