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Amazon ElastiCache
User Guide (API Version 2015-02-02)

Overview of Managing Access Permissions to Your ElastiCache Resources

Every AWS resource is owned by an AWS account, and permissions to create or access a resource are governed by permissions policies. An account administrator can attach permissions policies to IAM identities (that is, users, groups, and roles), and some services (such as AWS Lambda) also support attaching permissions policies to resources.

Note

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

When granting permissions, you decide who is getting the permissions, the resources they get permissions for, and the specific actions that you want to allow on those resources.

Amazon ElastiCache Resources and Operations

In Amazon ElastiCache, the primary resource is a cache cluster. Amazon ElastiCache also supports an additional resource type, a snapshot. However, you can create snapshots only in the context of an existing Redis cache cluster. A snapshot is referred to as subresource.

These resources and subresources have unique Amazon Resource Names (ARNs) associated with them as shown in the following table.

Resource Type ARN Format

Cache Cluster

arn:aws:elasticache:region:account-id:cluster:resource-name

Snapshot

arn:aws:elasticache:region:account-id:snapshot:resource-name

ElastiCache provides a set of operations to work with ElastiCache resources. For a list of available operations, see Amazon ElastiCache Actions.

Understanding Resource Ownership

A resource owner is the AWS account that created the resource. That is, the resource owner is the AWS account of the principal entity (the root account, an IAM user, or an IAM role) that authenticates the request that creates the resource. The following examples illustrate how this works:

  • If you use the root account credentials of your AWS account to create a cache cluster, your AWS account is the owner of the resource (in ElastiCache, the resource is the cache cluster).

  • If you create an IAM user in your AWS account and grant permissions to create a cache cluster to that user, the user can create a cache cluster. However, your AWS account, to which the user belongs, owns the cache cluster resource.

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

Managing Access to Resources

A permissions policy describes who has access to what. The following section explains the available options for creating permissions policies.

Note

This section discusses using IAM in the context of Amazon ElastiCache. It doesn't provide detailed information about the IAM service. For complete IAM documentation, see What Is IAM? in the IAM User Guide. For information about IAM policy syntax and descriptions, see AWS IAM Policy Reference in the IAM User Guide.

Policies attached to an IAM identity are referred to as identity-based policies (IAM polices) and policies attached to a resource are referred to as resource-based policies. Amazon ElastiCache supports only identity-based policies (IAM policies).

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 an ElastiCache resource, such as a cache cluster, parameter group, or security group.

  • Attach a permissions policy to a role (grant cross-account permissions) – You can attach an identity-based permissions policy to an IAM role to grant cross-account permissions. For example, the administrator in Account A can create a role to grant cross-account permissions to another AWS account (for example, Account B) or an AWS service as follows:

    1. Account A administrator creates an IAM role and attaches a permissions policy to the role that grants permissions on resources in Account A.

    2. Account A administrator attaches a trust policy to the role identifying Account B as the principal who can assume the role.

    3. Account B administrator can then delegate permissions to assume the role to any users in Account B. Doing this allows users in Account B to create or access resources in Account A. The principal in the trust policy can also be an AWS service principal if you want to grant an AWS service permissions to assume the role.

    For more information about using IAM to delegate permissions, see Access Management in the IAM User Guide.

The following is an example policy that allows a user to perform the DescribeCacheClusters action for your AWS account. In the current implementation, ElastiCache doesn't support identifying specific resources using the resource ARNs (also referred to as resource-level permissions) for any API actions, so you must specify a wildcard character (*).

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{ "Version": "2012-10-17", "Statement": [{ "Sid": "DescribeCacheClusters", "Effect": "Allow", "Action": [ "elasticache:DescribeCacheClusters"], "Resource": "*" } ] }

For more information about using identity-based policies with ElastiCache, see Using Identity-Based Policies (IAM Policies) for Amazon ElastiCache. For more information about users, groups, roles, and permissions, see Identities (Users, Groups, and Roles in the IAM User Guide.

Resource-Based Policies

Other services, such as Amazon S3, also support resource-based permissions policies. For example, you can attach a policy to an S3 bucket to manage access permissions to that bucket. Amazon ElastiCache doesn't support resource-based policies. 

Specifying Policy Elements: Actions, Effects, Resources, and Principals

For each Amazon ElastiCache resource (see Amazon ElastiCache Resources and Operations), the service defines a set of API operations (see Actions). To grant permissions for these API operations, ElastiCache defines a set of actions that you can specify in a policy. For example, for the ElastiCache snapshot resource, the following actions are defined: CreateSnapshot, DeleteSnapshot, and DescribeSnapshots. Note that, performing an API operation can require permissions for more than one action.

The following are the most basic policy elements:

  • Resource – In a policy, you use an Amazon Resource Name (ARN) to identify the resource to which the policy applies. For ElastiCache resources, you always use the wildcard character (*) in IAM policies. For more information, see Amazon ElastiCache Resources and Operations.

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

  • Effect – You specify the effect when the user requests the specific action—this can be either allow or deny. If you don't explicitly grant access to (allow) a resource, 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). ElastiCache doesn't support resource-based policies.

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

For a table showing all of the Amazon ElastiCache API actions, see ElastiCache 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 the conditions 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 Amazon ElastiCache. 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.