Scenario 3 – Receiving unauthorized errors (401) while invoking APIs


Referring to my blog on Azure API Management Troubleshooting Series, this is the third scenario of the lab. Please make sure you have followed the lab setup instructions as per this, to recreate the problem.

 

Symptom

The ‘Echo API’ suddenly started throwing diverse types of HTTP 401 – Unauthorized errors while invoking the operations under it. ‘Create resource’ and ‘Retrieve resource’ operations are showing the below error message:

{
  "statusCode": 401,
  "message": "Access denied due to invalid subscription key. Make sure to provide a valid key for an active subscription."
}

whereas rest of the operations are showing

{
  "statusCode": 401,
  "message": "Access denied due to missing subscription key. Make sure to include subscription key when making requests to an API."
}

The expected HTTP response code for all the operations is 200, however the response body will vary as the backend API always echoes whatever you send as a request body in addition to headers.

 

Troubleshooting

  • To get access to the API, developers must first subscribe to a product. When they subscribe, they get a subscription key which is sent as a part of request header that is good for any API in that product. "Ocp-Apim-Subscription-Key" is the request header sent for the subscription key of the product that is associated with this API. The key is filled in automatically.
  • Hence from the error – “Access denied due to invalid subscription key. Make sure to provide a valid key for an active subscription", it’s quite clear that we are sending a wrong value of ‘Ocp-Apim-Subscription-Key’ request header while invoking ‘Create resource’ and ‘Retrieve resource’ operations.
  • You can check your subscription key for a particular product from APIM Developer portal by navigating to Profile page after sign-in as shown below.
  • Click on the Show button to see the subscription keys for respective products you have subscribed to.

 

subscription_key

 

  • If you check the headers being sent from Test tab, you notice that the value of ‘Ocp-Apim-Subscription-Key’ request header is wrong. You might be wondering how come that is possible, because APIM automatically fills this request header with the right subscription key !
  • Let's check the ‘Frontend’ definition of ‘Create resource’ and ‘Retrieve resource’ operations under ‘Design’ tab. Upon careful inspection you would notice that these operations have got a wrong hard coded value of ‘Ocp-Apim-Subscription-Key’ request header added under "Headers" tab. This is the culprit !
  • Please go ahead and remove it, this should resolve the invalid subscription key problem, but still you would get missing subscription key error.

So now... it brings us to the second part of the problem, we are getting the below error:

HTTP/1.1 401 Unauthorized

Content-Length: 152
Content-Type: application/json
Date: Sun, 29 Jul 2018 14:29:50 GMT
Vary: Origin
WWW-Authenticate: AzureApiManagementKey realm="https://pratyay.azure-api.net/echo",name="Ocp-Apim-Subscription-Key",type="header" {
  "statusCode": 401,
  "message": "Access denied due to missing subscription key. Make sure to include subscription key when making requests to an API."
}
  • For that go to the ‘Echo API’ settings and check if it is associated with any of the available products. If not, then you must associate this API with a product so that you get a subscription key.

 

Developers must first subscribe to a product to get access to the API. When they subscribe, they get a subscription key that is good for any API in that product. If you created the APIM instance, you are an administrator already, so you are subscribed to every product by default.

Happy Learning !

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