Running AWS CLI commands within a Greengrass component

Question

I'm trying to run various AWS CLI commands within my Greengrass component. Even with a maximally permissive policy for my thing I'm running into various errors:
```
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "*",
      "Resource": "*"
    }
  ]
}
```
For `aws iot describe-endpoint --endpoint-type iot:CredentialProvider` I get the following error from my component:
```
An error occurred (AccessDeniedException) when calling the DescribeEndpoint operation: User: arn:aws:sts::[REDACTED]:assumed-role/GreengrassV2TokenExchangeRole/[REDACTED] is not authorized to perform: iot:DescribeEndpoint because no identity-based policy allows the iot:DescribeEndpoint action.
```
For `aws iot-data get-thing-shadow --thing-name my_thing --shadow-name my_shadow_name shadow.json` I get the error:
```
An error occurred (ForbiddenException) when calling the GetThingShadow operation: None.
```
For `aws s3 cp --recursive --no-progress "${s3_folder_path}" "${download_folder}"`:
```
fatal error: An error occurred (AccessDenied) when calling the ListObjectsV2 operation: Access Denied.
```
However, `aws sts get-caller-identity --query Arn --output text` gives the expected correct `GreengrassV2TokenExchangeRole` role with a certificate containing the policy shown above.

Are these indicative of a particular issue? Is there a way to test if the policy is being applied as I would expect? Are calls with AWS CLI just not supported within Greengrass components?

Accepted Answer

Hi,

This is happening because you did not allow your Greengrass device to make those API calls. I believe the policy you pointed out is the IoT Policy and not IAM. You need to edit the IAM role which the IoT Role Alias points to for your Greengrass device. 
Read more here: https://docs.aws.amazon.com/greengrass/v2/developerguide/device-service-role.html.

Cheers,

Michael

Running AWS CLI commands within a Greengrass component

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