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import logging
import tempfile
import email
from email.message import Message
from email.header import Header
from email.MIMEMultipart import MIMEMultipart
from email.parser import Parser
from StringIO import StringIO
import gnupg
logger = logging.getLogger(__name__)
COPY_HEADERS = ('Subject', 'Message-ID', 'Date', 'To', 'From')
class MemoryHoleHeader(Header):
def __init__(self, name, value):
self._name = name
self._value = value
self._h = Header(value, header_name=name)
self.signed_by = set([])
self.encrypted_by = set([])
self._firstlinelen = self._h._firstlinelen
self._chunks = self._h._chunks
self._continuation_ws = self._h._continuation_ws
self._charset = self._h._charset
@property
def protection_level(self):
return ProtectionLevel(self.signed_by, self.encrypted_by)
def __repr__(self):
return '<MemoryHoleHeader(%s) [%s: %s]>' % (
self.protection_level.score, self._name, self._value)
class MemoryHoleMessage(Message):
def __init__(self, msg, gpg):
self._msg = msg
self._gpg = gpg
verified = verify_signature(msg, gpg)
self.signed = verified.valid
self._mh_headers = {}
inner_headers = extract_wrapped_headers(msg)
for name, value in inner_headers.items():
mhh = MemoryHoleHeader(name, value)
mhh.signed_by.add(verified.key_id)
self._mh_headers[name] = mhh
self._charset = self._msg._charset
self._headers = self._msg._headers
self._payload = self._msg._payload
self.preamble = self._msg.preamble
def get_protected_header(self, header_name):
return self._mh_headers.get(header_name)
# TODO add is_tampered_header
# TODO add __getattr__, lookup the protected headers first
def extract_wrapped_headers(msg):
top_payload = msg.get_payload()[0]
if top_payload.get_content_type() == 'multipart/mixed':
headers = _extract_attached_headers(top_payload)
return headers
def verify_signature(msg, gpg):
if not msg.get_content_type() == 'multipart/signed':
logger.error('attempted to verify signature, but msg is not signed')
return False
payloads = msg.get_payload()
body = payloads[0]
attached_sig = payloads[1]
if not attached_sig.get_content_type() == 'application/pgp-signature':
logger.error('expected an attached signature')
return False
sig = _extract_sig_block(attached_sig.as_string())
fd, sig_fname = tempfile.mkstemp()
with open(sig_fname, 'w') as sigfile:
sigfile.write(sig)
body = body.as_string().replace('\n', '\r\n')
verified = gpg.verify_file(StringIO(body), sig_file=sig_fname)
return verified
def protect_message(basemsg, gpg, do_sign=True, boundary=None,
sign_digest_algo='SHA512', passphrase=None):
msg = email.message.Message()
_msg = MIMEMultipart(
_subtype="signed", micalg="pgp-%s" % sign_digest_algo.lower(),
protocol="application/pgp-signature")
for hdr in COPY_HEADERS:
msg[hdr] = basemsg[hdr]
for hdr in _msg.keys():
msg[hdr] = _msg[hdr]
if boundary:
msg.set_boundary(boundary())
wrapper = _wrap_with_header(basemsg, boundary=boundary)
msg.attach(wrapper)
if do_sign:
payload = wrapper.as_string().replace('\n', '\r\n')
sig = gpg.sign(
payload, detach=True,
digest_algo=sign_digest_algo, clearsign=False,
passphrase=passphrase)
signed_msg = _make_signature_subpart(sig)
msg.attach(signed_msg)
return msg
def _extract_sig_block(text):
sep = '\n'
BEGIN = '-----BEGIN PGP SIGNATURE-----'
sig_lines = text.split(sep)
return sep.join(sig_lines[sig_lines.index(BEGIN):])
def _extract_attached_headers(msg):
def split_header(line):
sep = ': '
split = line.split(sep)
return (split[0], sep.join(split[1:]))
first = msg.get_payload()[0]
if first.get_content_type() == 'text/rfc822-headers':
raw = first.get_payload()
headers = dict([
split_header(line) for line in filter(None, raw.split('\n'))])
return headers
def _build_embedded_header(msg):
r = ''
for x in COPY_HEADERS:
if msg.get(x):
r += x + ': ' + msg.get(x) + '\n'
return r
def _boundary_factory(start):
counter = {'value': ord(start)}
def _gen_boundary():
boundary = chr(counter['value']) * 12
counter['value'] -= 1
return boundary
return _gen_boundary
def _wrap_with_header(msg, boundary=None):
body = email.message.Message()
body.set_payload(msg.get_payload())
body.add_header('Content-Type', msg['Content-Type'])
emh = email.message.Message()
emh.set_type('text/rfc822-headers')
emh.add_header('Content-Disposition', 'attachment')
emh.set_payload(_build_embedded_header(msg))
del emh['MIME-Version']
wrapper = email.message.Message()
wrapper.set_type('multipart/mixed')
if boundary:
wrapper.set_boundary(boundary())
wrapper.set_payload([emh, body])
del wrapper['MIME-Version']
return wrapper
def _make_signature_subpart(signature):
message = Message()
message['Content-Type'] = 'application/pgp-signature; name="signature.asc"'
message.set_payload(str(signature))
return message
if __name__ == "__main__":
import os
import sys
import logging
if os.environ.get('DEBUG'):
logging.basicConfig(level=logging.DEBUG)
if len(sys.argv) != 3:
print("Usage: memoryhole mail_path key_path")
sys.exit()
msg_path = sys.argv[1]
key_path = sys.argv[2]
parser = Parser()
gpg = gnupg.GPG(
binary='/usr/bin/gpg',
homedir='/tmp/memoryhole-tests/', use_agent=False)
with open('tests/corpus/OpenPGP/' + key_path + '.key') as key_f:
key_data = key_f.read()
gpg.import_keys(key_data)
with open('tests/corpus/OpenPGP/' + key_path + '.pgp') as key_f:
key_data = key_f.read()
gpg.import_keys(key_data)
# if not gpg.list_keys():
# key_input = gpg.gen_key_input(key_length=1024, key_type='RSA')
# gpg.gen_key(key_input)
with open(msg_path) as f:
basetext = f.read()
basemsg = parser.parsestr(basetext)
boundary = _boundary_factory('c')
msg = protect_message(
basemsg, gpg, boundary=boundary,
sign_digest_algo='SHA256', passphrase='_' + key_path + '_')
print msg.as_string()
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