def make_dhfield(self, modp_options, sigmai):
dhs = []
for modp in modp_options:
p = dh.primes[modp]
g = dh.generators[modp]
x = crypto.srand(2**(2 * self.n - 1), p - 1)
# FIXME this may be a source of performance issues
e = crypto.powmod(g, x, p)
self.xes[modp] = x
self.es[modp] = e
if sigmai:
dhs.append(
base64.b64encode(crypto.encode_mpi(e)).decode('utf-8'))
name = 'dhkeys'
else:
He = crypto.sha256(crypto.encode_mpi(e))
dhs.append(base64.b64encode(He).decode('utf-8'))
name = 'dhhashes'
return nbxmpp.DataField(name=name, typ='hidden', value=dhs)
def make_identity(self, form, dh_i):
if self.negotiated['send_pubkey']:
if self.negotiated['sign_algs'] == (XmlDsig + 'rsa-sha256'):
pubkey = secrets.secrets().my_pubkey(self.conn.name)
fields = (pubkey.n, pubkey.e)
cb_fields = [
base64.b64encode(crypto.encode_mpi(f)) for f in fields
]
pubkey_s = b'<RSAKeyValue xmlns="http://www.w3.org/2000/09/xmldsig#"'
'><Modulus>%s</Modulus><Exponent>%s</Exponent></RSAKeyValue>' % \
tuple(cb_fields)
else:
pubkey_s = b''
form_s2 = ''.join(nbxmpp.c14n.c14n(el, self._is_buggy_gajim()) for el \
in form.getChildren())
old_c_s = self.c_s
content = self.n_o + self.n_s + crypto.encode_mpi(dh_i) + pubkey_s + \
self.form_s.encode('utf-8') + form_s2.encode('utf-8')
mac_s = self.hmac(self.ks_s, content)
if self.negotiated['send_pubkey']:
signature = self.sign(mac_s)
sign_s = '<SignatureValue xmlns="http://www.w3.org/2000/09/xmldsig#">'
'%s</SignatureValue>' % base64.b64encode(signature)
if self.negotiated['send_pubkey'] == 'hash':
b64ed = base64.b64encode(self.hash(pubkey_s))
pubkey_s = '<fingerprint>%s</fingerprint>' % b64ed
id_s = self.encrypt(pubkey_s + sign_s)
else:
id_s = self.encrypt(mac_s)
m_s = self.hmac(self.km_s, crypto.encode_mpi(old_c_s) + id_s)
if self.status == 'requested-e2e' and self.sas_algs == 'sas28x5':
# we're alice; check for a retained secret
# if none exists, prompt the user with the SAS
self.sas = crypto.sas_28x5(m_s, self.form_o.encode('utf-8'))
if self.sigmai:
# FIXME save retained secret?
self.check_identity(tuple)
return (nbxmpp.DataField(name='identity',
value=base64.b64encode(id_s).decode('utf-8')),
nbxmpp.DataField(name='mac',
value=base64.b64encode(m_s).decode('utf-8')))
def encrypt_stanza(self, stanza):
encryptable = [
x for x in stanza.getChildren()
if x.getName() not in ('error', 'amp', 'thread')
]
# FIXME can also encrypt contents of <error/> elements in stanzas @type =
# 'error'
# (except for <defined-condition
# xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/> child elements)
old_en_counter = self.c_s
for element in encryptable:
stanza.delChild(element)
plaintext = ''.join(map(str, encryptable))
m_compressed = self.compress(plaintext)
m_final = self.encrypt(m_compressed)
c = stanza.NT.c
c.setNamespace('http://www.xmpp.org/extensions/xep-0200.html#ns')
c.NT.data = base64.b64encode(m_final).decode('utf-8')
# FIXME check for rekey request, handle <key/> elements
m_content = (''.join(map(str, c.getChildren()))).encode('utf-8')
c.NT.mac = base64.b64encode(self.hmac(self.km_s, m_content + \
crypto.encode_mpi(old_en_counter))).decode('utf-8')
msgtxt = '[This is part of an encrypted session. ' \
'If you see this message, something went wrong.]'
lang = os.getenv('LANG')
if lang is not None and lang != 'en': # we're not english
msgtxt = _('[This is part of an encrypted session. '
'If you see this message, something went wrong.]') + ' (' + \
msgtxt + ')'
stanza.setBody(msgtxt)
return stanza
def accept_e2e_alice(self, form, negotiated):
"""
'Alice Accepts', continued
"""
self.encryptable_stanzas = ['message']
self.sas_algs = 'sas28x5'
self.cipher = AES
self.hash_alg = sha256
self.compression = None
self.negotiated = negotiated
accept = nbxmpp.Message()
feature = accept.NT.feature
feature.setNamespace(nbxmpp.NS_FEATURE)
result = nbxmpp.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=nbxmpp.DataField(name='FORM_TYPE', value='urn:xmpp:ssn'))
result.addChild(node=nbxmpp.DataField(name='accept', value='1'))
result.addChild(node=nbxmpp.DataField(
name='nonce', value=base64.b64encode(self.n_o).decode('utf-8')))
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[0]) for rs 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).decode('utf-8') for rshash in \
rshashes]
result.addChild(
node=nbxmpp.DataField(name='rshashes', value=rshashes))
result.addChild(node=nbxmpp.DataField(
name='dhkeys',
value=base64.b64encode(crypto.encode_mpi(e)).decode('utf-8')))
self.form_o = ''.join(nbxmpp.c14n.c14n(el, self._is_buggy_gajim()) \
for el in 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):
"""
4.3 esession response (bob)
"""
response = nbxmpp.Message()
feature = response.NT.feature
feature.setNamespace(nbxmpp.NS_FEATURE)
x = nbxmpp.DataForm(typ='submit')
x.addChild(
node=nbxmpp.DataField(name='FORM_TYPE', value='urn:xmpp:ssn'))
x.addChild(node=nbxmpp.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=nbxmpp.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
modp_f = form.getField('modp')
if not modp_f:
return
self.modp = int(modp_f.getOptions()[group_order][1])
x.addChild(node=nbxmpp.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_f = form.getField('dhhashes')
if not dhhashes_f:
return
dhhashes = dhhashes_f.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]).decode('utf-8')
x.addChild(node=nbxmpp.DataField(name=name, value=b64ed))
self.form_o = ''.join(nbxmpp.c14n.c14n(el, self._is_buggy_gajim()) for \
el in form.getChildren())
self.form_s = ''.join(nbxmpp.c14n.c14n(el, self._is_buggy_gajim()) for \
el in x.getChildren())
self.status = 'responded-e2e'
feature.addChild(node=x)
if not_acceptable:
response = nbxmpp.Error(response, nbxmpp.ERR_NOT_ACCEPTABLE)
feature = nbxmpp.Node(nbxmpp.NS_FEATURE + ' feature')
for f in not_acceptable:
n = nbxmpp.Node('field')
n['var'] = f
feature.addChild(node=n)
response.T.error.addChild(node=feature)
self.send(response)
def verify_identity(self, form, dh_i, sigmai, i_o):
m_o = base64.b64decode(form['mac'])
id_o = base64.b64decode(form['identity'])
m_o_calculated = self.hmac(self.km_o,
crypto.encode_mpi(self.c_o) + id_o)
if m_o_calculated != m_o:
raise NegotiationError(
'calculated m_%s differs from received m_%s' % (i_o, i_o))
if i_o == 'a' and self.sas_algs == 'sas28x5':
# we don't need to calculate this if there's a verified retained secret
# (but we do anyways)
self.sas = crypto.sas_28x5(m_o, self.form_s.encode('utf-8'))
if self.negotiated['recv_pubkey']:
plaintext = self.decrypt(id_o)
parsed = nbxmpp.Node(node='<node>' + plaintext + '</node>')
if self.negotiated['recv_pubkey'] == 'hash':
# fingerprint = parsed.getTagData('fingerprint')
# FIXME find stored pubkey or terminate session
raise NotImplementedError()
else:
if self.negotiated['sign_algs'] == (XmlDsig + 'rsa-sha256'):
keyvalue = parsed.getTag(name='RSAKeyValue',
namespace=XmlDsig)
n, e = (crypto.decode_mpi(
base64.b64decode(keyvalue.getTagData(x)))
for x in ('Modulus', 'Exponent'))
eir_pubkey = RSA.construct((n, int(e)))
pubkey_o = nbxmpp.c14n.c14n(keyvalue,
self._is_buggy_gajim())
else:
# FIXME DSA, etc.
raise NotImplementedError()
enc_sig = parsed.getTag(name='SignatureValue',
namespace=XmlDsig).getData()
signature = (crypto.decode_mpi(base64.b64decode(enc_sig)), )
else:
mac_o = self.decrypt(id_o)
pubkey_o = b''
c7l_form = self.c7lize_mac_id(form)
content = self.n_s + self.n_o + crypto.encode_mpi(dh_i) + pubkey_o
if sigmai:
self.form_o = c7l_form.encode('utf-8')
content += self.form_o
else:
form_o2 = c7l_form.encode('utf-8')
content += self.form_o.encode('utf-8') + form_o2
mac_o_calculated = self.hmac(self.ks_o, content)
if self.negotiated['recv_pubkey']:
hash_ = crypto.sha256(mac_o_calculated)
if not eir_pubkey.verify(hash_, signature):
raise NegotiationError(
'public key signature verification failed!')
elif mac_o_calculated != mac_o:
raise NegotiationError(
'calculated mac_%s differs from received mac_%s' % (i_o, i_o))
def get_shared_secret(self, e, y, p):
if (not 1 < e < (p - 1)):
raise NegotiationError('invalid DH value')
return crypto.sha256(crypto.encode_mpi(crypto.powmod(e, y, p)))
def sign(self, string):
if self.negotiated['sign_algs'] == (XmlDsig + 'rsa-sha256'):
hash_ = crypto.sha256(string)
return crypto.encode_mpi(app.pubkey.sign(hash_, '')[0])
def accept_e2e_bob(self, form):
"""
4.5 esession accept (bob)
"""
response = nbxmpp.Message()
init = response.NT.init
init.setNamespace(nbxmpp.NS_ESESSION_INIT)
x = nbxmpp.DataForm(typ='result')
for field in ('nonce', 'dhkeys', 'rshashes', 'identity', 'mac'):
# FIXME: will do nothing in real world...
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 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 = b''
srses = secrets.secrets().retained_secrets(self.conn.name,
self.jid.getStripped())
rshashes = [
base64.b64decode(rshash)
for rshash in form.getField('rshashes').getValues()
]
for s in srses:
secret = s[0]
if self.hmac(self.n_o, secret) in rshashes:
srs = secret
break
# other shared secret
# (we're not using one)
oss = b''
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, b'Shared Retained Secret')
else:
srshash = crypto.random_bytes(32)
x.addChild(
node=nbxmpp.DataField(name='FORM_TYPE', value='urn:xmpp:ssn'))
x.addChild(node=nbxmpp.DataField(
name='nonce', value=base64.b64encode(self.n_o).decode('utf-8')))
x.addChild(node=nbxmpp.DataField(
name='srshash', value=base64.b64encode(srshash).decode('utf-8')))
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()