Fix regression in telnet service

A regression in the telnet service occured where the Realm/portal
required by AuthenticatingTelnetProtocol in twisted was removed.

opencanary/modules/telnet.py

@@ -1,14 +1,24 @@
 from opencanary.modules import CanaryService
 
+from zope.interface import implementer
 from twisted.application import internet
 from twisted.internet.error import ConnectionDone, ConnectionLost
 from twisted.internet import protocol
+from twisted.cred import portal
 from twisted.cred import credentials
 from twisted.conch.telnet import AuthenticatingTelnetProtocol
 from twisted.conch.telnet import ITelnetProtocol
 from twisted.conch.telnet import TelnetTransport
 from twisted.conch.telnet import ECHO
 
+@implementer(portal.IRealm)
+class Realm:
+    def requestAvatar(self, avatarId, mind, *interfaces):
+        if ITelnetProtocol in interfaces:
+            av = MyTelnet()
+            av.state = 'Command'
+            return ITelnetProtocol, av, lambda:None
+        raise NotImplementedError("Not supported by this realm")
 
 class CanaryTelnetTransport(TelnetTransport):
     def dataReceived(self, data):
@@ -24,7 +34,6 @@ def connectionLost(self, reason):
             return
         TelnetTransport.connectionLost(self, reason)
 
-
 class AlertAuthTelnetProtocol(AuthenticatingTelnetProtocol):
     def connectionMade(self):
         # p/Cisco telnetd/ d/router/ o/IOS/ cpe:/a:cisco:telnet/ cpe:/o:cisco:ios/a
@@ -68,9 +77,11 @@ def __init__(self, config=None, logger=None):
             self.banner += b"\n"
 
     def getService(self):
+        r = Realm()
+        p = portal.Portal(r)
         f = protocol.ServerFactory()
         f.canaryservice = self
         f.logger = self.logger
         f.banner = self.banner
-        f.protocol = lambda: CanaryTelnetTransport(AlertAuthTelnetProtocol)
+        f.protocol = lambda: CanaryTelnetTransport(AlertAuthTelnetProtocol, p)
         return internet.TCPServer(self.port, f, interface=self.listen_addr)