`credentialScope` is not applied

[angelsl]

Environment

• Elixir & Erlang versions (elixir --version): 1.10.3
• ExAws version: 2.1.3
• HTTP client version: Hackney 1.16.0

Current behavior

credentialScope from priv/endpoints.exs does not seem to be applied:

iex(11)> ExAws.Operation.JSON.new(:iot, %{http_method: :get, path: "/things/receiver-test-test"}) |> ExAws.request()
{:error,
 {:http_error, 403,
  %{
    body: "{\"message\":\"Credential should be scoped to correct service: 'execute-api'. \"}",
    headers: [
      {"Date", "Tue, 07 Jul 2020 18:24:21 GMT"},
      {"Content-Type", "application/json"},
      {"Content-Length", "77"},
      {"Connection", "keep-alive"},
      {"x-amzn-RequestId", "..."},
      {"x-amzn-ErrorType", "InvalidSignatureException"},
      {"x-amz-apigw-id", "..."}
    ],
    status_code: 403
  }}}

Expected behavior

The request should succeed.

[benwilson512]

Hi @angelsl please provide more information, how have you configured ExAws's credentials?

[angelsl]

As part of configuration:

config :ex_aws,
  access_key_id: "...",
  secret_access_key: "...",
  region: "ap-southeast-1"

Specifying service_override works as a workaround. (Also, I had to use RestQuery instead of JSON.)

ExAws.request(%ExAws.Operation.RestQuery{http_method: :get, path: "/things/receiver-test-test", service: :iot }, service_override: :"execute-api")
{:ok,
 %{
   body: "...",
   headers: [
     {"Date", "Tue, 07 Jul 2020 18:43:16 GMT"},
     {"Content-Type", "application/json"},
     {"Content-Length", "285"},
     {"Connection", "keep-alive"},
     {"x-amzn-RequestId", "..."},
     {"Access-Control-Allow-Origin", "*"},
     {"x-amz-apigw-id", "..."},
     {"X-Amzn-Trace-Id", "..."}
   ],
   status_code: 200
 }}

[benwilson512]

I still don't understand this error. please provide more information about what should be happening, what is credentialScope?

[angelsl]

I'm referring to this.

When making an AWS request, you use your access key and secret key to derive a HMAC key to sign the request. The credential scope is used in the derivation.

For most services, the credential scope is identical to the service name. For some services, it is not. iot is one such service.

[angelsl]

Basically, what should be happening is that ExAws uses the correct credential scope based on the service name specified. The data is even there in priv/endpoints.exs—it just doesn't seem to be used at the moment.

[benwilson512]

Got it, thanks! I'll look into it.

[devstopfix]

I am willing to look at this, would be useful in removing the override needed in #1023 ?

[bernardd]

@devstopfix I'm not actually sure if it would be useful in removing it - my reading of this bug is that the overrides aren't actually working in the first place. But I haven't really looked into this issue at all since I took over from Ben, so do please feel free to do any digging you like and let us know what you find.