Microsoft Azure OAuth Client Credentials Token gets "AuthorizationFailed" response - azure

Question

I want create APIM subscriptions through rest api, And was able to do it successfully by following this Microsoft doc, https://learn.microsoft.com/en-us/rest/api/apimanagement/current-ga/subscription.
And for Authentication I am generating a bearer token using ROPC grant type(My UserName & Password). Everything works fine with this flow.
But i dont want to configure my username & password in a application to get a bearer token, instead i followed Client-Credentials grant type(get token by client id & secret), i am able to generate token, but when i use that token to create subscription in APIM, i am getting a exception
The client '0--e' with object id '0--e' does not have authorization to perform action 'Microsoft.ApiManagement/service/subscriptions/write'
Is it possible to add a AAD application inside APIM AccessControl(IAM) to grant permission.
Or is this any other way to do this? or ROPC is the only way?
Can someone please help.

Answer 1

Yes, you can grant permission to AAD application (service principal) in APIM Access Control (IAM) by assigning it API Management Service Contributor role.
I tried to reproduce the same in my environment and got the below results:
I have generated one access token using Client-Credentials grant type like below:
When I used the above token to create APIM subscription with below query, I got the same error:
PUT https://management.azure.com/subscriptions/subid/resourceGroups/rg1/providers/Microsoft.ApiManagement/service/apimService1/subscriptions/testsub?api-version=2021-12-01
{
"properties": {
"ownerId": "/subscriptions/subid/resourceGroups/rgname/providers/Microsoft.ApiManagement/service/servicename/users/xxxxxxxxxxx",
"scope": "/subscriptions/subid/resourceGroups/rgname/providers/Microsoft.ApiManagement/service/servicename/products/xxxxxxxxxxx",
"displayName": "testsub"
}
}
Response:
To resolve the error, you need to grant API Management Service Contributor role for that application like below:
Go to Azure Portal -> APIM Services -> Your APIM -> Access control (IAM) -> Add role assignment
After granting the above role, I generated the access token again and ran the same query as below:
PUT https://management.azure.com/subscriptions/subid/resourceGroups/rg1/providers/Microsoft.ApiManagement/service/apimService1/subscriptions/testsub?api-version=2021-12-01
Response:
When I checked the Portal, APIM subscription got created successfully like below:
Reference:
How to use Role-Based Access Control in Azure API Management | Microsoft Docs