FHIR Chat · How to authenticate with C# FHIR API to post to simplifier

Stream: implementers

Topic: How to authenticate with C# FHIR API to post to simplifier

Chris Munro (Sep 01 2017 at 10:25):

I'm trying to post a structure definition to a simplifier project, I have the project endpoint and tried the following but get an error 'unauthorised' using the code below

var uri = new Uri(simplifierEndpoint);
var uriWithCred = new UriBuilder(uri) { UserName = "myusername", Password = "mypassword" }.Uri;
var client = new FhirClient(uriWithCred);

FhirXmlParser parser = new FhirXmlParser();
StructureDefinition stdef = parser.Parse<StructureDefinition>(XMLstr); //XMLstr is file with profile
client.Create<StructureDefinition>(stdef);

I'm wondering if @Mirjam Baltus , @Ewout Kramer or @Michel Rutten could help?

Michel Rutten (Sep 01 2017 at 10:52):

Hi @Chris Munro, you should add the credentials to the http headers. In Forge we use a small utility class:

var _basicAuthDecorator = new BasicAuth(endpoint, credentials);
// ...
using (var client = new SimplifierWebClient(Timeout))
{
    // add basic authentication
    _basicAuthDecorator.AddAuthentication(client.Headers);

    client.Encoding = Encoding.UTF8;
    client.DownloadString(...)
}

--- BasicAuth.cs ---

using System;
using System.Net;
using System.Text;

namespace Forge.ViewModels
{
    public sealed class BasicAuth
    {
        private readonly string authenticationType;
        private readonly ICredentials credentials;
        public Uri ServerUrl { get; private set; }

        // Initialize the endpoint URL and the credentials for authentication
        public BasicAuth(Uri serverUrl, ICredentials credentials)
        {
            this.credentials = credentials;
            ServerUrl = serverUrl;
            authenticationType = "Basic ";
        }

        // Initialize the endpoint URL and the credentials for authentication
        public BasicAuth(string serverUrl, ICredentials credentials) : this(new Uri(serverUrl), credentials)
        {
        }

        // Add basic authentication to the request
        public void AddAuthentication(WebHeaderCollection headers)
        {
            if (credentials == null) return; // no credentials given, proceed without authentication
            var networkCredentials = credentials.GetCredential(ServerUrl, authenticationType);
            if (networkCredentials.UserName == null) return; // no credentials given, proceed without authentication
            var encodedCredentials = Convert.ToBase64String(Encoding.UTF8.GetBytes(networkCredentials.UserName + ":" + networkCredentials.Password));
            headers[HttpRequestHeader.Authorization] = authenticationType + encodedCredentials;
        }
    }
}

Chris Munro (Sep 01 2017 at 14:11):

Thanks @Michel Rutten, is the URL https://stu3.simplifier.net/ELabTest2 the correct one to put in? I tried even with postman to post an XML file to this URL with the username/password in the header and I get a 404 not found error

Michel Rutten (Sep 01 2017 at 14:23):

Hi @Chris Munro, the project url appears to be correct.

I forgot to mention that you need to hook/override FhirClient.(On)BeforeRequest and add credential headers, e.g. using

basicAuthDecorator.AddAuthentication(rawRequest.Headers);

I can succesfully publish profiles to my Forge STU3 demo project on Simplifier, so there are no issues on the server.

Michel Rutten (Sep 01 2017 at 14:35):

I just realized that the logic I posted earlier is for retrieving a list of personal projects from Simplifier. This is a custom operation, not a FHIR call.

To actually publish a profile to Simplifier, Forge uses a specialized FhirClient with OnBeforeRequest hook to add http heades for credentials (using BasicAuth utility class above):

public sealed class SimplifierFhirClient : FhirClient
{
    private readonly BasicAuth basicAuthDecorator;

    public SimplifierFhirClient(Uri serverUrl, ICredentials credentials, bool verifyFhirVersion = false) : base(serverUrl, verifyFhirVersion)
    {
        basicAuthDecorator = new BasicAuth(serverUrl, credentials);
    }

    public SimplifierFhirClient(Uri serverUrl, string projectName, ICredentials credentials, bool verifyFhirVersion = false)
        : this(new Uri(serverUrl, projectName), credentials, verifyFhirVersion)
    {
    }

    protected override void BeforeRequest(HttpWebRequest rawRequest, byte[] body)
    {
        base.BeforeRequest(rawRequest, body);
        // ER 22-03-2016 add default accept [Spark: bugfix 9c64d8a3 (8/1/2016)]
        PreferredFormat = ResourceFormat.Json;
        basicAuthDecorator.AddAuthentication(rawRequest.Headers);
    }

    // DEBUGGING
#if DEBUG
    protected override void AfterResponse(HttpWebResponse webResponse, byte[] body)
    {
        base.AfterResponse(webResponse, body);

        // var s = System.Text.Encoding.UTF8.GetString(body);
        // System.IO.File.WriteAllText(@"D:\test.xml", s)
    }
#endif

}

Here's the calling logic:

            var client = new SimplifierFhirClient(url, new NetworkCredential(userName, password));

            T result;
            if (string.IsNullOrEmpty(resource.Id))
            {
                result = client.Create(resource);
            }
            else
            {
                result = client.Update(resource);
            }

Chris Munro (Sep 01 2017 at 15:04):

Fab! Thank you @Michel Rutten that's really helpful. I was getting into a bit of a mess but with the last post I've managed to get it working.

Michel Rutten (Sep 01 2017 at 15:07):

Great, happy to help out!
Sorry for the confusing first post. Friday afternoon... ;p

Last updated: Apr 12 2022 at 19:14 UTC

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FHIR Chat · How to authenticate with C# FHIR API to post to simplifier · implementers