def send_fingerprint_mail(self, my_DHIs, my_id, other_DHIs, other_id):
self.logger.info("sending fingerprint to %s" % my_id)
my_segs = my_id.split("@", 1)
my_name = my_segs[0]
my_host = my_segs[1]
other_segs = other_id.split('@', 1)
other_name = other_segs[0]
other_host = other_segs[1]
drunk = GetFPrintMail(my_DHIs, my_name, other_DHIs, other_name)
mfp = MIMEText("<html><body><p>Hello %(my_name)s,</p>\n\n<p>Your e-mail conversation with %(other_id)s was encrypted via the awesome Axonaut e-mail encryption service. To verify the identity of %(other_name)s, compare the following fingerprints with your partner.</p>\n\n<p>They should match with the corresponding fingerprints we sent to %(other_name)s otherwise you might be a victim of an active attack!</p>\n\n<pre>%(drunk)s</pre>\n\n<p>Best regards,<br/>\nyour friendly Axonauts</p>\n</body></html>" % {"my_name": my_name, "other_name": other_name, "other_id": other_id, "drunk": drunk}, "html")
mfp["From"] = "mailadmin@%s" % my_host
mfp["To"] = my_id
mfp["Subject"] = "Axonaut Key-Fingerprints for %s" % other_id
sendmimemail(mfp, mfp["From"], my_id)
def encrypt_and_send_mail(self, mail, axolotl):
self.logger.info("encrypting message %s" % mail["id"])
# Assemble the message that we shall encrypt.
msg = MIMEText(mail["body"])
for k, v in mail["headers"]:
msg[k] = v
raw = msg.as_string()
self.logger.debug(raw)
# Encrypt the message and wrap it up in a new envelope, then send it to
# the recipient.
encoded = binascii.b2a_base64(axolotl.encrypt(raw))
menv = MIMEText(encoded)
menv["From"] = mail["from"]
menv["To"] = mail["to"]
menv["Subject"] = "Axolotl-encrypted Message"
menv["Content-Type"] = "message/x-axonaut"
sendmimemail(menv, mail["from"], mail["to"])
def process_inbound(self, in_mail):
"""
Function to decrypt an incoming mail. Responds to a key request if necessary.
"""
my_id = in_mail["to"]
other_id = in_mail["from"]
self.logger.info("inbound mail from %s to %s" % (my_id, other_id))
content_type = None
msg_id = None
for k, v in in_mail["headers"]:
kl = k.lower()
if kl == "content-type":
content_type = v.lower()
if kl == "message-id":
msg_id = v
in_mail["id"] = msg_id
self.logger.debug("content_type = %s" % content_type)
self.logger.debug("message_id = %s" % in_mail["id"])
conv_hash = hashlib.sha1(my_id + ":" + other_id).hexdigest()
handshake_path = self.handshakes_dir + "/" + conv_hash
queue_path = self.queues_dir + "/" + conv_hash
# Encrypted messages targeted at a local user need to be decrypted
# before they are relayed. The encryption status is indicated by a
# special content type. Two cases are possible: Either the Axolotl
# handshake has been completed, in which case loadState() succeeds and
# the message may be decrypted normally. Or the handshake is in progress
# or has not been started at all, in which case no decryption is
# possible. In the latter case, we might want to inform the sender about
# the situation.
if content_type == "message/x-axonaut":
try:
a = self.makeAxolotl(my_id)
a.loadState(my_id, other_id)
self.decrypt_and_send_mail(in_mail, a)
a.saveState()
except:
self.logger.warning("unable to decrypt message: %s" % in_mail["id"])
msg = MIMEMultipart()
msg["Subject"] = "Message cannot be decrypted, return to sender"
msg["From"] = my_id
msg["To"] = other_id
msg_txt = MIMEText("The attached message was received by the sender, but cannot be decrypted. This indicates that no secure Axolotl conversation has been established beforehand.", "plain")
raw_msg = MIMEText(in_mail["body"])
for k, v in in_mail["headers"]:
raw_msg[k] = v
raw = raw_msg.as_string()
mret = MIMEText(raw)
mret["Content-Type"] = "message/rfc822"
mret["Content-Disposition"] = "attachment"
msg.attach(msg_txt)
msg.attach(mret)
sendmimemail(msg, my_id, other_id)
# If we receive a key response, we have initiated the key exchange and
# may now finish it with the information provided by our peer. To ensure
# secrecy, truncate the temporary pre-keys that were stored for the
# handshake to zero.
elif content_type == "message/x-axonaut+keyrsp":
self.logger.debug("received keyrsp from %s" % other_id)
a = self.makeAxolotl(my_id)
hs = pickle.load(open(handshake_path, "r"))
a.state = hs["state"]
a.handshakePKey = hs["pub"]
a.handshakeKey = hs["priv"]
segments = in_mail["body"].split('\n')
DHIs = binascii.a2b_base64(segments[0].strip())
DHRs = binascii.a2b_base64(segments[1].strip()) if segments[1].strip() != "none" else None
handshakePKey = binascii.a2b_base64(segments[2].strip())
a.initState(other_id, DHIs, handshakePKey, DHRs, verify=False)
# This part is simply informing the user on our end with the hashes
# of both identity keys. These must be compared through a secure
# second channel of communication to ensure all security properties.
self.send_fingerprint_mail(a.state['DHIs'], my_id, DHIs, other_id)
if os.path.isdir(queue_path):
for d in os.listdir(queue_path):
msg = pickle.load(open(queue_path + "/" + d))
self.encrypt_and_send_mail(msg, a)
shutil.rmtree(queue_path)
a.saveState();
open(handshake_path, "w").truncate()
# If we receive a key request, we are able to finalize the key exchange
# and initialize the Axolotl state. In addition to that, we have to mark
# this combination of sender/receiver as established by touching the
# corresponding file in the handshakes directory.
elif content_type == "message/x-axonaut+keyreq":
try:
segments = in_mail["body"].split('\n')
DHIs = binascii.a2b_base64(segments[0].strip())
DHRs = binascii.a2b_base64(segments[1].strip())
handshakePKey = binascii.a2b_base64(segments[2].strip())
self.logger.debug("received keyreq from %s" % other_id)
except Exception as e:
self.logger.exception("invalid keyreq received: %s" % e)
return
try:
a = self.makeAxolotl(my_id)
a.loadState(my_id, other_id)
self.logger.warning("received keyreq event though already exchanged")
except:
a = self.makeAxolotl(my_id)
a.initState(other_id, DHIs, handshakePKey, DHRs, verify=False)
# This part is simply informing the user on our end with the
# hashes of both identity keys. These must be compared through a
# secure second channel of communication to ensure all security
# properties.
self.send_fingerprint_mail(a.state['DHIs'], my_id, DHIs, other_id)
out_mail_body = "%s\n%s\n%s" % (
binascii.b2a_base64(a.state["DHIs"]).strip(),
binascii.b2a_base64(a.state["DHRs"]).strip() if a.state["DHRs"] != None else "none",
binascii.b2a_base64(a.handshakePKey).strip())
self.logger.info("sending keyrsp to %s" % other_id)
krsp_msg = MIMEText(out_mail_body)
krsp_msg["From"] = my_id
krsp_msg["To"] = other_id
krsp_msg["Subject"] = "Axolotl Key Response"
krsp_msg["Content-Type"] = "message/x-axonaut+keyrsp"
sendmimemail(krsp_msg, my_id, other_id)
a.saveState()
os.mknod(handshake_path)
return
def process_outbound(self, in_mail):
"""
Function to encrypt an outgoing mail. Also makes a new key request if the partner key is not available.
"""
my_id = in_mail["from"]
other_id = in_mail["to"]
self.logger.info("outbound mail from %s to %s" % (my_id, other_id))
content_type = None
msg_id = None
for k, v in in_mail["headers"]:
kl = k.lower()
if kl == "content-type":
content_type = v.lower()
if kl == "message-id":
msg_id = v
in_mail["id"] = msg_id
self.logger.debug("content_type = %s" % content_type)
self.logger.debug("message_id = %s" % in_mail["id"])
conv_hash = hashlib.sha1(my_id + ":" + other_id).hexdigest()
handshake_path = self.handshakes_dir + "/" + conv_hash
queue_path = self.queues_dir + "/" + conv_hash
# Encrypt all messages that are not already encrypted.
if content_type != "message/x-axonaut":
# Figure out the next queue file name in case we need to keep the
# message around for later delivery.
i = 1;
path = None
while path == None or os.path.exists(path):
path = "%s/%04i" % (queue_path, i)
i = i + 1
# Check whether we already have established a handshake. If this is
# not the case, send a keyreq message to the recipient that contains
# our half of the key exchange information. The message that was
# originally intended for dispatch is stored in a queue for later
# delivery as soon as the encryption keys have been negotiated.
if not os.path.exists(handshake_path):
self.logger.debug("sending keyreq to %s" % other_id)
a = self.makeAxolotl(my_id)
out_mail_body = "%s\n%s\n%s" % (
binascii.b2a_base64(a.state["DHIs"]).strip(),
binascii.b2a_base64(a.state["DHRs"]).strip(),
binascii.b2a_base64(a.handshakePKey).strip())
self.logger.debug("queuing message %s" % in_mail["id"])
if not os.path.exists(queue_path):
os.makedirs(queue_path)
pickle.dump(in_mail, open(path, "w"))
kreq_msg = MIMEText(out_mail_body)
kreq_msg["From"] = my_id
kreq_msg["To"] = other_id
kreq_msg["Subject"] = "Axolotl Key Request"
kreq_msg["Content-Type"] = "message/x-axonaut+keyreq"
sendmimemail(kreq_msg, my_id, other_id)
# The following is an ugly hack: pyaxo expects an Axolotl object
# to be created and the keys negotiated before the object is
# destroyed and the state saved to disk. This does not work in
# our case, since we need to wait for a potentially long period
# of time until we can finalize the handshake. Therefore we
# serialize the Axolotl state and especially the handshake pre-
# keys to disk, such that we may resume the handshake at a later
# stage.
pickle.dump({
"state": a.state,
"pub": a.handshakePKey,
"priv": a.handshakeKey
}, open(handshake_path, "w"))
else:
# If we've come this far, the handshake has been initiated. That
# is, at least the keyreq message has been sent to the peer. Two
# things may now happen: Either the Axolotl conversation is
# already initialized, in which case loadState() will succeed
# and we may continue to encrypt our message. Or the state has
# not yet been initialized, and an exception is thrown. In case
# of the exception we store the message in the queue for later
# encryption, as soon as the handshake terminates.
try:
a = self.makeAxolotl(my_id)
a.loadState(my_id, other_id)
self.encrypt_and_send_mail(in_mail, a)
a.saveState()
except:
self.logger.info("queuing message %s (key response pending)" % in_mail["id"])
if not os.path.exists(queue_path):
os.makedirs(queue_path)
pickle.dump(in_mail, open(path, "w"))