"Getting started with AWS IoT Core" Shadow Python scripts get connection exception

Question

Using "Getting started with AWS IoT Core" to generate Python scripts. The basicPubSub.py sample script works fine. The Shadow examples, basicShadowDetailListener.py, basicShadowUpdater.py and ThingShadowEcho.py all get connection timeout exception when run.

2022-04-03 13:08:49,371 - AWSIoTPythonSDK.core.protocol.mqtt_core - ERROR - Connect timed out
Traceback (most recent call last):
  File "/home/pi/connect_device_package/aws-iot-device-sdk-python/samples/basicShadow/basicShadowDeltaListener.py", line 110, in 
    myAWSIoTMQTTShadowClient.connect()
  File "/usr/local/lib/python3.9/dist-packages/AWSIoTPythonSDK/MQTTLib.py", line 1278, in connect
    return self._AWSIoTMQTTClient.connect(keepAliveIntervalSecond)
  File "/usr/local/lib/python3.9/dist-packages/AWSIoTPythonSDK/MQTTLib.py", line 520, in connect
    return self._mqtt_core.connect(keepAliveIntervalSecond)
  File "/usr/local/lib/python3.9/dist-packages/AWSIoTPythonSDK/core/protocol/mqtt_core.py", line 199, in connect
    raise connectTimeoutException()
AWSIoTPythonSDK.exception.AWSIoTExceptions.connectTimeoutException

The IoT client and Shadow client appear to have the same connection configuration parameters

# AWSIoTMQTTShadowClient configuration
myAWSIoTMQTTShadowClient.configureAutoReconnectBackoffTime(1, 32, 20)
myAWSIoTMQTTShadowClient.configureConnectDisconnectTimeout(10)  # 10 sec
myAWSIoTMQTTShadowClient.configureMQTTOperationTimeout(5)  # 5 sec

# AWSIoTMQTTClient connection configuration
myAWSIoTMQTTClient.configureAutoReconnectBackoffTime(1, 32, 20)
myAWSIoTMQTTClient.configureOfflinePublishQueueing(-1)  # Infinite offline Publish queueing
myAWSIoTMQTTClient.configureDrainingFrequency(2)  # Draining: 2 Hz
myAWSIoTMQTTClient.configureConnectDisconnectTimeout(10)  # 10 sec
myAWSIoTMQTTClient.configureMQTTOperationTimeout(5)  # 5 sec

Answer

Hi,

the IoT policy that is created by the "getting started" guide in the IoT Core console does not have permissions to interact with the shadow.

1. The shadow delta listener uses by default the client id *basicShadowDeltaListener* which is not allowed in the policy.
2. The policy does not include permissions to interact with the device shadow topics

For me the following modified policy works with the *basicShadowDeltaListener* in case you use *repost* as thing name and client id:

```
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "iot:Publish",
        "iot:Receive",
        "iot:RetainPublish"
      ],
      "Resource": [
        "arn:aws:iot:REPLACE_WITH_YOUR_AWS_REGION:REPLACE_WITH_YOUR_AWS_ACCOUNT_NUMBER:topic/sdk/test/java",
        "arn:aws:iot:REPLACE_WITH_YOUR_AWS_REGION:REPLACE_WITH_YOUR_AWS_ACCOUNT_NUMBER:topic/sdk/test/Python",
        "arn:aws:iot:REPLACE_WITH_YOUR_AWS_REGION:REPLACE_WITH_YOUR_AWS_ACCOUNT_NUMBER:topic/topic_1",
        "arn:aws:iot:REPLACE_WITH_YOUR_AWS_REGION:REPLACE_WITH_YOUR_AWS_ACCOUNT_NUMBER:topic/topic_2",
        "arn:aws:iot:REPLACE_WITH_YOUR_AWS_REGION:REPLACE_WITH_YOUR_AWS_ACCOUNT_NUMBER:topic/$aws/things/repost/shadow/*"
      ]
    },
    {
      "Effect": "Allow",
      "Action": "iot:Subscribe",
      "Resource": [
        "arn:aws:iot:REPLACE_WITH_YOUR_AWS_REGION:REPLACE_WITH_YOUR_AWS_ACCOUNT_NUMBER:topicfilter/sdk/test/java",
        "arn:aws:iot:REPLACE_WITH_YOUR_AWS_REGION:REPLACE_WITH_YOUR_AWS_ACCOUNT_NUMBER:topicfilter/sdk/test/Python",
        "arn:aws:iot:REPLACE_WITH_YOUR_AWS_REGION:REPLACE_WITH_YOUR_AWS_ACCOUNT_NUMBER:topicfilter/topic_1",
        "arn:aws:iot:REPLACE_WITH_YOUR_AWS_REGION:REPLACE_WITH_YOUR_AWS_ACCOUNT_NUMBER:topicfilter/topic_2",
        "arn:aws:iot:REPLACE_WITH_YOUR_AWS_REGION:REPLACE_WITH_YOUR_AWS_ACCOUNT_NUMBER:topicfilter/$aws/things/repost/shadow/*"
      ]
    },
    {
      "Effect": "Allow",
      "Action": "iot:Connect",
      "Resource": [
        "arn:aws:iot:REPLACE_WITH_YOUR_AWS_REGION:REPLACE_WITH_YOUR_AWS_ACCOUNT_NUMBER:client/sdk-java",
        "arn:aws:iot:REPLACE_WITH_YOUR_AWS_REGION:REPLACE_WITH_YOUR_AWS_ACCOUNT_NUMBER:client/basicPubSub",
        "arn:aws:iot:REPLACE_WITH_YOUR_AWS_REGION:REPLACE_WITH_YOUR_AWS_ACCOUNT_NUMBER:client/repost",
        "arn:aws:iot:REPLACE_WITH_YOUR_AWS_REGION:REPLACE_WITH_YOUR_AWS_ACCOUNT_NUMBER:client/sdk-nodejs-*"
      ]
    }
  ]
}
```

You can find more information about IoT Policies in the [developer guide](https://docs.aws.amazon.com/iot/latest/developerguide/iot-policies.html).

KR,
Philipp

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