From d95a22393dcad545eb2d736e3fd33858cbbac4f8 Mon Sep 17 00:00:00 2001
From: drebs <drebs@leap.se>
Date: Thu, 7 Nov 2013 14:52:20 -0200
Subject: Do not encrypt already encrypted mails in SMTP relay.
---
...re-4324_prevent-double-encryption-when-relaying | 2 +
mail/src/leap/mail/smtp/smtprelay.py | 60 ++++++++++++++--------
2 files changed, 42 insertions(+), 20 deletions(-)
create mode 100644 mail/changes/feature-4324_prevent-double-encryption-when-relaying
diff --git a/mail/changes/feature-4324_prevent-double-encryption-when-relaying b/mail/changes/feature-4324_prevent-double-encryption-when-relaying
new file mode 100644
index 0000000..a3d70a9
--- /dev/null
+++ b/mail/changes/feature-4324_prevent-double-encryption-when-relaying
@@ -0,0 +1,2 @@
+ o Prevent already encrypted outgoing messages from being encrypted again.
+ Closes #4324.
diff --git a/mail/src/leap/mail/smtp/smtprelay.py b/mail/src/leap/mail/smtp/smtprelay.py
index 92a9f0e..14de849 100644
--- a/mail/src/leap/mail/smtp/smtprelay.py
+++ b/mail/src/leap/mail/smtp/smtprelay.py
@@ -284,7 +284,8 @@ class SMTPDelivery(object):
# try to find recipient's public key
try:
address = validate_address(user.dest.addrstr)
- pubkey = self._km.get_key(address, OpenPGPKey)
+ # verify if recipient key is available in keyring
+ self._km.get_key(address, OpenPGPKey) # might raise KeyNotFound
log.msg("Accepting mail for %s..." % user.dest.addrstr)
signal(proto.SMTP_RECIPIENT_ACCEPTED_ENCRYPTED, user.dest.addrstr)
except KeyNotFound:
@@ -510,15 +511,13 @@ class EncryptedMessage(object):
@param signkey: The private key used to sign the message.
@type signkey: leap.common.keymanager.openpgp.OpenPGPKey
"""
- # 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)
+ move_headers(self._origmsg, newmsg)
# create 'application/octet-stream' encrypted message
encmsg = MIMEApplication(
- self._km.encrypt(origmsg.as_string(unixfrom=False), pubkey,
+ self._km.encrypt(self._origmsg.as_string(unixfrom=False), pubkey,
sign=signkey),
_subtype='octet-stream', _encoder=lambda x: x)
encmsg.add_header('content-disposition', 'attachment',
@@ -538,22 +537,20 @@ class EncryptedMessage(object):
@param signkey: The private key used to sign the message.
@type signkey: leap.common.keymanager.openpgp.OpenPGPKey
"""
- # 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)
+ move_headers(self._origmsg, newmsg)
# apply base64 content-transfer-encoding
- encode_base64_rec(origmsg)
+ encode_base64_rec(self._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)
+ g.flatten(self._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 self._origmsg.is_multipart():
if not msgtext.endswith("\r\n"):
msgtext += "\r\n"
# calculate signature
@@ -561,23 +558,46 @@ class EncryptedMessage(object):
clearsign=False, detach=True, binary=False)
sigmsg = PGPSignature(signature)
# attach original message and signature to new message
- newmsg.attach(origmsg)
+ newmsg.attach(self._origmsg)
newmsg.attach(sigmsg)
self._msg = newmsg
def _maybe_encrypt_and_sign(self):
"""
- Encrypt the message body.
+ Attempt to encrypt and sign the outgoing message.
- Fetch the recipient key and encrypt the content to the
- recipient. If a key is not found, then the behaviour depends on the
- configuration parameter ENCRYPTED_ONLY_KEY. If it is False, the message
- is sent unencrypted and a warning is logged. If it is True, the
- encryption fails with a KeyNotFound exception.
+ The behaviour of this method depends on:
- @raise KeyNotFound: Raised when the recipient key was not found and
- the ENCRYPTED_ONLY_KEY configuration parameter is set to True.
+ 1. the original message's content-type, and
+ 2. the availability of the recipient's public key.
+
+ If the original message's content-type is "multipart/encrypted", then
+ the original message is not altered. For any other content-type, the
+ method attempts to fetch the recipient's public key. If the
+ recipient's public key is available, the message is encrypted and
+ signed; otherwise it is only signed.
+
+ Note that, if the C{encrypted_only} configuration is set to True and
+ the recipient's public key is not available, then the recipient
+ address would have been rejected in SMTPDelivery.validateTo().
+
+ The following table summarizes the overall behaviour of the relay:
+
+ +---------------------------------------------------+----------------+
+ | content-type | rcpt pubkey | enforce encr. | action |
+ +---------------------+-------------+---------------+----------------+
+ | multipart/encrypted | any | any | pass |
+ | other | available | any | encrypt + sign |
+ | other | unavailable | yes | reject |
+ | other | unavailable | no | sign |
+ +---------------------+-------------+---------------+----------------+
"""
+ # pass if the original message's content-type is "multipart/encrypted"
+ self._origmsg = self.parseMessage()
+ if self._origmsg.get_content_type() == 'multipart/encrypted':
+ self._msg = self._origmsg
+ return
+
from_address = validate_address(self._fromAddress.addrstr)
signkey = self._km.get_key(from_address, OpenPGPKey, private=True)
log.msg("Will sign the message with %s." % signkey.fingerprint)
--
cgit v1.2.3