AWS::KMS::Key
The AWS::KMS::Key
resource specifies a symmetric or asymmetric customer master key (CMK)
in AWS Key Management Service (AWS KMS).
You can use symmetric CMKs 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 CMKs to encrypt data stored in AWS
services that are integrated with AWS KMS
You can use asymmetric CMKs to encrypt and decrypt data or sign messages and verify signatures.
If you change the value of a Replacement
property, such as KeyUsage
or KeySpec
, on an existing CMK, the existing CMK is scheduled for deletion and a new CMK is created with the specified value.
While scheduled for deletion, the existing CMK becomes unusable. If you don't cancel the scheduled deletion of the existing CMK outside of CloudFormation, all data encrypted under the existing CMK becomes unrecoverable when the CMK 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
, "PendingWindowInDays" :Integer
, "Tags" :[ Tag, ... ]
} }
YAML
Type: AWS::KMS::Key Properties: Description:
String
Enabled:Boolean
EnableKeyRotation:Boolean
KeyPolicy:Json
KeySpec:String
KeyUsage:String
PendingWindowInDays:Integer
Tags:- Tag
Properties
Description
-
A description of the CMK. Use a description that helps you to distinguish this CMK 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 customer master key (CMK) is enabled. Disabled CMKs cannot be used in cryptographic operations.
When
Enabled
istrue
, the key state of the CMK isEnabled
. WhenEnabled
isfalse
, the key state of the CMK isDisabled
. The default value istrue
.The actual key state of the CMK 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 CMK, see Key state: Effect on your CMK 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 customer master key (CMK). By default, automation key rotation is not enabled.
When you enable automatic rotation, AWS KMS automatically creates new key material for the CMK 365 days after the enable (or reenable) date and every 365 days thereafter. AWS KMS retains all key material until you delete the CMK.
For detailed information about automatic key rotation, see Rotating customer master 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 CMK. The key policy must observe the following rules.
-
The key policy must allow the caller to make a subsequent PutKeyPolicy request on the CMK. This reduces the risk that the CMK 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 CMKs 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 CMK to create. The default value,
SYMMETRIC_DEFAULT
, creates a CMK with a 256-bit symmetric key for encryption and decryption. For help choosing a key spec for your CMK, see How to Choose Your CMK Configuration in the AWS Key Management Service Developer Guide.The
KeySpec
property (CustomerMasterKeySpec
type) determines whether the CMK contains a symmetric key or an asymmetric key pair. It also determines the encryption algorithms or signing algorithms that the CMK supports. You can't change theKeySpec
after the CMK is created. To further restrict the algorithms that can be used with the CMK, 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 CMK, the existing CMK is scheduled for deletion and a new CMK is created with the specifiedKeySpec
value. While the scheduled deletion is pending, you can't use the existing CMK. Unless you cancel the scheduled deletion of the CMK outside of CloudFormation, all data encrypted under the existing CMK becomes unrecoverable when the CMK is deleted.Note AWS services that are integrated with AWS KMS
use symmetric CMKs to protect your data. These services do not support asymmetric CMKs. For help determining whether a CMK is symmetric or asymmetric, see Identifying Symmetric and Asymmetric CMKs in the AWS Key Management Service Developer Guide. AWS KMS supports the following key specs for CMKs:
-
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: Replacement
-
KeyUsage
-
Determines the cryptographic operations for which you can use the CMK. The default value is
ENCRYPT_DECRYPT
. This property is required only for asymmetric CMKs. You can't change theKeyUsage
value after the CMK is created.Important If you change the
KeyUsage
of an existing CMK, the existing CMK is scheduled for deletion and a new CMK is created with the specifiedKeyUsage
value. While the scheduled deletion is pending, you can't use the existing CMK. Unless you cancel the scheduled deletion of the CMK outside of CloudFormation, all data encrypted under the existing CMK becomes unrecoverable when the CMK is deleted.Select only one valid value.
-
For symmetric CMKs, omit the property or specify
ENCRYPT_DECRYPT
. -
For asymmetric CMKs with RSA key material, specify
ENCRYPT_DECRYPT
orSIGN_VERIFY
. -
For asymmetric CMKs with ECC key material, specify
SIGN_VERIFY
.
Required: No
Type: String
Allowed values:
ENCRYPT_DECRYPT | SIGN_VERIFY
Update requires: Replacement
-
PendingWindowInDays
-
Specifies the number of days in the waiting period before AWS KMS deletes a CMK 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 customer master key (CMK) from a CloudFormation stack, AWS KMS schedules the CMK 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 CMK isPending Deletion
, which prevents the CMK from being used in cryptographic operations. When the waiting period expires, AWS KMS permanently deletes the CMK.You cannot use a CloudFormation template to cancel deletion of the CMK after you remove it from the stack, regardless of the waiting period. If you specify a CMK in your template, even one with the same name, CloudFormation creates a new CMK. To cancel deletion of a CMK, use the AWS KMS console or the CancelKeyDeletion operation.
For information about the
PendingDeletion
key state, see Key state: Effect on your CMK in the AWS Key Management Service Developer Guide. For more information about deleting CMKs, see the ScheduleKeyDeletion operation in the AWS Key Management Service API Reference and Deleting customer master keys in the AWS Key Management Service Developer Guide.Minimum: 7
Maximum: 30
Required: No
Type: Integer
Update requires: No interruption
Tags
-
An array of key-value pairs to apply to this resource.
Note Tagging or untagging a CMK can allow or deny permission to the CMK. 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 AWS KMS customer master key (CMK), such as
arn:aws:kms:us-west-2:111122223333:key/1234abcd-12ab-34cd-56ef-1234567890ab
.For information about the key ARN of a CMK, see Key ARN in the AWS Key Management Service Developer Guide.
KeyId
-
The key ID of the AWS KMS customer master key (CMK), such as
1234abcd-12ab-34cd-56ef-1234567890ab
.For information about the key ID of a CMK, see Key ID in the AWS Key Management Service Developer Guide.
Examples
Create a symmetric CMK
The following example creates a symmetric CMK. The key policy for the CMK
allows Alice
to manage the key and allows Bob
to view the CMK
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 CMK", "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::123456789012: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::123456789012: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 CMK 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::123456789012: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::123456789012:user/Bob Action: - kms:DescribeKey - kms:Encrypt - kms:Decrypt - kms:ReEncrypt* - kms:GenerateDataKey - kms:GenerateDataKeyWithoutPlaintext Resource: '*'
Create a symmetric CMK with a resource tag
The following example creates a symmetric CMK with one resource tag.
JSON
{ "Resources" : { "myKey" : { "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
Resources: myKey: 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
See also
-
Creating keys in the AWS Key Management Service Developer Guide.
-
CreateKey in the AWS Key Management Service API Reference.
-
Customer master keys in the AWS Key Management Service Developer Guide.