prompt with SAS during 3 message negotiation

src/chat_control.py

@@ -1957,7 +1957,8 @@ class ChatControl(ChatControlBase):
 			if not self.session:
 				self.session = gajim.connections[self.account].make_new_session(self.contact.jid)
 
-			self.session.negotiate_e2e()
+			# XXX decide whether to use 4 or 3 message negotiation
+			self.session.negotiate_e2e(False)
 
 	def got_connected(self):
 		ChatControlBase.got_connected(self)

src/common/stanza_session.py

@@ -357,8 +357,8 @@ class EncryptedStanzaSession(StanzaSession):
 		content = self.n_s + self.n_o + self.encode_mpi(self.d) + pubkey_b
 
 		if sigmai:
-			form_b = c7l_form
-			content += form_b
+			self.form_b = c7l_form
+			content += self.form_b
 		else:
 			form_b2 = c7l_form
 			content += self.form_b + form_b2
@@ -384,6 +384,9 @@ class EncryptedStanzaSession(StanzaSession):
 		if self.sas_algs == 'sas28x5':
 			self.sas = self.sas_28x5(m_a, self.form_b)
 
+			if self.sigmai:
+				self.check_identity()
+			
 		return (xmpp.DataField(name='identity', value=base64.b64encode(id_a)), \
 						xmpp.DataField(name='mac', value=base64.b64encode(m_a)))
 
@@ -606,8 +609,6 @@ class EncryptedStanzaSession(StanzaSession):
 
 		self.negotiated = negotiated
 
-		self.form_b = ''.join(map(lambda el: xmpp.c14n.c14n(el), form.getChildren()))
-
 		accept = xmpp.Message()
 		feature = accept.NT.feature
 		feature.setNamespace(xmpp.NS_FEATURE)
@@ -648,6 +649,9 @@ class EncryptedStanzaSession(StanzaSession):
 			result.addChild(node=xmpp.DataField(name='rshashes', value=rshashes))
 			result.addChild(node=xmpp.DataField(name='dhkeys', value=base64.b64encode(self.encode_mpi(e))))
 		
+			self.form_b = ''.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_alices_identity(result, e):

src/gajim.py

@@ -1765,11 +1765,15 @@ class Interface:
 		elif session.status == 'requested-e2e' and form.getType() == 'submit':
 			negotiated, not_acceptable, ask_user = session.verify_options_alice(form)
 
+			if session.sigmai:
+				session.check_identity = lambda: negotiation.show_sas_dialog(jid, session.sas)
+
 			if ask_user:
 				def accept_nondefault_options(widget):
 					dialog.destroy()
 
 					negotiated.update(ask_user)
+				
 					session.accept_e2e_alice(form, negotiated)
 
 				def reject_nondefault_options(widget):