refactored identity verification
public key authentication
This commit is contained in:
Brendan Taylor
parent
4bfe14d3cf
commit
8675731f8d
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@ -16,9 +16,12 @@ import xmpp.c14n
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from Crypto.Cipher import AES
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from Crypto.Hash import HMAC, SHA256
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from Crypto.PublicKey import RSA
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import base64
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XmlDsig = 'http://www.w3.org/2000/09/xmldsig#'
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class StanzaSession(object):
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def __init__(self, conn, jid, thread_id, type):
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self.conn = conn
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@ -189,6 +192,11 @@ class EncryptedStanzaSession(StanzaSession):
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self.c_o = (self.c_o + 1) % (2 ** self.n)
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return self.encode_mpi_with_padding(self.c_o)
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def sign(self, string):
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if self.negotiated['sign_algs'] == (XmlDsig + 'rsa-sha256'):
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hash = self.sha256(string)
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return self.encode_mpi(gajim.interface.pubkey.sign(hash, '')[0])
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def encrypt_stanza(self, stanza):
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encryptable = filter(lambda x: x.getName() not in ('error', 'amp', 'thread'), stanza.getChildren())
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@ -317,84 +325,117 @@ class EncryptedStanzaSession(StanzaSession):
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macable = filter(lambda x: x.getVar() not in ('mac', 'identity'), kids)
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return ''.join(map(lambda el: xmpp.c14n.c14n(el), macable))
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def verify_alices_identity(self, form, e):
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m_a = base64.b64decode(form['mac'])
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id_a = base64.b64decode(form['identity'])
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def verify_identity(self, form, dh_i, sigmai, i_o):
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m_o = base64.b64decode(form['mac'])
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id_o = base64.b64decode(form['identity'])
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m_a_calculated = self.hmac(self.km_o, self.encode_mpi(self.c_o) + id_a)
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m_o_calculated = self.hmac(self.km_o, self.encode_mpi(self.c_o) + id_o)
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if m_a_calculated != m_a:
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raise exceptions.NegotiationError, 'calculated m_a differs from received m_a'
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if m_o_calculated != m_o:
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raise exceptions.NegotiationError, 'calculated m_%s differs from received m_%s' % (i_o, i_o)
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# check for a retained secret
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# if none exists, prompt the user with the SAS
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if self.sas_algs == 'sas28x5':
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self.sas = self.sas_28x5(m_a, self.form_b)
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if i_o == 'a' and self.sas_algs == 'sas28x5':
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# XXX not necessary if there's a verified retained secret
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self.sas = self.sas_28x5(m_o, self.form_s)
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mac_a = self.decrypt(id_a)
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if self.negotiated['recv_pubkey']:
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plaintext = self.decrypt(id_o)
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parsed = xmpp.Node(node='<node>' + plaintext + '</node>')
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form_a2 = self.c7lize_mac_id(form)
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if self.negotiated['recv_pubkey'] == 'hash':
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fingerprint = parsed.getTagData('fingerprint')
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mac_a_calculated = self.hmac(self.ks_o, self.n_s + self.n_o + self.encode_mpi(e) + self.form_a + form_a2)
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# XXX find stored pubkey or terminate session
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raise 'unimplemented'
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else:
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if self.negotiated['sign_algs'] == (XmlDsig + 'rsa-sha256'):
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keyvalue = parsed.getTag(name='RSAKeyValue', namespace=XmlDsig)
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if mac_a_calculated != mac_a:
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raise exceptions.NegotiationError, 'calculated mac_a differs from received mac_a'
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n, e = map(lambda x: self.decode_mpi(base64.b64decode(keyvalue.getTagData(x))), ('Modulus', 'Exponent'))
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eir_pubkey = RSA.construct((n,long(e)))
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def verify_bobs_identity(self, form, sigmai):
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m_b = base64.b64decode(form['mac'])
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id_b = base64.b64decode(form['identity'])
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pubkey_o = xmpp.c14n.c14n(keyvalue)
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else:
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# XXX DSA, etc.
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raise 'unimplemented'
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m_b_calculated = self.hmac(self.km_o, self.encode_mpi(self.c_o) + id_b)
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if m_b_calculated != m_b:
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raise exceptions.NegotiationError, 'calculated m_b differs from received m_b'
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mac_b = self.decrypt(id_b)
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pubkey_b = ''
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enc_sig = parsed.getTag(name='SignatureValue', namespace=XmlDsig).getData()
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signature = (self.decode_mpi(base64.b64decode(enc_sig)),)
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else:
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mac_o = self.decrypt(id_o)
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pubkey_o = ''
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c7l_form = self.c7lize_mac_id(form)
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content = self.n_s + self.n_o + self.encode_mpi(self.d) + pubkey_b
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content = self.n_s + self.n_o + self.encode_mpi(dh_i) + pubkey_o
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if sigmai:
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self.form_b = c7l_form
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content += self.form_b
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self.form_o = c7l_form
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content += self.form_o
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else:
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form_b2 = c7l_form
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content += self.form_b + form_b2
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form_o2 = c7l_form
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content += self.form_o + form_o2
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mac_b_calculated = self.hmac(self.ks_o, content)
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mac_o_calculated = self.hmac(self.ks_o, content)
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if self.negotiated['recv_pubkey']:
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hash = self.sha256(mac_o_calculated)
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if mac_b_calculated != mac_b:
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raise exceptions.NegotiationError, 'calculated mac_b differs from received mac_b'
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if not eir_pubkey.verify(hash, signature):
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raise exceptions.NegotiationError, 'public key signature verification failed!'
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elif mac_o_calculated != mac_o:
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raise exceptions.NegotiationError, 'calculated mac_%s differs from received mac_%s' % (i_o, i_o)
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def make_alices_identity(self, form, e):
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form_a2 = ''.join(map(lambda el: xmpp.c14n.c14n(el), form.getChildren()))
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if self.negotiated['send_pubkey']:
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if self.negotiated['sign_algs'] == (XmlDsig + 'rsa-sha256'):
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fields = (gajim.interface.pubkey.n, gajim.interface.pubkey.e)
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cb_fields = map(lambda f: base64.b64encode(self.encode_mpi(f)), fields)
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pubkey_s = '<RSAKeyValue xmlns="http://www.w3.org/2000/09/xmldsig#"><Modulus>%s</Modulus><Exponent>%s</Exponent></RSAKeyValue>' % tuple(cb_fields)
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else:
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pubkey_s = ''
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form_s2 = ''.join(map(lambda el: xmpp.c14n.c14n(el), form.getChildren()))
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old_c_s = self.c_s
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content = self.n_o + self.n_s + self.encode_mpi(e) + self.form_a + form_a2
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content = self.n_o + self.n_s + self.encode_mpi(e) + pubkey_s + self.form_s + form_s2
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mac_a = self.hmac(self.ks_s, content)
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id_a = self.encrypt(mac_a)
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if self.negotiated['send_pubkey']:
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signature = self.sign(mac_a)
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sign_s = '<SignatureValue xmlns="http://www.w3.org/2000/09/xmldsig#">%s</SignatureValue>' % base64.b64encode(signature)
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if self.negotiated['send_pubkey'] == 'hash':
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b64ed = base64.b64encode(self.hash(pubkey_s))
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pubkey_s = '<fingerprint>%s</fingerprint>' % b64ed
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id_a = self.encrypt(pubkey_s + sign_s)
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else:
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id_a = self.encrypt(mac_a)
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m_a = self.hmac(self.km_s, self.encode_mpi(old_c_s) + id_a)
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# check for a retained secret
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# if none exists, prompt the user with the SAS
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if self.sas_algs == 'sas28x5':
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self.sas = self.sas_28x5(m_a, self.form_b)
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self.sas = self.sas_28x5(m_a, self.form_o)
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if self.sigmai:
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self.check_identity()
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return (xmpp.DataField(name='identity', value=base64.b64encode(id_a)), \
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xmpp.DataField(name='mac', value=base64.b64encode(m_a)))
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def make_bobs_identity(self, form, d):
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pubkey_b = ''
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form_b2 = ''.join(map(lambda el: c14n.c14n(el), form.getChildren()))
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content = self.n_o + self.n_s + self.encode_mpi(d) + pubkey_b + self.form_b + form_b2
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form_s2 = ''.join(map(lambda el: xmpp.c14n.c14n(el), form.getChildren()))
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content = self.n_o + self.n_s + self.encode_mpi(d) + pubkey_b + self.form_s + form_s2
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old_c_s = self.c_s
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mac_b = self.hmac(self.ks_s, content)
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@ -430,13 +471,17 @@ class EncryptedStanzaSession(StanzaSession):
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# unsupported options: 'iq', 'presence'
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x.addChild(node=xmpp.DataField(name='stanzas', typ='list-multi', options=['message']))
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x.addChild(node=xmpp.DataField(name='init_pubkey', value='none', typ='hidden'))
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x.addChild(node=xmpp.DataField(name='resp_pubkey', value='none', typ='hidden'))
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x.addChild(node=xmpp.DataField(name='init_pubkey', options=['none', 'key', 'hash'], typ='list-single'))
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# XXX store key, use hash
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x.addChild(node=xmpp.DataField(name='resp_pubkey', options=['none', 'key'], typ='list-single'))
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x.addChild(node=xmpp.DataField(name='ver', value='1.0', typ='hidden'))
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x.addChild(node=xmpp.DataField(name='rekey_freq', value='4294967295', typ='hidden'))
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x.addChild(node=xmpp.DataField(name='sas_algs', value='sas28x5', typ='hidden'))
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x.addChild(node=xmpp.DataField(name='sign_algs', value='http://www.w3.org/2000/09/xmldsig#rsa-sha256', typ='hidden'))
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self.n_s = self.generate_nonce()
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@ -449,7 +494,7 @@ class EncryptedStanzaSession(StanzaSession):
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x.addChild(node=self.make_dhfield(modp_options, sigmai))
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self.sigmai = sigmai
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self.form_a = ''.join(map(lambda el: xmpp.c14n.c14n(el), x.getChildren()))
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self.form_s = ''.join(map(lambda el: xmpp.c14n.c14n(el), x.getChildren()))
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feature.addChild(node=x)
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@ -459,7 +504,7 @@ class EncryptedStanzaSession(StanzaSession):
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# 4.3 esession response (bob)
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def verify_options_bob(self, form):
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negotiated = {}
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negotiated = {'recv_pubkey': None, 'send_pubkey': None}
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not_acceptable = []
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ask_user = {}
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@ -511,6 +556,19 @@ class EncryptedStanzaSession(StanzaSession):
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if not 'logging' in ask_user:
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not_acceptable.append(name)
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elif name == 'init_pubkey':
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for x in ('key'):
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if x in options:
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negotiated['recv_pubkey'] = x
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break
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elif name == 'resp_pubkey':
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for x in ('hash', 'key'):
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if x in options:
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negotiated['send_pubkey'] = x
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break
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elif name == 'sign_algs':
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if (XmlDsig + 'rsa-sha256') in options:
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negotiated['sign_algs'] = XmlDsig + 'rsa-sha256'
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else:
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# XXX some things are handled elsewhere, some things are not-implemented
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pass
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@ -565,8 +623,8 @@ class EncryptedStanzaSession(StanzaSession):
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b64ed = base64.b64encode(to_add[name])
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x.addChild(node=xmpp.DataField(name=name, value=b64ed))
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self.form_a = ''.join(map(lambda el: xmpp.c14n.c14n(el), form.getChildren()))
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self.form_b = ''.join(map(lambda el: xmpp.c14n.c14n(el), x.getChildren()))
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self.form_o = ''.join(map(lambda el: xmpp.c14n.c14n(el), form.getChildren()))
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self.form_s = ''.join(map(lambda el: xmpp.c14n.c14n(el), x.getChildren()))
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self.status = 'responded-e2e'
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@ -597,6 +655,18 @@ class EncryptedStanzaSession(StanzaSession):
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else:
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negotiated['logging'] = self.logging_preference()[0]
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for r,a in (('recv_pubkey', 'resp_pubkey'), ('send_pubkey', 'init_pubkey')):
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negotiated[r] = None
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if a in form.asDict() and form[a] in ('key', 'hash'):
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negotiated[r] = form[a]
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if 'sign_algs' in form.asDict():
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if form['sign_algs'] in (XmlDsig + 'rsa-sha256',):
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negotiated['sign_algs'] = form['sign_algs']
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else:
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not_acceptable.append(form['sign_algs'])
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return (negotiated, not_acceptable, ask_user)
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# 'Alice Accepts', continued
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@ -637,7 +707,7 @@ class EncryptedStanzaSession(StanzaSession):
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if self.sigmai:
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self.kc_o, self.km_o, self.ks_o = self.generate_responder_keys(self.k)
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self.verify_bobs_identity(form, True)
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self.verify_identity(form, self.d, True, 'b')
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else:
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secrets = gajim.interface.list_secrets(self.conn.name, self.jid.getStripped())
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rshashes = [self.hmac(self.n_s, rs) for rs in secrets]
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@ -649,7 +719,7 @@ class EncryptedStanzaSession(StanzaSession):
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result.addChild(node=xmpp.DataField(name='rshashes', value=rshashes))
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result.addChild(node=xmpp.DataField(name='dhkeys', value=base64.b64encode(self.encode_mpi(e))))
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self.form_b = ''.join(map(lambda el: xmpp.c14n.c14n(el), form.getChildren()))
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self.form_o = ''.join(map(lambda el: xmpp.c14n.c14n(el), form.getChildren()))
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# MUST securely destroy K unless it will be used later to generate the final shared secret
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@ -682,13 +752,15 @@ class EncryptedStanzaSession(StanzaSession):
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e = self.decode_mpi(base64.b64decode(form['dhkeys']))
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p = dh.primes[self.modp]
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# XXX return <feature-not-implemented> if hash(e) != He
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k = self.get_shared_secret(e, self.y, p)
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self.kc_o, self.km_o, self.ks_o = self.generate_initiator_keys(k)
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# 4.5.2 verifying alice's identity
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self.verify_alices_identity(form)
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self.verify_identity(form, e, False, 'a')
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# 4.5.4 generating bob's final session keys
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@ -721,17 +793,8 @@ class EncryptedStanzaSession(StanzaSession):
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x.addChild(node=xmpp.DataField(name='nonce', value=base64.b64encode(self.n_o)))
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x.addChild(node=xmpp.DataField(name='srshash', value=base64.b64encode(srshash)))
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form_b2 = ''.join(map(lambda el: xmpp.c14n.c14n(el), x.getChildren()))
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old_c_s = self.c_s
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mac_b = self.hmac(self.ks_s, self.n_o + self.n_s + self.encode_mpi(self.d) + self.form_b + form_b2)
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id_b = self.encrypt(mac_b)
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m_b = self.hmac(self.km_s, self.encode_mpi(old_c_s) + id_b)
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x.addChild(node=xmpp.DataField(name='identity', value=base64.b64encode(id_b)))
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x.addChild(node=xmpp.DataField(name='mac', value=base64.b64encode(m_b)))
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for datafield in self.make_bobs_identity(x, self.d):
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x.addChild(node=datafield)
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init.addChild(node=x)
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@ -769,7 +832,7 @@ class EncryptedStanzaSession(StanzaSession):
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# 4.6.2 Verifying Bob's Identity
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self.verify_bobs_identity(form, False)
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self.verify_identity(form, self.d, False, 'b')
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# Note: If Alice discovers an error then she SHOULD ignore any encrypted content she received in the stanza.
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if self.negotiated['logging'] == 'mustnot':
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@ -104,6 +104,7 @@ from chat_control import ChatControlBase
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from atom_window import AtomWindow
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import negotiation
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import Crypto.PublicKey.RSA
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from common import exceptions
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from common.zeroconf import connection_zeroconf
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@ -1393,6 +1394,7 @@ class Interface:
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if os.path.isfile(path_to_original_file):
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os.remove(path_to_original_file)
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# list the retained secrets we have for a local account and a remote jid
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def list_secrets(self, account, jid):
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f = open(secrets_filename)
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@ -1404,6 +1406,7 @@ class Interface:
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f.close()
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return s
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# save a new retained secret
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def save_new_secret(self, account, jid, secret):
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f = open(secrets_filename, 'r')
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secrets = pickle.load(f)
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@ -2559,6 +2562,10 @@ class Interface:
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gobject.timeout_add(200, self.process_connections)
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gobject.timeout_add(500, self.read_sleepy)
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# public key for XEP-0116
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# XXX os.urandom is not a cryptographic PRNG
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self.pubkey = Crypto.PublicKey.RSA.generate(384, os.urandom)
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if __name__ == '__main__':
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def sigint_cb(num, stack):
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sys.exit(5)
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