GPGME¶ ↑

This README is better viewed through the YARD formatted documentation: www.rubydoc.info/github/ueno/ruby-gpgme for latest github version, or www.rubydoc.info/gems/gpgme for latest gem release.

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Requirements¶ ↑

• Ruby 1.8 or later

• GPGME 1.1.2 or later

• gpg-agent (optional, but recommended)

Installation¶ ↑

$ gem install gpgme

API¶ ↑

GPGME provides three levels of API. The highest level API is as simple as it gets, the mid level API provides more functionality but might be less user-friendly, and the lowest level API is close to the C interface of GPGME.

The highest level API¶ ↑

For example, to create a cleartext signature of the plaintext from stdin and write the result to stdout can be written as follows.

crypto = GPGME::Crypto.new
crypto.clearsign $stdin, :output => $stdout

The mid level API¶ ↑

The same example can be rewritten in the mid level API as follows.

plain = GPGME::Data.new($stdin)
sig   = GPGME::Data.new($stdout)
GPGME::Ctx.new do |ctx|
  ctx.sign(plain, sig, GPGME::SIG_MODE_CLEAR)
end

The lowest level API¶ ↑

The same example can be rewritten in the lowest level API as follows.

ret = []
GPGME::gpgme_new(ret)
ctx = ret.shift
GPGME::gpgme_data_new_from_fd(ret, 0)
plain = ret.shift
GPGME::gpgme_data_new_from_fd(ret, 1)
sig = ret.shift
GPGME::gpgme_op_sign(ctx, plain, sig, GPGME::SIG_MODE_CLEAR)

As you see, it’s much harder to write a program in this API than the highest level API. However, if you are already familiar with the C interface of GPGME and want to control detailed behavior of GPGME, it might be useful.

Usage¶ ↑

All the high level methods attack the mid level GPGME::Ctx API. It is recommended to read through the GPGME::Ctx.new methods for common options.

Also, most of the input/output is done via GPGME::Data objects that create a common interface for reading/writing to normal strings, or other common objects like files. Read the GPGME::Data documentation to understand how it works. Every time the lib needs a GPGME::Data object, it will be automatically converted to it.

Crypto¶ ↑

The GPGME::Crypto class has the high level convenience methods to encrypt, decrypt, sign and verify signatures. Here are some examples, but it is recommended to read through the GPGME::Crypto class to see all the options.

• Document encryption via GPGME::Crypto#encrypt:

crypto = GPGME::Crypto.new
crypto.encrypt "Hello world!", :recipients => "someone@example.com"

• Symmetric encryption:

crypto = GPGME::Crypto.new :password => "gpgme"
crypto.encrypt "Hello world!", :symmetric => true

• Document decryption via GPGME::Crypto#decrypt (including signature verification):

crypto.decrypt File.open("text.gpg")

• Document signing via GPGME::Crypto#sign. Also the clearsigning and detached signing.

crypto.sign "I hereby proclaim Github the beneficiary of all my money when I die"

• Sign verification via GPGME::Crypto#verify

sign = crypto.sign "Some text"
data = crypto.verify(sign) { |signature| signature.valid? }

Key¶ ↑

The GPGME::Key object represents a key, and has the high level related methods to work with them and find them, export, import, deletetion and creation.

• Key listing

GPGME::Key.find(:secret, "someone@example.com")
# => Returns an array with all the secret keys available in the keychain.
#    that match "someone@example.com"

• Key exporting

GPGME::Key.export("someone@example.com")
# => Returns a GPGME::Data object with the exported key.

key = GPGME::Key.find(:secret, "someone@example.com").first
key.export
# => Returns a GPGME::Data object with the exported key.

• Key importing

GPGME::Key.import(File.open("my.key"))

• Key validation

GPGME::Key.valid?(public_key)
# => Returns wheter this key is valid or not

• TODO: Key generation

Engine¶ ↑

Provides three convenience methods to obtain information about the gpg engine one is currently using. For example:

• Getting current information

GPGME::Engine.info.first
     # => #<GPGME::EngineInfo:0x00000100d4fbd8
            @file_name="/usr/local/bin/gpg",
            @protocol=0,
            @req_version="1.3.0",
            @version="1.4.11">

• Changing home directory to work with different settings:

GPGME::Engine.home_dir = '/tmp'

Round trip example using keychain keys¶ ↑

Rather than importing the keys it’s possible to specify the recipient when performing crypto functions. Here’s a roundtrip example, and note that as this is for a console, the conf.echo = false line is to stop IRB complaining when echoing binary data

# Stop IRB echoing everything, which errors with binary data.
# Not required for production code
conf.echo = false

class PassphraseCallback
  def initialize(passphrase)
    @passphrase = passphrase
  end

  def call(*args)
    fd = args.last
    io = IO.for_fd(fd, 'w')
    io.puts(@passphrase)
    io.flush
  end
end

# recipients can be found using $ gpg --list-keys --homedir ./keychain_location
# pub   2048R/A1B2C3D4 2014-01-17
# Use that line to substitute your own. 2048R is the key length and type (RSA in this case)

# If you want to substitute a non-default keychain into the engine do this:
# home_dir = Rails.root.join('keychain_location').to_s
# GPGME::Engine.set_info(GPGME::PROTOCOL_OpenPGP, '/usr/local/bin/gpg', home_dir)
# Note GPG executable location will change across platforms

crypto = GPGME::Crypto.new
options = {:recipients => 'A1B2C3D4'}

plaintext = GPGME::Data.new(File.open(Rails.root.join('Gemfile')))

data = crypto.encrypt plaintext, options

f = File.open(Rails.root.join('Gemfile.gpg'), 'wb')
bytes_written = f.write(data)
f.close

puts bytes_written

crypto = GPGME::Crypto.new
options = {:recipients => 'A1B2C3D4', :passphrase_callback => PassphraseCallback.new('my_passphrase')}

cipthertext = GPGME::Data.new(File.open(Rails.root.join('Gemfile.gpg')))

data = crypto.decrypt cipthertext, options
puts data

Contributing¶ ↑

To run the local test suite you need bundler and gpg:

bundle
rake compile   # simple rake task to compile the extension
rake           # runs the test suite

License¶ ↑

The library itself is licensed under LGPLv2.1+. See the file COPYING.LESSER and each file for copyright and warranty information.