System-assigned managed identity to request an access token

Question

I have an Azure Function app, calls Azure text translate service restful API endpoint. https://api.cognitive.microsofttranslator.com/translate?api-version=3.0&to=zh Now I want to use the system assigned managed identity to request an access token and use that token to authenticate (bearer token in http header). However, I got an error below. Here is my code to request access token. Does anyone have clue?
var azureServiceTokenProvider = new DefaultAzureCredential(options);

            AccessToken accessToken = await azureServiceTokenProvider.GetTokenAsync(new TokenRequestContext(new[] { "https://api.cognitive.microsofttranslator.com/.default" }));

Failed to translate. The exception is: Azure.Identity.AuthenticationFailedException: ManagedIdentityCredential authentication failed: Service request failed.
Status: 500 (Internal Server Error)

Content:
{"statusCode":500,"message":"An unexpected error occured while fetching the AAD Token.","correlationId":"3588c043-9b25-471f-b7b6-415905a000f0"}

Answer 1

Hello Chunhui You,

It looks like you are trying to use the system assigned identity to get the access token to use on the Azure AI service API call. Like this example:

https://learn.microsoft.com/en-us/azure/ai-services/translator/document-translation/how-to-guides/create-use-managed-identities

First I suggest to verify the endpoint url and the procedure itself, here an example using Service principal that also can help you to setup your call on function app:

https://learn.microsoft.com/en-us/azure/ai-services/authentication?tabs=powershell#sample-request

You can follow this documentation:

• https://learn.microsoft.com/en-us/azure/ai-services/translator/reference/v3-0-reference#authentication
• https://learn.microsoft.com/en-us/azure/ai-services/translator/reference/v3-0-reference#authentication

Please take a look on the information shared and reach out again if you need more assistance.

Luis