AWS::KMS::Key - AWS CloudFormation
SyntaxPropertiesReturn valuesExamplesSee also

AWS::KMS::Key

The AWS::KMS::Key resource specifies a symmetric or asymmetric KMS key in AWS Key Management Service (AWS KMS).

Note

AWS KMS is replacing the term customer master key (CMK) with AWS KMS key and KMS key. The concept has not changed. To prevent breaking changes, AWS KMS is keeping some variations of this term.

You can use symmetric KMS keys to encrypt and decrypt small amounts of data, but they are more commonly used to generate data keys and data key pairs. You can also use symmetric KMS key to encrypt data stored in AWS services that are integrated with AWS KMS. For more information, see What is AWS Key Management Service? in the AWS Key Management Service Developer Guide.

You can use asymmetric KMS keys to encrypt and decrypt data or sign messages and verify signatures. To create an asymmetric key, you must specify an asymmetric KeySpec value and a KeyUsage value.

Important

If you change the value of a Replacement property, such as KeyUsage or KeySpec, on an existing KMS key, the existing KMS key is scheduled for deletion and a new KMS key is created with the specified value.

While scheduled for deletion, the existing KMS key becomes unusable. If you don't cancel the scheduled deletion of the existing KMS key outside of CloudFormation, all data encrypted under the existing KMS key becomes unrecoverable when the KMS key is deleted.

Syntax

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

JSON

{
  "Type" : "AWS::KMS::Key",
  "Properties" : {
      "Description" : String,
      "Enabled" : Boolean,
      "EnableKeyRotation" : Boolean,
      "KeyPolicy" : Json,
      "KeySpec" : String,
      "KeyUsage" : String,
      "MultiRegion" : Boolean,
      "PendingWindowInDays" : Integer,
      "Tags" : [ Tag, ... ]
    }
}

YAML

Type: AWS::KMS::Key
Properties: 
  Description: String
  Enabled: Boolean
  EnableKeyRotation: Boolean
  KeyPolicy: Json
  KeySpec: String
  KeyUsage: String
  MultiRegion: Boolean
  PendingWindowInDays: Integer
  Tags: 
    - Tag

Properties

Description

A description of the KMS key. Use a description that helps you to distinguish this KMS key from others in the account, such as its intended use.

Required: No

Type: String

Minimum: 0

Maximum: 8192

Update requires: No interruption

Enabled

Specifies whether the KMS 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 KMS key might be affected by actions taken outside of CloudFormation, such as running the EnableKey, DisableKey, or ScheduleKeyDeletion operations.

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

EnableKeyRotation

Enables automatic rotation of the key material for the specified KMS key. By default, automatic key rotation is not enabled.

AWS KMS does not support automatic key rotation on asymmetric KMS keys. For asymmetric KMS keys, omit the EnableKeyRotation property or set it to false.

When you enable automatic rotation, AWS KMS automatically creates new key material for the KMS key 365 days after the enable (or reenable) date and every 365 days thereafter. AWS KMS retains all key material until you delete the KMS key. For detailed information about automatic key rotation, see Rotating KMS keys 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 KMS key. The key policy must conform to the following rules.

  • The key policy must allow the caller to make a subsequent PutKeyPolicy request 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 AWS principal (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).

If you are unsure of which policy to use, consider the default key policy. This is the key policy that AWS KMS applies to KMS keys that are created by using the CreateKey API with no specified key policy. It gives the AWS account that owns the key permission to perform all operations on the key. It also allows you write IAM policies to authorize access to the key. For details, see Default key policy in the AWS Key Management Service Developer Guide.

Minimum: 1

Maximum: 32768

Required: Yes

Type: Json

Update requires: No interruption

KeySpec

Specifies the type of KMS key to create. The default value, SYMMETRIC_DEFAULT, creates a KMS key with a 256-bit symmetric key for encryption and decryption. For help choosing a key spec for your KMS key, see How to choose Your KMS key configuration in the AWS Key Management Service Developer Guide.

The KeySpec property determines whether the KMS key contains a symmetric key or an asymmetric key pair. It also determines the encryption algorithms or signing algorithms that the KMS key supports. You can't change the KeySpec after the KMS key is created. To further restrict the algorithms that can be used with the KMS key, use a condition key in its key policy or IAM policy. For more information, see kms:EncryptionAlgorithm or kms:Signing Algorithm in the AWS Key Management Service Developer Guide.

Important

If you change the KeySpec of an existing KMS key, the existing KMS key is scheduled for deletion and a new KMS key is created with the specified KeySpec value. While the scheduled deletion is pending, you can't use the existing KMS key. Unless you cancel the scheduled deletion of the KMS key outside of CloudFormation, all data encrypted under the existing KMS key becomes unrecoverable when the KMS key is deleted.

Note

AWS services that are integrated with AWS KMS use symmetric KMS keys to protect your data. These services do not support asymmetric KMS keys. For help determining whether a KMS key is symmetric or asymmetric, see Identifying Symmetric and Asymmetric KMS keys in the AWS Key Management Service Developer Guide.

AWS KMS supports the following key specs for KMS keys:

  • Symmetric key (default)

    • SYMMETRIC_DEFAULT (AES-256-GCM)

  • Asymmetric RSA key pairs

    • RSA_2048

    • RSA_3072

    • RSA_4096

  • Asymmetric NIST-recommended elliptic curve key pairs

    • ECC_NIST_P256 (secp256r1)

    • ECC_NIST_P384 (secp384r1)

    • ECC_NIST_P521 (secp521r1)

  • Other asymmetric elliptic curve key pairs

    • ECC_SECG_P256K1 (secp256k1), commonly used for cryptocurrencies.

Required: No

Type: String

Update requires: No interruption

KeyUsage

Determines the cryptographic operations for which you can use the KMS key. The default value is ENCRYPT_DECRYPT. This property is required only for asymmetric KMS keys. You can't change the KeyUsage value after the KMS key is created.

Important

If you change the KeyUsage of an existing KMS key, the existing KMS key is scheduled for deletion and a new KMS key is created with the specified KeyUsage value. While the scheduled deletion is pending, you can't use the existing KMS key. Unless you cancel the scheduled deletion of the KMS key outside of CloudFormation, all data encrypted under the existing KMS key becomes unrecoverable when the KMS key is deleted.

Select only one valid value.

  • For symmetric KMS keys, omit the property or specify ENCRYPT_DECRYPT.

  • For asymmetric KMS keys with RSA key material, specify ENCRYPT_DECRYPT or SIGN_VERIFY.

  • For asymmetric KMS keys with ECC key material, specify SIGN_VERIFY.

Required: No

Type: String

Allowed values: ENCRYPT_DECRYPT | SIGN_VERIFY

Update requires: No interruption

MultiRegion

Creates a multi-Region primary key that you can replicate in other AWS Regions.

Important

If you change the MultiRegion property of an existing KMS key, the existing KMS key is scheduled for deletion and a new KMS key is created with the specified Multi-Region value. While the scheduled deletion is pending, you can't use the existing KMS key. Unless you cancel the scheduled deletion of the KMS key outside of CloudFormation, all data encrypted under the existing KMS key becomes unrecoverable when the KMS key is deleted.

For a multi-Region key, set to this property to true. For a single-Region key, omit this property or set it to false. The default value is false.

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.

You can create a symmetric or asymmetric multi-Region key, and you can create a multi-Region key with imported key material. However, you cannot create a multi-Region key in a custom key store.

To create a replica of this primary key in a different AWS Region , create an AWS::KMS::ReplicaKey resource in a CloudFormation stack in the replica Region. Specify the key ARN of this primary key.

Required: No

Type: Boolean

Update requires: No interruption

PendingWindowInDays

Specifies the number of days in the waiting period before AWS KMS deletes a KMS 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 KMS key from a CloudFormation stack, AWS KMS schedules the KMS 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 KMS key is Pending Deletion or Pending Replica Deletion, which prevents the KMS key from being used in cryptographic operations. When the waiting period expires, AWS KMS permanently deletes the KMS key.

AWS KMS will not delete a multi-Region primary key that has replica keys. If you remove a multi-Region primary key from a CloudFormation stack, its key state changes to PendingReplicaDeletion so it cannot be replicated or used in cryptographic operations. This state can persist indefinitely. When the last of its replica keys is deleted, the key state of the primary key changes to PendingDeletion and the waiting period specified by PendingWindowInDays begins. When this waiting period expires, AWS KMS deletes the primary key. For details, see Deleting multi-Region keys in the AWS Key Management Service Developer Guide.

You cannot use a CloudFormation template to cancel deletion of the KMS key after you remove it from the stack, regardless of the waiting period. If you specify a KMS key in your template, even one with the same name, CloudFormation creates a new KMS key. To cancel deletion of a KMS key, use the AWS KMS console or the CancelKeyDeletion operation.

For information about the Pending Deletion and Pending Replica Deletion key states, 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

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.

For information about tags in AWS KMS, see Tagging keys in the AWS Key Management Service Developer Guide. For information about tags in CloudFormation, see Tag.

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 1234abcd-12ab-34cd-56ef-1234567890ab.

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 KMS key, such as arn:aws:kms:us-west-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab.

For information about the key ARN of a KMS key, see Key ARN in the AWS Key Management Service Developer Guide.

KeyId

The key ID of the KMS key, such as 1234abcd-12ab-34cd-56ef-1234567890ab.

For information about the key ID of a KMS key, see Key ID in the AWS Key Management Service Developer Guide.

Examples

Create a symmetric KMS key

The following example creates a symmetric KMS key. The key policy for the KMS key allows Alice to manage the key and allows Bob to view the KMS key and use it in cryptographic operations. It also allows the AWS account (root) full access to the key. This prevents you from losing control of the key if both Alice and Bob are deleted from the account.

JSON

"myKey" : {
  "Type" : "AWS::KMS::Key",
  "Properties" : {
    "Description" : "An example symmetric KMS key",
    "EnableKeyRotation": true,
    "PendingWindowInDays": 20,
    "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:user/Alice" },
          "Action": [
            "kms:Create*",
            "kms:Describe*",
            "kms:Enable*",
            "kms:List*",
            "kms:Put*",
            "kms:Update*",
            "kms:Revoke*",
            "kms:Disable*",
            "kms:Get*",
            "kms:Delete*",
            "kms:ScheduleKeyDeletion",
            "kms:CancelKeyDeletion"
          ],
          "Resource": "*"
        },
        {
          "Sid": "Allow use of the key",
          "Effect": "Allow",
          "Principal": { "AWS": "arn:aws:iam::111122223333:user/Bob" },
          "Action": [
            "kms:DescribeKey",
            "kms:Encrypt",
            "kms:Decrypt",
            "kms:ReEncrypt*",
            "kms:GenerateDataKey",
            "kms:GenerateDataKeyWithoutPlaintext"
          ], 
          "Resource": "*"
        }    
      ]
    }
  }
}

YAML

myKey:
  Type: AWS::KMS::Key
  Properties:
    Description: An example symmetric KMS key
    EnableKeyRotation: true
    PendingWindowInDays: 20
    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:user/Alice
        Action:
        - kms:Create*
        - kms:Describe*
        - kms:Enable*
        - kms:List*
        - kms:Put*
        - kms:Update*
        - kms:Revoke*
        - kms:Disable*
        - kms:Get*
        - kms:Delete*
        - kms:ScheduleKeyDeletion
        - kms:CancelKeyDeletion
        Resource: '*'
      - Sid: Allow use of the key
        Effect: Allow
        Principal:
          AWS: arn:aws:iam::111122223333:user/Bob
        Action:
        - kms:DescribeKey
        - kms:Encrypt
        - kms:Decrypt
        - kms:ReEncrypt*
        - kms:GenerateDataKey
        - kms:GenerateDataKeyWithoutPlaintext
        Resource: '*'

Create a symmetric KMS key with a resource tag

The following example creates a symmetric KMS key with one resource tag.

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.

JSON

"myKeyWithTag": {
    "Type": "AWS::KMS::Key",
    "Properties": {
        "KeyPolicy": {
            "Version": "2012-10-17",
            "Id": "key-default-1",
            "Statement": [
                {
                    "Sid": "Enable IAM User Permissions",
                    "Effect": "Allow",
                    "Principal": {
                        "AWS": {
                            "Fn::Join": [
                                "",
                                [
                                    "arn:aws:iam::",
                                    {
                                        "Ref": "AWS::AccountId"
                                    },
                                    ":root"
                                ]
                            ]
                        }
                    },
                    "Action": "kms:*",
                    "Resource": "*"
                }
            ]
        },
        "Tags": [
            {
                "Key": {
                    "Ref": "Key"
                },
                "Value": {
                    "Ref": "Value"
                }
            }
        ]
    },
    "Parameters": {
        "Key": {
            "Type": "String"
        },
        "Value": {
            "Type": "String"
        }
    }
}

YAML

myKeyWithTag:
  Type: 'AWS::KMS::Key'
  Properties:
    KeyPolicy:
      Version: 2012-10-17
      Id: key-default-1
      Statement:
        - Sid: Enable IAM User Permissions
          Effect: Allow
          Principal:
            AWS: !Join 
              - ''
              - - 'arn:aws:iam::'
                - !Ref 'AWS::AccountId'
                - ':root'
          Action: 'kms:*'
          Resource: '*'
    Tags:
      - Key: !Ref Key
        Value: !Ref Value
  Parameters:
    Key:
      Type: String
    Value:
      Type: String

Create an asymmetric KMS key

The following example creates an RSA asymmetric KMS key for signing and verification. For an asymmetric KMS key, you must specify KeySpec and KeyUsage properties. The EnableKeyRotation property must be omitted or set to false.

JSON

"RSASigningKey" : {
  "Type" : "AWS::KMS::Key",
  "Properties" : {
    "Description" : "RSA-3047 asymmetric KMS key for signing and verification",
    "KeySpec" : "RSA_3072",
    "KeyUsage" : "SIGN_VERIFY",
    "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:Describe*",
            "kms:Enable*",
            "kms:List*",
            "kms:Put*",
            "kms:Update*",
            "kms:Revoke*",
            "kms:Disable*",
            "kms:Get*",
            "kms:Delete*",
            "kms:ScheduleKeyDeletion",
            "kms:CancelKeyDeletion"
          ],
          "Resource": "*"
        },
        {
          "Sid": "Allow use of the key",
          "Effect": "Allow",
          "Principal": { "AWS": "arn:aws:iam::111122223333:role/Developer" },
          "Action": [
            "kms:Sign",
            "kms:Verify",
            "kms:DescribeKey"
          ], 
          "Resource": "*"
        }    
      ]
    }
  }
}

YAML

RSASigningKey:
  Type: AWS::KMS::Key
  Properties:
    Description: RSA-3047 asymmetric KMS key for signing and verification
    KeySpec: RSA_3072
    KeyUsage: SIGN_VERIFY
    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:Describe*
        - kms:Enable*
        - kms:List*
        - kms:Put*
        - kms:Update*
        - kms:Revoke*
        - kms:Disable*
        - kms:Get*
        - kms:Delete*
        - kms:ScheduleKeyDeletion
        - kms:CancelKeyDeletion
        Resource: '*'
      - Sid: Allow use of the key
        Effect: Allow
        Principal:
          AWS: arn:aws:iam::111122223333:role/Developer
        Action:        
        - kms:Sign
        - kms:Verify
        - kms:DescribeKey
        Resource: '*'

Create a multi-Region primary key

The following example creates 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.

To replicate this primary key into a different AWS Region, use the AWS::KMS::ReplicaKey CloudFormation resource.

JSON

"myPrimaryKey" : {
  "Type" : "AWS::KMS::Key",
  "Properties" : {
    "Description" : "An example multi-Region primary key",
    "MultiRegion": true,
    "EnableKeyRotation": true,
    "PendingWindowInDays": 10,
    "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:user/Alice" },
          "Action": [
            "kms:ReplicateKey",
            "kms:Create*",
            "kms:Describe*",
            "kms:Enable*",
            "kms:List*",
            "kms:Put*",
            "kms:Update*",
            "kms:Revoke*",
            "kms:Disable*",
            "kms:Get*",
            "kms:Delete*",
            "kms:ScheduleKeyDeletion",
            "kms:CancelKeyDeletion"
          ],
          "Resource": "*"
        },
        {
          "Sid": "Allow use of the key",
          "Effect": "Allow",
          "Principal": { "AWS": "arn:aws:iam::111122223333:user/Bob" },
          "Action": [
            "kms:DescribeKey",
            "kms:Encrypt",
            "kms:Decrypt",
            "kms:ReEncrypt*",
            "kms:GenerateDataKey",
            "kms:GenerateDataKeyWithoutPlaintext"
          ], 
          "Resource": "*"
        }    
      ]
    }
  }
}

YAML

myPrimaryKey:
  Type: AWS::KMS::Key
  Properties:
    Description: An example multi-Region primary key
    MultiRegion: true
    EnableKeyRotation: true
    PendingWindowInDays 10
    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:user/Alice
        Action:
        - kms:ReplicateKey
        - kms:Create*
        - kms:Describe*
        - kms:Enable*
        - kms:List*
        - kms:Put*
        - kms:Update*
        - kms:Revoke*
        - kms:Disable*
        - kms:Get*
        - kms:Delete*
        - kms:ScheduleKeyDeletion
        - kms:CancelKeyDeletion
        Resource: '*'
      - Sid: Allow use of the key
        Effect: Allow
        Principal:
          AWS: arn:aws:iam::111122223333:user/Bob
        Action:
        - kms:DescribeKey
        - kms:Encrypt
        - kms:Decrypt
        - kms:ReEncrypt*
        - kms:GenerateDataKey
        - kms:GenerateDataKeyWithoutPlaintext
        Resource: '*'

See also