How to pass the inbound request body to the backend service in Azure API Gateway

Question

I am trying to generate the Active Directory Token via the Azure API gateway. For that i have created a API operation on my Azure API Gateway which accepts the following body parama.

  {
     "client_id" :"****************",
     "scope":"https://graph.windows.net/.default",
     "client_secret":"****************",
     "grant_type":"client_credentials"  
  }

Whenever I try to test this the body is set for the inboud process but not able to forward the same to the backend service which is https://login.microsoftonline.com/{{ID}}/oauth2/v2.0/token/ so I modified my inboud policy as below but still no luck.

        <set-method>POST</set-method>
    <set-variable name="requestBodyData" value="@(context.Request.Body.As<string>(preserveContent: true))" />
    <set-header name="Content-Type" exists-action="override">
        <value>"application/x-www-form-urlencoded"</value>
    </set-header>
    <rewrite-uri template="/" />
    <set-body>@{
          return "client_id=*******&scope=https://graph.windows.net/.default&client_secret=*******&grant_type=client_credentials";
      }</set-body>
    <!--  Don't expose APIM subscription key to the backend. -->
    <set-header name="Ocp-Apim-Subscription-Key" exists-action="delete" /> 

Any leads would be appriciated.

Answer 1

Set <set-backend-service base-url="https://login.microsoftonline.com/{tenantId}/oauth2/v2.0/token" /> under inbound attribute.

Here is a similar issue you could refer to.

Answer 2

Got it , removed the headed and the method from the inbound policy and updated the inbound policy as :-

    <set-variable name="client_id" value="********" />
    <set-variable name="scope" value="********"" />
    <set-variable name="client_secret" value="********" />
    <set-variable name="grant_type" value="********" />
    <rewrite-uri template="/" />
    <set-body>@{
        return "client_id="+(context.Variables["client_id"])+"&scope="+(context.Variables["scope"])+"&client_secret="+(context.Variables["client_secret"])+"&grant_type="+(context.Variables["grant_type"]);
        }</set-body>
    <!--  Don't expose APIM subscription key to the backend. -->
    <set-header name="Ocp-Apim-Subscription-Key" exists-action="delete" />