This script converts an AWS secret access key into an SMTP password for SES.

ses-credential-generator.rb

#!/usr/bin/env ruby

require 'openssl'
require 'base64'
require 'io/console'

VERSION = "\x02".force_encoding('BINARY').freeze
MESSAGE = 'SendRawEmail'.freeze

digest = OpenSSL::Digest.new('sha256')

print 'Please enter your secret access key: '
key = nil
STDIN.noecho do
  key = gets.chomp
end

puts

signature = OpenSSL::HMAC.digest(digest, key, MESSAGE)

signature_with_version = VERSION + signature

smtp_password = Base64.encode64(signature_with_version).chomp

puts smtp_password

This is based on the algorithm documented here.