roles-lambda.py

import boto3
'''

'''
def lambda_handler(context, event):

    sts_connection = boto3.client('sts')
    acct_b = sts_connection.assume_role(
        RoleArn="arn:aws:iam::ACCOUNTID:role/s3_read_only",
        RoleSessionName="cross_acct_lambda"
    )
    
    ACCESS_KEY = acct_b['Credentials']['AccessKeyId']
    SECRET_KEY = acct_b['Credentials']['SecretAccessKey']
    SESSION_TOKEN = acct_b['Credentials']['SessionToken']

    # create service client using the assumed role credentials, e.g. S3
    client = boto3.client(
        's3',
        aws_access_key_id=ACCESS_KEY,
        aws_secret_access_key=SECRET_KEY,
        aws_session_token=SESSION_TOKEN,
    )

    return "Hello from Lambda"