Refresh AWS MFA credentials

refresh_aws_mfa_creds.rb

#! /usr/bin/env ruby

##
# Retrieve MFA credentials using the default profile and saving them to the mfa profile.
# Old credentials are removed in this process.
#

require 'json'

AWS_CREDS_FILE_PATH = File.join(ENV['HOME'], '.aws/credentials')

mfa_devices = `AWS_PROFILE=default aws iam list-mfa-devices`
device_serial_number = JSON.parse(mfa_devices)['MFADevices'][0]['SerialNumber']

print "MFA code: "
token_code = STDIN.gets.chomp

# puts token_code

raw_creds = `AWS_PROFILE=default aws sts get-session-token --duration-seconds 129600 --serial-number #{device_serial_number} --token-code #{token_code}`
creds = JSON.parse(raw_creds)['Credentials']

formatted_creds = "aws_access_key_id = #{creds['AccessKeyId']}\n" \
                  "aws_secret_access_key = #{creds['SecretAccessKey']}\n" \
                  "aws_session_token = #{creds['SessionToken']}\n"

current_creds_file_content = File.read(AWS_CREDS_FILE_PATH)
new_creds_file_content = current_creds_file_content.gsub(/(?<=\[mfa\]\n)([^\n]+\n){3}/, formatted_creds)

puts raw_creds
puts "==> New Credentials File with Expiration: #{creds['Expiration']}\n\n",
     new_creds_file_content

File.write(AWS_CREDS_FILE_PATH, new_creds_file_content)