How Amazon ECR Public works with IAM

Before you use IAM to manage access to Amazon ECR, you should understand what IAM features are available to use with Amazon ECR. To get a high-level view of how Amazon ECR and other AWS services work with IAM, see AWS services that work with IAM in the IAM User Guide.

Amazon ECR identity-based policies

With IAM identity-based policies, you can specify allowed or denied actions and resources as well as the conditions under which actions are allowed or denied. Amazon ECR supports specific actions, resources, and condition keys when managing a public registry and the resources in a public registry. The image pull permissions can't be changed because Amazon ECR Public repositories are public accessible. To learn about all of the elements that you use in a JSON policy, see IAM JSON policy elements reference in the IAM User Guide.

Actions

Administrators can use AWS JSON policies to specify who has access to what. That is, which principal can perform actions on what resources, and under what conditions.

The Action element of a JSON policy describes the actions that you can use to allow or deny access in a policy. Policy actions usually have the same name as the associated AWS API operation. There are some exceptions, such as permission-only actions that don't have a matching API operation. There are also some operations that require multiple actions in a policy. These additional actions are called dependent actions.

Include actions in a policy to grant permissions to perform the associated operation.

Policy actions in Amazon ECR Public use the following prefix before the action: ecr-public:. For example, to grant someone permission to create a public Amazon ECR repository with the Amazon ECR Public CreateRepository API operation, you include the ecr-public:CreateRepository action in their policy. Policy statements must include either an Action or NotAction element. Amazon ECR defines its own set of actions that describe tasks that you can perform with this service.

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

"Action": [
      "ecr-public:action1",
      "ecr-public:action2"

You can specify multiple actions using wildcards (*). For example, to specify all actions that begin with the word Describe, include the following action:

"Action": "ecr-public:Describe*"

To see a list of Amazon ECR actions, see Actions, Resources, and Condition Keys for Amazon ECR Public in the IAM User Guide.

Resources

Administrators can use AWS JSON policies to specify who has access to what. That is, which principal can perform actions on what resources, and under what conditions.

The Resource JSON policy element specifies the object or objects to which the action applies. Statements must include either a Resource or a NotResource element. As a best practice, specify a resource using its Amazon Resource Name (ARN). You can do this for actions that support a specific resource type, known as resource-level permissions.

For actions that don't support resource-level permissions, such as listing operations, use a wildcard (*) to indicate that the statement applies to all resources.

"Resource": "*"

An Amazon ECR public repository resource has the following ARN. You don't use a Region name in the ARN.

arn:${Partition}:ecr-public::${Account}:repository/${Repository-name}

For more information about the format of ARNs, see Amazon Resource Names (ARNs) and AWS Service Namespaces.

For example, to specify the my-repo public repository in your statement, use the following ARN:

"Resource": "arn:aws:ecr-public::123456789012:repository/my-repo"

To specify all public repositories that belong to a specific account, use the wildcard (*):

"Resource": "arn:aws:ecr-public::123456789012:repository/*"

To specify multiple resources in a single statement, separate the ARNs with commas.

"Resource": [
      "resource1",
      "resource2"

To see a list of Amazon ECR Public resource types and their ARNs, see Resources defined by Amazon ECR Public in the IAM User Guide. To learn with which actions you can specify the ARN of each resource, see Actions defined by Amazon ECR.

Condition Keys

Administrators can use AWS JSON policies to specify who has access to what. That is, which principal can perform actions on what resources, and under what conditions.

The Condition element (or Condition block) lets you specify conditions in which a statement is in effect. The Condition element is optional. You can create conditional expressions that use condition operators, such as equals or less than, to match the condition in the policy with values in the request.

If you specify multiple Condition elements in a statement, or multiple keys in a single Condition element, AWS evaluates them using a logical AND operation. If you specify multiple values for a single condition key, AWS evaluates the condition using a logical OR operation. All of the conditions must be met before the statement's permissions are granted.

You can also use placeholder variables when you specify conditions. For example, you can grant an IAM user permission to access a resource only if it is tagged with their IAM user name. For more information, see IAM policy elements: variables and tags in the IAM User Guide.

AWS supports global condition keys and service-specific condition keys. To see all AWS global condition keys, see AWS global condition context keys in the IAM User Guide.

Amazon ECR supports using some global condition keys. To see all AWS global condition keys, see AWS global condition context keys in the IAM User Guide.

To see a list of Amazon ECR Public condition keys, see Condition keys defined by Amazon ECR Public in the IAM User Guide. To learn with which actions and resources you can use a condition key, see Actions defined by Amazon ECR.

Examples

To view examples of Amazon ECR identity-based policies, see Amazon ECR public identity-based policy examples.

Amazon ECR resource-based policies

Resource-based policies are JSON policy documents that specify what actions a specified principal can perform on an Amazon ECR Public resource and under what conditions. Amazon ECR supports resource-based permissions policies for Amazon ECR public repositories. Resource-based policies let you grant usage permission to other accounts on a per-resource basis. You can also use a resource-based policy to allow an AWS service to access your Amazon ECR public repositories.

To enable cross-account access, you can specify an entire account or IAM entities in another account as the principal in a resource-based policy. Adding a cross-account principal to a resource-based policy is only half of establishing the trust relationship. When the principal and the resource are in different AWS accounts, you must also grant the principal entity permission to access the resource. Grant permission by attaching an identity-based policy to the entity. However, if a resource-based policy grants access to a principal in the same account, no additional identity-based policy is required. For more information, see How IAM roles differ from resource-based policies in the IAM User Guide.

The Amazon ECR Public service supports only one type of resource-based policy called a repository policy, which is attached to a repository. This policy defines which principal entities (accounts, users, roles, and federated users) can perform actions on the repository.

To learn how to attach a resource-based policy to a repository, see Public repository policies in Amazon ECR Public.

Examples

To view examples of Amazon ECR resource-based policies, see Public repository policy examples in Amazon ECR Public.

Amazon ECR IAM roles

An IAM role is an entity within your AWS account that has specific permissions.

Using temporary credentials with Amazon ECR

You can use temporary credentials to sign in with federation, assume an IAM role, or to assume a cross-account role. You obtain temporary security credentials by calling AWS STS API operations such as AssumeRole or GetFederationToken.

Amazon ECR Public supports using temporary credentials.

Service-linked roles

Service-linked roles allow AWS services to access resources in other services to complete an action on your behalf. Service-linked roles appear in your IAM account and are owned by the service. An IAM administrator can view but not edit the permissions for service-linked roles.

Amazon ECR Public does not support service-linked roles.