keychain

#!/usr/bin/env ruby
#
# Example usage:
# $ ruby ~/bin/keychain USER@gmail.com imap.gmail.com
# => S3KRETZ
#
# ARGV[0] = 'Account' in Keychain.app
# ARGV[1] = 'Name' in Keychain.app
# On first use for any password, it will prompt for 'Always Allow', 'Deny', 'Allow [Once]'.
# If you want to use it without human interaction, you need to select Always Allow

require 'open3'

class Keychain
  attr_accessor :account, :name, :user

  BIN = '/usr/bin/security'

  def initialize(account, name, user = ENV['USER'])
    @account, @name, @user = account, name, user
  end

  def execute_command(cmd)
    o, e, s = Open3.capture3(cmd)
  end

  def extract_password(stderr)
    first_match = stderr.split("\n")
                        .grep(/password: /)
                        .first
    password = if first_match
                 first_match[/\Apassword: "(.*)"/]; $1
               else
                 nil
               end
  end

  def get_internet_password
    get_password(account, name, 'find-internet-password')
  end

  def get_generic_password
    get_password(account, name, 'find-generic-password')
  end

  def keychain
    "/Users/#{user}/Library/Keychains/login.keychain"
  end

  def get_password(account, name, type = 'find-internet-password')
    cmd = "#{BIN} -v #{type} -g -a #{account} -s #{name} #{keychain}"

    _, e, _ = execute_command(cmd)
    extract_password(e)
  end
end

def main
  account, name = ARGV.values_at(0, 1)

  key = Keychain.new(account, name)
  possible_passwords = key.get_internet_password || key.get_generic_password

  puts possible_passwords
end

main