def start(self):
if self.protocol is None:
query = QueryMessage(versions=self.supported_versions)
self.send_message(query.encode())
self.sent_query = True
else:
pass # never restart the AKE as it creates a security risk which allows man-in-the-middle attacks even after the session was encrypted and verified using SMP
def handle_input(self, content, content_type):
# handle fragments
if content.startswith(('?OTR|', '?OTR,')):
content = self.fragment_handler.process(content, protocol=self.protocol)
else:
self.fragment_handler.reset()
# handle OTR messages
if content.startswith('?OTR:'):
if self.protocol is None and self.sent_query and content[OTRProtocol.marker_slice] in OTRProtocol.commit_markers:
protocol_class = OTRProtocol.with_marker(content[OTRProtocol.marker_slice])
if protocol_class.__version__ in self.supported_versions:
self.protocol = protocol_class(self)
if self.protocol is not None:
return self.protocol.handle_input(content, content_type)
elif content.startswith('?OTR'):
try:
query = QueryMessage.decode(content)
except ValueError:
pass
else:
if self.protocol is None:
common_versions = self.supported_versions.intersection(query.versions)
if common_versions:
self.protocol = OTRProtocol.with_version(max(common_versions))(self)
self.protocol.start()
else:
pass # never restart the AKE as it creates a security risk which allows man-in-the-middle attacks even after the session was encrypted and verified using SMP
raise IgnoreMessage
try:
error = ErrorMessage.decode(content)
except ValueError:
pass
else:
if self.protocol is not None:
raise OTRError(error.error)
# handle non-OTR messages
if self.encrypted:
raise UnencryptedMessage
else:
if self.protocol is None and content_type.startswith('text/') and TaggedPlaintextMessage.__tag__.prefix in content:
query = TaggedPlaintextMessage.decode(content)
common_versions = self.supported_versions.intersection(query.versions)
if common_versions:
self.protocol = OTRProtocol.with_version(max(common_versions))(self)
self.protocol.start()
return query.message
return content
