OAuth HTTP Client Factory

The DNVGL.OAuth.Api.HttpClient package is a .NET library which provides a factory for producing authenticated HttpClients for API integration via OAuth.

Developers can use this library to create HttpClient instances which will be pre-authenticated for API requests based on provided configuration.

This package supports two type of credential authentication:

• User credentials - A user may authenticate by providing a username and password via a UI.
• Client credentials - A service or application may provide a client id and secret to silently authenticate.

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Package Install

Ensure you have configured to package NuGet Package Source or find the instructions here.

Package Manager Console

PM> `Install-Package DNVGL.OAuth.Api.HttpClient`

Basic example

1. Configuration

Setup API http client configuration in appsettings.json file:

  {
    "ApiHttpClientOptions": [
      {
        "Name": "userCredentialsClient",
        "Flow": "user-credentials",
        "BaseUri": "<BaseUri>",
        "SubscriptionKey": "<SubscriptionKey>"
      },
      {
        "Name": "clientCredentialsClient",
        "Flow":"client-credentials",
        "BaseUri": "<BaseUri>",
        "SubscriptionKey": "<SubscriptionKey>"
        "OAuthClientOptions": {
          "Authority": "<Authority>",
          "ClientId": "<ClientId>",
          "ClientSecret": "<ClientSecret>",
          "Resource": "<Resource>",
          "Scopes": [ "<Scope>", "offline_access" ],
          "CallbackPath": "<CallbackPath>"
        }
      }
    ]
  }

The package injects an IHttpClientFactory which is able to provide multiple HttpClients for different purposes. The HttpClients may all be configured through a configuration section in which the individual client configurations are listed with a unique Name which is used to request HttpClients with the corresponding configurations.

The configuration shown above lists 2 HttpClients. The first with name "userCredentialsClient" is an example of a configuration which would honour the signed in user's credentials for the API for which it makes requests. The second with name "clientCredentialsClient" provides configuration for a client which would be authenticated via the client credential flow with a client id and secret to make requests in an API. This configuration would allow us to request either type of HttpClient by requesting it from from the HttpClientFactory by providing one of the two names: "userCredentialsClient" or "clientCredentialsClient" in the method call to the HttpClientFactory.

2. Registration

Call the ServiceCollection extension method AddOAuthHttpClientFactory to register an instance of the IHttpClientFactory in to your project in your Startup.cs file.

The below code is retrieving the configuration from the "OAuthHttpClientOptions" section defined in apsettings.json above.

public void ConfigureService(IServiceCollection services)
{
  ...
  services.AddOAuthHttpClientFactory(Congiuration.GetSection("ApiHttpClientOptions").Get<IEnumerable<OAuthHttpClientOptions>>());
  ...
}

If you require a HttpClient applying the user credential flow you should also include the web authentication (AddOidc) and token cache handling (AddDistributedMemoryCache) from the DNVGL.OAuth.Web package. Include the NuGet package in your project and call the required methods as below:

public void ConfigureService(IServiceCollection services)
{
  ...
  services.AddDistributedMemoryCache();
  ...
  var oidcOptions = new OidcOptions
  {
    Authority = "<Authority>",
	  ClientId = "<ClientId>",
	  ClientSecret = "<ClientSecret>",
		Resource = "<Resource>",
	  Scopes = new[] { "<Scope>", "offline_access" },
	  ResponseType = OpenIdConnectResponseType.Code
  };
  services.AddOidc(oidcOptions);
  ...
  services.AddOAuthHttpClientFactory(Congiuration.GetSection("ApiHttpClientOptions").Get<IEnumerable<OAuthHttpClientOptions>>());
  ...
}

If you only require HttpClients applying the client credential flow the DNVGL.OAuth.Web package is not required.

3. Request a client

Resolve IHttpClientFactory to create user-credential or client-credential HttpClient to access web API.

public class TestController
{
  private readonly IHttpClientFactory _httpClientFactory;

  public TestController(IHttpClientFactory httpClientFactory)
  {
    _httpClientFactory = httpClientFactory;
  }

  public User DoSomethingWithSignInUser(string id)
  {
    var client = _httpClientFactory.Create("userCredentialsClient");
    ...
  }

  public Company DoSomethingWithService(string id)
  {
    var client = _httpClientFactory.Create("clientCredentialsClient");
    ...
  }
}