KMSArnCSVBuilderLambda.py

import boto3
from botocore.client import Config
from datetime import datetime, timedelta
import json


bucket = 'yours3bucket'
KeyArnKey = 'MyKMSArns.csv'

KMSClient = boto3.client('kms')

def lambda_handler(event, context):
    s3resource = boto3.resource('s3', config=Config(signature_version='s3v4'), region_name="us-east-1")
  
    AllKMSKeys = KMSClient.list_keys()
    
    KeyArnList = []
    for key in AllKMSKeys['Keys']:
        KeyARN = key['KeyArn']
        KeyArnList.append(KeyARN)

    locals3Client = boto3.client('s3', 
        config=Config(signature_version='s3v4'), 
        region_name="us-east-1"
    )

    KeyArnList = (json.dumps(KeyArnList)).replace("[","")
    KeyArnList = KeyArnList.replace("]","")
    KeyArnList = KeyArnList.replace(" ","")
    
    response = locals3Client.put_object(
        Body=KeyArnList,
        Bucket=bucket,
        Key=KeyArnKey,
        ContentEncoding='ascii'
    )