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#--
# Copyright (c) 2009 Marc Dequènes (Duck) <Duck@DuckCorp.org>
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#
#++

require 'gpgme' # >= 1.0.2 needed for :always_trust sign option

# Attempt to handle PGP/GPG features in a RFC3156-compliant way
#
# notes: These methods have been designed to be able to sign, crypt,
# or sign+crypt with RFC 1847 Encapsulation. There is no
# support (yet?) for the combined method described in chapter
# 6.2 of RFC3156.
module TMail
class Mail
def is_pgp_signed?
content_type == "multipart/signed" and
header['content-type'].params['protocol'] == "application/pgp-signature" and
parts.size == 2 and
parts[1].content_type == "application/pgp-signature"
end

def pgp_signature
return nil unless is_pgp_signed?
parts[1].decoded
end

def pgp_signed_part
return nil unless is_pgp_signed?
parts[0]
end

def verify_pgp_signature
return nil unless is_pgp_signed?

content = parts[0].to_rfc3156
sig = pgp_signature()

sigs_check = nil
GPGME.verify(sig, content) do |signature|
sigs_check ||= []
sigs_check << signature
end

sigs_check
end

def is_pgp_encrypted?
content_type == "multipart/encrypted" and
header['content-type'].params['protocol'] == "application/pgp-encrypted" and
parts.size == 2 and
parts[0].content_type == "application/pgp-encrypted" and
parts[1].content_type == "application/octet-stream"
end

def pgp_crypt_info
return nil unless is_pgp_encrypted?
a = parts[0].body.split("\n").collect{|l| l.chomp.split(": ") if l =~ /: / }.compact.flatten
Hash[*a]
end

def pgp_encrypted_part
return nil unless is_pgp_encrypted?
parts[1].body
end

def pgp_decrypt(&passphrase_callback)
return nil unless is_pgp_encrypted?
protocol_version = pgp_crypt_info()["Version"].to_i
raise NotImplementedError, "pgp-encrypted protocol version #{protocol_version} is not implemented" unless protocol_version == 1

encrypted_data = pgp_encrypted_part()
GPGME.decrypt(encrypted_data, {:passphrase_callback => method(:gpg_passphrase_callback_wrapper),
:passphrase_callback_value => passphrase_callback, :textmode => true})
end

def pgp_crypt(crypters_id)
crypters_id = [crypters_id] unless crypters_id.is_a? Array
crypters = crypters_id.collect{|key_id| gpg_key(key_id, false) }
GPGME.encrypt(crypters, self.to_s, {:armor => true, :always_trust => true})
end

def pgp_sign(signers_id, &passphrase_callback)
signers_id = [signers_id] unless signers_id.is_a? Array
signers = signers_id.collect{|key_id| gpg_key(key_id, true) }
# we don't use GPGME.sign(), because we need to get operation information to get the hash_algo and compute the micalg parameter
gpg = GPGME::Ctx.new({:signers => signers, :passphrase_callback => method(:gpg_passphrase_callback_wrapper),
:passphrase_callback_value => passphrase_callback, :armor => true})
gpg.add_signer(*signers)
sig_data = GPGME::Data.new
gpg.sign(GPGME::Data.new(self.to_rfc3156), sig_data, GPGME::SIG_MODE_NORMAL)
hash_algo = GPGME.gpgme_op_sign_result(gpg).signatures.first.hash_algo
micalg = "pgp-" + GPGME.gpgme_hash_algo_name(hash_algo).downcase
sig_data.seek(0, IO::SEEK_SET)
{:signature => sig_data.read, :micalg => micalg}
end

def to_rfc3156
# using RAW part, without any decoding
# remove last EOL due to MIME protocol and properly convert all EOL to CRLF
raw.chomp.gsub(/\r?\n/, "\r\n")
end

def create_encrypted(crypters_id)
clear_data = build_intermediate_mail()
encrypted_data = clear_data.pgp_crypt(crypters_id)

# build properly encrypted mail
# (preserving headers from original mail)
mail = TMail::Mail.new
mail.copy_headers_from(self)
mail.set_content_type("multipart", "encrypted", {'boundary' => TMail.new_boundary, "protocol" => "application/pgp-encrypted"})
mail.transfer_encoding = "7bit"
mail['content-disposition'] = nil
mail.body = "This mail is a RFC3156 encrypted message.\n"
mail.parts.clear

# cryptographic info
p_pgp = TMail::Mail.new
p_pgp.set_content_type("application", "pgp-encrypted")
p_pgp.transfer_encoding = "7bit"
p_pgp.content_disposition = "inline"
p_pgp.body = "Version: 1\n"
mail.parts << p_pgp

# encrypted message
p_encrypted = TMail::Mail.new
p_encrypted.set_content_type("application", "octet-stream")
p_encrypted.transfer_encoding = "7bit"
p_encrypted.content_disposition = "inline"
p_encrypted.body = encrypted_data
mail.parts << p_encrypted

# store the calculated content, to be able to use parsing methods
mail.write_back

mail
end

def create_signed(signers_id)
data = build_intermediate_mail()
sign_data = data.pgp_sign(signers_id) do |uid_hint, passphrase_info, prev_was_bad|
yield(uid_hint, passphrase_info, prev_was_bad)
end

# build properly signed mail
# (preserving headers from original mail)
mail = TMail::Mail.new
mail.copy_headers_from(self)
mail.set_content_type("multipart", "signed", {'boundary' => TMail.new_boundary, 'protocol' => "application/pgp-signature", 'micalg' => sign_data[:micalg]})
mail.transfer_encoding = "7bit"
mail['content-disposition'] = nil
mail.body = "This mail is a RFC3156 signed message.\n"
mail.parts.clear

# signed message
p_signed = data
mail.parts << p_signed

# signature
p_signature = TMail::Mail.new
p_signature.set_content_type("application", "pgp-signature")
p_signature.transfer_encoding = "7bit"
p_signature.content_disposition = "inline"
p_signature.body = sign_data[:signature]
mail.parts << p_signature

# store the calculated content, to be able to use parsing methods
mail.write_back

mail
end

def create_signed_and_encrypted(signers_id, crypters_id)
create_signed(signers_id) do |uid_hint, passphrase_info, prev_was_bad|
yield(uid_hint, passphrase_info, prev_was_bad)
end.create_encrypted(crypters_id)
end

def copy_headers_from(mail)
mail.header.keys.each do |h|
self[h] = mail[h].to_s
end
end

protected

def build_intermediate_mail
# build a fake mail to get the generated content to be crypted/signed
fake_mail = TMail::Mail.new
fake_mail['content-type'] = self['content-type'].to_s
fake_mail.transfer_encoding = self.transfer_encoding if self.transfer_encoding
fake_mail.content_disposition = self.content_disposition if self.content_disposition
if self.multipart?
self.each_part {|p| fake_mail.parts << p }
else
fake_mail.body = self.body
end

# store the calculated content, to be able to use parsing methods
fake_mail.write_back

fake_mail
end

def gpg_key(fingerprint, secret = false)
gpg = GPGME::Ctx.new
gpg.get_key(fingerprint, secret)
end

def gpg_passphrase_callback_wrapper(hook, uid_hint, passphrase_info, prev_was_bad, fd)
io = IO.for_fd(fd, 'w')
io.puts hook.call(uid_hint, passphrase_info, prev_was_bad)
io.flush
end

def raw
@port.read_all
end
end
end
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