Custom Connector OAuth2.0 with grant type client credential

[Syndicate_Admin]

Hi PowerApps Community,

I am currently facing an issue with the custom connector creation.

Due to security requirement, I can only use OAuth2.0.

However, I have only the Token url. There is no Authorization url or Refresh url provided.

When will Microsoft be able to allow grant type selection (e.g. grant type=client credentials)

https://docs.microsoft.com/en-us/connectors/custom-connectors/connection-parameters

Thanks!

[joelzehring]

Thanks for posting this. I'm facing the same issue. Custom connectors seem like a great idea, but there are so many caveats that have prevented me from using this feature in multiple usecases!

[Syndicate_Admin]

Hopefully they will implement the grant type client credentials feature soon @Syndicate_Admin 

[JoshuaKooistra]

Thank you for the link that shows that Microsoft doesn't support this. I've spent many hours now running in circles trying to find any way to get this to work. Whenever anything looked hopeful it swiftly hit a dead end.

Where do we go to add our voice to those wanting to see this implemented?

[jackmarrows]

I was able to get around this limitation with some customer code (4. Code section when creating your connector).

May be slightly different to yours, I was authenticating against AWS Cognito but should be similar.

public class Script : ScriptBase
{
    public override async Task<HttpResponseMessage> ExecuteAsync()
    {
        string url = @"<Your Token URL>/oauth2/token";
        string body = "grant_type=<Your Grant Types URL Encoded>";
        var data = Encoding.Default.GetBytes(body);

        HttpRequestMessage authTokenRequest = new HttpRequestMessage(new HttpMethod("POST"), new Uri(url));
        authTokenRequest.Content = new StringContent(body, new UTF8Encoding(), "application/x-www-form-urlencoded");
        authTokenRequest.Headers.Add("Authorization", "Basic <Your Client Credentials>");
        HttpResponseMessage authTokenResponseresponse = await this.Context.SendAsync(authTokenRequest, this.CancellationToken).ConfigureAwait(continueOnCapturedContext: false);       
        var responseString = await authTokenResponseresponse.Content.ReadAsStringAsync();
        Dictionary<string, string> authTokenData = JsonConvert.DeserializeObject<Dictionary<string, string>>(responseString);
        this.Context.Logger.LogDebug(0, authTokenData["token_type"], null);
        this.Context.Request.Headers.Add("Authorization",Convert.ToString(authTokenData["token_type"]) + " " + Convert.ToString(authTokenData["access_token"]));

        HttpResponseMessage response = await this.Context.SendAsync(this.Context.Request, this.CancellationToken).ConfigureAwait(continueOnCapturedContext: false);       
        return response;
    }
}

[JoshuaKooistra]

I did get around it eventually as well.
The method I used was to leave out the custom connector all together. I used the HTTP connector/action in the flow to perform the authorization POST.

It required storing the username and password in variables then using the compose action with the base64() expression to encode it for the header, and after the Post it needed a Parse JSON action to retrieve the authorization token to use in other HTTP actions.
It's not ideal, but it works for now.

I also ran into an API that uses the password grant type for oauth2.0. You can manually edit the swagger code in the custom connector and get successful test connection for this grant type, but you can't save the connector like that. Using the HTTP action appears to be the only viable way for that connection type as well, but there are security concerns with that.

[systema365]

I'm wondering if anyone has tried setting up a API proxy via Azure API Management to get around this?

This way too you could have a central repository for all API's and authenticate with your Azure AD.  Just a thought - I'm thinking of doing this approach as well, but wanted to see if anyone has already tried it.

[pc_avo]

---

@JoshuaKooistra wrote:

Thank you for the link that shows that Microsoft doesn't support this. I've spent many hours now running in circles trying to find any way to get this to work. Whenever anything looked hopeful it swiftly hit a dead end.

Where do we go to add our voice to those wanting to see this implemented?

---

I just added a vote here https://ideas.powerautomate.com/d365community/idea/c4437fa0-bef7-406a-b42f-309b1bdcc782 ... it's only been open for 3 years so maybe there's still hope 😉

[anadam1124]

@JoshuaKooistra 
Could you share how you did it?
The API I am trying to consume requires authorization in the header and I set it up like this

I verified that the variable Authorization is in the format of "Basic <Client_ID:Client_Secret>(Base64 encoded)", but I still get the error of "error":"invalid_request","error_description":"Request is missing grant type."

[JoshuaKooistra]

It will vary a bit depending on the API requirements I think. In general I initialize three string variables.

The base url as I will generally use this more than once

The accessID/APIkey

The secret.

Then I base64 encode the id an secret using a compose step with base64 and concat expressions. This is the step I think you're missing.

base64(concat(variables('AccessID'),':',variables('Secret')))

Then I do the POST. The options for this will be dependent on what the API requires.

From there you need to run the flow and get the output so you can set up a parse json step and get the access_token, passing that into your GET/POST requests.

[anadam1124]

@JoshuaKooistra 
Thank you very much for your information.
I set it up as you advised, but I still get the same error saying that "Request is missing grant type." It is probably something specific to the API. Something I cannot understand is that with Postman it works without any error, but not with Power Automate flow.

[anadam1124]

@JoshuaKooistra 
It worked !!!

Thank you again.

[JoshuaKooistra]

That's great! It should make it that much easier to set up the next time.