Giving Amazon Managed Service for Prometheus permission to send alert messages to your Amazon SNS topic

You must give Amazon Managed Service for Prometheus permission to send messages to your Amazon SNS topic. The following policy statement will give that permission. It includes a Condition statement to help prevent a security problem known as the confused deputy problem. The Condition statement restricts access to the Amazon SNS topic to allow only operations coming from this specific account and Amazon Managed Service for Prometheus workspace. For more information about the confused deputy problem, see Cross-service confused deputy prevention.

To give Amazon Managed Service for Prometheus permission to send messages to your Amazon SNS topic

1. Open the Amazon SNS console at https://console.aws.amazon.com/sns/v3/home.

2. In the navigation pane, choose Topics.

3. Choose the name of the topic that you are using with Amazon Managed Service for Prometheus.

4. Choose Edit.

5. Choose Access policy and add the following policy statement to the existing policy.

   {
       "Sid": "Allow_Publish_Alarms",
       "Effect": "Allow",
       "Principal": {
           "Service": "aps.amazonaws.com"
       },
       "Action": [
           "sns:Publish",
           "sns:GetTopicAttributes"
       ],
       "Condition": {
           "ArnEquals": {
               "aws:SourceArn": "workspace_ARN"
           },
           "StringEquals": {
               "AWS:SourceAccount": "account_id"
           }
       },
       "Resource": "arn:aws:sns:region:account_id:topic_name"
   }

   [Optional] If your Amazon SNS topic is service side encryption (SSE) enabled, you need to allow Amazon Managed Service for Prometheus to send messages to this encrypted topic by adding the kms:GenerateDataKey* and kms:Decrypt permissions to the AWS KMS key policy of the key used to encrypt the topic.

   For example, you could add the following to the policy:

   {
     "Statement": [{
       "Effect": "Allow",
       "Principal": {
         "Service": "aps.amazonaws.com"
       },
       "Action": [
         "kms:GenerateDataKey*",
         "kms:Decrypt"
       ],
       "Resource": "*"
     }]
   }

   For more information, see AWS KMS Permissions for SNS Topic.

6. Choose Save changes.

Note

By default, Amazon SNS creates the access policy with condition on AWS:SourceOwner. For more information, see SNS Access Policy.

Note

IAM follows the Most-restrictive policy first rule. In your SNS topic, if there is a policy block that is more restrictive than the documented Amazon SNS policy block, the permission for the topic policy is not granted. To evaluate your policy and find out what's been granted, see Policy evaluation logic.

Cross-service confused deputy prevention

The confused deputy problem is a security issue where an entity that doesn't have permission to perform an action can coerce a more-privileged entity to perform the action. In AWS, cross-service impersonation can result in the confused deputy problem. Cross-service impersonation can occur when one service (the calling service) calls another service (the called service). The calling service can be manipulated to use its permissions to act on another customer's resources in a way it should not otherwise have permission to access. To prevent this, AWS provides tools that help you protect your data for all services with service principals that have been given access to resources in your account.

We recommend using the aws:SourceArn and aws:SourceAccount global condition context keys in resource policies to limit the permissions that Amazon Managed Service for Prometheus gives to Amazon SNS to the resource. If you use both global condition context keys, the aws:SourceAccount value and the account in the aws:SourceArn value must use the same account ID when used in the same policy statement.

The value of aws:SourceArn must be the ARN of the Amazon Managed Service for Prometheus workspace.

The most effective way to protect against the confused deputy problem is to use the aws:SourceArn global condition context key with the full ARN of the resource. If you don't know the full ARN of the resource or if you are specifying multiple resources, use the aws:SourceArn global context condition key with wildcards (*) for the unknown portions of the ARN. For example, arn:aws:servicename::123456789012:*.

The policy shown in Giving Amazon Managed Service for Prometheus permission to send alert messages to your Amazon SNS topic shows how you can use the aws:SourceArn and aws:SourceAccount global condition context keys in Amazon Managed Service for Prometheus to prevent the confused deputy problem.