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"""
SleekXMPP: The Sleek XMPP Library
Copyright (C) 2011 Nathanael C. Fritz
This file is part of SleekXMPP.
See the file LICENSE for copying permission.
"""
import ssl
import logging
from sleekxmpp.util import sasl
from sleekxmpp.util.stringprep_profiles import StringPrepError
from sleekxmpp.stanza import StreamFeatures
from sleekxmpp.xmlstream import RestartStream, register_stanza_plugin
from sleekxmpp.plugins import BasePlugin
from sleekxmpp.xmlstream.matcher import MatchXPath
from sleekxmpp.xmlstream.handler import Callback
from sleekxmpp.features.feature_mechanisms import stanza
log = logging.getLogger(__name__)
class FeatureMechanisms(BasePlugin):
name = 'feature_mechanisms'
description = 'RFC 6120: Stream Feature: SASL'
dependencies = set()
stanza = stanza
default_config = {
'use_mech': None,
'use_mechs': None,
'min_mech': None,
'sasl_callback': None,
'security_callback': None,
'encrypted_plain': True,
'unencrypted_plain': False,
'unencrypted_digest': False,
'unencrypted_cram': False,
'unencrypted_scram': True,
'order': 100
}
def plugin_init(self):
if self.sasl_callback is None:
self.sasl_callback = self._default_credentials
if self.security_callback is None:
self.security_callback = self._default_security
creds = self.sasl_callback(set(['username']), set())
if not self.use_mech and not creds['username']:
self.use_mech = 'ANONYMOUS'
self.mech = None
self.mech_list = set()
self.attempted_mechs = set()
register_stanza_plugin(StreamFeatures, stanza.Mechanisms)
self.xmpp.register_stanza(stanza.Success)
self.xmpp.register_stanza(stanza.Failure)
self.xmpp.register_stanza(stanza.Auth)
self.xmpp.register_stanza(stanza.Challenge)
self.xmpp.register_stanza(stanza.Response)
self.xmpp.register_stanza(stanza.Abort)
self.xmpp.register_handler(
Callback('SASL Success',
MatchXPath(stanza.Success.tag_name()),
self._handle_success,
instream=True))
self.xmpp.register_handler(
Callback('SASL Failure',
MatchXPath(stanza.Failure.tag_name()),
self._handle_fail,
instream=True))
self.xmpp.register_handler(
Callback('SASL Challenge',
MatchXPath(stanza.Challenge.tag_name()),
self._handle_challenge))
self.xmpp.register_feature('mechanisms',
self._handle_sasl_auth,
restart=True,
order=self.order)
def _default_credentials(self, required_values, optional_values):
creds = self.xmpp.credentials
result = {}
values = required_values.union(optional_values)
for value in values:
if value == 'username':
result[value] = creds.get('username', self.xmpp.requested_jid.user)
elif value == 'email':
jid = self.xmpp.requested_jid.bare
result[value] = creds.get('email', jid)
elif value == 'channel_binding':
if hasattr(self.xmpp.socket, 'get_channel_binding'):
result[value] = self.xmpp.socket.get_channel_binding()
else:
log.debug("Channel binding not supported.")
log.debug("Use Python 3.3+ for channel binding and " + \
"SCRAM-SHA-1-PLUS support")
result[value] = None
elif value == 'host':
result[value] = creds.get('host', self.xmpp.requested_jid.domain)
elif value == 'realm':
result[value] = creds.get('realm', self.xmpp.requested_jid.domain)
elif value == 'service-name':
result[value] = creds.get('service-name', self.xmpp._service_name)
elif value == 'service':
result[value] = creds.get('service', 'xmpp')
elif value in creds:
result[value] = creds[value]
return result
def _default_security(self, values):
result = {}
for value in values:
if value == 'encrypted':
if 'starttls' in self.xmpp.features:
result[value] = True
elif isinstance(self.xmpp.socket, ssl.SSLSocket):
result[value] = True
else:
result[value] = False
else:
result[value] = self.config.get(value, False)
return result
def _handle_sasl_auth(self, features):
"""
Handle authenticating using SASL.
Arguments:
features -- The stream features stanza.
"""
if 'mechanisms' in self.xmpp.features:
# SASL authentication has already succeeded, but the
# server has incorrectly offered it again.
return False
enforce_limit = False
limited_mechs = self.use_mechs
if limited_mechs is None:
limited_mechs = set()
elif limited_mechs and not isinstance(limited_mechs, set):
limited_mechs = set(limited_mechs)
enforce_limit = True
if self.use_mech:
limited_mechs.add(self.use_mech)
enforce_limit = True
if enforce_limit:
self.use_mechs = limited_mechs
self.mech_list = set(features['mechanisms'])
return self._send_auth()
def _send_auth(self):
mech_list = self.mech_list - self.attempted_mechs
try:
self.mech = sasl.choose(mech_list,
self.sasl_callback,
self.security_callback,
limit=self.use_mechs,
min_mech=self.min_mech)
except sasl.SASLNoAppropriateMechanism:
log.error("No appropriate login method.")
self.xmpp.event("no_auth", direct=True)
self.xmpp.event("failed_auth", direct=True)
self.attempted_mechs = set()
return self.xmpp.disconnect()
except StringPrepError:
log.exception("A credential value did not pass SASLprep.")
self.xmpp.disconnect()
resp = stanza.Auth(self.xmpp)
resp['mechanism'] = self.mech.name
try:
resp['value'] = self.mech.process()
except sasl.SASLCancelled:
self.attempted_mechs.add(self.mech.name)
self._send_auth()
except sasl.SASLFailed:
self.attempted_mechs.add(self.mech.name)
self._send_auth()
except sasl.SASLMutualAuthFailed:
log.error("Mutual authentication failed! " + \
"A security breach is possible.")
self.attempted_mechs.add(self.mech.name)
self.xmpp.disconnect()
else:
resp.send(now=True)
return True
def _handle_challenge(self, stanza):
"""SASL challenge received. Process and send response."""
resp = self.stanza.Response(self.xmpp)
try:
resp['value'] = self.mech.process(stanza['value'])
except sasl.SASLCancelled:
self.stanza.Abort(self.xmpp).send()
except sasl.SASLFailed:
self.stanza.Abort(self.xmpp).send()
except sasl.SASLMutualAuthFailed:
log.error("Mutual authentication failed! " + \
"A security breach is possible.")
self.attempted_mechs.add(self.mech.name)
self.xmpp.disconnect()
else:
if resp.get_value() == '':
resp.del_value()
resp.send(now=True)
def _handle_success(self, stanza):
"""SASL authentication succeeded. Restart the stream."""
try:
final = self.mech.process(stanza['value'])
except sasl.SASLMutualAuthFailed:
log.error("Mutual authentication failed! " + \
"A security breach is possible.")
self.attempted_mechs.add(self.mech.name)
self.xmpp.disconnect()
else:
self.attempted_mechs = set()
self.xmpp.authenticated = True
self.xmpp.features.add('mechanisms')
self.xmpp.event('auth_success', stanza, direct=True)
raise RestartStream()
def _handle_fail(self, stanza):
"""SASL authentication failed. Disconnect and shutdown."""
self.attempted_mechs.add(self.mech.name)
log.info("Authentication failed: %s", stanza['condition'])
self.xmpp.event("failed_auth", stanza, direct=True)
self._send_auth()
return True
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