Richard Basson

Posted on May 30, 2022 • Updated on Jul 23, 2023

AWS Cognito — Client credentials flow .NET 6

#aws #dotnet #cognito #api

AWS Cognito User pool creation

Navigate to the AWS Cognito service page

Click on create user pool

Step 1: Configure sign-in experience

Select Email and click next

Step 2: Configure security requirements

Under password policy select cognito defaults
Under Multi-factor authentication select No MFA
Under User account recovery select Enable self-service account recovery and then Email Only
Click next

Step 3: Configure sign-up experience

Keep all selections as default and click next

Step 4: Configure message delivery

Select Send email with Cognito and keep the rest of the configuration as default then click next

Step 5: Integrate your app

Configure the User pool name with your preferred naming convention
Select Confidential client
Configure the App client name
Click next

Step 6: Review and create

Review your configuration
Click Create user pool

User Pools

See your created user pool

Application configuration and resource server creation

Navigate to your created user pool

Navigate to the App Integration tab

Step 1: Create Domain

On the Domain section click on Actions and then click on Create Cogniro domain
Enter a unique domain prefix
Click Create Cognito domain

Step 2: Create Resource server

Click Create resource server
Configure the resource server name and identifier
Create custom scopes for your application to use when authenticating
Click create resource server

Step 3: Configure client application

Select the app client you created
Under Hosted UI click edit
Under Hosted sign-up and sign-in pages select the identity provider cognito user pool
Select Client Credentials OAuth 2.0 Grant type
Select the custom scope you created and want to assign to the application
Click Save changes

Create Weather API

Step 1: Create API

Create a API project if you don’t have one

Step 2: Add NuGet packages

Add the following NuGet packages:

Step 3: Setup auth in Program.cs

Add this block of code to the Program.cs under the builder.

builder.Services.AddCognitoIdentity();

builder.Services.AddAuthentication(options =>
{
    options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
    options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
})
.AddJwtBearer(options =>
{
    options.Authority = builder.Configuration["AWSCognito:Authority"];
    options.TokenValidationParameters = new TokenValidationParameters
    {
        ValidateIssuerSigningKey = true,
                ValidateAudience = false
    };
});

Add the following under app.UseHttpsRedirection(); in Program.cs

app.UseAuthentication();
app.UseAuthorization();

Add the following using's to the Program.cs

using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.IdentityModel.Tokens;

Your Program.cs will end up looking like this when you’re done.

using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.IdentityModel.Tokens;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

builder.Services.AddCognitoIdentity();

builder.Services.AddAuthentication(options =>
{
    options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
    options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
})
.AddJwtBearer(options =>
{
    options.Authority = builder.Configuration["AWSCognito:Authority"];
    options.TokenValidationParameters = new TokenValidationParameters
    {
        ValidateIssuerSigningKey = true,
        ValidateAudience = false
    };
});

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.UseAuthentication();
app.UseAuthorization();

app.MapControllers();

app.Run();

Step 4: Setup configuration file

Add this section to the appsettings.Development.json file

This URL for the authority is made up of the following

https://cognito-idp.{region}.amazonaws.com/{userpoolid}


  "AWSCognito": {
    "Authority": "[https://cognito-idp](https://cognito-idp/).{region}.amazonaws.com/{userpoolid}"
  }

You can find the user pool id in AWS on the Amazon Cognito page under user pools

Step 5: Add authorize attribute to GetWeatherForecast endpoint

In the WeatherForecastController.cs add the Authorize attribute to the GetWeatherForecast endpoint and add Microsoft.AspNetCore.Authorization to the usings.

using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;

namespace AWSCognitoWeatherAPI.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class WeatherForecastController : ControllerBase
    {
        private static readonly string[] Summaries = new[]
        {
        "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
    };

        private readonly ILogger<WeatherForecastController> _logger;

        public WeatherForecastController(ILogger<WeatherForecastController> logger)
        {
            _logger = logger;
        }

        [Authorize]
        [HttpGet(Name = "GetWeatherForecast")]
        public IEnumerable<WeatherForecast> Get()
        {
            return Enumerable.Range(1, 5).Select(index => new WeatherForecast
            {
                Date = DateTime.Now.AddDays(index),
                TemperatureC = Random.Shared.Next(-20, 55),
                Summary = Summaries[Random.Shared.Next(Summaries.Length)]
            })
            .ToArray();
        }
    }
}

Call the Weather Forecast API using Postman

Step 1: Create new collection

Create a new collection for the API
Add new request to the collection for the weather forcast endpoint (https://localhost:7214/WeatherForecast)

Step 2: Setup Collection Auth

Click on the Weather Forcast API collection and navigate to the Authorization tab
From the Type dropdown select OAuth 2.0
In the Configure New Token Section give the token a name
In Grant Type dropdown select Client Credentials
In the app integration section of the user pool in AWS get the domain url
Add the domain to the Access Token URL section in postman and append it with /oauth2/token
Get the client id from the client app in AWS
Get the client secret from the client app in AWS
Get the custom scope form the Hosted UI
Add the clientid, client secret and scope in postman
Click get new access token
Click use token on the pop-up
On the Weather Forecast request under the Authorization tab ensure the Type is set to Inherit auth from parent.