OpenID Connect Client Library for native Applications

OidcClient is a portable library (Desktop .NET, UWP, Xamarin iOS & Android) that provides a couple of helpers typically needed by native applications to implement user authentication and access token requests using OpenID Connect and OAuth 2.0:

• Creating authorization requests
• Parsing authorization responses
• WebView/Browser interaction
• Validating identity tokens
• Requesting access and refresh tokens
• Refresh token management

We follow the recommendations from OAuth 2.0 for Native Apps and implement OpenID Connect Hybrid Flow and PKCE for maximum security.

Setup

The OidcClientOptions class lets you set up the parameters for communicating with the OpenID Connect provider. Here you specify the base address of the provider, client ID, client secret, scopes and redirect URI.

var authority = "https://demo.identityserver.io";

var options = new OidcClientOptions (
    authority: authority,
    clientId: "native",
    clientSecret: "secret",
    scope: "openid profile api offline_access",
    redirectUri: "com.mycompany.myapp://callback");

Optionally you can also pass in an implementation of a web view. The samples repository has sample web views for WinForms (.NET Desktop) and the Universal Windows Platform. Feel free to contribute to add more platforms.

Requesting tokens

The OidcClient class supports two modes to interact with the token provider

• generation of requests and parsing of response message. Interaction with the web view is done manually
• the web view interaction is encapsulated

Manual

To generate the authorize start URL and the necessary artifacts like nonce, code verifier and challenge, call PrepareLoginAsync. This will return a state object that will be used later to validate the response.

var client = new OidcClient(options);
var state = await _client.PrepareLoginAsync();

You can now launch your favourite browser using the StartUrl property returned from the state object.

var safari = new SafariServices.SFSafariViewController (new NSUrl (_state.StartUrl));

In this mode, it is also your responsibility to capture the full return URL after the authentication is done. You can pass the URL back to OidcClient to do the parsing and validation. If successful, the LoginResult result returned will contain the claims of the user, access token and refresh token:

var result = await client.ValidateResponseAsync (url, state);

var sb = new StringBuilder (128);
foreach (var claim in result.Claims) 
{
    sb.AppendFormat ("{0}: {1}\n", claim.Type, claim.Value);
}

sb.AppendFormat ("\n{0}: {1}\n", "refresh token", result.RefreshToken);
sb.AppendFormat ("\n{0}: {1}\n", "access token", result.AccessToken);

TokenTextView.Text = sb.ToString ();

Encapsulated Web View

You can also wrap the web view interaction in an IWebView. If such an implementation exists, you can simply call LoginAsync and get back the LoginResult directly:

var result = await oidcClient.LoginAsync();

Calling APIs

You now have everything you need to call APIs. You can use the access token to authenticate against the API, and the refresh token (if requested) to refresh an expired access token.

If you want to automate token handling, you can also use our RefreshTokenHandler which will take care of setting tokens on outgoing requests as well as refreshing tokens if the API returns a 401.

The handler is available as a standalone class, as well a directly from the LoginResult:

var apiClient = new HttpClient(result.Handler);
apiClient.BaseAddress = new Uri("https://demo.identityserver.io/api/");

var result = await apiClient.GetAsync("resource");

OSS FTW!

OidcClient is based on the following OSS projects:

• IdentityModel
• PCLCrypto
• Jose-Pcl
• Json.Net