1 files changed, 94 insertions, 0 deletions
diff --git a/src/mailman_pgp/pgp/mime_multisig.py b/src/mailman_pgp/pgp/mime_multisig.py
new file mode 100644
index 0000000..ff9039e
--- /dev/null
+++ b/src/mailman_pgp/pgp/mime_multisig.py
@@ -0,0 +1,94 @@
+# Copyright (C) 2017 Jan Jancar
+#
+# This file is a part of the Mailman PGP plugin.
+#
+# 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/>.
+
+""""""
+import copy
+from email import message_from_string
+from email.encoders import encode_7or8bit
+from email.mime.application import MIMEApplication
+from email.mime.multipart import MIMEMultipart
+
+from mailman.email.message import MultipartDigestMessage, Message
+
+from mailman_pgp.pgp.mime import MIMEWrapper
+from mailman_pgp.utils.email import copy_headers
+
+
+class MIMEMultiSigWrapper(MIMEWrapper):
+    """"""
+    _signature_preamble = \
+        'This is an OpepPGP/MIME signed message' \
+        '(RFC 4880, 3156 and draft-ietf-openpgp-multsig).\n' \
+        'see https://tools.ietf.org/html/draft-ietf-openpgp-multsig-02' \
+        'for more details.'
+
+    def _wrap_signed_multiple(self, msg, signature):
+        """
+        As per https://tools.ietf.org/html/draft-ietf-openpgp-multsig-02.
+
+        :param msg:
+        :param signature:
+        :return:
+        """
+        micalg = ', '.join(self._micalg(sig.hash_algorithm)
+                           for sig in signature)
+        out = MultipartDigestMessage('signed', micalg=micalg,
+                                     protocol=MIMEWrapper._signed_type)
+        out.preamble = MIMEMultiSigWrapper._signature_preamble
+
+        second_part = MIMEMultipart()
+        for sig in signature:
+            sig_part = MIMEApplication(_data=str(sig),
+                                       _subtype=MIMEWrapper._signature_subtype,
+                                       _encoder=encode_7or8bit,
+                                       name='signature.asc')
+            sig_part.add_header('Content-Description',
+                                'OpenPGP digital signature')
+            sig_part.add_header('Content-Disposition', 'attachment',
+                                filename='signature.asc')
+            second_part.attach(sig_part)
+        out.attach(copy.deepcopy(msg))
+        out.attach(second_part)
+        copy_headers(msg, out)
+        return out
+
+    def sign(self, key, hash=None):
+        if self.is_signed():
+            payload = next(iter(self.get_signed()))
+            signature = next(iter(self.get_signature()))
+            signature |= key.sign(payload, hash=hash)
+            return self._wrap_signed_multiple(self.msg, signature)
+        else:
+            super().sign(key, hash)
+
+    def decrypt(self, key):
+        pmsg = next(iter(self.get_encrypted()))
+        decrypted = key.decrypt(pmsg)
+
+        dmsg = decrypted.message
+        if isinstance(dmsg, bytearray):
+            dmsg = dmsg.decode(decrypted.charset or 'utf-8')
+
+        out = message_from_string(dmsg, _class=Message)
+        if decrypted.is_signed:
+            if len(decrypted.signatures) != 1:
+                out = self._wrap_signed_multiple(out,
+                                                 decrypted.detached_signature)
+            else:
+                out = self._wrap_signed(out, decrypted.signatures.pop())
+        copy_headers(self.msg, out)
+        return out