This gist contains the Resources section of template.yaml from the blog-create-evergreen-golden-amis repository. It shows the IAM policy for the Amazon SNS Topic resource.

blog-create-evergreen-golden-amis-template-resources-amazonsnstopicpolicy.yaml

# IAM role that will be attached to the AWS SNS Topic. This will allow AWS EventBridge events to publish messages to it
  EvergreenAMISNSTopicPolicy:
    Type: AWS::SNS::TopicPolicy
    Properties: 
      PolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Sid: __default_statement_ID
            Effect: Allow
            Principal:
              "AWS": "*"
            Action:
            - sns:GetTopicAttributes
            - sns:SetTopicAttributes
            - sns:AddPermission
            - sns:RemovePermission
            - sns:DeleteTopic
            - sns:Subscribe
            - sns:ListSubscriptionsByTopic
            - sns:Publish
            Resource: !Ref EvergreenAMISNSTopic
            Condition:
              StringEquals:
                "AWS:SourceOwner": !Ref 'AWS::AccountId'
          - Sid: Allow_CloudWatchEvents_To_Publish
            Effect: Allow
            Action:
            - sns:Publish
            Principal:
              "Service": "events.amazonaws.com"
            Resource: !Ref EvergreenAMISNSTopic
      Topics: 
        - !Ref EvergreenAMISNSTopic