cross account lambda

index.py

# Steps to use:
#  - For each account, create a cross-account role in the target account(s) -
#     in this case I called my role "bsi_lambda_full".  Make sure the target account
#     roles grant sufficient IAM privs for the operations in the Lambda fxn.
#  - The role that the Lambda account executes under in the master account only needs
#     to grant "sts:AssumeRole" to the "lambda.amazonaws.com" AWS principal.
#  - On each of the target account roles, specify the principal as the *ARN
#      of the role* that the Lambda executes under in the master account.
#  - Create an env var for the Lambda called "acct_nums", whose value is a
#      pipe-delimited ("|") list of account numbers, e.g. 000000000000|111111111111|222222222222
#  - Run it!

import os
import boto3

def lambda_handler(event, context):
    print(boto3.__version__)
    for acct_num in os.environ['acct_nums'].split("|"):
        client = boto3.client('sts')
        xa_req = client.assume_role(
            RoleArn='arn:aws:iam::'+acct_num+':role/bsi_lambda_full',
            RoleSessionName='bsi-lambda-'+acct_num
        )
        creds = xa_req['Credentials']
        ec2 = boto3.resource(
            'ec2',
            aws_access_key_id=creds['AccessKeyId'],
            aws_secret_access_key=creds['SecretAccessKey'],
            aws_session_token=creds['SessionToken'],
            region_name='us-west-2'
        )
        for i in range(0, 10):
            vol = ec2.create_volume(
                Size=20,
                AvailabilityZone='us-west-2b',
                VolumeType='gp2',
                Encrypted=False,
            )
            tags = ec2.create_tags(
                Resources=[vol.id],
                Tags=[
                    {
                        'Key': 'CreatedBy',
                        'Value': 'XALambda'
                    },
                    {
                        'Key': 'Iter',
                        'Value': str(i)
                    }
                ]
            )
    return 0