Identity and access management in Amazon VPC Transit Gateways

AWS uses security credentials to identify you and to grant you access to your AWS resources. You can use features of AWS Identity and Access Management (IAM) to allow other users, services, and applications to use your AWS resources fully or in a limited way, without sharing your security credentials.

By default, IAM users don't have permission to create, view, or modify AWS resources. To allow a user to access resources such as a transit gateway, and to perform tasks, you must create an IAM policy that grants the user permission to use the specific resources and API actions they'll need, then attach the policy to the group to which that user belongs. When you attach a policy to a user or group of users, it allows or denies the users permission to perform the specified tasks on the specified resources.

Example policies to manage transit gateways

The following are example IAM policies for working with transit gateways.

Create a transit gateway with required tags

The following example enables users to create transit gateway. The aws:RequestTag condition key requires users to tag the transit gateway with the tag stack=prod. The aws:TagKeys condition key uses the ForAllValues modifier to indicate that only the key stack is allowed in the request (no other tags can be specified). If users don't pass this specific tag when they create the transit gateway, or if they don't specify tags at all, the request fails.

The second statement uses the ec2:CreateAction condition key to allow users to create tags only in the context of CreateTransitGateway.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "AllowCreateTaggedTGWs",
            "Effect": "Allow",
            "Action": "ec2:CreateTransitGateway",
            "Resource": "arn:aws:ec2:region:account-id:transit-gateway/*",
            "Condition": {
                "StringEquals": {
                    "aws:RequestTag/stack": "prod"
                },
                "ForAllValues:StringEquals": {
                    "aws:TagKeys": [
                        "stack"
                    ]
                }
            }
        },
        {
            "Effect": "Allow",
            "Action": [
                "ec2:CreateTags"
            ],
            "Resource": "arn:aws:ec2:region:account-id:transit-gateway/*",
            "Condition": {
                "StringEquals": {
                    "ec2:CreateAction": "CreateTransitGateway"
                }
            }
        }
    ]
}

Working with transit gateway route tables

The following example enables users to create and delete transit gateway route tables for a specific transit gateway only (tgw-11223344556677889). Users can also create and replace routes in any transit gateway route table, but only for attachments that have the tag network=new-york-office.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "ec2:DeleteTransitGatewayRouteTable",
                "ec2:CreateTransitGatewayRouteTable"
            ],
            "Resource": [
                "arn:aws:ec2:region:account-id:transit-gateway/tgw-11223344556677889",
                "arn:aws:ec2:*:*:transit-gateway-route-table/*"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "ec2:CreateTransitGatewayRoute",
                "ec2:ReplaceTransitGatewayRoute"
            ],
            "Resource": "arn:aws:ec2:*:*:transit-gateway-attachment/*",
            "Condition": {
                "StringEquals": {
                    "ec2:ResourceTag/network": "new-york-office"
                }
            }
        },
        {
            "Effect": "Allow",
            "Action": [
                "ec2:CreateTransitGatewayRoute",
                "ec2:ReplaceTransitGatewayRoute"
            ],
            "Resource": "arn:aws:ec2:*:*:transit-gateway-route-table/*"
        }
    ]
}