Assume IAM role and then generate pre-signed URL i

Question

I am trying to assume an IAM role and then use Amazon S3 by generating a presigned URL in order to access an S3 bucket in it. This is how I have configured my code in Python :

def create_dynamicurl(key, expiration):
    client = boto3.client('sts')
    assumed_role_object  = client.assume_role(DurationSeconds=3600,RoleArn='arn:aws:iam::123456789555:role/sample-S3AssumeRole',RoleSessionName='sampleSession',)
    temp_credentials = assumed_role_object['Credentials']
    s3_resource = boto3.resource('s3' , aws_access_key_id=temp_credentials['AccessKeyId'],aws_secret_access_key=temp_credentials['SecretAccessKey'],aws_session_token=temp_credentials['SessionToken'])
    bucket_name = s3_resource.bucket
    params = {
        'Bucket': bucket_name,
        'Key': key
    }
    s3 = boto3.client('s3')
    url = s3.generate_presigned_url('get_object', Params=params, ExpiresIn=expiration)
    log.info('******URL******: %s' % url)
    return (url)

Is this the correct approach??

I was getting the error botocore.exceptions.NoCredentialsError: Unable to locate credentials while running the code.

Answer 1

After you Assume Role, you can use the credentials like this:

sts_client = boto3.client('sts')
assumed_role_object  = sts_client.assume_role(DurationSeconds=3600,RoleArn='arn:aws:iam::123456789555:role/sample-S3AssumeRole',RoleSessionName='sampleSession',)
temp_credentials = assumed_role_object['Credentials']

session = Session(aws_access_key_id     = temp_credentials['AccessKeyId'],
                  aws_secret_access_key = temp_credentials['SecretAccessKey'],
                  aws_session_token     = temp_credentials['SessionToken'])

assumed_client = session.client('s3')
url = assumed_client.generate_presigned_url('get_object', Params=params, ExpiresIn=expiration)

I didn't test it, but you should get the general idea.

Answer 2

I made slight modification to John's answer and now its working as expected:

    def create_dynamicurl(bucket ,key, expiration):
     client = boto3.client('sts')
     assumed_role_object  = client.assume_role(DurationSeconds=3600,RoleArn=123456789555:role/sample-S3AssumeRole',RoleSessionName='sampleSession',)
    temp_credentials = assumed_role_object['Credentials']
    session = boto3.session.Session(aws_access_key_id=temp_credentials['AccessKeyId'],
                                    aws_secret_access_key=temp_credentials['SecretAccessKey'],
                                    aws_session_token=temp_credentials['SessionToken'])

    s3_resource = session.resource('s3')
    bucket_name = s3_resource.Bucket(bucket).name
    params = {
        'Bucket': bucket_name,
        'Key': key
    }
    s3 = boto3.client('s3')
    url = s3.generate_presigned_url('get_object', Params=params, ExpiresIn=expiration)
    log.info('******URL******: %s' % url)
    return (url)

@John , thank you for the inspiration.