Create read-only and read-write IAM users using an Amazon SDK

Create functions that wrap IAM user actions.

import logging
import time

import boto3
from botocore.exceptions import ClientError

import access_key_wrapper
import policy_wrapper

logger = logging.getLogger(__name__)
iam = boto3.resource("iam")

def create_user(user_name):
    """
    Creates a user. By default, a user has no permissions or access keys.

    :param user_name: The name of the user.
    :return: The newly created user.
    """
    try:
        user = iam.create_user(UserName=user_name)
        logger.info("Created user %s.", user.name)
    except ClientError:
        logger.exception("Couldn't create user %s.", user_name)
        raise
    else:
        return user



def update_user(user_name, new_user_name):
    """
    Updates a user's name.

    :param user_name: The current name of the user to update.
    :param new_user_name: The new name to assign to the user.
    :return: The updated user.
    """
    try:
        user = iam.User(user_name)
        user.update(NewUserName=new_user_name)
        logger.info("Renamed %s to %s.", user_name, new_user_name)
    except ClientError:
        logger.exception("Couldn't update name for user %s.", user_name)
        raise
    return user



def list_users():
    """
    Lists the users in the current account.

    :return: The list of users.
    """
    try:
        users = list(iam.users.all())
        logger.info("Got %s users.", len(users))
    except ClientError:
        logger.exception("Couldn't get users.")
        raise
    else:
        return users



def delete_user(user_name):
    """
    Deletes a user. Before a user can be deleted, all associated resources,
    such as access keys and policies, must be deleted or detached.

    :param user_name: The name of the user.
    """
    try:
        iam.User(user_name).delete()
        logger.info("Deleted user %s.", user_name)
    except ClientError:
        logger.exception("Couldn't delete user %s.", user_name)
        raise



def attach_policy(user_name, policy_arn):
    """
    Attaches a policy to a user.

    :param user_name: The name of the user.
    :param policy_arn: The Amazon Resource Name (ARN) of the policy.
    """
    try:
        iam.User(user_name).attach_policy(PolicyArn=policy_arn)
        logger.info("Attached policy %s to user %s.", policy_arn, user_name)
    except ClientError:
        logger.exception("Couldn't attach policy %s to user %s.", policy_arn, user_name)
        raise



def detach_policy(user_name, policy_arn):
    """
    Detaches a policy from a user.

    :param user_name: The name of the user.
    :param policy_arn: The Amazon Resource Name (ARN) of the policy.
    """
    try:
        iam.User(user_name).detach_policy(PolicyArn=policy_arn)
        logger.info("Detached policy %s from user %s.", policy_arn, user_name)
    except ClientError:
        logger.exception(
            "Couldn't detach policy %s from user %s.", policy_arn, user_name
        )
        raise

Create functions that wrap IAM policy actions.

import json
import logging
import operator
import pprint
import time

import boto3
from botocore.exceptions import ClientError

logger = logging.getLogger(__name__)
iam = boto3.resource("iam")

def create_policy(name, description, actions, resource_arn):
    """
    Creates a policy that contains a single statement.

    :param name: The name of the policy to create.
    :param description: The description of the policy.
    :param actions: The actions allowed by the policy. These typically take the
                    form of service:action, such as s3:PutObject.
    :param resource_arn: The Amazon Resource Name (ARN) of the resource this policy
                         applies to. This ARN can contain wildcards, such as
                         'arn:aws:s3:::my-bucket/*' to allow actions on all objects
                         in the bucket named 'my-bucket'.
    :return: The newly created policy.
    """
    policy_doc = {
        "Version": "2012-10-17",
        "Statement": [{"Effect": "Allow", "Action": actions, "Resource": resource_arn}],
    }
    try:
        policy = iam.create_policy(
            PolicyName=name,
            Description=description,
            PolicyDocument=json.dumps(policy_doc),
        )
        logger.info("Created policy %s.", policy.arn)
    except ClientError:
        logger.exception("Couldn't create policy %s.", name)
        raise
    else:
        return policy



def delete_policy(policy_arn):
    """
    Deletes a policy.

    :param policy_arn: The ARN of the policy to delete.
    """
    try:
        iam.Policy(policy_arn).delete()
        logger.info("Deleted policy %s.", policy_arn)
    except ClientError:
        logger.exception("Couldn't delete policy %s.", policy_arn)
        raise

Create functions that wrap IAM access key actions.

import logging
import boto3
from botocore.exceptions import ClientError

logger = logging.getLogger(__name__)

iam = boto3.resource("iam")

def create_key(user_name):
    """
    Creates an access key for the specified user. Each user can have a
    maximum of two keys.

    :param user_name: The name of the user.
    :return: The created access key.
    """
    try:
        key_pair = iam.User(user_name).create_access_key_pair()
        logger.info(
            "Created access key pair for %s. Key ID is %s.",
            key_pair.user_name,
            key_pair.id,
        )
    except ClientError:
        logger.exception("Couldn't create access key pair for %s.", user_name)
        raise
    else:
        return key_pair



def delete_key(user_name, key_id):
    """
    Deletes a user's access key.

    :param user_name: The user that owns the key.
    :param key_id: The ID of the key to delete.
    """

    try:
        key = iam.AccessKey(user_name, key_id)
        key.delete()
        logger.info("Deleted access key %s for %s.", key.id, key.user_name)
    except ClientError:
        logger.exception("Couldn't delete key %s for %s", key_id, user_name)
        raise

Use the wrapper functions to create users with differing policies and use their credentials to access an Amazon S3 bucket.

def usage_demo():
    """
    Shows how to manage users, keys, and policies.
    This demonstration creates two users: one user who can put and get objects in an
    Amazon S3 bucket, and another user who can only get objects from the bucket.
    The demo then shows how the users can perform only the actions they are permitted
    to perform.
    """
    logging.basicConfig(level=logging.INFO, format="%(levelname)s: %(message)s")
    print("-" * 88)
    print("Welcome to the AWS Identity and Account Management user demo.")
    print("-" * 88)
    print(
        "Users can have policies and roles attached to grant them specific "
        "permissions."
    )
    s3 = boto3.resource("s3")
    bucket = s3.create_bucket(
        Bucket=f"demo-iam-bucket-{time.time_ns()}",
        CreateBucketConfiguration={
            "LocationConstraint": s3.meta.client.meta.region_name
        },
    )
    print(f"Created an Amazon S3 bucket named {bucket.name}.")
    user_read_writer = create_user("demo-iam-read-writer")
    user_reader = create_user("demo-iam-reader")
    print(f"Created two IAM users: {user_read_writer.name} and {user_reader.name}")
    update_user(user_read_writer.name, "demo-iam-creator")
    update_user(user_reader.name, "demo-iam-getter")
    users = list_users()
    user_read_writer = next(
        user for user in users if user.user_id == user_read_writer.user_id
    )
    user_reader = next(user for user in users if user.user_id == user_reader.user_id)
    print(
        f"Changed the names of the users to {user_read_writer.name} "
        f"and {user_reader.name}."
    )

    read_write_policy = policy_wrapper.create_policy(
        "demo-iam-read-write-policy",
        "Grants rights to create and get an object in the demo bucket.",
        ["s3:PutObject", "s3:GetObject"],
        f"arn:aws:s3:::{bucket.name}/*",
    )
    print(
        f"Created policy {read_write_policy.policy_name} with ARN: {read_write_policy.arn}"
    )
    print(read_write_policy.description)
    read_policy = policy_wrapper.create_policy(
        "demo-iam-read-policy",
        "Grants rights to get an object from the demo bucket.",
        "s3:GetObject",
        f"arn:aws:s3:::{bucket.name}/*",
    )
    print(f"Created policy {read_policy.policy_name} with ARN: {read_policy.arn}")
    print(read_policy.description)
    attach_policy(user_read_writer.name, read_write_policy.arn)
    print(f"Attached {read_write_policy.policy_name} to {user_read_writer.name}.")
    attach_policy(user_reader.name, read_policy.arn)
    print(f"Attached {read_policy.policy_name} to {user_reader.name}.")

    user_read_writer_key = access_key_wrapper.create_key(user_read_writer.name)
    print(f"Created access key pair for {user_read_writer.name}.")
    user_reader_key = access_key_wrapper.create_key(user_reader.name)
    print(f"Created access key pair for {user_reader.name}.")

    s3_read_writer_resource = boto3.resource(
        "s3",
        aws_access_key_id=user_read_writer_key.id,
        aws_secret_access_key=user_read_writer_key.secret,
    )
    demo_object_key = f"object-{time.time_ns()}"
    demo_object = None
    while demo_object is None:
        try:
            demo_object = s3_read_writer_resource.Bucket(bucket.name).put_object(
                Key=demo_object_key, Body=b"AWS IAM demo object content!"
            )
        except ClientError as error:
            if error.response["Error"]["Code"] == "InvalidAccessKeyId":
                print("Access key not yet available. Waiting...")
                time.sleep(1)
            else:
                raise
    print(
        f"Put {demo_object_key} into {bucket.name} using "
        f"{user_read_writer.name}'s credentials."
    )

    read_writer_object = s3_read_writer_resource.Bucket(bucket.name).Object(
        demo_object_key
    )
    read_writer_content = read_writer_object.get()["Body"].read()
    print(f"Got object {read_writer_object.key} using read-writer user's credentials.")
    print(f"Object content: {read_writer_content}")

    s3_reader_resource = boto3.resource(
        "s3",
        aws_access_key_id=user_reader_key.id,
        aws_secret_access_key=user_reader_key.secret,
    )
    demo_content = None
    while demo_content is None:
        try:
            demo_object = s3_reader_resource.Bucket(bucket.name).Object(demo_object_key)
            demo_content = demo_object.get()["Body"].read()
            print(f"Got object {demo_object.key} using reader user's credentials.")
            print(f"Object content: {demo_content}")
        except ClientError as error:
            if error.response["Error"]["Code"] == "InvalidAccessKeyId":
                print("Access key not yet available. Waiting...")
                time.sleep(1)
            else:
                raise

    try:
        demo_object.delete()
    except ClientError as error:
        if error.response["Error"]["Code"] == "AccessDenied":
            print("-" * 88)
            print(
                "Tried to delete the object using the reader user's credentials. "
                "Got expected AccessDenied error because the reader is not "
                "allowed to delete objects."
            )
            print("-" * 88)

    access_key_wrapper.delete_key(user_reader.name, user_reader_key.id)
    detach_policy(user_reader.name, read_policy.arn)
    policy_wrapper.delete_policy(read_policy.arn)
    delete_user(user_reader.name)
    print(f"Deleted keys, detached and deleted policy, and deleted {user_reader.name}.")

    access_key_wrapper.delete_key(user_read_writer.name, user_read_writer_key.id)
    detach_policy(user_read_writer.name, read_write_policy.arn)
    policy_wrapper.delete_policy(read_write_policy.arn)
    delete_user(user_read_writer.name)
    print(
        f"Deleted keys, detached and deleted policy, and deleted {user_read_writer.name}."
    )

    bucket.objects.delete()
    bucket.delete()
    print(f"Emptied and deleted {bucket.name}.")
    print("Thanks for watching!")