AWS::KMS::ReplicaKey - AWS CloudFormation

AWS::KMS::ReplicaKey

The AWS::KMS::ReplicaKey resource specifies a multi-Region replica key that is based on a multi-Region primary key.

Multi-Region keys are an AWS KMS feature that lets you create multiple interoperable KMS keys in different AWS Regions. Because these KMS keys have the same key ID, key material, and other metadata, you can use them to encrypt data in one AWS Region and decrypt it in a different AWS Region without making a cross-Region call or exposing the plaintext data. For more information, see Using multi-Region keys in the AWS Key Management Service Developer Guide.

A multi-Region primary key is a fully functional symmetric or asymmetric KMS key that is also the model for replica keys in other AWS Regions. To create a multi-Region primary key, add an AWS::KMS::Key resource to your CloudFormation stack. Set its MultiRegion property to true.

A multi-Region replica key is a fully functional symmetric or asymmetric KMS key that has the same key ID and key material as a multi-Region primary key, but is located in a different AWS Region of the same AWS partition. There can be multiple replicas of a primary key, but each must be in a different AWS Region .

A primary key and its replicas have the same key ID and key material. They also have the same key spec, key usage, key material origin, and automatic key rotation status. These properties are known as shared properties. If they change, AWS KMS synchronizes the change to all related multi-Region keys. All other properties of a replica key can differ, including its key policy, tags, aliases, and key state. AWS KMS does not synchronize these properties.

Syntax

To declare this entity in your AWS CloudFormation template, use the following syntax:

JSON

{ "Type" : "AWS::KMS::ReplicaKey", "Properties" : { "Description" : String, "Enabled" : Boolean, "KeyPolicy" : Json, "PendingWindowInDays" : Integer, "PrimaryKeyArn" : String, "Tags" : [ Tag, ... ] } }

YAML

Type: AWS::KMS::ReplicaKey Properties: Description: String Enabled: Boolean KeyPolicy: Json PendingWindowInDays: Integer PrimaryKeyArn: String Tags: - Tag

Properties

Description

A description of the KMS key.

The default value is an empty string (no description).

The description is not a shared property of multi-Region keys. You can specify the same description or a different description for each key in a set of related multi-Region keys. AWS Key Management Service does not synchronize this property.

Required: No

Type: String

Minimum: 0

Maximum: 8192

Update requires: No interruption

Enabled

Specifies whether the replica key is enabled. Disabled KMS keys cannot be used in cryptographic operations.

When Enabled is true, the key state of the KMS key is Enabled. When Enabled is false, the key state of the KMS key is Disabled. The default value is true.

The actual key state of the replica might be affected by actions taken outside of CloudFormation, such as running the EnableKey, DisableKey, or ScheduleKeyDeletion operations. Also, while the replica key is being created, its key state is Creating. When the process is complete, the key state of the replica key changes to Enabled.

For information about the key states of a KMS key, see Key state: Effect on your KMS key in the AWS Key Management Service Developer Guide.

Required: No

Type: Boolean

Update requires: No interruption

KeyPolicy

The key policy that authorizes use of the replica key.

The key policy is not a shared property of multi-Region keys. You can specify the same key policy or a different key policy for each key in a set of related multi-Region keys. AWS KMS does not synchronize this property.

The key policy must conform to the following rules.

  • The key policy must give the caller PutKeyPolicy permission on the KMS key. This reduces the risk that the KMS key becomes unmanageable. For more information, refer to the scenario in the Default key policy section of the AWS Key Management Service Developer Guide .

  • Each statement in the key policy must contain one or more principals. The principals in the key policy must exist and be visible to AWS KMS. When you create a new AWSprincipal (for example, an IAM user or role), you might need to enforce a delay before including the new principal in a key policy because the new principal might not be immediately visible to AWS KMS. For more information, see Changes that I make are not always immediately visible in the AWS Identity and Access Management User Guide.

  • The key policy size limit is 32 kilobytes (32768 bytes).

Minimum: 1

Maximum: 32768

Required: Yes

Type: Json

Update requires: No interruption

PendingWindowInDays

Specifies the number of days in the waiting period before AWS KMS deletes a replica key that has been removed from a CloudFormation stack. Enter a value between 7 and 30 days. The default value is 30 days.

When you remove a replica key from a CloudFormation stack, AWS KMS schedules the replica key for deletion and starts the mandatory waiting period. The PendingWindowInDays property determines the length of waiting period. During the waiting period, the key state of replica key is Pending Deletion, which prevents it from being used in cryptographic operations. When the waiting period expires, AWS KMS permanently deletes the replica key.

You cannot use a CloudFormation template to cancel deletion of the replica after you remove it from the stack, regardless of the waiting period. However, if you specify a replica key in your template that is based on the same primary key as the original replica key, CloudFormation creates a new replica key with the same key ID, key material, and other shared properties of the original replica key. This new replica key can decrypt ciphertext that was encrypted under the original replica key, or any related multi-Region key.

For detailed information about deleting multi-Region keys, see Deleting multi-Region keys in the AWS Key Management Service Developer Guide.

For information about the PendingDeletion key state, see Key state: Effect on your KMS key in the AWS Key Management Service Developer Guide. For more information about deleting KMS keys, see the ScheduleKeyDeletion operation in the AWS Key Management Service API Reference and Deleting KMS keys in the AWS Key Management Service Developer Guide.

Minimum: 7

Maximum: 30

Required: No

Type: Integer

Update requires: No interruption

PrimaryKeyArn

Specifies the multi-Region primary key to replicate. The primary key must be in a different AWS Region of the same AWSpartition. You can create only one replica of a given primary key in each AWS Region .

Important

If you change the PrimaryKeyArn value of a replica key, the existing replica key is scheduled for deletion and a new replica key is created based on the specified primary key. While it is scheduled for deletion, the existing replica key becomes unusable. You can cancel the scheduled deletion of the key outside of CloudFormation.

However, if you inadvertently delete a replica key, you can decrypt ciphertext encrypted by that replica key by using any related multi-Region key. If necessary, you can recreate the replica in the same Region after the previous one is completely deleted. For details, see Deleting multi-Region keys in the AWS Key Management Service Developer Guide

Specify the key ARN of an existing multi-Region primary key. For example, arn:aws:kms:us-east-2:111122223333:key/mrk-1234abcd12ab34cd56ef1234567890ab.

Required: Yes

Type: String

Minimum: 1

Maximum: 2048

Update requires: Replacement

Tags

Assigns one or more tags to the replica key.

Note

Tagging or untagging a KMS key can allow or deny permission to the KMS key. For details, see Using ABAC in AWS KMS in the AWS Key Management Service Developer Guide.

Tags are not a shared property of multi-Region keys. You can specify the same tags or different tags for each key in a set of related multi-Region keys. AWS KMS does not synchronize this property.

Each tag consists of a tag key and a tag value. Both the tag key and the tag value are required, but the tag value can be an empty (null) string. You cannot have more than one tag on a KMS key with the same tag key. If you specify an existing tag key with a different tag value, AWS KMS replaces the current tag value with the specified one.

When you assign tags to an AWSresource, AWSgenerates a cost allocation report with usage and costs aggregated by tags. Tags can also be used to control access to a KMS key. For details, see Tagging keys.

Required: No

Type: List of Tag

Update requires: No interruption

Return values

Ref

When you pass the logical ID of this resource to the intrinsic Ref function, Ref returns the key ID, such as mrk-1234abcd12ab34cd56ef1234567890ab.

For more information about using the Ref function, see Ref.

Fn::GetAtt

The Fn::GetAtt intrinsic function returns a value for a specified attribute of this type. The following are the available attributes and sample return values.

For more information about using the Fn::GetAtt intrinsic function, see Fn::GetAtt.

Arn

The Amazon Resource Name (ARN) of the replica key, such as arn:aws:kms:us-west-2:111122223333:key/mrk-1234abcd12ab34cd56ef1234567890ab.

The key ARNs of related multi-Region keys differ only in the Region value. For information about the key ARNs of multi-Region keys, see How multi-Region keys work in the AWS Key Management Service Developer Guide.

KeyId

The key ID of the replica key, such as mrk-1234abcd12ab34cd56ef1234567890ab.

Related multi-Region keys have the same key ID. For information about the key IDs of multi-Region keys, see How multi-Region keys work in the AWS Key Management Service Developer Guide.

Examples

Create a multi-Region replica key

The following example creates a multi-Region replica key in the local Region based on a multi-Region primary key in the US West (Oregon) (us-west-2) Region.

If the key ARN specified by the PrimaryKeyArn property doesn't identify a multi-Region primary key, or if a related multi-Region key already exists in the local Region, the operation fails. The example specifies a description, a key policy, and a waiting period for key deletion (PendingWindowInDays). These properties are independent of the primary key and related replica keys in other AWS Regions.

JSON

"Resources": { "myReplicaKey": { "Type": "AWS::KMS::ReplicaKey", "Properties": { "PrimaryKeyArn": "arn:aws:kms:us-west-2:111122223333:key/mrk-1234abcd12ab34cd56ef1234567890ab", "Description": "Example replica key", "EnableKeyRotation": true, "PendingWindowInDays": 7, "KeyPolicy": { "Version": "2012-10-17", "Id": "key-default-1", "Statement": [ { "Sid": "Enable IAM User Permissions", "Effect": "Allow", "Principal": { "AWS": "arn:aws:iam::111122223333:root" }, "Action": "kms:*", "Resource": "*" }, { "Sid": "Allow administration of the key", "Effect": "Allow", "Principal": { "AWS": "arn:aws:iam::111122223333:role/admin" }, "Action": [ "kms:Create*", "kms:Delete*", "kms:Disable*", "kms:Describe*", "kms:Enable*", "kms:Get*", "kms:List*", "kms:Put*", "kms:Revoke*", "kms:UpdateAlias", "kms:ScheduleKeyDeletion", "kms:CancelKeyDeletion" ], "Resource": "*" }, { "Sid": "Allow use of the key", "Effect": "Allow", "Principal": { "AWS": "arn:aws:iam::111122223333:role/developer" }, "Action": [ "kms:DescribeKey", "kms:Encrypt", "kms:Decrypt", "kms:ReEncrypt*", "kms:GenerateDataKey", "kms:GenerateDataKeyWithoutPlaintext" ], "Resource": "*" } ] } } } }

YAML

Resources: myReplicaKey: Type: 'AWS::KMS::ReplicaKey' Properties: PrimaryKeyArn: >- arn:aws:kms:us-west-2:111122223333:key/mrk-1234abcd12ab34cd56ef1234567890ab Description: Example replica key PendingWindowInDays: 7 KeyPolicy: Version: 2012-10-17 Id: key-default-1 Statement: - Sid: Enable IAM User Permissions Effect: Allow Principal: AWS: 'arn:aws:iam::111122223333:root' Action: 'kms:*' Resource: '*' - Sid: Allow administration of the key Effect: Allow Principal: AWS: 'arn:aws:iam::111122223333:role/admin' Action: - 'kms:Create*' - 'kms:Delete*' - 'kms:Describe*' - 'kms:Disable*' - 'kms:Enable*' - 'kms:Get*' - 'kms:List*' - 'kms:Put*' - 'kms:Revoke*' - 'kms:UpdateAlias' - 'kms:UpdateDescription' - 'kms:ScheduleKeyDeletion' - 'kms:CancelKeyDeletion' Resource: '*' - Sid: Allow use of the key Effect: Allow Principal: AWS: 'arn:aws:iam::111122223333:role/developer' Action: - 'kms:DescribeKey' - 'kms:Encrypt' - 'kms:Decrypt' - 'kms:ReEncrypt*' - 'kms:GenerateDataKey' - 'kms:GenerateDataKeyWithoutPlaintext' Resource: '*'

See also