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-rw-r--r--src/leap/mail/smtp/rfc3156.py379
-rw-r--r--src/leap/mail/smtp/smtprelay.py140
2 files changed, 478 insertions, 41 deletions
diff --git a/src/leap/mail/smtp/rfc3156.py b/src/leap/mail/smtp/rfc3156.py
new file mode 100644
index 0000000..dd48475
--- /dev/null
+++ b/src/leap/mail/smtp/rfc3156.py
@@ -0,0 +1,379 @@
+# -*- coding: utf-8 -*-
+# rfc3156.py
+# Copyright (C) 2013 LEAP
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+"""
+Implements RFC 3156: MIME Security with OpenPGP.
+"""
+
+import re
+import base64
+from abc import ABCMeta, abstractmethod
+from StringIO import StringIO
+
+from email.mime.application import MIMEApplication
+from email.mime.multipart import MIMEMultipart
+from email import errors
+from email.generator import (
+ Generator,
+ fcre,
+ NL,
+ _make_boundary,
+)
+
+
+#
+# A generator that solves http://bugs.python.org/issue14983
+#
+
+class RFC3156CompliantGenerator(Generator):
+ """
+ An email generator that addresses Python's issue #14983 for multipart
+ messages.
+
+ This is just a copy of email.generator.Generator which fixes the following
+ bug: http://bugs.python.org/issue14983
+ """
+
+ def _handle_multipart(self, msg):
+ """
+ A multipart handling implementation that addresses issue #14983.
+
+ This is just a copy of the parent's method which fixes the following
+ bug: http://bugs.python.org/issue14983 (see the line marked with
+ "(***)").
+
+ :param msg: The multipart message to be handled.
+ :type msg: email.message.Message
+ """
+ # The trick here is to write out each part separately, merge them all
+ # together, and then make sure that the boundary we've chosen isn't
+ # present in the payload.
+ msgtexts = []
+ subparts = msg.get_payload()
+ if subparts is None:
+ subparts = []
+ elif isinstance(subparts, basestring):
+ # e.g. a non-strict parse of a message with no starting boundary.
+ self._fp.write(subparts)
+ return
+ elif not isinstance(subparts, list):
+ # Scalar payload
+ subparts = [subparts]
+ for part in subparts:
+ s = StringIO()
+ g = self.clone(s)
+ g.flatten(part, unixfrom=False)
+ msgtexts.append(s.getvalue())
+ # BAW: What about boundaries that are wrapped in double-quotes?
+ boundary = msg.get_boundary()
+ if not boundary:
+ # Create a boundary that doesn't appear in any of the
+ # message texts.
+ alltext = NL.join(msgtexts)
+ boundary = _make_boundary(alltext)
+ msg.set_boundary(boundary)
+ # If there's a preamble, write it out, with a trailing CRLF
+ if msg.preamble is not None:
+ preamble = msg.preamble
+ if self._mangle_from_:
+ preamble = fcre.sub('>From ', msg.preamble)
+ self._fp.write(preamble + '\n')
+ # dash-boundary transport-padding CRLF
+ self._fp.write('--' + boundary + '\n')
+ # body-part
+ if msgtexts:
+ self._fp.write(msgtexts.pop(0))
+ # *encapsulation
+ # --> delimiter transport-padding
+ # --> CRLF body-part
+ for body_part in msgtexts:
+ # delimiter transport-padding CRLF
+ self._fp.write('\n--' + boundary + '\n')
+ # body-part
+ self._fp.write(body_part)
+ # close-delimiter transport-padding
+ self._fp.write('\n--' + boundary + '--' + '\n') # (***) Solve #14983
+ if msg.epilogue is not None:
+ self._fp.write('\n')
+ epilogue = msg.epilogue
+ if self._mangle_from_:
+ epilogue = fcre.sub('>From ', msg.epilogue)
+ self._fp.write(epilogue)
+
+
+#
+# Base64 encoding: these are almost the same as python's email.encoder
+# solution, but a bit modified.
+#
+
+def _bencode(s):
+ """
+ Encode C{s} in base64.
+
+ :param s: The string to be encoded.
+ :type s: str
+ """
+ # We can't quite use base64.encodestring() since it tacks on a "courtesy
+ # newline". Blech!
+ if not s:
+ return s
+ value = base64.encodestring(s)
+ return value[:-1]
+
+
+def encode_base64(msg):
+ """
+ Encode a non-multipart message's payload in Base64 (in place).
+
+ This method modifies the message contents in place and adds or replaces an
+ appropriate Content-Transfer-Encoding header.
+
+ :param msg: The non-multipart message to be encoded.
+ :type msg: email.message.Message
+ """
+ orig = msg.get_payload()
+ encdata = _bencode(orig)
+ msg.set_payload(encdata)
+ # replace or set the Content-Transfer-Encoding header.
+ try:
+ msg.replace_header('Content-Transfer-Encoding', 'base64')
+ except KeyError:
+ msg['Content-Transfer-Encoding'] = 'base64'
+
+
+def encode_base64_rec(msg):
+ """
+ Encode (possibly multipart) messages in base64 (in place).
+
+ This method modifies the message contents in place.
+
+ :param msg: The non-multipart message to be encoded.
+ :type msg: email.message.Message
+ """
+ if not msg.is_multipart():
+ encode_base64(msg)
+ else:
+ for sub in msg.get_payload():
+ encode_base64_rec(sub)
+
+
+#
+# RFC 1847: multipart/signed and multipart/encrypted
+#
+
+class MultipartSigned(MIMEMultipart):
+ """
+ Multipart/Signed MIME message according to RFC 1847.
+
+ 2.1. Definition of Multipart/Signed
+
+ (1) MIME type name: multipart
+ (2) MIME subtype name: signed
+ (3) Required parameters: boundary, protocol, and micalg
+ (4) Optional parameters: none
+ (5) Security considerations: Must be treated as opaque while in
+ transit
+
+ The multipart/signed content type contains exactly two body parts.
+ The first body part is the body part over which the digital signature
+ was created, including its MIME headers. The second body part
+ contains the control information necessary to verify the digital
+ signature. The first body part may contain any valid MIME content
+ type, labeled accordingly. The second body part is labeled according
+ to the value of the protocol parameter.
+
+ When the OpenPGP digital signature is generated:
+
+ (1) The data to be signed MUST first be converted to its content-
+ type specific canonical form. For text/plain, this means
+ conversion to an appropriate character set and conversion of
+ line endings to the canonical <CR><LF> sequence.
+
+ (2) An appropriate Content-Transfer-Encoding is then applied; see
+ section 3. In particular, line endings in the encoded data
+ MUST use the canonical <CR><LF> sequence where appropriate
+ (note that the canonical line ending may or may not be present
+ on the last line of encoded data and MUST NOT be included in
+ the signature if absent).
+
+ (3) MIME content headers are then added to the body, each ending
+ with the canonical <CR><LF> sequence.
+
+ (4) As described in section 3 of this document, any trailing
+ whitespace MUST then be removed from the signed material.
+
+ (5) As described in [2], the digital signature MUST be calculated
+ over both the data to be signed and its set of content headers.
+
+ (6) The signature MUST be generated detached from the signed data
+ so that the process does not alter the signed data in any way.
+ """
+
+ def __init__(self, protocol, micalg, boundary=None, _subparts=None):
+ """
+ Initialize the multipart/signed message.
+
+ :param boundary: the multipart boundary string. By default it is
+ calculated as needed.
+ :type boundary: str
+ :param _subparts: a sequence of initial subparts for the payload. It
+ must be an iterable object, such as a list. You can always
+ attach new subparts to the message by using the attach() method.
+ :type _subparts: iterable
+ """
+ MIMEMultipart.__init__(
+ self, _subtype='signed', boundary=boundary,
+ _subparts=_subparts)
+ self.set_param('protocol', protocol)
+ self.set_param('micalg', micalg)
+
+ def attach(self, payload):
+ """
+ Add the C{payload} to the current payload list.
+
+ Also prevent from adding payloads with wrong Content-Type and from
+ exceeding a maximum of 2 payloads.
+
+ :param payload: The payload to be attached.
+ :type payload: email.message.Message
+ """
+ # second payload's content type must be equal to the protocol
+ # parameter given on object creation
+ if len(self.get_payload()) == 1:
+ if payload.get_content_type() != self.get_param('protocol'):
+ raise errors.MultipartConversionError(
+ 'Wrong content type %s.' % payload.get_content_type)
+ # prevent from adding more payloads
+ if len(self._payload) == 2:
+ raise errors.MultipartConversionError(
+ 'Cannot have more than two subparts.')
+ MIMEMultipart.attach(self, payload)
+
+
+class MultipartEncrypted(MIMEMultipart):
+ """
+ Multipart/encrypted MIME message according to RFC 1847.
+
+ 2.2. Definition of Multipart/Encrypted
+
+ (1) MIME type name: multipart
+ (2) MIME subtype name: encrypted
+ (3) Required parameters: boundary, protocol
+ (4) Optional parameters: none
+ (5) Security considerations: none
+
+ The multipart/encrypted content type contains exactly two body parts.
+ The first body part contains the control information necessary to
+ decrypt the data in the second body part and is labeled according to
+ the value of the protocol parameter. The second body part contains
+ the data which was encrypted and is always labeled
+ application/octet-stream.
+ """
+
+ def __init__(self, protocol, boundary=None, _subparts=None):
+ """
+ :param protocol: The encryption protocol to be added as a parameter to
+ the Content-Type header.
+ :type protocol: str
+ :param boundary: the multipart boundary string. By default it is
+ calculated as needed.
+ :type boundary: str
+ :param _subparts: a sequence of initial subparts for the payload. It
+ must be an iterable object, such as a list. You can always
+ attach new subparts to the message by using the attach() method.
+ :type _subparts: iterable
+ """
+ MIMEMultipart.__init__(
+ self, _subtype='encrypted', boundary=boundary,
+ _subparts=_subparts)
+ self.set_param('protocol', protocol)
+
+ def attach(self, payload):
+ """
+ Add the C{payload} to the current payload list.
+
+ Also prevent from adding payloads with wrong Content-Type and from
+ exceeding a maximum of 2 payloads.
+
+ :param payload: The payload to be attached.
+ :type payload: email.message.Message
+ """
+ # first payload's content type must be equal to the protocol parameter
+ # given on object creation
+ if len(self._payload) == 0:
+ if payload.get_content_type() != self.get_param('protocol'):
+ raise errors.MultipartConversionError(
+ 'Wrong content type.')
+ # second payload is always application/octet-stream
+ if len(self._payload) == 1:
+ if payload.get_content_type() != 'application/octet-stream':
+ raise errors.MultipartConversionError(
+ 'Wrong content type %s.' % payload.get_content_type)
+ # prevent from adding more payloads
+ if len(self._payload) == 2:
+ raise errors.MultipartConversionError(
+ 'Cannot have more than two subparts.')
+ MIMEMultipart.attach(self, payload)
+
+
+#
+# RFC 3156: application/pgp-encrypted, application/pgp-signed and
+# application-pgp-signature.
+#
+
+class PGPEncrypted(MIMEApplication):
+ """
+ Application/pgp-encrypted MIME media type according to RFC 3156.
+
+ * MIME media type name: application
+ * MIME subtype name: pgp-encrypted
+ * Required parameters: none
+ * Optional parameters: none
+ """
+
+ def __init__(self, version=1):
+ data = "Version: %d" % version
+ MIMEApplication.__init__(self, data, 'pgp-encrypted')
+
+
+class PGPSignature(MIMEApplication):
+ """
+ Application/pgp-signature MIME media type according to RFC 3156.
+
+ * MIME media type name: application
+ * MIME subtype name: pgp-signature
+ * Required parameters: none
+ * Optional parameters: none
+ """
+ def __init__(self, _data, name='signature.asc'):
+ MIMEApplication.__init__(self, _data, 'pgp-signature',
+ _encoder=lambda x: x, name=name)
+ self.add_header('Content-Description', 'OpenPGP Digital Signature')
+
+
+class PGPKeys(MIMEApplication):
+ """
+ Application/pgp-keys MIME media type according to RFC 3156.
+
+ * MIME media type name: application
+ * MIME subtype name: pgp-keys
+ * Required parameters: none
+ * Optional parameters: none
+ """
+
+ def __init__(self, _data):
+ MIMEApplication.__init__(self, _data, 'pgp-keys')
diff --git a/src/leap/mail/smtp/smtprelay.py b/src/leap/mail/smtp/smtprelay.py
index 96eaa31..d9bbbf9 100644
--- a/src/leap/mail/smtp/smtprelay.py
+++ b/src/leap/mail/smtp/smtprelay.py
@@ -19,24 +19,38 @@
LEAP SMTP encrypted relay.
"""
-from zope.interface import implements
+import re
from StringIO import StringIO
+from email.Header import Header
+from email.utils import parseaddr
+from email.parser import Parser
+from email.mime.application import MIMEApplication
+
+from zope.interface import implements
from OpenSSL import SSL
from twisted.mail import smtp
from twisted.internet.protocol import ServerFactory
from twisted.internet import reactor, ssl
from twisted.internet import defer
from twisted.python import log
-from email.Header import Header
-from email.utils import parseaddr
-from email.parser import Parser
-
from leap.common.check import leap_assert, leap_assert_type
from leap.common.events import proto, signal
from leap.keymanager import KeyManager
from leap.keymanager.openpgp import OpenPGPKey
from leap.keymanager.errors import KeyNotFound
+from leap.mail.smtp.rfc3156 import (
+ MultipartSigned,
+ MultipartEncrypted,
+ PGPEncrypted,
+ PGPSignature,
+ RFC3156CompliantGenerator,
+ encode_base64_rec,
+)
+
+# replace email generator with a RFC 3156 compliant one.
+from email import generator
+generator.Generator = RFC3156CompliantGenerator
#
@@ -260,7 +274,8 @@ class SMTPDelivery(object):
raise smtp.SMTPBadRcpt(user.dest.addrstr)
log.msg("Warning: will send an unencrypted message (because "
"encrypted_only' is set to False).")
- signal(proto.SMTP_RECIPIENT_ACCEPTED_UNENCRYPTED, user.dest.addrstr)
+ signal(
+ proto.SMTP_RECIPIENT_ACCEPTED_UNENCRYPTED, user.dest.addrstr)
return lambda: EncryptedMessage(
self._origin, user, self._km, self._config)
@@ -303,6 +318,16 @@ class CtxFactory(ssl.ClientContextFactory):
return ctx
+def move_headers(origmsg, newmsg):
+ headers = origmsg.items()
+ unwanted_headers = ['content-type', 'mime-version', 'content-disposition',
+ 'content-transfer-encoding']
+ headers = filter(lambda x: x[0].lower() not in unwanted_headers, headers)
+ for hkey, hval in headers:
+ newmsg.add_header(hkey, hval)
+ del(origmsg[hkey])
+
+
class EncryptedMessage(object):
"""
Receive plaintext from client, encrypt it and send message to a
@@ -343,6 +368,10 @@ class EncryptedMessage(object):
# initialize list for message's lines
self.lines = []
+ #
+ # methods from smtp.IMessage
+ #
+
def lineReceived(self, line):
"""
Handle another line.
@@ -360,9 +389,8 @@ class EncryptedMessage(object):
"""
log.msg("Message data complete.")
self.lines.append('') # add a trailing newline
- self.parseMessage()
try:
- self._encrypt_and_sign()
+ self._maybe_encrypt_and_sign()
return self.sendMessage()
except KeyNotFound:
return None
@@ -372,7 +400,7 @@ class EncryptedMessage(object):
Separate message headers from body.
"""
parser = Parser()
- self._message = parser.parsestr('\r\n'.join(self.lines))
+ return parser.parsestr('\r\n'.join(self.lines))
def connectionLost(self):
"""
@@ -416,7 +444,7 @@ class EncryptedMessage(object):
message send.
@rtype: twisted.internet.defer.Deferred
"""
- msg = self._message.as_string(False)
+ msg = self._msg.as_string(False)
log.msg("Connecting to SMTP server %s:%s" % (self._config[HOST_KEY],
self._config[PORT_KEY]))
@@ -442,46 +470,76 @@ class EncryptedMessage(object):
d.addErrback(self.sendError)
return d
- def _encrypt_and_sign_payload_rec(self, message, pubkey, signkey):
+ #
+ # encryption methods
+ #
+
+ def _encrypt_and_sign(self, pubkey, signkey):
"""
- Recursivelly descend in C{message}'s payload encrypting to C{pubkey}
- and signing with C{signkey}.
+ Create an RFC 3156 compliang PGP encrypted and signed message using
+ C{pubkey} to encrypt and C{signkey} to sign.
- @param message: The message whose payload we want to encrypt.
- @type message: email.message.Message
@param pubkey: The public key used to encrypt the message.
@type pubkey: leap.common.keymanager.openpgp.OpenPGPKey
@param signkey: The private key used to sign the message.
@type signkey: leap.common.keymanager.openpgp.OpenPGPKey
"""
- if message.is_multipart() is False:
- message.set_payload(
- self._km.encrypt(
- message.get_payload(), pubkey, sign=signkey))
- else:
- for msg in message.get_payload():
- self._encrypt_and_sign_payload_rec(msg, pubkey, signkey)
+ # parse original message from received lines
+ origmsg = self.parseMessage()
+ # create new multipart/encrypted message with 'pgp-encrypted' protocol
+ newmsg = MultipartEncrypted('application/pgp-encrypted')
+ # move (almost) all headers from original message to the new message
+ move_headers(origmsg, newmsg)
+ # create 'application/octet-stream' encrypted message
+ encmsg = MIMEApplication(
+ self._km.encrypt(origmsg.as_string(unixfrom=False), pubkey,
+ sign=signkey),
+ _subtype='octet-stream', _encoder=lambda x: x)
+ encmsg.add_header('content-disposition', 'attachment',
+ filename='msg.asc')
+ # create meta message
+ metamsg = PGPEncrypted()
+ metamsg.add_header('Content-Disposition', 'attachment')
+ # attach pgp message parts to new message
+ newmsg.attach(metamsg)
+ newmsg.attach(encmsg)
+ self._msg = newmsg
+
+ def _sign(self, signkey):
+ """
+ Create an RFC 3156 compliant PGP signed MIME message using C{signkey}.
- def _sign_payload_rec(self, message, signkey):
- """
- Recursivelly descend in C{message}'s payload signing with C{signkey}.
-
- @param message: The message whose payload we want to encrypt.
- @type message: email.message.Message
- @param pubkey: The public key used to encrypt the message.
- @type pubkey: leap.common.keymanager.openpgp.OpenPGPKey
@param signkey: The private key used to sign the message.
@type signkey: leap.common.keymanager.openpgp.OpenPGPKey
"""
- if message.is_multipart() is False:
- message.set_payload(
- self._km.sign(
- message.get_payload(), signkey))
- else:
- for msg in message.get_payload():
- self._sign_payload_rec(msg, signkey)
-
- def _encrypt_and_sign(self):
+ # parse original message from received lines
+ origmsg = self.parseMessage()
+ # create new multipart/signed message
+ newmsg = MultipartSigned('application/pgp-signature', 'pgp-sha512')
+ # move (almost) all headers from original message to the new message
+ move_headers(origmsg, newmsg)
+ # apply base64 content-transfer-encoding
+ encode_base64_rec(origmsg)
+ # get message text with headers and replace \n for \r\n
+ fp = StringIO()
+ g = RFC3156CompliantGenerator(
+ fp, mangle_from_=False, maxheaderlen=76)
+ g.flatten(origmsg)
+ msgtext = re.sub('\r?\n', '\r\n', fp.getvalue())
+ # make sure signed message ends with \r\n as per OpenPGP stantard.
+ if origmsg.is_multipart():
+ if not msgtext.endswith("\r\n"):
+ msgtext += "\r\n"
+ # calculate signature
+ signature = self._km.sign(msgtext, signkey, digest_algo='SHA512',
+ clearsign=False, detach=True, binary=False)
+ sigmsg = PGPSignature(signature)
+ # attach original message and signature to new message
+ newmsg.attach(origmsg)
+ newmsg.attach(sigmsg)
+ self._msg = newmsg
+
+ def _maybe_encrypt_and_sign(self):
"""
Encrypt the message body.
@@ -504,7 +562,7 @@ class EncryptedMessage(object):
log.msg("Will encrypt the message to %s." % pubkey.fingerprint)
signal(proto.SMTP_START_ENCRYPT_AND_SIGN,
"%s,%s" % (self._fromAddress.addrstr, to_address))
- self._encrypt_and_sign_payload_rec(self._message, pubkey, signkey)
+ self._encrypt_and_sign(pubkey, signkey)
signal(proto.SMTP_END_ENCRYPT_AND_SIGN,
"%s,%s" % (self._fromAddress.addrstr, to_address))
except KeyNotFound:
@@ -513,5 +571,5 @@ class EncryptedMessage(object):
# rejected in SMTPDelivery.validateTo().
log.msg('Will send unencrypted message to %s.' % to_address)
signal(proto.SMTP_START_SIGN, self._fromAddress.addrstr)
- self._sign_payload_rec(self._message, signkey)
+ self._sign(signkey)
signal(proto.SMTP_END_SIGN, self._fromAddress.addrstr)