AWS Secrets Manager
User Guide

Secrets Manager Lambda Rotation Template: RDS MySQL Single User

The following is the source code that's initially placed into the Lambda rotation function when you choose the SecretsManagerRDSMySQLRotationSingleUser template option from the AWS Serverless Application Repository. This template is automatically used to create the function when you enable rotation by using the Secrets Manager console. (In the console, you specify that the secret is for an Amazon RDS MySQL database, and that you want to rotate the secret using the credentials that are stored in the same secret.)

To create this function manually, follow the instructions at Rotating AWS Secrets Manager Secrets for Other Databases or Services, and specify this template.

For more information about the rotation strategy that's implemented by this function, see Rotating AWS Secrets Manager Secrets for One User with a Single Password.

This function is written in Python, and uses the AWS Boto3 SDK for Python.

# Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved. # SPDX-License-Identifier: MIT-0 import boto3 import json import logging import os import pymysql logger = logging.getLogger() logger.setLevel(logging.INFO) def lambda_handler(event, context): """Secrets Manager RDS MySQL Handler This handler uses the single-user rotation scheme to rotate an RDS MySQL user credential. This rotation scheme logs into the database as the user and rotates the user's own password, immediately invalidating the user's previous password. The Secret SecretString is expected to be a JSON string with the following format: { 'engine': <required: must be set to 'mysql'>, 'host': <required: instance host name>, 'username': <required: username>, 'password': <required: password>, 'dbname': <optional: database name>, 'port': <optional: if not specified, default port 3306 will be used> } Args: event (dict): Lambda dictionary of event parameters. These keys must include the following: - SecretId: The secret ARN or identifier - ClientRequestToken: The ClientRequestToken of the secret version - Step: The rotation step (one of createSecret, setSecret, testSecret, or finishSecret) context (LambdaContext): The Lambda runtime information Raises: ResourceNotFoundException: If the secret with the specified arn and stage does not exist ValueError: If the secret is not properly configured for rotation KeyError: If the secret json does not contain the expected keys """ arn = event['SecretId'] token = event['ClientRequestToken'] step = event['Step'] # Setup the client service_client = boto3.client('secretsmanager', endpoint_url=os.environ['SECRETS_MANAGER_ENDPOINT']) # Make sure the version is staged correctly metadata = service_client.describe_secret(SecretId=arn) if "RotationEnabled" in metadata and not metadata['RotationEnabled']: logger.error("Secret %s is not enabled for rotation" % arn) raise ValueError("Secret %s is not enabled for rotation" % arn) versions = metadata['VersionIdsToStages'] if token not in versions: logger.error("Secret version %s has no stage for rotation of secret %s." % (token, arn)) raise ValueError("Secret version %s has no stage for rotation of secret %s." % (token, arn)) if "AWSCURRENT" in versions[token]: logger.info("Secret version %s already set as AWSCURRENT for secret %s." % (token, arn)) return elif "AWSPENDING" not in versions[token]: logger.error("Secret version %s not set as AWSPENDING for rotation of secret %s." % (token, arn)) raise ValueError("Secret version %s not set as AWSPENDING for rotation of secret %s." % (token, arn)) # Call the appropriate step if step == "createSecret": create_secret(service_client, arn, token) elif step == "setSecret": set_secret(service_client, arn, token) elif step == "testSecret": test_secret(service_client, arn, token) elif step == "finishSecret": finish_secret(service_client, arn, token) else: logger.error("lambda_handler: Invalid step parameter %s for secret %s" % (step, arn)) raise ValueError("Invalid step parameter %s for secret %s" % (step, arn)) def create_secret(service_client, arn, token): """Generate a new secret This method first checks for the existence of a secret for the passed in token. If one does not exist, it will generate a new secret and put it with the passed in token. Args: service_client (client): The secrets manager service client arn (string): The secret ARN or other identifier token (string): The ClientRequestToken associated with the secret version Raises: ValueError: If the current secret is not valid JSON KeyError: If the secret json does not contain the expected keys """ # Make sure the current secret exists current_dict = get_secret_dict(service_client, arn, "AWSCURRENT") # Now try to get the secret version, if that fails, put a new secret try: get_secret_dict(service_client, arn, "AWSPENDING", token) logger.info("createSecret: Successfully retrieved secret for %s." % arn) except service_client.exceptions.ResourceNotFoundException: # Generate a random password passwd = service_client.get_random_password(ExcludeCharacters='/@"\'\\') current_dict['password'] = passwd['RandomPassword'] # Put the secret service_client.put_secret_value(SecretId=arn, ClientRequestToken=token, SecretString=json.dumps(current_dict), VersionStages=['AWSPENDING']) logger.info("createSecret: Successfully put secret for ARN %s and version %s." % (arn, token)) def set_secret(service_client, arn, token): """Set the pending secret in the database This method tries to login to the database with the AWSPENDING secret and returns on success. If that fails, it tries to login with the AWSCURRENT and AWSPREVIOUS secrets. If either one succeeds, it sets the AWSPENDING password as the user password in the database. Else, it throws a ValueError. Args: service_client (client): The secrets manager service client arn (string): The secret ARN or other identifier token (string): The ClientRequestToken associated with the secret version Raises: ResourceNotFoundException: If the secret with the specified arn and stage does not exist ValueError: If the secret is not valid JSON or valid credentials are found to login to the database KeyError: If the secret json does not contain the expected keys """ # First try to login with the pending secret, if it succeeds, return pending_dict = get_secret_dict(service_client, arn, "AWSPENDING", token) conn = get_connection(pending_dict) if conn: conn.close() logger.info("setSecret: AWSPENDING secret is already set as password in MySQL DB for secret arn %s." % arn) return # Now try the current password conn = get_connection(get_secret_dict(service_client, arn, "AWSCURRENT")) if not conn: # If both current and pending do not work, try previous try: conn = get_connection(get_secret_dict(service_client, arn, "AWSPREVIOUS")) except service_client.exceptions.ResourceNotFoundException: conn = None # If we still don't have a connection, raise a ValueError if not conn: logger.error("setSecret: Unable to log into database with previous, current, or pending secret of secret arn %s" % arn) raise ValueError("Unable to log into database with previous, current, or pending secret of secret arn %s" % arn) # Now set the password to the pending password try: with conn.cursor() as cur: cur.execute("SET PASSWORD = PASSWORD(%s)", pending_dict['password']) conn.commit() logger.info("setSecret: Successfully set password for user %s in MySQL DB for secret arn %s." % (pending_dict['username'], arn)) finally: conn.close() def test_secret(service_client, arn, token): """Test the pending secret against the database This method tries to log into the database with the secrets staged with AWSPENDING and runs a permissions check to ensure the user has the corrrect permissions. Args: service_client (client): The secrets manager service client arn (string): The secret ARN or other identifier token (string): The ClientRequestToken associated with the secret version Raises: ResourceNotFoundException: If the secret with the specified arn and stage does not exist ValueError: If the secret is not valid JSON or valid credentials are found to login to the database KeyError: If the secret json does not contain the expected keys """ # Try to login with the pending secret, if it succeeds, return conn = get_connection(get_secret_dict(service_client, arn, "AWSPENDING", token)) if conn: # This is where the lambda will validate the user's permissions. Uncomment/modify the below lines to # tailor these validations to your needs try: with conn.cursor() as cur: cur.execute("SELECT NOW()") conn.commit() finally: conn.close() logger.info("testSecret: Successfully signed into MySQL DB with AWSPENDING secret in %s." % arn) return else: logger.error("testSecret: Unable to log into database with pending secret of secret ARN %s" % arn) raise ValueError("Unable to log into database with pending secret of secret ARN %s" % arn) def finish_secret(service_client, arn, token): """Finish the rotation by marking the pending secret as current This method finishes the secret rotation by staging the secret staged AWSPENDING with the AWSCURRENT stage. Args: service_client (client): The secrets manager service client arn (string): The secret ARN or other identifier token (string): The ClientRequestToken associated with the secret version """ # First describe the secret to get the current version metadata = service_client.describe_secret(SecretId=arn) current_version = None for version in metadata["VersionIdsToStages"]: if "AWSCURRENT" in metadata["VersionIdsToStages"][version]: if version == token: # The correct version is already marked as current, return logger.info("finishSecret: Version %s already marked as AWSCURRENT for %s" % (version, arn)) return current_version = version break # Finalize by staging the secret version current service_client.update_secret_version_stage(SecretId=arn, VersionStage="AWSCURRENT", MoveToVersionId=token, RemoveFromVersionId=current_version) logger.info("finishSecret: Successfully set AWSCURRENT stage to version %s for secret %s." % (version, arn)) def get_connection(secret_dict): """Gets a connection to MySQL DB from a secret dictionary This helper function tries to connect to the database grabbing connection info from the secret dictionary. If successful, it returns the connection, else None Args: secret_dict (dict): The Secret Dictionary Returns: Connection: The pymysql.connections.Connection object if successful. None otherwise Raises: KeyError: If the secret json does not contain the expected keys """ # Parse and validate the secret JSON string port = int(secret_dict['port']) if 'port' in secret_dict else 3306 dbname = secret_dict['dbname'] if 'dbname' in secret_dict else None # Try to obtain a connection to the db try: conn = pymysql.connect(secret_dict['host'], user=secret_dict['username'], passwd=secret_dict['password'], port=port, db=dbname, connect_timeout=5) return conn except pymysql.OperationalError: return None def get_secret_dict(service_client, arn, stage, token=None): """Gets the secret dictionary corresponding for the secret arn, stage, and token This helper function gets credentials for the arn and stage passed in and returns the dictionary by parsing the JSON string Args: service_client (client): The secrets manager service client arn (string): The secret ARN or other identifier token (string): The ClientRequestToken associated with the secret version, or None if no validation is desired stage (string): The stage identifying the secret version Returns: SecretDictionary: Secret dictionary Raises: ResourceNotFoundException: If the secret with the specified arn and stage does not exist ValueError: If the secret is not valid JSON """ required_fields = ['host', 'username', 'password'] # Only do VersionId validation against the stage if a token is passed in if token: secret = service_client.get_secret_value(SecretId=arn, VersionId=token, VersionStage=stage) else: secret = service_client.get_secret_value(SecretId=arn, VersionStage=stage) plaintext = secret['SecretString'] secret_dict = json.loads(plaintext) # Run validations against the secret if 'engine' not in secret_dict or secret_dict['engine'] != 'mysql': raise KeyError("Database engine must be set to 'mysql' in order to use this rotation lambda") for field in required_fields: if field not in secret_dict: raise KeyError("%s key is missing from secret JSON" % field) # Parse and return the secret JSON string return secret_dict