Jwt Bearer and dependency injection

Question

I am trying to configure my Jwt Bearer issuer key but, in production usually, I use Azure Key Vault wrapped by a KeyManager. The KeyManager class is configured in Dependency Injection but, in ConfigureServices method I cannot use that (obviously), but if I cannot use that I cannot retrieve my key.

My solution at the moment is to build a temporary service provider and use it, but I think is not the state of the art (and I need to create two copies of singletons, not the best).

services.AddAuthentication(options =>
{
    options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
    options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
    options.DefaultSignInScheme = JwtBearerDefaults.AuthenticationScheme;
}).AddJwtBearer(JwtBearerDefaults.AuthenticationScheme, options =>
{
    ServiceProvider sp = services.BuildServiceProvider();
    IKeyManager keyManager = sp.GetService<KeyManager>();

    options.TokenValidationParameters = new TokenValidationParameters
    {
        ValidateIssuerSigningKey = true,
        IssuerSigningKey = keyManager.GetSecurityKeyFromName("jwt").Result,

        ValidIssuer = "https://api.example.com",
        ValidateIssuer = true
    };

    options.Audience = "https://api.example.com";
    options.Authority = "https://api.example.com";

    options.SaveToken = true;
});

Answer 1

Use Options pattern and implement IConfigureNamedOptions<JwtBearerOptions>:

public class ConfigureJwtBearerOptions : IConfigureNamedOptions<JwtBearerOptions>
{
    private readonly IKeyManager _keyManager;

    public ConfigureJwtBearerOptions(IKeyManager keyManager)
    {
        _keyManager = keyManager;
    }

    public void Configure(JwtBearerOptions options)
    {
        options.TokenValidationParameters = new TokenValidationParameters
        {
            ValidateIssuerSigningKey = true,
            IssuerSigningKey = _keyManager.GetSecurityKeyFromName("jwt").Result,

            ValidIssuer = "https://api.example.com",
            ValidateIssuer = true
        };

        options.Audience = "https://api.example.com";
        options.Authority = "https://api.example.com";

        options.SaveToken = true;
    }

    public void Configure(string name, JwtBearerOptions options)
    {
        Configure(options);
    }
}

In Startup.cs:

services.AddAuthentication(options =>
{
    options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
    options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
    options.DefaultSignInScheme = JwtBearerDefaults.AuthenticationScheme;
}).AddJwtBearer();

services.ConfigureOptions<ConfigureJwtBearerOptions>();