Adding a Managed Policy to an IAM User

The following example adds the managed policy AmazonS3FullAccess to the IAM user my_groovy_user in the us-west-2 region.

# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
# SPDX - License - Identifier: Apache - 2.0

require 'aws-sdk-iam'

# Attaches a policy to a user in AWS Identity and Access Management (IAM).
#
# Prerequisites:
# - The user in IAM.
#
# @param iam [Aws::IAM::Client] An initialized IAM client.
# @param user_name [String] The name of the user.
# @param policy_arn [String] The Amazon Resource Name (ARN) of the policy.
# @return [Boolean] true if the policy was attached; otherwise, false.
# @example
#   exit 1 unless alias_created?(
#     Aws::IAM::Client.new,
#     'my-user',
#     'arn:aws:iam::aws:policy/AmazonS3FullAccess'
#   )
def policy_attached_to_user?(iam_client, user_name, policy_arn)
  iam_client.attach_user_policy(
    user_name: user_name,
    policy_arn: policy_arn
  )
  return true
rescue StandardError => e
  puts "Error attaching policy to user: #{e.message}"
  return false
end

# Full example call:
def run_me
  user_name = 'my-user'
  arn_prefix = 'arn:aws:iam::aws:policy/'
  policy_arn = arn_prefix + 'AmazonS3FullAccess'
  iam_client = Aws::IAM::Client.new

  puts "Attempting to attach policy with ARN '#{policy_arn}' to " \
    "user '#{user_name}'..."

  if policy_attached_to_user?(iam_client, user_name, policy_arn)
    puts 'Policy attached.'
  else
    puts 'Policy not attached.'
  end
end

run_me if $PROGRAM_NAME == __FILE__