Using passphrase callback in ruby gpgme

Question

I am using ruby gpgme gem (1.0.8). My passphrase callback isn't called:

def passfunc(*args)
  fd = args.last
  io = IO.for_fd(fd, 'w')
  io.puts "mypassphrase"
  io.flush
end

opts = {
  :passphrase_callback => method(:passfunc)
}
GPGME.decrypt(input,output, opts)

Does someone have working example of passphrase callback?

Answer 1

Sample of callback you can find in the following working example. It signs a file in detached mode, i.e., the signature file is separated from the original file. It uses the default keyring at ~/.gnupg or something like that. To use a different directory for your keyring, set the environment variable ENV["GNUPGHOME"]="" before call GPGME::sign().

#!/usr/bin/ruby
require 'rubygems'
require 'gpgme'

puts "Signing #{ARGV[0]}" 
input = File.open(ARGV[0],'r')

PASSWD = "abc"

def passfunc(hook, uid_hint, passphrase_info, prev_was_bad, fd)
    puts("Passphrase for #{uid_hint}: ")
    io = IO.for_fd(fd, 'w')
    io.write(PASSWD+"\n")
    io.flush
end

output = File.open(ARGV[0]+'.asc','w')

sign = GPGME::sign(input, {
        :passphrase_callback => method(:passfunc), 
        :mode => GPGME::SIG_MODE_DETACH
    })
output.write(sign)
output.close
input.close