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Introduction

In order to use the CoreOne Suite Application Interface (API) or to access another application connected via OpenID by means of an API user, an access token must be resolved. This article describes how such an access token can be resolved.

Preconditions

The following preconditions must be fulfilled in order to be able to redeem an Access Token.

1

Register application

The application from which you want to access the application interface must be registered in the CoreOne Suite and assigned a client_secret.

2

API users

You must have a user set up with the permissions to call the desired API function.

3

Token Endpoint

You need the URL on which the token endpoint is configured. This looks something like the following:

https://localhost:5000/.well-known/openid-configuration

Issue an access token (3rd party lib IdentityModel)

The easiest way to solve a valid AccessToken is by using the nuget-packages IdentityModel.

...

Code Block

language	c#

var disco = await DiscoveryClient.GetAsync(discoUri);
var tokenClient = new TokenClient(disco.TokenEndpoint, "client-name", "client-secret");
var tokenResponse = await tokenClient.RequestResourceOwnerPasswordAsync("username", "password", "scopes");
if (tokenResponse.IsError)
{
	throw new Exception(tokenResponse.Error);
}
return tokenResponse.AccessToken

Issue an Access Token (Manual)

If all preconditions are fulfilled, an access token can be issued via the following steps.

1

Determine the token endpoint

Call the Discovery Endpoint.

Code Block

language	c#

private static async Task<string> GetTokenEndpointUri(string discoUri)
{
	using (var httpClient = new HttpClient())
	{
		//Create a simple GET-Request to the Discovery-Uri
		var discoDoc = await httpClient.GetStringAsync(discoUri);
		//return the property token_endpoint from GET-Response
		var discoElement = (dynamic)JsonConvert.DeserializeObject(discoDoc);
		return (string)discoElement.token_endpoint;
	}
}

2

Compiling the parameters

The following parameters must be included in the token request:

grant_type → password

username → The username of the API user
password → The password of the API user
scope → The desired scopes

3

Query the access token

A simple HTTP post to the previously determined token endpoint can resolve the access token.

Code Block

language	c#

using (var httpClient = new HttpClient())
{
	//Use Client-Identifier / Client-Secret for Basic-Authentication
	httpClient.DefaultRequestHeaders.Authorization = new BasicAuthenticationHeaderValue(tokenRequest.ClientIdentifier, tokenRequest.ClientSecret);
	//Create a POST request to the token-endpoint with data in FormUrlEncoded format
	var tokenResponse = await httpClient.PostAsync(tokenRequest.TokenEndppointUri, new FormUrlEncodedContent(new Dictionary<string, string>
	{
		{"grant_type" , "password"},
		{"username", "someUserName" },
		{"password", "somePassword" },
		{"scope",  "openid c1s_api roles" })}
	}));
	//return the property access_token from POST-Response
	var tokenResponseDoc = await tokenResponse.Content.ReadAsStringAsync();
	var tokenElement = (dynamic)JsonConvert.DeserializeObject(tokenResponseDoc);
	var result = (string)tokenElement.access_token;
}

Complete example (Manual)

The above simplified example can be found here in complete form.

Code Block

language	c#

using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Threading.Tasks;
using Newtonsoft.Json;

namespace ConsoleResourceOwnerFlowRefreshToken
{
    public class Program
    {
        public static void Main(string[] args) => MainAsync().GetAwaiter().GetResult();

        private static async Task MainAsync()
        {
            string tokenEndpoint = null;
            while (tokenEndpoint == null)
            {
                Console.Clear();
                Console.WriteLine("Get TokenEndpoint");
                try
                {
                    tokenEndpoint = await GetTokenEndpointUri("https://localhost:5000/.well-known/openid-configuration");
                }
                catch (Exception e)
                {
                    Console.WriteLine();
                    Console.WriteLine($"Error: {e}");
                    Console.WriteLine();
                    Console.WriteLine("Press q to quit or any other key to retry");
                    if (char.ToLower(Console.ReadKey().KeyChar) == 'q')
                        return;
                    tokenEndpoint = null;
                }
            }
            var tokenRequest = new TokenRequest
            {
                TokenEndppointUri = tokenEndpoint,
                Scopes = new[] { "openid", "c1s_api", "roles" },
                ClientIdentifier = "anyClient",
                ClientSecret = "anySecret",
                Username = "someUserName",
                Password = "someUserPassword"
            };
            do
            {
                Console.Clear();
                try
                {
                    Console.WriteLine($"Token-Endpoint: {tokenEndpoint}");
                    Console.WriteLine();
                    var token = await GetToken(tokenRequest);
                    Console.WriteLine(token ?? "null");
                }
                catch (Exception e)
                {
                    Console.WriteLine($"Error: {e}");
                }
                Console.WriteLine();
                Console.WriteLine("Press q to quit or any other key to renew token");
            } while (char.ToLower(Console.ReadKey().KeyChar) != 'q');
        }

        private static async Task<string> GetToken(TokenRequest tokenRequest)
        {
            using (var httpClient = new HttpClient())
            {
                //Use Client-Identifier / Client-Secret for Basic-Authentication
                httpClient.DefaultRequestHeaders.Authorization = new BasicAuthenticationHeaderValue(tokenRequest.ClientIdentifier, tokenRequest.ClientSecret);
				
                //Create a POST request to the token-endpoint with data in FormUrlEncoded format
                var tokenResponse = await httpClient.PostAsync(tokenRequest.TokenEndppointUri, new FormUrlEncodedContent(new Dictionary<string, string>
                {
                    {"grant_type" , "password"},
                    {"username", tokenRequest.Username },
                    {"password", tokenRequest.Password },
                    {"scope",  string.Join(" ", tokenRequest.Scopes)}
                }));
                //return the property access_token from POST-Response
                var tokenResponseDoc = await tokenResponse.Content.ReadAsStringAsync();
                var tokenElement = (dynamic)JsonConvert.DeserializeObject(tokenResponseDoc);
                return (string)tokenElement.access_token;
            }
        }

        private static async Task<string> GetTokenEndpointUri(string discoUri)
        {
            using (var httpClient = new HttpClient())
            {
                //Create a simple GET-Request to the Discovery-Uri
                var discoDoc = await httpClient.GetStringAsync(discoUri);
                //return the property token_endpoint from GET-Response
                var discoElement = (dynamic)JsonConvert.DeserializeObject(discoDoc);
                return (string)discoElement.token_endpoint;
            }
        }
    }
	
	public class TokenRequest
    {
        public string TokenEndppointUri { get; set; }
        public string ClientIdentifier { get; set; }
        public string ClientSecret { get; set; }
        public string Username { get; set; }
        public string Password { get; set; }
        public string[] Scopes { get; set; }
    }
}

Postman

In Postman, a token can also be solved directly. For this, the type OAuth 2.0 must be selected under Authorization.

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Versions Compared

Old Version 13

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Key

Introduction

Preconditions

Issue an access token (3rd party lib IdentityModel)

Issue an Access Token (Manual)

Complete example (Manual)

Postman

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