Use GetKeyPolicy with an AWS SDK or CLI

To copy a key policy from one KMS key to another KMS key

The following get-key-policy example gets the key policy from one KMS key and saves it in a text file. Then, it replaces the policy of a different KMS key using the text file as the policy input.

Because the --policy parameter of put-key-policy requires a string, you must use the --output text option to return the output as a text string instead of JSON.

aws kms get-key-policy \
    --policy-name default \
    --key-id 1234abcd-12ab-34cd-56ef-1234567890ab \
    --query Policy \
    --output text > policy.txt

aws kms put-key-policy \
    --policy-name default \
    --key-id 0987dcba-09fe-87dc-65ba-ab0987654321 \
    --policy file://policy.txt

This command produces no output.

For more information, see PutKeyPolicy in the AWS KMS API Reference.

class KeyPolicy:
    def __init__(self, kms_client):
        self.kms_client = kms_client

    @classmethod
    def from_client(cls) -> "KeyPolicy":
        """
        Creates a KeyPolicy instance with a default KMS client.

        :return: An instance of KeyPolicy initialized with the default KMS client.
        """
        kms_client = boto3.client("kms")
        return cls(kms_client)


    def get_policy(self, key_id: str) -> dict[str, str]:
        """
        Gets the policy of a key.

        :param key_id: The ARN or ID of the key to query.
        :return: The key policy as a dict.
        """
        if key_id != "":
            try:
                response = self.kms_client.get_key_policy(
                    KeyId=key_id,
                )
                policy = json.loads(response["Policy"])
            except ClientError as err:
                logger.error(
                    "Couldn't get policy for key %s. Here's why: %s",
                    key_id,
                    err.response["Error"]["Message"],
                )
                raise
            else:
                pprint(policy)
                return policy
        else:
            print("Skipping get policy demo.")