def fail_bad_negotiation(self, reason, fields=None):
'''sends an error and cancels everything.
if fields is None, the remote party has given us a bad cryptographic value of some kind
otherwise, list the fields we haven't implemented'''
err = xmpp.Error(xmpp.Message(), xmpp.ERR_FEATURE_NOT_IMPLEMENTED)
err.T.error.T.text.setData(reason)
if fields:
feature = xmpp.Node(xmpp.NS_FEATURE + ' feature')
for field in fields:
fn = xmpp.Node('field')
fn['var'] = field
feature.addChild(node=feature)
err.addChild(node=feature)
self.send(err)
self.status = None
self.enable_encryption = False
# this prevents the MAC check on decryption from succeeding,
# preventing falsified messages from going through.
self.km_o = ''
def receive_chat_msg(self, jid, msgtxt):
'''simulate receiving a chat message from jid'''
msg = xmpp.Message()
msg.setBody(msgtxt)
msg.setType('chat')
tim = time.localtime()
encrypted = False
self.sess.received(jid, msgtxt, tim, encrypted, msg)
def on_ok_button_clicked(self, widget):
acceptance = xmpp.Message(self.jid)
acceptance.setThread(self.session.thread_id)
feature = acceptance.NT.feature
feature.setNamespace(xmpp.NS_FEATURE)
form = self.data_form_widget.data_form
form.setAttr('type', 'submit')
feature.addChild(node=form)
gajim.connections[self.account].send_stanza(acceptance)
self.window.destroy()
def on_cancel_button_clicked(self, widget):
rejection = xmpp.Message(self.jid)
rejection.setThread(self.session.thread_id)
feature = rejection.NT.feature
feature.setNamespace(xmpp.NS_FEATURE)
x = xmpp.DataForm(typ='submit')
x.addChild(node=xmpp.DataField('FORM_TYPE', value='urn:xmpp:ssn'))
x.addChild(node=xmpp.DataField('accept', value='false', typ='boolean'))
feature.addChild(node=x)
gajim.connections[self.account].send_stanza(rejection)
self.window.destroy()
def reject_negotiation(self, body=None):
msg = xmpp.Message()
feature = msg.NT.feature
feature.setNamespace(xmpp.NS_FEATURE)
x = xmpp.DataForm(typ='submit')
x.addChild(node=xmpp.DataField(name='FORM_TYPE', value='urn:xmpp:ssn'))
x.addChild(node=xmpp.DataField(name='accept', value='0'))
feature.addChild(node=x)
if body:
msg.setBody(body)
self.send(msg)
self.cancelled_negotiation()
def terminate(self):
# only send termination message if we've sent a message and think they
# have XEP-0201 support
if self.last_send > 0 and \
(self.received_thread_id or self.last_receive == 0):
msg = xmpp.Message()
feature = msg.NT.feature
feature.setNamespace(xmpp.NS_FEATURE)
x = xmpp.DataForm(typ='submit')
x.addChild(
node=xmpp.DataField(name='FORM_TYPE', value='urn:xmpp:ssn'))
x.addChild(node=xmpp.DataField(name='terminate', value='1'))
feature.addChild(node=x)
self.send(msg)
self.status = None
def accept_e2e_bob(self, form):
response = xmpp.Message()
init = response.NT.init
init.setNamespace(xmpp.NS_ESESSION_INIT)
x = xmpp.DataForm(typ='result')
for field in ('nonce', 'dhkeys', 'rshashes', 'identity', 'mac'):
assert field in form.asDict(), "alice's form didn't have a %s field" \
% field
# 4.5.1 generating provisory session keys
e = crypto.decode_mpi(base64.b64decode(form['dhkeys']))
p = dh.primes[self.modp]
if crypto.sha256(crypto.encode_mpi(e)) != self.negotiated['He']:
raise exceptions.NegotiationError, 'SHA256(e) != He'
k = self.get_shared_secret(e, self.y, p)
self.kc_o, self.km_o, self.ks_o = self.generate_initiator_keys(k)
# 4.5.2 verifying alice's identity
self.verify_identity(form, e, False, 'a')
# 4.5.4 generating bob's final session keys
srs = ''
srses = secrets.secrets().retained_secrets(self.conn.name,
self.jid.getStripped())
rshashes = [
base64.b64decode(rshash)
for rshash in form.getField('rshashes').getValues()
]
for (secret, verified) in srses:
if self.hmac(self.n_o, secret) in rshashes:
srs = secret
break
# other shared secret
# (we're not using one)
oss = ''
k = crypto.sha256(k + srs + oss)
self.kc_s, self.km_s, self.ks_s = self.generate_responder_keys(k)
self.kc_o, self.km_o, self.ks_o = self.generate_initiator_keys(k)
# 4.5.5
if srs:
srshash = self.hmac(srs, 'Shared Retained Secret')
else:
srshash = crypto.random_bytes(32)
x.addChild(node=xmpp.DataField(name='FORM_TYPE', value='urn:xmpp:ssn'))
x.addChild(node=xmpp.DataField(name='nonce',
value=base64.b64encode(self.n_o)))
x.addChild(node=xmpp.DataField(name='srshash',
value=base64.b64encode(srshash)))
for datafield in self.make_identity(x, self.d):
x.addChild(node=datafield)
init.addChild(node=x)
self.send(response)
self.do_retained_secret(k, srs)
if self.negotiated['logging'] == 'mustnot':
self.loggable = False
self.status = 'active'
self.enable_encryption = True
if self.control:
self.control.print_esession_details()
def accept_e2e_alice(self, form, negotiated):
self.encryptable_stanzas = ['message']
self.sas_algs = 'sas28x5'
self.cipher = AES
self.hash_alg = SHA256
self.compression = None
self.negotiated = negotiated
accept = xmpp.Message()
feature = accept.NT.feature
feature.setNamespace(xmpp.NS_FEATURE)
result = xmpp.DataForm(typ='result')
self.c_s = crypto.decode_mpi(base64.b64decode(form['counter']))
self.c_o = self.c_s ^ (2**(self.n - 1))
self.n_o = base64.b64decode(form['my_nonce'])
mod_p = int(form['modp'])
p = dh.primes[mod_p]
x = self.xes[mod_p]
e = self.es[mod_p]
self.d = crypto.decode_mpi(base64.b64decode(form['dhkeys']))
self.k = self.get_shared_secret(self.d, x, p)
result.addChild(
node=xmpp.DataField(name='FORM_TYPE', value='urn:xmpp:ssn'))
result.addChild(node=xmpp.DataField(name='accept', value='1'))
result.addChild(node=xmpp.DataField(name='nonce',
value=base64.b64encode(self.n_o)))
self.kc_s, self.km_s, self.ks_s = self.generate_initiator_keys(self.k)
if self.sigmai:
self.kc_o, self.km_o, self.ks_o = self.generate_responder_keys(
self.k)
self.verify_identity(form, self.d, True, 'b')
else:
srses = secrets.secrets().retained_secrets(self.conn.name,
self.jid.getStripped())
rshashes = [self.hmac(self.n_s, rs) for (rs, v) in srses]
if not rshashes:
# we've never spoken before, but we'll pretend we have
rshash_size = self.hash_alg.digest_size
rshashes.append(crypto.random_bytes(rshash_size))
rshashes = [base64.b64encode(rshash) for rshash in rshashes]
result.addChild(
node=xmpp.DataField(name='rshashes', value=rshashes))
result.addChild(node=xmpp.DataField(
name='dhkeys', value=base64.b64encode(crypto.encode_mpi(e))))
self.form_o = ''.join(
map(lambda el: xmpp.c14n.c14n(el), form.getChildren()))
# MUST securely destroy K unless it will be used later to generate the
# final shared secret
for datafield in self.make_identity(result, e):
result.addChild(node=datafield)
feature.addChild(node=result)
self.send(accept)
if self.sigmai:
self.status = 'active'
self.enable_encryption = True
else:
self.status = 'identified-alice'
def respond_e2e_bob(self, form, negotiated, not_acceptable):
response = xmpp.Message()
feature = response.NT.feature
feature.setNamespace(xmpp.NS_FEATURE)
x = xmpp.DataForm(typ='submit')
x.addChild(node=xmpp.DataField(name='FORM_TYPE', value='urn:xmpp:ssn'))
x.addChild(node=xmpp.DataField(name='accept', value='true'))
for name in negotiated:
# some fields are internal and should not be sent
if not name in ('send_pubkey', 'recv_pubkey'):
x.addChild(
node=xmpp.DataField(name=name, value=negotiated[name]))
self.negotiated = negotiated
# the offset of the group we chose (need it to match up with the dhhash)
group_order = 0
self.modp = int(form.getField('modp').getOptions()[group_order][1])
x.addChild(node=xmpp.DataField(name='modp', value=self.modp))
g = dh.generators[self.modp]
p = dh.primes[self.modp]
self.n_o = base64.b64decode(form['my_nonce'])
dhhashes = form.getField('dhhashes').getValues()
self.negotiated['He'] = base64.b64decode(
dhhashes[group_order].encode('utf8'))
bytes = int(self.n / 8)
self.n_s = crypto.generate_nonce()
# n-bit random number
self.c_o = crypto.decode_mpi(crypto.random_bytes(bytes))
self.c_s = self.c_o ^ (2**(self.n - 1))
self.y = crypto.srand(2**(2 * self.n - 1), p - 1)
self.d = crypto.powmod(g, self.y, p)
to_add = {
'my_nonce': self.n_s,
'dhkeys': crypto.encode_mpi(self.d),
'counter': crypto.encode_mpi(self.c_o),
'nonce': self.n_o
}
for name in to_add:
b64ed = base64.b64encode(to_add[name])
x.addChild(node=xmpp.DataField(name=name, value=b64ed))
self.form_o = ''.join(
map(lambda el: xmpp.c14n.c14n(el), form.getChildren()))
self.form_s = ''.join(
map(lambda el: xmpp.c14n.c14n(el), x.getChildren()))
self.status = 'responded-e2e'
feature.addChild(node=x)
if not_acceptable:
response = xmpp.Error(response, xmpp.ERR_NOT_ACCEPTABLE)
feature = xmpp.Node(xmpp.NS_FEATURE + ' feature')
for f in not_acceptable:
n = xmpp.Node('field')
n['var'] = f
feature.addChild(node=n)
response.T.error.addChild(node=feature)
self.send(response)
def negotiate_e2e(self, sigmai):
self.negotiated = {}
request = xmpp.Message()
feature = request.NT.feature
feature.setNamespace(xmpp.NS_FEATURE)
x = xmpp.DataForm(typ='form')
x.addChild(node=xmpp.DataField(
name='FORM_TYPE', value='urn:xmpp:ssn', typ='hidden'))
x.addChild(node=xmpp.DataField(
name='accept', value='1', typ='boolean', required=True))
# this field is incorrectly called 'otr' in XEPs 0116 and 0217
x.addChild(node=xmpp.DataField(name='logging',
typ='list-single',
options=self.logging_preference(),
required=True))
# unsupported options: 'disabled', 'enabled'
x.addChild(node=xmpp.DataField(name='disclosure',
typ='list-single',
options=['never'],
required=True))
x.addChild(node=xmpp.DataField(
name='security', typ='list-single', options=['e2e'
], required=True))
x.addChild(node=xmpp.DataField(
name='crypt_algs', value='aes128-ctr', typ='hidden'))
x.addChild(node=xmpp.DataField(
name='hash_algs', value='sha256', typ='hidden'))
x.addChild(
node=xmpp.DataField(name='compress', value='none', typ='hidden'))
# unsupported options: 'iq', 'presence'
x.addChild(node=xmpp.DataField(
name='stanzas', typ='list-multi', options=['message']))
x.addChild(node=xmpp.DataField(name='init_pubkey',
options=['none', 'key', 'hash'],
typ='list-single'))
# XXX store key, use hash
x.addChild(node=xmpp.DataField(
name='resp_pubkey', options=['none', 'key'], typ='list-single'))
x.addChild(node=xmpp.DataField(name='ver', value='1.0', typ='hidden'))
x.addChild(node=xmpp.DataField(
name='rekey_freq', value='4294967295', typ='hidden'))
x.addChild(node=xmpp.DataField(
name='sas_algs', value='sas28x5', typ='hidden'))
x.addChild(node=xmpp.DataField(
name='sign_algs',
value='http://www.w3.org/2000/09/xmldsig#rsa-sha256',
typ='hidden'))
self.n_s = crypto.generate_nonce()
x.addChild(node=xmpp.DataField(
name='my_nonce', value=base64.b64encode(self.n_s), typ='hidden'))
modp_options = [
int(g) for g in gajim.config.get('esession_modp').split(',')
]
x.addChild(node=xmpp.DataField(name='modp',
typ='list-single',
options=map(lambda x: [None, x],
modp_options)))
x.addChild(node=self.make_dhfield(modp_options, sigmai))
self.sigmai = sigmai
self.form_s = ''.join(
map(lambda el: xmpp.c14n.c14n(el), x.getChildren()))
feature.addChild(node=x)
self.status = 'requested-e2e'
self.send(request)