#!/usr/bin/ruby

=begin
Purpose: provide easy way to mangle auth parameters (un/pw)
Purpose/HL: painless migration from sendmail to vpopmail
Author: Michal Safranek <wejn@box.cz>
License: GPL v.2
Date: 20050715140500
Usage: printf "%s\0%s\0%s\0" wejnik kocicka Y123456 | \
	./chkpasswd-mangle ./aliases.yaml /var/vpopmail/bin/vchkpw id
	# aliases.yaml has "username: substitute\n" format (YAML's hash)
Requirements: Ruby/1.8.2 ( http://ruby-lang.org/ )
=end

require 'yaml'

if ARGV.size < 2
	# contract breached, throw temp error
	# we need: config program(s)
	Kernel.exit(111)
end

aliases = nil
aliases_file = ARGV.shift
run = ARGV

begin
	aliases = YAML.load_file(aliases_file)
	raise "bad config" unless aliases.respond_to?(:[])
rescue
	# bad config :(
	Kernel.exit(111)
end

begin
	input = IO.for_fd(3, 'r').read.split("\x0", -1)

	# Any mangling you can imagine can take place here.
	input[0] = aliases[input[0]] unless aliases[input[0]].nil?

	# ok, let's proxy it
	rd, wr = IO.pipe
	unless fork
		# child
		rd.close
		wr.write(input.join("\x0"))
		wr.close
	else
		# parent
		wr.close
		io = IO.for_fd(3, 'r').reopen(rd)
		exec(*run)
	end
rescue
	# Exception, thus throw temp error
	Kernel.exit(111)
end