Am I allowed to connect to arbitrary RDS DB instances if given the RDS DbiResourceId?

1
votes

I am checking the steps of setting up IAM auth in RDS: https://aws.amazon.com/premiumsupport/knowledge-center/users-connect-rds-iam/ And one of the steps is to attach the IAM role with proper permission: https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/UsingWithRDS.IAMDBAuth.IAMPolicy.html

{
   "Version": "2012-10-17",
   "Statement": [
      {
         "Effect": "Allow",
         "Action": [
             "rds-db:connect"
         ],
         "Resource": [
             "arn:aws:rds-db:us-east-2:1234567890:dbuser:db-ABCDEFGHIJKL01234/db_user"
         ]
      }
   ]
}

The resource follows this format: 

arn:aws:rds-db:region:account-id:dbuser:DbiResourceId/db-user-name

If I understand correctly, as long as I know someone's account-id, DbiResourceId and db-user-name (or maybe db-user-name as I can use wildcard?), then I am able to connect to that DB instance, right?

This sounds insecure. Did I miss anything?

1
amazon-web-servicesamazon-ec2amazon-rdsamazon-iam

1 Answers

3
votes

No this would not be possible. The only want to interact with this resource would be to assume a role in the target account.

You can use an IAM role to allow someone (a trusted principal) in a different account to access resources in your account. Roles are the primary way to grant cross-account access. However, with some AWS services, you can attach a policy directly to a resource (instead of using a role as a proxy). To learn the difference between roles and resource-based policies for cross-account access, see How IAM Roles Differ from Resource-based Policies in the IAM User Guide