Policy Structure

The following topics explain the structure of an IAM policy.

Topics

Policy Syntax

An IAM policy is a JSON document that consists of one or more statements. Each statement is structured as follows:

{
  "Statement":[{
    "Effect":"effect",
    "Action":"action",
    "Resource":"arn",
    "Condition":{
      "condition":{
        "key":"value"
        }
      }
    }
  ]
}

There are various elements that make up a statement:

Effect: The effect can be Allow or Deny. By default, IAM users don't have permission to use resources and API actions, so all requests are denied. An explicit allow overrides the default. An explicit deny overrides any allows.
Action: The action is the specific API action for which you are granting or denying permission. To learn about specifying action, see Actions for Amazon EC2.
Resource: The resource that's affected by the action. Some Amazon EC2 API actions allow you to include specific resources in your policy that can be created or modified by the action. To specify a resource in the statement, you need to use its Amazon Resource Name (ARN). For more information about specifying the arn value, see Amazon Resource Names for Amazon EC2. For more information about which API actions support which ARNs, see Supported Resource-Level Permissions for Amazon EC2 API Actions. If the API action does not support ARNs, use the * wildcard to specify that all resources can be affected by the action.
Condition: Conditions are optional. They can be used to control when your policy will be in effect. For more information about specifying conditions for Amazon EC2, see Condition Keys for Amazon EC2.

For more information about example IAM policy statements for Amazon EC2, see Example Policies for Working With the AWS CLI or an AWS SDK .

Actions for Amazon EC2

In an IAM policy statement, you can specify any API action from any service that supports IAM. For Amazon EC2, use the following prefix with the name of the API action: ec2:. For example: ec2:RunInstances and ec2:CreateImage.

To specify multiple actions in a single statement, separate them with commas as follows:

"Action": ["ec2:action1", "ec2:action2"]

You can also specify multiple actions using wildcards. For example, you can specify all actions whose name begins with the word "Describe" as follows:

"Action": "ec2:Describe*"

To specify all Amazon EC2 API actions, use the * wildcard as follows:

"Action": "ec2:*"

For a list of Amazon EC2 actions, see Actions in the Amazon EC2 API Reference.

Amazon Resource Names for Amazon EC2

Each IAM policy statement applies to the resources that you specify using their ARNs.

Important

Currently, not all API actions support individual ARNs; we'll add support for additional API actions and ARNs for additional Amazon EC2 resources later. For information about which ARNs you can use with which Amazon EC2 API actions, as well as supported condition keys for each ARN, see Supported Resource-Level Permissions for Amazon EC2 API Actions.

An ARN has the following general syntax:

arn:aws:[service]:[region]:[account]:resourceType/resourcePath

service: The service (for example, ec2).
region: The region for the resource (for example, us-east-1).
account: The AWS account ID, with no hyphens (for example, 123456789012).
resourceType: The type of resource (for example, instance).
resourcePath: A path that identifies the resource. You can use the * wildcard in your paths.

For example, you can indicate a specific instance (i-1234567890abcdef0) in your statement using its ARN as follows:

"Resource": "arn:aws:ec2:us-east-1:123456789012:instance/i-1234567890abcdef0"

You can also specify all instances that belong to a specific account by using the * wildcard as follows:

"Resource": "arn:aws:ec2:us-east-1:123456789012:instance/*"

To specify all resources, or if a specific API action does not support ARNs, use the * wildcard in the Resource element as follows:

"Resource": "*"

The following table describes the ARNs for each type of resource used by the Amazon EC2 API actions.

Resource Type	ARN
All Amazon EC2 resources	arn:aws:ec2:*
All Amazon EC2 resources owned by the specified account in the specified region	arn:aws:ec2:region:account:*
Customer gateway	arn:aws:ec2:region:account:customer-gateway/cgw-id Where cgw-id is cgw-xxxxxxxx
DHCP options set	arn:aws:ec2:region:account:dhcp-options/dhcp-options-id Where dhcp-options-id is dopt-xxxxxxxx
Image	arn:aws:ec2:region::image/image-id Where image-id is the ID of the AMI, AKI, or ARI, and account isn't used
Instance	arn:aws:ec2:region:account:instance/instance-id Where instance-id is i-xxxxxxxx or i-xxxxxxxxxxxxxxxxx
Instance profile	arn:aws:iam::account:instance-profile/instance-profile-name Where instance-profile-name is the name of the instance profile, and region isn't used
Internet gateway	arn:aws:ec2:region:account:internet-gateway/igw-id Where igw-id is igw-xxxxxxxx
Key pair	arn:aws:ec2:region:account:key-pair/key-pair-name Where key-pair-name is the key pair name (for example, `gsg-keypair`)
Network ACL	arn:aws:ec2:region:account:network-acl/nacl-id Where nacl-id is acl-xxxxxxxx
Network interface	arn:aws:ec2:region:account:network-interface/eni-id Where eni-id is eni-xxxxxxxx
Placement group	arn:aws:ec2:region:account:placement-group/placement-group-name Where placement-group-name is the placement group name (for example, `my-cluster`)
Route table	arn:aws:ec2:region:account:route-table/route-table-id Where route-table-id is rtb-xxxxxxxx
Security group	arn:aws:ec2:region:account:security-group/security-group-id Where security-group-id is sg-xxxxxxxx
Snapshot	arn:aws:ec2:region::snapshot/snapshot-id Where snapshot-id is snap-xxxxxxxx or snap-xxxxxxxxxxxxxxxxx, and account isn't used
Subnet	arn:aws:ec2:region:account:subnet/subnet-id Where subnet-id is subnet-xxxxxxxx
Volume	arn:aws:ec2:region:account:volume/volume-id Where volume-id is vol-xxxxxxxx or vol-xxxxxxxxxxxxxxxxx
VPC	arn:aws:ec2:region:account:vpc/vpc-id Where vpc-id is vpc-xxxxxxxx
VPC peering connection	arn:aws:ec2:region:account:vpc-peering-connection/vpc-peering-connection-id Where vpc-peering connection-id is pcx-xxxxxxxx

Many Amazon EC2 API actions involve multiple resources. For example, AttachVolume attaches an Amazon EBS volume to an instance, so an IAM user must have permission to use the volume and the instance. To specify multiple resources in a single statement, separate their ARNs with commas, as follows:

"Resource": ["arn1", "arn2"]

For more general information about ARNs, see Amazon Resource Names (ARN) and AWS Service Namespaces in the Amazon Web Services General Reference. For more information about the resources that are created or modified by the Amazon EC2 actions, and the ARNs that you can use in your IAM policy statements, see Granting IAM Users Required Permissions for Amazon EC2 Resources in the Amazon EC2 API Reference.

Condition Keys for Amazon EC2

In a policy statement, you can optionally specify conditions that control when it is in effect. Each condition contains one or more key-value pairs. Condition keys are not case sensitive. We've defined AWS-wide condition keys, plus additional service-specific condition keys.

If you specify multiple conditions, or multiple keys in a single condition, we evaluate them using a logical AND operation. If you specify a single condition with multiple values for one key, we evaluate the condition using a logical OR operation. For permission to be granted, all conditions must be met.

You can also use placeholders when you specify conditions. For example, you can grant an IAM user permission to use resources with a tag that specifies his or her IAM user name. For more information, see Policy Variables in the IAM User Guide.

Amazon EC2 implements the AWS-wide condition keys (see Available Keys), plus the following service-specific condition keys. (We'll add support for additional service-specific condition keys for Amazon EC2 later.)

Important

Many condition keys are specific to a resource, and some API actions use multiple resources. If you write a policy with a condition key, use the Resource element of the statement to specify the resource to which the condition key applies. If not, the policy may prevent users from performing the action at all, because the condition check fails for the resources to which the condition key does not apply. If you do not want to specify a resource, or if you've written the Action element of your policy to include multiple API actions, then you must use the ...IfExists condition type to ensure that the condition key is ignored for resources that do not use it. For more information, see ...IfExists Conditions in the IAM User Guide.

Condition Key	Key/Value Pair	Evaluation Types
ec2:AccepterVpc	"ec2:AccepterVpc":"vpc-arn" Where vpc-arn is the VPC ARN for the peer VPC	ARN, Null
ec2:AvailabilityZone	"ec2:AvailabilityZone":"az-api-name" Where az-api-name is the name of the Availability Zone (for example, `us-west-2a`) To list your Availability Zones, use describe-availability-zones	String, Null
ec2:EbsOptimized	"ec2:EbsOptimized":"optimized-flag" Where optimized-flag is `true` \| `false`	Boolean, Null
ec2:ImageType	"ec2:ImageType":"image-type-api-name" Where image-type-api-name is `ami` \| `aki` \| `ari`	String, Null
ec2:InstanceProfile	"ec2:InstanceProfile":"instance-profile-arn" Where instance-profile-arn is the instance profile ARN	ARN, Null
ec2:InstanceType	"ec2:InstanceType":"instance-type-api-name" Where instance-type-api-name is the name of the instance type.	String, Null
ec2:Owner	"ec2:Owner":"account-id" Where account-id is `amazon` \| `aws-marketplace` \| aws-account-id	String, Null
ec2:ParentSnapshot	"ec2:ParentSnapshot":"snapshot-arn" Where snapshot-arn is the snapshot ARN	ARN, Null
ec2:ParentVolume	"ec2:ParentVolume":"volume-arn" Where volume-arn is the volume ARN	ARN, Null
ec2:PlacementGroup	"ec2:PlacementGroup":"placement-group-arn" Where placement-group-arn is the placement group ARN	ARN, Null
ec2:PlacementGroupStrategy	"ec2:PlacementGroupStrategy":"placement-group-strategy" Where placement-group-strategy is `cluster`	String, Null
ec2:ProductCode	"ec2:ProductCode":"product-code" Where product-code is the product code	String, Null
ec2:Public	"ec2:Public":"public-flag" Where public-flag for an AMI is `true` \| `false`	Boolean, Null
ec2:Region	"ec2:Region":"region-name" Where region-name is the name of the region (for example, `us-west-2`). To list your regions, use describe-regions.	String, Null
ec2:RequesterVpc	"ec2:RequesterVpc":"vpc-arn" Where vpc-arn is the VPC ARN for the requester's VPC	ARN, Null
ec2:ResourceTag/tag-key	"ec2:ResourceTag/tag-key":"tag-value" Where tag-key and tag-value are the tag-key pair	String, Null
ec2:RootDeviceType	"ec2:RootDeviceType":"root-device-type-name" Where root-device-type-name is `ebs` \| `instance-store`	String, Null
ec2:Subnet	"ec2:Subnet":"subnet-arn" Where subnet-arn is the subnet ARN	ARN, Null
ec2:Tenancy	"ec2:Tenancy":"tenancy-attribute" Where tenancy-attribute is `default` \| `dedicated` \| `host`	String, Null
ec2:VolumeIops	"ec2:VolumeIops":"volume-iops" Where volume-iops is the input/output operations per second (IOPS); the range is 100 to 20,000	Numeric, Null
ec2:VolumeSize	"ec2:VolumeSize":"volume-size" Where volume-size is the size of the volume, in GiB	Numeric, Null
ec2:VolumeType	"ec2:VolumeType":"volume-type-name" Where volume-type-name is `gp2` for General Purpose SSD volumes, `io1` for Provisioned IOPS SSD volumes, `st1` for Throughput Optimized HDD volumes, `sc1` for Cold HDD volumes, or `standard` for Magnetic volumes.	String, Null
ec2:Vpc	"ec2:Vpc":"vpc-arn" Where vpc-arn is the VPC ARN	ARN, Null

For information about which condition keys you can use with which Amazon EC2 resources, on an action-by-action basis, see Supported Resource-Level Permissions for Amazon EC2 API Actions. For example policy statements for Amazon EC2, see Example Policies for Working With the AWS CLI or an AWS SDK .

Checking that Users Have the Required Permissions

After you've created an IAM policy, we recommend that you check whether it grants users the permissions to use the particular API actions and resources they need before you put the policy into production.

First, create an IAM user for testing purposes, and then attach the IAM policy that you created to the test user. Then, make a request as the test user.

If the action that you are testing creates or modifies a resource, you should make the request using the DryRun parameter (or run the CLI command with the --auth-dry-run option). In this case, the call completes the authorization check, but does not complete the operation. For example, you can check whether the user can terminate a particular instance without actually terminating it. If the test user has the required permissions, the request returns DryRunOperation; otherwise, it returns UnauthorizedOperation.

If the policy doesn't grant the user the permissions that you expected, or is overly permissive, you can adjust the policy as needed and retest until you get the desired results.

Important

It can take several minutes for policy changes to propagate before they take effect. Therefore, we recommend that you allow five minutes to pass before you test your policy updates.

If an authorization check fails, the request returns an encoded message with diagnostic information. You can decode the message using the DecodeAuthorizationMessage action. For more information, see DecodeAuthorizationMessage in the AWS Security Token Service API Reference, and decode-authorization-message in the AWS Command Line Interface Reference.

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