From: Daniel Frank <ruby-talk-2597@...>
Date: 2010-01-17T20:22:55+09:00
Subject: GPGME gem - cannot figure out how to decrypt data

Hello,

I'm pretty new to ruby and this is my first real program I'm writing.
Currently I face an issue with the GPGME gem that I cannot figure out 
how to solve: The GPGME::decrypt method does not seem to work as I 
expect it, after reading the documentation.
In fact the program seems to hang somewhere during the decryption. My 
guess is that something is wrong with my passphrase callback method, but 
I cannot figure out how this needs to be done, as the examples for the 
gem does not contain a decryption example, only a signing example from 
which I have copied the passphrase callback method, but the method does 
not seem to work, as the callback method seems to be called with no 
arguments.

I have written a test script to work on this problem, it can be found at 
the end of the email.
When it hangs after the passphrase callback, after waiting about 10 
seconds I'm pressing ^C to interrupt the script. The output of the test 
script is as follows:
$ RUBYOPT=rubygems ruby test.rb
pwd:
xxx
encrypting
dumping to file
decrypting
Passphrase callback
^C/var/ruby/1.8/gem_home/gems/gpgme-1.0.8/lib/gpgme.rb:1212:in 
`decrypt_verify': Interrupt
         from 
/var/ruby/1.8/gem_home/gems/gpgme-1.0.8/lib/gpgme.rb:134:in `decrypt'
         from 
/var/ruby/1.8/gem_home/gems/gpgme-1.0.8/lib/gpgme.rb:943:in `new'
         from 
/var/ruby/1.8/gem_home/gems/gpgme-1.0.8/lib/gpgme.rb:130:in `decrypt'
         from test.rb:51:in `decrypt'
         from test.rb:43:in `run_test'
         from test.rb:33:in `initialize'
         from /usr/ruby/1.8/lib/ruby/1.8/singleton.rb:94:in `new'
         from /usr/ruby/1.8/lib/ruby/1.8/singleton.rb:94:in `instance'
         from test.rb:56

$ gpg --decrypt edata

You need a passphrase to unlock the secret key for
user: "xxxx xxxxxxxxxxxx <none@xxxx.xxxxxx.de>"
4096-bit RSA key, ID D2BBECEB, created 2010-01-12 (main key ID ADE8309D)

gpg: encrypted with 4096-bit RSA key, ID D2BBECEB, created 2010-01-12
       "xxxx xxxxxxxxxxxx <none@xxxx.xxxxxx.de>"
Dummy test data
Dummy test data
Dummy test data
Dummy test data
Dummy test data


The fact that gpg is able to decrypt the data shows that the encryption 
of the data is working perfectly fine, I just cannot figure out how to 
do the decryption in GPGME.
A google search for GPGME::decrypt did not help, I could not find 
anything besides the documentation of the module.





Script:
#!/usr/bin/env ruby

require 'singleton'
require 'gpgme'

class SMGConfig
         include Singleton
         attr_accessor :gpg_key
         attr_accessor :gpg_password
         def initialize()
                 @gpg_key = 'ADE8309D'
                 puts "pwd:"
                 @gpg_password = gets
         end
end

#def passfunc(hook, uid_hint, passphrase_info, prev_was_bad, fd)
#        config = SMGConfig.instance
#        puts "Passphrase callback"
#        io = IO.for_fd(fd, 'w')
#        io.puts(config.gpg_password)
#        io.flush
#end
def passfunc()
         SMGConfig.instance.gpg_password
end

class GPG
         include Singleton
         def initialize()
                 @config = SMGConfig.instance
                 run_test()
         end
         def run_test()
                 # Run a test if gpg is able to start and encrypt and 
decrypt data reliably with the known password
                 data = "Dummy test data\n" * 5
                 puts "encrypting"
                 edata = encrypt(data)
                 puts "dumping to file"
                 File.open('edata', 'w') { | f | f.write(edata) }
                 puts "decrypting"
                 ddata = decrypt(edata)
                 puts "GPG failed to initialize" if !(data.eql?(ddata))
                 puts "done run_test"
         end
         def encrypt(data)
                 edata = GPGME::encrypt(@config.gpg_key, data)
         end
         def decrypt(edata)
                 GPGME::decrypt(edata, { :passphrase_callback => passfunc })
         end
end

$stdout.sync = true
x = GPG.instance