Get access token in MVC application

Question

I am trying to retrieve the access token so I can store it, and pass it to an ExchangeService later on. Startup.Auth looks like this:

 app.UseOpenIdConnectAuthentication(
            new OpenIdConnectAuthenticationOptions
            {
                ClientId = clientId,
                Authority = authority,
                UseTokenLifetime = false,
                /*
                * Skipping the Home Realm Discovery Page in Azure AD
                * http://www.cloudidentity.com/blog/2014/11/17/skipping-the-home-realm-discovery-page-in-azure-ad/
                */
                Notifications = new OpenIdConnectAuthenticationNotifications
                {
                    RedirectToIdentityProvider = OpenIdConnectNotification.RedirectToIdentityProvider,
                    MessageReceived = OpenIdConnectNotification.MessageReceived,
                    SecurityTokenReceived = OpenIdConnectNotification.SecurityTokenReceived,
                    SecurityTokenValidated = OpenIdConnectNotification.SecurityTokenValidated,
                    AuthorizationCodeReceived = OpenIdConnectNotification.AuthorizationCodeReceived,
                    AuthenticationFailed = OpenIdConnectNotification.AuthenticationFailed
                },

            });

then in SecurityTokenValidated I did this:

public static async Task<Task>  SecurityTokenValidated(SecurityTokenValidatedNotification<OpenIdConnectMessage, OpenIdConnectAuthenticationOptions> context)
    {
        string aadInstance = ConfigurationManager.AppSettings["ida:AADInstance"];
        string clientId = ConfigurationManager.AppSettings["ida:ClientId"];
        var authContext = new AuthenticationContext(aadInstance + "/oauth2/token", false);
        var authResult =await authContext.AcquireTokenByAuthorizationCodeAsync(context.ProtocolMessage.Code,
            new Uri(aadInstance), new ClientAssertion(clientId, "‎5a95f1c6be7bf3c61f6392ec84ddd044acef61d9"));
        var accessToken = authResult.Result.AccessToken;
        context.AuthenticationTicket.Identity.AddClaim(new Claim("access_token", accessToken));
        return Task.FromResult(0);
    }

I don't get any errors but the application hangs on this line:

 var accessToken = authResult.Result.AccessToken;

The ClientAssertion was constructed using a thumbprint of a SSL certificate that I have installed in IIS, not sure if the certificate is the wrong type...

UPDATE: I updated the SecurityTokenValidated to reflect Saca's comment but I get an "AADSTS50027: Invalid JWT token. Token format not valid" error this way. I also tried this code:

   string aadInstance = ConfigurationManager.AppSettings["ida:AADInstance"];
            string clientId = ConfigurationManager.AppSettings["ida:ClientId"];
            var authContext = new AuthenticationContext(aadInstance, false);
            var cert = new X509Certificate2("...", "...");
            var cacert = new ClientAssertionCertificate(clientId, cert);
            var authResult = await authContext.AcquireTokenByAuthorizationCodeAsync(context.ProtocolMessage.Code, new Uri(aadInstance), cacert);
            var accessToken = authResult.AccessToken;
            context.AuthenticationTicket.Identity.AddClaim(new Claim("access_token", accessToken));
            return Task.FromResult(0);

but this way I get "AADSTS70002: Error validating credentials. AADSTS50012: Client assertion contains an invalid signature."

Answer 1

The application hangs because your blocking on the result of an async taskby accessing the .Result of authResult.

You should change that to:

public static async Task SecurityTokenValidated(SecurityTokenValidatedNotification<OpenIdConnectMessage, OpenIdConnectAuthenticationOptions> context)
{
    string aadInstance = ConfigurationManager.AppSettings["ida:AADInstance"];
    string clientId = ConfigurationManager.AppSettings["ida:ClientId"];
    var authContext = new AuthenticationContext(aadInstance + "/oauth2/token", false);
    var authResult = await authContext.AcquireTokenByAuthorizationCodeAsync(context.ProtocolMessage.Code,
        new Uri(aadInstance), new ClientAssertion(clientId, "‎5a95f1c6be7bf3c61f6392ec84ddd044acef61d9"));
    var accessToken = authResult.AccessToken;
    context.AuthenticationTicket.Identity.AddClaim(new Claim("access_token", accessToken));
}

Answer 2

I managed to get the access token tike this:

 public static async Task<Task> SecurityTokenValidated(SecurityTokenValidatedNotification<OpenIdConnectMessage, OpenIdConnectAuthenticationOptions> context)
    {
        string aadInstance = ConfigurationManager.AppSettings["ida:AADInstance"];
        string clientId = ConfigurationManager.AppSettings["ida:ClientId"];
        string clientSecret = ConfigurationManager.AppSettings["ida:ClientSecret"];
        string source = ConfigurationManager.AppSettings["ExchangeOnlineId"];

        var authContext = new AuthenticationContext(aadInstance, false);
        var credentials = new ClientCredential(clientId, clientSecret);
        var appRedirectUrl = context.Request.Scheme + "://" + context.Request.Host + context.Request.PathBase + "/";
        var authResult = await authContext.AcquireTokenByAuthorizationCodeAsync(context.ProtocolMessage.Code, new Uri(appRedirectUrl), credentials, source);
        var accessToken = authResult.AccessToken;
        var applicationUserIdentity = new ClaimsIdentity(context.OwinContext.Authentication.User.Identity);
        applicationUserIdentity.AddClaim(new Claim("AccessToken", accessToken));
        context.OwinContext.Authentication.User.AddIdentity(applicationUserIdentity);
        return Task.FromResult(0);
    }

Initially I wanted to use a ClientAssertion so I don't have to expose the client Secret but it's too much work managing the certificate...