client-credentials.md

title	Customizing Client Credentials Token Management
description	Learn how to customize client credentials token management including client options, backchannel communication, and token caching configurations.
sidebar	label order Client Credentials 1
redirect_from	/foss/accesstokenmanagement/advanced/client_credentials/

The most common way to use the access token management for machine to machine communication is described here - however you may want to customize certain aspects of it - here's what you can do.

Client options

You can add token client definitions to your host while configuring the ASP.NET Core service provider, e.g.:

services.AddClientCredentialsTokenManagement()
  .AddClient("invoices", client =>
  {
        client.TokenEndpoint = "https://sts.company.com/connect/token";

    	client.ClientId = "4a632e2e-0466-4e5a-a094-0455c6105f57";
    	client.ClientSecret = "e8ae294a-d5f3-4907-88fa-c83b3546b70c";
    	client.ClientCredentialStyle = ClientCredentialStyle.AuthorizationHeader;
                        
    	client.Scope = "list";
    	client.Resource = "urn:invoices";
  })

You can set the following options:

• TokenEndpoint - URL of the OAuth token endpoint where this token client requests tokens from
• ClientId - client ID
• ClientSecret - client secret (if a shared secret is used)
• ClientCredentialStyle - Specifies how the client ID / secret is sent to the token endpoint. Options are using the authorization header, or POST body values (defaults to header)
• Scope - the requested scope of access (if any)
• Resource - the resource indicator (if any)

Internally the standard .NET options system is used to register the configuration. This means you can also register clients like this:

services.Configure<ClientCredentialsClient>("invoices", client =>
{
    client.TokenEndpoint = "https://sts.company.com/connect/token";

    client.ClientId = "4a632e2e-0466-4e5a-a094-0455c6105f57";
   	client.ClientSecret = "e8ae294a-d5f3-4907-88fa-c83b3546b70c";

    client.Scope = "list";
    client.Resource = "urn:invoices";
});

Or use the IConfigureNamedOptions if you need access to the ASP.NET Core service provider during registration, e.g.:

public class ClientCredentialsClientConfigureOptions : IConfigureNamedOptions<ClientCredentialsClient>
{
    private readonly DiscoveryCache _cache;

    public ClientCredentialsClientConfigureOptions(DiscoveryCache cache)
    {
        _cache = cache;
    }
    
    public void Configure(string name, ClientCredentialsClient options)
    {
        if (name == "invoices")
        {
            var disco = _cache.GetAsync().GetAwaiter().GetResult();

            options.TokenEndpoint = disco.TokenEndpoint;
            
            client.ClientId = "4a632e2e-0466-4e5a-a094-0455c6105f57";
   	    client.ClientSecret = "e8ae294a-d5f3-4907-88fa-c83b3546b70c";

    	    client.Scope = "list";
    	    client.Resource = "urn:invoices";
        }
    }
}

You will also need to register the config options, for example:

services.AddClientCredentialsTokenManagement();

services.AddSingleton(new DiscoveryCache("https://sts.company.com"));
services.AddSingleton<IConfigureOptions<ClientCredentialsClient>, 	
	ClientCredentialsClientConfigureOptions>();

Backchannel communication

By default, all backchannel communication will be done using a named client from the HTTP client factory. The name is Duende.AccessTokenManagement.BackChannelHttpClient which is also a constant called ClientCredentialsTokenManagementDefaults.BackChannelHttpClientName.

You can register your own HTTP client with the factory using the above name and thus provide your own custom HTTP client.

The client registration object has two additional properties to customize the HTTP client:

• HttpClientName - if set, this HTTP client name from the factory will be used instead of the default one
• HttpClient - allows setting an instance of HttpClient to use. Will take precedence over a client name

Token caching

By default, tokens will be cached using the IDistributedCache abstraction in ASP.NET Core. You can either use the in-memory cache version, or a real distributed cache like Redis.

For development purposes, you can use the MemoryDistributedCache:

services.AddDistributedMemoryCache();

Note that MemoryDistributedCache will be cleared whenever the process is restarted. It won't be shared between multiple instances of your application in a load-balanced environment. As a result, a new token will have to be obtained when you restart your application, and each instance will obtain a different token.

For production deployments, we recommend using a distributed cache.

The built-in cache in Duende.AccessTokenManagment uses two settings from the options, which apply with any IDistributedCache:

services.AddClientCredentialsTokenManagement(options =>
    {
        options.CacheLifetimeBuffer = 60;
        options.CacheKeyPrefix = "Duende.AccessTokenManagement.Cache::";
    });

CacheLifetimeBuffer is a value in seconds that will be subtracted from the token lifetime, e.g. if a token is valid for one hour, it will be cached for 59 minutes only. The cache key prefix is used to construct the unique key for the cache item based on client name, requested scopes and resource.

Finally, you can also replace the caching implementation altogether by registering your own IClientCredentialsTokenCache.