Ruby GPGME - How to encrypt large files

I'm having difficulty to Encrypt large files (bigger than available memory) using GPGME in Ruby.

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

def gpgfile(localfile)
  crypto = GPGME::Crypto.new
  filebasename = File.basename(localfile)
  filecripted = crypto.encrypt File.read(localfile), :recipients => "[email protected]", :always_trust => true
  File.open("#{localfile}.gpg", 'w') { |file| file.write(filecripted) }
end

gpgpfile("/home/largefile.data")

In this case I got an error of memory allocation: "read: failed to allocate memory (NoMemoryError)"

Someone can explain me how to read the source file chunk by chunk (of 100Mb for example) and write them passing by the crypting?

Solution

The most obvious problem is that you're reading the entire file into memory with File.read(localfile). The Crypto#encrypt method will take an IO object as its input, so instead of File.read(localfile) (which returns the contents of the file as a string) you can pass it a File object. Likewise, you can give an IO object as the :output option, letting you write the output directly to a file instead of in memory:

def gpgfile(localfile)
  infile = File.open(localfile, 'r')
  outfile = File.open("#{localfile}.gpg", 'w')

  crypto = GPGME::Crypto.new    
  crypto.encrypt(infile, recipients: "[email protected]",
                         output: outfile,
                         always_trust: true)
ensure
  infile.close
  outfile.close
end

I've never used ruby-gpgme, so I'm not 100% sure this will solve your problem since it depends a bit on what ruby-gpgme does behind the scenes, but from the docs and the source I've peeked at it seems like a sanely-built gem so I'm guessing this will do the trick.