Overview of managing access permissions to your CloudFront resources - Amazon CloudFront

Overview of managing access permissions to your CloudFront resources

Every AWS resource is owned by an AWS account, and permissions to create or access a resource are governed by permissions policies.

Note

An account administrator (or administrator user) is a user that has administrator privileges. For more information about administrators, see IAM Best Practices in the IAM User Guide.

When you grant permissions, you decide who gets the permissions, the resources they get permissions for, and the actions that they get permission to perform.

ARNs for CloudFront resources

All CloudFront resources—including distributions, invalidations, origin access identities, and functions—use the same format for Amazon Resource Names (ARNs):

arn:aws:cloudfront::AWS_account_ID:resource_type/resource_ID

CloudFront provides API actions to work with each of these types of resources. For more information, see the Amazon CloudFront API Reference. For a list of actions and the ARN that you specify to grant or deny permission to use each action, see CloudFront API permissions: actions, resources, and conditions reference.

Understanding resource ownership

An AWS account owns the resources that are created in the account, regardless of who created the resources. Specifically, the resource owner is the AWS account of the principal entity (that is, the root account, an IAM user, or an IAM role) that authenticates the resource creation request.

The following examples illustrate how this works:

  • If you use the root account credentials of your AWS account to create a distribution, your AWS account is the owner of the distribution.

  • If you create an IAM user in your AWS account and grant permissions to create a distribution to that user, the user can create a distribution. The AWS account that created the user owns the distribution.

  • If you create an IAM role in your AWS account with permissions to create a distribution, anyone who can assume the role can create a distribution. Your AWS account, to which the role belongs, owns the distribution.

Managing access to resources

A permissions policy specifies who has access to what. This section explains the options for creating permissions policies for CloudFront. For general information about IAM policy syntax and descriptions, see the AWS IAM Policy Reference in the IAM User Guide.

Policies attached to an IAM identity are referred to as identity-based policies (IAM policies), and policies attached to a resource are referred to as resource-based policies. CloudFront does not support resource-based policies, but it does support resource-level policies. For more information about the types of permissions policies that CloudFront supports, see Managing access to resources.

Identity-based policies (IAM policies)

You can attach policies to IAM identities. For example, you can do the following:

  • Attach a permissions policy to a user or a group in your account – An account administrator can use a permissions policy that is associated with a particular user to grant permissions for that user to create a distribution.

  • Attach a permissions policy to a role (grant cross-account permissions) – You can grant permissions to perform CloudFront actions to a user that was created in another AWS account. To do so, you attach a permissions policy to an IAM role, and then you allow the user in the other account to assume the role. The following example explains how this works for two AWS accounts, account A and account B:

    1. Account A administrator creates an IAM role and attaches to the role a permissions policy that grants permissions to create or access resources that are owned by account A.

    2. Account A administrator attaches a trust policy to the role. The trust policy identifies account B as the principal that can assume the role.

    3. Account B administrator can then delegate permissions to assume the role to users or groups in account B. This allows users in account B to create or access resources in account A.

    For more information about how to delegate permissions to users in another AWS account, see Access Management in the IAM User Guide.

The following example policy allows a user to perform the CreateDistribution action to programmatically create a distribution for your AWS account:

{ "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Action": [ "cloudfront:CreateDistribution" ], "Resource":"*" } ] }

For information about the permissions required to perform operations by using the CloudFront console, see Permissions required to use the CloudFront console. For more information about attaching policies to identities for CloudFront, see Using identity-based policies (IAM policies) for CloudFront. For more information about users, groups, roles, and permissions, see Identities (Users, Groups, and Roles) in the IAM User Guide.

Resource-level policies

In some scenarios, you might want to grant a specific level of access to a resource that you specify; for example, access to only specific actions on that resource. One way that some AWS services implement this is to allow you to directly attach a policy on the resource. For example, that’s how Amazon S3 and Elasticsearch implement resource access control. CloudFront allows the same flexibility but uses a different method. Instead of attaching a policy to a resource, you specify the resource in a policy.

For example, the following policy shows how you might allow update, delete, and create invalidations access to a distribution that you specify by the distribution’s ARN. This policy grants the permissions necessary to complete these actions from the AWS API or AWS CLI only. (To use this policy, replace the italicized text in the example policy with your own resource information.)

{ "Version": "2012-10-17", "Statement": [ { "Sid": "VisualEditor0", "Effect": "Allow", "Action": [ "cloudfront:CreateDistribution", "cloudfront:Get*", "cloudfront:List*" ], "Resource": "*" }, { "Sid": "VisualEditor1", "Effect": "Allow", "Action": [ "cloudfront:UpdateDistribution", "cloudfront:DeleteDistribution", "cloudfront:CreateInvalidation", ], "Resource": "arn:aws:cloudfront::123456789012:distribution/EDFDVBD6EXAMPLE" } ] }

Tag-based policies

When you design IAM policies, you might set granular permissions by granting access to specific resources. As the number of resources that you manage grows, this task becomes more difficult. Tagging resources and using tags in policy statement conditions can make this task easier. You grant access in bulk to any resource with a certain tag. Then you repeatedly apply this tag to relevant resources, during creation or later.

Note

Using tags in conditions is one way to control access to resources and requests. For information about tagging in CloudFront, see Tagging Amazon CloudFront Distributions.

Tags can be attached to the resource or passed in the request to services that support tagging. In CloudFront, resources can have tags, and some actions can include tags. When you create an IAM policy, you can use tag condition keys to control:

  • Which users can perform actions on a distribution, based on tags that it already has.

  • What tags can be passed in an action's request.

  • Whether specific tag keys can be used in a request.

For the complete syntax and semantics of tag condition keys, see Control Access Using IAM Tags in the IAM User Guide.

For example, the AWSCloudFrontFullAccess managed user policy gives users unrestricted permission to perform any CloudFront action on any resource. The following policy restricts this power and denies unauthorized users permission to create CloudFront production distributions.

To implement the restriction using tags, it denies the CreateDistribution action if the request specifies a tag named stage with one of the values gamma or prod. In addition, the policy prevents these unauthorized users from tampering with the stage of production environments by not allowing tag modification actions to include these same tag values or to completely remove the stage tag. A customer’s administrator must attach this IAM policy to unauthorized IAM users, in addition to the managed user policy.

{ "Version": "2012-10-17", "Statement": [ { "Effect": "Deny", "Action": [ "cloudfront:CreateDistribution", "cloudfront:TagResource" ], "Resource": "*", "Condition": { "StringEquals": { "aws:RequestTag/stage": [ "gamma", "prod" ] } } }, { "Effect": "Deny", "Action": [ "cloudfront:TagResource", "cloudfront:UntagResource" ], "Resource": "*", "Condition": { "ForAnyValue:StringEquals": { "aws:TagKeys": [ "stage" ] }, "StringEquals": { "aws:ResourceTag/stage": [ "gamma", "prod" ] } } } ] }

Specifying policy elements: resources, actions, effects, and principals

CloudFront includes API actions (see Amazon CloudFront API Reference) that you can use on each CloudFront resource (see ARNs for CloudFront resources). You can grant a user or a federated user permission to perform any or all of these actions.

The following are the basic policy elements:

  • Resource – You use an Amazon Resource Name (ARN) to identify the resource that the policy applies to. For more information, see ARNs for CloudFront resources.

  • Action – You use action keywords to identify resource operations that you want to allow or deny. For example, depending on the specified Effect, the cloudfront:CreateDistribution permission allows or denies the user permissions to perform the CloudFront CreateDistribution action.

  • Effect – You specify the effect, either allow or deny, when a user tries to perform the action on the specified resource. If you don't explicitly grant access to an action, access is implicitly denied. You can also explicitly deny access to a resource, which you might do to make sure that a user cannot access it, even if a different policy grants access.

  • Principal – In identity-based policies (IAM policies), the user that the policy is attached to is the implicit principal. For resource-based policies, you specify the user, account, service, or other entity that you want to receive permissions (applies to resource-based policies only).

    CloudFront does not support resource-based policies, but it does support resource-level policies. For more information about the types of permissions policies that CloudFront supports, see Managing access to resources.

For more information about IAM policy syntax and descriptions, see the AWS IAM Policy Reference in the IAM User Guide.

For a table showing all of the CloudFront API operations and the resources that they apply to, see CloudFront API permissions: actions, resources, and conditions reference.

Specifying conditions in a policy

When you grant permissions, you can use the IAM policy language to specify when a policy should take effect. For example, you might want a policy to be applied only after a specific date. For more information about specifying conditions in a policy language, see Condition in the IAM User Guide.

To express conditions, you use predefined condition keys. There are no condition keys specific to CloudFront. However, there are AWS-wide condition keys that you can use as appropriate. For a complete list of AWS-wide keys, see Available Keys for Conditions in the IAM User Guide.