Add better certificate handling.

Certificate host names are now matched (using DNS, SRV, XMPPAddr, and
Common Name), along with expiration check.

Scheduled event to reset the stream once the server's cert expires.

Handle invalid cert trust chains gracefully now.

sleekxmpp/xmlstream/xmlstream.py

@@ -35,7 +35,7 @@ from xml.parsers.expat import ExpatError
 
 import sleekxmpp
 from sleekxmpp.thirdparty.statemachine import StateMachine
-from sleekxmpp.xmlstream import Scheduler, tostring
+from sleekxmpp.xmlstream import Scheduler, tostring, cert
 from sleekxmpp.xmlstream.stanzabase import StanzaBase, ET, ElementBase
 from sleekxmpp.xmlstream.handler import Waiter, XMLCallback
 from sleekxmpp.xmlstream.matcher import MatchXMLMask
@@ -181,6 +181,9 @@ class XMLStream(object):
         
         #: The domain to try when querying DNS records. 
         self.default_domain = ''
+
+        #: The expected name of the server, for validation.
+        self._expected_server_name = ''
     
         #: The desired, or actual, address of the connected server.
         self.address = (host, int(port))
@@ -313,8 +316,9 @@ class XMLStream(object):
         self.dns_service = None
 
         self.add_event_handler('connected', self._handle_connected)
-        self.add_event_handler('session_start', self._start_keepalive)
         self.add_event_handler('disconnected', self._end_keepalive)
+        self.add_event_handler('session_start', self._start_keepalive)
+        self.add_event_handler('session_start', self._cert_expiration)
 
     def use_signals(self, signals=None):
         """Register signal handlers for ``SIGHUP`` and ``SIGTERM``.
@@ -500,10 +504,17 @@ class XMLStream(object):
                 self.socket.connect(self.address)
 
                 if self.use_ssl and self.ssl_support:
-                    cert = self.socket.getpeercert(binary_form=True)
-                    cert = ssl.DER_cert_to_PEM_cert(cert)
-                    log.debug('CERT: %s', cert)
-                    self.event('ssl_cert', cert, direct=True)
+                    self._der_cert = self.socket.getpeercert(binary_form=True)
+                    pem_cert = ssl.DER_cert_to_PEM_cert(self._der_cert)
+                    log.debug('CERT: %s', pem_cert)
+                    
+                    self.event('ssl_cert', pem_cert, direct=True)
+                    try:
+                        cert.verify(self._expected_server_name, self._der_cert)
+                    except cert.CertificateError as err:
+                        log.error(err.message)
+                        self.event('ssl_invalid_cert', cert, direct=True)
+                        self.disconnect(send_close=False)
 
             self.set_socket(self.socket, ignore=True)
             #this event is where you should set your application state
@@ -767,12 +778,27 @@ class XMLStream(object):
                 self.socket.socket = ssl_socket
             else:
                 self.socket = ssl_socket
-            self.socket.do_handshake()
 
-            cert = self.socket.getpeercert(binary_form=True)
-            cert = ssl.DER_cert_to_PEM_cert(cert)
-            log.debug('CERT: %s', cert)
-            self.event('ssl_cert', cert, direct=True)
+            try:
+                self.socket.do_handshake()
+            except:
+                log.error('CERT: Invalid certificate trust chain.')
+                self.event('ssl_invalid_chain', direct=True)
+                self.disconnect(self.auto_reconnect, send_close=False)
+                return False
+
+            self._der_cert = self.socket.getpeercert(binary_form=True)
+            pem_cert = ssl.DER_cert_to_PEM_cert(self._der_cert)
+            log.debug('CERT: %s', pem_cert)
+            self.event('ssl_cert', pem_cert, direct=True)
+
+            try: 
+                cert.verify(self._expected_server_name, self._der_cert)
+            except cert.CertificateError as err:
+                log.error(err.message)
+                self.event('ssl_invalid_cert', cert, direct=True)
+                if not self.event_handled('ssl_invalid_cert'):
+                    self.disconnect(self.auto_reconnect, send_close=False)
 
             self.set_socket(self.socket)
             return True
@@ -780,6 +806,26 @@ class XMLStream(object):
             log.warning("Tried to enable TLS, but ssl module not found.")
             return False
 
+    def _cert_expiration(self, event):
+        """Schedule an event for when the TLS certificate expires."""
+
+        def restart():
+            log.warn("The server certificate has expired. Restarting.")
+            self.reconnect()
+
+        cert_ttl = cert.get_ttl(self._der_cert)
+        if cert_ttl is None:
+            return
+
+        if cert_ttl.days < 0:
+            log.warn('CERT: Certificate has expired.')
+            restart()
+
+        log.info('CERT: Time until certificate expiration: %s' % cert_ttl)
+        self.schedule('Certificate Expiration',
+                      cert_ttl.seconds,
+                      restart)
+
     def _start_keepalive(self, event):
         """Begin sending whitespace periodically to keep the connection alive.
 
@@ -1298,9 +1344,16 @@ class XMLStream(object):
             except (Socket.error, ssl.SSLError) as serr:
                 self.event('socket_error', serr, direct=True)
                 log.error('Socket Error #%s: %s', serr.errno, serr.strerror)
+            except ValueError as e:
+                msg = e.message if hasattr(e, 'message') else e.args[0]
+
+                if 'I/O operation on closed file' in msg:
+                    log.error('Can not read from closed socket.')
+                else:
+                    self.exception(e)
             except Exception as e:
                 if not self.stop.is_set():
-                    log.exception('Connection error.')
+                    log.error('Connection error.')
                 self.exception(e)
 
             if not shutdown and not self.stop.is_set() \