AWS: Boto3: AssumeRole example which includes role usage

Question

I'm trying to use the AssumeRole in such a way that i'm traversing multiple accounts and retrieving assets for those accounts. I've made it to this point:

import boto3
stsclient = boto3.client('sts')

assumedRoleObject = sts_client.assume_role(
RoleArn="arn:aws:iam::account-of-role-to-assume:role/name-of-role",
RoleSessionName="AssumeRoleSession1")

Great, i have the assumedRoleObject. But now i want to use that to list things like ELBs or something that isn't a built-in low level resource.

How does one go about doing that? If i may ask - please code out a full example, so that everyone can benefit.

Answer 1

You can assume role using STS token, like:

class Boto3STSService(object):
    def __init__(self, arn):
        sess = Session(aws_access_key_id=ARN_ACCESS_KEY,
                       aws_secret_access_key=ARN_SECRET_KEY)
        sts_connection = sess.client('sts')
        assume_role_object = sts_connection.assume_role(
            RoleArn=arn, RoleSessionName=ARN_ROLE_SESSION_NAME,
            DurationSeconds=3600)
        self.credentials = assume_role_object['Credentials']

This will give you temporary access key and secret keys, with session token. With these temporary credentials, you can access any service. For Eg, if you want to access ELB, you can use the below code:

self.tmp_credentials = Boto3STSService(arn).credentials

def get_boto3_session(self):
    tmp_access_key = self.tmp_credentials['AccessKeyId']
    tmp_secret_key = self.tmp_credentials['SecretAccessKey']
    security_token = self.tmp_credentials['SessionToken']

    boto3_session = Session(
        aws_access_key_id=tmp_access_key,
        aws_secret_access_key=tmp_secret_key, aws_session_token=security_token
    )
    return boto3_session

def get_elb_boto3_connection(self, region):
    sess = self.get_boto3_session()
    elb_conn = sess.client(service_name='elb', region_name=region)
    return elb_conn