AWS IOT - Credential should be scoped to correct service

Question

I am trying to access a simple AWS IOT REST service but I have not been able to do so successfully yet. Here is what I did.

1. I created an iam user in my aws and downloaded the access key and secret key
2. Logged into AWS IOT with that user and created a "thing"
3. From the thing's property I found the REST URL for the shadow
4. Used Postman with the new "aws signature" feature and provided it with the access key, secret key, region (us-east-1) and service name (iot)

5. Tried to "GET" the endpoint and this is what I got -

   { "message": "Credential should be scoped to correct service. ", "traceId": "be056198-d202-455f-ab85-805defd1260d" }

6. I thought there is something wrong with postman so I tried using aws-sdk-sample example of connecting to S3 and changed it to connect to the IOT URL. Here is my program snippet (Java)

   String awsAccessKey = "fasfasfasdfsdafs";
   String awsSecretKey = "asdfasdfasfasdfasdfasdf/asdfsdafsd/fsdafasdf";
   
   URL  endpointUrl = null;
   String regionName = "us-east-1";
   try {
       endpointUrl = new URL("https://dasfsdfasdf.iot.us-east-1.amazonaws.com/things/SOMETHING/shadow");
   }catch (Exception e){
       e.printStackTrace();
   }
   Map<String, String> headers = new HashMap<String, String>();
   headers.put("x-amz-content-sha256", AWSSignerBase.EMPTY_BODY_SHA256);
   
   AWSSignerForAuthorizationHeader signer = new AWSSignerForAuthorizationHeader(
           endpointUrl, "GET", "iot", regionName);
   String authorization = signer.computeSignature(headers,
           null, // no query parameters
           AWSSignerBase.EMPTY_BODY_SHA256,
           awsAccessKey,
           awsSecretKey);
   
   // place the computed signature into a formatted 'Authorization' header
   // and call S3
   headers.put("Authorization", authorization);
   String response = HttpUtils.invokeHttpRequest(endpointUrl, "GET", headers, null);
   System.out.println("--------- Response content ---------");
   System.out.println(response);
   System.out.println("------------------------------------");
   

This gives me the same error -

--------- Request headers ---------
x-amz-content-sha256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
Authorization: AWS4-HMAC-SHA256 Credential=fasfasfasdfsdafs/20160212/us-east-1/iot/aws4_request, SignedHeaders=host;x-amz-content-sha256;x-amz-date, Signature=3b2194051a8dde8fe617219c78c2a79b77ec92338028e9e917a74e8307f4e914
x-amz-date: 20160212T182525Z
Host: dasfsdfasdf.iot.us-east-1.amazonaws.com
--------- Response content ---------
{"message":"Credential should be scoped to correct service. ","traceId":"cd3e0d96-82fa-4da5-a4e1-b736af6c5e34"}
------------------------------------

Can someone tell me what I am doing wrong please? AWS documentation does not have much information on this error. Please help

Answer 1

Sign your request with iotdata instead if iot
example:

AWSSignerForAuthorizationHeader signer = new AWSSignerForAuthorizationHeader(
    endpointUrl, "GET", "iotdata", regionName);

Answer 2

In your 4th step, don't fill anything for Service Name. Postman will default the value with execute-api.

Hope this works!