A simple doveadm(1) pw "replacement" for BLF-CRYPT only

doveadm-pw-bcrypt.rb

#!/usr/bin/env ruby
# encoding: UTF-8

require 'bcrypt'
require 'optparse'
# see https://stackoverflow.com/questions/2338889/how-to-hide-password-input-from-terminal-in-ruby-script/11765329#11765329
require 'io/console'

options = {
  :cost   => 5,             # default, like doveadm
  :scheme   => 'BLF-CRYPT', # default, only one actually implemented
  :password => nil,
}

OptionParser.new do |opts|
  opts.banner = "usage: #$0 [options]"
  opts.on("-r ROUNDS", "number of rounds") do |r|
    n = r.to_i
    raise ArgumentError.new("#{r}: invalid number of round") unless n.between?(4, 31)
    options[:cost] = n
  end
  opts.on("-s SCHEME", "crypt scheme (only BLF-CRYPT is supported)") do |s|
    raise ArgumentError.new("#{s}: invalid scheme") unless s == 'BLF-CRYPT'
  end
  opts.on("-p password", "pass the password on the command line (insecure!)") do |p|
    options[:password] = p
  end
end.parse!

def interactive?
  STDIN.isatty
end

3.times do
  break if options[:password]
  STDERR.print 'Enter new password: ' if interactive?
  password = (interactive? ? STDIN.noecho(&:gets) : STDIN.gets)
  STDERR.puts if interactive?
  STDERR.print 'Retype new password: ' if interactive?
  repassword = (interactive? ? STDIN.noecho(&:gets) : STDIN.gets)
  STDERR.puts if interactive?
  if not password or not repassword
    # NOTE: doveadm behaviour, crypt an empty password when password or
    # repassword could not be read.
    options[:password] = ''
  elsif password.chomp! == repassword.chomp!
    options[:password] = password
  else
    STDERR.puts "Error: Passwords don't match!"
    # NOTE: doveadm behaviour, crypt an empty password when password and
    # repassword missmatch and it is not an interactive session.
    options[:password] = '' unless interactive?
  end
end

exit 1 unless options[:password]

bcrypted = BCrypt::Password.create(options[:password], cost: options[:cost])
STDOUT.printf "{%s}%s\n", options[:scheme], bcrypted.to_s

Gemfile

source 'https://rubygems.org'

gem 'bcrypt'

% bundle install && bundle exec ruby doveadm-pw-bcrypt.rb -r 10 -s BLF-CRYPT